Tooth Wear I

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 Definition  Wear

:

is a natural process that occurs whenever two or more surface move in contact .  It is , therefore, considered that wear of human natural dentition, to a certain extent, is a predictable physiological process result from continuous sliding contact between opposing teeth .

 Time

in contact is an important factor in determining the extent of wear, the possibility for wear is, therefore, greater among patients who retain natural teeth for many more years .

Factors affecting wear 1.

Force of mastication . If the force of mastication (chewing ) increased the wear will increase . e.g. bruxism and Para functional habits .

2. Sliding distance between opposing teeth.

If the sliding distance increased the wear will increase . 3. Contact area. Contact area ----- stress from opposing teeth -------- tooth wear .

4.Surface roughness and friction . The real contact area represented by the sum of the protruding surface spots, which are susceptible to deformation under load and reduce the actual contact area .  The

rough surface has a higher coefficient of friction and increase the wear rate .

5. Frequency and time of contact .

The increase of time and or frequency of occlusal contacts will lead to an increase in wear rate and volume e.g. bruxism and elderly patients . 6.Environmental factors . Low salivary PH , exposure to an abrasive atmosphere, and lack of salivary flow all increase tooth wear .

Dental terminology 

The term “ tooth surface loss “ embrace all the conditions that cause tooth wear which occur in the absence of dental plaque and caries and trauma. conditions that cause tooth wear include attrition , abrasion , erosion and abreactions.

Attrition  Attrition

is defined as the loss by wear of tooth structure or a restoration caused by mastication or contact between occluding or approximal surfaces (tooth to tooth contact ) .  All surface in contact, suffer from attrition including occlusal surfaces, incisal edges, palatal surfaces of maxillary anterior , and labial surfaces of mandibular anterior teeth.

 It

is suggested , however that proximal contact areas may exhibits slight wear too.  Attrition (as mentioned earlier) is a physiological phenomenon, unless it is sever and extensive in relation to age, where it will be considered pathological .  It is proposed in cases of loss of tooth substance due to attrition there appeared to be a compensatory mechanism “ generalized alveolar bone growth” .

Abrasion 

Abrasion is the pathological wear of tooth substance through biomechanical friction process other than mastication .



E.g. vigorous tooth brushing ,nail biting , pen biting, denture clasps in RPD .

 The

use vigorous tooth brushing with abrasive toothpaste or against exposed dentine is the most common cause of cervical tooth loss.

 Patients

suffering from abrasion usually have good oral hygiene but have multiple “abrasion lesions” .

 Abrasion

is more common in the left quadrant of right –handed patients and the right quadrant of left-handed people. It is also more common on the labial surfaces of teeth prominent in the arch ( e.g canines) .

Erosion  Erosion

is the progressive loss of hard dental tissues by chemical process not involving bacterial action .  Tooth substance loss usually occur as a result of erosion in coexistence with either attrition or abrasion .  Erosion in usually associated with exposure of dentine on the buccal or lingual surfaces .

 Cervical

surfaces may be more prone to erosion because these areas close to the gingival are less self- cleaning .  Another indication of erosion is the presence of exposed dentine on incisal or occlusal surfaces despite the young age of the patient .

 Lesions

caused by erosion tend to be smooth and rounded, in contrast to attrited surfaces, which tend to leave sharp edges.

 Erosion

can be classified to regurgitation erosion due to pregnancy sickness or sickness or digestive and psychological problems erosion , and medication – induced erosion .

Occlusal stresses ( Abfraction)

 Defined

as the loss of dental hard substance caused by biomechanical loading forces .

 These

lesions are caused by flexure and ultimate fatigue of enamel and dentine of susceptible teeth away , from the point of loading . Occlusal stress explain why cervical lesion not present on teeth adjacent to primary site; which seem to discount tooth-brushing abrasion or chemical erosion as sole cause of tooth loss .

 The

loss of tooth substance may depend on the direction, magnitude, frequency, duration and location of the force on the teeth. If occlusion is not ideal or if heavy occlusal trauma is present, significant lateral forces are generated, which cause the tooth to bend and create compressive and tensile stresses on tooth structure .

 The

region under greatest tensile stresses is the fulcrum located around the cement enamel junction .  Tensile forces disrupt chemical bonds between hydroxyapatite crystals in enamel.  Pilot study (Bevenius et al , 1993) showed no correlation between brushing habits and the location and severity of cervical lesion .

 Their

findings indicated a possible correlation between irregular lateral excursions and the severity and location of lesions .

Aetiological factors of tooth wear  It

may be impossible to identify a specific a etiological agent even after elborate history taking , examination and special diagnostic tests .

 Extensive

cases of tooth wear are often caused by a combination of factors . It is also difficult to say with certainty when the loss of tooth substance happened, whether it is a continuing process or whether it stopped long time ago

1.

Age The prevalence and severity of tooth wear lesions increase with age due to prolonged exposure to oral environment and increase of frequency of tooth contact . And development of unfavorable occlusal forces due to loss of teeth, management, reduce occlusal table ….. Rtc .

2. Gender . Tooth wear is more extensive in males probably because they have greater bite force. 3. Bite force . Increased bite force tends to increase tooth wear rate, as in males and bruxists.

4. Occlusal factors . The number of ( occluding teeth) may cause wear due to excessive loading on the remaining teeth.  Occlusal relationship (edge- to-edge and occlusal interferences ) may accelerate tooth wear .

5. Para functional activities and habits . Bruxism : compulsory grinding and clenching of teeth for nonfunctional purposes, where the frequency and the bite force increase dramatically and cause tooth substance loss force increase dramatically and cause tooth substance loss and increase tooth wear rate .

 Vigorous

horizontal tooth brushing with abrasive toothpaste causes cervical notched abrasion lesions .  Pen biting, pipe smoking, chewing tobacco, musicians (wind instrument), nail biting , occupations that involve holding objects between teeth like tailors and carpenters .

6. Dietary factors . High consumption of citrus fruits or juice, carbonated drinks ( Cock , pepsi, sprite and all fuzzy drinks), herbal tea, alcoholic drinks, natural yogurt, vitamine C tablets and vinegar due to their low PH.

 However,

low PH alone may be not as good indicator of a product’s erosive potential as its buffer capacity . 7. Digestive problems. Regurgitation of gastric acids or partially digested gastric contents into the oral cavity due to : A- Morning sickness during pregnancy .

B- Hiatus hernia, gastro-esophageal reflux, gastro ulcer . C- Chronic alcoholism with gastritis. D- psychological disorders such as anorexia and bulimia nervosa .  Regurgitation erosion commonly affects the palatal surfaces of the upper anterior teeth and the occlusal and buccal surfaces of lower posterior teeth .

 While

, dietary erosion usually affects the labial surfaces of upper anterior teeth.  This may results in thinning of maxillary enamel and dentine hypersensitivity . 8. Environmental and occupational factors . Tooth wear caused by acid exposure in the environment or under occupation circumstances such as battery-making workers, pickers, miners.

9. Low salivary flow. Low salivary flow can results from obstruction of the salivary duct, surgical excision , radiotherapy (dry mouth) . Low salivary flow reduces the lubrication effect, and reduces the buffering effect.

10. Medications . - Vita mine C tablets . - Aspirin tablets . - Effervescent vitamin C preparations . - Medications that reduce salivary flow such as tricycles antidepressants and antihypertensive .

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