DH 356 - Chapter 6 Tooth Development and Eruption.pptx

CHAPTER 6: TOOTH DEVELOPMENT AND ERUPTION DH 356 1 INITIAL CHAPTER OUTLINE Tooth development Initiation stage Bud stage Cap stage Bell stage Stages of apposition and maturation...

CHAPTER 6: TOOTH DEVELOPMENT AND ERUPTION DH 356 1 INITIAL CHAPTER OUTLINE Tooth development Initiation stage Bud stage Cap stage Bell stage Stages of apposition and maturation 2 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  Table 6-1 3 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  Table 6-1 (cont) 4 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Stages and Discussion with Developmental Considerations TOOTH DEVELOPMENT 5 TOOTH DEVELOPMENT Tooth development: : odontogenesis Primary dentition begins between the sixth and seventh week of prenatal development, Occurs during the embryonic period. Mature Tooth Figure 2-5 6 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  7 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  CASE STUDY 6.1 Age 5 YRS Scenario Sex Male A new patient has his first dental Chief “My son has a appointment. The Complaint really large father, a patient of baby tooth!” record, is None concerned about Medical a large “baby” History tooth. Current None A clinical Medications photograph was taken of the tooth. Social Likes to sing. There is one less History tooth noted in the arch of the primary dentition. An attempt was made to take a periapical radiograph of the region, but it will need to be Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, scheduled for the ed 2. Saunders, Philadelphia, 2009 future. 8 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. INITIATION STAGE 9 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. INITIATION STAGE Week 6 Ectoderm becomes the oral epithelium Neural crest cells form ectomesenchyme which develop deep to the oral epithelium Figure 6-1 10 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. INITIATION STAGE A basement membrane separates the oral epithelium and the ectomesenchyme (connective tissue) Week 7 The oral epithelium grows deeper into the ectomesenchyme producing the dental lamina. Figure 6-2 11 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING INITIATION STAGE Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 12 DEVELOPMENTAL DISTURBANCES DURING INITIATION STAGE Lack of initiation within the dental lamina results in the absence of a single tooth (partial) or multiple teeth (complete) produces anodontia. Partial anodontia (hypodontia) is more common:  permanent maxillary lateral incisors  third molars  mandibular second premolars. 13 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ECTODERMAL DYSPLASIA Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 14 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ECTODERMAL DYSPLASIA Elsevier, Imaging Consult, imaging.consult.com, 2009 15 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING INITIATION STAGE Abnormal initiation may result in the development of supernumerary teeth (hyperdontia) Initiated from the dental lamina Hereditary etiology 16 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING INITIATION STAGE Mesiodens: between the maxillary central incisors Distomolar: 4th molar Perimolar: extra premolars 17 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  SUPERNUMERARY TEETH Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 18 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BUD STAGE 19 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BUD STAGE – 2ND STAGE Week 8 Primary teeth This stage is named for an extensive proliferation or growth of the dental lamina into buds penetrating into the ectomesenchyme. maxillary arch and Figure 6-3 mandibular arch will each have 10 buds. 20 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BUD STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 21 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING BUD STAGE Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 22  Developmental Disturbances During Bud Stage MICRODONTIA: PEG LATERAL Fehrenbach MJ. Review of Tooth Development and Associated Developmental Disturbances, The Journal of Practical Hygiene, May-June 2000. 23 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. MACRODONTIA 2424 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE 25 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE – 3RD STAGE 9th and 10th weeks Be able to label this image!! Proliferation and differentiation Enamel knot Enamel organ Dental papilla Dental sac Figure 6-5 26 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL ORGAN This will be the future crown development. Will produce enamel Figure 6-5 27 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE: EARLY Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 28 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE: LATE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 29 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTAL PAPILLA dental papilla will produce: dentin and pulp A basement membrane still exists between the enamel organ and the dental papilla Figure 6-5 Is the site of the future dentinoenamel junction (DEJ). 