Evaluation of maxillary and mandibular growth patterns with cephalometric analysis based on cervical vertebral maturation: A Japanese cross-sectional study.

BACKGROUND: Appropriate maxillofacial growth and development evaluation is important for effective orthodontic treatment. Growth evaluation is based on physiological age determined by individual development, but not chronological age. One strategy for determining physiological age is using the cervical vertebral bone age. OBJECTIVES: This study aimed to clarify the standard size of the upper and lower jawbones in Japanese patients using the cervical vertebral maturation stages (CVMS) as an index and clarify the growth pattern. And to use the cervical spine age as a diagnostic aid in orthodontic treatment. MATERIAL AND METHODS: Random sampling was performed from the outpatients who visited the Orthodontics department, Tokyo Medical and Dental University Dental Hospital, and 400 patients were enrolled before treatment. Lateral cephalometric radiographs were obtained to measure the height and length of the mandible and the maxilla length with cephalometric analysis. Standard values were calculated for each cervical-spine-age group to analyze changes during mandibular and maxillary growth. Furthermore, we compared the differences between males and females. The Kruskal-Wallis test was used to compare cervical-spine-age groups, and the Steel-Dwass test was used for multiple comparisons. The reliability of CVMS was confirmed by calculating the weighted kappa coefficient (κ). RESULTS: κ for the degree of intra-evaluator agreement and the degree of the inter-evaluator agreement were calculated, and both indicated almost perfect agreement. We found that the distance between the anterior nasal spine (ANS) and posterior nasal spine (PNS) (i.e., ANS-PNS) increased significantly between CVMS II and CVMS III in males. The distance between Articulare (Ar) and Gonion (Go) (i.e., Ar-Go) and the distance between Go and Pogonion (Pog) (i.e., Go-Pog) increased significantly between CVMS III and CVMS IV in males. CONCLUSION: The findings suggested that CVMS is a reliable indicator of the growth stage of the maxilla and mandible.

PQBP1, an intellectual disability causative gene, affects bone development and growth.

Polyglutamine tract-binding protein 1 (PQBP1), an intellectual disability causative gene, is involved in transcriptional and post-transcriptional regulation of gene expression in animals, and possibly also in plants. In our previous work, reduced brain size, associated with an elongated cell cycle duration in neural stem cells (NSCs), was observed in the NSCs conditional Pqbp1 gene knockout (cKO) mice, which mimic microcephaly patients. However, the physiological significance of PQBP1 in bone metabolism has not been elucidated. Here, we analyzed the bone phenotype of nestin-Cre Pqbp1-cKO mice. Surprisingly, the Pqbp1-cKO mice were significantly shorter than control mice and had a lower bone mass, shown by micro-computed tomography. Furthermore, bone histology showed impaired bone formation in the Pqbp1-cKO mice as well as a chondrocyte deficiency. Real-time PCR analysis showed reduced osteoblast- and chondrocyte-related gene expression in the Pqbp1-cKO mice, while the osteoclast-related gene expression remained unchanged. These results suggest that PQBP1 in bone marrow mesenchymal stem cells may play a crucial role in bone formation and cartilage development.

An orthodontic-orthognathic patient with obstructive sleep apnea treated with Le Fort I osteotomy advancement and alar cinch suture combined with a muco-musculo-periosteal V-Y closure to minimize nose deformity.

In some severe skeletal Class III patients, mandibular setback surgery using sagittal split ramus osteotomy (SSRO) is performed to correct mandibular protrusion. However, in patients diagnosed with obstructive sleep apnea syndrome (OSAS), the risk of OSAS worsening as a result of the SSRO is very high. Maxillary advancement could reduce the degree of mandibular retropositioning and expand the skeletal framework in the pharyngeal region, leading to enlargement of the airway. However, nasal deformity is an undesirable outcome of the procedure. This case report describes a 23-year-old man with a retruded maxilla and OSAS. The maxillary retrusion was treated using Le Fort I osteotomy with an alar cinch suture and a muco-musculo-periosteal V-Y closure (ACVY). After treatment, better occlusal relationships and improvement in OSAS were observed. Thus, an ACVY could minimize nasolabial deformity.

