Clinical evaluation of posterior zirconia-based and porcelain-fused-to-metal crowns with a vertical preparation technique: an up to 5-year retrospective cohort study.

OBJECTIVE: To evaluate the clinical conditions of single-unit posterior restorations on teeth prepared without finishing line, after 5.6 years of clinical service. MATERIALS AND METHODS: 50 crowns (25 zirconia-based (Zr) and 25 porcelain-fused-to-metal (PFM)) were selected from 34 patients. The restorations were evaluated according to the California Dental Association (CDA) Quality Criteria, and periodontal variables were studied in the abutment teeth compared with the unrestored contralateral teeth. Variables were examined using Mann-Whitney and Pearson´s Chi-Square tests (α = 0.05). The success of the prosthesis was calculated using Kaplan-Meier test. RESULTS: CDA Quality Criteria was considered satisfactory-excellent in all restorations except for one of them, due to chipping on a PFM crown. At, 66 months, the success rates for PFM and Zr crowns were 85.7 % and 100 %, respectively. The plaque index (PI) showed that the restored abutment teeth accumulated significantly less plaque than the control teeth, but the gingival index (GI) was statistically higher in the abutment teeth. In 80 % of cases the probing depth (PB) was ≤3 mm. In addition, in 21 % of the cases, gingival recession was less than 2 mm. The restoration material had a statistically significant effect on GI and PB, with Zr crowns showing less inflammation and less deep pockets than PFM restorations. On the contrary, greater gingival recession was found at the margins of the Zr crowns when compared to the PFM. No statistical differences were found between the two materials in the GI. CONCLUSIONS: Cemented crowns on vertical preparations show good clinical behavior after 5 years. The periodontal parameters (PI, GI, PD) of the Zr restorations are significantly better than those of PFM, with the exception of gingival recession. CLINICAL RELEVANCE: The use of restorations on vertically prepared teeth is a suitable alternative to classical horizontal preparations.

"Comparative study of conventional anesthesia technique versus computerized system anesthesia: a randomized clinical trial".

OBJECTIVE: The aim of the present study was to compare in terms of pain perception the use of conventional anesthesia and a computerized system. MATERIALS AND METHODS: Forty patients in need for extractions, dental restorative, or periodontal treatment bilaterally, were selected. Each patient served as his/her own control being subjected to two anesthesia techniques: conventional and electronically controlled anesthesia with Calaject® (Rønvig Dental MFG, Daugaard, Denmark). Each patient received both treatments in a blind way 1 week apart. The order was previously randomized. After performing the anesthesia (upper dental nerve, palatal posterior nerve, or inferior alveolar nerve), the patients evaluated their pain sensation with a visual analogue scale (VAS) (0-10). After treatment, the patients were asked about the presence of pain during the procedure. Finally, the patients selected their preference between the conventional and electronic anesthesia technique. Differences in assessment of pain's injection were analyzed using the Wilcoxon test and the Kruskal-Wallis test (α = 0.05). RESULTS: The mean general pain experienced was 3.73 (1.55 SD) for the conventional anesthesia, and 1.95 (0.53 SD) for computerized anesthesia. Statistical differences (p < 0.05) were found. There was no difference between the treatments (p value = 0.061). Most patients did not feel any pain during the treatment. Finally, 92.5% of the patients preferred the electronic system. CONCLUSIONS: Computerized anesthesia system produces significantly less pain compared with a conventional anesthesia syringe. Although both obtained sufficient anesthetic depth to perform treatments, the majority of patients chose electronic anesthesia as the most satisfactory. CLINICAL RELEVANCE: Computerized anesthesia devices are valid and more comfortable alternative to conventional anesthesia.

Influence of conventional and digital intraoral impressions on the fit of CAD/CAM-fabricated all-ceramic crowns.

OBJECTIVES: To compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions. METHODS: Thirty patients with 30 posterior teeth with a prosthetic demand were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (Ultrafast Optical Sectioning technology) (digital group, D) and 2-step silicone impression technique (conventional group, C). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation using ultra-flow silicone. Each crown was embedded in resin to stabilize the registered interface. Specimens were sectioned in buccolingual orientation, and internal misfit was measured at different areas using stereomicroscopy (×40). Data was analysed using Student's t test and Mann-Whitney test (α = 0.05). RESULTS: No statistically significant differences were found (P > 0.05) between two groups. The mean internal misfit and mean marginal misfit were 170.9 µm (SD = 119.4)/106.6 µm (SD = 69.6) for group D and 185.4 µm (SD = 112.1)/119.9 µm (SD = 59.9) for group C. CONCLUSION: Ceramic crowns fabricated using an intraoral scanner are comparable to elastomer conventional impressions in terms of their marginal and internal fits. The mean marginal fit in both groups was within the limits of clinical acceptability. CLINICAL SIGNIFICANCE: Impressions based on Ultrafast Optical Sectioning technology can be used for manufacturing ceramic crowns in a normal workflow, with the same results as silicone conventional impressions.