Background

Triggered host defense responses initiate inflammation of the peri-implant soft tissue (peri-implant mucositis), which can lead to loss of peri-implant supporting bone (peri-implantitis), and eventually, result in implant failure [1]. An increasing prevalence of peri-implantitis has been described in recent literature [2], with current incidence ranging from 1 to 47%. A non-linear, accelerating pattern of progress is suggested for the majority of cases, with an occurring onset within 3 years of function [3]. As for periodontal disease, the presence of micro-organisms is an important factor for the development of an inflammatory response in peri-implant tissue [4]. In order to effectively treat the peri-implant inflammation, disruption of microbial adhesion and reduction of biofilm accumulation on the implant surface is probably of eminent importance.

A number of mechanical interventions (e.g., abrasive air powder, teflon curettes, ultrasonic devices) and chemical agents (e.g., chlorhexidine, hydrogen peroxide) solely or in combination have been described as methods for implant surface decontamination in both in vivo and in vitro studies, in both a surgical and non-surgical setting ([5–12]). According to different reviews on in vivo and in vitro mechanical debridement [13–17], a gold standard mechanical debridement regimen still does not exists. Possibly, the implant surface roughness and screw-shaped design of dental implants may compromise an effective mechanical intervention. Therefore, the additional use of chemical agents for implant decontamination may be advocated.

Antimicrobial solutions have been studied in different clinical studies [9, 10, 18, 19]. No superior clinical effectiveness has been shown in a single study for a specific chemical decontamination protocol (for reviews see [17, 20, 21]). However, studies using acids at low pH (<2) have shown potentially beneficial antiseptic effects [22–29]. Especially, results on decontamination with phosphoric acid might be promising. Wiltfang et al. [27] showed that surface decontamination with phosphoric acid (pH 1) in a surgical treatment protocol resulted in complete elimination of the bacterial microflora. Also, results of a short-term clinical trial by Strooker et al. [26] showed an instant greater reduction of colony-forming units on the implant surface when using phosphoric etching gel (pH 1). In addition, animal studies [30, 31] showed re-osseointegration and direct bone-to-implant contact when acids were used. Therefore, phosphoric acids might be considered a potentially feasible decontaminating agent.

Thus far, the use of phosphoric acid etching gel as decontaminating agent has not been evaluated in a randomized controlled trial. The aim of the present randomized controlled trial is to evaluate the short-term microbiological and clinical effectiveness of 35% phosphoric etching gel as a decontaminating agent of the implant surface during resective surgical treatment of peri-implantitis.