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The muscles for opening the jaw, know as accessory muscles of mastication, are mainly located under the chin.
Alveolar or Alveolus
That portion of the upper and lower jaws that contain the teeth and form the dental arches. Once the natural teeth have been removed, the alveolus loses its reason for existence and will slowly begin to atrophy or disappear. In some cases, this can lead to difficulty in wearing artificial teeth (dentures).
Ankylosis
The fusion of bone to bone in one of the body's joints. When this occurs, the joint becomes inflexible and useless. It may also mean the fusion of a tooth to bone. Alkylosed teeth present difficult extraction cases. An ankylosed jaw joint can lead to the inability to effectively move the jaws. This can make chewing, swallowing, talking, and other functional aspects of the jaws difficult.
Anterior Maxillary Osteotomy
An osteotomy, or separation, of the anterior maxilla (front part of the upper jaw) for the purpose of putting it into a more anatomically correct position with the rest of the jaw. This procedure is generally done to set back and/or raise the anterior segment of bone and teeth of the upper jaw.
Apertognathia
An open-bite deformity - the existence of an open bite, meaning that several teeth may not be touching when the jaws are closed or biting. This most often occurs in the area of the front teeth, but can also exist in the back teeth as well. An open-bite deformity is generally the result of the downward overgrowth of the back part of the upper jaw. It can also be caused by inappropriate growth of the lower jaw or mandible.
Arthrogram
Visualization of a joint by x-ray study after injecting of an opaque dye into the joint space.
Arthroplasty
The surgical repair of a joint - in the case of the jaws, the temporomandibular joint, or jaw joint. It may consist of repairing the cartilage, which is what the disc or meniscus is made of, or removal of the disc (meniscoplasty).
Arthroscopy
Direct joint visualization by means of an arthroscope. An arthroscope (endoscope) is a device consisting of a tube and optical system for examining the interior of the joint.
Articulator
An instrument on which dental study models are mounted or attached, which simulates the hinge movements or actions of the jaw. There are two types of articulators:
The more sophisticated and complex anatomical articulator
The simpler functional articulator
When doing this double-jaw surgery, the anatomical articulator is used. One function of the articulator is in doing model surgery, which is a three-dimensional aid in surgical planning.
Asymmetry
A structural imbalance on either the right or left side of the face that occurs in certain jaw deformities. The "lopsidedness" or imbalance is usually caused by either an undergrowth or overgrowth of one of the several of the facial bones.
Augmentation Genioplasty
Advancing or strengthening the chin by using either bone or an Alloplast material, such as silicone. A "weak chin" is the result of deficiency in the front portion of the lower jaw.
Autogenous Bone Graft
Bone borrowed from one part of the body (generally the iliac crest of the hip, or possible rib), which is then transferred to the area needed. In certain orthognathic surgical procedures, bone is needed, and harvesting it from the patient's own body is frequently done. In certain TMJ total joint replacements a rib graft will be performed rather that using a metal joint prothesis.
Bruxism
The abnormal habit or grinding or clenching the teeth together, particularly while asleep. Jaw clenching can be a conscious or unconscious habit, and it can be damaging to the teeth, gums, bone and periodontium. It can also produce muscle pain and sensitivity.
Cephalometric X-Ray
An x-ray taken with the patient's head in a specific, fixed position, from which standardized measurements can be made. Its purpose is for evaluation facial growth and development, including dental, bony, and soft-tissue profiles and their inter-relationships. A cephalometric x-ray is required in doing an orthognathic workup or treatment planning.
Cheloplasty
The surgical correction or alteration of deformities of the lips, with an eye toward restoring them functionally and aesthetically to their normal size and shape.
Cleft Lip
A congenital hole in the roof of the mouth that may involve not only the hard palate, but the soft palate as well. It may also extend into the area containing teeth, and it is caused by a lack of fusion of the two halves of the maxilla, or upper jaw, during fetal growth and development.
Nutritional
Genetic
Traumatic
Metabolic
The older the mother is during pregnancy, the greater the incidence of cleft lip/palate.
