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PubMed1990

[The application of repelling magnets to distal movement of maxillary molars. Report of three cases].

Report on three cases of maxillary first molar distalization with the aid of intra-arch repelling magnets were presented in this paper. Two cases were Class II malocclusion and one was a Class I discrepancy case whereby all resulted in rapid distalization of the upper first molars into Class I molar relationship in a relatively short time. Despite the unwanted rotation and tipping of the molars and the anteriors occurred slightly, numerous advantages of the repelling magnetic system were noted applicable to early mixed dentition cases to obtain the sufficient space of the molars rapidly. Moreover, since this is a fixed appliance, no patient cooperation was necessary. In conclusion, this magnetic system was found to be an effective device for molar distalization.

Humans↗
PubMed1990

[Orthodontic uprighting mandibular second molars].

Two cases of impaction of the mandibular second molar treated by means of orthodontic techniques, were presented. It takes about 6 to 8 months for uprighting mandibular second molar. There is no significant difference in the uprighting times between in the case of extraction of the third molar or not. We consider that the corticotomy of the diatal part of the mandibular second molar shortens the uprighting times of the mandibular second molar. Treatment results of both cases were favorable at 2 years after uprighting of the mandibular second molar.

Humans↗
PubMed1990

[Some aspects of third molars with regard to the development of malocclusions].

Although the orthodontist is constantly aware of the developing third molar and its possible effects on the dentition during and after orthodontic treatment, the relationship between the third molar and the development of malocclusion had not been resolved. To attempt to clarify some of the problems associated with the third molar, an analysis of the factor in fluencing on the dentition and denture frame was performed. In this study, twenty-one adult cases which had no prothodontic correction of the tooth shape and orthodontic treatment with at least three wisdom teeth were used for evaluation of the denture frame structure and occlusion. The case which impacted third molar (M3 impacted group) showed less than 25 degree mandibular plane angle (FH-MP) without exception, while the case which the third molar erupted (M3 erupted group) were able to divide into high angle (more than 30 degree of FH-MP) and low angle (less than 29 degree of FH-MP) groups. The M3 impacted with low angle group and M3 erupted with low angle group showed relatively normal occlusion and favorable denture frame structure, but M3 erupted with high angle group indicated that the denture frame composition was affected by posterior discrepancy especially the steepness of occlusal plane which might be the over eruption of posterior teeth. The M3 erupted with high angle group also included two cases of severe anterior open-bite with skeletal deformity. These findings suggest that the posterior discrepancy due to existence of third molars influence on the dento-facial-skeletal structure and development of malocclusions.

Adult↗
PubMed1989

[Correlations between first molar eruption, caries incidence and caries experience in primary school children].

A follow-up study was made on the results of oral health examinations which had been conducted for six years on a total of 871 primary school children in the 1st grade (age, 6 years) till they became sixth graders (460 boys and 411 girls). The findings are as follows: 1. When they were first graders, the oral health examination revealed their 56% had erupted the upper first molar, and 73% the lower first molar. 2. The incidence of caries in the upper first molar had occurred mostly between one and two years after eruption. After three to four years, more than half of the pupils had this particular tooth decayed. In the case of the lower first molar, caries had started to develop within one year after eruption. After two years, caries was evident in more than half of the examinees. 3. In the sixth graders, the number of DMF teeth per child came to 3.9 and the DMF teeth rate stood at 17%. Both the number of DMF teeth and the DMF teeth rate were larger in girls than in boys. The rate for an intact first molar teeth were 32% in the upper jaw and 15% in the lower jaw. These rates were lower in girls than in boys. 4. The shorter the period between the eruption of the first molars in both jaws and the caries incidence, the larger the number of the DMF teeth and the DMF teeth rate at sixth graders. For the prevention of caries in permanent teeth, special care should be taken during the short period of time following eruption.

Child↗
PubMed1989

[The relationship between the movement of molars and the transmitted mechanism of orthodontic forces in extraoral anchorage (2)].

