Effects of tooth bleaching on shear bond strength of brackets rebonded with a self-etching adhesive system.

The purpose of this study was to ascertain the effects of tooth bleaching on the shear bond strength of orthodontic brackets rebonded with a self-etching adhesive system. A total of 39 premolars were collected and divided into three equal groups: in group 1 bracket bonding was performed without bleaching treatment; specimens in group 2 were bonded immediately after bleaching; and group 3 teeth were bleached, then immersed in artificial saliva and left for 7 days before bonding. The shear bond strength was measured, with the bonding/debonding procedures repeated once after the first debonding, and the bracket/adhesive failure modes were evaluated by the adhesive remnant index after each debonding. Excepting the mean shear bond strength for group 2 after the first debonding, the overall mean values reached the minimum clinical requirement of 6 MPa. The mean values at the first and second debondings were significantly higher in groups 1 and 3 than in group 2. Between groups 1 and 3, significant differences were noted at the first debonding, but not at the second debonding. Group 2 showed significant differences in mean shear bond strength between the first and second debondings. Bond failure at the enamel-adhesive interface occurred more frequently in group 2 than in groups 1 or 3 after the first debonding. The bracket-rebonding procedure can recover the reduced shear bond strength caused by immediate bonding after bleaching to a clinically acceptable level, but not to the prebleaching level.

Prevalence of cariogenic and periodontopathic bacteria in Japanese children in the primary and mixed dentitions.

AIM: The purpose of the present study was to evaluate the relationship between infection with cariogenic bacteria or periodontal pathogens and the oral condition of children in the primary and mixed dentition stages. METHOD: Children aged 3 to 11 years were selected Detection of cariogenic and periodontopathic bacteria and single nucleotide polymorphism (SNP) analyses were performed, and the prevalence of infection with cariogenic bacteria or periodontal pathogens based on caries experience and dental stage was compared. RESULTS: The prevalence of Streptococcus mutans in both stages was significantly higher in the caries group than in the caries-free group. The prevalence of Streptococcus sobrinus was significantly higher in the caries group only in the mixed dentition stage. The prevalence ofperiodontal pathogens was significantly higher in the mixed dentition stage than in the primary dentition stage, regardless of caries experience. However, there were no significant differences in the prevalence of the periodontal pathogens between the primary dentition and mixed dentition stages, based on caries experience. CONCLUSION: Our data suggested that cariogenic and periodontopathic bacteria have different infection patterns, and that the period of infection with these bacteria also differs.

Maxillary first molar agenesis and other dental anomalies.

OBJECTIVE: To explore the association of maxillary first molar agenesis with other dental anomalies in Japanese orthodontic patients. MATERIALS AND METHODS: A total of 32 subjects with one or two congenitally missing maxillary first molars (group M) were selected and divided into group 1M (12 subjects with one maxillary first molar missing) and group 2M (20 subjects with two maxillary first molars missing). As controls, 32 sex-matched subjects without agenesis of maxillary first molars were collected (group C). Panoramic and periapical radiographs, cephalograms, study models, intraoral photographs, and anamnestic data were used to identify anomalies of permanent teeth. Chi-square, Fisher's exact, Kruskal-Wallis, and Steel-Dwass tests were used to make statistical comparisons. RESULTS: The prevalence rates of tooth agenesis other than the maxillary first molars and advanced tooth agenesis, with third molars excluded, were significantly higher in group 2M than in group C. The absence of second premolars was most common. The prevalence rate of third molar agenesis was significantly higher in groups 1M and 2M than in group C. The occurrence of symmetrical agenesis of the mandibular third molars was particularly notable in group 2M as compared to group 1M, in which maxillary third molar agenesis was predominant. There was no significant association between maxillary first molar agenesis and other dental anomalies, except for agenesis of teeth other than maxillary first molars. CONCLUSION: Agenesis of maxillary first molars is associated with a higher prevalence of other permanent tooth agenesis and advanced tooth agenesis.

