fluorapatite and Tooth-Fractures

Encompassing a vast array of materials, today's all-ceramic systems are suitable for a large range of indications in almost all areas of fixed restorative dentistry.. The authors describe five clinical cases involving different indications to illustrate the use of different ceramic materials and combinations of materials. They describe the collaboration between the dentist and dental technician for single-tooth restorations and for complex cases, including all stages of the restorative procedures from treatment planning with an analytic wax-up to the selection of appropriate materials, tooth preparation and cementation.. The patients described experienced significant functional and esthetic improvement, even those who had severely discolored teeth. This was possible because the authors executed the working steps in a strictly synchronized manner and selected the restorative materials carefully to meet the specific needs of each patient.. All-ceramic systems have expanded the range of restorative treatment options significantly; at the same time, their handling has been simplified substantially. The use of lithium disilicate glass-ceramic-and zirconium oxide-based frameworks along with an identical veneering ceramic enables the dental care professional to cover almost all indications in fixed prosthodontics while achieving the same esthetic results.

Topics: Adolescent; Adult; Apatites; Cementation; Ceramics; Crowns; Dental Bonding; Dental Materials; Dental Porcelain; Dental Prosthesis; Dental Prosthesis Design; Dental Veneers; Dentinogenesis Imperfecta; Denture, Partial, Fixed; Esthetics, Dental; Female; Humans; Incisor; Inlays; Male; Middle Aged; Patient Care Planning; Tooth Fractures; Tooth Preparation; Tooth Wear; Zirconium

This in vitro study investigated the null hypothesis that metal-free crowns induce fracture loads and mechanical behavior similar to metal ceramic systems and to study the fracture pattern of ceramic crowns under compressive loads using finite element and fractography analyses.. Six groups (n = 8) with crowns from different systems were compared: conventional metal ceramic (Noritake) (CMC); modified metal ceramic (Noritake) (MMC); lithium disilicate-reinforced ceramic (IPS Empress II) (EMP); leucite-reinforced ceramic (Cergogold) (CERG); leucite fluoride-apatite reinforced ceramic (IPS d.Sign) (SIGN); and polymer crowns (Targis) (TARG). Standardized crown preparations were performed on bovine roots containing NiCr metal dowels and resin cores. Crowns were fabricated using the ceramics listed, cemented with dual-cure resin cement, and submitted to compressive loads in a mechanical testing machine at a 0.5-mm/min crosshead speed. Data were submitted to one-way ANOVA and Tukey tests, and fractured specimens were visually inspected under a stereomicroscope (20×) to determine the type of fracture. Maximum principal stress (MPS) distributions were calculated using finite element analysis, and fracture origin and the correlation with the fracture type were determined using fractography.. Mean values of fracture resistance (N) for all groups were: CMC: 1383 ± 298 (a); MMC: 1691 ± 236 (a); EMP: 657 ± 153 (b); CERG: 546 ± 149 (bc); SIGN: 443 ± 126 (c); TARG: 749 ± 113 (b). Statistical results showed significant differences among groups (p < 0.05) represented by different lowercase letters. Metal ceramic crowns presented fracture loads significantly higher than the others. Ceramic specimens presented high incidence of fractures involving either the core or the tooth, and all fractures of polymer crown specimens involved the tooth in a catastrophic way. Based on stress and fractographic analyses it was determined that fracture occurred from the occlusal to the cervical direction.. Within the limitations of this study, the results indicated that the use of ceramic and polymer crowns without a core reinforcement should be carefully evaluated before clinical use due to the high incidence of failure with tooth involvement. This mainly occurred for the polymer crown group, although the fracture load was higher than normal occlusal forces. High tensile stress concentrations were found around and between the occlusal loading points. Fractographic analysis indicated fracture originating from the load point and propagating from the occlusal surface toward the cervical area, which is the opposite direction of that observed in clinical situations.

Topics: Aluminum Oxide; Aluminum Silicates; Animals; Apatites; Bisphenol A-Glycidyl Methacrylate; Cattle; Chromium Alloys; Composite Resins; Crowns; Dental Porcelain; Dental Stress Analysis; Dentin-Bonding Agents; Finite Element Analysis; Glass Ionomer Cements; Lithium Compounds; Materials Testing; Metal Ceramic Alloys; Polyethylene Glycols; Polymethacrylic Acids; Post and Core Technique; Potassium Compounds; Resin Cements; Silicate Cement; Stress, Mechanical; Tooth Fractures; Zinc Phosphate Cement

Topics: Aluminum Silicates; Apatites; Ceramics; Dental Porcelain; Dental Prosthesis Design; Dental Veneers; Esthetics, Dental; Glass; Humans; Male; Tooth Attrition; Tooth Discoloration; Tooth Fractures; Tooth Preparation, Prosthodontic