Association among craniofacial morphology, ethnicity, and risk of pediatric sleep-related breathing disorders: A multicenter study.

INTRODUCTION: Craniofacial morphology and ethnicity may be risk factors for sleep-related breathing disorder (SRBD) in children but have not yet been assessed in an international multicenter study. The objectives of this study were to assess the association among craniofacial features, self-reported ethnicity, and risk of SRBD in children undergoing orthodontic treatment. METHODS: Children aged 5-18 years who presented for orthodontic evaluation were enrolled in the United States, South Africa, South Korea, Saudi Arabia, and Japan. The risk of SRBD was defined as answering ≥0.33 positive responses to the Pediatric Sleep Questionnaire. Craniofacial features included measurements in sagittal and vertical dimensions to evaluate the cranial base, maxillomandibular and dental relationships, and nasopharyngeal airway dimensions. Logistic regression was performed to assess the association among craniofacial features, ethnicity, age, body mass index, and risk of SRBD. RESULTS: Data were obtained from 602 patients from 5 sites. A total of 76 patients (12.6%) had a risk of SRBD. The mean age was 12.5 years. Male gender (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.0-3.4; P = 0.041), Middle Eastern ethnicity (OR, 10.2; 95% CI, 4.1-25.4; P = 0.001), body mass index (OR, 1.1; 95% CI, 1.04-1.10; P = 0.001), gonial angle (OR, 0.91; 95% CI, 0.85-0.98; P = 0.011), and inferiorly positioned hyoid (OR, 1.1; 95% CI, 1.0-1.2; P = 0.002) were significantly associated with the risk of SRBD. CONCLUSIONS: In an ambidirectional cohort study across 5 sites, male gender, Middle Eastern ethnicity, body mass index, gonial angle, and inferiorly positioned hyoid were associated with the risk of SRBD in children undergoing orthodontic treatment.

Multinational study on profile preference of laypersons.

BACKGROUND: This study aimed to assess the facial profile preferences of lay people in seven locations from different countries and whether their place of residence, sex, age, race, education, or income influenced the decision. METHODS: After altering the lip and nose in 1 mm increments in the sagittal and sagittal/vertical directions, 50 profile silhouettes with white-like facial features were rated by evaluators. The soft tissue values were integrated into the profiles, and profile preferences were identified for each location. An ANOVA with post hoc Tukey test was used to compare the differences in mean preference in each location. A multivariable regression model was used to assess the effect of the demographics of the evaluator on preference. RESULTS: Thirteen profiles were ultimately analyzed. The mean for profile preference was significantly different across locations (P < 0.0001). For evaluators in the United States and Lebanon, the most preferred profile had the original lip and original nose. In Switzerland and South Africa, retrusive lips, and a small and less upturned nose was most preferred. In Japan and Saudi Arabia, the most preferred profile had the original lip and a protrusive nose that was less upturned. A protrusive lip with a small, upturned nose was preferred in Turkey. Profile change (P < 0.0001), location (P < 0.0001), sex (P < 0.0001), and race (P = 0.02) were significant confounders; in contrast, age, education, and income were not significant. CONCLUSIONS: Profile preference is different among the seven locations. For the most part, lay people prefer profiles within one SD from white norms. Also, an upturned nose is the least favored in most of the locations. Sex and race are also significant confounders. CLINICAL RELEVANCE: An orthodontic treatment plan decision is affected by an individual's preference for their facial appearance. This study helps clinicians understand how racial and regional differences may affect patients' preferences and, therefore, their expectations for orthodontic treatment results.

Mesiodistal angulation and developmental stages of unerupted mandibular second premolars in nonsyndromic oligodontia.

INTRODUCTION: Oligodontia is a serious developmental dental anomaly that requires long-term multidisciplinary treatment, but its clinical characteristics are not well understood because it is rare. This study evaluated the mesiodistal angulation and developmental stages of unerupted mandibular second premolars (MnP2s) in orthodontic patients with nonsyndromic oligodontia. METHODS: Thirty-seven patients with oligodontia with at least 1 unerupted MnP2 in Demirjian's developmental stages between D and G were selected. Age- and sex-matched patients without tooth agenesis, excluding third molars, were selected as the control group. Mesiodistal angulation between the long axis of the available MnP2 and the mandibular plane was measured on panoramic radiographs. RESULTS: The MnP2 was significantly more distally angulated in the oligodontia group than in the control group. The developmental stage of the MnP2 in the oligodontia group was significantly delayed (1.04 ± 0.26 years; 95% confidence interval, 0.53-1.55 years). No correlation between the mesiodistal angulation and the developmental stage of the MnP2 was found in both groups. CONCLUSIONS: Significant distal angulation and delayed developmental stages of MnP2s were found in patients with nonsyndromic oligodontia compared with age- and sex-matched patients without agenesis of permanent teeth, excluding third molars. However, no significant correlation was found between them. Regardless of the severity of the distal angulation of MnP2, observing delayed dental development in each patient is important.

