• 대한치과교정학회지
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• 제46권5호
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• pp.280-289
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• 2016

Objective: The aim of this study was to analyze tooth movement and arch width changes in maxillary dentition following nonextraction treatment with orthodontic mini-implant (OMI) anchorage in Class II division 1 malocclusions. Methods: Seventeen adult patients diagnosed with Angle's Class II division 1 malocclusion were treated by nonextraction with OMIs as anchorage for distalization of whole maxillary dentition. Three-dimensional virtual maxillary models were superimposed with the best-fit method at the pretreatment and post-treatment stages. Linear, angular, and arch width variables were measured using Rapidform 2006 software, and analyzed by the paired t -test. Results: All maxillary teeth showed statistically significant movement posteriorly (p < 0.05). There were no significant changes in the vertical position of the maxillary teeth, except that the second molars were extruded (0.86 mm, p < 0.01). The maxillary first and second molars were rotated distal-in ($4.5^{\circ}$, p < 0.001; $3.0^{\circ}$, p < 0.05, respectively). The intersecond molar width increased slightly (0.1 mm, p > 0.05) and the intercanine, interfirst premolar, intersecond premolar, and interfirst molar widths increased significantly (2.2 mm, p < 0.01; 2.2 mm, p < 0.05; 1.9 mm, p < 0.01; 2.0 mm, p < 0.01; respectively). Conclusions: Nonextraction treatment with OMI anchorage for Class II division 1 malocclusions could retract the whole maxillary dentition to achieve a Class I canine and molar relationship without a change in the vertical position of the teeth; however, the second molars were significantly extruded. Simultaneously, the maxillary arch was shown to be expanded with distal-in rotation of the molars.

• Restorative Dentistry and Endodontics
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• 제26권6호
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• pp.464-484
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• 2001

When restoring a tooth, the dentist tries to choose the ideal material for existing situation. One criterion that is considered is its suitability for restoring coronal strength. As more tooth structure is removed, the cusps are weakened and susceptible to fracture. Further, this increased deformation may cause the formation of intermittent gaps at the margin between the hard tissue and the restoration, facilitating marginal leakage. The improvements in ceramic materials now make it possible for alternatives to amalgams, composites, and cast metal to be of offered for posterior teeth. Of the materials used, ceramics most closely approximates the properties of enamel. The introduction of computer-aided design/computer-aided manufacture(CAD/CAM) systems to restorative dentistry represents a major technological breakthrough. It is possible to design and fabricate ceramic restorations at a single appointment. Additionally, CAD/CAM systems eliminate certain errors and inaccuracies that are inherent to the indirect method and provide an esthetic restoration. The aim of this investigation was to study the loading characteristics of CAD/CAM ceramic inlay and to compare the stress distribution and displacement associated with different designs of cavity(the isthmus width and cavity depth). A human maxillary left first premolar was prepared with standard mesio-occlusal cavity preparation, as recommended by the manufacturer Ceramic inlay was fabricated with CEREC 2 CAD/CIM equipment and cemented into the prepared cavity. Three dimensional model was made by the serial photographic method. The cavity width was varied $\frac{1}{3}$, $\frac{1}{2}$ and $\frac{2}{3}$ of intercuspal distance between buccal and lingual cusp tip. The cavity depth was varied 1.5mm and 2.3mm. So six models were constructed to simulate six conditions. A point load of 500N was applied vertically onto the first node of the lingual slope from the buccal cusp tip. The stress distribution and displacement were solved using ANSYS finite element program(Swanson Analysis System). (omitted)

• 대한소아치과학회지
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• 제27권1호
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• pp.122-134
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• 2000

