Sens Tooth
Thursday November 7 , 2002

Dear Dr. Mady: Just over a year ago I had a back molar's filling replaced with a new white filling since it was leaking. Since then I experience sensitivity to "cold" on initial contact. Simultaneously I hear a "snap" or "crack" sound in the tooth. The dentist examined my tooth and said it looked ok. What could be causing the sound and when should the sensitivity go away? -Kathy C.

Dear Kathy: It is possible that there is one of a few different scenarios taking place here. You have to realize that I have not examined your tooth so my speculation is merely derived from your brief description.

Very often after a new filling is placed or an old restoration is replaced with a new one, the tooth can become sensitive. This sensitivity is usually a reaction to hot and cold if it is present, but often will disappear within a couple of weeks after treatment is completed.

The cause can be attributed to marginal leakage of your new resin restoration, or from the filling depth being so large that it approaching very close to the pulp or nerve of the tooth, or from a high bite that is keeping the nerve irritated. There is also a possibility that your tooth has a crack in it.

If the integrity of the margins is the culprit, your dentist will merely have to re-seal those margins with resin bonding agent and composite resin. This may instantly correct the sensitivity problem especially if combined with a desensitizing procedure and fluoride treatment.

If the restoration is so deep due to previous leakage and caries (decay) or from fracture, then the pulp of the tooth may be constantly attacked and may even be necrotizing or degenerating slowly. In this case temperature sensitivity can be extremely prevalent. It is when the temperature sensitivity lasts longer than a few seconds and even lingers into an ache, that root canal therapy may be indicated. This is where the nerve of the tooth is removed from within the root(s) and replaced with a rubber-like material and then the tooth is strengthened with the proper type of restoration.

Whenever a dentist places a filling, they always check the bite pressure on the tooth in question with articulating paper. This is an ink paper that marks any high spots on the tooth during biting and those areas can then be adjusted and polished. Occasionally the patient may not bite the same way when frozen as they do when eating or when the freezing goes away. If this is the case and if the bite is left even slightly high or causes even a bit of interference during chewing, you may hear sounds as the tooth is hit, or a situation known as Acute Reversible Pulpitis may exist. This is an inflammation of the nerve that is reversible if your dentist calibrates the bite properly. The theory behind this is that if one tooth has even slightly more biting pressure on it than the others, then each time you chew, that particular tooth takes more force than the rest of the teeth. The muscles of mastication used for chewing are extremely powerful and this minor discrepancy can make a huge difference. It sounds like this may be the closest thing to what it happening to you here.

If the bite is adjusted to be optimal, and the problem still persists only when biting, then your dentist may want to investigate the possibility of a cracked tooth and placement of an onlay or crown if all variables warrant it. If a crack is not diagnosed, another option prior to root canal treatment and crown fabrication is filling replacement. Some composite restorations shrink as a result of excess polymerization shrinkage during light curing of the material, for various reasons including type of material and amount placed at each increment. If this is the situation, the shrinkage can cause the bonded cusps of the tooth to be slightly pulled together. If this occurs, then each time you bite directly on that tooth, you will experience a sharp shooting pain. Typically you will not feel cold sensitivity from too much polymerization shrinkage, but you may if the material closest to the pulpal floor or nerve is not cured or hardened well. In this case the sensitivity may never resolve itself.

It sounds like the best option for you is to have your dentist re-check and fine tune your bite in that area, re-seal the margins and contemplate further investigation including filling replacement or temporary sedative filling placement if required. If this does not help, root canal treatment and crown fabrication may be an option, especially if the problems you are having are decreasing your everyday quality of life.

This column is reprinted with the permission of the author and The Windsor Star. "Ask the Dentist" is written by Windsor dentist (and ECDS member), Dr. David Mady Jr.. The column appears the first Thursday of each month in the Windsor Star. Readers with questions can write to "Ask The Dentist", c/o The Windsor Star, 167 Ferry St., Windsor Ontario, N9A 4M5



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