Comparative Efficacy of Digital vs Conventional Impressions in Orthodontics

Thesis Abstract

This study investigates the comparative efficacy of digital versus conventional impressions in orthodontics, addressing inconsistencies in clinical performance, patient experience, and downstream lab workflow that may influence treatment accuracy and outcomes. The aim is to determine whether digital impression systems provide superior, equivalent, or inferior orthodontic accuracy and patient-reported experience compared with conventional impression methods, and to identify factors that modulate these effects. Specific objectives include (1) quantifying trueness and precision of digital versus conventional impressions across multiple malocclusion categories, (2) evaluating intra- and inter-operator reliability for each impression modality, (3) comparing patient comfort, preference, and perceived chair time between techniques, (4) assessing downstream effects on appliance fit, wire sequencing, and adjustment frequency in the first six months of treatment, and (5) exploring cost-effectiveness implications from clinic and patient perspectives. A parallel, prospective, randomized controlled trial design is employed. The population comprises patients aged 12–25 years requiring fixed orthodontic appliances at a university-affiliated orthodontic clinic. A total sample of 320 participants will be recruited and randomized equally (n=160 per arm) to receive either digital intraoral scanning or conventional polyvinyl siloxane impressions for bracket bonding. Data collection instruments include calibrated 3D scanner-based measurements for trueness and precision (using best-fit analysis against STL reference models), intra- and inter-operator reliability assessments, validated patient experience questionnaires (Likert-scale), time-motion recording for chair and procedure times, and clinical records for attachment fit, bonding errors, appliance adjustments, and treatment progression over six months. Instrument validity will be established through pilot testing and cross-validation with expert opinions; reliability will be evaluated via test-retest and inter-rater agreement (Intraclass Correlation Coefficient and Cohen’s kappa where appropriate). Analytical methods comprise descriptive statistics to summarize measurements, followed by inferential analyses including paired and independent samples t-tests, repeated-measures ANOVA to evaluate changes over time, and multivariate regression to identify predictors of impression accuracy and clinical outcomes. For non-normally distributed data, non-parametric equivalents (Mann-Whitney U, Wilcoxon signed-rank) will be applied. A multilevel modeling approach will account for clustering at patient and operator levels. A cost-effectiveness analysis will be conducted using incremental cost-utility ratios, incorporating direct costs, chair time, material costs, and utility gains from reduced retakes. The study will be guided by the Technology Acceptance Model and the Theory of Planned Behavior to interpret patient and clinician adoption patterns, while the study will test the null hypothesis of no difference between modalities for primary outcomes (impression accuracy and bracket fit) and secondary outcomes (patient experience, chair time, and treatment efficiency). Expected findings anticipate that digital impressions will demonstrate non-inferior or superior trueness and precision relative to conventional impressions in most malocclusion categories, with higher patient-reported comfort and shorter chair times. It is hypothesized that digital impressions will yield fewer bracket bonding errors and reduced need for occlusal adjustments in early treatment stages, translating into improved treatment efficiency and reduced cumulative appointment numbers over six months. Potential subtype differences are anticipated, with greater benefits of digital workflows in complex arch configurations and in cases requiring lingual or palatal captures. The study is expected to reveal a favorable cost-effectiveness profile for digital impressions in high-volume clinics, particularly when factoring labor and material savings and reduced retakes. The contribution to knowledge includes robust, externally valid evidence on the comparative clinical performance, patient experience, and economic implications of digital versus conventional impressions in orthodontics, addressing a current gap in standardized cross-study conclusions and informing evidence-based clinical guidelines, purchasing decisions, and training curricula. The conclusion will discuss the conditions under which digital impressions confer clear advantages and scenarios where conventional methods remain viable, with recommendations for practice integration, clinician training, and future research exploring long-term outcomes and scanner evolution.