Morphometric assessment of the mandibular retromolar space for orthodontic molar distalization: A systematic review of CT and CBCT evidence

Abstract

Background

Anatomical variability of the mandibular retromolar space (MRS) plays a decisive role in planning mandibular molar distalization; however, available evidence remains fragmented across heterogeneous tomographic studies.

Objective

To synthesize current evidence derived from computed tomography (CT) and cone-beam computed tomography (CBCT) regarding morphometric factors influencing MRS and their implications for orthodontic distalization.

Methods

A systematic search was conducted in MEDLINE, LILACS, Scopus, Web of Science, and Google Scholar in accordance with PRISMA guidelines. Observational studies evaluating MRS using CT or CBCT in adult populations were included. Data extraction focused on skeletal classification, vertical facial pattern, sex, age, and third-molar status. Methodological quality was assessed using the Joanna Briggs Institute critical appraisal tools.

Results

Fourteen studies met the inclusion criteria, comprising samples from China, South Korea, Egypt, Turkey, India, Japan, and Taiwan, with a mean age of 25.8 years. A skeletal Class III pattern consistently exhibited the greatest MRS, followed by Class I and Class II. Normodivergent individuals demonstrated larger MRS values compared with hyperdivergent or hypodivergent patients. Third-molar position and angulation, rather than mere presence, were identified as key determinants of the effective distalization limit. Sex-related differences were inconsistent across studies, and the influence of age varied. The internal (lingual) cortical plate emerged as the principal anatomical boundary restricting mandibular molar distalization.

Conclusions

Mandibular retromolar space is strongly influenced by skeletal classification, vertical growth pattern, and third-molar morphology. Pre-treatment CBCT assessment is essential to identify anatomical constraints, prevent cortical interference, and optimize individualized orthodontic biomechanics. Future multicenter studies employing standardized CBCT protocols are needed to enhance the clinical applicability of these findings across diverse populations.