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Binding of brain-derived neurotrophic factor (BDNF) to its receptor tyrosine kinase B (TrkB) is essential for the development of the hippocampus, which regulates memory and learning. Decreased masticatory stimulation during growth reportedly increases BDNF expression while decreasing TrkB expression in the hippocampus. Increased BDNF expression is associated with Wnt family member 3A (Wnt3a) expression and decreased expression of Rho GTPase Activating Protein 33 (ARHGAP33), which regulates intracellular transport of TrkB. TrkB expression may be decreased at the cell surface and affects the hippocampus via BDNF/TrkB signaling. Mastication affects cerebral blood flow and the neural cascade that occurs through the trigeminal nerve and hippocampus. In the current study, we hypothesized that decreased masticatory stimulation reduces memory/learning in mice due to altered Wnt3a and ARHGAP33 expression, which are related to memory/learning functions in the hippocampus. To test this hypothesis, we fed mice a powdered diet until 14 weeks of age and analyzed the BDNF and TrkB mRNA expression in the right hippocampus using real-time polymerase chain reaction and Wnt3a and ARHGAP33 levels in the left hippocampus using western blotting. Furthermore, we used staining to assess BDNF and TrkB expression in the hippocampus and the number of nerve cells, the average size of each single cell and the area of intercellular spaces of the trigeminal ganglion (TG). We found that decreased masticatory stimulation affected the expression of BDNF, Wnt3a, ARHGAP33, and TrkB proteins in the hippocampus, as well as memory/learning. The experimental group showed significantly decreased numbers of neurons and increased the area of intercellular spaces in the TG. Our findings suggest that reduced masticatory stimulation during growth induces a decline in memory/learning by modulating molecular transmission mechanisms in the hippocampus and TG., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study investigates rhythmic jaw movement (RJM) patterns and masticatory muscle activities during electrical stimulation in two cortical masticatory areas in obese male Zucker rats (OZRs), compared to their counterparts-lean male Zucker rats (LZRs) (seven each). At the age of 10 weeks, electromyographic (EMG) activity of the right anterior digastric muscle (RAD) and masseter muscles, and RJMs were recorded during repetitive intracortical micro-stimulation in the left anterior and posterior parts of the cortical masticatory area (A-area and P-area, respectively). Only P-area-elicited RJMs, which showed a more lateral shift and slower jaw-opening pattern than A-area-elicited RJMs, were affected by obesity. During P-area stimulation, the jaw-opening duration was significantly shorter ( p < 0.01) in OZRs (24.3 ms) than LZRs (27.9 ms), the jaw-opening speed was significantly faster ( p < 0.05) in OZRs (67.5 mm/s) than LZRs (50.8 mm/s), and the RAD EMG duration was significantly shorter ( p < 0.01) in OZRs (5.2 ms) than LZR (6.9 ms). The two groups had no significant difference in the EMG peak-to-peak amplitude and EMG frequency parameters. This study shows that obesity affects the coordinated movement of masticatory components during cortical stimulation. While other factors may be involved, functional change in digastric muscle is partly involved in the mechanism.

The aim of the study was to address the genioglossus muscle physiological and histological changes after unilateral nasal obstruction in growing rats. Fifty-four 6-day-old male Wistar albino rats were randomly divided into control (n = 27) and experimental (n = 27) groups. Unilateral nasal obstruction was performed at 8 days old. Contractile properties of the genioglossus whole muscle were measured at 5-, 7- and 9-week-old, including the twitch and tetanic forces, contraction time, half-decay time, and fatigue index. The histological characteristics of the genioglossus were also evaluated at 5-, 7- and 9-week-old, analyzing the myosin heavy chain composition of the slow, fast, IIa and IIb muscle fiber type, by measuring the number, rate, diameter and cross-sectional area. The maximal twitch force, and tetanic force at 60 Hz and 80 Hz force was significantly increased at all ages after nasal obstruction. The fatigue index was decreased at 5 weeks-old after nasal obstruction. The diameter and cross-sectional area of the fast, IIa and IIb muscle fiber types were increased at 7 and 9 weeks after nasal obstruction, while only the diameter of IIa type and cross-sectional area of IIb type were increased at 5 weeks-old after nasal obstruction. Nasal obstruction during growth affects the whole genioglossus muscle contractile properties and histological characteristics, increasing its force, the diameter and area of its muscle fibers. These changes in the genioglossus muscle may affect the normal growth, development and function of the craniofacial complex., (© 2023. The Author(s).)

