Assessment of bone density changes following two-jaw surgery using multidetector computed tomography: A pilot study / 대한치과교정학회지

Objective@#The aim of this retrospective study was to evaluate the pre- and postsurgical bone densities at alveolar and extra-alveolar sites following twojaw orthognathic surgery. @*Methods@#The sample consisted of 10 patients (mean age, 23.2 years; range, 18.0–27.8 years; 8 males, 2 females) who underwent two-jaw orthognathic surgery. A three-dimensional imaging program (Invivo 5) was used with multidetector computed tomography images taken preand postoperatively (obtained 32.3 ± 6.0 days before surgery and 5.8 ± 2.6 days after surgery, respectively) for the measurement of bone densities at the following sites: (1) alveolar bone in the maxilla and mandible, (2) extra-alveolar sites, such as the top of the head, menton (Me), condyle, and the fourth cervical vertebrae (C4). @*Results@#When pre- and postsurgical bone densities were compared, an overall tendency of decrease in bone density was noted. Statistically significant reductions were observed in the densities of cancellous bone at several areas of the maxillary alveolar bone; cortical and cancellous bone in most areas of the mandibular alveolar bone; cortical bone in Me; and cancellous bone in C4. There was no statistically significant difference in bone density in relation to the depth of the alveolar bone. In a comparison of the bone densities between groups with and without genioplasty, there was almost no statistically significant difference. @*Conclusions@#Accelerated tooth movement following orthognathic surgery may be confirmed with reduced bone density. In addition, this study could offer insights into bone metabolism changes following orthognathic surgery, providing direction for further investigations in this field.

Evaluation of factors influencing the success rate of orthodontic microimplants using panoramic radiographs / 대한치과교정학회지

OBJECTIVE@#The purpose of this study was to investigate factors influencing the success rate of orthodontic microimplants (OMIs) using panoramic radiographs (PRs).@*METHODS@#We examined 160 OMIs inserted bilaterally in the maxillary buccal alveolar bone between the second premolars and first molars of 80 patients (51 women, 29 men; mean age, 18.0 ± 6.1 years) undergoing treatment for malocclusion. The angulation and position of OMIs, as well as other parameters, were measured on PRs. The correlation between each measurement and the OMI success rate was then evaluated.@*RESULTS@#The overall success rate was 85.0% (136/160). Age was found to be a significant predictor of implant success (p 0.05). The highest success rate was observed for OMIs with tips positioned on the interradicular midline (IRML; central position). Univariate analyses revealed that the OMI success rate significantly increased with an increase in the OMI length and placement height of OMI (p = 0.001). However, in simultaneous analyses, only length remained significant (p = 0.027). Root proximity, distance between the OMI tip and IRML, interradicular distance, alveolar crest width, distance between the OMI head and IRML, and placement angle were not factors for success. Correlations between the placement angle and all other measurements except root proximity were statistically significant (p < 0.05).@*CONCLUSIONS@#Our findings suggest that OMIs positioned more apically with a lesser angulation, as observed on PRs, exhibit high success rates.

Relationship between maturation indices and morphology of the midpalatal suture obtained using cone-beam computed tomography images / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to determine whether predicting maturation of the midpalatal suture is possible by classifying its morphology on cone-beam computed tomography (CBCT) images and to investigate relationships with other developmental age indices. METHODS: The morphology of the midpalatal suture was assessed by using CBCT images of 99 patients. Axial plane images of the midpalatal suture were classified into five stages according to the classification scheme. To make the assessment more accurate, the morphology and fusion of the midpalatal suture were additionally investigated on coronal cross-sectional planar images and volume-rendered images. Bone age was evaluated using the hand and wrist method (HWM) and cervical vertebrae method (CVM); dental age (Hellman's index), sex, and chronological age were also assessed. To evaluate relationships among variables, Spearman's rho rank test was performed along with crosstabs using contingency coefficients. RESULTS: The HWM and CVM showed strong correlations with the maturation stage of the midpalatal suture, while other indices showed relatively weak correlations (p < 0.01). Through crosstabs, the HWM and CVM showed high association values with CBCT stage; the HWM demonstrated slightly higher values (p < 0.0001). Based on the HWM, the midpalatal suture was not fused until stage 6 in both sexes. CONCLUSIONS: Among developmental age indices, the HWM and CVM showed strong correlations and high associations, suggesting that they can be useful in assessing maturation of the midpalatal suture.

