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Purpose To evaluate the failure load of 3D-printed denture resin material and teeth before and after dynamic loading. Materials and methods A total of 40 specimens were fabricated following ISO/TS 19736 and were divided into two equal groups. In the test group, the cylindrical base and denture teeth were 3D printed separately and then luted together. In the control group, the specimens were fabricated from conventional heat-cured polymethyl methacrylate (PMMA) and commercially available denture teeth using the compression-molding technique. Ten specimens from each group were subjected to dynamic load of 50 N for 250,000 cycles in a chewing simulator. All specimens were subjected to static load of 50 N using Instron machine with a crosshead speed of 1 mm/minute until fracture. The fractured surfaces were analyzed using field emission scanning electron microscopy. The failure loads were calculated and compared using analysis of variance (P Results All specimens survived the loading, undergoing 250,000 cycles without fracture. The mean failure load was influenced by fabrication technique and was significantly higher for the 3D-printed test group (P = .028). 3D-printed teeth showed a mixed mode of fracture, whereas in the control group, the specimens showed cohesive fracture within the teeth. Conclusion The fabrication technique has an influence on the mode of failure between acrylic teeth and resin base material. Cohesive failure in teeth was predominant in the conventional group, suggesting possibly higher bond strength between the teeth and resin base in this group. The observed failure modes reveal that both fabrication techniques exhibited satisfactory bond strength. Chewing simulation did not significantly influence the bond strength of any of the tested groups.

Purpose To evaluate the effect of build direction on the surface roughness (Ra) of stereolithography (SLA) printed full-coverage anterior dental restorations before and after surface polishing. Materials and methods A total of 45 full-coverage dental restorations were 3D printed using the SLA additive manufacturing technique. Five groups were defined based on the build angles: 90, 120, 135, 150, and 180 degrees. The Ra was measured with the contact profilometer to evaluate the arithmetic average of the absolute Ra value on the labial surface before and after polishing procedures. Data were analyzed using two-way ANOVA, and statistical significance was set at α = .05. Results The highest Ra was recorded in specimens printed with the 90-degree build angle, whereas the lowest values were recorded in specimens printed with the 180-degree build angle (P = .000). In all groups, the Ra values measured after polishing were significantly lower than prepolished values (P = .000), with no difference among the different build angles. Conclusion Build angle significantly influenced the Ra of the SLA-printed full-coverage restorations. Polishing minimized the effect of build angle on the Ra. The 180-degree build angle is recommended when SLA printing an anterior restoration, as it provides the lowest Ra values and also requires a minimal support area and minimal number of support structures.

The aim of this study was to evaluate the adhesion and biofilm formation of Candida albicans (C. albicans) on conventionally fabricated, milled, and 3D-printed denture base resin materials in order to determine the susceptibility of denture contamination during clinical use. Specimens were incubated with C. albicans (ATCC 10231) for 1 and 24 h. Adhesion and biofilm formation of C. albicans were assessed using the field emission scanning electron microscopy (FESEM). The XTT (2,3-(2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide) assay was used for the quantification of fungal adhesion and biofilm formation. The data were analyzed using GraphPad Prism 8.02 for windows. One-way ANOVA with Tukey’s post hoc testing were performed with a statistical significance level set at α = 0.05. The quantitative XTT biofilm assay revealed significant differences in the biofilm formation of C. albicans between the three groups in the 24 h incubation period. The highest proportion of biofilm formation was observed in the 3D-printed group, followed by the conventional group, while the lowest candida biofilm formation was observed in the milled group. The difference in biofilm formation among the three tested dentures was statistically significant (p < 0.001). The manufacturing technique has an influence on the surface topography and microbiological properties of the fabricated denture base resin material. Additive 3D-printing technology results in increased candida adhesion and the roughest surface topography of maxillary resin denture base as compared to conventional flask compression and CAD/CAM milling techniques. In a clinical setting, patients wearing additively manufactured maxillary complete dentures are thus more susceptible to the development of candida-associated denture stomatitis and accordingly, strict oral hygiene measures and maintenance programs should be emphasized to patients.

Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical histology and long-term clinical trials are rare. This investigation comprised (1) 8-year clinical follow-up of one-piece ZC or titanium (Ti) implants supporting full overdentures and (2) histomorphometric analysis of the same implants in an animal model, comparing implants with various surface treatments. Methods: (1) Clinical trial: 24 completely edentulous participants (2 groups of N = 12) received 7 implants (one-piece ball-abutment ZC or Ti; maxilla N = 4, mandible N = 3) restored with implant overdentures. Outcomes after 8-years included survival, peri-implant bone levels, soft-tissue responses, and prosthodontic issues. (2) Preclinical trial: 10 New Zealand sheep received 4 implants bilaterally in the femoral condyle: Southern Implants ZC or Ti one-piece implants, identical to the clinical trial, and controls: Southern ITC® two-piece implants with the same surface or Nobel (NBC) anodised (TiUnite™) surface. %Bone-implant contact (%BIC) was measured after 12 weeks of unloaded healing. Results: 8 of 24 participants (33%) of an average age of 75 ± 8 years were recalled; 21% of original participants had died, and 46% could not be contacted. 80.4% of implants survived; excluding palatal sites, 87.5% of Ti and 79% of ZC implants survived. All failed implants were in the maxilla. Three ZC implants had fractured. Bone loss was similar for Ti vs. ZC; pocket depths (p = 0.04) and attachment levels (p = 0.02) were greater for Ti than ZC implants. (1.7 ± 1.6 mm vs. 1.6 ± 1.3 mm). All implants in sheep femurs survived. %BIC was not statistically different for one-piece blasted surface Ti (80 ± 19%) versus ZC (76 ± 20%) or ITC® (75 ± 16 mm); NBC had significantly higher %BIC than ITC (84 ± 17%, p = 0.4). Conclusion: Short-term preclinical results for ZC and Ti one-piece implants showed excellent bone-implant contact in unloaded femoral sites. This differed from the long-term clinical results in older-aged, edentulous participants. While ZC and Ti implants showed equivalent performance, the risks of peri-implantitis and implant loss in older, completely edentulous patients remain a significant factor.

