Steps for taking a programmed approach to ensure By John C. Cranham, DDS

When I travel providing educational programs, I come in contact with hundreds of dentists. I am fortunate to be able to speak with these dentists and discuss what is important to them and what works–or doesn’t–within their practices. I have found successful practices exhibit both predictability and efficiency.

Predictability is extremely important as uncertainty about the final result can be extremely stressful. I’m sure, at some point in your career, you have experienced lying in bed the night before the delivery of a large case and feeling anxious about the final outcome. You probably ask yourself the same questions I do such as: will it fit, will the lab mount it correctly and will the color match be acceptable. You probably also wonder about the margins and if you have removed the correct amount of tooth structure for your chosen restoration material. Predictability is the first key to truly enjoying the practice of dentistry. It is the factor that allows for tremendous confidence not only in procedural outcome, but also in building trust with your patients.

Whether we want to admit it, we are ‘on the clock’ when performing dental procedures. Focusing on efficiency is absolutely essential and should be constantly evaluated. Taking a systematic approach to all the procedures in the practice will increase the quality of the end result because you will do things the same way every time. Airline pilots have a preflight checklist. They depend on this efficient tool to avoid mistakes. In restorative dental procedures, preventing mistakes equates to less remakes–due to fit, color and missed mountings. These common mistakes eat away at your profits and limit your fun and satisfaction. Efficient systems will allow you to perform necessary procedures more rapidly with more consistent results. Hence, efficiency not only increases profitability, it also increases predictability and the quality of the end result.

This article was written to provide a step-by-step approach to tooth preparation.

The concept of the mini-tooth prep
The most commonly placed indirect restorative material is still the Porcelain Fused to Metal (PFM) crown. I favor using a restorative material manufactured by Captek. I believe it is one of the hottest new materials on the market. Captek has developed a contemporary metal ceramic that dramatically increases the esthetics of the traditional PFM, while decreasing the amount of tooth reduction. This is all accomplished without sacrificing strength.

Figure 1: Preop view of tooth 30, post endodontic treatment, resin build-up complete

The first goal of tooth preparation is to know exactly what the final preparation should look like. In other words how much tooth reduction is needed to provide the optimum thickness for restorative material. With a posterior Captek preparation this means 1-1.2mm axial reduction and 2mm occlusal reduction. The reduction however, must allow for proper retention and resistance form which means a minimal wall height of 3mm, with 6-10 degrees of taper. The reduction also must follow the contours of the tooth. Thus all irregularities in the preparation should be removed through proper build-up procedures, to provide ideal form (Fig. 1). Note that the ideal preparation is simply a smaller version of the existing tooth. By properly visualizing the ideal contours of the final preparation, a systemic approach can be designed to get the job done.

Customize your bur blocks
The first step is to correctly choose your burs. By knowing the ideal depths and shape of your preparation, burs can be selected based on the diameter, shape and margin design. Brassler representatives are an unbelievable resource when it comes to bur selection. If you show them your preparation goals, they will guide you to the burs that will predictably get you to your desired shape. To maximize the efficiency, super-coarse burs should be selected for gross reduction followed by medium coarse burs to smooth and polish the preparation. Once the burs are selected they can be organized into customized bur blocks. Brassler will laser etch the bur numbers onto these bur blocks at no charge, to assist in setup. This is an unbelievable service, that will help the entire practice in the predictability, efficiency and consistency of your restorative services. Fig. 2 depicts the customized blocks used in my practice. One is for preparation and one is for finishing. These bur setups allow me to do all restorative procedures performed in my practice.

Figure 2: Customized bur blocks: Captek bur kit, John C. Cranham Prep Kit, John C. Cranham Finishing Kit

The other option is to purchase a block specific for the procedure. Captek has spent a great deal of time and effort developing a product called, Brassler Captek Prep Kit (Fig. 2). Many dentists were consulted on the development of this product. It will do a great job not only for Captek restorations, but also on many other restoration types. This ‘kit’ has an excellent variety of super coarse and medium coarse burs that will get the job done. Whatever product you decide to use, well organized burs are the first step to consistently achieving ideal preparations.

