• 대한소아치과학회지
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• 제10권1호
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• pp.77-83
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• 1983

The purpose of this study was to observe the microleakage of a pit and fissure sealant at the tooth-restoration interface. One hundred and sixty-seven extracted permanent and deciduous teeth were used and some simple mechanical pretreatment were done before etching. The degree of microleakage was assessed by $Ca^{45}$ after 24 hours, and 2 months. The results were as follows: 1. Among total 167 teeth, 53 teeth (32%) were demonstrated the microleakage. 2. After 2 months the leakage was increased from 22 percent to 35 percent in permanent teeth, and from 32 percent to 43 percent in primary teeth. 3. The group treated by fluoride paste was demonstrated the largest leakage, 50 percent in primary teeth and 33 percent in permanent teeth. There are more leakage in primary teeth (38%) than permanent teeth (28%).

• 대한소아치과학회지
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• 제24권3호
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• pp.487-494
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• 1997

It is rare to find multiple supernumerary teeth in individuals with no other associated diseases or syndromes. 'Non-Syndrome multiple supernumerary teeth' reviewed by Yusof(1990) have more frequency of occurrence in the mandibular region. Especially, mandibular premolar region appears to be the site of predilection for no n-syndrome multiple supernumerary teeth. Also, these may develop after most permanent teeth have erupted, thus their effect upon the occlusion is limited. In this case, the patient had 20 supernumerary teeth without other associated diseases or syndromes. All of the supernumerary teeth were impacted, and thirteen of them were found in the premolar region. In the radiographic and clinical finding, other specific complication resulted from the supernumerary teeth weren't observed.

• 치과방사선
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• 제15권1호
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• pp.41-49
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• 1985

The purpose of this study was to evaluate the initial and postoperative radiographic features of the endodontic treated teeth. The author examined the radiographs which comprise 114 teeth with 155 canals of 64 persons. The following factors were considered; Age, sex, tooth location, number of root canals, postoperative periods, initial diagnosis, and radiographic findings, postoperative radiographic findings. The apical levels of the root fillings were 76.8% to apex, 19.0% underfilling, 3.9% overfilling. The following results were obtained. 1. Of the 93 teeth which revealed initial periapical rarefaction, 66 teeth (71.0%) had showed complete bone healing, 19 teeth (20.4%) decreased rarefaction, 6 teeth (6.5%) no change, 2 teeth (2.2%) increased rarefaction after 20.0 months mean healing time. 2. 21 teeth which had no initial periapical rarefaction showed no occurrence of new periapical rarefaction. 3. Of the 66 teeth completely healed, 53 teeth (80.3%) had showed reappearance of lamina dura, 64 teeth (97.0%) reappearance of periodontal ligament space after 23.4 months mean healing time.

• Medical Lasers
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• 제10권4호
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• pp.214-219
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• 2021

Background and Objectives To evaluate the difference in near-infrared (810 nm) laser energy transmission through teeth with and without cracks. Materials and Methods Extracted teeth were sectioned and examined visually for the presence of cracks with the aid of photographs and a trans-illuminator. Fourteen sections, each with cracks (Group A) and no cracks (Group B) were identified and placed 15 mm from the tip of a 300 micron fiber, prior to activation with an 810 nm diode laser (0.1W, 50 ms interval,100 ms duration). A power meter positioned behind the tooth recorded the average energy that was transmitted through the samples. Unpaired t-test analysis was used to determine if the tooth sections with cracks allowed higher power passage compared to sound teeth. Results The mean power recording for the cracked teeth (Group A) was significantly greater (p = 0.0005) than that for the non-cracked teeth (Group B). Conclusion Within the limitations of this study, it is evident that significantly higher laser energy passes through teeth with cracks in comparison to teeth without cracks. A recent clinical study has also shown that lasers could be used to assess symptomatic cracked teeth. Hence, further research is required to determine the relative increase in energy required to identify symptomatic cracked teeth.

