Purpose: The present study aims to to compare the marginal adaptation of single unit metal coping with the conventional casting technique using A metal ring and A technique that uses a ringless system using a stereomicroscope. Materials and Methods: A stainless steel master die assembly was fabricated simulating a prepared crown. 30 wax patterns were fabricated which were divided into two groups. 15 with metal ring investment system and 15 with ringless investment system and the marginal adaptation between the die and patterns were compared and measured using Optical stereomicroscope. Results: The mean marginal adaptation of group 1 copings was found to be 89.570±3.82μm and of group 2 copings were found to be 51.605±3.89μm with the difference being statistically highly significant (P< 0.001). Which shows the mean marginal adaptation was higher in Group 2 (ring investment system) as compare to Group 1 (metal ring investment system) Conclusion The marginal adaptation of the Metal copings obtained in ringless investment system more accurate than those of the metal ring investment system. The ringless investment system can produce better fiiting and acceptable single unit restorations in fixed prosthodontics.
Keywords: Metal ring investment system, Ringless investment system , marginal adaptation, phosphate-bonded investment.