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 rater's 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.

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.

Influence of gingival display on smile aesthetics in Japanese.

The aim of this study was to evaluate the influence of the amount of gingival display on smile aesthetics as assessed by Japanese orthodontists and dental students. A coloured photograph of a smiling female, displaying the first molar to first molar, whose upper lip was tangent to the upper gingival margin of the upper central incisors (zero point), was constructed from different subjects. Gingival displays were modified by moving the teeth within the lip frame in 1 mm increments, from -5 to 5. Using a visual analogue scale (VAS), 31 Japanese orthodontists and 55 Japanese dental students rated the attractiveness of the 11 smiles with altered gingival display. There was no significant difference when judging the effects of the gingival display on the smile attractiveness between the male and the female raters for both the orthodontists and dental students. Kruskal-Wallis tests revealed significant differences in the median aesthetic scores for both the orthodontists and dental students. For the orthodontists, the median aesthetic score increased gradually from -5 to 0 mm and then decreased from 0 to 5 mm. In particular, it decreased to become clinically significant (15 per cent VAS difference) from 0 to 3 mm. For the dental students, the median aesthetic score increased gradually from -5 to -2 mm and then decreased from -2 to 5 mm. The dental students were less tolerant of a more 'gummy' smile than the orthodontists.

Comparison of the kinetic frictional force between conventional plastic brackets with thermoplastic low-friction module ligation and self-ligating brackets.

AIM: To compare the kinetic frictional force of a conventional plastic preadjusted bracket with thermoplastic low-friction module ligation and a self-ligating bracket. MATERIALS AND METHODS: The testing model consisted of four 0.022-inch conventional plastic preadjusted brackets; four 0.022-inch self-ligating brackets for the first premolar, canine, and lateral and central incisors; and a 0.014-inch superelastic nickel-titanium and a 0.019 × 0.025-inch stainless steel wire. The brackets were either aligned for both wires or out of line by 0.5, 1.0, 1.5, and 2.0 mm for only the 0.014-inch superelastic wire. The wires were pulled for 3.0 mm at a speed of 0.1 mm per second. Unpaired t tests were used to compare the mean differences of the measurements between the two bracket systems with both wires. RESULTS: No significant difference in the kinetic frictional force between the two bracket systems and the two wires were found for the 0.014-inch superelastic wire at 0-mm deflection. CONCLUSION: Both bracket systems demonstrate low friction, which is beneficial for effective orthodontic tooth movement with light forces.

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.

Frictional resistance in plastic preadjusted brackets ligated with low-friction and conventional elastomeric ligatures.

OBJECTIVE: To compare frictional resistance of the plastic preadjusted brackets ligated with the low-friction ligatures with those of the conventional elastomeric ligatures. DESIGN: In vitro study. SETTING: Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. MATERIALS AND METHODS: The testing model consisted of four 0.022-inch plastic preadjusted brackets for the first premolar, the canine, the lateral incisor, and the central incisor. A superelastic nickel-titanium 0.014-inch wire and a stainless steel 0.019 x 0.025-inch wire were used for this test. The brackets were either aligned or out of line by 0.5, 1.0, 1.5 and 2.0 mm for the 0.014-inch wire and aligned for the 0.019 x 0.025-inch wire. The frictional forces in plastic preadjusted brackets with low-friction ligatures and conventional elastomeric ligatures were measured at a pulling speed of 0.1 mm/second. Welch t-tests were used to compare the mean differences of each testing measurement between the low-friction and the conventional elastomeric ligatures. RESULTS: In both use of the superelastic nickel-titanium 0.014-inch wire and the stainless steel 0.019 x 0.025-inch wire, the brackets with the low-friction ligatures showed significantly lower frictional forces than those of the conventional elastomeric ligatures in both aligned and all misaligned brackets (P < 0.0001). CONCLUSION: The study found the significantly lower frictional forces for the low-friction ligatures than those of the conventional elastomeric ligatures.

Mechanomyogram and electromyogram analyses during isometric contraction in human masseter muscle.

