Evaluation of the Functional Treatment of Patients With Skeletal Class II Malocclusion Using Low-Level Laser Therapy-Assisted Twin-Block Appliance: A Three-Arm Randomized Controlled Trial

Abstract

Background Different techniques have been used to reduce functional treatment time including low-level laser therapy (LLLT), and the majority of studies have been conducted on animals. Therefore, the aim of the current study was to evaluate the effects of LLLT on improving orthodontic functional treatment using the Twin-Block (TB) appliance. Materials and methods This study was a three-arm, parallel-group randomized controlled trial. Patients were selected using the following inclusion criteria: skeletal Class II Division 1 malocclusion resulting from mandibular retrognathia (angle between the anterior cranial base and the NB plane (i.e., SNB angle): 73°-78°), the sagittal skeletal discrepancy angle (ANB angle) between 4° and 9°, and overjet between 5 and 9 mm. Forty-eight patients were randomly allocated into three equal groups. In the LLLT-TB group, the low-level laser device was used with a wavelength of 808 nm and power of 250 mW in addition to functional treatment with a Twin-Block appliance. The laser was applied on the skin at the bilateral temporomandibular joint (TMJ) regions, at five points, each point received 5 J of the laser for 20 seconds. The laser course was twice a week in the first month, every two weeks in the second month, and every three weeks up to the end of the treatment. The second group (the TB group) received functional treatment with a Twin-Block appliance, while patients in the third group (the untreated control group (UCG)) were observed for nine months without any intervention. Results There were statistically significant differences in treatment periods between the LLLT-TB group and the TB group (129 days and 235 days, respectively, P-value<0.001). The change in the effective mandibular length (Co-Gn) was the highest in the LLLT-TB group compared with the TB and the UCG groups (4.41 mm, 3.66 mm, and 1.07 mm, respectively; P-value<0.001). Conclusions The application of low-level laser therapy on the condylar regions accelerated the functional treatment in skeletal Class II malocclusion patients by approximately 45% and increased the bone growth and mandibular length. The improvement in the SNB angle was similar in both interventional groups. Irradiation of low-level laser stimulated bone growth at the condyles and did not cause anterior movement of the temporomandibular joint following functional orthopedic correction.

Keywords: acceleration of bone formation; class ii malocclusion; duration of treatment; functional treatment; low-level laser therapy; mandibular length; mandibular retrognathism; temporomandibular joint; tmj morphology; twin block.

Figure 1. Consolidated Standards of Reporting Trials (CONSORT) flow diagram of patients' recruitment, entry into the trial, and their follow-up

Figure 2. The design of the Twin-Block appliance that was used in the current study

(A) A frontal view of the appliance in situ. (B) An occlusal view of the upper removable plate with an expansion screw. (C) An occlusal view of the lower plate.

Figure 3. The locations of the five points irradiated by the laser beam (front, upper, lower, and behind condyle, intra-articular)

Figure 4. Cephalometric measurements on the tracings of the radiographs

(A) Angular measurements. (B) Linear measurements. Po: uppermost point on the margin of the external auditory meatus; Y: Y-axis angle: anterior inferior angle formed by the intersection of the NS plane and the NSGn plane; A: point of most concavity on the contour of the anterior upper jaw close the root apices of the upper incisors; B: point of most concavity on the contour of the anterior lower jaw close to the root apices of the lower incisors; Or: most inferior point on the lower margin of the orbit; Bo: point at the intersection of the occipital condyle and the foramen magnum at the highest notch posterior to the occipital condyle; Ba: most anterior point on the foramen magnum; Pog: most prominent point on the anterior margin of the chin; Id: point that is located between the lower central incisors at the level of the interdental crest of the alveolus; Pr: point that is located between the upper central incisors at the level of the interdental crest of the alveolus; PTM: point located at the 11-o'clock position on the posterior border the pterygomaxillary fissure; NS: plane that connects points N and S. Abbreviations: Appendix.