The cortical masticatory area (CMA) regulates masticatory movements. However, there is limited information regarding the effect of respiratory disturbances on the functional development of the CMA. This study aimed to examine the effect of chronic unilateral nasal obstruction (UNO) on the CMA during the growth period. Forty-eight 8-day-old male Wistar albino rats were randomized into control (CONT, n = 24) and UNO (n = 24) groups. Arterial oxygen saturation (SpO 2 ) and the number of positive intracortical microstimulation (ICMS) sites in the anterior digastric (AD) muscle were recorded at 5, 7, and 9 weeks of age. ICMS was performed under anesthesia. The CONT group exhibited significantly higher SpO 2 values than the UNO group at each age. Furthermore, the number of positive ICMS sites in the AD muscle was significantly higher in the UNO group than in the CONT group at each age. The right AD was more strongly affected by UNO than the left AD. In addition, it was found that the P-area was more strongly affected by UNO than the A-area. These findings suggest that UNO during development induces changes in the motor representation in the CMA, which may affect respiratory and orofacial functions in rats. Therefore, we suggest that the development of respiratory dysfunction needs to be monitored and corrected promptly to avoid complications in physiological function., (Copyright © 2022 Elsevier B.V. All rights reserved.)

There is accumulating evidence that nasal obstruction induces high-level brain dysfunction, including memory and learning deficits. We previously demonstrated that unilateral nasal obstruction (UNO) during the growth period increases the expression of brain-derived neurotrophic factor (BDNF). The expression of BDNF is regulated by the Wnt/β-Catenin pathway, which is linked to neuronal differentiation, proliferation, and maintenance. However, little is known about whether Wnt3a protein expression could be an index for modulations analyses in the Wnt/β-Catenin pathway caused by UNO during the growth period. This study aimed to investigate the effects of UNO during the growth period on the Wnt/β-Catenin pathway in the hippocampus using combined behavioural, biochemical, and histological approaches. Male BALB/C mice were randomly divided into the control (CONT; n = 6) and experimental (UNO; n = 6) groups. Blood oxygen saturation (SpO 2 ) levels were measured, and a passive avoidance test was performed in mice aged 15 weeks. Brain tissues were subjected to immunohistochemistry, real-time reverse transcription-polymerase chain reaction, and western blot analysis. Compared with control mice, UNO mice had lower SpO 2 levels and exhibited memory/learning impairments during behavioural testing. Moreover, Wnt3a protein, BDNF mRNA, and tyrosine kinase receptor B (TrkB) mRNA expression levels were significantly lower in the hippocampus in the UNO group than in the CONT group. Our findings suggested that UNO during the growth period appeared to modulate the hippocampal Wnt/β-catenin pathway and BDNF production in association with TrkB mRNA reduction, thereby resulting in memory and learning impairments., (© 2021 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear. This study sought to evaluate the effect of occlusal hypofunction on neuromuscular development of jaw muscle activities and cortically-induced rhythmic jaw movements (RJMs) in growing rats. Sixty-four 2-week-old male albino Wistar rats were divided into the control (fed normal diet) and experimental (fed soft diet) groups soon after weaning. Electromyographic activity was recorded at 5, 7, 9, and 11 weeks from the right masseter and anterior digastric along with RJMs. We found a significantly longer onset latency and smaller peak-to-peak amplitude in the experimental group than that in the control group. The RJMs showed an increase in gape size and lateral excursion until up to 9 weeks in both groups. However, both the average gape size and lateral excursion were significantly smaller in the experimental group than that in the control group after 9 weeks. The jaw movement pattern also showed a significant decrease at the maximum opening period in the experimental group. Our findings indicate that inadequate occlusal function during growth alters neuromuscular control of masticatory behaviors and impairs the pattern of RJMs.

