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Fiber-type differences in masseter muscle associated with different facial morphologies
Anthea Rowlerson1, Gwénaël Raoul, Yousif Daniel
1Applied Biomedical Research Group, Guy's, King's and St. Thomas' School of Biomedical Sciences, Kings College, London, United Kingdom.
Summary
Masseter muscle fiber composition significantly influences vertical bite characteristics. Open bites correlate with Type I fibers, while deep bites show increased Type II fibers, impacting dental development.
Area of Science:
- Orthodontics and Dental Development
- Muscle Physiology
- Skeletal Biology
Background:
- Muscle forces significantly impact dental and skeletal development.
- Quantifying these influences is challenging due to complex physiological interactions during growth.
Purpose of the Study:
- To analyze the fiber-type composition of the masseter muscle.
- To correlate muscle fiber characteristics with malocclusion types and vertical bite dimensions.
Main Methods:
- Biopsy samples from 44 subjects undergoing malocclusion surgery were analyzed.
- Immunostaining identified four myosin heavy chain fiber types.
- Fiber diameter and occupancy percentages were quantified and statistically analyzed.
Main Results:
- Significant differences in masseter muscle fiber occupancy were observed across vertical bite dimensions.
- Type I fiber occupancy increased in open bites; Type II increased in deep bites.
- Class III malocclusions showed variations in fiber area related to bite type, with deep bites exhibiting larger Type I and hybrid fiber areas.
Conclusions:
- Vertical bite characteristics are demonstrably influenced by masseter muscle fiber composition.
- Further research with larger cohorts is needed to explore associations with sagittal jaw relationships.