Digital Dentures: A Complete Game Changer for Local Dental Labs
The need to replace lost teeth has haunted humans since the beginning of time. False teeth have been made out of human and other animal teeth since around 700 BCE and this technique was still popular up until the mid 19th Century. The first modern looking dentures were made in Japan in the 16th Century of wood and they continued to be made until the beginning of the 20th Century. No, George Washington did not have a set of wooden dentures. Instead, in the 17-18th Centuries dentures were made of gold, lead, ivory, human and other animal teeth. The 19th Century saw the invention of hard rubber dentures and the 20th Century plastic dentures were invented. Now, in the 21st Century we have a revolutionary new way to make dentures called digital dentures!
Twentieth Century plastic dentures are still made to this day all over the world. They are made by first making a very accurate impression of the mouth and then constructing a base plate and occlusion rims. These are essentially wax rims that are molded by the dentist to show how wide the mouth is, where the lips go, how high the smile line is, where the midline of the teeth are located and how wide the smile is by showing where the canines are located in the smile line. The upper and lower record bases and occlusion rims are then “glued” together to simulate the bite and sent to the local dental lab to be processed. The lab man then sets the actual denture teeth that will be in the finished dentures in the wax on the occlusion rims so they can be tried into the mouth to see how they look. Once the aesthetics have been worked out with the wax try-in, the dentures are processed by boiling out the wax and replacing the wax with denture plastic.
Below are the well known problems with the way we make dentures using wax bites and wax rims to set up denture teeth.
- Wax is not very hard and it shrinks, creeps and expands a great deal according to the temperature and position the dentures are stored at between appointments. Error!
- The denture teeth set in wax may have looked great inside the mouth, but when the lab courier picks them up and transports them around town in a hot/cold car before bringing them to the lab, the teeth may shift in the wax. By the time they are ready for the dental lab technician to process the dentures, the teeth are no longer in the right position. Error!
- Not all dental laboratories have a certified dental lab technician setting up their teeth in ideal occlusion. Instead, someone taught the tech how to set teeth. They may not have a formal lab education themselves. Unfortunately, this may mean that the denture teeth may have excessive grinding on the biting surfaces of the patient’s expensive denture teeth to force them to fit inside the bite. A good dental lab tech knows to do most of the grinding on the neck of the tooth that will be processed into the wax instead of grinding away the anatomy of the biting surfaces. Error! Good dental lab technicians are hard to find and that is why dentists are constantly on the look-out for the best ones in their area.
- During the final processing of the dentures, plastic is packed around the denture teeth and cured under heat and pressure. During this process the curing plastic shrinks and distorts. Error!
Four to seven dental appointments later the dentures are back at the dental office and ready for delivery. If all the above errors were not kept to a minimum, the dentures will needed more adjustments and may feel loose frustrating not only the dentist, but the patient as well.
Before now, making dentures were just as much an art as a science. Many dentists didn’t like to make them because of all the built in errors and the final product was to unpredictable. With these errors it was hard to satisfy many of the more demanding denture patients and many dentists shied away from making them because of those reasons. “Denture Mills” have sprung up all over the place to fill in the private practice void and in many instances can make you a set of dentures in a single day at a low bargain price. Unfortunately, bait and switch tactics and using inferior quality materials are rampant in the usual Denture Mill. This fast pace industry has given dentistry a bad name over the last decade.
Digital dentures has removed most of the guess work and replaced it with a solid well thought out technique to deliver a great set of teeth to even the most demanding patient.
With Avadent digital dentures there is no wax and none of the usual errors of conventional dentures (Unless you choose to do an Advanced Try-in appointment with a much more stable plastic/wax). All of the information is collected on the first appointment and two weeks later the dentures are delivered. When the dentures are delivered, all the supplies that you used to make the dentures are restocked (additional $99)! Amazing!
The process is as follows:
- In the Avadent starter kit is a set of 1 large, 2 medium and 1 small thermoplastic trays to be used as custom trays. If the patient has an existing set of dentures you can either make a putty mold inside the existing dentures to form the thermoplastic trays over or you can shape the trays in the mouth directly. The trays are placed into a water bath (bath cup and digital thermometer provided) 70℃ or 160℉ for 60 seconds. The starter kit comes with a specially formulated scannable border molding and wash polyvinyl siloxane (PVS) to make a very accurate final impression. Place a border molding bead of heavy base PVS around and on top of the outside rim of the custom tray and one small spot into the palate. Then place it into the mouth and shape the lips and frenum. Then follow with a light based PVS washing shaping the lips and frenum again. These impressions are never poured up in stone, but instead are scanned and digitized at the lab. I just wish they made the border molding heavy base PVS a different color than the thermoplastic trays. It is very hard to know if it is tray or border molding showing through the thin based wash PVS. You will sometime (almost always) have to trim the thermoplastic trays, especially the lower. I found it just as easy to form the trays in the mouth as I did on the putty PVS models. Mark the vibrating line with a Thompson stick and re-insert the upper final impression to transfer the position of the post-dam. Then use a marker to place where you want the end of the denture to be.
