Publications by authors named "Burak Yilmaz"

170 Publications

Effect of crown height on the screw joint stability of zirconia screw-retained crowns.

J Prosthet Dent 2021 Apr 8. Epub 2021 Apr 8.

Professor, Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio.

Statement Of Problem: Medium- to long-term data for the performance of zirconia crowns with titanium (Ti) bases are sparse, particularly when the crown height space and occlusal loads are high.

Purpose: The purpose of this in vitro study was to assess the effect of the height of zirconia screw-retained implant crowns with a Ti base on the screw joint stability after cyclic loading. A secondary aim was to investigate the survival of zirconia crowns of different heights after cyclic loading.

Material And Methods: Twenty-one internal connection implants were secured between fiberglass-reinforced epoxy resin sleeves. Mandibular first molar monolithic zirconia crowns with 3 different heights (6 mm, 10 mm, and 14 mm) were milled and bonded to the Ti bases (n=7). The screws were tightened to 30 Ncm, and a 30-degree 120-N cyclic load was applied to the crowns at 2 Hz for 5 million cycles. After 5 million cycles, the crowns were evaluated for stability, and the same protocol was repeated for 275-N and 435-N loads for 5 million cycles each. After loading, the detorque values were recorded. Failure was characterized based on whether the crown, screw, and/or implant fracture was observed. The detorque values were analyzed by using a 1-way-ANOVA with the restricted maximum likelihood estimation. The percentage of torque loss was calculated. The LIFETEST procedure was used to analyze the survival probability of the groups (α=.05).

Results: The effect of crown height on the detorque values of screws was not found to be statistically significant (P>.05). The mean detorque value for 6-mm crowns was 23.5 Ncm, 24.4 Ncm for 10-mm crowns, and 22.1 Ncm for 14-mm crowns. A significant effect of crown height was found on the survival (P=.006), and the time-to-failure survival of 14-mm crowns was significantly lower than the survival of 6 mm and 10 mm crowns (P=.020), where no failures were observed. Four 14-mm crowns failed between the 1 and 2 million cycles after the loads were increased to 435 N. The failure modes were the same for all the crowns, implants, and screws fractured.

Conclusions: When the tested internal connection implant was used, the crown height did not affect the detorque values, and 14-mm crowns performed similarly to the shorter crowns in terms of torque loss after cyclic loading. However, survival of the 14-mm crown-implant complex was lower, resulting in screw and implant fractures.
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http://dx.doi.org/10.1016/j.prosdent.2021.02.027DOI Listing
April 2021

Effect of guide sleeve material, region, diameter, and number of times drills were used on the material loss from sleeves and drills used for surgical guides: An in vitro study.

J Prosthet Dent 2021 Apr 5. Epub 2021 Apr 5.

Associate Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio.

Statement Of Problem: How material loss from sleeves and drills is affected when different guide sleeve materials and different sizes of implant drills are used for different regions of surgical guides is unclear.

Purpose: The purpose of this in vitro study was to compare the amount of material loss from different guide sleeves (zirconia and cobalt-chromium) and drills of different diameters during osteotomy preparation in different regions.

Material And Methods: Three tooth-supported surgical guides with sleeve holes positioned in the first premolar and second molar sites were prepared. Guide sleeves (Ø 2.20 mm, 3.40 mm, and 4.05 mm) were milled from zirconia (n=60) and cobalt-chromium (n=60) blocks. A total of 12 titanium nitride-coated stainless steel twisted drills (n=6 per sleeve material) of different diameters (Ø 2.00, 3.20, 3.85 mm) were used with corresponding sleeves during the drilling. The weight loss from the drills and the volume loss from the guide sleeves after drilling were analyzed by using multiple linear mixed effect models (α=.05).

Results: According to the 4-way ANOVA for volume loss from sleeves, no significant interaction was found among the 4 main effects (number of times a drill was used, region, diameter, and material), but interactions between the number of times a drill was used and diameter (P=.001) and between the number of times the drill was used and material were significant (P<.001). For weight loss from the drills, a significant interaction was detected between the number of times the drill was used and diameter (P=.024).

Conclusions: Less sleeve material was lost when zirconia sleeves were used. All sleeves had more material loss in the molar region than in the premolar region. The diameter had varying effects on the amount of material loss from drills and sleeves. The sleeve material and the region did not affect the material loss from drills.
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http://dx.doi.org/10.1016/j.prosdent.2020.12.036DOI Listing
April 2021

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

J Prosthodont 2021 Mar 5. Epub 2021 Mar 5.

Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, OH, USA.

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.
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http://dx.doi.org/10.1111/jopr.13352DOI Listing
March 2021

Effect of thermocycling on the surface properties of resin-matrix CAD-CAM ceramics after different surface treatments.

J Mech Behav Biomed Mater 2021 05 18;117:104401. Epub 2021 Feb 18.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Division of Restorative and Prosthetic Dentistry, The Ohio State University, Ohio, USA.

Purpose: To evaluate the effect of thermocycling on the water contact angle (WCA), surface roughness (SR), and microhardness (MH) of resin-matrix computer-assisted design and computer-assisted manufacturing (CAD-CAM) ceramics after different surface treatments (conventional polishing or 2 different surface sealants).

Material And Methods: Two different types of resin-matrix CAD-CAM ceramics; a nanoparticle-filled resin (CeraSmart; CS) and a resin nanoceramic (Lava Ultimate; LU) were tested. Rectangular-shaped plates (1 mm-thick) were divided into 3 groups (n = 8) in terms of surface treatment methods applied: conventional polishing (control) or 2 surface sealants (Optiglaze (OG) and Palaseal (PS)). Scanning electron microscope images ( × 1000 and × 700 magnifications) of each material were taken from 2 additional specimens before surface treatments. After surface treatments, WCAs of deionized water, SR, and MH values of specimens were measured. All specimens were subjected to 5000 thermocycling and measurements were repeated. SR, WCA, and MH data before and after thermocycling were compared by using a 2-way ANOVA (α=.05).

