Symmetrical agenesis of the mandibular third molars and agenesis of other teeth in a Japanese orthodontic population.

This study was conducted to investigate the association between symmetrical agenesis of the mandibular third molars and agenesis of other teeth in Japanese orthodontic patients. A sample of 64 patients with symmetrical agenesis of the mandibular third molars and without agenesis of the maxillary third molars was selected as the third molar agenesis group. In addition, 585 patients with all 4 third molars were selected as controls. The main materials examined for diagnosis of tooth agenesis were panoramic radiographs. The prevalence rate of tooth agenesis was compared between the groups using the chi-squared or Fisher's test, and the odds ratio. Significantly increased occurrence of overall agenesis of the maxillary lateral incisors, and overall and symmetrical agenesis of other teeth including the maxillary and mandibular second premolars and mandibular first molars were observed in the patients with symmetrical agenesis of the mandibular third molars and without agenesis of the maxillary third molars. Irrespective of the presence or absence of symmetrical agenesis of the mandibular third molars, no significant differences in the prevalence rates of overall or symmetrical agenesis of other teeth and specific teeth were noted between the sexes or between the right and left sides of the jaws in the patients without maxillary third molar agenesis. (J Oral Sci 58, 171-176, 2016).

Patterns of bilateral agenesis of maxillary third molars and agenesis of other teeth.

The purpose of this study was to investigate the patterns of bilateral agenesis of maxillary third molars and other tooth agenesis in Japanese orthodontic patients. A group of 262 subjects with bilateral agenesis of maxillary third molars (group A) was divided into three subgroups: group 1A consisting of 114 subjects without agenesis of mandibular third molars; group 2A, 31 subjects with unilateral agenesis of mandibular third molars; and group 3A, 117 subjects with agenesis of all third molars. As controls, 926 other subjects without third molar agenesis were selected (group C). Panoramic radiographs were mainly used to examine for tooth agenesis. The Chi square test and odds ratio were used to make statistical comparisons. The prevalence rates of agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, and bilateral agenesis of maxillary lateral incisors and second premolars were significantly higher in any one of the third molar agenesis groups than in the control group. Characteristically, no significant increase in occurrence of bilateral agenesis of mandibular second premolars was demonstrated by the subjects with bilateral agenesis of maxillary third molars. Irrespective of whether unilateral or bilateral agenesis of mandibular third molars is present or not, the Japanese orthodontic patients with bilateral agenesis of maxillary third molars exhibited a significantly increased occurrence of unilateral or bilateral agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, except for bilateral agenesis of mandibular incisors and second premolars.

Association between third molar agenesis patterns and agenesis of other teeth in a Japanese orthodontic population.

The purpose of this study was to investigate the patterns of third molar agenesis and incidence of agenesis of other permanent teeth in a Japanese orthodontic patient group. A total of 417 Japanese subjects (134 males and 283 females) with agenesis of one or more third molars were divided into four groups according to the agenesis pattern, and 874 other Japanese subjects (302 males and 572 females) without third molar agenesis were assigned to a control group. Panoramic radiographs and medical and dental records were used to examine for tooth agenesis. The Chi-square test and odds ratio were used to make statistical comparisons. The prevalence of third molar agenesis worked out at 32.3% with no statistically significant gender difference. A high prevalence rate of agenesis of third molars, unilateral or bilateral, could be considered characteristic of the Japanese orthodontic population. Significant increases in occurrence of oligodontia, and unilateral or bilateral agenesis of other teeth, including maxillary lateral incisors and maxillary and mandibular second premolars, were observed in all or almost all of the third molar agenesis groups, compared with the controls. A significantly increased prevalence rate of mandibular lateral incisor agenesis was observed in almost all of the third molar agenesis groups. The Japanese patients with third molar agenesis had a significantly increased occurrence of oligodontia, and unilateral or bilateral agenesis of maxillary and mandibular lateral incisors and second premolars, except for bilateral agenesis of mandibular lateral incisors.

Association of agenesis of mandibular lateral incisors with other dental anomalies in a Japanese population.

PURPOSE: The purpose of this study was to explore the association of mandibular incisor agenesis with other dental anomalies in Japanese orthodontic patients. METHODS: A total of 52 subjects with 1 or 2 congenitally missing permanent mandibular lateral incisors (group A) were selected and divided into group 1a (26 subjects with 1 lateral incisor missing) and group 2a (26 subjects with 2 lateral incisors missing). Fifty two sex-matched subjects without agenesis of the mandibular lateral incisor served as controls (group C). Radiographs, study models, and medical and dental records were used to identify anomalies of teeth. RESULTS: The prevalence rate of agenesis of teeth other than the mandibular lateral incisors and third molars was significantly increased in group A. Agenesis of the maxillary second premolars was significantly increased in groups 2a and A. Significantly increased prevalence rates of symmetrical tooth agenesis, with third molars excluded, and third molar agenesis were observed in group 1a and A. CONCLUSIONS: Japanese subjects with agenesis of 1 or 2 permanent mandibular lateral incisors have significantly increased prevalence rates of other permanent tooth agenesis and symmetrical tooth agenesis.

Patterns of tooth agenesis in Japanese subjects with bilateral agenesis of mandibular second premolars.

The aim of this study was to explore the patterns of tooth agenesis in Japanese orthodontic patients with bilateral agenesis of mandibular second premolars. A total of 80 Japanese orthodontic patients with 2 congenitally missing mandibular second premolars were selected as the subjects of this study (experimental group). Another 80 individuals without bilateral agenesis of mandibular second premolars were collected for comparison (control group). The 2 groups were matched with regard to sex. Radiographs, dental casts and records of medical and/or dental treatment were used to identify tooth agenesis. The Chi-square test, odds ratio, and test for equality were used to make statistical comparisons. The prevalence rates of other types of tooth agenesis were significantly higher in the experimental group than in the control group. The occurrence of agenesis of maxillary and mandibular lateral incisors and third molars, and maxillary second premolars was also significantly higher in the experimental group than in the control group. Significantly increased prevalence rates of symmetrical tooth agenesis, with third molars included, and oligodontia were observed in the experimental group. Japanese subjects with bilateral agenesis of mandibular second premolars are at significantly high risk of agenesis of other types of permanent teeth, symmetrical tooth agenesis and oligodontia.

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.

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.