To evaluate the oral health-related quality of life (OHRQoL) of patients rehabilitated with conventional or 3D-printed implant overdentures.A randomized clinical trial (RCT) was designed. Twenty-eight completely edentulous participants were randomly allocated into two equal groups. All participants received two implants with ball attachments. Participants in the control group were rehabilitated with conventionally manufactured polymethyl methacrylate (PMMA) maxillary complete dentures (CDs) and mandibular implant overdentures, while those in the intervention group received digital light processing (DLP)-printed photopolymerizable PMMA maxillary CDs (NextDent) and mandibular implant overdentures. Follow-up appointments were scheduled at 3, 6, and 12 months where Oral Health Impact Profile 19 (OHIPEDENT19) data were used to assess the OHRQoL of the participants. Denture retention was measured using a digital force gauge device.The OHRQoL values were significantly higher (less improvement) in the conventional overdenture group at 6 months (P = 0.02) and 12 months (P = 0.04). A statistically significant difference was found between the mean retention values of the conventional and 3D-printed overdenture groups. For all the follow-up periods, the mean retention values were higher for the 3D-printed overdenture group (P = 0.001).3D-printed overdentures may represent an alternative to conventionally fabricated ones. This study represents a stepping stone and proof of concept that support the potential future use of 3D-printed dentures.

Recent burgeoning development in material science has introduced a 3D-printable, nanohybrid composite resin restorative material. However, its performance has not yet been investigated. This study evaluates the stain susceptibility and efficacy of different stain removal techniques. A total of 120 labial veneers were fabricated using milling (n = 60) and SLA 3D-printing (n = 60). Based on the immersion media: coffee, tea and artificial saliva, each group was divided into three sub-groups (n = 20). Stain susceptibility was evaluated by calculating color difference (∆E00) at 12 and 24 days using a spectrophotometer against black and white backgrounds. Collected data were analyzed with ANOVA and Tukey’s post hoc test (p &lt, 0.05). A significant interaction effect was found between the staining mediums and fabrication methods in both black and white backgrounds (p &lt, 0.001). 3D-printed restorations showed significantly higher stain susceptibility than milled restorations (p &lt, 0.001). Prolonged immersion time increased the color difference in both groups. In-office bleaching was more effective in stain removal in both 3D-printed and milled restoration groups. The susceptibility of the presented novel 3D-printed restorative material to color changes in different immersion mediums was clinically not-acceptable. The clinicians might expect the need to replace the restoration after 1–2 years and thus, recommendation for the use of such a material as a permanent restoration cannot be made but rather as a long-term temporary restoration.

Purpose: To evaluate the microbial flora in peri-implant sulcular fluid of edentulous patients rehabilitated with ball and socket and locator retained mandibular 2-implant overdentures.Materials and Methods: 14 edentulous patients were recruited to receive two mandibular implant overdentures and new conventional maxillary complete dentures. Mandibular implant overdentures (MIODs) were retained either by locator or ball attachment systems in random order. After 6 months of function, the attachment systems in the existing dentures were replaced with the other type of attachment. The prevalence of streptococci and staphylococci species (spp.) was analyzedusing blood-agar media at 3, 6 and 9 weeks after pick-up of attachments. The data was then collected, tabulated and statistically analyzed using SPSS. Results: No significant difference was found in bacterial count of either Streptococcus or Staphylococcus spp. between two attachment systems (Ball and socket, Locator) at any of the evaluated time intervals with P-value > 0.05Conclusions: Within the limitations of this study, it can be concluded that there is no difference in microbial flora between the two attachment systems. It can also be suggested that the locator attachments are valid treatment alternative for ball abutments to retain mandibular 2-implant overdentures from a biological point of view.