Results: A significant interaction was found between the surface treatment and the material for WCA after thermocycling (P < .001), for SR before thermocycling (P = .014), and for MH both before and after thermocycling (P < .001). SEM images before surface treatments revealed that the surface of CS was mechanically rougher with a more microretentive topography compared with the surface of LU. No significant correlation was found between SR and WCA (P > 0.05).

Conclusions: Thermocycling affected the SR, MH, and WCA of all resin-matrix CAD-CAM ceramics.
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http://dx.doi.org/10.1016/j.jmbbm.2021.104401DOI Listing
May 2021

Influence of cyclic loading on load-to-failure of different ceramic CAD-CAM implant-supported single crowns.

Int J Prosthodont 2021 Feb 26. Epub 2021 Feb 26.

Purpose: To compare the load to failure values of different ceramic CAD/CAM implant crown materials with drilled screw access holes with and without cyclic loading applied.

Materials And Methods: Forty zirconia abutments with a titanium base were pre-loaded onto implants to support maxillary right first premolar crowns that were milled from four different CAD/CAM ceramic materials (zirconia reinforced lithium silicate, hybrid ceramic, lithium disilicate, and zirconia; n = 10 each). After cementing the crowns, screw access channels were prepared by drilling through occlusal surfaces. Half of the specimens were subjected to cyclic loading for 5 million cycles at 2 Hz (n = 5/material). After cyclic loading, vertical loads were applied to failure, and the load to failure values of all crowns were recorded and statistically analyzed. Two-way analysis of variance was used with restricted maximum likelihood estimation and Tukey-Kramer adjustments (α = .05).

Results: During cyclic loading, the zirconia abutment in one lithium disilicate specimen cracked at 2 million cycles, as well as a zirconia-reinforced lithium silicate crown. Results for the load to failure test series showed statistical differences between the materials. Zirconia resulted in significantly higher failure loads when compared to the other materials (P < .001). Cyclic loading did not significantly affect the load to failure values.

Conclusion: Cyclic loading did not significantly influence the load to failure of any of the materials tested. Zirconia crowns with drilled screw access channels cemented on zirconia abutments with a titanium base had higher load to failure values compared to the other ceramic crown materials.
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http://dx.doi.org/10.11607/ijp.6510DOI Listing
February 2021

The effect of scanned area on the accuracy and time of anterior single implant scans: An in vitro study.

J Dent 2021 Feb 26:103620. Epub 2021 Feb 26.

Department of Reconstructive Dentistry and Gerodontology, University of Bern, Freiburgstrasse 7, 3007 Bern, Switzerland. Electronic address:

Objectives: To investigate the effect of scanned area on the accuracy and scan time of intraoral scans of an anterior implant.

Materials And Methods: Three operators experienced in intraoral scanning (at least 2-year experience) performed partial and complete-arch scans (n = 10) of a dentate resin model with an implant at left central incisor site by using an intraoral scanner (Trios3; 3Shape, Copenhagen, Denmark). Each partial- or complete-arch scan was superimposed to a reference scan from a laboratory scanner (Ceramill Map 600; Amann Girrbach AG). Mean distance (selected 7 points) and angular (mesiodistal and buccolingual) scanbody deviations in test scans (trueness) and their variance (precision) were calculated. Linear-regressions (trueness), two-sided F-tests with a Bonferroni correction (precision), and multiple linear regressions (scan time), with the operator as a covariate were applied (alpha = .05).

Results: Interactions were found between the scanned area and the operator for their effect on trueness of all points and angles, except for point 6 at implant-abutment connection in mesiodistal plane (p < .05). No significant difference was found between the precision of partial and complete-arch scans for all operators (p > .05). Partial-arch scan times were significantly shorter, overall, and for each operator (p < .001). No significant effect of scan time was found on the trueness of partial- and complete-arch scans (p > .05).

Conclusions: Partial and complete-arch scans of anterior single implants with an intraoral scanner resulted in similar accuracies, and were not influenced by the operator or the scan time. Scan times of partial-arch scans were significantly shorter.

Clinical Significance: Partial-arch scans can be used for the fabrication of monolithic anterior single implant crowns because the scans can be completed in shorter times without compromising the accuracy.
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http://dx.doi.org/10.1016/j.jdent.2021.103620DOI Listing
February 2021

Effects of sintering time on translucency and color of translucent zirconia ceramics.

J Esthet Restor Dent 2021 Feb 27. Epub 2021 Feb 27.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objective: To investigate the effect of sintering time on translucency and color of translucent zirconia ceramics.

Materials And Methods: Sixty translucent zirconia (5Y-TZP) specimens (12 × 1.6 mm, Katana (KAT) and NexxZr (NEX)) were divided into six groups (n = 10) according to sintering time; 1, 2 (specified by manufacturer-control), and 3 hs. Color differences (ΔEab) within same material when sintered using different times and between materials when same sintering time was used were calculated, as well as translucency parameters (TP) after the use of each sintering time. Data for ΔEab and TP were analyzed with two-way ANOVAs, pairwise comparisons, and Fisher's LSD Test (Post-hoc).

Results: When 1 or 3 h were used, color difference from the color of specimens when manufacturer-specified time (2 h) was used was similar for both KAT and NEX. ΔEab values of NEX were significantly higher than KAT when sintered for 1 or 3 h (P < 0.001). TP increased for KAT when sintered for 1 h, and was higher than NEX. TP for NEX increased when sintered for 3 h (P < 0.001), but was not significantly different than that of KAT.

Conclusions: Effect of 1 or 3-h sintering on color was similar for both zirconias. For NEX, this effect resulted in greater differences from the color of specimens when manufacturer-specified time was used. Sintering for 1 h increased the translucency of KAT.

Clinical Significance: When high translucency is desired, clinicians may prefer 1-h sintering for KAT zirconia. When lower translucency is desired, 3-h sintering for NEX can be used. However, for NEX, the color after 1- or 3-h sintering was different than the color obtained with manufacturer-specified time, and this difference may affect the final color of restoration compared to the final color when manufacturer-specified time is used.
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http://dx.doi.org/10.1111/jerd.12723DOI Listing
February 2021

Management of a partially edentulous patient with idiopathic root resorption by using digital and conventional implant planning technologies.

