¶ Chapter 3 — ANATOMY OF FACIAL AND ORAL STRUCTURES
Reference Edition
This chapter is part of the Air Force Dental Laboratory Manual (2005) – Digitally Restored Edition.
This edition preserves the original publication while correcting OCR errors, restoring formatting, reconstructing damaged tables where necessary, and improving digital readability.
The technical content has not been rewritten, modernized, expanded, or altered.
It is provided as a professional reference. Modern instructional material is published separately throughout DentalTechnology.org.
¶ Section 3A — Overview of Anatomy
¶ 3.1. Introduction
The study of anatomy has a language all its own, and its terms have evolved over many centuries. Many anatomical terms are difficult to remember and pronounce. In order to communicate with other dental professionals, you must learn and understand the language and structures of oral and dental anatomy.
¶ 3.2. General Reference Terms
3.2.1. Anterior and posterior describe the front-to-back relationship of one part of the body to another. Anterior is toward the front; posterior is toward the back. For example, the ear is posterior to (in back of) the eye; the nose is anterior to (in front of) the ear, etc.
3.2.2. The words internal and medial are synonyms as are external and lateral. These terms describe the sideways relationship of one part of the body to another, using the midsagittal plane (paragraph 3.3) as a reference. For example the ear is external (or lateral) to the eye because the ear is further from the midsagittal plane. The eye is internal (or medial) to the ear because it is closer to the midsagittal plane.
3.2.3. The long axis is the longitudinal center line of the body or any of its parts.
¶ 3.3. Body Planes
The study of geometry shows that a plane is perfectly flat, is infinitely long and wide, and has no depth. For the purpose of this text, a plane is a real or imaginary slice made completely through a body. In anatomy, the slice is made to study the details of the cut surfaces. The cut surfaces are called sections or views. Planes can pass through a body in an infinite number of ways. Common planes that produce standard views include sagittal, frontal, and transverse planes (Figures 3.1 and 3.2).
3.3.1. The sagittal plane parallels the long axis and divides a body into right and left parts (Figure 3.1)
A midsagittal plane divides bodies into equal right and left sides.
3.3.2. The frontal plane parallels the long axis and divides a body into anterior and posterior parts (Figure 3.1)
3.3.3. The transverse (horizontal) plane divides a body into upper and lower parts (Figure 3.2)
More specifically, it is a slice that passes through a body at right angles (90 degrees) to the sagittal and frontal planes.
¶ 3.4. Bony Elevations
3.4.1. Tubercle, eminence, and tuberosity all describe rather small, somewhat circular areas raised above the general level of the surrounding bone. The person who originally described these areas specifically labeled an elevation of bone falling in this category as an eminence, tuberosity, or tubercle. As far as relative shape and size are concerned, there is little to distinguish among these kinds of elevations. They just have to be memorized according to the names they carry.
3.4.2. A ridge is a linear elevation on the surface of a bone or tooth. A mylohyoid ridge is one example.
3.4.3. A process is a very prominent projection from the central mass of a bone; for example, zygomatic process.
3.4.4. A condyle is a rounded, convex, smooth surface on one of the bones that forms a movable joint. The condyle of the mandible is discussed in depth in paragraph 3.18.
Figure 3.1. Sagittal and Frontal Planes.
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MIDSAGITTAL
PLANE
FRONTAL
PLANE
Figure 3.2. Transverse Plane.
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TRANSVERSE
PLANE
¶ 3.5. Bone Depressions and Channels
3.5.1. A fovea is a shallow, cup-shaped depression or pit. An example of this is the palatine fovea.
3.5.2. A fossa is a more or less longitudinal, rounded depression in the surface of a bone.
3.5.3. A canal is a tubular channel through bone. The channel has at least one entrance and one exit hole. A canal’s entrance or exit hole is called a foramen.
¶ 3.6. Joints
Joints can be classified in a number of ways. One of the ways is the kind of movement the structure of the joint allows. The three kinds of joints found in the human skull are as follows:
3.6.1. Synarthrosis or Immovable Joint. Most skull bones are joined together along highly irregular, jigsaw puzzle-like lines called sutures. A suture joint is classified as a synarthrosis. Bones joined along suture lines in the skull are not totally immobile. Movement occurs, but it is very limited.
3.6.2. Ginglymodiarthrodial Joint. Literally defined, this is a freely movable, gliding, hinge joint. This relationship of one bone to another allows the greatest range of movement of any joint type. The term ginglymodiarthrodial specifically describes the temporomandibular joint that unites the lower jaw with the rest of the skull.
3.6.3. Ellipsoidal Joint. This is the type of joint existing between the occipital bone of the skull and the first vertebra of the spinal column. There are two axes of motion at right angles to each other in this joint, and both axes pass through the same bone. This arrangement enables you to nod your head and rotate it from side to side.
¶ Section 3B — Bony Anatomy of the Head (Skull)
¶ 3.7. Introduction
The skull is that portion of the human skeleton that makes up the bony framework of the head. For descriptive purposes, the skull is divided into an upper, dome-shaped, cranial portion; and a lower or facial portion composed of the eye sockets, nasal cavities, and both jaws (Figure 3.3). The adult skull is composed of 22 bones (8 cranial and 14 facial).
¶ 3.8. Cranial Bones
The eight bones of the cranium are the frontal, parietal (right and left), occipital, temporal (right and left), sphenoid, and ethmoid. NOTE: The shape and arrangement of these eight bones form a bony shell (cranium) that has a central cavity containing the brain. The arched roof of the cranial cavity is called the vault, and the floor of the cavity is called the base.
¶ 3.9. Facial Bones
The 14 bones in the facial portion of the skull are the maxilla, palatine, zygoma, lacrimal, nasal, inferior concha, vomer, and mandible. NOTE: There is only one vomer and one mandible in a skull; however, the other facial bones are paired.
¶ Section 3C — Cranial and Facial Bones of Primary Interest
¶ 3.10. Overview
3.10.1. Artificial replacements for missing natural teeth (dental prostheses) must be made to fit jaw contours and work in harmony with muscle activity. Therefore, this discussion will center on those facial bones that give shape to soft tissues within the mouth and serve as anchorage sites for muscles that move the lower jaw and give shape to the lower one-half of the face.
3.10.2. Cranial bones of primary interest are the frontal, parietal, temporal, and sphenoid.
3.10.3. Facial bones of primary interest are the maxilla, palatine, zygoma, and mandible. NOTE: It is important to remember the particular features of these bones for subsequent reference in this publication and, in fact, for your entire technical career.
