DH 356 Chapter 14 - Components of the Periodontium.pptx

Chapter 14: Periodontium DH 356 1  Components of the Periodontium The periodontium consists of the supporting soft and hard dental tissue between and including the tooth and the alveolar bone. Figure 14-1...

Chapter 14: Periodontium DH 356 1  Components of the Periodontium The periodontium consists of the supporting soft and hard dental tissue between and including the tooth and the alveolar bone. Figure 14-1 2 Chapter 14: Cementum 3  Cementum The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament. Figure 14-2 4  Cementum  Mature cementum is by weight 65% inorganic (or mineralized) material, 23% organic material, and 12% water.  This crystalline formation of mature cementum consists of mainly calcium hydroxyapatite, with the chemical formula Ca10(PO4)6(OH)2. Figure 2-1 5  Cementum Levels Enamel Dentin Cementum Alveolar Bone ~Mineral 96% 70% 65% 60% levels ~ Organic 1% organic, 20% organic, 23% organic, 25% organic, and water 3% water 10% water 12% water 15% water levels The calcium hydroxyapatite found in cementum is similar to that found in higher percentages in both enamel and dentin, but more closely resembles the percentage found in bone tissue, such as alveolar bone tissue. 6 Dental sac 7  Cementum Development  Cementum, which develops from the dental sac  forms on the root after the disintegration of Hertwig epithelial root sheath (HERS).  This disintegration allows the undifferentiated cells of the dental sac to come into contact with the newly Figure 6-19 formed surface of root dentin, inducing these cells to become cementoblasts. 8  Cementum Development  The cementoblasts then disperse to cover the root dentin area and undergo cementogenesis, laying down cementoid.  During the later stages of apposition, many of the cementoblasts become entrapped by the cementum they produce, becoming cementocytes. Figure 6-20 9  Histology of Cementum  Cementum is composed of a mineralized fibrous matrix and cells.  The fibrous matrix consists of both Sharpey fibers and intrinsic nonperiodontal fibers.  Sharpey fibers are a portion of the collagen fibers from the periodontal ligament that are each partially inserted into the outer part of the cementum at 90 degrees, or a right angle, to the cemental surface. Figure 14-2 10  Histology of Cementum  Acellular cementum (AC) without cementocytes makes up the first layers of cementum deposited at the DCJ over the dentin (D). Figure 14-11A 11 Histology of Cementum Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 12  Histology of Cementum  Microscopic appearance of cellular cementum with its cementocytes (arrows).  The cementocytes are within their lacunae, and their canaliculi are oriented toward the periodontal ligament Figure 14-7 (PDL) for nutrition. 13 Comparison of Two Types of Cementum 14 Histology of Cementum This way to PDL! Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 15  Histology of Cementum  Reversal lines and arrest lines in cementum with embedded cementocytes (white arrows) that has undergone repair.  On the surface of the cementum are the cementoblasts (dark arrows) with the surrounding periodontal ligament (P). Figure 14-9 16  Histology of Cementum  The three transitional interfaces that may be present at points along the CEJ.  One situation is that cementum may overlap enamel (15%).  Another situation is that they may meet end-to-end (52%). Figure 14-8A  Finally, there may be a gap between enamel and cementum, leaving dentin exposed (33%). 17  Histology of Cementum The CEJ may exhibit all of these patterns in an individual’s oral cavity, and there is even considerable variation when one tooth is traced circumferentially. Figure 14-8B 18  Clinical Considerations for Cementum  Hypercementosis at the root apex.  This is due to traumatic occlusal forces of a tooth on a microscopic view with dentin (D), cementum (C), and radicular pulp tissue (P) noted in the root area. Figure 14-12A 19  for Cementum: Hypercementosis Figure 14-12 20  for Cementum: Hypercementosis Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 21  Clinical Considerations for Cementum  Resorption of the apex of the roots on maxillary anteriors occurs with trauma such as with rapid orthodontic movement.  Also mechanical or chemical stimuli such as infection or pressure could be involved. Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 22  Chapter 14: Alveolar Bone 23  Alveolar Bone  Like all bone, mature alveolar bone is by weight 60% inorganic (or mineralized) material, 25% organic material, and 15% water.  