Transforming Subgingival Scaling: Short-Term Efficacy of No-Incision Micro-Flap Technique in Periodontal Treatment

Summary

This study demonstrates that the no-incision micro-flap technique (NMFT) enhances short-term subgingival scaling efficacy in moderate periodontal pockets by improving visualization, achieving superior probing depth reduction and bleeding control compared to conventional scaling.

Abstract

Conventional subgingival scaling and root planing (SRP) is typically performed without direct visualization, relying solely on tactile feedback, which limits the efficacy of calculus removal—particularly in deeper periodontal pockets. This study aimed to introduce and evaluate the no-incision micro-flap technique (NMFT), a four-handed, non-surgical modification designed to enhance subgingival visibility without requiring additional equipment such as a periodontal endoscope. In this split-mouth randomized controlled trial, 20 patients with generalized chronic periodontitis (Stage II–III) underwent NMFT-aided SRP on one side and conventional SRP on the contralateral side. Periodontal parameters, including probing depth (PD), clinical attachment loss (CAL), and bleeding on probing (BOP), were assessed at baseline, 6 weeks, and 3 months post-treatment. A total of 1,629 sites with baseline PD ≥ 4 mm were analyzed. At 3 months, the NMFT group demonstrated a significantly greater mean PD reduction compared to the control group (between-group difference: 0.5 mm; 95% CI: 0.26–0.81; P = 0.007, with the most pronounced effect observed in moderate pockets (4–6 mm), where an additional 0.7 mm reduction was achieved (P < 0.001). BOP rates were also significantly lower in the NMFT group in both 6 weeks (between-group difference = 7.2%, P = 0.028) and 3 months (between-group difference = 9.1%, P = 0.003). However, no significant inter-group differences in CAL gain were found. These findings indicate that NMFT enhances short-term SRP efficacy by improving visualization and debridement thoroughness, particularly in shallow-to-moderate pockets, offering a practical and accessible alternative to conventional blind SRP in resource-limited settings. Larger-scale validation is warranted to support its broader clinical adoption.

Introduction

Periodontal disease is a chronic inflammatory disorder triggered by microbial biofilms that leads to progressive destruction of the supporting periodontal tissues. Severe periodontitis represents a major cause of tooth loss worldwide¹. The primary goals of periodontal therapy include plaque control, inflammation resolution, and restoration of periodontal tissue function². Non-surgical periodontal therapy, a well-established approach, aims to control microbial infection through the removal of bacterial biofilms, calculus, and endotoxins from periodontally affected root surfaces³. As a cornerstone of non-surgical treatment, subgingival scaling and root planing (SRP)—performed with either manual instruments or ultrasonic devices—plays a crucial role in achieving these therapeutic objectives⁴.

Conventional SRP is typically performed without direct visualization, relying instead on tactile feedback to guide calculus removal⁵. This "blind" approach presents significant challenges, particularly given the complex morphology of root surfaces and the often smooth, burnished appearance of subgingival calculus, which hinders accurate assessment of debridement completeness⁶. Consequently, residual calculus is frequently observed following SRP, especially in pockets ≥4 mm deep, with prevalence increasing proportionally to pocket depth⁷. In sites with probing depths >5 mm, residual deposits may persist in over 90% of cases despite SRP⁸. These residual calculus deposits, along with inadequately planed root surfaces, can serve as niches for bacterial recolonization and biofilm reformation, potentially leading to persistent inflammation and disease recurrence⁹.

To enhance the visualization of calculus removal, periodontal endoscopy has emerged as a primary auxiliary tool in recent years¹⁰. It enables subgingival imaging of periodontal tissues with magnification capabilities ranging from 24 to 48 times¹¹. Periodontal endoscope-assisted SRP outperforms traditional SRP in terms of clinical efficacy, improving the rate of calculus removal, particularly in deep periodontal pockets, and offering a potentially better long-term prognosis^12,13. Despite these advantages, the widespread adoption of periodontal endoscopy remains constrained by several practical barriers, including a steep learning curve, technique sensitivity, increased procedural time, and substantial costs associated with equipment and maintenance—factors that particularly limit its use in primary care and resource-limited settings^5,14.

Inspired by the visualization principles of periodontal endoscopy, yet seeking a more accessible alternative, we developed a no-incision micro-flap technique (NMFT) based on a four-handed operating approach (Figure 1). The term "micro-flap" herein refers to the gentle, instrument-assisted separation of the gingival margin from the tooth surface using ultrasonic scalers, which creates a minimal opening for visual access without the need for surgical incisions or flap reflection—distinguishing it from conventional microsurgical approaches that involve deliberate tissue incision and reflection. This technique leverages the inflammatory characteristics of periodontitis-affected gingiva—typically edematous, friable, and loosely attached—which allows gentle separation from the tooth surface using ultrasonic instruments without requiring surgical incisions (Figure 1A and 1B). Enhanced visualization is achieved through two key maneuvers: (1) continuous aspiration of sulcular fluid and hemorrhage by an assistant using high-volume suction (Figure 1D), and (2) illumination and reflection via a high-definition intraoral mirror (Figure 1C). This combined approach facilitates direct or mirror-reflected visualization of subgingival calculus, thereby reducing reliance on tactile sensation alone.