Comparing bond strengths of brackets on primary teeth with 3 different primers.

PURPOSE: The purposes of this study were to: (1) examine the shear bond strengths (SBSs) of orthodontic brackets bonded to primary teeth with conventional, self-etching, and moisture-insensitive primers; and (2) evaluate the mode of bracket failure. METHODS: Seventy-eight human primary teeth were divided equally into 6 groups: (1) the enamel surface was etched, and a conventional primer was applied under dry conditions; (2) the enamel surface was dried, and a self-etching primer was applied; (3) the enamel surface was etched, and a moisture-insensitive primer was applied under dry conditions; (4-6) the same adhesives were used as those in groups 1 to 3, but before priming, each tooth was moistened. Metal brackets were bonded with adhesive. SBSs were measured using a universal testing machine, and the bracket/adhesive failure modes were evaluated with the adhesive remnant index. RESULTS: A notable drop in bond strength and a high incidence of bond failure at the enamel-adhesive interface were found in group 4. There was no significant difference in mean SBSs among the other groups. CONCLUSION: These adhesive systems under specific conditions enable us to use a primary tooth in the sectional bracket appliance as the anchor tooth, thus helping improve the outcome of early treatment for malocclusion.

Effects of premolar extractions on Bolton overall ratios and tooth-size discrepancies in a Japanese orthodontic population.

INTRODUCTION: The purpose of this study was to investigate the effects of premolar extractions on the Bolton overall ratios and overall tooth-size discrepancies in a Japanese orthodontic population. METHODS: Mesiodistal tooth widths were measured on 198 pretreatment dental casts of subjects with Class I, Class II, and Class III malocclusions. The overall ratios and tooth-size discrepancies were determined before and after hypothetical premolar extractions. Before and after extractions, the subjects were divided into small, normal, and large overall ratio groups categorized by the Bolton standard deviation definition, and into small, normal, and large correction groups by the actual amount of change calculated for tooth-size correction in millimeters. Extractions were performed in the following combinations: (1) all first premolars, (2) all second premolars, (3) maxillary first and mandibular second premolars, and (4) maxillary second and mandibular first premolars. For statistical evaluations, analysis of variance, Kruskal-Wallis, Friedman, Scheffé, Bonferroni, and Tukey tests were performed. RESULTS: The overall ratios decreased in every malocclusion group after extraction of any combination of premolars. The decreases were significantly notable in combinations 2 and 4. Some subjects in the normal overall ratio and maxillary and mandibular correction groups moved into the clinically significant tooth-size discrepancy group after premolar extraction, and the reverse was also true. CONCLUSIONS: In formulating a treatment plan involving premolar extractions, orthodontists should consider that the overall ratios might decrease, and normal and clinically significant tooth-size discrepancies could change mutually after extractions.

Cephalometric evaluation of maxillary sinus sizes in different malocclusion classes.

We found few studies on the association between maxillary sinus size and malocclusion in an electronic search using PubMed. The purpose of this study was to investigate maxillary sinus size in different malocclusion groups and the association between maxillary sinus size and dentofacial morphology by the use of lateral cephalometric radiographs. A total of 120 lateral cephalograms were used. These radiographs were derived from subjects with skeletal Class I, Class II, and Class III malocclusions, classified on the basis of the A-N-B angle. Each malocclusion group consisted of 20 boys and 20 girls ranging in age from 12 to 16 years. Two linear measurements and three area measurements were made to evaluate maxillary sinus size, and four angular and eight linear measurements were made to evaluate dentofacial morphology. Analysis of variance and Pearson's correlation analysis were performed for statistical comparison. The maxillary sinuses showed no significant differences in size between the different classes of skeletal malocclusion or between sexes. However, the maxillary sinus measurements were significantly correlated with several dentofacial morphological measurements. When formulating an orthodontic treatment plan, orthodontists should take into consideration the fact that the patients 12 to 16 years old with large cranial bases and nasomaxillary complexes tend to have larger maxillary sinuses, but there is no significant association between maxillary sinus size and the A-N-B angle denoting the sagittal skeletal jaw relationship.

