• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.130-135
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• 2010

Ectopic eruption is caused by an abnormal direction of eruptive path, most common in maxillary first molar, mandibular lateral incisor, and maxillary canine, and sometimes mandibular first molar. Ectopic eruption of first molar leads to abnormal root resorption of second deciduous molar, which, if left untreated, could cause premature loss of second deciduous molar; mesial tilting and rotation of first permanent molar; lack of space for eruption of second premolar; and occlusal problems. Therefore early treatment is advised when diagnosed as ectopic eruption. Treatment of ectopic eruption in the first permanent molar involves providing proper guidance for the direction of eruption using interproximal wedging and distal tipping methods while preserving second deciduous molar. This case report shows satisfactory results of the ectopic eruption of mandibular first molars in young patients who were treated with Humphrey appliance and Halterman appliance.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.287-300
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• 2018

The aim of this study was to compare the morphological characteristics of two types of stainless steel permanent molar crowns using three-dimensional scanners and the morphological changes of these crowns after crimping. Two types of stainless steel permanent molar crowns, PO-96 and PERMACROWN were scanned using three-dimensional scanner. Crown size, crown index (ratio of buccolingual diameter to mesiodistal diameter at height of contour), cervical convergency of crown were measured. Stainless steel crowns were crimped and re-scanned with three-dimensional scanner. Morphological changes of stainless steel permanent molar crowns were analyzed. As for the crown index, maxillary PERMACROWN was larger buccolingually and smaller mesiodistally than maxillary PO-96 and mandibular PERMACROWN was smaller buccolingually and larger mesiodistally than mandibular PO-96. Maxillary PO-96 was more convergent to cervical mesiodistally than maxillary PERMACROWN and mandibular PO-96 was more convergent to the cervical mesiodistally, buccolingually than mandibular PERMACROWN. Both types of stainless steel permanent molar crowns showed reduction of cervical circumference after crimping. Two products were morphologically different in crown size, shape and cervical convergence. Although both types of stainless steel permanent molar crowns are pre-contoured type, additional crimping is needed to achieve better marginal adaptation.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.226-232
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• 2010

Incidence of tooth impaction varies from 5.6 to 18.8% of the population. Failure of eruption of the first and second permanent molars is rare; the prevalence in the normal population is 0.01% in case of the first permanent molar, and 0.06% in case of the second permanent molar. Permanent molars are particularly important for providing sufficient occlusal support and co-ordinating facial growth. Failure of eruption of permanent molars may result in various complications such as decrease in vertical dimension, posterior open bite, extrusion of antagonistic teeth, resorption and inclination of adjacent teeth, formation of cyst and so on. Treatment options of impacted teeth are periodic observation, surgical exposure, surgical exposure with subluxation, orthodontic relocation, and surgical extraction before prosthetic treatment. Early diagnosis and treatment are important, because delayed treatment induces various problems such as decreased spontaneous eruptive force, decreased successful percentage, increased treatment period, increased various complications. Prevalence of the failure of mandibular first molars is rare but eruptive guidance before extraction of impacted teeth is necessary due to importance of permanent molars. We reported two cases of surgical exposure of impacted mandibular first molar. In these cases, we could observe different result of the impacted mandibular first molar after surgical exposure.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.574.1-574
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• 2001

Maxillary first molar, the "6-year molar", is the tooth largest in volume and most complex in root and root canal anatomy. Therefore, maxillary first molar is possibly the most treated, least understood. It is the posterior tooth with the highest endodontic failure rate and unquestionably one of the most important teeth. The earliest permanent posterior tooth to erupt, the mandibular first molar seems to be the most frequently in need of endodontic treatment.(omitted)

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.219-227
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• 2020

Tooth eruption involves a complex developmental process of tooth migration from the dental follicular origin to the final occlusion position in the oral cavity via the alveolar process. Disturbance of tooth eruption can occur at any point in a series of eruption stages; however, horizontal impaction of the mandibular first molar and primary retention of the primary mandibular second molar are rarely observed simultaneously. This study describes the treatment for two cases of horizontally impacted first molar with primary retention of primary molar. The primary retention of the primary mandibular second molar was extracted, and orthodontic traction was applied to the horizontally impacted primary mandibular first molar. Subsequently, displacement of the premolar tooth bud was improved and space regaining for eruption was achieved, guiding to normal eruption of the first molar.

