• The korean journal of orthodontics
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• v.43 no.6
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• pp.271-278
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• 2013

Objective: The purposes of this study were to determine the accuracy of crown and root length measurements of premolars using cone-beam computed tomography (CBCT) and to generate reference CBCT-based data on incisor, canine, and premolar lengths in patients with malocclusions. Methods: Imaging was performed using a CBCT scanner with a 0.292-mm voxel size and 12-bit grayscale. The CBCT-based length measurements were compared with direct measurements of 94 subsequently extracted premolars without metal restorations using the paired t-test. Furthermore, the crown and root lengths of incisors, canines, and premolars in 62 Korean patients with malocclusions were measured using CBCT, and Pearson's correlation coefficients were calculated to examine the relationship between the crown and root length measurements of each tooth type. Results: The differences between the CBCT-based and direct measurements of the extracted premolars were not significant, with 95% limits of agreement of -0.90 to 0.90 mm for crown length and -1.23 to 1.18 mm for root length. Weak positive correlations between the crown and root length measurements were observed for the mandibular canine and premolars. Conclusions: The CBCT-based measurements showed a wider range of limits of agreements for root length than for crown length. The CBCT-based data can be used as a reference for evaluating root length and resorption of teeth without metal restorations in patients with malocclusions.

• The Journal of Advanced Prosthodontics
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• v.12 no.3
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• pp.157-166
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• 2020

PURPOSE. The aim of this study was to evaluate the clinical performance and reliability of plasma sprayed nanostructured zirconia (NSZ) coating. MATERIALS AND METHODS. This study consisted of three areas of analysis: (1) Mechanical property: surface roughness of NSZ coating and bond strength between NSZ coating and titanium specimens were measured, and the microstructure of bonding interface was also observed by scanning election microscope (SEM). (2) Biocompatibility: hemolysis tests, cell proliferation tests, and rat subcutaneous implant test were conducted to evaluate the biocompatibility of NSZ coating. (3) Mechanical compatibility: fracture and artificial aging tests were performed to measure the mechanical compatibility of NSZ-coated titanium abutments. RESULTS. In the mechanical study, 400 ㎛ thick NSZ coatings had the highest bond strength (71.22 ± 1.02 MPa), and a compact transition layer could be observed. In addition, NSZ coating showed excellent biocompatibility in both hemolysis tests and cell proliferation tests. In subcutaneous implant test, NSZ-coated plates showed similar inflammation elimination and fibrous tissue formation processes with that of titanium specimens. Regarding fatigue tests, all NSZ-coated abutments survived in the five-year fatigue test and showed sufficient fracture strength (407.65-663.7 N) for incisor teeth. CONCLUSION. In this study, the plasmasprayed NSZ-coated titanium abutments presented sufficient fracture strength and biocompatibility, and it was demonstrated that plasma spray was a reliable method to prepare high-quality zirconia coating.

• The korean journal of orthodontics
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• v.47 no.1
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• pp.39-49
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• 2017

Objective: This retrospective, cross-sectional study aimed to establish reference data for normal crown and root lengths and the root-crown ratios (R/C ratios) for the mature maxillary and mandibular incisors in a Korean population by using cone-beam computed tomography (CBCT). Methods: We included 672 Korean patients (141 men and 531 women; mean age, $27.2{\pm}7.7years$) who underwent CBCT examinations during various dental treatments. Crown and root lengths and the R/C ratios of the maxillary and mandibular incisors were measured using CBCT data, which were analyzed to detect significant differences between demographic factors as well as sagittal and vertical skeletal or occlusal relationships. Results: Teeth of the same type in each half-arch were symmetrical. The mean R/C ratios varied from 1.1 to 1.2 for the maxillary incisors and from 1.3 to 1.4 for the mandibular incisors. Crown and root lengths were greater in men than in women, regardless of tooth type. Root lengths and R/C ratios for the mandibular incisors were significantly greater in patients with skeletal Class II malocclusion or an excessive overjet than in the other patients. The R/C ratios for the mandibular incisors were lower in patients with an open bite than in those with a normal or deep bite. Moreover, the R/C ratios for the mandibular incisors increased with age. Conclusions: The data obtained in our study can serve as reference values for crown and root lengths and the R/C ratios for the maxillary and mandibular incisors in the Korean population.

