March 1, 2007
by David Avery, AAS, CDT and Edward J. Swift, Jr., DMD, MS
The contemporary clinician faces many challenges in the routine practice of general dentistry. The required range of abilities and knowledge grows almost exponentially as dental science benefits from the effects of the digital transfer of data. Yet restoration of the maxillary anterior teeth remains one of the most difficult clinical challenges for both the dentist and the patient. This discussion presents such a case illustrating contemporary technology combined with time proven esthetic procedures, both clinical and laboratory.
A 37-year-old male patient presented with generally good periodontal health. His chief complaint was displeasing esthetics of the maxillary central incisors. Tooth #1-1 was affected with white enamel mottling and tooth #2-1 had a previous Class IV fracture restored with aging, discolored composite resin (Fig. 1). Periodic re-fractures of the composite restoration occurred due to occlusal interference from a labially malpositioned opposing tooth #4-1. Otherwise, the existing alignment, length, color, and general contours were acceptable to the patient.
The patient’s goals and clinical condition merited conventional enamel reduction for feldspathic porcelain veneers fabricated on refractory dies to restore the two maxillary central incisors. Clinical research has demonstrated that when etched feldspathic ceramic is bonded to etched enamel the tooth is restored beyond its original strength. Enamoplasty of the incisal edges of # 3-1 & 4-1 to eliminate traumatic occlusal contacts were also indicated.
Accurate laboratory communication of detailed color and surface morphology is critical to the successful delivery of undetectable indirect anterior restorations. The subjectivity involved in assessing color continues to be one of the most difficult remaining barriers to communication between the dentist and technician. With the evolving development of dental materials science and esthetics knowledge to match the artistry of natural dentition, our profession continues to advance the field of esthetic restorative dentistry. We now have materials and technologies available to us that make undetectable indirect restorations possible on a consistent basis, if we record and relate accurate color/shading information to the laboratory technician.
Determination of the proper shade required for a restoration is highly subjective, and heavily dependent upon illumination, environment, and the receiver’s eye. As a general rule, dental laboratories define a 6 % remake rate as an expected cost of doing business. At least half of these remakes (3%) are color-related and occur as a result of inadequate or inaccurate data provided or misinterpretation by the technician. Chief among the many elements that may compromise accurate color assessment is inconsistent type and quantity of light source.
The Optilume Trueshade lighting device from Optident (Clinical Research Dental) provides a user friendly, cost effective alternative to the more expensive digital shade matching technologies currently available (Fig. 2). Its two LED light sources provide a constant 5500K environment for viewing the teeth compared to shade guides. They are positioned at 45 angles to eliminate reflective washout of the teeth, allowing needed visibility of the colors and nuances present in natural dentition. The device also has a control dial for increasing or decreasing the intensity of the light while maintaining the crucial 5500K to better evaluate value comparisons to the appropriate shade tabs.
This apparatus is an excellent adjunct to digital photography. It provides an ideal environment for the clinical staff or technician to determine the correct value, hue, chroma and surface morphology (Fig. 3). The digital images can then be captured with appropriate shade tabs with greater certainty.
DIGITAL PHOTOGRAPHY SHADE COMMUNICATION HINTS:
* Always display the shade designation of the shade tab in the image.
* Shoot multiple images and edit later, after patient is dismissed.
* Shoot at 45 to display the color characteristics hue, chroma, value and location and degree of translucency (Fig. 4).
* Shoot perpendicular to the teeth to display surface texture and anatomy (Fig. 5).
After anesthesia, conventional intra-enamel preparations were accomplished using the Nixon Porcelain Veneer Kit II (Brasseler). Facial enamel generally was prepared to a depth of 0.5 mm, and the incisal edges were reduced to ensure a 1.0mm thickness of ceramic. The fractured mesio-incisal edge of 2-1 was smoothed and blended into the normally reduced disto-incisal area. The preparations included an “incisal wrap” of approximately 1mm also, with a chamfer margin around the entire periphery. Final finish and refinements were accomplished utilizing a fine Two-Striper chamfer diamond (Premier). Prior to final margination and in anticipation of the impression, #000 Ultrapak (Ultradent) retraction cord was placed (Fig. 6).
The retraction cord was left in place for the final impression, which was generated with Affinity VPS impression material (Clinical Research Dental). Light body material was syringed onto the prepared teeth and the heavy body loaded tray was seated. Final intra-oral set occurred in 2.5 minutes and the tray was removed, inspected for accurate detail and sent to the laboratory (Fig. 7).
A pre-treatment impression was made using Affinity Crystal. (Clinical Research Dental) (Fig. 8). This clear and relatively rigid PVS impression material was used in a tray without any tray adhesive, and was removed from the tray to be used as a matrix for the provisionals. Following tooth preparation, and obtaining the final impression and bite registration, Temptation provisional material (Clinical Research Dental) was syringed into the clear matrix, which was re-inserted over the prepared teeth (Fig. 9).
