Intrinsic staining of the teeth, unlike extrinsic stains, can’t be treated with bleaching. Various causes of such discolouration can be any disturbance in normal tooth structure formation, like trauma, excess fluoride intake , taking medication (esp. tetracycline), vitamin deficiency or any hereditary disorder (eg: amelogenesis imperfecta, dentinogenesis imperfecta, and other developmental disorders).
Fluorosis of teeth occurs due to excessive intake of fluoride when tooth is getting calcified. Depending on severity, it affects both shape and colour of the teeth, hence compromising the cosmetics. Trauma to the developing tooth bud can cause hypoplastic defect which appears white in colour. Tetracycline stains and developmental disorders also produce characteristic staining and latter also cause changes in shape of teeth making them more prone to dental caries.
Treatment required for any of such condition depends on the severity of the discolouration and need to restore back the form of the tooth. Usually, microabrasion and macroabrasion do not provide satisfactory results in badly discoloured teeth which make patients conscious.
A definite treatment involves a partial coverage (veneers) or full coverage (crowns) of teeth with tooth coloured material. Crowns being more retentive than veneers because of the more surface area covered and the grip they take over the tooth, can be made of either entirely of the most aesthetic material, porcelain (hence, metal free crowns) or porcelain fused to metal (PFM crowns). However, veneers have to be made up entirely of either composite or porcelain.
Before starting the fabrication of crowns and veneers, the teeth requiring the treatment are prepared. Slight tooth structure is removed from all around the tooth if crown, and just from the visible outer surface (labial /buccal) in case of veneer.
Both kind of crowns and porcelain veneers are made and processed in the dental laboratories using replica model of the patient’s prepared tooth/teeth, hence requiring more than single visit to the dental clinic. In case of PFM crowns, the base of the crown is formed by an inert alloy material, over which a layer of porcelain is placed and fused to underlying metal alloy at high temperature, hence making the crown looking natural. While, the metal free crowns are computer aided designed and machined in the laboratory out of the porcelain block, using the duplicate model of the tooth. After the crowns are obtained from the laboratory, the can be properly fitted on the patients prepared teeth using bonding and cementation. Porcelain veneers are also prepared in the same way as pure porcelain crowns, just that they cover lesser surface area of teeth. However, composite veneers can be done in single sitting of the treatment as they can be directly fabricated and bonded over the prepared teeth surfaces in dental office, then skipping the lab work.