Patterns of adenoid and tonsil growth in Japanese children and adolescents: A longitudinal study.

Lymphoid tissues, such as adenoids (Ad) and tonsils (Tn), are suggested to undergo hypertrophy during childhood and involution in adulthood. Enlargement of Ad and Tn can cause transient obstruction of the respiratory airways, thus inducing obstructive sleep apnoea. To date, the standard Ad and Tn sizes have not been reported, and there are no explicit objective criteria for evaluating their sizes or deducing whether they have enlarged, reduced, or remained constant over time. Our previous cross-sectional study revealed the age-dependent airway occupation ratio of Ad and Tn in Japanese individuals. We conducted a longitudinal observational study of the Ad and Tn sizes in Japanese individuals aged 6-20 years. Ninety individuals were retrospectively enrolled. The average and standard deviation of the sizes was calculated in 5 age-based groups.

Differential changes in the adenoids and tonsils in Japanese children and teenagers: a cross-sectional study.

When adenoids (Ad) and tonsils (Tn) become hypertrophied, craniofacial and general body growth is affected. However, there are no objective explicit criteria for evaluating the size of the Ad and Tn, and their respective growth patterns remain unclear. This study determined the average proportions of the Ad and Tn sizes to the upper airway area at various developmental stages in Japanese individuals. Lateral cephalometric radiographs were obtained from 300 Japanese children and teenagers (150 boys and 150 girls, aged 6-20 years), and the respective proportions of Ad to the nasopharynx (Ad/Np) and Tn to the oropharynx (Tn/Op) in the upper airway were determined. Average and standard deviation (SD) were calculated for each of the 5 age groups: lower primary school, upper primary school, junior high school, senior high school, and young adults. We investigated the correlation between age and growth patterns of Ad and Tn, and determined the average Ad/Np and Tn/Op. There was an age-related decrease in Ad and Tn size, and a significant positive correlation between Ad/Np and Tn/Op values in the upper primary school group. Both Ad/Np and Tn/Op decrease as individuals approach adulthood. However, the growth patterns of the Ad/Np and Tn/Op differ from each other.

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.

Nasomaxillary hypoplasia with a congenitally missing tooth treated with LeFort II osteotomy, autotransplantation, and nickel-titanium alloy wire.

INTRODUCTION: In some skeletal Class III adult patients with nasomaxillary hypoplasia, the LeFort I osteotomy provides insufficient correction. This case report describes a 20-year-old woman with a combination of nasomaxillary hypoplasia and a protrusive mandible with a congenitally missing mandibular second premolar. METHODS: We performed a LeFort II osteotomy for maxillary advancement. Autotransplantation of a tooth was also performed; the donor tooth was used to replace the missing permanent tooth. To increase the chance of success, we applied light continuous force with an improved superelastic nickel-titanium alloy wire technique before extraction and after transplantation. RESULTS: The patient's profile and malocclusion were corrected, and the autotransplanted tooth functioned well. The postero-occlusal relationships were improved, and ideal overbite and overjet relationships were achieved. CONCLUSIONS: The methods used in this case represent a remarkable treatment.

Effect of unilateral nasal obstruction on tongue protrusion forces in growing rats.

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.

Asymmetric severe skeletal Class II division 1 patient with temporomandibular joint disorder treated with zygomatic anchorage devices and Ni-Ti alloy wires.

