Three-unit CAD/CAM-generated lithium disilicate FDPs after a mean observation time of 46 months.

OBJECTIVES: Lithium disilicate can easily be machined by CAM techniques in its metasilicate status. Due to slightly inferior material properties, the material is not yet recommended for three-unit fixed dental prosthesis (FDP) as it is the case for the press material up to the second bicuspid. Therefore, the aim of this clinical study was to evaluate the performance of CAD/CAM-fabricated lithium disilicate FDPs. MATERIALS AND METHODS: A total of 32 anterior and posterior FDPs were provided for 32 patients. Twelve FDPs were fabricated chair-side. The first recall took place 6 months after insertion and then annually. The FDPs were rated according to biological and technical complications. As failure, those events were defined, which led to the removal of a FDP. The failure-free (survival) rate and the complication-free rate were calculated according to Kaplan-Meier. RESULTS: After a mean observation time of 46 months (SD ± 8.4 months), three endodontic complications in two FDPs, two minor chippings, and one catastrophic fracture occurred. One FDP had to be removed due to persisting undefined complaints. Thus, the failure-free rate and the complication-free rate were revealed as 93 and 83 %, respectively. CONCLUSIONS: Despite the limited observation period, the results are promising, especially due to the fact that the fractured FDP did not fulfill the recommended connector dimensions. CLINICAL RELEVANCE: Inserted as a full-contour three-unit FDP within its indications, the CAD/CAM lithium disilicate ceramic offers an appropriate alternative to layered restorations.

The clinical accuracy of single crowns exclusively fabricated by digital workflow--the comparison of two systems.

OBJECTIVES: The purpose of the study was to compare the accuracy of crowns exclusively fabricated by the digital workflow of two systems. The null hypothesis stated was: Both systems do not differ with respect to marginal and internal accuracy. MATERIALS AND METHODS: In 14 patients, 13 molars and 1 premolar were prepared. Each preparation was scanned intraorally with two different digital impression systems, Lava COS and Cerec AC. On the basis of these data, Lava DVS crowns [DVS] and Vita Rapid Layering Technique crowns [RLT] were fabricated, respectively. Both systems contained of a zirconia framework and a digitally fabricated silicate ceramic veneering. The marginal and internal fit of the crowns was documented by a replica technique. The replicas were examined under microscope with a magnification of ×200. The Wilcoxon signed rank test was applied in order to test if the values of the two systems showed significant differences at p ≤ 0.05. RESULTS: The results were as follows in micrometers (±standard deviation): at the marginal gap, 51 (±38) for [DVS] and 83 (±51) for [RLT]; mid-axial, 130 (±56) for [DVS] and 128 (±66) for [RLT]; axio-occlusal, 178 (±55) for [DVS] and 230 (±71) for [RLT]; and centro-occlusal, 181 (±41) for [DVS] and 297 (±76) for [RLT]. According to the Wilcoxon signed rank test, the results differed significantly at the marginal, axio-occlusal, and centro-occlusal gaps. CONCLUSIONS: The null hypothesis had to be rejected. CLINICAL RELEVANCE: The exclusively digital workflow on the basis of intraoral digital impressions delivered clinically satisfying results for single crowns with both systems.