Statement of Problem: Hinging mandibular overdentures retained by anterior interforaminal implants results in denture rotation and posterior basal bone resorption. Wide spread implant distribution and posterior implant placement can improve overdenture support. Aim of study: To evaluate the biomechanical aspects of novel implant distribution used to support mandibular overdentures and compare it with commonly used design. The novel design consists of mid-symphyseal and bilateral posterior implants in the first molar region as opposed to conventional design with anterior mid-symphyseal and bilateral implants in the canine region.Materials and Methods: Two finite element models were created. In the two models a mid-symphyseal implant was simulated. In the first model (D1), 2 more implants were placed in the canine region bilaterally while for the second model (D2), the 2 additional implants were placed posteriorly in the first molar region. Unilateral vertical and oblique loads were applied on central fossa of right first molar and palatal aspect of central incisors in each model. Von Mises stress distribution was evaluated in the implants and peri-implant bone. Denture displacement was also calculated for each model. Results: There was a slight increase in maximum Von-Mises stress values recorded in both implants and peri-implant bone under both vertical and oblique load in D2 when compared to D1. D1 showed higher denture displacement values when compared to D2. Conclusions: Posterior implant placement resulted in improved denture support and minimal denture displacement on the expense of transferring extra load to the posterior implants. However, increased functional load on posterior implants is expected to have a positive effect on preservation of the residual alveolar ridge. D2 is an acceptable alternative prosthodontic design to D1 when anatomical factor permits.

Osseodensification is a technique that aims at bone preservation and compaction either through nonsubtractive drilling or implants with a special thread design. This can increase quantity and density of periimplant bone. This review represents a summary and a critical appraisal of the studies regarding osseodensification in the literature.Three databases were searched: PubMed (MEDLINE), Cochrane Library, and Latin American and Caribbean center on health sciences information (LILACS). Studies were screened by title/abstract according to predetermined eligibility criteria. Full texts of 7 eligible articles were read among which 2 were excluded and 5 articles were included and underwent qualitative synthesis.Studies advocating osseodensification are sparse and mainly animal studies of low evidence level. High risk of bias and low correlation between used animal models and human bone were detected in most of the studies.Although osseodensification seems to be a very promising technique, the findings are inconclusive and should be cautiously interpreted. Well-designed animal and human studies of longer follow-up periods are required before implementing such technique in regular daily practice.

PURPOSE: The purpose of this study was to clinically evaluate retentive characteristics of Retentive.Sil 600 attachment system and to compare it to that of Nylon cap in ball- retained mandibular implant overdentures. Materials and Methods : Fourteen completely edentulous patients were included for this trial; seven patients /group following strict inclusion and exclusion criteria. The participants were randomly allocated to receive either nylon cap (control group) or Retention.Sil (intervention group) on ball abutments to retain 2-midsymphseal mandibular implant overdentures. Retention values of both attachment systems were evaluated in Newtons (N), at baseline during time of denture insertion and thereafter at 3, 6, 9 and 12 months follow-up periods. Further the effect of time on retentive characteristics of both attachment systems was evaluated. The data was tabulated and statistically analysed using SPSS software. Results: Nylon cap showed significantly higher mean retention values compared to Retention.Sil group at each of the observation periods P ≤0.05. In nylon caps group, there was a significant, gradual increase in retention values by time except at 6 and 9 months follow-up periods where the increase was non-significant. In Retention.Sil 600 group, retention gradually decreased by time. This decrease was statistically significant (P=0.00).Conclusions: Within the limitations of this study, it can be concluded that retentive characteristics of any given attachment system is changeable overtime. Retention.Sil could be attachment of choice for retaining mandibular overdentures if reduced denture retention is required in cases with poor manual dexterity or temporarily for replacement of nylon caps of stud attachments when subjected to wear. Gradual decrease in retention of Retention.Sil over time merits further investigation to evaluate the durability of the material over extended follow-up periods.

This study was conducted to provide an understanding of the biomechanical behavior ofdifferent diameters MDIs and compare it with conventional diameter implants when supportingan overdenture . Three different models were designed .The first model has two standard diameterimplants (3.8x12mm) (D1), the second (D2) has 2 mini-dental implants (2.4x12mm) and the thirdmodel (D3) has 2 of ultra-small diameter (1.8 x 12mm) all implants were placed at canines region.3D finite elements stress analysis was performed to evaluate biomechanical situation in both theimplants and the peri-implant bone under vertical and oblique loading of the overdentures. It can beconcluded that the stress values affecting the peri-implant bone and the implants are reciprocal todental implant diameter and the use of MDIs as overdenture abutments should be limited to caseswith limited bone quantity.

Purpose: This comparative controlled trial (CCT) evaluates the survival rate of implants placedinto fresh extraction sockets and compare it with implants placed in healed sites in type 2 diabetic,completely edentulous subjects rehabilitated with mandibular implant overdentures (MIODs) followinga delayed loading protocol and opposed with conventional complete dentures.Materials and Methods: Fourteen implants were placed in seven well-controlled diabeticsubjects as determined by Glycosylated hemoglobin (HbA1c) values before implant placement(baseline) and throughout the follow-up period. Each patient received two implants; one implant inhealed canine site and the other was immediately inserted following the extraction of an existingperiodontally hopeless canine. The implants were uncovered approximately 3 months after placementand restored with bar-retained overdenture. The patients were scheduled for regular follow-upappointments and for data collection. Kaplan-Meier analysis was used to calculate implant survivalfrom time of prosthesis placement through 24-month follow-up period.Results: No implant failed in the delayed placement group within the 2 years study period,whereas in the immediate group two implants failed in two patients following the prosthetic loadingat one-year follow-up period resulting in 71.2% implant survival rate. HbA1c levels ranging from7.4 to 8.0 percent were identified in two patients with implant failures. There was no statisticallysignificant difference in survival rate between immediate and delayed implants in type 2 Diabeticsubjects rehabilitated with MIOD s (P=0.141).Conclusions: Within the limitations of this study, insufficient evidence exists to recommendimmediate implant placement in type 2 diabetic subjects rehabilitated with MIODs.

