• The korean journal of orthodontics
• /
• v.38 no.4
• /
• pp.228-239
• /
• 2008

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion. Methods: A 3D finite element method was used to model the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) Into 1 mm thick cortical bone with a pre-drilled hole of 0.9 mm in diameter. A total of 1,800 analysis steps was used to simulate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, was observed in the bone along the whole length of the microimplant. At the bone in the vicinity of the screw tip, strains of higher than 100% was recorded. The insertion torque was calculated at approximately 1.2 Ncm which was slightly lower than those measured from the animal experiment using rabbit tibias. Conclusions: The insertion process of a microimplant was successfully simulated using the 3D finite element method which showed that bone strains from a microimplant insertion might have a negative impact on physiological remodeling of bone.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.47 no.5
• /
• pp.373-381
• /
• 2021

Objectives: In the present study, the effects of sagittal split ramus osteotomy (SSRO) combined with intraoral vertical ramus osteotomy (IVRO) for the treatment of asymmetric mandible in class III malocclusion patients were assessed and the postoperative stability of the mandibular condyle and the symptoms of temporomandibular joint disorder (TMD) evaluated. Materials and Methods: A total of 82 patients who underwent orthognathic surgery for the treatment of facial asymmetry or mandibular asymmetry at the Department of Oral and Maxillofacial Surgery, Dong-A University Hospital, from 2016 to 2021 were selected. The patients that underwent SSRO with IVRO were assigned to Group I (n=8) and patients that received bilateral SSRO (BSSRO) to Group II (n=10, simple random sampling). Preoperative and postoperative three-dimensional computed tomography (CT) axial images obtained for each group were superimposed. The condylar position changes and degree of rotation on the superimposed images were measured, and the changes in condyle based on the amount of chin movement for each surgical method were statistically analyzed. Results: Group I showed a greater amount of postoperative chin movement. For the amount of mediolateral condylar displacement on the deviated side, Groups I and II showed an average lateral displacement of 0.07 mm and 1.62 mm, respectively, and statistically significantly correlated with the amount of chin movement (P=0.004). Most of the TMD symptoms in Group I patients who underwent SSRO with IVRO showed improvement. Conclusion: When a large amount of mandibular rotation is required to match the menton to the midline of the face, IVRO on the deviated side is considered a technique to prevent condylar torque. In the present study, worsening of TMD symptoms did not occur after orthognathic surgery in any of the 18 patients.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.46 no.2
• /
• pp.173-182
• /
• 2019

Vertical facial growth triggers the rotation of mandible to move the chin point to the downward and backward direction, which showed remarkably effective result making the less prominent chin. Recently, the intraoral removable appliance utilizing class III elastic demonstrated the vertical growth trigger mechanism. The treatment change was very fast and wearing was quite easy, compared to extraoral appliances. The purpose of this study was to verify the duration of the treatment on class III malocclusion using intraoral removable appliances, which designed to accelerate vertical facial growth. 56 patients were selected with the complaint of the protruded mandible and class III malocclusion (overjet : -3 - 0 mm, overbite : 0 - 4 mm). Information like; age at start, duration of the treatment events, type of the treatment, overjet, overbite etc. was collected and calculated. The average age of the patients delivering the initial brace was $8.75{\pm}1.10year$. Most of the anterior crossbite was resolved within 6 months. The total treatment period was $21.79{\pm}10.73months$ with the additional procedures like the alignment of anterior teeth and torque control using additional removable and fixed orthodontic appliances. The correlation study showed that patient's cooperation (p = 0.000) and the use of fixed appliance (p = 0.032) were significantly influenced on treatment duration.

• Restorative Dentistry and Endodontics
• /
• v.32 no.4
• /
• pp.385-396
• /
• 2007

The aims of this study were to compare the shaping effect and safety between single length technique recommended by manufacturer and crown-down technique using Mtwo rotary file and to present a modified method in use of Mtwo file. Sixty simulated root canal resin blocks were used. The canals were divided into three groups according to instrument and the manner of using methods. Each group had 20 specimens. Group MT was instrumented with single length technique of Mtwo, group MC was instrumented with crown-down technique of Mtwo and group PT was instrumented with crown-down technique of ProTaper. All of the rotary files used in this study were operated by an electric motor. The scanned canal images of before and after preparation were superimposed. These superimposed images were evaluated at apical 1 to 8 mm levels Angle changes were calculated. The preparation time, weight loss, instrument failure and binding, canal aberrations, and centering ratio were measured. Statistical analysis of the three experimental groups was performed with ANOVA and Duncan's multiple range tests for post-hoc comparison and Fisher's exact test was done for the frequency comparison. In total preparation time, group MT and group MC were less than group PT. In the aberrations, group MT had more elbows than those of group MC and group PT. The binding of group MC was least and group MT was less than group PT (P < 0.05). Under the condition of this study, crown-down technique using Mtwo rotary file is better and safer method than single length technique recommended by the manufacturer.