Multicentre prospective evaluation of implant-assisted mandibular removable partial dentures: surgical and prosthodontic outcomes

ObjectiveTo determine implant survival and prosthodontic maintenance of implant-assisted mandibular removable partial dentures in a multicentre prospective study up to 10years. Materials and methodsForty-eight participants with mandibular distal extension partial dentures were selected. A control group of 12 New Zealand participants had new conventional mandibular partial dentures made. Three test groups of 36 participants in New Zealand (n=12), the Netherlands (n=12) and Colombia (n=12) had bilateral distal implants placed. Surgical and prosthodontic outcomes were documented with only healing caps placed (Stage 1) and with an attachment system (Stage 2). ResultsNo implants failed after 3years. Four late implant failures in three participants occurred in New Zealand (two unilateral implant failures after 5 and 8years and two bilateral implant failures in the same participant after 6 and 10years); two unilateral late implant failures occurred in the Netherlands and no late failures in Colombia. Implant survival rate was 92% by 10years. Resonance frequency measurements were taken at surgery implant stability quotient (ISQ) 62.447.46; range 40 - 79), baseline (ISQ 63.22 +/- 6.17; range 50 - 74) and after 3years (ISQ 66.38 +/- 6.77; range 55 - 83). In New Zealand and Colombia, measured crestal bone levels were 2.03 +/- 0.71mm and 2.20 +/- 0.81mm, respectively, at baseline and 3years. For Stage I, principal prosthodontic maintenance issues were loose healing caps among 10 New Zealand participants, four Colombian participants and one Netherlands participant. For Stage 2, matrix activation and overdenture puncture fractures resulted in 41 events (25 participants) in New Zealand over 10years, whilst over 3years, there were 14 events in nine Colombian participants and six events in five Netherlands participants. ConclusionThis clinical multicentre research complements previous case reports, case series, retrospective and prospective studies on the notion of implant-assisted removable partial dentures for partially edentulous patients. Late implant failures and increased prosthodontic maintenance when an attachment system is used identify the need for further research, including more robust statistical analyses.