30 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. HISTOLOGY Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 31 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE The remaining ectomesenchyme surrounding the outside of the cap or enamel organ condenses into the dental sac. In the future, the capsule‑like dental sac will produce the periodontium: the supporting tissue types of the tooth: cementum, periodontal ligament, and alveolar bone. A basement membrane still Figure 6-5 separates the enamel organ and dental sac. 32 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE At the end of the cap stage, these three embryological structures: enamel organ, dental papilla, and dental sac —are now considered together to be the tooth germ, These initial tooth germs will develop into the primary dentition. 33 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TOOTH GERM COMPONENTS DURING CAP STAGE TABLE 6-4 Enamel organ: Formation of tooth bud in a cap shape with deep central depression- Future enamel Dental papilla: Condensed mass of ectomesenchyme within the concavity of the enamel organ - Future dentin and pulp Dental sac: Condensed mass of ectomesenchyme surrounding the outside of the enamel organ - Future cementum, periodontal ligament, alveolar bone 34 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TOOTH GERM Tooth germ in cross section with enamel organ (A), dental papilla (B), and dental sac (C). 35 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE Permanent dentition development 10th week of prenatal development Appears as an extension of the dental lamina into the ectomesenchyme lingual to the developing primary tooth germs. Its site of origin is called the successional dental lamina. Figure 6-26 36 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. SUCCEDANEOUS VS. NONSUCCEDANEOUS Permanent teeth formed with primary predecessors are called succedaneous Include anterior teeth and premolars Replace the primary anterior teeth and molars, respectively. The permanent molars are nonsuccedaneous have no primary predecessors 37 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CAP STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 38 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING CAP STAGE Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 39 DEVELOPMENTAL DISTURBANCES DURING CAP STAGE enamel organ may abnormally invaginate into the dental papilla Dens in dente or dens invaginatus. 40 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENS IN DENTE Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 41 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING CAP STAGE Gemination occurs as the single tooth germ tries unsuccessfully to divide into two tooth germs Results in a large, single‑rooted tooth with a common pulp cavity. 42 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. GEMINATION Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 43 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING CAP STAGE Fusion results from the union of two adjacent tooth germs Possibly resulting from pressure Leads to a broader, falsely macrodontic tooth similar to gemination. 44 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FUSION Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 45 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING CAP STAGE Teeth may also have tubercles or extra cusps that appear as small, round enamel extensions. 46 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE 47 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE – 4TH STAGE Be able to label this image! 11th and 12th week for primary dentition Ongoing processes of proliferation, differentiation, and morphogenesis to form a bell shape Figure 6-7 48 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE The outer cuboidal cells of the enamel organ = enamel epithelium (OEE). The OEE will serve as a protective barrier for the rest of the enamel organ during enamel production. The innermost tall columnar cells of the enamel organ = inner enamel epithelium (IEE). In the future, the IEE will differentiate into enamel‑secreting cells, ameloblasts. A basement membrane remains between the IEE and the adjacent dental papilla. Figure 6-7 49 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE Between the outer and inner enamel epithelium are two layers: the stellate reticulum and the stratum intermedium. The more outer-placed stellate reticulum consists of star‑shaped cells in many layers, forming a network. The more inner-placed stratum intermedium is made up of a compressed layer of flat to cuboidal cells. Help support the production of enamel. Figure 6-7 50 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 51 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. STELLATE RETICULUM The stellate reticulum is a celluar group located in the center of the enamel organ of a developing tooth. These cells are star shaped Synthesize glycosaminoglycans. As glycosaminoglycans are produced, water is drawn in between the cells which stretches them apart. As they are moved farther away from one another with the production of glycosaminoglycans, the stellate reticula maintain contact with one another through cell junctions by way of desmosomes, resulting in their unique star-shaped appearance. 