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Purpose: To evaluate the dimensional changes in the alveolar crest after buccal overbuilding was performed prior to tooth extraction in a dog model., Materials and Methods: At the test sites, alveolar crest overbuilding was performed on the buccal aspect of the distal root of the third premolar using xenograft covered with a collagen membrane. No treatment was applied at the control sites. After 3 months, the distal roots of both third premolars were extracted and implants were immediately placed into the alveolus, allowing nonsubmerged healing. After 3 months, biopsy samples were collected., Results: Upon histologic analysis, no statistically significant differences in hard tissue dimensions were found. The buccal bone plate at the test sites presented a tendency for higher resorption compared to the control sites. However, if the contribution of the residue of biomaterial is considered, a higher volumetric gain was registered at the test than at the control sites., Conclusions: The buccal overbuilding performed prior to tooth extraction did not contribute to the preservation of the alveolar crest dimensions after extraction. This could be due to failure to incorporate the graft into the newly formed bone.

Purpose: The aim of this study was to determine the possibility and extent of artifact reduction by an optimized use of cone beam computed tomography (CBCT) parameter configuration (geometric resolution, implant geometric parameters, and image analyses). It furthermore sought to determine the distance from correctly reproduced bone tissue to an implant, where the grayscale values are equal to the pre-implantation values., Materials and Methods: Titanium implants were inserted into pig tibia under standardized conditions. CBCT investigations in the form of bone density mapping were performed under various CBCT settings and implantation situations. The circumference of the implants was measured in order to determine the extent of metal artifacts. This was done by determining grayscale and comparing it to the bone area prior to implantation., Results: Using CBCT to determine bone density postimplantation showed a correlation in dependence of CBCT parameter configuration. Higher resolution led to a better detection of correct bone density values in the peri-implant region. Normal bone density values can be recognized at a distance of 370 μm from the implant surface, when the spatial resolution is 125 μm. Therefore, higher resolution in CBCT is accompanied by an improved bone detection in peri-implant bone, despite the presence of metal artifacts. Peri-implant bone defects that extend 400 μm around implants were reliably detected by using a spatial resolution of 125 μm. In specimens, where multiple implants are present in one line, pronounced artifact formations were present. The artifacts were visible as a combination of streak-like hardening and extinction effects., Conclusion: Bone geometric data and density values may be determined correctly in close proximity to the implant surface, and can detect peri-implant bone defects. When multiple implants are placed, the implant radiation direction geometry must be considered.

Purpose: Alveolar ridge preservation procedures have been advocated to minimize postextraction dimensional loss. There is a need for systematic analyses of clinical factors affecting the outcomes of these procedures in order to improve their clinical outcomes. This systematic review and meta-analysis aimed to assess the efficacy of alveolar ridge preservation procedures in terms of hard tissue dimensional changes and to determine clinical factors affecting outcomes of these procedures., Materials and Methods: Studies comparing alveolar ridge preservation procedures with tooth extraction alone that reported quantitative outcomes for hard tissue dimensional changes were included. The primary outcome variable was horizontal dimensional changes of alveolar bone. Subgroup analyses evaluated effects of wound closure, flap elevation, type of grafting materials, use of barrier membranes, use of growth factors, socket morphology, and the position of teeth on outcomes of alveolar ridge preservation procedures., Results: Twenty-one studies were included, and quantitative analyses were performed for seven outcome variables. Significant differences between alveolar ridge preservation and control sites were found for six outcome variables, all favoring alveolar ridge preservation procedures. The magnitude of effect for the primary outcome variable (horizontal dimensional changes of alveolar bone) was 1.86 mm (95% CI = 1.44, 2.28; P < .001). This magnitude of effect for the primary variable (as determined by subgroup analysis) was also significantly affected by type of wound closure (P = .033), type of grafting materials (P = .001), use of barrier membranes (P = .006), use of growth factors (P = .003), and socket morphology (P < .001)., Conclusion: Alveolar ridge preservation procedures are effective in minimizing postextraction hard tissue dimensional loss. The outcomes of these procedures are affected by morphology of extraction sockets, type of wound closure, type of grafting materials, use of barrier membranes, and use of growth factors.

Purpose: In this prospective study, the regenerative potential and pathways of a new injectable bone substitute (IBS) material composed of beta-tricalcium phosphate (β-TCP) and hyaluronan were investigated for its application in alveolar bone regeneration within extraction sockets., Materials and Methods: The bone substitute material was implanted in 44 extraction sockets after removal of teeth not worth preserving in the maxillary and mandibular arches of 21 patients. Four months after augmentation, bone biopsy samples were harvested simultaneously with implant placement for histologic and histomorphometric analysis of tissue reaction and determination of tissue formation (newly formed bone, connective tissue, and remaining IBS) within the augmentation bed. Furthermore, the inserted bone-level implants (C-Tech Esthetic Line) were followed up clinically and radiologically for at least 1 year after prosthetic loading to determine the potential impact of tissue reaction to the IBS on implant stability and performance., Results: The histologic and histomorphometric analyses revealed a gentle tissue reaction with mainly mononuclear and only few multinucleated giant cells within the implantation bed. Histomorphometric analysis revealed mainly newly formed bone tissue (44.92% ± 5.16%) and connective tissue (52.49% ± 6.43%). Only a few remnants of the IBS (2.59% ± 2.05%) could be found. The IBS, with its easy application and fluidity, seemed to be suitable for three-dimensional stable defects such as the intact extraction socket., Conclusion: The IBS contributed to an osteoconductive tissue reaction while undergoing a time-controlled degradation. Clinical and radiological follow-up investigation of the implants inserted in the regenerated area revealed that the IBS contributed to a long-term stable implantation bed for dental implants. The appearance of the IBS can be described as a bulk that is formed within the augmentation bed and that promotes new bone formation through an osteoconductive procedure.

Purpose: To evaluate histologically and histomorphometrically the effect of a delayed load on healing at implants with a moderately rough surface., Materials and Methods: Two solid titanium screw-shaped devices, 5 mm long and 3.5 mm in diameter, were inserted in the distal segments of the alveolar ridge of 16 volunteer patients in a nonsubmerged fashion. After 2 months, one implant was loaded, while the other was left unloaded. After 2 months, the two implants were collected from 10 patients using a sonic instrument, and ground sections were prepared from the biopsy specimens. Histomorphometric analyses were performed., Results: After 4 months of healing, biopsy specimens from 10 patients were available for analyses (n = 10). The total bone-to-implant contact percentage was 86.8% ± 6.5% and 84.6% ± 3.7% for loaded and unloaded implants, respectively. New bone was represented by 85.5% ± 6.7% and 83.4% ± 3.9% at the loaded and unloaded sites, respectively. A very small amount of old parent bone was found. The density of the mineralized bone was 76.8% ± 8.3% for the loaded sites and 74.1% ± 10.5% for the unloaded sites. The percentages of new and old bone densities were 69.0% ± 8.3% and 7.8% ± 3.9% at the loaded sites, and 65.9% ± 10.3% and 8.2% ± 4.5% at the unloaded sites, respectively. No statistically significant differences were disclosed., Conclusion: Applying a delayed load to implants supporting single crowns did not yield statistically significant differences, and only a tendency of higher osseointegration and bone density was observed at loaded sites compared with the unloaded sites.

Purpose: Evidence on the outcomes of functional loading placed in recombinant human bone morphogenetic protein 2 (rhBMP-2)/acellular collagen sponge (ACS)-induced bone is lacking. The aim of this study was to verify whether guided bone regeneration (GBR) with rhBMP-2/ACS enhances regeneration of missing bone and osseointegration of dental implants subject to functional loading., Materials and Methods: Two bilateral standardized large saddle-type defects (≈10 × 10 × 6 mm) were surgically created in each mandible of seven beagle dogs 2 months after tooth extraction. Defects were immediately reconstructed randomly using rhBMP-2 (O-BMP or InFuse) soaked in ACS, deproteinized bovine bone mineral (DBBM) granules, or ACS alone as surgical control and subsequently covered with collagen membrane. Screw-type sand-blasted, acid-etched dental implants were placed 3 months later into the reconstructed defects and into adjacent bone. Osseointegration was allowed to progress for 3 months before functional loading of 3 months until sacrifice., Results: Significantly more bone fill was radiographically observed for GBR with rhBMP-2/ACS (O-BMP: 92.5%, InFuse: 79%) in comparison to the DBBM (52%) and ACS alone groups (56.6%). Osseointegration was achieved and maintained in all experimental defects challenged by prostheses-driven functional load. The bone density ranged from 37.49% in the ACS group to 64.9% in the rhBMP-2/ACS (InFuse) group with no significance. The highest mean percentage of BIC was found in rhBMP-2/ACS (InFuse: 52.98%) with no statistical difference. Crestal bone resorption was observed around implants placed in reconstructed areas without any significant difference., Conclusion: GBR with rhBMP-2/ACS provided the greatest bone fill among the three treatment procedures. GBR with rhBMP-2/ACS showed efficacy for placement, osseointegration, and functional loading of titanium implants in alveolar ridge defects.