The maturation of rhythmic jaw movements (RJMs) and related neuromuscular control has rarely been studied in animals, though this process is essential for regulating the development of stomatognathic functions. Previous studies have shown that occlusal hypofunction during growth alters masticatory performance. However, little is known about patterns of cortically-induced RJMs under conditions of soft-diet feeding during development. The aim of this study is to clarify the effect of low occlusal loading on the pattern of cortically induced RJMs and related neuromuscular responses in growing rats. Sixty-four 2-week-old male albino Wistar rats were randomly divided into two groups and fed on either a normal diet (control) or soft diet (experimental) soon after weaning. At 5, 7, 9, and 11 weeks of age, electromyographic (EMG) activity was recorded from the right masseter and anterior digastric muscles along with corresponding kinematic images in RJMs during repetitive intracortical microstimulation of the left cortical masticatory area (CMA). Rats in both groups showed an increase in gape size and lateral excursion until 9 weeks of age. The vertical jaw movement speed in both groups showed no significant difference between 5 and 7 weeks of age but increased with age from 9 to 11 weeks. Compared to the control group, the average gape size and vertical speed were significantly lower in the experimental group, and the pattern and rhythm of the jaw movement cycle were similar between both groups at each recording age. EMG recordings showed no age-related significant differences in onset latency, duration, and peak-to-peak amplitude. Moreover, we found significantly longer onset latency, smaller peak-to-peak amplitude, and greater drop-off mean and median frequencies in the experimental group than in the control group, while there was no significant difference in the duration between groups. These findings indicate that a lack of enough occlusal function in infancy impedes the development of patterns of RJMs and delays the neuromuscular response from specific stimulation of the CMA., (Copyright © 2020 Aung, Kato, Abe, Ogawa, Ishidori, Fujita, Okihara, Kokai and Ono.)

Background: Haemodynamics during recovery after teeth clenching is poorly understood., Objective: To clarify factors influencing tissue blood oxygenation recovery after clenching with altered muscle activity and duration, but constant total muscle activity., Methods: The following tasks were based on constant maximum voluntary clenching (100% MVC): (a) 50% MVC × 30 seconds; (b) 30% MVC × 50 seconds; and (c) 10% MVC × 150 seconds. Tissue oxygenated (oxy-Hb), deoxygenated (deoxy-Hb) and total haemoglobin (total-Hb) were recorded using near-infrared spectroscopy in the masseter muscle during recovery after each task. Participants rested for 30 seconds before each task; average resting values were set as baseline. Respective ratios to baseline at 20, 60, 120 and 180 seconds after each task were calculated; the tasks were compared at each time point using one-way repeated-measures ANOVA., Results: Oxy-Hb and total-Hb decreased and deoxy-Hb increased during the tasks and recovered thereafter. For Task 3, not all values recovered to baseline, even after 180 seconds (oxy-Hb: 96.85%, total-Hb: 98.31%, deoxy-Hb: 102.98%). Oxy-Hb (after 180 seconds, Task 1-Task 3: P < .001, Task 2-Task 3: P = .013) and total-Hb (after 180 seconds, Task 1-Task 3: P < .001, Task 2-Task 3: P = .005) were significantly lower, and deoxy-Hb (after 180 seconds, Task 1-Task 3: P < .001, Task 2-Task 3: P = .005) was significantly higher for Task 3 than other tasks, at all times during and after recovery., Conclusion: Despite the same total muscle activity, weak-force, long-duration clenching is more harmful than strong-force, short-duration clenching, suggesting a greater effect of awakening bruxism than sleep bruxism on myalgia., (© 2019 John Wiley & Sons Ltd.)