3.10.4. Paragraph 3.11 through 3.14 highlight the particular features of cranial and facial bones.
¶ 3.11. Frontal Bone
The frontal bone is a single bone forming the anterior of the cranial vault, the roof of the eye sockets, and a small portion of the nasal cavity. A temporal line can be found on both lateral surfaces of the frontal bone. The line begins in the region of the eye socket and proceeds posteriorly, often dividing into superior and inferior temporal lines near the posterior border of the frontal bone (Figure 3.4).
Figure 3.3. Bones of the Skull.
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PARIETAL
BONE
FRONTAL BONE
SPHENOID BONE
NASAL BONE
LACRIMAL
BONE
ETHMOID BONE
ZYGOMA
MAXILLA
OCCIPITAL
BONE
TEMPORAL BONE
MANDIBLE
FRONTAL BONE
PARIETAL
BONE
SPHENOID
BONE
ETHMOID
BONE
ZYGOMA
MAXILLA
MANDIBLE
TEMPORAL
BONE
LACRIMAL
BONE
NASAL BONE
VOMER
INFERIOR
CONCHA
¶ 3.12. Parietal Bones
Parietal bones are located between the occipital and frontal bones to form the largest portion of the top and sides of the cranium. The paired parietal bones are marked by two semicircular bony ridges, the superior and inferior temporal lines, which are the posterior continuation of the frontal bone's temporal line. The superior and inferior temporal lines rim the area of origin of the temporalis muscle (Figure 3.4).
Figure 3.4. Lateral View of the Skull (Selected Structures).
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TEMPORAL LINES
ZYGOMATIC ARCH
ZYGOMATIC PROCESS
(MAXILLA)
CUSPID EMINENCE
TEMPOROMANDIBULAR JOINT
MASTOID PROCESS
STYLOID PROCESS
RAMUS
ANGLE
ZYGOMA
EXTERNAL OBLIQUE RIDGE
MENTAL FORAMEN
¶ 3.13. Temporal Bones
Temporal bones are the paired bones forming a portion of the right and left sides of the skull below the parietal bones. The temporal bones extend down onto the under surface of the cranium and contribute to the formation of the cranial base. Each temporal bone articulates with the parietal above, the sphenoid in front, and the occipital bone behind (Figures 3.3, 3.4, and 3.5). The significant features of the temporal bone are the mastoid process, styloid process, zygomatic process, glenoid fossa, articular eminence, and auditory canal or external auditory meatus as follows:
3.13.1. The mastoid process is a rounded, downward projection on the posterior part of the temporal bone. This process presents a roughened exterior surface for attaching several muscles of the neck.
3.13.2. The styloid process is a slender, tapering spur of bone projecting downward from the under surface of the temporal bone. This process has sites of attachment for multiple muscles and ligaments, which then go to the mandible, hyoid bone, throat, and tongue.
3.13.3. The zygomatic process is a projection from the approximate center of each temporal bone extending forward to form a part of the zygomatic arch or cheek bone. This arch (or so-called cheekbone) is not one continuous bone, but is made up of a number of parts. The zygomatic process of the temporal bone forms the posterior part.
3.13.4. The glenoid fossa (mandibular fossa) is a deep hollow on the under surface of the base of the zygomatic process. The base of the zygomatic process is the place where the process originates from the central mass of the temporal bone.
3.13.5. The articular eminence is a ramp-shaped prominence extending forward and downward from the anterior boundary of the glenoid fossa.
3.13.6. The auditory canal or external auditory meatus is a hole in the bone found posterior to the glenoid fossa. It leads from the outside surface of the base of the zygomatic process to the inner portions of the ear.
Figure 3.5. Lateral View of the Skull (Selected Features).
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FRONTAL
ZYGOMA (CUT)
MAXILLA
INCISIVE FOSSA
CANINE EMINENCE
PTERYGOMAXILLARY NOTCH
PTERYGOID PROCESS
PARIETAL
SPHENOID
TEMPORAL
EXTERNAL AUDITORY MEATUS
STYLOID PROCESS
GLENOID FOSSA
ARTICULAR EMINENCE
ZYGOMATIC PROCESS (CUT)
¶ 3.14. Sphenoid Bone
The sphenoid bone resembles a bat with wings extended. It consists of a central portion or body which is situated in the middle of the base of the skull and three pairs of processes: two laterally extended greater wings, two downward projecting pterygoid processes, and two lesser wings. The features of the sphenoid bone we will discuss are the greater wings, spine of the sphenoid, and pterygoid processes.
3.14.1. A greater wing (Figure 3.5) forms part of the surface contour of the cranium anterior to the temporal bone, and it also forms part of the eye socket.
3.14.2. The spine of the sphenoid is just inferior to the lateral, posterior, inferior border of the greater wing of the sphenoid bone. The spine of the sphenoid is the site of attachment of the sphenomandibular ligament.
3.14.3. The pterygoid process (Figures 3.5, 3.6, and 3.7) extends downward from the junction of the body and greater wing of the sphenoid on the right and left side. The pterygoid process is formed by the union of two bony plates. The depression between the two plates is called the pterygoid fossa. The pterygoid process is a site of origin for the medial and lateral pterygoid muscles.
Figure 3.6. Lateral View of the Maxilla.
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PTERYGOID PROCESS (SPHENOID BONE)
PTERYGOID HAMULUS
TUBEROSITY
ZYGOMATIC PROCESS
ALVEOLAR PROCESS
FRONTAL PROCESS
INCISIVE FOSSA
CANINE EMINENCE
¶ 3.15. Maxillae
Maxillae or upper jawbones are paired bones that unite in the midline. They give shape to the middle face, form a portion of the floor of the eye socket and lateral wall of the nose, form the anterior two-thirds of the hard palate, and support the natural teeth in bony sockets (Figures 3.6, 3.7, and 3.8). Each maxilla (singular) is irregularly shaped. It is made up of a body and four processes called the nasal process, zygomatic process, alveolar process, and palatine process as follows:
3.15.1. The nasal process forms a portion of the lateral wall of the nose. Another name for the nasal process is the frontal process.
3.15.2. The zygomatic process of the maxilla joins with the zygoma which, in turn, unites with the zygomatic process of the temporal bone to form the zygomatic arch (or cheekbone). Although popular, the term “cheekbone” is incorrect because this so-called single bone is actually made up of three parts.