Purpose: When failing front teeth are replaced by implants, vestibular bone deficiencies frequently require augmentation, even though the amount of missing alveolar volume may vary. The objective of this study was to analyze the horizontal alveolar ridge dimension after implant placement and simultaneous augmentation, and to compare it to the condition at the contralateral natural site., Materials and Methods: Forty-eight patients with a failing maxillary incisor received an immediate or early implant (Straumann Bone Level), according to a randomized study protocol. The vestibular wall of the implant site was reconstructed and moderately overcontoured with bovine hydroxyapatite and a collagen membrane (BioOss, BioGide, Geistlich). Provisional restoration followed either immediately, or after a 6-week healing period. To investigate the vestibular volume 6 months after surgery, a plaster model of the maxilla was scanned with cone beam computed tomography (CBCT; Morita 3D) and evaluated using coDiagnostiX software (Dental Wings). Statistical analysis comprised one- and two-sample t tests., Results: The ridge volume was not significantly influenced by the treatment schedule. The vestibular segments had a mean ± SD volume of 207.9 ± 102.5 mm³ for the implant sites, and 202.1 ± 101.5 mm³ for the corresponding natural sites (P = .28). The difference in vestibular volume between implant sites and natural tooth sites was 10.4 ± 36.2 mm³ for immediate implantation, and 0.00 ± 31.1 mm³ for early implantation (P = .32). Comparing immediate and early restoration, a difference of 0.4 mm³ and 12.5 mm³ between the implant and contralateral site was found (P = .23)., Conclusion: Six months after treatment, no significant differences between the alveolar volumes at augmented implant sites and natural sites were found. Moderate buccal overcontouring may have been beneficial to achieve a symmetrical contour. Long-term follow-up investigation will document if the restored volume remains stable over time.

Purpose: The main aim of this study was to evaluate the influence of four different abutment materials and the adhesive joint of two-piece abutments on the cervical implant bone and soft tissue., Materials and Methods: Sixty-four titanium implants (Camlog Conelog; 4.3 ± 9 mm) were placed bone level into the edentulous arches of four minipigs. Four different types of abutments were placed at implant exposure: zirconium dioxide, lithium disilicate, and titanium bonded to a titanium luting base with resin cement; one-piece titanium abutments served as the control. The animals were sacrificed 6 months after implant exposure, and the bone-to-implant contact (BIC) area, sulcus depth, the length of the junctional epithelium and the connective tissue, the biologic width, and first cervical BIC-implant shoulder distance were measured using histomorphometry and light and fluorescence microscopy., Results: Overall, 14 implants were lost (22%). At exposure, the implant shoulder-bone distance was 0.6 ± 0.7 mm. Six months later, the bone loss was 2.1 ± 1.2 mm measured histomorphometrically. There was a significant difference between the two measurements (P ≤ .0001). No significant influence could be found between any of the abutment materials with regard to bone loss or soft tissue anatomy (P > .05), with the exception of zirconium dioxide and onepiece titanium abutments when measuring the length of the junctional epithelium (P ≤ .01). The maxilla provided significantly more soft tissue and less bone loss compared with the mandible (P ≤ .02)., Conclusion: All tested abutment materials and techniques seem to be comparable with regard to soft tissue properties and the cervical bone level.

Purpose: Concerns have been expressed about the possibility of high insertion torque (IT) causing necrosis, impaired osseointegration, and crestal bone loss over time. The present study investigated the relationship between primary stability and implant success, including early and late maintenance of crestal bone levels., Materials and Methods: Implants were placed in patients at three study centers. Every effort was made to achieve the highest possible primary stability, which was measured with IT and implant stability quotient (ISQ). The IT and ISQ at insertion and reopening (3 to 4 months), as well as bone levels at several points in time, were recorded. The correlations between IT, ISQ, and immediate and 3-year crestal bone loss were investigated through linear regression analyses., Results: Average IT was 76.1 ± 20.8 Ncm, while the average ISQ score was 80.4 ± 8.4. The implant success rate at 36 months was 98.6%. The crestal bone loss around most implants (41.0%) ranged from 0.05 to 0.5 mm. None of the osseointegrated implants had crestal bone loss greater than 2.5 mm. The linear regression analysis showed no correlation among early or 3-year crestal bone loss and IT, ISQ at surgery, and ISQ at reopening., Conclusion: The implants studied avoided any negative effects deriving from the high IT values (≥ 50 Ncm) applied during 3 years of follow-up.

Purpose: The aim of this study was to evaluate the degree of resorption that occurs following a period of consolidation in alveolar distraction osteogenesis and assess the amount of overcorrection necessary to achieve the planned height., Materials and Methods: A retrospective observational study was conducted comprising 19 surgically treated patients, where a total of 19 extraosseous distractors were placed. All patients undergoing surgery had a panoramic radiograph and a computed tomography scan, both at the end of distraction and at the end of the consolidation period. To assess the degree of resorption, the distance from the mandibular border, maxillary sinus floor, or nasal floor to the limit of the crestal bone following consolidation was compared with the height recorded at the end of the distraction period., Results: Resorption occurred in all cases ranging from 7% to 25%., Conclusion: The presence of resorption reported from this study indicates that an overcorrection of at least 20% may be necessary when distraction osteogenesis is performed.

Purpose: The purpose of this prospective study was to assess the change of marginal bone level around three different types of external-hex implants after 5 years using radiography., Materials and Methods: Included in this study were 54 patients randomly put into three different groups; rough-surface implants (Brånemark), machined coronal aspect implants (Restore), and microthreaded coronal aspect implants (Hexplant). Clinical and radiographic assessments were performed contemporaneously with implant loading (baseline) and at 1, 3, and 5 years post-functional loading. A mixed-model analysis was employed to examine mean marginal bone change significance in the three treatment groups., Results: In a total of 31 out of 54 patients, 81 of 135 implants remained to the end of the study. At 5 years, the microthreaded coronal aspect implants had 0.61 ± 0.32 mm mean crestal bone loss; the rough-surface implants without microthread, 0.99 ± 0.38 mm; and the machined coronal aspect implants, 1.06 ± 0.39 mm. The rough-surface implants and the machined coronal aspect implants did not exhibit statistically significantly different marginal bone loss, whereas the microthreaded coronal aspect implants exhibited significantly less marginal bone loss (P = .0015)., Conclusion: In this research, rough-surface implants with microthreads showed positive long-term effects in preserving peri-implant bone level against functional loads when compared with implants lacking these aspects at the coronal part. Most of the bone loss was shown within 1 year of loading, and all types of implants stabilized after 1 year.

Purpose: The purpose of this study was to determine the amount and localization of functional stresses in implants placed in two different bone types (type 3 and type 4) with three different crown heights in the atrophic posterior maxilla using finite element analysis., Materials and Methods: A three-dimensional finite element model of the posterior maxilla was created from a computerized tomography image by using the Marc 2005 (MSC Software) program. Three different crown/implant ratios (1/1, 1.5/1, 2/1) in the first molar tooth zone were modeled. Type 3 and type 4 bone quality according to the classification system of Lekholm and Zarb was created. The total oblique force of 300 N with a 30-degree angle was applied from the locations of the mesiobuccal cusp (150 N) and the distobuccal cusp (150 N) of first molar teeth., Results: For the implants, the highest stresses were observed around the implant neck at the crown/implant ratio of 2/1 (430.57 MPa). As the crown/implant ratio increased two times, the von Mises stresses increased at a rate of 47%. The highest tensile values exceeded the ultimate tensile strength of the cortical bone for all the designs. Also, the highest compressive values exceeded the ultimate compressive strength of the cortical bone in the 2/1 design for type 3 bone, and in the 1.5/1 and 2/1 designs for type 4 bone. As the crown/implant ratio increased from 1/1 to 2/1, the highest tensile value and the highest compressive value increased 13%. For the spongious bone, as the crown/implant ratio increased, the highest tensile value increased 42% and 85%, respectively. Tensile stresses increased at a rate of 26% in the 1/1 ratio, 30% in the 1.5/1 ratio, and 32% in the 2/1 ratio when the density of spongious bone decreased. Compression-related values also increased 34% in the 1/1 ratio, 35% in the 1.5/1 ratio, and 36% in the 2/1 ratio when the density of spongious bone decreased., Conclusion: Compressive and tensile stresses formed mostly at the alveolar bone around the implant neck that was cortical bone. Thus, it had to be preserved during the surgical procedures. Deformation due to the stresses had great importance for the type IV spongious bone due to the increase caused by the higher crown height levels.

