Rammelsberg, Peter

Purpose: To generate data on the long-term survival of metal-ceramic resin-bonded fixed partial dentures (RBFPDs). Materials and Methods: A total of 89 patients received 94 RBFPDs, 5 of whom (women n = 1; men n = 4) received 2 RBFPDs each. All RBFPDs were fabricated as two-retainer end-abutment metal-ceramic restorations. Clinical follow-ups were performed 6 months after cementation and then annually thereafter. The mean observation time was 7.5 years. Cox regression was performed to test the effects of the variables: gender, location, arch, design, use of rubber dam, and adhesive luting system. Survival and success were calculated using Kaplan-Meier curves. As a secondary objective, patient and dentist satisfaction with the esthetics and function of the RBFPDs was evaluated. The significance level was set at α = .05 for all calculations. Results: Estimated Kaplan-Meier failure-free survival was 97.5% (standard error [SE] 1.7) after 5 years and 83.3% (SE 5.3) after 10 years. Calculated intervention-free survival (success) was 90.1% (SE 3.4) after 5 years and 65.5% (SE 6.7) after 10 years. Debonding-free survival was 92.6% (SE 2.9) after 5 years and 80.6% (SE 5.4) after 10 years. Cox regression revealed that none of the four tested variables had a significant effect on the incidence of complications in RBFPDs. Patient and dentist satisfaction with RBFPD esthetics and function was consistently high throughout the observation period. Conclusions: Within the limitations of an observational study, RBFPDs achieved clinically successful outcomes over a mean observational period of 7.5 years.

Purpose: To examine the effects of anodization and different surface modifications of titanium on bond strength to 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) resin cement. Materials and Methods: Grade 5 titanium alloy disks (n = 160) were assigned to one of five prebonding surface treatment study groups (polished; polished and anodized; polished, etched, and anodized; sandblasted; sandblasted and anodized). Disks were adhesively bonded with 10-MDP resin cement (Panavia 21; bonding area: 3.3 mm in diameter) to composite resin cylinders. In each study group, tensile bond strength tests were conducted after 24 ± 1 hours and after 6 months (180 ± 2 days) of water storage (n = 16 specimens per water storage subgroup). Debonded specimens were stereomicroscopically analyzed to determine their fracture mode. Statistics included one-way and multifactorial ANOVA and Tukey post hoc tests (α = .05). Results: Anodization and water storage did not significantly (P ≥ .389) affect tensile bond strength. Although subgroups of polished samples had significantly (P ≤ .031) lower bond strengths (subgroup mean values: 20 to 26 MPa) than etched or sandblasted samples (subgroup mean values: 29 to 33 MPa), they nonetheless exceeded the empirical threshold of 10 MPa used as a criterion for clinical recommendation. The fracture mode of all test specimens was predominantly cohesive. Conclusions: Anodization of titanium surfaces can be performed without weakening the adhesion of 10-MDP–based resin cement to titanium.

Eine Verankerung von Teilprothesen mithilfe von Doppelkronen liefert gute Überlebensraten und weitere ästhetische und funktionelle Vorteile. Entwicklungen im Bereich des CAD/CAM bringen auch in der Doppelkronentechnik eine Vielzahl an Innovationen hervor, mit welchen sich der vorliegende Beitrag befasst. Es werden die aktuelle Literaturlage zu Komplikationen und Überleben von Doppelkronen zusammengefasst, die Eigenheiten des Fräsverfahrens im Vergleich zum Gussverfahren für Kobalt-Chrom-Legierungen betrachtet und die vorhandenen Daten zu alternativen CAD/CAM-Materialien vorgestellt. Schließlich werden die Implikationen der digitalen Konstruktions- und Fertigungstechniken auf eine möglicherweise vereinfachte und breitere Anwendung von Doppelkronenprothesen diskutiert. Keywords: Teilprothetik, CAD/CAM, Doppelkronen

Tissue retraction devices (TRDs) are used for head and neck radiotherapy to displace soft tissues and fixate the mandible. They can increase the accuracy of irradiation and reduce its side effects, such as oral mucositis. However, no method has been described for fabrication of TRDs in edentulous patients. In this case report, an edentulous 67-year-old patient undergoing radiotherapy of the tongue was provided with a TRD. The tongue was immobilized, ensuring irradiation consistency and the retraction of healthy oral tissues. Using 3D printing, an efficient workflow for fabrication of TRDs based on the patient's existing complete prostheses can be realized.

