Reduced mastication during growth inhibits cognitive function by affecting trigeminal ganglia and modulating Wnt signaling pathway and ARHGAP33 molecular transmission.

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.

Effect of Obesity on Masticatory Muscle Activity and Rhythmic Jaw Movements Evoked by Electrical Stimulation of Different Cortical Masticatory Areas.

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.

Histological and contractile changes in the genioglossus muscle after nasal obstruction in growing rats.

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.

Unilateral nasal obstruction affects development of cortical orofacial motor representation in the cortical masticatory area of growing rats.

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 (SpO2) 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 SpO2 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.

Nasal obstruction during the growth period modulates the Wnt/ß-catenin pathway and brain-derived neurotrophic factor production in association with tyrosine kinase receptor B mRNA reduction in mouse hippocampus.

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/ß-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/ß-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/ß-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 (SpO2 ) 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 SpO2 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/ß-catenin pathway and BDNF production in association with TrkB mRNA reduction, thereby resulting in memory and learning impairments.

Effects of low occlusal loading on the neuromuscular behavioral development of cortically-elicited jaw movements in growing rats.

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.

Functional Analysis of Rhythmic Jaw Movements Evoked by Electrical Stimulation of the Cortical Masticatory Area During Low Occlusal Loading in Growing Rats.

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.

Evaluation of tissue oxygen saturation of the masseter muscle during standardised teeth clenching.

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.

Long-term stability after multidisciplinary treatment involving maxillary distraction osteogenesis, and sagittal split ramus osteotomy for unilateral cleft lip and palate with severe occlusal collapse and gingival recession: A case report.

In this report, we describe a case involving a 34-year-old woman who showed good treatment outcomes with long-term stability after multidisciplinary treatment for unilateral cleft lip and palate (CLP), maxillary hypoplasia, severe maxillary arch constriction, severe occlusal collapse, and gingival recession. A comprehensive treatment approach was developed with maximum consideration of strong scar constriction and gingival recession; it included minimum maxillary arch expansion, maxillary advancement by distraction osteogenesis using an internal distraction device, and mandibular setback using sagittal split ramus osteotomy. Her post-treatment records demonstrated a balanced facial profile and occlusion with improved facial symmetry. The patient's profile was dramatically improved, with reduced upper lip retrusion and lower lip protrusion as a result of the maxillary advancement and mandibular setback, respectively. Although gingival recession showed a slight increase, tooth mobility was within the normal physiological range. No tooth hyperesthesia was observed after treatment. There was negligible osseous relapse, and the occlusion remained stable after 5 years of post-treatment retention. Our findings suggest that such multidisciplinary approaches for the treatment of CLP with gingival recession and occlusal collapse help in improving occlusion and facial esthetics without the need for prostheses such as dental implants or bridges; in addition, the results show long-term post-treatment stability.

Cone-beam computed tomography-based diagnosis and treatment simulation for a patient with a protrusive profile and a gummy smile.

For patients with bimaxillary protrusion, significant retraction and intrusion of the anterior teeth are sometimes essential to improve the facial profile. However, severe root resorption of the maxillary incisors occasionally occurs after treatment because of various factors. For instance, it has been reported that approximation or invasion of the incisive canal by the anterior tooth roots during retraction may cause apical root damage. Thus, determination of the position of the maxillary incisors is key for orthodontic diagnosis and treatment planning in such cases. Cone-beam computed tomography (CBCT) may be useful for simulating the post-treatment position of the maxillary incisors and surrounding structures in order to ensure safe teeth movement. Here, we present a case of Class II malocclusion with bimaxillary protrusion, wherein apical root damage due to treatment was minimized by pretreatment evaluation of the anatomical structures and simulation of the maxillary central incisor movement using CBCT. Considerable retraction and intrusion of the maxillary incisors, which resulted in a significant improvement in the facial profile and smile, were achieved without severe root resorption. Our findings suggest that CBCT-based diagnosis and treatment simulation may facilitate safe and dynamic orthodontic tooth movement, particularly in patients requiring maximum anterior tooth retraction.

Nasal obstruction during adolescence induces memory/learning impairments associated with BDNF/TrkB signaling pathway hypofunction and high corticosterone levels.

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.

A patient with mandibular deviation and 3 mandibular incisors treated with asymmetrically bent improved superelastic nickel-titanium alloy wires.

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.

Stability of secondarily inserted orthodontic miniscrews after failure of the primary insertion for maxillary anchorage: Maxillary buccal area vs midpalatal suture area.

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.

Unilateral nasal obstruction induces degeneration of fungiform and circumvallate papillae in rats.

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.

Prognosis of primary and secondary insertions of orthodontic miniscrews: What we have learned from 500 implants.

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.

Unilateral nasal obstruction affects motor representation development within the face primary motor cortex in growing rats.

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 (SpO2) 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.

Effects of increased occlusal vertical dimension on the jaw-opening reflex in adult rats.

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.

Features in subjects with the frontal occlusal plane inclined toward the contralateral side of the mandibular deviation.

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.

Unilateral Nasal Obstruction during Later Growth Periods Affects Craniofacial Muscles in Rats.

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 (SpO2) 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 SpO2 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, SpO2 decreased until 5 weeks of age, and remained relatively stable until 11 weeks of age. The SpO2 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.

Retrospective study of 100 autotransplanted teeth with complete root formation and subsequent orthodontic treatment.

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.