각화치은, 부착치은의 폭경, 치은열구의 깊이에 대해 성인에서는 많은 연구가 있었으나 아동에서의 연구는 드물었기 때문에, 유치열기, 혼합치열기 및 영구치열기의 모든 치아에 대하여 아동의 협측 각화치은 및 부착치은의 폭경과 치은열구 깊이에 대한 정상치를 구하고, 악골의 발육 및 치아의 맹출과의 관련성을 고찰하며, 점막치은 문제의 발현빈도를 조사하고자 하였다. 결론은 다음과 같다. 1. 유치열의 부착치은 폭경은 상악 유측절치 및 유견치에서 각각 3.50mm, 3.55mm로 최대값을, 하악 제1유구치에서 1.34mm로 최소값을 나타내었다. 영구치열의 경우에는 상악 측절치에서 3.00mm로 최대값을, 하악 제1소구치에서 0.55mm로 최소값을 나타내었다. 상하악 동명치아 비교시 상악 치아가 하악 치아보다 더 큰 값을 나타내었고, 남녀간 차이에는 특별한 규칙이 발견되지는 않았다. 2. 연령증가에 따른 부착치은 폭경의 변화 양상은 유치열의 경우 유견치, 제1유구치, 제2유구치에서 6세부터 증가하였다. 영구치의 경우 남자에서는 하악 중절치와 상악 제 1대구치의 측정값만이 연령에 따른 증가 추세를 나타냈으나(p<0.05), 여자에서는 상하악 중절치 측절치 및 상악 제1대구치에서 통계적으로 유의성 있는 각화치은 폭경의 증가 추세를 관찰할 수 있었다(p<0.05). 3. 치아교대기에서 부착치은 폭경의 차이는 남자 상악 중절치를 제외한 모든 경우에 유치에서의 측정값이 영구치에서의 측정값보다 큰 것으로 나타났다(p<0.05). 4. 6제부터 12세까지는 각화치은의 폭경과 치은열구의 깊이는 대부분 유치 초기값보다 그 계승영구치 최종값이 더 높은 값을 나타냈으나(p<0.05), 부착치은의 폭경에서는 유치 초기와 그 계승영구치 최종값사이에 통계적으로 유의성 있는 차이가 나타나지 않았다. 5. 점막치은 문제 발현 빈도는 남녀에 상관없이 유치열은 상하악 제 1유구치가, 영구치열은 상하악 모두 제 1소구치가 최고치를 나타냈으며 유치에서보다 그 대응 계승영구치에서 그 빈도가 더욱 높게 나타났다. 연령증가에 따라 점막치은 문제의 발현 빈도는 유치열, 영구치열에서 모두 감소하였으나, 하악 제1유구치, 하악 영구 견치, 제1, 제2소구치의 경우 연령의 증가와 상관없이 비슷하게 유지되거나 증가하는 경향을 보였다.

• Journal of Periodontal and Implant Science
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• 제47권1호
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• pp.41-50
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• 2017

Purpose: The aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging. Methods: We evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically. Results: The detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than $100{\mu}m$. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform. Conclusions: We were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

• 구강회복응용과학지
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• 제17권4호
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• pp.257-274
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• 2001

To properly prepare teeth, dentists require a direct view of the working area and are often placed in a difficult position, moreover, a high proportion of dentists suffer from headache and back pain. Dentists who make use of the dental mirror and position their patients carefully to gain a proper view report less headache, pain and discomfort in the shoulders. It is recommended that dentists learn the "Home Position(H.P.)" which among the various "Random Position(R.P.)" methods, enables dentists to approach their patients in a stable posture. The purpose of this study was to compare tooth preparation in the H.P. and the R.P., and evaluate the clinical efficacy of the H.P.. Tooth preparation for a full cast crown was performed on the maxillary left 1st molar using the H.P. and the R.P., and the shapes of the prepared tooth surfaces at the two different operating positions were compared. The amount of occlusal reduction, marginal width, height, and axial taper were measured and analyzed. A T-test was performed separately to compare the results of the H.P. and the R.P. with respect to the accuracy of the corresponding tooth reduction. The results were as follows. ; 1. The amount of occlusal reduction was excessive on the mesiobuccal cusp(P<0.05), and deficient on the lingual cusp in the H.P.(P<0.01). In the R.P., this was excessive on the buccal cusp and deficient on the fossa and distolingual cusp(P<0.01). 2. The amounts of marginal width were excessive in all areas except on the lingual and mesial surfaces in the H.P. and lingual surface in the R.P.(P<0.01). 3. The marginal heights were achieved more accurately in the R.P. than the H.P.(P<0.01). 4. Axial surface taper was excessive in all areas in the H.P.(P<0.01). But the axial taper of measured areas was even, and tooth is more like to retain its original axis after reduction. In the R.P., axial surface taper was excessive on the mesial and buccal area, and deficient on the distolingual area(P<0.01), and therefore, the axis of the prepared teeth was tipped in the distolingual direction. 5. The times needed for preparation were 12 minutes and 49 seconds in the H.P., and 11 minutes and 35 seconds in the R.P., and the R.P. was statistically faster(P<0.01). The tooth preparation in the H.P. achieved its goal, in that it enabled the operator to make even tooth reduction. In conclusion, the H.P. system offers an improved method that can be used in clinic after specific training.

