Dental Anatomy

Card Set Information

Dental Anatomy
2010-12-12 00:06:18
Chapter six

Development, form, and eruption
Show Answers:

  1. define odontogenesis
    tooth development that takes place in many stages
  2. does odontogenesis have a clear cut beginning or end point between these stages?
  3. what is an example of another physiological process that occurs during the stages of odontogenesis that parallels the odontogenesis stage?
    formation of other embronic structures such as the face
  4. what organ in the body has the longest developmental period?
    the teeth
  5. when does primary dentition develop?
    during the embryonic and fetal period
  6. when is most of the permanent dentition formed?
    during the fetal period
  7. does tooth development continue after birth?
    yes, specifically the 2nd and 3rd molars
  8. what is the initiation stage? and when does it take place?
    • first stage of tooth development
    • takes place during the embryonic period at 6-7th week of prenatal development
  9. what physiological process involved in the intitiation stage?
    induction-an interaction between embryonic tissues
  10. __________tissues influence________________tissues, in order for _______________ to occur but the mechanisms are unknown
    • mesenchymal
    • ectodermal
    • initiation of odontogenesis
  11. define stomodeum
    embryo's primitive mouth
  12. when is the stomodeumlined with ectoderm?
    beginning of the 6th week
  13. what does oral epithelium form from?
    the outer portion or ectoderm
  14. describe the what the oral epithelium consists of and what it will become.
    2 horse-shoe shaped bands of tissue at the surface of the stomodeum which will become the uppr and lower jaws
  15. where did ectomesenchyme form from?
    from the ectoderm
  16. what is the ectomesenchyme influenced by?
    neural crest cells
  17. what is forming at the same time as the oral epithelium?
    ectomesenchyme, forms deep to the forming oral epithelium
  18. what does the basement membrane in teh stomodeum do?
    separates the oral epithelium from the ectomesenchyme
  19. when does the dental lamina form?
    later portion of 7th week
  20. what process produces the dental lamina layer?
    the oral epithelium growing deeper and deeper into the ectomesenchyme
  21. the production of dental lamina starts from the____________and progresses_______________
    • midline
    • posteriolry
  22. name 3 developmental disturbances that occur in the initiation stage of tooth development
    • anodotia
    • ectodermal dysplasia
    • supernumerary teeth
  23. what is anodontia?
    lack of initiation; absence of single or multiple teeth
  24. where does anodontia most commonly occur?
    with permanent maxillary lateral incisors, third molars, and mandibular 2nd premolars
  25. what are some other causes of anodontia besides lack of initiation?
    • indocrine dysplasia
    • systemic disease
    • excessive radiation exposure
  26. what is ectodermal dysplasia?
    syndrome associated with anodontia
  27. what is supernumerary teeth?
    abnormal initiation leading to the development of extra teeth
  28. where does supernumerary teeth often occur?
    • between the maxillary central incisors
    • distal to the maxillary 3rd molars
    • premolar region of both arches
  29. how do teeth appear in the case of supernumerary teeth?
    • smaller than normal-and may be accidently discovered on a radiographic exam
    • may or may not be erupted
    • may cause crowding
  30. what is the second stage of odontogenesis called?
    the bud stage
  31. when does the bud stage take place?
    beginning of the 8th week of prenatal development for the primary dentition
  32. what physiological process occurs during the bud stage?
    • extensive proliferation or growth of the dental lamina into buds penetrating into the ectomesenchyme
    • proliferation of underlying ectomesenchyme
  33. at the end of the proliferation process, both the future mandible and maxillary arches will each have how many tooth buds?
  34. what structure still remains between the bud and the growing mesenchyme throughout proliferation?
    a basement membrane
  35. what does each bud eventually develop into?
    a tooth germ and its supporting tissues
  36. is there any cellular structure change during the bud stage of tooth development?
  37. what happens to the dental lamina in areas where teeth will not be forming?
    it remains thickened and later disintegrates as developing oral mucosa comes to line the oral cavity
  38. name 2 common dental developmental disturbances that occur during the bud stage
    • macrodontia
    • microdontia
  39. what is macrodontia? what causes it?
    • abnormal proliferation leading to a single tooth or entire dentition to be larger than normal
    • it's hereditary
  40. Is macrodontia a result of splitting or fusion of enamel organs?
  41. What is microdontia? And what causes it?
    • abnormal proliferation leading to single tooth or entire dentition developing smaller than normal
    • it's hereditary
  42. where does microdontia most commonly occur?
