Analysis of load transfer and stress distribution by splinted and unsplinted implant-supported fixed cemented restorations

Controversy remains over the rehabilitation of implant-supported restorations regarding the need to splint adjacent implant-supported crowns. This study compared the effects of simulated occlusal loading of three implants restored with cemented crowns, splinted versus unsplinted. Three adjacent screw-shaped implants were passively inserted into three holes drilled in a photo-elastic model. Two combinations of cemented restorations were fabricated; three adjacent unsplinted and three adjacent splinted crowns. Strain gauges were connected to the implant necks and to the margins of the overlaying crowns. Fifteen axial static loads of 20-kg loadings were carried out right after each other via a custom-built loading apparatus. Strain gauges located on the implant neck supporting splinted restoration demonstrated significantly (P < 0·001) more strain (sum of strains = 3348·54 microstrain) compared with the single crowns (sum of strains = 988·57 microstrain). In contrast, significantly (P < 0·001) more strain was recorded on the strain gauges located on the restoration margins of the single crowns (sum of strains = 756·32 microstrain) when compared with splinted restorations (sum of strains = 186·12 microstrain). The concept of splinting adjacent implants to decrease loading of the supporting structures may require re-evaluation. The clinical relevance of these findings needs further investigation.