Lehmann, Karl Martin

Aim: To optimize the esthetics of ceramic restorations, it is important to determine accurately the effects of various parameters on the final color of the restoration. However, there is a lack of information on what determines the color of translucent feldspathic veneers formed using ceramics such as Vita Mark II. The aim of this study was to evaluate the effects of the ceramic layer thickness, cement color, and abutment tooth color on the color of the feldspathic ceramic veneer restoration. Material and methods: A total of 30 all-ceramic monolithic veneers (Vita Mark II) were fabricated using a CAD/CAM system. The crowns were divided into three groups of differing ceramic thickness (0.4-, 0.7-, and 1.0-mm thick). Each type of crown was seated on six different-colored abutment teeth (1M1 [reference], 1M2, 2M2, 3M2, 4M2, and 5M2) using seven different try-in paste colors. The color of the resulting restoration was evaluated using spectrophotometry with a spot-measurement device (Vita Easyshade Advance 4.0). Color data are expressed in CIE L*a*b* system coordinates, and color differences ΔE relative to the reference tooth were calculated and analyzed using one-way analysis of variance (ANOVA) with the Bonferroni post hoc test at α = 0.05. Results: The color difference ΔE of the feldspathic all-ceramic veneer system was significantly affected by the thickness of the ceramic layer, the cement color, and the abutment tooth color (P 0.05). The smallest values of ΔE compared with the reference color were found when try-in pastes shade -3 was used. As the thickness of the ceramic layer increased, a significant decrease in ΔE was found. As the color of the abutment tooth varied from light to dark, a significant increase was found in ΔE. Conclusion: The thickness of the ceramic layer, the cement color, and the abutment tooth color significantly affected the color of the resulting CAD/CAM feldspathic ceramic veneer restoration.

Ziel: Es ist wichtig, den Einfluss verschiedener Parameter auf die endgültige Farbe der Restauration genau zu kennen, um mit Keramikrestaurationen die bestmögliche Ästhetik zu erreichen. Es gibt jedoch nicht genügend Daten dazu, welche Faktoren die endgültige Farbe von Veneerrestaurationen aus transluzenter Feldspatkeramik, wie z. B. Vita Mark II, bestimmen. Ziel dieser Studie war es, den Einfluss der Keramikschichtdicke, der Zementfarbe und der Stumpffarbe auf die Farbe von Feldspatkeramik-Veneers zu untersuchen. Material und Methode: Insgesamt 30 vollkeramische monolithische Veneers (Vita Mark II) wurden mit einem CAD/CAM-System hergestellt. Es wurden drei Gruppen mit unterschiedlicher Keramikdicke (0,4 mm, 0,7 mm und 1,0 mm) gebildet. Jede Veneerart wurde unter Verwendung von sieben verschiedenen Try-in-Pasten-Farben auf sechs verschiedenfarbige Stümpfe gesetzt (1M1 [Referenz], 1M2, 2M2, 3M2, 4M2 und 5M2). Mit einem Spotmessgerät (Vita Easyshade Advance 4.0) wurde anschließend die Farbe der endgültigen Restauration spektralfotometrisch bestimmt. Die Farbdaten wurden als Koordinaten im CIEL*a*b*-Farbraum ausgegeben, die Farbabstände (∆E) relativ zur Referenzrestauration berechnet und mittels einfaktorieller Varianzanalyse mit dem Bonferroni-Post-hoc-Test statistisch ausgewertet (α = 0,05). Ergebnisse: Der Farbabstand (∆E) des monolithischen Feldspatkeramik-Veneersystems wurde signifikant von der Dicke der Keramikschicht, der Zement- und der Stumpffarbe (p 0,05) beeinflusst. Der kleinste ∆E-Wert im Vergleich zur Referenzfarbe ergab sich, wenn die Try-in-Paste der Farbe -3 benutzt wurde. Mit zunehmender Dicke der Keramikschicht zeigte sich eine signifikante Verringerung von ∆E. Die Veränderung der Stumpffarbe von hell nach dunkel ergab eine signifikante Zunahme von ∆E. Schlussfolgerung: Die Dicke der Keramikschicht, die Zement- und die Stumpffarbe veränderten die Farbe der endgültigen CAD/CAM-gefertigten Feldspatkeramik-Veneerversorgung signifikant.