Purpose: To evaluate the influence of fabrication method and finish line design on marginal and internal fit of full-coverage interim restorations. Methods: Four typodont models of maxillary central-incisor were prepared for full-coverage restorations. Four groups were defined; knife-edge (KE), chamfer (C), rounded-shoulder (RS), rounded-shoulder with bevel (RSB). All preparations were digitally scanned. A total of 80 restorations were fabricated; 20 per group (SLA/3D-printed n = 10, milled n = 10). All restorations were positioned on the master die and scanned using micro-computed tomography. The mean gaps were measured digitally (ImageJ). The results were compared using MANOVA (α =.05). Results: Internal and marginal gaps were significantly influenced by fabrication method (P =.000) and finish-line design (P =.000). 3D-Printed restorations showed statistically significant lower mean gap compared to milled restorations at all points (P =.000). The mean internal gap for 3D-printed restorations were 66, 149, 130, 95 μm and for milled restorations were 89, 177, 185, 154 μm for KE, C, RS, RSB respectively. The mean absolute marginal discrepancy in 3D-printed restorations were (30, 41, 30, 28 μm) and in milled restorations were (56, 54, 52, 38 μm) for KE, C, RS, RSB respectively. Conclusions: The fabrication methods showed more of an influence on the fit compared to the effect of the finish-line design in both milled and printed restorations. SLA-printed interim restorations exhibit lower marginal and internal gap than milled restorations. Nonetheless, for both techniques, all values were within the reported values for CAD/CAM restorations. Significance: 3D-printing can offer an alternative fabrication method comparable to those of milled restorations.

Polyetheretherketone (PEEK) composites are biocompatible materials that may overcome the esthetic and allergic problems of titanium dental implants. However, their potential for osseointegration with a subsequent survival rate is still questionable. The aim of this study was to evaluate the surface roughness and wettability of different surface-treated filled and unfilled PEEK specimens, which may be indicative of the osseointegration behavior and potential use of PEEK as an implant material. Unfilled, ceramic-filled (CFP) and carbon fiber-reinforced (CFRP) PEEK discs were prepared and left untreated or were surface treated with 50 μ, 110 μ, or 250 μ aluminum oxide particles. The roughness average (Ra) value of each disc was evaluated using a contact stylus profilometer. Their contact angles were measured to evaluate their wettability, which was compared among PEEK discs using ANOVA, followed by Bonferroni test for pairwise comparisons (P ≤ .05). Regarding the surface roughness, a significant difference was found between unfilled and filled PEEK when untreated and bombarded with 50 or 110 microns of aluminum oxide particles. For the contact angle, a significant difference was found only among the untreated PEEK materials. Among the evaluated PEEK materials, CFRP50, CFRP110 and CFP110 showed the most favorable Ra values with good wettability properties, thus being potential substrates for dental implants.

Purpose The aim of this study was to evaluate the dimensional accuracy, surface topography of a custom designed, 3D-printed zirconia dental implant and the mechanical properties of printed zirconia discs. Materials and methods A custom designed implant was 3D-printed in zirconia using digital light processing technique (DLP). The dimensional accuracy was assessed using the digital-subtraction technique. The mechanical properties were evaluated using biaxial flexure strength test. Three different build angles were adopted to print the specimens for the mechanical test; 0°( V ertical), 45° ( O blique) and 90°(Horizontal) angles. The surface topography, crystallographic phase structure and surface roughness were evaluated using scanning electron microscopy analysis (SEM), X-ray diffractometer and confocal microscopy respectively. Results The printed implant was dimensionally accurate with a root mean square (RMSE) value of 0.1 mm. The Weibull analysis revealed a statistically significant higher characteristic strength (1006.6 MPa) of 0° printed specimens compared to the other two groups and no significant difference between 45° (892.2 MPa) and 90° (866.7 MPa) build angles. SEM analysis revealed cracks, micro-porosities and interconnected pores ranging in size from 196 nm to 3.3 µm. The mean Ra (arithmetic mean roughness) value of 1.59 µm (±0.41) and Rq (root mean squared roughness) value of 1.94 µm (±0.47) was found. A crystallographic phase of primarily tetragonal zirconia typical of sintered Yttria tetragonal stabilized zirconia (Y-TZP) was detected. Conclusions DLP prove to be efficient for printing customized zirconia dental implants with sufficient dimensional accuracy. The mechanical properties showed flexure strength close to those of conventionally produced ceramics. Optimization of the 3D-printing process parameters is still needed to improve the microstructure of the printed objects.

