ObjectiveThis 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).MethodsWe included 672 Korean patients (141 men and 531 women; mean age, 27.2 ± 7.7 years) 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.ResultsTeeth 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.ConclusionsThe 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.
ObjectiveThe aims of this study were to assess the direction and degree of lip-line cant in Korean adult orthodontic patients and to identify the effects of sex and age on changes in the cant severity.MethodsIn this cross-sectional retrospective study, lip-line cant was measured in the frontal photographs of 585 Korean patients (92 men and 493 women) aged 18-48 years. The outcome variables (direction and degree of lip-line cant) were assessed in terms of predictor variables (sex, age, sagittal skeletal relationship, and menton deviation angle).ResultsThe direction of lip-line cant did not differ according to sex, age, or skeletal classification. Patients had 1.6° of lip-line cant on average before orthodontic treatment. Middle-aged adults displayed a significant trend toward a lower degree of lip-line cant compared to younger adults (p < 0.01). Multiple linear regression analysis showed that the degree of lip-line cant was weakly negatively correlated with age (p < 0.001).ConclusionsWhile the direction of lip-line cant did not differ according to the parameters explored here, the degree of cant was correlated with age in adults, independent of menton deviation. Specifically, middle-aged adults tended to display significantly lower degrees of lip-line cant than did younger adults.
Orthodontic facemasks are extraoral orthodontic appliances that influence maxillary and mandibular development in children with skeletal Class III malocclusion. While a facemask is most effective in patients before the growth spurt, skin irritation is common during the treatment. Therefore, this retrospective study aimed to investigate the prevalence and pattern of such skin changes and identify their possible associated risk factors. We included 177 patients with skeletal Class III malocclusion who underwent facemask therapy. Patient age and sex, orthodontic parameters expressing the severity of malocclusion, the presence of complaints in the temporomandibular joint (TMJ) areas, and the level of patient cooperation were evaluated. Additionally, the severity and onset time of skin reactions were further analyzed. The results indicated that 43.5% of patients developed skin changes typical of irritant contact dermatitis. Skin irritation was significantly associated with the presence of TMJ complaints and female sex. Furthermore, skin irritation was more common in younger patients. Clinicians should pay special attention to the skin areas that come into contact with the appliance during each follow-up visit to detect potential problems. Moreover, patients and their parents should be given adequate information about the possibility, prevention, and management of skin problems during facemask therapy.
연세대학교 치과대학 구강생물학교실, 3 연세대학교 치과대학 교정학교실Purpose: Due to the presence of various muscles around lips, variety of facial expression can be made and changes from aging process such as wrinkles can develop on the facial skin by the action of multiple muscles. In animals, skin and muscles are developed in the entire body. On contrast, they are well developed only in the face and just one is present in the neck and the palm. Alar band was defined as outer wrinkle formed by zygomaticus minor muscle, which is common in Koreans. This study aimed to investigate clinical prevalence of alar band. Materials & Methods: Subjects were chosen from 780 new patients who visited private clinic in Gyeonggi province for orthodontic treatment. Presence of alar band was examined from the smile extraoral photos. Correlation among skeletal form, lip protrusion, gender, and age were evaluated. Results: Prevalence of alar band was higher in women (27.9%) than in men (18.5%) with statistical significance (p<0.05). With respect to age, prevalence of alar band was 19.4% in age 0-9 y, 16.9% in age 10-19 y, 31.2% in age 20-29 y, 39.5% in age 30-39, 56.5% in age 40-49. Prevalence was gradually increased from patients in their 20s to patients in their 40s and statistical significance was found (p<0.001). Concerning SN_NP, prevalence was 26.2% in normodivergent facial type, 22.0% in hyperdivergent facial type, and 32.2% in hypodivergent facial type. Hypodivergent facial group had higher prevalence but statistical significance was not observed. Statistically significant difference was not found regarding upper lip. However, prevalence of the alar band was 26% in patients with normal lower lip, 14.7% in patients with pretruded lower lip, and 33.3% in retruded lower lip. The prevalence was higher in patients with retruded lower lip with statistical significance (p< 0.05). Conclusions: 27.8% on previous anatomical study and this study showed 27.8% prevalence of alar band in clinical smile photographs. Clinical photograph study showed that alar band was more prominent in women, older people, and people with retruded lips with statistical significance. This will provide valuable diagnostic information for esthetic consideration. (J Korean Acad Esthet Dent 2015;24(1):4-12)
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