Oral

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Figure 1 Sagittal sections through Carnegie stage 22 (right) and 23 (left)

human embryos showing the formation of the palate. At stage 22 the tongue
occupies the common oronasal cavity, whereas at stage 23 the tongue is depressed
and the forming palate intervenes between the oral and nasal cavities.
Figure 2 Coronal sections through Carnegie stage 22 (left) and 23 (right) human
embryos showing the formation of the palate. The palatal shelves are independent
on either side of the tongue and depress it as the shelves extend toward the
midline.
Figure 3 Human embryo at 62 days. The entire embryo has been stained with
alizarin red, which preferentially stains mineralized bone, to show the
membranous bones forming in association with the skull and face.
Figure 4 Rat embryo at 16 days stained with alizarin red (to show bone) and
alcian blue (to show cartilage). No ossification is detectable at this stage.
Figure 5 Rat embryo at 17 days stained with alizarin red (to show bone) and
alcian blue (to show cartilage). Note the membranous bone formation lateral to
Meckel’s cartilage and the formation of the condylar cartilage.
Figure 6 Rat embryo at 19 days. Mandible stained with alizarin red (to show
bone) and alcian blue (to show cartilage) showing the primary (Meckel’s) and
secondary (condylar, coronoid, angular, and alveolar) cartilages associated with
the membranous bone forming the body of the mandible.
Figure 7 Coronal section through a developing embryo. A number of developmental
features are apparent. The tongue is easily identified. Note Meckel’s
cartilage and intramembranous ossification of the forming mandible lateral to
it. The forming mandible is growing alveolar plates to surround a bud stage
tooth germ. In the developing upper jaw, a cap stage can be seen.
Figure 8 Late cap stage of tooth development. The forming tooth is undergoing
histodifferentiation, and the dental papilla and dental follicle can be clearly
distinguished. Note the enamel knot.
Figure 9 Bud stage of tooth development. Note the accumulation of
ectomesenchymal cells around the epithelial bud.
Figure 10 High-power view of a developing tooth bud.
Figure 11 Early cap stage of tooth development. The enamel organ is expanding,
but folding is just beginning.
Figure 12 Early cap stage of tooth development. The enamel organ is undergoing
histodifferentiation, and the dental papilla and dental follicle can be clearly
distinguished. Note the enamel knot.
Figure 13 Late cap stage of tooth development. The enamel organ has folded,
producing a concavity into which the ectomesenchymal cells of the papilla
accumulate. Intramembranous bone formation has initiated around the developing
tooth crown.
Figure 14 High magnification of a late cap stage tooth organ. Note the
difference in structural appearance between the inner and outer dental epithelia
and the concentration of ectomesenchymal cells facing the inner dental
epithelium.
Figure 15 Cap stage tooth bud. The enamel knot is an accumulation of epithelial
cells on the internal aspect of the inner dental epithelium.
Figure 16 The enamel cord is a condensation of epithelial cells that extends
from the inner to the outer dental epithelium.
Figure 17 Bell stage of tooth development. The primary tooth has acquired its
final shape but not its final size.
Figure 18 High-power view of the four layers of the enamel organ. (Courtesy P.
Tambasco de Oliveira.)
Figure 19 Bell stage of tooth development. Both dentinogenesis and amelogenesis
have begun (dentin, pink; enamel, purple) at the cusp tip. Note collapse of the
stellate reticulum where mineralized matrix has been formed.
Figure 20 Bell stage of tooth development. Both dentinogenesis and amelogenesis
have begun (dentin, pink; enamel, purple) at the cusp tip. Crown pattern
formation has folded the inner dental epithelium upward to bring the ameloblasts
close to the blood vessels situated outside the outer dental epithelium—the
so-called collapse of the stellate reticulum.
Figure 21 Forming root. Hertwig epithelial root sheath (HERS) is present at the
leading root edge.
Figure 22 Body of the mandible. The outer layers consist of compact bone,
between which is a supporting network of trabecular bone.
Figure 23 Phase-contrast micrograph of woven bone. Note the random organization
of the refringent collagen fibrils.
Figure 24 Ground section of lamellar bone. The osteon represents the basic
structural unit. It consists of concentric lamellae that form a cylinder of bone
with a vascular canal, the Haversian canal, at its center.