Condyle
The articulating or joint portion of the lower jaw. The condyle is the "ball" that fits into the fossa, or socket, of the temporal bone, forming the hinge known as the temporomandibular joint (TMJ).
Condylectomy
A partial or complete removal of the head of the mandibular condyle to correct and ankylosis, remove a growth or tumor, or to repair the joint through arthroplasty.
Coronoid Process
A process on the anterior upper end of the ramus of the mandible that serves fro attachment of the temporalis muscle.
Crossbite
An occlusal disharmony of the teeth, in which the buccal or outside cusps of the lower on mandibular teeth are lateral to those of the upper or maxillary teeth. This can be caused by a developmental widening of the lower jaw or a narrowing of the upper jaw.
CT (Computed Tomography)
The use of regular x-rays which are passed through the area of interest in a "slice", then analyzed by exceedingly complex computerized detectors to produce an extraordinary image of a "cut" through the area of interest, free from overlying structures, with superb detail and contrast. The CT gives very limited image, however, of the disc and soft tissues.
Deepbite Deformity
A condition in which the lower front teeth have migrated past the upper front teeth to the point of touching or nearly touching the roof of the mouth. This condition can be caused by either a DEFICIENCY in the horizontal growth of the lower jaw or an EXCESS in the horizontal growth of the upper. A Class II malocclusion usually exists. When a deepbite is caused by the lower jaw, the face is usually shortened.
Dental Arch
The horseshoe-shaped sections of the upper and lower jaws that contain the teeth and their periodontal attachments.
Dental Impression
The imprint of all or part of the dental arch, individual teeth, or cavity preparations, for the purpose of records or restorative procedures.
Dental Midline
The line that divides the teeth on the right and left sides. The dental and skeletal midlines should be the same.
Dentofacial Deformity - Jaw Deformity
A variety of growth deformities of the facial skeleton, including the maxilla, nose, zygoma, and mandible, that influence soft-tissue draping, dental relationships, and the general relationship of the facial bones to the skull. Jaw deformities may be defined as excesses and/or deficiencies in the transverse, horizontal, or vertical components. It may occur in one bone or in a combination of bones and is correctable through the orthognathic process. It is believed that over 11.5 million Americans have a jaw deformity.
Diagnostic Study Models
Dental study models are made from impressions or molds taken of the upper and lower jaws for the purpose of studying the teeth, their size, relationship, bite, and abnormalities that may exist in this portion of the jaws. Study models are a major component of orthognathic records.
Distal
Farthest from the center, from a medial line, or from the trunk. Opposed to proximal. In dental usage, distal refers to teeth farther from the middle of the given arch.
Facial Midline
The midline of the face as separated by the right and left halves.
Facial Thirds
The face is divided into three thirds, which are fairly equal dimension. The upper third of the face is the forehead, from the hairline to the bridge of the nose between the eyebrows. The middle third of the face is from between the bridge of the nose at the eyebrows to just beneath the nose, and the lower third of the face is that space beneath the nose to just below the chin.
Orthognathics attempts to achieve facial balance between the middle and lower thirds of the face in vertical, transverse, and horizontal dimensions. Clinical examination and measurements are critical in proper diagnosis and treatment planning for skeletal corrections in this area.
Fibromyalgia
A chronic, painful muscle condition characterized by painful skeletal muscles and other soft tissue throughout the body. Some of the common characteristics are: generalized muscle soreness and stiffness lasting more that three months, poor sleep with morning fatigue and stiffness, tenderness at 11 of 18 specific sites, and normal blood results.
Fixation
Intermaxillary Fixation (IMF) or Maxillomandibular Fixation. The vertical fixation or wiring of a broken jaw or jaw that has had orthognathic surgery, bringing the upper and lower jaws into a functional relationship (normal bite) using elastics, wires, orthodontic braces, arch bars, splints, or a combination of these. "Having your jaws wired shut."
Skeletal Fixation. The fixing of the facial bones, either directly or indirectly, using wires, pins, plates, or splints. Fixation is generally temporary, and may last anywhere from two to ten weeks. Indirect wires one and splints are removed once healing has been assured, while fixed wires, plates, or screws remain.
