Aim: To evaluate the effectiveness of a flapless surgical approach in the treatment of peri-implantitis and to explore the factors influencing disease resolution.

Material and Methods: This case series involved patients with at least one implant diagnosed with peri-implantitis treated with a flapless surgical approach. Treatment consisted on mechanical debridement and chemical decontamination of the implant surface plus mucosal curettage combined with/without systemic antimicrobials and/or prostheses modification. Follow-up visits for supportive peri-implant care (SPIC) were scheduled at 6 and 12 weeks, and then every 3 months during the first 12 months. Clinical and radiographic parameters were assessed at baseline, 3 months and 12 months. Disease resolution defined as residual probing depths < 5 mm, ≤ 1 point of BOP, absence of suppuration and absence of progressive bone loss compared to pre-treatment bone levels was the main outcome variable. Multilevel regression analyses was used to identify predictors affecting the probability of disease resolution.

INTRODUCTION

Peri-implant diseases, especially peri-implantitis, represent a growing public health problem due to their high prevalence and the associated consequences (implant and implant-supported prosthesis loss). In addition, given the complex histopathology and the accelerated pattern of disease progression, peri-implantitis is considered one of the most challenging biological complications to treat.

A step-by-step approach has been proposed in the Clinical Practice Guidelines to maintain healthy peri-implant tissues and to manage peri-implant diseases, recommending that the treatment of peri-implantitis should start with a non-surgical step. However, systematic reviews have shown limited predictability and conflicting results for non-surgical treatment , suggesting that clinical and patient-reported benefits remain to be proven. Consequently, surgical interventions are frequently recommended due to the advantage of gaining access to remove the biofilm from the implant surface. However, treatment success based on clinical and radiographic outcomes,, for patients enrolled in regular post-treatment supportive care, are within 33-75% at the implant level following non-reconstructive surgical protocols and 51-58% with surgical reconstructive therapy.

To compensate the limited access to the implant surface, recent studies are including the curettage as part of the non-surgical treatment with promising results. With this procedure the granulation tissue is removed from the peri-implant mucosa and, if extended, it can also detach the periosteum and obtain direct access to the crestal bone and the entire contaminated implant surface. Given the inability of the peri-implant connective tissue to separate the inflammatory cell infiltrate from the crestal bone, gaining access to this critical area with a low morbidity procedure may represent an interesting alternative treatment strategy. With this modification, the treatment may be considered a minimally invasive surgery, with clear advantages for the patient in comparison to conventional open flap surgical techniques. This treatment strategy, however, needs to be further studied.

The objective of this case series was to evaluate the effectiveness of a flapless surgical approach in patients with peri-implantitis in terms of disease resolution and to explore the involved factors after a follow-up of 12 months.

MATERIAL AND METHODS

Study design and ethical considerations

This retrospective case-series was reported according to the Strengthening the Reporting of Observational studies in Epidemiology guidelines and was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained in accordance with local standards, along with local ethical committee approval

Patient screening

Patients referred to a private practice in Madrid, Spain, for the treatment of peri-implantitis and who met the inclusion criteria were consecutively recruited from from January to June 2023, were recruited for the study. The inclusion criteria for patients were as follows: i) > 18 years old; ii) presence before treatment of at least one implant diagnosed with peri-implantitis following the case definition of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions, defined as probing pocket depth > 6 mm combined with bleeding on probing and/or suppuration and progressive bone loss in relation to the radiographic bone level assessment at 1 year following the delivery of the implant-supported prosthetics reconstruction. In the absence of initial radiographs, radiographic evidence of bone level ≥3 mm was considered; iii) follow-up period after treatment of at least 12 months. Subjects were excluded if they were i) pregnant or breast-feeding; ii) had systemic contraindications to receive treatment; iii) had presence of implant-supported removable overdentures; iv) present implant mobility before treatment; or v) present inability or unwillingness to give informed consent.

Intervention

A single experienced periodontist with 2.5 X magnification loops performed the interventions in all the patients. Patients were treated in 1-2 sessions within a period of 7 days, with a minimum of 90 minutes per session. Implant-supported restorations were unscrewed when full access to the implant surface and surrounding bone crest was not guaranteed. Unscrewed prostheses were modified in the laboratory if they were not cleansable (allowing implant hygiene access for biofilm removal) or to eliminate/reduce porcelain in direct contact with the bone when it was present. All the restorations were relocated at the end of each intervention session. After local anesthesia, a periodontal ultrasonic stainless-steel tip was used for supra- and sub-mucosal mechanical debridement . Next, a Columbia 4R/4L curette was used around the implant in a circular motion until a bone exposure of 2-3 mm was achieved. Mucosal curettage was simultaneously performed to remove the granulation tissue adjacent to the contaminated implant surfaces. After obtaining access to the implant surface, ultrasonic instrumentation was repeated and air polishing with an erythritol powder was applied submucosally with the aim of a periodontal probe to separate and retract the peri-implant mucosa during the procedure. Hydrogen peroxide 3% was used to irrigate the implant surface for 2 minutes, followed by a rinse with saline. Oral hygiene instructions were given in detail at the end of the treatment. Systemic antibiotics, when prescribed, were metronidazole 500 mg every 8 h for 7 days or azithromycin 500 mg every 24 h for 3 days. If patients were already taking amoxicillin or need antibiotic prophylaxis for systemic reasons, it was maintained until the prescription ended (7 days).

Supported peri-implant care program

Follow-up visits for SPIC were scheduled at 6 and 12 weeks, and then every 3 months during the first 12 months. After 12 months and according to the patient risk profile, SPIC was recommended every 3-6 months. Oral hygiene was individually reinforced at each visit as needed.

