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The Kois Dento-Facial Analyzer (KDFA) is used by clinicians to mount maxillary casts and to evaluate and treat patients. Limited information is available for understanding whether the KDFA should be considered as an alternative to an arbitrary facebow. The purpose of this clinical study was to evaluate and compare maxillary casts mounted by using the KDFA with casts mounted by using the Panadent Pana-Mount Facebow (PMF) and a kinematic axis (KA) facebow. Fifteen participants were enrolled in the study. Three maxillary impressions were made of each study participant. One cast from each study participant was mounted on an articulator by means of the KDFA, PMF, and KA. A standardized photograph of each mounting was made, and the condylar center-incisor distance and the occlusal and incisal plane angles were measured. A randomized complete block design analysis of variance (RCBD) (α=.05) and post hoc tests (Tukey-Kramer HSD) were used to evaluate the occlusal and incisal plane angles and the condylar center-incisor distance. Compared with the occlusal plane angle (OPA), the KDFA mounted the maxillary cast at an angle that was statistically lower than those of PMF and KA (P <.001). The KDFA and the PMF condylar center-incisor distances were both significantly greater than that of KA (P =.01). No differences were found between the incisal plane angle (IPA) on maxillary casts mounted with the KDFA, KA, or PMF (P=.16). The KDFA and PMF mounted the maxillary casts in a position that was farther from the axis when compared with the KA mounted casts. The KDFA resulted in a lower articulator OPA compared with both PMF and KA. No difference was found between the IPAs of the KDFA, PMF, and KA. [ABSTRACT FROM AUTHOR]

More translucent dental zirconias have been developed by incorporating the cubic phase and reducing the tetragonal phase content that undergoes transformation toughening, leading to reduced mechanical properties. Whether the clinically relevant mechanical property of the edge chipping toughness of the material is also reduced is unclear. The purpose of this in vitro study was to evaluate the edge chipping toughness and translucency of translucent zirconia, 3mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), and lithium disilicate. Two translucent zirconia products, Katana and Lava Esthetic; one 3Y-TZP, Lava Plus; and one lithium disilicate, IPS e.max Press were prepared and tested for phase composition via X-ray diffraction (XRD) (n=3), translucency via a spectrophotometer (n=20), and edge chipping via a universal testing machine with a custom-machined specimen holder and diamond indenter (n=20). The 3Y-TZP and lithium disilicate served as the optimal control materials for edge chipping and translucency, respectively. Translucency was compared with 1-way ANOVA and edge toughness with ANCOVA (α=.05). The XRD showed the 3Y-TZP to be almost completely tetragonal phase compared with the 2 translucent zirconia products that were predominantly cubic. Katana UTML and IPS e.max Press had a statistically similar (P >.05) translucency that was significantly (P <.05) greater than that of Lava Esthetic and Lava Plus. The edge toughness of Katana UTML was 304 N/mm, IPS e.max Press was 354 N/mm, Lava Esthetic was 394 N/mm, and Lava Plus was 717 N/mm, with significance rankings of Katana UTM

Soft-tissue attachment to different surfaces may play a pivotal role in the long-term success of dental implants. However, studies on the issue, especially on newer materials, are sparse. The purpose of this in vitro study was to evaluate the viability and adhesion of human gingival fibroblasts (HGFs) on different implant abutment materials with specific surface modifications. One hundred and fifty specimens in 6 experimental groups were evaluated: smooth-machined titanium alloy (Ti), laser-modified titanium (TiL), smooth-machined polyetheretherketone (PEEK) (P), laser-modified PEEK (PL), plasma-treated PEEK (PP), laser- and plasma-treated PEEK (PLP). Machined Ti was considered as the control group. Surface roughness (S a), water contact angle (WCA), and X-ray photoelectron spectroscopy (XPS) were measured. HGF attachment and proliferation were observed at 1, 3, and 7 days after cell seeding. Comparison of the means among the groups was performed with 1-way analysis of variance (ANOVA) with post hoc comparison using the Tukey test (α=.05). S a values of the laser modified groups were significantly higher than those of the nonmodified (smooth-machined) groups (P <.001). WCAs were significantly different among PEEK groups, and plasma-sprayed groups had the lowest WCAs. XPS analysis of both Ti and PEEK groups showed laser treatment did not have any significant effect on the surface composition of the PEEK as the same bonds with similar ratio/fraction were detected in the spectrum of the modified specimens. Scanning electron microscopy (SEM) revealed more functionally oriented HGF cells on the laser-grooved surfaces. On the first, third, and seventh day of proliferation, the titanium groups showed no significant differences (P >.05). On the first and third days of proliferation, the plasma sprayed groups (PP, PLP) showed significantly greater proliferation than all experimental groups (P <.001). On the seventh day of proliferation, statistically significant differences were observed between all PEEK groups and between all PEEK groups and the Ti group (P <.001), with the exception of the PL and P groups and the PLP and Ti groups (P >. 05). Laser-modified titanium and PEEK surfaces led to guided gingival fibroblast attachment. Plasma treatment of PEEK surfaces increased the wettability of this polymer and improved proliferation of HGF. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) technology has been introduced for printing metal dental restorations from Co-Cr base alloys or Au-Pt high noble alloys. However, information regarding the fit of restorations fabricated by using this technique is limited. The purpose of this in vitro study was to determine the effect of 3 different finish line designs on the marginal and internal gaps of metal copings made from a base (Co-Cr), high noble (Au-Pd-Ag), and noble alloy (Co-Pd) by using the SLM technology. Three Ivorine right maxillary central incisors were prepared with a chamfer, deep chamfer, or shoulder finish line. The preparations were scanned by using a TRIOS scanner, and a total of 90 dies were printed using DPR 10 Resin (30×3 finish line designs). Ten SLM copings were fabricated for each margin design and metal alloy combination for a total of 90 copings (10×3 finish line designs×3 alloys). Copings were cemented onto dies using an autopolymerizing composite-resin luting material. All coping-die assemblies were sectioned buccolingually by using a low-speed diamond saw, and images were obtained by using an inverted bright field metallurgical microscope at ×100 magnification. Marginal and internal gaps were measured at 5 locations: buccal margin, midfacial, incisal, midlingual, and lingual margin. After gap measurements, representative specimens were embedded in autopolymerizing resin and prepared for metallographic examination. A 2-way multivariate analysis of variance (MANOVA) was conducted to determine the overall significance, followed by ANOVA for each dependent variable (α=.05). The results indicated that alloy type and finish line had a significant influence on marginal gap of copings (P <.001). Relative to the internal gap, alloy type had a significant effect (P <.001), but the type of finish line had no statistically significant influence (P =.337). No statistically significant interactions occurred. Base alloys were printed with almost no observable porosity, whereas noble and high noble alloys exhibited hot tears and porosity. Thefinish line type did not influence the internal gap between copings and dies, whereas the alloy type influenced the marginal gap between copings and dies. SLM-fabricated Co-Cr copings on teeth prepared with a deep chamfer finish line demonstrated the lowest marginal gap. [ABSTRACT FROM AUTHOR]