Caries risk factors in children under treatment with sectional brackets.

OBJECTIVE: To longitudinally investigate the caries risk levels in children undergoing orthodontic treatment with sectional brackets. MATERIALS AND METHODS: A total of 42 children scheduled for orthodontic treatment with sectional orthodontic appliances participated in this study. They were divided into two groups based on decayed, missing, and filled permanent and deciduous teeth (DMFT/dmft) scores and counts of mutans streptococci (MS) prior to treatment. One was the low caries risk group (n = 26) and the other was the high caries risk group (n = 16). Paraffin-stimulated whole saliva was collected for examination of salivary flow rate, buffer capacity, and MS and lactobacilli (LB) levels before treatment, 2 and 4 months after appliance placement, and 2, 4, and 8 months after appliance removal. RESULTS: The pretreatment salivary flow rates, buffer capacity, and MS levels remained statistically unchanged during and after active orthodontic treatment in both groups. The levels of LB in the high caries risk group were significantly elevated by appliance placement, but upon appliance removal started to fall significantly and came a little short of the pretreatment levels. In the low caries risk group, the pretreatment levels of LB remained statistically unchanged during and after treatment. There were no significant differences in salivary flow rate or buffer capacity, but there were significant differences in MS and LB scores between the two groups at every measurement time. CONCLUSIONS: In children undergoing orthodontic treatment with sectional brackets, LB levels are an important part in making caries risk assessment.

Thresholds for clinically significant tooth-size discrepancy.

OBJECTIVE: To determine an appropriate threshold for clinically significant tooth-size discrepancy using both a Bolton standard deviation (SD) definition and a millimetric definition. MATERIALS AND METHODS: Mesiodistal tooth widths were measured in 250 pretreatment dental casts of patients with Class I, Class II, and Class III malocclusions. The anterior and overall ratios and the required amount of maxillary and mandibular corrections were calculated. The casts were divided into small, normal, and large groups according to the anterior and overall ratios categorized by the Bolton SD definition, and into small, normal, and large groups according to the required amount of maxillary and mandibular corrections expressed in millimeters. RESULTS: The small and large anterior ratio groups which fell under the category of the 2 SD threshold did not always need maxillary or mandibular corrections greater than 2 mm, while the small and large overall ratio groups always needed maxillary and mandibular corrections greater than 2 mm. The small and large maxillary correction groups in the 2 mm threshold category did not always have anterior or overall ratios greater than 2 SDs from the Bolton mean. However, the small and large mandibular correction groups always had anterior ratios greater than 2 SDs and did not always have overall ratios greater than 2 SDs. CONCLUSIONS: The tooth-size discrepancies could be better expressed in terms of both percentage and actual amount of millimeters required for correction. The ratios outside 2 SDs from the Bolton mean and the discrepancies requiring more than 2 mm of maxillary and/or mandibular corrections are recommendable as the appropriate thresholds for clinical significance.

Shear bond strength of brackets rebonded with a fluoride-releasing and -recharging adhesive system.

OBJECTIVE: To ascertain the effects of repeated bonding on the shear bond strength of orthodontic brackets bonded with a fluoride-releasing and -recharging adhesive system with a self-etching primer in comparison with two other types of adhesive system. MATERIALS AND METHODS: A total of 48 premolars were collected and divided equally into three groups of 16. Each group was assigned one of three adhesive systems: Transbond XT, Transbond Plus, or a fluoride-releasing and -recharging adhesive system, Beauty Ortho Bond. Shear bond strength was measured 24 hours after bracket bonding, with the bonding/debonding procedures repeated twice after the first debonding. A universal testing machine was used to determine shear bond strengths, and bracket/adhesive failure modes were evaluated with the adhesive remnant index after each debonding. RESULTS: At every debonding sequence, all of these three adhesive systems had a shear bond strength of 6 MPa, which is a minimum requirement for clinical use. Transbond XT and Transbond Plus had significantly higher mean shear bond strengths than did Beauty Ortho Bond at each debonding. No significant differences in mean bond strength were observed between the three debondings in each adhesive system. Bond failure at the enamel/adhesive interface occurred more frequently in Beauty Ortho Bond than in Transbond XT or Transbond Plus. CONCLUSIONS: The fluoride-releasing and -recharging adhesive system with the self-etching primer (Beauty Ortho Bond) had clinically sufficient shear bond strength in repeated bracket bonding; this finding can help orthodontists to decrease the risk of damage to enamel at debonding.

