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Predictable Restorative Excellence Part II By: John C. Cranham, DDS

More by this author (2)
Recently, I wrote about the direct relationship between predictability and the many positive trends found within the fabric of well-run dental practices. These attributes are increased production, decreased overhead, increased profitability, decreased stress and the overall happiness of the entire dental team. Becoming predictable in everyday procedures should be the primary focus of every dental practice because without it there is great uncertainty and incredible stress.

Previously, I focused on a step-by-step approach to tooth preparation. I suggested that by using bur organization and following a set sequence, your team would be consistently able to prepare teeth more efficiently and with a higher degree of quality. Making an ideal final impression follows a similar pattern. Learning a tried and true technique, which will consistently capture the necessary details within the impression, is a necessary component for a dental practice doing any amount of indirect restorative dentistry. Unfortunately, it has been my experience when discussing this matter with hundreds of lab owners consistent excellent impressions are rare. This article will provide guidelines for improving impression taking and acheiving consistent results for restorations.

Start with healthy tissue
It is important to understand that in fabricating an indirect restoration the purpose of the impression is not to simply capture the details of the hard tissues but also to capture the stable relationship of the gingival tissues. If we do indirect restorative procedures in the presence of gingival inflammation, no matter how “good” the impression, the final restorative result will likely be inadequate. Placing the final crown, when the gingival tissues return to normal size, shape and contour, will many times cause exposure of a margin. While the crown may fit fine, esthetically this is below the patient’s expectations. Beginning with healthy tissues will also simplify the impression making process. Bleeding tissues, while they can be controlled, should not be “the norm.” Taking patients through proper periodontal procedures, and completing all necessary preliminary mouth preparation will add tremendous predictability to all indirect aesthetic/restorative dental procedures.

Soft tissue management
Occassionally it is necessary to control a minor amount of gingival bleeding during a restorative procedure. Inadvertently nicking the tissues during margin refinement, while not being our goal, does occur. It is essential to have the ability to quickly control hemostasis. Viscostat from Ultradent dispensed from its Dental Infusor, is a fast, predictable way to obtain 100% control.

Start with an impressable preparation
Most restorative dentists do not trim their own dies. While many teaching institutions recommend this, with consistently excellent impressions, it is an unnecessary step. It is important for dentists to prepare teeth in a way so the margins are easily identifiable. This means teeth should be prepared with a consistent margin design 360 degrees around the tooth. If a contemporary metal ceramic material is your restorative choice, then a chamfer margin with the same general look should be utilized. If you prefer more of a knife edge or even a shoulder, the key is to develop a preparation style your dental laboratory will expect. Avoid having a margin that starts as a chamfer, then turns into a knife edge and ends in a shoulder. These become very difficult to read and trim. Preparing teeth with consistent margin design will add tremendous predictability in the precise reproduction of your preparations.

Consistent margin placement
Consistent margin placement is key to providing the patient with a restoration that will meet their esthetic goals and the optimum health of the restorative result. Not preparing far enough into the gingival sulcus will lead to esthetic problems, while going too deep will invade the biologic width.

By beginning with healthy tissue, with normal probing depths, a technique can be employed to consistently place the margin half the depth of the healthy pocket. If the pocket is 2.5mm deep, then the margin should be placed 1.2mm underneath the tissue. This will create an invisible margin, and one that exists in a healthy relationship within the periodontal structures.

Retraction options
There are many excellent ways to retract tissue if the only goal is to simply expose the gingival margin. Laser troughing and electrosurgical procedures are both excellent ways to expose the restorative margins. Retraction cord, while more time consuming, can be used to more predictably place the margin in the ideal zone within the gingival sulcus.

A two cord technique is described here to accomplish this goal. The technique described in this article is a modification of this process utilizing contemporary materials.

 A step-by step approach to an ideal final impression
 Start with an impressable preparation


Fig. 1

Figure 1 illustrates a tooth prepared for a Captek crown. The preparation has adequate reduction as described in Part One of this series, and has been smoothed and polished. The margin design is that of a chamfer, around the entire circumference of the tooth. Employing this type of preparation guideline, will dramatically increase the readability of your impressions, because your laboratory will know exactly what they are looking for. Whatever margin design you personally prefer, keeping it consistent will increase the quality and predictability of the final restorative result.

