Background: To effectively disrupt microbial biofilm and remove dental calculus with minimal damage to the root surface and soft tissues with limited patient discomfort constitute a significant tenet of periodontal therapy. The aim of the present prospective 12-month study was to compare clinical and microbiological effects following an erythritol air-polishing vs. conventional mechanical debridement of furcation defects in a cohort of periodontal maintenance patients.

Methods: Twenty patients with grade II mandibular molar furcation defects volunteered to enroll in this study. In a split-mouth design, two furcation sites in each patient were randomly assigned to either receive subgingival debridement using erythritol air-polishing (test) or conventional ultrasonic/curette debridement (control) at baseline, and at 3, 6, 9 and 12 months. Probing depth, clinical attachment level and bleeding on probing were recorded at 3-month intervals. Subgingival microbiological samples obtained at baseline, 6 and 12 months were analyzed using checkerboard DNA-DNA hybridization. Discomfort from treatment was scored at 12 months using a visual analogue scale.

INTRODUCTION.Traditionally, periodontal debridement is accomplished using curettes, sonic or ultrasonic scalers, all presenting comparable outcomes.1,2 However, periodic root instrumentation may lead to dental hard tissue3-6 and soft tissue damage,7 and sensitivity due to exposure of dentinal tubules.8-10 Air-polishing using low abrasive glycine or trehalose powder has been shown to reach similar clinical outcomes as hand and ultrasonic instrumentation, but with less hard tissue loss.11-16 Moreover, air-polishing provides superior outcomes relative to patient comfort and time efficiency.7,11,12,14 Recently, a low abrasive erythritol powder with comparable physical properties to glycine air-polishing powder was introduced for subgingival air-polishing.17 Erythritol, a non-toxic, chemically neutral and completely water-soluble polyol is widely used in food industry as an artificial sweetener. Two studies comparing conventional mechanical debridement with erythritol air-polishing, reported similar results in supportive periodontal therapy (SPT) relative to clinical and microbiological outcomes.18,19 Such observations are also reflected in a systematic review concluding that air-polishing systems as a monotherapy are comparable to conventional therapy in patients undergoing SPT in single- and multi-rooted teeth without furcations.20 Moreover, inhibitory effects on pathogenic bacteria including Porphyromonas gingivalis have also been observed.21 To the investigator's knowledge, no prospective studies investigating the efficacy of a low abrasive erythritol air-polishing system in molar furcation defects during SPT have been reported. The objective of this 12-month prospective study was to compare clinical and microbiological effects following an erythritol air-polishing system vs. conventional mechanical debridement of furcation defects in a cohort of periodontal maintenance patients.

METHOD AND MATERIALS. The study protocol and informed consent following the Helsinki Declaration of 1975 (version 2008) was approved by the Medical Research Ethics Committee (2016/793), University of Bergen, Norway. Participating subjects read and signed the informed consent prior to enrolling in the study.

Prestudy calibration and training. Two operators performed the clinical aspects of this study. Author TS, masked to treatment assignments, performed all clinical recordings and sampling, author IU performed all treatments.

Sample size. The sample size estimation was based on change in PD. A difference of 0.5 mm was considered clinically relevant.22 Standard deviation of the difference between repeated PD measurements from the intra-calibration exercise was 0.5 mm. A power analysis based on 20 subjects and with the level of significance (α) set to 0.05, resulted in 98.9% power to detect a true difference of 0.5 mm.

Treatments. Following baseline examination, mandibular jaw quadrants were randomized (coin toss) to either receive debridement using the erythritol powder/air-polishing system (test) or conventional ultrasonic/curette instrumentation (control) using a split-mouth study design. Sequence of treatments was randomized in a similar fashion. Treatments were delivered at baseline, and repeated at 3, 6, 9 and 12 months. Test sites thus received root debridement using the low abrasive erythritol powder (Air-flow powder plus®, EMS, Nyon, Switzerland ) applied through a Perio-Flow hand piece connected to an airflow unit (Air-Flow Master®, EMS, Nyon, Switzerland). The hand piece was fitted with a nozzle for subgingival delivery directing the power/air jet perpendicular to the root surface at the water exit at the tip of the nozzle. The nozzle was inserted to the apical aspect of furcation sites with PD≥ 4 mm using striking movements over the furcation area for 5 sec.12 Sites adjoining the test site with PD≥ 4 mm were similarly treated.

Control sites were debrided using an ultrasonic scaler (Piezon Master 400 Perio Slim Tip®; Electro Medical System, Nyon, Switzerland) with power set at 75% and water as coolant, and root planed with sharp curettes (Gracey SAS, Hu-Friedy, Chicago, IL, USA).

Patients were returned to their regular SPT upon completion of study. Gingival crevicular fluid assessments. Gingival crevicular fluid (GCF) was recorded at baseline, and at 6 and 12 months. Briefly, furcation sites were isolated with cottons rolls, cleaned for supragingival plaque, and air-dried. A perio paper strip was then placed 1-2 mm into the orifice of the site and left in place for 30 sec. Next, the perio strip was inserted into the Periotron 8000® (Oraflow, Smithtown, NY, USA) calibrated to estimate the volume of GCF collected.

Microbiological assessments. At baseline, and at 6 and 12 months the supragingival area above the furcation site was wiped clean using sterile cotton pellets. Three sterile paper points were then inserted into the pocket of the furcation site. The paper points were kept in place 20 sec27 removed and immersed into pre-reduced, anaerobic transport medium (PRAS; Dental Transport Medium, Morgan Hill, CA, USA).

Pain experience assessments. Visual analogue scale (VAS) scores were used to estimate patient discomfort experienced during test and control treatment.31 Scoring was performed at 12 months following completion of the debridement with 0="no pain" and 100="worst pain I can imagine".

Statistical analysis Data were entered into MS-Excel (Microsoft, Redmond, WA, USA ) proofed for errors and then imported into Stata, version 15 (StataCorp, College Station, TX, USA).

Summary statistics (means ± SEM) for the clinical variables were calculated for the test and control at baseline, and at 6 and 12 months. Due to the repeated nature of data, a mixed effect model taking into consideration incomplete data at 12 months was applied to analyze the data at patient and tooth level. Time and treatment were considered fixed factors. Mixed models were applied for both primary and secondary outcome variables.

For testing differences in microbial composition at test and control sites harboring different proportions of bacteria >105 at baseline, and at 6 and 12 months, logistic regression models with robust standard error were applied. VAS scores were analyzed using ordinary linear regression models with robust standard error. The level of significance was set at 0.05.

Inclusion Criteria:

1. Received supportive periodontal therapy (SPT) every 3-6 months for 2-3 years following periodontal therapy.
2. Having bilateral non-mobile, fully erupted mandibular first, second or third molars with degree II furcation defects.
3. PD≥4 mm with bleeding or pus on probing. -

Exclusion Criteria:

1. Mobile mandibular molars, molars with clinical or radiographic evidence of supra-/subgingival calculus or apical pathology.

2. Use of systemic antibiotics within 6 months or SPT within 3 months of study.

3. Any current medical condition affecting periodontal treatment or use of the abrasive air-polishing device.

4. Subjects with diabetes, cancer, HIV/aids, acute infections, disorders that may compromise wound healing, or pregnant women.

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Two operators performed the clinical aspects of this study. Author TS, masked to treatment assignments, performed all clinical recordings and sampling, author IU performed all treatments. All analyses were performed by a statistician (SAL) who had not taken part in data collection or treatments.