Marginal Biofilm Distribution and Periodontal Response to Supragingival and Juxtagingival Aligner Designs (BIOFILM-ALIGN)

Marginal Biofilm Distribution and Periodontal Response to Supragingival and Juxtagingival Aligner Designs: A Prospective Split-Mouth Clinical Study

• This prospective, longitudinal, within-person (split-mouth) clinical study evaluates the influence of two clear aligner trimming-line designs on marginal soft-tissue biofilm distribution and periodontal tissue response over a six-month period.
• Two trimming-line designs are compared. The supragingival design has a straight, horizontal edge that extends approximately 2 mm onto the marginal gingiva, resting in direct contact with the gingival surface but not entering the gingival sulcus. The juxtagingival design follows the scalloped contour of the gingival margin and terminates at the free gingival margin, without covering the gingiva and without entering the sulcus.
• Each participant receives both designs simultaneously, one per dental arch, and therefore serves as their own control. The assignment of each design to an arch is determined by the treating clinician according to the orthodontic treatment indications and is not randomized.
• The primary outcome is the percentage of sites with bleeding on probing per arch at six months. Secondary outcomes are bleeding on probing at three months, mean probing depth, maximum probing depth, and the Turesky-Quigley-Hein plaque index, with three exploratory photographic soft-tissue variables describing marginal gingival plaque presence, vestibular interdental papilla plaque presence, and the marginal demarcation pattern. Clinical and photographic assessments are performed at baseline (before aligner delivery), at three months, and at six months.
• All aligners are fabricated from a tri-layer clear aligner material (CA Pro, SCHEU-DENTAL GmbH, Iserlohn, Germany) by a single orthodontic laboratory.

Study Overview

• Status: Active, not recruiting
• Conditions: Periodontal Diseases; Gingivitis; Dental Plaque
• Intervention / Treatment: Device: Supragingival aligner trimming-line; Device: Juxtagingival festooned aligner trimming-line

