A randomized clinical trial comparing the clinical fit and chairside adjustment time for implant-supported crowns fabricated by fully digital and partially digital techniques.

STATEMENT OF PROBLEM: Implant-supported crowns made in both fully and partially digital workflows have been evaluated, but these studies have been mainly performed in vitro. Moreover, data on the comparison of clinical fitting and adjustment time for implant-supported crowns are limited. PURPOSE: The purpose of this randomized clinical trial was to evaluate the clinical fit and adjustment time for implant-supported crowns produced by a partially and fully digital workflow in partially edentulous participants. MATERIAL AND METHODS: Twenty-eight participants who had received 2 adjacent implants in posterior sites were enrolled, each receiving 2 custom titanium abutments and a splinted monolithic zirconia restoration. Restorations of the control group (n=14) were produced from a digital scan and a cast-free digital workflow, while the restorations of the test group (n=14) were from a conventional impression and a partially digital workflow. A blinded investigator delivered the restorations. The clinical adjustment was performed incrementally, and a digital chronometer recorded the time required for the evaluation and adjustment at each step. An independent t test, Mann-Whitney U test, and the Fisher exact test were used to evaluate the results (α=.05). RESULTS: The total mean adjustment time in the control group (12.49 minutes) was significantly longer than that of the test group (11.27 minutes) (P<.001). For the occlusal contact points, significantly less clinical adjustment time was required with the cast-free digital workflow (5.31 minutes) than with the model-based partially digital workflow (6.06 minutes) (P=.001). On other surfaces, no significant difference was found between the 2 groups (P>.05). All crowns could be successfully delivered after 2 clinical appointments (impression and delivery). Remakes were not necessary for any restorations in the test or control group. CONCLUSIONS: The parameters of occlusal adjustment time and total adjustment time of the fully digital workflow were significantly shorter than those of the partially digital workflow.

The Influence of Dental Shade Guides and Experience on the Accuracy of Shade Matching.

AIM: There is limited and inconsistent information on some factors affecting visual shade selection. The aim of this study was to evaluate the influence of shade guide type and professional experience on shade-matching results. MATERIALS AND METHODS: Thirty Dental students (DS), 30 General dentists (GDs) and 30 Dental specialists (S) participated in this study. The participants were asked to match six target tabs using two dental shade guides: Vitapan Classical (VC) and Vitapan 3D-Master (3D). An intraoral spectrophotometer was used for color measurement of target tabs and selected tabs. The color difference (ΔE) values between the target tab and selected tab were calculated. Data were analyzed using analysis of variance (ANOVA) and paired f-test (α = 0.05). Results of the first five best matches for each target tab were expressed as ΔE1 to ΔE5. Differences in the mean values of ΔE1 to ΔE5 between VC and 3D were compared using descriptive statistics. RESULTS: There were no significant differences among the three participating groups in ΔE values when the 3D was used (p = 0.389). However, significant differences were found with VC (p < 0.001). The ΔE values achieved from the 3D were significantly lower than those from VC for DS and S (p = 0.001 and p < 0.001, respectively). For each of the first five best matches, the mean ΔE values from the 3D were smaller than the corresponding values of VC. CONCLUSION: The type of dental shade guide affected the shade-matching results. The level of experience was not found to be an influential factor in shade matching when 3D-Master shade guide was used. CLINICAL SIGNIFICANCE: Compared with Vitapan Classical shade guide, use of the Vitapan 3D-Master shade guide improves shade-matching results. KEYWORDS: Color, Experience, Gender, Selection, Shade, Visual. How to cite this article: Nakhaei M, Ghanbarzadeh J, Amirinejad S, Alavi S, Rajatihaghi H. The Influence of Dental Shade Guides and Experience on the Accuracy of Shade Matching. J Contemp Dent Pract 2016;17(1):22-26. Source of support: This study was supported by a grant (No. 920903) from the Vice Chancellor for Research of Mashhad University of Medical Sciences. The results presented here are based on undergraduate thesis (No. 2686) submitted to Mashhad School of Dentistry and Dental Research Center. CONFLICT OF INTEREST: None.

Effect of tightening torque on the marginal adaptation of cement-retained implant-supported fixed dental prostheses.

BACKGROUND: The final position of the abutment changes with the amount of tightening torque. This could eventually lead to loss of passivity and marginal misfit of prostheses. The aim of this study was to evaluate the effect of three different tightening torques on the marginal adaptation of 3-unit cement-retained implant-supported fixed dental prostheses (FDPs). MATERIALS AND METHODS: Two implants (Straumann) were inserted in an acrylic block so that one of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a 15° angulated abutment were connected to the vertically and obliquely installed implants, respectively, so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast. Abutments were tightened with 10, 20, and 35 Ncm torques, respectively. Following each tightening torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation of the retainers was evaluated using stereomicroscope. FDPs were then removed from the abutments and were sectioned at the connector sites. The retainers were luted again on their respective abutments. Luting procedures and marginal adaptation measurement were repeated. Data were analyzed by ANOVA and least significant difference tests (α = 0.05). After cutting the FDP connectors, the independent samples t-test was used to compare misfit values (α = 0.05). RESULTS: Following 10, 20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers of FDPs significantly increased (P < 0.05). There was no significant difference between the marginal discrepancies of these two retainers (P > 0.05). The marginal gap values of angulated abutment retainers (ANRs) were significantly higher than those of the straight abutment after cutting the connectors (P = 0.026). CONCLUSION: Within the limitations of this study, the marginal misfit of cement-retained FDPs increased continuously when the tightening torque increased. After cutting the connectors, the marginal misfit of the ANRs was higher than those of the straight abutment retainers.

Shade matching performance of dental students with three various lighting conditions.

AIM: To evaluate the ability of dental students to match shades under three various light conditions. MATERIALS AND METHODS: Sixty senior dental students participated in this study. All students were tested for color deficiency using Ishahara's tests. Nine classical vita shade tabs were randomly selected and their identification codes were concealed. The students were asked to match these 9 selected items by using a complete vita shade guide under three various light conditions (natural light, clinical light, and correcting light source). The chosen shade tabs were recorded and the correct matches were counted. Scores were calculated by adding the number of correct matches. RESULTS: The mean values of correct match scores with natural light, clinical light and correcting light source were 4.82, 4.75 and 6.82, respectively. There was no significant difference in correct matches scores between men and women, nor among various vita A, B, C and D shades. CONCLUSION: The students showed a better performance in shade matching under the correcting light source than natural light and clinical light. Gender had no effect on shade matching selection and there was no difference in shade matching ability among vita A, B, C, D shades. CLINICAL SIGNIFICANCE: Shade matching performance is significantly improved with correcting light source.