The hippocampus is an important brain region involved in memory and learning. Brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), and phospho-p44/p42 mitogen-activated protein kinase (MAPK) are known to contribute to hippocampal memory/learning. The present study aimed to clarify the effects of nasal obstruction during the growth period on memory/learning in an animal model, using combined behavioral, biochemical, and histological approaches. Male BALB/C mice underwent unilateral nasal obstruction (UNO) by cauterization at 8 days of age and were subjected to Y-maze and passive avoidance tests at 15 weeks of age. The serum corticosterone levels were measured using an enzyme-linked immunosorbent assay, and brain tissues were subjected to hematoxylin-eosin staining and histological analysis or homogenization and Western blot analysis. Compared with control mice, UNO mice had lower blood oxygen saturation levels and exhibited apparent memory/learning impairments during behavioral testing. Additionally, the UNO group had higher hippocampal BDNF levels and serum corticosterone levels, lower hippocampal TrkB and phospho-p44/p42 MAPK levels, and reduced neuron numbers relative to controls. Our findings suggest that UNO during adolescence affects the hippocampus and causes memory/learning impairments., (© 2018 Wiley Periodicals, Inc.)

Background: In clinical orthodontic treatment, chronic respiratory disturbance or mouth breathing has been concerned symptoms and screening criteria. In this study, to analyze the relation between nasal obstruction and taste sensing, a unilateral nasal obstruction model was performed to investigate the taste papillae and taste buds in rats., Methods: Fourteen 6-day-old male Wistar rats were randomly divided into control and experimental groups (n = 7 each). The experimental group underwent unilateral nasal obstruction at 8 days of age. The rats were euthanized at 9-week-old. The morphology of the circumvallate papillae and taste buds were identified by immunohistochemical methods. The fungiform papillae were visualized with 1% methylene blue and sectioned for taste bud observation., Results: Some defects in the gustatory epithelium were observed after unilateral nasal obstruction. Rats in the experimental group had significantly fewer fungiform papillae and smaller volumes of taste bud. In circumvallate papillae, smaller total taste bud area was found in experiment group., Conclusion: Findings in the present study suggest that nasal obstruction might have significant influences on the gustatory function via morphologic change in the taste papillae and taste buds in tongue area., (Copyright © 2017. Published by Elsevier B.V.)

Introduction: Few studies have examined the secondary insertion of orthodontic miniscrews after failure of the first insertion. We investigated both the primary and secondary success rates of miniscrews used for maxillary anchorage and compared the stability of the maxillary buccal area (MB) and the midpalatal suture area (MP)., Methods: In total, 387 miniscrews were primarily inserted into the MB (between the second premolar and first molar); of these, 81 (20.9%) miniscrews lacked stability and were reinserted into the MB (same position or more distal position) or the MP. Additionally, 84 miniscrews were primarily inserted into the MP; 13 (15.5%) of those lacked stability and were reinserted into the MP. We calculated and compared the primary and secondary success rates in each area. Moreover, we investigated the factors affecting clinical success., Results: Although the success rate of the secondary insertion was significantly lower than that of the primary insertion into the MB, miniscrews inserted into the MP were stable in both primary and secondary insertions. The screw length was significantly associated with the stability of miniscrews inserted into the MB., Conclusions: For secondary insertions, miniscrews placed in the MP may be more stable than those inserted in the MB., (Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Skeletal and dental discrepancies cause asymmetric malocclusions in orthodontic patients. It is difficult to achieve adequate functional occlusion and guidance in patients with congenital absence of a mandibular incisor due to the tooth-size discrepancy. Here, we describe the orthodontic treatment of a 22-year-old woman with an asymmetric Angle Class II malocclusion, mandibular