Note from Ron Cox:
The following article was provided by one of our clients, Dr. Thomas Natale, a leading dental care provider in Woodinville. Cox Dental Lab has a long and successful record of real collaboration and teamwork with Dr. Natale on a wide range of cases ranging from standard to complex.
We asked him to share some best practices information focused on how to develop a good crown restoration. For more information regarding Woodinville Dental Care, please visit www.www.woodinvilledental.net
We welcome articles related to the latest industry trends and best practices from all of our clients. If interested, please contact me at 425-402-4774.
Developing a good crown restoration
By Dr. Thomas M. Natale, DDS
After thinking over the question of how to best prepare and impress acrown for restoration I have come up with the following thoughts. In my opinion there are several factors that influence and contribute to a good restoration. The most critical issue is the determination, energy and desire of the dentist to be the best he/she can be. I believe it is incumbent upon each individual dentist to develop his/her own method using all the information, data, studies, literature and experience each has in dealing with patients. I think it can be summed up with the statement “‘effort trumps talent”and that by evaluating our own work with the help of our lab person we can all do very good work. It goes without saying that each of us must be able to accept constructive criticisms and use it to modify our technique. Our lab person can be our greatest ally and friend.
There is no one way to resolve any dental problem or issue is that decay, fracture, infection, pain, poor esthetics or loss of function. The complexity of the parameters, which invariably compound one problem upon another dictate many competing alternatives, each having associated benefits and compromises. When the dentists own strengths and weaknesses are compiled on top of the patient’s problem it becomes a judgment that each dentist needs to make using their own reason and experience.
The question of how best to restore a tooth needing a crown needs to be ultimately answered by each dentist taking into account their individual strengths and weaknesses.(what are the problems and what is causing the difficulty) Without a doubt I feel the diagnosis is of paramount importance and should be addressed fully before any treatment is started clinically. The critical decisions that follow diagnosis and planning are influenced to such a degree by the diagnosis that treatment can be rendered far less than adequate if an incorrect diagnosis is made. Again this is a place our lab people can help us even before we have begun treatment.
With regard to crown restorations the general order I use is as follows:
1. Determine the design and material to be used
2. Address any obvious aberrations and enlist lab and or consultants for help
3. Enlist any specialists
4. Prepare the tooth
5. Make an impression of the preparation
6. Send to lab
7. Reevaluate restoration and preparation with lab ( I still do this after 30+ years)
8. Make changes to correct problems of design or procedure and reevaluate again and again until all problems are resolved.
9. Cement restoration
To the actual procedure of preparing and fabricating a crown restoration here is my personal method.
1. Determine material to be used (porcelain, gold, zirconium, titanium, silver, plastic, SS, etc.)
2. Decide on best design to accommodate concerns (esthetic’s, strength, longevity, cost, patient preference, occlusion)
3. Initial reduction of tooth starting with occlusal followed by axial reduction being careful to not prepare the tooth subgingivally at this point. It should still be an ideal preparation with regard to amount of tooth structure and shape is concerned. I use burs that are made by Brasseler and Premier as well as Komet. I do not think it is particularly important which ones you use. I am partial to a tapered, flat-ended diamond for the axial reduction and use several different sizes depending on the tooth. I use a large football shape and a barrel shape for the occlusal and lingual reduction again using various sizes to fit the tooth.
4. The tooth next has gingival retraction cord (with Styptin on cord) placed by my assistant at this point. (This is a great time to relax for few minutes) We usually use two different sizes with the smaller size going in first. (I use Ultradent 0-3 sizes as well as Crown Pak 4 ply and occasionally cotton pellets or suture) The choice here is to place the smallest cord that will fit and give us enough room to finish the preparation without harming the gingival. This should be left to sit at least five minutes.
5. The preparation is then extended apically to clear all old fillings, decay and fractures as long as they do not extend below the bone level. Here I tend to use the same tapered diamond that was used in the initial reduction. I will use round burs if the decay is extensive.
6. At this point I will remove all old filling material and any remaining decay from the tooth. I then fill all undercuts and try to idealize the shape of the prep using Vitrabond, composite, glass ionomer or occasionally amalgam. The entire prep is then smoothed and all preparation angles are rounded so that there are no sharp angles anywhere.
7. The margins are finished with either a round-ended, flat-ended or tapered pointed diamond (My choice is Premier’s Two Striper #256.9F which has approximately a 45* angle on the point) depending on the prep choice and materials to be used. I will sometimes make a chamfer margin and sometimes make an angled (45*) margin of about 2-3 mm wide, or very infrequently make a butt margin. To be honest I am not sure it really matters which design is best as long as it is well done and completely captured in the impression.
8. The retraction cord is compressed or reinserted at this point and the entire prep should be completely visible including all margins. If possible I would like to actually get beyond the margins by 1+ mm.
9. The impression is now made. I use Kerr’s Extrude light body, low consistency and Extra heavy body (blue and purple) which I place Extrude in the sulcus and on the prep followed by a gentle stream of air until it is thinned out completely ( tooth will look like it has been painted light blue. (I can see the margins completely at this point) I then recover the prep with Extrude while my assistant is filling the tray with Extra. I do not think it really matters what impression material is used or for that matter what technique is employed. My choice is based entirely on the color blue. I can see it easier both in the final impression and also in the first placement on the tooth.
10. A temporary is now made with either an aluminum shell, Protemp, or acrylic and should always fill the space and fit the occlusion. Sometimes we will extend beyond the margins and sometimes we will leave it short but the proximal and occlusal contacts are always solid.
At this point the soft tissue should not have been cut or abraded. In no case do we ever cut tissue in the anterior if we are going to capture an impression on that day. If there is any problem with homeostasis it is always an anesthetic problem and a simple injection of a small amount of anesthetic with vasoconstrictor will achieve a controlled field.
Although I can not remember everything I have ever done I know that for the past 20 years I have not prepped an anterior tooth and taken an impression the same day. My normal sequence is to prepare an anterior tooth and place a temporary with ideal margins and contours that will be copied in the final restoration on the first appointment and then to follow up in one week with the final prep and impression. The initial preparation does not extend below the FGM; however I will fully scale and clean below the gum line. For the most part all preparations are done with a prep margin only about ½ mm sub gingival in the anterior and may even be supragingival if the esthetic’s are not compromised. After the prep has been extended we do not attempt to extend the temporary margins. I want that area to heal without any interference or foreign matter.
One final thought, except in extreme cases (maybe one in forty) I believe and practice using the approach that I must be able to see everything I am doing while I am doing it. This of course means I have to have an excellent assistant, adequate anesthesia, and enough light and patient cooperation. As we all know there are sometimes when this is virtually impossible (deep distal of a second molar), however in these cases it is still necessary that I be able to see and evaluate the preparation before impressing.
Cox’s state-of-the-art dentistry lab prides itself on being on the cutting-edge of dentistry to provide the most advanced products along with excellent customer service. Cox specializes in most all crown and bridge needs, from simple to the most advanced cases. For more information call425-402-4774.