Rigid Fixation. Fixing two halves of an osteotomy or fracture site with screws or plates in such a fashion that the bones are "rigidly fixed", thus allowing the jaws to be kept open (or closed) for only a short period of time during the healing period. Rigidly-fixed jaw surgery sites avoid the need for wiring the jaw shut.
Surgical Splint A plastic and/or acrylic splint used to key in the dental arches (teeth) for maximum accuracy during orthognathic surgery. It is employed to maintain the tissues in their position following surgery and is fabricated from the bite obtained through model surgery.
Suspension Wires Temporary wires used to stabilize an osteotomized or surgically bone (usually the maxilla), which may be suspended from the zygomatic arch (cheekbones), the infraorbital rim (lower eye rim), or the lateral piraform aperature (a side of the nose), for the purpose of adding bracing and stability during the healing process. These wires are removed once healing has occurred.
Intra-Osseous/Transosseous/Direct Bone Wiring Stabilization of an osteotemized bony part or parts by direct fixation to one another with surgical wires, screws, pins, or plates. These are generally not removed.
Genioplasty
A surgical augmentation (increase) or reduction of the side of the chin. This operation is generally done within the mouth, and the materials used may be bone or an implant material, such as silicone. Reduction genioplasty reduces the size of the chin, and this done by either repositioning chin bone or surgically reducing it.
An excessive amount of growth of the lower jaw, producing a protrusive or prognathic chin (prognathism) and a Class III malocclusion (lower teeth forward of the upper teeth).
Hyperesthesia
A decreased sensation or numbness when a painful stimuli is applied. This is generally due to a bruising, with subsequent swelling or a sensory nerve, as a result of jaw surgery or an injury. Also known as "hypoesthesia".
Hyperplasia
An increase in the size of a tissue or organ due to an increase in the number of cells. Hyperplasia usually implies growth. Hyperplastic tissue is tissue that is abnormally growing.
Hypertrophy
The increase in the size of an organ or tissue because of an increase in the size of the individual cells. Hypertrophy is usually the result of some form of chronic irritation. The individual cells begin to slowly take on fluid, which collectively create a swelling.
Lateral Pterygoid Muscle
The muscles that are responsible for the side to side (lateral) movement of the jaw. They originate at he same regions of the cranium as the medial pterygoid muscles and extend backward and outward toward the condyles.
Lateralgnathia
A horizontal deformity to one or the other side of the upper or lower jaws in relationship to the rest of the face. A facial asymmetry.
LeFort I Maxillary Osteotomy
A common orthognathic surgical procedure. A transverse or horizontal separation of the dentoalveolar process of the maxilla to include the palate, floor of the nose, and the maxillary sinuses for the purpose of widening, narrowing, lengthening, shortening, or leveling the upper jaw so that it can be placed in harmony with the other facial bones, as well as the skull. This operation is done within the mouth and is called a "down fracture". It can be done in one or several segments. The development of the Le Fort I maxillary osteotomy was a major breakthrough in the development of orthognathic surgery.
LeFort II Osteotomy
An osteotomy of the nasal maxillary complex (nose and upper jaw) of the middle third of the face. This is done for the purpose of repositioning this complex to correct a disharmony and to normalize its relationship with the adjacent bony structures. It is generally done to bring that portion of the face forward.
LeFort III Osteotomy
A surgical separation of the naso-maxillary/malar complex (nose, upper jaw, and cheekbones) of the middle third of the face for the purpose of putting it into harmony and balance with the lower jaw and skull, both functionally and aesthetically, It is generally done to bring the entire middle third of the face forward.
Ligament
A band or sheet of strong fibrous connective tissue connecting the articular ends of bones serving to bind them together and to both facilitate of limit motion. Ligaments also connect bones, cartilages and other structures and serve for support or for attachment of fascia or muscles.
Malar Bone/Zygoma
The cheek bone. The malar bone fuses with the upper jaw bone (maxilla), the frontal bone, and the temporal bone. It gives shape and contour to the side of the middle third of the face.
