學習目標. Summary 參考資料. Alveolar Bone. Bone. Alveolar Bone & Osseointegrated Implants. 口腔胚胎及組織學 Oral embryology & histology

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1 口腔胚胎及組織學 Oral embryology & histology Alveolar Bone & Osseointegrated Implants 林靜毅 Jerry Lin DDS, DMSc Diplomate, American Board of Periodontology 台北醫學大學牙醫學士哈佛大學口腔生物醫學博士哈佛牙醫學院牙周病專科醫師哈佛牙醫學院牙周病學客座講座台大牙周病科兼任主治醫師台北醫學大學助理教授美國牙周病醫學會院士 學習目標 能了解頭臉部及口腔之發育 結構與功能, 並發展能有效吸收與傳播相關資訊之辭彙, 將胚胎及組織學上之基本概念, 應用於臨床上之診斷與治療 參考資料 1.Illustrated Dental Embryology, Histology, and Anatomy: Mary Bath-Balogh, Margaret J. Fehrenbach, 2nd Edition, Elsevier Saunders, Esstential of Oral Histology and Embryology--A clinical approach: James K Avery, Denial J Chiego,Jr 3rd Edition, Elsevier Mosby, Ten Cate's Oral Histology: Development, Structure, and Function: Nanci Anatonio, 6th ed. Mosby, 2003 Summary 提供學生探討頭臉部及口腔之發育, 認識牙齒及口腔組織之正常顯微結構, 並了解其功能與結構之關係, 進而對生理 病理與臨床牙科學上之問題能做比較與思考, 為各牙科臨床科目之重要基礎課程 Alveolar Bone Bone The thickened ridge of bone that contains the tooth sockets on bones that bear teeth Characteristics Compact bone Cancellous bone; trabecullar bone; spongy bone Composition of bone 67% of inorganic substance - Hydroxyapatite 33% of organic substance 28% of type I collagen 5% of noncollagenous protein such as bone sialoprotein, osteocalcin, osteocectin, osteopontin, proteoglycans, growth factors, serum protein 1

2 Microscopic layers Circumferential lamellae Concentric lamellae Interstitial es lamellae eae Basic metabolic unit of bone osteon or called harversian system Volkmann canals connects harversian canals Bone Cells Osteogenic cells form & maintain bone Osteoprogenitors preosteoblasts p Osteoblasts Osteocytes Bone lining cells Osteoclasts resorb bone 2

3 Osteoblasts & Preosteoblasts Mononucleated cells Synthesize collagenous and noncollagenous bone matrix proteins osteoid Arising from pluripotent stem cells Plump, cuboidal cells or slightly flattened cells Also secret cytokines and growth factors When bone is no longer forming, osteoblasts flatten substantially, extending along the bone surface. These cells, called bone lining cells, contain few synthetic organelles Bone Lining Cells Entrapped osteoblasts within the matrix secreted by themselves The more rapid the bone formation; the more osteocytes are present After the formation, osteocytes become reduced in size Lacuna; canaliculi Osteocytes Multinucleated Found against the bone surface Hollowed-out out depressions, called Howship s lacunae The cell membrane of osteoclast is thrown into a myriad of deep folds ruffled border Osteoclasts Possessing Tartrateresistant acid phosphatase The arginine-glycineaspartic acid (RGD) containing molecules such as bone sialoprotein and osteopontin on bone surfaces may facilitate osteoclast adhesion and formation of the sealing zone Osteoclasts Enzymes: acid phosphatase, lysosomal enzyme RER Golgi ruffled border (in transport vesicles) sealing zone Proton pump function Resorption sequence Attachment of osteoclasts to the mineralized surface Creation of a sealed acidic microenvironment by proton pump Degradation of the exposed matrix by released enzymes; acid phosphatase, cathepsin B Endocytosis at the ruffled border transcytosis Osteoclasts 3

4 Regulation of bone cell formation Transcription factors: Runx2 & Osterix Bone forming cells originated from mesenchymal stem cells while osteoclasts from hematopoietic precursors of the monocyte/macrophage lineage The differentiation of osteoclasts was modulated by stromal cells and osteoblasts via secreted molecules: receptor-activated nuclear factorκb (RANK) and its ligand (RANKL), which expressed on the plasma membrane of stromaland osteoblastic cells Osteoprotegrin (OPG) Endochondral Bone Formation Intramembranous Bone Formation Bone develops directly within the soft connective tissue Mesenchymal cells osteoblasts produce bone matrix Cranial bone, maxilla, mandible, midshaft of long bones The first embryonic bone is termed woven bone, which was then matured into lamellar bone The process by which the overall size and shape of bones is established Bone is being formed rapidly and primarily on the periosteal surface, while bone is also being destroyed along the endosteal surface and within the osteons of compact bone Bone turnover rates of 30% to 100% per year in growing children; while 5% per year for compact bone and 15% per year for trabecular bone in adults Bone turnover does not stop but slow down to a balance Bone turnover occurs in discrete, focal areas involving groups of cells called bone remodeling or basic multicellular units Five phases Activation Resorption Reversal Formation resting As osteoclasts move through compact bone, a resorption channel is created The leading edge fo resorption is termed cutting cone, which is characterized by a scalloped array of resorption lacunae (Howship s lacunae) The cutting cone is followed by an active bone formation called filling cone where osteon is formed by osteoblasts 4

5 Osseointegrated Implants Teeth versus dental implants Macroscopically Cementum versus Titanium oxide layer Microscopically PDL versus direct bone contact Soft tissue level Osseointegration Osseointegration Per-ingvar Brånemark An intimate bone-to-implant apposition Direct bone anchorage concept First clinical report was published in 1977 First endosteal implants placed in human were in 1965 A direct connection between bone and implant without interposed soft tissue layers A direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant Macroscopically Hard Tissue Interface 5

6 Microscopically Microscopically Implant Surfaces Rough surface Machined surface (not smooth) Turned Rough surface Sandblasted Acid-etched Anodized Coated surface Plasma-sprayed Hydroxyapatite-coated Calcium phosphate-coated Machined versus Rough Surface Histologically 6

7 Vascularity Tooth Implant 7