Purpose: The aim of this study was to evaluate the effect of the build orientation/build angle on the dimensional accuracy of full-coverage dental restorations manufactured using digital light-processing technology (DLP-AM). Materials and Methods: A full dental crown was digitally designed and 3D-printed using DLP-AM. Nine build angles were used: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. The specimens were digitally scanned using a highresolution optical surface scanner (IScan D104i, Imetric). Dimensional accuracy was evaluated using the digital subtraction technique. The 3D digital files of the scanned printed crowns (test model) were exported in standard tessellation language (STL) format and superimposed on the STL file of the designed crown [reference model] using Geomagic Studio 2014 (3D Systems). The root mean square estimate (RMSE) values were evaluated, and the deviation patterns on the color maps were further assessed. Results: The build angle influenced the dimensional accuracy of 3D-printed restorations. The lowest RMSE was recorded for the 135-degree and 210-degree build angles. However, the overall deviation pattern on the color map was more favorable with the 135-degree build angle in contrast with the 210-degree build angle where the deviation was observed around the critical marginal area. Conclusions: Within the limitations of this study, the recommended build angle using the current DLP system was 135 degrees. Among the selected build angles, it offers the highest dimensional accuracy and the most favorable deviation pattern. It also offers a self-supporting crown geometry throughout the building process.

Objectives: To investigate the osseo-integrative behavior of untreated (UCFP) and sandblasted ceramic filled PEEK (SCFP) implants in comparison with titanium implants through measurement of bone implant contact (BIC) and bone density (BD). Materials and methods: Nine implants from each type were inserted into 9 dogs in which every experimental dog received the three different implants in the lower border of the mandible. The animals were euthanized after 3 months and extracting bone blocks containing implants followed by blocks preparation for histological examinations. Results: BIC and BD were significantly higher in titanium and SCFP compared with UCFP group (p =.007) and (p =.012), respectively. Aluminum blasting increased the bone ingrowth and bone implant contact when compared to machined surfaces of untreated PEEK implants. Conclusion: In conclusion, sandblasting with 110 µm aluminum oxide particles can be proposed as a suitable surface treatment that enhances hydrophilicity of CFP. Further in vivo animal studies are still needed to confirm the findings of this study.

Statement of problem The number of implants required for the rehabilitation of completely edentulous mandibles has been controversial. The use of a greater number of implants can produce favorable biomechanical outcomes. However, this will lead to high costs and may require complex surgical procedures. Therefore, the minimum number of implants that can produce desirable outcomes should be used. Purpose The purpose of this 3D finite element study was to compare the biomechanics of mandibular 3-implant-supported to 4-implant-supported prostheses. The opposing occlusion was a maxillary complete denture or natural dentition. Material and methods Two finite element analysis mandibular anatomic models were created. Implants were virtually placed in the mandibular lateral incisor and second premolar region bilaterally in the 4-implant-supported prosthesis model. For the 3-implant-supported model, they were placed in the midline and bilaterally in the second premolar region. Screw-retained polymethyl methacrylate prostheses were designed. Reverse engineering was used to convert standard tessellation language files into computer-aided design solid models. Vertical and oblique loading was applied twice: simulating an opposing maxillary complete denture and a natural dentition. Von Mises stresses and equivalent strains generated in the peri-implant bone, implants’ von Mises stresses and the maximum vertical displacement of the prosthesis were recorded. Results All recorded outcomes reported higher values for the 3-implant-supported prosthesis compared with the 4-implant-supported models for both applied loads. When opposed by a maxillary complete denture, maximum strain values for the 3-implant-supported (2.3×103 μe) and 4-implant-supported (1.6×103 μe) models were less than the different threshold limits for the bone resorption reported (3×103, 3.6×103, 6.6×103 μe). When opposed by a maxillary natural dentition, maximum strain values for the 3-implant-supported (4.10×103 μe) and 4-implant-supported (3.88×103 μe) models were less than the highest reported threshold limit for bone resorption (6.6×103 μe) in contrast with other reported threshold limits (3×103, 3.6×103 μe). In both designs irrespective of the magnitude and direction of loading, the maximum recorded von Mises stresses of the implants (126 MPa) and denture displacement (3.24×102 μm) were less than titanium’s yield strength of (960 to 1180 MPa) and the displacement values (5.2×103 to 8.8×103 μm) reported in the literature. Conclusions When opposed by a complete denture, recorded biomechanical outcomes for the 3- and 4-implant-supported designs were within physiologic limits. When opposed by a natural dentition, the von Mises stresses of the implants and denture displacement values for both designs were within a favorable mechanical range, whereas peri-implant stresses and strain exceeded most reported physiologic tolerance levels of bone except for the 6.6×103 μe threshold limit for the bone resorption reported.

This study evaluated the effect of build direction on the flexure strength of stereolithography (SLA), 3D-printed hybrid composite resin material. A total of 26 bar-shaped specimens were 3D-printed using SLA-based printer. The specimens were divided into two groups based on build direction (n = 13); vertically (V), horizontally (H) printed groups. The layer thickness was 0·05 mm. Three-point bending test was performed using a universal testing machine, with a load-cell of 250 N at 1 mm min−1 crosshead speed until failure of the specimens. The fractured surfaces were analyzed using scanning electron microscopy (SEM). The mean flexure strength for (V) and (H) printed specimens was 88.2 and 90.5 MPa respectively (P > .05). Fractographic analysis revealed brittle abrupt fracture pattern for (V) group and a ductile, slow pattern with layer delamination for H-group. Though there was no statistical difference in flexure strength between the test groups, the fractographic analysis revealed that the fracture mode was different.