Sites with residual PPD > 5 mm with BOP after 3 months were re-instrumented as previously described without any further systemic antibiotic. Implants presenting progressive clinical and/or radiographic worsening despite re-instrumentation were referred for an open flap debridement procedure or for explantation in case implants were mobile or broken during the follow-up (including those adjacent implants becoming useless due to restorable reasons).

Data collection

Baseline patient and implants characteristics

At baseline, the following patient characteristics were registered: age, gender, smoking habit, number of cigarettes per day, presence/absence of potentially related systemic diseases (i.e. diabetes, hypothyroidism, osteoporosis, anxiety and/or depression disorders), diagnosis of periodontitis, periodontitis stage (I-IV), if the patient was periodontally stable defined as bleeding on probing < 10% of sites, no probing depths > 4 mm that bleed on probing and lack of progressive periodontal destruction, type of toothbrush (manual or powered) and full mouth plaque score.

The following characteristics of the included implants were recorded at baseline: implant site (anterior, premolar, molar), implant arch (maxilla, mandible), implant diameter (i.e < 4 mm, > 4 and < 5mm or > 5 mm), type of prosthesis (single crown, fixed partial prosthesis), prosthesis retention (screw retained/cemented), time since implant placement, prosthesis material (i.e. metal-porcelain, zirconia or metal-resin), access to oral hygiene before treatment, prosthesis removal during the treatment, prosthesis modification as part of the treatment, vestibule depth (i.e. shallow or deep), presence of keratinized mucosa (< 2 mm or > 2 mm), presence of intermediate abutment and abutment height (< 2 mm or > 2 mm).

Clinical parameters

A previously calibrated examiner carried out all clinical measurements. Patients were examined for peri-implant parameters pre-operatively and twice post intervention, at 3 months and 12 months after treatment. Implants were measured using a UNC 15 manual periodontal probe at six sites per implant to the nearest mm for probing pocket depth and dichotomously scored at six sites per implant for bleeding on probing , suppuration and presence/absence of biofilm detected by the periodontal probe (implant plaque score).

Radiographic parameters

Measurements of radiographic outcomes were done by an independent and calibrated examiners. The calibration exercise consisted on repeated measurements of 40 randomly selected radiographs. The achieved inter-examiner intraclass correlation coefficient for marginal bone levels was 0.99 (95% confidence interval: [0.97; 0.99]). Standardized intra-oral periapical radiographs were taken using a long-cone paralleling technique. The radiographs were taken before intervention and at 12 months after treatment. Each radiograph was calibrated using the implant length as the fixed reference and the following linear measurements were carried out using an image analysis software to the nearest 0.1 mm: i) marginal bone levels (vertical distance expressed in mm from the implant shoulder to the most coronal interproximal bone implant contact at mesial and distal sides); ii) vertical intra-bony defect depth (vertical linear distance expressed in mm measured from the bone crest to the most coronal interproximal bone implant contact at mesial and distal sides); and iii) intra-bony defect width (horizontal linear distance expressed in mm measured between the mesial and distal interproximal bone crest and the implant surface).

Disease resolution

The endpoint of the treatment and primary outcome of the study was the composite outcome disease resolution, defined as concomitant residual probing depths < 5 mm, < 1 point of BOP, absence of suppuration and absence of progressive bone loss compared to pre-treatment bone levels.

Data Analyses

Clinical and radiographic parameters were expressed as means and standard deviations for continuous variables and as absolute and relative frequencies for categorical variables at baseline, 3-months and > 12 months. Differences were analyzed using analysis of variance and the chi-squared test. Adjustment for multiple comparisons (pairwise tests) were performed using the Bonferroni correction method. A p value <0.05 was considered as statistically significant.

The primary outcome variable was disease resolution at the last follow-up examination. To identify factors affecting the probability of treatment success, a multiple logistic multilevel model was used. The hierarchical analysis included the patient at the higher level and the implant at the lower level. The logit function was applied to link the linear model with the probability of the binary event. The independent factors examined included treatment factors (i.e. systemic antimicrobial prescribed), patient-related data (age, gender, smoking habit, systemic diseases, diagnosis of periodontitis, use of manual or powered-toothbrushes, full-mouth plaque score and compliance with supportive peri-implant care program), and implant- and prostheses-related data (number of affected implants, jaw, location, implant surface and diameter, time since implant placement, type of prostheses, prostheses retention and material, etc.). The model was built with the intercept as a random term. All variables were assessed by the Wald test in a bivariate analysis, and only statistically significant variables (P < 0.05) were retained in the multiple model. The treatment factor (i.e the systemic antimicrobial prescribed, if any) were forced into the final model, and a possible interaction between the factor and the covariates was explored. Results were expressed as odds ratios (ORs) including 95% confidence intervals (CIs).

Inclusion Criteria:

• > 18 years old
• presence before treatment of at least one implant diagnosed with peri-implantitis following the case definition of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions, defined as probing pocket depth > 6 mm combined with bleeding on probing and/or suppuration and progressive bone loss in relation to the radiographic bone level assessment at 1 year following the delivery of the implant-supported prosthetics reconstruction. In the absence of initial radiographs, radiographic evidence of bone level ≥3 mm was considered; - follow-up period after treatment of at least 12 months

Exclusion Criteria:

• pregnant or breast-feeding
• had systemic contraindications to receive treatment
• had presence of implant-supported removable overdentures
• present implant mobility before treatment
• present inability or unwillingness to give informed consent.

patients diagnosed with peri-implantitis in need of treatment

Share of the protocol, results will be available in the publication