Figure 25 Lamellar bone visualized by phase-contrast microscopy. Note the
concentric lamellae that form the osteon.
Figure 26 Interstitial lamellae (fragments of preexisting concentric lamellae)
are interspersed between osteons, and circumferential lamellae enclose the outer
and inner aspects of bone.
Figure 27 Osteocytes are entrapped within bone. These cells reside in lacunae,
and their processes in interconnecting canaliculi (arrows) form an extensive
network.
Figure 28 High magnification of an osteon showing its concentric lamellae, the
centrally located Haversian canal, and the osteocyte lacunae interspersed among
the lamellae.
Figure 29 Intramembranous bone formation in the region of the future mandible;
plump-looking osteoblasts line forming bone surfaces.
Figure 30 The presence of numerous osteoclasts associated with this trabecula
of embryonic bone suggests that it is being turned over rapidly.
Figure 31 Trabecular bone. All the cell types associated with bone can be
recognized in this micrograph.
Figure 32 Osteocytes are usually found within the calcified matrix but can also
be present within osteoid (asterisks).
Figure 33 Histochemical detection of tartrate-resistant acid phosphatase
activity, a marker for osteoclasts in the primary spongiosa of the rat tibia
growth plate.
Figure 34 Human osteoclasts stained for tartrate-resistant acid phosphatase.
Note the presence of multiple nuclei in these cells.
Figure 35 Endochondral ossification in the rat tibia growth plate. The section
is stained with von Kossa's stain to reveal mineral distribution (black
deposits).
Figure 36 Mineral deposition starts in the calcification zone of the growth
plate.
Figure 37 High magnification of mineralized cartilage in the growth plate. Note
that mineral (black deposits) is only present in the longitudinal septae.
Figure 38 Light micrograph of intramembranous bone formation in the rat
calvarium. The first step is condensation of ectomesenchymal cells between the
skin and developing brain.
Figure 39 As intramembranous bone formation progresses, ectomesenchymal cells
differentiate into osteoblasts that form woven cancellous bone.
Figure 40 Cross section of the cartilage model of a digit. Before the start of
intramembranous bone formation, alkaline phosphatase activity appears in the
connective tissue surrounding the anlage (perichondrium) and periosteum in areas
of vascular invasion.
Figure 41 Vascular invasion of the cartilage model of a digit. Alkaline
phosphatase–positive cells from the periosteum accompany the vascular elements
and accumulate at the center of ossification.
Figure 42 The center of ossification of the cartilage model of a digit in
longitudinal section. Alkaline phosphatase activity is present both in the
center of ossification and the periosteum.
Figure 43 Section showing the hard and soft tissues of the tooth.
Figure 44 Tooth bud at the stage when both enamel and dentin formation begins.
Figure 45 Incisal tip of a tooth just before the start of the enamel layer
formation.
Figure 46 Aand B,Early crown stage of tooth development. Dentin (D) and enamel
(E) have begun to form at the crest of the folded inner dental epithelium
(incisal tip). There is a reduction in the amount of stellate reticulum (SR) in
the region where matrix deposition has occurred. Note the developmental gradient
in cell differentiation from the tip toward the cervical portion of the tooth
crown. Am, Ameloblasts; Od, odontoblasts; ODE, outer dental epithelium; SI,
stratum intermedium; PD, predentin.
Figure 47 Secretory stage amelogenesis. Tomes’ processes jut into enamel and
in certain species in a "picket fence" appearance. The line at the base of the
ameloblasts represents the proximal cell web (pcw), and that at the apex, the
distal cell web (dcw).
Figure 48 Histologic section of a decalcified tooth along the slope of the cusp
showing an incisal to cervical gradient in enamel maturation. As maturation
progresses, enamel matrix is lost and mineral content increases. Almost mature
enamel (top right) appears whitish because mineral has been removed and there is
very little matrix left in this area. Note the striae of Retzius and morphology
of maturation stage ameloblasts (no Tomes’ process).
Figure 49 Maturation stage of amelogenesis. A,Smooth-ended ameloblasts. Note
that the three other layers of enamel organ have amalgamated together to form a
highly infolded and vascular layer, the papillary layer. Ameloblasts undergo
modulation, a process by which their apexes alternate between a smooth-ended
border (A) and a ruffle-ended border (B).
