Hideki Ioi

Root Resorption and Immune System Factors in the Japanese

The objective of this study was to determine whether there is an association between excessive root resorption and immune system factors in a sample of Japanese orthodontic patients. The records of 60 orthodontic patients (18 males, age 17.7 +/- 5.7 years; 42 females, age 16.4 +/- 6.0 years) and 60 pair-matched controls (18 males, age 15.9 +/- 4.5 years; 42 females, age 18.5 +/- 5.2 years) based on age, sex, treatment duration, and the type of malocclusion were reviewed retrospectively. The validity of our hypothesis was tested using the logistic regression analysis. The pretreatment records revealed that the incidence of allergy and root morphology abnormality was significantly higher in the root resorption group (P = .030 and .001), with a mean odds ratio of 2.794 and 6.317 and 95% confidence interval of 1.107-7.053 and 2.043-19.537, respectively. The incidence of asthma also tended to be higher in the root resorption group. From these results, we concluded that allergy, root morphology abnormality, and asthma may be high-risk factors for the development of excessive root resorption during orthodontic tooth movement in Japanese patients.

Effects of Buccal Corridors on Smile Esthetics in Japanese

OBJECTIVE To test the hypothesis that the amount of buccal corridor has no influence on smile evaluations of Japanese orthodontists and dental students. MATERIALS AND METHODS One photograph of a smiling female, displaying first molar to first molar, was constructed. Buccal corridors were modified digitally in 5% increments, from 0% to 25% buccal corridor compared with the inner commissural width. Using a visual analog scale (VAS), 32 Japanese orthodontists and 55 Japanese dental students rated the attractiveness of six smiles with altered buccal corridors. The Wilcoxon rank-sum test was conducted to compare the distributions of the median scores between the male and female raters for each of the rater groups. Differences in the median esthetic scores were analyzed using the Kruskal-Wallis test. We used 15% VAS difference to determine the clinical significance of the esthetic scores. RESULTS There was no significant difference in judging the effects of buccal corridors on the smile attractiveness between the male and female raters for both the orthodontists and dental students. There were significant differences in the median esthetic scores for both the orthodontists and dental students. The median esthetic score decreased to become clinically significant from 10% to 25% buccal corridor for both the orthodontists and dental students. CONCLUSIONS The hypothesis was rejected. Both the orthodontists and dental students preferred broader smiles to medium or narrow smiles.

Effect of Facial Convexity on Antero-posterior Lip Positions of the Most Favored Japanese Facial Profiles

Soft tissue analyses are basic tools in planning orthodontic treatment. However, the perception of a well-balanced Japanese facial profile has not yet been established, particularly with respect to changes in facial convexity. The purpose of this study was to assess and determine the range of antero-posterior (A-P) lip positions of the top three most favored, well-balanced profiles from a series of various facial silhouettes with changing facial convexity. The average profile was constructed from the profiles of 30 Japanese males and females with Class I occlusions. Changes in facial convexity were established by altering the A-P chin position by protruding or retruding the chin in increments of 5 degrees and 10 degrees from the average profile. A series of 11 profiles were developed from each of the four changes in facial convexity. The lips were then protruded or retruded in one-mm increments from the average profile. Forty orthodontists were asked to rate the top three most favored, well-balanced profiles. We found that the raters tended to prefer more retruded lip positions as facial convexity decreased, for both males and females. The raters also tended to prefer slightly more protruded lip positions as the facial convexity increased. Because chin position is inherent in each patient, others may equate a retrusive or protrusive chin with certain personalities, thus, it is important for orthodontists to take into account the balance between the lips and the chin.