Comparison of the bonding strengths of second- and third-generation light-emitting diode light-curing units / 대한치과교정학회지

OBJECTIVE: With the introduction of third-generation light-emitting diodes (LEDs) in dental practice, it is necessary to compare their bracket-bonding effects, safety, and efficacy with those of the second-generation units. METHODS: In this study, 80 extracted human premolars were randomly divided into eight groups of 10 samples each. Metal or polycrystalline ceramic brackets were bonded on the teeth using second- or third-generation LED light-curing units (LCUs), according to the manufacturers’ instructions. The shear bond strengths were measured using the universal testing machine, and the adhesive remnant index (ARI) was scored by assessing the residual resin on the surfaces of debonded teeth using a scanning electron microscope. In addition, curing times were also measured. RESULTS: The shear bond strengths in all experimental groups were higher than the acceptable clinical shear bond strengths, regardless of the curing unit used. In both LED LCU groups, all ceramic bracket groups showed significantly higher shear bond strengths than did the metal bracket groups except the plasma emulation group which showed no significant difference. When comparing units within the same bracket type, no differences in shear bond strength were observed between the second- and third-generation unit groups. Additionally, no significant differences were observed among the groups for the ARI. CONCLUSIONS: The bracket-bonding effects and ARIs of second- and third-generation LED LCUs showed few differences, and most were without statistical significance; however, the curing time was shorter for the second-generation unit.

Accuracy of three-dimensional printing for manufacturing replica teeth / 대한치과교정학회지

OBJECTIVE: Three-dimensional (3D) printing is a recent technological development that may play a significant role in orthodontic diagnosis and treatment. It can be used to fabricate skull models or study models, as well as to make replica teeth in autotransplantation or tooth impaction cases. The aim of this study was to evaluate the accuracy of fabrication of replica teeth made by two types of 3D printing technologies. METHODS: Fifty extracted molar teeth were selected as samples. They were scanned to generate high-resolution 3D surface model stereolithography files. These files were converted into physical models using two types of 3D printing technologies: Fused deposition modeling (FDM) and PolyJet technology. All replica teeth were scanned and 3D images generated. Computer software compared the replica teeth to the original teeth with linear measurements, volumetric measurements, and mean deviation measurements with best-fit alignment. Paired t-tests were used to statistically analyze the measurements. RESULTS: Most measurements of teeth formed using FDM tended to be slightly smaller, while those of the PolyJet replicas tended to be slightly larger, than those of the extracted teeth. Mean deviation measurements with best-fit alignment of FDM and PolyJet group were 0.047 mm and 0.038 mm, respectively. Although there were statistically significant differences, they were regarded as clinically insignificant. CONCLUSIONS: This study confirms that FDM and PolyJet technologies are accurate enough to be usable in orthodontic diagnosis and treatment.

Effects of various toothpastes on remineralization of white spot lesions / 대한치과교정학회지

OBJECTIVE: The purpose of this in vitro study was to examine the effects of fluoridated, casein phosphopeptide.amorphous calcium phosphate complex (CPP-ACP)-containing, and functionalized beta-tricalcium phosphate (fTCP)-containing toothpastes on remineralization of white spot lesions (WSLs) by using Quantitative light-induced fluorescence (QLF-D) Biluminator(TM) 2. METHODS: Forty-eight premolars, extracted for orthodontic reasons from 12 patients, with artificially induced WSLs were randomly and equally assigned to four treatment groups: fluoride (1,000 ppm), CPP-ACP, fTCP (with sodium fluoride), and control (deionized water) groups. Specimens were treated twice daily for 2 weeks and stored in saliva solution (1:1 mixture of artificial and human stimulated saliva) otherwise. QLF-D Biluminator(TM) 2 was used to measure changes in fluorescence, indicating alterations in the mineral contents of the WSLs, immediately before and after the 2 weeks of treatment. RESULTS: Fluorescence greatly increased in the fTCP and CPP-ACP groups compared with the fluoride and control groups, which did not show significant differences. CONCLUSIONS: fTCP- and CPP-ACP-containing toothpastes seem to be more effective in reducing WSLs than 1,000-ppm fluoride-containing toothpastes.

