Influence of preparation designs on marginal adaptation and failure load of full‐coverage occlusal veneers after thermomechanical aging simulation

Abstract

Objectives To evaluate the fracture resistance and marginal quality of maxillary molars restored using lithium disilicate glass‐ceramic (LDG) occlusal veneers with two preparation designs. Methods Sixteen extracted maxillary molars were assigned to two groups (n = 8). In group 1 (G1), the teeth received a preparation for a conservative full‐coverage occlusal veneer restoration with a 90° rounded shoulder margin. In group 2 (G2), the teeth underwent a 1‐mm cusp reduction with a marginal chamfer. LDG restorations (IPS e.max CAD) were obtained with the Cerec 3 CAD/CAM system and luted with Variolink II cement. After thermomechanical aging (1 250 000 cycles), the specimens were loaded to fracture. A semiquantitative marginal seal evaluation was performed observing resin replicas of the specimens at the scanning electron microscope. Cement thickness was assessed at the stereomicroscope on sectioned specimens. Collected data were statistically analyzed by parametric and nonparametric tests. Results The maximum load to fracture was 2395.01 ± 150.96 N in G1 and 2408.39 ± 112.66 N in G2. Most of the observed specimens exhibited restorable fractures and continuous margins. Cement thickness was 132 ± 38 μm in G1 and 150 ± 41 μm in G2. No differences between the groups emerged. Conclusion This study demonstrated similar satisfactory performance of the two considered preparations designs for occlusal veneer with LDG. Clinical Significance A new minimally invasive occlusal veneer preparation with marginal chamfer exhibited promising fracture resistance and marginal adaptation that were comparable to those of a standard conservative preparation for the restoration of molars with CAD/CAM lithium disilicate occlusal veneers.

Influence of Conventional Versus Digital Workflow on Marginal Fit and Fracture Resistance of Different Pressable Occlusal Veneers After Thermomechanical Fatigue Loading

“…(46) The circumferential fullcoverage preparation design chosen in this study was in agreement with the preparation guidelines for minimally invasive restorations shown in previous studies. (13,15,47) All the teeth were prepared using milling machine to ensure proper standardization for all the prepared teeth.…”

“…(2,6,9,10,11) Occlusal veneers consist of thin overlay coverage with non-retentive form. (13) The availability of ceramic materials that could be constructed in thin sections and still have high mechanical properties accompanied with improved bonding capabilities make the occlusal veneers a reliable successful prosthetic treatment option. Lithium disilicate glass ceramic is considered the strongest ceramic material that could meet these Results: The results of this study revealed that e.max processed by conventional wax technique recorded the highest vertical marginal gap mean values followed by Celtra processed by conventional wax technique then Celtra processed by CAD wax technique while e.max processed by CAD wax technique recorded the lowest mean values.…”

Microfiltración marginal en incrustaciones de cerómero tipo table top cementadas con cementos resinosos: autograbantes, universales y resina termoplastificada

“…Ultrafine occlusal veneers represent a conservative alternative to traditional techniques, they also allow only a strategic reduction of healthy dental structure or perhaps no preparation, dentists should ideally choose flat and circumferential designs to improve clinical performance and longevity, although other designs of preparations such as: occlusal veneers with circumferential shoulder line or occlusal veneers with intracoronal extension are also described [9][10] . However, studies in 2018 recommend designs of preparations such as those applied in this report, since these forms of preparation allow the dental technician to manufacture a well-adjusted and uniform thickness restoration and thus obtain a very low fracture and disunity rate 1,11 .…”

“…Las carillas oclusales ultrafinas representan una alternativa conservadora a las técnicas tradicionales, además permiten solo una reducción estratégica de la estructura dental sana o quizá ninguna preparación, los odontólogos deberían elegir de manera ideal, diseños planos y circunferenciales para mejorar el rendimiento clínico y longevidad, aunque también se describen otros diseños de preparaciones como: carillas oclusales con línea de hombro circunferencial o carillas oclusales con extensión intracoronal [9][10] ; sin embargo, estudios en el 2018 recomiendan diseños de preparaciones como las aplicadas en este reporte, puesto que estas formas de preparación le permiten al técnico dental, fabricar una restauración bien ajustada y de espesor uniforme y así obtener una tasa de fractura y desunión muy baja 1,11 .…”

“…La técnica de restauración indirecta se refiere a la fabricación de la restauración fuera de la cavidad oral en el laboratorio, después de lo cual se coloca en el diente con algún agente cementante; permite además de la fotopolimerización convencional, la utilización de calor (140°C), presión (0,6 MPa durante 10 min) y atmósfera de nitrógeno; mejorando las propiedades físicas, además se alcanza un mayor grado de polimerización y la contracción de polimerización no se produce en el diente preparado, por lo que se reducen las tensiones 1 .…”