• Journal of the korean academy of Pediatric Dentistry
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• v.8 no.1
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• pp.21-24
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• 1981

The author observed a case of ectopic erupted maxillary second premolars and impacted mandibular second premolars due to premature loss of the primary second molars. The treatments were done as follows: 1. In the maxilla, the teeth arrangement problem was corrected with removal of the ectopic erupted second premolars. 2. In the mandible, normal dentition was established with surgical removal of the left second premolar and removal of the permanent first molar in right side combined by orthodontic therapy.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.573-579
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• 2001

The purpose of this study was to investigate the characteristiss of korean multi-rooted teeth extracted by periodontal disease. A total of 182 extracted multi-rooted teeth were examined. The distance from the cementoenamel junction(CEJ) to the root groove and from the CEJ to the root division was measured. The frequency of the root grooves were calculated. The results are as follows : 1. Distances from CEJ to the root groove were $1.53{\cdot}1.60mm$ for maxillary first premolars mesial${\cdot}$distal sides, $1.26{\cdot}1.38{\cdot}1.75mm$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $1.38{\cdot}1.71{\cdot}1.41mm$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $0.98{\cdot}0.99mm$ for mandibular first molars buccal${\cdot}$lingual sides and $1.28{\cdot}1.35mm$ for mandibular second molars buccal${\cdot}$lingual sides. 2. The frequency of the root grooves were $17.4{\cdot}30.4%$ for maxillary first premolars mesial${\cdot}$distal sides, $44.4{\cdot}84.1{\cdot}67.5%$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $100{\cdot}90.3{\cdot}90.3%$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $42.9{\cdot}77.8%$ for mandibular first molars buccal${\cdot}$lingual sides and 90.6% for mandibular second molars buccal${\cdot}$lingual sides. 3. Distances from CEJ to the root division were $6.8{\cdot}7.2mm$ for maxillary first premolars mesial${\cdot}$distal sides, $3.3{\cdot}4.38{\cdot}4.34mm$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $3.67{\cdot}4.8{\cdot}4.07mm$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $3.1{\cdot}3.89mm$ for mandibular first molars buccal${\cdot}$lingual sides and $3.2{\cdot}4.06mm$ for mandibular second molars buccal${\cdot}$lingual sides.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.1
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• pp.19-25
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• 1993

The purpose of this study was to evaluate the prevalence and distribution of additonal root in the mandibular 1st molars and premolars by means of the analysis of the full mouth periapical radiographs in 6,082 patients visited the Dental Infirmary of Kyungpook National University Hospital from March 1989 to February 1993. The results were as follows: 1. The incidence of additional root in the mandibular 1st molars was revealed to be 9.32% in total examined patients, and there was a higher prevalence in males(I1.35%) than in females(7.46%). And bilateral occurrence was revealed to be 4.26%. 2. The incidence of additional root in the mandibular premolars was to be 3.57% in total examined patients, and there was a higher prevalence in males(4.28%) than in females(2.91%). And bilateral occurrence in the 1st premolars was revealed to be 1.53%.

• Proceedings of the KACD Conference
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• 2006.05a
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• pp.229-229
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• 2006

• The korean journal of orthodontics
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• v.26 no.1 s.54
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• pp.33-41
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• 1996

Retrostpective study of two groups of patients was conducted to evaluate the physiologic drift of the mandibular teeth following the extraction of four first premolars. The concept of physiologic drift, commonly referred to as 'driftodontics', following first premolar extractions has been gaining acceptance in the orthodontic community, the exact nature and amount of drift has not been adequately documented. There were also no guide lines as to when drift should be allowed to now. The purpose of this study was to quantify physiologic drift of the untreated mandibular dentition following extraction of the four first premolars during the early permanent and late permanent dentition stages. The early permanent dentition extraction sample(Group 1) included 26 Patients and the mean age at pretreatment was approximately 13.5 years. The observation period following extraction was approximately 6.96 months. The late permanent dentition extraction sample(Group 2) included 31 patients. The mean age at pretreatment was 21.3 years, followed by a observation period of 7.26 months. During the observation period, except for the extractions, no other mandibular therapy was rendered. Pre-and post-treatment lateral cephalograms and dental casts were analyzed. The obtained results were as follows 1. Group 2 showed marked changes in movements of the mandibular incisors and canines but minimal changes in molars. 2. The amount of changes in movements of the mandibular incisors and canines were significantly greater in Group 1 than in Group 2. The results showed no differences in rates of molar movements between groups. 3. Physiologic drift of the dentition produced desirable changes such as decreased Incisor Irregularity.

• Imaging Science in Dentistry
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• v.44 no.3
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• pp.221-227
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• 2014

Purpose: This study aimed to investigate the clinical anatomy of lower premolar roots in a Spanish population by using cone-beam computed tomography (CBCT), correlating findings with patient gender and tooth type. Materials and Methods: Using 70 CBCT images, we evaluated 126 healthy, untreated, well-developed lower premolars. The number and morphology of roots and root canals, and the foramina number were assessed. Results for gender and tooth type were compared using the chi-squared and ANOVA tests. Results: The average length of teeth and roots was significantly higher in men (p=0.00). All 126 premolars had a single root. One canal was found in 83.3% of the premolars, with no gender or tooth type differences; Vertucci configuration types I and V were the most prevalent. The first premolars showed significantly greater variability than the second premolars (p=0.03). A single apical foramen was found in 89.7% of the premolars, with no differences by tooth type. Women had a significantly higher prevalence of two apical foramina than men (p=0.04). Some degree of curvature was observed in 65% of the premolars, with no differences by gender or tooth type. A root angle of more than $20^{\circ}$ was found in 12.98% of the premolars, without any differences by gender or tooth. Conclusion: All premolars were single-rooted. One canal had the most prevalent morphology. More variability in canal anatomy was found in the first premolars. Curvatures greater than $20^{\circ}$ were found at less than 5 mm from the apex.