Purpose: To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex. Materials and Methods: In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm. Results: Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component. Conclusion: These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload.

Purpose: The aim of this in vitro study was to assess the increase in the polygonal area of implant-retained prosthesis supports in edentulous maxillae with the use of tilted distal implants compared with the use of straight distal implants, using a variety of implant lengths. Materials and Methods: A total of 25 DICOM datasets of atrophic edentulous maxillae were provided. Bone augmentations in the molar region had to be avoided. Two straight reference implants were virtually inserted in the anterior region. Two additional implants were placed far distally on both sides (4 groups: [1] straight, 12-mm length; [2] straight, 10 mm; [3] straight, 8 mm; [4] tilted, 12-16 mm). The resulting implant-supported polygon was measured for each of the 4 groups using three-dimensional planning software. Results: The mean sagittal depth of the supported polygon in Group 1 was 9.9 mm (standard deviation [SD] 4.4) on the right and 10.2 mm (SD 4.4) on the left, and it was 33.7 mm (SD 5.8) in width. For Group 2, the mean sagittal depth was 11.5 mm (SD 5.0) on the right and 11.9 mm (SD 4.7) on the left, and the width was 35.2 mm (SD 5.6). The measurements for Group 3 were 13.8 mm (SD 4.9) deep on the right, 13.8 mm (SD 5.1) deep on the left, and 37.0 mm (SD 5.4) in width. For Group 4, the depth was 15.8 mm (SD 4.9) on the right and 16.4 mm (SD 5.8) on the left, and the width was 39.0 mm (SD 5.1). Conclusion: The area of implant-retained prosthesis support can be enlarged by the use of tilted implants (12 to 16 mm in length, 42 to 45 degrees) compared to the use of straight 8-mm implants (resulting increase: about 15%).

Purpose: The fracture strengths of all-ceramic crowns cemented on titanium implant abutments may vary depending on crown materials and luting agents. The purpose of this study was to examine differences in fracture strength among crowns cemented on implant abutments using crowns made of seven different monolithic ceramic materials and five different luting agents. Materials and Methods: In total, 525 crowns (75 each of Vita Mark II, feldspathic ceramic [FSC]; Ivoclar Empress CAD, leucite-reinforced glass ceramic [LrGC]; Ivoclar e.max CAD, lithium disilicate [LiDS]; Vita Suprinity, presintered zirconia-reinforced lithium silicate ceramic [PSZirLS]; Vita Enamic, polymer-reinforced fine-structure feldspathic ceramic [PolyFSP], Lava Ultimate; resin nanoceramic [ResNC], Celtra Duo; fully crystallized zirconia-reinforced lithium silicate [FcZirLS]) were milled using a CAD/CAM system. The inner surfaces of the crowns were etched and silanized. Titanium implant abutments were fixed on implant analogs, and airborne-particle abrasion was used on their exterior specific adhesion surfaces (Al2O3, 50 μm). Then, the abutments were degreased and silanized. The crowns were cemented on the implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, GC FujiCEM, Panavia 2.0). After thermocycling for 5,000 cycles (5 to 55°C, 30 seconds dwell time), the crowns were subjected to fracture strength testing under static load using a universal testing machine. Statistical analyses were performed using analysis of variance (α = .0002) and the Bonferroni correction. Results: No significant difference among the luting agents was found using the different allceramic materials. Ceramic materials LiDS, PSZirLS, PolyFSP, and ResNC showed significantly higher fracture strength values compared with FSC, FcZirLS, and LrGC. The PSZirLS especially showed significantly better results. Conclusion: Within the limitations of this study, fracture strength was not differentially affected by the various luting agents. However, the fracture strength was significantly higher for PSZirLS, PolyFSP, ResNC, and LiDS ceramics than for the FSP, LrGC, and the FcZirLS ceramic with all luting agents tested. Keywords: CAD/CAM, cement, ceramic, fracture strength, implant, luting agents

