Bound by SiliconeThe sticky relationship between Dentists

and Dental Laboratories

Mark Jackson, RDTPrecision Ceramics Dental Laboratory, DAMASMontclair, CA

According to the FDA, the Dental Laboratory is a Medical Device Manufacturer and subject to FDA Good manufacturing Practices…..

The Dentist and the Dental Lab

But things haven’t always been like this!

During the middle ages and throughout the 19th century, dentistry was not a profession in itself, and often dental procedures were performed by barbers or general physicians.

Barbers usually limited their practice to extracting teeth which alleviated pain and associated chronic tooth infection.

The Dentist evolved from the Barber Shop

At the turn of the century, most dentists were expected to make their own dentures crowns and bridges, but by the 1900’s the dentists realized the economic benefits of finding specialized help.

The Dentist Evolved from the Barber Shop

Professional relations were best summarized in two simple words:

“Yes Doctor.”

The Dental Technician evolved from the “Plaster Monkey”

The “Plaster Monkey” was actually a term of endearment, and the “dental mechanic” became an important member of the dental team, though dentists still kept them closely supervised….and undereducated.

The Dental Technician evolved from the “Plaster Monkey”

Dental Technicians were forbidden to attend lectures and meetings, and in 1963, the NADL and ADA broke off relations.

It was a contentious time.

The Dental Technician evolved from the “Plaster Monkey”

Today’s credentialed technicians have strong backgrounds in material science, dental anatomy and CAD/CAM technology, and in some cases can earn more than a general dentist.

CDT, RDT & MDT Credentials

Despite some professional growing pains, and some sibling rivalry, we share a relationship that is mutually beneficial, financially rewarding and based on a shared respect.

HOWEVER….

But it’s still tenuous….

The dental impression is the key ingredient in our relationship, and can often make or break it. We depend on the quality, consistency and the technical

support provided by our impression material manufacturers.

Our Relationship is held together by a third party

Impressions are the foundation of everything we do.

It all starts with a great impression....

But usually not…..More than 50% of the impressions we receive are substandard, yet only 1-2% will be returned

Proper tray selection

Proper use of tray adhesive

Material properly mixed

Adequate volume of material

Adequate adhesion between

materials

No pressure points or tray pinching

No teeth contacting the tray

Good detail of margin (finish line)

Good detail of prepared teeth

No voids or pulls in the material that

will cause interference

What makes a “Good Impression?”

While this impression displays a number

of problems, it was clearly the improper

tray for this application. Improper tray

selection can cause tray flex and

rebound.

Proper Tray Selection

This tray had no adhesive at all, and

also shows signs of possible tray

distortion. Tray adhesives are

specifically formulated and not

interchangeable.

Proper Use of Tray Adhesive

With modern impression delivery systems,

mixing problems have been all but eliminated,

however glove contamination and chemicals

can inhibit polymerization and setting resulting

in tacky washed out appearance.

Improperly mixed material

Improperly filled impression trays

can result in missed anatomical

features or movement of the

material within the tray borders

Inadequate volume of material

Inadequate adhesion between

different impression materials can be

caused by contamination, exceeding

the working time or improper storage

of material.

Adequate adhesion between materials

This tray was either not positioned

properly, or was the wrong size. When

this happens, the tray can flex and

spring back, distorting the impression,

or in the best case hold the bite open.

Pressure points and tray pinching

Like the previous example of a pressure

point, this tray was either the wrong

size, or improperly positioned, but

instead of a soft tissue compression, we

have tooth-on-tray contact.

Teeth in contact with the tray

Poor gingival retraction and

syringing technique.

Margin discrepancies

Not bleeding the mixing tip or

poor syringing technique has

resulted in air folding or

entrapment

Margin discrepancies

Insufficient retraction or tearing

Margin discrepancies

Improper retraction, possible fluid

or chemical contamination

Margin discrepancies

Improper retraction allowing

blood or saliva to pool around the

prepared tooth. Exceeding

working time.