J Prosthet Dent 2021 Feb 23. Epub 2021 Feb 23.

Senior Lecturer, Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address:

This clinical report describes the rehabilitation of the maxillary arch of a partially edentulous patient with idiopathic root resorption, limited interarch distance, and a high smile line. Four implants were placed to provide a screw-retained fixed partial denture. The esthetic and functional challenges of a high smile line and limited interarch distance were addressed by using a combination of conventional and digital implant treatment technologies.
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http://dx.doi.org/10.1016/j.prosdent.2021.01.011DOI Listing
February 2021

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

Int J Prosthodont 2021 Feb 19. Epub 2021 Feb 19.

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.
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http://dx.doi.org/10.11607/ijp.7036DOI Listing
February 2021

Effect of cyclic loading on reverse torque values of angled screw channel systems.

J Prosthet Dent 2021 Feb 19. Epub 2021 Feb 19.

Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio; Associate Professor, Department of Reconstructive Dentistry and Gerodontology, University of Bern, School of Dental Medicine, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive, and Pediatric Dentistry, University of Bern, School of Dental Medicine, Bern, Switzerland.

Statement Of Problem: The angled screw channel concept has become popular. However, research is lacking as to how reverse torque values of nonaxially tightened implant crowns compare with axially tightened cement-retained crowns restored on angle-correcting abutments when subjected to long-term cyclic loading.

Purpose: The purpose of this in vitro study was to evaluate the ability of different 25-degree angled screw channel hexalobular systems to apply the target torque value on their screws, the effect of cyclic loading on their reverse torque values, and their survival compared with crowns cemented on conventional 0-degree screw channel abutments.

Material And Methods: A total of 28 implants were divided into 4 groups. Twenty-one angled screw channel crowns were fabricated at a 25-degree angle correction by using angled titanium (Ti) bases by 3 manufacturers DY (Dynamic Tibase), DE (AngleBase), and ASC (Angulated Screw Channel) (n=7). The fourth group, UB (Universal Base, Control), had cement-retained crowns with 25-degree custom-milled, angled zirconia abutments that were cemented onto their respective Ti bases (n=7). All implants were embedded in epoxy resin blocks and tightened to manufacturer recommended values: 35 Ncm for ASC, UB, and DE and 25 Ncm for DY. Initial torque values (ITV1) were recorded. After 24 hours, the reverse torque values (24hr-RTV1) were recorded. A new set of screws was then used for each group, and the initial torque values (ITV2) were recorded. Specimens were loaded at 2 Hz for 5 million cycles under a 200-N load, and reverse torque values (RTV2) were recorded. ANOVA (α=.05) was used to compare differences in the means of deviation of initial torque values and means of reverse torque values followed by a Tukey-Kramer post hoc analysis (α=.05). Preload efficiency was calculated for each system (RTV2/ITV2), and a survival analysis was performed by using the Lifetest procedure.

Results: A significant difference in the means of deviation of initial torque values of the groups with 25-degree torque application (DY, DE, and ASC) was found when compared with UB at 0 degrees. ASC and DE had lower initial torque values than UB (P<.001 and P=.003 for ASC ITV1 and ITV2, P<.001 and P=.006 for DE ITV1 and ITV2). A significant difference was found in mean reverse torque values both for after 24 hours and after cyclic loading among all groups (P<.001). A significant difference was found between mean reverse torque values before and after cyclic loading for each group (P<.001). Preload efficiency was 43.8% for DY, 46.8% for DE, 54.2% for ASC, and 48.5% for UB. No significant difference was found in the time-to-failure survival among groups (P>.05).

Conclusions: The hexalobular system of DY delivered comparable initial torque values to its target value at 25 degrees, similar to how UB (control group) delivered at 0 degrees. ASC and DE scored lower initial torque values than their target value compared with UB. The DY abutment, which had a lower manufacturer recommended torque value, had lower reverse torque values compared with those of other groups. Time-to-failure survival of all groups was similar. Fractures at the zirconia to titanium base connection were seen with ASC crowns.
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http://dx.doi.org/10.1016/j.prosdent.2020.12.020DOI Listing
February 2021

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

J Prosthet Dent 2021 Feb 11. Epub 2021 Feb 11.

Associate Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University, Columbus, Ohio. Electronic address:

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.
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http://dx.doi.org/10.1016/j.prosdent.2020.11.029DOI Listing
February 2021

Effect of mouth rinses on optical properties of CAD-CAM materials used for laminate veneers and crowns.

J Esthet Restor Dent 2021 Feb 10. Epub 2021 Feb 10.

Departments of Reconstructive Dentistry and Gerodontology, and Restorative, Preventive, and Pediatric Dentistry, University of Bern School of Dental Medicine, Bern, Switzerland.

Objective: The purpose of this study was to investigate the effect of mouth rinses on the color and translucency of three computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials in laminate veneer and crown thicknesses.

Methods: Specimens from two different 5Y-TZP zirconia (InCoris TZI (IT), and Zirkonzahn (ZH)) and lithium disilicate (IPS e.max CAD [IC]) in two different thicknesses (0.7 mm for laminate veneer, and 1.5 mm for crown) were sectioned. All specimens were colored with an A2-shade liquid, and the baseline color values were recorded according to the CIELab system with a spectrophotometer. Each group was divided into two subgroups (n = 15) according to the immersion solution: two different mouth rinses, KL (Klorhex), and LI (Listerine, cool mint) for 180 hours. The color coordinates (L*, a*, b*) of the specimens were measured before and after immersion in a mouth rinse, and TP and ΔE color differences were calculated by using the CIEDE2000 color difference formula. A 3-way ANOVA, Bonferroni test, and 1-sample t tests were used to analyze the data (α = 0.05).

