• The Journal of Korean Academy of Prosthodontics
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• v.29 no.3
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• pp.141-170
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• 1991

This study was to analyze the displacement and the magnitude and mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment teeth and the mandibular supporting bone when various abutment designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. The models of overdenture and mandibe with the canine and the second premolar remaining, were fabricated. In the first design, a 1 mm space was prepared between the denture and the dome abutment with the height of 2 mm(OS). In the second design, a contact between the denture and the occlusal third of the dome abutment with the hight of 2 mm was prepared(OC). In the third design, a 0.5 mm space was prepared between the denture and 8 degree tapered cylindrical abutments with the height of 7 mm(TS). In the fourth design, a contact between the denture and the occlusal two thirds of the conical abutments with the height of 7 mm was prepared(TC). In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 Kgs on the first molar region (P1) and 7 Kgs on the central incisor region (P2) in a vertical direction. The force of 10 Kgs was then applied distributively from the first premolar to the second molar of each motel in a vertical direction (P3). The results were as follows: 1. The vertical load on the central incisor region(P2) produced the higher displacement and stress concentration than that on the posterior region(P1, P3). 2. The case of space between abutment and denture base produced higher displacement than that of contact, and the case of long abutment produced higher displacement than that of short abutment because of low rigidity of denture base. 3. The magnitude of the torque and vertical force to the abutment teeth and the stress distribution to the denture base was higher in the telescope coping than in the overdenture coping. 4. The vertical load on the central incisor region(P2) produced higher equivalent stress in the mandible than that on the posterior region(P1, P3). 5. The case of space between abutment and denture base produced better stress distribution to the farther abutment from the loading point than that of contact. 6. In case of sound abutment teeth, the type of telescope coping can be used, hilt in case of weak abutment, the type of overdenture coping is considered to be favorable generally.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.1
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• pp.63-94
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• 1990

The purpose of this study was to analyze the displacement and the magnitude and the mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment tooth and the mandibular supporting bone when various denture base materials, such as acrylic resin and 0.5mm metal base, and various denture base designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. Mandibular arch models, with only canine remaining, were fabricated. In the first denture base design, a space, approximately 1mm thick, was prepared between the denture and the dome abutment. In the second denture base design, contact between the denture and the dome abutment was eliminated except the contact of the occlusal third of the abutment. In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle region, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 kgs on the first molar region(P1) and 7 kgs on the central incisal region (P2) in a vertical direction. Then the force of 10 kgs was applied distributively from the first premolar to the second molar of each model in a vertical direction(P3). The results were as follows. : 1. When the testing vertical loads were given to the selected points of the overdenture, the overdenture showed the rotatory phenomenon, as well as sinking and the displacements of alveolar ridge, abutment and lower border of mandible under the metal base overdenture were less than those under the acrylic resin overdenture. 2. The maximum principal stresses(the maximum tensile stresses) being considered, high tensile stresses occured at the buccal shelf area, the posterior region of the ridge crest and the anterior border region of the mandibular ramus. 3. The minimum principal stresses(the maximum compressive stresses) being considered, high compressive stresses occured at the inferior and posterior border region of the mandible, the mandibular angle and the posterior border region of the mandibular ramus. 4. The vertical load on the central incisal region(P2) produced higher equivalent stress in the mandible than that on any other region(P1, P3) because of the long lever arm distance from the fixed points to the loading point. 5. Higher equivalent stresses were distributed throughout the metal base overdenture than the resin base overdenture under the same loading condition. 6. The case of occlusal third contact of the abutment to the denture produced higher equivalent stresses in the abutment, the mandibular area around the abutment and the overdenture than the case of a 1mm space between the denture and the abutment. 7. Without regard to overdenture base materials and designs, the amounts and distribution patterns of equivalent stresses under the same loading condition were similar in the mucous membrane.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.2
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• pp.142-150
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• 2006