The relationship between the movement of molars and the transmission of orthodontic forces were especially studied about the upward pull of the outer bow in extraoral anchorage. Molar movements were theoretically analyzed from horizontal pull to upward angle of 40 degree. The transmission mechanism of the orthodontic force was studied from horizontal pull to 40 degree upward angle on each 5 degree with the holography experiment on a human dry skull. 1. Horizontal pull of the outer bow resulted in distal movement of the molar. The long axis of the molar was tipped distally. The dentofacial cranium transformed to the lower and backward direction. 2. When the outer bow was inclined at an upward angle of about 18 degree, the molar moved bodily to the distal and superior direction. But the dentofacial cranium transformed a little to the lower and backward direction. 3. When the outer bow was inclined from 25 to 30 degree upward angle, the molar rotated to the clockwise direction, and the dentofacial cranium rotated to the counter clockwise. The bending deformation was not observed on the dentofacial cranium. 4. The dentofacial cranium was compressed in the pull direction from 25 to 30 degree upward angle. These directions were clinically interpreted as inhibition of the downward and forward growth of the maxillary bone.

Dental Stress Analysis↗
PubMed1989

Calcification of the permanent first molars observed in panoramic radiographs.

We investigated the development (calcification) stages of the permanent first molars of Japanese children by classifying them into 14 stages by the criterion of Moorrees, et al., using 11,167 panoramic radiographs, 5,759 of boys and 5,408 of girls, between the ages of 2 years 0 months and 14 years 11 months. The following information was obtained from calculations of the average chronological ages for the development stages of these teeth. 1) The development of first molars was earlier in girls than boys. This was particularly true during the middle phase of development. 2) A first molar on one side developed at the same rate as its counterpart on the other side, regardless of differences in sex or arch. 3) In both boys and girls, the development of the mandibular first molars was about one month earlier than that of the maxillary first molars at each stage. 4) When these results were compared with those of Nolla, Moorrees and Haavikko, who pioneered this field of study, it was clear that the development of the teeth in Japanese is different from that in Caucasians. 5) We made charts of the development of the first molars in Japanese which can be applied in routine clinical practice.

Adolescent↗
PubMed1989

[A photoelastic study of the stress distribution in the surrounding tissues of the abutments of a fixed partial denture with tilted molar abutments].

The purpose of this study was to evaluate the stress distributions to the abutments of a fixed partial denture with tilted molar abutments. In cases of the lower 1st molar being missing four 2-dimensional photoelastic models with 3- unit fixed partial dentures of which the 2nd molars were tilted 0 degrees, 10 degrees, 20 degrees and 30 degrees toward the 2nd premolar were made. A vertical load of 50 lbs was applied to the 1st and 2nd molar in each case. Two-dimensional photoelastic stress analysis was used, and the stress areas were recorded photographically. The results were as follows; 1. When the vertical load was applied to pontic and 2nd molar on the central fossae, the magnitude of stress distribution of the surrounding tissues of the root of the 2nd premolar was increased incrementally with increasing inclination. 2. Under two loading conditions, the stress distributions were directed to the long axis of the abutments. 3. In this experiment, no stress distributions were observed on the mesial area of the mesial root of the second molar.

Dental Abutments↗
PubMedDate not supplied

Disturbed eruption of the lower second molar: clinical appearance, prevalence, and etiology.

Disturbed eruption of the second lower molar is a condition not often described in the dental literature. To study this aberration, 88 referred patients with 108 totally or partially impacted lower second molars were examined. The mean age of these patients was 15 years; 64 percent were male. A third molar was found adjacent to the affected second molar in 95 percent of cases. Local space shortage was seen in 90 percent of the cases. The prevalence of this disturbance overall is 1.5 per 1,000 individuals. Impactions in mesioangular and distoangular positions seemed to have been caused mostly by lack of space, whereas additional local factors had complicated many vertical impactions. Bite supervision should include early observance of the molar area for detection of disturbance in eruption of the lower second molar.