Results: The 3-way ANOVA revealed a significant interaction of material, thickness, and mouth rinse for translucency parameter and color difference (ΔE ) data (p < 0.001). TP decreased for both zirconia materials in laminate veneer thickness when immersed in LI mouth rinse (p < 0.05). No difference was found among the TP mean values of three materials in crown thickness after immersed in mouth rinses (p > 0.826). Both zirconia materials immersed in LI showed greater discoloration than after immersed in KL (p < 0.05). A significant difference was found in color change values among three materials for the laminate veneer thickness after immersed in LI (p < 0.001). However, all color difference values were within the clinical acceptability threshold, except for when ZH in laminate veneer thickness was immersed in LI.

Conclusions: The color change of ZH zirconia with LI mouth rinse in laminate veneer thickness was high. For both zirconia ceramics, translucency decreased and the color was less stable in laminate veneer thickness after immersed in LI compared to the crown thickness.

Clinical Significance: The results of this in vitro study suggest that long-term use of alcohol-containing mouth rinse may alter the optical properties of tested CAD-CAM materials in tested laminate veneer thickness. For color stability with the long term use of tested mouth rinses, lithium disilicate may be preferred for both types of restorations.
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http://dx.doi.org/10.1111/jerd.12720DOI Listing
February 2021

Effect of Impression Technique and Operator Experience on Impression Time and Operator-Reported Outcomes.

J Prosthodont 2021 Feb 2. Epub 2021 Feb 2.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Purpose: To investigate the effect of impression technique (conventional preliminary alginate and digital scan) and operator experience in impression making (experienced in digital and conventional, experienced in conventional and inexperienced in digital, and inexperienced in conventional and digital) on impression time, satisfaction and stress levels, and the preference of the operators.

Material And Methods: One patient was assigned for each of the 60 operators, who were experienced in impression techniques at different levels (Group 1: experienced in conventional and digital, Group 2: experienced in conventional and inexperienced in digital, Group 3: inexperienced in conventional and digital). They made conventional impressions (irreversible hydrocolloid) and digital scans (Trios 3) from the same patient. The impression times were recorded at each step (patient registration, maxillary arch, mandibular arch, and bite registration) and in total. A visual analog scale (VAS) was used for the operator satisfaction for applicability, comfort, and hygiene; the State-Trait Anxiety Inventory form (STAI-TX1) was used for stress, and a questionnaire was completed to measure the operator's impression preference. The data were analyzed with a 2-way ANOVA and Chi-square test (α = 0.05).

Results: A significant interaction was found between the operator experience in impression making and the impression technique on time for maxillary and mandibular arch impressions and total time (p ≤ 0.002). Operator experience and impression technique interaction had a significant effect on comfort and average VAS scores (p ≤ 0.016). Whereas, no significant effect of this interaction was found on stress (p ≥ 0.195). Operator experience in impression making had a significant effect on applicability (p < 0.001), and the impression technique had a significant effect on hygiene VAS scores (p < 0.001). Operators in Group 1 and Group 3 preferred the digital scans, however, operators in Group 2 had no preference (p = 0.022).

Conclusion: Operator experience in impression making and impression technique had varying effects on clinician's impression time, comfort, applicability, hygiene, and preference. Operators needed less time for the impressions they were experienced with. Operator stress level was not affected by the operator experience in impression making and the impression technique. Dental students and operators experienced in both techniques were satisfied with the digital scans and they preferred digital scans. Operators experienced with conventional impressions were satisfied with conventional impressions but didn't have a preference for the impression type.
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http://dx.doi.org/10.1111/jopr.13340DOI Listing
February 2021

Use of a new skin colour measurement method for the investigation of relationship between skin and tooth colour.

Eur Oral Res 2020 May;54(2):81-85

Auxillary Faculty, The Ohio State University College of Dentistry, Section of Restorative and Prosthetic Dentistry, Columbus, Ohio,Usa.

Purpose: There is conflicting information about the relationship between tooth color and skin color in the literature. The aim of the present study was evaluation of the correlation between L, a, b values of skin and tooth shade using a new skin color measurement method.

Materials And Methods: CIELab values of teeth were obtained through measurements from the middle third of the labial surfaces on central incisors of individuals using a clinical spectrophotometer. CIELab values of the skin were measured through facial images using a software which was manufactured for present study. A statistical analysis program (SAS 9.4) was used for the analysis of the data. Kolmogorov-Smirnow test, t-test, and multivariate regression analysis were used to evaluate the data (α=0.05).

Results: Correlations between variables revealed that while the lowest and statistically insignificant correlations were observed with a* values of the skin, significant correlations did not exceed moderate level (p < .05). When considering regression analysis results, b* values of the skin had a statistically significant effect in describing b* values of the tooth, while L* and a* values of the skin were observed to be insufficient in describing L* and a* values of the teeth.

Conclusion: Results of this study suggest that different significant correlations were observed between the skin and tooth color for different L*, a*, and b parameters (p <0.05 and p <0.01). The results indicated that skin color can be used for tooth color selection in case of loss of natural teeth or when discoloration is present on existing teeth.
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http://dx.doi.org/10.26650/eor.20200090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7787519PMC
May 2020

Displacement and performance of abutments in narrow-diameter implants with different internal connections.

J Prosthet Dent 2021 Jan 4. Epub 2021 Jan 4.

Associate Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University, Columbus, Ohio. Electronic address:

Statement Of Problem: Displacement of abutments into conical connection implants during screw tightening may also occur during functional loading, creating unsettling forces that may cause loss of preload. A recent conical-hexagon connection with double friction fit (conical-hexagon connection) could prevent this axial displacement.

Purpose: The purpose of this in vitro study was to measure the 3D axial displacement of abutments with a conical-hexagon connection or conical connection in narrow-diameter implants. Removal torque values (RTVs), preload efficiency, and survival after cyclic loading were also compared.