Zirconia and lithium disilicate have been commonly used as materials for tooth-supported complete-coverage restorations. Adhesive and conventional cements have been suggested for cementation of these restorations. However, evidence on the effect of cement type on the clinical outcomes of teeth restored with zirconia or lithium disilicate restorations is unclear. The purpose of this systematic review was to evaluate the clinical outcomes of teeth restored with zirconia or lithium disilicate restorations when adhesive or conventional cements are used. This systematic review adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered at the international prospective register of systematic reviews (PROSPERO) (CRD42018096493). An electronic search was performed in 2 databases (MEDLINE-PubMed and Cochrane Central), and a manual search, from January 2008 through January 2018. The primary clinical question was framed according to the Problem/Patient/Population, Intervention/Indicator, Comparison, Outcome (PICO) approach. The following question was the primary clinical question: "For patients requiring a single tooth-supported complete-coverage ceramic restoration, does adhesive cementation, as compared with conventional cementation, improve the clinical performance and limit the complications of this restoration?" The search included articles published in peer-reviewed journals in English and was limited to randomized clinical trials and prospective and retrospective clinical studies. Seventeen clinical studies met the eligibility criteria and were included for qualitative analysis. Included studies had 1280 participants who received 2436 zirconia and lithium disilicate crowns. The survival rates for adhesively cemented zirconia crowns ranged from 83.3% to 100%, whereas those reported for conventionally cemented zirconia crowns ranged from 82.0% to 100%. Survival rates for adhesively cemented lithium disilicate crowns ranged from 83.5% to 100%, whereas the survival rate reported for conventionally cemented lithium disilicate crowns was 98.5%. Commonly reported clinical complications included fracture of the veneering ceramic, crown fracture, and loss of crown retention. The mean follow-up time ranged from 25.5 months to 121.2 months. The studies that were assessed for risk of bias showed poor quality of evidence. Based on the available evidence and within the limitations of this systematic review, zirconia and lithium disilicate tooth-supported crowns exhibited comparable survival rates and complication patterns after adhesive or conventional cementation. [ABSTRACT FROM AUTHOR]

Abstract Statement of problem Debonding is the most common complication of fiber-reinforced posts (FRPs). Airborne-particle abrasion (APA) has been suggested to increase resin cement adhesion to the surface of FRPs. However, which abrasion protocol is the most favorable is unclear. Purpose The purpose of this in vitro study was to compare the surface roughness and characteristic failure load of three FRP systems following different APA protocols. Material and methods A total of 150 posts from 3 manufacturers (glass FRP, quartz FRP, and zirconia-enriched glass FRP) were randomly assigned to different surface treatments (NT: no treatment—control; E0: cleaned with 96% ethanol solution; E2: APA for 2 seconds/mm2—ethanol cleaned, E5: APA for 5 seconds/mm2—ethanol cleaned; and E10: APA for 10 seconds/mm2—ethanol cleaned) forming 15 groups in total. APA was performed with 50-μm aluminum oxide. Each post was observed under a 3-dimensional (3D) laser microscope, and average 3D surface roughness (Sa) was measured. Failure was induced with a universal testing machine. Two specimens per group were evaluated under the same microscope to evaluate failure patterns. Surface roughness data were analyzed with the Welch ANOVA (α=.05), followed by the post hoc Games-Howell test. Failure load differences were determined by 2-parameter Weibull statistics and likelihood ratio contour plots (95% confidence bounds). Results Statistically significant differences were found in the mean surface roughness among the groups (Welch ANOVA, P <.001). APA resulted in a significant surface roughness increase in all tested post systems. No surface roughness difference was found between surface treatments E2, E5, and E10 in any tested post systems. Weibull statistics and likelihood contour plots revealed a significant decrease in the characteristic failure load for glass FRP after surface treatment E2 (88.7 N) compared with the control (95.3 N). Quartz FRP showed a significant decrease in the characteristic failure load after surface treatment E5 (103.6 N) compared with the control (108.9 N). Zirconia-enriched glass FRP showed no significant decrease in the characteristic failure load after any of the tested surface treatments. Qualitative morphological changes and failure pattern differences were observed among the tested post systems after the different surface treatments. Conclusions APA significantly increased surface roughness in all post systems. APA effects on characteristic failure load were dependent on the material used. [ABSTRACT FROM AUTHOR]