PURPOSE : The 3rd molar extraction of mandible is common in out-patient office of oral and maxillofacial surgery. And it is dynamic minor operation with changes of vital signs. most of patients are already sensitive about their dental treatment. The changes of emotion are reached to the highest level when patients is laid down to be treated on unit chair. It can be induced to undesirable accidents as to this fear. The undesirable complications are nausea, vomiting, hyperventilation, dyspnea, syncope, shock and so on. The severe changes of vital signs may influence their behavior and make serious medical malpractice or suit such as fracture of dental instruments and injury of proximal area. METHOD AND PATIENTS : A total of 99 selected normal patients were reviewed. Among this, 70 patients(43 men, 27 women with statistical significance) were included in this study. Each steps(pre-anesthesis, 5 minutes after anesthesis, just after mucogingival incision, just after tooth section, just after suture and gauze biting) were investigated for a change of a vital signs. It is analyzed to 2 categories,"Means" and "Tendency". The "Means" is the amount of vital signs changed in comparison with pre-step during operation. That means is the amount of vital changes by each step operation. Next, " Tendency" is changes of vital signs in comparison with step1 during operation. RESULT : This is the changing tendency of vital signs with time. That is active effect of fear and pain. Thus this "Means" and "Tendency" will present a sudden changes of vital signs and it can lead to more safe treatment. CONCLUSION : Thus, the purpose of this study is, through careful operation in each step, to less on patients' complication and increase trust between patient and OMFS. This study is a first article shown with the amount of "Means" and "Tendency" in vital signs, when a third molar of mandible is extracted. This study will be base study of patients with general diseases, because it selected only patients without general diseases.

• Journal of The Korean Dental Society of Anesthesiology
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• v.4 no.2 s.7
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• pp.84-89
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• 2004

Background: Many studies on efficacy of preemptive analgesia have been processed in different ways. But the value of preemptive analgesia is still controversial. The goal of this study was to compare analgesic effect of an NSAID according to three different administration times for oral surgical pain. Patients and Methods: Using a randomized, parallel-group, single-center, and active-controlled test design, this study was conducted to healthy 80 patients undergoing a surgical removal of an impacted mandibular third molar requiring bone removal. The oral NSAID was first administered 1 hour preoperatively, or 1 hour postoperatively, or no scheduled administration in pre or postsurgery. Whenever patients felt at least moderate pain (score ${\ge}$ 5 on a 10-point scale) after surgery, they were instructed to take the same drug. Pain intensities and times to the first and second onset of postoperative pain from end of surgery were assessed for 24 hours. Results: Of the enrolled eighty subjects in this study, 25 patients were assigned to preemptive, 26 to post-treatment and 29 to no treatment group. The demographic distribution and duration of surgery in the three groups were statistically similar. The mean time to first onset of postoperative pain was significantly prolonged in post-treatment group (277.2 minutes, p < 0.05) compared to preemptive (158.4 minutes) and no treatment group (196.5 minutes). The mean time to second onset of postoperative pain was not significantly different among the three groups. No significant statistical difference was found among the mean pain intensities at the first and second onset of postoperative pain in the three groups. Conclusions: In this small selected group of subjects and limited study design, the analgesic effects of NSAID administered preoperatively were no longer effective for postoperative pain. The results in this population imply that scheduled postoperative analgesics before pain development are adequate for postoperative analgesia without preoperative administration.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.5
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• pp.485-493
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• 2007

