TRANSLATING DENTAL PERFORMANCE INTO ENGINEERING SCIENCE WITHIN A SENIOR CAPSTONE DESIGN PROJECT

A capstone senior design project in mechanical engineering at Western New England College was developed to provide a student the opportunity to work with dental professionals to determine the causes of porcelain crown failures, and to recommend improvements in crown design and installation [1].The project afforded the student a unique opportunity to understand how component performance as viewed by the engineer can differ greatly from that of the medical professional.From a dental perspective, performance was viewed as the durability of the crown when bonded using a dental adhesive.From an engineering perspective, this performance was quantified using measurements of material properties in both the bonded and unbonded conditions in both quasistatic and dynamic loading conditions, the later derived by relating approximate human bite forces and loading rates to dynamic modulus and energy absorption up to fracture.Charpy Impact tests were used to characterize energy absorption at moderate loading rates, and the Split Hopkinson Pressure Bar technique was used to determine both the energy absorbed and dynamic modulus at very high loading rates.The problem was complicated by difficulties in the determination of dynamic strength due to the brittle nature of the porcelain.The strength and fracture resistance of the porcelain material was greatly enhanced by the bonding adhesive, as supported by the locations of actual crown failures in patients which occurred away from the bonding region.The study resulted in a number of recommendations for improving performance through variations in crown geometry and bonding.A number of challenges were overcome regarding the management of a dentalmechanical engineering project as a balance between the expectations of the dentist and the requirements of the senior capstone design course needed to be achieved.