alveolar bone.pptx
TRANSCRIPT
Slide 1
1DEFINITIONLiving tissue, which makes up the body skeleton. Hardest structure possesses a certain degree of toughness and elasticity.
2FUNCTIONProvides shape and support for the bodySite of attachment for tendons and musclesProtects vital organsServes as a storage site for mineralsProvides the medium, the marrow for the development & storage of blood cells.3DIFFERENCE B/W IMMATURE (WOVEN) AND MATURE (LAMELLAR) BONEWOVEN BONELAMELLAR BONEImmatueCollagen fibres oriented in many directionsGreat amount of interfibrillar space occupied by mineral crystals
MatureDirection of collagen fibres in any given lamellae lies at right angles to that of adjacent lamellaeLess spaceDIFFERENCE B/W IMMATURE (WOVEN) AND MATURE (LAMELLAR) BONEWOVEN BONELAMELLAR BONEMatrix in H/E tinged with blue higher proteoglycan contentMore number of osteocytesCan be entirely removed by osteoclast
Uniform acidophilic staining
Comparitively lessOnly a portion of lamellar matrix of a given bone is resorbed at one time
ALVEOLAR BONEThe alveolar bone may be defined as that process of the maxilla and mandible that forms and supports the socket of the teeth
6Development of alveolar process:End of second month of fetal lifeBony septa develops b/w adjacent tooth germsAlveolar process develops only during eruption of teethDuring period of rapid growth a tissue may develop at the alveolar crest that combines characteristics of cartilage & bone. It is called chondroid bone
Alveolar Bone proper : Thin lamellae of bone that surrounds the root of tooth & gives attachment to principle fibres of PDL. It consist of Lamellated bone & Bundle bone
9Supporting alveolar bone: Bone surrounding the alveolar bone proper & supports the socket
ALVEOLAR BONE PROPERLamellated bone: Some lamellae are arranged roughly paralell to surface of adjacent marrow spacesOthers form haversian system
12Bundle bone:It is that bone in which the principle fibres of PDL are anchored. Radiographically bundle bone is also referred as lamina dura
ALVEOLAR BONE PROPERABP forming the inner wall of socket is perforated by many openings for interalveolar nerves and blood vessels is called as Cribriform Plate
Interdental & Interradicular septa contains perforation called Zuckerkandl & Hirschfeld canals (nutrient canals)
SUPPORTING ALVEOLAR BONECortical Plates:Consist of compact bone (which form outer & inner plates of alveolar process)Bone underlying the gingiva is called Cortical plateBoth Cribriform plate & cortical plate are Compact bone & separated by Spongy bone15SPONGY BONEFills the area b/w cortical plates & ABPStudy of roentgenograms permits classification of spongiosa into 2 main types
Type I Inter dental & Inter radicular trabeculae are regular & Horizontal in a ladder like arrangementEg: mandibleType II Irregularly arranged numerous delicate inter dental & inter radicular trabeculae.Eg: maxilla16SPONGY BONELacks distinct trajectory patternMore common in maxillaMarrow spaces in alveolar process may contain hematopoietic marrow, but usually they contain fatty marrow
In condylar process, angle of mandible, max tuberosity & in other isolated foci hematopoietic cellular marrow is found
CREST OF ALVEOLAR SEPTAShape of outline of CAS depends on position of adjacent teeth
If neighboring teeth is inclined the alveolar crest is oblique
Cortical bone & alveolar bone meet at the alveolar crest 1.5 2 mm below the level of CEJ on the tooth it surrounds 18
INTERNAL RECONSTRUCTION OF ALVEOLAR BONEAlterations in striations of alveolar bone coincide with physiologic eruptive movements of teeth
Movements directed mesioocclusally
At alveolar fundus continued apposition of bone recognised by resting lines separating parallel layers of bundle bone
20When bundle bone reached certain thickness it is resorbed partly from the marrow spaces & then replaced by lamellated bone or spongy trabeculae
Presence of bundle bone indicates level at which alveolar fundus was situated previously
During mesial drift of teeth: Bone apposed on distal & resorbed on mesial alveolar wall
Distal wall Entirely of bundle bone. Osteoclast in adjacent marrow space remove part of bundle bone, when it reaches certain thickness. In its place lamellated bone depositedMesial wall Sign of active resorption presence of howships lacunae containing osteoclast. Mesial drift doesnt occur as bodily movement ( bundle bone present in some areas)22Resorption does not involve the entire mesial surface of the alveolus at one and same time
Periods of resorption alternate with periods of rest & repair
Islands of bundle bone seperated from lamellated bone by reversal line that turn their convexities towards the lamellated bone
23During these changes : Compact bone replaced by spongy boneand spongy bone by compact bone
Occurs in physiologic mesial drift or in orthodontic mesial or distal movement of teeth
Interdental septum shows apposition on one surface & resorption on the other24CLINICAL CONSIDERATIONSBiological plasticity allows tooth movement during orthodontic forcesIncrease in Functional forces lead to bone formation while decreased forces lead to decrease in bone volumeDuring healing of fractures or extraction wounds embryonic bone formed later replaced by mature bone
25Socket after extraction empty with immature boneVisibility in X-ray lags 2 or 3 weeks behind actual formation of new boneCauses for bone resorption after tooth loss: Disuse atrophy, decreased blood supply, localised inflammation & unfavorable prosthetic pressureSurgical procedures like grafting can be done to stimulate bone formation
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