This is an excerpt from a comprehensive dental lecture on the principles and clinical procedures for fabricating complete dentures. The speaker, Dr. Christopher, begins by establishing the continued relevance of complete dentures in the 21st century, noting that despite declining rates of edentulism, an aging population presents dentists with increasingly complex cases.
A significant portion of the lecture is dedicated to the clinical findings and challenges in edentulous patients, with a primary focus on ridge resorption. The speaker details its causes (pressure and post-extraction ischemia), its consequences (loss of vertical dimension, pseudo-prognathism), and associated soft tissue pathologies like irritation fibromas, flabby ridges, and denture stomatitis. The importance of differential diagnosis for oral lesions is emphasized. The presentation then outlines a systematic clinical workflow, covering the initial impression, fabrication and fitting of custom trays, the final functional impression, and the maxillomandibular relationship record. Both conventional techniques (using wax rims and tools like the Centric Tray) and modern digital workflows (involving 3D-printed trays and needle point registration) are discussed. The lecture concludes with a foundational explanation of Arcon versus Non-Arcon articulators and their clinical importance.
Complete Denture Fabrication: A Clinical Overview
0:05:40 The Continued Need for Complete Dentures: Despite a general decline in total toothlessness (edentulism), the treatment remains relevant due to an aging population. These older patients often present more complex cases due to significant bone loss, medical comorbidities, and long-term denture wear.
0:19:33 Understanding Ridge Resorption: A primary challenge is ridge resorption, the progressive loss of the alveolar bone after tooth extractions. This process alters the jaw structure, typically making the lower jaw appear wider and the upper jaw narrower, which complicates denture stability and fit.
0:29:20 Causes of Bone Resorption: Resorption is caused by a combination of factors, including pressure from a denture base and impaired blood supply (local ischemia) in the bone following tooth extraction. Animal studies suggest there are critical pressure thresholds that, if exceeded, will lead to significant bone loss.
0:42:24 The Vicious Cycle of Pseudo-Prognathism: As the ridge resorbs, the vertical dimension of occlusion decreases, causing the mandible to over-rotate forward. This creates deflective contacts on the dentures, which generates horizontal forces and accelerates further, localized resorption.
0:47:37 Common Oral Pathologies in Edentulous Patients: The lecture highlights several tissue conditions dentists must identify, including irritation fibromas (epulis fissuratum) from ill-fitting denture flanges, flabby ridges, and denture stomatitis. It is critical to differentiate benign pressure sores from potentially malignant lesions like squamous cell carcinoma.
1:06:22 Key Patient Communication Points: Before treatment, patients must be educated on the limitations of complete dentures, including reduced chewing force, the likelihood of sore spots, the typical number of appointments (5-6), and the necessity for long-term maintenance like relines (approximately every 3 years).
1:09:30 The First Impression and Jaw Relationship: The initial clinical step involves taking a preliminary impression and recording a preliminary maxillomandibular relationship. The speaker discusses tools like the Ivoclar Centric Tray, which helps capture an initial vertical dimension and centric relation.
1:29:32 Fabricating and Using Custom Trays: Custom-made impression trays with occlusal rims are fabricated from the preliminary models. These are crucial for taking an accurate final impression and correctly establishing the occlusal plane, vertical dimension, and aesthetic landmarks like the midline and canine position.
1:37:37 Digital vs. Conventional Workflows: The speaker contrasts the traditional workflow using wax rims with modern digital approaches that utilize 3D-printed custom trays. These digital trays can be integrated with devices for a highly precise needle point registration to record the centric relation.
1:45:41 Taking the Final Functional Impression: Using the custom tray, a final impression is made that captures the soft tissues in a functional state (e.g., while moving the lips and tongue). A key goal for the upper denture is to achieve a good posterior palatal seal (PPS) for optimal retention.
1:55:52 The Importance of Articulator Choice: The lecture concludes by explaining the difference between Arcon and Non-Arcon articulators. An Arcon articulator correctly mimics jaw anatomy by having the condylar guidance fixed to its upper member, which prevents errors if the vertical dimension is altered during the fabrication process.