• Journal of Biosystems Engineering
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• 제13권4호
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• pp.9-19
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• 1988

The threshing of head-feed combine may be accomplished mainly by the action of impact between threshing teeth and rice. In this study, it was attempted to assess threshing performance characteristics of head-feed threshing teeth. And the characteristics of threshing teeth will be applied to the method which could analyze the time and order of impact between teeth and the rice, which was used as a basis for predicting the threshing performance and determining the optimum design parameters. The results of the study are summarized as follows: 1. About 50% of threshed material were threshed by the beginning 7 impacts on the rice bundle. Threshing torque decreased until 25 impacts and did not change thereafter. 2. There was significant difference in the threshability according to the shape of threshing teeth. The triangular-shaped tooth was the most efficient in threshability ratio and the semicircle-shaped tooth was the lowest. There was no significant difference in specific energy requirement for the varied teeth design. Torn-head ratio being generated by the semicircle-shaped and the triangular-shaped teeth in series was less than that by a single tooth with the triangular-shaped and the double setting of the triangular-shaped. Chaff generation ratio by the triangular-shaped and the semicircle-shaped teeth was less than the others tried. 3. The triangular-shaped teeth in series, which was newly designed for this study, showed an intermediate characteristics between the double setting of the triangular-shaped and the semicircle- shaped teeth. Threshability ratio of the triangular-shaped teeth in series was higher than that of the semicircle and lower than the double setting of the triangular-shaped tooth. Torn-head generation ratio for it was about same as that of the semicircle. Chaff being generated by the triangular-shaped teeth in series was about same as the double setting of the triangular-shaped teeth. 4. About 40% of threshed grains which passed through concave were concentrated under the threshing tooth and the rest of grains displayed a skew distribution toward the inlet of threshing chamber.

• 대한치과보철학회지
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• 제40권2호
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• pp.201-212
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• 2002

This study investigated the shear bond strengths between abrasion-resistant denture teeth and composite resins according to surface treatments. Denture teeth for this study were Trubyte IPN teeth(Dentsply Inc., USA) with interpenetrating polymer network and Endura Posterio (Shofu Inc. Japan) of composite resin teeth, and restorative composite resins were Clearfil FII (Kuraray, Japan) of the self-cured composite resin and Z100(3M Dental Product, USA) of the light-cured composite resin. Five different surface treatments were evaluated: (1) $50{\mu}m\;A1_2O_3$ sandblasting: (2) #100 carbide paper; (3) chloroform; (4) retentive holes; and (5) no treatment. After surface treatments, denture teeth were examined by scanning electron microscopy(SEM), and the maximum shear bond strengths between abrasion-resistant denture teeth and composite resins were measured using Instron. The results were as follows; 1. IPN teeth treated with sandblasting had the highest shear bond strength, and Endura treated with sandblasting and carbide paper had significantly greater shear bond strength than with any other surface treatment. 2. Regardless or composite resins, the shear bond strength on Endura was greater than on IPN teeth. 3. Regardless of denture teeth, the shear bond strength of Clearfil FII was greater han of Z100. 4. In appearance of SEM, IPN teeth treated with sandblasting showed generalized roughness on the all of surface, however, carbide paper treatment resulted in partly rough. Endura treated with sandblasting and carbide paper showed similar surface characteristics. Wetting denture teeth surface with chloroform removed the debris and created a particle-free and smooth surface.

• The Journal of Advanced Prosthodontics
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• 제11권3호
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• pp.187-192
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• 2019

PURPOSE. The purpose of this in vitro study was to investigate the fracture loads and modes of failure for the full range of natural teeth under simulated occlusal loading. MATERIALS AND METHODS. One hundred and forty natural teeth were taken from mandibles and maxillas of patients. There were 14 groups of teeth with 10 teeth in each group (5 males and 5 females). Each specimen was embedded in resin and mounted on a positioning jig, with the long axis of the tooth at an inclined angle of 30 degrees. A universal testing machine was used to measure the compression load at which fracture of the tooth specimen occurred; loads were applied on the incisal edge and/or functional cusp. RESULTS. The mean fracture load for the mandibular first premolar was the highest (2002 N) of all the types of teeth, while the mean fracture load for the maxillary first premolar was the lowest (525 N). Mean fracture loads for the mandibular and maxillary incisors, and the first and second maxillary premolars, had significantly lower values compared to the other types of teeth. The mean fracture load for the teeth from males was significantly greater than that for the teeth from females. There was an inverse relationship between age and mean fracture load, in which older teeth had lower fracture loads compared to younger teeth. CONCLUSION. The mean fracture loads for natural teeth were significantly different, with dependence on tooth position and the sex and age of the individual.