A new orthodontic force simulation system with a simulated periodontal ligament to measure the delivered force at the root apex.

OBJECTIVE: To develop a new orthodontic force simulation system with a simulated periodontal ligament (PDL) that enables measurement of the delivered force at the root apex and to clarify the relationship between the applied orthodontic force and the delivered force at the root apex. DESIGN: In vitro study. SETTING: Orthodontics department of a university, Tokyo, Japan. METHODS: A new orthodontic force simulation system that enables measurement of the force at the root apex of the maxillary central incisor, was developed. Lingual and intrusion movements were simulated with applied orthodontic force at three levels: 50, 100 and 200 gf. The delivered forces at the root apex were compared between the two movements. Furthermore, the ratio of delivered force at the root apex to the applied orthodontic force (the apex force ratio) was calculated. RESULTS: The magnitudes of delivered forces at the root apex were significantly greater in intrusion movement than in lingual movement (P < 0.01). The apex force ratios were in the range of 47.3%-56.2% for lingual movement and 85.6%-86.2% for intrusion movement. CONCLUSION: The present study, of a newly developed orthodontic force simulation system, showed that the characteristics of the delivered force at the root apex differed according to the direction of tooth movement.

Maxillary dimensions and arch shape with palatally displaced canines.

BACKGROUND/OBJECTIVES: The aim of this study was to explore the effect of palatally displaced canines on maxillary dimensions and arch shape. METHODS: Occlusal and skeletal landmarks were plotted on cone beam computed tomography (CBCT) images of 156 orthodontic patients: 78 with palatally displaced canines (PDC) (27 left, 28 right, and 23 bilateral) and 78 controls using Mimics™ (Materialise, Belgium). Arch forms were created, and arch width, depth, and skeletal dimensions were measured. T-test (P < 0.05) was used to compare the groups. Geometric Morphometrics (GM) analysis was used to compare the groups and to explore the pattern of covariation between two sets of landmarks. RESULTS: The unilateral PDC group showed an increased first premolar, second premolar, molar widths, and an increased molar depth. No significant difference was found in arch form. The skeletal measurements were generally larger in the PDC group, but the transverse measurements were the most significant. Discriminant Function Analysis (DFA) with cross-validation allowed an accurate classification of 85.9% of the control group and 66.7% of the PDC group. The Mahalanobis distance displayed significant differences among three combinations of groups. Strong covariance was found between the second premolar and all other landmarks. LIMITATIONS: The small sample sizes of the stratified groups precluded recognition of statistical significance. CONCLUSIONS: Patients with unilateral PDC displayed significantly wider first, second premolar, and first molar widths, and increased first molar depths. There were no significant differences in arch form; however, GM showed significant differences between the groups and a prominent covariance function for the 2nd premolars.

Relationship between dental and basal arch forms in mandibular anterior crowding.

INTRODUCTION: Positive correlations between the mandibular dental and basal arch forms in patients with minimum crowding have been observed; however, the relationship in orthodontic patients with mandibular anterior crowding (MnAC) remains unclear. Therefore, we evaluated this relationship in patients with MnAC requiring premolar extraction. METHODS: Thirty women with normal occlusion (mean age, 20.6 ± 2.5 years) and 30 women with Class I MnAC (mean age, 20.3 ± 2.9 years) were selected as control and MnAC groups, respectively. The widths and depths of the mandibular dental and basal arches at the FA and WALA points were measured and compared between groups. Relationships between the arch widths at the FA and WALA points were analyzed by Pearson correlation coefficient. RESULTS: Larger variances were found for dental arch widths at canine and premolars and depth at canine in the MnAC group. Positive correlations were observed between dental and corresponding basal arch widths for both groups, except at the canine in the MnAC group, and higher correlations were observed between dental arch widths for all teeth except the first molar and basal arch widths for posterior adjacent teeth when comparing the corresponding basal arch widths. CONCLUSIONS: The positive correlations observed between the dental and basal arch widths suggest the basal arch widths at the posterior adjacent tooth can be used as an additional reference to create an individualized postorthodontic dental arch form for MnAC patients.