3.15.3. The alveolar process surrounds the roots of the maxillary teeth, and the alveolar processes of both maxillae unite to form the maxillary arch. A maxillary tuberosity is found on both of the distal ends of the maxillary arch. Proceeding even further posteriorly, the maxillary tuberosities abruptly rise into deep depressions called the pterygomaxillary notches (hamular notches). The pterygoid process of the sphenoid bone joins with the posterior aspect of a maxilla to form a pterygomaxillary notch. The labial portion of the alveolar bone follows the contours of the natural tooth roots. That is, when a root is large and prominent, the labial alveolar bone over the root is raised in comparison to an alveolar area between roots. The labial alveolar bone covering the root of the maxillary canine stands out so much it has a specific name--the canine eminence.
3.15.4. The palatine processes of the maxillae join in the midline to form the anterior two-thirds of the hard palate. The midline junction of the right and left palatine processes is called the median palatine suture. An incisive foramen is found in the suture line immediately behind the central incisors. The foramen is an exit hole for nerves and blood vessels that supply palatal tissue (Figure 3.8).
Figure 3.7. Medial View of the Maxilla and Selected Adjacent Bones.
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FRONTAL PROCESS
MAXILLARY SINUS OPENING
PTERYGOID PROCESS
(SPHENOID BONE)
PTERYGOID HAMULUS
INCISIVE FORAMEN
PTERYOMAXILLARY NOTCH
PALATINE PROCESS OF MAXILLA
HORIZONTAL PLATE (PALATINE BONE)
¶ 3.16. Palatine Bones
3.16.1. The palatine bones are paired, U-shaped bones located between the maxillae and the sphenoid bone (Figures 3.7 and 3.8)
A palatine bone forms parts of the floor and outer wall of the nasal cavity, the floor of an eye socket, and the hard palate.
3.16.2. The horizontal plates of the palatine bones unite in the midline as the posterior continuation of the medial palatine suture. The anterior border of the horizontal plates of the palatine bones join with the posterior border of the palatine processes of the maxillae to form the transverse palatine suture. As discussed previously, the palatine processes of the maxillae form the anterior two-thirds of the hard palate, and the horizontal plates of the palatine bones make up the remaining posterior one-third.
¶ 3.17. Zygoma
The zygoma is situated laterally to the maxilla. When the zygomatic process of the maxilla, the zygoma, and the zygomatic process of the temporal bone are considered as a unit, the combination is called the zygomatic arch (Figure 3.4).
Figure 3.8. Occlusal View of the Maxilla.
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INCISIVE FORAMEN
MEDIAN PALATINE SUTURE
ALVEOLAR PROCESS (MAXILLA)
PALATINE PROCESS (MAXILLA)
TRANSVERSE PALATINE SUTURE
GREATER PALATINE FORAMEN
LESSER PALATINE FORAMEN
MAXILLARY TUBEROSITY
PTERYGOMAXILLARY NOTCH
PTERYGOID PROCESS (SPHENOID BONE)
PTERYGOID HAMULUS
HORIZONTAL PLATE (PALATINE BONE)
¶ 3.18. Mandible
3.18.1. The mandible (Figure 3.9) or lower jaw is one of the few movable bones of the skull. This bone gives shape to the lower portion of the face, provides sites of attachment for the muscles that make it move, forms the framework for the floor of the mouth, and supports the lower natural teeth.
3.18.2. The mandible is connected to the skull by the right and left temporomandibular joints. Within each joint, the condyle of the mandible fits into the glenoid fossa on the underside of the temporal bone. In its movements, the condyle also travels onto the temporal bone’s articular eminence.
3.18.3. The articular eminence projects downward and forward from the anterior border of the glenoid fossa. (See Section 3F for a detailed description of the temporomandibular joint.)
3.18.4. The most prominent features of the mandible are its horizontal body and two vertical projections known as rami (one projection = ramus)
The body is curved (somewhat like a horseshoe) at the posterior limits of the body, and the bone turns upward and slightly backward to form the ramus.
3.18.5. As the inferior edge of the mandible is traced from anterior to posterior, the sudden transition between the horizontal body and relatively vertical ramus is known as the mandibular angle (angle of the mandible)
Figure 3.9. Lateral and Medial Views of the Mandible.
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CONDYLE
NECK
CONDYLOID PROCESS
CORONOID PROCESS
ALVEOLAR PROCESS
MENTAL FORAMEN
RAMUS
BODY
ANGLE
Buccal SHELF
EXTERNAL OBLIQUE LINE
MANDIBULAR NOTCH
LINGULA
MANDIBULAR FORAMEN
MYLOHYOID LINE (INTERNAL OBLIQUE LINE)
SUBLINGUAL FOSSA
DIGASTRIC FOVEA
GENIAL TUBERCLE
3.18.6. Three processes are readily identifiable. The body of the mandible carries the alveolar process, which surrounds the root structure of individual teeth. The right and left alveolar processes combine to form the mandibular arch. Each ramus ends in two processes, an anteriorly positioned coronoid process and the more posterior condyloid process. The deep, U-shaped concavity between the two processes is called the mandibular notch. A condyloid process can be divided into a condyle and a neck. The top part of the condyle articulates with the glenoid fossa and articular eminence of the temporal bone to form the temporomandibular joint.
3.18.7. The external surface landmarks of the mandible are as follows.
3.18.7.1. The mental protuberance—a roughly triangular prominence occurring in the midline near the inferior border of the mandible (chin point)
3.18.7.2. The mental foramen—the anterior opening of the mandibular canal. The foramen is usually found between and slightly below the first and second premolar root tips. The inferior alveolar nerve passes within the mandibular canal and exits onto the exterior surface of the mandible through the mental foramen to become the mental nerve. Compression of the mental nerve by artificial dental replacements must be avoided because it will cause a feeling of pain or numbness.
3.18.7.3. The external oblique ridge (line)—which extends at an oblique angle across the external surface of the body of the mandible. This ridge begins at the lower anterior edge of the ramus, continues onto the body, and progressively thins out to end near the mental foramen. The external oblique ridge is most prominent in the molar area and forms a distinct ledge with relation to the base of the alveolar process. This ledge is called the buccal shelf.
3.18.8. Internal surface landmarks of the mandible are as follows.
3.18.8.1. The mylohyoid ridge—located on the internal surface of the mandible and occupying a position similar to the external oblique ridge on the external surface. The mylohyoid ridge passes forward and downward from the internal aspects of the ramus onto the body of the mandible and fades out near the midline. This ridge serves as the lateral line of origin for the mylohyoid muscle (the mylohyoid muscle forms the major portion of the floor of the mouth)
3.18.8.2. The genial tubercles—located slightly above the lower border of the mandible in the midline. These provide an attachment site for the geniohyoid muscle.