Material And Methods: Narrow-diameter implants with a conical connection (Osseospeed EV, 3.0×13 mm-AST) and narrow-diameter implants with a conical-hexagon connection (Eztetic, 3.1×13 mm) were embedded in resin rods (G10) (n=6). Six titanium abutments per system were used, and their spatial relationship to the implant platforms after hand tightening was determined by using 3D digital image correlation. The abutments were tightened to the manufacturers' specified values, and the abutments' relative position was recorded again. The displacement of the abutment after tightening was calculated. The implants were subjected to cyclic loading (5×10 cycles at 2 Hz) under 200-N loads at a 30-degree angle. After cyclic loading, the RTVs of screws were measured and compared with those specified by the manufacturers to calculate preload efficiency. ANOVA was used to compare the differences in displacements after tightening and to compare differences in RTVs after cyclic loading across the groups (α=.05).

Results: The mean displacement in the U direction (X-axis) for the AST was -0.7 μm and -4.7 μm for ZIM, with no statistical difference (P=.73). The mean displacement in the V direction (Y-axis) for AST was -37.0 μm, and -150.0 μm for ZIM, with significant statistical difference (P<.001). The mean displacement in the W direction (Z-axis) for AST was -0.9 μm, and -23.0 μm for ZIM, with no statistical difference (P=.35). The survival of groups was similar (P=.058). During cyclic loading, 3 AST specimens fractured. After cyclic loading, mean RTV for AST was -8.77 Ncm, and -14.24 Ncm for ZIM, and these values were significantly different (P=.04). Preload efficiency was 28.1% for AST and 41.5% for ZIM.

Conclusions: Greater abutment displacements were observed with the conical-hexagon connection, which required a higher torque, as specified by its manufacturer. The abutments displaced more in the V-axis in both implants. Only the conical connection implant (Ti Grade 4, commercially pure) had failures during cyclic loading, but the survival of the implants was similar. After cyclic loading, the abutment screws in both systems lost some of their torque value. The abutment screws of the conical-hexagon connection implant maintained preload more efficiently during cyclic loading than those of the conical connection implant.
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http://dx.doi.org/10.1016/j.prosdent.2020.11.008DOI Listing
January 2021

From a CAD/CAM-milled, allogeneic bone block to an implant-supported fixed partial denture with angulated screw channel: a case report.

Quintessence Int 2021 ;52(1):56-63

Augmentation of alveolar ridge defects is a technique-sensitive procedure in dental implantology. Depending on the size of the defect, it may be necessary to use autogenous bone blocks. However, patients may be against these blocks as these procedures are surgically invasive.
Case report: This report describes the restoration of a partially edentulous mandible, which suffered a major bone defect from the right canine to the third molar site after multiple implant losses. The use of a CAD/CAM allogeneic cancellous bone block from a living donor bone was planned for the reconstruction of the alveolar ridge at the defected site. A CBCT scan was taken and the virtual planning of the bone augmentation and placement of four implants was performed. The milled bone block was fixed for augmentation and the implants were placed using a CBCT-generated surgical guide. After osseointegration, a CAD/CAM-fabricated screw-retained metal-ceramic implant fixed partial denture with angulated screw channels was delivered.
Results: The use of CAD/CAM-milled, allogeneic bone block resulted in a time-efficient and simplified reconstruction of the defect because no donor site was used, and the fit of the block on the native bone was uneventful and fast. At the 1-year follow-up, an average peri-implant vertical soft tissue decrease of 1 mm on buccal and 0.3 mm on lingual sites was observed and the peri-implant tissues were healthy.
Conclusions: The long-term success of this CAD/CAM cancellous bone block needs to be evaluated in well-designed clinical studies.

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http://dx.doi.org/10.3290/j.qi.a45431DOI Listing
January 2021

Response to Letter to the Editor regarding "Wolfart and Yilmaz: A technique for facilitating open-tray implant impressions. J Prosthet Dent 2019;122:417-9."

J Prosthet Dent 2020 12 15;124(6):820-821. Epub 2020 Oct 15.

Professor, Department of Prosthodontics and Biomaterials, Center for Implantology, University Hospital Aachen, RWTH Aachen, Aachen, Germany.

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http://dx.doi.org/10.1016/j.prosdent.2020.09.009DOI Listing
December 2020

Flexural strength of CAD-CAM and conventional interim resin materials with a surface sealant.

J Prosthet Dent 2020 Dec 3;124(6):800.e1-800.e7. Epub 2020 Oct 3.

Associate Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Associate Professor, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland; Adjunct Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University, Ohio.

Statement Of Problem: The flexural strength of computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional interim resin materials when they are used with a surface sealant is unclear.

Purpose: The purpose of this in vitro study was to evaluate the flexural strength of different CAD-CAM polymethyl methacrylate (PMMA)-based polymers and conventional interim resin materials, autopolymerized bisacrylate composite resin and polyethyl methacrylate (PEMA) with and without a surface sealant after thermocycling.

Material And Methods: Fourteen rectangular-shaped specimens (25×2×2 mm) were fabricated from 5 different interim resin materials, 3 different CAD-CAM PMMA-based polymers: Polident-PMMA, Telio CAD, M-PM-Disc; 2 different conventional interim resin materials, and 1 autopolymerized bisacrylate composite resin: Acyrtemp and 1 PEMA resin: Bosworth Trim according to ISO 10477:2018. Two different types of surface treatments (n=7), conventional polishing and surface sealant application, were applied to 1 surface of the specimens. Ten thousand thermocycles were applied in distilled water for all specimens (5 °C and 55 °C). A 3-point bend test was used to measure the flexural strength of specimens in a universal testing device at a 1 mm/min crosshead speed. The flexural strength data (σ) were calculated in megapascals (MPa) and analyzed by using a 2-way ANOVA. Post hoc pairwise comparisons and independent t test analysis were done (α=.05).

Results: According to the 2-way ANOVA, material type (P<.001) significantly affected the flexural strength. Surface treatment type (P=.818) had no significant effect on flexural strength, and no significant interaction was found between material type and surface treatment type (P=.111). CAD-CAM PMMA-based polymers had significantly higher flexural strength than the conventional interim resin materials. However, no significant difference was found within groups of the same type. Also, no significant difference was found in flexural strength values between the conventional polishing and surface sealant groups within each interim resin material (P≥.162).

