Effects of 16% Carbamide Peroxide on Optical Properties of Thermally Aged Monolithic CAD-CAM Glass Ceramics with Different Surface Treatments.

This study aimed to investigate the effects of 16% carbamide peroxide (CP) on the relative translucency parameter (RTP) and color stability of thermally aged CAD-CAM glass-ceramics with glazing or polishing. Three different CAD-CAM blocks-feldspathic (VM), lithium disilicate (IPS), and zirconia-reinforced lithium silicate ceramic (VS)-were used in this study. The specimens were divided into two groups (n=10) according to surface treatments (glazing or polishing). Bleaching treatment with 16% CP was applied to the thermally aged specimens. A spectrophotometer (VITA Easyshade Advance) was used to measure the CIE L*a*b*coordinates of the specimens on white and black backgrounds, and RTP and color difference (ΔE00) values were calculated. The surface topography of the specimens and the atomic weight of the elements were analyzed with scanning electron microscopy and energy-dispersive x-ray. The data were analyzed by using the two-way ANOVA test for ΔE00 values and two-way repeated measures ANOVA test for RTP and color parameters values (a=0.05) and the Tukey post-hoc test was used for multiple comparisons of the groups. RTP values were statistically influenced by material type, bleaching, and finishing technique, and the interaction among these factors was found to be significant (p<0.05). ΔE00 values were statistically influenced by material type, finishing technique, and the interaction among these factors was also found to be significant (p<0.05). IPS presented significantly lower RTP and ΔE00 values for both glazed and polished surfaces (p<0.05). 16% CP bleaching agent caused changes in translucency of aged VM and IPS at different levels. Glazed surfaces presented higher color stability in comparison to mechanically polished surfaces for VS (p<0.05).

Screw stability of CAD-CAM titanium and zirconia abutments on different implants: An in vitro study.

BACKGROUND: Limited information is available regarding the removal torque values (RTVs) of screws of different abutment materials when used with different implants. PURPOSE: To evaluate the effect of implant type and abutment material (zirconia; Zir and titanium; Ti) on the RTVs of abutment screws after cyclic loading. MATERIALS AND METHODS: Internal conical connection implants (CC, OsseoSpeed TX) and modified internal conical connection implants (MCC, OsseoSpeed EV) (n = 10) were clamped in resin dies. Zir and Ti (N = 20) custom abutments were tightened to implants (20 Ncm for CC and 25 Ncm for MCC) as specified by their manufacturers. The abutments were cyclically loaded by using a sequentially increased loading protocol; 2-million cycles under 100 N, 3-million cycles under 200 N, and 2-million cycles under 300 N loads with 2 Hz. After 7 million cycles, RTVs (Ncm) were measured by using a torque gauge. The data were analyzed with ANOVA by using the restricted maximum likelihood estimation method. Tukey-Kramer adjustment was used for any significant interaction of implant-abutment pairs (α = 0.05). RESULTS: Two CC implants, 1 with Ti and 1 with Zir abutment, fractured during cyclic loading (under 300 N loads within the 6th and 7th million cycles) and discarded for statistical analysis. Only implant type had a significant effect on RTVs (p <0.001). Screws of Ti abutments on MCC implants had significantly higher RTVs than the screws of Ti (p = 0.003) and Zir (p = 0.005) abutments on CC implants. CONCLUSIONS: Implant type affected the RTVs, however, the RTVs were higher than the initial torque values for all groups. Screws of Ti abutments on implant, which required greater initial torque values had higher RTVs than the screws of Ti and Zir abutments on the implant that required smaller initial torque values. RTVs were similar for Zir and Ti abutment screws within each implant type.

Effect of Crown Height on the Screw Stability of Titanium Screw-Retained Crowns.

PURPOSE: The aim of this in vitro study was to evaluate the effect of crown height on the screw stability of screw-retained titanium implant crowns subjected to cyclic loading conditions. MATERIALS AND METHODS: Twenty-one implants with internal hex connections were placed in epoxy resin holders. Mandibular first molar screw-retained titanium implant crowns with UCLA type, crown-abutment connections were CAD/CAM fabricated. Seven crowns of 3 different heights (6 mm, 10 mm, and 14 mm) were made. The crowns were seated onto the implants and screws were tightened to 30 Ncm. The implants were clamped into holders and stepwise cyclic loads were applied to the occlusal surface at 30-degree angles to the long axes of the crowns. The detorque values were measured after each 5 million cycles. Before increasing the applied load, the crowns were secured with new screws and tightened to 30 Ncm. Failure times, survival estimates and detorque values were then analyzed. (alpha = 0.05). RESULTS: Crown height did not significantly affect detorque values. However, five 14-mm crowns failed with varying fractures during the 475 N loading condition. Overall, a significantly lower survival for 14 mm crowns was found compared to 6 mm and 10 mm crowns (p = 0.004). CONCLUSIONS: Crown heights of one-piece screw-retained titanium implant crowns did not significantly affect detorque values. Screw fracture, however, was greater for crown height of 14 mm than those of 6 mm and 10 mm.

