• Journal of Dental Anesthesia and Pain Medicine
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• v.16 no.2
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• pp.95-102
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• 2016

Background: Surgery on the lower impacted third molar usually involves trauma in the highly vascularized loose connective tissue area, leading to inflammatory sequelae including postoperative pain, swelling, and general oral dysfunction during the immediate post-operative phase. This study aimed to investigate the effectiveness of preoperative injection of a single dose of 8 mg dexamethasone for postoperative pain control in lower third molar surgery. Methods: A controlled, randomized, split-mouth, prospective study involving lower third molar surgery was performed in 31 patients. The randomized sampling group was preoperatively injected, after local anesthesia, with a single dose of dexamethasone (8 mg in 2 ml) through the pterygomandibular space; 2 ml of normal saline (with no dexamethasone) was injected as a placebo. Results: The pain VAS score was significantly different on the day of the operation compared to the first post-operative day (P = 0.00 and 0.01, respectively), but it was not significantly different on the third and seventh postoperative day between the control and study groups. There was a significant reduction in swelling on the second postoperative day, and a difference between the second postoperative day and baseline value in the study group (P < 0.05). Trismus was highly significantly different on the second postoperative day and between baseline and second postoperative day between the groups (P = 0.04 and 0.02, respectively). Descriptive statistics and independent-samples t- test were used to assess the significance of differences. Conclusions: Injection of 8 mg dexamethasone into the pterygomandibular space effectively reduced the postoperative pain and other postoperative sequalae.

• Imaging Science in Dentistry
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• v.46 no.1
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• pp.1-7
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• 2016

Purpose: This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. Materials and Methods: The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Results: Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, $P{\leq}0.01$). 50% of age estimates in the second part of the study fell within a range of error of ${\pm}1year$, while 75% fell within a range of error of ${\pm}2years$. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. Conclusion: The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.4
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• pp.171-183
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• 2023

Objectives: Understanding the lingual nerve's precise location is crucial to prevent iatrogenic injury. This systematic review seeks to determine the lingual nerve's most probable topographical location in the posterior mandible. Materials and Methods: Two electronic databases were searched, identifying studies reporting the lingual nerve's position in the posterior mandible. Anatomical data in the vertical and horizontal dimensions at the retromolar and molar regions were collected for meta-analyses. Results: Of the 2,700 unique records identified, 18 studies were included in this review. In the vertical plane, 8.8% (95% confidence interval [CI], 1.0%-21.7%) and 6.3% (95% CI, 1.9%-12.5%) of the lingual nerves coursed above the alveolar crest at the retromolar and third molar regions. The mean vertical distance between the nerve and the alveolar crest ranged from 12.10 to 4.32 mm at the first to third molar regions. In the horizontal plane, 19.9% (95% CI, 0.0%-62.7%) and 35.2% (95% CI, 13.0%-61.1%) of the lingual nerves were in contact with the lingual plate at the retromolar and third molar regions. Conclusion: This systematic review mapped out the anatomical location of the lingual nerve in the posterior mandible, highlighting regions that warrant additional caution during surgeries to avoid iatrogenic lingual nerve injuries.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.1
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• pp.30-42
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• 2023

Objectives: While the reliability of immediate implant placement in the maxillary molar has been discussed, its significance is questionable. There have been no guidelines for case selection and surgical technique for successful treatment outcomes of immediate maxillary molar implants. Therefore, in this study, we classified alveolar bone height and socket morphology of the maxillary molar to establish guidelines for immediate implant placement. Materials and Methods: From 2011 to 2019, we retrospectively analyzed 106 patients with 148 immediate implants at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Inclusion and exclusion criteria were applied, and patient characteristics and treatment results were evaluated clinically and radiologically. Results: A total of 29 tapered, sand-blasted, large-grit, and acid-etched (SLA) surfaces of implants were placed in 26 patients. The mean patient age was 64.88 years. Two implants failed and were reinstalled, resulting in a 93.10% survival rate. Fluctuating marginal bone level changes indicating bone regeneration and bone loss were observed in the first year following installation and remained stable after one year of prosthesis loading, with an average bone loss of 0.01±0.01 mm on the distal side and 0.03±0.03 mm on the mesial side. Conclusion: This clinical study demonstrated the significance of immediate implant placement in maxillary molars as a reliable treatment with a high survival rate using tapered SLA implants. With an accurate approach to immediate implantation, surgical intervention and treatment time can be reduced, resulting in patient satisfaction and comfort.

