• 구강회복응용과학지
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• 제16권2호
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• pp.79-92
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• 2000

The purpose of this study was to estimate the morphology and the size of permanent maxillary molar in Korean Adult. The 100 dental college students with a normal dentition and without any dental prosthesis and severe caries were selected for this study. The subjects were taken impression to make study model. On the study model, authour three times measured those sizes and estimated morphological structures with a calipers, a Boley gauge and a protractor. The results were as follows; 1. In the maxilary first molar's clinical crown height, mesiolingual cusp height was 6.34mm, mesiobuccal cusp height was 6.05mm, distobuccal cusp height was 5.20mm. And in the maxillary second molar's clinical crown height, mesiobuccal cusp height was 5.85mm, mesiolingual cusp height was 5.71mm, distobuccal cusp height was 5.51mm, distolingual cusp height was 3.53mm. This result considered that the maxillary first molar inclined to distobuccal, and the maxillary second molar more upright than the maxillary first molar. 2. In the width of clinical crown, the maxillary first molar was 10.43mm, the maxillary second molar was 10.20mm, and the difference between the first molar's width and the second molar's width was 0.23mm. 3. The crown thickness was measured divided into mesial buccolingual half and distal buccolingual half. The mesial buccolingual half was 11.14mm, and distal buccolingual half was 10.35mm in the maxillary first molar, and in the maxilary second molar, mesial buccolingual half was 11.25mm, and distal buccolingual half was 9.72mm. This result considered that height of convergency located in mesial half of crown. 4. In the buccal groove length, total length and ratio, the maxillary first molar was 52.5%, the maxillary second molar was 50%. And the development of buccal groove in the maxillary first molar was 59% in case of the well developed buccal groove and 41% in case of the weak developed one. And frequency of buccal pit of the maxillary first molar was 12.5%. Whereas, the frequency of buccal of the well developed buccal groove in the maxillary second molar was 37% and that of the weak developed one was 63%. And frequency of buccal pit of the maxillary second molar was not seen. 5. The 3 cusp type tooth cannot be found in the maxillary first molar and the frequency of 3 cusp type tooth in the maxillary second molar was as small as 6% 6. In the case of 4 cusp type tooth, the size of distal lingual cusp molar was difference between in the maxillary first molar and in the maxillary second molar by about 1mm. 7. The intercuspal distance was similar in the maxillary first premolar and second molar. And intercuspal distanc of mesial half of the maxillary first molar and the maxillary second molar was silmillar, too. 8. The an measurement of occlusal surface in 4 cusp type tooth showed that the angle of occlusal surface between the distobuccal and mesiolingual was an obtuse angle, and the angle of occlusal surface between mesiobuccal and distolingual was an acute angle in the both cases of maxillary first and second molar. 9. The measurements of the development of Carabelli cusp showed that the frequency of the well developed one was 7% and that of the weak developed one was 56% in the maxillary first molar. And there cannot be found the well developed one and can be found 2.5% only in the case of the weak developed one in the maxillary second molar. 10. The well developed oblique ridge in the maxillary first molar showed the 100% frequency and that in the maxillary second molar showed the 85.5% frequency. The frequency of mesiomarginal ridge tubercle in the maxillary first molar was 82% and that in the maxillary second molar was 30.5%. And the frequency of distal accessory tubercle in the maxillary first molar can be seen about 19% and that in the maxillary second molar can be seen about 12%.

• 대한소아치과학회지
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• 제21권2호
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• pp.486-490
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• 1994

Maxillary first molar is the key in normal occlusion. Mesial drifting of maxillary first molar result form early loss of second deciduous molar. Mesial drifted maxillary first molar was treated by headgear, Hawley appliance with screw, brasswire, etc. But, these appliance should be necessary for patients cooperation. Recently, several appliance for molar distalizing without patients cooperation has been introduced. We are reporting in this paper about distalizing of mesial drifted maxillary first molar because of early loss of deciduous second molar by open coil jig. Distalization of molar by open coil jig is predictable, rapid, painless method without mecesscity of patient cooperation.

• 대한치과교정학회지
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• 제11권2호
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• pp.101-108
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• 1981

This investigation was designed to compare the calcification degree of maxillary second permanent molar to mandibular second permanent molar in skeletal Class III Malocclusion. The material selected for this study consisted in standand lateral cephalogram study model and orthopantomogram of two hundred fifty seven Korean Children, one hundred twenty one boys and one hundred twenty four girls, aged 6 through 12 years, having skeletal Class III Malocclusion. On the basis of findigs of this study, the following results were obtained 1. In the stage of completion of crown, there was no significant difference in calcification degree between maxillary second molar and mandibular second molar of both boys and girls in skeletal Class III Malocclusion. 2. From 8 years of age at the stage of beginning root formation to 12 years of age, the calcification degree of mandibular second molar was more advanced than Maxillary second molar of both boys and girls in skeletal Class III Malocclusion.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.46.1-46.8
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• 2020

Objectives: This study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT). Materials and Methods: A total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at -1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t-test. Results: The prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and -3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar. Conclusions: The angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice.

