What causes a crown on a dental implant to move?
Frequently, when a dental implant-supported crown appears to be moving, the attachment fitting that connects the crown to the implant known as the “abutment” has actually loosened. When this occurs, the crown may be very difficult to remove without damaging or destroying it. If the dentist determines that the abutment is actually loose, and not the crown, there are generally two options.
If the crown can be separated from the abutment without damaging it, removing the crown and re-torquing the abutment retaining screw can be done. It may be a good idea to replace the abutment retaining screw. It is also a good idea to torque the retaining screw to the recommended setting, wait 10 or 15 minutes, and re-torque it. This compensates for cold-flow of the threads (or thread “creep”), which may occur—depending on what material the screw is made of.
If the crown cannot easily be removed from the abutment, the second option is to drill a hole through the crown to try and expose the drive socket of the abutment retaining screw. It may then be possible to retorque the abutment retaining screw through the crown. After this is done, the drive socket is filled with silicone, wax or other easily removable material, and a filling can be placed in the access hole.
Repeated loosening of abutment screws may be a sign that the implant is experiencing abnormally high biting forces. It may be necessary to remove the crown and abutment, and to fabricate a new implant crown which is stabilized by joining it to a neighboring tooth or crown. There are many ways of doing this, including two conjoined crowns and use of keyway attachments. The patient’s periodontal health and oral hygiene must be carefully considered before splinting two adjacent crowns, because cleaning between the two can be difficult. The occlusion should be evaluated and adjusted as necessary, and use of an occlusal guard may be recommended to further protect the implant abutment from loosening.
My temporary crown is loose. What should I do?
If you have recently had a tooth prepared for a crown, a temporary crown was likely placed. Temporary crowns are used for two main reasons:
- to minimize sensitivity of the exposed dentin (unless the tooth has had endodontic treatment)
- to prevent the adjacent and opposing teeth from changing positions relative to the prepared tooth
When a tooth is prepared, an impression is made to record not only the shape of the preparation, but also the precise location of the neighboring teeth in space. This allows the permanent crown to be made which will fit precisely into its proper position with the other teeth. If teeth move, the recorded position will no longer be accurate, and the permanent crown will not fit without adjustments. Significant adjustments can decrease the service life of the new crown.
If your temporary crown is loose, call and inform your dentist, so that the crown may be evaluated. If the crown stays in position and the tooth is not sensitive, the urgency for getting into your dentist may not be as great; however, if the crown comes off, it is important to get it back into position within a day, or teeth are more likely to move.
My permanent crown is loose. What should I do?
When a crown which has been successful in the mouth for an extended period of time loosens, it is often the underlying core buildup that has loosened. In such cases, the core buildup and crown may need to be redone. It is important to weigh the cost and likelihood of long-term success of replacing the core and crown against removing the tooth and replacing it (for example, with a fixed bridge or dental implant). Sometimes a loose crown which does not dislodge completely is due to a fracture in the roots. This is generally a serious problem and frequently results in loss of the tooth. If your crown is loose, see your dentist as soon as you can—especially if the tooth is painful, or you have swelling.
My temporary crown came off. What should I do?
Temporary crowns commonly dislodge and are often lost or swallowed. It is important that they be replaced, within a day if possible, to avoid movement of the adjacent and opposing teeth. Otherwise, the permanent crown being made to fit precisely with the other teeth may not fit, or may require excessive adjustment that can decrease its service life.
If your temporary crown has come off, let your dentist know. If a large piece of the tooth or core buildup is in the crown, it may be necessary to re-do the core buildup, crown preparation, and impression. Small pieces of core buildup or tooth structure which do not include the margin may fill in with crown cement when the permanent crown is seated. Only a dentist can tell for sure.
If you still have the crown, you can often hold it in place with a small dab of either toothpaste or petroleum jelly. You can also purchase temporary crown cement at most pharmacies. If your final crown is to be made entirely of ceramic, which will be bonded onto your tooth (as opposed to cemented traditionally), you may want to avoid temporary crown cements containing eugenol. Eugenol is an oily substance derived from cloves, which has the desirable property of soothing the nerve inside teeth with exposed dentin. However, it can also impair the bond strength of the bonding resin your dentist plans to use to attach your crown to your tooth.
My permanent crown came off. What should I do?
Crowns which have been present in the mouth for prolonged periods of time sometimes dislodge. Often this occurs while eating hard or sticky food. Hard food can also dislodge the core buildup under the crown from the tooth—a serious event, generally requiring the buildup and crown to be redone, if it is feasible to save the tooth at all.
The likelihood of long-term success with a new core buildup and crown must be weighed against options for removal and replacement of the tooth, like dental implants and fixed bridges. If sticky food merely pulled the crown off, and the tooth underneath is intact, it is often possible for the dentist to sandblast the inside of the crown and re-cement (or “lute”) the crown back onto the tooth. The dentist will clean the tooth thoroughly, and check it for decay, or other problems before re-cementing the crown.
If you have a crown which has come off, you should try and get into a dentist within 24-48 hours so that the adjacent and opposing teeth don’t start to move. Otherwise, it may be difficult to get the crown to seat fully back onto the tooth without adjusting it. Look inside the crown to see if it appears to contain any residual core buildup material. In most cases this will resemble blackish-silver metal or tooth-colored plastic, and will generally have a white cement line around it. If there is buildup material in the crown, the crown may not stay in place very well if you try and reposition it on the tooth.
If the crown will not stay in place, there is a risk it could be swallowed or inhaled (aspirated). Aspiration of a crown is a rare but serious event. If you’re in doubt, don’t put it back in the mouth. Call a dentist and get in as soon as possible. Often, a tooth which has been crowned for a long time will not be sensitive when the crown comes off, so pain is often not an issue. Avoid chewing on the tooth while the crown is off. Remember it was probably crowned to avoid fracturing.
If you can reposition the crown and it stays in place fairly well–and feels normal when you bite–keeping it in place until you can see your dentist can prevent movement of neighboring teeth. Be careful when you eat that you do not swallow it. Call your dentist and ask his/her advice about keeping the crown on the tooth before you can get in to see them. Sometimes they will recommend holding it in place temporarily with an over-the-counter crown cement, available at most pharmacies.
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