Conclusions: The flexural strength of CAD-CAM PMMA-based polymers was higher than the flexural strength of conventional bisacrylate composite resin and PEMA interim resin materials after thermocycling. The surface treatment type (conventional polishing and surface sealant application) was not found to affect the flexural strength of CAD-CAM PMMA-based polymers, conventional bisacrylate composite resin, or PEMA interim resin materials.
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http://dx.doi.org/10.1016/j.prosdent.2020.09.004DOI Listing
December 2020

Automatic Digital Design of the Occlusal Anatomy of Monolithic Zirconia Crowns Compared to Dental Technicians' Digital Waxing: A Controlled Clinical Trial.

J Prosthodont 2021 Feb 13;30(2):104-110. Epub 2020 Oct 13.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Purpose: Reconstructing the occlusal morphology of posterior teeth in definitive dental prosthesis can be challenging. The use of the correlation technique enables replication of the information and occlusal anatomy of interim dental prostheses to the definitive ones. The purpose of this controlled clinical trial was to compare the static and dynamic contacts (SDC) of monolithic zirconia crowns designed with correlation and library techniques.

Material And Methods: Twenty-four patients were included in the study for a total of 28 molars. For each abutment tooth, an interim crown was fabricated and two digital scans, with and without the interim crown in place were made. Two single crowns were designed using correlation and library techniques. Fifty-six monolithic zirconia crowns were milled. The interim and definitive crowns were evaluated intraorally for SDC by using a 24-μm-thick blue articulating foil. After removing the interim and definite crowns, extraoral photographs were taken to calculate the SDC area using software (ImageJ) and analyzed by the Kruskal-Wallis test.

Results: The average and ± standard deviation (SD) of area of the occlusal marks on interim crowns was 32.27 ± 3.45 mm . Definitive crowns designed by using the correlation technique had an area of 31.01 ± 3.73 mm ; the area in the library technique was 36.85 ± 5.78 mm . No statistically significant difference was found (p = 0.091) between the occlusal mark areas of the interim and definitive crowns designed by using the correlation technique. Whereas, there were significant differences between the areas of occlusal marks of the interim and definitive crowns designed by using the library technique, and between the areas of occlusal marks of definitive crowns designed by using the correlation and library techniques (p < 0.001).

Conclusion: The average area of the SDC of monolithic zirconia crowns designed by using the correlation technique was similar to that of interim crowns. The library technique was less effective when replicating the SDC compared to the correlation technique.
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http://dx.doi.org/10.1111/jopr.13268DOI Listing
February 2021

Use of a New-Generation Mini-Implant and Attachment System for Fabrication of a Maxillary Overdenture.

Int J Prosthodont 2020 Sep/Oct;33(5):576-581

A new-generation mini-implant system offers a polyether ether ketone matrix and a new-generation surface technology on its patrix. This clinical report describes the treatment of a patient with a new-generation mini-implant-retained maxillary overdenture.
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http://dx.doi.org/10.11607/ijp.6544DOI Listing
September 2020

A technique to fabricate an interim implant-supported fixed complete denture for immediate loading.

J Oral Implantol 2020 Aug 24. Epub 2020 Aug 24.

The Ohio State University Restorative and Prosthetic Dentistry 305 w12th Ave. UNITED STATES Columbus Ohio 43210 The Ohio State University.

Converting an acrylic resin removable complete prosthesis into a fixed implant-supported prosthesis to immediately load the implants can be a challenging procedure. Using acrylic resin to secure titanium interim copings intraorally may be a difficult task, and any process to facilitate this procedure may be advantageous for the clinician and the patient. This report describes a technique for facilitating the fabrication of an interim immediately loaded implant-supported fixed complete prosthesis. This technique and the materials used enabled the efficient fabrication and delivery of the prosthesis with an appropriate soft tissue surface and acrylic resin thickness without irritating newly sutured soft tissues.
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http://dx.doi.org/10.1563/aaid-joi-D-19-00374DOI Listing
August 2020

Accuracy of intraoral scanning in completely and partially edentulous maxillary and mandibular jaws: an in vitro analysis.

Clin Oral Investig 2021 Apr 19;25(4):1839-1847. Epub 2020 Aug 19.

Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Objectives: New generation intraoral scanners are promoted to be suitable for digital scans of long-span edentulous spaces and completely edentulous arches; however, the evidence is lacking. The current study evaluated the accuracy of intraoral scanning (IOS) in partially and completely edentulous arch models and analyzed the influence of operator experience on accuracy.

Materials And Methods: Four different resin models (completely and partially edentulous maxilla and mandible) were scanned, using a new generation IOS device (n = 20 each). Ten scans of each model were performed by an IOS-experienced and an inexperienced operator. An industrial high-precision scanner was employed to obtain reference scans. IOS files of each model-operator combination, their respective reference scan files (n = 10 each; total = 80), as well as the IOS files from each model generated by the same operator, were superimposed (n = 45; total = 360) to calculate trueness and precision. An ANOVA for mixed models and post hoc t tests for mixed models were used to assess group-wise differences (α = 0.05).

Results: The median overall trueness and precision were 24.2 μm (IQR 20.7-27.4 μm) and 18.3 μm (IQR 14.4-22.1 μm), respectively. The scans of the inexperienced operator had significantly higher trueness in the edentulous mandibular model (p = 0.0001) and higher precision in the edentulous maxillary model (p = 0.0004).

Conclusion: The accuracy of IOS for partially and completely edentulous arches in in vitro settings was high. Experience with IOS had small influence on the accuracy of the scans.

Clinical Relevance: IOS with the tested new generation intraoral scanner may be suitable for the fabrication of removable dentures regardless of clinician's experience in IOS.
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http://dx.doi.org/10.1007/s00784-020-03486-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7966190PMC
April 2021

The effect of scanner type and scan body position on the accuracy of complete-arch digital implant scans.