• 치위생과학회지
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• 제6권1호
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• pp.29-34
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• 2006

한국의 일반 성인과 교정환자 중 총생이 있는 사람의 치아크기와 치열궁 크기를 알아보기 위하여 경북 K대학 남녀학생 40명과 경북소재 E치과병원에 내원한 42명을 대상으로 치아크기,치열궁 폭경과 장경을 측정하여 비교하였다. 1. K 대학 학생의 치관의 근원심경은 상악 중절치, 상악 제2소구치, 하악 견치, 하악 제1대구치를 제외하고 모두 Wheeler의 치아크기 수치보다 컸다. 2. 정상군(noncrowded dentition group)의 치아크기는 남성군이 여성군보다 상하악 치아가 모두 컸다. 총생군(crowded dentition group)의 경우, 일반적으로 남성의 치아가 여성보다 컸으나, 상악 제 1 소구치, 하악 측절치, 하악 제 1소구치와 제 2소구치는 여성이 커다. 또한 정상군과 총생군과의 치아크기는 남녀 모두 총생군의 치아가 정상군보다 컸다. 3. 남성의 상악치아 근원심경 크기는 총생군이 정상군보다 치아크기가 컸고, 특히 제 2소구치는 0.65 mm의 편차를 나타내어 유의수준 P < 0.05에서 통계적인 유의성을 나타내었다. 남성의 상악 치열궁 폭경(arch width)과 장경(arch length)은 총생군이 정상군보다 0.38 mm, 0.62 mm각각 작게 나타내었다. 4. 남성의 하악 근원심경 크기는 총생군이 정상군보다 제1대구치를 제외하고 모두 컸으나, 통계적으로 유의하지 않았다. 하악의 치열궁 폭경은 총생군이 정상군보다 4.78mm의 작았으며 p < 0.01수준에서 통계적 유의성을 보였고, 치열궁 장경은 총생남성군이 정상남성군보다 2.08 mm가 작아 p < 0.05에서 통계적 유의성을 보였다. 특히 악궁의 크기편차는 상악치열궁보다 하악치열궁에서 크게 나타났다. 5. 정상여성군과 총생여성군의 상악 근원심경 치아크기는 총생군이 정상군보다 컸으며, 특히 상악 제 2소구치는 p < 0.05에서 통계적 유의성을 보였다. 여성상악의 치열궁 폭경(arch width)은 총생군이 정상군보다 3.18 mm의 작았으며 p < 0.001수준에서 통계적 유의성을 보였고, 치열궁 장경(arch length)은 총생군이 정상군보다 0.51 mm가 작았다. 여성의 상악치열궁은 남성의 상악치열궁보다 장경이나 폭경이 모두 작았다. 6. 정상여성군과 총생여성군의 하악 근원심경 치아크기는 총 생군이 정상군보다 모두 컸으며, 특히 하악 중절치, 견치, 제2소구치는 p < 0.01에서 통계적 유의성을 보였다. 여성의 하악치열궁 폭경은 총생군이 정상군보다 1.13 mm의 작았으며, 치열궁 장경(arch length)은 총생군이 정상군보다 0.24 mm가 작았다. 여성의 하악치열궁은 남성의 하악치열궁보다 장경이나 폭경이 모두 작았다.

• Imaging Science in Dentistry
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• 제49권4호
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• pp.257-263
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• 2019

Purpose: This study was performed to evaluate the dimensional accuracy of digital dental models constructed from cone-beam computed tomographic (CBCT) scans of polyvinyl siloxane (PVS) impressions and cast scan models. Materials and Methods: A pair of PVS impressions was obtained from 20 subjects and scanned using CBCT (resolution, 0.1 mm). A cast scan model was constructed by scanning the gypsum model using a model scanner. After reconstruction of the digital models, the mesio-distal width of each tooth, inter-canine width, and inter-molar width were measured, and the Bolton ratios were calculated and compared. The 2 models were superimposed and the difference between the models was measured using 3-dimensional analysis. Results: The range of mean error between the cast scan model and the CBCT scan model was -0.15 mm to 0.13 mm in the mesio-distal width of the teeth and 0.03 mm to 0.42 mm in the width analysis. The differences in the Bolton ratios between the cast scan models and CBCT scan models were 0.87 (anterior ratio) and 0.72 (overall ratio), with no significant difference (P>0.05). The mean maxillary and mandibular difference when the cast scan model and the CBCT scan model were superimposed was 53 ㎛. Conclusion: There was no statistically significant difference in most of the measurements. The maximum tooth size difference was 0.15mm, and the average difference in model overlap was 53 ㎛. Digital models produced by scanning impressions at a high resolution using CBCT can be used in clinical practice.