• The korean journal of orthodontics
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• v.10 no.1
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• pp.71-79
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• 1980

The purpose of this study was (1) to determine the prevalence of some causes by which dental occlusion might be affected , (2) to determine the prevalence of malocclusion, and types of molar, vertical incisor and horizontal incisor relationships, and (3) to examine the sex difference in the prevalence ratios, and (4) to determine the between-examiner differences in assessing types of dental occlusion. The material consisted of 1281 males and 811 females, total 2091 persons, aged 17 to 21 years. Two examiners who were graduate students in the orthodontic course, examined independently dental occlusion of the material. Before calculating the statistics, the subjects consisted of 156 mates and 164 females, total 320 persons, haying any one or more causes suspected to affect dental occlusion, was eliminated. Then the remained subjects, 1124 males and 647 females, total 1771 persons, were assessed. The results were as follows 1. The prevalence of some causes by which dental occlusion might be affected was 15.32 per cent. The missing rate of any one or more first molars was 8.85 percent, that of any one or more teeth positioned anterior to the first molar was 3.83 per cent. The prevalence of crossbite of the first molar was 0.48 per cent, that of retained primary teeth was 0.77 percent, and that of orthodontic treatment was 0.43 per cent. 8. The rate of between-examiner difference was 12.53 per cent in assessing the types of molar relationship, 18.86 percent in assessing the types of horizontal incisor relationship, and 26.37 percent in assessing the types of horizontal incisor relationship. 3. There was no sex difference in the prevalence ratios of the types of molar relationship. The prevalence of Class I molar relationship was 80.91 percent, that of Class II was 5,03, that of Class II subdivision was 4.01, Percent, that of Class III was 5.99 percent and that of Class III subdivision was 4.07 percent. 4. In the prevalence of the types of horizontal incisor relationship, there were no sex differences except that of Class II division 2. The prevalence of Class I horizontal incisor relationship was 73.12 percent, that of Class II division t was 12.03 percent, that of Class II division 2 was 6.58 percent in male and 4.33 percent in female, and that of Class III was 9.09 percent. 5. In the prevalence of the types of vertical incisor relationship, there were no sex differences except that of deep bite, The prevalence of open bite was 2.20 per cent, that of edge-to-edge bite was 9.15 percent, that of normal bite was 76,34 percent, and that of deep bite was 14.15 percent in male and 9.12 percent in female. 6. There was no sex difference in the prevalence of malocclusion the prevalence of malocclusion was 82.67 percent and that of normal occlusion was 17.33 percent. 7. There was a tendency that when Class I molar relationship changed to Class II, incisor relationships were to be larger overjet or upright upper incisors and deep bite, but when that changed to Class III molar relationship, these were to be cross bite and openbite.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.417-428
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• 2004

The purpose of this study was to evaluate the stress distributions at the periodontal ligament (PDL) and displacements of the maxillary first molar when mesially directed force was applied under various molar angulations and rotations. A three dimensional finite element model of the maxiilary first molar and its periodontal ligament was made Upright position, mesially angulated position by $20^{\circ}$ and distally angulated position of the same degree were simulated to investigate the effect of molar angulation. An anteriorly directed force of 200g countertipping moment of 1,800gm-mm (9:1 moment/force ratio) and counterrotation moment of 1,000gm-mm (5:1 moment/force ratio) were applied in each situation. To evaluate the effect of molar rotation on the stress distribution, mesial-in rotation by $20^{\circ}$ and the same amount of distal-in rotation were simulated. The same force and moments were applied in each situation. The results were as follows: In all situations, there was no significant difference in mesially directed tooth displacement Also, any differences in stress distributions could not be found, in other words. there were no different mesial movements. Stress distributions and tooth displacement of the $20^{\circ}$ mesially angulated situation were very similar with those of the $20^{\circ}$ distal-in rotated situation. The same phenomenon was obserned between the $20^{\circ}$ distally angulated situation and $20^{\circ}$ mesial-in rotated situation. When the tooth was mesially angulated, or distal-in rotated, mesially directed force made the tooth rotate in the coronal plane. with its roots moving buccally, and its crown moving lingually. When the tooth was distally angulated, or mesial-in rotated, mesially directed force made the tooth rotate in the coronal plane, with its roots moving lingually and its crown moving buccally. When force is applied to au angulated or rotated molar, the orthodontist should understand that additional torque control is needed to prevent unwanted tooth rotation in the coronal plane.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.137-144
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• 2009

