• Journal of the Korea Society of Computer and Information
• /
• v.23 no.3
• /
• pp.17-23
• /
• 2018

In this paper, we propose the automatic detection method which find the middle part of tooth crown to start individual tooth segmentation. There have been many studies on the automation of individual tooth segmentation, but there are still many problems for full automation. Detection of middle part of tooth crown used as initial information for individual tooth segmentation is closely related to performance, but most studies are based on the assumption that they are already known or they can be represented by using a straight line. In this study, we have found that the jawbone curve is similar to the tooth alignment curve by spatially analyzing the CT image, and propose a method to automatically detect the middle part of tooth crown. The proposed method successfully uses the jawbone curves to successfully create a tooth alignment curve that is difficult to detect. As the middle part of tooth crown is in the form of a tooth alignment curve, the proposed method detects the middle part of tooth crown successfully. It has also been verified by experiments that the proposed method works well on real dental CT images.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.4
• /
• pp.57-64
• /
• 2018

In this paper, we propose the automatic detection method for individual region separation using panorama image. Finding areas that contain individual teeth is one of the most important tasks in automating 3D models through individual tooth separation. In the conventional method, the maxillary and mandibular teeth regions are separated using a straight line or a specific CT slide, and the tooth regions are separated using a straight line in the vertical direction. In the conventional method, since the teeth are arranged in a curved shape, there is a problem that each tooth region is incorrectly detected in order to generate an accurate tooth region. This is a major obstacle to automating the creation of individual tooth models. In this study, we propose a method to find the correct tooth curve by using the jawbone curve which is very similar to the tooth curve in order to overcome the problem of finding the area containing the existing tooth. We have proposed a new method to accurately set individual tooth regions using the feature that individual teeth are arranged in a direction similar to the normal direction of the tooth alignment curve. In the proposed method, the maxillary and mandibular teeth can be more precisely separated than the conventional method, and the area including the individual teeth can be accurately set. Experiments using real dental CT images demonstrate the superiority of the proposed method.

• Journal of Korean society of Dental Hygiene
• /
• v.8 no.4
• /
• pp.43-53
• /
• 2008

Some female college students have to recognize and understand the actual conditions of the tooth bleaching, and effective consultation and training to provide basic data for the purpose of investigation. this study made a survey about recognize and understand the actual conditions of the tooth bleaching and oral health knowledge and generalization methods for 649 female college student in Daejeon and Jeonbuk areas during the period between March. 15 and April. 10,2008. The results were as follows: 1. Tooth Status was found low, self-discontent respondents Status 44.2% and average 31.1%, self-contentment were 14.8%. Tooth color was average respondents were 69.8%, yellow 29.0%, White 1.7% (p=0.001, p=0.030). 2. Tooth bleaching experience has not experienced the most the military was 86.4%, to the desired Tooth bleaching for the external beauty 44.2%, confidence of smile time 37.5%. self-discontent 10.7%(p=0.000, p=0.000). 3. Tooth health status satisfaction was dental hygiene students higher than non dental hygiene, and scaling knowledge of the Tooth bleaching effect was non dental hygiene higher than non dental hygiene(p=0.039, p=0.000). 4. General knowledge for Tooth bleaching was found high 96.1%, as for the recognition route, 55.6% were through broadcast medium(p=0.025, p=0.000). 5. Medical institution chosen for Tooth bleaching treatment method appears the most preferred by 79.9% to the dental hospital dental clinic. 6. Important to consider that the choice of Tooth bleaching was Tooth bleaching duration of 37.1% cost 33%, And when Tooth bleaching hoped to be long-lasting. In this research the high recognized of Tooth bleaching treatment, but very low Tooth bleaching experience female college students for the Tooth bleaching had the wrong information. Therefore, Tooth bleaching treatment and counseling that can be used to development and education were required to provide the correct information.

• Journal of Korean Academy of Nursing
• /
• v.38 no.6
• /
• pp.914-922
• /
• 2008

Purpose: To examine the effect of tooth-brushing education on the oral health of preschoolers. Methods: A quasi-experimental design with a non-equivalent control group was used. Two kindergartens were selected and 39 preschoolers from one kindergarten were assigned to the experimental group with tooth-brushing education and 39 from the other kindergarten to the control group. The tooth-brushing education program included 1 session on oral health education, individual tooth-brushing instruction for 1 week and supervised tooth-brushing after lunch for 4 weeks. Oral health behavior including use of tooth paste, tooth-brushing time and method of tooth-brushing, plague, streptococcus mutans, lactobacillus and dental caries were measured before and after the education. Fisher's exact test, t-test and paired t-test with the Window SAS 9.1 program were used to analyze the data. Results: A significant increase in the use of tooth paste, tooth-brushing time and the practice of correct tooth-brushing and a decrease in plague and development of dental caries were observed in the experimental group. Conclusion: This tooth-brushing education was partially effective in improving oral health of preschoolers.

• Computers and Concrete
• /
• v.31 no.2
• /
• pp.163-171
• /
• 2023

Face gear transmission is widely used in aerospace shunt-confluence transmission system. Tooth wear is one of the main factors affecting its bearing transmission performance. Furthermore, the installation errors of face gear are inevitable. In order to study the wear mechanism of face gear tooth surface with installation errors, based on tooth contact analysis numerical method and Archard wear theory, the UMESHMOTION subroutine in ABAQUS is developed.Combining with Arbitrary Lagrangian-Eulerian adaptive mesh technology, the finite element mesh wear model of abraded face gear pair is established.The preprocessing conditions are set to generate the inp files.Then,the inp files for each corner are imported and batch processed in ABAQUS.The loading tooth contact problem at each rotation angle is solved and the load distribution coefficient among gear tooth, tooth root bending stress, tooth surface contact stress and loaded transmission error are obtained. Results show that the tooth root wear is the most serious and the wear at the pitch cone is close to 0.The wear law of tooth surface along tooth width direction is convex parabola and the wear law along tooth height direction is concave parabola.

