Provisional crowns and bridges have few important roles during the time between tooth preparation and fitting the final restoration. They are are very important part of prosthetic therapy not only for esthetic but also for pulp tissue protection against physical, chemical, and thermal impact. They also need to provide maintenance of positional stability and occlusal function. Provisional restorations can even be a diagnostic tool not only a space maintainer. Properly contoured they act as a diagnostic tool to determine occlusion. Because all off these requirements need to be met, provisional restorations need to be as esthetic and as strong as the permanent restorations. They must satisfy biologic, mechanical, and esthetic demands including resistance to fracture, marginal fit, wear resistance, tissue compatibility, ease of manipulation, and cost. Good marginal fit of temporary crowns protects prepared tooth tissue and accurate margins that are neither over or under extended are need to prevent gingival hypertrophy, gingival recession, and hemorrhage during cementation. An optimal provisional fixed provisional restoration must protect the underlying preparation, pulp, and gums, and should provide health recovery to any traumatized soft tissues while the definitive restoration is being fabricated by the laboratory.
Among the requirements of a ideal provisional restoration material, marginal adaptation is the most important one. A good margin must provide preotect for the prepared tooth, as well as its gingival tissues which is necessary for further therapy. Marginal failure might lead to microleakage which is one of the the main causes of tooth sensitivity, postoperative sensitivity, and recurrent dental caries. This happens because there are many factors that can have infulence on marginal fit. The type of restorative material, dentinal fluids, material properties such as dissolution and coefficient of thermal expansion and polymerization shrinkage can affect marginal fit. Marginal failure may cause bacteria colonization in dentinal tubules through the restorationtooth gap which can lead to pulpitis in vital teeth due to bacteria toxins. This directly affect restoration longevity. Microleakage might be more present when the preparation margin is in dentin. This is quite possible in the cervical area and in elderly patients.