Figure 50 Once enamel is completely mature, the enamel organ forms the reduced
dental epithelium. At this stage, ameloblasts are no longer distinguishable.
Figure 51 Mature enamel. In decalcified preparation, the fully calcified enamel
is completely removed, leaving behind the space it occupied. Note also that the
enamel organ on the cuspal aspect of the tooth has reorganized into a reduced
dental epithelium in which individual cell layers cannot be distinguished.
Figure 52 Indicator dyes can be used to detect regional variations in pH along
the maturing enamel of rat incisors that correspond to the modulation cycle of
ameloblasts. (Courtesy C. E. Smith.)
Figure 53 Ground section viewed by contrast-phase microscopy. In a longitudinal
section of the tooth, the striae of Retzius are seen as a series of dark lines
extending from the dentinoenamel junction toward the tooth surface and capping
its tip.
Figure 54 Striae of Retzius manifest on the surface of the tooth as a series of
grooves called perikymata.
Figure 55 Striae of Retzius manifest on the surface of the tooth as a series of
wavelike grooves, or Hunter-Schreger bands, as seen in a decalcified section of
maturing enamel.
Figure 56 Transmitted light image of ground section showing the alternating
orientation of a group of rods in the region of Hunter-Schreger bands.
Figure 57 Phase-contrast microscopic image of the longitudinal ground section
of a calcified tooth.
Figure 58 Transmitted light image of cross-sectional ground section of a tooth
showing a lamella and concentric lines/bands representing the striae of Retzius.
Figure 59 Ground section of a tooth showing the disposition of striae of
Retzius and of enamel tufts at the dentinoenamel junction.
Figure 60 High magnification of the dentinoenamel junction.
Figure 61 Enamel tufts resemble tufts of grass in ground section.
Figure 62 Ground sections permit ready visualization of the scalloped
appearance of the dentinoenamel junction. Also note the complex trajectory of
the enamel rods in the inner enamel.
Figure 63 Enamel spindles represent odontoblast processes trapped in enamel.
Figure 64 Odontoblast differentiation and initial dentin formation. An
acellular zone separates the undifferentiated cells of the dental papilla from
the differentiating ameloblasts. The preodontoblasts gradually develop into tall
and polarized cells with their nucleus away from the matrix; they deposit at the
interface with ameloblasts.
Figure 65 Higher magnification of the acellular zone separating differentiating
odontoblasts and ameloblasts.
Figure 66 The first secretory products of odontoblasts accumulate as an
unmineralized layer, predentin, that gradually mineralizes to form mantle
dentin.
Figure 67 Thicker fibers of collagen (arrowheads) originate from between
odontoblasts and extend into the forming mantle predentin. These fibers are
referred to as von Korff’s fibers.
Figure 68 Mineralization foci appear in the initial matrix deposited by
odontoblasts. These foci eventually grow and coalesce to form the mantle dentin.
Figure 69 Primary dentin. Odontoblasts border the pulp chamber and line the
predentin surface. Below the odontoblasts is a cell-free zone followed by a
cell-rich zone.
Figure 70 Ground section of dentin stained to demonstrate dentin phosphophoryn
(mauve). Note its absence from mantle and reparative dentin. (Courtesy Takagi Y,
Sasaki S: J Oral Pathol15:463, 1986.)
Figure 71 Undemineralized section of the mature dentin-pulp complex. The
vascularity of the pulp is evident. The cell-free zone of Weil can be clearly
seen beneath the odontoblast layer.
Figure 72 Tooth section stained to demonstrate the nerves of the pulp. Note the
plexus beneath the odontoblast layer.
Figure 73 Histologic preparation illustrating the transformation of predentin
into mineralized dentin along a linear mineralization front (arrows).
Figure 74 Globular mineralization results in an irregular mineralization front
(arrows) at the predentin-dentin interface.
Figure 75 Odontoblasts have apical processes that remain in the matrix they
form.
Figure 76 Silver-stained section illustrating the globular nature of the
mineralization front.
Figure 77 Interglobular dentin represents unmineralized matrix regions
resulting from imperfect globular mineralization.
Figure 78 Ground section of dentin showing the dentinal tubules in which the
odontoblast processes run.