• Restorative Dentistry and Endodontics
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• 제47권3호
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• pp.33.1-33.10
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• 2022

Objectives: This study aimed to analyze the proximity of maxillary molar roots to their overlying cortical bone surfaces and the maxillary sinus. Materials and Methods: Cone-beam computed tomographic images of 151 patients with completely erupted upper molars that had 3 separate roots were studied. The following distances were measured: from the root apex to the cortical plate and maxillary sinus floor, and from the apical 3-mm level of the root to the cortical plate. Differences between groups were analyzed with 1-way analysis of variance and the Scheffé post hoc test, the significance of differences between cone-beam computed tomography views with the paired t-test, and the significance of differences among age groups with linear regression analysis. The significance level was set at p < 0.05. Results: The mesiobuccal and distobuccal root apexes of maxillary second molars were more distant from the buccal cortical plate than the maxillary first molars (p < 0.05). The apical 3-mm level of the mesiobuccal root of the first molar was closer to the buccal cortical bone than the second molar (p < 0.05). In the maxillary first molars, the thickness of the buccal cortical bone decreased in all roots with age (p < 0.05). In all root apexes of both molars, the difference in the vertical level between the maxillary sinus floor and the root apex increased with age (p < 0.05). Conclusions: Awareness of the anatomical profile of maxillary molar apices in relation to the cortical bones and maxillary sinus will be beneficial for apical surgery.

• 대한치과교정학회지
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• 제25권3호
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• pp.299-310
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• 1995

이 연구의 목적은 교정치료시 제2대구치의 위치변화를 알아보기 위함이다. 이를 위하여 제1대구치까지 banding하여 교정치료를 완료한 성인환자 64명을 Class I 발치군 15명, Class I 비발치군 12명, Class II 13명, Class III 14명으로 4개의 군으로 분류하고 치료전후의 두부방사선 계측사진을 분석하였다. 이 연구로부터 얻어진 결과는 다음과 같다. 1. Class I 발치군에서 하악 제2대구치는 제1대구치보다 적은 정출과 더 많은 원심경사를 보였고, 상악 제2대구치는 제1대구치와 유사한 정출과 근심경사를 보였다. 2. Class I 발치군에서 하악 제2대구치는 제1대구치에 비해 함입되고 유사한 원심경사를 보였으며, 상악 제2대구치는 제1대구치와 비슷하게 정출되었다. 3. Class II군에서 하악 제2대구치는 제1대구치에 비해 적은 정출을 보였고, 상악 제2대구치는 제1대구치보다 많은 정출을 보였다. 4. Class III군에서 하악 제2대구치는 제1대구치와 유사한 정출과 더 많은 원심경사를 보였으며, 상악 제2대구치는 제1대구치에 비해 적은 정출을 보였다. 5. 제2대구치 위치변화에 대한 각 군간의 비교시 FH plane에서 상악 제2대구치 치근 분기점까지 거리 변화는 Class I 발치군과 Class II, Class I 발치군과 Class III군에서 차이를 보였으며, 구개평면과 교합평면에 대한 상악 제2대구치의 각도 변화는 Class I 발치군과 Class III군에서 차이를 보였으며, 하악평면에 하악 제2대구치 치근분기점까지 거리변화는 Class I 발치군과 비발치군, Class I 비발치군과 Class II군, Class I 비발치군과 Class III군에서 차이를 보였으며, 하악 평면과 교합평면에 대한 하악 제2대구치의 각도 변화는 각 군간에 차이를 보이지 않았다.

• 대한치과교정학회지
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• 제43권5호
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• pp.218-224
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• 2013

Objective: To examine the effect of bite force on the displacement and stress distribution of orthodontic mini-implants (OMIs) in the molar region according to placement site, insertion angle, and loading direction. Methods: Five finite element models were created using micro-computed tomography (microCT) images of the maxilla and mandible. OMIs were placed at one maxillary and two mandibular positions: between the maxillary second premolar and first molar, between the mandibular second premolar and first molar, and between the mandibular first and second molars. The OMIs were inserted at angles of $45^{\circ}$ and $90^{\circ}$ to the buccal surface of the cortical bone. A bite force of 25 kg was applied to the 10 occlusal contact points of the second premolar, first molar, and second molar. The loading directions were $0^{\circ}$, $5^{\circ}$, and $10^{\circ}$ to the long axis of the tooth. Results: With regard to placement site, the displacement and stress were greatest for the OMI placed between the mandibular first molar and second molar, and smallest for the OMI placed between the maxillary second premolar and first molar. In the mandibular molar region, the angled OMI showed slightly less displacement than the OMI placed at $90^{\circ}$. The maximum Von Mises stress increased with the inclination of the loading direction. Conclusions: These results suggest that placement of OMIs between the second premolar and first molar at $45^{\circ}$ to the cortical bone reduces the effect of bite force on OMIs.

