• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.11 no.1
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• pp.75-78
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• 1981

The diagnostic value of a intra oral film is related to projecting technic and interpretation. The intra-oral film is a single plane representation of a three dimensional object, therefore superimposition is inevitablly present. The purpose of this article is to show how foreign objects in the jaw may be localized. The author used double exposure technics, that are changed angulation of vertical or horizontal to one film. The obtained results are as fallow: 1. In the upper anterior region, the moving distance of the labially impacted reference object was greater than that of the palatally impacted one. 2. In the upper molar region, the moving distance of the mesiobuccal root apex was the greatest and that of palatal root apex was the shortest. 3. In the lower molar region, the change of the alveolar bone level in the buccal side was greater than that of lingual side.

• The korean journal of orthodontics
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• v.41 no.3
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• pp.191-199
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• 2011

Objective: The purpose of this study was to investigate the stress distribution on the orthodontic mini-implant (OMI) surface and periodontal ligament of the maxillary first and second molars as well as the tooth displacement according to the OMI position in the dragon helix appliance during scissors-bite correction. Methods: OMIs were placed at two maxillary positions, between the first and the second premolars (group 1) and between the second premolar and the first molar (group 2). The stress distribution area (SDA) was analyzed by three-dimensional finite element analysis. Results: The maximal SDA of the OMI did not differ between the groups. It was located at the cervical area and palatal root apex of the maxillary first molar in groups 1 and 2, respectively, indicating less tipping in group 2. The minimal SDA was located at the root and furcation area of the maxillary second molar in groups 1 and 2, respectively, indicating greater palatal crown displacement in group 2. Conclusions: Placement of the OMI between the maxillary second premolar and the maxillary first molar to serve as an indirect anchor in the dragon helix appliance minimizes anchorage loss while maximizing the effect on scissors-bite correction.

• Journal of Periodontal and Implant Science
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• v.38 no.1
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• pp.15-22
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• 2008

Purpose: The attachment level is strongly associated with tooth loss and provides useful information on patterns of destruction of the periodontium. The presence of horizontal attachment loss would not be detected in clinical measurement. Therefore, the purpose of the present study was to estimate the patterns of periodontal destruction based on the attachment area and horizontal attachment loss in extracted teeth due to severe periodontitis. Materials and Methods: 307 teeth satisfied the criteria for assessment. An indirect method, based on digital images obtained from a digital camera and an image analysis program, was used to calculate the area of root surface and attachment loss and the extent of horizontal attachment loss. The data were analysed using SPSS. Results: No statistically significant differences among root surfaces were observed in anterior teeth on the loss of attachment area. However, in posterior teeth statistically significant differences in palatal surfaces of maxillary and mandibular premolar and molar surfaces compared with buccal surfaces were observed. Horizontal attachment loss was observed in 21.5% of the teeth examined. Frequency of horizontal attachment loss was highest in the maxillary first premolar (34.8%), followed by the maxillary second premolar (27.3%) and maxillary canine (25%). The mean length of horizontal attachment loss was 1.5mm. Conclusion: More meticulous examination will be needed of the palatal surfaces of maxillary and mandibular premolar and molar teeth. The percentage of teeth with horizontal attachment loss greater than 2.1 mm was 5.2%. Considering the length of curette blades, about 5.2% of teeth were not properly debrided. Therefore, Additional supportive therapy such as local drug delivery has to be considered in treatment of the first maxillary, second premolar and canine due to the high prevalence of horizontal attachment loss.

• The korean journal of orthodontics
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• v.43 no.1
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• pp.3-14
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• 2013

Objective: To evaluate the factors that affect torque control during anterior retraction when utilizing the C-retractor with a palatal miniplate as an exclusive source of anchorage without posterior appliances. Methods: The C-retractor was modeled using a 3-dimensional beam element (0.9-mm-diameter stainless-steel wire) attached to mesh bonding pads. Various vertical heights and 2 attachment positions for the lingual anterior retraction hooks (LARHs) were evaluated. A force of 200 g was applied from each side hook of the miniplate to the splinted segment of 6 or 8 anterior teeth. Results: During anterior retraction, an increase in the LARH vertical height increased the amount of lingual root torque and intrusion of the incisors. In particular, with increasing vertical height, the tooth displacement pattern changed from controlled tipping to bodily displacement and then to lingual root displacement. The effects were enhanced when the LARH was located between the central and lateral incisors, as compared to when the LARH was located between the lateral incisors and canines. Conclusions: Three-dimensional lingual anterior retraction of the 6 or 8 anterior teeth can be accomplished using the palatal miniplate as the only anchorage source. Using LARHs at different heights or positions affects the quality of torque and intrusion.