Tannerella forsythia and the HLA-DQB1 allele are associated with susceptibility to periodontal disease in Japanese adolescents.

Periodontal disease is a multiple factor disease caused by genetic factors, environmental factors, and periodontal bacteria (periodontal pathogens). The present study aimed to elucidate the risk factors for periodontal disease in Japanese adolescents. Subjects (11-16 years old) were classified into three groups: localized aggressive periodontitis (LAP), periodontal attachment loss (PAL), and periodontally healthy (PH) groups. Genomic DNA isolated from the buccal mucosa was used for single-nucleotide polymorphism analyses of the candidate genes (interleukin-1alpha-889; interleukin-1alpha +4845; interleukin-1beta +3954; an immunoglobulin G Fc gamma receptor, FcgammaRIIa-R/H131; and a human leukocyte antigen class II allele, HLA-DQB1) of aggressive periodontitis. Subgingival plaque samples obtained from the same subjects were used for 16S rRNAbased polymerase chain reaction analysis of five important periodontal pathogens (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola, and Tannerella forsythia). Tannerella forsythia was detected in the deepest periodontal pockets in all subjects in the LAP and PAL groups. The prevalence of an atypical BamHI restriction site in HLA-DQB1 of the LAP group was significantly higher than that in the PH and PAL groups. Furthermore, all subjects who had the atypical BamHI restriction site in HLA-DQB1 had T. forsythia infection. These results suggested that T. forsythia is associated with periodontal disease in Japanese adolescents and also suggested that HLA-DQB1 is related to LAP and is associated with T. forsythia infection.

Effects of maxillary second molar extraction on dentofacial morphology before and after anterior open-bite treatment: a cephalometric study.

The purpose of the present study was to probe into the effects of maxillary second molar extraction on dentofacial morphology by the use of cephalometric radiographs taken before and after anterior open-bite treatment. The subjects were 30 Japanese patients who had received multiloop edgewise archwire therapy without premolar extraction. They were divided into two groups. Group 1 consisted of 15 patients who had their maxillary second molars removed. Group 2 comprised 15 patients who had been treated without extraction of maxillary second molars. Lateral cephalograms were taken before and after treatment. Seventeen angular and 31 linear measurements were obtained from the lateral cephalograms. Paired and unpaired t tests were used to determine the significance of differences in measurements. The retrusion and extrusion of the maxillary incisors, the distal movement of the maxillary first molars, and the uprighting of the maxillary first premolars and the mandibular first molars were greater in group 1 than in group 2. Moreover, the maxillary first molars intruded significantly in group 1 but extruded insignificantly in group 2. Extraction of maxillary second molars, as well as nonextraction, can be an effective operating procedure for open-bite correction of the permanent dentition.

Tooth size discrepancies among different malocclusions in a Japanese orthodontic population.

