Townie Clinical: What You See Is What You Get...Or Is It? By: Michael A. Esposito, DDS

Is that impression you just took as accurate as it looks? Unfortunately, you never know for sure until it's too late. One of the most critical steps for a partial denture is the impression. If the impression isn't 100% accurate, the RPD framework will fit the stone model wonderfully, but when you attempt to insert it into the patient's mouth it will make O.J.'s courtroom glove demonstration seem like a cakewalk!

This was an all too common occurrence in my practice and it drove me to distraction. Actually, it drove me to make a post on DentalTown.com requesting advice. As usual, that advice came back in buckets. My fellow Townie friends had many questions, as well as many suggestions. After the smoke cleared it became apparent–my RPD design was not to blame, rather, my impression taking methods seemed to be the ineffective link.

I had been using the time-tested alginate material for my RPD impressions for as long as I could remember. The frameworks always seemed to fit the model marvelously. But why was I constantly holding my breath on the try-in date? As a matter of fact, the problems seemed so numerous I gave up and had the front desk add a half-hour appointment dedicated to just the framework try-in. I would usually get the frameworks seated after several adjustments but what a pain! Then Dr. Jim Dice, or "the Diceman" as we have come to call him on DT, suggested that I try something called the Accu-Dent System (Fig. 1) by Ivoclar Vivadent. I investigated the product and it intrigued me. Could this be the silver bullet I was searching for that would solve my problems?

Figure 1: Accu-Dent System 2

I happily discovered Ivoclar Vivadent's confidence in its product as it offered a 60-day guarantee. Further investigation revealed two separate systems: System 1 for complete dentures and System 2 for partial dentures. As the saying goes, in for a dime, in for a dollar. I purchased both and anxiously awaited my first impressions.

Both systems utilize various sized autoclavable "Accu-Trays" which hold a two-part impression material. For the removable System 2, the impression material consists of a Tray Accu-Gel and a Syringe Accu-Gel. According to the very thorough information package sent with the system these gels "are different, but chemically compatible irreversible hydrocolloids designed to work together in the mouth." Basically, they imitate a light and medium body impression technique used for crown and bridge impressions.

After working with the system for several cases, I was overjoyed! I don't know if any one product can qualify as a silver bullet, but the Accu-Dent system comes extremely close! OK, enough technical talk, let’s get down in the mouth and do one together.

Here's how I proceed. After the treatment plan is formulated and the patient decides on proceeding (in this case, with a lower partial denture) upper and lower study models are taken. For this set alginate impressions are adequate. After the models are poured, the case is reviewed for ideal clasp design and rest placement and the patient is appointed for three visits:

1) Half-hour appointment
Rest preps, take Accu-Dent System 2 Impression, opposing model, bite relation, tooth mold and shade selection.

2) Fifteen-minute appointment
Try-in framework with teeth set in wax

3) Fifteen-minute appointment
Insert and check final RPD.

Step-by-Step Details of Visit One Mrs. X is seated and a bur (I use a single bur from Parkell) is used to place the rest preps and guide planes. The rests are polished with fluted carbides and rubber points. Then bite registration with copper wax bite, shade and mold recorded. Now we're ready for the impression. The correct size Accu-Dent tray is selected and my assistant, Janice, prepares the syringe gel mixing according to the well-written directions (Fig. 2).

Figure 2: Mixing set-up

Tip #1
Of course, the next half of the battle is dealing with a superior lab. Here, Townie David_f came to my rescue when he suggested BonaDent labs in upstate New York. I contacted them and was immediately impressed with their professional approach, from the initial phone contact to the supervisor who soon after contacted me. The partials they fabricated were the most beautifully constructed I've seen in my many years of practice. If you are considering a switch I highly recommend them. BonaDent can be contacted at 1-800-732-6222.

Tip #2
Directions indicate a water temperature of 80-85 degrees, this works great but does not leave a lot of wiggle room. When first starting with this system, I strongly urge you to use a slightly cooler temp for the syringe gel. This will give you a little more time before it sets up and will thereby "fuse" with the tray gel properly.

Fig. 3: Pre-sure tip

Spreading a bead into the peripheral border

Load and set aside the syringe with the "Pre-Sure Tip" attached (Fig. 3)–the Pre-Sure Tip is an extremely clever device which allows you to express the gel very firmly against the teeth thereby getting an extremely detailed impression free of bubbles! As Janice prepares the tray gel, I dry the patients’ lower arch and when the tray is being loaded I take up the syringe and place the tip on the occlusal surface of the posterior teeth, begin expressing the material as you drag the tip towards the anterior, then rotate the tip 90 degrees to the facial when you reach the cuspid. Repeat on opposite side, then remove the Pre-Sure Tip and proceed to the vestibule and express a bead of gel from the hamular notch forward to the midline. Repeat on the opposite side. Then take the filled tray and seat downward until the gels merge. (Make sure surface of tray gel is wet.) Don't overseat it! Try to visualize the tray as more of a material "carrier" than a custom tray. You can then gently pull on the patients lips to border mold or you can have them help by extending their lips themselves. I have found the Accu-Dent gels to be far superior to run of the mill alginate in its ability to capture the smallest soft tissue attachments without any distortion. The material has the characteristics which allow it to be "self-supporting" in that it will hold its shape in all important border molding areas without the support of a tray.

Tip #3
If you have the patient assist you in molding the borders be very careful they don't overdo it. If the material is compressed too much it may become overly thin and distort when the model is poured. I now find it is easier to have the patient relax as I gently pull the lip up and AWAY from the tray.

This may all sound a bit complicated but really only takes a few minutes from start to finish. Believe me, the effort is worth it when you see how beautiful the impression and subsequent models look!

Visit Two
The case I've demonstrated in the photos was a challenge due to the large lingual tori (Fig. 5). I worked with the lab on the design and the results were outstanding. At try-in the patient couldn't believe how comfortable it felt! (Fig. 6) The RPD seated without any difficulty and was a perfect fit–no hangups anywhere. This is the way it should be, no adjusting, grinding, pounding, pleading or nasty expletives!

Fig. 5: Final Impression–note how the large lingual tori were captured

Final impression top view

Model after casting fabricated

Wax try-in on model

Fig. 6: Patient try-in occlusal view

Visit Two
The lab has returned the processed RPD and it is inserted without a hitch. This is no fluke, the system works!

I have found the Accu-Dent System to be invaluable for other procedures as well. I routinely employ these impressions for the fabrication of the most exact fitting bleaching trays and night guards I've ever received.

Recently, I decided to give the Glidewell "Extra Comfort Bite Splint" a try (Fig. 7). This tray has a hard outer layer and a softer inner layer. Glidewell immediately answered all my questions and had a tech follow up on the case. I inserted the appliance (fit was flawless) and it met with rave reviews from the patient. Another win-win situation with great materials and a lab willing to go the extra yard for customer satisfaction. Glidewell can be contacted at 1-800-727-8334. Recently, I decided to give the Glidewell "Extra Comfort Bite Splint" a try (Fig. 7). This tray has a hard outer layer and a softer inner layer. Glidewell immediately answered all my questions and had a tech follow up on the case. I inserted the appliance (fit was flawless) and it met with rave reviews from the patient. Another win-win situation with great materials and a lab willing to go the extra yard for customer satisfaction. Glidewell can be contacted at 1-800-727-8334.

Fig. 7: Glidewell Extra Comfort Bite Splint

Glidewell even sent along a huge stack of patient brochures personalized with my name and address. All at no charge. Now that's the kind of service I can appreciate!

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Cost Analysis Accu-Dent System 1: $275 Accu-Dent System 2: $275 Approximate per impression cost using either Accu-Dent System: $2.45 Approximate Lab cost of Completed Lower RPD: $275 My Lower RPD Fee: $1500 Cost: Lab $275 + Impression $2.45 = $277.45 Profit: $1500 - $277.45 = $1222.55 Total Chairside time: 1 hour!

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My Field Trip to Ivoclar Vivadent in Buffalo, NY
When I realized one of Ivoclar Vivadent main offices was only fifteen minutes from my wife's parents house in Buffalo, NY, I contacted their Marketing Communications guru, John Isherwood. I wanted to see if a visit could be arranged during my family's sojourn there over the Thanksgiving Day weekend.

As it developed, the only day I was available was the Friday after Thanksgiving. John informed me that the building was shut down over the holiday for a long weekend, hmm, but he said enthusiastically "don't worry, we'll get you in, some way it WILL be arranged"!

(Left to Right) John Isherwood, Marketing Communications Specialist and Dr. Michael Gaglio Director of Education

Dr. Mike Esposito at Ivoclar Vivadent

Yes, thanks to John and Dr. Michael Gaglio ( Ivoclar Vivadent's Director of Education), I got the VIP grand tour from both of them! Let me tell you, it is one incredible facility. If you ever get the chance, don't pass the opportunity to tour the 70,000 sf building packed with the highest tech research and testing labs I've ever seen. Add to this their onsite training facilities for lab techs and dentists, primo clinical office set-up, and spacious A/V auditorium. Let's just say I was extremely impressed!

Dr. Gaglio spoke about the best and brightest products that Ivoclar Vivadent has on the market. Some I was already acquainted with: Empress, Heliomolar (now available in a "Heavy body" version), Systemp, Excite, Tetric Ceram, Variolink II...the list seems endless.

The fact these two individuals cheerfully interrupted a busy family weekend just to satisfy my curiosity spoke volumes. They do appear to be genuinely interested in us "little guys" operating far from the high-tech centers. For that I am grateful. The hour and a half that I spent there flew by as if it were 15 minutes...don't worry, I shall return.

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Townie-in-training, Dr. Esposito’s daughter, Elise

About the Author Michael A. Esposito, DDS is a wet-gloved dentist in Stroudsburg, PA. He is a dental consultant to local nursing home facilities and was a part-time clinical instructor at SUNY at Buffalo School of Dental Medicine from 1983 to 1986. Dr. Esposito can be reached for comment at espo28@fast.net. He can also be reached at his office: 570-421-0431