Thoma, Andrea

Purpose: The aim of this research was to assess survival and complication rates of tooth- and implant-supported fixed dental prostheses (FDPs) and single crowns (SCs) after 5 years of function in a specific patient population group who underwent comprehensive prosthetic treatment. Materials and Methods: This retrospective study included a convenience sample of 52 patients who met specific inclusion and exclusion criteria and were treated during two specific courses as part of the undergraduate curriculum. The patients' prosthodontic treatment comprised 296 tooth-supported and 37 implant-supported SCs together with 76 tooth-supported and 15 implant-supported FDPs. Pre- and posttreatment clinical examinations included screening for biologic and technical complications, probing pocket depth, bleeding on probing (BoP), and plaque control record (PCR) as well as intraoral radiographs. Information was obtained from the patients about dental hygiene and dental visits, treated complications, and patient satisfaction during the observation period. Descriptive statistics were employed. Results: Forty-five patients were followed for a mean observation period of 5.26 ± 0.47 years. The survival rates were 99.0% for tooth-supported SCs, 98.7% for tooth-supported FDPs, and 100% for implant-supported FDPs and SCs. Loss of vitality was observed in 2.9% of all abutment teeth deemed to be vital initially. Endodontic complications occurred in 5% and root fracture in 2.5% of nonvital abutment teeth. Caries was found in 0.4% of abutments. No framework or implant fractures were observed, but fracture of the veneering ceramic affected 3.8% of FDPs. The mean BoP was 21.5% ± 9.9%, and the mean PCR was 22.8% ± 16.5%. A high satisfaction rating was provided by 82.2% of patients. Conclusions: High survival and relatively few complication rates were observed for all prescribed FDPs over the observation period.

Objective: To evaluate whether post materials affect the color of roots, composite cores, and all-ceramic crowns. Method and Materials: Forty extracted human incisors were divided into four groups. White posts made of zirconia (Zi) or glass fiber (Gf) and gray posts made of titanium (Ti) or carbon fiber (Cf) were randomly assigned to the roots. Composite cores and glass-ceramic crowns were made. The color of the roots, cores, and crowns was captured (Spectroshade). The mean color difference (mΔE) among the groups was calculated for the following comparisons: A-root: empty root versus post and core; B-root: post and core with and without cement; C-core: white versus gray posts and cores; D-lower third of crown versus original ceramic ingot; E-center of crown versus ingot. Statistical analysis was performed by ANOVA, Kruskal-Wallis, and Sheffé tests. Results: White, as well as gray posts, induced little changes of the root color (A, B). Gray posts led to a significant discoloration of the cores (C: mΔEZi 2.0 ± 0.7, mΔEGf 1.5 ± 0.6, mΔETi 12.9 ± 5.9, mΔECf 11.2 ± 5.3; P .0001, Kruskal-Wallis) resulting in a grayish discoloration of the crowns' lower thirds (D: mΔEZi 5.7 ± 0.8, mΔEGf 6.0 ± 1.2, mΔETi 3.5 ± 1.1, mΔECf 3.9 ± 0.9; P .0001, Kruskal-Wallis). In the center of the crowns, all posts and cores induced a similar color difference (E). Conclusion: A grayish gingival shadowing cannot be reduced with white posts. In combination with glass-ceramic crowns, white posts and cores are esthetically beneficial. Schlagwörter: glass fiber, post, post and core, titanium, zirconia

Objective: To assess the accuracy of fit of frameworks on implants processed with electrical discharge machining (EDM) or the Cresco technique (Astra Tech). Method and Materials: On 12 identical master casts with implants at positions 9(21), 11(23), and 13(25), high-gold alloy frameworks were produced by standard casting procedure. Six frameworks were used for the Cresco technique (group CRE) by employing specific fixed partial denture supports. The remaining 6 frameworks were cast with prefabricated gold copings and served as control. The finished frameworks were screwed onto implant 25 of the corresponding master cast. Dimensions of the marginal gaps were measured at 4 locations on each implant under the scanning electron microscope, applying the replica technique. Subsequently, the control group was processed by EDM (SAE EDM 2000) (group EDM) and analyzed alike. Statistical analysis of the results was performed with Kruskal-Wallis and Mann-Whitney U tests. Results: The mean marginal gaps were measured as follows (CRE / EDM / control): position 25: 0.0 µm / 1.0 ± 1.6 µm / 1.5 ± 2.1 µm; position 23: 5.2 ± 5.6 µm / 18.7 ± 29.3 µm / 23.6 ± 30.7 µm; and position 21: 36.0 ± 21.6 µm/ 40.7 ± 31.0 µm / 46.0 ± 41.1 µm. The only statistically significant difference was found at location 23 between group CRE on one side and both group EDM and control on the other side. The strong increase of misfit for group CRE from location 23 to location 21 indicates that laser welding is the crucial parameter in this technique. Conclusion: The Cresco technique has a potential to reduce the marginal gap between implants and suprastructures. Schlagwörter: Cresco, electrical discharge machining, fixed partial denture, implant, marginal fit, suprastructure