Clinical Corner: Information on Dental Procedures

Articles

What's Hot: Dr. Glazer on Jazz
Combating Hidden Decay with Early Detection
Atraumatic Removal of Defective Crowns
Balancing: The Art, Science and Business of Dentistry
Intra-Oral Preparation of Titanium Abutments in Order to Obtain Ideal Angulations and Contours
SS White Express Line High Speed Laboratory Metal Finishing Burs
Direct Preparation Of Preexisting Implant Abutments For Case Rehabilitation
Flextime Xtreme: The 80/20 Rule
Fast and Smooth - Efficient Crown Preparation With Carbide Instruments
When Advancing the Bur, One Can Feel the Presence of Dentinal Caries
Precision Trimming and Finishing of Current Dental Restorations Using the Safe End Bur System
Indirect Restorative Tooth Preparation: Extreme Efficiency and Accuracy
Creating Maximum Efficiency and Accuracy In Indirect Restorative Tooth Preparation
Preparation Protocol To Ensure Predictable Aesthetic Restorations
Tooth Preparation Mastering Quality and Efficiency
Fissurotomy: Proactive Treatment for Incipient Decay
Anatomically Adapted Carbide Finishing Burs - Creating Super-Smooth Composite Surfaces in Two Steps
Directions for Use: Dr. David Clark Kit
Placing Traditional Sealants with Enhanced Magnification: Methodology to Increase Both Short-term and Long-term Success - David Clark, DDS
How to Quickly and Conservatively Restore a Natural Shine after Orthodontic Bracket Removal
SS White Surgical Length Oral Surgery Burs: Atraumatic Removal of Teeth for Maximum Bone Preservation

"Atraumatic Removal of Defective Crowns"

Howard E. Strassler, DMD, FADM
Professor and Director of Operative Dentistry
Department of Restorative Dentistry
University of Maryland Dental School
Baltimore, Maryland

Over the years, many devices have been designed to remove crowns and bridges from abutment
teeth.^1-5 These crowns and bridges may be fabricated from dental acrylics cemented to the abutment teeth with nonrigid temporary cements, or they may be definitive restorations fabricated from cast metal, porcelain-metal, ceramic, or composite resin cemented with more rigid cements. While the removal of temporary crowns and bridges is usually very straightforward, the removal of a definitive cast crown with an unknown cement is more challenging. For a temporary crown or bridge, the restoration can be removed using a hand instrument, usually a scaler or large spoon excavator, or crown-removing pliers or a hemostat exerting force parallel to the long axis of the tooth. The crown or bridge is gently moved until the cement seal is broken. The restoration is then easily and atraumatically removed by breaking the weak cement seal between tooth and restoration.¹

Unfortunately, the routine removal of temporary restorations does not parallel the decisions that must be made when a patient presents with a defective crown and bridge that need to be removed and replaced with a new restoration. The same techniques used for the removal of temporary restorations can lead to disastrous results. While there are many designs of crown removers that use a bumping force created by a weight sliding on a bar or an air-driven motor to knock the crown or bridge off the tooth, these devices are radical and can cause considerable damage.² When a crown-and-bridge bumper is used to remove an existing restoration, the practitioner usually doesn't know what cement was used to place the restoration. Whether a highly retentive, adhesive resin-modified glass ionomer cement or resin cement was used, or a traditional zinc phosphate cement, the overriding goal when removing the crown or bridge is to do it without causing any damage to the abutment tooth, the periodontal supporting apparatus, or the pulp. A crown bumper, even if it is well controlled, can cause fracture of the crown of the tooth, root fracture, pulpal injury, or injury of the periodontal ligament. The author has personally witnessed defective crowns and bridges that, when removed with a crown bumper, have either fractured the abutment tooth at the gingival line, fractured the root, or luxated the tooth out of the socket. In several cases, the tooth needed endodontic therapy. The dental students or practitioners did not know how to control the forces of the device, nor did they know how many hits on the tooth were necessary before changing techniques. For this reason, the rationale and technique for safe and atraumatic removal of defective crowns and bridges using a Great White® dentated bur (SS White Burs, Inc.) and a Christensen Crown Remover (Hu-Friedy® Manufacturing Co., Inc.) are presented in this article.

Unique Characteristics of the Great White® Bur

Not all burs are created equal. Burs are designed with different flute numbers and configurations specific to the tasks they are to accomplish. Finishing burs have more flutes that are closer together for the finishing of dental materials. Operative preparation burs have fewer flutes that are either straight-bladed (plain) or crosscut. Straight-bladed burs cut smoothly but are slower, especially with harder materials; crosscut burs can cut faster but create more vibration. Great White® burs are engineered to be more dentated than crosscut burs and have a unique geometry in the design of their blades, which creates a bur that cuts quickly with less vibration when cutting into tooth structure or dental materials. This translates into less stress on the tooth, its supporting periodontal structures, and pulp. Also, because there is less bounce when initiating a cut, less stress is placed on the bearings of the handpiece. Since many times clinicians cannot know what type of metal was used for a crown, an aggressive metal-cutting bur should be used. The Great White® fulfills this requirement and is an effective and efficient bur for removal of amalgam, composite resin, cast gold, and direct gold restorations that need replacement. It can also be used for tooth preparations and endodontic access through tooth, crowns, or other restorative materials.

