The Effect of Splinting Implant-Supported Restorations on Stress Distribution of Different Crown-Implant Ratios and Crown Height Spaces

PurposeTo assess whether splinting can counterbalance the detrimental effects of varying the crown-to-implant (C/I) ratio and crown height space (CHS) by decreasing nonaxial overload stresses.Materials and MethodsThree implants were inserted into a photoelastic block model. Two strain gauges were cemented onto the neck of each implant on the buccal and lingual aspects and provided a simultaneous direct reading of strain. Four groups of splinted cement-retained restorations with C/I ratios of 1:1, 1:1.5, 1:1.75, and 1:2 were used. CHSs were 10, 15, 17.5, and 20 mm, respectively. Fifteen static loadings were carried out simultaneously with 20-kg weights via a custom-built loading apparatus at 30° to the vertical axis.ResultsOcclusal force application at 30° showed a statistically significant increase in both buccal (1,911.65 ± 110 vs 3,252.06 ± 150) and palatal (35.58 ± 7 vs 286.85 ± 15) microstrain values as the C/I ratio increased from 1:1 to 1:1.5 (P < .001). Force application at 30° in cases with C/I ratios of 1:1.75 and 1:2 resulted in fracture of the abutment screw followed by dislodgement of the crowns. Failures were noted at a CHS of 15 mm or greater.ConclusionsIn this biomechanical mode, splinting does not prevent prosthetic failure when the CHS is 15 mm or greater. Vertical bone augmentation is highly recommended in cases with a CHS of 15 mm or greater.