Chairside CAD/CAM technology in a general practice has many advantages: the ability to restore teeth in a single visit saving the patient and dentist time and money, lab savings for the dentist, control of the final result, and easy remakes to change color or design.
Another huge advantage is the elimination of provisional restorations. Provisionals do play an important and necessary role when esthetic and occlusion concerns need to be corrected prior to cementing final restorations. However, provisionals do have disadvantages, especially when unhealthy tissue is present. The roughness of the provisional material and the integrity of the provisional margins often hinder the healing of the surrounding tissue and increase treatment time. Utilizing CAD/CAM technology allows porcelain glazed surfaces that reduce plaque accumulation, closed margins, and ideally shaped contours to direct the growth of new tissue.
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Case Report
A 30-year-old female fractured her anterior crown on tooth # 8 (Figs. 1-3). The crown was originally placed 7-10 years earlier. The patient gave a history of constant bleeding when flossing around the crown. She would like for the crown to be replaced as well as the crown next to it, #9, due to esthetic reasons. Her esthetic concerns were to make the crowns slightly shorter because she felt she was "bumping them" and to also make the color match the adjacent teeth. She also wanted both to match in shape.
A closer examination was performed radiographically, visually using loupes and digital photography. Due to the inflamed gum tissue and depth of the crowns' margins below the sulcus, the possibility of biologic width invasion was noted.
A treatment plan was agreed upon by both the patient and the doctor to restore both crowns and allow the tissue to heal. The use of glazed porcelain crowns would be kinder to the tissue and retain less plaque than temporary crowns. If the tissue would not respond well, then osseous crown lengthening would be performed and new crowns would be made. The patient was very enthusiastic about this treatment plan as she did not want temporary crowns.
With the use of cheek retractors (OptraGate), the remaining porcelain was removed from #8 using diamond burs and electric hand pieces.
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The author was very careful not to traumatize the surrounding tissue; however, excessive bleeding occurred after removal of the remaining porcelain (Fig. 4). Before removing the crown on #9, the author chose to control the bleeding on #8. A homeostatic control agent (Expasyl) was injected into the sulcus (Fig 5) and allowed to sit for 5 minutes. After this time the material was rinsed out. The bleeding had stopped completely at this time (Fig 6).
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The crown on #9 was then removed by cutting a groove through the facial with a cross-cut carbide bur and high-speed electric drill. The cross-cut carbide bur coupled with the torque of an electric handpiece easily cut through the zirconium core. A crown remover hand instrument was used to separate the crown and remove the two halves. The two preps were then finalized (Fig. 7) and 00-size retraction cord was placed around both preps for five minutes and removed.
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Both preps were scanned simultaneously intra-orally (Fig 8) using a laser-based CAD/CAM scanner (E4D Dentist System). Because the E4D is a laser-based system, no powder or opaque medium was necessary to acquire the digital impression. In the inflamed areas, this is a tremendous benefit by not introducing foreign powder that could be integrated into the wound. An initial scan is taken to ensure an accurate capture of the incisal edge of #9.
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Then the Rapid Scan™ function expedites the process by capturing the anterior quadrant automatically while rotating the camera along the facial, incisal, and lingual surfaces. Bite registration material (Futar Scan), Huntington Beach, CA) is then placed over both preps and allowed to set fully. There isn't a specific type of bite registration material required for the E4Dsystem to scan successfully. While still on the preparations, the bite registration is scanned allowing the software to create the virtual antagonist.
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A library tooth was chosen that matched the closest to the shape of #9 (Fig. 10). The E4D Dentist System can utilize the preoperative condition or a wax-up if the contour is ideal, or the clinical operator can choose from one of several libraries to have the Autogenesis function place a properly aligned proposal.
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Both crowns are then virtually placed onto both preps. The software's process of Autogenesis™ customizes the initial proposals based on the adjacent teeth and the bite registration's relationship to the preparations (Fig 11).
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The virtual bite relationship of the lower incisors is then used to establish proper anterior coupling (Figs. 12 and 13).
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Ideal interproximal contacts are then easily created using the color coded contact strength function (Fig. 14). The user may opt to go with the default settings, or easily make custom adjustments using an array of design tools.
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Subtle anterior anatomy is automatically placed in the virtual restorations when they were first created. The anatomy, shape, embrasures, and lengths are now finalized using both gross movement and detailed oriented tools appropriate to the clinical application and to satisfy the patient's desired outcome (Fig. 15). By designing the restorations in front of the patient, the convenience and the software's ease of use allows for quick manipulation of the virtual restorations, taking into account her own input as well.
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The View Material Thickness tool (Fig. 16) easily color codes the entire surfaces of the restoration indicating where additional adjustments should be made to ensure the clinical success of this case based on the material selection.
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The two crowns are then sent to the mill to fabricate the restorations out of a block of porcelain (Shade B1, IPS Empress CAD MultiBlock). These blocks have the advantage of having both color and translucent layers built into them. The software allows the crown to be virtually moved up and down within the block to allow for more or less translucency and color (Fig. 17). This is represented by the red and blue transition on the screen. By using a porcelain block with these types of layers, the crowns will be milled not just based to achieve proper function, but to also obtain a beautiful and natural appearance without the need to cut-back and layer.
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The two milled crowns are placed on the preps (Fig. 18) to verify fit, contacts and shape prior to glazing.
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After the crowns are glazed with only a slight amount of white/grey stain placed along the incisal edge to enhance the halo effect using the same quality materials laboratories use, they were bonded on (Fig. 19) with resin cement ( RelyX Veneer, 3M Dental).
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After one week, the gum tissue is healing nicely and the interproximal papilla is returning (Figs. 20-22).
Conclusion
The use of chairside CAD/CAM technology allowed the case to be completed in a single visit without the use of provisional restorations. The results exceeded the patient's expectations esthetically, and she loved the convenience of not having to go weeks with provisionals and to return for the final seating. If complete healing is not achieved, it will be very simple and inexpensive for the dentist to have a periodontist treat the biologic width invasion if that is the case and remake the crown on #8. The intuitive software and precise milling abilities of the E4D Dentist System has greatly improved the quality, convenience, and satisfaction of dentistry I am able to provide my patients.