Evaluation of the relationship between upper incisor exposure and cephalometric variables in Korean young adults / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to classify Korean young adults into 3 groups on the basis of upper incisor exposure rates (UIERs) and to compare the skeletal, dental, and soft tissue variables. METHODS: Samples were obtained from 127 students at the College of Dentistry, Wonkwang University in South Korea. Facial photographs of frontal posed smiles and lateral cephalograms of the subjects were taken. The subjects were divided into 3 groups on the basis of UIERs and 20 measurements were compared among the 3 groups. The correlations between the variables were determined. RESULTS: Male and female subjects showed significant differences in the group distribution. Male subjects showed higher frequencies of low smiles, and female subjects showed higher frequencies of high smiles. The vertical height of the anterior alveolar process of the maxilla directly correlated with the UIER. However, the UIER showed no significant correlation with the vertical height of the anterior basal bone or the inclination of the upper incisor axis. In female subjects, the upper central incisor clinical crown length showed an inverse correlation with the UIER. However, this variable showed no significant correlation with the UIER in male subjects. CONCLUSIONS: The UIER was directly correlated with the levator muscle activity of the upper lip and inversely correlated with the upper lip thickness, yet there was no correlation between the UIER and upper lip length at rest.

Evaluation of mesiodistal tooth axis using a CBCT-generated panoramic view / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to confirm the reliability of a cone beam computed tomography (CBCT)-generated panoramic view based on a CBCT 3D image and to find the most helpful 2D panoramic image compared with CBCT 3D image when examining the mesiodistal tooth axis. METHODS: A test model was constructed according to cephalometric norms. The test model was repeatedly repositioned for CBCT and panoramic radiographic imaging. Panoramic radiographs were acquired at each of the following 3 occlusal plane positions: -5degrees, 0degrees, and +5degrees. Measurements of mesiodistal tooth axis in CBCT 3D image, CBCT-generated panoramic view, and panoramic radiographs were compared. RESULTS: Compared with the CBCT-generated panoramic view, CBCT 3D image showed significant difference in the mesiodistal tooth axis in the premolars and no significant difference in the mesiodistal tooth axis in the incisors and canines. Mesiodistal tooth axis on the CBCT-generated panoramic view was significantly different from that on panoramic radiographs. CONCLUSIONS: CBCT-generated panoramic view can be a useful tool for evaluating mesiodistal tooth axis.

The comparison of the frictional force by the type and angle of orthodontic bracket and the coated or non-coated feature of archwire / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the difference in frictional resistance among metal, ceramic, self-ligation brackets and coated or non-coated Ni-Ti archwires at various bracket-archwire angulations during the sliding movement of an orthodontic archwire, using an orthodontic sliding simulation device. METHODS: Four types of bracket (Micro-arch Perpect Clear2 Clippy-C and Damon3 and 5 types of orthodontic archwire (0.014", 0.016", and 0.016" x 0.022" inch coated Ni-Ti, and 0.016" and 0.016" x 0.022" inch Ni-Ti) were used. Further, the bracket-archwire angles were set at 4 different angulations: 0degrees, 3degrees, 6degrees, and 9degrees. RESULTS: The frictions from all the experimental groups were found to be significantly increased in order of self-ligation brackets, Micro-arch and Perpect Clear2 (p < 0.001). The presence of a coat had no effect on the friction of the same sized archwires at 0degrees and 3degrees bracket-archwire angles (p < 0.001). Coated archwires had significantly higher frictions than the same sized non-coated archwires at 6degrees and 9degrees bracket-archwire angles (p < 0.001). The frictions increased significantly as the bracket-archwire angles were increased (p < 0.001). CONCLUSIONS: The use of self-ligation brackets will be beneficial in clinical situations where a low frictional force is required. Further, in cases where crowding is not severe, the use of coated archwires should not cause problems. However, more additional explanation is required considering the fact that the damage of coated archwire and exposure of the metal portion in case of binding and notching and the effects of saliva were not taken into account.

