Clinical Instructions for the Dentist
How to use the cracked tooth model in a clinical practice.

1. Ask the patient at the new or recall exam if they have any occasional biting sensitivity to foods like grain bread or muesli or have sensitivity to hot or cold (print this question on new patient forms).

2. If yes, check all posterior teeth, especially heavily filled ones, using the the 'Tooth Slooth'@ or 'Frac Finder (this applies pressure to each cusp selectively and will reveal any painful cracks).

3. If they have sensitivity to hot and/or cold question them about biting sensitivity. In many cases, a crack in the tooth will lead to temperature sensitivity because of bacterial entry to the tubules via the crack, and the sucking/pumping action caused by flexure within the tooth results in subsequent inflammation of the pulp. Differential diagnosis to consider includes caries, trauma, abfraction or abrasion and erosion.

4. When using the tooth slooth, make sure the patient bites at "critical mass" pressure. This means that in order to correctly diagnose the problem, you have to get the patient to bite hard enough to simulate conditions in the mouth during normal, "absent minded" chewing. During normal chewing, a piece of grain may suddenly put significant and unexpected pressure on the cusp and flex it sufficiently to cause pain. False negative readings can be obtained because the patient is being too timid ? often because they know it will hurt when you get the right spot.

5. When a diagnosis of cracked cusp is made show them the filling side of the model. Put your finger on the cracked cusp and push it out and use wording such as ? "When you bite on your tooth, sometimes you get food pressure on one corner of the tooth, and it flexes out microscopically like on this cross section. The crack goes into the sensitive part of the tooth and hurts the nerve inside here and lets bacteria in that make it react to hot and cold. Just like a crack in a glass windscreen, it usually gets bigger with time, and can cause the nerve to die, and probably start an abscess, which would require root canal therapy."

6. I once had a patient who insisted I replace his PFM crown at my expense because I drilled a hole in it for endo. Unfortunately, when expense is involved, patients do not necessarily think fairly or rationally and you would be unwise not to take this into account in your case presentation. According to case presentation experts Korpi and Hendrikensen it is important for the patient to fully own their problem [psychologically]. If you talk too much and IMPOSE a solution on them with out them actively seeking it [some would say begging for it], then if something goes wrong with YOUR crown then in their mind YOU should fix it. And of course a percentage of cases will require endodontics and even extraction, so this IS going to happen to you at some time. Therefore it may be best to pause a moment after you have presented the model to let them reflect on their problem and even ask you what can be done. Then you can present the treatment options FROM THE BOTTOM UP ? explaining the difficulties inherent in each of the inferior options e.g. ortho band, then concluding with what 1 have found to be far and away the most predictable and reliable solution ? full coverage with a PFM. Even an Empress@ onlay is not predictable.

7. To explain the solution, try something like this:"The problem is the crack in your tooth, not the filling, and we have to splint it together to stop it opening and closing. You could put a new filling in there, but that doesn't stop the tooth flexing out (flex out the rubber model as you say this) ? I've tried it and it's a waste of money. The only real way to stop this flexing out is to bind it together with a cap or a crown so that the harder you bite the harder it squeezes the crack together, like this "Turn the model to show crown cross section. (NB You can, if you wish, put a cut in the crown side of the model to simulate the crack ? simply use any sharp knife. You can also put a secondary cut in the other side to show a midline crack which is very serious).......

8. Now cover yourself for the cases that go bad ? "Even with the best treatment, some nerves go on to die regardless of what we do. So you are fully informed of all the possible problems I want you to read this brochure (Give them the Cracked Tooth Syndrome Patient Education Leaflet included with this model, or similar). You have now warned them about the risk of endo or possibly extraction, and the chance of needing a hole drilled through their new crown. Make sure you or your assistant record ''PEL 2a given" on the patient's card, as your record of exactly what information you gave the patient, so you are protected later on.

9. Schedule the crown prep appointment. You can discuss the risk factors and cementing option's now or later. For permanent cementing Gluma 3@ and Fuji Plus@ work well ? or for long term temporary cementing (until the pulp status is determined) ? use super EBA very soft 1 RM, Ledermix @ cement, or Tempbond@ with or without notches cut into the crown and prep to improve retention. These options are discussed in the Patient Education Leaflet, so read this first so you know what they are talking about.

We hope you enjoy using the Cracked Tooth Model and Patient Education Leaflet. In our experience it has nearly eliminated the problems that go with treating this difficult and often ongoing problem and has made it easier for patients to come to grips with their need for a crown, and any problems that flow from it.