Clin Implant Dent Relat Res 2020 Aug 8;22(4):533-541. Epub 2020 Jul 8.

Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio, USA.

Background: How the accuracy of complete-arch implant scans is affected when different intraoral scanners (IOSs) are used and the effect of scan body position on the accuracy are not well-known.

Purpose: To compare the scan accuracy (trueness and precision) of a recently introduced IOS (Virtuo Vivo) to a commonly used IOS (TRIOS 3) and the scans of a laboratory scanner (LBS; Cares 7 SERIES) in a completely edentulous maxilla with four implants. It was also aimed to evaluate the effect of scan body position on the accuracy.

Materials And Methods: Multi-unit scan bodies were tightened on a poly(methyl methacrylate) edentulous maxillary model with four implants. A master reference model (MRM) stereolithography (STL) file was generated by scanning the model with a high-precision scanner. The model was scanned with three different scanners (n = 10); two different IOSs and a LBS. STL files were superimposed over the MRM.

Results: For trueness, scan body position (P = .004) and scanner type (P < .001) had a significant effect on distance deviation and a significant interaction was found (P = .001). For angular deviation, only scanner type had a significant effect (P = .028). For precision, significant difference was found for distance (P = .011) and angular deviations (P = .020) between different scanner types.

Conclusions: One scanner type was not superior to others when both trueness and precision were considered. Position of the scan body affected the distance deviation (trueness).
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http://dx.doi.org/10.1111/cid.12919DOI Listing
August 2020

Fortification of traditional egg pasta (erişte) with edible insects: nutritional quality, cooking properties and sensory characteristics evaluation.

J Food Sci Technol 2020 Jul 9;57(7):2750-2757. Epub 2020 Mar 9.

Gastronomy and Culinary Arts Department, Faculty of Arts and Design, Alanya Hamdullah Emin Paşa University, Alanya, Antalya Turkey.

Proximate composition, cooking quality and sensory characteristics of traditional Turkish egg pasta, erişte, fortified with edible insect and legume flours were evaluated. Egg pasta samples were produced using different blends of wheat flour: legume (lentil and white kidney bean) flour and wheat flour: edible insect (mealworm and grasshopper) flour. Optimum cooking time significantly ( < 0.05) increased with the fortification of egg pasta. The fortification of egg pasta with edible insect flours resulted in a reduced volume expansion from 236.7% (control) to 215.6% and 196.9% for grasshopper flour (W:G) and mealworm flour (W:M) samples, respectively. On the other hand, W:M and W:G samples exhibited significantly ( < 0.05) higher nutritional profile in terms of protein, ash and crude fiber content. Results showed that the smoothness of pasta was also influenced; strengthened by addition of white kidney bean flour and weakened by the addition of grasshopper flour. The received scores from sensory evaluation showed that flours including lentil flour (W:L) and white kidney bean flour (W:B) samples had higher flavor and overall acceptability values with compared to the mealworm flour (W:M), grasshopper flour (W:G) and control sample (C).
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http://dx.doi.org/10.1007/s13197-020-04315-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271303PMC
July 2020

Comparison of strains for new generation CAD-CAM implant-supported crowns under loading.

Clin Implant Dent Relat Res 2020 Jun 6;22(3):397-402. Epub 2020 Apr 6.

Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.

Purpose: The behavior of implant-crowns fabricated from recently introduced CAD-CAM zirconia-reinforced lithium silicate ceramic (ZLS) or a hybrid ceramic containing resin-reinforced glass network (HC) for strains around the implant platform is not well-known. A force absorption capacity of the latter has been claimed by the manufacturer. The aim of this study was to measure and compare recently introduced ZLS and HC with commonly used CAD-CAM implant crown materials for strain distribution around the implant platform.

Methods: Four implants (Legacy 1; Implant Direct) were placed into a resin block. Zirconia abutments (Straight contoured stock abutment; Implant Direct) were torqued into the implant fixtures to support crowns that were milled from a virtual design using four different CAD-CAM materials (Vita Suprinity PC (ZLS), Vita Enamix (HC), IPS Emax, ZirCAD Zirkonzahn) (N = 20). The crowns were cemented with a resin cement, loaded and strain values were recorded. Three-dimensional digital image correlation (3D-DIC) was used to measure compressive and tensile strains around the implant platforms. The tensile and compressive strains were recorded for each test and first analyzed for equality of variance using Levene's test, and further tested using a 2-way ANOVA repeated measures analysis of variance (α = .05).

Results: The data analysis showed no statistically significant effect of crown material on the generated strains (P > .05). Compressive strains were significantly higher than the tensile strains (P < .05). One of the HC crowns fractured during loading.

Conclusions: Strains generated around implant platform when new generation CAD-CAM crown materials were used was similar to strains observed when CAD-CAM zirconia and lithium disilicate crowns were used. New generation crown materials did not have a significant load absorption effect to change or minimize the strains generated around the implant platform.
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http://dx.doi.org/10.1111/cid.12894DOI Listing
June 2020

Clinical performance and patient satisfaction obtained with tooth-supported ceramic crowns and fixed partial dentures.

J Prosthet Dent 2020 Oct 3;124(4):446-453. Epub 2020 Jan 3.

Senior Lecturer, Division of Fixed Prosthodontics and Biomaterials, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland.

Statement Of Problem: Studies reporting survival rates along with patient-centered outcomes are necessary to select the appropriate restorative material for crowns and fixed partial dentures (FPDs). However, studies that report the survival and complication rates of lithium disilicate crowns and the performance of zirconia FPDs compared with metal-ceramic FPDs are lacking.

Purpose: The purpose of this clinical study was to assess the failure and complication incidence of tooth-supported ceramic crowns and FPDs in function for at least 5 years. Groups included were pressed lithium disilicate crowns (CP), veneered pressed lithium disilicate crowns (CV), and computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate crowns (CC). Veneered zirconia-based FPDs (FPDC) were compared with metal-ceramic FPDs (FPDM). Outcomes were survival and failure, success and complications, periodontal conditions, and patient satisfaction assessed at 2 examinations (at baseline ≥1 year after delivery and at the follow-up examination ≥5 years of function).