OBJECTIVE: To identify the possible sex differences in anterior and overall tooth size ratios and to evaluate whether any differences exist in tooth size ratios and distributions of subjects with clinically significant tooth size discrepancies among Angle Class I, Class II, and Class III malocclusion groups with the corresponding skeletal characteristics in a Japanese population. MATERIALS AND METHODS: Each malocclusion group comprised 60 subjects (30 males and 30 females). The mesiodistal width from first molar to first molar was measured on each pretreatment cast to the nearest 0.01 mm using digital calipers, and the anterior and overall ratios were calculated. Student's t-test, Welch t-test, analysis of variance, and chi2-test were performed for statistical analysis. RESULTS: No statistically significant sex differences were found in anterior or overall ratio in any group. No significant differences in anterior or overall ratios were found among the malocclusion groups. No significant differences were found between the distributions of subjects with clinically significant tooth size discrepancies, categorized by the Bolton standard deviation definition and by the actual amount of change calculated for tooth size correction in millimeters, among the malocclusion groups except for the mandibular correction for the overall ratio between Class I and Class III subjects. CONCLUSION: Bolton's values can be used with confidence for the typical Japanese orthodontic population. The use of the actual millimeters of correction for the tooth size ratios could help orthodontists avoid underestimating the prevalence of clinically significant tooth size discrepancies.

Comparison of shear bond strengths of orthodontic brackets bonded to deciduous and permanent teeth.

INTRODUCTION: This study was conducted (1) to compare the bond strengths of identical orthodontic brackets bonded to deciduous and permanent teeth with either of 2 primer/adhesive systems and (2) to evaluate the modes of bracket/adhesive failure. METHODS: Thirty-four permanent teeth and 34 deciduous teeth were collected. To these freshly extracted teeth, metal brackets were bonded with 2 primer/adhesive systems. These specimens were divided into 4 groups. In group I, consisting of 17 permanent teeth, the brackets were bonded with an acid-etching adhesive system; in group II, the self-etching adhesive system was used for bonding the brackets to 17 permanent teeth; in group III, consisting of 17 deciduous teeth, the acid-etching adhesive system was used; and in group IV, the self-etching adhesive system was used for bonding the brackets to 17 deciduous teeth. Shear bond strength was measured with a universal testing machine, and the mode of bracket/adhesive failure was determined according to the adhesive remnant index. RESULTS: The shear bond strengths of all 4 groups exceeded what is believed to be clinically sufficient strength of 6 to 8 MPa. Whether deciduous or permanent teeth, there were no significant differences in shear bond strength between the acid-etching and self-etching adhesive systems. The shear bond strengths of the brackets bonded to the deciduous teeth with either adhesive system were lower than those to the permanent teeth. Bond failure occurred at the enamel-adhesive interface more frequently in the self-etching adhesive system than in the acid-etching adhesive system. CONCLUSIONS: Bond strengths of brackets were lower with deciduous teeth but were high enough for clinical purposes.

Effects of moisture conditions of dental enamel surface on bond strength of brackets bonded with moisture-insensitive primer adhesive system.

The purposes of this study were to evaluate the effects of different degrees of water contamination on the shear bond strength of orthodontic brackets bonded to dental enamel with a moisture-insensitive primer (MIP) adhesive system and to compare the modes of bracket/adhesive failure. A total of 68 human premolars were divided into four groups by primers and enamel surface conditions (desiccated, blot dry, and overwet). In group I, the hydrophobic Transbond XT primer adhesive system was used under desiccated conditions for bonding the brackets; in group II, the hydrophilic Transbond MIP adhesive system was used under desiccated conditions; in group III, the hydrophilic Transbond MIP adhesive system was used under blot dry conditions; and in group IV, the hydrophilic Transbond MIP adhesive system was used under overwet conditions. Shear bond strength was measured with a universal testing machine, and the mode of bracket/adhesive failure was determined according to the adhesive remnant index. The mean shear bond strengths were not significantly different among groups I, II, and III, and were higher than the clinically required range of 6 to 8 MPa. The mean shear bond strength achieved in group IV was significantly lower than that achieved in groups I, II, and III, and also lower than the clinically required values. Bond failure occurred at the enamel-adhesive interface more frequently in group IV than in groups I and III. To achieve clinically sufficient bond strengths with the hydrophilic MIP adhesive system, excess water should be blotted from the water-contaminated enamel surface.

Rat wild-type parathyroid hormone receptor (PTH-R) and mutant PTH-R(P132L) show the different intracellular localization in vitro.