• The Journal of the Korean dental association
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• v.21 no.12 s.175
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• pp.1005-1010
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• 1983

To study the eruption process of the permanent tooth, esp., 1st molar, the author took 303 cases of oblique cephalogram (Male. 162 cases, Female: 141 cases) from age 3 to 8 yea old children, and observed the vertical change and axial change. The result were as follow: 1. The mesial end of upper 1st molar was closer to the occlusal plane than the distal, and they were erupting toward the occlusal plane by aging. In the case of lower 1st molar, the distal end was closer to the occlusal plane than the mesial and the occlusion showed the tendency to accord with the plane to be settled by aging. 2. Eruption rate of the upper and lower 1st permanent molar increased rapidly at 5 or 6 years of age. 3. Axial inclination of lower 1st permanent molar to the mandibular plane decreased gradually from 3 years of age, except for 6 years of age. There was some increase at 5 or 6 years of age.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.2
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• pp.147-153
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• 2017

This study assessed the association between ectopic eruption of the maxillary first permanent molar and skeletal malocclusion in 5- to 10-year-old children. As subjects, 786 children who attended the Wonkwang University Dental Hospital for orthodontic diagnosis were included. Children with unerupted first permanent molars or fully erupted second permanent molars were excluded. The study group demonstrated ectopic eruption of the maxillary first permanent molar, while the control group did not. Cephalometric radiographs taken between January 2003 and August 2015 were analyzed. Skeletal class III malocclusion was detected in 57.0% of the study group, which differed significantly from that in the control group (p<0.05). The SNA, ANB angles, and A to N-perpendicular distance were significantly smaller, whereas the A-B plane angle and APDI were significantly greater in the study group than in the control group (p<0.05). The SNB and mandibular plane angles were not significantly different between the groups. Thus, maxillary undergrowth is a risk factor for ectopic eruption of the maxillary first permanent molar.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.98-102
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• 2000

Ectopic eruption is out of a normal position by local eruption disturbance in the developing permanent molar. The prevalence of ectopic eruption is reported to be the between 2 and 6%, most often associated maxillary first permanent molar whereas, the occurrence for the mandibular is quite rare. The etiologic factors of ectopic eruption are inadequate arch length, lack of growth in the posterior region of the jaw, mesially inclined eruption path of first permanent molars, abnormally large first permanent molars, hereditary factor and a stainless steel crown which has been improperly restored. Ectopic eruption can be treated by the use of brass wire, separating elastics, distal disking and Humphrey appliance and the use of removable appliance and cervical traction headgear after extraction of the second primary molar. This case was that lower right first permanent molar was mesially tilted state by locking on the stainless steel crown of a lower right second primary molar. The stainless steel crown was removed and Humphrey appliance was set. Like this case, ectopic eruption could be happened by the stainless steel crown which improperly restored. In restoration of the stainless steel crown, selection of proper size, trimming and contouring are very important.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.15 no.1
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• pp.67-74
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• 1985

The incidence and associated dental abnormalities of taurodontism were studied radiographically (panoramic view) in 1895 patients of deciduous dentition and 2167 patients of permanent dentition who had visited to the Department of Oral Radiology, Kyung Hee University in Korea. The obtained results were as follows: 1. The prevalence of taurodontism was 3.59% in the deciduous dentition group, and 1.8% in the permanent dentition group. 2. There was no definite sex difference in the deciduous dentition, and the permanent dentition group. The type of mesotaurodontism was predominent in the deciduous dentition group, and hypotaurodontism in the permanent dentition group. 4. The vast majority of this abnormalities had occurred in the mandibular 1st deciduous molar in the deciduous dentition group, and mandibular 2nd permanent molar in the permanent dentition group. 5. Of the cases with taurodontism, the deciduous dentition group revealed 95.6% bilaterally, and 82% bilaterally in the permanent dentition group. 6. Multiple teeth occurance, not single tooth only, were involved in 98.5% of the cases in the deciduous dentition group, and 82% in the permanent dentition group.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.89-100
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• 2005

The purpose of this study was to analyze the morphometrics of primary second molar and permanent first molar. Samples were consisted of normal occlusion in the primary dentition(50 males and 50 females) and permanent dentition(43 males and 43 females). Their upper and lower plaster casts were used and their measuring points were decided, through 3-dimensional laser scanning(3D Scanner, DS4060, LDI, U.S.A.), fitting standard horizontal plane were made for measuring the intercuspal distance, volume of intercuspal area and section curve. The results were as follows; 1. Average distance from the fit plane to the cusp tips of mandibular primary second molar was smaller than any other tooth. (0.05-0.09 mm in male and 0.04-0.09 mm in female). 2. Intercuspal distances of mandibular primary second molar and permanent first molar were larger in male than in female. Especially, there was statistical significance in primary second molar(p<0.05). 3. Intercuspal distance between distobuccal and distolingual cusp was larger in maxillary primary second molar, except cross intercuspal distances. And distances between distal and distolingual cusp, in mandibular primary second molar, between mesiolingual and mesiobuccal cusp, in maxillary first molar, and between distolingual and mesiolingual cusp, in mandibular first molar were larger than any other intercuspal distance. 4. Volume of intercuspal area of primary second molar and permanent first molar was larger in mandible than in maxilla and that of permanent first molar was 1.40-1.75 times of primary second molar (p<0.05). Also it was larger in male than in female, but there was no statistical significance. 5. In most cases, section curves were wider and deeper in permanent dentition than in primary dentition. Except cross intercuspal distances, in maxilla, section curve between mesiobuccal and mesiolingual cusp was the deepest in both dentition. In mandible, section curve between distobuccal and distal cusp was the deepest in permanent dentition and between distolingual and distal cusp was the deepest in primary dentition.