Abstract Statement of problem Research evaluating load-to-failure of pressed lithium disilicate glass-ceramic (LDGC) with a clinically validated test after adjustment and repair procedures is scarce. Purpose The purpose of this in vitro study was to investigate the effect of the simulated chairside adjustment of the intaglio surface of monolithic pressed LDGC and procedures intended to repair damage. Material and methods A total of 423 IPS e.max Press (Ivoclar Vivadent AG) disks (15 mm diameter, 1 mm height) were used in the study. The material was tested by using an equibiaxial loading arrangement (n≥30/group) and a contact pressure test (n≥20/group). Specimens were assigned to 1 of 14 groups. One-half was assigned to the equibiaxial load test and the other half underwent contact pressure testing. Testing was performed in 2 parts, before glazing and after glazing. Before-glazing specimens were devested and entered in the test protocol, while after-glazing specimens were devested and glazed before entering the test protocol. Equibiaxial flexure test specimens were placed on a ring-on-ring apparatus and loaded until failure. Contact pressure specimens were cemented to epoxy resin blocks with a resin cement and loaded with a 50-mm diameter hemisphere until failure. Tests were performed on a universal testing machine with a crosshead speed of 0.5 mm/min. Weibull statistics and likelihood ratio contour plots determined intergroup differences (95% confidence bounds). Results Before glazing, the equibiaxial flexural strength test and the Weibull and likelihood ratio contour plots demonstrated a significantly higher failure strength for 1EC (188 MPa) than that of the damaged and/or repaired groups. Glazing following diamond-adjustment (1EGG) was the most beneficial post-damage procedure (176 MPa). Regarding the contact pressure test, the Weibull and likelihood ratio contour plots revealed no significant difference between the 1PC (98 MPa) and 1PGG (98 MPa) groups. Diamond-adjustment, without glazing (1EG and 1PG), resulted in the next-to-lowest equibiaxial flexure strength and the lowest contact pressure. After glazing, the strength of all the groups, when subjected to glazing following devesting, increased in comparison with corresponding groups in the before-glazing part of the study. Conclusions A glazing treatment improved the mechanical properties of diamond-adjusted IPS e.max Press disks when evaluated by equibiaxial flexure and contact pressure tests. [ABSTRACT FROM AUTHOR]

Statement of problem Currently, dental articulators can recreate mandibular movements and occlusal contacts. However, whether virtual articulators can also provide information about occluding dental surfaces, functional movements, and the mandibular condyles is unclear. Purpose The purpose of this in vitro study was to evaluate the occluding surfaces on dental casts obtained from a patient and approximate them to a hemispherical contact model. Both models were tested by digitizing the Dentatus ARL dental articulator. Material and methods A combination of photogrammetry and structure from motion methods were used to scan a Dentatus ARL articulator and representative dental casts. Using computer-aided engineering and finite element analysis, contact points and action vectors to the forces on occluding surfaces and condyles were obtained for cast and hemispherical models. This experiment was performed using centric occlusion and 3 different condylar inclinations. The Kruskal-Wallis 1-way analysis of variance on ranks test was used to allow all pairwise comparisons between condylar inclination and mechanical action vector values in each location (α=.05). Results Action vectors from the cast model and each location of the hemispherical model were calculated to show the mechanical consequences and the similarity among models. Overall, no significant differences were observed for action vectors (A20 versus A40 versus A60) at each location (dental cast/hemisphere, right condylar, and left condylar) in the analysis of dental casts and the hemisphere model (.382≤ P ≤.999). Conclusions This study provided graphical information that may assist the dental professional in determining which occlusal contacts should be modified to attain condylar and balanced centric occlusion. [ABSTRACT FROM AUTHOR]

In managing loose abutment screws, locating precisely the position of the screw access channel is difficult. This technique describes the use of cone-beam computed tomography (CBCT) and surgical guide planning software to locate the screw access channel with the intention of retrieving a loosened cement-retained implant-supported prosthesis. The method minimizes damage to the abutment crown assembly. [ABSTRACT FROM AUTHOR]

Statement of problem The die contour can affect the emergence profile of prosthetic restorations. However, little information is available regarding the congruency between a stereolithographic (SLA) die and its corresponding natural tooth. Purpose The purpose of this vitro study was to evaluate the shapes of SLA die in comparison with the subgingival contour of a prepared tooth to be restored with a ceramic crown. Material and methods Twenty extracted human teeth, 10 incisors, and 10 molars, were disinfected and mounted in a typodont model. The teeth were prepared for a ceramic restoration. Definitive impressions were made using an intraoral scanner from which 20 SLA casts with removable dies were fabricated. The removable dies and corresponding human teeth were digitized using a 3-dimensional desktop scanner and evaluated with computer-aided design software. The subgingival morphology with regard to angle, length, and volume at the buccolingual and mesiodistal surfaces and at zones A, B, C, and D were compared. Data were first analyzed with repeated measures analysis of variance (ANOVA), using locations (buccolingual and mesiodistal), zones (A, B, C, and D), and model type (SLA and Natural) as within-subject factors and tooth type (molar and incisor) as the between-subject factor. Post hoc analyses were performed to investigate the difference between natural teeth and corresponding SLA models, depending upon the interaction effect from the repeated measures ANOVA (α=.05). Results For angle analysis, the incisor group demonstrated a significant difference between the natural tooth and SLA die on the buccolingual surfaces ( P <.05), whereas the molar group demonstrated a significant difference at the mesiodistal surfaces ( P <.05). For the evaluation of length and volume, the incisor group showed significant differences in zone D on both the buccolingual ( P <.05) and the mesiodistal ( P <.05) surfaces. However, significant differences in zones C ( P <.05) and D ( P <.05) on the buccolingual surfaces and in all zones on the mesiodistal surfaces were observed in the molar group. Conclusions For the comparison of angles, SLA dies did not replicate the subgingival contour of natural teeth on the buccolingual surfaces of the incisal groups. For the comparison of length and volume, SLA dies were more concave and did not replicate the subgingival contour of natural teeth in the incisal and molar groups. [ABSTRACT FROM AUTHOR]