Purpose: The aim of this study was to determine if self-threading dental implants placed using stopper drills to bicortically engage both the alveolar crest and sinus floor (bicortical fixation) achieved primary and/or secondary stability comparable to that of short implants only engaging alveolar crest cortical bone (unicortical fixation) or implants engaging both the crest and sinus floor but via greenstick fracture and grafting (indirect sinus elevation)., Materials and Methods: Thirty-eight patients exhibiting 7 to 11 mm of bone coronal to the sinus floor as confirmed by preoperative CBCT were recruited. Forty-five implants were randomly assigned to one of the placement techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla while using different surgical techniques. An Osstell ISQ was employed immediately after implant placement to measure stability six times in a buccolingual dimension. Secondary stability was measured at stage-two surgery after a 3- to 6-month healing period., Results: The greatest primary implant stability was achieved via indirect sinus elevation. However, no statistically significant difference was found among the three surgical techniques (P = .13; bicortical fixation: 71.4 [standard error = 2.1]), unicortical fixation: 69.6 [2.1], indirect sinus elevation: 75.9 [2.3]). The three techniques had similar secondary stability (P > .999; 79.9 [1.2], 80.0 [1.2], and 80.0 [1.3], respectively). Baseline residual ridge height measured on CBCT was similar (P = .1; 8.8, 9.9, and 9.4 mm, respectively), but implant diameter and length placed in the maxilla differed (P = .03/P < .001; 4.7/11.4 mm, 4.3/8.1 mm, and 4.7/11.8 mm, respectively). Primary implant stability was significantly correlated to CBCT bone density (r = 0.37)., Conclusion: Primary and secondary implant stabilities of bicortical fixation did not differ significantly from those of unicortical fixation and indirect sinus elevation. However, use of the bicortical fixation technique is warranted since it is simpler and more economical than indirect sinus elevation; plus, it allows for longer implants than the unicortical fixation while yielding similar secondary implant stability.

Purpose: The aim of this study was to assess the efficacy of alveolar vertical distraction osteogenesis and autogenous bone grafting in terms of bone gain, bone resorption, and implant survival and success rates and investigate the relationship between bone gain and resorption after alveolar vertical distraction osteogenesis., Materials and Methods: A systematic search was done using MEDLINE, EMBASE, the Cochrane Library, and KoreaMed from inception to April 30, 2014. Supplementary manual searches of published full-text articles were also performed., Results: Searches of four electronic databases and manual searches resulted in 1,538 articles. After selection, four studies were included in the systematic review and meta-analysis. The difference in bone gain at the end of distraction or bone grafting was statistically significant (weighted mean difference [WMD] 1.86, 95% CI 0.03 to 3.69, P = .05; heterogeneity: I(2) = 78%, P = .01). However, there was not a statistically significant difference between alveolar distraction osteogenesis and onlay bone grafting (WMD 0.30, 95% CI -0.99 to 1.59, P = .065). Bone resorption between the end of treatment and the time of implant placement was not statistically significant (WMD -0.12, 95% CI -1.10 to 0.85, P = .80; heterogeneity: I(2) = 78%, P = .01). A simple equation related to bone gain and resorption after alveolar vertical distraction was induced from these results., Conclusion: There was not a statistically significant difference between alveolar distraction osteogenesis and onlay bone grafting in terms of bone gain and bone resorption.

Purpose: To evaluate changes in sinus dimensions immediately postoperatively and 1 year later using a composite of bovine-derived xenograft and autogenous bone for lateral bone augmentation of the maxillary sinus., Materials and Methods: Patients who underwent lateral wall sinus augmentation procedures without concomitant implant placement were considered for this retrospective analysis if they had three consecutive panoramic radiographs: pretreatment (T0), immediately after lateral wall sinus augmentation (T1), and approximately 1 year postoperatively (T2). Eighteen subjects aged 47 to 69 years were included. The surgical protocol included grafting with a composite of bovine-derived xenograft and autogenous bone (9:1 ratio). Digital panoramic radiographs were transferred into measurement software, and the following measurements were performed: (1) vertical distance from the alveolar crest to the height of the augmented material, (2) sagittal area of the grafted area, and (3) vertical distance from the alveolar crest to the roof of the maxillary sinus. All measurements were performed by one examiner. Double measurements were performed in nine patients at T2, and the calculated Cronbach's alpha statistic was very high (.9658 to .9882)., Results: The mean overall sinus sagittal area was 1,330 ± 481 mm2 prior to the grafting procedure, when it decreased to 858.2 ± 436 mm2 (range, 380.7 to 2,134 mm2) immediately postoperatively (P = .0035) and remained stable at 1 year (mean, 882.2 ± 384 mm2, P > .05). Similarly, the overall area of the grafted material at the time of surgery was 468.3 ± 208 mm2 and was only slightly reduced at 1 year (422.2 ± 193 mm2). The midsagittal graft height at T1 (mean, 20.67 ± 4.5 mm) was insignificantly and minimally reduced at 1 year (mean, 19.35 ± 4.9 mm)., Conclusion: The linear dimensions of composite bone-derived xenograft/autogenous bone grafts following lateral wall sinus augmentation exhibited minimal changes during the 8- to 12-month healing period.

Purpose: Reduction of alveolar height and width after tooth extraction may present problems for implant placement, since bone volume is important for biologic and esthetic reasons. The aim of this study was to assess bone healing of large bone defects grafted with collagen sheets and maintenance of reactive soft tissue, evaluating cone beam computed tomography (CBCT) scans and histomorphometric results., Materials and Methods: Patients presented large bone defects after tooth extractions. Reactive soft tissue was left in the defects filled by collagen sheets. Vertical bone volume was assessed by CBCT examinations before tooth extractions and 3 months later. At 3 months, cylinder bone samples were obtained for histology and histomorphometry analysis., Results: Twenty-six patients were included in the clinical study. Examined defects reported mean bone gain of 12.13 ± 3.91 mm, and mean vertical bone levels showed a statistically significant increase (P < .05) at 3 months after extraction. Histologic examinations revealed bone formation; mean vital bone measurements were 41.59% ± 5.80%, and connective tissue percentages averaged 50.37% ± 7.73%., Conclusion: Reactive soft tissue left in large bone defects after tooth extraction and grafted collagen may support a significant vertical bone gain and vital bone formation.

Purpose: To assess the methodologic quality of systematic reviews on the effect of platform switching upon peri-implant marginal bone loss., Materials and Methods: An electronic literature search of several databases was conducted by two reviewers. Articles were considered for quality assessment if they met the following inclusion criterion: systematic reviews that aimed at investigating the effect of platform switching/mismatch on marginal bone levels around dental implants. Two independent examiners evaluated the review publications using two quality-ranking scales (assessment of multiple systematic reviews [AMSTAR] and Glenny checklist). Descriptive statistics were used to summarize the results, and Cohen's kappa coefficients were calculated to appraise interrater agreement of each checklist., Results: Overall, five systematic reviews (including three of them with meta-analysis) were evaluated. The mean AMSTAR score ± standard deviation was 8.4 ± 2.6 (range, 4 to 11), and the mean Glenny score was 10.8 ± 2.9 (range, 6 to 14), showing high statistical correlation (rs = 0.98, P = .005). Cohen interexaminer test yielded values of κ = 0.88 and κ = 0.86 for the AMSTAR and Glenny checklist, respectively. The AMSTAR items rated positive in 78%, whereas 18% met the criteria for "no" and 4% were "not applicable." Only one review article met all criteria. Items of the Glenny checklist rated positive in 73% and negative in 27%. All but one study with the lowest quality scores (finding no difference) demonstrated a clinical benefit of implant platform switching in preserving the peri-implant marginal bone loss., Conclusion: According to the quality-ranking scales appraised, substantial methodologic variability was found in systematic assessment of benefits with the platform switching concept to preserve peri-implant bone level. High-quality systematic reviews, however, generally favored platform switching over platform matching.

Purpose: Implant design and the implant-abutment interface have been regarded as key influences on crestal bone maintenance over time. The aim of the present study was to determine crestal bone changes around implants placed at different depths in a dog model., Materials and Methods: Thirty-six two-piece dental implants with a medialized implant-abutment interface and Morse taper connection (Ankylos, Dentsply) were placed in edentulous areas bilaterally in six mongrel dogs. On each side of the mandible, three implants were placed randomly at the bone crest, 1.5 mm subcrestally, or 3.0 mm subcrestally. After 3 months, the final abutments were torqued into place. At 6 months, the animals were sacrificed and samples taken for microcomputed tomographic (micro-CT) and histologic evaluations., Results: Micro-CT analysis revealed similar crestal or marginal bone loss among groups. Both subcrestal implant groups lost significantly less crestal and marginal bone than the equicrestal implants. Bone loss was greatest on the buccal of the implants, regardless of implant placement depth. Histologically, implants placed subcrestally were found to have bone in contact with the final abutment and on the implant platform., Conclusion: Implants with a centralized implant-abutment interface and Morse taper connection can be placed subcrestally without significant loss of crestal or marginal bone. Subcrestal placement of this implant system appears to be advantageous in maintaining bone height coronal to the implant platform.