• 치위생과학회지
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• 제4권1호
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• pp.21-25
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• 2004

현대사회에서는 생활환경의 변화와 교통사고의 증가에 의해 해마다 소아의 외상의 증가하고 있는데 구강조직에 대한 외상성 손상을 완전히 치단하는 데에는 한계가 있어 외상성 치아손상에 관한 실태를 조사 분석함으로써 외상처치와 예방에 필요한 기초자료를 제시하고자 강릉대학교 치과병원 소아치과에 2000년 10월 4일부터 2004년 2월 27일까지 외상을 주소로 내원한 113명의 환자를 대상으로 조사 분석한 결과 다음과 같은 결론을 얻었다. 1. 연구대상자의 성별에서는 2.05:1의 비율로 남자의 경우가 외상빈도가 더 높게 나타났다. 평균 연령은 남자 5.27세, 여자 5.27세로 차이가 없었고, 전체 연령중 2세에서 외상환자가 제일 많았다(21.2%) 2. 외상부위별 내원기간을 조사한 결과 유치는 당일(34.4%)에 내원한 경우가 가장 많았고, 영구치는 1일 후(38.8%)에 내원한 경우가 가장 많았다. 3. 외상부위별 치아손상의 원인을 분석한 결과 넘어진 경우가 유치 59.4%, 영구치 55.1%, 물체에 부딪친 경우 유치 26.6%, 영구치 26.5%로 나타나 대부분 넘어지거나 부딪쳐서 외상이 발생한 것으로 나타났다. 4. 성별에 따른 치아손상이 발생한 장소는 가정인 경우가 남자 42.1%, 여자 35.1%로 남녀모두 가정에서 외상이 가장 많이 발생하였다. 외상부위에 따른 치아손상 발생한 장소로는 유치는 가정(59.4%)에서 가장 많이 발생하였고, 영구치는 유치원 및 학교(28.6%)에서 가장 많이 발생하였다. 5. 외상부위에 따라 치아손상을 받은 치아의 수를 분석한 결과 유치는 2개(56.3%), 1개(31.3%), 3개와 4개 이상 각각(6.3%), 순으로 나타났으며, 영구치는 2개(46.9%), 1개(28.6%) 4개 이상(16.3%), 3개(8.2%) 순으로 영구치인 경우 4개 이상인 경우도 비교적 높게 나타났다. 6. 성별에 따른 치아손상이 발생한 부위로는 남자 유치 56.6%, 영구치 43.4%, 여자 유치 56.8%, 영구치 43.2%로 남녀 모두 유치에서 외상이 가장 많이 발생하였다. 7. 유치와 영구치의 치아손상부위는 상악 전치부가 거의 대부분을 차지하고, 유치(75%)와 영구치(63.8%) 모두 상악 중절치에서 외상율이 높게 나타났다. 8. 전체적인 외상성 치아손상에 따른 외상종류의 조사결과는 동요 30.2%, 치관파절 28.0%, 함입 14.7%, 진탕 8.9%, 완전 탈구 7.1%, 정출 2.2%, 변위 1.8% 순으로 나타났다. 유치와 영구치별로 외상성 치아손상의 종류를 분류하였을 때 유치는 동요(35.8%)가 가장 많이 나타났고, 파절에서 치관파절은 영구치(44.8%)에서 많이 발생하였다. 9. 외상부위에 따른 외상성 치아손상처치는 처치없이 경과관찰을 한 경우가 유치는 43.2%, 영구치 38.9%로 나타났으며, 치료한 경우 유치는 치수절제술(22.0%), 영구치는 임시적산부식레진수복(19.5%)을 가장 많이 사용하였다.

