Regressive Alterations of Teeth
With increasing oral health awareness and the advances in healthcare delivery system the incidence of carious lesions and periodontal diseases have drastically reduced over the ages. As such many individuals tend to retain healthy teeth even in their old age. However, these teeth are subject to functional wear and tear in addition to the natural age-related regressive alterations affecting the tooth and its supporting structures.
Eccles in 1982 described ‘tooth surface loss’ or ‘tooth wear’ as pathological loss of tooth tissue by a disease process rather than dental caries. Tooth wear was earlier referred to as wasting diseases affecting teeth.
Mair in 1992 described the term ‘non-carious cervical lesions’ or ‘cervical wear’ to refer to loss of tooth substance at the cementoenamel junction. These non-carious cervical lesions include cervical erosion, abrasion and abfraction. Clinical studies by Kitchin (1941) have shown that cervical wear lesions are often situated on the vestibular surfaces of teeth, seldom on lingual surfaces and rarely on proximal surfaces. These are also more pronounced on incisors, canines, and premolars and more prevalent in the maxilla than in the mandible.
Pindborg defined attrition as the loss of enamel, dentin or restoration by tooth-to-tooth contact. Tooth-to-tooth friction causes the form of wear called ‘attrition’. Two types of attrition have been described. They are physiologic and pathologic.
Physiologic attrition is referred to as the gradual and regular loss of tooth structure as a result of normal mastication. However, pathologic attrition is confined to local areas or specific groups of teeth caused by abnormal friction.
The physiologic causes for attrition include mastication and deglutition. Pathologic causes that cause attrition are abnormal occlusion, bruxism and habits such as tobacco and betel chewing and defective tooth structure such as in dentinogenesis imperfecta.
Attrition involves occlusal/proximal surfaces of teeth. It occurs more frequently in males than in females due to greater masticatory forces. It appears as a small polished facet on cusp tips and causes flattening of incisal edges in case of anterior teeth (Figure 1). The wear will lead to exposure of the dentin causing hypersensitivity. The worn surfaces of opposing teeth occlude together very accurately. Wear of the proximal surface causes decrease of arch length. Lambrechts et al (1989) reported that the rate of attrition is about 29 μm/year for molars and 15 μm/year for premolars.
Yip et al (2004) studied the differential wear of teeth and restorative materials. They found that the lowest wear rates for restorations and the opposing dentition occur with metal alloys, machined ceramics, and microfilled and micro-fine hybrid resin composites.
Radiographically the morphology of the crowns is lost and the occlusal and incisal edges of teeth are bereft of the radiopaque enamel cap. The curved cuspal edges are reduced to single flat plane. The incisocervical length of the crown is shortened. Owing to the secondary dentin formation, the size of the pulp chambers are reduced. In severe cases, the pulp chamber and the pulp canals may be obliterated. Occasionally, hypercementosis may be seen associated with attrited teeth.
Attrition of teeth leads to esthetic and functional disturbances. Dentinal hypersensitivity is usually the most common complaint. Severe attrition leads to pulpal exposure (Figure 2), non-vital teeth and periapical pathology. The razor sharp cuspal or incisal edges of teeth may cause traumatic ulcers.
Figure 2 Severe attrition of the mandibular incisors causing exposure of the pulp. Photograph also showing attrition of incisal edges of maxillary central incisors. Courtesy: Department of Oral Medicine and Radiology, MCODS, Mangalore
It is often believed that generalized attrition will also result in a reduction in occlusal face height (vertical dimension of occlusion). However, it has been often noticed that in spite of the extensive loss of tooth surface the resting facial height appears to remain unaltered primarily because of dentoalveolar compensation. Bruxism-associated attrition may be associated with temporomandibular dysfunction.
Patients should be educated regarding the consequences of attrition. Sharp edges of teeth can be smoothened. Desensitizing toothpastes will help patients presenting with dentinal hypersensitivity. A soft bite guard will help break the habit of bruxism and prevent further loss of tooth structure.
Pathologic wearing away of tooth substance through some abnormal mechanical process especially in the presence of abrasive materials is known as abrasion. It usually occurs on exposed root surfaces of teeth. Different foreign bodies produce different patterns of abrasion. Most common type of abrasion is toothbrush and dentifrices (toothpaste and/or tooth powder) abrasion. Many of the residents in the villages of the Indian subcontinent use charcoal, brick and ash to cleanse teeth. These indigenous dentifrices abrade teeth further.