Purpose: To prospectively evaluate peri-implant bone and soft tissue dimension changes around adjacent implants placed at different horizontal interimplant distances., Materials and Methods: Thirty partially edentulous patients, who underwent rehabilitation with two adjacent implant-supported crowns as part of their treatment plan, were assigned to three groups based on their prosthetic needs. Patients in group A (10 patients, 20 implants) were to have two implants placed at a 2-mm interimplant distance, patients in group B (10 patients, 20 implants) were to have two implants placed at a 3-mm interimplant distance, and patients in group C (10 patients, 20 implants) were to have two implants placed at an interimplant distance of > 4 mm according to their prosthetic needs. All patients received single-crown restorations after 3 months. Clinical examinations were performed at the time of crown placement (T3), and 6 months (T6), 12 months (T12), and 24 months (T24) after implant placement. Peri-implant bone levels were assessed radiographically at the time of implant placement (T0), and at T3, T12, and T24., Results: One patient from group C did not return for follow-up examinations after implant placement. The mean (± standard deviation) horizontal interimplant distance was 1.97 ± 0.44 mm for implants in group A, 3.12 ± 0.15 mm for implants in group B, and 5.3 ± 0.64 mm for implants in group C. For group A, the mean marginal bone loss was 0.29 ± 0.51 mm at the T0-T3 interval, 0.31 ± 0.36 mm at the T0-T12 interval, and 0.27 ± 0.33 mm at the T0-T24 interval. For group B, the mean marginal bone loss was 0.16 ± 0.29 mm at the T0-T3 interval, 0.20 ± 0.28 mm at the T0-T12 interval, and 0.23 ± 0.28 mm at the T0-T24 interval. For group C, the mean marginal bone loss was 0.51 ± 0.84 mm at the T0-T3 interval, 0.45 ± 0.72 mm at the T0-T12 interval, and 0.44 ± 0.74 mm at the T0-T24 interval. For group A, the mean midproximal bone loss was 0.33 ± 0.50 mm at the T0-T3 interval, 0.45 ± 0.35 mm at the T0-T12 interval, and 0.40 ± 0.32 mm at the T0-T24 interval. For group B, the mean midproximal loss was 0.31 ± 0.37 mm at the T0-T3 interval, 0.32 ± 0.39 mm at the T0-T12 interval, and 0.33 ± 0.42 mm at the T0-T24 interval. For group C, the mean midproximal bone loss was 0.40 ± 0.44 mm at the T0-T3 interval and 0.41 ± 0.50 mm at both the T0-T12 and T0-T24 intervals. There were no statistically significant differences in marginal and midproximal bone crest loss between the different groups at any time point., Conclusion: The study failed to support the hypothesis that horizontal interimplant distance has an effect on peri-implant bone and soft tissue dimension changes for implants with internal conical implant-abutment interface connection and platform-switching characteristics.

Purpose: To evaluate the efficacy, associated morbidity, and results of a three-dimensional reconstruction technique for repairing severe defects of the maxilla using a calvarial autogenous bone graft and a soft tissue double-layered surgical approach in preparation for placing dental implants., Materials and Methods: Bone defects of the maxilla consecutively reconstructed with calvarial autologous graft in the authors' institution were retrospectively evaluated. Patients with combined maxilla alveolar ridge defects with a width less than 4 mm and a height less than 7 mm (to the level of the maxillary sinus or the nostril), with at least three teeth involved, were included in the study. Calvarial bone blocks were sagittally sectioned in fine layers and fixed three-dimensionally in a boxlike structure with particulate bone inside. The purpose was to obtain an adequate amount of vertical and horizontal alveolar bone to enable restoration with dental implants at least 3.4 mm in diameter and 11 mm in length., Results: Eleven reconstructive procedures were performed in 10 patients. Bone graft integration was successful in all of them. No major complications were observed in the donor cranial site. A mean bone gain of 5.04 mm (range, 3.4 to 7.8 mm) in height was obtained (standard deviation [SD], 1.69). The implant surgery was performed between the 15th and 19th weeks. A total of 28 implants were placed, and the mean follow-up time was 45 months (range, 23 to 65 months; SD, 12). The mean graft vertical resorption was 0.78 mm (range, 0.50-1.50 mm; SD, 0.00) 41 months after implant fixation., Conclusion: Three-dimensional reconstruction technique using calvarial bone grafts to restore severe segmental or crestal bone defects in the maxilla is an effective and predictable procedure that can increase the horizontal and vertical bone volume in preparation for the successful placement of dental implants.

Purpose: The aim of this study was to determine, before implant placement, the outcome of ridge preservation surgery after extractions of one or more adjacent teeth on the dimensions of the edentulous ridge., Materials and Methods: Nineteen extraction sites in four dogs were randomly divided into three groups: group 1 = single premolars (n = 7 sites); group 2 = two adjacent premolars (n = 6 sites); group 3 = three adjacent premolars (n = 6 sites). Extraction was followed by ridge preservation surgery using a combination of xenograft and collagen membrane after full-thickness flap reflection. All animals were sacrificed 4 months later, and each extraction site was sectioned in the sagittal plane so that alveolar bone measurements could be made in both the buccolingual and apicocoronal directions using microcomputed tomography., Results: Mean buccolingual width of the ridges postsurgery was 4.80 ± 2.78 mm, 4.98 ± 2.65 mm, and 4.79 ± 2.79 mm in groups 1, 2, and 3, respectively. The mean vertical distance from the cementoenamel junction to the crest of the ridge was 1.94 ± 0.42 mm, 2.05 ± 0.48 mm, and 2.60 ± 0.67 mm in groups 1, 2, and 3, respectively. No statistically significant difference was seen between single and multiple extraction sites., Conclusion: Ridge preservation surgery results in a similar pattern of bone remodeling in the horizontal and vertical dimensions of the edentulous ridge after single and multiple adjacent tooth extractions.

Purpose: Ridge expansion is used to widen narrow ridges with adequate height for implant placement. This human case series presents the clinical and histologic results of delayed expansion of mandibles by ultrasonic surgery., Materials and Methods: Patients with residual alveolar ridge width between 2.3 and 4.1 mm in the coronal area of the posterior mandible were included in the study. First, four linear corticotomies were carried out by ultrasonic surgical device. Four weeks later, adequate bone expansion with a combination of scalpels, thin chisels, and threaded osteotomes that did not compromise cortical vascularization was performed, and two implants per ridge were inserted. Any gaps were filled with corticospongious porcine biomaterial. Three months after implant placement, healing caps were inserted, and bone cores were harvested from the regenerated areas for histologic analysis. Crestal width was recorded at each surgery., Results: The postoperative course was uneventful in all 32 patients (64 implants) who took part in the study, and the implant success rate was 96.88% at 3 months. The mean increase in ridge width was 5.17 ± 0.86 mm. The histologic specimens showed a mixture of new bone and particles of biomaterial, as well as newly formed bone. Histomorphometry demonstrated that 64% ± 3.1% of the specimen was composed of newly formed bone, 8% ± 0.8% was made up of marrow spaces, and 27% ± 2.6% comprised the residual grafted biomaterial., Conclusion: This study showed that mandibular ridge expansion using a delayed split-crest technique by means of ultrasonic surgery and association with biomaterial led to good horizontal bone gain, with no fractures of the buccal plate, and a high implant success rate. The histologic specimens showed newly formed bone and good integration of the biomaterial.

Purpose: While the ability of various grafting materials to preserve extraction socket morphology has been adequately reviewed, the quality of the grafted bone in the socket is not as well understood. This systematic review aimed to compare the proportion of vital bone and connective tissue between grafted and naturally healed sockets., Materials and Methods: An electronic search of five databases (from 1965 to November 2011) and a hand search of peer-reviewed journals for relevant articles were performed. Human clinical trials that compared histologic components of soft and hard tissues in augmented sockets and naturally healed sites, with at least five samples per group, were included., Results: Eight studies (five randomized controlled trials and three controlled clinical trials) were included. The mean percentages of vital bone and connective tissue in natural healing sockets were 38.5% ± 13.4% and 58.3% ± 10.6%, respectively. Limited evidence (one to two articles for each material) implied that vital bone fraction was not different with demineralized allografts and autografts and increased by 6.2% to 23.5% with alloplasts in comparison to nongrafted sites. Four studies investigating the effect of xenografts were available, with equivocal results. The difference in the mean percentage of vital bone ranged from -22.2% (decrease) to 9.8% (increase). Connective tissue content decreased with the use of the aforementioned bone substitutes. Considerable residual hydroxyapatite and xenograft particles (15% to 36%) remained at a mean of 5.6 months after socket augmentation procedures., Conclusions: Based on a limited number of prospective comparative studies, the use of grafting materials for socket augmentation might change the proportion of vital bone in comparison to sockets allowed to heal without grafting. Whether these changes in bone quality will influence implant success and peri-implant tissue stability remains unknown.

Purpose: To evaluate the biologic width dimensions around implants with nonmatching implant-abutment diameters., Materials and Methods: Five canines had their mandibular premolars and first molars removed bilaterally and replaced with 12 implants that had nonmatching implant-abutment diameters. On one side, six implants were placed in a submerged surgical approach, and the other side utilized a nonsubmerged approach. Two of the implants on each side were placed either 1 mm above, even with, or 1 mm below the alveolar crest. Two months later, gold crowns were attached, and the dogs were sacrificed 6 months postloading. Block sections were processed for histologic and histomorphometric analyses., Results: The bone level, connective tissue length, epithelial dimension, and biologic width were not significantly different when the implants were initially placed in a submerged or nonsubmerged surgical approach. The bone level was significantly different around implants placed 1 mm above the crest compared to implants placed even with or 1 mm below the alveolar crest. The connective tissue dimension was not different for any implant level placement. The epithelial dimension and biologic width were significantly greater for implants placed 1 mm below the alveolar crest compared to implants placed even with or 1 mm above the alveolar crest. For five of six implant placements, connective tissue covered the implant/abutment interface., Conclusions: This study reveals a fundamental change in the biologic response to implants with nonmatching implant-abutment diameters. Unlike implants with matching implant-abutment diameters, the connective tissue extended coronally past the interface (microgap). This morphologic tissue alteration represents a significant change in the biologic reaction to implant-abutment interfaces and suggests that marginal inflammation is eliminated or greatly reduced in these implant designs.

