With increasing public interest in dental and facial aesthetics, there has been increasing recognition that oral disorders can have a significant impact on physical, social, and psychological well-being[1,2]. Orthodontic treatment accounts for a large proportion of the total treatments performed in the department of pediatric dentistry.

Choi et al. [3] reported that orthodontic treatment accounted for 21.5% of total treatments performed in a department of pediatric dentistry in 2000, with the rate increasing to 35.9% in 2005. Son et al. [4] observed a change in practice patterns in the department of pediatric dentistry from 2001 to 2008, where orthodontic treatments composed 22.8% of total treatments in 2001 but 37.5% in 2008. In a recent study by Seo et al. [5], the proportion of patients seeking orthodontic treatment in recent years has declined from 25.0% in 2006 to 21.4% in 2015.

This study conducted an investigation on the distribution of pediatric malocclusion patients who visited the Department of Pediatric Dentistry, Seoul National University Dental Hospital (SNUDH) from 2017 to 2019, and received an orthodontic diagnosis.

The purpose of the study was to examine pediatric orthodontic patients regarding skeletal pattern as determined with lateral cephalometric analysis and to analyze the correlation between skeletal pattern and probable related clinical characteristics. Also, the study aimed to aid clinicians in establishing orthodontic treatment plans based on investigations of the modality of orthodontic treatment by skeletal classification.

The protocol was approved by the Institutional Review Board of School of Dentistry, Seoul National University (IRB No. S-D20200020).

This study conducted an investigation on 580 pediatric orthodontic patients who visited the Department of Pediatric Dentistry, SNUDH from 2017 to 2019, based on associations with chief complaints, age, sex, skeletal pattern, treatment methods, and anterior crossbite prevalence.

Patients 7 or 8 years old were most common, making up about half of the total subjects, followed by those 9 or 10 years of age. The average eruption age of the maxillary central incisors is 6.81 years in male patients and 6.73 years in female patients in Korea, while the average age of eruption of the maxillary lateral incisors is 7.78 years in male patients and 7.65 years in female patients[9]. The most common age groups coincide with eruption of maxillary anterior permanent teeth. This indicates that caregivers largely recognize the need for orthodontic treatment after emergence of the maxillary anterior teeth, which is aesthetically important. When children’ s teeth do not achieve the norm for esthetic appearance, caregiver response to sociocultural expectations motivates desire for orthodontic treatment[10]. Yang and Choi[11] reported the 8- and 9-year-olds as the largest age group that visited the Department of Pediatric Dentistry for orthodontic treatment in 2000. Both studies of Koo et al. [12] and Cho et al. [13] reported an 8-year-old age largest group in 2009 and 2015. The 7-year-old group was largest in the present study. Compared with previous studies, the age of patients at visit for orthodontic treatment is decreasing, indicating increasing parental recognition on malocclusion and need for early orthodontic treatment.

An investigation on chief complaints was conducted to examine the motivation and purpose of pediatric patients to visit the department of pediatric dentistry for orthodontic treatment. When assessing the distribution of chief complaints, the reasons that patients wanted orthodontic treatment were various. The largest proportion of patients who visited for orthodontic treatment due to anterior crossbite was consistent with previous studies[14-16]. The percentage of patients with anterior crossbite increased from 28.0% in 2009 to 43.3% in present study period[12]. Anterior crossbite as the most common complaint is likely because it can be easily noticed by patients and caregivers. This suggests that parental awareness of anterior crossbite malocclusion has increased and leads them to pursue early orthodontic treatment.

Regarding horizontal skeletal pattern, 54.2% of patients showed a skeletal class I pattern, 22.2% of patients showed a skeletal class II pattern, and 23.6% of patients showed a skeletal class III pattern. In comparison with previous studies that classified orthodontic patients using the same criteria of ANB value, changes in distribution of skeletal pattern of malocclusion patients who visited the department of pediatric dentistry were observed. In the study of Koo et al. [12], the percentages of skeletal Class I, II, and III were 52.0%, 29.0%, and 19.0%. The percentages in the study of Cho et al. [13] were 48.1%, 28.7%, and 23.2%, respectively. The overall distributions of skeletal patterns were similar. Over time, the proportion of skeletal class III pattern increased, whereas the proportion of skeletal class II pattern decreased. In the survey of 7- to 18-year-old Korean adolescents[17], 52.6% of class III, 52.2% of class II, and 44.4% of class I malocclusion patients recognized the need for orthodontic treatment. Comparing the degree of awareness of need for orthodontic treatment, the increase in skeletal class III patients is because this relationship has a larger non-favorable effect on the aesthetics of facial features relative to other skeletal patterns[18]. Relatively long period and high level of difficulty of skeletal class III treatment may have led more patients to visit the dental hospital rather than private clinics. Although the perception of need for orthodontic treatment for class II patients was similar to that of class III patients, the actual patient visit rate was low regarding awareness of need for treatment.

