A 20% benzocaine mucoadhesive patch was associated with lower reported pain than benzocaine gel during dental injections in a randomized trial of 36 healthy patients. On the patient-rated 11-point Numeric Rating Scale, scores were lower at both the cheek-side, or buccal, and palate-side, or palatal, injection sites. On a second, observer-rated measure, scores were lower with the patch at the palatal site, but the buccal comparison was not statistically significant.
A comparison within the same mouth
The trial was conducted at Mashhad University of Medical Sciences and involved 36 healthy patients requiring bilateral maxillary dental extractions. It used a split-mouth design: participants received the patch and gel on opposite sides of the mouth, with the side assigned at random. That arrangement made each patient an internal comparison for the two treatments.
The researchers set out to test a novel engineered bilayer, or two-layer, mucoadhesive patch against benzocaine gel as a way to reduce injection pain. Its base layer used chitosan, gelatin and glycerin; its adhesive layer contained sodium carboxymethylcellulose, gelatin, pectin, 20% benzocaine and methylene blue. The comparison product was 20% benzocaine gel.
The treatments were not applied for the same length of time. Gel was applied for 30 seconds, while the patch was applied for 10 minutes. Local anesthesia followed after a 10-minute waiting period between sides. This matters because the trial changed both the delivery format and the exposure time, leaving open how much of the difference was related to the patch itself rather than the longer application.
The patient ratings were the clearest signal
Pain was quantified in two ways. Patients reported pain on the 11-point Numeric Rating Scale, known as NRS-11, while an observer-rated Sound, Eye, Motor scale, or SEM, provided a second measure. The researchers used Shapiro-Wilk, Wilcoxon signed-rank, Mann-Whitney U and Spearman correlation tests, with a significance threshold of 0.05.
The clearest result came from the patients' own ratings. NRS-11 pain scores were significantly lower with the patch than with gel at the buccal site and at the palatal site. For both comparisons, the reported P value was below 0.05. The supplied results do not include the exact scores, effect sizes or confidence intervals, so they establish the direction of the reported difference but do not show how large the gap was.
The observer ratings gave a more mixed picture. At the palatal site, SEM scores were significantly lower with the patch than with gel, with a reported P value of 0.011. At the buccal site, SEM scores did not differ significantly, with a reported P value of 0.075. The authors therefore concluded that the patch lowered self-reported pain at both sites and observer-rated pain at the palatal site.
Age, sex and baseline anxiety level, assessed with the Beck Anxiety Inventory, were included as covariates, or factors examined alongside the treatment comparison. None was associated with pain scores in the reported analysis.
The result has clear boundaries
The trial's evidence is confined to a defined group: healthy patients requiring bilateral maxillary extractions at Mashhad University of Medical Sciences. The reported outcomes were injection-pain scores. The findings therefore do not establish how the patch would perform in broader dental populations or in routine injections. Because exact pain scores, effect sizes and confidence intervals were not reported, the size of any practical advantage remains unclear.
The trial had ethics approval, was registered with IRCT20230125057218N1, was reported in accordance with CONSORT, and obtained written informed consent from participants or legal guardians.
The study was funded by Mashhad University of Medical Sciences. The authors declared no competing interests, and the datasets used or analyzed are available from the corresponding author on reasonable request. The article is published as a version of record.
Paper data and sources
Original title: Mucoadhesive patch versus benzocaine gel for reducing injection pain: a split-mouth randomized clinical trial.
Authors: Rasoul Sahebalam, Azarnoosh Sheibani, Hossein Bagheri et al.
Journal/Repository: Oral and maxillofacial surgery
Status: Peer-reviewed
First online: 2026-08-21
DOI: 10.1007/s10006-026-01615-8
Original paper · Full text