Malocclusion
Any deviation from a physiologically acceptable relationship of the upper and lower teeth with each other. Malocclusions have been divided into several categories (See Occlusion).
Mandible
The lower jaw. A bilateral-joined bone divided into a horizontal component (the body) and a vertical component (the ramus). It joins at the chin, (the sympasis), and hinges with the temporal bone, called the temporomandibular joint (jaw joint). There is a disc or meniscus (cartilage) that interfaces between the bones of this joint, which serves as a buffer or cushion between the two bones.
Mandibular Advancement
Advancing the mandible surgically by using a variety of surgical techniques, the most common of which is modified, sagittal-split osteotomy, This technique creates a telescoping effect to ensure bone to bone contact during the healing period.
Mandibular Condyle
The hinge or articulating portion of the mandible that helps to form the temporomandibular joint (jaw joint) - "ball and socket" relationship.
Mandibular Deficiency Syndrome - Retrognathia
A horizontally underdeveloped mandible, in which a person can have a receding chin, as Class II malocclusion (lower teeth behind upper teeth), often times a deep bite, and occasionally a shortened face. The temporomandibular joint may also be involved, and sometimes myofacial pain (muscle pain) may exist. The mandibular deficiency syndrome can be classified as to Type I, II, or III, with the classification being dependant upon the mandibular plane angle, which is either a steepening or a leveling of the lower jaw in relationship to a horizontal line.
Mandibular Set Back
Setting back the lower jaw by using one of several available surgical techniques, the most common of which is the MODIFIED SAGITTAL-SPLIT OSTEOTOMY. The mandible is set back when there is a leveling of the lower jaw (horizontal mandibular excess).
Manipulation
Skillful or dextrous treatment or procedure involving the use of the hands. Oral Manipulation is the manual stretching of the jaw joint under sedation.
MRI (Magnetic Resonance Imaging)
Computer-aided analysis, without using x-rays or without injection, produces critical features that are detailed and accurate images of bone and soft tissue. The MRI's use a powerful magnetic field with radio frequency pulse used to activate the structures being imaged.
Maxilla
The upper jaw, which contains the upper teeth, the palate, the maxillary sinuses, the floor of the nose, and part of the orbital rim. The maxilla frequently can have growth deformities, correctable with orthognathic surgery.
Medial Pterygoid
Greek term for "wing-shaped". The medial pterygoid muscle parallels the masseter on the inside of the jaw. The masseter and the medial pterygoid muscles form a sort of sling around the angle of the mandible and work together to pull it shut. Closing muscle.
Meniscus-Disc Cartilage
This tissue is composed of a tough, fibrocartilaginous material that acts as an interface between the bones making up the jaw joint. It can withstand, without being injured, the normal functions of the joint. It does not have blood vessels or nerves, and therefore in itself cannot be painful. When cartilage is displaced, a series of symptoms can develop, and these may include:
Ringing in the ears
Dizziness
Pain in the joint
A burning sensation in the area
A transient loss of hearing
Jaw dysfunction
Frequently, there is clicking and popping of the joint. If symptoms occur, the disc can be either repaired or replaced. The procedure used to repair the jaw joint is called an arthroplasty.
Micrognathia
An abnormally small or underdeveloped lower jaw, as compared with the rest of the facial bone or structures.
Millimeter
One thousandth of a meter. There are 25.4 millimeters to the inch. When measuring the range of motion of the oral opening (mouth) a practitioner will measure from the bottom of the front incisor to the top of the bottom inciso. This increment of measurement will be done in millimeters.
Model Surgery
A three-dimensional aid in determining the exact dimensions that must be added or removed in order to put the upper and lower jaws into skeletal and dental harmony and balance. It is from model surgery that the surgical splint is fabricated and used at the time of surgery. A combination of the prediction tracing ( S.T.O. ) and model surgery brings accuracy to the operative technique. Orthognathic surgery is one of the only surgeries that is done twice: first on the models and then on the operating room.
Muscles of Mastication
These muscles are know as the chewing muscles and produce all the movements of the jaw. These muscles extend between the cranium and the mandible on each side of the head.
Myofacial Pain
Pain involving the muscles of the head, neck, and upper back.