• Archives of Plastic Surgery
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• v.35 no.3
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• pp.273-278
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• 2008

Purpose: The most widely accepted protocol for alveolar cleft reconstruction is to repair it during the mixed dentition stage. There were lower resorption rate (about 88%) at this stage. However we found some cases that need repeated bone grafting. Therefore we sought to analyze the cause of repeated alveolar bone grafting in connection with other factors. Methods: From January 2000 to January 2006, thirty-nine secondary alveolar bone grafts with iliac crest spongiosa were carried out. In 39 patients, 5 patients who had significant bone graft resorption received repeated alveolar bone graft. In all the cases, the causes of repeated bone grafts were dental root exposure(angulation), and the deficiency of the bony support for lateral incisor or canine eruption. In 3 cases, there was deficiency of the alveolar bone at the cleft side. There was the need of repeated bone grafts for orthodontic treatment in 2 cases and for application of dental implants in 1 case. Results: During the follow-up period, the clinical and radiologic examinations showed that repeated alveolar bone grafts were maintained successfully without any complications. The volume of the repeated bone graft was sufficient for orthodontic treatment and implantation. Conclusion: The essential conditions for successful alveolar bone grafting includes the status of cleft sided teeth, further treatment and planed schedule, as well as canine eruption. Alveolar bone grafting has to be performed with difference of each case in mind.

• The korean journal of orthodontics
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• v.42 no.5
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• pp.227-234
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• 2012

Objective: To evaluate the presurgical orthodontic tooth movement of mandibular teeth after dental decompensation for skeletal Class III deformities on the basis of vertical skeletal patterns. Methods: This cohort was comprised of 62 patients who received presurgical orthodontic treatment. These patients were divided into 3 groups according to their vertical skeletal patterns. Changes in the positions of the mandibular central incisor, canine, premolar, and 1st molar after presurgical orthodontic treatment were measured using a cone-beam computed tomography (CBCT) superimposition method. Results: The incisors moved forward after dental decompensation in all 3 groups. The canines in group I and the 1st premolars in groups I and III also moved forward. The incisors and canines were extruded in groups I and II. The 1st and 2nd premolars were also extruded in all groups. Vertical changes in the 1st premolars differed significantly between the groups. We also observed lateral movement of the canines in group III and of the 1st premolar, 2nd premolar, and 1st molar in all 3 groups (p < 0.05). Conclusions: Movement of the mandibular incisors and premolars resolved the dental compensation. The skeletal facial pattern did not affect the dental decompensation, except in the case of vertical changes of the 1st premolars.

• The korean journal of orthodontics
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• v.46 no.6
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• pp.395-408
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• 2016

We report a case involving a young female patient with severe mandibular retrognathism accompanied by mandibular condylar deformity that was effectively treated with Le Fort I osteotomy and two genioplasty procedures. At 9 years and 9 months of age, she was diagnosed with Angle Class III malocclusion, a skeletal Class II jaw relationship, an anterior crossbite, congenital absence of some teeth, and a left-sided cleft lip and palate. Although the anterior crossbite and narrow maxillary arch were corrected by interceptive orthodontic treatment, severe mandibular hypogrowth resulted in unexpectedly severe mandibular retrognathism after growth completion. Moreover, bilateral condylar deformities were observed, and we suspected progressive condylar resorption (PCR). There was a high risk of further condylar resorption with mandibular advancement surgery; therefore, Le Fort I osteotomy with two genioplasty procedures was performed to achieve counterclockwise rotation of the mandible and avoid ingravescence of the condylar deformities. The total duration of active treatment was 42 months. The maxilla was impacted by 7.0 mm and 5.0 mm in the incisor and molar regions, respectively, while the pogonion was advanced by 18.0 mm. This significantly resolved both skeletal disharmony and malocclusion. Furthermore, the hyoid bone was advanced, the pharyngeal airway space was increased, and the morphology of the mandibular condyle was maintained. At the 30-month follow-up examination, the patient exhibited a satisfactory facial profile. The findings from our case suggest that severe mandibular retrognathism with condylar deformities can be effectively treated without surgical mandibular advancement, thus decreasing the risk of PCR.

