Esthetic and functional restorative dentistry is dependent upon outcome-based thinking, design and application. Correct tooth preparation reduction is important to achieve predictable and long-lasting ceramic restorations. Inadequate ceramic thickness may result in improper shade, inadequate strength and potential failure of the restoration due to fracture. It is critical to incorporate strategies and techniques for accomplishing predictable results during the tooth reduction phase of restoration.
Every material requires specific thickness for strength and durability. In the Restorative Design Workshop, a systematic tooth reduction approach is outlined. Depth reduction burs are utilized to provide controlled tooth removal. The design of the bur eliminates guesswork of tooth reduction. The definitive depths produced from these burs guide the restorative dentist toward an ideal preparation contour.
The technique of drawing red pencil lines in the depth cuts is introduced to provide a frame of reference as to the extent of tooth reduction. The participants are instructed to maintain these red lines throughout the tooth preparation process. Visual evidence of these lines at the completion of reduction and refinement provides confidence as to the amount of tooth removal.
There is never a workshop where at least one participant questions the sterility of the red pencil. In the past, we have jokingly asked the participants to take the “sterile red pencil” from the drawer to mark the teeth.” Generally, there is laughter from the group. But in reality, there is genuine concern for having our instruments and materials “sterile.” It is in the best interest of the patient to maintain cleanliness in all we do.
The question of sterility is important and valid. As dentists, we practice sterile technique routinely. Instruments, gauze and cotton rolls are sterilized in our packs and trays for each and every patient. We don't think twice about that process. But the “sterile pencil” question was bothersome to me. An assumption was inferred that red pencils could not be made sterile.
As I thought about this dilemma, it occurred to me that my office routinely places wooden cotton applicators (“Q-tips”) into each of my instrument packs prior to sterilization. As they do not “burn up” during a high heat cycle, I proposed that possibly red pencils could be included in the packs as well.
Pencils are made from graphite rather than lead. The solid graphite core is a combination of graphite and a clay binder. The casing around the graphite is typically made from wood, but plastic and other materials are used as well. The casing is not bound to the graphite core. The consistency of the core determines the hardness or softness of the pencil. The more clay, the harder the pencil’s lead.
Pencils are classified by degree of hardness and blackness. The scale ranges from zero to nine. One end of the scale designates hardness, “H.” The other end is softness, “B.” The harder the pencil, the lighter the color. Conversely, the darker the pencil, the blacker the color. A #2H pencil is softer than a #3H pencil. A soft pencil will leave a greater trail of core material than a harder pencil.
Colored pencil lead contains a wax or oil-based pigment. The amount of color pigment determines the color intensity of the core. Colored pencils vary greatly in quality, concentration of pigment, solubility and softness.
I ran a test by placing a red/blue pencil into a sterilization bag. My biggest concern was whether the red lead would melt in the high heat of the autoclave. Depending upon the amount of wax, the red pencil could be rendered unusable.
To my pleasure, I discovered that the red pencil underwent the sterilization process successfully. Aside from the outer paint covering blistering from the high heat, the pencil and point were intact. The prepared teeth depth cuts can be adequately marked with the sterilized pencil!
Multiple sterilization cycles will result in the complete loss of external red pencil paint. However, the pencil will continue to work for tooth reduction marking. I suggest sharpening the pencil after each use, prior to the subsequent sterilization cycle.
An alternative method for creating sterile marking pencils with sharp points could be to include a metal mechanical pencil in the patient packets. The mechanical pencil could be routinely sterilized and the pencil tip advanced, as needed, for sharpness.
As a side note, black pencils are not recommended for this tooth-marking process. Black graphite particles have the potential to become ingrained into tooth structure and previous restorations. This could negatively interfere with tooth shade and brightness value. Using a soft black pencil would be even worse.
I hope this article and experiment provide some insight into preparation design and eliminate any uneasiness around the “sterile” red pencil tooth-marking dilemma.