Adolescent↗
PubMed1994

Tooth movement following third molar removal.

The mandibular dental arches of 45 young adults (mean age = 24.3 years) were analyzed by measuring study casts taken immediately before and twelve weeks after the removal of impacted third molar teeth. Arch length and width were measured at predetermined points on the study casts. The results showed significant buccal movement of mandibular second molar teeth following surgery (p < 0.01). Bilateral mesioangular impactions were associated with larger increases in mandibular arch width following surgery than unilateral mesioangular impactions or other classes of impaction (p < 0.05). The greatest amount of tooth movement was observed in cases where mandibular second molars had a pre-operative lingual inclination. It is hypothesised that mesioangularly impacted mandibular third molars can produce sufficient force to displace the adjacent second molar teeth in a lingual direction and when the adjacent third molar is removed this movement is reversed by functional forces.

Adolescent↗
PubMed1993

Study on morphology of mandibular corpus and ramus influencing the eruption of mandibular first permanent molar.

The mandibular first permanent molar has been reported to be the first permanent tooth to erupt. However, according to the recent reports, a considerable increase in the number of children has been observed with the eruption of the mandibular first permanent molar after the eruption of the mandibular central incisor. The purpose of this study is to investigate whether there is any morphological difference in the mandible including the mandibular corpus and the ramus between the subjects with the mandibular first permanent molar erupting prior to the mandibular central incisor (Group A) and the subjects with the mandibular central incisor erupting prior to the mandibular first permanent molar (Group B). Lateral, posteroanterior, 45-degree oblique cephalometric radiographs and dental plaster models were used as the materials. Based on the data statistically analyzed, the results are summarized as follows: 1. No significant differences were found in the conventional angular lateral cephalometric measurements between the two groups. 2. No significant difference was found in the mandibular length between the two groups. 3. Significant differences were found in the mandibular corpus and the ramus between the two groups. In other words, the children in Group A have a narrower ramus, longer corpus and a larger eruption space for the mandibular first permanent molar than the children in Group B. These results indicate that even though there was no significant difference in the anteroposterior dimension of the mandible between the two groups, the internal proportion of the mandible represented as the ratio between the corpus and ramus was significantly different. This may suggest that the different proportional constituents of the mandible have a close relationship with the eruption timing of the mandibular first permanent molar.

Cephalometry↗
PubMed1993

An investigation of accessory foramina in furcation areas of human primary molars: Part 1. SEM observations of frequency, size and location of accessory foramina in the internal and external furcation areas.

Although the existence of accessory foramina in the furcation area and roots of permanent teeth has been demonstrated, the presence of accessory foramina in furcation areas of primary molars is less certain. This investigation was conducted to determine the presence or absence of accessory foramina in the furcation areas of human primary molars using the scanning electron microscope (SEM). Twenty extracted, carious and noncarious human primary molars were placed in fixative and then mounted in a hard tissue cutting machine: ten teeth were cut transversely 2.0mm coronal to the floor of the pulpal chamber and ten teeth were cut transversely 2.0mm apical to the external furcation. Both the internal and external furcation surfaces of these sectioned molars were debrided with sodium hypochlorite/hydrogen peroxide solutions to remove organic materials, which might obscure visibility of possible foramina and then rinsed in water and dried. The tissues were then prepared for and examined by SEM. Twenty percent of the molars examined by SEM on the internal furcation surface and 50% of the molars examined by SEM on the external furcation surface demonstrated accessory foramina.

Child↗
PubMed1996

Congenitally absent third molars in 12 to 16 year old Singaporean Chinese patients: a retrospective radiographic study.

