Ceramic veneers provide a wonderful restorative material to change shade, correct tooth positions and restore ideal function to natural teeth. When implemented precisely, there is long-term predictability and tremendous patient satisfaction. Proper tooth preparation is paramount for success and longevity.
In Spear’s “Restorative Design” workshop, Dr. Bob Winter and I teach participants the understanding and skills necessary in the preparation of crowns, veneers and partial coverage restorations. The system of depth cutting burs and diamonds helps each clinician achieve predictable success in the various tooth preparation designs.
“Restorative Design” introduces participants to the importance of smooth and precise margins that create more predictable impressions or scans and helps provide minimal film thickness for adhesion. This smoothness comes from using fine diamonds at low speed. Electric motor handpieces are critical instruments for achieving these refined margins.
[RESTORATIVE DESIGN PATHWAY: Learn more about the courses in Dr. Bob Winter’s Spear Online pathway, which addresses crowns, veneers, veneerlays, onlays, inlays and the materials and techniques needed for successful outcomes.]
The following images provide a visual overview of the process and outcome of these restorative design techniques.
One of the most challenging veneer preparation aspects for dentists is achieving smooth and precise interproximal margins. These margins must not leave unsupported enamel. As shown in the image, enamel rods are oriented perpendicular to the external tooth surface. Unsupported enamel rods will fracture following veneer adhesion and result in marginal staining and secondary caries. It is critical that the interproximal margins are managed appropriately to eliminate this complication.
Breaking interproximal contact during veneer preparation allows for better veneer esthetics and contour, plus easier insertion and improved dental hygiene The goal is to balance conservative concepts and yet provide adequate interproximal opening for structure and convenience. The “Tornado Technique” of interproximal veneer preparation helps manage both parameters.
I will use my patient, Kathy, as an example for implementing the Tornado Technique for veneer preparation. Due to her esthetic and functional needs, Kathy requires anterior restorations.
It is paramount to begin with the end in mind, relative to tooth preparation, and it is necessary to “visualize” the required tooth preparation before applying a bur to the tooth. This is referred to as “outcome-based design.”
The diagnostic wax-up was fabricated. This photo is an occlusal view of the mock-up prior to tooth preparation. Her treatment plan is to utilize ceramic veneers on teeth #8 and #9. Teeth #6, #7, #10 and #11 will be full coverage due to the existing large lingual restorations. We will concentrate our attention to the veneer preparations.
Proper interproximal margin placement is crucial for veneer esthetic success and dental hygiene. In ideally arranged teeth, it is recommended that the interproximal cavosurface margin be placed at least 1mm lingual or palatal to the height of the interproximal papilla.
Additionally, the prepared margin is to be finished perpendicular to the external surface of the tooth. In this way, the enamel rods will not be left unsupported. The yellow dotted lines indicate the external tooth surface contour. The blue dot represents the position of the interproximal papilla. The red line designates the finish margin position 1 mm lingual to the papilla.
The amount of tooth preparation is dependent upon the desired shade changes needed, as well as the ceramic material of choice selected for strength. The key is to prepare the interproximal cavosurface margin perpendicular to the outer surface of the tooth.
The image provides a visual of the proposed veneer preparation and the direction and position of the finish line. Note the 90-degree margin positioning at the cavosurface.
By beginning with a vision of the outcome, it becomes easier to achieve the desired end result in preparing the teeth for ceramic veneers. This image of Kathy’s veneer preparations verifies that the requirements were accomplished.
The dotted lines that overlay this image provide reference to the preparation contours. The real challenge of the veneer preparations is establishing the proper margins at the interproximal. This is where the “Tornado Technique” of interproximal tooth preparation comes into play.
The action and movement of a tornado provides the analogy of the “Tornado Technique” for veneer preparation. A tornado (a dental handpiece) develops a tight spinning form (a diamond bur) that rises from a definitive point on the ground (the tooth margin).
Once formed and rotating, the tornado tracks in a definitive direction (handpiece moving interproximal 1mm) then suddenly “spins off” in a lateral direction (diamond bur rotating “spins off” 90 degrees from cavosurface).
The photo of Kathy’s veneer preparation provides a visual of the Tornado Technique. The black dot is representative of the diamond in the handpiece. The handpiece is moved interproximal 1mm lingual to the height of the papilla. As the proper margin position is reached, the handpiece is allowed to “spin off” the tooth to create a 90-degree margin. The black dots and arrows represent the effective movement of the handpiece to create the outcome desired.
This final photo represents Kathy’s provisional restorations. The tissue health and the ease of maintenance are indicative of the proper margin positioning and contouring.
I hope this Tornado Technique provides a solid visual image for clinically preparing interproximal veneer margins in a strategic and effective manner.
Jeffrey Bonk, D.D.S., is a member of Spear Resident Faculty.