The mean and standard deviation values of lateral cephalometric measurements were calculated according to skeletal class pattern. According to McNamara[8], the norm for McA is 0 mm in mixed dentition and 1 mm in adult female and adult male patients. The norm for McPog is -8 to -6 mm in mixed dentition and -2 to 4 mm in adults. Due to growth of the mandible, McPog moves forward about 0.5 mm per year. The average McPog of skeletal class II patients was -10.6 mm, below the normal range proposed by McNamara[8], indicating retrognathic mandible. Smaller corpus length in skeletal class II patients indicates hypogrowth of the mandible. McNamara[19] reported that mandibular skeletal retrusion was the most common characteristic of class II subjects in his study. This is consistent with the horizontal relationship of the jaws of skeletal class II pattern shown in the present study. More skeletal class II patients presented a retruded maxilla (29.5%) than a protruded maxilla (13.9%) and retruded mandible (72.1%) than a protruded mandible (3.9%). These tendencies suggest that the main cause of skeletal class II malocclusion lies in the mandible rather than the maxilla. The mean values of McA and McPog of skeletal class III pattern were -2.8 mm and -2.8 mm, respectively, suggesting retrusion of the maxilla and protrusion of the mandible. Larger corpus length was noted in skeletal class III, meaning hypergrowth of the mandible. This coincides with the study of Guyer et al. [20], which reported that juvenile and adolescent class III patients generally showed retrusive maxilla with protrusive mandible. This is related to the horizontal positions of the maxilla and mandible shown in the skeletal class III pattern of the present study. More patients showed a retruded maxilla (72.3%) than a protruded maxilla (0.0%) and a protruded mandible (52.0%) than a retruded mandible (8.8%). This result implies that both jaws are factors in the occurrence of a skeletal class III relationship, and retrusion of the maxilla is somewhat more likely to play a role.

In this study, 55.0% of patients presented the brachyfacial type, 31.9% of patients presented the mesofacial type, and 13.1% of patients presented the dolichofacial type. Koo et al. [12] reported the mesofacial type in 41.0% of patients, followed by brachyfacial type (35.0%) and dolichofacial type (24.0%). Cho et al. [13] reported that 65.0% of the patients showed mesofacial type, 19.3% for dolichofacial type, and 15.8% for brachyfacial type. The proportion of brachyfacial type increased over time for vertical skeletal pattern, whereas the frequency of mesofacial and dolichofacial types decreased. In the brachyfacial type, the proportion decreased in the order of skeletal classes III, I, and II; in the dolichofacial type, the proportion increased in the same order. These findings seem to be influenced by positioning of the mandible. Mandibular clockwise rotation tended to be stronger in dolichofacial subjects than in brachyfacial subjects. In the dolichofacial type, the mandible may rotate clockwise and tend to retreat horizontally, producing a large proportion of skeletal class II pattern cases.

The rate of orthodontic treatment carried out after diagnosis was 85.7% and was highest for skeletal class III patients. Early or phase I orthodontic treatment refers to treatment that precedes the conventional treatment protocol of fixed orthodontic appliances. Due to the nature of pediatric dentistry, most patients who started the orthodontic treatment at SNUDH received early orthodontic treatment. Excluding the fixed orthodontic appliance, early orthodontic treatment was received by about 80% of the total patients. The most common technique was removable orthodontic appliances and rapid palatal expansion with facemasks. The timing and necessity of initial orthodontic treatment depend on patient situation. For skeletal class III patients, several studies have suggested early intervention before the age of 10 years[21,22]. Therefore, it can be inferred that the majority of skeletal class III patients was treated with rapid palatal expansion with a facemask. Two-stage orthodontic treatment for skeletal class II patients was not as effective compared to 1-stage orthodontic treatment and there was no advantage in final treatment result[23,24]. Thus, the proportion of fixed orthodontic appliance of class II patients was higher compared to other skeletal patterns. Future research on treatment methods performed in pediatric dentistry should examine the changes in orthodontic treatment modality.

This study aimed to examine the pediatric orthodontic patients as the proportion of orthodontic treatment has increased in pediatric dental clinics. However, this study analyzed only orthodontic patients who visited the Department of Pediatric Dentistry at SNUDH, which may differ from the distribution of patients at local dental clinics or dental hospitals in other regions. Future studies involving more patients will be needed to better assess the overall distribution of pediatric patients who undergo orthodontic treatment and to compare with the epidemiologic prevalence of pediatric malocclusion.

Within the limitation of this study, pediatric orthodontic patients were analyzed by skeletal pattern using lateral cephalometric analysis to determine the association between skeletal patterns and possible related clinical traits. The orthodontic treatment modality for each skeletal pattern was investigated for reference in therapeutic planning. A total of 580 patients who visited and received orthodontic diagnosis in the Department of Pediatric Dentistry, SNUDH from 2017 to 2019 was included in this investigation. The 7-year-old group was the largest in the overall age distribution. Skeletal class I pattern accounted for 54.2% of patients, followed by skeletal class III pattern (23.6%), and skeletal class II pattern (22.2%). Retrusion of both jaws in skeletal class I, normal positioned maxilla with retrusive mandible in skeletal class II, and retrusive maxilla and protrusive mandible in skeletal class III were the largest subgroups by skeletal pattern. The age of patients at which they visit for orthodontic treatment has decreased. The proportion of skeletal class III patients and the prevalence of anterior crossbite have increased over the years, whereas the proportion of skeletal class II patients has decreased.