Purpose: Heart rate variability(HRV) is the clinical consequence of various influences of the autonomic nervous system(ANS) on heart beat. HRV can estimate the potential physiologic rhythm from the interval between consecutive beats(RR interval or HRV data). It is known as RSA which represents respiration-related HR rhythmic oscillation. Previous studies demonstrated a specific breathing pattern(0.1Hz, 6breaths/min) to improve a physiological body condition related to the stress. In this paper, the level of stress would be evaluated in terms of three phases of the dental treatment, combined with 6breaths/min. Methods: These phases include before, during and after tooth extraction or anesthesia or something.36 patients' stresses were assessed using HRV stress analyzer in each phase in Kangdong Sacred Heart Hospital, and Chuncheon Sacred Heart Hospital, Hallym University Medical Center from Jun. to Sept. of 2007. HRV 5-min data collected were analyzed in time-domain and frequency-domain to evaluate the activity of autonomic nervous system(ANS) which represents the level of stress. Results: All HRV parameters including HF(high frequency), LF(low frequency) and LF/HF ratio showned a significant change affecting the ANS balance. There was a 6.4% difference between R(LF/HF)s on general breathing pattern for balance of Autonomic nervous system, but on controlled breathing pattern, 0.1Hz, was made narrow till 1.4%. The activity of ANS has increased by 1.4% on general breathing pattern, and by 2.9% on controlled breathing pattern, 0.1Hz. Conclusion: After analysis of preoperative stress changes and effect of breathing pattern of 0.1 Hz on the stress in 36 patients who have undergone third molar extraction, following was concluded. In the preoperative stage, the sympathetic change was the greatest?after the?anesthetic injection, and stress was relieved by controlling the breathing pattern to a frequency of 0.1Hz.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.228-239
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• 2007

Statement of problem: Following tooth loss, the edentulous alveolar process of maxilla is affected by irreversible reabsorption process, with progressive sinus pneumatization leads to leaving inadquate bone height for placement of endosseous implants. Grafting the floor of maxillary sinus by sinus lifting surgery and augmentation of autologous bone or alternative bone material is a method of attaining sufficient bone height for maxillary implants placement and has proven to be a highty successful. Purpose: This study was undertaken to clarify the morphometric characteristics of inferior maxillary sinus and alveolar process for installation of implants. Material and method: Nineteen skulls (37 sinuses, 10M / 9F) obtained from the collection of the department of anatomy and cell biology of Hanyang medical school were studied. The mean age of the deceased was 69.9 years (range 44 to 88 years). The distance between alveolar border and inferior sinus margin at each tooth, the height of alveolar process and the thickness of cortical bone of the outer and inner table of alveolar process and the inferior wall of maxillary sinus were measured. Results and Conclusion: 1. The septum of inferior maxillary sinus were observe 28 sides (76.%) and located at the third molar (52.6%) and the second molar (26.3%). The deepest points of inferior border of maxillary sinus were located the first or second molar. The distance between alveolar margin and the deepest point of inferior maxillary sinus is $9.7{\pm}4.9mm$. 2. The length of the outer table of alveolar process were $4.9\sim28.2mm$ and the shortest point was between the first and the second molors. The thickness of them were $0.9\sim3.2mm$. The length of the inner table of alveolar process were $7.4\sim25.8mm$ and the shortest point was between the first and the second molars. The thickness of the were $0.9\sim4.6mm$. The results of this study are useful anatomical data for installing of maxillary implants.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.43 no.3
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• pp.160-165
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• 2017

Objectives: Dry socket may occur secondary to the removal of any tooth. However, most dry socket cases develop in the third molar region. Dry socket is multifactorial in nature and has been treated using various modalities with varying success rates. This study assessed the efficacy of platelet rich fibrin (PRF) in established dry socket. Materials and Methods: Ten patients of either sex aged from 41 to 64 years with established dry socket according to established criteria were treated using PRF. Evaluation was performed by observing the reduction of pain using visual analogue scale, analgesic tablet use over the follow-up period, and healing parameters. Results: Pain was reduced on the first day in all patients with decreased analgesic use. Pain was drastically reduced during follow-up on the first, second, third, and seventh days with a fall in pain score of 0 to 1 after the first day alone. The pain scores of all patients decreased to 1 by the first day except in one patient, and the scores decreased to 0 in all patients after 48 hours. Total analgesic intake ranged from 2 to 6 tablets (aceclofenac 100 mg per tablet) over the follow-up period of 7 days. Healing was satisfactory in all patients by the end of the seventh day. Conclusion: PRF showed early pain reduction in established dry socket with minimal analgesic intake. No patients had allergic reactions to PRF as it is derived from the patient's own blood. PRF showed good wound healing. Our study suggests that PRF should be considered as a treatment modality for established dry socket.