Margin discrepancies and lack of detail

This impression has voids and pulls

caused by exceeding working time,

moving the tray after seating, or not

enough material. These defects can

interfere with occlusion and mounting

models

Pulls or voids that can cause interference

Communicating with our Dentist clients

Evaluating remakes

Every impression would be a perfect one, that had been inspected by the dentist, and was free of the defects we just discussed, but that is rarely the case….

In a perfect world…..

Most dental laboratories have a profit margin of 10% or less. That means they may have to do as many as 19 units at no profit to pay for a single remake.

Remake evaluation

Every remake is evaluated to determine the nature of the failure. In some cases it is laboratory error or product failure, and sometimes it is doctor error.

Remake evaluation

The easiest way to see if the impression was the problem is to simply insert the new die into the old impression and look for the discrepancy.

Remake evaluation

A common problem is misreading the margin, usually caused by a bad impression, though technician error does happen too.

Remake evaluation

Frankly, the lab takes some blame due to errors in mixing stone, applying surfactant or surface disinfectants, though we try to automate these processes when possible.

Remake evaluation

But in an overwhelming number of cases the problem can be traced back to a bad impression. In some cases we accepted them when we really should have sent them back.

Remake evaluation

There’s never time to do it right

And it’s even less likely there will be time to do it over!

This is where many of us revert back to our primordial roots, avoid confrontation and “do our best” at the doctors instruction

Remake evaluation

At Precision Ceramics……

We take the “passive aggressive”approach…

The “habitual offender” card

PCDL tips for reducing remakes

Carefully inspect your impression before releasing your patient. Any pull, voids, bubbles, unset or sticky material indicates contamination or a mixing problem. This will lead to a remake.

  If you use a desensitizing substance on prepared teeth, apply it AFTER taking your

impression. These substances effect impression materials and if used improperly will guarantee a remake.

  Retraction cord containing epinephrine, or other material containing epinephrine

will cause deterioration, sticky or unset margins in some impression materials. AGGRESSIVELY rinse and clean the prepared teeth before injecting your wash material.

  Materials containing Ferrite sulfate will cause some impression materials to not set

properly, especially in thin areas such as margins. Save yourself a remake; clean and rinse your preps well before taking the impression

  If you are using “sideless” triple trays, PLEASE check to see that the patient did not

bite into, or onto the tray. If they did, when we mount the models, the bite will be off, and you will lose precious time adjusting the occlusion and possibly ruining the crown, or sending it back for repairs. A preliminary check could save hundreds of dollars later. 

PCDL tips for reducing remakes PLEASE take some time to make sure your temporaries are in occlusion, and that contacts are tight. For long

span bridges, or cosmetic make-overs, consider our lab processed temporaries. Believe it or not, we have seen three and four unit bridge cases with single crown temporaries on the abutments. That’s a great way to guarantee your bridge will NOT fit!

We recommend a two cord technique. A combination of #00 and #2 cords will provide adequate retraction for nice clear exposure of your margins.

  For anterior cases, please send an impression of the temporaries, or a diagnostic wax up, so that we can try and

match patient expectations. Photos, shade maps and other tools will ensure a happy patient and a happy doctor.  When injecting wash impression around the margins, use a stirring motion and “jiggle” the material constantly to

avoid air bubbles or voids. Never stop and restart an impression. If you don’t think the cartridge has enough material left to completely encircle the prep, use a new cartridge. If the case has loose tissue, of if the prep is very subgingival, use the cartridge tip to push the tissue away as you inject the material to prevent it from laying over onto the margin.

  DO NOT use the “touch” technique to determine if your impression is set; use an inexpensive egg timer or other

timing device. The manufacturer has done extensive tests to determine the best setting time and conditions. The material you are touching has been exposed to air, and may set before the was material has, and it is important to have this part intact and accurate. Don’t touch; thime it or you may end up remaking it.

  All crown preps should have adequate prep reductions of at least 1.5 mm for both PFM and All Ceramic Crowns.  

Note: 7 out of 10 tips are impression related!

Sometimes, we just can’t rehabilitate a doctor on our own..

We call in reinforcements!

Kerr Rep