3.18.8.3. The sublingual fossa—a shallow concavity housing a portion of the sublingual gland. This depression occurs just above the anterior part of the mylohyoid ridge.
3.18.8.4. The mandibular foramen—located in almost the exact center of the inner surface of the mandibular ramus. It opens into the mandibular canal.
3.18.8.5. The lingula—a bony prominence on the anterior border of the mandibular foramen.
3.18.8.6. The digastric fovea—a depression found on both sides of the midline near the inferior lingual border of the mandible.
¶ 3.19. Hyoid Bone
3.19.1. Any discussion of muscles that move the lower jaw and their points of anchorage must include the hyoid bone. The hyoid is a U-shaped bone located anterior to the spinal column between the mandible and the larynx (voice box).
3.19.2. There is no joint-like union between the hyoid and any other bone. It is suspended between the mandible above and the clavicle (collar bone) below by suprahyoid (above the hyoid) and infrahyoid (below the hyoid) muscle groups. Some of the suprahyoid muscles act to depress the lower jaw. Those suprahyoid muscles that act to depress the mandible are described in Section 3D.
¶ Section 3D — Muscles of Mastication and Depressors of the Mandible
¶ 3.20. Muscle Fibers and Movements
3.20.1. A person’s ability to move part of the body depends on a group of specialized cells called muscle fibers. Muscle fibers have the ability to contract or shorten when stimulated by nerve impulses. A typical muscle consists of a mass of muscle fibers bound together by connective tissue.
3.20.2. A muscle can generate varying degrees of power. This variation in power is directly proportional to the number and type of fibers within the muscle that are contracting at any given time. Muscles can also stretch, but only because a muscle located elsewhere has contracted and forced the extension. This performance of an action by one muscle that is opposed by the action of another muscle is called antagonism. The simplest way to express this is that muscles can only pull; they cannot push.
3.20.3. The two ends of a voluntary muscle usually attach to different bones. In some instances, one end of a muscle may attach in soft tissue such as skin. Some of the very small muscles that give expression to the face have both ends attached to soft tissue. In any case, the muscle attachment site that remains relatively stationary when the muscle contracts is known as the origin. The muscle attachment site having the greater movement during the contraction is called the insertion. A description of the movements, which take place as a result of muscle contraction, is called the action.
3.20.4. Two muscle groups are responsible for executing the movements the mandible is capable of making--the muscles of mastication and the depressor muscles of the mandible. The muscles of mastication enable the lower jaw to make closing, opening, protrusive, and retrusive movements along with movements to the right and left sides. The depressors of the mandible act to open the lower jaw wide--a function the muscles of mastication cannot perform.
¶ 3.21. Muscles of Mastication
There are four paired muscles of mastication; masseters (Figure 3.10), temporalis (Figure 3.10), medial pterygoids (Figure 3.11), and lateral pterygoids (Figure 3.12).
Figure 3.10. Masseter and Temporalis Muscles.
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Masseter Muscle
Temporalis Muscle
3.21.1. Masseter.
3.21.1.1. Origin. The origin is the zygomatic arch.
3.21.1.2. Insertion. The masseter muscle inserts on the lateral surface of the ramus of the mandible (Figure 3.10).
3.21.1.3. Action. The primary function of the masseter is to elevate the mandible. The masseter may also aid in the protruding of the mandible.
3.21.2. Temporalis.
3.21.2.1. Origin. The origin of this muscle is broadly spread out (fan-shaped) on the side of the skull (Figure 3.10). It covers the majority of the temporal bone and lesser portions of the frontal and parietal bones. The upper margin of the muscle follows the superior temporal line.
3.21.2.2. Insertion. The temporalis muscle inserts on the coronoid process of the mandible.
3.21.2.3. Action. The temporalis muscle acts in unison with the masseter and medial pterygoid muscles to close the jaws. Very importantly, it also helps to retrude or pull back the mandible.
Figure 3.11. Medial View of the Medial Pterygoid Muscle.
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LATERAL PTERYGOID
MASSETER
MEDIAL PTERYGOID
3.21.3. Medial Pterygoid.
3.21.3.1. Origin. The origin of this muscle is the palatine bone and pterygoid process of the sphenoid bone (Figure 3.11).
3.21.3.2. Insertion. The medial pterygoid inserts on the medial (internal) surface of the ramus of the mandible.
3.21.3.3. Action. The medial pterygoid acts with the masseter and temporalis muscles to close the lower jaw. Some authors claim that when one medial pterygoid muscle contracts independently of its paired mate, it helps move the mandible sideways.
3.21.4. Lateral Pterygoid.
3.21.4.1. Origin. The origin of this muscle is the pterygoid process and greater wing of the sphenoid (Figure 3.12).
3.21.4.2. Insertion. This muscle inserts into the neck of the condyloid process of the mandible.
3.21.4.3. Action. When both lateral pterygoid muscles contract together, the mandible is pulled forward into protrusion. (Coincident with a prot rusive movement, the mandible opens slightly.) When one muscle contracts independently of the other, the mandible pivots and shifts to the opposite side (lateral excursion).
Figure 3.12. Lateral View of the Lateral Pterygoid Muscle.
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LATERAL PTERYGOID
MEDIAL PTERYGOID
¶ 3.22. Depressor Muscles
The depressor muscles of the mandible all have the hyoid bone in common as an attachment site. When the hyoid bone is immobilized by a contraction of the muscles below it, the contraction of the depressor muscles located between the hyoid bone and the mandible pulls the mandible downward (opening the mouth). The suprahyoid depressors of the mandible are the mylohyoid (Figure 3.13), geniohyoid (Figure 3.13), and digastric muscles (Figure 3.14).
3.22.1. Mylohyoid Muscle Attachment Sites. The paired mylohyoid muscles are attached to the mylohyoid lines on the internal surfaces of the mandible, the right and left mylohyoid muscles join in the midline to form the floor of the mouth, and the posterior end of this midline junction attaches to the hyoid bone (Figure 3.13).
3.22.2. Geniohyoid Muscle Attachment Sites. The two geniohyoid muscles are found next to each other on each side of the midline and directly on top of the mylohyoid muscles. The sites of the attachment are the genial tubercles and the hyoid bone (Figure 3.13).
3.22.3. Digastric Muscle Attachment Sites. The digastric muscle bundle is divided into an anterior belly and a posterior belly by a short tendon. This interm ediate tendon passes through a loop of fibrous tissue secured to the body of the hyoi d bone. The end of the anterior belly attaches
to the digastric fovea and the posterior belly fastens onto the mastoid process of the temporal bone (Figure 3.14).
