Influence of keratinized tissue on spontaneous exposure of submerged implants: classification and clinical observations

Aim The reasons for spontaneous early exposure (SEE) of dental implants during healing have not been established yet. The objective of this study was to assess whether the width of keratinized tissue (KT) and other site-related conditions could be associated with implants€™ SEE. Materials and methods Data from 500 implants placed in 138 non-smoking patients, between September 2009 and June 2010, were evaluated. Implants were submerged and allowed to heal for 3 to 6 months. At baseline, the following conditions were documented: the presence of keratinized tissue width > 2 mm; the type of implant site (i.e. fresh extraction socket or edentulous alveolar ridge); concomitant use of guided tissue regeneration. During the healing period, the occurrence of partial or total implants SEE was recorded; thus, a mixed-effects logistic regression analysis was performed to investigate the association between implant site conditions and implant exposure. Results One hundred and eighty-five implants (37.0%) remained submerged after healing and were classified as Class I, whereas 215 (43.0%) showed partial spontaneous early exposure (SEE) at the first week after implant placement (Class II), and 100 implants (20.0%) developed more extensive exposures (Class III). The variables, baseline width of KT (p = 0.18), fresh extraction socket (p = 0.88) and guided tissue regeneration (GTR) plus bone substitutes (p = 0.42), were not found to be correlated with implants` SEE, with an odds ratio (OR) of 1.29 (95% confidence interval: -0.12-0.63), 1.03 (95% confidence interval: -0.46-0.53) and 1.22 (95% confidence interval: -0.29-0.68), respectively. Conclusion It was not possible to establish an association between SEE and some implant-related factors; therefore, further investigations focused on the reasons associated to implants€™ SEE are needed.