Statement of problem Two novel restorative materials, a polymer infiltrated ceramic network (PICN) and a resin nanoceramic (RNC), for computer-assisted design and computer-assisted manufacturing (CAD-CAM) applications have recently become commercially available. Little independent evidence regarding their mechanical properties exists to facilitate material selection. Purpose The purpose of this in vitro study was to measure the edge chipping resistance and flexural strength of the PICN and RNC materials and compare them with 2 commonly used feldspathic ceramic (FC) and leucite reinforced glass-ceramic (LRGC) CAD-CAM materials that share the same clinical indications. Material and methods PICN, RNC, FC, and LRGC material specimens were obtained by sectioning commercially available CAD-CAM blocks. Edge chipping test specimens (n=20/material) were adhesively attached to a resin substrate before testing. Edge chips were produced using a 120-degree, sharp, conical diamond indenter mounted on a universal testing machine and positioned 0.1 to 0.7 mm horizontally from the specimen’s edge. The chipping force was plotted against distance to the edge, and the data were fitted to linear and quadratic equations. One-way ANOVA determined intergroup differences (α=.05) in edge chipping toughness. Beam specimens (n=22/material) were tested for determining flexural strength using a 3-point bend test. Weibull statistics determined intergroup differences (α=.05). Flexural modulus and work of fracture were also calculated, and 1-way ANOVA determined intergroup differences (α=.05) Results Significant ( P <.05) differences were found among the 4 CAD-CAM materials for the 4 mechanical properties. Specifically, the material rankings were edge chipping toughness: RNC>LRGC=FC>PICN; flexural strength: RNC=LRGC>PICN>FC; flexural modulus: RNCLRGC=PICN>FC. Conclusions The RNC material demonstrated superior performance for the mechanical properties tested compared with the other 3 materials. [ABSTRACT FROM AUTHOR]

Statement of problem The effect of toothbrushing on extrinsically stained pressable ceramic materials is unknown. Purpose The purpose of this in vitro study was to investigate the effects of toothbrushing on the shade and surface roughness of extrinsically stained, pressable ceramics. Material and methods Two materials, leucite-based (IPS Empress Esthetic [EE]; Ivoclar Vivadent AG) and lithium disilicate-based ceramic (IPS e.max Press [EP]; Ivoclar Vivadent AG), were studied. For each material, 24 disk-shaped specimens, 10 mm (diameter)×3 mm (height) were fabricated. Three different methods (n=8) of applying extrinsic stains were performed on each material: glazed only (G, control group); stained then glazed (SG); and stained and glazed together (T). The specimens were brushed with a multistation brushing machine under a load of 1.96 N at a rate of 90 strokes per minute with a soft and straight toothbrush (Oral-B #35) and a 1:1 toothpaste and distilled water slurry. Shade and roughness were measured at baseline and at 72, 144, 216, and 288 hours, which is equivalent to 3, 6, 9, and 12 years of simulated toothbrushing for 2 minutes twice a day. A repeated measures ANOVA with staining technique as a fixed factor was used to evaluate shade and roughness (α=.05). Results For EE groups, no significant change was found after 12 years of simulated toothbrushing regarding shade and surface roughness, irrespective of staining techniques ( P >.05). However, EP groups demonstrated a significant shade change and an increase in surface roughness after 12 years of simulated toothbrushing. Shade change was found to depend on the method of applying stain. For the EP-SG technique, a significant shade change was observed only at the 9- to 12-year interval ( P =.047). However, the EP-T technique demonstrated a significant difference in shade between baseline and 3 years ( P =.005) and in the 6- to 9-year interval ( P =.005). Surface roughness was only significantly affected at baseline and 3 years for the EP-T group ( P =.005). Conclusions For the shade and surface roughness of the EE groups, no statistically significant difference was found after 12 years of toothbrushing, irrespective of the staining technique. The shade and surface roughness of the EP groups were significantly statistically affected by toothbrushing time; only shade changes were found to depend on technique. [ABSTRACT FROM AUTHOR]

Statement of problem The Kois Dento-Facial Analyzer System (KDFA) is used by clinicians to mount maxillary casts and evaluate and treat patients. Limited information is available for understanding whether the KDFA should be considered as an alternative to an earbow. Purpose The purpose of this study was to evaluate maxillary casts mounted using the KDFA with casts mounted using Panadent's Pana-Mount Facebow (PMF). Both articulation methods were compared against a lateral cephalometric radiograph. Material and methods Fifteen dried human skulls were used. Lateral cephalometric radiographs and 2 maxillary impressions were made of each skull. One cast from each skull was mounted on an articulator by means of the KDFA and the other by using the PMF. A standardized photograph of each articulation was made, and the distance from the articular center to the incisal edge position and the occlusal plane angle were measured. The distance from condylar center to the incisal edge and the occlusal plane angle were measured from cephalometric radiographs. Finally, the 3-dimensional position of each articulation was determined with a Panadent CPI-III. A randomized complete block design analysis of variance (RCBD) and post hoc tests (Tukey-Kramer HSD) (α=.05) were used to evaluate the occlusal plane angle and axis-central incisor distance. A paired 2-sample t test for means (α=.05) was used to compare the X, Y, and Z distance at the right and left condyle. Results The KDFA and PMF mounted the maxillary cast in a position that was not statistically different from the skull when comparing the occlusal plane angle ( P =.165). Both the KDFA and the PMF located the maxillary central incisor edge position in a significantly different position compared with the skull ( P =.001) but were not significantly different from each other. The 3-dimensional location of the maxillary casts varied at the condyles by approximately 9 to 10.3 mm. Conclusion The KDFA mounted the maxillary cast in a position that was not statistically different from the PMF when comparing the incisal edge position and the occlusal plane angle. Both the KDFA and the PMF located the maxillary incisal edge position in a significantly different position compared with the anatomic position on dried human skulls. [ABSTRACT FROM AUTHOR]