    • permanent maxillary lateral incisors (peg laterals)
    • permanent 3rd molars (peg molars)
  43. what can complete macro and microdontia be due to?
    dysfunction of the pituitary gland
  44. when does the cap stage of tooth development occur?
    • during 9th and 10th week of prenatal development
    • it is the third stage of tooth development
  45. name the physiological processes that occur in the cap stage
    • proliferation
    • differentiation
    • morphogenesis
  46. describe proliferation as it pertains to the cap stage of tooth development
    it is unequal growth in different parts of the tooth bud, which leads to the formation of a cap shape attached to the dental lamina.
  47. which types of differentiation are active during the cap stage of tooth development?
    • cytodifferentiation
    • histodifferentiation
    • morphodifferentiation
  48. What is the predominant physoilogical process during the cap stage of tooth development?
  49. what structure is formed from morphogenesis in the cap stage of tooth development?
    a primordium of the tooth, or tooth germ
  50. define tooth germ. What will it develop into
    • primoridium of tooth which develops with a specific form
    • primary dentition
  51. what does the tooth germ consist of?
    • enamel organ
    • dental papilla
    • dental sac
  52. define enamel organ. what will it eventually form?
    • depression in the deepest part of the dental lamina forming a cap
    • it will form the enamel for outer surface of the tooth
  53. what was the enamel organ originally derived from?
    the ectoderm
  54. define dental papilla. What will it eventually become?
    • mass with in the concavity of the cap of the enamel organ
    • it will eventually become the dentin and pulp of tooth
  55. where was the dental papilla originally derived from?
    the ectomesenchyme deep to the buds- the ectomesenchyme condensed into a mass within the concavity of the enamel organ
  56. What structure (regarding tooth development) is influenced by neural crest cells?
    ectomesenchyme - ectomesenchyme forms dental papilla which will become dentin and pulp, which is the part of your tooth that has NERVES **neural crest cells**
  57. Does a basement membrane still exist between the now enamel organ and the dental papilla?
  58. what does the basement membrane between the enamal organ and the dental papilla eventually become?
    the dentinoenamel junction
  59. define dental sac (dental follicle).
    the remaining ectomesenchyme that's not the dental papilla, it surrounds the enamel organ
  60. what does the dental sac eventually produce?
    • peridontium:
    • perio ligament
    • cementum
    • alveolar bone
  61. what separates the enamal organ and the dental sac?
    a basement membrane
  62. when is initiation occuring for anterior teeth of the permanent dentition?
    in the 10th week
  63. where does the primoridium for the intially formed permanent teeth (successional dental lamina) appear?
    as an extension of the dental lamina into the extomesenchyme lingual to the developing primary tooth germs.
  64. define successional dental lamina.
    primoridium of the permanent dentition, that extends from the dental lamin into the ectomesenchyme lingual to the forming of primary tooth germs.
  65. Where do non-succadaneous (permanent molars) teeth develop from?
    from a posterior extension of the dental lamina distal to the primary 2nd molar's dental lamina
  66. name 4 common developmental disturbances during the cap stage
    • dens in dente
    • germination
    • fusion
    • tubercles
  67. what is dens in dente
    enamel organ abnormally invaginates into the dental papilla; usually leave the tooth with a deep lingual pit, which can lead to pulpal exposure and pathology and possible endo therapy
  68. how does dens in dente appear on a radiograph? what causes it?
    • appears as a tooth within a tooth
    • it has hereditary factors involved
  69. what teeth does dens in dente commonly affect?
    permanent maxillary incisors, especially the lateral incisors
  70. what is germination
    single tooth germ unsuccessfully attempt to divide into two. which results in single-rooted tooth with common pulp cavity, and the tooth exhibits twining in crown area.
  71. where does germination usually occur?
    usually in anterior teeth in either dentition
  72. what causes germination? and what problems can it create?
    • can be hereditary
    • creates problems with spacing and appearance
  73. what is fusion?
    reults from the union of 2 adjacent tooth germs, possibly due to pressure in the area. There are 2 distinct pulp cavities, but enamel, dentin, and pulp are united
  74. where does fusion usually occur?
    • in crown area of tooth, bt can involve both crown and root
    • occurs in anterior teeth of primary dentition
  75. what are tubercles? And what may they be due to?
    • extra cusps or extensions of enamel
    • may be due to trauma, pressure, metabolic disease
  76. where are tubercles usually found?
