• Journal of the Korean Wood Science and Technology
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• v.50 no.5
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• pp.353-364
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• 2022

The crystalline domain of thermosetting urea-formaldehyde (UF) resins at low formaldehyde-to-urea (F/U) molar ratios (≤ 1.0) is known to be responsible for their poor performance as wood adhesives. Crystallization has been observed in 1.0 F/U UF resins during the addition reaction stage and at the end of the synthesis process (neat UF resins). The crystallinity and X-ray diffraction (XRD) spectra of the uncured neat UF resins, on the other hand, differed significantly from those of the cured neat UF resins, raising the possibility that their crystal structures were also different. This study demonstrates for the first time that the crystalline domains in 1.0 F/U UF resins generated from uncured and cured samples are identical. Despite having a lower crystallinity value, the synchrotron XRD patterns of purified neat UF resins were equivalent to the XRD patterns of cured neat UF resins. Transmission electron microscope images of the cured UF resins showed that the crystals were lamellar structures. This finding suggests that the crystal at low molar ratio UF resins are isotropic polycrystals with random orientation.

• Journal of Dental Anesthesia and Pain Medicine
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• v.15 no.3
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• pp.121-128
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• 2015

Background: The authors studied the hemodynamic effect influent by using the novel high concentration of lidocaine HCl for surgical removal impacted lower third molar. The objective of this study was to evaluate the hemodynamic change when using different concentrations of lidocaine in impacted lower third molar surgery. Methods: Split mouth single blind study comprising 31 healthy patients with a mean age of 23 years (range 19-33 years). Subjects had symmetrically impacted lower third molars as observed on panoramic radiograph. Each participant required 2 surgical interventions by the same surgeon with a 3-week washout period washout period. The participants were alternately assigned one of two types of local anesthetic (left or right) for the first surgery, then the other type of anesthetic for the second surgery. One solution was 4% lidocaine with 1:100,000 epinephrine and the other was 2% lidocaine with 1:100,000 epinephrine. A standard IANB with 1.8 ml volume was used. Any requirement for additional anesthetic and patient pain intra-operation was recorded. Post-operatively, patient was instructed to fill in the patient report form for any adverse effect and local anesthetic preference in terms of intra-operative pain. This form was collected at the seven day follow up appointment. Results: In the 4% lidocaine group, the heart rate increased during the first minute post-injection (P < 0.05). However, there was no significant change in arterial blood pressure during the operation. In the 2% lidocaine group, there was a significant increase in arterial blood pressure and heart rate in the first minute following injection for every procedure. When the hemodynamic changes in each group were compared, the 4% lidocaine group had significantly lower arterial blood pressure compared to the 2% lidocaine group following injection. Post-operatively, no adverse effects were observed by the operator and patient in either local anesthetic group. Patients reported less pain intra-operation in the 4% lidocaine group compared with the 2% lidocaine group (P < .05). Conclusions: Our results suggest that a 4% concentration of lidocaine HCl with 1:100,000 epinephrine has better clinical efficacy than 2% lidocaine HCl with 1:100,000 epinephrine when used for surgical extraction of lower third molars. Neither drug had any clinical adverse effects.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.233-248
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• 1991

The purpose of this study was to qunatatively analyze the stress patterns induced in the abutment, superstructure, supporting bone and to determine the deflection of abutment and superstructure by appling occlusal force to natural teeth supported fixed prostheses and implant-supported fixed prostheses. The analysis has been conducted by using the two dimensional finite element method. The implant and natural tooth-supported bridge has a first molar pontic supported by mandibular second bicuspid and implant posterior retainer, which were rigidly(Model A) or flexible(Model B). The natural teeth-supported bridge has a first molar pontic supported by mandibular second bicuspid and second molar, which were rigidly splinted together(Model C). 63.5kg(Load P1) of localized load on central fossa of first molar pontic and 24kg(Load P2) of distributed load on each occlusal surface were applied respectively. 1. The coronal portion of premolar pontic and posterior abutment in fixed partial denture deflected inferiorly in order of Model B, Model C and Model A under Load P1 and Load P2. 2. Mesial displacement of the coronal portion of premolar showed in Model A, Model B and Model C under Load P1, but mesial displacement of that in Model B and distal displacement of that in Model A and Model C showed under Load P2. 3. Mesial displacement of the coronal portion of the pontic and distal displacement of the coronal portion of posterior abutment showed in Model A, Model B and Model C under Load P1 and Load P2. Displacement in the case of Model B was greater than that of Model A and Model C. 4. In the case Model A under Load P1 and Load P2, high stress apically was concentrated in the mesiocervical portion of the posterior abutment than in the disto-cervical portion of the premolar. 5. In the case of Model B under Load P1 and Load P2 high stress was concentrated in the case of the premolar than in that of posterior abutment and high stress especially was concentrated in the connected portion of pontic and posterior abutment. 6. In the case of Model C under Load P1 and Load P2, high stress was concentrated in the distal area of the cornal portion of premolar and the mesial area of the coronal portion of posterior abutment, and stress pattern was anteroposterially symmetric around the pontic. 7. Load P1 and Load P2 compared, stress magnitude was different but stress pattern was similar in Model A, Model B and Model C. 8. Under Load P1 and P2, stress magnitude in the mesial distal portion and the portion of root apex of the posterior abutment was in order of Model B, Model A and Model C.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.523-533
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• 2004

