Overcontour

Crowns should replicate the natural tooth being restored. If the crown is larger than the natural tooth it will trap bacteria which can cause decay or periodontal gum disease.

Symptons of overcontour include bleeding gums around the crown or darkening of the gum margin around the crowns . Before turning bluish at the gum margin the gums at the crown margin may turn red and bleed. Healthy gums do not bleed.

Malocclusion

After cementing the crown the dentist may need to make slight adjustments in the bite. If properly done it is usually not necessary to grind the opposing teeth in the opposing jaw. For instance, slight grinding of the new crown may occur for an upper crown but grinding the opposite lower teeth to accommodate the new crown should not be needed. If excessive grinding occurs the underlying metal of a new porcelain fused to metal may be exposed or TMD(temporomandibular disorder) or painful jaw spasms may result.

Inadequate embrasure space

New crowns should have adequate space to floss between the teeth. If floss shreds or is inaccessible the embrasure space between the adjacent teeth or crown is insufficient .

Biologic width space

New crowns should not impinge upon the underlying bone and connective tissue fibers overlying the bone . If crowns are prepared too deep the gum tissue in time will be irritated, inflamed and will recede or develop pathologic gum pockets.

Open Margin

The most common error is cementing a crown with unsealed margin that will leak and likely collect bacterial plaque with resulting decay and/or periodontal gum disease. Dentists should check circumferentially with a sharp explorer both before at try in and afer cementation for open margins. If marginal opening is diagnosed, the crown should be returned to the dental laboratory for construction of a new crown.

Shy margin

A crown which does not completely cover the prepared tooth surface over which the crown is designed to be cemented is defective and requires a new crown whose margin is not shy of covering the prepared tooth surfaces. Shy margins predispose to tooth sensitivity and the exposed dentin is vulnerable to decay.

Color

Patients with the dentist's assistance can pre-select a shade to blend with existing teeth or create an entirely new smile if multible teeth will be crowned. A natural tendency is for the patient to select the whitest shade in the shade guide. If too white a shade is selected the refrigerator look is not natural and may look like false teeth.

Midline

Crowns should be centered so that the midline of the lips match the center line separating the right side from the left side. A disharmony between the crowns shifted to one side or another from the midline of the lips is unesthetic.

Cant

The upper crowned teeth should be at the same level as a ruler level with the center of each eye. Otherwise the teeth will be tilted to one side and not level with facial features. A face bow should be used to establish a level plane of occlusion which is like a carpenter's leveler before sending the molds to the dental laboratory.

Longevity

Crowns are built to last for 10 or more years before wear or esthetic changes with adjacent teeth require new crowns

Bruxism

Grinding or clenching can cause excessive teeth wear or predispose to TMD (temporomandibular disorder) muscle jaw pain. Night guards worn over the teeth at night protect against excessive teeth wear on the biting surfaces.

Necessity

Decay or wear is the primary reason for crowning teeth. Overtreatment with excessive number of crowns is tempting for some dentists since crowns are the big ticket expense item in a dentist's profit statement. If in doubt, select another dentist for a second opinion after first obtaining a written estimate from the first dentist.

Alternatives

Bleaching and/or orthodontics is the most conservative, least invasive and least expensive alternative to crowns done for esthetic reasons. Bleaching can be done at home with bleaching trays provided by the dentist to lighten teeth color. Removable braces such as clear Invisiline provide a permanent solution without grinding the teeth down to stubs for crowns. Invisiline may be completed in months rather than the longer treatment with braces.

Other alternatives include adding plastic restorative materials such as the newer composites which can be done in one sitting and avoid waiting for the dental lab to construct crowns. For immediate esthetic needs, such as an upcoming wedding, composite can provide a less expensive, quicker and yet long lasting result.

Porcelain veneers only remove a portion of the outer enamel and some of the tooth side but avoids grinding the enamel off entirely or the backside of the tooth. There is a small 1 percent or less chance of a root canal from grinding the entire tooth for a crown. Root canals should be avoided entirely with a porcelain veneer placed on the upper or lower front teeth if correctly prepared into enamel only, rather than drilled past the enamel into dentin.

Specialists

Prosthodontists have completed two to three year specialty training in crown construction after dental school training. Most are members of the American College of Prosthodontists or may be Board certified as a diplomate of the American Board of Prosthodontics.

Cosmetic dentistry is not a recognized as a specialty by the American Dental Association since all dentists are trained to provide functional and esthetic restorations.