52 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. STRATUM INTERMEDIUM The stratum intermedium in a developing tooth is a layer of two or three cells, like a layer cake, between the inner enamel epithelium and the newly forming cells of the stellate reticulum. It first appears during the early bell stage of tooth development, at around the fourteenth week of prenatal development. This layer, along with the inner enamel epithelium, is responsible for the tooth enamel formation. 53 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE The dental papilla differentiates into two types of tissue in layers: the outer cells of the dental papilla and the central cells of the dental papilla. Outer cells of the dental papilla will differentiate into odontoblasts Inner cells will become the pulp. The outer dental sac increases in the amount of Figure 6-8 collagen fibers 54 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 55 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 56 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BELL STAGE Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 57 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL ORGAN IN BELL STAGE Outer enamel epithelium (OEE): Outer cuboidal cells of enamel organ; serves as protective barrier for enamel organ Stellate reticulum: More outer star-shaped cells in many layers, forming a network within the enamel organ; supports the production of enamel matrix Stratum intermedium: More inner compressed layer of flat to cuboidal cells; supports the production of enamel matrix Inner enamel epithelium (IEE): Innermost tall, columnar cells of enamel organ; will differentiate into ameloblasts that form enamel matrix 58 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION STAGE & MATURATION STAGE 59 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION AND MATURATION The final stages of odontogenesis include apposition, during which the enamel, dentin, and cementum are secreted in successive layers. These tissue types are initially secreted as a matrix, which is an extracellular substance that is partially calcified yet serves as a framework for later calcification. The other final stage, maturation, is reached when the dental tissue types subsequently fully mineralize. 60 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TOOTH DEVELOPMENT Crown Formation With Enamel and Dentin Apposition and Maturation 61 CROWN FORMATION Tooth development begins in the crown and then proceeds to the root. Figure 6-27A 62 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF PREAMELOBLASTS IEE in the bell‑shaped enamel organ, grow even more columnar or elongate They differentiate into preameloblasts. During this differentiation, IEE cells undergo repolarization. Preameloblasts will first induce dental papilla cells to differentiate into dentin-forming cells (odontoblasts) and then Figure 6-9 will differentiate themselves into cells that secrete enamel (ameloblasts). 63 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF ODONTOBLASTS AND DENTIN MATRIX After the IEE differentiates into preameloblasts, the outer cells of the dental papilla are induced by the preameloblasts to differentiate into odontoblasts. These cells also undergo repolarization. These cells are also lined up adjacent to the basement membrane but in a mirror‑image orientation compared with the preameloblasts. Figure 6-10 The odontoblasts now begin dentinogenesis, which is the apposition of dentin matrix, or predentin, on their side of the basement membrane. 64 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF ODONTOBLASTS AND DENTIN MATRIX Thus the odontoblasts start their secretory activity some time before enamel matrix production begins. The dentin layer in any location in a developing tooth is slightly thicker than the corresponding layer of enamel matrix. Figure 6-10 65 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF ODONTOBLASTS AND DENTIN MATRIX Figure 6-11 66 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  FORMATION OF AMELOBLASTS, DENTINOENAMEL JUNCTION, AND ENAMEL MATRIX After the differentiation of odontoblasts from the outer cells of the dental papilla and their formation of predentin, the basement membrane between the preameloblasts and the odontoblasts disintegrates. This disintegration of the basement membrane allows the preameloblasts to come into contact with the newly formed predentin. This induces the preameloblasts to differentiate into ameloblasts. Figure 6-12 67 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DIFFERENTIATION OF AMELOBLASTS Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 68 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF AMELOBLASTS, DENTINOENAMEL JUNCTION, AND ENAMEL MATRIX Ameloblasts begin amelogenesis, or the apposition of enamel matrix, laying it down on their side of the now disintegrating basement membrane. The enamel matrix is secreted from Tomes’ process, an angled part of each ameloblast that faces the disintegrating basement membrane created as the ameloblasts move away from the dentin interface. Figure 6-12 69 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF AMELOBLASTS, DENTINOENAMEL JUNCTION, AND ENAMEL MATRIX With the enamel matrix in contact with the predentin, mineralization of the disintegrating basement membrane now occurs, forming the dentinoenamel junction (DEJ) Figure 6-12 70 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL MATRIX FORMATION Figure 12-2A 71 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. FORMATION OF AMELOBLASTS, DENTINOENAMEL