• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.12 no.1
• /
• pp.57-61
• /
• 1982

The author has made a study on the classification of the mandibular 3rd molars of Korean youths through dental radiography by means of Pell & Gregory's classification and on the prevalence of the dental caries of distal surface of the mandibular 2nd molar adjacent to the mandibular 3rd molars turned anteriorly. The results are as follow; 1. It was found that the largest case number was class I (272 cases, 52.9%) in the relation of the tooth to the ramus of the mandible and 2nd molar. 2. The mesio-angular position was the largest number (239 cases, 46.5%) in the relation of the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 3. The mesio-angular position of class I was the largest number (140 cases, 27.2 %) in the relation of the tooth to the ramus of the mandible and 2nd molar and the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 4. The average angle of the long axis of mandibular 3rd molar in mesioangular position or horizontal position to the occlusal plane was 143° 5. Mandibular 3rd molar with lesion such as dental caries or pericoronitis was 73 cases (14.2). 6. The caries incidence rate of the distal surface of the 2nd molar was about 3.1%.

• The korean journal of orthodontics
• /
• v.17 no.2
• /
• pp.321-333
• /
• 1987

The purpose of this study was to observe the changes of the lower 3rd molars following the extraction of the lower 2nd molars by Lateral Cephalograms and Orthopantomograms. The subjects consisted of twenty malocclusion, 7 males 13 females, were 19 year 5 month old at the removal of the lower 2nd molars, 19 year 1 month old at the end of the orthodontic supervision after the removal of the lower 2nd molars (mean age) The obtained results were as follows, 1 It is recommended to extract the lower 2nd molars when the lower 3rd molars are Nolla's Stage 4 or 5 2 With the pre-extraction variables obtained by factor analysis, it was possible to predict the long axis of the lower 3rd molars after 2nd molar extraction. 3 There were no impacted 3rd molars.

• The Journal of the Korean dental association
• /
• v.55 no.2
• /
• pp.128-138
• /
• 2017

Objective: The aim is to evaluate the potential of the mesiodens through the comparative inorganic analysis of 3rd molar teeth prior to clinical study. Material and methods: The extracted mesiodens and the 3rd molar teeth were prepared. The teeth are prepared as in the process of the autogenous tooth bone graft. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis was performed for inorganic analysis. Results: Rough and porous surfaces were observed in all materials in SEM analysis. Ca/P ratio of mesiodens was 1.55 and the 3rd molar was 1.22 in EDS analysis. XRD analysis shows that the 3 main peaks position were similar. This means that the graft materials are very similar to that of the crystallinity. Conclusions: The mesiodens and the 3rd molar teeth are very similar to the inorganic component. These results provide the reasonable rationale that mesiodens can be used as autogenous tooth bone graft in a clinic.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.33 no.1
• /
• pp.25-33
• /
• 2017

The lower $2^{nd}$ molar eruption is beginning to mesiolingually, then rotate to distobuccally so it has a tendency to be tilted and impacted mesially. Signs and symptoms of impacted $2^{nd}$ molar are similar to impacted $3^{rd}$ molar's. However, treatment plan for impacted $2^{nd}$ molar is different from that of impacted $3^{rd}$'s. The former is the preservation and uprighting of $2^{nd}$ molar so that it could act to recovery of mastication, symmetrical facial growth, maintaining the symmetry of dental arch, stable occlusion, while the latter is the extraction of tooth. If the uprighting treatment is planned, most proper protocol of treatment and the additional treatment opition should be applied with consideration for it's crown exposure, present of $3^{rd}$ molar which interrupt the uprighting process, extrusion of opposite tooth. Although it could not improve the esthetic result, it could prevent many dental problems. Therefore, uprighting for impacted lower $2^{nd}$ molar is meaningful treatment.

• The korean journal of orthodontics
• /
• v.24 no.4 s.47
• /
• pp.841-849
• /
• 1994

This study was conducted on 342 patients(male 157, female 185)aged 8 to 15 years old, who visited Dankook University Dental Hospital. Pre-orthodontic treatment orthopantomograms were used to assess the dental calcification stages of mandibular 3rd molar, 2nd molar, 2nd premolar and 1st premolar by 8 stages.(by Demirjian) Hand-wrist radiogrms were used to evaluate the skeletal maturity in 11 stages.(by Fishman) Following results were obtained after investigating the correlationship between dental calcification and skeletal maturity 1. Chronologic age showed high correlation to dental calcification and skeletal maturity. 2. Dental calcification and skeletal maturity showed high correlation and no statistical difference was observed between male and female. 3. SMI stages 1 to 4 showed high statiscal significance to mandibular 2nd molar, 2nd premolar and 1st premolar. SMI stages 5 to 8 showed high stastical significance to mandibular 2nd molar, 2nd premolar. SMI stages 9 to 11 showed high statistical significance to mandibular 3rd molar.