• 한국치위생학회지
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• 제11권1호
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• pp.127-136
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• 2011

Objectives : The writer aimed to examine the dynamic aspect on damage and to be conducive to the swift cure according to right treatment to educate prevention of injury through surveying on the number of the damaged teeth given injury, tooth kind, type in damage, place and cause for being damaged, frequency by month and by time level, and location of the damaged tooth. Methods : Targeting 343 teeth of receiving injury in 201 patients who visited the department of pediatric dentistry, the department of preservation, and the oral and maxillofacial surgery in a dental hospital in Cheonan city from April 2007 to April 2009, by having the dental injury as the main reason, the following conclusions were obtained. Results : 1. Deciduous teeth were indicated to be the highest in imperfect luxation with 60.7%, and were indicated to be in order of crown fracture with 25.5%, root fracture with 12.4%, and perfect luxation with 1.4%. The permanent teeth were indicated to be the highest in crown with 58.1%, and were indicated to be in order of imperfect luxation with 27.3%, root fracture with 13.1%, and perfect luxation with 1.5%(p<0.001). 2. In case of deciduous teeth for a place with damage, the home was indicated to be the highest with 31.7%. The permanent teeth were indicated to be the highest(p<0.001) in the road and stairs with 40.4%. As to a cause for damage, both deciduous and permanent teeth were indicated to be the highest(p<0.001) in a cause for falling with 53.1% and 30.8%, respectively. 3. As for a treatment method, in case of deciduous teeth, the close observation was indicated to be the highest with 46.9%. In permanent teeth, the resin restoration was indicated to be the highest(p<0.001) with 22.2%. Dental injuries in deciduous teeth and permanent teeth are showing diverse aspects. Conclusions : It is important to arrange guidelines on cure of the damaged teeth by injury through continuing a dynamic research on these aspects. Also, the damage in deciduous teeth may have direct and indirect influence upon growth in successional permanent teeth. Thus, through careful treatment, the injury needs to be minimized. It is considered to be likely necessary for a right coping method when injury occurs, and above all, for enough prior education so that injury cannot occur.

• 대한소아치과학회지
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• 제30권2호
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• pp.210-216
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• 2003

이중치는 쌍생치와 융합을 포함한다. 선천적인 결손치는 치아가 하나이상 없는 상태를 의미한다. 이 연구의 목적은 익산시 유치원 어린이에서의 이중치와 선천적 결손치의 유병율을 조사하는 것이다. 조사 인원은 569명의 남아와 462명의 여아로 1,031명의 어린이를 대상으로 하였으며 연령은 17개월에서 84개월의 연령이내였다. 이중치는 다양한 진단학적 치료적 문제를 가진다. 쌍생치는 하나의 치배가 두개의 치관을 형성하는 것으로 정의되며 임상적으로 동일한 두 개의 치관이 나뉘어져 거울상(mirror image)으로 보이게 된다. 융합치는 두 개의 치배가 합쳐져서 형성된 것으로 물리적인 힘이나 압력이 두 개의 정상적으로 분리된 치배를 접촉시켜 발생하는 것으로 알려져 있다. 융합은 두개의 정상치아 사이에서 나타나거나 혹은 정상치아와 과잉치 사이에서 나타나는데 후자의 경우 쌍생치와 구별하기 힘들다. 1,031명중 23명(11명의 남아, 12명의 여아)이 이중치를 보이고 17명(8명 남아, 9명 여아)은 선천적 결손치를 보였다. 이중치의 유병율은 2.2%였다. 선천적 결손치의 유병율은 1.6%였다. 피검자중 1명은 이중치와 결손치를 가지고 있었다. 유치열기의 이중치와 선천적 결손치에서 모두 남녀간에 통계학적으로 유의한 차이가 없었다(p>0.05).