Takashi S. Kajii

Long-term effects of prostaglandin E2 on the mineralization of a clonal osteoblastic cell line (MC3T3-E1)

Prostaglandin (PG) E2 is thought to be a mediator of the effect of mechanical stress on bone formation, but its effects on osteoblasts have not yet been fully described. Here, the effects of the continuous application of PGE2 and indomethacin, an inhibitor of prostaglandin G/H synthase (cyclo-oxygenase), on the proliferation, differentiation and mineralization of a clonal osteoblastic cell line, MC3T3-E1, were investigated. The cells were cultured in media with either a high (1 microg/ml) or a low (1 ng/ml) concentration of PGE2, with indomethacin (1 microg/ml) and, as a control, with neither agent. The effects of PGE2 and indomethacin were assessed quantitatively. Indomethacin and a high concentration of PGE2 increased the total protein compared to the control and low-PGE2 cultures. 7 days after confluence, alkaline phosphatase (ALP) activity within the cells and extracellular matrices increased. This increase was highest with indomethacin and lowest with a high concentration of PGE2. ALP activity also increased in the medium, but only 21 days after confluence; the effects of the agents were similar to those on the cells and matrices. The accumulation of calcium, inorganic phosphate and hydroxyproline was highest with indomethacin. PGE2 production was at its maximum when the cells were at confluence and was inhibited by indomethacin. Specific [3H]PGE2 binding to the microsomal fraction of the cell was also measured to examine the expression of the PGE2 receptor. The amount of [3H]PGE2 binding per mg of protein was highest at confluence, then decreased and again increased in the mineralizing stage. These results suggest that indomethacin increases ALP activity and the accumulation of mineralized tissue in MC3T3-E1 cells, presumably by inhibiting the production of PGE2. PGE2 could signal the suppression of mineralization as early as confluence.

Agenesis of Third Molar Germs Depends on Sagittal Maxillary Jaw Dimensions in Orthodontic Patients in Japan

The aim of this study was to determine the correlation between congenitally missing third molar tooth germs and sagittal maxillomandibular jaw dimensions in orthodontic patients in Japan. The subjects were 391 patients from the orthodontic clinic of the Hokkaido University Dental Hospital who were less than 15 years of age. Assessments were made from panoramic radiographs and lateral cephalograms. The subjects were divided into a maxillary/mandibular third molar absent and an existent group. The ANB angle and the sagittal dimensions of the nasal floor (ANS-PNS), maxillary basal bone (Mx), mandibular corpus (Go-Pog), and mandibular basal bone (Mn) were measured. Logistic regression analysis was used to estimate associations between third molar agenesis and these measures. The following results were obtained: (1) The frequency of the maxillary third molar agenesis significantly increased with decreasing Mx (odds ratio = 0.559, 95% confidence interval = 0.377 - 0.829). The frequency of the mandibular third molar agenesis also increased with decreasing Mx (odds ratio = 0.532, 95% confidence interval = 0.330 - 0.856). (2) There were no significant correlations between Mn and mandibular third molar agenesis. These results suggest that agenesis of third molar germs does not depend on anteroposterior dimensions of the mandible but depends on anteroposterior dimensions of the maxilla in Japanese orthodontic patients.

Monocortical mandibular bone grafting for reconstruction of alveolar cleft.

Objective To assess and develop a monocortical mandibular bone grafting procedure for reconstruction of alveolar cleft. Design Prospective study. Setting Hokkaido University Hospital. Patients Forty-two consecutive Japanese patients who had been treated for a total of 48 clefts according to a strict clinical protocol. Mean age at bone grafting was 6 years 11 months. Interventions Bone grafting was performed by harvesting lateral cortical bone plates from the symphysis and/or body and then placing them on the labial and palatal openings of the alveolar process defect. No particulate bone grafts were packed into the bony cavity. Mean follow-up after bone grafting was 37 months. Main Outcome Measures Status of the grafted area and eruption of cleft-adjacent teeth were assessed prospectively using computed tomography and periapical radiography. Results At 6 months postoperatively, computed tomography showed sufficient bone bridge formation at the cleft site in 85.4% of clefts. Periapical radiography showed ≥75% of the root surfaces of cleft-adjacent teeth were covered with spanning bone in 83.3% of clefts. In 92.6% of clefts in which the cleft-adjacent canine was uncovered with bone during follow-up, the canines erupted spontaneously. Conclusions Monocortical mandibular bone grafting appears extremely effective for sufficient bone bridge formation and facilitation of cleft-adjacent teeth eruption. The procedure is advantageous in that the quantity of bone required per unit volume of cleft defect is relatively reduced, and larger clefts can thus be treated.