It is seen frequently on exposed root surfaces and in cervical regions of labial and buccal surfaces due to overzealous toothbrushing in horizontal manner. Maxillary teeth are involved more than mandibular teeth, and left side is affected commonly in case of right-handed persons and vice versa. It appears as a V-shaped or a wedge-shaped ditch on the root side of the cementoenamel junction in teeth with some gingival recession (Figure 3). The exposed dentin appears highly polished (Figure 4). Improper use of dental floss and tooth picks may also produce such lesions on the exposed proximal root surfaces.
In habitual pipe smokers, notching of teeth can be seen that conforms to the shape of the pipe stem. It can also be seen as occupation-related oral finding in carpenters and tailors who hold objects against the teeth during work. Exposure of dentinal tubules and the consequent irritation of odontoblastic processes stimulates the formation of secondary dentin.
Grippo et al (2004) described a term, ‘masticatory abrasion’ to refer to tooth wear on the occlusal or incisal surfaces due to friction from the food bolus. They reported that the masticatory abrasion can also occur on the facial and lingual aspects of teeth as coarse food is forced against these surfaces by the tongue, lips and cheeks during mastication.
Radiographically, abrasive lesions caused by toothbrush are seen as half-moon shaped, well-defined radiolucent areas in the cervical regions of the teeth. These defects are usually seen involving the maxillary premolar teeth.
However, abrasive lesions caused by dental floss are usually slender half-moon-shaped radiolucent areas in the proximal regions of the neck of the teeth. Owing to the normal flossing pattern, the distal surface of teeth exhibit relatively deeper radiolucent areas compared to the mesial surfaces of teeth. Pulp chambers may be obliterated.
Patients should be educated regarding the correct brushing and flossing technique. They should be advised to discontinue any deleterious habits associated with their occupations. Use of abrasive dentifrices should be strongly discouraged.
Pulpal exposure is rarely a complication of cervical abrasion as the formation of secondary dentin protects the pulp from being involved. Dentinal hypersensitivity when present can be managed with the use of desensitizing toothpastes and mouthrinses.
Grippo et al (2004) quoting the description of erosion by The American Society for Testing and Materials Committee on Standards proposed that the term erosion should be replaced by the term corrosion. The American Society for Testing and Materials Committee on Standards defines erosion as ‘the progressive loss of a material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid, impinging solid or liquid particles’. In order to explain this in simple terms Grippo gave an example of river water flowing forcefully against the bridge supports leading to its erosion.
Clinically, erosions appear as wide, polished and smooth areas on the enamel approximating the cervical margin of the tooth (Figure 5). The erosive areas are almost always shallow and exhibit ‘scooped-out’ architecture. The common teeth to be affected by erosion are the anterior teeth.
Frequent episodes of vomiting as seen in pregnancy, acid reflux or regurgitation, anorexia nervosa and bulimia cause corrosion of teeth. Bodecker (1945) showed that the gingival crevicular fluid is acidic and may cause corrosion when in contact with the cervical regions of the teeth.
Typically, the enamel is translucent and thin. The common sites for erosion are the palatal surfaces of anterior teeth and occlusal surfaces of posterior teeth. Occasionally other sites that may be affected include the areas of pooling of the contents of the gastric reflux.
Another term used with regards to regurgitation of the acidic contents is stress reflux syndrome. This syndrome typically affects young working adults. The acidic reflux usually occurs during the working hours at day. The regurgitated acidic contents are held in the mouth before being swallowed again. This syndrome produces erosion of the buccal surfaces of mandibular posterior teeth.
Laine (2002) described the effect of pregnancy on periodontal and dental health. He reported that the tooth environment is significantly altered in pregnancy. He stated that a number of salivary cariogenic microorganisms may increase in pregnancy, along with decrease in salivary pH and buffer effect.
Rockenbach et al (2006) studied the salivary flow rate, pH, and concentrations of calcium, phosphate and sIgA in Brazilian pregnant and non-pregnant women. In their study, there was no difference in salivary flow rates and concentrations of total calcium and phosphate between pre/>