Restorative dentistry: Tooth preparation techniques for porcelain laminate veneers

Unit of Operative Dentistry and Endodontology, University Dental Hospital of Manchester.
British dental journal (Impact Factor: 0.81). 09/2000; 189(5):260-262. DOI: 10.1038/sj.bdj.4800739

ABSTRACT Objective The purpose of this study was to determine the effect that two guides to tooth preparation had on an operator's ability to appropriately and consistently prepare teeth for porcelain laminate veneers.Study designIn-vitro studyMaterials and methods Thirty typodont central incisor teeth were randomly allocated into three groups and a general dental practitioner was asked to prepare the teeth for porcelain laminate veneers. Group A were prepared freehand while Groups B and C were prepared with the assistance of a silicone index and depth preparation bur respectively. Images of the prepared teeth were used to calculate the mean labial depth of preparation and incisal reduction of teeth in each group.Results The mean labial reduction for Groups A, B and C was 0.37 mm (SD 0.13), 0.62 mm (SD 0.17) and 0.61 mm (SD 0.15) and the mean incisal reduction for Groups A, B and C was 1.0 mm (SD 0.28), 1.0 mm (SD 0.38) and 1.03 mm (SD 0.26) respectively.Conclusion It is suggested that consideration be given to the use of a silicone index or depth gauge bur when teeth are prepared for porcelain laminate veneers.

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    ABSTRACT: The purpose of this study was to use finite element stress analysis to examine the relative importance of variables such as porcelain laminate veneer (PLV) extensions, loading angle, and loading level for the case of feldspathic ceramic veneering of teeth to manage diastema. A 3D maxillary central incisor including its internal anatomy and morphology was constructed with ANSYS software for different extensions of PLV. Internal boundaries defining the dentinoenamel junction, the pulp-dentinal junction, the interface between the enamel-luting cement, and the porcelain-luting cement were well defined. The von Mises stresses distribution and stress intensity were analyzed on the free extension of PLV for varying extensions, various angulations (0 degrees , 30 degrees , and 60 degrees ) on the incisal edge, and for different loading levels (50, 150, and 250 N). The numerical values of stress were recorded. A significant difference in stress was observed. Increased stresses occurred with increased extensions, angulations, and loading levels. At 0 degrees angulation, compressive stresses were visualized in finite element analysis for various magnitudes of force. Higher stress values of 182 MPa and 211 MPa were obtained for the 2.5-mm extension in the mesial surface and in both proximal surfaces for 0 degrees angulation at 250 N magnitude of force. The stress occurring at 30 degrees and 60 degrees angulations was the combination of compressive and tensile stress. Higher values of 261 MPa and 232 MPa were observed when forces were applied on the mesial extension of the PLV and on both the proximal surfaces for 2.5 mm at 30 degrees , 250 N magnitude of force. A maximum stress value of 507 MPa was observed when PLV were increased in mesial width by 2.5 mm for 60 degrees angulation at 250 N magnitude of force. The extensions of PLV in diastema closure have more of an esthetic than functional consideration, but critical factors such as angulations and the loading level acting on the free extension of PLV are important.
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    ABSTRACT: The aim of this clinical study was to observe the service duration of porcelain laminate veneers (PLVs) and to estimate the influence of the categorical covariates such as location, tooth vitality, preparation depth, incisal, gingival and proximal finishing lines, and peripheral tissue type on the survival rates of event-free and overall service duration. A total of forty patients (26 women, 14 men; age range: 16 to 50) who had received 200 PLVs were evaluated in this study. Median follow-up time was 67.25 weeks with a range of 12 to 72 weeks. Fifteen of the restored teeth were nonvital, while the remaining 185 were vital. Categorical covariates related to the restoration design (localization, vitality, preparation depth, incisal, proximal, and gingival finishings, and surrounding tissue type) were recorded in order to estimate their influence on the survival rates. Survival rates of the event-free and overall service duration were calculated with the Kaplan-Meier analysis and Mantel log rank test. Twelve failures were observed. The most frequent failure type (11 units) was debonding of the restoration from the abutment tooth. Nine of them were rebonded and the remaining 2 were remade with a different preparation design. The last failure was observed as a coronal fracture at the cervical level. The overall survival rates were 99.5%, 99%, 97.5%, 94.9%, 94.4% and 93.8% at weeks 8, 9, 11, 15, 16, and 34, respectively, with a mean estimate of 68.45 weeks. PLVs exhibited good clinical results with their conservative specifications and high survival rates. The preparation and design specifications affect the service duration of PLVs.
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    ABSTRACT: The aim of this study was to evaluate the internal adaptation and marginal properties of ceramic laminate veneers fabricated using pressable and machinable CAD/CAM techniques. 40 ceramic laminate veneers were fabricated by either milling ceramic blocks using a CAD/CAM system (group 1 n=20) or press-on veneering using lost wax technique (group 2 n=20). The veneers were acid etched using hydrofluoric acid, silanated, and cemented on their corresponding prepared teeth. All specimens were stored under water (37 °C) for 60 days, then received thermocycling (15,000 cycles between 5 and 55 °C and dwell time of 90 s) followed by cyclic loading (100,000 cycles between 50 and 100 N) before immersion in basic fuchsine dye for 24 h. Half of the specimens in each group were sectioned in labio-lingual direction and the rest were horizontally sectioned using precision cutting machine (n=10). Dye penetration, internal cement film thickness, and vertical and horizontal marginal gaps at the incisal and cervical regions were measured (α=0.05). Pressable ceramic veneers demonstrated significantly lower (F=8.916, P<0.005) vertical and horizontal marginal gaps at the cervical and incisal margins and lower cement film thickness (F=50.921, P<0.001) compared to machinable ceramic veneers. The inferior marginal properties of machinable ceramic veneers were associated with significantly higher microleakage values. Pressable ceramic laminate veneers produced higher marginal adaptation, homogenous and thinner cement film thickness, and improved resistance to microleakage compared to machinable ceramic veneers. The manufacturing process influences internal and marginal fit of ceramic veneers. Therefore, dentist and laboratory technicians should choose a manufacturing process with careful consideration.
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