Case Study: A Digital Solution for the Classic Cracked Tooth

Monday, October 21, 2013

A common problem for our patients, teeth with single cusp fractures are a regular part of a dental practice. When they have a horizontal fracture, these teeth can be easily restored with a chairside CAD/CAM system, as in this case completed with CEREC by Sirona Dental Systems.

The patient presented with a fractured cusp.

Fig. 1The patient presented with a fractured cusp.

The patient presented during an emergency visit with a disto-lingual cusp fracture, horizontal in nature (Fig. 1). She had been chewing on ice when it fractured. Knowing this, it was anticipated that other cusps were in jeopardy of fracturing as well. With removal of the composite, a crack line was seen under the mesio-lingual cusp as well, and an onlay for both cusps was planned. Because the mesio-lingual cusp had not fractured, more tooth structure could be left in the area, remained supragingival, and the preparation continued to the fractured area of the adjacent cusp.

A scan of the prepared tooth captured with the CEREC Omnicam.

Fig. 2A scan of the prepared tooth captured with the CEREC Omnicam.

The subgingival area of the disto-lingual cusp was easily accessed with a diode laser. Both contacts were opened in order to support the end of the fracture lines and restore incipient carious lesions. Because the buccal cusps appeared intact, they were left as is, and a conservative preparation completed (Fig. 2).

The preparation quadrant, opposing quadrant, and an articulating “bite” imaging session were completed with the CEREC Omnicam. This took about 2 minutes in total, and the scan was even used to analyze the preparation. Analysis of the preparation is a major advantage for dental digital impression systems. The preparation can be seen live through the video stream, and in color. This allows the clinician to see areas that need improvement such as margin smoothness, draw, divergent walls, etc. If something should be corrected, it can be done at that moment and a new scan can then be taken.

The onlay restoration is designed in the CEREC software.

Fig. 3 The onlay restoration is designed in the CEREC software.

The CEREC software utilized a mathematical calculation to determine the proposal, and the contacts were customized (Fig. 3). The onlay was then milled out of an intermediate stage of the lithium disilicate material, e.max CAD (Fig. 4). Because it has minimal shrinkage during crystallization, the intermediate restoration can be tried in the mouth and the fit confirmed (Fig. 5).

The onlay is digitally seated in the IPS e.max CAD block prior to milling.

Fig. 4 The onlay is digitally seated in the IPS e.max CAD block prior to milling.

Because of the material’s minimal shrinkage, the milled onlay is tried in prior to crystallization and finishing.

Fig. 5 Because of the material’s minimal shrinkage, the milled onlay is tried in prior to crystallization and finishing.

The onlay was crystallized in a speed cycle which only takes fifteen minutes, and then bonded in with Multilink Automix Self Adhesive Resin Cement (Fig. 6). Total time for the emergency visit was just about an hour and thirty minutes, but most importantly the patient left with great enthusiasm for the speed and effective treatment I provided via chairside CAD/CAM technology and said she will be referring her friends because of it.

The case was completed in approximately 90 minutes.

Fig. 6 The case was completed in approximately 90 minutes.

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