The autocure provisional material was allowed to reach an initial set in approximately two minutes and was removed to prevent locking them in place. The provisionals were trimmed using diamond disks and carbide finishing burs. Besides the obvious importance of an acceptable esthetic result, the provisionals should have good marginal adaptation and appropriate embrasure form. The provisionals were fabricated as a single unit, both for convenience and to help improve retention.
The completed provisionals were temporarily cemented utilizing TempBond Clear (Kerr) resin-based provisional cement to spot-etched enamel with no bonding agent. After cement cleanup, the provisional veneers were coated with Tempglaze (Clinical Research Dental), which was light-cured to provide an esthetic, stain resistant surface (Fig. 10).
The master casts and working dies are fabricated as normal. The dies are duplicated with vinyl-polysiloxane impression material and refractory investment material (Fig. 11).
This well documented technique provides the best opportunity for intimate, uniform adaptation of ceramic material to the prepared tooth structure interface. The incremental application of powdered ceramic allows the ceramist the maximum level of control required to create thin matching restorations over varying backgrounds, as in this case. The challenging area of discrepancy in this case was the fractured mesio-incisal corner of # 2-1 compared to the intact substrate present on #1-1 (Fig. 12). Dentin shaded ceramic was applied to this area creating a matching substrate density to the prepared #1-1.
As illustrated in this case, when no color change is required between the remaining enamel and the veneered ceramic the “contact lens effect” technique is
applicable. This is created by applying transparent enamel ceramic at the cervical margins of the restoration. This transparency creates a chameleon-like effect when the completed restoration comes into contact with the adjacent tooth structure. The transparent porcelain and resin cement take on the color of the marginal tooth structure creating visually undetectable supra-gingival margins.
The remaining dentin and incisal effect powders were applied to both veneers, completing the porcelain application phase (Fig. 13). After firing, final contours and surface morphology were accomplished with rotary instruments. The final ceramic glaze cycle was fired and polishing with Brasseler Dialite wheels, diamond polishing paste and rag wheel provided the desired surface luster. The restorations were devested from the refractory dies, margins refined with a rubber wheel and etched for 60 seconds with a 5% hydrofluoric acid gel.
A local anesthetic (Septocaine) was administered by infiltration. Retraction cord (size 000, Ultrapak) was placed and the provisional veneers were removed by applying pressure at the distal margins with a hand instrument. The teeth were cleaned with flour of pumice slurry. The veneers were tried in individually and dry to assess fit and marginal adaptation. No adjustments were required on either.
The veneers were tried in together and wet, to assess the overall fit and esthetics. No adjustment was required to seat the veneers together, and the esthetic result appeared to be good. For further evaluation of color, the veneers were tried in using Variolink Veneer (Ivoclar Vivadent) translucent try-in paste. It was determined that the shade would be appropriate using a translucent resin cement, so no other try-in pastes were evaluated. The water-soluble try-in paste was rinsed from the veneers. The intaglio surfaces, which had been etched by the laboratory, were silanated.
After etching the teeth with phosphoric acid, Excite adhesive was applied to the tooth and veneer surfaces. Translucent Variolink Veneer resin cement was applied to the veneers. The loaded veneers were applied to the teeth with finger pressure. The fit was such that no tack-down curing was necessary. Most of the excess cement was removed using a brush, explorer, and Mylar strips.
A thin bead of cement was left at the gingival margin, and the cement was cured using multiple exposures with an LED curing unit (LE Demetron 2, Kerr Demetron). Glycerin gel was applied over the margins to prevent air inhibition. Final excess was removed from the margins using a #12 scalpel blade. The occlusion was checked and adjusted slightly using instruments from the Nixon Porcelain Veneer Kit II, and the margins were refined in some areas, particularly along the lingual. All adjusted areas were polished using the Brasseler Dialite system.
There are many options available to us as we approach these types of cases, ranging from the most conservative option of direct resin bonding to the most invasive option, full-coverage all-ceramic or PFM crowns. Many times the clinician is drawn to a specific material or technique based on limited availability from the laboratory technician with whom they work, or a lack of experience with a specific technique or material.
The old adage “If all you have is a hammer, everything is a nail” comes to mind when this topic arises. The results presented here met the patient’s desires for esthetics and durability, and likely will serve him well for many years to come. The conservative intra-enamel preparations retained tooth structure for the inevitable re-treatments that the young patient will require in a normal life span.
David Avery, AAS, CDT, director of Training & Education, Dake Precision Dental Laboratory, Carlotte, NC.
Edward J. Swift, Jr., DMD, MS, Professor and Chair, Department of Operative Dentistry University of North Carolina, Chapel Hill, NC.
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