The purpose of this study was to evaluate the alveolar bone surface following root separation angle in the mandibular second molars. The fifty mandibular second molars(which were extracted) were selected, and the alveolar bone surface following root separation angle of the selected teeth were evaluated. The results were obtained as follows; 1. The root separation angle of fifty mandibular second molars were divided into three groups. The first $group(10-20^{\circ})$ was made up of ten teeth, the second $group(20-30^{\circ})$ was made up of fifteen teeth, and the third group(30-40$^{\circ}$) was made up of twenty-five teeth. 2. The mean root separation angle was $28.1^{\circ}$. The mean alveolar bone rate on the mesial surface of the mesial root was 44.27%, on the distal surface of the mesial root was 36.52%, on the mesial surface of the distal root was 33.45%, and on the distal surface of the distal root was 25.28%. 3. The mean alveolar bone rate on the distal surface of the mesial root, which composed the root separation area, was 32.95% in the first group, 36.06% in the second group, and 38.22% in the third group. The mean alveolar bone rate in the mesial surface of the distal root was 31.40% in the first group, 31.93% in the second group, and 35.18% in the third group. 4. The positive correlation was found between the root separation angle and the alveolar bone rate in the root separation area.(P<0.05) Although the mandibular second molar is a very important tooth in the oral cavity, its treatment and diagnosis is very difficult due to the variation of its root form. When periodontal disease involves the mandibular second molar, the result of this study assists in its treatment and diagnosis.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.649-653
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• 2001

The Chiari malformation is a deformation within the central nervous system which the lower brain stem and the cerebellum migrate into the foramen magnum causing herniation. In 1891, Arnold Chiari classified such symptoms into 3 categories. This case report is of a 8-year-old female with the complaint of a slight facial swelling and pain on the upper right molar during tooth brushing since 10 days before. Clinical examination showed gingival pocket formation on distal of the upper right first molar with pain and mobility of the tooth. Radiographic examination showed generalized low bone density in the upper molar area, and especially no bone support above the upper right and left first molars were noted. With a temporary diagnosis of Early-onset periodontitis, consultations with medical doctors for the possibility of an underlying systemic disease were made during periodontal treatment. 3D CT was taken with after a final diagnosis of Chiari malformation. Generalized thinning and defect of the cranial bone was noted and the foramen magnum was slightly enlarged. The occipital and maxillary bone was low in density, and the alveolar bone of maxillary posterior teeth was especially almost non-existing causing the upper right and left first molar to be floating. For this, the patient went under consultation with the department of neurosurgery and is still under observation. Periodontitis in childreren is very rare. When symptoms of periodontitis appear in a child, due to the possibility of an underlying systemic disease such as leukemia, histiocytosis X, and hypophosphatasia, proper examinations should be carried out so that the primary factor the symptoms can be treated.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.1
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• pp.27-31
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• 2010

Purpose of study: The purpose of this study was to provide adequate diagnostic guideline for the maxillary sinuses prior to dental implant treatment for edentulous posterior maxillary areas. For this purpose, our procedure involves the estimation of the remaining alveolar bone height, the examination of the anatomical variation in the maxillary sinuses (e.g. sinus septum), and the evaluation of the incidence of preoperative pathological conditions in the maxillary sinuses. Materials and Methods: We selected 189 patients to undergo computerized tomography (CT) in order to account for the posterior maxillary anatomy found in patients of Korean ethnicity. We evaluated the following using Dentascan software: Remaining alveolar bone height, incidence of sinus septum, and rate of preoperative pathologic conditions in the maxillary sinus. The average amount of remaining alveolar bone height was analyzed using the student's t-test for differences according to anatomical site, and the ANOVA was used for the differences according to age group with the level of significance set at 0.05. Results: Alveolar bone heights of upper first premolar, second premolar, first molar, and second molar was 12.24 mm, 10.37 mm, 7.16 mm, and 7.15 mm, respectively with statistical significance (P < 0.05). Incidence of sinus septum as an anatomic variation was 17 out of 189 cases (9.0%). Incidence of mucosal thickening as a pathologic variation was 82 out of 189 cases (43.4%). Conclusion: In treatment planning of posterior maxillary edentulous area of Koreans, the consideration of augmentation surgery for maxillary sinus is required in maxillary molar area before dental implant installation, and preoperative screening of the asymptomatic maxillary sinuses can be regarded as a reasonable preoperative procedure in the planning of dental implant treatment on the posterior maxillary edentulous area.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.207-217
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• 1999

