Clinical Evaluation of Digital Versus Conventional Impression in Edentulous Patients With Flabby Ridge. A Randomized Controlled Clinical Trial

Participants and setting A total of 26 participants who met all pre-defined inclusion criteria were consecutively enrolled in the study. All eligible patients presenting to the outpatient clinic at the Department of Prosthodontics, Delta University for Science and Technology, during the defined recruitment period were screened for inclusion.

Design The study utilized a crossover design, where participants were randomly assigned to receive complete dentures fabricated by using two different techniques for complete denture fabrication: Group I dentures were fabricated using the conventional window technique impression and Group II denture were fabricated using Digital impression technique. A new complete denture was delivered for each participant after 6 months, with those initially receiving Group I dentures transitioning to Group II dentures, and vice versa.

Randomization The randomization sequence was generated by a statistician using a computer-generated list of random numbers at a 1:1 allocation ratio, independent of the study's clinical team. A non-clinical assistant, who was not involved in patient recruitment or assessment, prepared the opaque, sequentially numbered, sealed envelopes and was responsible for their safekeeping in a locked cabinet. The Principal Investigator (D.E.) was responsible for screening and enrolling eligible participants. Assignment was performed by an independent dental assistant immediately prior to implementing the assigned impression technique by opening the next sequential envelope, thus ensuring adequate allocation concealment.

Interventions For Group I dentures, Window Technique Impression was employed to make the final impression, and the sequence of steps was as follows: The primary alginate impression of the edentulous maxilla was made with stock edentulous trays. Anterior maxillary flabby tissue was palpated and identified intraorally using large ball burnisher and outlined with an indelible pencil. The impression was repositioned in the patient's mouth and the markings made with an indelible pencil were transferred onto the impression surface. The impression was then poured using Type III dental stone, and one sheet of modeling wax was adapted as a spacer.

Border molding of the custom trays were made using tracing compound to capture functional extension. Then the custom tray was opened in the area of flabby tissues guided by the indelible pencil marks on the primary cast. Zinc oxide eugenol paste was loaded onto the tray to record the non-flabby tissues, ensuring detailed and stable impressions of these areas. A light coat of impression plaster was applied on the flabby ridge area using a small brush through the window area. Because the window exposes the flabby tissue, plaster captures its detail without compressing or displacing it, thereby preventing dislodgement of the denture during function and improving stability. The window technique impression was then scanned using a desktop extra-oral scanner. The scanner is equipped with four 5 MP cameras and Blue LED Multi-line technology, achieving an accuracy of 5 μm (ISO) / 8 μm. Prior to analysis, artifacts such as air bubbles and voids on the palatal surface of the WTI models were digitally removed to fabricate a 3D-printed model.