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Quality Resource Guide –

Managing the Patient with a Worn Dentition 2nd Edition

www.metdental.com

Treatment Planning

hen confronted with a complicated

restorative challenge such as worn

dentition, the clinician should return

to the basics of treatment planning, beginning

with the patient interview. What is the patient’s

chief concern? The inability to eat, tooth sensitivity

and poor esthetics are common complaints of the

patient with a worn dentition.

Patients provide important information. They

may relate a history of bruxism, bulimia, or

gastroesophageal reflux disease (GERD); though

individuals with eating disorders might be unwilling

to disclose these problems. Inquiring into dietary

habits may reveal behaviors such as fresh fruit

mulling or the swishing of carbonated beverages,

which can erode tooth surfaces.

2,3

The patient can

be asymptomatic and unaware of the presence

of any of etiologic factors. Referral for medical

evaluation is often indicated in such situations,

which can lead to counseling for any eating

disorders. Many patients will admit to poor dietary

habits that can result in enamel dissolution. Referral

to nutritional counseling will often benefit these

patients.

A thorough review of the medical history, soft

tissue examination, appropriate radiographic

images, periodontal probing, and analysis of the

periodontal tissues and the charting of existing

dental restorations and caries lesions are always

appropriate components of a comprehensive

oral examination. If the dentition appears to be

abnormally worn, the clinician should next evaluate

the interocclusal contacts between maxillary and

mandibular teeth and their contribution to the wear

problem using a diagnostic mounting.

Gypsum casts made from accurate alginate

impressions are sufficient for this purpose.

The

casts should be mounted on a semi-adjustable

articulator with accurate facebow and interocclusal

records to properly position them on the articulator.

The facebow (Figure 12) relates the maxillary cast

to the axis of rotation of the patient’s mandibular

condyles and the Frankfort horizontal plane (or

an equivalent third reference point). This allows

the mounted casts to mimic the patient’s occlusal

relationships and mandibular movements. This

mounting can be useful in identifying occlusal

discrepancies and determining how to correct them.

Interocclusal records orient the mandibular cast to

the maxillary cast and are made in centric relation

position (CR). CR is “the relationship of the mandible

to the maxilla when properly aligned condyle/

disc assemblies are in the most anterior superior

position against the eminentia irrespective of tooth

position or vertical dimension.”

In contrast, maximum intercuspation (MI) is an

acquired occlusal position where there is maximum

contact between maxillary and mandibular teeth.

CR is selected for mounting the casts because it

is a physiologic, functional, repeatable position.

Methods to guide the patient into CR when making

interocclusal records include: tongue positioning;

chin point guidance;

bilateral manipulation;

the use of a positioning jig;

and the use of a leaf

guage.

18,19

After CR is obtained, the interocclusal

record is made using low-resistance media such as

wax, zinc oxide and eugenol, or polyvinylsiloxane

bite registration material.

When occluding casts are mounted in CR, the

initial occlusal contact may be on a single tooth

which prevents the mandible from closing into

MI without first shifting anteriorly and/or laterally.

Over 90% of the population exhibit a discrepancy

between CR and MI.

20-24

These premature contacts

or interferences can be a causative factor for

excessive wear of teeth.

Occlusal Analysis

pposing posterior teeth in an ideal occlusion

are located directly over one another so

that occlusal forces load them in an axial

direction (Figures 13 and14). The root structure of

posterior teeth and the orientation of the periodontal

ligaments provide excellent resistance to axial

forces. Maxillary and mandibular anterior teeth

meet at an angle (Figure 13) causing the maxillary

anterior teeth to be loaded in a transverse direction.

Consequently, anterior teeth cannot withstand

heavy occlusal forces.

The position of the anterior teeth forward of the

muscles of mastication and the TMJ (a fulcrum)

creates a class III lever (Figure 15). In this

configuration, the greatest occlusal forces occur on

the teeth nearest the fulcrum. Therefore, occlusal

forces on anterior teeth are low compared to

posterior teeth.

In addition, anterior teeth utilize

proprioceptive indicators to prevent overloading.

25,26

Figures 13 and 14

Anterior teeth are not positioned to take the force of closure of the mandible.

The posterior teeth

will take the force of mandibular closure down the long axis of the individual teeth.

Figure 12

The use of the facebow will relate the maxil-

lary cast to the axis of rotation, the Frankfort

horizontal plane and the plane of occlusion.

Figure 15

The ideal occlusal model will demonstrate

a class III lever.