Multivariate analysis of factors affecting dental arch relationships in Japanese unilateral cleft lip and palate patients at Hokkaido University Hospital

Abstract The aims of this study were to evaluate the dental arch relationship (degree of malocclusion) of Japanese patients with unilateral cleft lip and palate (UCLP) at Hokkaido University Hospital and to assess the various congenital and environmental factors that affect dental arch relationship in UCLP patients. Dental models of 140 subjects with UCLP were taken before orthodontic treatment. The mean age of the subjects was 6.85 ± 1.56 (mean ± S.D.) years. Surgeons from Hokkaido University Hospital performed the primary surgery. The dental arch relationships of the 140 subjects were assessed by applying the 5-year-old index and the Goslon Yardstick. The intra- and interexaminer agreement was evaluated using weighted kappa statistics. Associations between various factors and dental arch relationships were assessed using logistic regression analysis. Sixty-nine percent and 79% of the subjects were classified into favorable group (category rating 1, 2 and 3) using the 5-year-old index and the Goslon Yardstick, respectively. Using crude and stepwise regression analyses, significant associations were found between palatoplasty with exposed raw surface and dental arch relationship (judged by the Goslon Yardstick). Family history of skeletal Class III also seemed to be correlated with the dental arch relationship. This multivariate analysis suggested that palatoplasty with exposed raw surface was significantly correlated with the dental arch relationship of UCLP patients at Hokkaido University Hospital.

Postnatal treatment factors affecting craniofacial morphology of unilateral cleft lip and palate (UCLP) patients in a Japanese population

We have evaluated the craniofacial morphology of Japanese patients with unilateral cleft lip and palate (UCLP) and assessed the various postnatal factors that affect it. Lateral cephalograms of 140 subjects (mean (SD) aged 7 (2) years) with UCLP were taken before orthodontic treatment. Surgeons from Hokkaido University Hospital had done the primary operations. The craniofacial morphology was assessed by angular and linear cephalometric measurements. Cheiloplasty, palatoplasty, and preoperative orthopaedic treatment were chosen as postnatal factors. To compare the assessments of the postnatal factors, we made angular and linear cephalometric measurements for each subject and converted them into Z scores in relation to the mean (SD) of the two variables. Subjects treated by the modified Millard cheiloplasty had larger sella-nasion-point A (SNA) and nasion-point A-pogonion (NA-POG) measurements than subjects treated by the modified Millard with a vomer flap cheiloplasty. Two-stage palatoplasty showed consistently better craniofacial morphology than the other palatoplasty. Subjects who had preoperative orthopaedic treatment with a Hotz plate had significantly larger upper incisor/sella-nasion (U1-SN) measurements than who had no preoperative orthopaedic treatment or an active plate. We conclude that in subjects treated by a modified Millard type of cheiloplasty, a two-stage palatoplasty, and a Hotz plate there were fewer adverse effects on craniofacial morphology.

The effects of palatoplasty and pre-surgical infant orthopedic treatment on occlusion in unilateral cleft lip and palate patients

Abstract Purpose The aim of this study was to evaluate the effect of pre-surgical infant orthopedic treatment (Hotz plate) and type of palatoplasty on the dental arch relationship and the dental arch morphology of unilateral cleft lip and palate (UCLP) patients. Materials and methods Seventy-four children with UCLP were divided into three groups. One group had undergone one-stage palatoplasty without Hotz plate (OSP w/o H), the second had undergone one-stage palatoplasty with Hotz plate (OSP w/H), and the third had undergone two-stage palatoplasty with Hotz plate (TSP w/H). We evaluated the dental models which were taken during initial examination at our orthodontic clinic, using the Goslon Yardstick, the 5-year-old index, and dental model analysis. Results Regarding both indices, there were no significant differences among the three groups. However, the dental arch width between maxillary deciduous canines in OSP w/H and TSP w/H was significantly greater than that of OSP w/o H. The dental arch width at the maxillary deciduous second molars in TSP w/H was significantly greater than in OSP w/H and OSP w/o H. Conclusion Dental arch relationship in UCLP patients was not influenced by the type of palatoplasty and the use of pre-surgical infant orthopedic treatment. Our results suggest that pre-surgical infant orthopedic treatment results in the increase of anterior dental width, whereas two-stage palatoplasty is significantly effective for increasing posterior dental width in UCLP patients.