Purpose: The aim of the present study was to evaluate the effect of the build angle and the support configuration (thick versus thin support) on the dimensional accuracy of 3D-printed full-coverage dental restorations. Materials and Methods: A full-coverage dental crown was digitally designed and 3D-printed using stereolithography-additive manufacturing (SLA-AM) technology. Nine different angles were used during the build process: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. In each angle, the crown was printed using a thin and a thick support type, resulting in 18 specimens. The specimens were digitally scanned using a highresolution optical surface scanner (IScan D104i; Imetric 3D). The dimensional accuracy was evaluated by digital subtraction technique. The 3D digital files of the scanned printed crowns (test model), exported in standard tessellation language (STL) format, were superimposed with the STL file of the designed crown (reference model) using Geomagic Studio 2014 (3D Systems). Results: The root mean square estimate value and color map results suggest that the build angle and support structure configuration have an influence on the dimensional accuracy of 3D-printed crown restorations. Among the tested angles, the 120-degree build angle showed a minimal deviation of 0.029 mm for thin support and 0.031 mm for thick support, indicating an accurate fit between the test and reference models. Furthermore, the deviation pattern observed in the color map was homogenously distributed and located further away from the critical marginal area. Conclusions: Within the limitations of this study, the selection of build angle should offer the crown the highest dimensional accuracy and self-supported geometry. This allows for the smallest necessary support surface area and decreases the time needed for finishing and polishing. These properties were mostly observed with a build angle of 120 degrees combined with a thin support type.

The goal of the current publication is to provide a comprehensive literature review on the topic of dental implant materials. The following paper focuses on conventional titanium implants and more recently introduced and increasingly popular zirconia implants. Major subtopics include the material science and the clinical considerations involving both implant materials and the influence of their physical properties on the treatment outcome. Titanium remains the gold standard for the fabrication of oral implants, even though sensitivity does occur, though its clinical relevance is not yet clear. Zirconia implants may prove to be promising in the future; however, further in vitro and well-designed in vivo clinical studies are needed before such a recommendation can be made. Special considerations and technical experience are needed when dealing with zirconia implants to minimize the incidence of mechanical failure.

Purpose: The purpose of this study was to determine the prosthodontic outcomes of one-piece zirconia implants and their attachment systems in edentulous participants with maxillary and mandibular overdentures after 1 year of a randomized controlled trial. Materials and Methods: Random allocation of 24 edentulous participants (age range: 45 to 86 years) into titanium (control) or zirconia (test) groups using onepiece implants and a planned unsplinted prosthodontic design was performed. Four maxillary implants (one midpalatal; three anterior crestal) and three mandibular implants (one midsymphyseal; two bilateral distal) were conventionally loaded with the overdentures. Similar attachment systems were used throughout: ball abutment–type patrices (diameter: 2.25 to 3.1 mm as part of the one-piece implants) and custommade plastic matrices (with or without metal housings depending on the patrix size). Prosthodontic outcomes were documented during the first year of the clinical trial. Results: Following three deaths and two dropouts, there were 19 participants who were available at the 1-year recall. Of these participants, 3 had early maxillary implant failure and had to be converted to conventional maxillary complete dentures opposing mandibular implant overdentures. There were 79 maintenance events, 34 in the titanium (control) group and 45 in the zirconia (test) group. Patrix loss occurred as a result of three zirconia implant fractures (one mandibular and two crestal maxillary implants). Maintenance events were principally the replacement of matrices and overdenture fracture. Although relines and replacement overdentures also occurred, overall there were no significant differences in prosthodontic maintenance between the control and test groups. A six-field prosthodontic-success analysis table showed no statistically significant difference between the two groups; however, 50% of participants in each group were allocated to the retreatment (repair) field, which produced a low prosthodontic success rate. Conclusions: Removable overdentures can be used on both one-piece titanium and zirconia implants with these attachment systems, due to no difference in prosthodontic maintenance and success. Before recommending routine use of a “metal-free” overdenture treatment option in clinical practice, consideration must be given to the success of the implants themselves

OBJECTIVE The objective of this study was to assess 1-year clinical success of one-piece zirconia implants compared with similar-design titanium implants, in the context of a novel protocol for implant distribution. MATERIALS AND METHODS Twenty-four edentulous participants were randomly allocated to one-piece titanium or zirconia implant group. Each participant received four implants in the maxilla (mid-palatal and three anterior crestal implants) and three implants in the mandible (mid-symphyseal and two bilateral distal implants). Conventional loading protocol was followed. Marginal bone remodeling and clinical success of implants were evaluated. The data were statistically analyzed, and risk predictors for implant failures were evaluated. RESULTS There was no significant difference in the survival rate between the two groups. In the mandible, the survival rate of titanium implants was 95.8% vs. 90.9% for the zirconia implants. The corresponding values in the maxilla were 71.9% and 55%, respectively. Three implants in the zirconia group fractured. Statistically significant less marginal bone loss was observed around titanium implants (0.18 mm) compared with the zirconia group (0.42 mm). The prediction model revealed a higher risk for implant failures in the maxilla (P < 0.0001). CONCLUSION The outcome of this study indicates caution before recommendation can be made for the use of single-piece zirconia implants for overdenture support. Their use should be limited to cases with proven allergy to titanium. This is mainly due to the increased bone loss and higher fracture rate observed for zirconia implants. Future biomaterial research should focus on producing surface characteristics on zirconia implants with outcomes similar to those established for the optimum osseointegration of titanium implants.

