In vitro comparison of the compressive strengths of seven different provisional crown materials

Abstract

Provisional crowns may be used for many weeks during healing of soft tissues, while other dental procedures are being performed and whilst the permanent restorations are being fabricated. The provisional occlusion they present serves a diagnostic purpose for fine tuning biological and biomechanical requirements. They need to be strong enough to withstand masticatory forces during this time, as it is costly, inconvenient and time consuming to repair breakages. There is no ideal provisional crown material, and new products appear on the market regularly. Dentists need to know which perform best in terms of strength, durability, ease of use, aesthetics and cost to facilitate selection and purchase. This study was undertaken to compare the compressive strengths of seven different provisional crown materials, consisting of three acrylic resins, three composites and one CAD/CAM fabricated sample set. A custom-made stainless steel split mould was constructed having a circular opening of 4mm in diameter and 6mm in-depth and was used to prepare ten specimens for each material. For the composites, the various materials were syringed into the circular openings and compacted using a ball burnisher. After five minutes, specimens were removed. The heat cured acrylic resin specimens were further processed in a pressure pot for five minutes. All samples were stored in distilled water at 370C for 24 hours before being tested. Test specimens were mounted into a jig on the Instron machine and loaded under a compressive force until they fractured or the compression limit was reached. The forces applied were recorded and used for statistical analysis. The results may help clinicians to select the most appropriate material for each clinical situation.