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Alveolar process

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Alveolar process
Human jaws, with anterior portion of alveolar processes cut away towards the right
Details
Identifiers
Latinos alveolaris
MeSHD000539
TA98A02.1.12.035
TA2791
FMA59487 52897, 59487
Anatomical terms of bone

The alveolar process (/ælˈviːələr/)[1] is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity.

Terminology

The term alveolar ('hollow') refers to the cavities of the tooth sockets, known as dental alveoli.[2] The alveolar process is also called the alveolar bone or alveolar ridge.[3] The curved portion is referred to as the alveolar arch.[4] The alveolar bone proper, also called bundle bone, directly surrounds the teeth.[5] The term alveolar crest describes the extreme rim of the bone nearest to the crowns of the teeth.[6] The portion of alveolar bone between two adjacent teeth is known as the interdental septum (or interdental bone).[7]

The connected, supporting area of the jaw (delineated by the apexes of the roots of the teeth) is known as the basal bone.[8]

Structure

Cutaway view of teeth and their situation in the jaws (c. 1910)

On the maxilla, the alveolar process is a ridge on the inferior surface, making up the thickest part of the bone. On the mandible it is a ridge on the superior surface. The structures hold the teeth and are encased by gums as part of the oral cavity.[9] Either alveolar process comprises cells, nerves, blood vessels, lymphatic vessels, and periosteum.[6] The alveolar crest terminates uniformly at about the neck of the teeth (within about 1 to 2 mm in a healthy specimen).[10][11]

The alveolar process proper encases the tooth sockets, and contains a lining of compact bone around the roots of the teeth, called the lamina dura.[6] This is attached by the periodontal ligament (PDL) to the root cementum.[6] Although the alveolar process is composed of compact bone, it may be called the cribriform plate because it contains numerous holes where Volkmann's canals 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.[6]

The supporting alveolar bone consists of both cortical (compact) bone and trabecular bone. 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.[11] The trabecular bone consists of cancellous bone that is located between the alveolar bone proper and the cortical plates.[12]

Composition

Alveolar bone is 67% inorganic material, composed mainly of the minerals calcium and phosphate. The mineral salts it contains are mostly in the form of calcium hydroxyapatite crystals.[13] The remaining alveolar bone (33%) is organic material, consisting of 28% collagen (mostly type I) and 5% non-collagenous protein.[13]

The cellular component of bone consists of osteoblasts, osteocytes and osteoclasts.[13]

Clinical significance

Alveolar bone loss

This X-ray film reveals some bone loss on the right side of the mandible. The associated teeth exhibit poor crown-to-root ratios and may be subject to secondary occlusal trauma.

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.[14] 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.[15]

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.[16] 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.[17]

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.[18]

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.[18]

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.[18]

During chronic periodontal 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 (or lighter).[6]

Alveolar bone grafting

Alveolar bone grafting in the mixed dentition is an essential part of the reconstructive journey for cleft lip and palate patients. The reconstruction of the alveolar cleft can provide both aesthetic and practical advantages to the patient.[19] 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.[20] 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.[20]

  • 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.[20]
  • 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 pre-requisites 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.[20]
  • 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.[20]

References

  1. ^ Entry "alveolar" in Merriam-Webster Online Dictionary
  2. ^ "alveolar | Origin and meaning of alveolar". Online Etymology Dictionary. Retrieved 31 August 2021.{{cite web}}: CS1 maint: url-status (link)
  3. ^ Bath-Balogh & Fehrenbach 1997, p. 195.
  4. ^ Sazonova, O.; Vovk, O.; Hordiichuk, D.; Ikramov, V. (February 2019). "Anatomical Features Of The Maxillary Alveolar Arch In Adulthood". Georgian Medical News (287): 111–114. ISSN 1512-0112. PMID 30958300.
  5. ^ Araujo M, Lindhe J (2003). "The Edentulous Alveolar Ridge.". In Lindhe J, Karring T, Lang NP (eds.). Clinical Periodontology and Implant Dentistry (5th ed.). Oxford: Blackwell Munksgaard. p. 53–63.
  6. ^ a b c d e f Bath-Balogh & Fehrenbach 1997, p. 196.
  7. ^ Bath-Balogh & Fehrenbach 1997, p. 199–200.
  8. ^ Bath-Balogh & Fehrenbach 1997, pp. 195–197.
  9. ^ Walker, William B. (1990), Walker, H. Kenneth; Hall, W. Dallas; Hurst, J. Willis (eds.), "The Oral Cavity and Associated Structures", Clinical Methods: The History, Physical, and Laboratory Examinations (3rd ed.), Boston: Butterworths, ISBN 978-0-409-90077-4, PMID 21250078, retrieved 30 August 2021
  10. ^ Bath-Balogh & Fehrenbach 1997, pp. 196, 198.
  11. ^ a b Ten Cate's Oral Histology, Nanci, Elsevier, 2013, page 219
  12. ^ Bath-Balogh & Fehrenbach 1997, pp. 198–99.
  13. ^ a b c Bathla, Shalu (2017). Textbook of Periodontics (1st ed.). New Delhi: Jaypee Brothers. pp. 37–39. ISBN 978-9386261731. OCLC 971599883.
  14. ^ Bar-Shavit Z (December 2007). "The osteoclast: a multinucleated, hematopoietic-origin, bone-resorbing osteoimmune cell". Journal of Cellular Biochemistry. 102 (5): 1130–9. doi:10.1002/jcb.21553. PMID 17955494.
  15. ^ Philias R, Garant PR (2003). Oral cells and tissues. Chicago: Quintessence Pub. Co. ISBN 978-0867154290. OCLC 51892824.
  16. ^ Leone CW, Bokhadhoor H, Kuo D, Desta T, Yang J, Siqueira MF, et al. (April 2006). "Immunization enhances inflammation and tissue destruction in response to Porphyromonas gingivalis". Infection and Immunity. 74 (4): 2286–92. doi:10.1128/IAI.74.4.2286-2292.2006. PMC 1418897. PMID 16552059.
  17. ^ Graves DT, Li J, Cochran DL (February 2011). "Inflammation and uncoupling as mechanisms of periodontal bone loss". Journal of Dental Research. 90 (2): 143–53. doi:10.1177/0022034510385236. PMC 3144100. PMID 21135192.
  18. ^ a b c Bath-Balogh & Fehrenbach 1997.
  19. ^ Coots BK (November 2012). "Alveolar bone grafting: past, present, and new horizons". Seminars in Plastic Surgery. 26 (4): 178–83. doi:10.1055/s-0033-1333887. PMC 3706037. PMID 24179451.
  20. ^ a b c d e Lilja J (October 2009). "Alveolar bone grafting". Indian Journal of Plastic Surgery. 42 Suppl (3): S110-5. doi:10.4103/0970-0358.57200. PMC 2825060. PMID 19884665.{{cite journal}}: CS1 maint: unflagged free DOI (link) Material was copied from this source, which is available under a Creative Commons License.

Sources


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