• The korean journal of orthodontics
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• v.44 no.6
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• pp.281-293
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• 2014

Objective: Esthetic improvements during orthodontic treatment are achieved by changes in positions of the lips and surrounding soft tissues. Facial soft-tissue movement has already been two-dimensionally evaluated by cephalometry. In this study, we aimed to three-dimensionally assess positional changes of the adult upper lip according to simulated maxillary anterior tooth movements by white light scanning. Methods: We measured changes in three-dimensional coordinates of labial landmarks in relation to maxillary incisor movements of normal adults simulated with films of varying thickness by using a white light scanner. Results: With increasing protraction, the upper lip moved forward and significantly upward. Labial movement was limited by the surrounding soft tissues. The extent of movement above the vermilion border was slightly less than half that of the teeth, showing strong correlation. Most changes were concentrated in the depression above the upper vermilion border. Labial movement toward the nose was reduced significantly. Conclusions: After adequately controlling several variables and using white light scanning with high reproducibility and accuracy, the coefficient of determination showed moderate values (0.40-0.77) and significant changes could be determined. This method would be useful to predict soft-tissue positional changes according to tooth movements.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.704-709
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• 2006

Ectopic eruption should be understood as a change in the course of the normal eruption path of a dental bud at any moment in its origin. Transposition is a unique and extreme form of ectopic eruption. The treatment for ectopic eruption and transposition is various from simple observation to surgical exposure and orthodontic traction, according to direction of erupting tooth degree of developing root apex and eruption space etc. Autotransplantation is transplantation of tooth from one area of the mouth to another in the same individual or is moving a eruption tooth into extraction socket or surgically prepared socket, and autotransplantation is considered as a treatment of choice for the ectopic eruption when orthodontic traction is unable or when tooth movement is limited. These cases which were treated with autotransplantation of maxillary lateral incisor and maxillary canine were reported, and good esthetic and functional result were induced.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.295-317
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• 1991

The discrepancy between centric relation and centric occlusion have a great role on the successful prosthodontic and occlusal treatment. This study was performed to investigate the effect of the discrepancy between centric relation and centric occlusion on condylar guidance inclination and Bennett shift (immediate and progressive side shift). Sixteen adults who have physiologically normal occlusion and are free of TMJ dysfunction were selected. The amount of the sagittal CR-CO discrepancy in lower anterior incisor was obtained by Saphon Visi-Trainer. The amount of the CR-CO discrepancy in condylar level was measured on the individualized corrected tomography. Pantronic survey was performed by using a arbitrary hinge axis according to manufacturer's direction. All subjects were divided into two groups, group I (small) and group II (large), according to the amount of CR-CO discrepancy. At first the amount of the CR-CO discrepancy in condylar level between two groups was compared and then the condylar guidance inclination and Bennett shift between two groups were compared and analyzed. The results were as follows; 1. The average CR-CO discrepancy in lower anterior incisors was 0.7mm superoinferiorly, 0.49mm anteroposteriorly, and 0.88 mm in total. The average CR-CO discrepancy in condylar level was 0.43mm. 2. The CR-CO discrepancy measured on teeth level and condylar level were highly correlated (p<0.01). 3. The correlation of the condylar position in the glenoid fossa between two groups was not statistically significant. 4. The large CR-CO discrepancy group showed greater amount of Bennett shift and condylar guidance inclination, but there is no statistical significancy. 5. It seems that the CR-CO discrepancy have greater effect on progressive side shift than other elements of mandibular movements.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.256-261
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• 2000

Trauma to the tooth is the most common accidents in pediatric dentistry and tooth fracture occurs frequently. Fracture is classified into crown fracture, root fracture, and crown-root fracture which involves both. Also, it is classified into simple or complicated fracture depending on whether the pulp is exposed or not. When the fracture is extended down to the subgingival level following the long axis of the root, or when more than 1/3 of the root is involved, extraction is the primary treatment. But alternative treatment such as extruding the root fragment with orthodontic force and restoring it, or intentionally extracting the tooth and replanting it to a position which it can be restored. This is a case report on intentional replantation of a traumatized maxillary central incisor with crown-root fracture of a patient with mixed dentition. The teeth was extracted and immediate endodontic treatment, retrograde filling and resin restoration were carried out.