The aim of the study was to determine the retentive strength of monolithic all-ceramic crowns cemented on titanium implant abutments. 225 crowns (75 crowns each of Mark II, Empress CAD, and e.max CAD) were milled using a CAD/ CAM system. The crowns were cemented onto sandblasted titanium implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, Fujicem, and Panavia 2.0). After thermocycling, the crowns were removed using a universal testing machine. The location of luting agent residue on the abutment and inner crown surfaces was evaluated. Statistical analysis was performed uisng ANOVA with the Bonferroni correction. In comparing the luting agents, no significant difference was found between Vita Mark II and Empress CAD. For e.max CAD, the luting agent RelyX Unicem had a significantly higher mean retentive strength than did Multilink Implant (p = 0.003) or Panavia 2.0 (p = 0.001). In comparing the ceramic materials, e.max CAD showed significantly higher pull-off strengths than the other two ceramic materials when the luting agents RelyX Unicem and Fujicem were used (all p 0.001). The residues of nearly all luting agents were located entirely or almost entirely (75%-100%) on the inner crown surfaces of all ceramic materials, except for the luting agent GC Fujicem, which left more luting agent residue (0%-75%) on the abutment surfaces of all ceramic materials. In comparing the five luting agents, significant differences in the resulting retentive strength were only found for the ceramic material e.max CAD. The other ceramic materials did not show significant differences in retentive strength, independent of the luting agent. Keywords: implant, ceramic, retentive strength, CAD/CAM, luting agent, cement

Purpose: To evaluate factors promoting mucositis and peri-implantitis (plaque accumulation, poor peri-implant soft tissue health, bone loss) with regard to prosthetic attachment systems consisting of implant-supported bar-retained overdentures. Materials and Methods: Patients who received TiOblast implants to support overdentures retained by either (1) prefabricated bars with or without extensions or (2) cast bars were recalled and examined clinically and radiographically. Plaque Index (PI), Sulcus Bleeding Index (SBI), probing pocket depth (PPD), and peri-implant bone loss were measured. Peri-implant tissue health was assessed, and the presence of mucositis and peri-implantitis was recorded. One-way analysis of variance with the Bonferroni adjustment was used to compare groups (α = .05). Results: Five to 10 years after prosthetic loading, 107 patients who received 516 TiOblast implants were evaluated; 31 of these patients were treated with 131 implants to support bar-retained overdentures. PI, SBI, PPD, and pathologic bone loss were least common in the group with prefabricated bars, followed by the group with prefabricated bars with extensions, and were most common in the group with cast bars. Plaque accumulation and pathologic bone loss values were higher with implants that supported mandibular bar-retained overdentures than with those supporting maxillary bar-retained overdentures. However, these differences among attachment systems or between maxillary and mandibular implants were not significant (P > .05). Mucositis was observed in one implant in the group with prefabricated bars, four implants in the group with prefabricated bars with extensions, and four implants in the group with cast bars. Peri-implantitis was observed in one implant of the cast bar group. Conclusions: Five to 10 years after prosthetic loading, no significant difference in PI, SBI, PPD, pathologic bone loss, or peri-implant tissue conditions among the different bar designs tested was observed. Keywords: bar design, bone loss, dental implant, mucositis, overdenture, peri-implantitis

Objective: CAD/CAM is based on optical or mechanical scanning of tooth surfaces. The aim of this in vitro study was to investigate the influence of three different scan sprays on the proliferation, viability, and adenylate kinase (ADK) release of human fibroblasts. Method and Materials: Three different scan sprays (ScanDry, ScanSpray Luer Classic, and CEREC Optispray) were tested in vitro to determine their effects on proliferation, viability, and ADK release of human periodontal fibroblasts. A defined amount of the test material was sprayed into 96 multiwell plates, dried, and incubated with fibroblasts. The LIVE/DEAD Viability Assay, a two-color fluorescence-based method, was used to determine the cytotoxic potential (the AlamarBlue Assay for the proliferation rate and the ToxiLight BioAssay for the release of ADK). Results: There were differences between the scan sprays concerning inhibition of the proliferation and viability of fibroblasts. All materials inhibited the fibroblast proliferation and viability compared with the control group (P .001), and there were also significant differences among the scan spray groups. The scan sprays led to a greater release of ADK, but a significant difference could be found only between ScanSpray Luer Classic and CEREC Optispray (P .009). Conclusion: The results of this study proved that the scan sprays do not induce a significantly higher ADK release than the control group. The inhibiting effect on the fibroblast proliferation can be attributed to a material-independent phenomenon. Further experiments are necessary to validate the present data. Keywords: CAD/CAM, CEREC, cytocompatibility, in vitro, optical scanning, scan spray

