Better manufacturing starts with deeper understanding of tooth. Tooth discoloration is a common problem that can affect people of all ages and can occur in both milk and permanent teeth. Tooth discoloration is a multifactorial disease in which different parts of the teeth can absorb different pigments. This is determined by the anatomical characteristics of the teeth. We study the etiology and mechanisms of tooth discoloration with the aim of explaining the complexity of tooth discoloration.
The Natural Color of Healthy Teeth
Teeth are multicolored. The different thicknesses and colors of the cervical, incisal and central portions of the teeth reflect the different colors and translucency of the enamel and dentin. The color of healthy teeth is mainly determined by dentin and is influenced by the following factors:
- The color of the enamel covering the crown
- The translucency of enamel, which varies with different degrees of calcification
- The thickness of enamel, which is greater at the occlusal or incisal edge of the tooth and thinner at the cervical third.
- The intensity, thickness, structure of the dentin.
- Presence of secondary or tertiary dentin trauma
- Existing restorations.
Types of Tooth Discoloration
Stains after odontogenesis (posteruptive)
Daily Acquired Pigments
Daily-acquired pigments are typical exogenous pigments that cause staining on the outer surface of teeth and can be removed by dental cleaning.
- Plaque: Plaque biofilm and calculus on the tooth surface make the teeth look yellow.
- Tobacco: Tobacco components dissolve in saliva, lowering its pH and penetrating into pits and fissures more easily. Teeth have a brown or brown appearance.
- Food and drink: Drinking coffee, tea, red wine, cola, etc., or eating berries, curry, etc., can make the tooth surface absorb pigment.
- Poor oral hygiene: Poor oral hygiene can lead to green, dark brown, or orange staining of the teeth by color-producing bacteria, usually found on the buccal surfaces of maxillary teeth.
- Swimmer’s calculus: This is a yellow to dark-brown stain that occurs on the facial and lingual or palatal surfaces of the anterior teeth of patients who swim and train extensively. Both primary and secondary dentitions are affected. It appears that prolonged exposure to pool water can cause stains to develop on swimmers’ teeth.
Dental caries (both primary and secondary) may confer a discolored appearance around areas of bacterial stagnation, or leaking restorations. Arrested caries has a brown discoloration because the breakdown products react with decalcified dentin; this is similar to the discoloration of the pellicle.
Color changes in the teeth result from surface and subsurface changes. The degree of manifestation is related to tooth anatomy, structural hardness, and the amount of use and abuse. The following factors are encountered with increasing age:
- Enamel changes: There may be both thinning and texture changes.
- Dentin deposition: Secondary and tertiary dentin deposition, pulp stones, and dentin aging all cause the tooth to appear darker.
- Salivary changes: Salivary content and composition may change with advancing age. Whitening treatment is normally successful in this age group provided there is sufficient enamel available to whiten.
Functional and Parafunctional Changes
Tooth wear may give a darker appearance to the teeth because of the loss of tooth surface.
- Erosion is the progressive loss of hard dental tissues by a chemical process not involving bacterial action. This dissolution of enamel by acid causes the tooth to appear discolored because the dentin is more yellow in color.
- Attrition is defined as wear of the occlusal surfaces or proximal surfaces of the tooth caused by mastication or contact between occluding surfaces. It affects the occlusal and incisal surfaces.
- Abrasion is defined as the loss by wear of tooth substance or a restoration by factors other than tooth contact. It is usually caused by abnormal rubbing of a nondental
object such as a pipe, hairclip, or musical instrument. It is often caused by overly vigorous tooth brushing. This loss of enamel causes exposure of dentin, which makes the tooth appear more yellow.
Function and parafunction may cause loss of the incisal edges and exposure of underlying dentin, which is susceptible to color change from absorption and deposition of reparative dentin. Fracture lines develop as white cracks but darken on exposure to absorptive surface stains. Changes in color and texture affect the color and light reflectiveness.
Mouthwash containing chlorhexidine causes superficial black and brown staining of the teeth. The staining is enhanced in the presence of tea and coffee. It may be related to the precipitation of chromogenic dietary factors onto the teeth and mucous membranes. It is probable that the associated cationic group attaches chlorhexidine to the tooth, whereas the other cationic group producing the bactericidal effect can attach the dietary factors, such as gallic acid derivatives (polyphenols) found in foods and beverages such as tea and coffee and tannins from wine to the molecule and hence to the tooth surface.
Metals such as copper, nickel, and iron can cause staining of teeth. Copper ions, when they occur in the water in certain areas, can cause staining of teeth. Workers in the copper and nickel industries have also shown green staining on the teeth. The combination of plaque occurring around metallic orthodontic brackets can cause green line staining. Excessive iron intake can cause cervical staining, usually darkbrown or black in color. The taking of iron supplements can cause black staining of the teeth and tongue; black stains have also been noted on the teeth of ironworkers
Tannins and chromogens
Some stains are easier to remove by whitening than others. Different stains require different approaches to removal. Biologic and environmental variables affect the tenacity of the different stains. Tannin stains from tea and coffee are more tenacious and may take three or four power whitening sessions or a longer period of home whitening to remove. Tannins are composed of polyphenols such as catechins and leucoanthocyanins, and it is the gallic acid derivatives in the polyphenols that cause the yellow-brown stain. The tannins may also act as stain promotors.