• 대한치과교정학회지
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• 제38권4호
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• pp.265-274
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• 2008

3D CT를 이용하여 파노라마에서 얻어진 상악 매복 견치 위치 정보의 유용성을 평가하기 위해, 상악 견치 매복을 주소로 경북대학교병원에 내원한 환자를 대상으로 파노라마 방사선 사진과 3D CT에서의 매복 견치의 위치를 평가하였다. 대상은 25명(남자 7명, 여자 18명)으로 평균 나이는 10.9세(범위 : 8.2 - 15.7세)이며, 35개의 상악 매복 견치증례를 분석하여 다음의 결과를 얻었다. 첫째, 파노라마 방사선 사진은 확대되어 촬영되므로 3D CT의 계측치보다 상악 견치의 tooth length, crown width, vertical distance 그리고 lateral shift값에서 큰 값을 가졌다. 단, angulation to occlusal plane은 파노라마에서 더 작은 값으로 계측되었다. 둘째, 파노라마 방사선 사진상 상악 견치가 구개측으로 매복된 경우, angulation to occlusal plane은 3D CT보다 작게 측정되고 vertical distance는 더 크게 측정되었다. 셋째, 파노라마 방사선 사진에서 상악 매복 견치의 tooth length, crown width 그리고 순측으로 매복된 경우 상악 견치의 angulation to occlusal plane은 3D CT와 근접된 계측치를 가졌다. 또한 CT와 비교하였을 때, 치근 흡수 정도 평가에 대한 파노라마 방사선 사진의 감수성은 33.3%인 것으로 측정되었다. 파노라마 방사선 사진은 협측 매복견치의 위치는 실제와 유사하다고 생각되나 구개측 매복의 경우 3D CT보다 더 높게, 각도는 더 작게 나타나는 등 상당한 차이가 있어 CT를 이용한 추가적인 검사가 필요하다고 생각된다.

• 대한치과교정학회지
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• 제24권4호
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• pp.773-785
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• 1994

It has been generally believed that the impaction or eruption of mandibular third molars has significant correlations with the growth of the mandible, size of mandibular arch and size of teeth. The purpose of this study was to examine if there is any correlation between the status of eruption of mandibular third molars and the amount of mandibular crowding. The effect of missing of third moalrs to mandibular crowding was studied as well. 140 adult students of Yonsei University were selected and divided into three groups according to the status of mandibular third molars, Group 1) congenital missing group, Group 2) eruption group, and Group 3) impaction group. The tooth size, dimensions of the mandibular dental arch, and the amount of crowding were measured and compared. Results were as follows ; 1. There was no statistically significant difference in tooth size between the missing group and the eruption group(p<0.05). Impaction group showed larger total tooth material, inci- sal tooth material, and individual tooth size except central incisors compared to missing group (p<0.05). Impaction group showed larger total tooth material, incisal tooth material compared to eruption group as well(p<0.05). When individual tooth size was compared, impaction group had larger central incisors, canines, and second premolars than eruption group(p<0.05). 2. Missing group showed larger intermolar width than impaction group and it was stati- stically significant(p<0.05). 3. When compared the amount of total crowding, impaction group showed the largest am- ount of crowding, then eruption group, and missing group showed the least amount of crowding respectively(p<0.05). There was no statistically significant difference between missing stoup and eruption group in the amount of incisal crowding(p<0.05). Impaction group show- ed the largest amount of incisal crowding among all three groups(p<0.05).

• Journal of Periodontal and Implant Science
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• 제28권3호
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• pp.517-523
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• 1998

The purpose of this study was to investigate the width of attached gingiva of young adults with healthy gingiva. We compared the differences according to the tooth location. The width of attached gingiva of maxilla and mandible was measured by histochemical method. The results were as follows: 1. The width of buccal keratinized gingiva in maxilla was widest in incisors(5.2-5.6mm) and narrowest in first bicuspids(4.4-4.5mm). 2. The width of buccal keratinized gingiva in mandible was widest in incisors(4.3-4.5mm) and narrowest in first bicuspids(3.2-3.3mm). 3. The width of lingual keratinized gingiva in mandible was widest in first molars(5.5-5.6mm) and narrowest in incisors(2.9-3.0mm). 4. The width of buccal attached gingiva in maxilla was widest in incisors(4.1-4.4mm) and narrowest in molars (3.0mm). 5. The width of buccal attached gingiva in mandible was widest in incisors(3.2-3.4mm) and narrowest in second molars (1.7-1.8mm). 6. The width of lingual attached gingiva in mandible was widest in first molars(3.5-3.7mm) and narrowest in incisors(1.9-2.1mm).