There are several approaches to fabricating conventional complete removable dentures. The classic approach typically involves at least five separate clinical appointments that are separated by the time required to complete the necessary laboratory work.
The classic approach has proven to provide predictable outcomes for most edentulous patients and their dentist/technician team. While it is absolutely necessary for some patients, the classic approach also has the disadvantage of requiring significant treatment time. Several techniques have been proposed to shorten the time required to fabricate a new set of dentures. Unfortunately, some of these approaches are shortcuts that come with the significant risk of an unpredictable outcome.
As an example, some authors propose eliminating the trial denture appointment to eliminate chair time from the fabrication process. While true, this would save one appointment compared to the classic approach, the risk is an unpredictable esthetic or functional outcome. Skipping the try-in appointment means neither clinician nor patient would have the opportunity to critically evaluate things like tooth position, tooth arrangement, tooth color, occlusal vertical dimension or the occlusal contacts.
The risk to the clinician is that if any of these elements needs to be changed, significantly more time will now be required to re-do several steps. Certainly, this is an obvious example, but the bottom line is that when the time to manage error is factored into treatment time, unpredictable outcomes tend to increase treatment time rather than decrease it. With that in mind, any approach clinicians seek to improve efficiency should provide a patient outcome as good or better than the traditional approach.
Improving clinical efficiency through shortened treatment time
One of the easiest methods for improving efficiency involves the impression – or, rather, the trays being utilized for the definitive impression. According to the classic approach, a preliminary impression would be made to fabricate a preliminary cast. That cast is subsequently used to fabricate the custom tray used with the definitive impression. While predictable, this approach comes at the cost of essentially two clinical appointments to make the definitive impression.
The patient in Figure 2 presented with a hopeless dentition. Rather than proceed with an immediate denture approach, this patient preferred to have the remaining teeth removed and began the denture fabrication following initial healing. In order to fabricate removable complete dentures for the now edentulous patient, custom trays were fabricated following the classic technique: preliminary impression, preliminary cast and definitive impression utilizing custom trays. The time-consuming sequence for tray fabrication is summarized in Figure 3.
An alternative to the custom tray fabrication demonstrated in the case above would be to use a stock tray that allows for customization. Figures 4 and 5 show two stock (pre-manufactured) edentulous impression trays. What makes these trays special is the ability to customize the shape by heating the material. Once the tray material is chilled, the changes to the tray form are preserved. Customizing the trays allows for border molding and definitive impression making in a way similar to using an entirely custom tray.
The primary advantage to using a customizable tray is combining the first two clinical appointments of the classic approach into a single definitive impression appointment and, as a result, going from five clinical appointments to four without compromise to the overall outcome of the case.
Additional options for definitive edentulous impression trays
If the patient has existing dentures, the “old” dentures can be quite useful in the fabrication of a new denture or set of dentures. One option for exploiting the existing dentures is to use the actual dentures as the impression tray. If the dentures fit reasonably well, a wash impression could be made inside the existing denture. However, there are two problems with this approach.
The first problem is the time involved to pour and articulate the case means the patient may be without their dentures for several hours (or longer if the case is going to the dental laboratory).
The second problem exists if the denture does not fit well, particularly if it is over-extended. The only way to avoid propagating the over-extension into the impression would mean altering the existing denture by reducing the extension. Permanently altering the patient's existing denture puts the clinician at significant risk should problems develop in the future.
Clinicians can avoid those problems entirely by copying or duplicating the existing dentures. The duplicate denture can be used as the custom impression tray for the definitive impression and, because it is a duplicate, the denture flange or any other part of the denture can be altered without fear.
Duplicating the existing denture requires some additional effort and yet the improvement in efficiency is significant. In the previous techniques the preliminary impression appointment was unnecessary, resulting in reducing the total number of appointments from five to four. With duplicate dentures the number of clinical appointments can be reduced further by taking advantage of the teeth being present.
Having the tooth position recorded in the duplicate denture/custom tray allows the clinician to evaluate and modify both esthetic and function details. Once the impressions have been made, the clinician can evaluate lip support and tooth position. Changes can be made directly to the duplicate denture and then transferred to the technician both physically and through photographs. The occlusal vertical dimension can be evaluated and altered if necessary, then interocclusal records can be made. The effort to duplicate the dentures pays off by allowing all the procedures that typically happen and the third appointment to be performed in the same clinical appointment in which the definitive impressions are made.
Methods for duplicating removable complete dentures
There are several options for duplicating complete dentures. Generally, the techniques could be broken down into analog approaches and digital approaches.
With analog duplication techniques, alginate or lab putty is used with a flask to capture the three-dimensional contours of the denture. When the alginate or lab putty has set, the denture is removed and the void filled with an autopolymerizing resin.
Digital approaches to denture duplication involve scanning the denture with a chairside scanner, lab scanner or CBCT. The resulting file can then be manipulated as necessary before digital manufacture. Due to the costs of milling and the need to mill from a puck, most denture duplicates will probably be printed when done in the dental office.
What if I can't duplicate the dentures?
Despite the advantages that a duplicate denture impression technique provides, there may be times when the duplication process is either not available or not practical. In those cases, the existing denture can still provide value for the clinician seeking to shorten time to the definitive denture.
Laboratory putty or impression silicone can be used to make a cast from the existing denture. The silicone cast is flexible enough to be separated from the existing denture with minimal risk from damaging the denture base. While flexible, the silicone case is firm enough to fabricate the custom impression tray without distortion. As with the denture duplication, this process is reasonable to delegate to a trained team member.
Bottom line: clinical efficiency is important with any procedure. Unanticipated clinical appointments negatively impact clinical efficiency and, as a result, reduce potential profits and our overall satisfaction with a case. The techniques here are realistic options to help maximize clinical efficiency without sacrificing the patient outcome.
Darin Dichter, D.M.D., is a member of Spear Resident Faculty.
A Critical Analysis of Mid-Century Impression Techniques for Conventional Dentures (Boucher, 1951)
An introduction to Denture Simplification (Pound & Murrell, 1971)
Predictable Impression Procedures for Complete Dentures (Felton, Cooper & Scurria, 1996)
Critical Review of Some Dogmas in Prosthodontics (Carlsson, 2009)
Predictable Edentulous Final Impressions in a Single Visit (Little, Knight & Graham)
Building the Edentulous Impression- A Layering Technique Using Multiple Viscosities of Impression Material (Massad et al., 2006)
Taking Advantage of Existing Dentures (Vig, 1971)
Use of Existing Dentures for the Production of New Prostheses (Anderson & Storer, 1973)
Diagnostic Procedures Using the Patient's Existing Dentures (Sprigg, 1983)