Purpose: To determine the optimal dilation pixel size distance from the mini-implant interface needed to compensate for the metal artifact on micro-computed tomography (micro-CT) for bone morphometric analysis., Materials and Methods: A total of 72 self-drilling mini-implants were placed into the buccal alveolar bone of six male beagle dogs. After 12 weeks of orthodontic loading, specimens were harvested and scanned with micro-CT (Skyscan 1076) at a resolution of 9 μm. Using the reload plug-in and dilation procedure of CTAn, the percentage of bone-implant contact (BIC) and bone volume density (BV/TV, bone volume/total volume), respectively, were measured from one to seven pixels from the metal implant surface. Each pixel size of dilation (PSD) were compared with that of a ground histologic section, and the optimal PSD for bone morphometric analysis using micro-CT was determined., Results: BIC values from micro-CT analysis decreased when the PSD increased (P < .05). BIC from micro-CT showed the highest correlation coefficient with BIC from histologic slides when the PSD was 5 to 7 (P < .05), whereas BV/TV from micro-CT showed a very high correlation with BV/TV from histologic slides in all ranges (P < .0001)., Conclusion: To measure BIC and BV/TV using micro-CT, at least 5 PSD from the metal implant surface is needed.

Purpose: To explore the possibility and evaluate the clinical outcome of accomplishing maxillary internal sinus floor augmentation through the use of a piezoelectric osteotome in conjunction with dental implant placement and to discuss this technique., Materials and Methods: Patients attending the outpatient clinic of the Department of Dental Implantology, Hospital of Stomatology, Tongji University, between July 2007 and September 2009, who had insufficient bone volume to harbor endosseous implants at least 8 mm long in the lateral/posterior maxilla because of sinus pneumatization were enrolled in the study. Sinus augmentations were accomplished with a piezoelectric osteotome, followed by implant placement, either immediately or delayed (6 months after augmentation, if the residual ridge height was less than 4 mm)., Results: Thirty patients with 36 maxillary molar sites with insufficient alveolar bone height as a result of pneumatization of the sinus were included in this study. The residual vertical bone height ranged from 2 to 8 mm. Twenty-eight implants were placed into 24 patients immediately after sinus augmentation. Another eight implants were placed into 6 patients 6 months after sinus augmentation. Only one sinus membrane perforated (failure rate: 2.78%). Only one implant was lost during the observation period. No other implant mobility or rapid bone loss was seen during a follow-up period of 5 to 27 months., Conclusions: Application of a piezoelectric osteotome for internal sinus elevation simplified manipulation of the membrane and greatly reduced the chance of perforation. The pressure gradient between sinus and implant cavity was helpful in accomplishing this technique.

Purpose: This cone beam computed tomography study (CBCT) evaluated horizontal and vertical dimensional changes to the facial bone following maxillary anterior single immediate implant placement and provisionalization., Materials and Methods: CBCT scans taken immediately after (T1) and 1 year after surgery (T2) were evaluated. The midsagittal cut of each implant was identified, and measurements were made at predetermined levels. Horizontal facial bone thickness (HFBT) was measured at 0, 1, 2, 4, 6, 9, and 12 mm apical to the implant platform. Vertical facial bone level (VFBL) was the perpendicular distance from the implant platform (0) to the most coronal point of the facial bone. Measurements were recorded and changes between T1 and T2 were calculated. The data were analyzed statistically at a significance level of α = 0.05., Results: CBCT scans of 21 patients were analyzed. At T2, the mean HFBT changes ranged from -1.23 to -0.08 mm at the seven different levels evaluated. The mean VFBL change was -0.82 mm. The HFBT changes at the 1- to 9-mm levels were not significantly different from one another, but they were significantly smaller than the change at the 0-mm level and significantly greater than the change at the 12-mm level. Significant positive correlations were observed only between horizontal and vertical changes and between horizontal change and initial VFBL at the implant platform. While the VFBL of eight implants (38%) was apical to the implant platform at T2, none was noted at T1., Conclusions: Dimensional changes to the peri-implant facial bone following maxillary anterior single immediate implant placement and provisionalization should be expected. The greatest HFBT change was noted at the implant platform level, in part because HFBT change is correlated to the initial VFBL and the change in VFBL at that level.

Purpose: The aim of this clinical investigation was to evaluate marginal bone remodeling and soft tissue health surrounding a novel one-piece implant system over a 3-year study period., Materials and Methods: Subjects missing at least one tooth in either arch were consecutively enrolled in this open prospective 3-year investigation. Five clinics were invited to participate. Strict inclusion and exclusion criteria were used. Marginal bone levels were evaluated using radiographs taken at implant insertion, 6 months, and annually thereafter. Plaque and bleeding indices were recorded at 3 and 6 months and 1 and 3 years following implant insertion. The shapes of papillae were evaluated at implant insertion with the provisional restoration in place, at the insertion of the definitive restoration, and at the 3-year follow-up, using Jemt's papilla index. Life tables and the Mann-Whitney U test were used for statistical analyses., Results: Fifty-six patients were restored with a total of 82 one-piece implants; 47 patients attended the 3-year appointment. One implant had to be removed 1 month postinsertion, giving a cumulative survival rate of 98.8% for the 3-year study period. Most bone resorption (mean, 1.19 ± 1.38 mm; n = 61) occurred during the first year of function, while there was minimal change in mean marginal bone levels between 1 and 3 years (-0.07 ± 1.07 mm; n = 58). Normal peri-implant mucosa was registered for more than 81% of the sites, and no visible plaque was registered for more than 54% of the sites., Conclusion: This prospective 3-year multicenter study showed stable marginal bone levels, good soft tissue health, and a high implant survival rate, supporting the hypothesis that the presented one-piece implant system has the capacity to maintain both hard and soft tissues after the first year of initial bone remodeling.

Purpose: To evaluate the soft and hard tissue response to orthodontic implant site development (OISD) (ie, forced extraction), to measure the amount of tissue that was regenerated and its relationship to the amount of orthodontic vertical tooth movement, to evaluate the tissue response in teeth with different degrees of periodontal attachment loss, to understand the limits of OISD, and to evaluate the implant survival rate., Materials and Methods: A total of 32 hopeless teeth were treated with OISD, and 27 implants were placed in 13 patients consecutively. The level of periodontal attachment on the teeth to be extracted, amount of augmented alveolar bone, changes in soft tissue volume, and the rate of orthodontic tooth movement were recorded., Results: Mean values after OISD were as follows: orthodontic extrusive movement, 6.2 ± 1.4 mm; bone augmentation, 4 ± 1.4 mm; coronal movement of the gingival margin, 3.9 ± 1.5 mm; coronal movement of the mucogingival junction, 2.1 ± 1.3 mm; keratinized gingival augmentation, 1.8 ± 1.1 mm; gingival thickness (buccolingual dimension) augmentation, 0.7 ± 0.4 mm; recession, 1.8 ± 1.2 mm; bone augmentation/orthodontic movement ratio (efficacy), 68.9% ± 17.3%; gingival augmentation/orthodontic movement ratio (efficacy), 65.2% ± 19.9%; and pocket depth reduction, 1.8 ± 0.9 mm. The implant survival rate was 96.3%., Conclusions: OISD was a viable treatment for these hopeless teeth to regenerate hard and soft tissues. Its efficacy was about 70% for bone regeneration and 60% for gingival augmentation. The residual attachment level on the tooth was not a limitation. OISD might be a valuable treatment option to regenerate tissues for implant site development in patients in need of conventional orthodontic therapy.

Purpose: The aim of this study was to compare the survival of implants placed in mature bone with the survival of implants placed in fresh extraction sockets in the same patients., Materials and Methods: A retrospective study of patients treated simultaneously with at least one immediate and one nonimmediate implant was carried out for the period 2005 to 2008. Data were recorded for patient age and sex; implant length, diameter, and position; and, for postextraction implants, distance between the implant and the alveolar bone., Results: One thousand twenty-two implants were placed in 150 patients; 480 were placed immediately and 542 were placed in mature bone. The mean implant survival rate was 93.4%; survival rates were 93.8% for immediate implants and 93.2% for nonimmediate implants. The failure rate in the maxilla was 5.2% and in the mandible it was 2.8%. The failure rate for immediate implants in the posterior maxilla was 8.5%, which was statistically significantly higher than for implants placed elsewhere. Of the failed implants, 72% were early failures., Conclusions: The survival rate of implants placed in fresh extraction sockets was similar to that of implants placed in mature bone. A statistically significantly higher failure rate was seen with immediate implants placed in the posterior maxilla.

