Kyung Hwa Kang

Accuracy of three-dimensional printing for manufacturing replica teeth

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.

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 β-tricalcium phosphate (fTCP)-containing toothpastes on remineralization of white spot lesions (WSLs) by using Quantitative light-induced fluorescence (QLF-D) Biluminator™ 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™ 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.

Unilateral Mandibular Widening with Distraction Osteogenesis

Mandibular widening with distraction osteogenesis (DO) has been shown to be an acceptable and stable treatment modality. Mandibular widening with DO is useful in relieving crowding and for restoring a rotated mandibular arch segment to its original condition. This is especially true when a patient has a unilateral medial displacement of the proximal segment of the mandible or a unilateral Brodie bite. This case report shows the application of mandibular widening with DO for skeletal reconstruction and prosthodontic preparation in a patient with unilateral medial displacement of the proximal segment of the mandible. The design of the osteotomy line and the placement of the distractor must be taken into consideration in a detailed procedure for unilateral mandibular widening of the mandible.

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

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.