Consecutive tooth agenesis patterns in non-syndromic oligodontia.

Agenesis of two or more consecutive adjacent permanent teeth (consecutive tooth agenesis, CTA) is a serious manifestation of oligodontia requiring long-term, multi-disciplinary treatment. Therefore, the present study investigated the characteristics of the CTA pattern in orthodontic patients with non-syndromic oligodontia. Using panoramic radiographs, the number of agenetic permanent teeth excluding third molars in non-syndromic orthodontic patients was evaluated, and patients with six or more agenetic teeth (oligodontia group, n = 97) and with one to five agenetic teeth (hypodontia group, n = 107) were selected. The numbers of CTA including third molars in each quadrant and in each patient were compared between the groups. Each quadrant with CTA of patients was categorized into one of the following four types: (I) involves anterior teeth only; (II) involves posterior teeth only; (IIIA) includes anterior and posterior teeth; and (IIIB) separate in the anterior and posterior teeth. CTA in at least one quadrant was found in 91.8 and 4.7% of patients in the oligodontia and hypodontia groups, respectively. The highest frequency CTA patterns included agenesis of the first and second premolars and of the second and third molars in the oligodontia and hypodontia groups, respectively. In the oligodontia group, type IIIA was significantly more frequent in the maxillary than in the mandibular quadrant. Most oligodontia patients who visit orthodontic clinics have CTA. A rare but severe CTA pattern that continues from the anterior to posterior segments is more frequent in the maxillary than in the mandibular quadrant.

Impact of the prefabricated forms of NiTi archwires on orthodontic forces delivered to the mandibular dental arch.

BACKGROUND: Although preformed archwires with a variety of arch forms are currently commercially available, the effects of variation in the shape of these archwires on the orthodontic force at each tooth are not well understood. Therefore, we evaluated the forces delivered by various types of commercially available preformed nickel-titanium alloy (NiTi) archwires in a simulated mandibular dental arch. METHODS: Sixty-three types of 0.019 × 0.025-inch preformed NiTi archwires from 15 manufactures were selected for analysis. The intercanine width (ICW) and intermolar width (IMW) of each archwire were measured at the mean canine and first molar depths of 30 untreated subjects with normal occlusions. Each archwire was placed in a multi-sensor measurement system simulating the mandibular dental arch of subjects with normal occlusions, and orthodontic forces in the facial-lingual direction at the central incisors, canines, and first molars were measured. Correlations between the ICW, IMW, and ICW/IMW ratio of archwires and the delivered forces were analyzed. The archwires were classified into the following four groups according to the ICW and IMW: Control group, ICW and IMW are within the means ± standard deviations of the normal ranges; Ovoid group, narrow ICW and IMW; Tapered group, narrow ICW; and Square group, narrow IMW. The forces were compared among these groups for each tooth. RESULTS: Significant correlations between the measured archwire width and force to each tooth were found, except between IMW and forces at the central incisors and canines. Significant differences in the forces were found among all groups, except between the Ovoid and Tapered groups at all teeth and between the Ovoid/Tapered and Control groups at the first molar. Significantly greater orthodontic forces in the facial direction were delivered at the central incisors by the archwires in the Ovoid and Tapered groups when compared with the archwires in the other groups. CONCLUSION: These findings suggest that there is a possible risk of a clinically significant level of unfavorable orthodontic force being delivered to the mandibular incisors in labial inclination when using a preformed archwire with an ICW that is narrower than the dental arch.

Evaluations of the facial attractiveness of young women with severe maxillary anterior crowding by orthodontists and laypeople with and without orthodontic treatment experience in Japan.

