The effect of splinting crowns on multiple adjacent implants: a retrospective study

Abstract

Purpose: The purpose of this study was to retrospectively evaluate the effects of splinting implant crowns against nonsplinted crowns on the failures and complications of multiple adjacent implants. Material and methods: A retrospective chart review was conducted of all registered implant patients treated at the University of Minnesota School of Dentistry from 1988 to 2018. A total of 2738 implants within 1171 sections of 890 patients were examined retrospectively using an inclusion criteria of (1) two or more adjacent implants (section) present and (2) implants were restored by splinted crowns (Splinted group) or nonsplinted (individual) crowns (Nonsplinted group). Results: An average follow-up interval was significantly longer (p < 0.0001) for Splinted (median 5.52 [IQR 1.97, 9.67] years) compared to Nonsplinted (3.76 [1.49, 6.54] years). Splinted group’s Hazard ratio (HR) for implant failure was 0.67 (95% CI 0.35–1.31, p = 0.24) relative to Nonsplinted, and estimated 5- and 10-year failures rates were 2.5 (1.3–3.7) vs. 3.0 (1.9–4.0)% and 8.7 (6.1–11.3) vs. 8.6 (5.7–11.3)%, respectively. Splinted group’s HR for total complication relative to Nonsplinted was 0.98 (95% CI 0.71–1.36, p = 0.92) and estimated 5- and 10-year complication rates were 24.7 (21.7-27.5) vs. 23.7 (21.1-26.3)% and 38.1 (34.2-41.7) vs. 42.1 (37.2-46.6)%, respectively. Three most common complications (Splinted/Nonsplinted, 10-year estimates) were crown decementation/dislodgement (20.8/13.0%), peri-implantitis (12.2/13.1%), and screw loosening (5.9/12.8%), while 3 failure causes (5-year estimates) were peri-implantitis (1.8/1.3%), implant fracture/metal collar flowering (0.3/1.1%), and soft tissue encapsulation (0.1/0.2%). When 380 Lifecore implants with higher failure rates (8.4% in 7.2 years) were excluded, the implant failure HR became lower 0.46 (0.22–0.99, p = 0.05) indicating significantly lower implant failure risk in Splinted compared to Nonsplinted, while the total complication HR did not change much 0.95 (0.64–1.40, p = 0.79). When compared per section, Splinted total complication HR went down to 0.75 (0.55–1.02, p = 0.07), indicating lower risk for complication in Splinted sections compared to Nonsplinted sections. Conclusion: The trends of implant therapy of multiple adjacent implants have changed over the last three decades. The effects of splinting crowns of multiple adjacent implants were not significant in reducing implant failures or total complications. However, when the Lifecore implants mainly used in Splinted group during earlier phase (1988 – 2003) were excluded, the Splinted group showed significantly lower implant failure risk than Nonsplined group.