When it comes to developing a successful treatment plan, few things are as important as the need for accurate, usable bite records. In fact, Dr. Peter Dawson believes that one of the biggest—but yet easily fixable—flaws most dentists make is not verifying that the intended joint position is both achieved and recorded accurately. Not only does this oversight lead to frustration, wasted time, and errors in treatment planning, not properly recording your patients’ centric relations can and will cause unacceptable grinding on new restorations. That’s why it’s imperative for complete dentists to take the time and effort needed to ensure they attain accurate, usable bite records.
First and foremost, it’s important to remember that the preciseness of the determination of centric relation can easily be lost if not matched by the preciseness of the intraocclusal bite record combined with an acceptable facebow record. What’s more, some dentists will argue that it’s nearly impossible to repeatedly find centric relation. However, tests have proven that centric relation can be reproduced on mounted casts to needlepoint accuracy. And best of all, it’s a process that can be learned in just a few hours time. But, you must be certain to stay clear of the following problems that may impact the accuracy of your bite records:
· Improper manipulation
· Lack of guidance or verification of centric relation
· Flimsy bite-recording materials
· Too-deep indentations in the bite material
· Use of easily distorted, soft waxes
· Nonexistent indentations in the bite record
· Unstable bite-recording materials that may warp or distort
Despite all these possible problems that may impact the accuracy of any bite record, it still remains the best way to accurately verify a patient’s centric relation. That’s why you should keep the following five criteria in mind as you make an intraocclusal bite record:
· The bite record must not cause any movement of teeth or displacement of soft tissue.
· It must be possible to verify the accuracy of the interocclusal record in the mouth.
· The bite record must fit the casts as accurately as it fits the mouth.
· It must be possible to verify the accuracy of the bite record on the casts.
· The bite record must not distort during storage or transportation to the laboratory.
When attempting to verify centric relation, all five of the above criteria should be met, especially if you choose to take a wax bite record, easily the most popular method of recording centric relation. The following will illustrate how:
1. Choose the right type of wax. Although wax is the most popular method for recording CR, it is also the most easily abused. That’s because the quality of the wax can have a profound impact on the quality of the records. For example, the wax must be soft enough so the teeth do not move during recording. What’s more, once the wax is cooled it must remain brittle hard, so no damage can be done to the wax during transport or mounting. The right kind of wax should break with a snap when it is bent.
Although you are certainly free to choose whichever wax you like, Dr. Dawson highly recommends Delar wax, which is a brittle-hard wax that is supplied in wafers that are thicker at the front for more even penetration by the teeth from back to front.
2. Soften the wax. Since the wax is so hard, it will be necessary for you to soften it through the use of a small torch, being careful not to overheat the wax. Be sure to flame both sides of the wax carefully, striving to attain a slight shine on both sides of the wax. You’ll then want to allow a few seconds just for the heat to penetrate the wax.
3. Insert in the mouth. Once the wax has been softened to a slight sheen, you’ll want to begin the actual process of recording the bite. Insert the wax into the patient’s mouth and place it against the upper arch, pressing against the arch to ensure you indent the wax with the teeth.
4. Manipulate the mandible. Now that the wax has been comfortably placed into the patient’s mouth against the upper arch, ask your assistant to hold the wafer in place to free your hands for mandible manipulation into centric relation.
5. Verify centric relation. Once the wax has been seated against the upper arch and you have had the chance to place your hands on the lower jaw for manual manipulation, you’ll want to make sure the joints are properly seated. Take the time here to load test your patient to ensure the joints are in the appropriate placement.
6. Have the patient close into the wax. Maintain firm, upward pressure on the condyles as the patient closes into the wax. If not, patients may have a tendency to protrude at the start of closing into anything between the teeth.
7. Check the premolars. At this point, you want to make sure the first premolars have made a definite indentation in the wax. This step will help make sure that the posterior teeth will recorded with indentations that will hold the casts in a stable relationship with the bite record.
8. Remove the wax and begin trimming it. While the wax is still warm, you want to remove it from the patient’s mouth and begin trimming it back to the indentations of the buccal cusp tips so the fit of the bite record can be verified in the mouth. You’ll also want to make sure that you have made a perfect tooth-wax-tooth fit by checking for voids or cracks between the teeth and the bite record.
9. Verify the bite record. Now is the moment of truth. Submerge the wax into a glass of cold water to return it to a brittle-hard state. Then, return the wax to the mouth and seat the condyles and load test the patient for verification of centric relation. Hold the condyles firmly in centric relation while the mandible hinges to bring the teeth into maximal contact with the bite record. Make sure that both sides of the arch contact simultaneously with no premature contact or deflection into the hard wax. Finally, make sure that there are no voids between the teeth and the wax at complete closure.
10. Check for soft tissue impingement. You’ll now want to examine the bite record to that it is not being effected by any soft tissue. If there is any soft tissue contact at gingival margins, take this opportunity to trim these sections back. If you find that the wax is difficult to manipulate, feel free to re-soften the wax with the torch once again. However, be certain to only warm the wax where the indentation of the teeth has been made. You can then re-insert the wax and place it back against the upper teeth and mandible, closing the patient into it to adjust it as necessary. Once inserted, it should extend directly across the arch without touching any palatial tissue.
11. Store in water. Now that you have verified centric relation and made an accurate bite record, you’ll want to store the wax until you use. The easiest way to do this is to float it in a cup of water in a sealed plastic container, such as a Tupperware jar. One of the more common mounting problems can be attributed to casts that haven’t been carefully handled.
Although some may argue that taking a wax bite record is the most time-consuming process for verifying centric relation, chances are that they’re not doing it properly. In fact, the wax bite technique is the simplest and fastest way to record centric relation. What’s more, it is also the most accurate way to mount casts, because the casts fit neatly into the record with very little movement.