INTRODUCTION: Maxillary anterior crowding (MxAC) has been considered to be an esthetically favorable characteristic of young women in Japan. It has been hypothesized that laypeople and orthodontists have different esthetic preferences; however, to date, this has not been investigated in detail. Therefore, the present study compared the facial attractiveness of women with MxAC and the interpretation of MxAC among orthodontists and laypeople with and without orthodontic treatment experience in Japan. METHODS: Thirty-eight orthodontists, 42 laypeople with orthodontics (patients), and 43 laypeople without orthodontics (laypeople) evaluated the attractiveness of resting and smiling frontal images of 12 women with MxAC (MxAC models; mean age, 21.7 ± 2.6 years) and 12 women with normal occlusion (normal models; mean age, 20.1 ± 0.7 years) using a visual analog scale. In addition, they responded to a questionnaire that asked them to select the terms most closely associated with MxAC. All evaluators and models were Japanese. RESULTS: For all evaluator groups, the facial attractiveness of the MxAC models was significantly lower than that of the normal models for both the resting and smiling images. For MxAC models, orthodontists evaluated resting images more attractive than smiling images, whereas laypeople evaluated smiling images more attractive than resting images. Significantly more patients and laypeople than orthodontists selected "cute" as the term most closely associated with MxAC (P <0.05). CONCLUSIONS: The orthodontists, patients, and laypeople showed a different tendency in their facial attractiveness preferences. Regardless of their orthodontic experience, the laypeople showed more positive interpretations of MxAC than orthodontists. This finding seems to be influenced by Japanese culture, which values irregularity in nature as one form of beauty.

Sexual dimorphism of tooth agenesis patterns in non-syndromic oligodontia in Japanese patients.

OBJECTIVE: Wide individual variation observed in tooth agenesis patterns in patients with non-syndromic oligodontia could be affected by sexual dimorphism. Therefore, the present study investigated sex-associated differences in tooth agenesis patterns in patients with non-syndromic oligodontia. DESIGN: Subjects were 108 male (ages 7-46 years) and 184 female (ages 7-43 years) orthodontic patients missing ≥6 permanent teeth, excluding third molars. The number of agenetic teeth per patient, excluding third molars, and the prevalence of agenesis of each tooth type were evaluated using panoramic radiographic images. Rankings of the most common tooth agenesis patterns in the maxillary and mandibular arches were calculated. The number of agenetic teeth per patient was compared between sexes using the Mann-Whitney test. The prevalence of tooth agenesis for each tooth type was compared between sexes using the χ2 and Fisher's exact tests with Bonferroni correction. RESULTS: No significant sex difference in the distribution of the number of agenetic teeth was observed. The prevalence of agenesis of the maxillary second premolars was significantly higher in females (P < 0.007) and the prevalence of agenesis of the mandibular central incisors was significantly higher in males (P < 0.007). Sexual dimorphism was observed in the highly ranked tooth agenesis patterns. CONCLUSIONS: No significant difference in the severity of tooth agenesis was observed between sexes; however, sexual dimorphism was observed in the tooth agenesis patterns of patients with non-syndromic oligodontia. Although various tooth agenesis patterns were identified, sex-specific tendencies suggest that categories can be utilized in future epidemiologic research and planning.

Impact of passive self-ligation and conventional elastic ligation on orthodontic force in the simulation of a mandibular lateral incisor linguoversion.

INTRODUCTION: This study compared three-dimensional forces delivered to the displaced tooth and its adjacent teeth between passive self-ligation (PSL) and conventional elastic ligation (CL) in simulation of mandibular lateral incisor linguoversions. METHODS: A multisensor system was used to measure three-dimensional forces delivered to brackets attached to the mandibular left central incisor, lateral incisor, and canine (FDI tooth numbers 31, 32, and 33, respectively). Two ligation methods (PSL and CL), 3 nickel-titanium (0.014-inch) archwires similar to the arch form of normal occlusion, and 2 displacements (1 and 4 mm) were tested. RESULTS: In 1-mm displacement, forces were significantly smaller in CL than in PSL at 32 in the labial direction and larger at 31 in the mesial direction for all 3 types of archwires (P <0.01 for both). For 2 of 3 archwires, forces were larger in CL than in PSL at 33 in the lingual direction (P <0.01). In 4-mm displacement, forces were significantly larger in CL than in PSL at 31 in the mesial direction and significantly smaller in CL than in PSL at 33 in the distal direction for all 3 archwires (P <0.05 and P <0.01, respectively). Mean forces in the vertical direction were small, ranging from -0.05 to 0.05 N. CONCLUSIONS: Under a small amount of displacement, force magnitude in PSL was smaller than that in CL at the displaced tooth in labial-lingual directions. Under a large amount of displacement, a more "open coil spring effect" was significantly obtained in CL than PSL at both adjacent teeth of the displaced tooth.