Figure 3.13. Mylohyoid and Geniohyoid Muscles.
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HYOID BONE
GENIAL TUBERCLES
MYLOHYOID GENIOHYOID
MYLOHYOID GENIOHYOID
HYOID BONE
¶ Section 3E — Facial Expression Muscles
¶ 3.23. Maintaining Facial Muscle Support
3.23.1. Eight paired muscles of expression in coordination with the single orbicularis oris muscle, control the movements of the lips and cheeks (Figure 3.15). The teeth and alveolar processes of the jaws support this group of muscles against collapse into the oral cavity. When natural teeth are extracted, facial muscle support must be maintained by replacing the missing teeth.
3.23.2. A person’s appearance can be dramatically affected by the position of the artificial teeth. Inadequate support makes people look older; excessive support distorts a person’s features by making them appear stretched. The muscles of facial expression also play an important part in forming the anterior and lateral portions of maxillary and mandibular impression borders. This is because all of these muscles can alter the depth of vestibular sulci in one way or another. (See paragraphs 3.37.12 and 3.38.6.)
3.23.3. If impression borders are not properly extended and shaped, the muscles act to unseat the dentures. The influence of the muscles of facial expression on denture borders is described in Chapter 7.
Figure 3.14. Oblique View of the Mylohyoid and Digastric Muscles.
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STYLOMANDIBULAR LIGAMENT
STYLOID PROCESS
MASTOID PROCESS
(TEMPORAL BONE)
DIGASTRIC MUSCLE
(POSTERIOR BELLY)
MYLOHYOID MUSCLE
FASCIAL LOOP FOR
DIGASTRIC TENDON
HYOID BONE
THYROID CARTLIDGE
DIGASTRIC FOVEAS
DIGASTRIC MUSCLE
(ANTERIOR BELLY)
INFRAHYOID MUSCULATURE
¶ 3.24. Orbicularis Oris
3.24.1. This ring-like muscle lies within the upper and lower lips and completely surrounds the opening to the mouth. When the orbicularis oris contracts, it causes the lips to close.
3.24.2. The orbicularis oris has no real bony origin. Instead, it is entirely rimmed by the insertions of other muscles of facial expression, most of which do originate on bone. Certain muscles of expression that insert into the orbicularis oris act to draw the corners of the mouth backward, while some depress the lower lip and others elevate the upper lip.
¶ 3.25. Levator Labii Superioris Muscle
This facial expression muscle is flat and triangular. It is positioned lateral to the nose and has an origin by two heads; the frontal process of the maxilla and the inferior margin of the orbit. These unite at one insertion point in the fibers of the orbicularis oris beneath the nostrils. The levator labii superioris muscle acts to elevate the upper lip, widen the nasal opening, and raise the corner of the nose.
¶ 3.26. Zygomaticus Major Muscle
The zygomaticus major muscle is oblong, flat, and cylindrical. It is positioned lateral to and above the angle of the mouth. It originates at the zygomatic bone, lateral to the levator labii superioris muscle, and inserts in skin just superior to and at the angle of the mouth. The muscle’s action is to draw the angle of the mouth laterally and upward.
¶ 3.27. Levator Anguli Oris Muscle
The levator anguli oris muscle is flat and triangular. Its position is in the levator anguli oris fossa of the maxilla, covered by the levator labii superioris muscle. The levator anguli oris originates in the canine fossa and inserts at the angle of the mouth. It has three actions; it lifts the angle of the mouth upward, lifts the lower lip, and helps close the mouth.
Figure 3.15. Muscles of Facial Expression.
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LEVATOR LABII SUPERIORIS
ZYGOMATICUS MINOR
LEVATOR ANGULI ORIS
ZYGOMATICUS MAJOR
RISORIUS
DEPRESSOR LABII INFERIORIS
BUCCINATOR
DEPRESSOR ANGULI ORIS
MENTALIS
ORBICULARIS ORIS
¶ 3.28. Risorius Muscle
The risorius muscle is flat and triangular. With a position lateral to the angle of the mouth, it originates in tissue over the masseter muscle and parotid gland. The risorius has an insertion at the angle of the mouth with the depressor anguli oris muscle. Its action is to draw the angle of the mouth laterally causing a smile and dimple.
¶ 3.29. Depressor Labii Inferioris Muscle
With a flat and quadrangular shape, this muscle covers the mental foramen. It has an origin along the lower border of the mandible and inserts into the skin of the lower lip. When contracted, it acts to depress and invert the lower lip.
¶ 3.30. Depressor Anguli Oris Muscle
Shaped flat and triangular, the depressor anguli oris muscle covers the depressor labii inferioris muscle. It also has an origin along the lower border of the mandible just beneath the mental foramen. With an insertion at the angle of the mouth, it acts to draw the angle upward.
¶ 3.31. Mentalis Muscle
The mentalis is a short, thick, cylindrical muscle positioned on the bony prominence of the chin, deep to the depressor labii inferioris muscle. Its origin on the mandible is also deep to the depressor labii inferioris. When contracting, it lifts and wrinkles the skin of the chin and pulls tissue below the lips towards the lower anterior teeth.
¶ 3.32. Buccinator Muscle
3.32.1. The buccinator muscle is a thin, broad band of muscle tissue that forms the innermost muscle wall of a cheek.
3.32.2. A buccinator muscle has three sites of origin. They are the pterygomandibular raphe (ligament), which originates behind the maxillary tuberosity and inserts at the posterior end of the mandible’s mylohyoid line; the buccal surface of the alveolar process in the maxilla immediately above the root tips of the molar teeth; and the external oblique ridge of the mandible.
3.32.3. The muscle fibers of the buccinator run parallel to the occlusal plane of the teeth and have a broad zone of insertion into the orbicularis oris at the corner of the mouth. Besides being muscles of facial expression, some anatomists classify the buccinators as accessory muscles of mastication.
3.32.4. The primary functions of these muscles are to pull the corners of the mouth laterally and hold food between the teeth while chewing.
¶ 3.33. Platysma Muscle
The platysma is a thin broad band of muscle that originates over the pectoralis major and deltoid muscles. Its insertion is the inferior border of the mandible and the skin of the lower face. The platysma acts to draw the corners of the mouth down and aids in depression of the mandible.
