ACQUIRED DEFECTS OF THE TEETH

Wearing away of teeth caused by tooth-to-tooth friction as caused by the action of chewing or clenching of teeth.

Attrition is the loss of teeth structure by mechanical forces from opposing teeth.

According to the classic definition, attrition was considered to be a physiologic process occurring primarily from tooth contact during mastication.

ATTRITION

Predisposing factors:• The most common cause of

attrition is bruxism. • Functional habits are those such

as chewing and swallowing, which usually puts very little force on opposing teeth.

•  

Parafunctional habits, such as clenching and clicking the teeth together nervously, place greater amounts of forces on opposing teeth and begin to wear the teeth.

As expected, wear usually begins on the incisal or occlusal surfaces.

Characteristic Features:The wear from attrition may be

seen on the occlusal surfaces of posterior teeth, the incisal edges of anterior teeth, the palatal surfaces of maxillary anterior teeth, and the labial surfaces of mandibular anterior teeth.

The affected surfaces are usually hard, smooth, and shiny.

The areas of attrition may exhibit a yellowish-brown discoloration if the wear has penetrated the dentin.

Abrasion is the loss of tooth structure by mechanical forces from a foreign element.

ABRASION

Predisposing factors:1- Vigorous horizontal tooth brushing.

The most common cause of abrasion, we can see notching teeth at the cervical area ( the thinnest part of enamel)

2- nail biting, pen biting and pipe smoking.

3- denture clasps in RPD. 4- Abrasive tooth pasts and powders.

Some smokers use a whitening abrasive powder or pastes to remove stains but it is very abrasive.

5- Hard tooth brushes

Clinical appearance:It can be angular “V” shaped at the

cervical area or can be rounded, dish shape .

Usually it affects teeth in the left quadrant of right handed patients and vice versa.

Affect labial surfaces of prominent teeth , canines and premolars(most pronounced teeth in the jaw) at the cervical area bec of brushing.

Abfraction is a wedge-shaped/ usually V- shaped cervical lesion that results from repeated tooth flexure caused by occlusal loading.

It is non carious cervical lesions and it is not caused by tooth brushing only but there is occlusal force and tensile stress so we expect abrasion lesion to become more severe in bruxist patients and that may cause microfracture of cervical enamel rods.

ABFRACTION

Mechanism (Stress corrosion theory):

Force on occlusal surface will cause flexure at the pivot (fulcrum at the CEJ), it is away from initial contact (the contact at the occlusal surface but the lesion at the CEJ).

So the difference between abrasion and abfraction :

Abrasion is the loss of tooth structure by mechanical forces from a foreign element.

Abfraction is the loss of tooth structure from flexural forces.-The loss of tooth substance may depend on the direction, magnitude, frequency, duration and location of the force on the teeth.

Abfraction lesion is located subgingivally away from tooth brush which support another factors.

If it is abrasion we expect the lesion to be higher at the cervical margin.

 irreversible loss of tooth structure due to chemical dissolution by acids not of bacterial origin.

EROSION

CAUSES:RegurgitationReflex of acidic contents from the

stomach, we have to type of regurgitation:

Involuntary regurgitation: related to disease, surgical problem or pathology in GIT

1- gastrointestinal problems, like esophagus regurgitation.

2- Chronic alcoholism: not the alcohol it self that attack the tooth but alcoholism cause damage to the lining of stomach which will cause regurgitation or reflex of acidic contents to attack the teeth as well so it is indirectly affecting the tooth structure.

Voluntary regurgitation Voluntary vomiting caused by some

psychological diseases and eating disorders:

serious fatal psychological diseases with high mortality rate, western disease between models, singers and actresses due to exaggerated concern of body image and how they look, it affects female more than male. they induce vomiting to loss their weight bec they think that they are fat.

1- Anorexia nervosa 2- Bulimia nervosa

Environmental Flow of Saliva• It is secondary cause of tooth wear, • Saliva has: - a buffering effect: it will buffer the acid we ingest bec most drinks

have a pH less than 4 - lubricating effect reduce the effect of rubbing the teeth against

each other • so if you have a reduced salivary flow that mean the same amount

of acid will be more effective in weakening the teeth. • That happens usually with cancer patients or in salivary glands disease. Reduced flow and rate: Xerostomia, Sogren syndrome, radiotherapy( those patient with radiotherapy

have a very weak teeth and they get a new carious lesion every week)

• Enamel has matted appearance. • Dentine may be exposed with continuous erosion which

will cause (Capping: cavity within dentine with raised enamel margins bec dentine is softer than enamel)

• palatal erosion related to intrinsic and extrinsic acids. • Outstanding restorations. in some patients we find the

margins of the amalgam restoration are above the cavity preparation that bec the surrounding tooth structure is being eroded while amalgam is resistant to acid so we will see this filling is outstanding of the cavity margins.

• Increase in translucency of anterior teeth. • Cervical surfaces may be more prone to erosion because

these areas close to the gingiva are less self-cleaning and food and beverages may be harboured on the tooth surface for longer periods of time.

Clinical Apperance of Erosion