This lecture provides a comprehensive overview of the clinical and laboratory procedures for fabricating complete dentures, contrasting traditional analog workflows with modern digital dentistry techniques. The presentation details the entire process, starting with initial impressions using specialized trays (e.g., frame cutback, centric tray) and the fabrication of custom trays with occlusal rims. It includes an in-depth discussion on the classification and use of articulators (Arcon vs. Non-Arcon), various occlusal concepts for denture stability (e.g., balanced, lingualized, spherical), and the principles of dental aesthetics, including tooth shape, proportions, and arrangement. The lecture critically examines different digital workflows, from those that mirror conventional steps to streamlined systems like the Baltic Denture System, weighing their pros and cons regarding precision, materials, cost, and clinical time. The presentation concludes with final fabrication steps, emphasizing the importance of remounting for occlusal adjustments, and provides evidence-based patient aftercare considerations.
Complete Denture Fabrication: From Conventional to Digital
0:00:34 Impression Trays and Techniques: The process begins with initial impressions using specialized trays like the frame cutback tray for a non-compressed impression of the lower jaw and a centric tray to record the maxilla-mandibular relationship.
1:34 Marking and Outlining: Outlining custom tray margins is crucial. Traditional pencils do not comply with medical device regulations; alternatives like bio-ink can be imprecise. A common practice is to mark the plaster cast after the impression is taken.
4:55 Determining Vertical Dimension: The vertical dimension of occlusion (the patient's bite height) is established by measuring the patient's vertical dimension at rest (using marks on the nose and chin) and subtracting approximately 2 mm.
6:36 Fabricating Custom Trays and Occlusal Rims: Based on the initial impressions, a dental technician fabricates custom trays (using autopolymer or light-curing materials) and attaches wax occlusal rims, which are used to refine the bite and aesthetics.
14:08 Fitting and Checking Custom Trays: In the clinic, the fit of the custom trays is checked. The vertical dimension and the orientation of the occlusal plane are re-verified before taking the final impression.
17:56 Final Functional Impression: A detailed final impression is taken in steps. This includes "border molding" to capture the muscle attachments at the edge of the denture, a "wash" impression for overall fit, and creating a posterior palatal seal on the upper denture, which is critical for suction and retention.
24:07 Understanding Articulators: The lecture explains the different types of articulators used to simulate jaw movement. The Arcon design is preferred as it maintains a constant condylar path angle, while the Non-Arcon design can introduce errors when changing the vertical dimension.
32:38 Digital Articulators and Challenges: Digital systems simulate articulators but face challenges in accurately replicating individual jaw movements, which the speaker notes is "not yet convincing" in many commercial systems.
Conventional: Requires 5-6 patient appointments (initial impression, final impression, wax try-in, insertion, and adjustments).
Digital (Standard): Follows the same number of appointments, but the laboratory steps are performed using CAD/CAM technology.
Digital (Streamlined, e.g., Baltic Denture System): Aims to reduce appointments to as few as two by using a single, combined impression and relationship record, but this sacrifices the crucial try-in step and limits occlusal customization.
Pros: High precision from milled bases, potential for better materials, and the ability to easily reproduce a spare denture from saved digital files.
Cons: High initial investment, potential for high residual monomer in 3D-printed materials, and streamlined workflows may compromise clinical control and final fit.
1:04:42 Principles of Dental Aesthetics: Achieving an aesthetic result is critical for patient satisfaction. Key considerations include:
Proportions: The 80% width-to-height ratio for anterior teeth is often more aesthetically pleasing than the famous "Golden Proportion."
Arrangement: The incisal edge of the upper teeth should run parallel to the lower lip when smiling. A midline deviation of up to 3mm is often unnoticeable to laypersons.
1:31:30 Posterior Tooth Arrangement: Posterior teeth should be set in the "neutral zone" between the tongue and cheeks to ensure stability. Using narrower artificial teeth is recommended as it reduces the pressure on the underlying gums during chewing.
1:47:21 Occlusal Concepts for Complete Dentures: Unlike natural teeth, complete dentures require an occlusal scheme that promotes stability. Balanced occlusion, where teeth on both sides of the arch contact during lateral movements, is a common concept used to prevent the dentures from tipping.
1:53:36 The Importance of Remounting: After the denture is fabricated, it is crucial to perform a remounting procedure. The dentures are placed back on the articulator using a new bite record from the patient to precisely adjust the occlusion and correct any errors that occurred during processing.
1:56:46 Aftercare and Evidence: There is surprisingly little high-quality evidence to support certain long-held beliefs, such as the superiority of a two-step impression. Patients are generally advised not to wear dentures at night to reduce mucosal inflammation and lower the risk of pneumonia in elderly patients.