Purpose: The aim of the present study was to perform a finite element (FE) analysis of a modified sinus elevation procedure involving additional implantation of a cortical bone graft block for stabilization of an implant. A secondary aim was to compare the modified sinus augmentation with the standard technique and to determine whether the FE model to replace a dental implant can be simplified into a cylinder without compromising the accuracy of the outcome., Materials and Methods: Based on computed tomography data, three-dimensional FE models of half of a maxilla were created. A basic model was generated to analyze a conventional sinus elevation procedure and another was created for the modified version, which involved insertion of a cortical bone graft block. Two implant models were used in the premolar region: a typical threaded endosseous dental implant and a simplified 4 x 10-mm cylinder. Occlusal loads were applied in axial, mediotrusive, and laterotrusive directions, and perfect bonding was assumed to be present at all interfaces., Results: The maximum von Mises stresses were significantly lower for the sinus graft models with added cortical bone than for the conventional sinus elevation under all types of loads. No significant difference was observed between the use of threaded implants and the simplified implant cylinders., Conclusion: The addition of a cortical bone graft may be a useful approach to decrease stresses around implants placed into the grafted sinus.

Purpose: Different graft materials have been proposed to minimize the reduction in ridge volume after tooth extraction. The aim of the present study was to compare the use of synthetic magnesium-enriched hydroxyapatite (MHA) with porcine bone (PB) grafts in fresh sockets by histologic and histomorphometric analyses., Materials and Methods: Forty-five fresh extraction sockets were selected in 15 patients. A split-mouth design was used: 15 sockets received MHA in one side of the jaw (MHA group), 15 sockets on the other side received PB (PB group), and 15 random unfilled sockets were considered the control group. Four months after surgery, cylindric bone specimens were harvested for histologic and histomorphometric analyses., Results: Histologic examinations revealed an absence of inflammatory cells, bone formation in all treated sites, and the presence of biomaterial particles and connective tissue. Mean vital bone measurements for the MHA, PB, and control groups were 36.5% ± 2.6%, 38.0% ± 16.2%, and 30.3% ± 4.8%, respectively. Statistically significant differences were found between the MHA and control groups and between the PB and control groups; differences between the MHA and PB groups were not significant. Connective tissue percentages averaged 33.3% ± 1.5% for the MHA group, 25.3% ± 9.4% for the PB group, and 58.3% ± 7.1% for the control group. Statistically significant differences were found between all groups. Residual graft material occupied 32.2% ± 3.2% of the MHA-grafted sites and 36.6% ± 4.8% of the PB sites. This difference was not statistically significant., Conclusions: Within the limits of this study, histologic examination showed the same biologic behavior in bone formation and resorption processes for the two examined biomaterials.

Purpose: Resolution of defects surrounding dental implants can be achieved through the placement of rough-surfaced implants with bone substitutes. The aim of this study was to evaluate the effect of biphasic calcium phosphates (BCP) on the healing of circumferential bone defects surrounding dental implants., Materials and Methods: The premolars were removed in four mongrel dogs, and three different types of experimental sites were created: BCP, control, and ungrafted sites. In all groups, implants were placed in the edentulous area. In the BCP group, gap defects with 2-mm diameters were surgically created around each implant and the defects were filled with BCP bone substitute. In the control group, gap defects were not made around the implants. In the sham surgery group, gap defects were prepared but were not filled with BCP bone substitute. The defects were evaluated histologically and histometrically after 8 and 16 weeks. One-way analysis of variance and the independent t test were used for statistical analysis (α = .01)., Results: Histometric measurements in the groups after 8 weeks showed the smallest remaining defect depths (RDDs) in the control group (17%). The RDD in the BCP group (39%) was greater than in the control group, and the ungrafted sites group had the greatest RDD (62%). There was no difference in bone-to-implant contact among the groups. Histometric measurements at 16 weeks showed that the RDD in the ungrated sites group (57%) was greater than in both the control (12%) and the BCP (31%) groups., Conclusion: Within the limitations of this study, BCP bone substitute contributed to defect resolution and maintained space for new bone ingrowth before 8 weeks. No additional contribution to defect resolution by BCP was found after 8 weeks.

Purpose: In this prospective study, bone formation in human extraction sockets augmented with Bio-Oss Collagen after a 12-week healing period was quantified and compared to bone formation in unaugmented extraction sockets., Materials and Methods: Selected patients with four-walled extraction sockets were included in this prospective study. After extraction, the sockets were randomly augmented using Bio-Oss Collagen or left to heal unfilled without raising a mucoperiosteal flap. At the time of implant placement, histologic specimens were obtained from the socket and analyzed. Statistical analysis was performed using the Wilcoxon signed-rank test., Results: Twenty-five patients with a total of 39 sockets (20 augmented, 19 unaugmented) were included in the study and the histologic specimens analyzed. All specimens were free of inflammatory cells. The mean overall new bone formation in the augmented sites was 25% (range, 8%-41%) and in the unaugmented sockets it was 44% (range, 3%-79%). There was a significant difference in the rate of new bone formation between the grafted and ungrafted sockets and a significant difference in the bone formation rate in the apical compared to the coronal regions of all sockets, independent of the healing mode., Conclusion: This descriptive study demonstrated that bone formation in Bio-Oss Collagen-grafted human extraction sockets was lower than bone formation in ungrafted sockets. Bone formation occurred in all specimens with varying degrees of maturation independent of the grafting material and was initiated from the apical region.

Purpose: Immediate loading has become an emerging technique because it has been shown to be a successful, time-saving procedure. Recently, immediate loading has been performed simultaneously with implant placement into fresh extraction sockets; excellent results have been achieved, but few reports are available with a long-term follow-up. The aim of the present study was to evaluate the difference in success rates in the maxilla between postextraction implants and implants placed in healed sites, both of which were immediately loaded, after a long-term follow-up., Materials and Methods: Between October 2001 and February 2003, 239 implants were inserted in 81 consecutively operated patients and immediately loaded; 138 implants were placed in fresh postextraction sites (57.7%) and 101 implants were placed in healed sites (42.3%). Two different implant systems were used in this study. Each implant was loaded within 72 hours of placement (60.3% at the time of surgery, 6.3% after 24 hours, 30.1% after 48 hours, and 3.3% after 72 hours). Preestablished success criteria were used to evaluate the success rate of the implants., Results: The mean follow-up was 6.7 years (range: 6.0 to 7.3 years). Only 8 of the 239 implants failed, for an overall success rate of 96.6%. Six of the failed implants were inserted in postextraction sites, and 2 had been placed in healed sites; the success rates were 95.7% and 98.0%, respectively. Statistical analysis revealed no significant differences between postextraction and healed sites., Conclusions: Immediate loading of immediate postextraction sites results in an implant success rate that is broadly comparable to that seen for implants placed in healed sites. Moreover, this procedure can provide predictable and favorable results in many different clinical conditions and for a long term.

Purpose: The aim of this article was to evaluate the effectiveness of various implant neck configurations in the preservation of marginal bone level as well as to identify the available scientific evidence., Materials and Methods: Online and hand searches of the literature published from 1976 through 2009 were conducted to identify studies dealing with modifications in the implant neck area and marginal bone loss for at least a 5-year observation period. The search terms that were used, alone or in combination, were "implant neck," "marginal bone loss," "neck design," "bone resorption," "bone remodeling," and "implant collar." Relevant studies were selected according to predetermined inclusion and exclusion criteria., Results: The initial search yielded 3,517 relevant titles and revealed eight different implant neck configurations and/or methods suggested for the preservation of marginal bone. These methods included changes in implant neck length and design, implant surface characteristics, implant diameter, and/or insertion depth; the addition of microthreads; the use of one-piece implants; and the concept of platform switching. After subsequent filtering, 20 studies were finally selected and involved the following methods: the use of microthreads (1 study); modifications in implant surface characteristics (11 studies), implant diameter (4 studies), or insertion depth (2 studies); the use of one-piece implants (3 studies); and platform switching (1 study). Because of the heterogeneity of the studies, it was not possible to analyze the data statistically. No evidence was found regarding the effectiveness of any specific modification in the implant neck area in preserving marginal bone or preventing marginal bone loss., Conclusion: The current literature provides insufficient evidence about the effectiveness of different implant neck configurations in the preservation of marginal bone. Long-term randomized controlled clinical trials are needed to elucidate the effects of such modifications.

Purpose: This prospective case series evaluated the use of a new synthetic resorbable membrane with autogenous bone, either alone or in combination with anorganic bovine bone-derived mineral, for horizontal ridge augmentation and subsequent implant placement., Materials and Methods: Particulated autogenous bone, either alone or in combination with anorganic bovine bone-derived mineral, was used for lateral ridge augmentation and covered with a new synthetic resorbable membrane (glycolide and trimethylene carbonate) to treat knife-edged ridges and prepare them for implant placement. Ridge measurements were obtained before and after augmentation, complications were recorded, and biopsy specimens were examined histologically., Results: Fifty-eight implants were placed in 22 patients with 25 surgical sites in knife-edged ridges. No complications were associated with this treatment. Clinical measurements revealed an average of 5.56 mm (± 1.45 mm) of lateral ridge augmentation after an average of 8.12 months (± 2.32 months) of graft healing. Clinically, all treated ridges were sufficient in width for subsequent implant placement. All implants have survived, with an average follow-up period of 45.88 months (± 12.43 months). Histologic analysis of the selected augmentation sites showed new bone formation and good incorporation of the bovine bone mineral particles., Conclusion: The high implant survival rate and the low complication rate show the potential of this technique for the treatment of horizontal augmentation of lateral ridges and the efficacy of the new resorbable synthetic membrane.