Third molars have been associated with a host of pathologies and there are risks involved with their surgical removal. They also have the highest incidence of congenital absence of all the permanent teeth. The aim of this study was to determine the prevalence and distribution of congenitally missing third molars in local Chinese patients. The orthopantomographic radiographs of 786 Singaporean Chinese patients aged 12 to 16 years were examined. It was found that 562 (71.5%) of the children had all 4 third molars. Varying degrees of third molar agenesis were noted in the other 224 (28.5%) children. Of these, 43 (5.5%) showed total absence of third molars. There was no significant difference in agenesis between the right and left sides and no sexual predilection was noted. However, more third molars were missing from the maxilla compared to the mandible, the ratio being 3:2.

Adolescent↗
PubMedDate not supplied

Alveolar bone height of primary and first permanent molars in healthy seven- to nine-year-old children.

The purpose of the study was to establish baseline values of the alveolar bone height of the primary molars and first permanent molars in sample of healthy U.S. seven- to nine-year-old children. Direct measurements of the distance from the cementoenamel junction (CEJ) to the alveolar crest (AC) on 223 pairs of bitewing radiographs from 223 subjects were made using a digimatic caliper under standardized conditions. The distance from the CEJ to the AC had medians from 0.58 mm to 1.39 mm (range 0.0 to 4.44 mm) for the primary molars and from 0.00 mm to 0.64 mm (range -1.35 to 2.15 mm) for the mesial aspect of the permanent molars. There were no statistically significant differences in the distance from CEJ to AC between teeth on the right and left sides of the mouth. The distances from CEJ to AC were always greater in the maxilla than in the mandible for similar primary molar sites, but only true for the mesial aspect of the permanent first molar at age nine. As a tooth is positioned more anteriorly in the mouth, the distance from CEJ to AC was greater. On the whole, males had greater distances than females and eight-year-olds had larger distances than seven- or nine-year-olds. Differences were observed in the measured distances for the different age and sex-groups and may be attributable to variations in eruption and exfoliation patterns. The distance was significantly greater in areas of interproximal restorations and open contacts, and there was a tendency for the distances to be greater in areas of interproximal caries.

Alveolar Process↗
PubMed1997

Follow up after root canal treatment of young permanent molars.

The purpose of the present study was to assess the success of root canal treatment in permanent molars of children and adolescents. Twenty-eight endodontically treated first permanent molars of 18 patients aged 8 to 16 years at the time of treatment were examined. The age of the patient at the time of treatment ranged from 8 to 16 years (mean age 12.4 +/- 2.3). The majority of the treatments were done on the mandibular teeth (67%). Nine patients had one treated molar, eight patients had two treated molars and one patient had three treated teeth. None of the patients had all four molars treated. The time elapsed from the root canal treatment until our examination ranged from 24 months to 77 months (mean time 45.1 +/- 19.1). The examination included clinical and radiological parameters as follows: sensitivity to percussion, mobility, quality of restoration (contact point reproduced, overhang, secondary caries), periapical lesions before and after treatment, external root resorption, furcation involvement and interproximal bone resorption. Treatment was considered completely successful if no pathology was found. Only 10 teeth (36%) demonstrated complete treatment success, less than previously reported. No significant differences between mandibular and maxillary teeth were found with respect to any of the variables. The results suggest that considering a number of multidisciplinary criteria for assessing success of root canal treatments in first permanent molars of children and young adolescents is essential, and provides a realistic success rate.

Adolescent↗
PubMed1997

Occlusal migration of the maxillary first primary molars subsequent to the loss of antagonists.

The purpose of this study was to observe the vertical changes in unopposed maxillary first primary molars longitudinally. The subjects of this study were 17 children whose lower first primary molars had to be extracted. Space closure were prevented by crown-loop space maintainers for all these children. Plaster casts were made every 4 months for 16 to 24 months after the extraction. These series of casts were standardized, and vertical changes of the maxillary first primary molars against the occlusal plane were measured using a micro-reader. The mean changes indicated that maxillary first primary molars without intercuspidation tend to drift toward the extraction space. On the control side with antagonists, the maxillary first molars seemed to move reversed to apical throughout the observation period. Accordingly, the results of this study showed new trends after the premature loss of primary molars. The vertical changes toward extraction space varied from -0.40 mm to 1.43 mm at the 16 months after extraction. Mean changes were small, but there were some individual differences in reaction, giving negative values. However, we should always be concerned about loss of arch length and also occlusal drift of unopposed teeth, because the vertical changes were greater than 1 mm at 16 months after extraction in some cases.