¶ Section 3F — Intraoral Soft Tissue Anatomy
¶ 3.34. Introduction
3.34.1. The muscles that form the sides, entrance, and floor of the oral cavity are the buccinators, orbicularis oris, and mylohyoids (in that order) (Figure 3.16)
3.34.2. The skin of the interior of the mouth is called oral mucous membrane or mucosa. In places like the alveolar processes and hard palate of the upper jaw, the mucous membrane is firmly and directly attached to bone. This kind of mucosa presents a stable surface. In other areas like the lips and the floor of the mouth, the mucous membrane covers active muscles that are constantly in motion. For example, the strong, muscular tongue is almost always moving.
3.34.3. A removable prosthesis is built to use stable mucosa for support and avoid areas of high muscle activity. There are soft tissue landmarks in the mouth that remain constant after natural teeth are extracted, and these landmarks are valuable aids in prosthesis construction.
Figure 3.16. Entrance and Sides of the Oral Cavity.
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ORBICULARIS
ORIS
DUCT OF
PAROTID
GLAND
BUCCINATOR
¶ 3.35. Mucous Membrane
Mucous membrane is the skin that lines the mouth (Figure 3.17 and 3.18).
3.35.1. Mucous Membrane of the Alveolar Process. The mucous membrane of the alveolar process is divided into gingiva and alveolar mucosa (Figure 3.17) as follows:
3.35.1.1. Gingiva. Gingiva covers the crestal three-fourths of the alveolar process. There are two kinds of gingiva, free and attached. Free gingiva is about 0.5 mm wide and is found at the neck of a tooth. Attached gingiva is continuous with the free gingiva and is tightly bound to bone. The attached gingival band varies between 2 and 9 mm wide; the widest part is found in the anterior regions.
3.35.1.2. Alveolar Mucosa. Alveolar mucosa covers the basal one-fourth of the alveolar process. Alveolar mucosa is very mobile because it is loosely bound to underlying bone.
Figure 3.17. Mucous Membrane of the Alveolar Process.
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GINGIVAL SULCUS
GINGIVAL LINE
FREE MARGINAL GINGIVA
ATTACHED GINGIVA
MUCOGINGIVAL JUNCTION
ALVEOLAR MUCOSA
EPITHELIAL ATTACHMENT
GINGIVAL SULCUS
LAMINA DURA
SPONGY BONE
LINGUAL CORTICAL PLATE
3.35.2. Mucous Membrane of the Hard Palate. The mucous membrane of the hard palate consists of attached gingiva.
¶ 3.36. Vestibule
The vestibules consist of two potential spaces. One vestibule is found between the facial aspect of the teeth and the internal surfaces of the cheeks and lips; the other vestibule is found between the lingual aspect of the mandibular teeth and the tongue (Figure 3.18).
¶ 3.37. Maxilla
(NOTE: See Figures 3.18, 3.19, and 3.20.)
3.37.1. Alveolar (Residual) Ridge. The alveolar (or residual) ridge is the remnant of the alveolar process which originally contained sockets for natural teeth. After natural teeth are extracted, the alveolar ridge can be expected to get smaller (resorb). The rate of resorption varies considerably from person to person.
3.37.2. Maxillary Tuberosity. The maxillary tuberosity is the most distal (posterior) portion of the maxillary alveolar ridge.
3.37.3. Pterygomaxillary (Hamular) Notch. The pterygomaxillary notch is a deep depression located posterior to the maxillary tuberosity. The depths of this depression are part of a series of guides used to determine the posterior border of a maxillary denture.
Figure 3.18. Lateral View of the Oral Cavity.
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Buccal FRENUM
TUBEROSITY
PTERYGOMAXILLARY NOTCH
RETROMOLAR PAD
RESIDUAL RIDGES
BUCCAL SHELF
FREE GINGIVA
ATTACHED GINGIVA
ALVEOLAR MUCOSA
SULCUS
VESTIBULE
CANINE EMINENCE
3.37.4. Palate. The palate extends from the roof of the mouth all the way back to the uvula as follows:
3.37.4.1. The hard palate is made up of the anterior two-thirds of the palatal vault supported by bone (the palatine processes of the maxillae and the horizontal plates of the palatine bones)
3.37.4.2. The soft palate is made up of the posterior one-third of the palatal vault not supported by bone. The soft palate is a muscular extension from the posterior edge of the hard palate, and the soft palate is very mobile, especially while speaking and swallowing.
3.37.5. Incisive Papilla. The incisive papilla is the raised soft tissue covering the incisive foramen located in the midline of the hard palate, immediately behind the central incisors. Because the incisive papilla is visible in the exact midline of the hard palate (just behind the natural central incisors), it is a reliable guide for determining the midline relationships of upper anterior denture teeth.
3.37.6. Rugae. Rugae are irregular ridges of fibrous tissue found in the anterior one-third of the hard palate.
3.37.7. Median Palatine Raphe. The median palatine raphe is a slight tissue elevation occurring in the midline of the hard palate immediately over the median palatine suture.
3.37.8. Vibrating Line. The vibrating line is the line of flexion between the hard and soft palates. The line most frequently falls between the two pterygomaxillary notches on or near the palatine foveae in the midline. When a dentist looks at a patient’s entire palatal vault, it is easy to see an abrupt transition between the unmoving hard palate and the highly mobile soft palate.
Figure 3.19. Occlusal View of the Maxilla.
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LABIAL VESTIBULE
RUGAE
LABIAL FRENUM
INCISIVE PAPILLA
RESIDUAL RIDGE
BUCCAL FRENUM
LABIAL SULCUS
PALATINE RAPHE
BUCCAL VESTIBULE
RESIDUAL RIDGE
SULCUS
TUBEROSITY
HARD PALATE
ALVOELAR PROCESS
VIBRATING LINE
SOFT PALATE
PTERYGOID-MAXILLARY NOTCH
PALATINE FOVEAE
3.37.9. Palatine Fovea. The palatine foveae are two depressions located on either side of the midline on or very near the vibrating line. They are made by two groupings of minor palatine salivary glands. NOTE: The vibrating line helps the dentist determine the posterior border of an upper denture. In the absence of specific instructions from a dentist, the pterygomaxillary notches and the palatine foveae are the guide for determining the posterior border of an upper denture.
3.37.10. Labial Frenum. The labial frenum is a narrow fold of oral mucosa found in the approximate midline. It extends from the inner surface of the lip to the labial surface of the alveolar ridge. When natural teeth are absent, the labial frenum is not a reliable guide for determining the midline of the face.