Surface roughness of high-performance polymers used for fixed implant-supported prostheses.

STATEMENT OF PROBLEM: High-performance polymers have been recommended by their manufacturers as a framework material for implant-supported fixed prostheses. However, little is known about the surface roughness of high-performance polymers in different compositions and whether they require layering with a composite resin or acrylic resin on the tissue surface. PURPOSE: The purpose of this in vitro study was to evaluate the surface roughness of different computer-aided design and computer-aided manufacture (CAD-CAM) high-performance polymers and the effect of polishing on their surface roughness. MATERIAL AND METHODS: Seventy high-performance polymer specimens (n=10) for 4 different polyetheretherketone (PEEK) brands (BRE, CP, ZZ, J), 1 polyetherketoneketone (PEKK) (PK), and 2 different fiber-reinforced composite resin (FRC) materials (T, TR) were milled from 7×8×30-mm CAD-CAM blocks. The surface roughness (Ra) of each specimen was measured on the same surfaces after milling (baseline) and after polishing by using a contact profilometer. Two-way repeated measures ANOVA (MIXED procedure) and the Bonferroni corrected t test (α=.05) were used to analyze the surface roughness data. RESULTS: No significant differences were found among high-performance polymers when the baseline surface roughness measurements of the materials were compared (P>.05). All materials (BRE, PK, CP, T, TR, ZZ), except for a PEEK material (J) (P<.05), had no significant differences in their surface roughness before and after polishing. After polishing, the surface roughness of the J PEEK material was higher than that of CP, PK, T, and ZZ (P<.05). CONCLUSIONS: The surface roughness of high-performance polymers in different compositions after milling was similar. Polishing increased the surface roughness of only one PEEK (J) material. All surface roughness values were above the clinical acceptability threshold of 0.2 µm.

Load to failure of high-density polymers for implant-supported fixed, cantilevered prostheses with titanium bases.

PURPOSE: To analyze the load to failure of different CAD/CAM high-density polymers (HDPs) and zirconia when titanium (Ti) bases were included in a cantilevered situation. MATERIALS AND METHODS: Five specimens were fabricated from five different CAD/CAM polymethyl methacrylate (PMMA) HDPs (Copratemp [CT]; Tempo-CAD [TC]; TD Dental [TD]; M-PM Disc-Pink [MPM]; M-PM Disc-White [MPMW]), and five specimens were prepared from a 3Y-TZP zirconia (FireZr [FZR]) (control). Ti bases (D Master Dental Implants) were cemented onto the specimens (8 mm [thickness] × 7 mm [width] × 30 mm [length]). Each specimen was fixated using a clamp for a cantilever loading distance of 10 mm. The load was applied on the cantilever until failure, and the maximum load to failure values (N) were analyzed by using analysis of variance (GLIMMIX procedure) with a lognormal error distribution in addition to the restricted maximum likelihood estimation method to eliminate the need for equality of variances and Tukey Honest Significant Difference (α = .05). RESULTS: Differences among load-to-failure values of HDPs were not significant (P > .05). However, zirconia had significantly higher load-to-failure values than HDPs (P < .001). The behavior of HDPs and zirconia under loading was different in terms of displacement. HDPs showed weaker but more ductile behavior than zirconia, which is stronger, but more brittle. CONCLUSION: Tested brands of HDPs performed similarly under loading. Zirconia with a Ti base showed higher strength compared to all tested HDPs with a Ti base. The loads that fractured the specimens with Ti bases were close to the maximum occlusal bite forces recorded in previous clinical studies.

Fabrication of a 3-dimensionally printed definitive cast for an obturator prosthesis by merging intraoral scan image with cone beam computed tomography data: A clinical report.

This clinical report focuses on the production of a 3-dimensionally printed definitive cast by using digital scans to fabricate an obturator prosthesis for a completely edentulous patient with a maxillary defect. A merged intraoral scanner image of the soft tissue anatomy of maxillary structures with volumetric data of the craniofacial hard and soft tissues obtained from a cone beam computed tomography scan was used to generate a virtual cast, producing the polyurethane definitive cast manufactured by using a 3-dimensional printer.

Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans.

