Helictites are, perhaps, the most delicate of cave formations. They are usually made of needle-form calcite and aragonite. Forms of helictites have been described in several types: ribbon helictites, saws, rods, butterflies, hands, curly-fries, and clumps of worms.. They typically have radial symmetry.
The temporomandibular joint (TMJ) is the joint where the mandible articulates with the cranium (Fig 8.1). The following characteristics make the TMJ a complex and unique joint: 1  It is classified as a compound joint even though it does not include three bone structures in the articulation.
1 As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc. 2  This permits simple chewing or grinding movements over a small range. 3  Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding.