This month I want to discuss one of the forgotten areas of dentistry: partial dentures. To get an idea of the current state of the industry, I recently spoke with one of this country’s most experienced partial-denture technicians. Jerry Lord is manager of the partial-denture department at Glidewell Laboratories, and has specialized in the field for almost 32 years. Following are excerpts from our conversation about some of the innovations in this often neglected area of dentistry.
MD: Jerry, dental journals I open seem to focus primarily on esthetic dentistry. There is article after article on prep and no-prep veneers, and various all-ceramic crown systems. How has esthetic dentistry affected partial-denture techniques?
JL: Esthetic dentistry has become a buzzword in the last 10 years, but we think of esthetic dentistry every time we design a partial denture, or every time we place a clasp. Today, there are several good esthetic partial options available. For example, you could use Valplast, Thermoflex, or actually design a clasp to engage the mesial or distal of a tooth to keep it from being seen. As opposed to crossing and engaging in a buccal undercut with a metal clasp, Thermoflex is an acetyl resin that comes in 16 Vita colors. We make flippers with Thermoflex clasps as well. This is a huge improvement over the typical flipper with which most practitioners are familiar. Valplast is another example of a great esthetic partial denture because you get the intimacy of fit, and the clasps match the gingival shade of the gingiva.
MD: I had no idea Thermoflex could be used to make a flipper. How does that work?
JL: The Thermoflex clasp would be used to clasp the same teeth that would usually be clasped with wrought wire. So, rather than having wires that were visible on the cuspids, now the cuspids and the molars can have Vita-colored clasps that blend in with the teeth much better than a stainless steel wire ever could. So you end up with an all-acrylic prosthesis without any wire clasps.
MD: What is one of the esthetic challenges in doing partial dentures on the maxilla?
JL: You’d be surprised at the number of cases where the upper anteriors are missing, and the lower anterior teeth have supererupted into that space. As a result, there is not enough vertical dimension present to be able to have space for relief, the partial framework, the acrylic, and the teeth. A great esthetic solution is to place metal linguals where the missing teeth were with belleGlass composite facings. This allows great esthetics on the partial denture without having to open the patient’s bite to accommodate new teeth on a partial.
MD: How do attachments affect partial-denture esthetics?
JL: When building a crown, if possible, the dentist should use an attachment such as an ERA or VKS attachment. If I use an attachment with a crown, I go claspless on that tooth. This is the ultimate in esthetics. When I design partial dentures, I do so as if I were designing the partial denture for myself. I use attachments whenever possible.
MD: What percent of dentists design their own cases, and what percent have you design their cases?
JL: About 50 percent of dentists design their own partial dentures, but only about 20 percent of them survey their models. Unfortunately, if dentists don’t survey their models, many times we can’t follow their designs because of a lack of undercut.
MD: What are the biggest problems you see from dentists regarding their partial-denture techniques?
JL: The choices of impression material, the impressions, and the bite. Doctors use heavy-body viscosities, or - even worse - putty material to save money. Unfortunately, these materials compress and move soft tissues. As a result, frameworks don’t fit. Dentists also take master impressions in flexible plastic trays. This can easily lead to distortion. It seems like dentists are used to using custom trays for full dentures but not partial dentures. It’s a shame because the fit of partial dentures is improved with custom trays. As far as bites go, often the doctor will inject the material, have the patient close down, but never reverify the bite. Doctors should trim back the bite so only the incisal edges of cusp tips are in the registration. Then the patient should bite back into it to make sure the edges were in the proper relationship to the jaw. When shipping, especially with a lower denture, many doctors pour the impression and send the models without a base. They often break in transit. Doctors should either pour a base before shipping the model, or use an impression material stable enough for a lab to do the pouring.
Dr. Michael DiTolla is director of clinical research and education at Glidewell Labs in Newport Beach, Calif., where he also teaches courses on topics such as esthetic and restorative dentistry. He teaches a two-day, live-patient, hands-on laser-training course that emphasizes diode and erbium lasers. He also teaches a two-day, hands-on digital photography course on intraoral and portrait photography, and image manipulation. For more information on these courses, e-mail Dr. DiTolla at [email protected] or call (888) 535-1289.