Influence of cavity design on quality of margin and marginal adaptation and microleakage of all-ceramic CAD/CAM inlays / 北京大学学报(医学版)

OBJECTIVE@#To investigate the influence of 135° and 90° cavity design on quality of margin and marginal adaptation and microleakage of all-ceramic computer aided design/computer aided manufacturing (CAD/CAM) inlays.@*METHODS@#One hundred extracted human molars were prepared by criteria of buccal occlusal (BO) inlay. On the buccal, the mesial margin was prepared as 135° bevel while the distal margin was prepared as butt-joint. All-ceramic restorations were made in the Sirona CEREC AC CAD/CAM system with VitaBlocs Mark Ⅱ, Upcera UP.CAD, IPS e.max CAD, Upcera Hyramic and Lava Ultimate. The gaps between each inlay's mesial margin-abutment and distal margin-abutment were recorded under an optical microscope. Each inlay was adhered to the abutment and aged by thermal cycling for 10 000 times. Each specimen was cut into 3 slices after staining. Dye penetration was evaluated under an optical microscope for mesial and distal margins.@*RESULTS@#Mean marginal integrity rate, mean marginal gap value and mean depth of microleakage of 135° margin of Group Upcera Hyramic and Lava Ultimate were significantly better than those of Group VitaBlocs Mark Ⅱ, Upcera UP.CAD and IPS e.max CAD(P < 0.05). Mean marginal gap value, mean depth of microleakage and scale of mean depth of microleakage of 90° margin of Group Upcera Hyramic and Lava Ultimate were significantly better than those of Group Upcera UP.CAD and IPS e.max CAD (P < 0.05) while mean marginal integrity rate was not significantly different (P>0.05). Mean marginal integrity rate of 90° margin was significantly better than that of 135° margin in each group (P < 0.05) while mean depth of microleakage between different margins was not significantly different in each group (P>0.05). Mean marginal gap value of 90° margin of Group VitaBlocs Mark Ⅱ and IPS e.max CAD was significantly better than that of 135° margin (P < 0.05) while there was not significant difference in other 3 groups between 90° and 135° margin (P>0.05). Scale of mean depth of microleakage of 135° margin of Group Upcera Hyramic and Lava Ultimate was significant better than that of 90° margin (P < 0.05) while there was not significantly different in other 3 groups between 90° and 135° margin (P>0.05).@*CONCLUSION@#The mesial and distal margins of abutement of all-ceramic inlay should be prepared as butt-joint.

Stress distribution of molars restored with minimal invasive and conventional technique: a 3-D finite element analysis

PURPOSE: This study aimed to analyze stress distribution and maximum von Mises stress generated in intracoronal restorations and in tooth structures of mandibular molars with various types of cavity designs and materials. MATERIALS AND METHODS: Threedimensional solid models of mandible molar such as O inlay cavity with composite and gold (OR-C, OG-C), MO inlay cavity with composite and gold (MR-C, MG-C), and minimal invasive cavity on occlusal and proximal surfaces (OR-M, MR-M) were designed. To simulate masticatory force, static axial load with total force of 200 N was applied on the tooth at 10 occlusal contact points. A finite element analysis was performed to predict stress distribution generated by occlusal loading. RESULTS: Restorations with minimal cavity design generated significantly lower values of von Mises stress (OR-M model: 26.8 MPa; MR-M model: 72.7 MPa) compared to those with conventional cavity design (341.9 MPa to 397.2 MPa). In tooth structure, magnitudes of maximum von Mises stresses were similar among models with conventional design (372.8 – 412.9 MPa) and models with minimal cavity design (361.1 – 384.4 MPa). CONCLUSION: Minimal invasive models generated smaller maximum von Mises stresses within restorations. Within the enamel, similar maximum von Mises stresses were observed for models with minimal cavity design and those with conventional design.

