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The alveolar process () or alveolar bone is the thickened ridge of
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
that contains the tooth sockets on the
jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...
bones (in humans, the
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...
and the
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
). The structures are covered by gums as part of the
oral cavity In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...
. The synonymous terms ''alveolar ridge'' and ''alveolar margin'' are also sometimes used more specifically to refer to the ridges on the inside of the mouth which can be felt with the
tongue The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste ...
, either on roof of the mouth between the upper teeth and the
hard palate The hard palate is a thin horizontal bony plate made up of two bones of the facial skeleton, located in the roof of the mouth. The bones are the palatine process of the maxilla and the horizontal plate of palatine bone. The hard palate spans t ...
or on the bottom of the mouth behind the lower teeth.


Terminology

The term ''alveolar'' () ('hollow') refers to the cavities of the tooth sockets, known as dental alveoli. The alveolar process is also called the ''alveolar bone'' or ''alveolar ridge''. The curved portion is referred to as the alveolar arch. The alveolar bone proper, also called bundle bone, directly surrounds the teeth. The term alveolar crest describes the extreme rim of the bone nearest to the crowns of the teeth. The portion of alveolar bone between two adjacent teeth is known as the interdental septum (or interdental bone). The connected, supporting area of the jaw (delineated by the apexes of the roots of the teeth) is known as the basal bone.


Structure

On the
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...
, the alveolar process is a ridge on the inferior surface, making up the thickest part of the bone. On the
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
it is a ridge on the superior surface. The structures hold the teeth and are encased by gums as part of the
oral cavity In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...
. Either alveolar process comprises cells, nerves,
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s,
lymphatic vessel The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph ve ...
s, and
periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. Endosteum lines the inner surface of the medullary cavity of all long bones. Structu ...
. The alveolar crest terminates uniformly at about the neck of the teeth (within about 1 to 2 mm in a healthy specimen).Ten Cate's Oral Histology, Nanci, Elsevier, 2013, page 219 The alveolar process proper encases the tooth sockets, and contains a lining of
compact bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...
around the roots of the teeth, called the lamina dura. This is attached by the periodontal ligament (PDL) to the root
cementum Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, ...
. Although the alveolar process is composed of compact bone, it may be called the
cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. ''sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It supp ...
because it contains numerous holes where
Volkmann's canals Volkmann's canals, also known as perforating holes or channels, are anatomic arrangements in cortical bones. Volkmann's canals are inside osteons. They interconnect the haversian canals with each other and the periosteum. They usually run at obtus ...
pass from the alveolar bone into the PDL. The alveolar bone proper is also called bundle bone because Sharpey's fibres, part of the PDL, are inserted there. Sharpey's fibres in alveolar bone proper are inserted at a right angle (just as with the cemental surface); they are fewer in number, but thicker in diameter than those found in cementum. The supporting alveolar bone consists of both cortical (compact) bone and
trabecular bone A trabecula (plural trabeculae, from Latin for "small beam") is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally has ...
. The cortical bone consists of plates on the facial and lingual surfaces of the alveolar bone. These cortical plates are usually about 1.5 to 3 mm thick over posterior teeth, but the thickness is highly variable around anterior teeth. The trabecular bone consists of
cancellous bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...
that is located between the alveolar bone proper and the cortical plates. The alveolar structure is a dynamic tissue which provides the jawbone with some degree of flexibility and resilience for the embedded teeth as they encounter numerous multi-directional forces.


Composition

Alveolar bone is 67% inorganic material, composed mainly of the minerals
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
and
phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...
. The
mineral salt Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...
s it contains are mostly in the form of calcium hydroxyapatite crystals. The remaining alveolar bone (33%) is
organic material Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
, consisting of 28% collagen (mostly type I) and 5% non-collagenous
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
. The cellular component of bone consists of osteoblasts,
osteocyte An osteocyte, an oblate shaped type of bone cell with dendritic processes, is the most commonly found cell in mature bone. It can live as long as the organism itself. The adult human body has about 42 billion of them. Osteocytes do not divide an ...
s and
osteoclast An osteoclast () is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated pro ...
s.


