# Cone-Beam Computed Tomography Evaluation of Bone Density After Sagittal Split Osteotomy Using the Novel Modification of Low Z Plasty Technique

## TL;DR

This study evaluates bone healing after a modified jaw surgery technique, finding reliable regeneration and fewer complications over 12 months.

## Contribution

A novel modification of the low Z plasty technique is introduced for mandibular setback surgery with favorable bone regeneration outcomes.

## Key findings

- Bone density at 12 months post-surgery showed no significant difference compared to earlier measurements.
- Cancellous and lingual regions healed faster than the buccal cortex.
- No postoperative complications like infection or non-union were observed.

## Abstract

Background and Objectives: This study aimed to assess the pattern and quantity of bone regeneration after mandibular setback surgery using a novel modification of the low Z plasty (NM-Low Z plasty) technique by measuring bone density (Hounsfield unit) at the osteotomy site over a 12-month postoperative period using cone-beam computed tomography (CBCT). Materials and Methods: This retrospective cohort study included six patients with skeletal Class III deformity who underwent bilateral sagittal split osteotomy (BSSO) setback using the NM-Low Z plasty technique between 2021 and 2023 at Thammasat University Hospital. CBCT images were obtained preoperatively and at 1 month, 6 months, and 12 months postoperatively. Bone density at the buccal, cancellous, and lingual aspects of the osteotomy gap was measured using Blue Sky Plan 4 software. The intraclass correlation coefficient was used to determine reliability. Descriptive statistics, repeated-measures analysis of variance and multiple linear regression analysis were performed for comparisons. Results: At 12 months postoperatively, bone density in all measured regions was not significantly different compared to the postoperative measurements, indicating sufficient bone regeneration. The cancellous and lingual cortical regions exhibited earlier recovery than the buccal cortex. No postoperative complications such as wound infection, delayed union, or non-union were reported. Conclusions: BSSO using the NM-Low Z plasty technique offers reliable bone healing outcomes with stable bone regeneration, thereby providing a viable alternative to conventional BSSO techniques. Radiographic evidence confirmed its clinical applicability and potential to reduce the incidence of postoperative complications.