Fig. 2
Fig. 3
Control the soft tissue through preliminary mouth preparation & chemotherapeutics
 Starting with a healthy mouth is the prerequisite of any restorative procedure. Proper preliminary mouth preparation should include any and all procedures to get the mouth completely free of disease prior to the final restorative phase. Healthy tissue is one of the goals to make our job easier and the final esthetic/restorative result more predictable.

Additionally, chemotherapeutic agents such as Viscostat (Ultradent Products-Fig. 2) can be used by directly applying it to the tissue to stop any localized bleeding, and also to soak the retraction cords (Fig. 3). This chemical agent (Ferric Sulfate) not only rapidly achieves hemostasis, it also fixes the tissue holding it in the retracted position for longer periods of time. This material is an important component of any restorative dentist’s armamentarium.

Fig. 4
Fig. 5
Fig. 6
Placement of first cord
Prior to final margin placement the first cord should be packed. A 00 Ultradent cord that has been soaked in Viscostat is placed into the depth of the sulcus (Fig. 4). As shown in Figure 5, the goal is to have it fit perfectly once around the tooth. Pressure should be applied so that the 00 cord is sitting at the base of the healthy pocket.

Margin refinement
Once the tissue has been retracted with the first cord, the margin is finished by dropping the margin to the top of the cord (Fig. 6). The placement of the cord will protect the biologic width and prevent going too far into the pocket. This is where this technique may have an advantage over laser or electrosurgical retraction. While the others can rapidly attain exposure of the restorative margin, there is greater risk to invade the biologic width, or leave the postoperative margin visible.

Fig. 7
Fig. 8
Addition of contemporary retraction material
A very popular method of obtaining ideal retraction involves the placement of two cords on top of one another within the pocket. This technique follows a similar path, but introduces a contemporary dental material called Expa-syl (Fig. 7) recently released by Kerr. This material has a clay-like consistency which is released (under pressure) around the gingival sulcus (Fig. 8). It has hemostatic agents within its body, and has the ability to absorb crevicular fluid. The most positive clinical effect observed is not just great retraction, but also a very dry field. There seems to be a complete absence of fluid around the preparation making a quality and ideal impression.

Fig. 9
Fig. 10
Fig. 11
Apply Pressure with Comprecap
After dispensing the appropriate amount of Expa-syl circumferentially around the tooth over the retraction cord (Fig. 9), place a Comprecap over the tooth. Comprecap’s are made by a company called Roeko and look like a hollowed-out cotton roll (Fig. 10). Open at one side, and slightly firmer, once over the prepared tooth, the patient can then bite on it pushing the Expa-syl further into the pocket (Fig. 11). This provides additional retraction, by forcing the tissue further away from the tooth. When you combine this with the additional hemostatic and drying properties of this material, it makes for a very predictable method for margin capture.


Fig. 12
Visually inspect retraction objectives
After washing away the Expa-syl (simply remove by spraying with 3-way syringe) and removing the retraction cord, a visual inspection is the final step before making the impression. This is when you should put on your loupes and with excellent lighting visually inspect the retracted tissue (Fig. 12). All margins should be easily seen with a minimum of .5mm of additional tooth structure apical to the margin. Figure 12 exhibits the ideal retraction goals.

Fig. 13
Fig. 14
Inject with quality impression material
A polyvinyl impression material such as Take One from Kerr can be utilized to complete the impression procedure. While this material has hydrophilic properties, every effort should be made to keep the field dry. Dry angles, cotton rolls and suction should be used to keep saliva out of the field, especially in the mandibular area. When injecting (Fig. 13), keep the tip angled at the margin and burnish the material around the tooth. The thixatropic nature of this material will allow it to flow upon itself eliminating voids, bubbles and fins that can find their way into an otherwise perfect impression.

Visually inspect impression
The final step is a visual inspection of the impression. Loupes or some sort of magnification should be used to check the details of the master impression. As previously mentioned all margins should be visible with a minimum of .5mm apical to the marginal tissues (Fig. 14).

 Conclusion
 Indirect restorative procedures can be a highly predictable and profitable component of any dental practice. To achieve this, however, the dental team must employ some simple, disciplined steps, to achieve consistent results. DT

Dr. John C. Cranham maintains 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 founded PRE (Predictable Restorative Excellence) Seminars that provide a combination 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 send him an email at: smiledoc@aol.com
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