Ziel: Im Rahmen dieser In-vitro-Untersuchung wurde durch Bestimmung der CIE-Koordinaten für Helligkeit, Sättigung und Farbe (lightness, chroma, hue: L*C*h°) an keramischen Proben die Übereinstimmung von dentalen Farbbestimmungssystemen mit einem CIE-konformen Referenzsystem untersucht. Material und Methode: Mit vier Farbbestimmungssystemen wurden unter standardisierten Versuchsbedingungen die L*C*h°-Farbkoordinaten keramischer Proben, die den Farben des Vita Linearguide 3D-Master entsprachen, bestimmt und mit den Ergebnissen eines CIE-konformen Referenzsystems verglichen. Folgende Systeme wurden verwendet: Vita Easyshade® Advance (System A), Degudent ShadepilotTM (B), X-Rite® ShadevisionTM (C) und Crystal Eye Olympus (D). Anschließend wurden die Unterschiede bezüglich der Regressionsgeraden zwischen den dentalen Farbbestimmungssystemen und dem Referenzsystem untersucht. Ergebnisse: Sämtliche Farbbestimmungssysteme zeigten hohe Intraklassen- Korrelationskoeffizienten (0,9771 bis 0,9999) bei der Bestimmung der L*C*h°-Farbkoordinaten. Die Regressionsgeraden der L*- und C*-Koordinaten des Geräts A waren im Vergleich zu dem Referenzsystem steiler, wohingegen die Regressionsgeraden der Systeme B, C und D nahezu parallel, jedoch mit einer Verschiebung zu der Regressionsgeraden des Referenzsystems verliefen. Die Regressionsgeraden der h°-Farbkoordinaten aller dentalen Farbbestimmungssysteme waren im Vergleich zu der Regressionsgeraden des Referenzsystems, die eine Steigung von 1 aufwies, ebenfalls nahezu parallel. Mit Ausnahme der L*- und h°-Farbkoordinaten des Farbbestimmungssystems A unterschieden sich die Systeme signifikant von dem Referenzsystem (P 0,0002). Schlussfolgerung: Die verwendeten Farbbestimmungssysteme zur dentalen Farbnahme zeigten bei Bestimmung der L*C*h°-Farbkoordinaten eine ausgezeichnete Reproduzierbarkeit, wobei sich jedoch signifikante Unterschiede im Vergleich zu dem Referenzsystem ergaben.

Objectives: This in vitro study evaluated the accordance of dental color measurement devices with a Commission Internationale de l'Eclairage (CIE)-compliant reference system, by comparing the CIE lightness, chroma, and hue (L*C*h°) color coordinates of ceramic samples. Methods: Four color measurement devices: Vita Easyshade® Advance (A); DeguDent Shadepilot™ (B); X-Rite® Shadevision™ (C); and Crystaleye Olympus (D), were compared with a CIE-compliant reference system by recording the L*C*h° color coordinates of ceramic samples matching the tooth colors of the Vita Linearguide 3D-Master®, under standardized test conditions. Differences between regression lines for the dental color measurement device data and regression lines for the CIE-compliant reference system data were evaluated. Results: All devices offered high intraclass correlation coefficients (0.9771- 0.9999) for the L*C*h° color coordinates. The regression lines of the L* and C* coordinates for device A were steeper than those of the CIE-compliant reference system; the regression lines for devices B, C, and D were nearly parallel to those of the reference system, but with an offset. The regression lines of the h° coordinates for all devices were almost parallel to those of the reference system, with slopes near 1. Excluding the L* and h° coordinate measurements of device A, the measurements with the devices exhibited deviations from the reference system that were greater than those expected by chance (P 0.0002). Conclusions: The dental color measurement devices assessed here offered excellent reproducibility, but showed significant deviations from the CIE-compliant reference system regarding the L*C*h° color coordinates.