Growth and development of the cranial base in mice that spontaneously develop anterior transverse crossbite

INTRODUCTION Homozygous brachymorphic (bm/bm) mice are characterized by disproportionately short stature. Anterior transverse crossbite sometimes develops spontaneously in inbred BALB/c-bm/bm mice that produce undersulfated glycosaminoglycans. The reason for inferior growth of the craniofacial structures of BALB/c-bm/bm mice has not been clarified. We focused on the spheno-occipital synchondrosis (SOS)-the growth site of the cranium-and investigated the growth pattern in the SOS of the BALB/c-bm/bm mice. METHODS The BALB/c-+/+ mice and BALB/c-bm/bm mice without malocclusion were used. Sagittal sections of the cranial bases were stained with hematoxylin and eosin, observed histologically, and used to measure the anteroposterior length and the percentage of active bone volume around the SOS. RESULTS In the histologic study, compared with the cartilage in the BALB/c mice, a bipolar column was not seen in the cartilage of the SOS in the BALB/c-bm/bm mice. The histomorphometric study showed that the anteroposterior length of the posterior cranial base was significantly shorter and the percentage of active bone volume was significantly smaller in the BALB/c-bm/bm mice than in the BALB/c mice. CONCLUSIONS The results suggested that normal endochondral growth is disturbed in the synchondrosis of the posterior base of the skull in BALB/c-bm/bm mice.

Histological and histochemical study of the spheno-occipital synchondrosis of the cranial base on BALB/c-bm/bm mouse

Abstract Murine brachymorphism (bm) has cartilage with undersulfated glycosaminoglycans. The reason for inferior growth of craniofacial structure in BALB/c bm homozygous mouse has not been clarified. The spheno-occipital synchondrosis, which is the growth site of the cranium, was histologically and histochemically investigated in this study. BALB/c mice and BALB/c-bm/bm mice were used. Sagittal sections of the cranial bases were stained by the method of hematoxylin and eosin, alcian blue critical electrolyte concentration, or sensitized high iron diamine method after treatment with/without testicular hyaluronidase. The results showed that chondroitin sulfate and keratan sulfate were undersulfated in the cartilage of the spheno-occipital synchondrosis in BALB/c-bm/bm mice. Sections stained using hematoxylin and eosin showed that columns of chondrocytes were irregular in arrangement, and normal endochondral ossification was not seen in the cartilage of the spheno-occipital synchondrosis in BALB/c-bm/bm mice.

Evaluation of effects of activator treatment on mandibular growth by analyzing components of condylar growth and mandibular rotation

Abstract Purpose The objective of this study is to clarify the effects of activator treatment on mandibular growth in relation to condylar growth and total rotation of the mandible, and to investigate the relationships between the treatment responses and pretreatment facial morphology. Materials and methods Thirty Japanese girls with Class II division 1 malocclusion treated with activator were examined. Mean age at the start of treatment was 9.6 ± 1.6 years. Mean treatment duration was 19 ± 4 months. Lateral cephalograms obtained before and after treatment were used to analyze skeletal changes during treatment. Regional superimposition analysis was performed to evaluate activator effects by decomposing the mandibular growth into condylar growth and mandibular total rotation. Results The changes in intermaxillary relationships were significantly correlated with vertical condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). The changes in the forward displacement of the mandible were significantly correlated with sagittal condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). Vertical condylar growth and mandibular total rotation were significantly correlated with pretreatment mandibular morphology (P < 0.05 and P < 0.01). Conclusion Both the sagittal condylar growth and counterclockwise mandibular total rotation attributed to activator treatment contribute to forward displacement of the mandible. The activator effects are expected greater in patients with flat mandibular plane, small gonial angle, backwardly inclined mandibular ramus and long posterior facial height.

Oxygen saturation and electromyographic changes in masseter muscle during experimental chewing of gum with harder texture

Abstract Objective. The purpose of this study was to clarify the relationship between changes in masseter muscle oxygenation measured by near-infrared spectroscopy (NIRS) and changes in the electromyographic (EMG) power spectrum during experimental chewing of gum with harder texture, to improve the understanding of the use of NIRS in assessing masseter muscle fatigue. Material and methods. Ten female volunteers with normal occlusion were examined. Mean age (standard deviation) was 28.4 (3.8) years. Mean fracture stress of gum was 12.5 × 104 N/m2. Subjects were instructed to chew gum for 60 s (75 strokes) on the voluntary chewing side at a pace of 1.25 strokes/s. Simultaneous recordings of NIRS and EMG signals from masseter muscle were performed during gum chewing. Results. Oxygen saturation levels decreased from the start of chewing, then stabilized with a break point between the two phases. The normalized EMG amplitude increased and the mean frequency of the EMG power spectrum decreased during gum chewing. The timing of break point appearance was related to the timing of a significant decrease in median frequency, but no clear relationships were found between break point appearance and increased EMG amplitude. Conclusions. These results suggest that the break point of the oxygen saturation curve, as obtained from NIRS measurements, could be used as an indicator of masseter muscle fatigue as assessed by a shift in the EMG power spectrum to lower frequencies.