Detailed Description

• BACKGROUND AND RATIONALE
• Clear aligner therapy is widely used in contemporary orthodontics. The geometry of the aligner trimming line at the gingival margin differs between two commonly used designs: a supragingival design that covers a band of marginal gingiva, and a juxtagingival design that follows the gingival contour. Biomechanical investigations have characterized how trimming-line geometry affects force transmission and retention, and a limited number of clinical reports have examined its periodontal effects. However, direct clinical comparisons of trimming-line geometry on periodontal outcomes remain scarce and have been limited largely to adolescent populations and to conventional periodontal indices; within-person comparisons in adults, and the distribution of biofilm on the marginal soft tissues, remain insufficiently characterized. This study addresses that gap.
• THE TWO TRIMMING-LINE DESIGNS The supragingival design has a straight, horizontal edge that extends approximately 2 mm onto the marginal gingiva, resting in direct contact with the gingival surface but not entering the gingival sulcus. The juxtagingival design follows the scalloped contour of the gingival margin and terminates at the free gingival margin, without covering the gingiva and without entering the sulcus. Both designs are produced from the same CE-marked tri-layer clear aligner material (CA Pro, SCHEU-DENTAL GmbH, Iserlohn, Germany) and are standard variations used in routine orthodontic practice. The intervention under study is the trimming-line design, a manufacturing parameter, not the aligner material or device itself.
• STUDY DESIGN This is a prospective, longitudinal, within-person (split-mouth) interventional study. Each participant receives both trimming-line designs simultaneously, one on the maxillary arch and one on the mandibular arch, and therefore serves as their own control. The unit of comparison is the dental arch within the participant. The split-mouth design controls for inter-individual variation in systemic health, oral hygiene, salivary characteristics, and baseline periodontal status. The within-person (split-mouth) design was chosen to maximize statistical efficiency in an exploratory clinical evaluation, with each participant serving as their own control.
• ALLOCATION RULE (NON-RANDOMIZED) Allocation of each design to an arch is not randomized. It follows a pre-specified rule based on the orthodontic treatment plan. The primary criterion is the magnitude of planned dental intrusion per arch, derived from the digital treatment setup prepared before aligner fabrication: the arch with the greater planned intrusion receives the supragingival design. When planned intrusion is equal on both arches or absent, a pre-specified alternating sequence in enrollment order is applied as a tiebreaker, with the first such participant receiving the supragingival design on the maxillary arch, the next on the mandibular arch, and so on. This produces an approximately balanced arch-level distribution. Planned intrusion magnitude is used only as the basis for this allocation rule; it is not entered as a covariate in the analysis, and the study does not analyze the relationship between intrusion magnitude and hard-tissue outcomes (root or alveolar bone).
• CLINICAL AND PHOTOGRAPHIC ASSESSMENTS Assessments are performed at baseline before aligner delivery (T0), at three months (T1, plus or minus 7 days), and at six months (T2, plus or minus 7 days). At each visit, full-mouth periodontal charting (probing depth and bleeding on probing) is performed first, on undisclosed tissue, by a calibrated examiner who is blinded to the trimming-line allocation; conventional plaque assessment is then performed using a two-tone disclosing agent and the Turesky-Quigley-Hein plaque index; and standardized intraoral photographs are obtained afterwards.
• EXPLORATORY PHOTOGRAPHIC VARIABLES Three photographic soft-tissue variables, namely marginal gingival plaque presence, vestibular interdental papilla plaque presence, and the marginal demarcation pattern, were developed for this study to describe the distribution of biofilm on the marginal gingival soft tissues, a dimension not captured by conventional hard-surface plaque indices. These variables are designated as exploratory. The photographs are de-identified, coded, and presented in randomized order to two independent blinded examiners, and inter-examiner agreement is assessed using the Cohen kappa coefficient.
• ANALYSIS The primary comparison is the within-person, between-arch difference in the percentage of sites with bleeding on probing at six months (T2), with baseline (T0) as the reference and each participant serving as their own control. The three-month (T1) assessment is analyzed as a secondary, intermediate time point describing the trajectory of periodontal response. The secondary validated outcomes, probing depth and the plaque index, are analyzed within the same within-person framework across all time points. The exploratory photographic variables are summarized descriptively, and their effect estimates are reported to inform the design of future confirmatory studies. All tests are two-sided, with the significance level set at 0.05.
• SAFETY Both trimming-line designs are standard variations used in routine clinical orthodontic practice with a CE-marked aligner material, and neither constitutes a novel or experimental device. Untoward periodontal or soft-tissue events occurring during the study are recorded at each scheduled visit and may be reported by participants between visits. Predefined clinical criteria are applied for the withdrawal of a participant when continued participation would no longer be in the participant's clinical interest.
• LIMITATIONS Allocation is not randomized and is tied to the planned intrusion per arch. Because intrusion magnitude is not adjusted for in the analysis, between-arch differences may partly reflect the clinically driven allocation rather than the trimming-line design alone; this is acknowledged in the interpretation of the results. The split-mouth design reduces inter-individual variation but cannot exclude arch-level biomechanical differences other than the trimming-line design.

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Romania
  • Sibiu County
    • Sibiu, Sibiu County, Romania, 550027
      • Aorys Clinic

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Permanent dentition
• Adult patients
• Mild to moderate crowding not requiring extractions for orthodontic purposes

Exclusion Criteria:

• Mouth breathing (may influence the status of the marginal periodontium)
• Periodontal involvement (gingivitis or periodontitis)
• Presence of fixed prosthetic restorations with incorrect marginal adaptation
• Deficient oral hygiene

