The purpose of this study was to investigate the changes and types of statistical methods used in the Korean Journal of Orthodontics (KJO) and the American Journal of Orthodontics and Dentofacial Orthopedics (AJODO) from 1999 to 2003. The frequency of use, transitions, assumption check of statistical methods and types of advanced statistical methods were examined from each journal. The study consisted of 247 articles published in the KJO and randomly chosen 50 articles per year which were original articles and used statistical methods. T-test, analysis of variance (ANOVA), correlation analysis, nonparametric analysis, regression analysis, chi-square test, factor analysis, were the order of statistical methods most frequently used in the KJO, while t-test, ANO VA, nonparametric analysis, correlation analysis, regression analysis, chi-square test, factor analysis, were the order of statistical methods used in the AJODO. The changes of statistical methods observed in the KJO were not significant (chi-square=17.4, p=0.6881), but the changes observed in the AJODO was seen to be significant (chi-square=42.4, p=0.0397). Some of the studies examined had overlooked the assumptions of the statistical methods employed. Data investigation such as outlier should be performed before analysis and alternative statistical approaches are applied for a small sample size. Types of advanced statistical methods were factor analysis and discriminant analysis in the KJO and Intention-To-Treat (ITT) analysis in clinical trials through multi-center, survival analysis and Generalized Estimating Equations (GEE) in the AJODO. Appropriate analysis approaches and interpretations should be applied for the correlated and repeated measurements of the orthodontic data set.
Dataset ; Orthodontics* ; Orthopedics* ; Sample Size

Objectives: The purpose of this study is to analyze the relationship between dental school students’admission scores and their grade point average (GPA) after admission, as well as the relationship between student admission scores at dental school and continuation into the residency program. Methods: This study analyzed data collected from students who entered dental school between 2013 and 2017. The outcome variables were dental school GPA and continuation into residency program. Explanatory variables included admission type (early decision admission/regular admission), academic achievements (undergraduate GPA, Dental Education Eligibility Test [DEET], Test of English Proficiency [TEPS], screening by document review, and in-depth interview score), age, sex, college alma mater, high school alma mater, college major, as well as students’ academic performance in dental school. Regression analysis was performed to determine which factors relating to dental school admissions score had an influence on academic performance in dental school, whereas logistic regression analysis was conducted to determine the students’ decision to pursue a residency. Results: Students who were foreign college graduates, majored in health sciences, accepted on the basis of early decision admission, female, or had a higher college GPA showed higher dental school GPA with statistical significance. Additionally, the likelihood of students pursuing residency was found to be higher in students who were female, of younger age, college graduates in Jeolla Provinces, or who had a higher dental school GPA. Conclusions To ensure regional equality of dental service quality, it is essential that high quality students pursue residency training. For further improvement of dental school, this study’s results can be used as a reference to make students coming from other regions pursue the residency program and contribute to the regional community.

PURPOSE: This study conducted an analysis of cost-effectiveness of the implant and conventional fixed dental prosthesis (CFDP) from a single treatment perspective. MATERIALS AND METHODS: The Markov model for cost-effectiveness analysis of the implant and CFDP was carried out over maximum 50 years. The probabilistic sensitivity analysis was performed by the 10,000 Monte-Carlo simulations, and cost-effectiveness acceptability curves (CEAC) were also presented. The results from meta-analysis studies were used to determine the survival rates and complication rates of the implant and CFDP. Data regarding the cost of each treatment method were collected from University Dental Hospital and Statistics Korea for 2013. Using the results of the patient satisfaction survey study, quality-adjusted prosthesis year (QAPY) of the implant and CFDP strategy was evaluated with annual discount rate. RESULTS: When only the direct cost was considered, implants were more cost-effective when the willingness to pay (WTP) was more than 10,000 won at 10th year after the treatment, and more cost-effective regardless of the WTP from 20th year after the prosthodontic treatment. When the indirect cost was added to the direct cost, implants were more cost-effective only when the WTP was more than 75,000 won at the 10th year after the prosthodontic treatment, more than 35,000 won at the 20th year after prosthodontic treatment. CONCLUSION: The CFDP was more cost-effective unless the WTP was more than 75,000 won at the 10th year after prosthodontic treatment. But the cost-effectivenss tendency changed from CFDP to implant as time passed.
Dental Prosthesis* ; Korea ; Patient Satisfaction ; Prostheses and Implants ; Prosthodontics ; Survival Rate

