Root-retained overdentures: Survival of abutment teeth with precision attachments on root caps depends on overdenture design.

Abstract

Root-retained overdentures (OD) are one treatment option for partially edentulous patients. However, the available evidence regarding factors influencing abutment survival in root-retained ODs is limited. This retrospective study included clinical examinations and evaluated the survival rate of roots restored with precision attachments soldered to post-and-core (gold cap) retained ODs, analysed with respect to various patient- and prosthesis-related factors. Patients receiving at least one OD with gold caps in the past were invited for comprehensive clinical examinations. The primary outcome parameter was the abutment survival rate over the observation period (2002-2016). Possible contributing factors (eg closed vs open OD design) were analysed. Analyses included Kaplan-Meier estimators, Cox regressions and hazard ratios (HR). 114 patients with 128 ODs originally retained by 280 abutments, with a cumulative total exposure time of 2035.4years, were examined. Twenty-seven abutment teeth (9.6%) were lost after a mean observation period of 7.9±3.4years. Significant factors associated with abutment loss were a closed, compared to an open OD design (HR 8.38 (95% CI 1.11-63.59), P=.040), which was independent of the number of abutments per OD. Furthermore, the loss rate was higher when the denture was not worn day-and-night (HR 3.52 (95% CI 1.32-9.40), P=.012). Oral hygiene behaviour was associated with higher HRs. ODs remain a viable treatment option for patients with few teeth remaining in the dental arch. It is advisable to choose an open design for the OD, irrespective of the number of abutment teeth. Furthermore, gold cap-retained ODs should not be removed overnight.