Taking the Guesswork Out of Tooth Placement

Jim Collis, CDT; and Jeffrey Slovick, DDS

August 2015 Issue - Expires August 31st, 2018

Inside Dental Technology

Abstract

When replacing an existing removable appliance when tooth arrangement needs to be revised, mounted study casts and the utilization of a silicone index accurately capturing the bite rim can contribute greatly to the successful placement of the teeth in the new setup. Accurate tooth placement eliminates or reduces the number of resets.

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Efficiency and accuracy are crucial to any restorative dental process. Minimizing the patient’s time in the dentist’s office is beneficial for all parties. When replacing an existing removable appliance, certain proactive measures taken by the dentist and technician can optimize the accuracy of the tooth placement and eliminate or reduce resets.

Case Report

A patient presented with the desire for a full upper denture to replace an existing upper denture, with opposing natural dentition. The patient said the existing upper denture showed too much of the teeth and desired the replacement denture’s tooth line to be higher. The patient was satisfied, however, with the facial placement of the teeth for lip support on the existing denture. The treatment team decided to raise the tooth line by approximately 2 mm to present a more natural appearance. At a later date, the lower dentition will be replaced with a partial denture when the patient’s budget permits.

A discussion between the dentist and laboratory was the basis for the development of the treatment plan for this. From the laboratory’s perspective, certain procedural items are necessary to achieve a more predictable outcome. Without these items, the laboratory must rely on guesswork. For this case, these items included a contoured bite rim (with the midline, high lip line, and cuspid lines clearly marked), an opposing study model, and a study model of the preexisting appliance. Together, these items help dental teams better identify a more precise placement of the anteriors for esthetic purposes.

The final upper cast was mounted using a KaVo PROTARevo 7 (KaVo, kavo.com) fully adjustable articulator and KaVo’s jig for average value articulator mounting (which is compatible with all KaVo articulators) (Figure 1). Next, the lower model was mounted to the upper cast with the contoured bite registration. A silicone index was made of the upper incisal edge of the rim in reference to the lower cast (Figure 2). The upper cast was removed from the articulator (which was facilitated by the magnetic mount), and a study model of the old denture was mounted to the lower cast. The study model of the old denture served as a reference to mark the position of the upper anterior teeth from the old upper denture onto the lower cast (Figure 3). This provided a point of reference to show how to adjust the teeth upward on the new denture. The plane of occlusion on a contoured bite rim does not always reflect where the incisal edges of the anterior teeth should be set, unless the dentist adjusts the incisal edge in the wax rim. In this case, the patient had an overbite, the incisal edge of which can be difficult to capture in a bite rim. For this reason, it was desirable to use the lines drawn from the study model and cross-reference them with the incisal edge of the bite rim for more precise tooth placement.

The author’s preference is to keep the rim intact for future reference. The rim contains valuable information that is lost if the laboratory sets the teeth onto the rim, even if the technician follows the lines and dimensions that the dentist set forth in the rim. Keeping the rim intact allows for later verification. If the dentist decides to make changes at the try-in stage, the original contoured rim would still serve as a guide for the adjustments. To keep the original contoured rim intact instead of setting the teeth into the rim, the author used a silicone index as a guide (Figure 4). This similarly serves as a guide to indicate whether the teeth should be moved up or down, buccal or facial. In this case, the dentist was able to accurately capture the incisal edge on the occlusal rim, so the teeth could be set to the silicone index.

The teeth used for the setup were Veracia SA (Shofu, shofu.com). When the setup was completed, the treatment team measured from the incisal edge of the try-in to the markings drawn from the study model on the lower cast, and the desired 2 mm of upward movement of the anterior teeth on the new setup was verified.

The case was sent to the dentist for final try-in to verify the bite, placement of the teeth, and occlusion. To further enhance the appliance, the base was naturalized using Ceramage Gum Color composites (Shofu) (Figure 5).

Conclusion

The laboratory must be proactive in communicating with the dentist not only about the treatment plan but also with respect to the procedural items needed to better ensure a successful outcome for the patient. Gathering these items minimizes the number of try-ins and appointments needed. In this case, because the laboratory was replacing an existing upper appliance, the laboratory needed a marked contoured bite rim, an opposing study model, and a study model of the preexisting appliance.

The information contained in these items allowed the laboratory to fabricate a try-in that satisfied the treatment plan in a timely and accurate manner.

Disclosure

This article was supplied by Shofu.

About the Authors

Jeffrey Slovick, DDS
Private Practice
Elmhurst, Illinois

Jim Collis, CDT
Owner of Collis Prosthodontic Laboratory
Mount Prospect, Illinois

Fig 1. Upper cast mounted using the average value mounting jig.

Figure 1

Fig 2. Silicone index of upper rim in reference to the lower cast.

Figure 2

Fig 3. The study model mounted to serve as a point of reference.

Figure 3

Fig 4. Silicone index in place with new base plate for setting of teeth.

Figure 4

Fig 5. Final naturalized wax try-in using colored wax.

Figure 5

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SOURCE: Inside Dental Technology | August 2015

Learning Objectives:

  • Recognize the importance of communicating with the dentist regarding tooth placement.
  • Understand how mounting a study cast of the existing appliance can be used as a reference for tooth placement.
  • Appreciate the value of using a silicone index to capture and verify records.

Disclosures:

The author reports no conflicts of interest associated with this work.