- Place a marker spot on the patients upper lip or nose and lower chin and measure the vertical dimension of occlusion (VDO) the final dentures will need. Use your usual technique to determine this space. The starter kit includes a caliper.
- Additionally, in the starter kit are 1 large, 2 medium and 1 small upper and lower proprietary base plates called the Anatomical Measuring Devices (AMD) that make record taking a snap. Using the supplied plastic calipers measure the distance between the 2 tuberosities and the 2 retromolar pads. Choose the appropriate base plates (default to the next smaller size so the coronoid process will not interfere with the lateral excursions during the gothic arch tracing) and in the upper place adhesive into tray and place PVS bite registration material inside the tray and make an impression of the upper arch inside the base plate (trim off the excess). Screw out the gothic arch pin as far as possible before you insert the upper part of the AMD so you will know if you will need to add the extender to the pin (the new style upper AMD has a plastic pin and screws and maybe more difficult to manipulate). You can always grind the base plate if it is a little too big, but remember to default to the next smaller tray. It is not necessary to make perfect impression inside the AMD’s, just cover enough of it to make a record of most of the ridge so it will be stable and hold into place. (Later at the lab the ridge in the final impression will be matched up with the ridge inside the base plate AMD to digitally mount the case. The materials are the same consistency so be sure to use the same pressure when making both the final impression and the base plate stabilization). Easy!
- On the front of the upper base plate is an adjustable lip bumper. Use the provided screw driver to move the bumper out to support the lip like you would if you were to shape the old style occlusion rim wax. This is much better than the wax occlusion rim because you can move the lip out and in with ease, instead of removing and replacing wax (the newer AMD has a clear plastic bumper that is a little harder to manipulate, but you can see the gothic pin through). Easy!
- There are two different types of lower base plates, but I will only discuss the one I like to use at this time. It is the flat plate for the “Gothic Arch” tracing. Place adhesive, then inject PVS bite registration material into the lower base plate and fit it to the lower arch just like you did with the upper. Most dentists never have done a gothic arch tracing to manufacture a denture. Taking the tracing often extends the number of appointment it takes to make a denture and complicates the process with extra parts and pieces. Usually only prosthodontists or specially trained general dentists go to the trouble to do this tracing. The gothic arch tracing it considered the most accurate way to find the proper jaw position to set the teeth at (centric relation). The Avadent digital denture technique allows a quick, accurate and simple way to do this tracing. OPTION: You can spray Green Occlude occlusal spray on the lower base plate to accentuate the gothic arch tracing. With the newer ADM trays green spray is needed because the pin is plastic and will not mark the lower tray. Easy!
In the middle of the upper base plate is an adjustable tracing pen that can be adjusted to open or close the VDO (the newer AMD the tracing pen is made of plastic). If the pin is not long enough to touch the lower plate, the kit has pin extenders that simply screw over the shorter built in one. Use the previously placed dots on the upper lip and chin to adjust the base plates to the proper VDO with the screw driver provided. Use the caliper reading from the VDO reading you obtained in the beginning of the appointment.
- Now have the patient move their lower jaw through right/left and protrusive excursions to use the VDO pin to mark on the lower plate base plate a “Gothic Arch” tracing (will need green occlude spray on lower tray with the newer ADM plastic pins). Remove the lower base plate, take a round bur and drill a small dimple in the point intersection of the gothic tracing and replace back into the mouth. This tray was actually too big and almost traced right off the back of the plate!
- Replace the lower AMD and allow the upper pin to slide into the bur hole on the lower. Make sure both trays are stable on the arches. Inject PVS bite registration material between the upper and lower base plates to completely secure the centric relation bite. Be sure not to cover the lip bumper. If bite material gets on the lip bumper, simple take out the entire apparatus and use a scalpel to remove the excess and replace it back into the mouth.
- Provided in the starter kit is a combination fox plane/earless face bow (I call it the “Angulator”). Snap it completely through the lip bumper and into the base plate, firmly. Line the top of the angulator with the interpupillary line and record the angle on the prescription form. Numbers higher than 10 mean the teeth cant to the left and lower than 10 to the right. (I suggested to Avadent to only put the numbers on one side. I got confused when reading one side then the other because if you don’t really look at the scale on each side carefully, you could miss that the numbers ago up on one side and down on the other. What is 9 on one side may be mistaken as 11 on the other if you are not careful).