Shear bond strength of ceramic brackets bonded with antimicrobial monomer-containing self-etching primer / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to determine (1) the shear bond strength (SBS) of an antimicrobial monomer-containing self-etching primer according to ceramic bracket types and (2) the bracket-adhesive failure mode using an adhesive remnant index (ARI). METHODS: A total of 90 extracted human teeth were randomly divided into 6 groups. Each group consisted of one of two ceramic brackets (monocrystalline, polycrystalline) and one of three primers (Transbond XT primer, Transbond Plus SEP, Clearfil Protect Bond) with each group containing 15 specimens. The SBS was measured, and adhesive residues left on the tooth surface were assessed. RESULTS: The SBS of polycrystalline ceramic bracket groups was significantly higher than that of the monocrystalline ceramic bracket groups (p < 0.001). The SBS of Transbond XT primer groups was significantly higher than those of Transbond Plus SEP groups and Clearfil Protect Bond groups (p < 0.001). All the groups showed bonding failures between the bracket base and adhesive. CONCLUSIONS: The combination of a self-etching primer with a monocrystalline bracket is recommended for clinical use, considering its acceptable SBS and mode of failure.

Efficiency of ceramic bracket debonding with the Er:YAG laser / 대한치과교정학회지

OBJECTIVE: The aim of this study was to find out whether Er:YAG laser can aid in debonding ceramic brackets, and to see what kind of method will be the most appropriate for debonding. METHODS: One hundred and ninety teeth, monocrystalline brackets (MISO(TM), HT, Ansan-Si, Korea), polycrystalline brackets (Transcend(TM) series 6000, 3M Untek, Monrovia, CA, USA) and the KEY Laser3 (KavoDental, Biberach, Germany) were used. Experimental groups were classified according to the type of ceramic brackets, and the amount of laser energy (0, 140, 300, 450, 600 mJ). After applying laser on the bracket at two points at 1 pulse each, the shear bond strength was measured. The effect of heat caused by laser was measured at the enamel beneath the bracket and pulp chamber. After measuring the shear bond strength, adhesive residue was evaluated and enamel surface was investigated using SEM. RESULTS: All ceramic bracket groups showed a significant decrease in shear bond strength as the laser energy increased. The greatest average temperature change was 3.78degrees C on the enamel beneath the bracket and 0.9degrees C on the pulp chamber. Through SEM, crater shape holes caused by the laser was seen on the enamel and adhesive surfaces. CONCLUSIONS: If laser is applied on ceramic brackets for debonding, 300 - 450 mJ of laser energy will be safe and efficient for monocrystalline brackets (MISO(TM)), and about 450 mJ for polycrystalline brackets (Transcend(TM) series 6000).

Treatment of skeletal Class II adult patient with vertical and transverse problems caused by nasal airway obstruction using microimplant anchorage / 대한치과교정학회지

This case report describes the treatment of an adult patient with a Class I canine and molar relationship but a convex profile with a retrognathic mandible and marked lip protrusion, as well as an excessive lower anterior facial height and reduced transverse width on both arches due to a nasal airway obstruction. The constricted arches were expanded by surgically-assisted rapid palatal expansion and the application of a Schwarz appliance to the maxilla and mandible. Acceptable facial balance was obtained using contemporary directional force technology with microimplant anchorage (MIA), which provided horizontal and vertical anchorage in the maxillary and mandibular posterior teeth, as well as intrusion and torque control in the maxillary anterior teeth, resulting in a favorable counterclockwise mandibular response. The total treatment period was 29 months and the results were acceptable for 13 months after debonding.