• Journal of Periodontal and Implant Science
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• v.27 no.3
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• pp.585-595
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• 1997

Removal of subgingival calculus is essential for the success in periodontal treatment. Subgingival instrumentation is used for the removal of all bacterial plaque and calculus. In this study, two types of anterior curet were used on ant. teeth to conduct subgingival scaling and root planing. The remaining amount of calculus was evaluated according to type of instrument, depth of pocket, and tooth surface. 24 teeth extracted from patients being treated at Dan Kook University dept. Perio. were used. 4 surfaces per tooth a total of 96 areas were evaluated. 12 teeth treated with Gracey No. 1-2 was used as the control group and 12 teeth treated with Mini-five curet No. 1-2 was the experimental group. The 4 surfaces of the teeth {buccal, mesial, lingual or palatal, distal) were observed under a stereomicroscope and the images were captured 3 times per surfaced with a CCD. The image were observed on the monitor using a $10{\times]10$ grid produced with the Microsoft power point. The amount of calculus remaining was evaluated 3 times per surface. The results were as follows. 1. There was no significant difference in remaining calculus according to the pre-treatment pocket depth, and tooth position{Mx. or Mn). 2. The Mini-five curet showed better results than the Gracey curet but there was no statistically significant difference. 3. In both Gracey curet group and Mini-five curet group the lingual(or palatal) surface showed significant difference compared to the other surfaces(p<0.05). From the results above, it is thought that when treating ant. teeth consideration of the tooth surface is more important than the choice of instrument.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.437-448
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• 2021

The purpose of this study is to analyze morphological characteristics of maxillary primary molar's root and root canal. 268 children aged 3 - 7 years (175 boys, 93 girls) who had CBCT (152 children) and 3D CT (116 children) taken in Seoul National University Dental Hospital from January 2006 to April 2020 were included. The number of roots and root canals were analyzed in 1002 teeth without any root resorption or periapical pathologies. Curvature, angulation, length of root and root canal, as well as cross-sectional shapes of the root canal were analyzed in 218 teeth. By using Mimics and 3-Matics software, volume, surface area, and volume ratio of root canal was analyzed in 48 teeth. More than half of maxillary primary molars have 3 roots and 3 root canals. The degree of symmetry of root canal type was about 0.63 (Cohen's kappa coefficient). The most frequent shape of roots and canals was linear in 1^st primary molars and curved in 2^nd primary molars. Angulation, length of root and root canals was the largest on palatal roots. Most teeth showed ovoid or round shapes at apex. The largest root canal volume, surface area, volume ratio was found in the palatal roots.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.18.1-18.9
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• 2020

Objectives: The purpose of this study was to evaluate the void of root canal filling over time when a calcium silicate sealer was used in the single gutta-percha cone technique. Materials and Methods: Twenty-four J-shaped simulated root canals and twenty-four palatal root canals from extracted human maxillary molars were instrumented with ProFile Ni-Ti rotary instruments up to size 35/0.06 or size 40/0.06, respectively. Half of the canals were filled with Endoseal MTA and the other half were with AH Plus Jet using the single gutta-percha cone technique. Immediately after and 4 weeks after the root canal filling, the samples were scanned using micro-computed tomography at a resolution of 12.8 ㎛. The scanned images were reconstructed using the NRecon software and the void percentages were calculated using the CTan software, and statistically analyzed by 1-way analysis of variance, paired t-test and Tukey post hoc test. Results: After 4 weeks, there were no significant changes in the void percentages at all levels in both material groups (p > 0.05), except at the apical level of the AH Plus Jet group (p < 0.05) in the simulated root canal showing more void percentage compared to other groups. Immediately after filling the extracted human root canals, the Endoseal MTA group showed significantly less void percentage compared to the AH Plus Jet group (p < 0.05). Conclusions: Under the limitations of this study, the Endoseal MTA does not seem to reduce the voids over time.

