Do statistical heterogeneity methods impact the results of meta- analyses? A meta epidemiological study.

BACKGROUND: Orthodontic systematic reviews (SRs) use different methods to pool the individual studies in a meta-analysis when indicated. However, the number of studies included in orthodontic meta-analyses is relatively small. This study aimed to evaluate the direction of estimate changes of orthodontic meta-analyses (MAs) using different between-study variance methods considering the level of heterogeneity when few trials were pooled. METHODS: Search and study selection: Systematic reviews (SRs) published over the last three years, from the 1st of January 2020 to the 31st of December 2022, in six main orthodontic journals with at least one MA pooling five or lesser primary studies were identified. Data collection and analysis: Data were extracted from each eligible MA, which was replicated in a random effect model using DerSimonian and Laird (DL), Paule-Mandel (PM), Restricted maximum-likelihood (REML), Hartung Knapp and Sidik Jonkman (HKSJ) methods. The results were reported using median and interquartile range (IQR) for continuous data and frequencies for categorical data and analyzed using non-parametric tests. The Boruta algorithm was used to assess the significant predictors for the significant change in the confidence interval between the different methods compared to the DL method, which was only feasible using the HKSJ method. RESULTS: 146 MAs were included, most applying the random effect model (n = 111; 76%) and pooling continuous data using mean difference (n = 121; 83%). The median number of studies was three (range 2, 4), and the overall statistical heterogeneity (I2 ranged from 0 to 99% with a median of 68%). Close to 60% of the significant findings became non-significant when HKSJ was applied compared to the DL method and when the heterogeneity was present I2>0%. On the other hand, 30.43% of the non-significant meta-analyses using the DL method became significant when HKSJ was used when the heterogeneity was absent I2 = 0%. CONCLUSION: Orthodontic MAs with few studies can produce different results based on the between-study variance method and the statistical heterogeneity level. Compared to DL, HKSJ method is overconservative when I2 is greater than 0% and may result in false positive findings when the heterogeneity is absent.

Why do patients transition between orthodontic appliances? A qualitative analysis of patient decision-making.

OBJECTIVES: To gain an in-depth understanding of patients' decision-making processes when choosing to transition to a different orthodontic appliance (OA). METHODS: This was a retrospective qualitative study using one-on-one in-depth semi-structured interviews. Patients were recruited through purposive convenience sampling. Participants who had elected to transition from and to one of these OAs: metal brackets, tooth-coloured brackets, or clear aligners before the end of treatment were recruited. Recruitment ceased when data saturation was achieved. The interviews were audio-recorded, transcribed verbatim and analysed using thematic analysis. RESULTS: Twenty-three adult participants (12 males, 11 females) with their ages ranging from 18 to 52 years were interviewed. The analysis of the data revealed that participants perceived two reasons for the transition: (1) insufficient initial information and (2) evolving life circumstances and personal style. Data analysis of participants who expressed a notable discrepancy between their expectations and the reality of the OA they chose revolved around three themes: (a) health benefits and threats, (b) personal control, and (c) financial considerations. Data analysis of participants who described transitioning between OAs due to changes in personal circumstances and style, revealed two themes: (a) change in personal values and motivations and (b) change in social and psychological influence. CONCLUSIONS: This qualitative study highlighted the complex multifactorial nature of patient decision-making when choosing and transitioning OAs. Orthodontists can benefit from understanding these factors to engage in thorough patient-centered counselling, provide tailored treatment recommendations, and optimize the choice of appliances.