title: Tooth structure and fracture strength of cavities.
abstract: This study evaluated, in vitro, the loss of tooth substance after cavity preparation for direct and indirect restorations and its relationship with fracture strength of the prepared teeth. Sixty sound human maxillary first premolars were assigned to 6 groups (n=10). MOD direct composite cavities (Groups I, II and III) and indirect inlay cavities (Groups IV, V and VI) were prepared maintaining standardized dimensions: 2-mm deep pulpal floors, 1.5-mm wide gingival walls and 2-mm high axial walls. Buccolingual width of the occlusal box was established at 1/4 (Groups I and IV), 1/3 (Groups II and V) or 1/2 (Groups III and VI) of the intercuspal distance. Teeth were weighed (digital balance accurate to 0.001 g) before and after preparation to record tooth substance mass lost during cavity preparation. The prepared teeth were submitted to occlusal loading to determine their fracture strength using a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed by two-way ANOVA and Tukey test (alpha= 0.05). 1/4-inlay cavities had higher percent mean mass loss (9.71%) than composite resin cavities with the same width (7.07%). 1/3-inlay preparations also produced higher percent mean mass loss (13.91%) than composite resin preparations with the same width (10.02%). 1/2-inlay cavities had 21.34% of mass loss versus 16.19% for the 1/2-composite resin cavities. Fracture strength means (in kgf) were: GI = 187.65; GII = 143.62; GIII = 74.10; GIV = 164.22; GV = 101.92; GVI = 50.35. Statistically significant difference (p<0.05) were observed between Groups I and IV, II and V, III and VI. Higher tooth structure loss and lower fracture strength were recorded after preparation of inlay cavities, regardless of the width of the occlusal box, compared to the direct composite resin cavities.
authors.affiliation: Department of Operative Dentistry, Endodontics, and Dental Materials, School of Dentistry of Bauru, University of São Paulo, Bauru, SP, Brazil. jomond@fob.usp.br
authors.forename: José
authors.initials: J
authors.lastname: Mondelli
authors.forename: Fábio
authors.initials: F
authors.lastname: Sene
authors.forename: Renata Pereira
authors.initials: RP
authors.lastname: Ramos
authors.forename: Ana Raquel
authors.initials: AR
authors.lastname: Benetti
mesh_terms: D001641:Bicuspid; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000145:classification* / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D003782:Dental Pulp / Q000473:pathology; D003793:Dental Restoration, Permanent / Q000145:classification; D006801:Humans; D007284:Inlays; D008422:Materials Testing; D009929:Organ Size; D013314:Stress, Mechanical; D019228:Tooth Crown / Q000473:pathology; D014082:Tooth Fractures / Q000209:etiology* / Q000503:physiopathology
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D003776:Dental Porcelain