Form and Function

Skilled dental technicians should have a fundamental medical knowledge, which will enable them to produce functional dental prostheses. In dentistry, prosthetic work is objectively assessed using criteria based on the form and function of anatomical tissue structures. Anatomy is therefore a primary discipline for dental technicians.

Anatomy is the study of the structure and form of the human body as well as animal and plant bodies (Fig 1-1). The word anatomy is derived from Greek and means "to dissect or dismember." When the human body is dissected and examined, the position, shape, and composition of the organs and organ systems can be defined. Macroscopic anatomy involves describing the form and structure of what is visible to the naked eye; microscopic anatomy, on the other hand, involves examination of the structure of organs and tissues that can only be seen under the microscope. Focus directed specifically to the positions of the organs and the relations of the organs and tissues to each other is known as topographical anatomy (ie, describing position). However, focus directed to the tissues themselves and their constituents is known as histology (ie, the study of tissues). Cytology (ie, the study of cells) is a specific branch of histology.

The study of form and organization (ie, the study of interactions), mutual influences, and interdependence of organs and organ systems is carried out using techniques that involve studying the processes of life; this discipline is known as physiology. All normal processes in the human body and any normal demands on organs and tissues are therefore considered physiologic. For example, chewing hard foods, which puts strain on the teeth because they are embedded in the jaw, is a physiologic process (and a physiologic stress) because the tissues involved were created for this very purpose and designed to withstand this type of strain. Meanwhile, the discipline of pathology focuses on the abnormal changes in the body as well as the causes of diseases and their courses; changes due to disease are therefore known as pathologic disorders.

While medical practitioners draw on their experiences of anatomy, physiology, and pathology in their daily practice of treating patients, dental technicians do not interact with patients directly but rather base their restorations on physical reproductions (models) of the patients' teeth. Therefore, a sound knowledge of anatomy, physiology, and pathology is essential for any dental technician. The goal of any artificial replacement, whether it be for the teeth, parts of the alveolar ridge, or mucous membrane, is to integrate this prosthesis with the living structures; not only is the form being replaced, but function is also being restored. In other words, the dental prosthesis should not only replace the tissue but should also function in the same way as the original tissue.

Law of form and function

There is a close link between the unique form of a tissue (eg, of teeth) and the function it is intended to carry out.This relationship has led to the establishment of the law of form and function, which states that a tissue developed for a specific purpose takes on a specific form for that purpose. This law also states that when the function of the tissue changes, its form alters to the same extent and vice versa.

Disuse atrophy is a particular aspect of the law of form and function, and it may explain the association between the form and the function of a tissue. If a leg is immobilized in a plaster cast after a fracture, the muscles begin to waste away and weaken because they are not being used; their form or shape therefore changes. However, this process is reversible. If the leg is used again after the fracture has healed, the muscles return to their original form. Atrophy is the wasting away of tissue caused by lack of nutrition, while disuse atrophy is specifically a shrinking of tissue caused by reduced blood flow when there is a lack of use.

Once this association between form and function is established, it becomes clear that a denture, like any other component in the body, must have the correct anatomical form in order to function reliably. An artificial prosthesis that does not have the correct form cannot fulfill the original function of the tissue.