Digital VS Conventional Altered Cast Technique for Mandibular Bilateral Distal Extension RPDs

Digital VS Conventional Altered Cast Technique for Mandibular Bilateral Distal Extension Removable Partial Denture

This study aims to compare outcomes of digitally created altered casts with conventional altered casts in mandibular bilateral distal-extension cases.

Study Overview

• Status: Completed
• Conditions: Dentures; Digital; Mandibular Dimensions
• Intervention / Treatment: Procedure: Digital workflow and Digital altered cast; Procedure: Conventional Altered Cast Technique

Detailed Description

Partially dentate adults represent an increasing proportion of the population, driven by increased life expectancy and a demographic shift from total edentulism toward partial edentulism. Fabrication of removable partial dentures for distal extension edentulous ridges presents significant clinical complexity because the teeth and residual ridge possess fundamentally different degrees of displaceability. Optimum denture support re-quires recording teeth in anatomical form and the mucosa in functional form .

The altered cast impression technique , introduced by Applegate, remains one of the most widely accepted methods for achieving optimal tissue support and accurate denture base positioning relative to tooth abutments . removable partial dentures fabricated using altered cast impression technique demonstrate improved patient comfort and preservation of oral health . However, despite these advantages, debate persists regarding the clinical significance of altered cast impression technique over single-impression techniques .

Recent advances in computer-aided design and computer-aided manufacturing have transformed the removable partial dentures framework, opening new pathways in the fabrication of RPD through additive and subtractive manufacturing . Digital intraoral scanning offers advantages, including reduced dimensional error, improved efficiency, and real-time feedback on impression accuracy and extension [13-16]. However, intraoral scanning techniques are inherently mucostatic and image-based, rendering the recording of functional impression impossible, a limitation acknowledged as necessary for optimal support in distal extension removable partial dentures . Lab scanning of conventionally prepared altered casts pre-pared by traditional methods fails to eliminate inherited errors from cast separation and reassembly.

Recent studies have introduced hybrid digital workflows that combine functional registration of the edentulous ridge with mucostatic scanning of the remaining oral structures in an effort to reproduce conventional clinical procedures while improving efficiency and precision . Most investigations on digital technology in RPD have concentrated on methods for fabricating metal frameworks and evaluating their performance.

This study aims to compare outcomes of digitally created altered casts with conventional altered casts in mandibular bilateral distal-extension cases.

• Study Type: Interventional
• Enrollment (Actual): 7
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Egypt
  • Tanta, Egypt
    • Tanta University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Patients presented with bilateral, well-formed mandibular distal extension residual ridges covered by keratinized mucosa, with a minimum thickness of 1.5-3 mm .
• Each participant had a sound first or second premolar serving as the terminal abutment, with a crown-to-root ratio of ≥ 1:2.
• Comprised fully or partially dentate maxillary arches, an Angle Class I molar relationship, and adequate interarch space (7-8 mm) to accommodate the prosthesis .

Exclusion Criteria:

• The presence of systemic conditions affecting bone metabolism or healing
• pathological conditions in the edentulous area (e.g., residual cysts, retained roots, or severe ridge re-sorption);
• parafunctional habits such as bruxism, clenching, or tongue thrusting
• pro-nounced anatomical undercuts in the lingual mandible or adjacent to abutment teeth that could impede denture fabrication or insertion.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Digital workflow and Digital altered cast group; Digital selective tissue placement was performed within the same Exocad design project using the free-form scan-data tool, paint and pull feature to apply the principles of selective tissue pressure technique . Using free form mesh editing tools, the buccal shelf area opposing teeth 37 and 47 was identified, and controlled tissue ward displacement of the mucosal surface was simulated while monitoring the magnitude of displacement on sectional views and with digital measurement tools. Figure 2B, F The modified mandibular dataset was saved as the digitally altered cast STL (DA), which served as the basis for the digital RPD design and subsequent denture base fabrication.	Procedure: Digital workflow and Digital altered cast; The RPD design features of fully digitally fabricated RPD illustrated in Figure 2A. Digital selective tissue placement was performed within the same Exocad design project using the free-form scan-data tool, paint and pull feature to apply the principles of selective tissue pressure technique . Using free form mesh editing tools, the buccal shelf area opposing teeth 37 and 47 was identified, and controlled tissue ward displacement of the mucosal surface was simulated while monitoring the magnitude of displacement on sectional views and with digital measurement tools.
Experimental: Conventional workflow and conventional altered cast group; For the CA cast technique, one of the SLM frameworks (MF2) was adapted on the stone master cast and used as a functional impression tray (Acrostone Dental Manufacturing, Cairo, Egypt) over the distal extension areas. A selec-tive pressure impression was made according to the traditional altered cast protocol, with the distal saddle areas repoured in dental stone to obtain the CA cast. This CA was then digitized using a desktop scanner (Dove Technologies, Suzhou, China) to produce the CA cast STL. Wax rims were used to verify the jaw relationship, and the maxillary cast was mounted using a facebow transfer on a semi adjustable articulator (A7 Plus, Bio-Art Equi-pamentos Odontológicos Ltda., São Carlos, SP, Brazil), while the mandibular cast was mounted in maximum intercuspation.	Procedure: Conventional Altered Cast Technique; For the CA cast technique, one of the SLM frameworks (MF2) was adapted on the stone master cast and used as a functional impression tray (Acrostone Dental Manufacturing, Cairo, Egypt) over the distal extension areas. A selec-tive pressure impression was made according to the traditional altered cast protocol, with the distal saddle areas repoured in dental stone to obtain the CA cast. This CA was then digitized using a desktop scanner (Dove Technologies, Suzhou, China) to produce the CA cast STL. Wax rims were used to verify the jaw relationship, and the maxillary cast was mounted using a facebow transfer on a semi adjustable articulator (A7 Plus, Bio-Art Equi-pamentos Odontológicos Ltda., São Carlos, SP, Brazil), while the mandibular cast was mounted in maximum intercuspation. Semi anatomic acrylic teeth (Acrostone Dental Manufacturing, Cairo, Egypt.) were arranged, and wax try ins were evaluated intraorally in a conventional manner prior to processing.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Assessment of the condition of ridge mucosal covering of the Removable Partial Denture constructed out of digitally altered model.	at 15 days, 3 months and 6 months .

Secondary Outcome Measures

Outcome Measure	Time Frame
Denture base fit by Pressure Indicating Paste	one month

Collaborators and Investigators

• Sponsor: Tanta University

Study record dates

Study Major Dates

• Study Start (Actual): May 30, 2021
• Primary Completion (Actual): November 30, 2024
• Study Completion (Actual): November 30, 2024

Study Registration Dates

• First Submitted: May 1, 2026
• First Submitted That Met QC Criteria: May 7, 2026
• First Posted (Actual): May 13, 2026

Study Record Updates

• Last Update Posted (Actual): May 13, 2026
• Last Update Submitted That Met QC Criteria: May 7, 2026
• Last Verified: May 1, 2021

More Information

Terms related to this study

• Keywords: Digital; mandibular; Removable Partial Dentures; Altered Cast Techniques
• Other Study ID Numbers: R-RP-5-21-10

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No