Clinical significance


Alveolar bone loss

Bone is lost through the process of resorption which involves osteoclasts breaking down the hard tissue of bone. A key indication of resorption is when scalloped erosion occurs. This is also known as Howship's lacuna. The resorption phase lasts as long as the lifespan of the osteoclast which is around 8 to 10 days. After this resorption phase, the osteoclast can continue resorbing surfaces in another cycle or carry out apoptosis. A repair phase follows the resorption phase which lasts over 3 months. In patients with periodontal disease, inflammation lasts longer and during the repair phase, resorption may override any bone formation. This results in a net loss of alveolar bone. Alveolar bone loss is closely associated with periodontal disease. Periodontal disease is the inflammation of the gums. Studies in osteoimmunology have proposed 2 models for alveolar bone loss. One model states that inflammation is triggered by a periodontal pathogen which activates the acquired immune system to inhibit bone coupling by limiting new bone formation after resorption. Another model states that cytokinesis may inhibit the differentiation of osteoblasts from their precursors, therefore limiting bone formation. This results in a net loss of alveolar bone.


Developmental disturbances

The developmental disturbance of anodontia (or hypodontia, if only one tooth), in which tooth germs are congenitally absent, may affect the development of the alveolar processes. This occurrence can prevent the alveolar processes of either the maxillae or the mandible from developing. Proper development is impossible because the alveolar unit of each dental arch must form in response to the tooth germs in the area.


Pathology

After extraction of a tooth, the clot in the alveolus fills in with immature bone, which later is remodeled into mature secondary bone. Disturbance of the blood clot can cause alveolar osteitis, commonly referred to as "dry socket." With the partial or total loss of teeth, the alveolar process undergoes resorption. The underlying basal bone of the body of the maxilla or mandible remains less affected, however, because it does not need the presence of teeth to remain viable. The loss of alveolar bone, coupled with attrition of the teeth, causes a loss of height of the lower third of the vertical dimension of the face when the teeth are in maximum intercuspation. The extent of this loss is determined based on clinical judgment using the Golden Proportions. The density of the alveolar bone in a given area also determines the route that dental infection takes with abscess formation, as well as the efficacy of local infiltration during the use of local anesthesia. In addition, the differences in alveolar process density determine the easiest and most convenient areas of bony fracture to be used, if needed during tooth extraction of impacted teeth. During chronic
periodontal Periodontology or periodontics (from Ancient Greek , – 'around'; and , – 'tooth', genitive , ) is the specialty of dentistry that studies supporting structures of teeth, as well as diseases and conditions that affect them. The supporting ...
disease that has affected the periodontium (periodontitis), localized bone tissue is also lost. The radiographic integrity of the lamina dura is important in detecting pathological lesions. It appears uniformly
radiopaque Radiodensity (or radiopacity) is opacity to the radio wave and X-ray portion of the electromagnetic spectrum: that is, the relative inability of those kinds of electromagnetic radiation to pass through a particular material. Radiolucency or hypod ...
(or lighter).