Purpose: To investigate the effect of training on scanning accuracy of complete arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated performance of CAS) and nonspecific training (simple use of an intraoral optical scanner for a sextant scan in the context of a CAD/ CAM teaching module). Materials and Methods: A total of 36 students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of CAS sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student had to perform 10 CAS per scanning session. Sessions were scheduled at T0, T1, and T2 for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students completed a CAD/CAM teaching module, which included fabrication of a monolithic crown in a fully digital chairside workflow. Results: In all groups, repeated CAS resulted in improved scanning accuracy. Participation in the CAD/CAM module had a positive effect on initial accuracy for CAS. Mean absolute deviations in cross-arch distance were 84 μm (T0), 68 μm (T1), and 63 μm (T2) for group 3S; 79 μm (T0) and 61 μm (T2) for group 2S; and 67 μm (T2) for group 1S. Conclusion: To perform CAS with the best possible accuracy, specific training is highly recommended. In addition, nonspecific training leads to an improvement in initial scanning accuracy.

Purpose: To investigate the effect of training on scanning times of complete-arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated practice of CAS) and nonspecific training (simple use of an intraoral scanner for a sextant scan in the context of a student CAD/ CAM course). Methods: Thirty-six students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of specific CAS training sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student performed 10 CAS per scanning session. These sessions were scheduled at baseline (T0), T1 (2 weeks after T0), and T2 (4 weeks after T0) for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students participated in a CAD/CAM course (3 weeks after T0) in which a monolithic crown was fabricated in a fully digital chairside workflow. The scanning time was measured as the time between the activation and termination of the scanning mode of the intraoral device. Data were analyzed using SPSS Statistics 25 (IBM). The level of significance was set to α = .05. Results: A continual decrease in scanning time was observed for all groups as experience in intraoral scanning increased. The mean scanning times were as follows: for group 3S, 305 seconds at T0, 246 seconds at T1, and 233 seconds at T2; for group 2S, 380 seconds at T0 and 303 seconds at T2; and for group 1S, 355 seconds at T2. When compared to group 1S after it had received nonspecific training only, the effect of a single specific training session in groups 3S and 2S was not significant (P = .4428). However, two specific training sessions had a significant effect on scanning time compared to nonspecific training only (P = .0005). Conclusion: Training does affect the scanning time required for CAS. To perform such scans in a time-efficient manner, dental practitioners should undertake training that comprises at least 12 CAS.

Purpose: To evaluate the dimensional accuracy of impressions made using a new fast-setting polyether material. Materials and Methods: A metallic reference model with two crown preparations, one inlay preparation, and three stainless steel precision balls was digitized to create a digital reference model. Sixteen one-step impressions were made for each of the four study groups, differing in impression material (regularsetting polyether [RSP] vs fast-setting polyether [FSP]) and technique (monophase vs dualphase), for a total of 64 specimens. Plaster casts fabricated from these impressions were digitized using 3D scans. Global accuracy was studied by evaluating distance and angle deviations between the replica and the reference model. Local accuracy was described in terms of trueness and precision of the aligned individual abutment tooth surfaces. Results: For all impression materials and techniques, the local accuracy at the abutment tooth level was excellent. For surfaces prepared for crowns, mean trueness was 10 μm, and mean precision 12 μm. Inlay surfaces were associated with higher inaccuracies (mean trueness 21 μm and mean precision 37 μm). The greatest global inaccuracies were generally measured for the cross-arch span, with mean distance changes between –55 μm and –94 μm. For all aspects of studied accuracy, impressions with FSP were at least comparable to those fabricated with RSP. Conclusion: Within the limitations of this study, all tested polyether materials would allow for clinically acceptable impression making. The new fast-setting material could be an alternative to regular-setting polyether materials, especially for single crowns and small fixed partial dentures.