• The Journal of Korean Academy of Prosthodontics
• /
• v.42 no.1
• /
• pp.11-20
• /
• 2004

Problem : The several studies were reported to the effects of individual tooth tray with the parallel tooth, but not reported to the effect of individual tooth tray with severe undercut in impression making. Purpose : The purpose of this study is to examine the effect of individual tooth tray; 1) the accuracy of impression in terms of distance. 2) reproducibility of pocket. Material and methods : In this study, a metal model with 3 teeth including tooth prepared 30-degree undercut and gingival crevice of the depth 5mm, width 0.4mm was cast. Impressions of the metal model were taken in 5 times used 4 kinds of impression materials with individual tooth tray and another impression taking were made with conventional method without individual tooth, used same materials, procedure. The stone models were made. Distances between abutments were measured with a Micromeasurescoup-mm. Result : The following results were obtained ; 1. In the comparisonof inter-abutment distance between parallel tooth without individual tooth tray, 4elastomeric materials have not significant difference to the metal model(p>0.05). 2. In the comparisonof inter-abutment distance with undercut tooth without individual tooth tray, 4elastomeric materials have a significant difference to the metal model(p<0.05), especially polyether's dimensional change is large. 3. If individual tooth tray was used to take impression in abutment teeth with severe undercut, more stable results was achieved easily than conventional method. (p>0.05). 4. It is not true that the pressure of impression material with individual tooth tray increased to gingival sulcus. Conclusion : By the results, I knew the fact that individual tooth tray was useful impression method on the teeth with severe undercut for the dimensional stability. Also, I could not confirm the fact that individual tooth tray would increase the penetrating pressure into cervice.

• Tribology and Lubricants
• /
• v.5 no.2
• /
• pp.107-112
• /
• 1989

This paper deals with strength analysis of tooth and method of manufacture of external tooth profile in harmonic drive. From the calculation of load imposed on the contact teeth, moximum contact stress is investigated to design the addendum modification coefficient. New tooth profile of the external gear is generated according to the law of gearing, assuming that internal gear has involute tooth profile. External tooth profile can't be manufactured by conventional exclusive tools which have pressure angle of 20$\circ$. The method to design cutter tooth profile is presented.

• Tribology and Lubricants
• /
• v.30 no.4
• /
• pp.212-217
• /
• 2014

A counter gear transmits the rotation angle, so the angular velocity ratio of the gear does not necessarily need to be constant in the meshing process. As a pinion has a small number of teeth when combined with an internal gear for counters, tooth interference can occur with the use of an involute curve. This paper introduces circular arcs that represent a tooth profile and fillet for the profile design of a pinion through the combination of arcs with lines. The straight line of a rack tooth represents the profile of a mating internal gear. Thus, the circular arc and line maintain contact during the rotation of the counter gear. This paper presents an analysis of the meshing of the circular arc tooth and rack tooth along with the properties of the counter gear, such as the change in rotational velocity and amount of backlash. The contact ratio of the counter gear is 1 because the tooth contact occurs between circular arcs and line. The initial position of tooth contact, which denotes the simultaneous contact of two teeth, is found. As the rotation of the pinion, only one tooth keeps the contact situation. This meshing property is analyzed by the geometrical constraints of the tooth profile in contact and the results are presented as graphical diagrams in which tooth-arc movements are superimposed.

• Korean Journal of Environmental Biology
• /
• v.26 no.1
• /
• pp.36-41
• /
• 2008

Induction of morphological deformities in Chironomus riparius larvae was assessed after exposure to 0.3, 1, 10 and 30 ${\mu}g\;L^{-1}$ potential endocrine disruption chemicals, Diethylhexyl phtalate (DEHP). We observed and subdivide types of mentum deformities and counted the incidence of mentum deformities. The mortality was not increased according to concentrations of DEHP, while was depend on the exposed days. The incidence of mentum deformities for MLT (median lateral teeth), LT (lateral teeth), and MIX (MLT+LT) of the mentum morphological structure showed MLT (2.8$\sim$11.4%)>LT (2.8$\sim$2.9%)>MIX (2.8$\sim$3.0%). The type of mentum deformities on C. riparius was classified six groups following exposure to DEHP. The incidence rate was occupied following to tooth addition (4.3%), tooth split (2.8%), tooth deletion (2.4%), tooth fusion (1.4%), $K"{o}hn$ gap (0.5%) and abnormal shape (0.5%). Especially tooth split and tooth fusion were observed in DEHP treated conditions.

• Imaging Science in Dentistry
• /
• v.40 no.2
• /
• pp.89-91
• /
• 2010

Impaction of tooth is a situation in which an unerupted tooth is wedged against another tooth or teeth or otherwise located so that it cannot erupt normally. The supernumerary tooth is also called as hyperdontia and defined as the condition of having additional tooth to the regular number of teeth. The most common supernumerary tooth is a mesiodens, which is a mal-formed, peg-like tooth that occurs between the maxillary incisors. The supernumerary tooth is commonly impacted but they are frequently impacted on maxilla. Ectopic impaction of supernumerary tooth on mandibular condyle, coronoid process, ascending ramus, and pterygomandibular space is very rare condition. In this case, we report a case of impacted supernumerary tooth on mandibular sigmoid notch without definite pathologic change.