Institutes such as the Las Vegas Institute offer commercial weekend courses costing the dentist up to $l0,000 for the 2 day course. These short one or two day courses do not qualify the dentist to announce the dentist as an ADA approved an ADA approved specialist. At least 2 or more years of postgraduate specialty training is required to become an ADA recognized specialist in which the dentist must complete and pass exams. No written exams or skill testing is done with such short 2 day or even one week courses.

Baterica and Root Resorption

Crowns should replicate the natural tooth being restored. If the crown is larger than the natural tooth it will trap bacteria which can cause decay or periodontal gum disease.

Root resorption or root shortening occurs with orthodontic treatment . A minor amount such as a millimeter is not clinically significant if the roots are long pre-treatment. If one half or more of the root is resorbed, the tooth is at risk for premature tooth loss and is sensitive when chewing.

To avoid significant root resorption occurring the orthodontist should have ordered baseline pre-treatment individual periapical x-rays of each tooth in a full mouth set of x-rays. Panorex full mouth x-rays which use an external x-ray unit do not provide adequate detail of root length or shape.

Short, narrow or tapered roots predispose to root resorption and are a warning sign to the orthodontist to carefully monitor the patient during orthodontic treatment, particularly if treatment is extended past two years. Monitoring should include periodic individual periapical x-rays of the upper and lower incisor teeth which are the most vulnerable to root resorption. Also the orthodontist should check for excessive tooth mobility or looseness beyond ordinary looseness associated with orthodontic tooth movement.

If significant root resorption occurs, orthodontic treatment should be discontinued or at the very least a rest period of 3 to 4 month of no active tooth movement . When orthodontics is resumed, it should be done slowly and with monitoring x-rays of the resorped roots taken every 3 months.

During Teeth Cleaning

Orthodontic appliances collect bacterial plaque and increase the risk of gum disease during orthodontic treatment. Teeth cleaning every 6 months or sooner is a necessary preventive measure. At the cleaning visit the dentist or hygienist should use a periodontal gum measuring probe to check for diseased gum pockets and/or gum recession. Any diagnosed periodontal gum disease should be treated before orthodontics is continued.

Prevention

Gum disease is preventable with regular dental care. On initial and recall visits the dentist and/or hygienist should probe for gum pockets of 4 millimeter or greater depth and record 4 to 6 gum probe measurements per tooth on the patient's chart. Also teeth mobility, gum recession and bleeding on probing should be checked and recorded for later comparison at subsequent visits. Full mouth x-rays should be taken at the new patient exam and bite wing x-rays taken annually and full mouth x-rays repeated every 3 to 5 years. Periodontal bone loss is detectable on x-rays which indicate consultation with a periodontal disease specialist or periodontist. Gum surgery may be necessary to rebuild or repair lost bone with bone grafts to prevent tooth loss.

Short fill

Filling of the root canal should be within a half millimeter of the root tip or apex. Short fills, 2 millimeters or more, predispose to bacterial contamination of the underfilled root canal with resulting abscess or chronic inflammation necessitating extraction.

Overfill

Filling of the root canal should end at the root tip apex. Overextended filling materials can penetrate the underlying main sensory nerve in the lower jaw or into the sinus in the upper jaw. Persistent numbness and/or pain in the lip and chin is symptomatic of overfill of lower posterior teeth. A post-treatment x-ray will show the overfill. If overfill impinges the lower jaw nerve, a 3D x-ray should be taken and referral to an maxillo-facial microsurgeon to evaluate for immediate decompression surgery to remove the overfill before the nerve becomes irreversibly injured from chemical toxicity and inflammatory pressure.

Some root canal filling pastes are not FDA approved and contain harmful toxic paraformaldehyde and lead which mummify sensory nerves. No U.S. dental school recommend these pastes but a few dentists continue to mistreat patients with these pastes which are infamous for causing permanent lip numbness.

Perforation

Filing instruments or placement of posts on completion of root canal treatment may penetrate the root side and cause abscess or endodontic failure. Mid-treatment x-rays can avoid this mishap with careful measurements ensuring instruments are placed inside the root canal space and not off angled and out the root side.

Implants

Root formed implants surgically placed in the bone are predictably long lasting and are preferable to bridges for tooth replacement. Bridges necessitate grinding down adjacent teeth for replacement of a tooth and require bridge cleaners for flossing underneath the bridged false tooth.

Implants drilled too deep can penetrate the underlying main sensory jaw nerve and cause permanent lip and chin numbness and/or pain. 3D x-rays show the exact position of the jaw nerve and guide the surgeon pre-operatively where to place the implant drill to avoid injury to the jaw nerve. If severe pain and/or numbness persist one week after implant placement the implant should be backed out a thread or two or removed. A 3D x-ray will show if the jaw nerve was penetrated with the implant drill.