How do the dimensions of peri‐implant mucosa affect marginal bone loss in equicrestal and subcrestal position of implants? A 1‐year clinical trial

Abstract

IntroductionThere is evidence that the apico‐coronal implant position and the mucosal phenotype can affect the extent of peri‐implant bone loss. This clinical trial analyzes the bone remodeling and marginal bone loss that occur around conical‐connection implants placed equicrestally and subcrestally, assessing the effect of the peri‐implant soft‐tissue phenotype.MethodsFifty‐one patients received 56 implants of distinct diameters (3.5 mm Ø n = 6; 4.3 mm Ø n = 41; 5 mm Ø n = 9) in the posterior part of the maxilla or mandible. The implants were placed equicrestally, 1 mm subcrestally and >1 mm subcrestally, depending on the initial supracrestal tissue height (STH). After 3 months of non‐submerged healing, single metal‐ceramic screw‐retained implant‐supported crowns were placed. Longitudinal measurements of STH, mucosal thickness and keratinized mucosa width (KMW) were made at the time of implant placement (T0), crown placement (T1), and after 3 (T2) and 6 months (T3) of prosthetic loading. At each of these points, a radiographic evaluation of bone remodeling and marginal bone loss was also performed.ResultsSTH was significantly greater for implants placed >1 mm subcrestally than for those placed 1 mm subcrestally. After 12 months of follow‐up, a very significant (p < 0.001) loss of KMW was observed, in addition to a marginal bone loss of 0.08 ± 0.1, 0.15 ± 0.2, and 0.14 ± 0.2 mm in the groups placed equicrestally, 1 mm subcrestally and >1 mm subcrestally, respectively. After the multiple linear regression, marginal bone loss was found to depend primarily on KMW (β = −0.43), while also being affected by STH (β = 0.32) and implant diameter (β = −0.28).ConclusionsMarginal bone loss may be influenced by the position with respect to the bone crest, as well as the KMW, STH, and implant diameter. However, more well‐controlled studies are needed to verify these above‐mentioned findings with different implant designs and connections.