AIMS: To investigate the relationship between mechanomyogram (MMG), electromyogram (EMG) and bite force during isometric contraction of the human masseter muscle. METHODS: Data were obtained from 16 healthy Japanese males (Mean age: 25.6 +/- 2.3 years). The measuring device for MMG consisted of an amorphous sensor and a small magnet. The bite force, MMG and EMG signals were recorded simultaneously during isometric contraction of the masseter muscle. The subjects were instructed to perform 0, 5, 10, 20, 30, 40, 50, and 60% maximal voluntary contractions (MVC) for 20 seconds. The average rectified value (ARV) for MMG and EMG were calculated from 1 to 5 second samples. The median frequency of the power spectrum (MFPS) for MMG and EMG were determined with the use of a fast Fourier transformation algorithm. RESULTS: The mean ARV for MMG increased up to 20% MVC and then gradually decreased at the higher force levels. The mean ARV for EMG increased with bite force in a monotonic fashion. The mean MFPS for MMG clearly increased up to 10% MVC and then gradually increased. On the other hand, the mean MFPS for EMG clearly increased up to 10% MVC, but then gradually decreased with bite force. CONCLUSION: These findings suggest that the MMG analysis combined with the EMG may be a more useful method for evaluating the status of the masseter muscle.

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.

TMJ osteoarthritis/osteoarthrosis and immune system factors in a Japanese sample.

OBJECTIVE: To determine whether there is an association between temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA) and immune system factors in a Japanese sample. MATERIALS AND METHODS: The records of 41 subjects (7 men, aged 22.0 +/- 3.8 years; 34 women, aged 24.8 +/- 6.3 years) and 41 pair-matched controls (7 men, aged 22.1 +/- 2.3 years; 34 women, aged 24.8 +/- 6.4 years) based on age and gender were reviewed. Information on medical history included local or systemic diseases, details on medication type and use, and the presence of allergies and asthma. Dental history questions referred to details regarding past oral injuries. The validity of the hypothesis, defining allergies and asthma as risk factors in OA, was tested by using a logistic regression analysis. RESULTS: The incidence of allergy was significantly higher in the TMJ OA (P = .008), with a mean odds ratio of 4.125 and a 95% confidence interval of 1.446-11.769. CONCLUSION: These results suggest that allergy may be a risk factor in association with TMJ OA in this Japanese sample.

Relationship between head posture and dentofacial morphology in patients with TMJ osteoarthritis/osteoarthrosis.

AIM: To test whether there is a relationship between head and cervical posture and dentofacial morphology in patients with temporomandibular joint osteoarthritis/osteoarthrosis (OA). METHODS: The subjects consisted of 34 Japanese females with TMJ OA (aged 24.7 +/- 6.1 years). Six craniocervical angular measurements were constructed for head posture. Two angular and 6 linear measurements were constructed for the skeletal relationship, while 1 angular and 6 linear measurements were constructed for the dental relationship. Pearson correlation coefficients were calculated between head posture and dentofacial variables. RESULTS: In the skeletal relationship, increased craniocervical angulations were significantly associated with a more posterior position of the maxilla, a decreased Frankfort to mandibular plane angle, decreased mandibular length, and a decreased lower facial height. In the dental relationship, increased craniocervical angulations were significantly associated with more posterior positions of the anterior teeth to the basal bone and decreased alveolar height of the anterior-posterior teeth. CONCLUSION: The hypothesis was rejected. These results suggest that an association may exist between head and cervical posture and dentofacial morphology in patients with TMJ OA.

Comparison of cephalometric norms between Japanese and Caucasian adults in antero-posterior and vertical dimension.

The aims of this study were to determine Japanese cephalometric norms in the antero-posterior and vertical dimension, and to test the hypothesis that there are racial differences in cephalometric measurements between Japanese and Caucasian norms. Radiographs were obtained from 25 healthy Japanese males (aged 25.1 +/- 2.7 years) and 24 healthy Japanese females (aged 23.6 +/- 1.3 years). Inclusion criteria were an ANB angle between 2 and 5 degrees, a normal occlusion with minor or no crowding, all teeth present except third molars, no previous orthodontic treatment, and no prosthetic replacement of teeth. Two angular and five linear measurements were constructed for the skeletal hard tissue analysis, one angular and six linear measurements for the dental hard tissue analysis, and two angular and seven linear measurements for the soft tissue analysis. The mean and standard deviations for the hard and soft tissue measurements were determined for each gender. Unpaired t-tests were used to determine the mean differences for each cephalometric measurement between the Japanese and the Caucasians. In the antero-posterior dimension, the Japanese subjects had a significantly more retruded chin position (P < 0.001), typically protruding mandibular incisors, and protruded lip positions compared with the Caucasian norms. In the vertical dimension, the Japanese had a significantly steeper mandibular plane (P < 0.01). The Japanese females had a significantly larger lower face height and increased dental height (P < 0.001). The results of this study suggest that these cephalometric measurements might be helpful to formulate treatment plans for Japanese patients.