deviation to the left, and 3 mandibular incisors. The anterior teeth and maxillary canines were crowded. We used an improved superelastic nickel-titanium alloy wire (Tomy International, Tokyo, Japan) to compensate for the asymmetric mandibular arch and an asymmetrically bent archwire to move the maxillary molars distally. A skeletal anchorage system provided traction for intermaxillary elastics, and extractions were not needed. We alleviated the crowding and created an ideal occlusion with proper overjet, overbite, and anterior guidance with Class I canine and molar relationships. This method of treatment with an asymmetrically bent nickel-titanium alloy wire provided proper Class I occlusion and anterior guidance despite the mandibular deviation to the left and 3 mandibular incisors, without the need for extractions., (Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Although the success of using orthodontic miniscrews for primary insertion has been reported in the literature, few studies have followed up on secondary insertions after failure of the first insertion. In this study, we investigated not only the primary but also secondary success rates of miniscrews and considered the risk factors influencing their stability., Methods: Five hundred miniscrews were inserted for orthodontic anchorage in 240 patients. Ninety-eight miniscrews lacked stability; thus, 77 of these were removed and reinserted. We calculated and compared the primary and secondary success rates of insertion. Moreover, we investigated which clinical parameters affected the stability of miniscrews., Results: The success rate of secondary insertion (44.2%) was significantly lower than that of primary insertion (80.4%). The screw length and jaw receiving the insertion were significantly associated with the stability of miniscrews. The 8.0-mm miniscrews were significantly more stable than the 6.0-mm miniscrews, and the success rate for insertions into the maxilla was significantly higher than that for the mandible., Conclusions: Secondary insertions lack stability; therefore, clinicians should be aware of the reduced success rate of reinsertion and know the risk factors to avoid failure of secondary insertions., (Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Postnatal growth is influenced by genetic and environmental factors. Nasal obstruction during growth alters the electromyographic activity of orofacial muscles. The facial primary motor area represents muscles of the tongue and jaw, which are essential in regulating orofacial motor functions, including chewing and jaw opening. This study aimed to evaluate the effect of chronic unilateral nasal obstruction during growth on the motor representations within the face primary motor cortex (M1). Seventy-two 6-day-old male Wistar rats were randomly divided into control ( n = 36) and experimental ( n = 36) groups. Rats in the experimental group underwent unilateral nasal obstruction after cauterization of the external nostril at 8 days of age. Intracortical microstimulation (ICMS) mapping was performed when the rats were 5, 7, 9, and 11 wk old in control and experimental groups ( n = 9 per group per time point). Repeated-measures multivariate ANOVA was used for intergroup and intragroup statistical comparisons. In the control and experimental groups, the total number of positive ICMS sites for the genioglossus and anterior digastric muscles was significantly higher at 5, 7, and 9 wk, but there was no significant difference between 9 and 11 wk of age. Moreover, the total number of positive ICMS sites was significantly smaller in the experimental group than in the control at each age. It is possible that nasal obstruction induced the initial changes in orofacial motor behavior in response to the altered respiratory pattern, which eventually contributed to face-M1 neuroplasticity. NEW & NOTEWORTHY Unilateral nasal obstruction in rats during growth periods induced changes in arterial oxygen saturation (SpO 2 ) and altered development of the motor representation within the face primary cortex. Unilateral nasal obstruction occurring during growth periods may greatly affect not only respiratory function but also craniofacial function in rats. Nasal obstruction should be treated as soon as possible to avoid adverse effects on normal growth, development, and physiological functions., (Copyright © 2017 the American Physiological Society.)