A replacement of proline with leucine at position 132 of the receptor for parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP), i.e., PTH-R, has been discovered in human Blomstrand's lethal chondrodysplasia. As skeletal deformities in this type of chondrodysplasia appear to compromise the receptor binding to its ligands, we examined the possibility that rat PTH-R carrying P132L mutation (PTH-R(P132L)) would result in abnormal intracellular localization. Osteoblastic MC3T3-E1 cells were transfected with expression vectors containing cDNAs encoding either wild-type PTH-R or mutant PTH-R(P132L). The cells expressing the wild-type PTH-R produced a receptor protein with a molecular mass of 66.3 kDa, which localized its immunoreactivity mainly on the cell surfaces. In contrast, the PTH-R(P132L) was hardly detected on the cell surfaces, but accumulated within the rough-surfaced endoplasmic reticulum. Consistent with this localization, the cells expressing the mutant receptor failed to generate cyclic AMP in response to PTH. Furthermore, a remarkably weaker intensity of the 66.3 kDa band compared with the wild-type counterpart suggests that PTH-R(P132L) is prone to degradation in the transfected cells. In summary, these findings indicate that defective transport of PTH-R(P132L) to the cell surface would be a molecular basis for Blomstrand's chondrodysplasia.

Congenitally missing mandibular incisors and mandibular symphysis morphology.

OBJECTIVE: To explore the association between congenital absence of permanent mandibular incisors and craniofacial and mandibular symphysis morphology in Japanese orthodontic patients. MATERIALS AND METHODS: A total of 27 girls with one or two congenitally absent mandibular incisors (group M) were selected and divided into group 1M (16 girls with the absence of one incisor) and group 2M (11 girls with the absence of two incisors). In addition, 20 other Japanese girls without hypodontia and with little or no mandibular incisor crowding were enrolled as a control (group C). Using the lateral cephalogram of each subject, 17 angular, 8 linear, and 3 area measurements were made for evaluation of craniofacial and mandibular symphysis morphology. The cephalometric data thus obtained were statistically analyzed and compared between the groups. RESULTS: A significantly greater retroclination of the retained mandibular incisors was found in group 1M than in group C. Groups 1M and M showed a significantly greater retroclination of mandibular alveolar bone than group C. Groups 2M and M exhibited a significantly smaller mandibular symphysis area than group C. CONCLUSION: The retroclination of the mandibular incisors and alveolar bone and the reduced mandibular alveolar bone area should be taken into consideration in planning orthodontic treatment on patients with congenitally missing permanent mandibular incisors.

Applicability of Bolton's tooth size ratios to a Japanese orthodontic population.

Previous studies have shown that tooth size ratios are ethnicity-, race-, and sex-specific. This study was carried out to determine anterior and overall ratios in a Japanese population and to compare them with Bolton's ratios. Numerical data were obtained from 60 pairs of dental casts of 30 male and 30 female Japanese orthodontic patients. The mesiodistal widths from first molar to first molar were measured on each cast to the nearest 0.01 mm, by using digital calipers, and the anterior and overall ratios were calculated. The Kolmogorov-Smirnov test, the parametric t test, and Student t test were used for statistical analyses. No statistically significant difference between men and women was found in either the anterior or overall ratio. The combined male and female anterior and overall ratios were 78.39 +/- 2.18% and 91.60 +/- 2.11%, respectively. The combined male and female anterior ratio showed a statistically significant difference from the Bolton standard, whereas the overall ratio showed no statistically significant difference. Significant discrepancies in the anterior and overall ratios were found in 21.6% and 8.3% of patients, respectively. A high prevalence rate of an anterior tooth size discrepancy more than 2SD above Bolton's mean was found. Bolton's anterior ratio was not applicable to the Japanese population, and specific standard tooth size ratios for the Japanese population are needed.

Shear bond strength differences of types of maxillary deciduous and permanent teeth used as anchor teeth.

