October 19, 2020
In the 1920s, Beverly McCollum introduced the world to a new branch in the study of human anatomy. McCollum along with his colleagues, instigated a brand new interest in the mechanism of how the lower jaw developed in conjunction with the teeth and the muscles attaching it to bring about the needed harmony of the face. He termed this field of study as Gnathology. Literally speaking, "gnath" means the jaw and logy means "to study."
The study of gnathic system had multifold effects. In a manner of connecting the dots, gnathology helped in understanding the relation upper and lower teeth and how they occluded with each other, how the upper and lower jaws developed in conjunction with each other, how the hinge joint near the ear responsible for the movement of lower jaw (temporomandibular joint) functioned and how the muscles attached to the jaws helped in chewing food. Let us understand how these micro elements form the macro element of gnathology.
A major contribution in the evolution of the human face came in response to the diet that we consumed. Today our diet has undergone many changes be it the consistency, texture, the way it is prepared, etc. The gnathic system developed and compensated accordingly. The lower jaw houses the lower teeth. The lower jaw bone (mandible) is the only bone on the face capable of movement in all possible planes. This movement of the mandible helps us grind our food effectively with the help of our teeth.
The type of teeth that help us in chewing are predominantly the molars, that are located in the back region of the mandible. These molars have hill-like prominences called cusps. The cusps of the lower and upper teeth help in a proper bite by occluding in a zigzag fashion. This helps in the temporomandibular joint (TMJ) close without any stress. Additionally, when we chew our food, there are various directions in which forces are applied. A proper bite helps in distributing these forces evenly.
What are gnathometers
Gnathology thus added a new element in the field of dentistry. Four decades after its introduction, instruments to know the accuracy of the gnathic system were made. These were known as gnathometers. The most commonly used device was the articulator. Over the a years, articulators too have developed from mechanical to digital to further strengthen our understanding of the gnathic system. These have helped us in attaining in each patient the concept of "organic occlusion."
Organic occlusion refers to the positioning of the teeth, so articulate, that it protects the overall harmony of the face both functionally and aesthetically. Articulators helped in achieving organic occlusion by helping us in knowing not only about the way the teeth occluded but also about the way the planes of the face changed based on the way the mouth opened and closed. The reason why this is important to know is directly related to the way dentists fabricate dentures.
Dentures are meant to replace lost teeth. Additionally, they are meant to replicate the function of the teeth too. In order to ensure this, the gnathic components like the teeth, jaw muscles, TMJ need to synchronise. When the teeth are placed, the muscles of the jaws need to be in a relaxed state. The TMJ too needs to open and close, and move side to side completely and easily as the dentures are placed in the mouth. Proper records of the patient when taken initially, are mounted on the articulator, following which the teeth are positioned and the dentures are made. The latest techniques involve a computerized 3D system for taking patient records. These records are then transferred to another digital system that fabricates the dentures. However, these technologies are still not utilized on a larger scale.
Gnathology has been challenged by another school of thought known as neuromuscular concept. In fact, the understanding of growth and development at the neurological and genetic level has strengthened the neuromuscular concept to the extent that gnathology is considered as an outdated concept by many. The neuromuscular concept dwells on the fact that the TMJ compensates with the help of the muscles, the way the teeth occluded with each other. This entire mechanism takes place through signalling and networking of various nerves with each other that activate the muscles accordingly.
Gnathology is at times referred as a precursor to the neuromuscular concept. However, it would be wrong to ascertain that completely. Both systems target the integrity of lower jaw and the way it works along with the teeth and muscles in all dimensions of mouth opening and closure. Old or new, this concept will always be utilized in order to get patients new teeth on dentures that are compatible with the surrounding tissues.