- On the lip bumper is a surface that you can write on with a pencil (the newer lip bumper is clear plastic and you need to use a sharpie marker). Scribe the proper incisal edge, midline, high lip line and canine positions.
- Provided in the starter kit are thin pieces of clear plastic film with different sized teeth printed on it. They come in small, medium and large. The large is 46mm between the the height of contours of the canines and the medium and small are 40mm. The only difference between the medium and small is the medium is 1mm longer incisally. Place flowable composite (not provided) on the back rougher side of the plastic strip and line it up with the midline and incisal edge you previously scribed on the lip bumper. This will give you a good idea how large you want to make the teeth in association with the high lip line. This will more accurately describes to the lab where you want the necks of the teeth to be and will let the patient see it as well. Write the neck number down on the lab script.
- The dentist then selects the appropriate color, type and size of teeth to be placed into the denture. As of now a limited number of style and brands are offered, but more are on the way.
If you have a special stock of the types of teeth that the lab uses, you can send those along with the case, they will credit you for their cost of the teeth(Although mentioned at my course this is not their official policy and not recommended at this time. This is because of the difficulty in tracking teeth, possible wrong size or color teeth, missing teeth in sets or possibly blemished teeth. Avadent wants to only use factory guaranteed pristine teeth for their digital denture product). IVOSTAR and BLUELINE from Ivoclar Vivadent and PORTRAIT IPN from Dentsply (premium). The premium teeth are an additional fee which is quite significant to the overall price of the processed dentures ($99 per arch, better ask!). The color of the acrylic base is also requested. This is not something I was use to specifying so I requested the shade guides from the manufactures and let the patient choose what they like: Pro Base Hot US-L (light), Lucitone 199 Original Shade (#688111), Lucitone 199 Light (#688211), Lucitone 199 Dark Pink (#688411), Diamond D Heat Cure Original, Diamond D Heat Cure LIght and Diamond D Heat Cure Dark Veined. Characterization is none, stippled, low, medium and high. You can even ask to copy the palatal rugae onto the palate of the denture if the patient wants to have a more natural feeling denture (Cool!). You can always polish it out later if it becomes bothersome.
- You do not have to pick out the specific numbers of the denture teeth to match the dentures since all the information provided allows the lab tech to do that for you on the computer. Easy!
- On the lab slip the dentist can check to have photos of the final set-up emailed to them if they want to approve the set-up before they are processed. The only problem with this is that the processing will not start until you approve the set-up. This may cause some logistical problems if you do not check your email regularly. If you want to do a wax try-in then you need to order that with your case (SEE Advanced Try-in protocol below).
- Finally you will have to specify the occlusion. Currently, they only place the teeth into lingualized occlusion and flat plane posterior teeth.
- Remove the whole apparatus, sterilize it with lab spray, put it into the provided plastic bag and wrap it all in bubble wrap. You should have 4 things to mail to the lab: upper impression, lower impression, the base plate apparatus and the Avadent lab slip. The starter kit includes shipping boxes and prepaid mailing slips. It doesn’t get any easier than that! The whole process will take about an hour with no side bookings and no hygiene. You can have your assistants make the PVS models of the dentures and be fitting the custom trays to speed things up.
I think they covered all the bases, don’t you? Can you think of anything that you do that they have not considered with this technique? If so, then add it to the comment section below.
At the Avadent Denture Lab
The Avadent digital dentures is owned by Global Dental Sciences and is located in Scottsdale, Arizona. This is the only problem I’ve seen with this system. The distance adds time onto the processing and locks out local dental labs from providing this serve. Avadent said they are addressing these concerns and will in the future be packaging it for local labs to use. I hope this technology will be provided on a local bases for a reasonable price in the near future.
- When the lab receives the case, the whole upper/lower impressions/ADM apparatus is scanned into the computer. The posterior smile line is calculated as 2/3 the way up the retromolar pad (if space provided, of course). The teeth are set digitally and can be in lingualized occlusion or zero degree posteriors. First, the teeth are set over the mandibular ridge and then the maxillary teeth are set to match. The computer automatically adjusts the occlusion and can be customized from this point to reflect any characterizations needed. (SEE Advanced Try-In Protocol below).
- At this point pictures of the set-up are e-mailed to the doctor for his/her final approval.
- The pink base is then CAD/CAM milled by a computer milling machine out of a solid block of perfectly cured denture colored methylmethacrylate. This is note worthy in that milling this from a solid block of previously cured acrylic means that there will NO distortion when it is milled out. No shrinkage from curing, therefor a much tighter and noticeable final fitting denture.