3.37.11. Buccal Frenum. The buccal frenum extends from the mucosa of the cheek to the buccal aspect of the alveolar ridge. There are two buccal frena. They are located on each side of the arch, usually in the first premolar region.
3.37.12. Sulci. The maxillary sulcus is a groove formed by the mucosa of the cheek or lip and the mucosa at the base of the alveolar ridge. The portion of the sulcus that lies between the labial and buccal frena is the labial sulcus. The part of the sulcus between the buccal frenum and the pterygomaxillary notch is the buccal sulcus. The muscles shaping the sulcus cause its depth to change with every facial expression.
Figure 3.20. Occlusal View of the Mandible.
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TONGUE
(CUT EDGES)
PALATOGLOSSUS
MUSCLE (CUT)
RETROMOLAR PAD
RESIDUAL RIDGE
BUCCAL VESTIBULE
LINGUAL VESTIBULE
FLOOR OF THE MOUTH
LINGUAL FRENUM
LABIAL VESTIBULE
RETROMYLOHYOID
SPACE
BUCCAL SHELF
BUCCINATOR
MUSCLE (CUT)
BUCCAL SULCUS
BUCCAL FRENUM
LABIAL SULCUS
SALIVARY CARUNCLE
LINGUAL SULCUS
LABIAL FRENUM
¶ 3.38. Mandible: (NOTE: See Figures 3.18, 3.20, and 3.21.)
3.38.1. Alveolar Ridge. After natural teeth are extracted, the remnant of the alveolar process is called the alveolar or residual ridge. As time goes on, a residual ridge usually resorbs (gets smaller).
3.38.2. Retromolar Pad. The retromolar pad is a pear-shaped mass of soft tissue located at the posterior end of the mandibular alveolar ridge (Figure 3.22). The retromolar pads are important for the following reasons:
3.38.2.1. When maxillary and mandibular natural teeth are brought together, a plane of contact automatically forms between the occlusal surfaces of the upper and lower teeth (occlusal plane). When this plane of contact is projected posteriorly, it intersects with the mandible at two points, one point on each side of the arch. These points are about two-thirds of the way up the height of the retromolar pads.
3.38.2.2. The position of the pads remains constant even after the natural teeth are extracted. Thus, the pads are an excellent guide for determining and setting the plane of occlusion between upper and lower denture teeth.
3.38.2.3. The pads serve as bilateral, distal support for a mandibular denture. Covering the pads with the denture base helps reduce the rate of alveolar ridge resorption.
Figure 3.21. View of the Labial Vestibules.
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BUCCAL FRENUM (MAXILLARY)
LABIAL FRENUM (MAXILLARY)
MAXILLARY VESTIBULE
VESTIBULE
GINGIVA
SULCUS
LABIAL FRENUM (MANDIBULAR)
MANDIBULAR VESTIBULE
BUCCAL FRENUM (MANDIBULAR)
Figure 3.22. Relationship of the Retromolar Pads to the Occlusal Plane.
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RETROMOLAR PAD
OCCLUSAL PLANE
3.38.3. Buccal Shelf. The buccal shelf is a ledge located buccal to the base of the alveolar ridge in the premolar and molar regions. Laterally, the shelf extends from the alveolar ridge to the external oblique line. A buccal shelf is barely observable when the alveolar ridge is large. (The shelf increases in size as the ridge resorbs.) The buccal shelf is a support area for a mandibular denture, especially when the remaining alveolar ridge is relatively small.
3.38.4. Mental Foramen.
3.38.4.1. The mental foramen is a hole in bone ordinarily found on the buccal surface of the alveolar ridge. It is located between and slightly below the root tips of the first and second premolars. There is no tissue bump over the hole as in the case of the incisive foramen.
3.38.4.2. When resorption of the alveolar ridge is drastic, the mental foramen is found below the oral mucosa on the crest of the alveolar process. In this case, relief of the denture is necessary to avoid excessive pressure on the nerve fibers exiting from this foramen. Compression results in loss of feeling in the lower lip. Relief in this case is defined as space provided between the undersurface of the denture and the soft tissue to reduce or eliminate pressure on certain anatomical structures.
3.38.5. Frena. The labial and buccal frena of the mandible are in corresponding positions to their counterparts in the maxilla. A lingual frenum can be seen in the floor of the mouth when the tongue is raised. The lingual frenum is present in the approximate midline and extends from the floor of the mouth to the lingual surface of the alveolar ridge.
3.38.6. Sulci. Sulci rise and fall with facial expressions and tongue movements. The labial sulcus of the lower jaw lies at the base of the alveolar ridge between labial and buccal frena. The buccal sulcus extends posteriorly from the buccal frenum to the buccal aspect of the retromolar pad. The lingual sulcus is the groove formed by the floor of the mouth as it turns up onto the lingual aspect of the alveolar ridge.
3.38.7. Floor of the Mouth. The anterior two-thirds of the floor of the mouth is formed by the union of the right and left mylohyoid muscles in the midline. The depth of the floor of the mouth in relation to the mandibular alveolar ridge constantly changes due to factors such as mylohyoid muscle contractions, tongue movements, and swallowing activities. The posterior one-third of the lingual sulcus area is called the retromylohyoid space. Distally, the palatoglossus muscle shapes the area.
¶ 3.39. Tongue
3.39.1. Overview.
3.39.1.1. The tongue is a muscular organ containing specialized cells for detecting the presence of chemicals in the food we eat (Figures 3.23 and 3.24). The brain interprets this chemical detection process as taste. The tongue’s many different sets of muscles enable it to make the complex movements associated with speaking and with chewing food. The constant motion of the tongue represents a powerful force, and no artificial dental replacement can restrict that motion for long.
3.39.1.2. If a prosthesis is not constructed to work in harmony with the tongue, the prosthesis will fail. For example, the tongue can maintain a denture in position or throw it out, depending on how the lingual surfaces and borders of the denture are shaped.
3.39.2. Muscle Groups. The tongue is animated by two muscle groups, the intrinsic and extrinsic, as follows:
3.39.2.1. Intrinsic muscles represent the substance of the tongue (Figure 3.23)
They are responsible for the tongue’s ability to change shape.
3.39.2.2. Extrinsic muscles originate at sites like the hyoid bone, styloid process of the temporal bone, and genial tubercles (Figure 3.24)
Extrinsic muscles proceed from their sites of origin and insert into the tongue’s mass. The extrinsic musculature enables the mass of the tongue to move from place to place within the mouth.
3.39.2.3. Intrinsic and extrinsic muscles do not act in isolation from one another. The smooth, precise tongue movements we take for granted are the result of finely coordinated contractions generated by appropriate muscles in both groups.
