Comparison of the accuracy of optical impression systems in three different clinical situations.

PURPOSE: To investigate the differences in accuracy (trueness and precision) of five different optical impression systems. MATERIALS AND METHODS: The accuracy of the following optical impression systems was tested: (1) CEREC Bluecam (BL; Dentsply Sirona), (2) CEREC Omnicam (OM, Dentsply Sirona); (3) PlanScan (PL; Planmeca); (4) True Definition Scanner (TD; 3M ESPE); and (5) Trios 3 (TR; 3Shape). A standard plastic study model represented a patient with a fully dentate maxilla (ANA-4 V CER, frasaco). Three clinical situations were simulated: Patient 1 (P1): fully dentate; Patient 2 (P2): anterior partial edentulism (two missing incisors); and Patient 3 (P3): posterior partial edentulism (P3) (missing premolar and molar). The models were scanned with a reference scanner (IScan D104i, Imetric), and the digitalized models were used as reference for all comparisons. Then, optical impressions were made for the three clinical scenarios (n = 10 per group). RESULTS: In situation P1, the TD group provided the highest trueness (180.2 ± 46.3µm). In situation P2, the highest trueness was found in the TD (97.9 ± 27.6 µm) and TR (105 ± 9.5µm) groups, and in situation P3, TR had the highest trueness (P < .05) with a median RMS value of 76.2 ± 5.6 µm. In terms of precision, TR provided the highest precision (P < .05) in all three clinical situations, with RMS values 76.7 ± 26 µm for P1, 46.8 ± 14.1 µm for P2, and 39.7 ± 9.1 µm for P3. CONCLUSION: Two optical impression systems (TR and TD) were superior to the other tested systems in most of the measurements. However, none of the tested systems was clearly superior with respect to both trueness and precision.

Marginal discoloration of all-ceramic restorations cemented adhesively versus nonadhesively.

BACKGROUND: The authors conducted a systematic review to correlate the clinical incidence of marginal discoloration of all-ceramic restorations with the mode of cementation (adhesive versus nonadhesive). TYPES OF STUDIES REVIEWED: The authors conducted a literature search by using electronic databases, relevant references, database citations and journal hand searches for clinical studies of marginal discoloration of all-ceramic restorations with a mean follow-up time of at least five years. The search period spanned January 1990 through February 2011. The authors reported and compared summary estimates and five-year event rates. RESULTS: The authors selected 16 studies for final analysis from an initial yield of 346 articles. The mean observation time ranged between five and 10 years. The majority of studies used adhesive luting procedures for definitive cementation. In only one study did investigators report regarding the incidence of marginal discoloration of both adhesively and nonadhesively cemented all-ceramic restorations, and the difference between the luting types in terms of discoloration was not statistically significant (P = .5). CLINICAL IMPLICATIONS: The results of this systematic review showed that there is a lack of studies with findings regarding marginal discoloration rates of nonadhesively luted all-ceramic restorations. Unacceptable marginal discoloration rates of adhesively luted all-ceramic prostheses were relatively low even at 10 years of service.