OBJECTIVE: To describe the orthodontic treatment of a nongrowing 30-year-old woman with asymmetric severe skeletal Class II malocclusions (asymmetric Angle Class II), large overjet (16 mm), large overbite (8 mm), two congenitally missing mandibular incisors (presenting a deciduous anterior tooth), and signs and symptoms of temporomandibular joint disorder (TMD). MATERIALS AND METHODS: We used novel improved super-elastic Ni-Ti alloy wires (ISWs) combined with Ni-Ti alloy coil springs, power hooks, and a zygomatic implant as reinforced anchorage to provide a constant and continuous mild force to the dentition. RESULTS: We successfully distalized maxillary molars, premolars, and retracted anterior teeth and corrected the asymmetric Angle Class II molar relationship using this system of zygomatic anchorage in conjunction with ISWs, Ni-Ti alloy open-coil springs, and crimpable power hook. The maxillary molars were distalized, and postero-occlusal relationships were improved to achieve Class I canine and molar relationships on both sides. Intrusion of the upper molars made the mandibular plane close. Ideal overbite and overjet relationships were established. Facial esthetics were improved with decreased upper and lower lip protrusion, and no symptoms of TMD were observed after treatment. CONCLUSION: The orthodontic treatment described here is a promising anchorage technique alternative to traditional techniques to improve severe skeletal Class II with TMD.

Liquid diet induces memory impairment accompanied by a decreased number of hippocampal neurons in mice.

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.

Asymmetrical distalization of maxillary molars with zygomatic anchorage, improved superelastic nickel-titanium alloy wires, and open-coil springs.

INTRODUCTION: In nongrowing patients with skeletal Class II malocclusion, premolar extraction or maxillary distalization can be used as camouflage treatment. Zygomatic anchorage enables distalization in uncooperative or noncompliant patients. We describe 1 such procedure in a 24-year-old woman. METHODS: We used novel improved superelastic nickel-titanium archwires combined with nickel-titanium open-coil springs to provide a constant and continuous low force to the dentition. RESULTS: We were able to successfully eliminate the protrusive profile and correct the Class II molar relationship using this system of zygomatic anchorage. The posterior occlusal relationships were improved to achieve Class I canine and molar relationships on both sides, and ideal overbite and overjet relationships were established. Facial esthetics was improved with decreased protrusion of the upper and lower lips. CONCLUSIONS: The method used here is a promising alternative to traditional distalization techniques and might offer an effective and simple means of distalizing maxillary molars in uncooperative patients.

Soft diet causes greater alveolar osteopenia in the mandible than in the maxilla.

OBJECTIVE: To investigate changes in the bony microstructure of the upper and lower alveolar bone during masticatory loading induced by soft diet feeding in growing rats. DESIGN: Three-week-old male Wistar rats were randomly divided into two groups. Rats were fed with either pellets [control group (n=6)] or a soft diet [experimental group (n=6)] for nine weeks. 3D-microstructure of the alveolar bone of the first molar region (M1) was examined by micro-CT analysis. RESULTS: Micro-CT images showed increased marrow spaces of the inter-radicular alveolar bone around the rat mandibular M1 in the experimental group compared with that in the control group. The bone volume/tissue volume ratio, trabecular thickness, trabecular number, mean intercept length, trabecular width and trabecular star volume for the mandibular M1 inter-radicular alveolar bone were lower in the experimental group than in the control group. Marrow space star volume was increased in the experimental group compared with the control group. CONCLUSIONS: These results suggest that alveolar osteopenia is more extensive in the mandible than the maxilla in rats that experience low masticatory loading during growth.

Functional adaptability of temporomandibular joint mechanoreceptors after an increase in the occlusal vertical dimension in rats.

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.

Functional changes of temporomandibular joint mechanoreceptors induced by reduced masseter muscle activity in growing rats.

OBJECTIVE: To determine the influence of masseter muscle activity during growth on the functional characteristics of temporomandibular joint (TMJ) mechanoreceptors. MATERIALS AND METHODS: Sixty-six 3-week-old male Wistar rats were divided into an experimental group, in which the masseter muscles were bilaterally resected at 3 weeks of age, and a control group. Single-unit activities of the TMJ mechanoreceptors were evoked by indirect stimulation of passive jaw movement. Electrophysiologic recordings of TMJ units were made at 5, 7, and 9 weeks of age. RESULTS: During this period, the firing threshold of the TMJ units was significantly lower and the maximum instantaneous frequency of the TMJ units was significantly higher in the experimental group than in the control group. CONCLUSION: Reduced masseter activity during the growth period alters the response properties of TMJ mechanoreceptors.