Selection criteria: This study comprises meta-analyses of studies examining the effect of treatment of edentulism with implant-retained mandibular overdentures. Initially 2262 non-duplicated articles were identified from the database searches, of which 37 were eligible for full-text searching. Twenty-seven were excluded because they failed to meet the inclusion criteria, their populations and outcomes overlapped, or their outcomes were outside the remit of the review. A total of 10 manuscripts on 7 randomized controlled trials were included in the meta-analysis. The sample sizes in these trials varied from 60 to 157 participants. The total number of different subjects included in the studies considered was 750. Some of the published papers included the same study populations but with different outcome measures, for example Awad et al and Thomason et al (oral health-related quality of life at 2 months and general satisfaction at 6 months, respectively). Study populations that appeared in more than 1 publication were included only once in the meta-analysis using the more informative publication for that outcome. The age range of those involved in the studies ranged from 35 to 80 years, and all patients wore conventional maxillary complete dentures and either mandibular implant-retained or conventional complete dentures. Outcomes were included with a follow-up period of at least 2 months.
Key study factor: Key study factors were the treatment with an implant-retained mandibular over denture of edentulous patients who had previously been treated with conventional complete dentures.
Main outcome measure: The primary outcomes were general satisfaction, oral health quality of life(QOL), and general health QOL measures. These patient-centred measures were used to assess the efficacy of the treatment provided. Outcomes of the meta-analysis are expressed in terms of effect size (ES).
Main results: Ten publications of 7 randomized controlled trials were identified, and 8 of these publications were used in the meta-analysis. For the effect of treatment on general patient satisfaction, from the 10 publications 6 studies with a population of 588 participants (n = 322 implant overdentures; n = 266 conventional dentures) were used. General satisfaction was expressed by the participants using a 100-mm visual analog scale or Likert-type response scale. The pooled ES was 0.80 (z = 3.56, 95% confidence interval [CI] 0.36-1.24, P = .0004) in favor of the implant overdenture. The standardized mean differences were positive in all of the studies. The P value for heterogeneity (chi2= 31.63, df = 5) was P less than .00001 and l(2)= 84%.For the effect of mandibular prosthesis on oral health-related QOL, the meta-analysis included only studies using the Oral Health Impact Factor (OHIP) as the measurement instrument. A total of 280 participants were therefore included in the analysis (n = 146 implant over-dentures; n = 134 conventional dentures). For the 3 pooled trials the ES was -0.41(z = 131, 95% CI -1.02 to 0.20, P = .19). Significant heterogeneity was again observed. The P value for heterogeneity (chi2 = 11.53, df = 2) was P equals .003 and l(2) equals 83%. In 2 of the 3 trials the 95% CI did not include an ES of zero. When the analysis was restricted to studies including populations that were recruited from the general population recruited via advertisement, the pooled ES values declined from -0.41 to -0.71 (z = 4.37, 95% CI -1.03 to -0.39, P < .0001), the -ve value for their ES were consistent with a significantly positive effect in favor of the implant overdenture treatment. For the effect of treatment on perceived general health, only 1 article was found that used a general instrument to measure this--the authors had used the SF-36 and found no difference between groups on any of the subscales--as no other study used a similar scoring method no further processing of the data was undertaken.
Conclusions: The analyses illustrate that patient general satisfaction and oral health-related QOL are greater with mandibular implant-retained overdentures than conventional dentures, but the magnitude of these effects remain uncertain, and heterogeneity of outcomes was observed. The review sheds no new light on the effect of the treatment on general health related QOL.