This crystalline formation consists of mainly calcium hydroxyapatite with the chemical formula of Ca10(PO4)6(OH)2. Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 24  Alveolar Bone Levels Enamel Dentin Cementum Alveolar Bone ~Mineral 96% 70% 65% 60% levels ~ Organic and 1% organic, 20% organic, 23% organic, 25% organic, water levels 3% water 10% water 12% water 15% water This calcium hydroxyapatite is similar to that found in higher percentages in both enamel and dentin, but is most similar to the levels in cementum. 25 Anatomy of the Jaws Figure 14-15A 26  Anatomy of the Jaws  The portion that contains the roots of the teeth is the alveolar bone (also called the alveolar process or alveolar ridge).  The portion apical to the roots of the teeth is the basal bone, which then forms the body of the maxilla or body of mandible. Figure 14-15B  Both the alveolar bone and the basal bone are covered by periosteum. 27  Anatomy of the Jaws  The alveolar bone proper is the lining of the tooth socket, or alveolus (plural, alveoli).  Although the alveolar bone proper is composed of compact bone, it may be called the cribriform plate because it contains numerous holes where Figure 14-15C Volkmann canals pass from the alveolar bone into the periodontal ligament (PDL). 28  Review Bone Histology: See Chapter 8  Overall structure with its lamellae forming osteons.  Note Volkmann canal and its communication with larger blood vessels external to the bone of the Haversian system in compact Figure 8-11A bone. 29  Review Bone Histology  Close‑up view of the structure, highlighting the individual osteons with their central Haversian canals, osteocytes, and canaliculi of the Haversian system in compact bone. Figure 8-11B 30  Alveolar Bone Development of the Jaws 31  Development of the Jaws  Both the maxilla and the mandible develop from tissue of the first branchial arch, or mandibular arch. Figure 5-5A 32 Development of the Mandible Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 33  Clinical Considerations for Alveolar Bone  With orthodontic therapy to produce tooth movement for repositioning, bone remodeling is forced.  The bands, wires, or appliances put pressure on one side of the tooth and adjacent alveolar bone, creating a compression zone in the PDL.  This compression in the PDL leads to bone resorption. On the opposite side of the tooth and bone, a tension zone develops in the PDL and causes the deposition of new bone. Figure 14-14 34  Clinical Considerations for Alveolar Bone  Mesial drift, or physiological drift, is a phenomenon in which all the teeth move slightly toward the midline of the oral cavity over time. Figure 20-21 35  Clinical Considerations for Alveolar Bone  The cell that causes resorption of bone is the osteoclast.  It is a large multinucleated cell located on the surface of secondary bone in a large, shallow pit created by this resorption, Howship lacuna. Figure 8-15 36  Fenestration  Where roots are prominent and the overlying bone very thin or with periodontal disease, the cortical bone may actually resorb locally, creating a window in the bone through which the root can be seen.  This window-like defect in the bone is referred to as a fenestration. Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 37  Dehiscence  In some cases, the rim of bone between the fenestration and the alveolar crest may disappear altogether and produce a defect known as a dehiscence. Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 38  Chapter 14: Periodontal Ligament 39  Periodontal Ligament  The periodontal ligament (PDL) is that part of the periodontium that provides for the attachment of the teeth to the surrounding alveolar bone by way of the cementum. Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 40  Periodontal Ligament  The PDL appears as the periodontal ligament space of 0.4 to 1.5 mm on radiographs, a radiolucent area (dark) between the radiopaque (light) lamina dura of the alveolar bone proper and the radiopaque (light) cementum. 41  Functions of the PDL  Compression  forces that occur during chewing and remain embedded in the alveolar bone  proprioception, or sensory innervation  brain can detect the forces being placed on the teeth and react accordingly. 42  Development of the Periodontal Ligament Similar to the alveolar bone, the PDL develops from the dental sac of the tooth germ. Figure 6-20 43  Histology of the Periodontal Ligament  As in all connective tissue, the fibroblast is the most common cell in the PDL. Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 44 Periodontal Ligament Principal Fiber Groups 45  Principal Fiber Groups  The main principal fiber group is the alveolodental ligament  consists of five fiber subgroups: alveolar crest, horizontal, oblique, apical, and interradicular on multirooted teeth. Figure 14-27 46 47  Principal Fiber Subgroups  Microscopic view of a part of the cross section of the tooth composed of cementum (C) and dentin (D) and highlighting the spokelike arrangement (arrows) of the alveolodental ligament, which originates in the alveolar bone proper (B) of the Figure 14-28 surrounding alveolus. 48  Principal Fiber Subgroups  The alveolar crest group of the alveolodental ligament originates in the alveolar crest of the alveolar bone proper and fans out to insert into the cervical cementum at various angles.  The function of the alveolar crest group is to resist tilting, intrusive, extrusive, and rotational forces. Figure 14-27 49  Principal Fiber Subgroups  The horizontal group of the alveolodental ligament originates in the alveolar bone proper, apical to its alveolar crest, and inserts into the cementum horizontally.  The function of the horizontal group is to resist tilting forces, which work to force the tooth to tip mesially, distally, lingually, or facially, and to Figure 14-27 resist rotational forces. 50  Principal Fiber Subgroups  The oblique group of the alveolodental ligament is the most numerous of the fiber subgroups and covers the apical two thirds of the root. This subgroup originates in the alveolar bone proper and extends apically to insert more apically into the cementum in an oblique manner.  The function of the oblique group is to resist intrusive forces, which try to push the tooth inward, as well as Figure 14-27 rotational forces. 51  Principal Fiber Subgroups  Photomicrograph of a tooth at the position of the oblique group of the alveodental ligament (P), which originates in the alveolar bone proper (B) and extends obliquely to insert more apically into the cementum (C; direction indicated by arrow). Figure 14-29 52  Principal Fiber Subgroups  The apical group of the alveolodental ligament radiates from the apical region of the cementum to insert into the surrounding alveolar bone proper.  The function of the apical group is to resist extrusive forces, which try to pull the tooth in an outward manner, and rotational forces. Figure 14-27 53  Principal Fiber Subgroups  The interradicular group of the alveolodental ligament is found only on multirooted teeth. This subgroup is inserted on the cementum of one root to the cementum of the other root (or roots) superficial to the interradicular septum and thus has no bony attachment.  This subgroup works together with the alveolar crest and apical groups to resist intrusive, extrusive, tilting, and Figure 14-27 rotational forces. 54  Principal Fiber Groups  Another principal ligament is the interdental ligament (or transseptal ligament), which inserts mesiodistally or interdentally into the cervical cementum of neighboring teeth over the alveolar crest of the alveolar bone proper.  Thus the fibers travel from cementum to cementum without any bony attachment, connecting all the teeth of the arch.  The function of the interdental ligament is to resist rotational forces Figure 14-31 and thus hold the teeth in interproximal contact. 55  Principal Fiber Subgroups  The circular ligament is considered a fiber subgroup of the gingival fiber group.  This fiber group is located in the lamina propria of the marginal gingiva.  The circular ligament encircles the tooth, as shown on a cross section of a tooth, interlacing with the other Figure 14-32 gingival fiber subgroup. 56  Principal Fiber Subgroups  The dentogingival ligament  most numerous subgroup of the gingival fiber group.  This fiber group inserts in the cementum on the root, apical to the epithelial attachment, and extends into the lamina propria of the marginal and attached gingiva. Figure 14-32 57  Principal Fiber Subgroups  Alveologingival fibers  These fibers radiate from the alveolar crest of the alveolar bone proper and extend coronally into the overlying lamina propria of the marginal gingiva.  Dentoperiosteal fibers  course from the cementum, near the CEJ, across the alveolar crest. Figure 14-32 58 Orthodontic Therapy Figure 14-14 59