Purpose: This case series evaluated the peri-implant tissue response following extraction and immediate placement and restoration of an implant in conjunction with subepithelial connective tissue grafting (SCTG) and bone grafting in the esthetic zone. Implant success rates and the peri-implant tissue response were also reported., Methods and Materials: Ten patients (four men, six women) with a mean age of 48 years (range, 35 to 70) underwent extraction and immediate tooth replacement with SCTG and were evaluated clinically and radiographically presurgically (T0), immediately after immediate tooth replacement and SCTG (T1), and at 3 months (T2), 6 months (T3), and 12 months (T4) after surgery. Data was analyzed using Friedman and Wilcoxon signed-ranks tests at the significance level of a = .05., Results: At 1 year, all implants remained osseointegrated, with an overall mean marginal bone change of +0.10 mm and a mean facial gingival level change of -0.05 mm. Modified Plaque Index scores showed that patients were able to maintain a good level of hygiene throughout the study. Papilla Index scores indicated that at T4, more than 50% papilla fill was observed in 80% of all sites., Conclusions: The results of this case series suggest that, in addition to a favorable implant success rate and peri-implant tissue response, the facial gingival level around single immediately placed implants can also be maintained following connective tissue grafting when proper three-dimensional implant positioning is achieved and bone is grafted into the implant-socket gap.

Purpose: The purpose of the present study was to compare the clinical and radiographic outcomes of single implants immediately placed and restored with two different implant-abutment connections., Materials and Methods: Forty subjects requiring single maxillary premolar replacement were consecutively included in this study and prospectively followed for 12 months. One implant was placed at the time of tooth extraction and immediately restored in each patient. Subjects were randomly selected to receive either prosthetic abutments with a Morse taper connection and a platform switch (test group) or conventional abutments with an internal connection and a matching diameter (control group). A provisional screw-retained crown was positioned and adjusted for nonfunctional loading within 24 hours. Four months later, the definitive crowns were delivered. Periodontal parameters and clinical and radiographic measurements of soft and hard tissue levels were recorded at the moment of prosthesis placement and at 4 and 12 months afterward. Means of the two groups were compared using paired and independent-sample t tests (P = .05)., Results: Of the 40 patients recruited, 38 (24 women and 14 men) completed the study. No implants were lost in the control group, whereas one implant failed in the test group. At the 12-month examination, no statistically significant differences were seen between the two groups for periodontal parameters, marginal soft tissue level change, or papilla height (P > .05), but greater marginal bone loss was observed at the control sites (0.51 ± 0.24 mm) compared to the test sites (0.2 ± 0.17 mm) (P = .0004)., Conclusion: Although the control group demonstrated a slight increase in marginal bone loss compared to the test group, the peri-implant soft tissues were very stable with both types of implant-abutment connection after 12 months of loading.

Purpose: Long-term success of dental implants has been demonstrated when placed simultaneously with or after a sinus augmentation procedure. However, optimal bone formation can be from 6 to 9 months or longer with grafting materials other than autogenous bone. For this reason, there is interest in any surgical technique that does not require autogenous bone harvesting, yet results in sufficient bone formation within a relatively short time frame., Materials and Methods: This study evaluated and compared bone formation following sinus-augmentation procedures using either an allograft cellular bone matrix (ACBM), containing native mesenchymal stem cells and osteoprogenitors, or conventional allograft (CA)., Results: Histomorphometric analysis of the ACBM grafts revealed average vital bone content of 32.5% ± 6.8% to residual graft content of 4.9% ± 2.4% for the 21 sinuses in the study, at an average healing period of 3.7 ± 0.6 months. Results for the CA, in the same time frame, were average vital bone content of 18.3% ± 10.6% to residual graft content of 25.8% ± 13.4%. A comparison of ACBM and CA grafts, for both vital and residual bone contents, showed P values of .003 and .002, respectively, indicating a statistically significant difference between the groups., Conclusion: The high percentage of vital bone content, after a relatively short healing phase, may encourage a more rapid initiation of implant placement or restoration when a cellular grafting approach is considered.

Purpose: The aim of the present study was to evaluate the validity of a new experimental microthreaded scalloped (MTS) implant design in comparison to a conventional flat-top (FT) implant by measuring the proximal bone loss at different interimplant distances in a canine model., Materials and Methods: MTS implants were placed in one side of the posterior mandible and conventional flat-top (FT) implants were placed in the other side of the mandible in 10 beagle dogs. In five dogs, four each of the MTS and FT implants were placed with an interimplant distance of 2 mm. In another five dogs, three each of the MTS and FT implants were placed at an interimplant distance of 5 mm. All 70 implants (35 MTS and 35 FT implants) were placed in a nonsubmerged (one-stage) manner. The animals were sacrificed 4 months after implant placement, and the crestal bone levels around the MTS and FT implants were measured and compared on radiographs and histologic sections., Results: The experimental MTS implants showed significantly less crestal bone loss (0.81 ± 0.34 mm) than the FT implants (1.60 ± 0.42 mm) on radiographs (P < .001). Histologic measurement also demonstrated that there was significantly less (P < .001) marginal bone loss around the MTS implants (0.74 ± 0.41 mm) than around the FT implants (1.53 ± 0.52 mm). There was no statistically significant difference in bone loss between the 2-mm and 5-mm interimplant distances for either MTS or FT implants (P > .05)., Conclusion: The experimental MTS implant was more effective in preserving the proximal bone than the conventional FT external-hex implant with the same surface. In this canine model, placement of the implants at either a 2-mm and or a 5-mm interimplant distance did not result in significant differences in marginal bone loss for both MTS and FT implants. This experiment demonstrated a potential benefit of the microthread design on a scalloped implant.

Purpose: The objective of this study was to assess the influence of mandibular morphology on the stress and strain distributions in the bone supporting an implant., Materials and Methods: Subjects were selected from patients with missing mandibular premolar teeth. Computed tomographic scans of the premolar region were classified into nine groups based on the overall bone morphology and the relative position of the alveolar crest. Finite element models of the bone on the basis of this classification, with inserted implants and superstructures, were constructed. A load of 200 N applied 30 degrees buccal from the vertical axis was directed toward the occlusal surface., Results: One hundred two partially (n = 98) and completely (n = 4) edentulous subjects were recruited. Their ages ranged from 40 to 79 years (mean age, 60.5 years; 41 men and 61 women). Approximately 56% of the patients showed bone widening in the caudal direction. The maximum compressive stresses were shown in the lingual cervical regions. An influence of overall bone morphology on stress distribution was not observed; however, the alveolar crest contour clearly affected the maximum stress and strain values. Compressive microstrain above 4,000 was observed only when the alveolar crest was lingually located relative to the body of the mandible. These high strain levels were concentrated at the lingual cervical margin, with volumes ranging from 0.04 to 0.07 mm3., Conclusion: The contour of the alveolar crest potentially plays a critical role in maintaining the bone levels surrounding implants.

Purpose: This systematic review and meta-analysis assessed the survival of immediately placed single implants in fresh molar extraction sites and immediately restored/loaded single molar implants in healed molar sites., Materials and Methods: A search of the main electronic databases, including the Cochrane Oral Health Group's Trials Register, was conducted up to November 1, 2008. The meta-analysis was prepared in accordance with the guidelines of the Academy of Osseointegration Workshop on the State of the Science on Implant Dentistry. The data were analyzed with statistical software., Results: For immediately placed molar implants, nine studies describing 1,013 implants were included to support a survival rate of 99.0%. There were no significant differences between immediate and delayed loading/restoration in molar sites (relative risk of 0.30, 95% confidence interval 0.05 to 1.61; P = .16). For immediate restoration/loading of single implants in healed molar sites, seven studies with 188 single implants were identified. In this case, the implant survival rate was 97.9%, with no difference between immediate and delayed loading (relative risk of 3.0, 95% confidence interval: 0.33 to 27.16; P = .33). Favorable marginal bone level changes in the immediate loading group were detected at 12 months (mean difference of -0.31, 95% confidence interval: -0.53 to -0.096; P = .005)., Conclusions: The protocols of immediate placement and immediate restoration/loading of single implants in mandibular molar regions showed encouraging results.

Purpose: To investigate the relationship between bone mineral density (BMD) before implant placement, implant stability measures at implant placement, and marginal bone loss of immediately loaded implants after 1 year in situ., Materials and Methods: Consecutively recruited patients received Straumann SLActive implants loaded with fixed provisional prostheses within 24 hours. BMD was measured from computed tomographic images before implant placement. Alveolar bone quality was assessed during surgery. Implant stability-both rotational and as measured with resonance frequency analysis-and marginal bone height were assessed at implant placement and after 1 year. The Pearson correlation coefficient was used to calculate correlations, and significance was considered when P < .05., Results: Twenty-one patients received 137 implants (87 in maxillae and 50 in mandibles). BMD was significantly correlated with bone quality classification in both arches (P < .001). Mean BMD was also significantly correlated with stability values (P < .001). Mean marginal bone loss at implant surfaces differed, but not significantly, at the 1-year follow-up, regardless of BMD values (P = .086) and measured stability (rotational stability P = .34, resonance frequency analysis P = .43) at implant placement., Conclusion: Within the limits of this study, it can be concluded that computed tomographic examination can be used as a preoperative method to assess jawbone density before implant placement, since density values correlate with prevailing methods of measuring implant stability. However, in the short time perspective of 1 year, there were no differences in survival rates or changes in marginal bone level between implants placed in bone tissue of different density.