Follow a step-by-step protocol
With any procedure in the practice, it is wise to develop a step-by-step approach. Tooth reduction is no exception. By systematizing this procedure, everyone in the practice will know what needs to be done to aid in the process. Assistants can easily set up the room properly. After sterilization, burs will be placed back into their proper place within the bur blocks. The following is a sequence that has worked great in my practice.

Figure 3: Break the interproximal contact with a 169L bur. Leave the lip of tooth structure to protect the adjacent tooth

Break Interproximal Contacts
To begin a crown preparation, it is best to remove the portion of the tooth, that may cause damage to the adjacent tooth. This can be done by using a 169L carbide bur. This thin bur is designed specifically for this purpose. One pass from buccal to lingual on the mesial and distal of the tooth to be prepared will accomplish this task. It is important to leave a small lip of tooth structure (Fig. 3) again to prevent inadvertently damaging the adjacent tooth. This lip can then be simply fractured off with an explorer or other such instrument. This will insure you leave a pristine surface on the adjacent tooth.

Figure 4: Facial depth cuts with 169L		Figure 5: Facial and lingual depth cuts completed with 169L. Depth approximately 1mm deep, facial depth cuts in two distinct planes

Facial & Lingual Depth Cuts
With the same 169L bur, prepare 3 facial depth cuts and two lingual depth cuts (Fig. 4) Completely sinking this bur into the tooth will be the first step in guaranteeing adequate tooth reduction. The depth cuts on the facial should follow the contour of the tooth. On the facial this requires the depth guides to be in two distinct planes. The first plane is parallel and begins at the gingival margin and is parallel with the lingual surface (Fig. 4). The second buccal plane is angled to follow the slope of the buccal cusps toward the occlusal surface. The lingual depth cuts are parallel to the facial contours first plane. Fig. 5 shows the facial and lingual depth cuts complete. They should be approximately 1mm deep.

Figure 6: Occlusal depth cuts with 330 bur. Sinking bur to depth of the cutting surface will provide 2mm guides		Figure 7: Occlusal depth cuts complete, note classic spider shaped pattern

Occlusal Depth Cuts
The 330 carbide bur is an ideal depth cutter for occlusal reduction. This is because the cutting surface of the bur is 2mm. Run a groove from mesial to distal, then three separate grooves running to the facial, and three grooves running to the lingual (Fig. 6). This will provide the classic “spider” grove pattern shown in Fig. 7.

Figure 8: Occlusal reduction provided with trapezoid shaped diamond bur. Cutting to the depth of the guide cuts will complete the occlusal reduction in one swipe		Figure 9: Occlusal reduction complete showing classic “deep V”. Critical to provide technician room for adequate occlusal morphology

Occlusal Gross Reduction
Now that the interproximal reduction has been completed it is possible to completely finish the occlusal reduction without hitting the adjacent teeth. To complete occlusal reduction use a trapezoid-shaped super coarse diamond bur to simply connect the dots. This will consistently remove the necessary amount of tooth structure. The diamond of choice is Brassler’s 5811-033 trapezoid-shaped super coarse bur (Fig. 8). This will complete the occlusal reduction to ideal specifications in one swipe. Note the classic “deep V” shape that is critical to provide adequate room for the ceramist to build in beautiful occlusal morphology (Fig. 9). Also due to the orientation of the curve of Wilson, the lingual cusps of the lower molars should be shorter than the buccal cusps. The opposite is true in the maxilla.

