Clinical Performance and Quality of Life of 3D-Printed Complete Dentures Under Digital vs Hybrid Workflows: A Randomized Crossover Trial (PRINT-DENT)

BACKGROUND Edentulism remains a significant public health concern, particularly among older adults, due to its impact on masticatory function, facial aesthetics, phonation, nutrition, and psychosocial well-being. Complete denture rehabilitation is the standard of care for edentulous patients; however, conventional fabrication techniques are associated with dimensional inaccuracies, multi-step laboratory procedures, and interoperator variability. The introduction of CAD-CAM systems and additive manufacturing (3D printing) offers potential advantages including improved precision, streamlined clinical workflows, and enhanced reproducibility. Despite growing clinical interest, robust evidence comparing digital and hybrid workflows - including patient-reported outcomes, clinical success, and objective functional measures such as masticatory force and denture wear - remains limited.

STUDY DESIGN Prospective, controlled, randomized, double-blind (participant and outcomes assessor), crossover clinical trial. No washout period between denture sets. Each participant receives two complete denture sets - one fabricated by digital workflow and one by hybrid workflow - in a randomized sequence. Total crossover phase: approximately 4 months per participant. Denture wear follow-up: 12 months from insertion of the second denture set.

PARTICIPANTS Completely edentulous adults aged 50-80 years requiring bimaxillary complete denture rehabilitation, attended at the UEES Dental Clinic. Recruitment is ongoing; first clinical appointments begin June 2026. Target sample: 28 participants (20 required for 83.7% power based on effect size d=1.25 from Peroz et al. 2024; 8 additional for anticipated dropout). Sample size calculated using G*Power 3.1, Wilcoxon-Mann-Whitney test, α=0.05, power=0.80.

INTERVENTIONS

Intervention A - Digital Workflow (3 clinical appointments):

Appointment 1: Intraoral scanning of edentulous ridges (TRIOS 5, 3Shape); digital recording of vertical dimension, intermaxillary relationship, and occlusal plane orientation.

Appointment 2: Clinical try-in of 3D-printed prototype (Asiga TRY resin, Asiga MAX 2 printer).

Appointment 3: Delivery of definitive 3D-printed complete denture (DentaBASE resin; VarseoSmile TriniQ teeth, BEGO).

Intervention B - Hybrid Workflow (5 clinical appointments):

Appointment 1: Preliminary impression and custom tray fabrication. Appointment 2: Functional impression with elastomeric materials. Appointment 3: Interocclusal registration (vertical dimension, centric relation, occlusal plane) with wax rims.

Appointment 4: Conventional wax try-in. Appointment 5: Delivery of definitive complete denture (conventionally impressed, digitally designed, additively manufactured base; DentaBASE resin; VarseoSmile TriniQ teeth, BEGO).

STUDY TIMELINE PER PARTICIPANT

Month 0: Insertion of Denture Set 1 (randomized: digital or hybrid) + baseline OHIP-EDENT + baseline T-Scan + baseline denture scan Month 2: 2-month control of Denture Set 1 + OHIP-EDENT + T-Scan + denture wear scan → Crossover: insertion of Denture Set 2 Month 4: 2-month control of Denture Set 2 + OHIP-EDENT (final crossover endpoint) + T-Scan + denture wear scan Months 4-16: Denture wear follow-up of Denture Set 2 at scheduled intervals (12-month longitudinal wear monitoring from insertion of Set 2)

RANDOMIZATION AND BLINDING Randomization sequences (A→B or B→A) generated by an external investigator using random.org. Concealed in sequentially numbered opaque sealed envelopes opened only after participant enrollment. The clinical operator cannot be blinded to the workflow; however, the participant and the outcomes assessor remain blinded throughout the study.

PRIMARY OUTCOME Oral health-related quality of life assessed by OHIP-EDENT total score at 4 time points across the crossover period.

SECONDARY OUTCOMES

Clinical success rate (composite: retention, stability, base adaptation, occlusal balance, need for adjustments) Maximum masticatory force (T-Scan; relative force and distribution) Denture wear - volumetric surface loss (mm³) via 3D STL superimposition over 12 months from Set 2 insertion Correlation between maximum masticatory force and denture wear

STATISTICAL ANALYSIS Normality assessed by Shapiro-Wilk test. Crossover comparisons (Obj. 1 and 2): paired t-test or Wilcoxon signed-rank test; categorical variables by McNemar's test; period and carryover effects evaluated. Longitudinal wear analysis (Obj. 8): repeated-measures ANOVA or Friedman test across time points; force-wear correlation by Pearson or Spearman coefficient. Significance: α=0.05. Missing data handled by intention-to-treat analysis where possible.

ETHICS Protocol approved by the Human Research Ethics Committee of Universidad de Especialidades Espíritu Santo (CEISH-UEES), Samborondón, Ecuador (March 2026). Conducted in accordance with the Declaration of Helsinki. Written informed consent obtained from all participants prior to enrollment.