• Journal of Veterinary Clinics
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• v.35 no.4
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• pp.137-140
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• 2018

A five-month-old toy poodle was referred for treatment of bilateral mandibular fractures. Preoperative skull and dental radiographs showed rostral mandibular fractures and permanent teeth that had not yet erupted. In addition to providing stability for the healing of fractures, it is very important to focus on restoring normal occlusion. The mandibular fractures were repaired using interdental wiring in a dentate area where the deciduous canines and fourth premolars were stable and could be used to anchor the interdental fixation. In the absence of an erupted permanent mandibular first molar, the modified Risdon wiring was performed using the deciduous mandibular fourth premolars as anchor teeth. An intraoral splint was placed on the mandibular teeth using self-curing composite resin. Five months after surgery, the patient had experienced no complications, and the permanent teeth had erupted normally. In this case, which involves a small-breed puppy with deciduous dentition, treatment with a wire-reinforced interdental splint using intact deciduous fourth premolar teeth as anchor teeth can be considered as a suitable method for rostral mandibular fracture restoration.

• The korean journal of orthodontics
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• v.45 no.4
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• pp.180-189
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• 2015

Objective: To compare the positions of the mandibular premolars in Angle Class I subjects according to vertical facial type. The results will provide a theoretical basis for predicting effective tooth movement in orthodontic treatment. Methods: Cephalometric parameters were determined using cone-beam computed tomography in 120 Angle Class I subjects. Subjects were categorized as short, normal, and long face types according to the Frankfort mandibular angle. Parameters indicating the position of the mandibular right premolars and the mandible were also measured. Results: The angle between the mandibular first premolar axis and buccal cortex, the distance between the root apex and buccal cortex, angle of vestibularization, arc of vestibularization, and root apex maximum movable distance were significantly greater in the short face type than in the long and norm face types. The angle between the mandibular second premolar axis and buccal cortex, the distance from root apex to buccal cortex, and the arc of vestibularization were significantly greater in the short face type than in the normal face type. Conclusions: There are significant differences in the mandibular premolar positions in Class I subjects according to vertical facial type.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.3
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• pp.293-299
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• 2008

Bite force is created by the force of adjacent teeth accompanied with tension of masticatory muscle. The bite force value is greater in male than in female and ha maximum value at first molar. Masseter muscle is associated with bite force and during muscle contraction the electric signal is expressed in EMG form. The aim of the study is to assess recovery time for masseter muscle activity and according to each part of bite force after open reduction with internal fixation when mandibular angle fracture and subcondyle fracture occurred. And to determine the appropriate period for mandibular fracture patients to have normal masticatory activity. 30 patients with normal bite condition was selected for control group and from April, 2007 to September, 2007, 20 patients who visited our department of oral and maxillofacial surgery of Dankook University, were selected for the study and were diagnosed as mandibular angle fracture and subcondyle fracture. For control group, the bite force for incisors, canine, premolars and molars and activity of the masseter muscle was measured and compared for 1, 2, 3, 4, 6 and 8 weeks. That was divided as fracture side and normal side. Mann-Whitney U test was performed for significant difference and the following result was obtained. 1. The maximum voluntary bite force for incisors, canine, premolars and molars portion were 0.113 kN, 0.182kN, 0.295kN and 0.486kN and the masseter muscle activity was 0.192 volts in the control group. 2. The maximum bite force at fracture side was recovered by 4th weeks for incisors, 6th weeks for canine and premolars and 8th weeks for molars and the masseter muscle activity was recovered by 6th weeks in the experimental group. 2. The maximum bite force at normal side was recovered by 4th weeks for incisors, 6th weeks for canine, premolars and molars and the masseter muscle activity was recovered by 3rd weeks in the experimental group. 3. The method for internal fixation by 2.0mm miniplates at both superior and inferior border had no complications according for twenty patients and had a satisfactory recovery. According to the result, patient with mandibular angle fracture and subcondyle fracture, 8 weeks was required for bite force recovery. Therefore, patients with open reduction and internal fixation under general anesthesis, it can be assumed that 8 weeks was needed after operation in order to have normal bite force and masseter muscle recovery.

• The korean journal of orthodontics
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• v.52 no.5
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• pp.354-361
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• 2022

Objective: To analyze the overall treatment effects in terms of the amount of uprighting with changes in the three-dimensional positions of the mandibular posterior teeth after applying the biocreative reverse curve (BRC) system. Methods: Thirty-four patients (mean age, 20.5 ± 8.56 years) were treated using the BRC system (mean period, 8.17 ± 2.19 months). Cone-beam computed tomography was performed before treatment and after treatment with the BRC system. The three-dimensional movement of each tooth was analyzed in the coordinate system at points on the crown and root apex. A paired t-test was used to analyze the treatment effects of the BRC system. Results: The application of the BRC system spanning from the first premolar to the second molar resulted not only in buccal and distal uprighting, but also in increased buccal and distal tipping of the teeth. The premolars and the first molar were extruded, and the second molar was intruded. Conclusions: When the BRC system is applied, simultaneous distal and buccal uprighting of the premolars and molars can be achieved bilaterally using a temporary skeletal anchorage device without unnecessary movement of the anterior teeth.