Considerations for vital teeth with porcelain fused to metal Crown
1. vital teeth with PFM Crown tooth preparation, Physiology, histology based fixed restorations of the basic principle is to do everything possible to save the energy, reach under the premise of restorative treatment, should be minimal cutting tooth structure. Tooth preparation and standards worn generally in reaction within the limits of the dental pulp. Damage of the dental pulp dentin and is worn, cut heat and is proportional to the resistance of the dental pulp. Dental pulp reaction size is measured by reaction of the cell layer of dentin. When it comes to cutting dentin dentine layer cell osmotic pressure and lower levels of infiltration, heavy nucleus being human dentin tubules, a large number of inflammatory cell infiltration, Pulpal hyperemia and pulp inflammation occurs. In addition, the older patients with aging generation of secondary dentine, pulp cavity become smaller, pulp treatment sensitivity decreases. Instead, constant pulp cavity in patients under 18 years of age, and Medullary angle and the mandible occurs is not yet fully mature, should be applied to PFM restoration, but patient exception to have root canal treatment.
2. tooth preparation operation points for attention of vital teeth grinding tooth preparation procedure should be strictly controlled in addition, positioning worn parts should be maintained and even distances of the Medullary cavity, while the procedure that must be used in cold water to cool and needle removal is not pressurized. Swendlow experiments: application of cooling methods to prepare cavity, cord thickness of only 0.3mm, not caused by endodontic lesions, generally in vital teeth tooth preparation can keep 1.0mm from the Medullary cavity (dentin and enamel thickness greater than 2mm). All in all, vital teeth, and should not be worn too much, so as not to damage the dental pulp, nor worn out too little, that restore the Crown shape is too large, or disclosed bottom metal color, affect the appearance, or a lack of bottom and the thickness of the porcelain, impact strength and restorations of Crown color.
3. the temporary Crown and its significance after the tooth preparation and completion impressions, you can use zinc oxide cement cement temporary crowns. Significance of the temporary Crown is: in addition to the prompt return of Crown shape, conducive to the appearance and features, more importantly avoid worn teeth are exposed and subject to external stimuli. Also prevents elongation of the jaw teeth, tooth preparation to maintain occlusal space.
4. after disinfection and cemented PFM try is complete, disinfection, bonded. Disinfectant substitute alcohol with Thymol, which has good permeability, stimulate the pulp. Cement porcelain Crown is vital key factors for success, preferably using water soluble cement zinc polycarboxylate, for its good bonding properties, particularly strong adhesion to dentin and metal, contains sodium monofluorophosphate ingredients, no free acid in the mix, and help secondary dentin formation. In clinical practice on zinc phosphate cements in vital teeth is disabled, because of its free phosphoric acid ingredients can irritate the pulp nerve, cause further damage to the odontoblasts.