J C Nickel1,2, A L Weber3, P Covington Riddle4, Y Liu5, H Liu2, L R Iwasaki1,2. 1. Department of Orthodontics and Dentofacial Orthopedics, University of Missouri-Kansas City, Kansas City, MO, USA. 2. Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City, Kansas City, MO, USA. 3. Private Practice, Kansas City, MO, USA. 4. Department of Orthodontics, University at Buffalo, Buffalo, NY, USA. 5. Department of Biostatistics and Epidemiology, East Tennessee State University, Johnson City, TN, USA.
Abstract
OBJECTIVES: To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm). SETTING AND SAMPLE POPULATION: University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasion-Gonion-Gnathion (SN-GoGn) angles ≥37° and ≤27°, respectively) consented to participate. MATERIALS AND METHODS: Numerical models calculated TMJ loads for a range of static biting based on subjects' three-dimensional anatomy. Subjects were trained to record jaw muscle electromyography (EMG) over 2 days and 2 nights in their natural environments. Laboratory EMG/bite-force calibrations determined subject-specific EMG for 20 N bite-force (T20Nave ). Jaw muscle use via duty factors (DF=muscle activity duration/total recording time, %) was determined from day and night recordings for muscle-specific thresholds from ≥5% to ≥80%T20Nave . ANOVA and Tukey's HSD post hoc tests assessed for group differences in mechanobehaviour (TMJ loads, DFs). Regression modelling correlated subjects' normalized TMJ loads, DFs and ramus height. RESULTS: Dolichofacial compared to brachyfacial subjects produced significantly higher (P<.05) TMJ loads, where ipsilateral loads were ≥20% larger for some biting angles, but had significantly less (all P<.05) masseter (day, night) and temporalis (night) DFs. Regression analysis showed a significant relationship amongst normalized TMJ loads, masseter DF and ramus height (R2 =.49). CONCLUSIONS: Mechanobehaviour showed significant differences between facial types and was correlated with ramus height.
OBJECTIVES: To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm). SETTING AND SAMPLE POPULATION: University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasion-Gonion-Gnathion (SN-GoGn) angles ≥37° and ≤27°, respectively) consented to participate. MATERIALS AND METHODS: Numerical models calculated TMJ loads for a range of static biting based on subjects' three-dimensional anatomy. Subjects were trained to record jaw muscle electromyography (EMG) over 2 days and 2 nights in their natural environments. Laboratory EMG/bite-force calibrations determined subject-specific EMG for 20 N bite-force (T20Nave ). Jaw muscle use via duty factors (DF=muscle activity duration/total recording time, %) was determined from day and night recordings for muscle-specific thresholds from ≥5% to ≥80%T20Nave . ANOVA and Tukey's HSD post hoc tests assessed for group differences in mechanobehaviour (TMJ loads, DFs). Regression modelling correlated subjects' normalized TMJ loads, DFs and ramus height. RESULTS: Dolichofacial compared to brachyfacial subjects produced significantly higher (P<.05) TMJ loads, where ipsilateral loads were ≥20% larger for some biting angles, but had significantly less (all P<.05) masseter (day, night) and temporalis (night) DFs. Regression analysis showed a significant relationship amongst normalized TMJ loads, masseter DF and ramus height (R2 =.49). CONCLUSIONS: Mechanobehaviour showed significant differences between facial types and was correlated with ramus height.
Authors: Paige Covington Riddle; Jeffrey C Nickel; Ying Liu; Yoly M Gonzalez; Luigi M Gallo; R Scott Conley; Robert Dunford; Hongzeng Liu; Laura R Iwasaki Journal: Angle Orthod Date: 2020-11-01 Impact factor: 2.079
Authors: Giovanni Bruno; Alberto De Stefani; Edoardo Conte; Manila Caragiuli; Marco Mandolini; Daniele Landi; Antonio Gracco Journal: Materials (Basel) Date: 2020-04-13 Impact factor: 3.623