    • permanent molars, especilly 3rd molars, but can be found on any tooth
    • also lingual extension on the cingulum of permanent maxillary anterior teeth, especially lateral incisors and canines
  77. when does the bell stage of tooth development occur for primary dentition?
    between the 11th and 12th week, it is the 4th stage
  78. what physiological processes occur in the bell stage of tooth development?
    continuation of the ongoing processes of proliferation, differentiation, and morphogenesis
  79. _____________on all levels occurs to it's furthest extent in the bell stage of tooth development.
  80. what results from the strong differentiation process in the bell stage of tooth development?
    4 different types of cells are found in the enamel organ
  81. name the 4 new cell types developed in the bell stage of tooth development.
    • inner enamel epithelium
    • outer enamel epithelium
    • stellate reticulum
    • stratum intermedium
  82. what has the cap shape of the enamal organ changed to in the bell stage?
    a bell shape
  83. what is happening to the dental sac during the bell stage of tooth development? what will this differentiate into?
    • increasing amount of collagen fibers are forming aroung the enamal organ
    • cementum, perioligament, and alveolar bone
  84. what is the outer enamel epithelium (OEE)? and what does it serve as?
    • outer cuboidal cells of enamel organ
    • pretective barrier for enamel organ
  85. what is the stellate reticulum? What is it's function?
    • more outer star-shaped cells in many layers, forming a network within the enamel
    • it supports the production of the enamel matrix
  86. what is the stratum intermedium? and what is it's function?
    • more inner layer of flat to cuboidal cells
    • it supports the production of the enamal matrix
  87. what is the inner enamel epithelium (IEE)? and what does it differentiate into?
    • innermost tall, columnar cells of enamel organ
    • differentiates into ameloblasts, and enamal matrix
  88. during the bell stage of tooth development, what other structure besides the enamel organ is undergoing extensive differentation?
    the dental papilla within the concavity of the enamel organ
  89. after extensive differentiation of the dental papilla during the bell stage of tooth development, what two types of tissues does it now consist of?
    • outer cells of dental papilla
    • inner cells of dental papilla
  90. what are outer cells of dental papilla? and what do they give rise to?
    • outer layer of cells of the dental papilla nearest the IEE, there is a basement membrane between these two layers
    • it will give rise to odonotoblasts that form the dentin matrix
  91. what will the inner cells of dental papilla differentiate into?
    pulp tissue
  92. What is the final stage of odontogenesis? And what happens in this stage?
    • Apposition
    • the enamel, dentin, and cementum are secreted in successive layers
  93. how are the enamel, dentin, and cementum initially secreted?
    as a matrix
  94. what is a matrix? And what does it serve for?
    extracellular substance that serves as framework for later calcification
  95. many inductions occur in the apposition stage of tooth development. wat tissues do these inductions occur between?
    between the ectodermal tissue of the enamal organ and mesenchymal tissues of the dental papilla and dental sac.
  96. what does the basement membrane do for the tissue of enamel organ and mesenchymal tissue?
    conveys communication between the tissues, and acts as a boundary
  97. why are interactions between ectodermal tissues and mesenchymal tissues during the apposition stage in tooth development necessary?
    for the production of enamel, dentin, and cementum by the proliferation of cellular byproducts
  98. what is maturation in tooth development?
    other final stage which is reached when the dental tissues are fully mineralized
  99. name 5 common developmental disturbances that occur in the apposition and maturation stages of tooth development
    • enamel dysplasia
    • enamel hypoplasia
    • enamel hypocalcification
    • amelogenesis imperfecta
    • dentinogenesis imperfecta
  100. what is enamel dysplasia?
    faulty development of the enamel resulting from interference of metabolic processes of ameloblasts. may involve individual areas (localized) or large number of ameloblasts (systematic)
  101. what is enamel hypoplasia?
    results from the quantity of enamel matrix; teeth appear pitted and grooved
  102. name and describe two conditions that count as enamal hypoplasia
    • hutchinson's incisors-crown has screwdriver shape with notched incisal edge
    • mulberry molars-have enamel tubercles on the occlusal surfaces
  103. what is enamel hypcalcification?
    disturbance results in the reduction of quality of enamel maturation- teeth appear more opaque, yellower, or browner due to intrinsic staining of enamel
  104. What is amelogenesis imperfecta?
    • enamel dysplasia which is hereditary, can affect all teeth of both dentitions
    • teeth have very thin enamel portions that chip off or have no enamel at all
    • crowns are yellow and composed of dentin
    • severe attrition can occur due to chewing
    • no treatment required, but may want to place crowns for appearanc and prevent further attrition
  105. what is dentinogenesis imperfecta?
