Restorative Dentistry Cuspal restorations Background.—Cusp fracture of restored posterior teeth is not uncommon but most can be restored. Adhesive restorations do not require extensive mechanical retention, which can prevent pulpal damage and other complications. Resin composite restorations have been believed to be inappropriate for occlusion-bearing restorations. Resin composite restorations can be made using direct or indirect techniques. The advantages of direct restorations are minimal intervention required, completion in a single treatment session, relatively low costs, and higher fracture resistance. Their drawback is polymerization shrinkage stress, but the configuration value is favorable for cusp-replacing restorations. The advantages of indirect restorations are lack of shrinkage problems, which produces better marginal adaptation; higher degree of polymerization; and the ability to shape external surfaces extra-orally. The indirect technique requires a diverging cavity, which requires the loss of tooth tissue. In addition, the relatively weak cement needed must adhere to the highly cured indirect restoration. A randomized controlled trial (RCT) was performed to compare the 5-year clinical performance of direct and indirect resin composite restorations for replacing cusps. Methods.—One hundred seventy-six restorations were made to restore maxillary premolars with Class II cavities and a missing cusp in 157 patients. Direct composite restorations were used in 92 cavities and indirect restorations in 84. Follow-up extended for at least 4.5 years (mean 5.6 years for direct and 6.0 years for indirect restorations), with survival rates determined using time to reparable failure and complete failure as the endpoints. Results.—Seventeen patients were lost to follow-up. Failures developed after a mean of 35.4 months for direct restorations and 37.4 months for indirect restorations. Complications at the restoration level, subsequent restorative treatment, or complications at the tooth level caused failure in 23 restorations, 8 of them direct and 15 indirect. Four failed restorations were restorable, and 3 indirect ones were re-cemented but failed 1 week to 7 months later. The reparable failures had a 5-year survival rate of 86.6%, and the complete failures had an 87.2% rate.
Mean survival time was estimated to be 106 months for reparable failures. The difference in survival between the direct and indirect restorations was not statistically significant. Direct restorations tended to fracture in the remaining cusp or suffer cohesive restoration failure. Indirect restorations were more likely to suffer dislodgement or dislodgement plus cohesive failure. Discussion.—The reported 5-year survival rates are comparable to values for extensive Class II restorations but lower than values for metal-ceramic crowns. Adhesive restorations offer minimal invasiveness and the possibility of repair, but repair may not be advantageous in terms of longevity of the restorations that replace cusps. Most failures were adhesive, which may be preventable by covering the remaining cusp, especially if it is a thin cusp prone to fracture. Cuspal coverage yields higher strength but also a higher risk of catastrophic failure. Catastrophic failure may be preventable by applying fibers, but this approach has not been confirmed clinically.
Clinical Significance.—The survival rates for direct restorations were better than for indirect restorations, but the difference was not statistically significant. Indirect restorations require more time and higher costs than direct restorations, making them less attractive to patients.
Fennis WM, Kuijs RH, Roeters FJ, et al: Randomized control trial of composite cuspal restorations; Five-year results. J Dent Res 93:3641, 2014 Reprints available from WM Fennis, Dept of Oral-Maxillofacial Surgery, Prosthodontics and Special Dental Care, Univ Medical Ctr Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands; e-mail: [email protected]