Methods: We used radio-telemetry to record daily muscle activity in New Zealand White rabbits (n=7). Daily muscle activity of the superficial masseter, temporalis and digastric muscles was expressed in burst numbers exceeding a certain percentage of daily peak-EMG. We used micro-computed tomography to determine the DMB, measured at various mandibular sites, including muscle attachments and locations without direct muscle influence.
Results: Comparison showed significant (p<0.01) differences in DMB between the various bone regions. Regions without direct muscle loading were highly mineralized (peak at 1081 ± 61 mg hydroxyapatite/cm3). The masseter and temporalis muscle attachment sites showed a similar distribution of their DMB (peaks at 593±103 and 620±132 mg/cm3), much lower than the site without direct muscle influence. The digastric attachment site showed an intermediate DMB (915±114 mg/cm3). Comparison of the inter-individual variations in DMB with the accompanying burst numbers showed no significant correlations.
Conclusion: Bone loading, expressed as number of muscle activity bursts, has a positive relationship with the rate of remodeling as indicated by the lower DMB at muscle attachment sites, compared to regions without direct applied muscular loading. Inter-individual variations in activity burst number cannot directly be linked to variations in the degree of mineralization.