Nasogastric Tube
A tube passed through the nose, into the esophagus, and finally into the stomach. In orthognathic surgery it is used to eliminate foreign material from the stomach and to reduce the chance of vomiting.
Occlusion
The way the teeth bite or come together. Occlusion may be normal or abnormal (malocclusion) and classified as follows:
Class I A Class I occlusion exists with the teeth in a normal relationship when the mesial-buccal cusp of the maxillary first permanent molar coincides with the buccal groove of the mandibular first molar.
Class II This occurs when the mandibular teeth are distal or behind the normal relationship with the maxillary teeth. This can be due to a deficiency of the lower jaw or an excess of the upper jaw, and therefore presents two types:
Division I, when the mandibular arch is behind the upper jaw with a consequential protrusion of the upper front teeth.
Division II exist when the mandibular teeth are behind the upper teeth, with a retrusion of the maxillary front teeth. Both of these malocclusions have a tendency toward a deep bite because of the uncontrolled migration of the lower front teeth "upwards".
Class III. This occurs when the lower dental arch is in front of (mesial to) the upper dental arch. People with this type of occlusion usually have a strong or protrusive chin, which can be due to either horizontal mandibular excess or horizontal maxillary deficiency. Commonly referred to as an underbite.
Orthognathics
The surgical orthodontic correction of jaw deformities, with the goal being to bring the bones, teeth, and soft tissues into harmony and balance, with an eye towards an optimum functional and aesthetic result. The word orthognathics means "straight jaws".
The surgical repositioning of the various bones of the face, to include the mandible, maxilla, zygoma (cheek bones) and the nose. This can be done in segments or as a whole and with a variety of combinations. The goal is to bring balance to the facial skeleton, to include the teeth, the bones, and the overlying soft tissues.
Ostectomy
The excision, sectioning, or cutting of a bone for the purpose of removing a portion of the bone and repositioning it into a more structurally balanced relationship with itself and adjacent structures.
Osteoplasty
A surgical procedure that is designed to change or modify the shape or configuration of a bone.
Osteotomy
The incision, sectioning, or cutting of a bone, without removing any of its parts, for the purpose of repositioning it into a structurally correct location with itself and adjacent structures.
Overbite
An extension of the upper teeth over the lower teeth in a vertical fashion. When the person is biting, it is difficult to see the lower front teeth if the overbite is excessive.
Overjet
A projection of the upper front teeth beyond the lower front teeth. Severe overjet gives the "buck-tooth look" and is usually caused by a skeletal deformity of the upper jaw.
Panoramic X-Ray
An extra-oral technique, using a moving x-ray tube to obtain a radiograph, or x-ray, containing the upper and lower teeth, as wall as the surrounding and supporting bones of the face. This is done on a single film and flattens out the face; thus, it is called a "panoramic view".
Paresthesia
A prolonged, altered sensation, tingling, or numbness due to a bruising of a sensory nerve. Paresthesia is a common side effect of orthognathic surgery.
Posterior Maxillary Osteotomy
An osteotomy where the bone is cut in the back portion of the upper jaw to correct a dimension and inaccuracy in its relationship to itself and other bones.
Prognathism
An obviously forward projection of the lower jaw or mandible beyond the upper jaw and beyond a normal distance from the cranial base due to a horizontal mandibular excess. It is consistent with a Class III malocclusion.
Reciprocal Click
A click in the temporomandibular joint that is felt or heard as the mouth opens and closes.
Retrodiscal Tissue
Inside the temporomandibular joint capsule, located just behind the disc, is connective tissue know as retrodiscal tissue. The retrodiscal tissue is composed partially of ligaments connecting the disc to the temporal bone of the condyle, but the primary composition is made up of a fairly loose spongy material.
Sagittal-Split Osteotomy
A surgical technique done in the mouth (intra-orally) for altering the position of the body of the mandible by splitting a portion of the jaw and ramus of the jaw on each side in the sagittal plane, thus creating a telescopic or sliding relationship. The sagittal plane is that plane created if you were to divide the body into a right and left half. This technique can be used for lengthening or shortening the lower jaw, with an assurance that there will be bone-on-bone during the healing.