Purpose: To evaluate the resistance to fracture in cantilevered fixed dental prostheses (cFDPs) of single implant-supported zirconia cantilevers in the anterior region. Materials and Methods: Thirty-two cemented and solely screw-retained cFDPs consisting of an implant-supported crown replacing the central incisor and an attached cantilever unit in the position of the lateral incisor in the maxilla were constructed by computer-aided design (CAD) and machined by computer-aided manufacturing (CAM). For the cemented solution, a cFDP was designed on top of a customized abutment luted to an adhesive base. For screw-retained cFDPs, abutment, cement gap, and restoration of the cementable design were combined. All cFDPs were veneered manually on the facial side. Half of the samples underwent artificial aging (thermocycling and chewing simulation) before fracture tests were conducted with loads applied to the pontic either parallel to the implant axis (axial loading on the pontic) or tilted lingually by α = 45 degrees (oblique loading on the pontic). Thus, there were eight groups differing in cFDP design, artificial aging, and load application (n = 8/group). If fracture (F_u,total) occurred within the implant components, the adhesive base was replaced by a cast CoCr base, and the cFDP's fracture resistance (F_u,cFDP) was also determined. Using statistical analyses (SPSS 24, IBM), factors affecting fracture resistance were identified. Results: F_u,total was mainly correlated to screw fractures and therefore not affected by cFDP design. Oblique loading on the pontic (F_u,total = 231 N - 352 N), however, led to a significant (P .001) decrease in ultimate load compared with axial loading on the pontic (F_u,total = 611 N - 815 N). In relation to F_u,total, F_u,cFDP was approximately twice as high for both loading conditions. Conclusion: When relating the results to maximum occlusal forces exerted in the maxillary anterior region, single implant-supported cFDPs can be a viable restorative treatment option. Keywords: CAD/CAM, extension bridge, fracture load, implant-supported, zirconia

Purpose: To assess the extent of differences between the oral health of people aged 50 and 70 years in a community-based setting. Materials and Methods: This research is part of the Interdisciplinary Study on Adult Development (ILSE). All participants lived in the city of Heidelberg, Germany. For the dental study, 194 participants born 1930–1932 (n = 88) or 1950–1952 (n = 106) underwent a comprehensive dental examination. For each participant the number of teeth present, the number of decayed, missing, and filled tooth surfaces (DMF-S), the Plaque Index (PI), the Gingiva Index (GI) and the Community Index of Periodontal Treatment Needs (CPITN) were determined. Depending on the structure of the data, differences between the birth cohorts were calculated by use of t tests or chi-squared tests. Multivariate analysis was also performed to assess possible effects of gender and birth cohort. Results: Oral health conditions were significantly worse among septuagenarians than among quinquagenarians. Besides poorer oral hygiene, as measured by use of PI and GI (p <0.001), periodontal conditions were worse for septuagenarians (p <0.001), who also had fewer natural teeth (p <0.002); the number of carious lesions was similar in the cohorts (p >0.05). These results were confirmed by multivariate analysis and seem to be mostly gender independent. Conclusions: Oral hygiene and health is poor for quinquagenarians and septuagenarians, with more problems associated with greater age but not with gender. Longitudinal studies are necessary to evaluate the intraindividual development of changes of oral health during ageing. Keywords: caries prevalence, periodontitis, oral health, oral hygiene, elderly people

Purpose: To determine the effects of ceramic-surface conditioning and aging on the bond strength between composite cement and zirconia-reinforced lithium-silicate glass-ceramics (ZLS) under simulated clinical conditions. Materials and Methods: ZLS disks (Celtra Duo, Dentsply Sirona, n = 110 test group n = 10, diameter: 8.3 mm, height: 3.4 mm) were assigned to four surface-conditioning groups: (I) 30 s of ~5% hydrofluoric-acid etching (Vita Ceramics Etch, Vita; HF), silanization (Calibra Silane; SIL); (II) successive contamination with saliva and silicone (CONT), HF, SIL; (III) CONT, tribochemical silicatization (CoJet), SIL; (IV) HF, SIL, application and light polymerization of an adhesive (Prime&Bond Active), CONT, reapplication and light polymerization of the adhesive. The ZLS disks were bonded to composite-resin cylinders in acrylic tubes (inner diameter: 3.3 mm) using self-adhesive composite cement (Calibra Universal). The tensile-bond strength (TBS) was measured after both 24 h and 6 months of water storage (WS). Additional aging protocols were tested for group I (3-day WS; 30-day WS including 7500 thermocycles between 6.5 and 60°C; 150-day WS including 37,500 thermocycles). Results: After 24 h, the mean TBS ranged between 21 MPa (group III) and 30-35 MPa (remaining groups). With the exception of 3-day WS, TBS was statistically significantly reduced by aging. The greatest reduction was observed for silicatized specimens (group III, mean TBS after aging: 9.8 MPa). Conclusion: Both ceramic surface conditioning and aging had a statistically significant effect on the bond strength between composite cement and ZLS. A treatment protocol based on tribochemical silicatization cannot be recommended for the adhesive cementation of ZLS. Keywords: acid etching, adhesive cementation, aging, air abrasion, all-ceramic, bond durability, composite cement, tensile bond strength