• The Journal of the Korean dental association
• /
• v.10 no.3
• /
• pp.169-171
• /
• 1972

Mr. yoon, 1 20 years old man, in good health, was treated for unhealing the extraction wound, pus discharge and sensation of dull pain on maxillary 2nd molar areas. Roentgenographic examination showed unerupted 3rd molar in left maxillary sinus. The tooth was located immediatly under the zygomatic bone and directed to median line. Radical operation of its sinusitis and extraction of the impacted wisdom tooth were performed by Caldwell-Luc's operation technique. In morphological aspects, the tooth has resemblance to normal wisdom tooth.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.22 no.2
• /
• pp.185-193
• /
• 1992

The purpose of this study was to evaluate the prevalence and distribution of tooth number anomaly by means of the analysis of panoramic radiographs in 6,531 patients visited the Dental Infirmary of Kyungpook National University Hospital from January 1983 to May 1992. The results were as follows: 1. The prevalence of congenitally missing teeth except third molar was revealed to be 10.8%, and there was a hihger prevalence in females(44.6%) than in males(55.4%). Mandibular 2nd premolars(23.2 %) were absent most frequently, followed by maxillary lateral incisors(18.4 %), mandibular lateral incisors(18.3%), and maxillary second premolars(15.4 %) in descending order of frequency. As to the number of congenitally missing teeth, the percentage of missing one tooth was 48%, missing two teeth was 35.4 %, missing three teeth was 6.6%. 2. he prevalence of congenitally missing third molars was revealed to be 39.7%. There was a higher prevalence n the maxilla(60.3%) than in the mandible(39.7%). Maxillary right 3rd molars(30.6%) were absent most frequently, followed by maxillary left 3rd molar(29.7%), mandibular right 3rd molar(202%), mandibular left 3rd molar(19.5%) in descending order of frequency. 3. The prevalence of supernumerary teeth was revealed to be 4.2%, and there was a higher prevalence in males(65.7%) than in females(34.3 ). They were ound most frequently in maxillary central incisor area(64.8%), followed by maxillary lateral incisor area(132%), posterior area of maxillary third molar(8.7%) in descending order of frequency. As to the number of supernumerary teeth; The percentage of one supernumerary tooth was 79.9%, two supernumerary teeth was 8.9%, three supernumerary teeth was 1.2 %.

• The Journal of the Korean dental association
• /
• v.13 no.6
• /
• pp.559-562
• /
• 1975

This is a case of the patient, a 15 -year-old girl, presented a marked necrotic osteomyelitis due to misusage of the arsenic compound for devitaliaztion of the lower right 2nd molar in the right posterior part of the mandible. She was obtained good satisfactory results by sequestrectomy of necrotic bone and by removing of lower right 2nd molar and unerupted 3rd molar tooth germ.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.4
• /
• pp.338-343
• /
• 2002

In this study, $Pb_{0.88}(La_{\alpha}Nd_{1-\alpha})_{0.08}(Mn_{1/3}Sb_{2/3})_{0.02}Ti_{0.98}O_3$ system ceramics with La molar ratio $\alpha$ variation were manufactured for 24 MHz class resonator application. Electromechanical coupling factor, mechanical quality factor and dynamic range of $3^{rd}$ overtone thickness vibration mode were measured as the variations of La and Nd molar ratio. Mechanical quality factor and dynamic range at $\alpha$ = 0.6 composition ceramics showed the highest value of 2691 and 52.37 dB, respectively. The temperature coefficient of resonant frequency measured from $-20^{\circ} to 80^{\circ}$ showed an excellent value of $5ppm/^{\circ}C$ at $\alpha$=1 composition ceramics.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.11 no.1
• /
• pp.25-39
• /
• 1984

The author has sought to determine the time and the sequence of permanent teeth eruption in Korean children. The study group consisted of 15,671 healthy children (male 8,015 ; female 7,656) aged 5-13 years old who lived in Seoul or Cheongju. The results were as follows : 1. The eruption times of permanent teeth were 0.45 years earlier in females than in males. 2. The ages corresponding to $ER_{50}$ of permanent teeth were as follows : In Maxilla 1) central incisor was 7.37 yrs 2) lateral incisor was 8.50 yrs 3) canine was 10.83 yrs 4) 1st premolar was 10.30 yrs 5) 2nd premolar was 11.09 yrs 6) 1st molar was 6.49 yrs 7) 2nd molar was 12.79 yrs In Mandible 1) central incisor was 6.40 yrs 2) lateral incisor was 7.41 yrs 3) canine was 10.18 yrs 4) 1st premolar was 10.26 yrs 5) 2nd premolar was 11.15 yrs 6) 1st molar was 6.32 yrs 7) 2nd molar was 12.05 yrs 3. The eruption sequence of permanent teeth by Z-test was as follow: In Male 1st : Mandibular 1st molar, and Mandibular central incisor 2nd : Maxillary 1st molar 3rd : Maxillary central incisor 4th : Mandibular lateral incisor 5th : Maxillary lateral incisor 6th : Mandibular canine, Maxillary and Mandibular 1st premolar 7th : Maxillary canine 8th : Maxillary and Mandibular 2nd premolar 9th : Mandibular 2nd molar 10th : Maxillary 2nd molar In Female 1st : Mandibular 1st molar, and Mandibular central incisor 2nd : Maxillary 1st molar 3rd : Mandibular lateral incisor, Maxillary central incisor 4th : Maxillary lateral incisor 5th : Mandibular canine, Maxillary and Mandibular 1st premolar 6th : Maxillary canine 7th : Maxillary and Mandibular 2nd premolar 8th : Mandibular 2nd molar 9th : Maxillary 2nd molar 4. The corresponding permanent teeth in the mandible generally erupted earlier than the corresponding permanent teeth in the maxilla by an average of 0.73 years, but the mean eruption time of mandibular 1st premolars was almost the same as those of maxillary 1st premolars, and the mean eruption time of mandibular 2nd premolars was 0.06 years later than those of maxillary 2nd premolars. 5. There is no significant difference between left and right arch in the eruption time and sequence. 6. Generally, the ages of permanent teeth eruption tended to be earlier than those of Dr. Cha's data from 1963.