Comparación de dos clasificaciones de preparaciones cavitarias y lesiones cariosas: Mount y Hume, y Black / Comparison of two classifications of cavity preparations and carious lesions: Mount & Hume, and Black

Introducción: en la práctica clínica de la estomatología es común encontrar profesionales que no conocen ni saben aplicar la clasificación de preparaciones cavitarias de Mount y Hume. En la literatura en idioma español es escasa la información acerca del tema, a pesar de que las entidades rectoras del gremio internacional la consideran vigente. Objetivo: comparar la clasificación de las preparaciones cavitarias dentales según Mount y Hume, modificada por Lasfargues y otros, con la de Black. Métodos: se realizó un estudio de revisión bibliográfica sobre la clasificación de las preparaciones cavitarias según Mount y Hume, en la que se incluyeron artículos publicados desde 2006 hasta 2014. Se revisaron revistas de impacto en Internet que tratan el tema (en: Google académico, Scopus, Scielo, Hinari, y Medline). Los términos utilizados fueron: new cavity classification, cavity design, preservation and restoration of tooth structure, enamel remineralization, Mount Hume Lasfargues Classification. Los 163 artículos obtenidos fueron tamizados; pero el estudio se ciñó solo a 52 artículos que trataban estas temáticas de manera más integral. Análisis e integración de la información: se consideró a la clasificación de Black como insuficiente en cuanto a las nuevas tecnologías y conceptos actuales orientadas al logro de terapias mínimamente invasivas. Mount y Hume demuestran con su clasificación las limitaciones de las preparaciones de Black. Consideraciones finales: la clasificación de Black presentó limitaciones en relación con la de Mount y Hume, y Lasfargues. Ambas clasificaciones deben coexistir, y es factible aplicarlas en la estomatología conservadora actual(AU)

Introduction: in dental practice it is common to find professionals who do not know or are unable to apply Mount & Hume's cavity preparation classification. Information about the subject is scarce in the literature published in Spanish, despite the fact that leading dental institutions worldwide consider it to have current validity. Objective: compare Mount & Hume's classification of dental cavity preparations as modified by Lasfargues and colleagues, with Black's. Methods: a bibliographic review was conducted of papers about Mount & Hume's classification of cavity preparations published from 2006 to 2014. The review included high impact online journals from the databases Google Scholar, Scopus, Scielo, Hinari and Medline. The search terms used were new cavity classification, cavity design, preservation and restoration of tooth structure, enamel remineralization, Mount Hume Lasfargues Classification. The 163 papers obtained were scanned, but the study was restricted to the 52 which dealt with the topic in a more comprehensive manner. Data analysis and integration: black's classification was considered to be insufficient in the light of the new technologies and current concepts about minimally invasive therapies. Mount & Hume's classification shows the limitations of Black's preparations. Final considerations: black's classification had limitations with relation to Mount & Hume's and Lasfargues'. Both classifications should coexist and it is feasible to apply them in current conservative dental practice(AU)

Mechanical test and two variable regression analysis of cavity design / 实用口腔医学杂志

Objective: To study the relationship between the depth and width of cavity design and to analyze the tendency of breaking load in preparations. Methods:Plaster models of mandibular first molar were prepared and magnified by 150%. Cavity on occlusal surface was designed and prepared in a cylinder shape with the depth(mm) of 3.0,4.5 and 6.0,and diameter(mm) of 3.0,4.5 and 6.0,respectively. 8 cavity samples were prepared for each design. The breaking load of the tooth models before and after restoration with self-curing resin was measured by Instron tester.Mechanical model static load test and two variable regression analysis were applied to study the mechanical property of the cavity design. Results:Before restoration, with the increase of depth and diameter, the incidence rate of tooth fracture increased. The width was the main factor. After restoration, the load was undertaken by restoration directly, and could be transfered to tooth and periodontal tissue through restoration uniformly. When the diameter of the cavity increased, the diameter of restoration also increased, and thus decreased the load on local structure of the tooth. With two-regression analysis, the regression equation and regression curve were obtained. Conclusion: The fracture of tooth before and after restoration is related to the diameter and depth of cavity design in cylinder shape. The regression equations of changing tendency of breaking load (Y) in preparation caused by the change of depth(X 1) and diameter(X 2) of cavity obtained by two-regression analysis are presented as follows: Before restoration: Y=1593.317-51.178 X 1-79.489X 2.After restoration:Y=1802.928 -192.461X 1+225.128X 2.