Nasal obstruction can occur at different life stages. In early stages of life the respiratory system is still under development, maturing during the growth period. Previous studies have shown that nasal obstruction in neonatal rats alters craniofacial function. However, little is known about the effects of nasal obstruction that develops during later growth periods. The aim of this study was to investigate the effects of nasal obstruction during later periods of growth on the functional characteristics of the jaw-opening reflex (JOR) and tongue-protruding muscles. In total, 102 6-day-old male Wistar rats were randomized into either a control or experimental group (both n = 51). In order to determine the appropriate timing of nasal obstruction, the saturation of arterial oxygen (SpO 2 ) was monitored at 8 days, and at 3, 5, 7, 9, and 11 weeks in the control group. Rats in the experimental group underwent unilateral nasal obstruction at the age of 5 weeks. The SpO 2 was monitored at 7, 9, and 11 weeks in the experimental group. The electromyographic responses of JOR and the contractile properties of the tongue-protruding muscles were recorded at 7, 9, and 11 weeks. In the control group, SpO 2 decreased until 5 weeks of age, and remained relatively stable until 11 weeks of age. The SpO 2 was significantly lower in the experimental group than in the control. In the experimental group, JOR changes included a longer latency and smaller peak-to-peak amplitude, while changes in the contractile properties of the tongue-protruding muscles included larger twitch and tetanic forces, and a longer half-decay time. These results suggest that nasal obstruction during later growth periods may affect craniofacial function.

Objective: Malocclusion with deep overbite and facial esthetics improve when facial height is intentionally increased during orthodontic extrusion of the posterior teeth. Thus, a better understanding of post-treatment stability of increased occlusal vertical dimension (iOVD) in adult patients is important. We focused on the jaw-opening reflex (JOR), which plays an important role in the control of jaw movements during mastication, and investigated the effects of iOVD on the JOR in rats with an electrophysiological technique., Design: One hundred and twenty 13-week-old male Wistar rats were randomly divided into control and experimental groups. Rats in the experimental group received a 2-mm buildup of composite resin on the maxillary molars at 13 weeks of age. The JOR was induced by low-intensity electrical stimulation of the left inferior alveolar nerve. The electromyographic responses were recorded from the digastric muscle at 13, 14, 15, 17, 19, and 23 weeks of age. JOR properties including latency, duration, and peak-to-peak amplitude were measured and compared between the groups., Results: The latency of the JOR was significantly longer and the peak-to-peak amplitude was significantly smaller in the experimental group than in the control group from 14 to 19 weeks of age, while the reflex duration was not significantly different. Intra-group comparisons of the latency and peak-to-peak amplitudes among rats 14-19 weeks of age were significantly different between the experimental group and the control group., Conclusions: iOVD affected the latency and amplitude of the JOR but not the duration. The JOR adapted after 10 weeks of iOVD., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Introduction: The frontal occlusal plane of the maxilla generally inclines toward the ipsilateral side of the mandibular deviation in subjects with facial asymmetry; however, a few patients with facial asymmetry have their frontal occlusal planes inclined toward the contralateral side. We aimed to investigate the morphologic and functional features of such patients., Methods: The subjects were 40 patients with facial asymmetry divided into 2 groups based on the inclination of the frontal occlusal plane toward the ipsilateral or the contralateral side. We analyzed lateral and posteroanterior cephalometric radiographs and occlusal variables and evaluated temporomandibular joint symptoms. Statistical comparisons were performed between the 2 groups (P <0.05)., Results: The posteroanterior cephalometry significantly differed between the ipsilateral and contralateral groups. Occlusal force and occlusal contact area were significantly larger, and temporomandibular joint symptoms were more frequently found on the side of the upward-inclined frontal occlusal plane than on the opposite side in both groups., Conclusions: The features in the contralateral group in terms of occlusal force and temporomandibular disorders were clinically significant. Clinicians should note that the conditions associated with the contralateral group require less presurgical decompensation., (Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Autotransplantation has become a major therapeutic option for replacing missing teeth in adult orthodontic patients. However, little systematic information is available about the long-term stability of autotransplanted teeth with complete root formation after the application of an orthodontic force. The objective of this study was to investigate the outcomes of autotransplanted teeth with complete