Sophisticated Laboratory Equipment

A Background Story mayo-hospitalTen years ago, one of Dr. Arthur Chal’s patients developed oral cancer and sought treatment at the Mayo Clinic, Phoenix, seeking the services of cancer specialist Karel deLeeuw, DDS, MD, Chief of Oral and Maxillofacial Surgery at Mayo. This led to Dr. deLeeuw and Dr. Chal becoming acquainted.

Impressed by Dr. Chal’s work, Dr. deLeeuw wanted to meet with him over lunch. He ended up getting a tour of Dr. Chal’s office, and in the course of the tour, took notice of the model work he saw in the laboratory portion of his office.

Because Dr. deLeeuw has a dental degree in addition to his MD degree, he knew what great dentistry should look like. He was impressed with the careful attention to detail and the superb model work he saw on cases in Dr. Chal’s lab that were in process.

After that, Dr. deLeeuw began referring Mayo Clinic patients to Dr. Chal—complex cases of patients who had failed dental work or particularly difficult problems. Later he sent his wife in to Dr. Chal for a full-mouth reconstruction and smile makeover with beautiful refractory porcelain veneers. After that was done, he sent his college-age daughter for cosmetic dentistry.

“It was the model work that I saw in the lab that let me know that not only was Art Chal a highly skilled restorative dentist, but that he cared enough about his work to give painstaking attention to every detail. The experiences I have had with him in the many cases I have sent to him, including members of my own family, have completely reinforced that initial perception. Art Chal is truly a master at what he does.”

– Karel A. deLeeuw, DDS, MD
Chief of Oral and Maxillofacial Surgery
Head and Neck Surgery
Department of Otorhinolaryngology
Mayo Clinic Hospital, Phoenix Campus
5777 E. Mayo Blvd., Phoenix, AZ 85054

Dr. Chal’s Commitment to Quality Dental Laboratory Work

This page of the website explores the laboratory work that prompted the endorsement by Dr. deLeeuw. Motivated by his passionate pursuit of excellence in dental care, Dr. Chal has made sure that his office has the necessary laboratory equipment to produce the highest quality of dentistry for his patients.

Most dental laboratory work starts with an impression of your teeth and oral tissues. If the impression isn’t perfectly accurate, nothing done later can make up the discrepancy, and the final restoration will be compromised. Dr. Chal has purchased the finest impression equipment and materials available, namely Permadyne polyether impression material, as mixed by the Penta-mix machine. This gives absolutely consistent mixing every time and reproduces the finest detail.

Permadyne polyether impression material is the material of choice for the German master dentists and technicians such as Willi Geller and Klaus Muterthies.

For the production of TMJ orthotics and for models of opposing teeth, however, a different type of impression material is optimal. In those cases, we use a warm hydrocolloid material. This requires special baths to keep the material at a uniform, fixed temperature until the moment it is placed in the mouth. Below is the machine used for that purpose:

After the impression is taken, it needs to be poured up in a gypsum material. There are many types of dental gypsum. Many dentists will use simple laboratory plaster—it’s simple and inexpensive. But when it sets it is relatively soft. This makes it easy to work with, but it also makes it susceptible to chips and fractures. And when it is mixed in a simple plaster bowl, it is again easy and convenient, but it will get bubbles incorporated into the model.

Dr. Chal uses resin-rock stone for his models. This is exceptionally hard—so hard that it has to be trimmed with a diamond abrasive wheel. And all mixing is done on a vibrator and under a vacuum to insure the elimination of bubbles.

Here is the vacuum mixing apparatus on top of the digital scale. Powders are measured to the fraction of a gram to insure accuracy and consistency.

The precision liquid dispenser, pictured below, insures that the liquid portion of the mix is also accurate. Most dentists will mix their gypsum products with plain water. Again, this is simple, inexpensive, and convenient. But resin-rock stone requires the use of water plus a liquid with special modifiers in it. Not as convenient, true, but it won’t chip and is exceptionally accurate.
Below is the vacuum mixer sitting on top of its mobile stand:
Below is the Foster heavy-duty vibrator that helps eliminate any entrapped air in the mix.


This is the diamond grinding wheel that is used to trim the resin-rock stone. A conventional dental grinding wheel is insufficient for trimming this material.


The end product is these models, pictured below. They have been mounted on a sophisticated articulator (engineering instrument) that reproduces the motions of a patient’s jaw.

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Even though dental schools teach the use of articulators, a recent survey by the trade journal, Laboratory Management Today revealed that fewer than 5 percent of cases submitted to dental laboratories in the United States are submitted on articulators. Fewer dentists still use articulators with this degree of sophistication.

Every laboratory-fabricated restoration is first created as a prototype before it is created in its final form. This begins with a laboratory preparation phase. He will drill on the models of your teeth on his laboratory workbench before he ever puts a drill in your mouth. Not only does the ensure that the goals he envisions for your case can actually be accomplished, but it maps out an exact plan for achieving those goals.

