CHAPTER 2 The tissues involved

in

implant procedures

Before attempting any kind of endosseous or subperiosteal implant procedure, it is necessary to have a thorough knowledge of the tissues involved. The normal structure and function of the tissues, the physical and chemical factors affecting their health, and their responses to trauma and other stimuli must be understood. These are basic considerations in evaluating when, where, and how to perform a dental implant.

Any dental implant intervention interrupts the normal sequence of events in a tissue. Whether or not the tissue can recover and resume its normal activities depends on factors that vary from tissue to tissue and from person to person. Recognizing these variations is the first step in performing a successful implant intervention. Many variations, such as individual differences in the structure of the jaws, are obvious. Others, equally important to recognize, are subtle and detectable only by laboratory techniques. Before examining the subtle variations it is important to review the normal range of obvious variations found in most presenting patients.

GROSS ANATOMY OF THE JAWS

The anatomy of the mandible and maxillae is familiar to all dentists; therefore, only a brief re-view seems necessary to orient the reader to those structures to be avoided in an implant intervention. The most important landmarks are the mandibular canal and mental foramen and the relative positions of the maxillary sinus and nasal vestibulum. These will be discussed and illustrated extensively, as they are prime factors in planning implant procedures.

Mandible

The mandible, or lower jaw, is a horseshoe-shaped body bearing at each end a flattened upward extension called the ramus (Fig. 2-1). The upper end of each ramus has two processes, an anterior coronoid process and a posterior condylar process. These articulate with the bones of the upper face, permitting movement of the mandible against the skull.

At birth the right and left halves of the mandible are joined only by fibrous tissue. During the second year of life, the halves fuse at the mental symphysis. Along the line of symphysis, on the outer surface, is a triangular-shaped mental protuberance. The lower angles of this protuberance form a mental tubercle on each side. This entire area, popularly called the chin, is an area of relatively thick bone. The thickness extends back along the lower border of the mandible, passing slightly upward to become continuous with the anterior border of the ramus. The thickened areas serve as attachment sites for the muscles.

Of prime importance in the mandible is the pathway of the mandibular branch of the trigeminal nerve and its accompanying vessels. The trigeminal, or fifth cranial, nerve is mainly responsible for the cutaneous supply of the face and scalp. In addition, it provides motor innervation for the muscles of mastication. The major portion is sensory and gives rise to three divisions: ophthalmic, maxillary, and mandibular. In the lower part of the face on each side, a branch of the trigeminal nerve passes between the processes of the ramus and into the mandible on its inner surface via the mandibular fora-

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