Complete dentures often require repair and maintenance procedures that require the original denture be sent to a laboratory. Some of these procedures might be laboratory relines, complex repairs, rebasing, denture tooth replacement, and laboratory duplication of an existing denture.
During the interim period unless the patient has a satisfactory spare denture, which could be an older denture that fits and functions reasonably well, the patient is left without a prosthesis.
For many patients, this is not acceptable for vanity reasons. In such cases, it is helpful to be able to provide a short-term interim prosthesis quickly and inexpensively – a vanity denture – that needs only to provide function for a few days to two weeks. High quality esthetics is not typically required in these situations, but the psychological impact of having to function without dentures for more than a few hours can be significant for the patient.
One technique to achieve this type of quick, in-house prosthesis involves duplication of the existing prosthesis using a Lang Denture Duplicator. According to the official instructions this technique involves a metal flask designed to be used with alginate as an investment medium (Fig. 1).
A mix of alginate (about nine scoops) in a thinner consistency than used for making impressions intraorally (approximately two measures of water in excess to the intraoral impression amount recommended by the alginate manufacturer) is placed in one half of the flask (Fig. 2), and the cameo surface of the denture (occlusal surface) is settled into the alginate to approximately 1-2 mm from the vestibular border.
The alginate investment is then trimmed to eliminate irregularities and undercuts (Fig. 3).
Once trimmed, the investment and denture are sprayed with Dentsply Sirona silicone spray to keep another mix of alginate from sticking to the first phase of the investment (Fig. 4).
Then, another mix of alginate is placed in the opposing half of the flask and into the intaglio surface of the denture, adapted either with digital manipulation or with a syringe (Fig. 5).
The flask is closed, and the sides are pressed together until the investment sets completely (Fig. 6).
When the alginate has set, the flask is separated, and the excess alginate flash is trimmed (Fig. 7).
The denture is removed, and the negative image of the denture can be clearly visualized and inspected (Figs. 8A-8B).
It is likely that some voids are present, which can be filled in with wax or more alginate if desired. Voids of less than 5 mm in width or depth in denture base areas are acceptable because the resulting positive artifacts on the replica denture can be removed in finishing and polishing; however, voids of any kind on the occlusal surfaces are difficult to manage and may require reinvesting of the cameo surface, which can be done without reinvesting the other surface if the denture can easily be repositioned.
Polyvinylsiloxane impression material
If a Lang Denture Duplicator is not readily available, or if a reusable investment is desired, then a novel alternative duplication procedure (Fig. 9) is utilizing vinyl polysiloxane impression material and a moderately flexible pressure-processed thermoplastic material that does not bond to acrylic like Copyplast.
In this technique, a vinyl polysiloxane putty mix, like Patterson Dental's Reflection, is made and placed on a flat, smooth workspace. Alternatively, an addition silicone laboratory putty, like Sil-Tech Plus, from Ivoclar Vivadent, may be used. The amount of putty should be sufficient to create an investment base that is at least 5 mm thick at the thinnest vertical portion and covers a horizontal area wide enough to extend at least 5 mm beyond the borders of the denture.
A medium viscosity vinyl polysiloxane impression material may be expressed into the intaglio aspect of the denture to capture the details of the edentulous ridge area (Figs. 10-11).
Then, the denture is inverted and seated into the putty base until approximately 2-3 mm of the borders are embedded in the impression material.
Once the vinyl polysiloxane has set for approximately 5 minutes – longer than the intraoral setting time recommended by the manufacturer because the cooler ambient and work surface temperatures will likely prolong setting time – the base of the investment should be trimmed so all horizontal areas are flat or slightly tapering downward away from the denture without significant voids while maintaining a seal with the denture (Fig. 12).
The vertical walls of the investment base should be trimmed perpendicular to the horizontal land areas and to the work surface or slightly tapering away from the denture to avoid undercuts (Fig. 13).
Copyplast is placed in Biostar or MiniStar. The Biostar and MiniStar have a heating element to heat thermoplastic materials to appropriate temperatures and are designed to adapt the materials to a model with positive pressure (Fig. 14).
Vacuum forming units utilize negative pressure to pull thermoplastic materials over a model, which typically does not create the level of detail required for denture duplication (Fig. 15).
Once the Copyplast has been allowed to cool on the bench top, the excess flash may be trimmed with utility scissors, and the flask assembly is separated and inspected for accuracy once the denture has been removed (Fig. 16).
Regardless of the flasking technique utilized, the first step of replicating the denture is to fabricate the duplicate denture teeth, which again can be accomplished using two techniques. The conventional method involves pouring a syrupy mix of tooth-colored polymethyl methacrylate suitable for making provisional restorations, like Jet, into the void created by the denture teeth (Fig. 17).
