TOOTH WEAR

WHAT IS TOOTH WEAR? Tooth wear has been defined as loss of tooth

substance resulting from abrasion, attrition and erosion acting singly or concurrently i.e. abfractions.

When wear is due to more than one predominant etiological factor, special terms have been suggested to highlight the multiplicity of causes. For example: abrosion demastication

TYPES OF TOOTH WEAR

AbrasionWear process involving foreign objects sliding or rubbing against the tooth surfaces.

AttritionWear process of the tooth substance by tooth-to tooth contact.

AbfractionNon-carious cervical lesions caused by tensile stress generated from occlusal loading, and micro fracture of cervical enamel rods.

ErosionLoss of dental hard tissues by non-bacteriogenic acid etching.

ABRASION

The combination of a hard toothbrush, an abrasive toothpaste and an intensive horizontal brushing technique is believed to cause well-defined, V-shaped notches in the cervical regions of one or more facial tooth surfaces, where the dentine and cementum are less wear-resistant than coronal enamel.

OTHER HABITS CAUSING ABRASION INCLUDE:

The misuse of dental floss and toothpick, and pipe-smoking.

Thread biting Holding hair-grips between the teeth can

lead to abrasion defects of incisal tooth edges in seamstresses and hairdressers, respectively.

ATTRITION Attrition resulting from tooth-to-tooth contact

(two-body wear) produces well defined wear facets on the functional surfaces of teeth in one jaw which match corresponding lesions on teeth in the other jaw

Para functional habits such as bruxism and clenching were also believed to be important factors in causing accelerated attrition.

OTHER FACTORS PREDISPOSING TO ATTRITION INCLUDE

developmental dental defects, coarse diet natural teeth opposing coarse porcelain

Attrition of incisal edges of 1/1 and pseudo-Class III incisal malocclusion.

Attrition of 1/ because of lack of posterior support.

ABFRACTION The concept of ‘stress-induced cervical

lesions’ was introduced to explain how wedge-shaped Class V lesions can be created by repeated compression and flexure of the teeth under occlusal loading. Dentine is more elastic than enamel and enamel rods can be fractured in such situations. In older adults, enamel crazing and micro fractures are more common.

o The term abfraction was used to describe this ‘stress corrosion’ mechanism

o The ‘stress corrosion’ theory has been supported by a number of observations:

• in vitro evidence of tensile stresses created in the cervical region under occlusal loading

• a high incidence in bruxists• lesions can be found on only one tooth in one

segment• lesions found in subgingival regions• the presence of such lesions in animals.

EROSION Erosion of tooth substance may be caused by

intrinsic or extrinsic acids, and modified by changes of salivary flow and constituents.

Acid erosion

Flow of Saliva

PATTERNS OF TOOTH WEAR IN EROSION Erosion can lead to old amalgam

restorations becoming outstanding

Erosion of palatal surfaces of 321/123 in a patient with bulimia nervosa.

DIAGNOSIS Before any intervention or restorative

treatment, the nature and duration of patient’s chief complaints and expectations must be ascertained.

Apart from using a routine medical questionnaire, emphasis may be placed on medical conditions predisposing to erosion due to gastro-esophageal reflux or reduced salivary flow.

Evaluation of the family and social history can reveal if the patient is under unusual stress, which may be related to bruxism, changes of diet and regurgitation.

Clinical examination of the dentition has two primary objectives:• To document and record the location,

appearance and degree of tooth wear.• To evaluate the progress of tooth wear over time.

Clinical examination can supplemented with high-density stone study casts, intra-oral photographs, radiographs and salivary tests.

PREVENTIVE AND INITIAL MANAGEMENT Before any definitive restorative treatment is

undertaken, plaque-induced dental disease such as caries and periodontal disease should be controlled.

The long term success of rehabilitation is dependent on good oral hygiene and regular maintenance.

Efforts should be made to eliminate or control the etiological factors.

RESTORATIVE MANAGEMENT OF TOOTH WEAR Tooth wear can be classified as physiological or

pathological, but no universally accepted guidelines are available to differentiate the two entities; the same loss of tooth substance may be regarded as physiological in an elderly person, but pathological in young one.

Clinical indications for restorative management:

Biological• Loss of tooth substance could lead to irregular tooth

surfaces which may enhance plaque retention• Pulpal exposure • Weakening of tooth structure

Functional• Loss of tooth substance cannot be compensated

by continuous eruption, and there is reduced masticatory efficiency because of occlusal wear.

Esthetic• Loss of tooth substance is esthetically

unacceptable to the patient.