root formation that underwent orthodontic treatment., Methods: One hundred teeth, autotransplanted in 89 patients, were examined over a mean observation period of 5.8 years. Orthodontic force was applied with nickel-titanium wires 4 to 8 weeks after autotransplantation. Root resorption, ankylosis, mobility, pocket depth, and inflammation at the recipient site were investigated clinically and with radiographs., Results: The survival rate of the autotransplanted teeth was 93.0%. Abnormal findings were found in 29 teeth, including 7 lost teeth, for a success rate of 71.0%. Donor tooth type and occlusal condition of the donor tooth before transplantation were associated with abnormal findings., Conclusions: The early application of orthodontic force may increase the success rate of autotransplanted teeth, and the type and presurgical occlusal condition of donor teeth affect the success rate., (Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Mouth breathing caused by nasal obstruction affects the normal growth and development of craniofacial structures, including changes in the orofacial muscles. Tongue muscles play an important role in patency of the pharyngeal airway, and changes in the breathing pattern may influence tongue function. The purpose of this study was to evaluate the effect of unilateral nasal obstruction during growth on contractile properties of the tongue-protruding muscles. Sixty 6-day-old male Wistar albino rats were divided randomly into control (n = 30) and experimental (n = 30) groups. Rats in the experimental group underwent a unilateral nasal obstruction after cauterization of the external nostril at the age of 8 days, and muscle contractile characteristics were measured at 5, 7, and 9 wk of age. The specific parameters measured were twitch force, contraction time, half-decay time, tetanic force, and fatigue index. Repeated-measures multivariate analysis of variance was used for intergroup and intragroup statistical comparisons. Twitch contraction force and half-decay time were significantly increased in the experimental group at all ages. Tetanic forces at 60 and 80 Hz were significantly higher in the experimental group at all ages. The fatigue index was decreased significantly in the experimental group at the age of 5 wk. These results suggest that early unilateral nasal obstruction may increase the contraction force of the tongue-protruding muscles and prolong the duration of muscle contraction, which may influence the shape and development of the craniofacial complex., (Copyright © 2015 the American Physiological Society.)

We report the successful treatment of a woman aged 25 years 3 months with bilateral cleft lip and palate. She had a protruded premaxilla, collapsed posterior segments, wide alveolar defects with oronasal fistulae, a congenital missing tooth, and severe facial asymmetry with a transverse occlusal cant. The comprehensive treatment approach included (1) premaxillary osteotomy combined with alveolar bone grafting to reposition the premaxilla and minimize the wide alveolar defects, (2) autotransplantation of a tooth with complete root formation to the grafted bone region to restore the missing tooth without a prosthesis such as a dental implant or bridge, and (3) 2-jaw surgery to improve facial asymmetry. The premaxillary osteotomy was managed orthodontically, in combination with bone grafting. The results suggest that surgical orthodontic treatment with tooth autotransplantation might be useful to improve the occlusion and facial esthetics without prosthetics., (Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

It is suggested that masticatory dysfunction affects the central nervous system; however, the underlying mechanism remains unknown. Brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, are known to play important roles in memory and learning. In this study, we examined the effects of mastication on memory, the expression levels of BDNF and TrkB, and the number of neurons in the hippocampus of mice. Male C57 BL/6J mice (3 weeks old) were randomly divided into the control group (N = 7) fed chow pellets and the experimental group (N = 7) fed a liquid diet, which reduces mastication during eating. At 14 weeks of age, we performed a passive avoidance test and found that memory and learning ability were impaired in the experimental group compared with the control group. After the behavioral experiment, brains were harvested and analyzed morphologically and biochemically. In the hippocampus of the experimental group, the expression levels of BDNF were significantly higher, whereas those of TrkB were lower than those of the control group. In the cerebral cortex, these levels remained unchanged between the two groups. The ratio of phospho-p44/42 ERK/pan ERK, a downstream molecule of BDNF/TrkB signaling, in the experimental group was significantly lower than that of the control group in the cortex and hippocampus. The number of pyramidal neurons in the hippocampus was lower in the experimental group than in the control group. These findings suggest that reduced mastication induced by a liquid diet in early childhood may impair memory and learning ability, accompanied by neuronal loss in the hippocampus., (© 2014 Wiley Periodicals, Inc.)

