Influence of different implant-abutment connection designs on the mechanical and biological behavior of single-tooth implants in the maxillary esthetic zone: A systematic review.

STATEMENT OF PROBLEM: A consensus regarding which implant-abutment connection type would perform best in the anterior maxilla is lacking. PURPOSE: The purpose of this systematic review was to determine the best implant-abutment connection type for anterior single-tooth implants considering esthetics, success, and survival rates. MATERIAL AND METHODS: An electronic search was conducted in MEDLINE, Scopus, Embase, and the Cochrane Library databases to identify clinical studies on single-tooth implants with external and internal hexagon, and/or Morse taper connections. These studies needed to describe at least one of the following outcomes: esthetic score, survival/success rate, or marginal bone loss. The included studies and reports were assessed for bias using the Cochrane risk of bias tool. RESULTS: Of the 891 articles identified, 29 were selected and analyzed. The most common technical complications were abutment screw loosening and crown-cement loosening, while dehiscence and recession were the most common biological complications. The most frequent complications were dehiscence for external hexagon, crown-cement loosening for the internal hexagon, and ceramic fracture for the Morse taper. Esthetics were favorable for all connections, but the internal hexagon performed better. However, better results for marginal bone loss, success, and survival were found for the Morse taper. The global annual failure rate was 0.90% and 0.2% for Morse taper, 0.3% for external hexagon, and 2.2% for internal hexagon. CONCLUSIONS: This review suggests that Morse taper performs better for survival, success, and marginal bone loss. Internal hexagon performed better for esthetic parameters. Additional controlled studies are needed to provide stronger evidence because the evidence generated in this study was considered low.

Spectrophotometric analysis of clinical factors related to the color of ceramic restorations: A pilot study.

STATEMENT OF PROBLEM: Shade matching natural teeth with ceramic restorations is still an esthetic, clinical challenge. PURPOSE: The purpose of this prospective clinical study was to evaluate the influence of color-related factors on the color variation of ceramic restorations based on spectrophotometric analysis. MATERIAL AND METHODS: Color records were obtained from 11 participants who received 38 lithium disilicate restorations. CIELab color coordinates were measured with a spectrophotometer on the ceramic restoration, tooth (baseline), prepared tooth, and luted ceramics. Color variation (ΔE00) was calculated for each variable (luting agent and restoration type, tooth substrate shade, ceramic thickness, and translucency parameters) measured at baseline on the prepared tooth and after cementation of the restorations. Confidence intervals (CI) for the means (95% CI) were calculated, and the ΔE00 values and CIELab individual color coordinates were compared for each pair of variable by using the Student t test or Welch test (α=.05). RESULTS: Greater color variation values were observed between measurements obtained on the prepared tooth and luted restoration. The lower ΔE00 values were observed over darker tooth substrate measured at baseline and after luting (P=.007). CONCLUSIONS: The 3 conditions evaluated presented clinically visible color differences, highlighting the importance of clinical evaluations on the visual color acceptability limits for restorations, which are usually defined in laboratory studies. The lithium disilicate ceramic showed lower masking ability over darker tooth substrate, whereas the coordinates L*, a*, and b* were cementation-dependent.

Influence of remaining coronal thickness and height on biomechanical behavior of endodontically treated teeth: survival rates, load to fracture and finite element analysis.

Objective To evaluate the effect of restorative strategy (fiber post vs cast post and core), coronal height (0 mm vs 2 mm) and thickness (higher than 1 mm vs lower than 1 mm) on survival rate, fracture resistance and stress distribution. Material and Methods Seventy-two bovine teeth were cleaned and allocated in six groups (n = 12). Twenty-four teeth were sectioned at 13 mm length (no remaining coronal structure) and forty-eight were sectioned at 15 mm (2 mm remaining coronal structure). Half of the forty-eight had remaining coronal thickness lower than 1 mm and the other half had thickness higher than 1 mm. All root canals were prepared at 10 mm (luting length), fiber posts were cemented in thirty-six specimens and cast post and core in other thirty-six. All teeth were restored with metallic crowns. Specimens were submitted to 1.5 million cycles (100 N, 45°, 10 Hz at 2 mm below incisal edge) and evaluated at each 500,000 cycles to detect failures. Specimens that survived were submitted to load to fracture test. Bidimensional (Rhinoceros® 4.0) models were obteined survival data submitted to Kaplan-Meier (α=0.05) analysis and load to fracture values submitted to ANOVA and Tukey tests (α=0.05). Results Groups without remaining coronal structure showed survival rates lower than other groups (p=0.001). ANOVA showed higher values of load to fracture for groups with coronal thickness higher than 1 mm (p=0.0043). Finite element analysis showed better stress distribution in groups with remaining coronal structure and restored with fiber post. Conclusion Specimens without remaining coronal structure have lower survival rates. Specimens with remaining structure lower than 1 mm and without coronal structure support the same load to fracture value independently of the restorative strategy.

Influence of remaining coronal thickness and height on biomechanical behavior of endodontically treated teeth: survival rates, load to fracture and finite element analysis

Abstract Objective To evaluate the effect of restorative strategy (fiber post vs cast post and core), coronal height (0 mm vs 2 mm) and thickness (higher than 1 mm vs lower than 1 mm) on survival rate, fracture resistance and stress distribution. Material and Methods Seventy-two bovine teeth were cleaned and allocated in six groups (n = 12). Twenty-four teeth were sectioned at 13 mm length (no remaining coronal structure) and forty-eight were sectioned at 15 mm (2 mm remaining coronal structure). Half of the forty-eight had remaining coronal thickness lower than 1 mm and the other half had thickness higher than 1 mm. All root canals were prepared at 10 mm (luting length), fiber posts were cemented in thirty-six specimens and cast post and core in other thirty-six. All teeth were restored with metallic crowns. Specimens were submitted to 1.5 million cycles (100 N, 45°, 10 Hz at 2 mm below incisal edge) and evaluated at each 500,000 cycles to detect failures. Specimens that survived were submitted to load to fracture test. Bidimensional (Rhinoceros® 4.0) models were obteined survival data submitted to Kaplan-Meier (α=0.05) analysis and load to fracture values submitted to ANOVA and Tukey tests (α=0.05). Results Groups without remaining coronal structure showed survival rates lower than other groups (p=0.001). ANOVA showed higher values of load to fracture for groups with coronal thickness higher than 1 mm (p=0.0043). Finite element analysis showed better stress distribution in groups with remaining coronal structure and restored with fiber post. Conclusion Specimens without remaining coronal structure have lower survival rates. Specimens with remaining structure lower than 1 mm and without coronal structure support the same load to fracture value independently of the restorative strategy.