Correlation between implant long axis position relative to crown and incidence of complications

Abstract

Background The goal of successful implant and prosthodontic therapy is to replace one or more missing teeth in the prosthodontically correct position allowing for optimal function, esthetics and durability. There are numerous discussions about whether the implant position relative to its crown can influence the occurrence of complications and overall success of implant-prosthodontic therapy. Aim/Hypothesis The aim of this study was to investigate the influence of the implant long axis position relative to the crown center and occurrence of technical and biological complications, in implant-borne single crowns and FPDs. Material and Methods A total of 141 subjects with cemented (GIC, FujiCem, GC Corp., Japan) implant-supported prosthodontic appliances (single crowns and FDPs) at premolar and molar regions were followed during a period of 1 to 5 years. All subjects had received AstraTech TX implants, Dentsply Sirona Implant Co. Orthopantomogram was made the day of crown FPD cementation and every year consecutively during regular check-ups. At check-ups the following complications were registered- fracture of ceramics, construction or abutment, cement loosening, BOP and periimplant bone loss. The OPGs were used to register relation between implant long axis position relative to the center of the crown (central, mesial, distal positions). Presence of micro-gaps were registered when observed. Results Total of 141 subjects were examined (100 male and 41 female) between the age of 35 and 80 years. Positions of implant long axis relative to its crown were: 42 in the mesial, 68 in center and 31 in distal third of crown. Micro-gap was present in 33 implant-borne crowns. Biological complications were: bone loss (⅓ of implant length - 12, ⅔ of implant length - 12), implant loss - 14, BOP - 6. Technical complications were: abutment fracture - 8, ceramics fracture -10, abutment screw loosening - 7 and cement loosening - 4. Multivariate ANOVA demonstrated significant correlation (P<0.05) between implant long axis position relative to crown center and occurrence of both technical and biological complications. Conclusion and Clinical Implications Implant long axis position relative to the center of the crown seems to be correlated to the occurrence of biological and technical complications. The results of the study underline the importance of correct prosthodontically driven implant positioning. Further research is needed.