• The korean journal of orthodontics
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• v.46 no.4
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• pp.228-241
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• 2016

Objective: Root mobility due to reciprocating movement of the tooth (jiggling) may exacerbate orthodontic root resorption (ORR). "Jiggling" describes mesiodistal or buccolingual movement of the roots of the teeth during orthodontic treatment. In the present study, buccolingual movement is described as "jiggling." We aimed to investigate the relationship between ORR and jiggling and to test for positive cell expression in odontoclasts in resorbed roots during experimental tooth movement (jiggling) in vivo. Methods: Male Wistar rats were divided into control, heavy force (HF), optimal force (OF), and jiggling force (JF) groups. The expression levels of cathepsin K, matrix metalloproteinase (MMP)-9 protein, interleukin (IL)-6, cytokine-induced neutrophil chemoattractant 1 (CINC-1; an IL-8-related protein in rodents), receptor activator of nuclear factor ${\kappa}B$ ligand (RANKL), and osteoprotegerin protein in the dental root were determined using immunohistochemistry. Results: On day 21, a greater number of root resorption lacunae, which contained multinucleated odontoclasts, were observed in the palatal roots of rats in the JF group than in rats from other groups. Furthermore, there was a significant increase in the numbers of cathepsin K-positive and MMP-9-positive odontoclasts in the JF group on day 21. Immunoreactivities for IL-6, CINC-1, and RANKL were stronger in resorbed roots exposed to jiggling than in the other groups on day 21. Negative reactivity was observed in the controls. Conclusions: These results suggest that jiggling may induce ORR via inflammatory cytokine production during orthodontic tooth movement, and that jiggling may be a risk factor for ORR.

• Imaging Science in Dentistry
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• v.47 no.3
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• pp.181-187
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• 2017

Purpose: The purpose of this study was to measure the buccal bone thickness and angulation of the maxillary incisors and to analyze the correlation between these parameters and the root position in the alveolar bone using cone-beam computed tomography (CBCT). Materials and Methods: CBCT images of 398 maxillary central and lateral incisors from 199 patients were retrospectively reviewed. The root position in the alveolar bone was classified as buccal, middle, or palatal, and the buccal type was further classified into subtypes I, II, and III. In addition, the buccolingual inclination of the tooth and buccal bone thickness were evaluated. Results: A majority of the maxillary incisors were positioned more buccally within the alveolar bone, and only 2 lateral incisors(0.5%) were positioned more palatally. The angulation of buccal subtype III was the greatest and that of the middle type was the lowest. Most of the maxillary incisors exhibited a thin facial bone wall, and the lateral incisors had a significantly thinner buccal bone than the central incisors. The buccal bone of buccal subtypes II and III was significantly thinner than that of buccal subtype I. Conclusion: A majority of the maxillary incisor roots were positioned close to the buccal cortical plate and had a thin buccal bone wall. Significant relationships were observed between the root position in the alveolar bone, the angulation of the tooth in the alveolar bone, and buccal bone thickness. CBCT analyses of the buccal bone and sagittal root position are recommended for the selection of the appropriate treatment approach.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.3
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• pp.149-157
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• 2016

Tooth preparation design is essential for successful laminate veneer treatment. Preservative tooth preparation limited on enamel, supra-margin advantageous for plaque control, and maintaining contact points known as a standard concept. However, the tooth preparation design has been the controversial issue. In biomechanical considerations, the incisal coverage should be decided on esthetic needs and necessity for the anterior guidance reconstruction. In occasion for sufficient enamel thickness, preparation can prolong to the palatal side but not recommended at palatal concavity. Elongation to contact point is selective option according to the cases. If an old resin restoration located at contact area, laminate veneer should cover over half area of that after surface treatment. The laminate veneer can be also selected at a partially discolored tooth root canal therapy (RCT) and at this occasion, the fiber-reinforced composite (FRC) posts are recommended.