Sensory Nerves
The nerves that feel particular things such as; position, pressure, or pain. An afferent nerve conveying sensory impulses to the sensorium, or one composed of sensory fibers.
Short-Face Syndrome
The short-face syndrome is characterized by a shortening of the lower third of the face, due to either vertical maxillary deficiency or a Type I mandibular deficiency with a Class II deep bite. Diagnosis is confirmed by cephalometric analysis and a thorough clinical examination of the patient.
Stylohyoid Process
A pointed process of the temporal bone, projecting downward, and to which some of the muscles of the tongue are attached.
Subapical Osteotomy
An incision or cutting of the bone vertically, between or adjacent to the teeth and horizontally beneath the root ends of the teeth, for the purpose of leveling, widening, narrowing, or closing spaces. The most common area for this operation is the lower anterior segment containing the lower six teeth.
Surgical Splint
A plastic or acrylic split used to key in the dental arches for maximum accuracy during orthognathic surgery. It is employed to maintain the bones in their new position following orthognathic surgery and is fabricated on the bite obtained through model surgery. The splint is worn throughout the healing period.
Surgical Treatment Objective
Surgical Treatment Objective is an enhancement of the prediction tracing technique for the purpose of predicting the effects that surgery will have on the positioning of the facial bones, teeth, and overlaying soft tissues. It is a two-dimensional diagnostic tool that lends accuracy and predictability to treatment planning.
Temporalis Muscle
Muscle in the temporal fossa the elevates the mandible. This "closing" muscle looks like a partly spread fan on the side of the head. Its broad end originates high on the temple, so it is called the temporalis muscle.
Temporomandibular Joint - TMJ - Jaw Joint
The joint created by the glenoid fossa of the temporal bone and the condyle of the mandible (lower jaw). Interfaced between this "ball and socket" is the meniscus or disc (cartilage), which is braced into position in front by the external pterygoid muscle (jaw opening muscle) and posteriorly by the bilaminar zone (poster disc attachment). It is further strengthened by a capsule which covers the entire joint and is integrated with the other bracing tissues. The jaw joint or hinge allows us to open, close, protrude, and laterally move the lower jaw in chewing, talking, swallowing, and in all other functions that the movement of the lower jaw performs.
Temporal Bones (bones of the temple)
A bone on both sides of the skull at its base. Composed of squamous, mastoid, and petrous portions, the latter enclosing the organ of hearing.
Tinnitus
A subjective ringing, buzzing or tinkling sound in the ear.
Trismus
An inability to open the mouth due to muscle spasms, injury, a formation of scar tissues in the muscles of the jaws, or a bony union (ankylosis) in the temporomandibular joint - jaw joint.
Vertical Maxillary Excess - Long Face Syndrome
An overgrowth of the upper jaw or maxillary in the vertical dimension which if is in the front portion of the jaw, will allow an excess amount of tooth structure to show and will create an abnormal smile pattern, with an abundance of gingiva or gum tissue showing (gummy smile). Patients with exterior vertical maxillary excess have lip incompetence: that is, their lips do not come together in a relaxed fashion when the teeth are in occlusion and requiring the use of muscular force in order to bring the lips together, creating the "buck-tooth" appearance. The lower third of the face is out of proportion (too long) in length to the middle and upper thirds.
Vertical maxillary excess may also occur in the back area of the upper jaw, creating an open bite in the front (Apertognathia), but a normal amount of tooth structure showing. Lip incompetence is also a component of posterior vertical maxillary excess. Mouth breathing, a receded chin, inflamed gums, and frequently a Class II malocclusion are components of this syndrome. There also may be a high palatal vault, and a speech-articulation abnormality may exist.
Vertical Ramus Osteotomy
An osteotomy of the posterior ramus of the lower jaw or mandible in the vertical dimension, which can be performed within the mouth (intra-orally), or extra-orally, for the purpose of repositioning the mandible back (posteriorly). It is commonly used to correct the prognathic mandible (lantern jaw or horizontal mandibular excess).