Material And Methods: Eighty-two participants with 158 restorations (CP=39, CV=16, CC=20, FPDM=30, FPDC=53) were examined (2.38 ±0.96 years after delivery) to form the baseline data. For the prospective follow-up examination, 70 participants with 141 restorations (CP=39, CV=15, CC=16, FPDM=28, FPDC=43) were examined 4.08 ±0.36 years later.

Results: At the follow-up, restorations were in function for a mean of 6.44 ±1.14 years. Survival rates for crowns were 97.1% (CP=97.4%, CV=100%, and CC=93.8%) and 98.6% for FPDs (FPDM=96.4%, FPDC=100%). Among the 68 crowns, 1 technical and 4 biological complications were recorded. FPDs had more biological and technical complications than crowns (15/149 abutment teeth and 11/71 restorations). Technical complications were seen in 9.3% of zirconia FPDs compared with 25% for metal-ceramic FPDs. Complications were commonly observed at the baseline examination (crowns: 12/75 biological and 1/75 technical; FPDs: 40/174 abutment teeth with biological and 8/83 FPDs with technical complications). The periodontal conditions improved significantly after baseline. The patients reported a high level of satisfaction with the esthetics and function of the crowns and FPDs.

Conclusions: Survival rate for ceramic crowns and FPDs was 97.9% after a mean observation time of 6.44 ±1.14 years. Biological complications were more commonly observed than technical complications, and complications were more common in FPDs than in crowns. The complication rate was similar for zirconia FPDs and metal-ceramic FPDs. Adherence to strict maintenance measures may have reduced the risk of biological complications.
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http://dx.doi.org/10.1016/j.prosdent.2019.08.012DOI Listing
October 2020

Use of an attachment system with angulated abutments and polyetheretherketone inserts to retain a maxillary overdenture: A clinical report.

J Prosthet Dent 2020 Aug 29;124(2):129-134. Epub 2019 Nov 29.

Professor, Division of Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; Privat Docent, Division of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland.

This clinical report describes the rehabilitation of a maxillary edentulous arch with a current overdenture attachment system with angulated prefabricated abutments and polyetheretherketone (PEEK) inserts. Prefabricated angulated abutments were used on previously and recently placed diverging implants, which enabled a common path of insertion for the overdenture to be established during fabrication.
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http://dx.doi.org/10.1016/j.prosdent.2019.07.013DOI Listing
August 2020

Marginal fit of CAD-CAM monolithic zirconia crowns fabricated by using cone beam computed tomography scans.

J Prosthet Dent 2020 May 23;123(5):731-737. Epub 2019 Oct 23.

Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry, Columbus, Ohio.

Statement Of Problem: Information regarding the precision of monolithic zirconia crowns fabricated by using a standard computer-aided design and computer-aided manufacturing (CAD-CAM) workflow is available. However, information on the effect of a modified workflow using 3D laboratory scanning and/or cone beam computed tomography (CBCT) for monolithic zirconia crown fabrication is lacking.

Purpose: The purpose of this in vitro study was to evaluate the effect of different scans on the marginal fit of CAD-CAM monolithic zirconia crowns fabricated by 3D laboratory scanning and CBCT.

Material And Methods: An extracted maxillary left first molar was prepared and digitized by using a 3D laboratory scanner (D900; 3Shape A/S) (control group). The tooth was also scanned by CBCT (i-CAT; Imaging Sciences) to generate a second virtual 3D model (CBCTscan group). A tooth cast out of polyurethane (PU) (Zenotec Model; Wieland) was reproduced from the CBCT data by using a CAD software program (Dental System 2.6; 3Shape A/S) and milling machine (CORiTEC 550i; imes-icore) and further scanned by using the 3D laboratory scanner to generate a third virtual 3D model to represent a clinical scenario where a patient's cast is needed (PU3DLab group). A monolithic zirconia crown design (cement space: margin 40 μm, 1 mm above 70 μm) was used on the virtual models, and crowns were fabricated out of presintered zirconia blocks (ZenostarT4; Wieland) by using a 5-axis milling machine (CORiTEC 550i; imes-icore). The crowns were sintered (Sinterofen HT-S Speed; Mihm-Vogt), and the vertical marginal discrepancy (VMD) was measured by ×100-magnification microscopy. Measurements were made at 384 points in 3 groups of 16 specimens. The measurements for each specimen were averaged, and VMD mean values were calculated. The Kruskal-Wallis test was used for the statistical analysis (α=.05). The Mann-Whitney U test and Bonferroni adjustment were further used to compare the pairs (α=.017).

Results: The mean VMD value was 41 μm (median: 38 μm) for the control group, 44 μm (median: 42 μm) for the CBCTscan, and 60 μm (median: 58 μm) for the PU3DLab. No significant difference was found between control and CBCTscan groups (P=.274). However, there was a significant difference between control and PU3DLab and CBCTscan and PU3DLab groups (P<.001).

Conclusions: Marginal fit of the crowns fabricated by using the 3D laboratory scanner and through the direct use of CBCT was better than that of the crowns fabricated by using the workflow that combined the use of CBCT, PU cast, and 3D laboratory scanner. All tested protocols enabled the fabrication of monolithic zirconia crowns with a marginal discrepancy smaller than 120 μm.
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http://dx.doi.org/10.1016/j.prosdent.2019.05.029DOI Listing
May 2020

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

Clin Implant Dent Relat Res 2019 Dec 23;21(6):1132-1139. Epub 2019 Oct 23.

Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio.

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.
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http://dx.doi.org/10.1111/cid.12844DOI Listing
December 2019

A technique for facilitating open-tray implant impressions.

J Prosthet Dent 2019 Oct 24;122(4):417-419. Epub 2019 Sep 24.

Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University, Columbus, Ohio. Electronic address:

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http://dx.doi.org/10.1016/j.prosdent.2019.06.017DOI Listing
October 2019