When the shiny sheen of the liquid stage disappears, the acrylic has reached an elastic stage and can be sculpted and trimmed with a sharp instrument to create the gingival margin outline; however, it is difficult to visualize the gingival contours, and it is easy to damage the alginate, which would alter the cameo surface of the duplicate denture.
Once the tooth-colored methacrylate or bis-acryl resin has set until it is firm to the touch, the flask assembly is reassembled to confirm there is adequate space to allow full closure of the flask and for at least 2 mm of pink duplicate denture base. An advantage of the Copyplast/vinyl polysiloxane technique is that this space is easily visualized (Fig. 18).
If there is not enough space, then the intaglio aspect of the duplicated denture teeth can be adjusted with an acrylic bur. A better option for trimming the gingival contours of the duplicate denture teeth is to allow them to set completely until the exothermic reaction of the polymer is complete, and then the teeth can be removed from the flask and trimmed for appropriate gingival contour using rotary acrylic finishing instruments (Fig. 19).
When repositioning the trimmed duplicate denture teeth into an alginate flask, care must be taken not to alter the alginate, and complete reseating of the duplicate denture teeth is difficult to assess. This is a significant challenge with the alginate flasking technique. Another major advantage of the Copyplast/vinyl polysiloxane technique is that full seating of the duplicate denture teeth can be visualized easily (Fig. 20).
An alternative to using polymethyl methacrylate for duplicate denture teeth is a bis-acryl composite resin designed for making provisional crowns that may be injected into the Copyplast portion of the flask to create duplicate denture teeth in a similar manner (Fig. 21).
Filling the Copyplast is like the technique for making provisional fixed restorations. Once the bis-acryl has polymerized, the duplicate denture teeth can be removed from the Copyplast, and the gingival contours can be trimmed in a similar fashion to polymethyl methacrylate. If bis-acryl is used, then retentive features and diatorics should be carved into the intaglio surface of the duplicate denture teeth to create mechanical retention to the denture base (Fig. 22).
When using the alginate flask technique, pink denture repair polymethyl methacrylate, like Jet Denture Repair Material, is applied around the gingival aspect of the duplicate denture teeth and into any retentive features using a salt-and-pepper technique (Fig. 23) and allowed to reach a partial set to create a seal around the duplicate denture teeth in order to reduce flash during the next step.
Repair acrylic is mixed to a syrup consistency and poured into the investment void to create the denture base. Using a stone vibrating unit is necessary for void-free flow into the denture border areas (Fig. 24).
The flask is reassembled and stabilized (Fig. 25). Pressure applied during closing of the alginate flask to the acrylic is preferable.
The acrylic is allowed to cold cure in the flask, in a pressure pot if desired. When adequately cured, the flask assembly is separated, and the vanity denture is deflasked. When using the Copyplast/VPS duplicating flask, a bis-acryl composite resin denture reline material is preferable because of its viscosity and ability to easily close the flask bimanually without significant pressure and distortion of the flexible flask (Fig. 26A-C).
If voids are present due to air entrapment using either technique, repairs can be done using similar materials (Fig. 27).
Standard finishing and polishing procedures used for any resin or acrylic appliance is performed to create a smooth, reasonably acceptable interim prosthesis (Fig. 28).
The vanity denture is then ready to be seated in the patient's mouth (Fig. 29).
It is common for the denture stability and retention to be somewhat compromised due to the nature of a flexible flasking medium used in these techniques. Therefore, a temporary soft chairside reline material of clinician's preference can be placed according to standard techniques.
Occlusion should be grossly adjusted using standard techniques, with the goal of having generally stable centric contacts and no destabilizing excursive contacts to create reasonable comfort and stability for a brief period of time.
Due to the imprecise nature of these chairside duplicating techniques, detailed occlusal refinement is not a reasonable expectation for the purpose of a vanity denture. The patient may also be advised to use an over-the-counter denture adhesive according to the manufacturer's instructions to maximize their quality of life while using the vanity denture.
A chairside denture duplication procedure, whether using the Lang Denture Duplicator or an alternative technique using Copyplast and vinyl polysiloxane impression material, can provide an adequate and valuable service for most patients who are not willing to function without their original denture during a short interim when their prostheses must be absent for laboratory repair procedures.
Typically, the esthetics and function are less than optimal, and the durability of provisional vanity dentures is unpredictable. Therefore, the patient must be informed of these expectations ahead of time as part of the informed consent process.
Kevin D. Huff, D.D.S., M.A.G.D., is a diplomate of the American Board of Orofacial Pain. He is a member of Spear Visiting Faculty, a moderator on the Spear Talk online forum and a contributor to Spear Digest.