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Supragingival Trimming-Line Design; Dental arch fitted with a clear aligner trimmed with a supragingival straight-cut margin. The aligner edge extends approximately 2 mm onto the marginal gingiva, in direct contact with the gingival surface but without entering the gingival sulcus. Assigned to the arch with the greater planned intrusion; when planned intrusion is equal or absent on both arches, assignment follows a pre-specified alternating sequence in enrollment order.	Device: Supragingival aligner trimming-line; Clear aligner trimmed with a supragingival straight-cut margin extending approximately 2 mm onto the marginal gingiva, in direct contact with the gingiva but not entering the sulcus. Fabricated from CA Pro tri-layer thermoplastic material (SCHEU-DENTAL GmbH, Iserlohn, Germany; CE-marked) by Orto Performance Orthodontic Laboratory, Cluj-Napoca, Romania. The intervention under study is the trimming-line design, not the aligner material; material and thickness are identical to the comparator.
Active Comparator: Juxtagingival Festooned Trimming-Line Design; Contralateral dental arch, within the same participant, fitted with a clear aligner trimmed with a juxtagingival festooned margin that follows the scalloped contour of the gingival margin and terminates at the free gingival margin, without covering the gingiva and without entering the sulcus. Assigned to the arch with the lesser or no planned intrusion.	Device: Juxtagingival festooned aligner trimming-line; Clear aligner trimmed with a juxtagingival festooned margin following the scalloped gingival contour, terminating at the free gingival margin without covering the gingiva or entering the sulcus. Fabricated from CA Pro tri-layer thermoplastic material (SCHEU-DENTAL GmbH, Iserlohn, Germany; CE-marked) by Orto Performance Orthodontic Laboratory, Cluj-Napoca, Romania. The intervention under study is the trimming-line design, not the aligner material; material and thickness are identical to the comparator.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Bleeding on probing at 6 months (percentage of sites per arch)	Percentage of sites with bleeding on probing within each dental arch. Bleeding on probing is recorded as present or absent within approximately 10 to 15 seconds after gentle probing at six sites per tooth (mesiobuccal, mid-buccal, distobuccal, mesiolingual, mid-lingual, distolingual) using a calibrated periodontal probe. The percentage is calculated as the number of bleeding sites divided by the total number of scorable sites in the arch, multiplied by 100. The two arches within each participant are compared by trimming-line design. The primary endpoint is the within-person, between-arch difference at 6 months (T2), with baseline (T0) as the reference. The 3-month (T1) assessment is analyzed as a secondary, intermediate time point and does not contribute to the primary comparison.	Baseline (T0, before aligner delivery) and 6 months (T2)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Bleeding on probing at 3 months (intermediate, percentage of sites per arch)	Percentage of sites with bleeding on probing within each dental arch at the 3-month assessment, recorded and computed identically to the primary outcome (six sites per tooth, present or absent within approximately 10 to 15 seconds of gentle probing), compared between arches by trimming-line design. This intermediate time point describes the trajectory of periodontal response and is not the primary comparison.	3 months (T1)
Mean probing depth (per arch)	Arithmetic mean of probing depth values (mm) within each dental arch, measured at six sites per tooth using a calibrated periodontal probe, calculated separately for each arch and compared by trimming-line design.	Baseline (T0), 3 months (T1), and 6 months (T2)
Maximum probing depth (per arch)	The greatest single probing depth value (mm) recorded within each dental arch, calculated separately for each arch and compared by trimming-line design.	Baseline (T0), 3 months (T1), and 6 months (T2)
Turesky-Quigley-Hein plaque index (per arch)	Mean plaque score on the Turesky-Quigley-Hein ordinal scale (0 to 5), recorded on the vestibular surfaces of teeth after application of a two-tone plaque-disclosing agent (Rondell, Directa AB, Sweden), calculated separately for each dental arch and compared by trimming-line design.	Baseline (T0), 3 months (T1), and 6 months (T2)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Marginal Gingival Plaque Presence (MGPP%)	Percentage of tooth-associated gingival units showing disclosed plaque on the vestibular aspect of the free gingival margin (within 0 to 2 mm of the gingival crest), scored as present or absent per unit from standardized intraoral photographs by two independent blinded examiners, calculated per arch.	Baseline (T0), 3 months (T1), and 6 months (T2)
Vestibular Interdental Papilla Plaque Presence (VIPPP%)	Percentage of interdental papillary units showing disclosed plaque on the visible vestibular aspect of the interdental papilla, scored as present or absent per unit from standardized intraoral photographs by two independent blinded examiners, calculated per arch.	Baseline (T0), 3 months (T1), and 6 months (T2)
Marginal Demarcation Pattern (MDP)	Categorical classification of the predominant pattern of disclosed marginal plaque distribution on the buccal gingiva, scored per arch from standardized intraoral photographs by two independent examiners blinded to allocation. The categories are morphological, not ordinal severity levels: 0 = absent (no disclosed plaque pattern on the marginal gingiva); 1 = diffuse (disclosed plaque scattered over the gingiva without a defined coronal outline); 2 = papillary (disclosed plaque confined to the interdental papillae); 3 = linear/band (a continuous, clearly demarcated horizontal band of disclosed plaque spanning the buccal aspect of two or more adjacent teeth, including the papilla between them). The numeric codes denote distinct categories and not increasing severity; the predominant pattern is recorded for each arch. Inter-examiner agreement is assessed using the Cohen kappa coefficient for nominal categories.	Baseline (T0), 3 months (T1), and 6 months (T2)