OBJECTIVE: To systematically review previous studies and to assess, via a subgroup meta-analysis, the combined odds ratio (OR) of prognostic factors affecting the success of miniscrew implants (MIs) inserted into the buccal posterior region. METHODS: Three electronic searches that were limited to articles on clinical human studies using MIs that were published in English prior to March 2015 were conducted. The outcome measure was the success of MIs. Patient factors included age, sex, and jaw of insertion (maxilla vs. mandible), while the MI factors included length and diameter. A meta-analysis was performed on 17 individual studies. The quality of each study was assessed for non-randomized studies and quantified using the Newcastle-Ottawa Scale. The meta-analysis outcome was a combined OR. Subgroup and sensitivity analyses based on the study design, study quality, and sample size of miniscrews implanted were performed. RESULTS: Significantly higher success rates were revealed for MIs inserted in the maxilla, for patients ≥ 20 years of age, and for long MIs (≥ 8 mm) and MIs with a large diameter (> 1.4 mm). All subgroups acquired homogeneity, and the combined OR of the prospective studies (OR, 3.67; 95% confidence interval [CI], 2.10-6.44) was significantly higher in the maxilla than that in the retrospective studies (OR, 2.10; 95% CI, 1.60-2.74). CONCLUSIONS: When a treatment plan is made, these risk factors, i.e. jaw of insertion, age, MI length, and MI diameter, should be taken into account, while sex is not critical to the success of MIs.
Humans ; Jaw ; Maxilla ; Odds Ratio ; Outcome Assessment (Health Care) ; Prospective Studies ; Retrospective Studies ; Risk Factors ; Sample Size

PURPOSE: Use of inappropriate statistical methods may lead to incorrect conclusions and a waste of valuable resources. The goal of this study was to assess the frequency and the types of several common statistical errors in the published articles of the Journal of the Korean Academy of Prosthodontics (JKAP) for a 5-year period. MATERIALS AND METHODS: Of 336 articles in the JKAP published from 2006 to 2010, 255 articles using statistics were reviewed and classified by statistical method and year. The frequency and types of the statistical methods were examined, and the statistical errors were evaluated by the appropriateness of the experimental design, assumption check, independent outcomes, proper sample size and suitable use of statistical method. Statistical guidelines were completed based on the appropriateness. RESULTS: Of the 255 articles using statistics, 193 articles (75.9%) used inferential statistics and 153 articles used SPSS statistical software (60.0%). Of the articles using inferential statistics, the three most frequently used statistical methods were ANOVA (41.5%), t-test (20.0%), and the nonparametric method (16.9%). The average rate of statistical errors was 61.2 percent, similar to the rate reported by several studies completed for the medical journal. CONCLUSION: After the whole analysis of the difference among the groups, post-hoc tests for the pairwise comparisons are required. The optimal sample size calculation is an essential part of this study protocol. To minimize the occurrence of statistical errors, statistical guidelines were developed according to each statistical test procedure and will contribute to the academic improvement in the JKAP.
Prosthodontics ; Research Design ; Sample Size

PURPOSE: This study aimed to identify the range of normal facial asymmetry using three-dimensional CT and to develop a simple method of diagnosis of facial asymmetry. MATERIALS AND METHODS: Twenty eight adults with normal occlusion (16 males and 12 females; mean age 24 years and 1 month) were selected, whose faces were assessed to be symmetric by an orthodontist. Three-dimensional reconstructions were obtained utilizing spiral CT scans and an oral and maxillofacial radiologist evaluated nineteen anatomic landmarks in three-dimensional coordinates. Facial asymmetry index of each landmark was caluculated. RESULTS: The range of normal facial asymmetry of each landmark was identified using mean and standard deviation of facial asymmetry index. CONCLUSION: The range of normal facial asymmetry identified in this study may be used as a diagnostic standard for facial asymmetry analysis.
Adult ; Anatomic Landmarks ; Diagnosis ; Facial Asymmetry* ; Female ; Humans ; Male ; Tomography, Spiral Computed

OBJECTIVE: The purpose of this study was to investigate whether the craniofacial patterns of Korean children with snoring and adenotonsillar hypertrophy (ATH) could be categorized into characteristic clusters according to age. METHODS: We enrolled 236 children with snoring and ATH (age range, 5–12 years) in this study. They were subdivided into four age groups: 5–6, 7–8, 9–10, and 11–12 years. Based on cephalometric analysis, the sagittal and vertical skeletal patterns of each individual were divided into Class I, II, and III, as well as the normodivergent, hypodivergent, and hyperdivergent patterns, respectively. Cluster analysis was performed using cephalometric principal components in addition to the age factor. RESULTS: Three heterogeneous clusters of craniofacial patterns were obtained in relation to age: cluster 1 (41.9%) included patients aged 5–8 years with a skeletal Class I or mild Class II and hyperdivergent pattern; cluster 2 (45.3%) included patients aged 9–12 years with a Class II and hyperdivergent pattern; and cluster 3 (12.8%) included patients aged 7–8 years with a Class III and hyperdivergent pattern. CONCLUSIONS: This study found that the craniofacial patterns of Korean children with snoring and ATH could be categorized into three characteristic clusters according to age groups. Although no significantly dominant sagittal skeletal discrepancy was observed, hyperdivergent vertical discrepancy was consistently evident in all clusters.
Age Factors ; Child* ; Cluster Analysis* ; Humans ; Hypertrophy ; Snoring*

