D-RaCe instruments were associated with significantly less residual filling material than ProTaper Universal Retreatment instruments and hand files. Hedström files removed significantly less dentine than both rotary NiTi systems. Retreatment with rotary NiTi systems resulted in a high incidence of procedural errors.

Objectives A university-based randomized clinical study evaluated the 5-year performance of chairside-fabricated zirconia-reinforced lithium silicate (ZLS)-ceramic partial crowns. Material and methods Forty-five patients were restored with 61 chairside-fabricated ZLS-restorations (Cerec SW 4.2, Dentsply Sirona, Germany; Vita Suprinity, Vita Zahnfabrik, Germany). Deviating from the manufacturers’ recommendations, restorations with reduced minimum material thicknesses (MMT) were fabricated: group 1, MMT = 0.5–0.74 mm (n = 31); group 2, MMT = 0.75–1.0 mm (n = 30). For luting, a self-adhesive cement (SAC) or a total-etch technique with a composite cement (TEC) was applied. Statistical evaluation was performed by time-to-event analysis (Kaplan–Meier). Possible covariates of the survival (SVR) and success rates (SCR), evaluated in a Cox regression model, were MMT, restoration position (premolar/molar), and cementation technique (SAC vs. TEC). Results Forty patients (54 restorations, premolars, n = 23; molars, n = 31) participated in the 5-year follow-up. Five losses due to ceramic fractures occurred in group 1 (n = 28) (SVR: 83.0% [95% confidence interval (CI): 0.71–0.96]). Group 2 (n = 26) showed no losses (SVR: 100%). The success rate for partial crowns placed on premolars was 100% and 69% (95% CI: 0.54–0.84) for molar restorations. Recementation was required in 4 restorations with SAC (SCR: 86% [95% CI: 0.73–0.99]; SCR-DC: 100%). Restorations in group 2 showed a significantly reduced risk of material fracture hazard ratio (HR) = 0.09, p = 0.0292) compared with the restorations in group 1. Molar partial crowns showed an increased risk for a clinical intervention (HR = 5.26, p = 0.0222) compared to premolar restorations. Conclusions Material thickness and position of the restoration are risk factors influencing the survival and success rate of ZLS-ceramic partial crowns. Clinical relevance Observation of an MMT of at least 0.75–1.0 mm for ZLS-ceramics is essential to avoid material-related fractures. Clinical trial registration: German Clinical Trails Register (trial number: DRKS00005611)

No abstract

Box-Plot-Diagramm zur Darstellung der Wurzelkanalfüllungsreste (in %) nach der Revision (HF=Hedström-Feile, D-R= D-RaCe/BioRaCe, PTR=ProTaperRetreatment/ProTaper)…………………………………..49 Abb. 5.10: Mean-Plot-Diagramm zur Darstellung der Mittelwerte von Wurzelkanalfüllungsresten (in %) nach der Revision (HF=Hedström-Feile, D-R= D-RaCe/BioRaCe, PTR=ProTaperRetreatment/ProTaper)…………………………………..50 Abb. 5.11: Darstellung der gelb markierten Wurzelkanalfüllung vor (links) und nach (rechts) der Revision mit Hedström-Feilen………………………………52 Abb. 5.12: Darstellung der gelb markierten Wurzelkanalfüllung vor (links) und nach (rechts) der Revision mit D-RaCe/BioRaCe……………………………..52 Abb. 5.13: Darstellung der gelb markierten Wurzelkanalfüllung vor (links) und nach (rechts) der Revision mit ProTaper Retreatment und ProTaper……....53 Abb. 5.14: Instrumentenfraktur D2 (D-RaCe) links und D3 (ProTaper-Retreatment) rechts………………………………………………………………….……..54 Abb. 5.15: Laterale Perforation innerhalb der ProTaper-Retreatment/ProTaper-Gruppe……………………………………………………………………….54

Tooth fractures are a common cause of tooth loss, frequently starting as enamel cracks. However, methods for the detection of enamel cracks are poorly investigated. The aim of the study was the validation of three clinical methods for the detection of enamel cracks: dental operating microscope (DOM), near-infrared transillumination (NIR), and fiber-optic transillumination (FOTI), with hard-tissue slices serving as controls. A total of 89 extracted teeth, set up as diagnostic models, were investigated, and the maximum crack depth was scored by two examiners. The actual crack depth was determined microscopically (25×) using horizontal sections. The accuracy of each method was analyzed using receiver operating characteristic (ROC) curves. Across all tooth surfaces, the area under the curve (AUC) amounted to 0.57 (DOM), 0.70 (FOTI), and 0.67 (NIR). For crack detection on vestibular/oral surfaces, the AUC was 0.61 (DOM), 0.78 (FOTI), and 0.74 (NIR); for proximal surfaces, it was 0.59 (DOM), 0.65 (FOTI), and 0.67 (NIR). However, the actual crack depth was underestimated with each method (p < 0.001). Under in vitro conditions, FOTI and NIR are suitable for detection of enamel cracks, especially on vestibular and oral tooth surfaces. However, an exact estimation of crack depth is not possible. Therefore, FOTI and NIR seem to be helpful for the clinical detection of enamel cracks.

No abstract

The aim of this study was to evaluate dental students' retention of factual and procedural knowledge gained in a preclinical course in operative dentistry during a clinical dental curriculum. In 2017, all 157 seventh- to tenth-semester dental students at a dental school in Germany were asked to repeat the same written examination performed at the end of the preclinical course in the sixth semester. The examinations consisted of 30 multiple-choice questions covering factual and procedural knowledge. The percentage of correctly answered questions per exam and differences in correct answers between the original examination and the re-examination (per question) were analyzed. Students were also asked to self-rate their percentage of correctly answered questions and their knowledge in various disciplines of operative dentistry at the times of the original examination and the re-examination. After exclusions, data were analyzed for 129 students, for a participation rate of 82%. For the seventh- and tenth-semester students, the results on the original examination and the re-examination were not significantly different, while the eighth- and ninth-semester students performed significantly better on the original examination than the re-examination. In all semesters, procedural knowledge remained stable between the original examination and the re-examination, while factual knowledge decreased slightly. Their performance on the original examination was underestimated by the eighth- and ninth-semester students. All the students underestimated their performance on the re-examination. Students mostly rated their knowledge level significantly higher on the original examination than on the re-examination. Overall, this study found that factual and procedural knowledge gained in a preclinical course in operative dentistry was not increased during the clinical dental curriculum.