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.

Inclusion criteria

Patients aged 14 to 35 years

Requiring comprehensive fixed orthodontic treatment with brackets on both arches

Good general health with no contraindications to orthodontic treatment

Presence of at least 10 permanent teeth per arch suitable for bracket bonding

Ability and willingness to comply with study visits and follow-up for at least 12 months

Parent/guardian consent and child assent obtained as appropriate

Exclusion criteria

Presence of systemic diseases or conditions that affect oral health or healing (e.g., uncontrolled diabetes, immunosuppression)

Teeth with significant enamel defects, restorations, or caries in bonding areas

Patients currently undergoing or who have undergone orthodontic treatment previously

History of allergy or sensitivity to dental adhesives or related materials

Patients with poor oral hygiene or active periodontal disease

Use of medications known to affect tooth enamel or oral tissues (e.g., long-term corticosteroids)

Inability to attend follow-up visits or anticipated lack of compliance

Participation in another clinical trial that could interfere with study outcomes