Objective: Nasal obstruction during growth changes craniofacial morphology and function. However, the etiological mechanisms of these changes are unknown. The aim of the present study was to investigate the effects of nasal obstruction during growth on the maturation of the jaw-opening reflex (JOR) using an electrophysiological technique. We focused on the oral sensory receptors that regulate the activities and reflexes of the orofacial muscles., Design: Sixty 6-day-old male Wistar rats were randomly divided into control and experimental groups (n = 30 each). The experimental group underwent unilateral nasal obstruction at 8 days of age. The JOR was evoked by bilateral, low-intensity electrical stimulation of the inferior alveolar nerve. The electromyographic responses were recorded bilaterally from the digastric muscles at 5, 7, and 9 weeks of age., Results: The latency of the JOR was significantly longer and the peak-to-peak amplitude was significantly smaller in the experimental group than in the control group at each age, while the duration was not significantly different. Intragroup comparison of the latency, peak-to-peak amplitude, and duration at 5, 7, and 9 weeks of age revealed no significant differences in either the control or experimental groups., Conclusions: Unilateral nasal obstruction during growth may have significant effects on maturation of craniofacial function., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: To investigate the effects of an experimentally-induced increase in the occlusal vertical dimension (iOVD) on the functional characteristics of temporomandibular joint (TMJ) mechanoreceptors in rats., Materials and Methods: Sixty 13-week-old male albino Wistar rats were divided into control and iOVD groups (30 animals each). The vertical dimension between the maxillary and mandibular molars in the iOVD group was increased by 2.0 mm with a build-up of resin on the maxillary molars. Single-unit activities of TMJ mechanoreceptors were evoked by passive jaw movement. Recording was performed from the gasserian ganglion 1 day and 1, 3, 5, 7, and 9 weeks after the establishment of iOVD., Results: Compared with the control group, the firing threshold was significantly lower at 1, 3, and 5 weeks after iOVD in the iOVD group. There were no significant differences in the firing threshold at 1 day, or 7 or 9 weeks. The maximum instantaneous firing frequency was significantly higher at 1, 3, and 5 weeks after iOVD in the iOVD group, but there were no significant differences at 1 day, or 7 or 9 weeks. There were no significant differences in the average firing frequency during the experimental period., Conclusions: The present study findings suggest that TMJ mechanoreceptors in adult rats may ultimately adapt to iOVD.

Objective: To investigate changes in functional characteristics of the temporomandibular joint (TMJ) mechanoreceptors under mandibular lateral shift., Materials and Methods: Forty 7-week-old male Wistar rats were divided into control and experimental groups. Rats in the experimental group received a modified guiding appliance (MGA) that was designed to shift the mandible to the left side in the occlusal position. Single-unit activities of the TMJ mechanoreceptors were evoked by indirect stimulation of passive jaw movement. Electrophysiologic recordings of TMJ units were obtained 1, 3, 5, 7, and 9 weeks after MGA setting from the gasserian ganglion., Results: At 1 week after mandibular shift, the firing thresholds were the lowest and the maximum instantaneous frequencies were the highest in TMJ units. At 5 weeks, the firing thresholds in the nonshifted side were significantly lower than those in the shifted side. The maximum instantaneous frequencies in the nonshifted side were significantly higher than those in the shifted side at 1, 5, and 7 weeks., Conclusion: These results suggest that the functional lateral shift of the mandible could alter the response properties of TMJ mechanoreceptors, particularly on the nonshifted side.