Figure 10: Facial and lingual gross reduction is completed with supercourse diamond, following the previously placed depth cuts		Figure 11: Gross reduction complete

Facial & Lingual Gross Reduction
With the occlusal reduction complete, and the facial and lingual depth cuts in place, the facial, interproximal and lingual gross reduction can be completed by simply “connecting the dots” (Fig. 10). Using a super coarse 5856-016 Brassler diamond, follow the contour of the gingival tissues, prepping to the depth of the previously placed guide cuts. Gross reduction is completed very quickly. Keeping the bur parallel to the long axis of the tooth will provide the ideal 6-10 degrees of taper. The second plan of reduction is prepared following the orientation of the natural buccal contours. Fig. 11 exhibits the completed gross reduction specifically for my restoration preference, a Captek crown.

Figure 12: Finished with a medium or fine diamond bur		Figure 13: Polishing with discs & cups to guarantee optimum fit of final restoration

Finishing & Polishing
Finishing and polishing is an extremely important and often overlooked step in proper tooth preparation. If an impression is made of a surface that is a little rough or irregular, these sharp angles will be transferred to die. It is very easy for these kinds of dies to get abraded. These abrasions will alter the dies’ shape, making them slightly smaller. This will lead to castings that are tight, or do not seat. Spending a little extra time with a medium or fine diamond such as Brassler’s 8856-016 will do a nice job. This can be followed up with discs and polishing cups. The goal is to provide a smooth impressible surface that will lack any sharp edges on the body of the preparation (Figs. 12, 13). Fig. 14 exhibits the “finished” crown preparation.

Figure 14: Preparation “finished”		Figure 15: Cord is packed as first step of margination

Margination
The final step in tooth preparation is margin placement. The goal should be to place the margin in such a position to maximize the esthetics, and not invade the biologic width. This can be easily accomplished by placing a Size 0 Ultradent cord into the sulcus (Fig. 15). Push the cord to the base of the sulcus, then using a medium coarse diamond bur (8856-016), drop the margin into the sulcus to the top of the cord. This will predictably place the margin in a place that is invisible, while protecting the biologic width (Fig. 16). At this point in the procedure the temporary restoration can be fabricated and the final impressions completed.

Figure 16: Using medium coarse diamond bur, margin is dropped to top of cord

By developing a customized plan, your team can assist you in completing restorative procedures that will ultimately increase both quality and efficiency because each of you will know exactly what to do. Taking the time to organize and develop customized bur blocks, combined with rehearsing this step-by-step approach will add quality, predictability, and profitability to your restorative practice. Details of obtaining predictably accurate final impressions will be discussed in the second part this series.

---

References:
Kois, JC: New Paradigms for anterior tooth preparation. Rationale and technique, Oral Health (88)4:19-30 1998

Kois, JC: Altering gingival levels: the restorative connection. Part 1: biologic variables. J Esthet Dent (1):3-9, 1994

Nixon, RL: Where did the where go? Biofunctional reconstruction with a bioesthetic concept and materials-Part I. Contemporary Esthetics 6(1):54-66 2002

Winter, RR. Achieving aesthetic ceramic restorations. J Calif Dent Assoc 1990; 18(9):21-24

Ingber, JS; Rose, LF; Coslet, JG. The “biologic width”-A concept in periodontics and restorative dentistry. Alpha Omegan 1977;70(3):62-65

---

Dr. John C. Cranham has a cosmetic oriented restorative practice in Chesapeake, VA, where he resides with his wife and three children. An honors graduate of the Medical College of Virginia in 1988, he maintains a strong relationship with his alma mater, as an Associate Clinical Professor, teaching Graduate Prosthodontics and AEGD programs.

John is an internationally recognized speaker on the Esthetic Principles of Smile Design, Contemporary Occlusal Concepts, Laboratory Communication and finding Happiness and Fulfillment in dentistry. Most recently, John has founded PRE (Predictable Restorative Excellence) Seminars which provide a combination of lecture, mobile hands-on programs, and intensive 2-3 day hands-on experiences at his office in Chesapeake, VA. John can be reached at 757-465-8900 or at smiledoc@aol.com