Comparison of lip positions in ancient Buddhas with Japanese adults.

OBJECTIVES: To compare the lip positions found in two ancient Buddha statues with the lip positions in contemporary Japanese adults. METHODS: The facial profiles of Yakushi-ji temple Sho Kannon (male) and Chugu-ji temple Bodhisattva (female), generally considered to be two of the most beautiful Buddha statues in existence, were compared with the facial profiles of 30 Japanese dental students. Profiles of the statues were measured on photographs and profiles of the adults on cephalometric radiographs. The adults comprised 15 men between 22 and 26 years of age (Mean age: 23.8+/-1.3 years) and 15 women between 22 to 25 years of age (Mean age: 22.9+/-1.0 years). RESULTS: The Buddha statues had retrusive lips compared with the lip positions in contemporary Japanese adults. CONCLUSION: Flat profiles may be favoured by Japanese adults who, typically, have protrusive lips.

Anteroposterior lip positions of the most-favored Japanese facial profiles.

INTRODUCTION: Soft tissue analysis is a basic tool in planning orthodontic treatment. However, the components of a well-balanced Japanese facial profile have not yet been established. The purpose of this study was to assess the most-favored or most well-balanced profile from a series of facial silhouettes with varying anteroposterior lip positions by a group of Japanese orthodontists and a group of young adult Japanese dental students. METHODS: Average female and male profiles were constructed from the profiles of 30 Japanese men and women with normal occlusions. The lips in each average profile were protruded or retruded in 1-mm increments, and the 13 images were arranged with the average profile in the center. Forty two orthodontists and 42 dental students were asked to select the 3 most-favored, well-balanced profiles for each sex and rank them in order of preference. RESULTS: Both the orthodontists and the students preferred a profile with slightly retruded lips. The dental students favored a more retruded lip position for women. The least-favored profile was the most protrusive. CONCLUSIONS: These findings suggest that Japanese orthodontists and young adults prefer a retruded profile, even though Japanese profiles have historically been characterized by more convex facial features.

Nickel allergy associated with a transpalatal arch appliance.

AIM: The purpose of this article was to present a case in which nickel sensitivity of the oral mucosa was demonstrated during the use of a transpalatal arch appliance (TPA). CASE REPORT: An 11-year 8-month old post-menarchal female presented for orthodontic treatment with Class III buccal segments and bilateral open bite. The treatment plan consisted of placing a rapid palatal expansion appliance (RPE) and a TPA with soldered lateral tongue cribs, in order to eliminate her tongue thrusting habit. 8 months into treatment, the gingiva of the right posterior segment began to hypertrophy, particularly around the bands of the right first molar and premolar. A patch test of 5% nickel sulfate indicated a positive reaction to nickel. The treatment was finished without the use of nickel titanium wires and the mucosa reaction resolved. The patient had had her ear pierced at age 2 days old, which was 11 years before orthodontic treatment was initiated. The literature shows that this exposure may have been the sensitizing event. CONCLUSIONS: While the nickel sensitive patient may not present an extreme medical risk, the orthodontist must be aware of the problem and the likelihood of treating patients with this condition. It appears that the reaction may vary from patient to patient. The practitioner should possess a basic understanding of the occurrence rate, sex predilection, and signs and symptoms of allergy to nickel, and should be familiar with the best possible alternative modes of treatment, to provide the safest, most effective care possible in these cases. Practitioners should be aware that symptoms of nickel allergy may closely mimic those of typical gingival changes during orthodontic treatment of circumpubertal children.