The aim of this study was to investigate the shapes and diameters of the physiological foramen and anatomy of the root canal at 3mm from apex in mandibular first molars. Sixty mandibular first molars were randomly selected. The apical anatomy of 60 mandibular first molars was investigated by means of a stereo microscope (60x magnification). The results were as follows; 1. There was a high percentage of two physiological foramina in mesial (61.67%) and one foramen in distal(71.66%) roots of mandibular first molars. 2. There was a high frequency of accessory foramina in mesial roots with one foramen (26.07%). 3. The diameters of physiological foramen was as follows: - 0.329mm in single mesial foramen - 0.266mm in mesiobuccal foramen and 0.246mm in mesiolingual foramen - 0.375mm in single distal foramen - 0.291mm in distobuccal foramen and 0.237mm in distolingual foramen 4. The most common physiological foramen shape was oval (69.93%). 5. The incidence of isthmus in mesial root at 3mm from apex was 55%. The 3mm-sections contained a complete isthmus 31.66% and a partial isthmus 23.34%. 6. 3mm from the apex, the most common canal shape was oval (50.64%). Knowledge of the apical anatomy of mandibular first molar would be necessary for success of surgical and nonsurgical endodontic treatment.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.410-418
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• 2016

This study examined the prevalence of MIH and severity of hypomineralization exhibited by MIH-affected tooth based on the clinical examination of 950 children between age 8 and 9 in the city of Jeonju. The etiology was also studied utilizing a questionnaire on the MIH risk factors. The prevalence of MIH was 7.1%. The examined MIH-affected teeth showed statically significant difference in the degree of their hypomineralization (p < 0.05). The permanent first molar showed greater frequency of MIH compared to the permanent incisor, and the MIH code 2a and 3 were only observed in the permanent first molar (p < 0.05). From the questionnaire, showed the significant relationship between the occurrence of MIH and risk factors such as stress and antibiotics intake during pregnancy, low birth weight and events like hospital admission, frequent respiratory infection, high fever and long-term antibiotics intake within the three years of children's lives (p < 0.05). Among all the possible risk factors, the antibiotics intake during pregnancy only showed high correlation with the incidence of MIH (p < 0.05).

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.61-74
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• 1998

The Purpose of this study was to investigate the stress distribution and tooth displacement at the initial phase produced by 5 types of molar uprighting springs using finite element method. The three dimensional finite element model of lower dentition, bone and springs was composed of 5083 elements and 2071 nodes. The results were as follows: 1. In case of helical spring and root spring, intrusion of lower canine and first premolar were observed md distal tipping, translation and extrusion of lower second molar were observed. 2. In case of T-loop, modified T-loop and box loop, intrusion and distal translation of lower second premolar were observed, and the largest crown distal tipping and translation of lower second molar were observed in T-loop and the smallest were observed in box loop. 3. In case of T-loop with cinch-bact crown distal tipping and translation of lower second molar were decreased, but extrusion was also decreased. 4. With increase of activation in T-loop, mesial translation and won distal tipping of lower second molar were increased and edentulous space was closing, but distal translation of second premolar was also increased. 5. With increase of tip-back bend in T--loop, distal tipping and translation of lower second molar were increased, but extrusion was also increased more largely.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.138-144
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• 2015

Effects of Co/Al and Si/Al molar ratios of cobalt incorporated SAPO-34 catalysts (CoAPSO-34) on their catalytic lifetime were investigated in dimethyl to olefin (DTO) reaction. The property of CoAPSO-34 catalysts was characterized using XRD, SEM, $^{29}Si$ MAS NMR, and $NH_3$-TPD techniques. First, the lifetime of CoAPSO-34 prepared by varying Co/Al molar ratios was improved than that of using the SAPO-34 catalyst, and the optimal Co/Al molar ratio was 0.0025. The total acid site amounts increased from 0.432 to 1.111 mmol/g with increasing Si/Al molar ratios from 0.05 to 0.20 while fixing a Co/Al molar ratio of 0.0025. However, the catalysts with too high acid site amounts were deactivated rapidly with blockages of the pores due to the fast accumulation of polycyclic aromatic hydrocarbons in the cage. Therefore, the CoAPSO-34 catalyst with a proper Si/Al molar ratio of 0.10 was the most superior in terms of the lifetime, which was improved by about 87% as compared with that of the SAPO-34 catalyst.