Influence of Modified Titanium Abutment Surface on Peri-Implant Soft Tissue Behaviour: A Systematic Review of Histological Findings

Purpose: The purpose of the present systematic review was to investigate at the histological level if a modified titanium surface abutment could affect the behaviour of soft peri-implant tissue (connective tissue adhesion and soft tissue inflammation). Materials and methods: An electronic databases research (MEDLINE/PubMed, Scopus, Web of Science, Cochrane Library) until 24 June 2019 for randomised controlled trials (RCTs), controlled clinical trials and non-randomised studies of interventions (NRSI) was performed. The focused question was: "In healthy patients with at least one titanium healing abutment connected to a dental implant, is the effect of a healing abutment surface modification different from machined titanium at the histological level?" The Cochrane Handbook for Systematic Reviews of Interventions to assess the risk of bias in individual studies was used for RCTs. The Newcastle-Ottawa quality assessment scale was used to evaluate NRSI. Results: In total, 192 records were evaluated for titles and abstracts. Seven studies were included in the review. Five of them reported an enhanced soft tissue adhesion in the modified abutment group without increasing the soft tissue inflammation. One study reported no significant differences among titanium-modified (double acid-etched) and titanium-machined groups. One author demonstrated at the 6-month follow-up period a higher level of inflammation around acid-etched surfaces, with a higher number of T and B lymphocytes and expression of vascular endothelial growth factor. Conclusions: Short-term data (< 6 months) suggested an enhanced connective fibre attachment next to titanium abutments with a modified surface and a similar inflammatory response, in comparison with machined surface titanium abutments. However, modified surfaces may lead to a long-term increased risk of a higher degree of inflammation in the peri-implant tissues. Due to limited available evidence, further long-term studies are needed to confirm these results.