"Assessment of mandibular buccal shelf dimension in different vertical facial growth pattern and its clinical implication for buccal shelf bone screw insertion - a cross-sectional study"

Abstract

Background:
The mandibular buccal shelf (MBS) has emerged as a reliable extra-alveolar site for orthodontic skeletal
anchorage. However, anatomical variations influenced by facial growth patterns may affect the quantity
of available bone and the stability of bone screws.
Objective:
To evaluate MBS dimensions in individuals with different vertical facial growth patterns and identify
the most favourable site for bone screw insertion using cone-beam computed tomography (CBCT).
Materials and Methods:
A cross-sectional CBCT study was conducted on 90 subjects aged 18–30 years, divided equally into
three groups according to facial growth pattern: average, horizontal, and vertical growers. CBCT scans
were analyzed using CS 3D imaging software. Transverse buccal cortical bone thickness was
measured at 6 mm and 11 mm apical to the cementoenamel junction (CEJ), while vertical bone
dimensions were assessed at 4 mm and 5 mm apical to the CEJ from the mesial aspect of the
mandibular first molar to the distal aspect of the second molar. Statistical analysis included ANOVA,
Tukey’s post hoc test, paired t-test, and independent t-test, with significance set at p < 0.05.
Results:
Mandibular buccal shelf dimensions varied significantly among facial growth patterns (p < 0.001).
Horizontal growers exhibited the greatest overall MBS dimensions (8.98 ± 2.00 mm), followed by
average growers (6.92 ± 2.04 mm), while vertical growers demonstrated the least bone availability (5.06
± 2.14 mm). Males showed significantly greater composite MBS dimensions than females (7.67 ± 2.88
mm vs. 6.30 ± 2.09 mm; p = 0.039). No significant differences were observed between right and left
sides, indicating bilateral symmetry. Both transverse and vertical dimensions increased progressively in
the posterior direction, with the greatest measurements recorded at the distal aspect of the mandibular
second molar, particularly at the 11 mm level from the CEJ.
Conclusion:
Mandibular buccal shelf dimensions are significantly influenced by facial growth pattern and gender.
Horizontal growers possess the most favourable bone characteristics for skeletal anchorage, whereas
vertical growers exhibit comparatively reduced bone availability. The distal aspect of the mandibular
second molar represents the most suitable site for MBS bone screw insertion across all facial growth
patterns. CBCT-based evaluation is recommended for individualized treatment planning and optimal
selection of insertion sites and screw dimensions.