Tooth agenesis patterns in Japanese orthodontic patients with nonsyndromic oligodontia.

INTRODUCTION: Tooth agenesis is the most common dental anomaly in humans and is often found in orthodontic patients. However, severe tooth agenesis (oligodontia) is rare and its characteristics are poorly understood. This study aimed to investigate tooth agenesis patterns of Japanese orthodontic patients with nonsyndromic oligodontia. METHODS: Panoramic radiographs of 228 orthodontic patients (141 females, 87 males) with nonsyndromic oligodontia were selected and permanent tooth agenesis excluding third molars was evaluated. Influence of cutoff age was tested, tooth agenesis patterns for each quadrant were calculated, and antagonistic maxillary and mandibular quadrants were merged as the occluding tooth agenesis pattern. Full-mouth tooth agenesis patterns were also evaluated. RESULTS: The highest prevalence of tooth agenesis was observed in maxillary and mandibular second premolars, followed by maxillary first premolars. Prevalence of a symmetric pattern between right and left quadrants was significantly higher than matched patterns between maxillary and mandibular antagonistic quadrants. Among 456 possible tooth agenesis patterns, 51 and 49 patterns were observed for the maxillary and mandibular quadrants, respectively, but 215 patterns for the occluding patterns were observed. In addition, 180 full-mouth tooth agenesis patterns were observed in the 228 patients. CONCLUSIONS: Distinct characteristics in highly ranked patterns were observed compared with studies from other geographic areas, especially in the maxillary arch. Occluding and full-mouth tooth agenesis patterns showed wide variation, suggesting difficulty in orthodontic diagnosis.

Cephalometric characteristics of postorthodontic female patients with attractive and unattractive frontal posed smiles.

OBJECTIVES:: To identify differences in skeletal, dental, and soft-tissue morphology between postorthodontic patients with attractive and unattractive frontal posed smiles. MATERIALS AND METHODS:: The attractiveness of close-up photographs of frontal posed smiles in 100 adult female patients after conventional orthodontic treatment was evaluated by 20 dental students (10 men, 10 women) using a visual analogue scale. Posttreatment cephalograms of the 20 patients with the most attractive smiles (attractive group; mean age 23.75 ± 3.35 years) and the 20 patients with least attractive smiles (unattractive group; mean age 23.11 ± 4.45 years) were selected, and 41 measurements were made and compared between groups using the Mann-Whitney U-test ( P < .05). RESULTS:: When compared with the attractive group, the unattractive group exhibited greater values for sella-nasion plane to mandibular plane, palatal plane to mandibular plane, anterior facial height, lower facial height, and lower facial height/anterior facial height as skeletal measurements; for occlusal plane to sella-nasion plane, palatal plane to occlusal plane, and maxillary central incisor to palatal plane as dental measurements; and for lower face, upper lip length, and upper lip superior to palatal plane as soft-tissue measurements. CONCLUSIONS:: Cephalometric analysis revealed that postorthodontic Japanese female patients with unattractive frontal posed smiles are characterized by a hyperdivergent skeletal pattern with extruded maxillary incisors and a steep occlusal plane, accompanied by a longer upper lip than patients achieving attractive posed frontal smiles.

Craniofacial morphology in women with Class I occlusion and severe maxillary anterior crowding.

INTRODUCTION: Our objective was to investigate craniofacial morphology in women with Class I occlusion and maxillary anterior crowding (MxAC) with bilateral palatal displacement of the lateral incisors and facial displacement of the canines. METHODS: Thirty-three women with normal occlusion (mean age, 20.7 ± 2.3 years) were selected as the control group, and 33 women with severe MxAC (mean age, 23.3 ± 3.8 years) with bilateral palatal and facial displacement of the lateral incisors and canines, respectively, were selected as the MxAC group. Mesiodistal tooth crown diameter, arch length discrepancy, facial-palatal displacement of lateral incisors and canines, and dental arch dimensions were measured. Fourteen skeletal and 10 dental cephalometric measurements were made. Medians, interquartile ranges, means, and standard deviations were calculated for each parameter, and the nonparametric Mann-Whitney U test (P <0.05) was used to compare the 2 groups. RESULTS: Compared with the control group, the MxAC group showed a significantly wider angle (P <0.05) and shorter length (P <0.01) in the cranial base, a smaller sagittal maxillary base (P <0.01), and a hyperdivergent skeletal pattern (P <0.01 and P <0.05). CONCLUSIONS: Women with Class I occlusion and severe MxAC exhibited a significantly wider angle and shorter length in the cranial base, a smaller sagittal maxillary base, and a hyperdivergent skeletal pattern. These skeletal and dental characteristics and cranial base dysmorphology may be helpful as potential indicators for orthodontic treatment with extractions.