Alveolar bone grafting

Alveolar bone grafting in the mixed dentition is an essential part of the reconstructive journey for cleft lip and cleft palate patients. The reconstruction of the alveolar cleft can provide both aesthetic and practical advantages to the patient. Alveolar bone grafting can also bring about the following benefits: stabilisation of the maxillary arch; aid of eruption of the canine and sometimes lateral incisor eruption; offering bony support to the teeth lying next to the cleft; elevate the alar base of the nose; aid sealing of oro-nasal fistula; permit insertion of a titanium fixture in the grafted region and achieve good periodontal conditions within and next to the cleft. Material was copied from this source, which is available under a Creative Commons License. The timing of the alveolar bone grafting takes into consideration both eruption of the canine and lateral incisor. The optimal time for bone grafting surgery is when a thin shell of bone still covers the soon erupting lateral incisor or canine tooth close to the cleft. * Primary bone grafting: Primary bone grafting is believed to: eliminate bone deficiency, stabilize pre-maxilla, synthesize new bone matrix for eruption of teeth in the cleft area and augment the alar base. However, the early bone grafting procedure is abandoned in most cleft lip and palate centres around the world due to many disadvantages, including serious growth disturbances of the middle third of the facial skeleton. The operative technique that involves the vomero-premaxillary suture was found to inhibit maxillary growth. * Secondary bone grafting: Secondary bone grafting, also referred to as bone grafting in the mixed dentition, became a well-established procedure after abandoning primary bone grafting. The prerequisites include precise timing, operating technique, and acceptably vascularized soft tissue. The advantages of primary bone grafting, which are allowing tooth eruption through the grafted bone, are retained. Furthermore, secondary bone grafting stabilizes the maxillary arch, thus enhancing the conditions for prosthodontic treatment such as crowns, bridges and implants. It also aids eruption of teeth, boosting the amount of bony tissue on the alveolar crest, permitting orthodontic treatment. Bony support to teeth adjacent to the cleft is a pre-requisite for orthodontic closure of the teeth in the cleft region. Hence, better hygienic conditions will be achieved which helps to lessen formation of caries and periodontal inflammation. Speech problems caused by irregular positioning of articulators, or leakage of air via the oronasal communication, may also be improved. Secondary bone grafting can also be used to augment the alar base of the nose to achieve symmetry with the non-cleft side, thereby enhancing facial appearance. * Late secondary bone grafting: Bone grafting has a lower success rate when performed after canine has erupted as compared to before the eruption. It has been found that the possibility for orthodontic closure of the cleft in the dental arch is smaller in patients grafted before canine eruption than those after the canine eruption. The surgical procedure includes drilling of several small openings through the cortical layer into the cancellous layer, facilitating growth of blood vessels into the graft.


Congenital epulis

Congenital epulis is a rare,
benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...
mesenchymal Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...
tumour which usually presents at birth. It can be found growing on the alveolar ridge of newborns, presenting as non-ulcerated, pedunculated, reddish pink masses of varying sizes and numbers. Congenital epulis can occur in either of the alveolar ridges, but they are found three times more frequently on the maxillary alveolar ridge than on the mandibular alveolar ridge. They also more commonly present in females compared to males. Diagnosis of the condition was previously incidental, however, with improvements in imaging technology, prenatal diagnosis is now possible at 26 weeks (about 6 months). Furthermore, these benign lesions can be treated by surgical excision.


Dentistry

The alveolar ridge is an area of particular interest in dentistry, as preservation of the ridges results in a higher success rate of therapeutic dental treatments.


Grafting materials

Grafting is an effective technique to reduce the inevitable changes in dimension of the alveolar ridge after tooth extraction. The type of grafting material is important as different materials are more effective than others in maintaining the alveolar ridge. No biomaterial can prevent alveolar bone loss entirely after extraction, however, there are five grafting materials with the greatest efficacy in height resorption prevention; three of which are
xenograft Xenotransplantation (''xenos-'' from the Greek meaning "foreign" or strange), or heterologous transplant, is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenograf ...
materials (Gen-Os, Apatos, and MP3), one a
platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...
concentrate (A-PRF) and one composed of A-PRF and the
allograft Allotransplant (''allo-'' meaning "other" in Greek) is the transplantation of cells, tissues, or organs to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, o ...
material AlloOss  combined. For the best outcomes with respect to horizontal alveolar ridge preservation, application of a xenogenic (non-living bone material from another species) or allogenic grafting material (bone donated by another human) surrounded by a resorbable collagen membrane or sponge is ideal. These membranes promote wound healing,
osteogenesis Osteoblasts (from the Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts funct ...
and have a high
biocompatibility Biocompatibility is related to the behavior of biomaterials in various contexts. The term refers to the ability of a material to perform with an appropriate host response in a specific situation. The ambiguity of the term reflects the ongoing de ...
. Other reliable options for surgeons may include Bio-Oss and Bio-Oss Coll, primarily due to the strong scientific evidence behind their efficacy and recorded successful outcomes particularly in lateral ridge augmentation surgery. L-PRF is also preferred in many clinical situations because of its low cost of preparation.  