• 대한치과교정학회지
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• 제43권2호
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• pp.101-109
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• 2013

Objective: To evaluate the efficiency of the Frog appliance (FA) alone or in combination with headgear for distalizing the maxillary molars. Methods: Fifty patients (25 males and 25 females) aged 12.6 - 16.7 years who received treatment for Class II malocclusion at the Orthodontic Clinic of Al-Baath University were selected for this study and randomly divided into 2 equal groups. Maxillary molar distalization was achieved using the FA alone (group 1) or a combination of the FA with high-pull headgear worn at night (group 2). Lateral cephalograms were obtained before and after treatment. Results: The maxillary molars moved distally by 5.51 and 5.93 mm in groups 1 and 2, respectively. Distal movements were associated with axial tipping by $4.96^{\circ}$ and $1.25^{\circ}$, and with loss of anchorage by mesial movement of the second maxillary premolars by 2.70 and 0.90 mm in groups 1 and 2, respectively. The combined use of the FA and nighttime high-pull headgear decreased the distalization time and improved the ratio of maxillary molar distalization movement relative to the overall opening space between the first maxillary molars and second premolars. Conclusions: The FA can effectively distalize the maxillary molars, this distalization associates with some unfavorable changes. Nighttime use of high-pull headgear combined with the FA can reduce these unfavorable changes and improve treatment outcomes.

• 대한소아치과학회지
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• 제43권3호
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• pp.284-291
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• 2016

본 연구는 이소맹출한 상악 제1대구치의 자율적 수정 가능성을 예측할 수 있는 진단적 기초를 제공하기 위하여 정상군과 가역성과 비가역성 이소맹출의 차이점을 비교 평가하고자 후향적으로 분석하였다. 상악 제1대구치와 인접치아 간의 장축과 교합평면간의 각도를 파노라마상에서 측정하였고, 제2유구치의 교합관계도 조사하였다. 이소맹출군과 정상군은 통계학적으로 유의한 차이를 보였지만(p < 0.05), 가역성과 비가역성 이소맹출군 간에는 통계학적으로 유의한 차이는 없었다(p > 0.05). 제2유구치와 제1대구치 그리고 제2대구치 치배 간의 각도는 정상군에 비해 이소맹출 군에서 작은 값을 보였으며, 근심 계단형이 이소맹출군에서 더 높은 빈도로 관찰되었다. 본 연구의 결과를 토대로 상악 제1대구치의 이소맹출은 상악 제1대구치와 제2대구치 치배의 각도와 관련이 있으며, 이소맹출한 상악 제1대구치는 상악 저성장의 3급 부정교합 환자에서 보다 빈번하게 나타나는 경향이 있는 것을 알 수 있었다.

• Journal of Periodontal and Implant Science
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• 제50권1호
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• pp.38-47
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• 2020

Purpose: The aim of this study was to investigate the available alveolar bone height between the maxillary molars and the sinus floor according to their anatomical relationship using cone-beam computed tomographic (CBCT) images. Methods: A total of 752 maxillary first (M1) and second molars (M2) on CBCT scans of 188 patients were selected. First, each maxillary molar was categorized as type 1, 2, 3, or 4 according to the relationship of the molar root with the maxillary sinus floor. The frequency distribution of each type was analyzed. Second, the shortest vertical distance (VD) of each molar was measured from the furcation midpoints of the roots to the lowest point of the sinus floor by 2 observers. Intraclass correlation coefficients and the t-test were calculated for the VD measurements. Results: For M1, type 3 was the most frequent, followed by type 2. For M2, type 3 was the most common, followed by type 1. The VD measurements of type 1 were 9.51±3.68 mm and 8.07±2.73 mm for M1 and M2, and those of type 3 were 3.70±1.52 mm and 4.03±1.53 mm for M1 and M2, respectively. The VD measurements of M2 were significantly higher in female patients than in male patients. Conclusions: Type 3 was the most frequent anatomical relationship in the maxillary molars, and showed the lowest alveolar bone height. This information will help clinicians to prevent complications related to the maxillary sinus during maxillary molar treatment and to predict the available bone height for immediate implant planning.