OBJECTIVES: We examined the association between alcohol consumption and incidence of colorectal cancer in elderly Koreans. METHODS: The cohort members (n=14,304) consisted of 4,834 males and 9,470 females derived from the Korea Elderly Pharmacoepidemiologic Cohort (KEPEC), a population-based dynamic cohort. They were aged 65 years old or older and lived in Busan between 1993-1998; they were beneficiaries of the Korean Medical Insurance Corporation (KMIC). Baseline information was surveyed by a self-administered, mailed questionnaire. This study population was restricted to 14,304 participants who reported alcohol drinking habits on the questionnaire and had not been diagnosed with colorectal cancer at baseline. The adjusted hazard ratios (aHR) of status, type, frequency and daily average amount of alcohol consumption were computed with Cox's proportional hazard model, with the never-drinkers as a reference group and controlling for age and gender. RESULTS: After 4.82 person-years of mean follow-up 112 cases of colorectal cancer occurred. The incidence densities of colorectal cancer were 161 (95% CI=123-200) for never-drinkers, 219 (95% CI=125-339) for ex-drinkers, and 137 (95% CI=84-189) for current-drinkers per 100,000 person-year. The status, type, frequency, and daily average amount of alcohol consumption were not significantly related to the incidence of colorectal cancer after controlling for age and gender. CONCLSIONS: There was no significant association between alcohol consumption and colorectal cancer among elderly people after controlling for age and gender.
Age Distribution ; Aged ; Alcohol Drinking/*epidemiology ; Cohort Studies ; Colorectal Neoplasms/*epidemiology ; Female ; Humans ; Korea/epidemiology ; Male ; Proportional Hazards Models ; Questionnaires ; Sex Distribution

PURPOSE: This study was aimed to compare skin entrance dose of digital radiography with that of film radiography and to show the dose reduction achievement with digital systems at 11 dental schools in Korea. MATERIALS AND METHODS: Forty six intraoral radiographic systems in 11 dental schools were included in this study. Digital sensors were used in 33 systems and film was used in 13 systems. Researchers and the volunteer visited 11 dental schools in Korea. Researchers asked the radiologic technician (s) at each school to set the exposure parameters and aiming the x-ray tube for the periapical view of the mandibular molar of the volunteer. The skin entrance doses were measured at the same exposure parameters and distance by the technician for each system with a dosimeter (Multi-O-Meter : Unfors instruments, Billdal, Sweden). RESULTS: The median dose was 491.2micronGy for digital radiography and 1, 205.0 microGy for film radiography. The skin entrance dose in digital radiography was significantly lower than that of film radiography (p< 0.05). CONCLUSIONS: Fifty-nine percent skin entrance dose reduction with digital periapical radiography was achieved over the film radiography in Korean dental schools.
Humans ; Korea ; Molar ; Radiographic Image Enhancement ; Radiography* ; Schools, Dental* ; Skin* ; Volunteers

Enlargement is an inherent property of X-rays which occurs when straight lines diverge from small a focal spot. The purpose of the present study was to evaluate the validity of the correction of gonial angle width enlarged on frontal cephalogram, using frontal and lateral cephalograms taken orthogonally from each other. In 40 adult individuals, frontal and lateral cephalograms were taken at a 90 degrees angle using the Head Posture Aligner. The angle width was measured on the frontal cephalogram and subsequently, the corrected angle width was calculated using the magnification rate of two cephalograms. Measured and corrected angle widths were compared with the measurement from the 3D CT image. The measurement on the frontal cephalogram showed a 9.10 mm of enlargement on average, ranging from 7.92 to 11.31 mm. Corrected angle width measurement showed a 0.14 mm difference with the 3D CT image measurement, which was not statistically significant. The results of the study indicate that actual angle width can be approached through calculation using frontal and lateral cephalograms taken orthogonally with the help of the Head Posture Aligner. The study also showed that the magnitude of correction error did not show a significant correlation with the amount of menton deviation, and it suggests that the present correction method is valid even in individuals with severe facial asymmetry.
Adult ; Facial Asymmetry ; Head ; Humans ; Posture