Case Report

A 62-year-old patient presented with a porcelain-metal crown on the mandibular first molar that had evidence of caries and a defective facial margin (Figure 2). The decision was made to replace the crown. To temporize the preparation once the crown was removed, an intraoral template was fabricated by making an impression of the defective crown with a medium-bodied vinyl polysiloxane impression material (Imprint^TM II, 3M Dental Products) in a bite impression tray. After the crown was removed, an automixing bisacryl composite temporary resin (CBV Temp, Den-Mat Corporation) was placed into the imprint of the crown to fabricate the temporary restoration.

Figure 2 Defective porcelain-metal crown on the mandibular first molar

A 62-year-old patient presented with a porcelain-metal crown on the mandibular first molar that had evidence of caries and a defective facial margin (Figure 2). The decision was made to replace the crown. To temporize the preparation once the crown was removed, an intraoral template was fabricated by making an impression of the defective crown with a medium-bodied vinyl polysiloxane impression material (ImprintTM II, 3M Dental Products) in a bite impression tray. After the crown was removed, an automixing bisacryl composite temporary resin (CBV Temp, Den-Mat Corporation) was placed into the imprint of the crown to fabricate the temporary restoration.

Figure 3 A Great White #1 bur cutting though the gingival margin of a porcelain-metal crown

Figure 4 A Great White #1 bur sectioning the facial surface of the crown

Figure 5 The crown is sectioned. The underlying dentin can be seen

To remove the defective crown, the tooth was anesthetized. A Great White® #1 was used in a high-speed handpiece with water spray to cut through the facial surface of the porcelain and metal. The gingival margin was sectioned first (Figure 3). The facial surface was then sectioned to the buccoocclusal line angle (Figure 4). The patient was told to be aware that, during the crown removal process, there would be cracking noises as the porcelain fractured from the metal of the crown.

When cutting through the existing crown, it is important that:

- The initial cut is made to visualize the metal of the crown, the cement line, and dentin of the crown preparations when you have cut through the metal (Figure 5).

- When sectioning the crown, the tooth not be cut into creating a notch; this can create a hazard to the tooth when the flat end of the crown splitter is placed into the notch as a purchase point to pry the crown apart.

- The crown be sectioned completely through the most gingival portion of the crown margin, so that when the crown is pried apart, there is no intact metal holding it together.

Once the crown was sectioned through to the buccoocclusal line angle, the Christensen Crown Remover tip was used to pry the crown apart (Figure 6). The Christensen Crown remover, designed by Gordon Christensen, DDS, has a notched tip and mini-elevator handle that provides for a secure grip and excellent control when breaking the cement seal of a sectioned crown (personal communication, Dr. Gordon Christensen, fall, 1997). In this case, it was necessary to cut to the occlusal surface so the crown could be pried apart. For anterior crowns, it may be necessary to cut through the incisal edge, and in some cases when a more adhesive resin cement was used, it may be necessary to section the crown through to the lingual surface.

Figure 6 The Christensen Crown Remover tip set into the notch. Note the gauze placed on lingual of the crown to catch any porcelain that fractures when the crown is pried apart

With the crown separated on the facial and occlusal surface, the flat ended tip of the crown splitter was placed into the facial slot and twisted, prying the crown apart. This prying apart broke the cement seal. The crown visibly shifted on the tooth (Figure 7). With the crown loosened, it was easily removed with a curved hemostat. Note the fractured porcelain and the sectioned crown (Figure 8). With the crown removed, the preparation could now be refined and temporized (Figure 9).

Figure 7 The crown is pried apart. Note the crown has dislodged from the tooth preparation

Figure 8 The crown after removal. Note the disto-occlusal porcelain that fractured during prying

Figure 9 The tooth preparation, ready for refinement and temporization

Conclusion

Once the decision is made to remove rather than repair a defective crown or bridge, it is removed from the abutment tooth or teeth in an atraumatic manner. Using the materials presented in this article, the task was found to be safely and easily accomplished.

1. Rosensteil SF, Land MF, Fujimoto J: Provisional restorations in Contemporary Fixed Prosthodontics. St. Louis: Mosby Books, pp 412-413, 2001.
2. Pruitt CO: A review of methods and instrumentation for removing crowns and bridges from prepared teeth. Gen Dent 42(4):320-326, 1994.
3. Parreira FR, O'Connor RP, Hutter JW: Cast prosthe-sis removal using ultrasonics and a thermoplastic resin adhesive. J Endodo 20(3):141-143, 1994.
4. Sutherland JK, Cheeseman SL: Multiple prosthodon-tic uses for permanent crown remover forceps. J Prosthet Dent 77(1):99-101, 1997.
5. Williamson RT, Breeding LC: Removing a cemented fixed prosthesis using a crown remover. J Prosthet Dent 69(6):634-635, 1993.