JUNCTION, AND ENAMEL MATRIX The odontoblasts, unlike the ameloblasts, will leave attached cellular extensions in the length of the predentin called the odontoblastic process. Each odontoblastic process is contained in a mineralized cylinder, the dentinal tubule. The cell bodies of odontoblasts will remain within pulp tissue. The cell bodies of the ameloblasts will be involved in the eruption and mineralization process but will be lost after eruption. Figure 6-12 72 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIN MATRIX FORMATION Figure 12-2B 73 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIN MATRIX FORMATION Figure 13-2 74 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIN MATRIX FORMATION Figure 13-3 75 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION STAGE Figure 6-13 76 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION STAGE Figure 6-14 77 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION AND MATURATION STAGES Figure 6-15A 78 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION AND MATURATION STAGES Figure 12-3 79 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. APPOSITION AND MATURATION STAGES Figure 6-15B 80 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. MATURE DENTAL TISSUE 81 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING APPOSITION AND MATURATION Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 82 DEVELOPMENTAL DISTURBANCES DURING STAGES OF APPOSITION AND MATURATION enamel dysplasia: factors may interfere with the metabolic processes of the ameloblasts, resulting in, which is the faulty development of enamel dysplasia. Local enamel dysplasia may result from trauma or infection occurring in a small group of ameloblasts. Systemic enamel dysplasia involves larger numbers of ameloblasts and may result from traumatic birth, systemic infections, nutritional deficiencies, or dental fluorosis (excess systemic fluoride level). 83 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL HYPOPLASIA Remember Syphilis? Enamel hypoplasia can be noted in the presence of Hutchinson incisors and mulberry molars teratogen This results from a reduction in the quantity of enamel matrix. As a result, the teeth appear with pitting and grooves in the enamel surface. Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 84 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL HYPOPLASIA CAUSED BY FEBRILE ILLNESS OR VITAMIN DEFICIENCY Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 85 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  ENAMEL HYPOCALCIFICATION Enamel hypocalcification results in reduction in the quality of the enamel maturation. The teeth appear more opaque, yellow, or even brown Turner spot/Turner tooth: single affected area 86 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTAL FLUOROSIS Enamel hypoplasia and hypocalcification may occur together dental fluorosis. Figure 12-5 87 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  DENTAL FLUOROSIS Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 88 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. AMELOGENESIS IMPERFECTA amelogenesis imperfecta hereditary etiology can affect all teeth of both dentitions. Figure 6-16A 89 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. AMELOGENESIS IMPERFECTA Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 90 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIN DYSPLASIA Faulty development of dentin Can result from an interference with the metabolic processes of the odontoblasts during dentinogenesis. 91 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIN DYSPLASIA Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 92 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTINOGENESIS IMPERFECTA Teeth appear more opaque or iridescent Figure 6-17 93 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTINOGENESIS IMPERFECTA Elsevier, Imaging Consult, imaging.consult.com, 2009 94 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TOOTH DEVELOPMENT REVIEW Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 95 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TOOTH DEVELOPMENT REVIEW Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 96 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT Root Dentin Formation Cementum and Pulp Formation 97 THE PROCESS OF ROOT DEVELOPMENT TAKES PLACE AFTER THE CROWN IS COMPLETELY SHAPED AND THE TOOTH IS STARTING TO ERUPT INTO THE ORAL CAVITY. Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 Periapical radiograph of lower right (from left to right) third, second, and first molars in different stages of development in an 11-year-old child. 98 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT The process of root development takes place after the crown is completely shaped and the tooth is starting to erupt into the oral cavity. The structure responsible for root development is the cervical loop. The cervical loop is the most cervical part of the enamel organ, a bilayer rim that consists of only IEE and OEE. 99 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CERVICAL LOOP The cervical loop area: (1) dental sac, (2) dental papilla, (3) odontoblasts, (4) dentin, (5) stellate reticulum, (6) OEE, (7) IEE, (8) ameloblasts, (9) enamel. Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 100 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT The cervical loop begins to grow deeper into the surrounding ectomesenchyme of the dental sac Hertwig epithelial root sheath (HERS). The function of this sheath or membrane is to shape the root(s) and induce dentin formation in the root area 101 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT Figure 6-18C 102 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT Figure 6-18A, B 103 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CASE STUDY 6.2 Age 22 YRS Scenario Sex Female A patient of record has just Height 5’ 7” started flossing before her first Weight 125 LBS appointment at the dental office BP 95/75 in many years. “There are She reports that Chief she feels “bumps” Complaint bumps on my upper molars on her maxillary when I floss.” molars when she flosses them. Medical Diabetic History mellitus type 1 Periodontal probing produces Insulin slight to moderate Current bleeding and a Medications injections periapical Student nurse radiograph is Social taken of the History Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, region. ed 2. Saunders, Philadelphia, 2009 104 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DENTIN FORMATION Root dentin forms when the outer cells of the dental papilla in the root area are induced to undergo differentiation and become odontoblasts. Lacking the intermediate layers of the stellate reticulum and stratum intermedium, the HERS may induce odontoblastic differentiation but fails to differentiate into enamel-forming ameloblasts. Figure 6-19 This accounts for the absence of enamel in the roots. 105 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DENTIN FORMATION After the differentiation of odontoblasts in the root area, these cells undergo dentinogenesis and begin to secrete predentin. As in the crown area, a basement membrane is located between the inner enamel epithelium of the sheath and the Figure 6-19 odontoblasts in the root area. 106 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DENTIN FORMATION When root dentin formation is completed, this part of the basement membrane also disintegrates, as does the entire HERS. After this disintegration of the root sheath, its cells may become the epithelial rests of Malassez (ERM). Figure 6-19 107 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DENTIN Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 108 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CEMENTUM AND PULP FORMATION The cementoblasts move to cover the root dentin area and undergo cementogenesis, laying down cementum matrix, or cementoid. Many cementoblasts become entrapped by the cementum they produce and become mature cementocytes. As the cementoid surrounding the cementocytes becomes Figure 6-20 calcified, or matured, it is then considered cementum. 109 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CEMENTOBLAST FORMATION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 110 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CEMENTUM AND PULP FORMATION As a result of the apposition of cementum over the dentin, the dentinocemental junction (DCJ) is formed. Also at this time, the central cells of the dental papilla are forming into the pulp. Figure 6-20 The pulp tissue is surrounded by the newly formed dentin. 111 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES WITH CEMENTAL FORMATION Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 112 CONCRESCENCE Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 113 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. PERIODONTAL LIGAMENT AND ALVEOLAR BONE DEVELOPMENT The ectomesenchyme from the dental sac begins to form the periodontal ligament (PDL) This process involves forming collagen fibers that are immediately organized into the fiber bundles of the PDL. The ends of these fibers insert into the outer part of Figure 6-20 the cementum and the surrounding alveolar bone to support the tooth. 114 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ROOT DEVELOPMENT Development of Multirooted Teeth 115  MULTIROOTED TEETH Differential growth of HERS causes the root trunk of the multirooted teeth to divide into two or three roots. 116 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. MULTIROOTED TEETH During the formation of the enamel organ on a multirooted tooth, elongation of its cervical loop occurs in such a way that long, tonguelike horizontal epithelial extensions or flaps develop within. The usually single cervical opening of the coronal enamel organ is then divided into two or three openings by these horizontal extensions. On the pulpal surfaces of these holes, dentin formation starts after the induction of the odontoblasts and disintegration of HERS and the associated basement membrane. Only at the periphery of each opening are cementoblasts induced to form cementum on the newly formed dentin. Two or three such extensions can be present on multirooted teeth, depending on the similar number of roots on the mature tooth. Root development then proceeds in the same way as described for a single‑rooted tooth. 