    • dentinal dysplasia which may be hereditary
    • blue/gray or brown with opalescent sheen
    • enamel is normal, but chips off due to lack of dentin support
    • results in dentinal crown leading to sever attrition
    • no treatment required but may want to place crowns for appearance and further attrition
  106. during what stage do IEE cells grow even more columnar or elongate?
    bell stage
  107. when IEE cells elongate and grow more columnar, what are they differentiating into?
  108. describe repolarization in regards to the IEE cells growing more columnar
    the nuclei of all the cells move away from the center and position themselves farthest away from the basement membrane
  109. what do the preameloblasts eventually differentiate into? And what do preameloblasts induce?
    • differentiate into cells secreting the enamel matrix
    • induce dental papilla cells to differentiate
  110. when are the outer cells of the dental papilla induced to differentiate into odontoblasts? Who induces them?
    • after the IEE differentiates into preameloblasts
    • preameloblasts induce them
  111. does repolarization occur in the dental papilla cells? If so, describe.
    • Yes
    • the nuclei move away from the center to the position farthest from the basement membrane, they are in a mirror image with the repolarized preameloblasts.
  112. what is dentinogenesis? And when does it happen?
    • production of the dentin matrix (predentin) on the odontoblast side of the basement membrane
    • it occurs after the odontoblasts have undergone repolarization
  113. why is the dentin layer slightly thicker than the corresponding layer of enamel matrix?
    because odontoblasts start their secretory activity before the enamel matrix production begins
  114. when does the basement membrane between preameloblasts and odontoblasts disintegrate? And why does it do so?
    • after the differentiation of odontoblasts and formation of predentin
    • it allows the preamaloblasts to come in contact with the new formed predentin, and induces preameloblasts to differentiate into ameloblasts
  115. where to ameloblasts begin amelogenesis (apposition of enamel matrix)?
    on their side of the now disintegrating basement membrane
  116. what is amelogenesis?
    apposition of enamal matrix
  117. define Tome's process
    a tapered portion of each ameloblast facing the disentegrating basement layer which secretes enamel matrix
  118. what is the dentinoenamel junction? And it forms as a result of what?
    • the inner junction between the dentin and enamel tissues
    • as a result of the mineralization of the disintegrating basement membrane and joining of the dentin and enamel matrixes
  119. define odontoblast process
    attached cellular extensions in the length of the predentin left by the odontoblasts
  120. what are the odontoblast processes contained in?
    dentinal tubule
  121. maturation of enamel and dentin occur___________and in different___________
    • later
    • processes
  122. where do cell bodies of odontoblasts end up?
    remain within pulp tissue
  123. where do cell bodies of ameloblasts end up?
    involved in eruption and mineralization process, but are lost after eruption
  124. when do the processes of root development occur?
    after the crown is completely shaped and the tooth is beginning to erupt into the oral cavity
  125. What structure is responsible for root development?
    cervical loop
  126. what type of tissue does the cervical loop consist of?
    only inner and outer enamel epithelium
  127. describe growth of the cervical loop
    it continues to grow deeper into the surrounding ectomesenchyme of the dental sac, elongating and moving away from the newly completed crown, enclosing more of dental papilla tissue
  128. what forms from the deeper growth of the cervical loop?
    Hertwig's epithelial root sheath
  129. what is the function of Hertwig's epithelial root sheath?
    functions to shape the root/roots and induce dentin formation in the root so it is continous with coronal dentin
  130. true or false. Root dentin forms in the same manner as crown dentin. dental papilla is induced to differentiate and become odontoblasts
  131. howcome there is no enamel in the roots?
    it is due to the absence of intermediate layers (stellate reticulum and stratum intermedium) HERS induces odontoblastic differentiation, but fails to differentiate into enamel forming ameloblasts
  132. in roots where does dentinogenesis begin? and what is formed as a result?
    • in the root
    • predentin is formed from it
  133. what happens to the basement membrane and HERS sheath when root formation is completed?
    they disintegrate
  134. define epithelial rests of malessez
    HERS roog sheath disintegrates and may become these groups of epithelial cells located in the mature perio ligament which may become cysitc and cause future problems
  135. name and describe a developmental disturbance that may occur during root development
    enamel pearls
  136. what are enamel pearls?
    misplaced ameloblasts migrating to the root area abnormally forming enamel on root surfaces
  137. how do enamel pearls appear on radiographs? What can they be confused as? And can they be removed?
