Treatment with zirconia-based all-ceramic crowns for molar teeth with metal antagonist occlusion should be undertaken with caution.

Purpose: The primary purpose of this study was to examine the clinical performance of monolithic zirconia single crowns in terms of short-term failure or complications. The secondary purpose was to detect the originating flaws of clinically failed monolithic zirconia crowns to find the causes of failure. Methods: A short-term prospective cohort study based on record evaluation and clinical examination of patients treated with tooth-supported monolithic zirconia crowns was performed in the

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The purpose of this study is to investigate the fit of zirconia cores and all-ceramic crowns prepared with different cervical margin designs. The radius of curvature between the axial wall and the occlusal surface was set to 1 mm in an abutment using the cervical shoulder marginal design (S) and to 0.2 and 0.5 mm in abutments with round shoulders (0.2RS and 0.5RS, respectively). The internal gaps of the cores were 45-138 μm (S), 41-141 μm (0.2RS), and 43-133 μm (0.5RS). The internal gaps of the all-ceramic crowns were 40-115 μm (S), 45-113 μm (0.2RS), and 42-126 μm (0.5RS). There were no significant differences in one-way ANOVA for any region in any marginal design before and after firing the porcelain. The marginal gaps between the all-ceramic crowns and dies were 27±25 (S), 30±29 (0.2RS), and 24±27 μm (0.5RS), again with no significant differences in one-way ANOVA.

The purpose of this study were: to perform stress analyses using three-dimensional finite element analysis methods; to analyze the mechanical stress of different framework designs; and to investigate framework designs that will provide for the long-term stability of both cantilevered fixed partial dentures (FPDs) and abutment teeth. An analysis model was prepared for three units of cantilevered FPDs that assume a missing mandibular first molar. Four types of framework design (Design 1, basic type; Design 2, framework width expanded buccolingually by 2 mm; Design 3, framework height expanded by 0.5 mm to the occlusal surface side from the end abutment to the connector area; and Design 4, a combination of Designs 2 and 3) were created. Two types of framework material (yttrium-oxide partially stabilized zirconia and a high precious noble metal gold alloy) and two types of abutment material (dentin and brass) were used. In the framework designs, Design 1 exhibited the highest maximum principal stress value for both zirconia and gold alloy. In the abutment tooth, Design 3 exhibited the highest maximum principal stress value for all abutment teeth. In the present study, Design 4 (the design with expanded framework height and framework width) could contribute to preventing the concentration of stress and protecting abutment teeth.

This study evaluated the influence of different finish line designs and abutment materials on the stress distribution of bilayer and monolithic zirconia crowns using three-dimensional finite element analysis (FEA). Three-dimensional models of two types of zirconia premolars - a yttria-stabilized zirconia framework with veneering ceramic and a monolithic zirconia ceramic - were used in the analysis. Cylindrical models with the finish line design of the crown abutments were prepared with three types of margin curvature radius (CR): CR = 0 (CR0; shoulder margin), CR = 0.5 (CR0.5; rounded shoulder margin), and CR = 1.0 (CR1.0; deep chamfer margin). Two abutment materials (dentin and brass) were analyzed. In the FEA model, 1 N was loaded perpendicular to the occlusal surface at the center of the crown, and linear static analysis was performed. For all crowns, stress was localized to the occlusal loading area as well as to the axial walls of the proximal region. The lowest maximum principal stress values were observed when the dentin abutment with CR0.5 was used under a monolithic zirconia crown. These results suggest that the rounded shoulder margin and deep chamfer margin, in combination with a monolithic zirconia crown, potentially have optimal geometry to minimize occlusal stress.

Interim restoration protects abutment teeth and periodontal tissues until prosthetic treatment ends with the fabrication of a definitive prosthesis, restores and maintains the functions and morphology of the stomatognathic system, and preserves the occlusal contact relationship. Temporary prostheses are used for a short time, to confirm the diagnosis and treatment plan. However, because interim restorations are used only briefly, their importance in ensuring the success of definitive prostheses is often overlooked. This review includes a comprehensive literature review of interim restoration of molars and summarizes the current clinical understanding and status of this functionally important area. Peerreviewed publications were identified by searching PubMed in November 2018. An interim restoration, even when used briefly, can help dentists evaluate many aspects of the treatment plan and contribute to accurate prognosis of prosthetic treatment.

The purpose of the present review was to survey the available literature on computer-aided design/computer-aided manufacturing (CAD/CAM)-produced resin composite materials to provide clinicians with a current overview of the key components necessary for daily clinical use. An electronic search was conducted in the PubMed database. Peer-reviewed articles in English language on the use of resin composites in CAD/CAM dental crowns were included. A total of 122 full-text articles were identified, 15 of which were selected during the initial review. Two additional articles were also discovered through a manual search, to obtain a final total of 17 articles included in the present review. Of these, 16 were to in vitro studies, and one was an in vivo study. Findings from the in vitro studies indicate that resin composite block materials for CAD/CAM applications demonstrate excellent physical properties and are appropriate for the clinical restoration of premolars and molars. However, the in vivo study reported a low 3-year success rate, but high survival rate for resin composite CAD/CAM crowns placed in the premolar region. The key to ensuring the successful prognosis of a resin composite CAD/CAM crown is to ensure that all steps—such as proper case selection, abutment tooth preparation, occlusal adjustment, and bonding—are accurately performed.