Statement of problem The inability to control die spacer thickness has been reported. However, little information is available on the congruency between the computer-aided design parameters for die spacer thickness and the actual printout. Purpose The purpose of this study was to evaluate the accuracy and precision of the die spacer thickness achieved by combining computer-aided design and 3-dimensional printing technology. Material and methods An ivorine maxillary central incisor was prepared for a ceramic crown. The prepared tooth was duplicated by using polyvinyl siloxane duplicating silicone, and 80 die-stone models were produced from Type IV dental stone. The dies were randomly divided into 5 groups with assigned die spacer thicknesses of 25 μm, 45 μm, 65 μm, 85 μm, and 105 μm (n=16). The printed resin copings, obtained from a printer (ProJet DP 3000; 3D Systems), were cemented onto their respective die-stone models with self-adhesive resin cement and stored at room temperature until sectioning into halves in a buccolingual direction. The internal gap was measured at 5 defined locations per side of the sectioned die. Images of the printed resin coping/die-stone model internal gap dimensions were obtained with an inverted bright field metallurgical microscope at ×100 magnification. The acquired digital image was calibrated, and measurements were made using image analysis software. Mixed models (α=.05) were used to evaluate accuracy. A false discovery rate at 5% was used to adjust for multiple testing. Coefficient of variation was used to determine the precision for each group and was evaluated statistically with the Wald test (α=.05). Results The accuracy, expressed in terms of the mean differences between the prescribed die spacer thickness and the measured internal gap (standard deviation), was 50 μm (11) for the 25 μm group simulated die spacer thickness, 30 μm (10) for the 45 μm group, 15 μm (14) for the 65 μm group, 3 μm (23) for the 85 μm group, and -10 μm (32) for the 105 μm group. The precision mean of the measurements, expressed as a coefficient of variation, ranged between 14% and 33% for the 5 groups. Conclusions For the accuracy evaluation, statistically significant differences were found for all the groups, except the group of 85 μm. For the precision assessment, the coefficient of variation was above 10% for all groups, showing the printer’s inability to reproduce the uniform internal gap within the same group. [ABSTRACT FROM AUTHOR]

Statement of problem Little peer-reviewed information is available regarding the accuracy and reproducibility of digitally fabricated casts compared to conventional nondigital methods. Purpose The purpose of this in vitro study was to compare the accuracy and reproducibility of a digital impression and cast fabrication with a conventional impression and cast fabrication. Material and methods Conventional impressions were made via a 1-step single viscosity technique with vinyl siloxanether material of a typodont master model, and conventional casts were cast from dental stone. Digital impressions were obtained with a digital scanner, and digital stereolithographic models were printed. The typodont and fabricated casts were digitized with a structured light scanner and saved in surface tessellation language (STL) format. All STL records were superimposed via a best-fit method. The digital impression and cast fabrication method was compared with the conventional impression and cast fabrication method for discrepancy, accuracy, and reproducibility. The Levene test was used to determine equality of variances, and a 1-way ANOVA was conducted to assess the overall statistical significance of differences among the groups (n=5, α=.05). Results No significant statistical difference was found between the digital cast and conventional casts in the internal area or finish line area ( P >.05). In addition, there was no statistically significant difference between these 2 techniques for a fixed dental prosthesis or single crown ( P >.05). However, statistically significant differences were observed for overall areas of the casts in terms of accuracy ( P <.01) and reproducibility ( P <.001). Digital impression and cast fabrication were less accurate and reproducible than conventional impression and cast fabrication methods. Conclusions No statistically significant difference was found between the digital cast and conventional cast groups in the internal and finish line areas. However, in terms of the reproducibility and accuracy of the entire cast area, the conventional cast was significantly better than the digital cast. [ABSTRACT FROM AUTHOR]

This report describes a method for fabricating access openings for implant-supported complete fixed dental prostheses (ICFP) by using a dental milling machine and silicone putty matrix. The method can help clinicians achieve the accurate and precise fabrication of access openings for ICFPs without excessive grinding. [ABSTRACT FROM AUTHOR]

Statement of problem Because polymer-based interim restorative materials are weak, even well-made restorations sometimes fail before the definitive restoration is ready for insertion. Therefore, knowing which fabrication procedures and service conditions affect mechanical properties is important, particularly over an extended period. Purpose The purpose of this study was to evaluate the effect of thermal treatment, surface sealing, thermocycling, storage media, storage temperature, and age on autopolymerizing poly(methylmethacrylate) and bis-acryl interim restorative materials. Outcome measures were flexural strength, Vickers surface microhardness, and impact strength. Material and methods Flexural strength and microhardness of poly(methylmethacrylate) (Jet Acrylic) and 2 bis-acryl-composite resin (Protemp 3 Garant and Integrity) interim restorative materials were evaluated as affected by storage media, storage temperature, storage time, thermocycling, postpolymerization thermal treatment, or application of a surface sealer. In total, 2880 beam specimens (25×2×2 mm) were fabricated. Mechanical property analyses were made at 10 days, 30 days, 6 months, and 1 year after specimen preparation. Flexural strength was determined by using a 3-point bending test in a universal testing machine with a 1 kN load cell at a crosshead speed of 5.0 mm min -1 . Fracture specimens were recovered and used for determining Vickers microhardness. Measurements were made with a 0.1 N load and 15 second dwell time. Three microhardness measurements were made for each specimen, and the mean was used for reporting Vickers microhardness. Notched impact specimens (64×12.7×6.35 mm) were fabricated from Jet, Protemp 3 Garant, and Integrity interim restorative materials, yielding 288 impact specimens. Impact strengths were assessed at 10 days, 30 days, 6 months, and 1 year with a 2 J pendulum. The effects of the various experimental treatments were determined and rank ordered with analysis of variance, F ratios, and least square means differences Student t tests (α=.05). Results All experimental treatments investigated had significant effects on flexural strength, with material ( P <.001) and thermocycling ( P <.001) being dominant. Moreover, all experimental treatments investigated had a significant overall impact on Vickers microhardness with material ( P <.001) and Palaseal glaze ( P <.001) showing large effects. Material ( P <.001) and age ( P =.010) had a significant effect on impact strength. Conclusions Mechanical properties of some interim polymeric materials can be improved by postpolymerization heat treatments or surface glazing. This procedure may extend the useful lifetime of some bis-acryl interim restorations. [ABSTRACT FROM AUTHOR]