The purpose of this study was to compare the retentive forces of various types of clasps for removable orthodontic appliances for primary and mixed dentition. Seven metal models of a single tooth and two teeth were made, including maxillary left primary canine, first primary molar, second primary molar and first molar. Retentive forces of Adams clasp, circumferential clasp(C clasp), Jackson clasp, Duyzing clasp, arrowhead clasp, ball clasp, eyelet clasp, and triangular clasp were measured by Universal Testing Machine(Zwick Z020, Germany). The obtained results were as follows. 1. Jackson clasp and Adams clasp showed the highest retentive force among single tooth clasps. 2. C clasp showed the lowest retentive force, and there was no statistically significant difference in retentive force between mesial end C clasp and distal end C clasp. 3. Eyelet clasp showed the highest, and ball clasp showed the lowest retentive farce among clasps for interdental undercut. 4. Triangular clasp showed higher retentive force than ball clasp.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.4
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• pp.349-352
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• 2001

Dental laser provides many advantages to the clinicians. Those are excellent hemostatic effect, good operating sight, minimal adjacent tissue injury, reduction of postoperative swelling & pain, reduction of postoperative infection, reduction of scar tissue & contraction, etc. The purpose of this study is to observe how these advantages work after surgical extraction of impacted third molar. From march 2000 to july 2000, we have randomly divided the patients who had been surgically extracted unilateral impacted third molar into two groups. The first group comprised $CO_2$ laser illumination with 3 watts, defocusing & continuous mode, rotating motion for about 3 minutes after finishing of surgical extraction & suture. The other group patients were not irradiated. The medications in two groups were same. We measured pain, swelling and trismus three times(pre-operation, first day after operation, and 7th day after operation). The number of the patients who had measured three times all are 64, laser irradiated groups are 36 and non-irradiated groups are 28. The age ranged from 19 to 50, with a mean of 27.9 years. The operative time ranged from 3 minutes to 50 minutes, with a mean of 12.1 minutes. In the $CO_2$ laser group, the pain intensity of the 7th day after operation was still increased significantly comparing with that of the pre-operation and the distance which were measured for the swelling was different significantly. In the other group, the mouth opening limitation was still decreased significantly.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.3
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• pp.431-443
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• 1994

As the dental arch is the curve connecting the cusp tip of tooth, the dental arch form, composing of the occlusion, is one the important factors of occlusal reconstruction. Many studies about the horizontal dental arch form have been reported, but until now, it is unclear to infer the position of the teeth in dental arch form, to evaluate the effect of the horizontal dental arch form on chewing movement. The purpose of this study is to make objective criteria to infer the position of the teeth in dental arch. In this study, 100 subjects with individdual normal occlusion were evaluated. By multiple regression analysis on the basis of the relation of the canine and the first molar, the positions of teeth in dental arch were inferred. According to buccolingual relationship of maxillary to mandibular posterior teeth, the dental arch forms were classified into five groups, i, e. the normal group, the group which the maxillary second molar positions buccal side, the group which the maxillary premolars position buccal side, the group which the maxillary premolar position lingual side. From the results, objective criterial to infer the positons of the first premolar, the second premolar, the second molar in dental arch were made.

• The Journal of Advanced Prosthodontics
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• v.1 no.3
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• pp.118-123
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• 2009

STATEMENT OF PROBLEM. Proper proximal contact is important for maintaining and stabilizing the dental arch. However, the proximal contact strength (PCS) is not a constant value and can be affected by a variety of factors. PURPOSE. This study examined the influences of postural changes on the posterior PCS. MATERIAL AND METHODS. Twelve adults with a normal occlusion and had not undergone prosthetic treatment or proximal restoration were participated in this study. A metal strip was inserted into the proximal surface and removed at a constant velocity. The contact strength was measured in every contact point between canine to second molar in both arches. The PCSs were obtained initially in the upright position, secondly in the supine position and finally in the upright position again. All measurements were repeated after a 2 hour period. Statistical analysis was carried out using the Friedman test (P < .05). RESULTS. Generally, a decrease in PCS occurred when the posture was changed from the initial upright to supine position, while it increased when the posture was changed from the supine to upright position. A significant change was observed in all areas except for between the canine-first premolar in the maxilla and between the first molar-second molar in the mandible areas. CONCLUSION. The posterior PCS, which dentists generally believe to be a static feature of occlusion, is affected significantly by posture.