Child↗
PubMed1998

The relationship between dental health and variations in the level of third molar removals experienced by populations.

OBJECTIVE: To determine the relationship between the dental health of populations and the removal of impacted third molars. DESIGN: Data were obtained for the reported episodes of care undertaken in NHS hospitals in England for the surgical removal of third molar teeth and also for the number of removals undertaken in NHS general dental practices in 1994/95. The dental health of the population within the at risk age group for removal of third molars was estimated by using the results of a large scale epidemiological study of twelve-year-old children which took place in 1988/9. The 12-year-old cohort examined would have been 18 years of age in 1994/95. The hospital and general practice data were standardised for age and size of health authority populations and combined on a weighted basis. SETTING: Data were identified which enabled levels of third molar surgery undertaken in the NHS for 23 health authorities in England, to be matched to the estimated dental health of their 18 year old populations. RESULTS: A negative correlation of r2 = 0.24 was demonstrated between the reported prevalence of third molar surgery and the dental health of populations. Surgery increased as the dental health of populations improved. CONCLUSIONS: This study demonstrates that a quarter of the variations in the provision of third molar surgery across health authorities in England is related to differences in the dental health of their populations.

Adolescent↗
PubMed1998

Space changes after premature loss of the mandibular primary first molar: a longitudinal study.

The purpose of this study was to evaluate the space changes after premature loss of the primary mandibular first molar. Twenty-one children (12 boys and 9 girls), with premature loss of the primary mandibular first molar, were selected from the children's dental clinic for this study. The age ranged from 5.1 to 7.2 years with an average of 6 years and 11 months. Mandibular study casts were made from alginate impression for each initial examination and a follow-up examination eight months later. Four measurements including D+E (first and second primary molars) space, arch width, arch length and arch perimeter were tested for comparisons between the initial examination and the follow-up examination eight months later. The D+E space of intact primary molars served as a control. The results showed that the D+E space on the extraction side after the follow-up examination eight months later was significantly shorter than the control side (p = 0.025) and less than the initial D+E space (p < 0.001). However, there were no significant differences on arch width, arch length, and arch perimeter between the initial examination and the follow-up examination eight months later (p > 0.05). It is concluded that the space change after the eruption of the first permanent molar in the mandible is mostly distal movement of the primary cuspid during the early stage of premature loss of the primary first molar.

Child↗
PubMedDate not supplied

Performance of sealants applied to first permanent molars in a dental school setting.

PURPOSE: The purpose of this study was to assess the performance of sealants placed by senior dental students as part of a comprehensive dental care program that included periodic patient recall. METHODS: The dental records of 100 patients ranging in age from 6 to 13 years were selected for review to determine the treatments provided for first permanent molars over time. Criteria for inclusion were: 1) at least five documented recall examinations and 2) all four first permanent molars had to have been treated with an occlusal pit and fissure sealant. The data collected included: 1) the age of the patient at the time of initial sealant placement; 2) the subsequent treatment provided to the first permanent molars, including retreatment with sealant or restoration and the date the services were provided; 3) the last date of follow-up examination in the pediatric dental program. RESULTS: A total of 400 molars were followed for an average of 54 months. Fifty-two percent of all molars received no further treatment after initial placement of sealant. Approximately 35% received retreatment with sealant only. The total number of molars receiving sealant material only was 343 (86%). The total number of teeth that were judged to require restoration was 57 (14%). No relationship was noted between the patient's age at placement of the occlusal sealant and sealant performance. CONCLUSION: In a dental school clinic, occlusal sealants were effective at preventing caries in a comprehensive care program that included periodic recall.

Adolescent↗