Purpose: The aim of this investigation was to evaluate whether the placement of medical-grade calcium sulfate hemihydrate (MGCSH) in fresh extraction sockets might affect the quality of newly formed bone and influence crestal bone changes., Materials and Methods: Forty patients who needed maxillary single-tooth extraction followed by implant insertion were enrolled in the study. Alveoli were required to have four remaining intact walls. After tooth extraction, 22 patients received MGCSH in the extraction sockets (test group), and 18 received no grafting material (control group). At the time of extraction and 3 months later (at implant placement surgery), vertical and horizontal socket dimensions were measured. In addition, during implant placement, tissue specimens were harvested for histologic and immunohistochemical evaluations. Comparisons of test and control tissues were performed with the unpaired Student t test., Results: Vertical resorption of the buccal socket walls and reduction of the buccopalatal width were more pronounced at control sites than at MGCSH sites (1.2 mm versus 0.5 mm, and 3.2 mm versus 2.0 mm, respectively). Formation of 100% living trabecular bone with woven and lamellar arrangements was found in both test and control sections. The average trabecular bone area fraction was greater in the grafted specimens than in control specimens (58.8% versus 47.2%). In the test group, the average percentage of lamellar bone increased from 16.4% to 43.6% from the crestal to the apical region and was greater than in unfilled specimens (11.1% coronally, 22.2% apically; P < .0001)., Conclusions: MGCSH seems to be effective in accelerating the bone healing process and minimizing alveolar ridge resorption in intact fresh extraction sockets.

Purpose: To evaluate the effects of implant geometry and collar macrostructure and microstructure on crestal bone height, mobility values, and attachment levels using two different types of radiographic analysis., Materials and Methods: Subjects included in this study were those who had single-tooth implants restored in the maxillary esthetic zone. Bone levels were measured from the implant-abutment (IA) interface on standardized radiographs at baseline and after 5 years using digital and standard methods. The digital method converted the radiographs into three-dimensional models based on radiodensity so that bone levels could be measured. Clinical attachment levels and Periotest values were recorded and all data were analyzed statistically., Results: The bone position from the IA interface for the rough-collar implant group was a mean of -0.61 +/- 0.08 mm and it was -1.55 +/- 0.10 mm for the smooth-collar implant group (-1.96 +/- 0.16 mm for implants with a stepped collar and -0.85 +/- 0.19 mm for implants with a straight collar). The mean bone level change over the 5-year period for the rough implants was -0.19 +/- 0.09 mm and it was -0.36 +/- 0.06 mm for the smooth implants. The crestal bone position relative to the implant at the time of surgery influenced mean bone level changes significantly. There were statistically significant differences in clinical attachment levels depending on implant location and on implant group and length., Conclusions: Implants with straight collars had less bone loss at the 5-year interval than implants with stepped collars. Bone level changes were greater when the implant was placed further subcrestal. The digitally converted radiographic method was significantly more precise for evaluating changes in bone levels. These findings suggest that implant geometry and implant surface roughness may play a significant role in bone level changes in the esthetic zone.

Purpose: The aim of this clinical trial was to evaluate the influence of gingival tissue thickness on crestal bone loss around dental implants after a 1-year follow-up., Materials and Methods: Forty-six implants (23 test and 23 control) were placed in 19 patients. The test implants were placed about 2 mm supracrestally, whereas the control implants were positioned at the bone level. Before implant placement, the tissue thickness at implant sites was measured with a periodontal probe. After healing, metal-ceramic cement-retained prostheses were constructed. According to tissue thickness, the test implants were divided into A (thin) and B (thick) groups. Intraoral radiographs were performed and crestal bone changes were measured at implant placement and after 1 year., Results: Mean bone loss around the test implants in group A (thin mucosa) was 1.61 +/- 0.24 mm (SE; range, 0.9 to 3.3 mm) on the mesial and 1.28 +/- 0.167 mm (range, 0.8 to 2.1 mm) on the distal. Mean bone loss in test group B (thick mucosa) implants was 0.26 +/- 0.08 mm (range, 0.2 to 0.9 mm) on the mesial aspect and 0.09 +/- 0.05 mm (range, 0.2 to 0.6 mm) on the distal aspect. Mean bone loss around control implants was 1.8 +/- 0.164 mm (range, 0.6 to 4.0 mm) and 1.87 +/- 0.166 mm (range, 0.0 to 4.1 mm) on the mesial and distal aspects, respectively. Analysis of variance revealed a significant difference in terms of bone loss between test A (thin) and B (thick) groups on both the mesial and the distal., Conclusion: Initial gingival tissue thickness at the crest may be considered as a significant influence on marginal bone stability around implants. If the tissue thickness is 2.0 mm or less, crestal bone loss up to 1.45 mm may occur, despite a supracrestal position of the implant-abutment interface.

Purpose: To quantitatively evaluate the combined influence of implant diameter and alveolar ridge width on crestal bone stress., Materials and Methods: ITI solid-screw implants, 10 mm in length and 3.3, 4.1, and 4.8 mm in diameter, and the alveolar bone were modeled using axisymmetric finite elements. Four different alveolar ridge geometries were selected for each implant: 5-, 6-, 7-, and 8-mm-wide ridges for the 3.3-mm implants; 6-, 7-, 8-, and 9-mm-wide ridges for the 4.1-mm implants; and 7-, 8-, 9-, and 10-mm-wide ridges for the 4.8-mm implants. A nonaxial oblique load of 100 N was applied at 30 degrees to the implant axis. Regression analysis was used to avoid ambiguity when estimating the peak stress occurring at the coronal contact point between the implant and the crestal bone, ie, the singularity point., Results: Peak stresses were dependent on both implant diameter and alveolar ridge width. Substantially lower stresses were recorded around the implants placed in narrower ridges., Conclusion: A regression analysis may be used to quantify the peak stress at the singularity point. An implant with a diameter that is at least half the ridge width is recommended to reduce the stress concentration in the crestal bone.

Purpose: Soft tissue closure is mandatory for optimal healing of extraction sites treated via guided bone regeneration. The objective of this study was to evaluate the efficacy of a flap design based on the extension of palatal tissues to obtain and maintain soft tissue coverage over grafted extraction sockets., Materials and Methods: Adult patients (n = 22) with at least two teeth indicated for extraction were treated. After atraumatic extraction, control sockets were filled with a composite graft (1:1) containing demineralized freeze-dried bone allografts and Bio-Oss. Experimental sockets were treated identically, except that an Atrisorb absorbable barrier membrane was also placed over the graft material before flap closure, which was obtained, in all sockets, by the coronal extension of a vascularized pedicle dissected from the periosteal aspect of the palate., Results: Primary tension-free wound closure was achieved at all treated sites. Exfoliation of the graft material during healing was not observed in either treatment group. High levels of soft tissue closure were maintained throughout the study period for both treatment groups, and membrane exposure was observed in only 7% of treated sites., Conclusion: On the basis of this study it appears that the reported technique was an adequate method of achieving and maintaining complete soft tissue coverage and promoting healing by primary intention in grafted extraction sockets in humans.

Purpose: This dog study sought to evaluate guided bone regeneration (GBR) in peri-implant defects following implantation of beta-tricalcium phosphate (beta-TCP) with and without osteoinductive recombinant human growth/differentiation factor-5 (rhGDF-5)., Materials and Methods: In five beagle dogs, all mandibular premolars and the first molar were extracted. After 2 months, six buccolingual critical-size defects were created, and an implant was inserted into the center of each defect. One defect was filled with beta-TCP coated with rhGDF-5 (600 microg/g beta-TCP) and covered with a titanium-reinforced e-PTFE membrane (GDF group). A second defect received the same treatment, but pure uncoated beta-TCP was used (TCP group). A third defect was filled with beta-TCP mixed with autograft and not protected with a membrane (control group). The remaining three defects were filled with other biomaterials. After 2 months, total new bone area, regenerated bone height, and residual amount of beta-TCP were determined histomorphometrically., Results: All implants osseointegrated. One membrane in each group became exposed. Mean new bone area for GDF, TCP, and control sites was 43.9 +/- 18.7 mm2, 32.3 +/- 16.1 mm2, and 13.1 +/- 4.0 mm2, respectively, with a significant difference between GDF and control groups. Mean regenerated bone height was 103.8 +/- 29.7%, 75.4 +/- 36.6%, and 67.2 +/- 19.1% for the GDF, TCP, and control groups, respectively. Mean residual matrix volumes were 25.9 +/- 13.6%, 30.0 +/- 13.0%, and 13.4 +/- 6.5%, respectively. Membrane protection of peri-implant defects filled with beta-TCP resulted in a stronger effect on bone regeneration, although this was not statistically significant. The most pronounced regenerative results were achieved in rhGDF-5/beta-TCP filled membrane-protected defects., Conclusion: Delivery of rhGDF-5 on beta-TCP might have the potential to enhance the results of GBR in peri-implant defects.