This prospective randomized crossover clinical trial evaluates and compares the clinical performance and oral health-related quality of life (OHRQoL) of complete dentures fabricated through two additive manufacturing workflows - digital and hybrid - in edentulous patients attending the Dental Clinic of Universidad de Especialidades Espíritu Santo (UEES), Samborondón, Ecuador.

In the digital workflow, complete dentures are fabricated using direct intraoral scanning of edentulous ridges, CAD design, and 3D printing. In the hybrid workflow, conventional functional impressions are digitized, followed by CAD design and additive manufacturing of the definitive dentures.

Each eligible participant receives two complete denture sets in a randomized crossover sequence (no washout period): Denture Set 1 is worn for 2 months, after which the participant crosses over to Denture Set 2, worn for an additional 2 months. Total active follow-up per participant is approximately 4 months. Following completion of the crossover phase, denture wear is monitored longitudinally for 12 months from the insertion of the second denture set (total study duration approximately 16 months per participant).

The study addresses three specific objectives:

To determine the clinical success rate of complete dentures fabricated by additive manufacturing under digital and hybrid workflows, evaluating retention, stability, denture base adaptation, occlusal balance, and need for clinical adjustments.

To evaluate the impact of complete denture treatment on OHRQoL using the validated OHIP-EDENT questionnaire, assessed at the insertion of each denture set and at the 2-month control of each period (4 measurement points total).

To evaluate the relationship between maximum masticatory force (T-Scan digital occlusal analysis system) and denture wear (volumetric 3D digital metrology via STL superimposition), with wear monitored over 12 months from insertion of the second denture set.

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.

Inclusion Criteria:

Completely edentulous (bimaxillary) Age between 50 and 80 years Able to understand and sign informed consent No cognitive or psychological deficits that interfere with study participation

Exclusion Criteria:

Unimaxillary edentulism Presence of Kelly syndrome Presence of flabby tissue on alveolar ridges No prior experience with complete dentures Chronic motor disorders that may compromise prosthetic function

Individual participant data that underlie the results reported in the published article, after de-identification, will be shared.

Beginning 6 months after article publication.

Researchers who provide a methodologically sound proposal. Requests should be directed to the principal investigator.