A systematic treatment approach should be used to manage characteristic worn dentitions involving different tooth surfaces and degree of severity. For practical reasons, the worn dentition can be classified according to location:

• Localized anterior tooth wear• Localized posterior tooth wear• Generalized tooth wear

When erosion is the primary etiological factor then the palatal surfaces of the upper anterior teeth are most commonly involved in tooth wear, less frequently the posterior teeth may also be affected in a localized manner.

Adhesive techniques with minimal tooth preparation should be employed if only the palatal tooth surfaces are affected. It is difficult to construct a crown on a shortened tooth without clinical crown lengthening surgery or subgingival placement of the crown margin.

As a result of compensatory tooth eruption and alveolar bone growth several methods are used to create interocclusal space needed for the management of localized tooth wear before the placement of the final restoration. These include:

Fixed or removable anterior bite planes ( Dahl appliance)

Tooth preparation at existing intercuspal position Occlusal adjustment In addition to these methods, provisional or permanent

restorations can be placed at increased OVD. These supra-occluding appliances are used as “individual Dahl appliances”.

With the Dahl appliance or individual supra-occluding restorations placed at increased OVD, a palatal platform should be present as an ‘ICP stop’ to dissipate occlusal forces more axially.

LONG TERM MANAGEMENT OF PATIENTS USING REMOVABLE PROSTHESIS The use of removable prostheses can be broadly

divided into two categories: First, those cases where the appearance of the

worn teeth is acceptable to the patient. In these circumstances management is directed at trying to prevent progression of the tooth surface loss.

Second, there are those cases where the appearance is unacceptable. In these circumstances treatment options can be divided broadly into:• tooth reduction and the provision of overdentures• treatment combining removable prostheses and

adhesive techniques• treatment combining fixed and removable prostheses.

1. MAINTENANCE ASSOCIATED WITHACCEPTING THE APPEARANCE In these cases, partial dentures are provided to

ensure there is adequate occlusal support. The maintenance in these cases is usually the least

demanding, because the degree of intervention necessary is limited and simple. This will consist of regular reviews, and very often the provision of a ‘soft, vacuum formed, night mouth guard’ to protect the remaining teeth.

The use of a night mouth guard is inadvisable where the tooth surface loss has an erosive component, e.g. gastric acid reflux, as some individuals may reflux ‘silently’ when supine during sleep.

2. MAINTENANCE ASSOCIATED WITH TOOTH REDUCTION AND THE PROVISION OF OVERDENTURES Where the tooth surface loss is severe, often

the most appropriate treatment is to reduce the worn teeth further and restore the missing crowns with an overdenture.

It is also necessary to consider that there is a consequence to the retention of overdenture abutments upon the success of the removable prosthesis. The retention of the overdenture abutments reduces the space for the artificial teeth and base. This increases the likelihood of fatigue fracture, particularly in those individuals who have a tooth clenching or grinding habit.

o It can be worth considering the use of porcelain teeth on the denture, as they have a high abrasion resistance, so will resist wear and help maintain the occlusal vertical dimension. However, porcelain teeth may crack and, if left rough following occlusal adjustment, will wear down natural teeth.

o In addition, attaching porcelain teeth to the denture can be particularly difficult if there is limited space available, as the means of mechanical retention may be ground away. An alternative would be to replace the occlusal surfaces of conventional resin teeth with cast gold alloy restorations.

3. MAINTENANCE ASSOCIATED WITH THE RESTORATION OF CASES WITH A COMBINATION OF ADHESIVE TECHNIQUES AND REMOVABLE APPLIANCESo Where possible, it is desirable to create canine

guidance using direct or indirect composite additions, or at least anterior group function. This can help protect remaining natural tooth substance from further wear in lateral excursive movements and will also help to protect restorations on the incisor teeth from unfavorable loading.

4. MAINTENANCE ASSOCIATED WITH THE RESTORATION OF CASES WITH A COMBINATION OF FIXED RESTORATIONS AND REMOVABLE APPLIANCES A tooth surface loss case, where the vertical

and horizontal jaw relations have been restored with a combination of full veneer crowns, a post and core-retained crown (upper left canine) and an upper removable partial overdenture in an older patient where the standard of oral hygiene was not ideal.

CONCLUSION: The causes of tooth surface loss are multi-

factorial and hence difficult to eradicate Treatments should be planned which would

enable the dentist to recover the situation with minimal inconvenience to the patient.

When considering possible treatment options for patients, especially those who have exhibited tooth surface loss, they should be made fully aware of the possibility of failure in the future of any restorative procedure carried out.

This is a consequence of continued wear and tear, which may cause the failure of even the most clinically and technically acceptable restoration.

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