Perspectives From A NM Tech To Create Predictable Results

By Bill Marais
Disa Dental Studio, Santa Monica, California

"Dental magicians, not technicians!" This aging cliche places in a nutshell the mammoth expectations often placed on technicians today. More often than not, technicians are asked to perform miracles in the lab environment - cases arrive "sans" (Latin meaning "without") vital information and the necessary tools essential for the successful delivery of that case. When dentists play their part right and provide us with these imperative tools and information, we can channel all our energy and artistic capabilities into creating beautiful restorations. The alternative being expending all our time and efforts in "just getting something to work" so that we can deliver the case the following week. Dr James Carlson once stated during a lecture before a group of dentists:" It is like throwing poop against the wall and all you hope is that it will just stick !!!!!!!" The only thing that suffers here is the outcome of the case!

I strongly believe that these following pointers will help us achieve more predictable and aesthetically pleasing restorations:

1. Never send multiple bites with the intentions of having the lab choose the "correct" bite.There is no means for a technician to make an accurate decision as to which bite is the correct one . This would honestly be a shot in the dark! There is only ONE bite we can work off and that is the one bite the dentist will choose and send to the lab. (I have had cases where I have received three or more bites - all apparently on trajectory - and then it is requested that I choose the bite that would work best! There is no possible means for me to depict a correct bite equivalent to that of the EMG reading!)

2. Don't ask the lab to open or close a bite on an articulator.
There is only one articulator where one can accurately open and close the bite and that is the "Patient".

3. Nothing beats working on/with the present condition.
Working with old impressions, wax-ups, models etc. will bring too many variables into the equation. This is simply asking for trouble!! Do not step over dollars to get to pennies. Make the effort and take the time to take new impressions, new bites, new photographs, etc. every time a new step is taken. I have a saying: "Fresh is Best!"

4. Include the hamular notches from day one of treatment.
These serve as an invaluable diagnostic tool and can save much time during the treatment of patient. For example, if HIP matches Symmetry bite, you do not have to include the Symmetry bite again. As long as photographs are provided, the HIP mounting can be used during the entire treatment!

5. All possible tools, including measurements, data and photographs should be sent to the lab at the very START of a case.
Before I begin work on a case, I insist on pre-ops, photographs, poly-vinyl impressions, hamular notches, symmetry bites and patient expectations. A technician can help tremendously in spotting any problems that just might arise during the treatment. Our hands are bound when doctors do not submit that clear vision leaving us blinded to any red flags that may occur.
Should the lab request more information, be open to providing them with what is needed during manufacturing. Bring the patient back to the chair and provide the necessary information/impressions, etc. to the lab. So many times I have had to listen to: "It is too much trouble for the patient and will cost (the doctor) too much money to bring him/her in again, so just go ahead as is!" In so doing, the doctor compromises the outcome of the case - just to save some money. It does not make any sense. This attitude is just tying our hands behind our backs and then the labs get blamed for all the remakes!
Our lab has made it policy that if a doctor refuses to provide the necessary information, we will not guarantee the outcome of the case AND we will charge for any remakes. It is sad that we have to take such a firm stand but I encourage all labs to adopt this policy - it will only get us (and more importantly, the patients) to a better place.

6. When shipping cases, always provide Poly-vinyls.
I guarantee that models will be damaged or lost. Poly-vinyls just always give us the option to start over which alginates do not.

7. Why rush cases?
So much time is spent stabilizing the patient to the correct bite and then we are expected to transfer all this information into the final restorations in less than two weeks. Why compromise all that hard work, time and effort? I equate the rush case to playing a perfect round of golf and going ten over on the last hole! If the lab requests more time, honor this. There is no reason to rush these cases for a wedding or a holiday in Europe - you are just asking for trouble!

8. Permit labs to use the tools they are most at ease using.
As an example, I have had doctors insist that I use a Specific Articulator. I cannot work on some articulators - they are just not ergonomic for my needs and it will affect the outcome of the case. NM dentistry is a "Feel" ,""A Comfort Level" and "A Trust" in the tools that we use to achieve predictable results! A type of articulator will not make a difference in the outcome of the NM case. Instead, the skills of the NM technician, the provided tools and information will predict the outcome of the case.

9. The doctor and the technician should never presume bites, measurements, etc. are correct.
You can never check too many times so let's all check each other's work. We all make mistakes as there are so many variables that can enter our NM world.

10. Have an open mind.
We don't know what we don't know. Neuromuscular dentistry is a journey, not a destination. We will all make errors. If we refrain from pointing fingers, take the time to learn from these mistakes and we selflessly share our knowledge, it will make us all stronger!

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A Material Selection –Which Ceramic to Choose?

by Yugo Hatai RDT
Smile by Yugo Pty Ltd, Sydney Australia

The field of dental ceramic materials has rapidly changed over the past decade. Traditional PFM restorations have shifted towards metal free restorations, making it essential for both the laboratory technician and dentist to understand when to choose the right ceramic materials. Which materials to choose is basically based on the amount of room the clinician prepares for the final restoration, the patient’s existing dental condition and the matching prepared tooth stump shade.


