DENTISTRY ARTICULATORS

Discuss the advantages and disadvantages of the range of articulators currently available in restorative dentistry



Discuss the advantages and disadvantages of the range of articulators currently available in restorative dentistry

Introduction

In the United Kingdom, the majority of orthodontists assess a patient's occlusion clinically and with the aid of study models trimmed to occlude in the inter-cuspal position. A minority of specialists in the UK and a rather larger proportion of American orthodontists advocate the use of articulated study models in all patients undergoing orthodontic treatment. These authors maintain that occlusion cannot be accurately assessed without articulation of the models using an inter-occlusal record taken on the retruded path of mandibular closure. The routine use of articulated study models involves considerable chairside and laboratory time. The purpose of this article is to examine the evidence for the use of articulators during orthodontic diagnosis and treatment, and to attempt to provide a rational basis for their use (Bates, 2006, 89).

Types of articulator

A dental articulator is an instrument that represents the temporomandibular joint and jaws, to which maxillary and mandibular study models are attached. Originally described as long ago as 1756 (Mitchell and Wilkie, 1978, 78), their use was, for many years, exclusive to restorative dentists and prosthodontists. An articulator provides a means of reproducing occlusal relationships outside the mouth, and is an indispensable aid for the fabrication of crowns and bridges.

A number of different types of articulator exist and these vary in their complexity. The simplest articulators incorporate average patient values to represent the inclination of the glenoid fossa and the condyle-fossa relationship, and so cannot accurately reproduce an individual's mandibular excursive movements. Semi-adjustable articulators can be modified by adjustment of the 'condyle-fossa' portion of the instrument using wax records of the patient in lateral and protrusive excursion. Fully adjustable articulators have a large range of adjustability in three dimensions, and are accordingly the most complex and expensive.

Validity of the technique

Any investigation must measure what it purports to measure if it is to contribute to a patient's management, i.e. it must be valid. An articulator must therefore be able to simulate an individual's jaw movement so that casts mounted on it can be observed to articulate in the same way as teeth in the mouth. As mandibular movements are influenced by many soft tissue factors, such as the ligaments of the temporomandibular joints and masticatory muscles, it is impossible for jaw movements to be precisely reproduced (Pameijer, 1985, 99).

Semi-adjustable articulators have a condylar path that is in a straight line, unlike the 'true' condylar path, which follows a curved path. Fully adjustable articulators have a number of interchangeable inserts that represent the glenoid fossae, and allow the curved protrusive and lateral movements of the temporomandibular joints to be reproduced. The significance of the condylar path depends upon the degree to which jaw movement is dictated by the condyles. In partially dentate and edentulous patients, guidance of the mandible during function is largely determined by the movement ...