Collaborators and Investigators

• Sponsor: George Emil Palade University of Medicine, Pharmacy, Sciences and Technology of Targu Mures
• Collaborators: Orto Performance Orthodontic Laboratory, Cluj-Napoca, Romania (aligner fabrication)
• Investigators: Study Chair: LUMINITA LAZAR, PhD, Professor, George Emil Palade University of Medicine, Pharmacy, Sciences, and Technology of Targu Mures, 38 Gheorghe Marinescu Street, 540139 Targu Mures, Romania

Publications and helpful links

General Publications

• Rouzi M, Zhang X, Jiang Q, Long H, Lai W, Li X. Impact of Clear Aligners on Oral Health and Oral Microbiome During Orthodontic Treatment. Int Dent J. 2023 Oct;73(5):603-611. doi: 10.1016/j.identj.2023.03.012. Epub 2023 Apr 25.
• Elshazly TM, Keilig L, Salvatori D, Chavanne P, Aldesoki M, Bourauel C. Effect of trimming line design and edge extension of orthodontic aligners on force transmission: An in vitro study. J Dent. 2022 Oct;125:104276. doi: 10.1016/j.jdent.2022.104276. Epub 2022 Aug 30.
• Rusu EP, Lazar AP, Erhan BL, Bud E, Pacurar M, Lazar L. Clear Aligner Therapy and Marginal Edge Design: Clinical and Laboratory Evidence on Periodontal and Biological Outcomes-A Scoping Review. Dent J (Basel). 2026 Feb 24;14(3):130. doi: 10.3390/dj14030130.
• Crego-Ruiz M, Jorba-Garcia A. Assessment of the periodontal health status and gingival recession during orthodontic treatment with clear aligners and fixed appliances: A systematic review and meta-analysis. Med Oral Patol Oral Cir Bucal. 2023 Jul 1;28(4):e330-e340. doi: 10.4317/medoral.25760.
• Favero R, Libralato L, Balestro F, Volpato A, Favero L. Edge level of aligners and periodontal health: a clinical perspective study in young patients. Dental Press J Orthod. 2023 Apr 14;28(1):e2321124. doi: 10.1590/2177-6709.28.1.e2321124.oar. eCollection 2023.
• Espana-Pamplona P, Bernes-Martinez L, Andres-Castello C, Bolas-Colvee B, Adobes-Martin M, Garcovich D. Changes in the Oral Microbiota with the Use of Aligners vs. Braces: A Systematic Review. J Clin Med. 2024 Dec 6;13(23):7435. doi: 10.3390/jcm13237435.
• Lyu X, Cao X, Yan J, Zeng R, Tan J. Biomechanical effects of clear aligners with different thicknesses and gingival-margin morphology for appliance design optimization. Am J Orthod Dentofacial Orthop. 2023 Aug;164(2):239-252. doi: 10.1016/j.ajodo.2022.12.014. Epub 2023 Mar 21.
• Elshazly TM, Bourauel C, Chavanne P, Elattar H, Keilig L. Numerical biomechanical finite element analysis of different trimming line designs of orthodontic aligners: An in silico study. J World Fed Orthod. 2024 Apr;13(2):65-71. doi: 10.1016/j.ejwf.2024.01.001. Epub 2024 Feb 23.

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2025
• Primary Completion (Estimated): July 1, 2026
• Study Completion (Estimated): July 1, 2026

Study Registration Dates

• First Submitted: June 6, 2026
• First Submitted That Met QC Criteria: June 6, 2026
• First Posted (Actual): June 11, 2026

Study Record Updates

• Last Update Posted (Actual): June 12, 2026
• Last Update Submitted That Met QC Criteria: June 10, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: dental plaque; bleeding on probing; gingival margin; split-mouth; clear aligner; trimming line; aligner trimming-line design; supragingival; juxtagingival; festooned margin; biofilm distribution; soft-tissue plaque; marginal gingiva; periodontal response; Turesky-Quigley-Hein plaque index; photographic assessment; marginal demarcation pattern
• Additional Relevant MeSH Terms: Mouth Diseases; Stomatognathic Diseases; Tooth Diseases; Infections; Gingival Diseases; Dental Deposits; Dental Plaque; Periodontal Diseases; Gingivitis
• Other Study ID Numbers: BIOFILM ALIGN-ORTHO

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be made publicly available, as the small single-site cohort (20 participants) cannot be fully de-identified without risk to participant confidentiality. De-identified data may be made available from the principal investigator on reasonable academic request, subject to an appropriate data-sharing agreement and ethics approval. Aggregate results will be reported in the doctoral thesis and in peer-reviewed publication.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No