Given this theoretical foundation, we conducted a randomized controlled trial to evaluate the short-term clinical efficacy of NMFT-aided SRP compared with conventional SRP in patients with chronic periodontitis. By providing partial visualization through simple instrumental modifications, NMFT represents a pragmatic compromise between completely "blind" conventional SRP and technologically demanding endoscopic approaches. This technique may offer a viable alternative for enhancing subgingival debridement in settings where endoscopic equipment is unavailable or impractical.

Protocol

This study is a single-center, split-mouth controlled, randomized controlled trial, reported in accordance with the CONSORT (Consolidated Standards of Reporting Trials) guidelines. The study was approved by the Medical Ethics Committee of Dongyang People's Hospital (Approval No.: 2024-YX-081) and registered on the Chinese Clinical Trial Registry (ChiCTR) number: ChiCTR2600124289. All participants provided written informed consent prior to enrollment. The study was conducted in compliance with the principles of the Declaration of Helsinki. We conducted a clinical study to evaluate and compare the effectiveness of NMFT-assisted SRP and conventional SRP. A total of 20 participants were enrolled in the study from December 2023 to November 2024.

Sample size estimation
Based on preliminary pilot data, the expected difference in probing depth (PD) reduction at 6 weeks between NMFT-assisted SRP and conventional SRP was 0.5 mm, with a pooled standard deviation of 0.8 mm. The significance level (α) was set at 0.05 (two-sided), and the test power (1-β) was set at 0.80. Using the sample size calculation formula for paired designs, the minimum required sample size was determined to be 16 patients. To account for an estimated dropout rate of approximately 20%, the study ultimately planned to include 20 patients.

Selection criteria
Inclusion criteria:(1) Patients with a diagnosis of generalized periodontitis, categorized as Stage II or III according to the 2017 world workshop on the classification of periodontal and peri-implant diseases and conditions, a widely accepted framework for periodontitis staging and grading¹⁵ requiring SRP following oral hygiene instruction and supragingival scaling; (2) A minimum of 20 natural teeth present in the oral cavity; (3) Systemically healthy with no significant medical conditions; Exclusion criteria: (1) Presence of defective dental restorations that could interfere with the examination; (2) Periodontal therapy performed within the past year; (3) Antibiotic use within the last 3 months; (4) Pregnant or lactating women; (5) Systemic diseases that could affect treatment outcomes (e.g., uncontrolled diabetes and immunocompromised conditions); (6) Unwillingness to participate in the study.

Randomization and allocation concealment
All patients were assigned sequential numbers (001–020). The treatment side (test/control) for each patient was determined using a random number table. The randomization rule was as follows: if the random number was odd, the left side was assigned to the experimental group (NMFT), and if the random number was even, the right side was assigned to the experimental group. Treatment was administered in two sessions, with the order of treatment initiation for either side determined by the patient. The complete raw dataset supporting the findings of this study is available in Supplementary File 1.

Interventions
Overview
All SRP treatments were completed in two sessions by the same board-certified periodontist with extensive clinical experience. Before each treatment session, patients received local anesthesia via appropriate infiltration injections of 4% articaine with 1:100,000 epinephrine. All patients included in this study were in the active phase of chronic periodontitis, with generalized inflammatory and friable gingiva, which facilitated the implementation of NMFT. At sites with thicker, fibrotic gingiva, the visibility of NMFT may be limited, and traditional SRP is still relied upon in such cases. During the procedure, continuous suction was used to control bleeding and ensure a clear field of vision.

NMFT-aided SRP
A subgingival ultrasonic scaler tip was used in low-power mode (power setting: 50–60% output power) to gently separate the gingival tissue. Enhanced visualization of subgingival calculus was achieved through the following steps: (1) An assistant used a high-suction evacuator for continuous suction of gingival crevicular fluid and blood to maintain a clear operative field (Figure 1). (2) A high-definition intraoral mirror was used to reflect light, allowing direct observation of subgingival calculus. (3) Gracey curettes were used for root surface planing, with an average operation time of approximately 5–7 min per tooth site. The smoothness of the root surface was subsequently verified using an 11/12 explorer. Each patient received personalized post-treatment instructions: brushing teeth twice daily using the modified Bass technique (bristles at a 45° angle) and performing interdental cleaning once daily using personalized interdental cleaning tools (interdental brushes/dental floss, selected based on the size of the interdental space).

