Orthodontic loading activates cell-specific autophagy in a force-dependent manner.

INTRODUCTION: Orthodontic tooth movement (OTM) relies on bone remodeling and controlled aseptic inflammation. Autophagy, a conserved homeostatic pathway, has been shown to play a role in bone turnover. We hypothesize that autophagy participates in regulating bone remodeling during OTM in a force-dependent and cell type-specific manner. METHODS: A split-mouth design was used to load molars with 1 of 3 force levels (15, 30, or 45 g of force) in mice carrying a green fluorescent protein-LC3 transgene to detect cellular autophagy. Fluorescent microscopy and quantitative polymerase chain reaction analyses were used to evaluate autophagy activation and its correlation with force level. Cell type-specific antibodies were used to identify cells with green fluorescent protein-positive puncta (autophagosomes) in periodontal tissues. RESULTS: Autophagic activity increased shortly after loading with moderate force and was associated with the expression of bone turnover, inflammatory, and autophagy markers. Different load levels resulted in altered degrees of autophagic activation, gene expression, and osteoclast recruitment. Autophagy was specifically induced by loading in macrophages and osteoclasts found in the periodontal ligament and alveolar bone. Data suggest autophagy participates in regulating bone turnover during OTM. CONCLUSIONS: Autophagy is induced in macrophage lineage cells by orthodontic loading in a force-dependent manner and plays a role during OTM, possibly through modulation of osteoclast bone resorption. Exploring the roles of autophagy in OTM is medically relevant, given that autophagy is associated with oral and systemic inflammatory conditions.

Orthognathic speech pathology: impacts of Class III malocclusion on speech.

INTRODUCTION: Patients with dentofacial disharmonies (DFDs) seek orthodontic care and orthognathic surgery to address issues with mastication, esthetics, and speech. Speech distortions are seen 18 times more frequently in Class III DFD patients than the general population, with unclear causality. We hypothesize there are significant differences in spectral properties of stop (/t/ or /k/), fricative (/s/ or /ʃ/), and affricate (/tʃ/) consonants and that severity of Class III disharmony correlates with the degree of speech abnormality. METHODS: To understand how jaw disharmonies influence speech, orthodontic records and audio recordings were collected from Class III surgical candidates and reference subjects (n = 102 Class III, 62 controls). A speech pathologist evaluated subjects and recordings were quantitatively analysed by Spectral Moment Analysis for frequency distortions. RESULTS: A majority of Class III subjects exhibit speech distortions. A significant increase in the centroid frequency (M1) and spectral spread (M2) was seen in several consonants of Class III subjects compared to controls. Using regression analysis, correlations between Class III skeletal severity (assessed by cephalometric measures) and spectral distortion were found for /t/ and /k/ phones. CONCLUSIONS: Class III DFD patients have a higher prevalence of articulation errors and significant spectral distortions in consonants relative to controls. This is the first demonstration that severity of malocclusion is quantitatively correlated with the degree of speech distortion for consonants, suggesting causation. These findings offer insight into the complex relationship between craniofacial structures and speech distortions.