Effects of retraction of anterior teeth and initial soft tissue variables on lip changes in Japanese adults

The aim of this study was to examine the effects of retraction of anterior teeth and the initial soft tissue profile variables on upper and lower lip changes in Japanese adults. Pre- and post-treatment cephalometric radiographs of 33 Japanese female adults (aged 23.0±5.0 years), with a Class II division 1 malocclusion, who had two or four first premolars extracted, were evaluated. Lateral cephalograms taken with the lips in a voluntary relaxed position were traced and compared. Nine linear and eight angular measurements were constructed for the hard tissue measurements and 16 linear and 2 angular for the soft tissue measurements. Stepwise multiple regression analysis revealed that the horizontal upper lip position could be explained by the position of the maxillary incisor cervical point and the occlusal plane to SN with a 54 percent contribution ratio, and horizontal lower lip position, maxillary incisor tip position, initial interlabial gap, and aesthetic line to the tip of lower lip with a 51 percent contribution ratio. All parameters employed explained the horizontal position of the upper and lower lip with higher than 96 percent confidence. While the horizontal positions could not be predicted by a limited number of parameters, the vertical positions of lips could be explained by three parameters with higher than 62 percent confidence. The predictability found in this study could be beneficial for orthodontists in treatment planning.

Effects of buccal corridors on smile esthetics in Japanese and Korean orthodontists and orthodontic patients

INTRODUCTION The purpose of this study was to evaluate the influence of the size of buccal corridors on the assessment of attractive smile esthetics by Japanese and Korean orthodontists and orthodontic patients. METHODS Buccal corridors were modified digitally from 0% to 25% compared with the inner intercommissural width. Using a visual analog scale, 41 Japanese and 25 Korean orthodontists, and 96 Japanese and 72 Korean orthodontic patients (15-29 years old) rated the attractiveness of 6 smiles with altered buccal corridors. The influence of the size of the buccal corridor on smile esthetics was assessed. RESULTS Although there was no significant sex difference in judging the effects of buccal corridors for the Korean and Japanese orthodontists, significant sex differences were shown for the Japanese orthodontic patients. There were significant differences in the 6 levels of median esthetic scores for all groups: 0%, 5%, and 10% buccal corridors in the smiles tended to be preferred to the other smiles, to become clinically significant for all groups. The median esthetic score decreased to become clinically significant from 10% to 15% buccal corridors for all groups. CONCLUSIONS Japanese and Korean orthodontists and orthodontic patients prefer narrow or medium buccal corridors to broad buccal corridors.

Capsaicin receptor expression in the rat temporomandibular joint

Experimentally, temporomandibular joint (TMJ) nerve units respond to capsaicin, which is used clinically to treat TMJ pain. However, the existence of capsaicin receptors in the TMJ has not previously been clearly demonstrated. Immunohistochemical analysis has revealed the presence of transient receptor potential vanilloid subtype 1 (TRPV1) expression in the nerves and synovial lining cells of the TMJ. TRPV1-immunoreactive nerves are distributed in the synovial membrane of the joint capsule and provide branches to the joint compartment. The disc periphery is supplied by TRPV1 nerves that are mostly associated with small arterioles, and occasional nerves penetrate to the synovial lining layer. Double immunofluorescence has shown that many TRPV1-immunoreactive nerves are labeled with neuropeptide calcitonin gene-related peptide, whereas few are labeled with IB4-lectin. The results provide evidence for the presence of TRPV1 in both nerves and synovial lining cells, which might thus be involved in the mechanism of nociception and inflammation in the TMJ.

Relationship between the unilateral TMJ osteoarthritis/osteoarthrosis, mandibular asymmetry and the EMG activity of the masticatory muscles: a retrospective study

