Initially, it was the relative location of the disc that drew attention as the causative factor in symptomatic TMJ patients. Hence, early diagnostic techniques centered on the anterior to posterior positioning of the disc. The pathologic diagnosis thus became one of disc displacement with or without reduction over the forward-translated mandibular condyle. Unfortunately, according to Dr. Mark A. Piper this approach has been too simplistic. "Normal" joint anatomy involves all of the joint structures, and each of the tissues must act in harmony with all of the other structures in order for the TMJ to function properly.
Normal joint anatomy involves harmony among several tissue types. In the temporomandibular joint, there are eight structures that interrelate with another. All of the joint structures must function in full coordination with one another to maintain normal joint mechanics.
The condylodiscal ligaments are intracapsular support structures that are responsible for maintaining the general posture of the disc superior to the condylar surface. These ligaments occupy the medial and lateral poles of the mandibular condyles, and they blend with the fibrous connective tissue of the medial and lateral portions of the disc. These ligaments are not weight-bearing structures. However, they play a vital role in maintaining the disc in proper alignment at both poles. Furthermore, these internal ligaments must remain tight enough to tether the disc, but at the same time, they must have enough laxity to allow the disc to assume a more posterior relation with respect to the condyle during forward translation. Like other ligaments, if the joint is hyperextended, these structures must hold up to these forces. Finally, although the condylodiscal ligaments function in harmony to hold the disc in alignment, they are independent structures and are functionally distinct. Hence, they may break down independently.
In the normal superior posturing of the mandibular condyle into centric relation, there is a specific volume available for each tissue. The retrodiskal attachment (RDA) is compacted. The posterior band (PB) of the disk is located just proximal to mid fossa. The anterior (AB) and posterior (PB) bands of the disk are vascularized (black arrows). The superior belly fibers of the lateral pterygoid muscle (SLP) insert partially into the disk and partially into the fovea of the condyle. The inferior belly fibers of the lateral pterygoid muscle (ILP) insert into the fovea of the condylar neck. Blood vessels (BV) penetrate from the lateral pterygoid muscle into the condyle.
With forward translation of the condyle, the retrodiskal attachment fills with shunted blood into the superior stratum (SS). The disk rotates more posteriorly over the condylar surface as both disk and condyle translate forward against the eminence. The posterior band (PB) of the disk temporarily thickens from shunting of blood into this area. The anterior band (AB) of the disk is compressed by the condyle, and blood is shunted out.
A patient with a normal bite has maximal intercuspation, which is when the tips of the teeth of both the upper and lower jaw interlock and there is no premature contact in the posterior (back) or anterior (front) teeth.
A patient with a normal functioning jaw will reach maximal intercuspation without displacing the condyles or disk and causing the soft tissues of the joint to adapt to accept the loading pressures.