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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