Effect of CAD-CAM ceramic materials on the color match of veneer restorations.

STATEMENT OF PROBLEM: With the different translucency levels and types of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic materials, choosing the most appropriate CAD-CAM ceramic materials to better reproduce the color appearance of natural teeth can be challenging. PURPOSE: The purpose of this in vitro study was to analyze the color differences between natural teeth and milled veneers fabricated with the different types of CAD-CAM ceramic materials. MATERIAL AND METHODS: Ten extracted maxillary central incisor teeth with the A2 shade in the body region were prepared for ceramic veneers. The veneer restorations were designed by using the duplicating method and fabricated from 9 milling blocks (IPS e.max CAD HT/LT, Lava Ultimate CAD HT/LT, VITA SUPRINITY HT/T, IPS Empress CAD HT/LT/Multi) in a dental milling unit (n=10). The bonding surface of the abutment tooth was coated with a thin layer of a separating agent, and the veneer specimen with resin cement was then bonded to the corresponding abutment tooth. A clinical spectrophotometer was used to measure the Commission Internationale de l'Eclairage Lab values of natural teeth, abutment teeth, and milled veneers in the cervical, body, and incisal regions. Color differences between the natural tooth and A2 shade tab (ΔE1) and between the milled veneer and natural tooth (ΔE2) were calculated. The ΔE2 values were compared with the perceptibility threshold (ΔE=2.6) and acceptability threshold (ΔE=5.5). The paired-samples t test, 1-way analysis of covariance, and 2-way ANOVA were used to analyze data (α=.05). RESULTS: The results of 1-way analysis of covariance showed that ceramic materials significantly affected the a∗ and b∗ values of the milled veneers (P<.001) but did not affect the L∗ values of the milled veneers (P>.05). The results of 2-way ANOVA indicated that the ΔE2 values were not significantly affected by different CAD-CAM ceramic materials (F=1.560, P=.138), while statistically significant differences were found in the veneer regions (F=6.588, P=.002). The ΔE2 values ranged from 2.41 to 5.36, less than the clinically acceptable color threshold of 5.5. CONCLUSIONS: The color parameters of milled veneers were affected by the different types of CAD-CAM ceramic materials. The color of the veneer restoration was able to match that of the natural tooth.

Development and preclinical evaluation of a biodegradable ventricular septal defect occluder.

OBJECTIVES: This study evaluated the feasibility, effectiveness, and safety of a biodegradable (BD) occluder for closure of ventricular septal defect (VSD) in an acute canine model. BACKGROUND: All current available VSD occluders are permanent implants which consist of a metal framework and synthetic fabrics. However, the septal occluder in vivo plays the role of a temporary bridge that facilitates the ingrowth of fibrous connective tissue and endothelialization. The ideal occluder may be a temporary scaffold which can be gradually absorbed in vivo and replaced by "native" tissue. METHODS: The BD VSD occluder consists of a polydioxanone (PDO) framework and two pieces of poly-L-lactic acid (PLLA) fabrics. Percutaneous transcatheter closure of interventionally created VSDs was performed in 16 dogs using the BD occluders. Follow-up consisted of electrocardiography, transthoracic echocardiography, and fluoroscopy from 1 week to 24 weeks post-implantation. Gross pathology and histopathology were obtained at 6, 12, and 24 weeks follow-up. RESULTS: Implantation of the BD occluders was successful in 15 animals. The devices became well integrated into the ventricular septum with complete endothelialization at 12 weeks after implantation. After 24 weeks in vivo, the PDO framework of devices was largely absorbed and replaced by the ingrowth of collagenous fibers, and the PLLA fabric within disks was partly degraded. Neither occluder dislocation nor VSD recanalization occurred during follow-up. CONCLUSIONS: The BD occluder proved safe and effective for VSD closure. This device is characterized by compatible mechanical properties, a fully BD property, and a good match between the degradation of occluder and the healing response of organism.