STATEMENT OF PROBLEM: Information regarding the effect of the height and position of a coded healing abutment (CHA) on the trueness of intraoral digital scans is lacking. PURPOSE: The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness (distance and angular deviations) of intraoral digital scans. MATERIAL AND METHODS: Scannable CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs (3 mm and 8 mm) on 2 implants at mandibular left second and first molar positions. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator to generate a total of 20 intraoral scan files. Master standard tessellation language (STL) files were created for both 3-mm and 8-mm CHA pairs by using a structured blue light scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS). These master STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Scans obtained by using the intraoral scanner were aligned to the reference scan by using a best-fit alignment to measure the distance and angular deviations. Two-way repeated-measures ANOVA was used to analyze the data, and the Tukey-Kramer test was used to determine significant differences among groups (α=.05). RESULTS: The CHA position had a significant effect on distance deviation (P<.001). However, no significant effect of CHA height on distance deviation was found. The interaction between CHA height and position had a significant effect on the angular deviation (P=.041). The 3-mm posterior CHA (P=.026) and 8-mm anterior CHA (P=.039) had significantly lower angular deviations than the 8-mm posterior CHA. CONCLUSIONS: The distance deviation of CHA was significantly influenced by position. CHAs in the anterior had lower distance deviations for both 3 mm and 8 mm. The effect of CHA height on distance deviation was found to be small and was affected by the location of the CHA. Height affected angular deviation depending on the position of the CHA. Both 3-mm posterior and 8-mm anterior CHAs showed lower angular deviations than the 8-mm posterior CHA.

Comparative analysis of denture base adaptation performance between pour and other conventional fabrication techniques.

STATEMENT OF PROBLEM: Studies assessing the comparative denture base adaptation performance of the pour technique for various palatal vault depths are sparse. PURPOSE: The purpose of this in vitro study was to investigate the denture base adaptation performance of the pour technique compared with other conventional fabrication techniques (light-polymerization, injection, compression molding) for shallow and deep palatal vault depths. MATERIAL AND METHODS: Edentulous maxillary study models with 2 palatal vault depths were prepared. Based on the power analysis, the sample size of each conventional fabrication technique was 12 (N=96). After denture bases for each technique had been fabricated on the casts according to the manufacturers' recommendations, the casts and the intaglio surfaces of the denture bases were scanned by using a laboratory scanner (InEos X5). The standard tessellation language (STL) files of the casts and the intaglio surfaces of acrylic resin bases were transferred into a software program (Romexis, version 5.0), and the software superimposed each cast and its corresponding denture base scan with the reference pyramids semi-automatically. After superimposition, the mean gap distances (mm) were calculated by using the software and recorded from the identified 4 specific regions (denture border apex, palate, ridge crest, and posterior palatal seal). A statistical analysis was performed by using the 3-factor factorial ANOVA. Post hoc comparisons among the subgroups were performed by using the Tukey HSD test. RESULTS: Two- and 3-way interactions among palatal vault depth, polymerization technique, and location variables were statistically significant (P<.05). For shallow palatal vault depth, injection and pour polymerization techniques demonstrated similar mean gap distances irrespective of location (P>.05). The light-polymerization technique showed the highest mean gap distances among the tested polymerization techniques in all regions except for the posterior palatal seal area (P<.05). CONCLUSIONS: The pour technique showed similar denture base adaptation to compression molding and injection. Light-polymerization exhibited the highest mean gap distance between the denture base and the cast for both palatal vault depths for most of the locations. A deep palatal vault depth led to inferior denture base adaptation performance for light-polymerization in the ridge crest and compression molding in the posterior palatal seal location.

Failure analysis of high performance polymers and new generation cubic zirconia used for implant-supported fixed, cantilevered prostheses.

BACKGROUND: The load-to-failure performance of computer-assisted design and computer-assisted manufacturing (CAD-CAM) high performance polymers (HPP) and new generation cubic zirconia (Zir) material when used with titanium (Ti) bases for implant-supported fixed prostheses with cantilevers is unknown. PURPOSE: To evaluate the load-to-failure performance of different CAD-CAM fabricated HPP and a new generation cubic Zir in a cantilevered situation when used with Ti bases. MATERIALS AND METHODS: Five specimens with a Ti base and five specimens without Ti bases were fabricated from seven different CAD-CAM HPPs (100% PEEK [J and CP], 80% PEEK with 20% filler [BRE], 80% PEKK with 20% filler [PK], ceramic reinforced PEEK [ZZ], interlaced fiberglass and resin [TR], fiber-composite material [T]). Five specimens with Ti base and two specimens without Ti base were prepared from a new generation cubic Zir (DD) and a 3Y-TZP Zir (FZR) as the control group (N = 84). All specimens (8 × 7 × 30 mm) were stabilized using a clamp attached to the first 20 mm of each specimen for a 10 mm cantilever. Static loading was applied vertically on the cantilever and the maximum load-to-failure values (N) were analyzed using a two-way ANOVA and t-test (alpha = .05). RESULTS: HPP and Zir specimens without Ti bases had significantly higher load-to-failure values than Ti based ones in all groups (P < .05). PK with Ti base had significantly lower load-to-failure values than other materials (P < .001). FZR showed significantly higher load-to-failure values than all HPPs and DD (P < .001). CONCLUSIONS: Load-to-failure values of HPPs and Zir were lower when Ti bases were used. New generation cubic Zir and all HPPs had lower load-to-failure values than FZR. HPPs performance varied among tested materials. PEKK with Ti base had the lowest load-to-failure value.