April 11, 2016
A dental articulator is a mechanical representation of the TMJ, the upper and the lower arches. Its relevance lies in the fact that impressions of the upper and lower teeth are mounted on it to simulate jaw movements. This reduces the need for repeated patient appointments as most of the prosthetic work can be done with the help of the articulator. It also removes the difficulties encountered while finishing the dentures within the mouth such as shifting of the denture base within the mouth, interfering saliva, tongue and the cheeks of the patient. Articulators are a must when doing full mouth rehabilitations and extensive prosthetic work like multiple crowns and bridges.
An understanding of the patient’s mandibular (lower jaw) movements and its relation to the upper jaw is essential for the success of prosthodontic treatment as well as treatment of TMJ disorders. Basic mandibular movements consist of simple opening and closing, forward (protrusive), backward (retrusive) and sideways (lateral). When dental treatment is being planned for missing teeth or construction of dentures or fixed restorations, these movements are taken into consideration for proper balancing and arrangement of artificial teeth and restorations.
Among these, the hinge axis is located for an accurate recording of the centric relation. The hinge axis is a hypothetical line that runs through the mandibular condyles on both sides of the jaw, corresponding to its center of rotation. Centric relation transfer to the articulator duplicates tooth contact as it is in the mouth and thereby assists in managing occlusal interference.
What is a Bennett movement and how does it relate to articulators?
However, mandibular movements are quite complex and the Bennett movement plays a major role in treatment planning and fabrication of dentures. The Bennett movement is a lateral movement of the mandible toward the working side as the non-working condyle moves forward.
When studied in detail, it becomes obvious that there are actually two movements in the Bennett movement - the immediate side shift and the progressive side shift. The immediate side shift is the position where the condyles move in a straight median while leaving the centric location. On the other hand, the progressive side shift results in formation of Bennet’s Angle in the horizontal plane between the condylar path and the sagittal plane (an imaginary line that divides the body vertically) during a side movement.
This Bennett’s Angle varies in every individual and its size influences the arrangement of the artificial teeth while fabricating dentures. It is important in determining the height of the cusps as well as groove placement so that there is no occlusal interference during jaw movements.
Types of Articulators
Several types of articulators exist with which some or all mandibular movements can be replicated.