At the diagnostic wax up stage, technicians can actually prepare the model the way the clinician would ideally prepare the tooth to achieve the required result. They can in turn pass that pre treatment information onto clinician. This type of communication helps both technicians and dentists to be on the same page prior to the final impression taking, thus avoiding the back and forth syndrome.

There are roughly four different type of materials available in the metal free market today.

A. Pressables (i.e; e.max, Empress 1and 2 and esthetic veneers) E.max is recommended over the other Empress systems for aesthetics and strength when layered. E.max can be either cemented or bonded depending on the particular condition. E.max is useful to fabricate in veneers, crowns, bridges, inlays/onlays or can be pressed over Zirconia for greater strength. When layered, necessary support is required to enhance the ratio of coping to layered porcelain to increase the longevity of the restorations. The thicker the un-layered coping, the greater the strength with a slight sacrifice in aesthetics.

B. Zirconia (i.e; Lava, Procera) Copings can be made either by CAD/CAM milling or by in-house milling machines. This is the strongest material in the metal free category. Higher ceramic skills are required to achieve life-like restorations compare to other metal free materials due to their lack of translucency. Extra support in coping design is required (i.e; marginal ridges, functional cusp, or where the layered porcelain exceeds more than 2mm) to maximize the longevity of the restorations. Thickness of Zirconia can be determined with radiographic analysis similar to PFMs. making it the most suitable material to mask the metal and discolored stump/cores. Generally 1.5-2.0 mm is required for adequate tooth preparation depth. Zirconia can be used for crowns, bridges, cantilever pontics Maryland bridges, and implant abutments.



C. Alumina (i.e: Procera) Alumina is stronger than pressables, but known to be weaker than Zirconia. It has high aesthetic characteristics compared to Zirconia in general due to the light transmission, however, the needs of Alumina have been reduced since Zirconia was introduced due to the lack of strength (700MPa) compare to Zirconia (over 1000Mpa). Alumina can be used for crowns, bridges and procera laminate (veneers).

D. Feldspathic (porcelain laminate veneer (PLV)) Feldspathic porcelain is the oldest system in metal free technology. It is a technique sensitive material compare to others, however aesthetically pleasing. I personally recommend this system when working on a single anterior tooth with conservative preparation bonded to enamel or when clinician wants to preserve tooth structure. The major difference between pressables and feldspathic porcelain is first the strength; in general, pressables are stronger, due to their density and secondly the control in color; any complicated shade is achievable with Porcelain Laminate Veneer (PLV).

Clinical Suggestions
The following table is a quick easy reference guide to help the dentist communicate with his/her lab the clinical concerns when choosing a particular ceramic material.

Click over the chart to enlarge

It is essential for clinician to make sure there is no sharp corners when preparing the teeth. With the final shade photo for the color match, it is recommended to take a photo of the matching tooth with a shade guide at the beginning of tooth preparation rather than at the end of the visit to avoid color changes from tooth dehydration.


Technical Point of View…
If heavy metal cores and or severely discolored tooth preparations are anticipated, the dentist can be advised to prepare the tooth more aggressively. This should be discussed with the lab technician prior to tooth preparation or at the diagnostic wax up planning stage in order to allow adequate room for the lab technician to achieve the desired result.

When using Zirconia Bridges, the gingival surface of the pontic should be pure polished Zirconia without layered porcelain to maximize the strength. Preparations with subgingival margins requesting Zirconia do not need to have porcelain margins.

When using pressbles, the functional cusps and any occlusal contacts should not be layered to maintain maximum strength. The Zirconia surface must be highly polished when coming in contact with opposing teeth to prevent wear. The contacting and gliding surface of the cuspid should be supported either with unlayered pressables or polished Zirconia backing.

Dentist should always provide a stump shade on all cases. The technician prefers extra information to successfully design and fabricate the case in order to prevent reprepping and remakes. By providing the proper information to the lab, guess work can be avoided to achieve a better result.

It is important that dentist and lab technician are on the same page at each stage of treatment. We are a team trying to achieve the same goal!

Correspondence to: Yugo Hatai yugo@smilebyyugo.com.au
www.smilebyyugo.com

© 2008 Occlusion Connections  All Rights Reserved

www.occlusionconnections.com/

Communicating Lab Needs - A Check List for the Dentist for Optimum Success

by Joe D’Ambrosia CDT
Roe Dental Laboratory, Garfield Hts, Ohio

The successful restoration of large esthetic and reconstructive cases largely depends upon a set of exacting study models, impressions, bites, photographs and explicit instructions. Each has its part to play during the process. The dentist is the “architect” on these cases and the laboratory is the dental “contractor”. Without the right set of “dental blueprints” these cases cannot be completed to everyone’s satisfaction. Without any one of these pieces of information these challenging cases can become more complicated than necessary and the results might be less than expected.

It is a given that the bite, the most challenging registration provided by the dentist, must be correct before any master impressions are taken. Bite registrations are achieved in various manners using TENsing, swallow bites, functional bites, K7 Instrumentation bites (e.g. Chan Scans) and then finally stabilizing the jaw position using a removable and/or a fixed orthotic to determine esthetics and functional occlusion.