Figure 3.23. Intrinsic Muscles of the Tongue.
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TRANSVERSE
MUSCLE
SUPERIOR
LONGITUDINAL
MUSCLE
VERTICAL
MUSCLE
INFERIOR
LONGITUDINAL
MUSCLE
Figure 3.24. Extrinsic Muscles of the Tongue.
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DORSUM OF TONGUE
GENIOGLOSSUS
STYLOGLOSSUS
HYOGLOSSUS
¶ 3.40. Major Salivary Glands
3.40.1. The three pairs of major salivary glands are the parotid, submandibular, and sublingual glands (Figure 3.25) as follows.
3.40.1.1. The parotid glands lie in front of and below the ears. Each discharges its secretion through the parotid duct (Stensen’s duct), which enters the mouth in the maxillary buccal vestibule opposite the second molar. The opening is usually marked by a papilla called the parotid papilla.
3.40.1.2. The submandibular glands are also called the submaxillary glands. The submandibular glands are found on the right and left sides, between the mandible and the midline, mostly below and partially above the mylohyoid muscle’s posterior edge. Each submandibular gland discharges its secretion through the submandibular duct (Wharton’s duct) which opens onto the floor of the mouth.
3.40.1.3. The sublingual glands are found beneath the surface of the floor of the mouth on top of the mylohyoid muscles; the lateral border of each gland rests in a corresponding sublingual fossa.
3.40.2. The sublingual duct (duct of Bartholin) either opens independently onto the floor of the mouth or joins the submandibular duct. The openings of the sublingual and submandibular ducts are located on an elevated line of mucous membrane on each side of the lingual frenum. These elevations are the sublingual caruncles.
Figure 3.25. Major Salivary Glands.
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BUCCINATOR MUSCLE
(CUT)
MINOR DUCT OPENING
TONGUE
SALIVARY CARUNCLE
MANDIBLE
(CUT EDGE)
SUBLINGUAL GLAND
MYLOHYOID MUSCLE
STENSEN'S DUCT
PAROTID GLAND
MASSETER MUSCLE
MANDIBLE
(CUT EDGE)
WHARTON'S DUCT
SUBMANDIBULAR GLAND
DIGASTRIC MUSCLE
¶ 3.41. Minor Salivary Glands
3.41.1. Small, minor salivary glands can be found in many places around the interior of the mouth, but the ones of particular interest are located in the palate (Figure 3.26). The greatest concentrations of minor palatine glands are found in the hard and soft palates, below the surface of the mucosa, and behind a line drawn between the first molars. Skin surface exit holes for gland ducts are liberally scattered throughout this area.
Figure 3.26. Minor Palatine Salivary Glands.
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Anatomical illustration of the human mouth and dental structure, showing teeth, jawbone, and surrounding bone tissue (no text or labels)
¶ Section 3G — Temporomandibular Joint
¶ 3.42. Formation of the Temporomandibular Joints
3.42.1. The right and left temporomandibular joints are the two places where the mandible connects with the rest of the skull (Figure 3.27)
In general terms, the temporomandibular joint is formed by the glenoid fossa (mandibular fossa) (paragraph 3.43) and articular eminence (paragraph 3.44) of the temporal bone and by the condyle of the mandible (paragraph 3.45) (Also see Section 3B.)
3.42.2. The fossa and eminence are separated from contact with the condyle by an articular disc. The condyle stays in the fossa during ordinary opening and closing (hinge) movements.
¶ 3.43. Glenoid Fossa
The glenoid fossa is a deep hollow on the undersurface of the zygomatic process of the temporal bone. The condyle stays in the fossa during ordinary opening and closing (hinge) movements.
¶ 3.44. Articular Eminence
The articular eminence is a ramp-shaped prominence that extends forward and downward from the anterior boundary of the glenoid fossa. During forward (protrusive) movements of the entire mandible, both condyles leave their fossae and move onto eminences. In lateral movements, one condyle usually stays in a fossa and the other condyle moves out of the fossa onto its eminence.
¶ 3.45. Condyle
The condyle is the oval- or kidney-shaped structure found on the end of the condyloid process of the mandible.
¶ 3.46. Articular Disc
The articular disc is a pad of tough, flexible fibrocartilage situated between the condyle and the glenoid fossa. The disc is a shock-absorbing mechanism. When the condyle moves out onto the articular eminence, the disc travels with it.
¶ 3.47. Synovial Cavities
The synovial cavities are also referred to as the upper and lower joint compartments. The upper synovial cavity is found between the top of the disc and the glenoid fossa. The lower synovial cavity is found between the bottom of the disc and the condyle of the mandible.
Figure 3.27. Temporomandibular Joint.
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GLENOID FOSSA
ARTICULAR EMINENCE
SYNOVIAL CAVITIES
LATERAL PTERYGOID MUSCLE
ARTICULAR DISC
MANDIBULAR CONDYLE
¶ 3.48. Synovial Membrane
The synovial membrane is the lining of a synovial cavity. The cells of the lining make a lubricating liquid called synovial fluid.
¶ 3.49. Capsule
3.49.1. The capsule is the major ligament of the temporomandibular joint. This ligamentous sleeve or capsule originates from the entire rim of the glenoid fossa and articular eminence, attaches to the edges of the articular disc, and passes to insert around the rim of the condyle.
3.49.2. The capsule holds the disc in place between the condyle and the fossa, it retains the synovial fluid in the upper and lower joint compartments, and it acts to prevent dislocation of the mandible. Some authors of anatomy texts mention a temporomandibular ligament, which is an anterior thickening of the capsule, not a separate ligament.
¶ 3.50. Auxiliary Ligaments
Auxiliary ligaments (Figure 3.28) generally act to restrict the condyle to a normal range-of-movement and prevent dislocation as follows:
3.50.1. The stylomandibular ligament originates on the styloid process of the temporal bone and inserts on the posterior border of the ramus near the angle.
3.50.2. The sphenomandibular ligament originates on the spine of the sphenoid bone and inserts on the anterior-superior of the mandibular foramen (lingula). The mandibular foramen is found on the internal surface of the ramus of the mandible.
Figure 3.28. Auxiliary Ligaments of the Temporomandibular Joint.
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TEMPOROMANDIBULAR LIGAMENT
ARTICULAR CAPSULE
SPHENOMANDIBULAR LIGAMENT
STYLOMANDIBULAR LIGAMENT
LATERAL ASPECT
MEDIAL ASPECT
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