Statement of problem In complete mouth reconstructive dentistry, the occlusal vertical dimension may be increased to provide adequate restorative space or to improve esthetics. The effect of increasing the occlusal vertical dimension on the smile is not well understood. Purpose The purpose of this study was to evaluate the effect of increasing the occlusal vertical dimension on the dimensions of the smile. Material and methods Thirty dental students, 12 men and 18 women between the ages of 21 and 30 years old, participated in this study. Polyvinyl siloxane occlusal registrations 2, 4, 6, and 8 mm in thickness were fabricated from articulated stone casts. Posed smile images at occlusal vertical dimension +0, +2, +4, +6, and +8 mm were made with a digital single lens reflex camera mounted on a tripod. A wall-mounted head-positioning device, modified from a cephalometric unit, was used to stabilize the head position. Interlabial gap height, intercommissural width, incisal edge to upper lip, and incisal edge–to–lower lip measurements were made with computer software. The smile index was obtained by dividing width by height. The display zone area was measured by using computer software tracing. One-way repeated measures ANOVA (α=.05) was used for statistical analysis. Results With an increase in the occlusal vertical dimension, the interlabial gap height, incisal edge to lower lip distance, and display zone area increased significantly ( P <.001), whereas the smile index decreased significantly ( P <.001). No significant changes were observed in the intercommissural width and incisal edge to upper lip distance. Conclusions The interlabial gap height, incisal edge–to–lower lip distance, and display zone area increase with increased occlusal vertical dimension. The smile index decreases with increased occlusal vertical dimension. However, the width of the smile and the length of the upper lip tend to remain unchanged. [ABSTRACT FROM AUTHOR]

Statement of problem: Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified. Purpose: The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys. Material and methods: Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05). Results: The alloy type had a significant effect on surface microhardness (P<.001). In contrast, the technique used for casting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high level of castability (98.5% on average) was achieved overall. The frequency of casting failures as a function of alloy type and casting method was determined. Failure was defined as a castability index score of <100%. Three of 28 possible comparisons between alloy and casting combinations were statistically significant. The results suggested that casting technique affects the castability index of alloys. Radiographic analysis detected large porosities in regions near the edge of the castability pattern and infrequently adjacent to noncast segments. All castings acquired traces of elements found in the casting crucibles. The grain size for each dental casting alloy was generally finer for specimens produced by the induction/vacuum-pressure method. The difference was substantial for JO and L. Conclusions: This study demonstrated a relation between casting techniques and some physical properties of metal ceramic casting alloys. [Copyright &y& Elsevier]

Statement of problem: Nonparallel implants, when used to retain overdentures, may present a restorative challenge, particularly when using attachments. Premature wear of the components and loss of retention may be observed, resulting in increased maintenance. Purpose: The purpose of this study was to compare the retentive behavior, over time, of spherical attachments when used in nonparallel and parallel implant scenarios in a cyclic testing mode. Material and methods: Thirty sets of 2-implant-supported overdenture models were evaluated: 4.0 × 13-mm implants (Astra-Tech Osseospeed) with 1.5-mm ball abutments (Astra-Tech) were used as the intraoral analog to the implants, and spherical attachments (Preci Clix) were used as the overdenture analog. Five different attachment and implant-abutment complex angulations were evaluated. Angulation was determined by deviation from the vertical reference plane. The groups consisted of the following: Group 0-0, 0-degree implants/0-degree attachments; Group 10-0, 10-degree implants/0-degree attachments; Group 15-0, 15-degree implants/0-degree attachments; Group 10-10, 10-degree implants/10-degree attachments; and Group 15-15, 15-degree implants/15-degree attachments. The specimens were subjected to cyclic loading (3500 cycles). Peak and valley retention loads were recorded at the first pull and then after every 100 cycles; therefore, 36 data points per specimen were recorded. Nonparametric analyses followed by post hoc analyses were conducted to test for differences in median peak load among groups (α=.05). Results: Peak load to dislodgment values for all groups ranged from 11.43 N to 23.56 N. Group 0-0 had the highest median retention value overall, 21.3 N, and Group 15-15 had the lowest median value, 17.3 N. Nonparametric analyses showed significant differences between Groups 0-0 and 15-15 (P=.014); and 10-0 and 15-15 (P=.002). Conclusions: Within the limitations of this study, it was observed that there was a decrease in retention in the groups with 30-degree divergent implants and divergent attachments compared to the groups with parallel implants and parallel attachments. In general, retention varied from 11 N to 23 N, and attachment retention stabilized after initial loss in most groups. (J Prosthet Dent 2009;101:231-238) [Copyright &y& Elsevier]