• Journal of The Korean Dental Society of Anesthesiology
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• v.11 no.1
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• pp.16-21
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• 2011

Background: Since introduced by Gow-Gates GA in 1973, Gow-Gates mandibular nerve block (GMNB) has played an important role in the area of dental local anesthesia. However, compared to the conventional inferior alveolar nerve block (IANB), this technique seems to fail to attract the attentions of general practitioners in South Korea. The aim of this study was to prove the clinical real value, mainly the anesthetic efficacy, of GMNB in minor oral surgery. Methods: The study group comprised 40 patients (15 males and 25 females) who were randomly allocated to receive GMNB or IANB for extraction of third molars. Both techniques utilized two 1.8 ml dental cartridges of 2% lidocaine including 1:100,000 epinephrine for each patient. Pulpal and gingival tissue anesthesia of mandibular premolars and molars were recorded at 0, 15 and 40 minutes after administration of local anesthetics using both an electric pulp tester and a sharp dental explorer. Results: The success rates of pulpal and gingival tissue anesthesia in the IANB group were not significantly different from the GMNB group in overall efficacy. Patient's and operator's satisfaction ratings were also not significantly different between two groups. Interestingly, the injection pain of GMNB group was significantly lower than that of IANB group. Conclusion: This study demonstrated that the anesthetic efficacy of pulpal and gingival tissue of GMNB was not inferior to that of IANB. The GMNB could be a good alternative of the IANB in most of minor oral surgical procedures.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.49.1-49.8
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• 2021

Objectives: To evaluate the fracture incidence of Reciproc R25 instruments (VDW) used during non-surgical root canal retreatments performed by students in a postgraduate endodontic program. Materials and Methods: From the analysis of clinical record cards and periapical radiographs of root canal retreatments performed by postgraduate students using the Reciproc R25, a total of 1,016 teeth (2,544 root canals) were selected. The instruments were discarded after a single use. The general incidence of instrument fractures and its frequency was analyzed considering the group of teeth and the root thirds where the fractures occurred. Statistical analysis was performed using the χ² test (p < 0.01). Results: Seven instruments were separated during the procedures. The percentage of fracture in relation to the number of instrumented canals was 0.27% and 0.68% in relation to the number of instrumented teeth. Four fractures occurred in maxillary molars, 1 in a mandibular molar, 1 in a mandibular premolar and 1 in a maxillary incisor. A greater number of fractures was observed in molars when compared with the number of fractures observed in the other dental groups (p < 0.01). Considering all of the instrument fractures, 71.43% were located in the apical third and 28.57% in the middle third (p < 0.01). One instrument fragment was removed, one bypassed, while in 5 cases, the instrument fragment remained inside the root canal. Conclusions: The use of Reciproc R25 instruments in root canal retreatments carried out by postgraduate students was associated with a low incidence of fractures.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.50 no.3
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• pp.153-160
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• 2024

Objectives: This study identifies factors for differential diagnosis among lesions by retrospectively comparing panoramic and cone-beam computed tomography images and analyzing the characteristics of lesions associated with impacted mandibular third molars (IMTs). Materials and Methods: A retrospective cohort study was conducted in patients who simultaneously underwent IMT extraction surgery and related benign tumor resection or cyst enucleation at our institution from 2017 to 2021. To compare the characteristics of each group, two comparative analyses were conducted. The first comparison considered the most frequently observed lesions associated with IMTs: dentigerous cysts, odontogenic keratocysts (OKCs), and ameloblastoma. The second comparison involved placing dentigerous cysts, which have a relatively low recurrence rate, into group A and placing OKC, ameloblastoma, and odontogenic myxoma, which have high recurrence rates, into group B. Results: Significant differences in the size of the lesion were found in the order of ameloblastoma, OKC, and dentigerous cyst (P<0.05). The buccolingual width of ameloblastoma differed significantly from that of the other groups, with no significant difference observed between the OKCs and dentigerous cysts (P=0.083). Conclusion: Patient age and lesion size differed significantly among lesion types associated with IMTs, with younger age and larger lesions for OKCs and odontogenic tumors. OKCs are likely to have a larger mesiodistal width than dentigerous cysts. The buccolingual width of ameloblastomas was larger than those of dentigerous cysts and OKCs.