A Split-Mouth Clinical Trial Evaluating the Bond Failure Rate of a New Etch-Free Orthodontic Adhesive

This is a prospective, randomized, split-mouth clinical trial designed to compare the bond failure rate, bonding efficiency, and enamel outcomes of a novel etch-free orthodontic adhesive with a conventional acid-etch adhesive over a 12-month follow-up period.

Background and Rationale Conventional orthodontic bonding requires phosphoric acid etching to create surface roughness for adhesive retention. While effective, this process irreversibly demineralizes enamel and may increase susceptibility to white spot lesions (WSLs), decalcification, and enamel fractures during bracket removal.

A new generation of self-adhesive bonding materials eliminates the etching step by bonding directly to enamel. This simplified approach may preserve enamel integrity, reduce chair time, and improve the patient experience while maintaining adequate bond strength.

The split-mouth design allows direct intra-patient comparison of the two bonding methods under identical oral conditions (hygiene, diet, occlusal forces), reducing inter-patient variability.

Study Design Type: Prospective, randomized, split-mouth trial

Population: 20 patients (ages ≥12 years) with permanent dentition undergoing fixed orthodontic treatment

Follow-up duration: 12 months post-bonding

Setting: University-based orthodontic clinic

Interventions Test Adhesive (Experimental): A commercially available etch-free adhesive system applied directly to enamel without acid etching or separate priming.

Control Adhesive: Conventional orthodontic adhesive applied following 37% phosphoric acid etching, primer, and adhesive placement.

Randomization and Bonding Procedure Each patient will receive both adhesives-one on the left side and one on the right-randomly assigned using a computer-generated randomization schedule and sealed envelopes.

Bonding will be performed by a calibrated operator using identical brackets and bonding techniques.

Control side: 37% phosphoric acid etch (30 seconds), rinse, dry, primer, and adhesive.

Experimental side: Etch-free adhesive applied directly per manufacturer instructions.

Bonding time for each side will be measured with a stopwatch.

Sample Size Justification Twenty patients will contribute approximately 212 bonded brackets (10-12 per side, excluding molars and second premolars). This sample size provides 80% power to detect a clinically meaningful difference in bond failure rates (expected 5% failure rate for the etch-free adhesive vs. 10% for conventional adhesive; α = 0.05), analyzed using McNemar's test for paired binary outcomes.

Outcome Measures Primary Outcome

Bracket Failure Rate: Number and location of dislodged brackets on test vs. control sides recorded at monthly visits.

Secondary Outcomes

Bonding Time: Measured in seconds per side.

Enamel Condition at Debonding: Assessed clinically and photographically by blinded evaluators.

Adhesive Remnant Index (ARI): Scored 0-3 after debonding.

White Spot Lesions (WSLs): Presence and severity assessed clinically and photographically at baseline and after 12 months using standardized scoring.

Patient-Reported Outcomes (if applicable): Discomfort related to bonding/debonding.

Data Collection and Management Data will be recorded using standardized forms and stored on secure, encrypted institutional servers.

Clinical photographs will document enamel condition and WSLs.

All data will be coded and de-identified. Only authorized study personnel will have access.

Ethical Considerations The study has been reviewed by the University of Maryland Institutional Review Board (IRB #HP-00115604) and determined to be minimal risk.

Written informed consent will be obtained from adult participants; minors will provide assent with parental consent.

Both adhesives are commercially available and widely used in clinical practice; no experimental drugs or devices are involved.

No additional radiographs or invasive procedures are required beyond standard care.

Participants may withdraw at any time without affecting their ongoing treatment.

This trial seeks to determine whether an etch-free adhesive can reduce enamel damage and improve bonding efficiency without compromising clinical performance.

Teeth on one randomized side of the mouth will be bonded with a novel self-adhesive orthodontic material that does not require prior acid etching or primer application.

Device: Etch-Free Adhesive

Teeth on the contralateral side of the mouth will be bonded using the standard orthodontic bonding protocol with 35-37% phosphoric acid etching, primer, and conventional resin adhesive.

Device: Conventional Etch-and-Bond Adhesive

A self-adhesive orthodontic bonding material applied directly to enamel without prior phosphoric acid etching or primer application. Brackets are bonded following the manufacturer's instructions.

A standard orthodontic bonding protocol using 35-37% phosphoric acid etching, primer application, and a conventional light-cure adhesive. Brackets are bonded following the manufacturer's recommended procedure.

Time frame: Through study completion, up to 12 months post-bonding (evaluated at each routine orthodontic visit).

The proportion of brackets bonded with each adhesive (etch-free vs. conventional) that experience bond failure over a 12-month follow-up period. A bond failure is defined as a clinically detached bracket requiring rebonding.

Time frame: At the initial bonding appointment (Day 1).

The time required to bond all brackets in one quadrant using either adhesive, measured in minutes using a digital timer.

Time frame: At debonding (approximately 12 months post-bonding or at completion of treatment).

The amount of adhesive remaining on the tooth surface after bracket removal, scored using the standardized Adhesive Remnant Index (0-3 scale).

Time frame: At debonding (approximately 12 months post-bonding).

Visual assessment of enamel for cracks, roughness, or damage after bracket removal, evaluated through clinical inspection and standardized digital photographs.

Time frame: At baseline (Day 1), 6 months, and 12 months post-bonding.

Incidence and severity of new white spot lesions on bonded teeth, assessed using a standardized WSL index at 6 and 12 months.

A Split-Mouth Clinical Trial Evaluating the Bond Failure Rate of a New Etch-Free Orthodontic Adhesive