Statement of problem: When performing an adjustment on metal-ceramic restorations, opaque porcelain may become exposed, particularly on the lingual surface of maxillary anterior teeth. It is generally believed that exposed opaque porcelain can be more abrasive and destructive to an opposing dentition than body porcelain, and that these teeth may require restoration as a consequence. Purpose: This study compared the debonding strengths of 2 types of porcelain, with and without opaque porcelain, to 2 types of dental casting alloys. Material and methods: Two porcelain systems, Ceramco3 and Vita 900, and 2 metal alloys, a high noble (Encore) and a base metal (Duceranium U), were used to fabricate and test 56 flexure bars in accordance with ISO 9693:1999(E): Metal-Ceramic Dental Restorative Systems. Half of the bars received opaque porcelain prior to body porcelain additions, and the other half did not. The metal-ceramic debonding strength was determined by using a 3-point flexure apparatus and a mechanical testing device (Instron). A center load was applied at a crosshead speed of 1.5 mm/min−1 until debonding occurred. In addition to the load-versus-displacement curve, a precision measurement microphone was used to assist in ascertaining the point in time when debonding occurred. Since the sound analysis and the mechanical test were started simultaneously, the debonding load could be more accurately determined. Data were statistically analyzed using 3-way analysis of variance, and all pairwise multiple comparisons were made with the Tukey HSD test (α=.05). Results: The difference in mean debonding strength values for opaqued and non-opaqued flexure bars were statistically significant (P=.028). The mean debonding strength values (MPa) for each metal-ceramic system were as follows: Encore-Opaque-Ceramco3 (EOC), 31.43 ± 6.92a; Encore-Opaque-Vita 900 (EOV), 30.37 ± 3.25a; Duceranium U-No Opaque-Ceramco3 (DNC), 29.20 ± 6.97a; Duceranium U-Opaque-Ceramco3 (DOC), 26.61 ± 4.98a; Duceranium U-Opaque-Vita 900 (DOV), 26.15 ± 4.29a; Encore-No Opaque-Vita 900 (ENV), 25.45 ± 4.04a; Encore-No Opaque-Ceramco3 (ENC), 23.96 ± 4.14a; Duceranium U-No Opaque-Vita 900 (DNV), 22.88 ± 6.15a. Identical superscript letters denote no significant difference among groups. The precision measurement microphone resulted in selection of a debonding strength/crack initiation load that was lower than the peak load recorded during strength testing. Conclusion: Initial debonding during crack initiation strength testing may not always correspond to the peak load recorded, but rather to the point on the load-versus-displacement curve beyond which the relationship is no longer a straight line. Presence of opaque porcelain generally increased the debonding strength for metal-ceramic systems; however, opaque porcelain may not be necessary for a clinically acceptable metal-ceramic bond for some metal-ceramic systems. [Copyright &y& Elsevier]

Statement of problem: There is no information regarding the cutting efficiency and the surface finish produced on ceramic implant abutments when using diamond rotary cutting instruments (DRCIs). Purpose: The purpose of this study was to determine which DRCIs are the most efficient in cutting aluminum oxide and zirconium oxide implant abutments and to evaluate which DRCIs create the prepared ceramic abutment with the least surface roughness. Material and methods: A cutting regimen with a high-speed handpiece, 25 mL/min water spray and a 102.1-g load at the DRCI/ceramic interface was used to section the 4 × 4-mm edge of blocks of aluminum oxide (CerAdapt and Ceramic Esthetic Abutment) and zirconium oxide (Esthetic Zirconium Abutment (Nobel Biocare NB) and ZiReal Post (3i)) provided by the manufacturers. Two different brands of zirconium oxide were tested. Eight DRCIs of different types (Brasseler 2856, 5856, and 6856, Premier 770, TS2000, and Axis 856TSC, 856SC, and 856C) were tested to section each ceramic material 6 times, using a new block and a new DRCI for each test. The surface roughness (Ra value) was measured using a surface profilometer both parallel and perpendicular to the cut surface. Cutting efficiency was measured 3 times for change in weight/length of time (g/sec). The data were analyzed with a 1-way ANOVA and Tukey HSD tests (α=.05). Results: For the 3i zirconium oxide, 2 types of DRCIs (Axis 856 TSC and Brasseler 2856) produced a significantly smoother (P<.001 and P<.0001, respectively) surface finish on the shank and tip but not on the start and end. For the NB zirconium oxide, only the Axis 856C consistently produced a significantly smoother (P<.01, P<.0001 and P<.0001, respectively) surface finish on the start, shank, and tip. There was no significant difference in surface roughness of the NB aluminum oxide with use of any of the DRCIs. The Premier 770 was significantly more efficient (P<.0001 for 150 seconds and P<.001 for 300 seconds) in cutting the 3i zirconium oxide. The Premier 770 was significantly more efficient (P<.0001) in cutting the NB zirconium oxide at 150 seconds. The Premier TS2000 was significantly more efficient (P<.0001) at 300 seconds. The Axis 856 TSC was significantly more efficient (P<.0001 for 150 seconds and P<.001 for 300 seconds) in cutting the NB aluminum oxide. Conclusion: For a smoother surface finish, Axis 856C should be used for the NB zirconium oxide abutment, and either Axis 856TSC or Brasseler 2856 should be used for the 3i zirconium oxide abutment. To complete gross reduction on the NB and 3i zirconium oxide abutments, Premier 770 and TS2000 were found to perform the best. Gross reduction on the aluminum oxide ceramic abutment from NB was most efficiently performed by Axis 856TSC. [Copyright &y& Elsevier]