Conventional SRP
The conventional treatment group received standard SRP, which was performed using a subgingival ultrasonic scaler tip and a full set of Gracey curettes (5/6, 7/8, 11/12, and 13/14). The treating clinician systematically evaluated the root surfaces with an 11/12 explorer to ensure complete calculus removal and optimal smoothness. The average treatment time per quadrant was approximately 25 ± 5 min for the NMFT group and 20 ± 4 min for the conventional SRP group. Although NMFT was slightly more time-consuming, visual assistance may enhance debridement efficiency. Each patient in the conventional treatment group received the same personalized post-treatment instructions as those in the NMFT-assisted SRP group. All the equipment used in the study is shown in Supplementary file 2.

Data collection and evaluation
The examiners underwent standardized calibration training prior to the study, including theoretical instruction and hands-on practice with models. Calibration consistency was assessed by repeatedly measuring periodontal sites (120 sites in total) on 10 non-study patients. The results showed an intraclass correlation coefficient (ICC) of 0.92 for PD measurements, 0.89 for clinical attachment loss (CAL), and a Kappa value of 0.85 for bleeding on probing (BOP), indicating good consistency and reliability among the examiners. At baseline, all participants underwent standardized periodontal examinations by a calibrated examiner blinded to group assignments. Using a UNC-15 periodontal probe, the examiner recorded PD, CAL, and BOP. The same blinded examiner conducted all follow-up assessments at approximately 6 weeks and 3 months post-SRP, following the same measurement protocol as at baseline. The primary outcome measures were changes in clinical periodontal parameters (PD, CAL, and BOP) after SRP.

Data analysis
Statistical analysis was performed using IBM SPSS Statistics software (version 26.0). Given the split-mouth design of this study, in which both sides of the same patient's mouth received NMFT-assisted SRP and conventional SRP, respectively, all comparisons of primary efficacy outcomes were conducted using paired-samples t-tests. Specifically, for continuous variables (e.g., reductions in PD, gains in CAL), paired-samples t-tests were used to compare the NMFT-treated side with the control side within each patient. For dichotomous variables (e.g., BOP-positive rate), paired-sample McNemar tests were used. The significance threshold was set at α = 0.05 (two-tailed), with P-values < 0.05 considered statistically significant. For patients who dropped out of the study, the intention-to-treat (ITT) principle was applied, with the last observation carried forward (LOCF) method used for primary outcome analysis. Sensitivity analysis was conducted using the complete dataset, and the results were consistent with the ITT analysis.

Results

In this study, 20 participants were included, randomized, and assigned to the treatments (Figure 2). All 20 participants completed the full course of treatment. At the 6-week follow-up, 16 participants were evaluated (2 only attended the 6-week follow-up, and 2 were lost to follow-up). At the 3-month follow-up, 15 participants were evaluated (1 only attended the 3-month follow-up, and 3 were lost to follow-up). All 20 participants were included in the final intention-to-treat analysis. In th...

Discussion

Traditional SRP is typically performed using a closed approach, relying primarily on tactile sensation rather than direct visualization. This "blind" technique may lead to either incomplete debridement or excessive removal of root structure⁵. To overcome these limitations, periodontal endoscopy has been developed as an adjunctive tool, providing magnification of 24 to 48 times, which enables direct visualization of subgingival calculus and root morphology¹¹

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
4% Articaine with 1:100,000 epinephrine	Pierre Roland, France	Articaine-4%	Local anesthetic for patient comfort during SRP procedures.
11/12 Dental Explorer	Hu-Friedy, Chicago, IL, USA	EXD-11/126	Used for tactile detection of calculus and root surface smoothness verification.
Gracey Curettes (5/6, 7/8, 11/12, 13/14)	Hu-Friedy, Chicago, IL, USA	GRA-5/6, etc.	Manual instruments for root planing after ultrasonic debridement.
High-definition Intraoral Mirror	Hanenkratt GmbH & Co. KG, Königsbach-Stein, Germany	REF-7115, etc.	Used for reflection and visualization of subgingival calculus during NMFT procedure.
High-suction Dental Ejector	Dong Guan Li Gang Medical Treatment Equipment Co., Ltd. Guangdong, China	N/A	Assistant-operated suction device for maintaining a clear operative field.
IBM SPSS Statistics	IBM Corporation, Armonk, NY, USA	Version 26.0	Statistical software for data analysis.
Ultrasonic Subgingival Scaler Tip	Sirona Dental Systems GmbH, Bensheim, Germany	SIROPERIO PE1, etc.	Ultrasonic insert used for calculus removal and gingival displacement.
UNC-15 Periodontal Probe	Hu-Friedy, Chicago, IL, USA	PCPUNC15	Standard probe for measuring PD, CAL, and BOP.