Dental implants

The alveolar ridge refers to one of the two thickened bony crests, that exists in the upper and lower portions of the jawbone and house the sockets of the teeth. As the rate of tooth loss in the population increases either due to early extraction, trauma, or other
systemic disease A systemic disease is one that affects a number of organs and tissues, or affects the body as a whole. Examples * Mastocytosis, including mast cell activation syndrome and eosinophilic esophagitis * Chronic fatigue syndrome * Systemic vas ...
s, the use of implant therapy has increased as a form of tooth replacement therapy. Dental implants are a way to replace missing teeth, as they consist of a titanium surgical component that is placed in the alveolar ridge of the jawbone. The implant then acts as a prosthetic device that can hold either a
crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
,
bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...
, or
denture Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, and are supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable ( removable partial denture or ...
on its external surface. For the implant placement to be successful, there needs to be enough alveolar bone to support and stabilize the dental implant. It has been determined that many factors can contribute to the loss of both the vertical and horizontal height of the alveolar bone. These factors can include resorption of the bone after tooth removal (affecting the quality and quantity of the bone), the presence of
periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main caus ...
, the age and gender of the patient, smoking habits, the presence of other systemic diseases, and oral hygiene habits. Although dental implants tend to have a high success rate, of about 99%, studies show that if an implant were to fail, it occurs more often in the front portion of the upper jaw. More research is required to determine why this occurs, but it has been theorized that the alveolar bone in the upper jaw has a thinner cortical plate and lower bone density than that of the lower jaw. As bone loss in the alveolar ridge becomes an increasing problem for the success of dental implants, research has been focused on the development of new surgical techniques and biomaterials that can be used to either maintain current bone levels, or to stimulate the growth of new alveolar bone through osteogenesis.


Articulation

Consonants In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are and pronounced with the lips; and pronounced with the front of the tongue; and pronounced wit ...
whose constriction is made with the tongue tip or
blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Histor ...
touching or reaching for the alveolar ridge are called alveolar consonants. Examples of alveolar consonants in English are, for instance, , , , , , like in the words ''tight, dawn, silly, zoo, nasty'' and ''lurid''. There are exceptions to this however, such as speakers of the
New York accent The phonology, sound system of New York City English is popularly known as a New York accent. The New York metropolitan area, New York metropolitan accent is one of the most recognizable accent (sociolinguistics), accents of the United States, ...
who pronounce and at the back of their top teeth ( dental stops). When pronouncing these sounds the tongue touches ( , or nearly touches ( the upper alveolar ridge, which can also be referred to as gum ridge. In many other languages, consonants transcribed with these letters are articulated slightly differently, and are often described as dental consonants. In many languages consonants are articulated with the tongue touching or close to the upper alveolar ridge. The former are called alveolar
plosives In phonetics, a plosive, also known as an occlusive or simply a stop, is a pulmonic consonant in which the vocal tract is blocked so that all airflow ceases. The occlusion may be made with the tongue tip or blade (, ), tongue body (, ), lips ...
(such as and ), and the latter alveolar
fricatives A fricative is a consonant produced by forcing air through a narrow channel made by placing two articulators close together. These may be the lower lip against the upper teeth, in the case of ; the back of the tongue against the soft palate in t ...
(such as and ) or (such as and ).


Culture

Other than a maxillar bridge made of gold, part of a mandible with teeth—which had been burned and broken around the alveolar process—was the only physical evidence used to confirm
Adolf Hitler Adolf Hitler (; 20 April 188930 April 1945) was an Austrian-born German politician who was dictator of Nazi Germany, Germany from 1933 until Death of Adolf Hitler, his death in 1945. Adolf Hitler's rise to power, He rose to power as the le ...
's
death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
in 1945. According to Eva Braun's purported Soviet autopsy report, the alveolar process was missing from her charred maxilla.


Gallery

Alveolar part of mandible - close up- anterior view.png, Superior area of the alveolar process on the mandible Gray157.png, The alveolar process of the maxilla is located at its inferior surface. Teeth - animation 01.gif, 3D animation showing placement of teeth in human skull Sobo 1906 326.png, In the oral cavity, the alveolar processes are covered by gums. Blausen 0863 ToothAnatomy 02.png, How the roots of the teeth, gums, and alveolar bone are related


References


Sources

*


External links

* Photo of model at Waynesburg College
skeleton/alveolarprocess
' *

{{Authority control Bones of the head and neck Dental anatomy Mouth