Statement of problem: There is currently no protocol for managing endodontic access openings for all-ceramic crowns. A direct restorative material is generally used to repair the access opening, rendering a repaired crown as the definitive restoration. This endodontic procedure, however, may weaken the restoration or initiate microcracks that may propagate, resulting in premature failure of the restoration. Purpose: The purpose of this in vitro study was to evaluate how an endodontic access opening prepared through an all-ceramic crown altered the structural integrity of the ceramic, and the effect of a repair of this access on the load to failure of an all-ceramic crown. Material and methods: Twenty-four alumina (Procera) and 24 zirconia (Procera) crowns were fabricated and cemented (Rely X Luting Plus Cement) onto duplicate epoxy resin dies. Twelve crowns of each were accessed to simulate root canal treatment therapy. Surface defects of all accessed specimens were evaluated with an environmental scanning electron microscope. The specimens were repaired with a porcelain repair system (standard adhesive resin/composite resin protocol) and were loaded to failure in a universal testing machine. Observations made visually and microscopically noted veneer delamination from the core, core fracture, shear within the veneer porcelain, or a combination thereof. A Kruskal-Wallis test was used to determine if a significant difference (α=.05) in load to failure existed between the 4 groups, and a Mann-Whitney test with a Bonferroni correction (P<.0125) was used for multiple comparisons. A Weibull analysis was also used to estimate the Weibull modulus and characteristic failure for each group. Results: All specimens exhibited edge chipping around the access openings. Some displayed larger chips within the veneering porcelain, and 4 zirconia crowns showed radial crack formation. There was a significant difference in load to failure among all groups with the exception of the alumina intact and repaired specimens (P=.695). The alumina crowns generally showed fracture of the coping with the veneering porcelain still bonded to the core, whereas the zirconia copings tended not to fracture but experienced veneering porcelain delamination. Conclusion: Endodontic access through all-ceramic crowns resulted in a significant loss of strength in the zirconia specimens but not in the alumina specimens. [Copyright &y& Elsevier]

Statement of the Problem: With the introduction of newer dental porcelains, there exists the need to evaluate different porcelain polishing systems available on the market., Purpose: The purpose of this study was to compare the surface roughness produced by 3 different porcelain polishing systems on an ultra-low fusing porcelain., Material and Methods: Sixty-three ultra-low fusing porcelain (Finesse) discs (10 x 2 mm) were fabricated and randomly divided into 3 groups (n=21). Both sides of each disc were abraded with a medium-grit diamond bur. One side was autoglazed and was considered a control. The other side was polished until the surface appeared shiny to the naked eye using 1 of 3 porcelain polishing kits (Axis Dental, Jelenko, and Brasseler systems). The surface of each disc was evaluated quantitatively with surface profilometry and qualitatively using scanning electron microscopy (SEM). A mean roughness profile (Ra) value was determined for each side of each specimen to describe the overall roughness of the surface. The Ra mean difference for each specimen was determined by subtracting the mean experimental readings (polished surface) from the mean control readings (glazed surface) and was used for the statistical analysis. The data were analyzed using analysis of variance followed by a Tukey multiple comparison test (alpha=.05). Representative specimens from each group were evaluated by scanning electron microscopy., Results: The Axis porcelain polishing system produced a smoother surface than the Brasseler or Jelenko systems (0.586 +/- 0.256, 0.306 +/- 0.238, and 0.277 +/- 0.230, respectively). No significant difference was found between the Jelenko and Brasseler porcelain polishing kits (F=10.6, P <.001). The images obtained through SEM were evaluated and found to be consistent with the profilometer readings., Conclusion: Within the limitations of this study, all 3 porcelain polishing systems produced a surface smoother than the autoglazed surface of Finesse. The Axis system provided a significantly smoother surface compared to the Brasseler and Jelenko polishing systems.

Statement of Problem: The effect of repeated applications of fluoride solutions and 10% carbamide peroxide on the surface roughness of newer dental porcelains is not completely known., Purpose: The purpose of this study was to compare the surface roughness of 3 different porcelains when exposed to 2 fluoride solutions, a 10% solution of carbamide peroxide, and distilled water., Material and Methods: Forty discs (10-mm diameter, 2 mm thick) were made of each of the following porcelains: feldspathic porcelain (Ceramco II), low-fusing porcelain (Finesse), and an aluminous porcelain (All-Ceram). Each disc was abraded with a medium-grit diamond bur and auto-glazed. One side of each disc was abraded with a diamond bur and polished using a porcelain polishing kit to simulate a chairside adjustment and polishing. The discs (10 specimens/group) were immersed in 1.23% APF, 0.4% stannous fluoride, 10% carbamide peroxide, and distilled water for 50 seconds (control). The discs in the 10% carbamide peroxide solution were immersed for 48 hours. The surface of each disc was evaluated with surface profilometry (0.1 mm/s speed, 600-microm range). The data were analyzed by factorial analysis of variance and a Tukey multiple comparison test, (alpha=.05)., Results: The data showed that the acidulated phosphate fluoride etched the auto-glazed surface of all 3 porcelains. For Finesse specimens, the mean Ra values for the auto-glazed surface were significantly higher than that of the control after immersion in 1.23% APF (mean Ra 0.3 +/- 0.06 microm, P<.031). All-Ceram auto-glazed surface specimens had a significantly higher mean Ra value when immersed in the 3 solutions than the control (1.23% APF, 0.4% stannous fluoride, and 10% carbamide peroxide, 0.245 +/- 0.115 microm, 0.22 +/- 0.104 microm, 0.22 +/- 0.04 microm, respectively; P<.002). Ceramco II specimens were affected by all 3 solutions, with the auto-glazed surface having higher Ra values (1.23% APF, 0.4% stannous fluoride, and 10% carbamide peroxide, with mean Ra values of 0.35 +/- 0.1 microm, 0.26 +/- 0.08 microm, and 0.24 +/-.0.05 microm, respectively, P=.001). Immersion in the 3 solutions had no effect on the polished surfaces of all-ceramic specimens tested., Conclusion: Prior to the use of fluoride and 10% carbamide peroxide, dentists should ascertain the type of porcelain restoration present to prevent a roughened surface from occurring.