Limited clinical research identifies prosthodontic perspectives of novel designs for zirconia implants supporting overdentures. Four pilot study participants were selected before a planned randomized clinical trial on zirconia implants supporting overdentures. Novel designs for maxillary four-implant overdentures (quadrilateral design) and mandibular three-implant overdentures (tripodal design) were used with 28 implants (maxilla, n = 16; mandible, n = 12). Four implants failed to achieve osseointegration prior to loading. At the 1-year follow-up appointment, all implants were surviving, the overdentures were in function, and there were no clinical signs of wear of the attachment system. A proof-of-principle for prosthodontic perspectives of a novel design using one-piece zirconia implants supporting maxillary and mandibular implant overdentures was achieved.

Purpose To evaluate the biomechanics of a novel implant placement distribution and compare it with that of conventional maxillary overdenture support using three-dimensional finite element analysis (FEA). The application of zirconia implants in the context of this novel design was also evaluated. Materials and methods Detailed FEA models were created to analyze the loading responses of two different distributions of implants to support maxillary overdentures. The two implant distributions were as follows: the conventional design (D1) included four unsplinted implants in the premolar regions, whereas the novel design (D2) included one midpalatal implant, bilateral canine/premolar implants, and one anterior off-center crestal implant. Anatomical models were created with computed tomographic data and static loads were applied axially and obliquely. Von Mises stresses and equivalent strains generated in peri-implant bone and first principal stresses in the implants were calculated, including any denture displacement. Results Comparable stress and strain values were seen in the peri-implant bone for both designs. A significant decrease in the first principal stresses of D2 implants was observed with oblique loads. The maximum equivalent strain produced in the peri-implant region was mostly within the range for bone augmentation. D2 displayed lower maximum displacement values than D1. Maximum tensile stresses in the zirconia implants for either design were well below their fracture strength. Conclusions A novel four-implant distribution involving midpalatal and crestal implants may be an alternative to the conventional design used for maxillary overdentures. This is particularly relevant when anatomical considerations prevent the placement of four anterior crestal implants. Zirconia implants may also be a valid option for a selected group of patients or for those requesting metal-free restorations. Prospective clinical studies are required to confirm these in vitro results.

Purpose: Different treatment protocols in terms of number, diameter, and suprastructure design have been proposed for immediately loaded implants that are used to support mandibular overdentures opposed by maxillary conventional dentures. The aim of this study was to investigate the influence of these protocols on survival rates as well as clinical and prosthodontic outcomes. Materials and Methods: Several electronic databases were searched for all relevant articles published from 1966 to June 2014. Only randomized controlled trials and prospective studies with a minimum follow-up of 12 months were selected. The primary outcomes of interest were the success and survival rates of the implants. Prosthodontic complications were also evaluated.Results: Fourteen studies fulfilled the inclusion criteria. Of the studies identified, nine were randomized controlled trials and five were prospective studies. The mean follow-up period was 3 years or less for the vast majority of the studies. The reported survival and success rates were comparable to that of conventional loading for most of the included studies. No specific immediate loading protocol seemed to perform better in terms of clinical and prosthodontic outcomes. Conclusion: Immediate loading protocols of mandibular overdentures seem to be a viable alternative to conventional loading. It was not possible to recommend a specific treatment protocol related to the number, diameter of the implants, and attachment system used. Long-term, well-designed studies comparing different immediate loading modalities could help to establish a protocol that delivers the most clinically predictable, efficient, and cost-effective outcome for edentulous patients in need of implant overdentures.

Statement of problem. The application of 3-dimensional printing technology is emerging in dentistry and is being increasingly used to fabricate dental restorations. To date, scientific evidence is lacking regarding the effect of different factors on the mechanical properties of the printed restorations with the additive manufacturing technique.Purpose. The purpose of this in vitro study was to evaluate the effect of build direction (layer orientation) on the mechanical properties of a novel 3-dimensionally (3D)-printed dental restorative material.Material and methods. Based on the printing direction, 2 groups were tested. In the first group (n=20), the specimens were vertically printed with the layers oriented perpendicular to the load direction. In the second group (n=20), the specimens were horizontally printed with the layers oriented parallel to the load direction. All specimens were fabricated using the DW028D 3D-printer. The specimens were loaded with a universal testing machine at a crosshead speed of 1 mm/min with a 10-kN load cell. The test was performed at room temperature (22°C) under dry testing conditions. The compressive strength was calculated for both groups, and the results were compared using the unpaired t test (α=.05).Results. The mean ±SD compressive strength for the vertically printed specimens was 297 MPa (±34) compared with 257 MPa (±41) for the horizontally printed specimens (P=.002).Conclusions. Within the limitations of this study, the layer orientation was found to influence the compressive strength of the material. Vertically printed specimens with the layers oriented perpendicular to load direction have improved mechanical properties more than horizontally printed specimens with the layers oriented parallel to load direction.