    • appear radiopaque
    • be confused as calculus
    • no
  138. define cementogenesis
    apposition of cementum occurs when HERS disintegrates allowing undifferentiated cells of the dental sac to come into contact with the newly formed surface of root dentin, inducing these cells to become immature cementoblasts
  139. what do cementoblasts do?
    move to cover the root dentin laying down cementum matrix known as cementoid
  140. what are cementocytes?
    cementoblasts entrapped in cementum
  141. what is cementum?
    matrued, calcified cementoid surrounding the cementocytes
  142. what is pulp made from?
    central cells of the dental papilla, it is surrounded by the new dentin
  143. what is a developmental disturbance in cementum and pulp formation?
  144. what is concrescence?
    • excess cementum formation; union of the root structure of two or more teeth thru the cementum only
    • teeth involved originally separate, but join as a result of excessive cementum deposition on one or more teeth after eruption
  145. where does concrescence usually occur? And what may be the cause?
    • in permanent maxillary molars
    • cause may be traumatic injury or crowding of teeth during apposition and maturation stage
  146. what do the periodontal ligament and alveolar bone develop from?
    • ectomesenchyme from denal sac forms the PDL
    • ectomesenchyme begins to mineralize and form the aveoli of the alveolar bone surrounding the PDL
  147. what are collogen fibers? And what is their function?
    • they are formed and immediately organized into fiber bundles of PDL
    • the ends of these fibers insert into the outer portion of the cementum and the surrounding alveolar bone for tooth support
  148. define root trunk
    structure where all multirooted teeth originate from, it is a single root
  149. what causes the root trunk to divide?
    differential growth in HERS
  150. what are 3 developmental disturbances during root formation?
    • dilaceration
    • flexion
    • accessory roots
  151. what is dilaceration?
    distorted roots or crown angulation in a formed tooth; it results from distortion of HERS caused by injury or pressure.
  152. what is flexion?
    deviation or bend restricted to only the root portion of the tooth-may be a result from trauma to developing tooth
  153. what are accessory roots?
    extra roots or supernumerary roots; may be due to trauma, injury, or pressure affecting HERS
  154. where do disturbances in root formations usually occur?
    in permanent third molars
  155. define active eruption of teeth
    actual vertical movement of the teeth
  156. define passive eruption
    occurs as we age as gingival recedes, no actual tooth movement occurs
  157. do mandibular or maxillary teeth passively erupt first?
  158. true or false. teeth in both jaw bons errupt in pairs
  159. do permanent teeth usually errupt in girls or boys first?
  160. abou what age to primary central incisors errupt?
    6 1/2 -8 months
  161. about what age do primary lateral incisors errupt?
    7-9 months
  162. about what age to first molars errupt?
    12-16 months
  163. about what age to primary canines usually errupt
    6-21 months
  164. about what age do second primary molars usually errupt
    21-30 months
  165. define reduced enamel epithelium
    it is layers of the enamel organ that are compressed and overly the new enamel surface
  166. what happens between the REE and oral epithelium to allow for the eruption process?
    they fuse togethe
  167. what process causes 'teething'?
    enzymes from REE disintegrate the central portion of the fused tissue, leaving an epithelial tunnel for the toothe to erupt through into the surroundingn oral epitheliaum of the oral cavity
  168. define Nasmyth's membrane
    residue formed on newly erupted tooth consisting of the fused tissue of the REE and oral epithelium as well as the dental cuticle placed by ameloblasts on new enamel. it is easily removeable
  169. define osteoclast
    absorb the alveolar bone between primary and permanent teeth during eruption
  170. odonoclasts
    cause resorption or removal of portions of the primary root of dentin and cementum as well as small protions of the enamel crown
  171. why is it important to keep primary teeth as long as possible?
    they serve as place holders for permanent teeth
  172. when do the permanent mandilbular central incisors usually errupt?
    • 6-7 yrs
    • 7-8 yrs
  173. when do the permanent mandibular lateral incisors usually errupt? maxillary?
    • 7-8 yrs
    • 8-9 yrs
  174. when do the permanent mandibular canines usually errupt? Maxllary?
    • 9-10 yrs
    • 11-12 yrs
  175. when do the permanent premolars usually errupt?
    10-12 years
  176. when do the permanent 1st molars usually errupt?
    6-7 yrs
  177. when do the permanent 2nd molars usually errupt?
    12-13 yrs
  178. when do the permanent 3rd molars usually errupt?
    17-22 yrs