Does an incomplete ferrule affect the fracture of endodontically treated teeth? A systematic review of in vitro studies.

OBJECTIVE: The purpose of this systematic review was to assess the impact of the incomplete ferrule on the fracture of endodontically treated teeth (ETT). DATA: The keywords such as "incomplete ferrule," "ferrule," "ferrule effect," "residual dentin," "remaining dentin," or "remaining coronal dentin" were used for searching, and only in vitro studies investigating the incomplete ferrule effect on natural teeth were included. SOURCES: PubMed, Medline, Embase, Cochrane Library, and Science Direct databases, and manual-searching. STUDY SELECTION: The search strategy yielded 1633 hits, and a total of 19 in vitro studies closely related to the effect of incomplete ferrule on ETT were included. CONCLUSION: The presence of an incomplete ferrule may significantly increase the fracture resistance of restored ETT, compared with restored ETT without ferrule. The number of residual axial walls of the incomplete ferrule may have an impact on the fracture resistance and fracture mode. The location of residual axial walls of the incomplete ferrule may affect the fracture resistance but not the fracture mode. CLINICAL IMPLICATIONS: Limited data suggest that the presence of incomplete ferrule has a positive effect on the fracture resistance of restored ETT. An incomplete ferrule can be an alternative for restoring ETT when a complete ferrule is not present. Nevertheless, further high-quality studies are still needed to offer more robust evidence and to take potential confounding factors into account.

Use of ceramic veneers for improving esthetics and extending the service life of an existing cement-retained implant-supported ceramic restoration: A clinical report with a 3-year follow-up.

This clinical report describes an approach for improving the esthetics and extending the service life of a cement-retained implant-supported ceramic single crown by using a ceramic veneer bonded to the conservatively prepared facial surface. The restoration satisfied the patient without removing and replacing the unesthetic implant-supported ceramic crown.

Digital technologies to facilitate minimally invasive rehabilitation of a severely worn dentition: A dental technique.

This technique report describes digital technologies to facilitate minimally invasive rehabilitation with computer-aided design and computer-aided manufacturing (CAD-CAM) veneers for a severely worn dentition. The lingual veneers without tooth preparation and occlusal veneers with minimal tooth preparation were designed from the digital scan of the interim restorations. To facilitate the cementation of multiunit lingual veneers on unprepared teeth, a custom 3D-printed guide was designed from the digital cast of the natural dentition with the lingual veneers. The guide reduced the technique sensitivity of freehand practice and allowed the verification of the complete seating of multiunit lingual veneers on unprepared teeth. The digital technique provided a valid and reliable approach to making and cementing multiple CAD-CAM veneers for the minimally invasive restoration of worn teeth.

The effect of implant neck microthread design on stress distribution of peri-implant bone with different level: A finite element analysis.

BACKGROUND/PURPOSE: Significant research has proposed that the implant with microthread in the neck can significantly reduce marginal bone loss, but whether it is consistent in the condition of marginal bone loss is still unknown. The objective of this study is to investigate the effect of microthread on stress distribution in peri-implant bone with different bone level using finite element analysis. MATERIALS AND METHODS: A series of computational models of mandible segments with different bone resorption and implant models with or without microthread in the neck was installed by computer-aided design software. The simulated occlusal force of 150N was applied buccolingually on the top center point of implant. The FEA was performed, and the von Mises stress, principal stress and shear stress in peri-implant bone were recorded and analyzed. RESULTS: In all models, the T-neck group exhibits higher von Mises stress and principal stress, as well as lower shear stress than S-neck group. Three types of stresses increase with the depth of bone resorption developed, but the differences of shear stress between two groups of implants were gradually decreased. CONCLUSION: The micro-thread design in implant neck can reduce marginal bone loss by decreasing shear stress in peri-implant bone, but this effect is gradually weakened with the decline of the marginal bone level.

Evaluation of a Novel Computer Color Matching System Based on the Improved Back-Propagation Neural Network Model.

PURPOSE: To explore the feasibility of a novel computer color-matching (CCM) system based on the improved back-propagation neural network (BPNN) model by comparing it with the traditional visual method. MATERIAL AND METHODS: Forty-three metal-ceramic specimens were fabricated by proportionally mixing porcelain powders. Thirty-nine specimens were randomly selected to train the BPNN model, while the remaining four specimens were used to test and calibrate the model. A CCM system based on the improved BPNN model was constructed using MATLAB software. A comparison of the novel CCM system and the traditional visual method was conducted by evaluating the color reproduction results of 10 maxillary central incisors. Metal-ceramic specimens were fabricated using two color reproduction approaches. Color distributions (L*, a*, and b*) of the target teeth and of the corresponding metal-ceramic specimens were measured using a spectroradiometer. Color differences (ΔE) and color distributions (ΔL*, Δa*, and Δb*) between the teeth and their corresponding specimens were calculated. RESULTS: The average ΔE value of the CCM system was 1.89 ± 0.75, which was lower than that of the visual approach (3.54 ± 1.11, p < 0.01). With respect to color distributions, substantial differences were found between the two color-matching systems, except for ΔL* (p > 0.05). CONCLUSION: The novel CCM system produced greater accuracy in color reproduction within the given color space than the traditional visual approach.