117 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. MULTIROOTED TEETH Elsevier, Imaging Consult, imaging.consult.com, 2009 118 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Note root development over time! Figure 6-22A 119 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Note root development over time! Figure 6-22B 120 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING ROOT FORMATION Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 121 DEVELOPMENTAL DISTURBANCES DURING ROOT FORMATION In some cases, misplaced ameloblasts can migrate to the root area, causing enamel to be abnormally formed over the cemental root surface, which produces an enamel pearl. Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 122 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ENAMEL PEARL Newman MG, Takei H, Carranza, FA. Carranza's Clinical Periodontology, ed 10. Saunders, Philadelphia, 2006 123 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CASE STUDY 6.2 Age 22 YRS Scenario Sex Female A patient of record has just Height 5’ 7” started flossing before her first Weight 125 LBS appointment at the dental office BP 95/75 in many years. “There are She reports that Chief she feels “bumps” Complaint bumps on my upper molars on her maxillary when I floss.” molars when she flosses them. Medical Diabetic History mellitus type 1 Periodontal probing produces Insulin slight to moderate Current bleeding and a Medications injections periapical Student nurse radiograph is Social taken of the Elsevier, Imaging Consult, imaging.consult.com, 2009 History region. 124 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING ROOT FORMATION Dilaceration results in either distorted root(s) or crown angulation in a formed tooth. It is caused by a distortion of HERS due to an injury or pressure; it can occur in any tooth or group of teeth during tooth development. 125 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DILACERATION Figure 17-36 126 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING ROOT FORMATION Teeth may also have extra or accessory roots (or supernumerary roots). Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 127 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACCESSORY ROOT Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 Mandibular canine and maxillary first premolar 128 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Primary Tooth Eruption and Shedding 129 ACTIVE ERUPTION After enamel apposition ceases in the crown area of each primary or permanent tooth, the ameloblasts place an acellular dental cuticle on the new enamel surface. In addition, the layers of the enamel organ are compressed, forming the reduced enamel epithelium (REE). Figure 6-23 130 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 131 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION The REE appears as a few layers of flattened cells overlying the new enamel surface. As this formation of the REE occurs for a primary tooth, it Figure 6-24 can begin to erupt into the oral cavity. 132 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 133 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 134 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION To allow for the eruption process, the REE first has to fuse with the oral epithelium lining the oral cavity. Second, enzymes from the REE then disintegrate the central part of the fused tissue, leaving an epithelial tunnel for the tooth to erupt through the surrounding oral epithelium into the oral cavity. 135 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 136 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION As a primary tooth actively erupts, the coronal part of the fused epithelial tissue peels back off the crown, leaving the cervical part still attached to the neck of the tooth. Figure 6-25 137 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Figure 6-25 138 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION This fused tissue that remains near the CEJ after the tooth erupts then serves as the initial junctional epithelium of the tooth and creates a seal between the tissue and the tooth surface. This tissue is later replaced by a definitive junctional epithelium (arrows) as the root is formed. Figure 10-7 139 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION The primary tooth is then lost, exfoliated, or shed, as the succedaneous permanent tooth develops lingual to it. Figure 6-27B 140 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Figure 6-27C 141 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION The process involving loss of the primary tooth consists of differentiation of osteoclasts, which absorb the alveolar bone between the two teeth, and odontoclasts, which cause resorption or removal of parts of the primary's root of dentin and cementum as well as Figure 6-28 small parts of the enamel crown. 