In the laboratory we must assume that the bites we receive are accurate unless a “tell-tale sign” alerts us to a possible bite problem in which case the doctor is consulted. The following is a list of “Lab Needs” that you, the dental Architect, must provide for optimum success.

DIAGNOSTIC APPOINTMENT

1.) Provide full arch pre-operative study models capturing peripheral borders, retro-molar pads and hamular notches. Anatomic landmarks are often referenced for mounting, plane of occlusion and tooth position.

2.) Provide full face (no lip retraction) photographs showing the relationship of the upper incisal edges to the lower lip line. Capture the patient’s entire head from slightly above the hair to slightly below the chin. This pose allows us to determine an accurate midline, the long axis and middle of the face, and the horizontal plane of the anterior teeth.

3.) Fox Plane Occlusal Registration (suggested) or a Facebow registration to determine the anatomically correct maxillary cast orientation.*

4.) Accurate, verified bite. Indicate if the bite registration is a Neuromuscular bite, Centric Relation bite or a Centric Occlusion bite registration.

5.) Fill out the lab Rx describing the desired anterior incisal edge length, A-P position, shape of teeth (smile guide photos are helpful). Indicate if the Golden Proportion formula for tooth length and width should be used and include any other pertinent information regarding the patient's particular needs to achieve the desired result.

PREPARATION APPOINTMENT

1.) Provide accurate upper and lower full arch “current condition” impressions or study models of the patients final adjusted (patient/doctor approved) provisional’s. Do not send the original diagnostic wax-up model since any adjustments to the provisionals made from the diagnostic wax-up will make the wax-up model inaccurate for cross mounting.

2.) Provide an accurate full arch opposing impression or model. The same care should be taken to provide good opposing models as is taken for master models. Distorted opposing models can cause inaccurate mountings and inaccurate occlusion as final laboratory porcelain equilibration will be completed against the opposing model.

3.) Provide a full, face forward, natural smile color photograph (no lip retraction) showing the relationship of the upper provisionalized incisal edges to the lower lip line. Capture the patients’ entire head from slightly above the hair to slightly below the chin. This photo’s allows us to see the midline, the long axis and middle of the face and the horizontal plane of the anterior teeth.

4.) Shade: close-up photograph of an open “lip-retracted” mouth holding the selected shade tabs’ next to the incisal edge of the natural tooth. Include and describe any patient specific shade-mapping instructions.

5.) Stump shade tab for “all ceramic” restorations should be recorded.

6.) Fox Plane or face bow registration.

7.) Send lab Rx with information on type of restoration (alloy type, all ceramic system desired, etc.) indicate bridge or singles, and any esthetic and functional information necessary (it is critical to indicate any changes needed to the study model in order to achieve the final desired result).

* Additional information regarding the Fox Place registration technique is documented in the following website www.claytonchandds.com/articles.php (Chan, C.A.: "A Review of the Clinical Significance of the Occlusal Plane"- It's Effect and Variation on Head Posture, ICCMO Anthology VIII, 2007).

Correspondance to: www.roedentallab.com

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VALUING THE LABORATORY DENTAL TECHNICIAN

CALLING ALL NM DENTAL TECHNICIANS!

The laboratory dental lab technicians expertise and insights are held in high honor and I want to hear from you on this blog.

Your expert insights and years of practical experience at the bench is a world often overlooked by the dental clinician. It is a world that is met with amazing challenges, skill and artistry to meet the demands and requirements of both patient and doctor. Clinicians are often unaware as to what is required to make the process smoother. Yes, we talk about impressions and bite records, but far too often it is far from desireable. What is the dental technician to do?

Good bite records, good photos are key...or the lab tech guesses...?

As dentists and one part of the complete dental team we need to know your valued input how we can help make your job easier and more fulfilling? We all know that through open communication and positive interactions we all will benefit on multiple levels to raise the bar and give the patient's what they deserve - Valued Quality Dentistry.

Plaster/stone room technicians we need your input?
Model technicians we need your perspectives?
Waxers we need your view points?
Ceramist we need your input and hear the realities of the end game?
Quality control department technicians, we need to hear the realities??

Post interesting photos of work in progress, things you see, the good and the bad....
All laboratories (large or small) and all technicians are invited to participate and give their insightful feedback on this blog to help the NM dental clinician understand what is required to meet the goals and objectives of high quality restorative dentistry for both phase I (orthotic stabilization) and phase II (restorative finishing) treatment.

Understanding what it takes to support the laboratory dental lab technician's needs to make effective mounting decisions to properly manage the doctors impressions, casts, registrations and mountings at the bench is key to the success of ALL neuromuscular dental technicians and clinicians.

I value the Laboratory Dental Technician and appreciate the time, effort, planning and details that go into each of my cases. There are numerous steps that need to take place as well as a number of talented hands and skills that must all come together to make it happen in the mouth!

Your Advocate,

Clayton Chan, DDS

© 2008 Occlusion Connections  All Rights Reserved

www.occlusionconnections.com/

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