OBJECTIVE: To compare the bond strengths of identical orthodontic brackets bonded to maxillary deciduous and permanent teeth, which were used as anchor teeth in sectional edgewise appliance therapy, and to evaluate the modes of bracket/adhesive failure. MATERIALS AND METHODS: A total of 28 human maxillary teeth were divided into four groups by tooth type: permanent first premolars (group I), permanent second premolars (group II), deciduous canines (group III), and deciduous second molars (group IV). Each group consisted of seven teeth. Metal premolar brackets were bonded to these specimens using an acid-etching adhesive system. Shear bond strengths were measured using a universal testing machine, and the bracket/ adhesive failure modes were evaluated with the Adhesive Remnant Index. RESULTS: The shear strengths of the bonds on the deciduous canines and second molars were significantly lower than those on the permanent first and/or second premolars. There were no significant differences in shear bond strength between the permanent first and second premolars, and between the deciduous canines and second molars. The shear bond strengths of all four tooth types were higher than the clinically sufficient range of strengths from 6 to 8 MPa. Bond failure at the enamel-adhesive interface occurred more frequently in the deciduous second molars than in the permanent first premolars. CONCLUSIONS: There were significant differences in shear bond strength among different permanent and deciduous tooth types, but deciduous teeth could be used as anchor teeth in orthodontic treatment with sectional edgewise appliances.

Hypodontia patterns and variations in craniofacial morphology in Japanese orthodontic patients.

OBJECTIVE: The purpose of this study was to explore the association of hypodontia patterns and variations in craniofacial morphology in Japanese orthodontic patients. MATERIALS AND METHODS: A total of 50 girls with hypodontia (the total group) were selected and categorized into anterior, posterior, and anterior-posterior groups according to the location of the congenitally missing teeth. By using the lateral cephalograms of each subject, 28 angular and 37 linear measurements were made. The cephalometric data were statistically analyzed and compared among the groups and with the Japanese cephalometric standards from 36 age-matched female subjects without hypodontia or malocclusion (the control group). RESULTS: Every hypodontia group showed shorter anterior and overall cranial base lengths, shorter maxillary length, greater retroclination and elongation of mandibular incisors, and a larger interincisal angle than the control group. The total and anterior-posterior groups especially exhibited a significantly more prognathic mandible, larger retroclination of maxillary incisors, and a more counterclockwise-rotated occlusal plane. Furthermore, these skeletal and dental deviations were more remarkable in the anterior-posterior group than in either the anterior or the posterior group. Anterior hypodontia exerted as much influence on craniofacial morphology as posterior hypodontia. CONCLUSIONS: When orthodontic treatment is performed on patients with hypodontia, not only the number but also the distribution of missing teeth should be taken into consideration, though there was no significant difference in craniofacial morphology between anterior hypodontia and posterior hypodontia.

Cephalometric evaluation of anterior open-bite nonextraction treatment, using multiloop edgewise archwire therapy.

There are very few reports of extensive and detailed cephalometric investigations of nonextraction treatment changes for patients with anterior open bite. The purpose of this study was to evaluate changes in dentomaxillofacial morphology by way of lateral and oblique cephalograms of patients who had undergone multiloop edgewise archwire (MEAW) therapy for anterior open-bite correction. The subjects consisted of 21 Japanese female patients who received MEAW therapy without premolar extraction. The mean pre- and posttreatment ages were 16 years 9 months and 19 years, respectively. Lateral and oblique cephalograms were taken before and after treatment. Fifteen angular and 29 linear measurements were obtained from the lateral cephalograms; 17 angular and 20 linear measurements were obtained from the oblique cephalograms. Treatment changes were evaluated by the paired t-test. The upward and forward rotational changes of the mandible consequent to the use of the MEAWs and anterior vertical elastics were larger than the downward and backward rotational changes of the mandible, due to the extrusion of the posterior teeth by leveling and alignment. The uprighting and retrusion of the premolars and molars, and the extrusion, uprighting, and/or retrusion of the incisors and canines played important roles in the anterior open-bite nonextraction treatment by dint of the MEAW technique.