Time series analysis of patients seeking orthodontic treatment at Seoul National University Dental Hospital over the past decade

Abstract

Objective: This paper describes changes in the characteristics of patients seeking orthodontic treatment over the past decade and the treatment they received, to identify any seasonal variations or trends.

Methods: This single-center retrospective cohort study included all patients who presented to Seoul National University Dental Hospital for orthodontic diagnosis and treatment between January 1, 2005 and December 31, 2015. The study analyzed a set of heterogeneous variables grouped into the following categories: demographic (age, gender, and address), clinical (Angle Classification, anomaly, mode of orthodontic treatment, removable appliances for Phase 1 treatment, fixed appliances for Phase 2 treatment, orthognathic surgery, extraction, mini-plate, mini-implant, and patient transfer) and time-related variables (date of first visit and orthodontic treatment time). Time series analysis was applied to each variable.

Results: The sample included 14,510 patients with a median age of 19.5 years. The number of patients and their ages demonstrated a clear seasonal variation, which peaked in the summer and winter. Increasing trends were observed for the proportion of male patients, use of non-extraction treatment modality, use of ceramic brackets, patients from provinces outside the Seoul region at large, patients transferred from private practitioners, and patients who underwent orthognathic surgery performed by university surgeons. Decreasing trends included the use of metal brackets and orthodontic treatment time.

Conclusions: Time series analysis revealed a seasonal variation in some characteristics, and several variables showed changing trends over the past decade.

Keywords: Orthodontics; Seasonal variation; Time series analysis; Trend.

Conflict of interest statement

The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.

Figures

Figure 1. A, The number of patients seeking orthodontic treatment. B, The trend component. C, Seasonal variation. D, A magnified view of the seasonal variation demonstrates peaks during each winter and summer.

Figure 2. A, The patients' median age is 19.5 years. B, Time series analysis shows a slightly decreasing trend in median age over time. C, Seasonal variation. D, A large-scale view of seasonal variation.

Figure 3. A, The proportion of male patients and of non-extraction treatment. B, The percentage of patients who underwent orthognathic surgery at the same institution.

Figure 4. The proportion of patients whose address was in Seoul and from Gyeonggi or other provinces.

Figure 5. Appliances used for Phase 2 treatment.

Figure 6. Orthodontic treatment time.