Objectives Two fractured one-piece experimental (commercially unavailable) zirconia implants were analyzed using scanning electron microscope (SEM) analysis to identify failure origins and aid in understanding the failure mechanisms. Modifications to the zirconia implant design are suggested to minimize such fracture incidences. Materials and methods Two zirconia implants fractured during the final torquing in the maxillary ridge using the prescribed hand torque wrench. The implants were subsequently retrieved and prepared for optical and SEM evaluation. Critical attention was given to the fractography (crack morphology) of the fractured implants to identify the fracture origin. Results Events related to initiation and propagation of the crack front could be detected from the morphology of the fractured surfaces. Unfavorable torque and bending forces applied on the implant during surgical placement and the inherent flaws in the material may have resulted in crack initiation and implant failure. Conclusions Caution must be exercised when placing zirconia implants in dense bone sites. Modification of surgical protocols for the intended implant site may be necessary. Improvement in design features specific to zirconia implants, and strict quality control during manufacture is essential to minimize the likelihood of fracture.

PURPOSE The purpose of this study was to compare the stress and strain occurring in peri-implant bone and implants used to support maxillary overdentures. Three-dimensional finite element analysis (3D FEA) was used to compare one-piece zirconia and titanium implants. MATERIALS AND METHODS Two types of implants were simulated using a 3D FEA model: one-piece zirconia and titanium implants (diameter, 3.8 × 11.5 mm) with 2.25-mm diameter ball abutments. In each simulation four implants were placed bilaterally in the canine/premolar region of an edentulous maxillary model. Static loads were applied axially and 20 degrees buccolingually on the buccal slope of the lingual cusps of posterior teeth of the first quadrant. Von Mises stresses and equivalent strains generated in peri-implant bone and first principal stresses in the implants were calculated. RESULTS Comparable stress and strain values were shown in the peri-implant bone for both types of implants. The maximum equivalent strain produced in the peri-implant region was mostly within the range for bone augmentation. Under oblique loading, maximum von Mises stresses and equivalent strain were more evident at the neck of the most distal implant on the loaded side. Under axial load, the stress and strain were transferred to the peri-implant bone around the apex of the implant. Maximum tensile stresses that developed for either material were well below their fracture strength. The highest stresses were mainly located at the distobuccal region of the neck for the two implant materials under both loading conditions. CONCLUSIONS From a biomechanical point of view, ceramic implants made from yttrium-stabilized tetragonal polycrystalline zirconia may be a potential alternative to conventional titanium implants for the support of overdentures. This is particularly relevant for a select group of patients with a proven allergy to titanium. Prospective clinical studies are still required to confirm these in vitro results. Different simulations presenting various cortical bone thicknesses and implant designs are required to provide a better understanding of the biomechanics of zirconia implants.

Objectives This qualitative study explored the perceptions of edentulous patients regarding their rehabilitation with maxillary and mandibular implant-supported overdentures employing a protocol that featured novel implant sites and distribution. Material and Methods In-depth semi-structured interviews were conducted with 16 participants who have taken part in a randomized controlled trial. Each received implant overdentures supported by either titanium or zirconia one-piece implants. Participants received four implants in the maxilla and three implants in the mandible. The implant distribution was: in the maxilla, a mid-palatal implant, and three anterior implants in the incisor and first premolar regions; in the mandible, a mid-symphseal implant, and bilateral distal implants in the first molar region. All interviews were conducted by a researcher not involved with the clinical aspect of the randomized controlled trial and were transcribed verbatim and analyzed using a thematic inductive analysis approach. Results The perceived advantages of the treatment were functional improvement and increased social confidence. Cost was a significant barrier for edentulous patients seeking implant treatment. Previous experience with complete dentures, age and length of treatment was further factors that influenced decisions regarding prosthodontic rehabilitation. The novel implant protocol was acceptable to patients. Conclusions Implant overdentures improve the quality of life of edentulous patients. Acceptance of dental implants may be increased by mitigating the cost of treatment. The mid-palatal implant site may be a potential alternative to extensive surgical procedures during the prosthodontic rehabilitation of atrophic maxillary ridges. The mandibular design offers patients the advantages of a removable prosthesis with increased retention.

The aim of this article is to systematically review the literature on prosthodontic maintenance requirements of maxillary implant overdentures with different prosthodontic designs.A standard approach of searching MEDLINE, PubMed, and Google Scholar databases as well as early online journal articles was followed. Hand-searching identified other relevant articles from the reference lists of the articles found. Selection criteria were details of prosthodontic maintenance related to different prosthodontic designs of maxillary implant overdentures, regardless of the dentition of the opposing arch or prosthesis.From a total of 58 relevant studies identified, only 18 met the criteria. Several categories were used to document the prosthodontic maintenance of maxillary implant overdentures, usually with four or more splinted or unsplinted implants using different attachment systems. Aspects of patrix and matrix maintenance were primarily reported, although soft tissue complications were described frequently. Subjective information on relines and the rationale for minimizing overdenture fractures was found.Prosthodontic maintenance requirements of maxillary overdentures are a direct consequence of the attachment system, together with differing numbers and distributions of implants. The reviewed literature does not provide a clear controlled indication of prosthodontic maintenance requirements of maxillary overdentures for different prosthodontic designs and attachment systems. Future standardization of maxillary implant overdenture design is recommended, and universally accepted criteria for reporting maxillary implant overdenture maintenance should be implemented to establish accurate comparative data analysis.