The purpose of this retrospective study was to investigate the relationship between the unilateral temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), mandibular asymmetry and electromyographic (EMG) activity of the masticatory muscles. Twenty-two Japanese women (aged 23.2 +/- 5.4 years) and 10 Japanese men (aged 22.4 +/- 2.8 years) exhibiting unilateral TMJ OA were included in this study. Two angular and seven linear measurements were obtained for the analysis of the skeletal hard tissues. The cephalometric measurement values (CV) were normalized using the CV ratio for the evaluation of the degree of mandibular asymmetry. The EMG was recorded during maximal voluntary clenching efforts for 10 s in the intercuspal position. The average values of integral EMG (iEMG) of three trials were normalized using the iEMG ratio for the evaluation of the functional balance of the masticatory muscles. The mandibular midline was shifted to the TMJ OA side with a median value of 9.85 mm. The CV ratio of the ramus height of the TMJ OA side was significantly smaller than that of the non-OA side. For the masseter muscle, the iEMG ratio of the TMJ OA side was significantly larger than that of the non-OA side (P < 0.05). These results suggest that unilateral TMJ OA is related to the dentofacial morphology, thus resulting in a mandibular midline shift to the affected side and it is associated with a masticatory muscle imbalance.

Comparison of anteroposterior lip positions of the most-favored facial profiles of Korean and Japanese people.

INTRODUCTION A consensus on the contemporary perception of beauty might have been developed between different countries because of increased worldwide access to variations in pleasing facial profiles. The objectives of this study were to determine, assess, and compare the ranges of values of the most-favored facial profiles rated by young Korean and Japanese adults. METHODS Average profiles were constructed from the profiles of 30 Japanese men and women with normal occlusions. A series of 13 profiles each was developed for men and women. In the series, the average profile was located in the center (number 7), and the lips were protruded or retruded in 1-mm increments from the average profile. Forty-six Korean dental students and 52 Japanese dental students were asked to rate the top 3 most-favored profiles. RESULTS Both the Korean and the Japanese dental students tended to select a slightly more retruded lip profile compared with the averages for men and women, and the tendency to prefer a more retruded lip position was evident for the women. CONCLUSIONS These findings suggest that young Korean and Japanese adults prefer a retruded profile, even though their profiles have historically been characterized by more convex facial features.

Evaluation of well-balanced lip position by Japanese orthodontic patients

INTRODUCTION The purposes of this study were to assess and determine the range of a well-balanced anteroposterior lip position as evaluated by orthodontic patients from a series of varying lip positions in facial silhouettes, and whether the raters sex and age were factors in the assessment. METHODS The average profiles were constructed from 30 Japanese male and female subjects with normal occlusion. A series of 13 profiles was developed for males and females, respectively. The lips were protruded or retruded by 1-mm increments from the average profile. One hundred fifty Japanese orthodontic patients were asked to choose the top 3 most-favored, well-balanced profiles for each sex. RESULTS The orthodontic patients tended to prefer a slightly retruded lip position than the average facial profile for both the male and female profiles. There was no significant difference between male and female raters in selecting the top 3 most-favored profiles. In the comparison of age groups, the over 30-year-old patients significantly preferred a more retruded lip position than did the 15- to 19-year-old and the 20- to 29-year-old patients for the female profile. CONCLUSIONS These results suggest that, when we formulate a treatment plan, we should ask the patients about lip position before we start treatment.

Effect of lower facial vertical proportion on facial attractiveness in Japanese

Abstract The purpose of this study was to assess the range of the top three most-favored facial profiles for each sex from a series of varying lower facial vertical proportion, and to evaluate clinically acceptable facial profiles for Japanese adults. Silhouettes of average male and female profiles were constructed from the profiles of 30 Japanese males and females with normal occlusions. Lower facial vertical proportions were increased or decreased by intervals of 5% of Sn–Me′ for each sex from the average profile. Forty-one orthodontists and 50 dental students were asked to select the 3 most-favored, well-balanced profiles for each sex. They were also asked to indicate whether they would seek surgical orthodontic treatment for each of the shorter or longer lower facial profiles if those images represented their own profile. For male profiles, both the orthodontists and dental students chose the average profile as the most-favored. For female profiles, the dental students chose a slightly shorter lower facial as the most-favored profile while the orthodontists chose the average profile. The dental students chose shorter lower facial profiles as more acceptable than longer lower facial profiles for females (p < 0.05). These findings suggest that an average lower facial profile tended to be favored overall by Japanese people, whereas for females a slightly shorter lower facial profile was favored by young adults.