The depth of the implant mucosal tunnel modifies the development and resolution of experimental peri-implant mucositis: A case-control study

Abstract

Background: Resolution and prevention of peri-implant mucositis are a key in preventing peri-implantitis. This case-control study aims to assess the modifying effect of a deep mucosal tunnel (DMT) on the induction and resolution phases of experimental peri-implant mucositis.

Methods: Nineteen subjects with a tissue level implant were assigned to cases (DMT, depth ≥3 mm) or controls (shallow mucosal tunnel ≤1 mm, SMT). Subjects underwent a standard experimental peri-implant mucositis protocol characterized by an oral hygiene optimization phase, a 3-week induction phase using an acrylic stent to prevent self-performed oral hygiene at the experimental implant, and a 3 + 2 weeks resolution phase. Modified plaque (mPI), gingival index (mGI) and peri-implant sulcus fluid IL-1β concentrations were measured over time. Differences between DMT and SMT were assessed with the Mann-Whitney test.

Results: Modified plaque index and mGI increased in parallel during the induction phase. After resumption of oral hygiene practice, mPI and mGI resolved towards baseline values in the SMT group. In DMT, mPI and mGI values diverged: plaque resolved but resolution of inflammation was delayed and of smaller magnitude during the first 3 weeks after resumption of oral hygiene. IL-1β concentrations were significantly higher in DMT at 21 days (end of induction) and during the resolution phase corroborating the clinical findings. Removal of the crown and submucosal professional cleaning were needed to revert mGI to baseline values in DMT implants.

Conclusions: The depth of the mucosal tunnel modifies the resolution of experimental peri-implant mucositis at transmucosal implants. This observation raises important questions on the effectiveness of self-performed oral hygiene in cases where implants are placed deeper and the ability to resolve mucositis and effectively prevent peri-implantitis in such situations.

Keywords: case-control study; dental implant; experimental gingivitis; mucositis prevention; peri-implant mucositis; peri-implantitis prevention; transmucosal implant.

Figure 1

Schematic illustration of experimental design and procedures

Figure 2

Diagram illustrating the depth of the mucosal tunnel at implants as assessed after corwn removal. Please note the position of the alveolar crest at the neighbouring teeth and with reference to the endosteal portion of the implant. MT: mucosal tunnel

Figure 3

Distance in mm from the bone crest of the adjacent tooth to the most coronal extent of radiographic bone to implant contact for shallow mucosal tunnel (SMT) implants (blue) and deeper mucosal tunnel (DMT) implants (red). This parameter describes the depth of the mucosal tunnel in DMT and SMT. Differences between groups are significant (p = 0.043)

Figure 4

Experimental peri‐implant mucositis time course showing the time course of modified plaque index (mPI), modified gingival index (mGI) and IL‐1b concentrations in (panel a, b and c), respectively. Shallow mucosal tunnel (SMT) is in blue and deeper mucosal tunnel (DMT) is in red. After a 4‐week period of oral hygiene, subjects were instructed to wear a stent during daily oral hygiene to avoid cleaning the experimental implant from day 0 to day 21. At day 21, professional tooth cleaning was performed and patients were instructed to resume normal oral hygiene until day 42. At day 42, crowns were removed and professional tooth cleaning extending in the submucosal area was performed and subjects were again instructed to continue regular oral hygiene practices. Significance of differences in the time courses was analysed as areas under the curve (AUC). No significant difference in AUC (p = 0.905) between DMT and SMT for mPI. Significant differences in AUC between DMT and SMT for mGI and IL‐1β were observed in the resolution phase. Asterisks placed next to the time point indicate significant inter‐group differences between DMT and SMT (Mann–Whitney U test with Bonferroni correction)

Figure 5

Box plots of peri‐implant crevicular fluid (PICF) IL‐1β concentrations across modified gingival index (mGI) values (site‐based analysis to validate measurements). A significant correlation between local mGI and IL‐1β concentrations in PICF was observed (Spearman correlation coefficient = 0.579, p < 0.001)