142 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 143 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION The process of shedding of the primary tooth is intermittent (“on again/off again”) because at the same time that osteoblasts differentiate to replace the resorbed bone, odontoblasts and cementoblasts also differentiate to replace the resorbed parts of the root. 144 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Permanent Tooth Eruption 145 PERMANENT TOOTH ERUPTION The succedaneous permanent tooth erupts into lingual to the roots of the shedding or shed primary tooth The only exception to this is the permanent maxillary incisors, which move to a more facial position as they erupt into the oral cavity. Figure 6-26 146 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ERUPTION LINGUAL Ibsen OAC, Phelan JA. Oral Pathology for Dental Hygienists, ed 5. WB Saunders, Philadelphia, 2009 147 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. PERMANENT TOOTH ERUPTION The process of eruption for a succedaneous tooth is the same as for the primary tooth: the REE fuses with the oral epithelium to create a tissue that degenerates, leaving an epithelial‑lined eruption tunnel. The process of the nonsuccedaneous permanent tooth's eruption is similar also, but no Figure 6-26 primary tooth is shed. 148 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. ACTIVE ERUPTION Figure 6-27A 149 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  ACTIVE ERUPTION Figure 6-27B Figure 6-27C 150 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.  Note eruption process over time! Figure 6-22A 151 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. Note eruption process over time! Figure 6-22B 152 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENT DISTURBANCES DURING ERUPTION Standring S: Gray's Anatomy, ed 40, Edinburgh, 2009, Churchill Livingstone 153 DEVELOPMENTAL DISTURBANCES DURING ERUPTION An odontogenic cyst that forms from the REE after the crown has completely formed and matured is the dentigerous cyst, or follicular Figure 6-30 cyst. 154 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIGEROUS CYST Elsevier, Imaging Consult, imaging.consult.com, 2009 155 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DENTIGEROUS CYST Nanci A. Ten Cate’s Oral Histology, ed 7. Mosby, St. Louis, 2008 156 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. DEVELOPMENTAL DISTURBANCES DURING ERUPTION If a dentigerous cyst appears on a partially erupted tooth, it is considered an eruption cyst and appears as fluctuant, blue, vesicle‑like gingival lesion. Figure 6-31 157 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. CLINICAL CONSIDERATIONS FOR TOOTH DEVELOPMENT 158 NASMYTH MEMBRANE A residue may form on newly erupted teeth of both dentitions that may leave the teeth extrinsically stained. This residue, Nasmyth membrane, consists of the fused tissue of the REE and oral epithelium as well as the dental cuticle placed by the ameloblasts on the new enamel surface. Figure 6-26 159 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. BOHN NODULES The white bumps present on the maxillary alveolar ridge are Bohn nodules. Fehrenbach, MJ, Weiner J. Saunders Review of Dental Hygiene, ed 2. Saunders, Philadelphia, 2009 160 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. PROBLEMS IN SPACING A permanent tooth often starts to erupt before the primary tooth is fully shed, possibly creating problems in spacing. Interceptive orthodontic therapy can prevent some of these situations. Thus it is important for children with prolonged retention of any primary teeth to seek early dental consultation. 161 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. RETAINED ROOT TIP Root fragments from primary molars may be left from the process and create periodontal complications for the permanent dentition; panoramic radiographs of the mixed dentition are important in order to monitor tooth development. Radiopaque area of the alveolar ridge with the structural appearance of the apical part of a tooth root. A thin periodontal ligament space is visible on the distal. Note the similarity of the radiodensity of the root tip and the adjacent premolar root. Fehrenbach, MJ, Personal Collection 162 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. TRAUMATIC INJURY RESPONSE Avulsed tooth, a tooth that is completely removed from the socket Ask patient to bring tooth in a wet handkerchief, milk, or water or in buccal vestibule (preferred mode of transport because of maintenance of hydration in saliva) purchased transport medium for sport teams is now available. 163 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. RESEARCH UPDATE STUDY: Preterm children with very low birth weight suffer from several neonatal and postnatal complications that may affect the mineralization of teeth. Clinical and morphological studies have shown enamel aberrations in teeth from preterm children. The chemical composition in enamel and dentin was compared in primary teeth from preterm children and full-term children, and the relationship between the chemical composition and the morphological appearance was investigated. Enamel and dentin in 17 exfoliated primary teeth, from 14 children with a gestational age below 29 wk, were investigated and compared with 36 exfoliated primary teeth from full-term children, using X-ray microanalyses (XRMA). 164 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved. RESEARCH UPDATE SUMMARY: In comparison with the teeth from the controls, the teeth from preterm children had a higher relative value of carbon (C), a lower relative value of calcium (Ca), a lower ratio of calcium/phosphorus (Ca/P) and a lower ratio of Ca/C throughout the outer part of the enamel. In dentin, the relative values for P were higher, and Ca/P ratio was lower, at the dentin- pulp junction. The Ca/P ratio indicated normal hydroxyapatite in the crystals in enamel and dentin. The lower ratio of Ca/C in the bulk and outer part of the enamel indicated more porous enamel. 165 Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.