CLINICAL FEATURE
Articulators, face bows and interocclusal records Articulation has been defined as the static and dynamic relationship between the occlusal surfaces of the teeth during function. Management of articulation in the dentition is one of the most important aspects of modern dentistry. Failure to manage articulation can result in problems for the patient and for the restorations placed by the dentist.
FIGURE 1: Class I articulator.
FIGURE 2: Class II articulator.
FIGURE 3: Class III articulator. This is a Whipmix® 2240 model.
FIGURE 4: Class IV articulator. This is a TMJ highly adjustable articulator.
FIGURE 5: A pantograph used to trace the true hinge axis of the mandibular condyles.
FIGURE 6: A Whipmix® facebow. The external acoustic meatus is used to support the bow posteriorly and position the arm over the hinge axis. The third point anteriorly is located 23mm below the nasion.
The articulator is an often-neglected tool at the dentist’s disposal. An articulator is any mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts can be attached to simulate some or all mandibular movements. With over a century of development, the modern dental articulator is a very useful tool in the dentist’s armamentarium. The articulator has three basic functions: 1. To study the static and dynamic relationships of the patient’s teeth, allowing the dentist to diagnose problems not readily apparent clinically.
Dr Paul Quinlan Specialist practice limited to prosthodontics and periodontics, Quinlan Dental Care, Dublin. www.quinlandentalcare.com
102 Journal of the Irish Dental Association | April/May 2016 : Vol 62 (2)
2. To plan treatment that involves the interrelationship of the teeth. 3. To fabricate a prosthesis, extra-orally in the dental laboratory, in harmony with the patient’s dentition. There are four basic articulator types available to the dentist. These have been classified as:1 1. Class I: A simple holding instrument capable of accepting a single static registration – vertical motion is possible (Figure 1). 2. Class II: An instrument that permits horizontal and vertical motion but does not orient the motion to the temporomandibular joints (Figure 2). 3. Class III: An instrument that simulates condylar pathways by using averages or mechanical equivalents for all or part of the motion, often referred to as ‘semi’ adjustable articulators. These instruments allow for orientation of the casts relative to the joints (Figure 3). 4. Class IV: An instrument that will accept three-dimensional dynamic registrations, often referred to as ‘fully’ or ‘highly’ adjustable articulators. These instruments allow orientation of the casts to the temporomandibular joints and simulate mandibular movements (Figure 4).