Variation in form of mandibular, light, round, preformed NiTi archwires.

OBJECTIVE: To evaluate the variation in form of nickel-titanium (NiTi) archwires by comparing them with the dental arch form of normal Japanese subjects before and after placing them in the first molar tubes. MATERIALS AND METHODS: The mandibular dental casts of 30 normal subjects were scanned, and the dental arch depths and widths from the canine to the first molar were measured. Standardized images of 34 types of 0.016-inch preformed NiTi archwires were also taken in a 37°C environment, and the widths were measured and then classified by cluster analysis. Images of these archwires placed in a custom jig with brackets attached at the mean locations of the normal mandibular central incisors and first molar were additionally taken. The widths of the pooled and classified archwires were then compared with the normal dental arch widths before and after placement in the jig and among the groups (P < .05). RESULTS: The archwires were classified into three groups: small, medium, and large. The archwire widths in the small and medium groups were narrower than those at all examined tooth widths, except in the case of the premolars of the medium group. After placement in the jig, the pooled archwire widths were found to be significantly narrower and wider at the canine and second premolar, respectively, than at the dental arch, but not in the individual comparisons between groups. CONCLUSION: The variation observed in the mandibular NiTi archwire forms significantly decreased following fitting into the normal positions of the first molars.

Dimensional analyses of frontal posed smile attractiveness in Japanese female patients.

OBJECTIVE: To identify appropriate dimensional items in objective diagnostic analysis for attractiveness of frontal posed smile in Japanese female patients by comparing with the result of human judgments. MATERIALS AND METHODS: Photographs of frontal posed smiles of 100 Japanese females after orthodontic treatment were evaluated by 20 dental students (10 males and 10 females) using a visual analogue scale (VAS). The photographs were ranked based on the VAS evaluations and the 25 photographs with the highest evaluations were selected as group A, and the 25 photos with the lowest evaluations were designated group B. Then 12 dimensional items of objective analysis selected from a literature review were measured. Means and standard deviations for measurements of the dimensional items were compared between the groups using the unpaired t-test with a significance level of P < .05. RESULTS: Mean values were significantly smaller in group A than in group B for interlabial gap, intervermilion distance, maxillary gingival display, maximum incisor exposure, and lower lip to incisor (P < .05). CONCLUSIONS: Significant differences were observed only in the vertical dimension, not in the transverse dimension. Five of the 12 objective diagnostic items were correlated with human judgments of the attractiveness of frontal posed smile in Japanese females after orthodontic treatment.

Prevalence and patterns of tooth agenesis in Angle Class II Division 2 malocclusion in Japan.

INTRODUCTION: The purpose of this study was to evaluate the prevalence and patterns of tooth agenesis in subjects with Angle Class II Division 2 malocclusion compared with general orthodontic patients in Japan. METHODS: Panoramic radiographs, dental casts, and cephalograms of 76 patients with Class II Division 2 malocclusions (52 female, 24 male) and 270 orthodontic patients as the control group (168 female, 102 male) who were 14 years of age or older were selected. The prevalences of tooth agenesis in this cohort and in each tooth type were calculated and compared between the groups with the chi-square test. Odds ratios and corresponding 95% confidence intervals were also calculated. RESULTS: The prevalence of tooth agenesis excluding the third molars was significantly higher in the Class II Division 2 group (22.4%) than in the control group (11.9%) (P <0.05); the odds ratio was 2.14 (95% CI, 1.12-4.12). A higher prevalence of tooth agenesis excluding the third molars was observed in the Class II Division 2 group for the mandibular second premolar (P <0.05) and the maxillary lateral incisor (P <0.01). The prevalence of third molar agenesis was also significantly higher in the Class II Division 2 group (42.1%) compared with the control group (26.7%) (P <0.05); the odds ratio was 2.00 (95% CI, 1.18-3.40). CONCLUSIONS: Compared with the general orthodontic patient population, permanent tooth agenesis was observed approximately 2 times more frequently, and a distinctive agenesis pattern was found in the Class II Division 2 group in Japan.