The photographs below are an example of a recent case. He has prepared the posterior teeth on the model to help him design the ideal occlusion for this patient. One of the things that makes this possible is the use of the sophisticated articulator (engineering instrument) that is capable of reproducing all of the natural movements of the patient’s jaw. As mentioned on the previous page, fewer than 5 percent of all dentists use these articulators, even though they were taught in dental school to use them. Fewer still use articulators with this degree of sophistication.

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As all well-trained cosmetic dentists know, the foundation of every successful smile design is the incisal edge of the front teeth. Placing this incisal edge accurately is not only fundamental to good esthetics, but is fundamental to proper speaking and jaw function. For this patient, where the incisal edge is in the correct position, it is important to keep that as a landmark while the posterior teeth are prepared. The posterior preparation is shown above.

Below, Dr. Chal has continued with this complete oral reconstruction by now preparing the anterior teeth on the model. The proper inter-occlusal dimension is now marked by the incisal guide pin that has been inserted in the front of the articulator.

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Following the tooth preparation, Dr. Chal uses a titanium-impregnated wax to reconstruct the teeth. This is not a simple matter. Jaw movements are extremely complex. There are protrusive, lateral, and up-and-down movements, and if there are any discrepancies, the patient can experience jaw disfunction, a disorder that is marked by spasms, headaches, and other maladies. Dr. Chal is an expert in jaw function and lectures on this topic to other dentists internationally. He collaborates with his expert laboratory technician, Rick Durkee, CDT, AAACD, to develop the architectural blueprint of the esthetic and functional reconstruction.

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As a patient, you will also be brought into this process. The fundamental requirement of all dental esthetics is that the smile needs to be pleasing to the patient. You will therefore have an opportunity to review the esthetics of the case at every point, so that when the work is done, it will not only be comfortable and functional for you, but you will be thrilled with the appearance.

In order to transfer this functional and esthetic design to your mouth, these models with the waxed teeth are duplicated with a special silicone material to help create a hard stone model of this design. In the photograph below, the duplicated models are shown on the left, and the clear plastic guides that transfer the design to the mouth are shown on the right.


Creating a clear plastic guide that has the level of accuracy that is needed requires more highly specialized equipment. Below is a photograph of Dr. Chal’s Biostar unit. It generates five atmospheres of pressure to create a highly accurate preparation guide and matrix for the stage one prototype restoration. The model is positioned on the unit, as shown, ready to create the guides.


This Biostar unit is not only used to create the preparation guides, but is also used to create prototype restorations. As mentioned above, every laboratory-fabricated restoration Dr. Chal makes is first created as a prototype, to make sure that it meets all the functional, comfort, and esthetic requirements of the patient. Accuracy is supremely important in this process.

The Biostar is also used for the creation of TMJ orthotics. These appliances are important in the treatment of TMJ disorders. They restore harmony to the jaw function of patients who many times have severe pain because of discrepancies in their bite. Accuracy is also important for these orthotics.

Then, once your surgical guides, prototypes, or TMJ orthotics have been fabricated, they need to be trimmed and polished at the Quatro Air Technologies grinding station.

Below is a photograph of some of the selection of burs, trimming stones, and polishers that are used. There are various types and grades of abrasives, and each has its specific purpose in the process.


Below is a photograph of the Quatro Air Technologies vacuum grinding station. The grinders, burs and polishers are held by the motor unit so that both hands can be used to hold and guide the restoration. The loose particles created by the grinding and polishing are picked up immediately by the vacuum.


Here Lesa is custom tinting the prototype for eventual glazing in the Triad oven, which is to the right of the lamp. She is highly skilled in the esthetic characterization of these restorations. Dr. Chal has treated many media and Hollywood patients who have been seen on television and on film wearing their prototype restorations, looking only like they had a beautiful, natural smile. But that is one of the purposes of the prototype—it needs to closely mimic the final result to help Dr. Chal know if any modifications are needed before the final restorations are created.


The next step is to clean the inside of the restoration with the glass bead blaster pictured below. This precision instrument, made by the German Denerica company, will clean the prototype restorations and the final zirconium or ceramic restorations. It is like a sand blaster, but it uses tiny glass beads instead of glass.


The glass bead blaster is accompanied by a vacuum unit below that separates out the debris from the glass beads.


The photograph below is of Dr. Chal’s porcelain furnace. Having this on the premises rather than in a distant laboratory the way most dentists do enables Dr. Chal’s expert crown and bridge technician, Rick Durkee, to customize the restorations right at the chairside. For example, when Jennifer was anxious to get her beautiful zirconium bridges in place in time for her wedding, Rick sat at this furnace and detailed the esthetics of her case while she sat fifteen feet away in the dental chair. (Click here to read about Jennifer’s case.) This Ney Centurion porcelain furnace is computer-controlled, and generates temperatures of up to 1700° F.


After final tinting and characterization and then being fired in the furnace, a zirconium bridge will come out looking like this:

The fit and appearance of the bridge is then verified on a precision model of the patient’s prepared teeth, as shown below.


The final step for the restoration is sterilization in the steam generator, pictured below. It steam cleans and sterilizes the restoration so it can be inserted in the patient’s mouth.

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