- The holes for the teeth are also CAD/CAM milled into the denture base. One of the few human tasks needed in the manufacturing of the digital denture is manually bonding the teeth to the denture base. The dental lab tech “bonds” each tooth into the proper milled socket in the newly constructed dentures. This bonding is supposed to be stronger than either the denture teeth or the denture base acrylic making it virtually impossible to have a tooth fall out over time.
- Once the teeth are bonded into the dentures the dentures are scanned again to assure they have the same occlusion as what is on the computer. If different, the lab tech will adjust the occlusion accordingly before shipping them out for delivery.
Total control over the whole process is very alluring and has many advantages. The ability to make beautiful bubble-free final impressions, the ease of finding the proper denture dimensions, a simplified way to find centric relationship, computerized occlusal tooth set-ups, milling from a solid block of cured acrylic, the optional ATI and verifying the denture set-up against a know computer template is all a formula for outstanding successful complete denture cases.
Quick Check List:
- Measure the upper and lower arch size
- Select the appropriate trays (select next smallest tray)
- Place trays in 160 F water bath for 60 seconds
- Mold trays in mouth (or on putty PVS model)
- Trim trays if necessary
- Heavy PVS on borders with stops on palate and ridges
- Wash with light base PVS
- Mark vibrating line with Thompson stick and re-insert into mouth to transfer
- Use maker to outline vibrating line on dry impression
- Place VDO spots on upper and lower (nose/lip/chin area)
- Measure with provided caliper
- Use impressions to select the upper/lower AMD
- Screw out the gothic pin all the way (to see if you need an extender with metal pin only)
- PVS bite registration in upper AMD (trim back from adjustable lip bumper)
- Adjust upper lip bumper to proper lip profile
- PSV bite registration in lower AMD
- Adjust the gothic arch pin to proper VDO
- Left/right/protrusive gothic arch tracing
- Dimple with bur at CR
- Replace the two AMD into mouth and allow pin to slide into dimple
- Register bite (without covering upper lip bumper with PVS bite registration material)
- Place “Angulator” and measure the Fox plane angle/earless facebow
- Pencil/sharpie in lip lines (incisal edge, midline, high lip line and canine positions)
- Composite glue the plastic film teeth into position on the upper ADM’s lip bumper and record the height level you want the necks of the teeth to be in relationship to the high smile line.
- Select teeth/gingiva/rugae
- Specify occlusion and the need for the Advanced Try-In (described below) or not
- Fill out lab slip, package and mail.
Advanced Try-In Protocol:
- Resetting anterior/posterior teeth
- Adjust buccal corridor
- Record base adjustments (PIP adjustments of record base/flanges, or even a complete reline of the record base)
Implant Retained Overdentures:
This process is exactly the same as with conventional dentures. The process works best with attachments that can be picked up such as locator attachments or “O” ring snaps. Simply make a final impression over the attachments and the lab will mill the spaces for you to pick up the attachments with cold cure at delivery.
When I blog about a product, my sword can swing both ways. I will let you have an honest accounting of what I experience so that you will be on the look-out for possible pitfalls. In the case of this digital denture case, the patient was extremely satisfied with the results,
This is my 2nd set of dentures and they are great. The look and fell are by far superior than the first. The technology that is used to fit them to my mouth was a lot easier to deal with and on my second and final visit everything went a lot smoother than I hoped for. Dr Kraver and his assistant where wonderful, caring and accommodating. Watching the birds in the aviary is a great distraction to what is being done not to mention T.V. I highly recommend Cape Dental Care for all your dental needs.
but I was not.
- I checked on the lab slip to have pictures of the set-up emailed to me before manufacturing, but didn’t receive any (they are new at this, too. November 2011).
- The set up had an anterior open bite.
- The occlusion was high on the posterior most teeth.
- The palatal tongue surface was pebbly (rugae that the patient oddly didn’t mind, interesting)
- The cant was off (in all honesty I think I may have read the “Angulator” wrong and wrote down 11 when I meant 9, oops!)
Denture Cost and Replenishment Kit:
A new caveat involving complete dentures is the ability to make an exact copy as a spare back-up denture at half the cost. With little more than a phone call or lab slip the patient can now have an exact duplicate of their original denture in just 2 weeks. I can see it now, “Buy one and get the second one for half off the original price!” Got to love marketing.
Global Dental Sciences, 15730 North 83rd Way, Suite 101, Scottsdale, AZ 85260. 480-275-2736. 1-855-282-3368 (Toll Free). 480-471-8763 (Fax). email: email@example.com, http://www.avadent.com
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Department of Complete Denture Prosthodontics, Nihon University School of Dentistry at Matsudo, Matsudo City, Chiba, Japan.