Influences of archwire size and ligation method on the force magnitude delivered by nickel-titanium alloy archwires in a simulation of mandibular right lateral incisor linguoversion.

The present study investigated the influence of archwire size and ligation method on the force magnitude delivered by nickel-titanium alloy archwires to 4 incisor brackets (42, 41, 31, and 32) in a simulation of mandibular right lateral incisor linguoversion. The force delivered by 0.014 and 0.016 inch nickel-titanium alloy archwires was measured using a newly developed multi-sensor measuring system and the mean force magnitudes were compared between different archwire sizes when using conventional ligation (CL) with elastic modules or self-ligating (SL) brackets by three-way ANOVA and post-hoc Bonferroni's tests. The mean force magnitudes for the brackets were significantly decreased in the order of 42, 41, 31, and 32 (p<0.01). The force magnitude was significantly larger in CL than SL at 42, 31, and 32 (p<0.05). In conclusion, the ligation method affected the force magnitude at 4 incisor brackets. Despite the ligation method, archwire size affected the force magnitude from 42 to 31.

Mesiodistal inclination of the unerupted second premolar in the mandible of Japanese orthodontic patients with incisor agenesis.

OBJECTIVE: To elucidate the mesiodistal inclination of the unerupted mandibular second premolar (MnP2) in cases of mandibular incisor (MnIc) agenesis and unilateral MnP2 agenesis. MATERIALS AND METHODS: Twenty-two cases of unilateral MnP2 agenesis (MnP2 agenesis group) and a control group (control group A) of 22 cases without permanent tooth agenesis excluding third molars were selected. Thirty-six cases of MnIc agenesis (MnIc agenesis group) and another control group (control group B) of 36 subjects were also selected. Mesiodistal inclination of the unerupted MnP2 on the panoramic X-rays was measured according to the distal angle and premolar-molar angle using the methods of Shalish et al. and Baccetti et al., respectively. Differences in mean values of the angular measurements between agenesis groups and corresponding controls were investigated (unpaired t-test). RESULTS: In the MnP2 agenesis group, the mean distal angle decreased 12.3° and the mean premolar-molar angle increased 13.3° for the MnP2 compared with control group A (both P < .001). In the MnIc agenesis group, no significant differences in the means of those angles for the MnP2 were found when compared with control group B. CONCLUSION: In Japanese orthodontic patients, there is a relationship between unilateral MnP2 agenesis and the mesiodistal angulation of the unerupted MnP2. However, no significant relationship was observed between MnIc agenesis (which relationship is often seen in Asian populations) and the position of the unerupted MnP2. These results suggest that different genetic factors are involved in MnP2 agenesis and MnIc agenesis.

The core of allosteric motion in Thermus caldophilus L-lactate dehydrogenase.

For Thermus caldophilus L-lactate dehydrogenase (TcLDH), fructose 1,6-bisphosphate (FBP) reduced the pyruvate S(0.5) value 10(3)-fold and increased the V(max) value 4-fold at 30 °C and pH 7.0, indicating that TcLDH has a much more T state-sided allosteric equilibrium than Thermus thermophilus L-lactate dehydrogenase, which has only two amino acid replacements, A154G and H179Y. The inactive (T) and active (R) state structures of TcLDH were determined at 1.8 and 2.0 Å resolution, respectively. The structures indicated that two mobile regions, MR1 (positions 172-185) and MR2 (positions 211-221), form a compact core for allosteric motion, and His(179) of MR1 forms constitutive hydrogen bonds with MR2. The Q4(R) mutation, which comprises the L67E, H68D, E178K, and A235R replacements, increased V(max) 4-fold but reduced pyruvate S(0.5) only 5-fold in the reaction without FBP. In contrast, the P2 mutation, comprising the R173Q and R216L replacements, did not markedly increase V(max), but 10(2)-reduced pyruvate S(0.5), and additively increased the FBP-independent activity of the Q4(R) enzyme. The two types of mutation consistently increased the thermal stability of the enzyme. The MR1-MR2 area is a positively charged cluster, and its center approaches another positively charged cluster (N domain cluster) across the Q-axis subunit interface by 5 Å, when the enzyme undergoes the T to R transition. Structural and kinetic analyses thus revealed the simple and unique allosteric machinery of TcLDH, where the MR1-MR2 area pivotally moves during the allosteric motion and mediates the allosteric equilibrium through electrostatic repulsion within the protein molecule.