Posterior indirect adhesive restorations (PIAR): preparation designs and adhesthetics clinical protocol

Posterior indirect adhesive restorations (PIAR) are very common nowadays in clinical practice. The indirect approach is often indicated by a need for cuspal coverage (one or more cusps). With the adhesthetics protocol, the first step is to perform a cavity analysis evaluating the resistance of the tooth after restoration. The structures to be evaluated are, in sequence, the interaxial dentin, ridges, roof of the pulp chamber, and cusps. To improve the strength, the cusps should be covered, when required. The build-up for PIAR is performed with an adhesive technique, and, if possible, with low-shrinkage materials. The use of an adhesive post is not required, but not contraindicated if performed with a conservative approach on the root canal. Different preparation designs can be chosen. The butt joint, the most common with an adhesive technique, is used to protect the cusp when it is evaluated to be too fragile. A variant of the butt joint, the bevel, is useful for esthetic purposes or for providing more space or more enamel surface on the peripheral part of the preparation. The shoulder is useful if a cervical grasp is required, but is usually indicated when a previous cusp fracture needs to be restored. The veneerlay combines an overlay design with a buccal veneer when there are specific esthetic needs. In the interproximal areas, the preparation designs can be classified as: slot - the most common; bevel - useful in some cases to restore the ridge with a more conservative approach; ridge up - useful to preserve the ridge (a very important structure to maintain the resistance of the tooth) even when cuspal coverage is required. Ridge up can have two variants: ridge preservation and ridge coverage. More than one preparation design is used in many cases in the same preparation, taking into consideration the specific situation of the tooth and its different areas, in order to balance the prognosis with a conservative approach.