Figure 79 The junction between primary and secondary dentin is characterized by
a change in the direction of dentinal tubules (arrowheads).
Figure 80 Cellular cementum. Cementocytes have extensive cell processes that
point toward the root surface. This calcified ground section shows the lacunae
and canaliculi that accommodate the cementocyte bodies and processes,
respectively.
Figure 81 Pulp stone (false). Note the concentric layers of matrix and the
absence of cells. Its proximity to dentin surface suggests that it may
eventually become embedded in it (attached pulp stone).
Figure 82 Ectopic calcification. Illustrated here is a «free» pulp stone; it
is not attached to dentin. Note the concentric layering of its matrix, which
reflects a phasic growth pattern. (Courtesy P. Tambasco de Oliveira.)
Figure 83 A tooth and mandible cut in the sagittal plane. (Courtesy P. Tambasco
de Oliveira.)
Figure 84 Histologic preparation illustrating the tissues supporting and
investing the tooth. These consist of cementum, periodontal ligament, alveolar
bone, and that part of the gingiva facing the tooth.
Figure 85 The undersurface of a developing root. The apical foramen is still
widely open and will close when root formation is completed.
Figure 86 Forming root. Hertwig epithelial root sheath is present only on the
advancing root edge.
Figure 87 Histologic section through an elongating root. The apical foramen is
widely open and delimited by a slight inward inflection of Hertwig epithelial
root sheath, called the diaphragm.
Figure 88 Histologic section of the advancing root edge in a rat molar during
acellular extrinsic fiber cementum (AEFC) formation. In the rat, Hertwig
epithelial root sheath (HERS) is still present when radicular dentin calcifies.
Figure 89 Periodontal tissues. Note the presence of epithelial cell rests of
Malassez along the root surface.
Figure 90 Remnants of Hertwig epithelial root sheath persist in the periodontal
ligament (PDL) as clusters of cells called epithelial rests of Malassez (ERM).
Cb, Cementoblast; Cc, cementocyte; CIFC, cellular intrinsic fiber cementum.
Figure 91 Light micrograph of a porcine forming root. Epithelial cell rests of
Malassez (ERM) are present in the periodontal ligament (PDL) close to the
surface of acellular extrinsic fiber cementum (AEFC) and sometimes appear as
relatively long strands of cells.
Figure 92 In a tangential section to the tooth surface, the epithelial cell
rests of Malassez appear to form a network.
Figure 93 Epithelial cell rests of Malassez. Note the abundance of
heterochromatin in the nuclei.
Figure 94 Collagen fiber bundles (arrows) pass between cementoblasts and insert
into cementum.
Figure 95 Section of a human tooth extracted for orthodontic reasons. The
periodontal ligament had been destroyed during extraction, but cementoblasts and
fiber fringes extending between them are still visible.
Figure 96 In ground sections, the granular layer of Tomes’ process (GLT)
appears as a region containing dark polymorphic structures at the interface
between dentin and cementum, here of the acellular extrinsic fiber variety
(AEFC).
Figure 97 Ground section showing the transition between acellular extrinsic
(AEFC) and cellular intrinsic (CIFC) fiber cementum. Note the lacunae occupied
by cementoblasts in cellular cementum.
Figure 98 In some cases, cementum overlaps enamel at its cervical extremity.
This cementum is generally of the acellular afibrillar variety; in a porcine
specimen, the overlapping cementum is of the cellular variety, particular to
this animal species.
Figure 99 Phase-contrast image of the cementoenamel junction. In some cases,
cementum and enamel do not abut, leaving a region of exposed dentin (arrow)
between them that may lead to tooth sensitivity. (Courtesy P. Tambasco de
Oliveira.)
Figure 100 Phase-contrast image of cementoenamel junction. In the majority of
cases cementum and enamel meet end to end (arrow) along the cervical margin of
the crown. (Courtesy P. Tambasco de Oliveira.)
Figure 101 Low-power view of the tooth support tissues.
Figure 102 Periodontal tissues. Note the longitudinal lines in cementum
resulting from its appositional deposition.
Figure 103 The periodontal ligament is a highly cellular and vascular
connective tissue.
Figure 104 A,Histologic section of periodontal tissues examined by transmitted
light. AEFC, Acellular extrinsic fiber cementum. B, Same section examined by
polarized light, which allows for readily seen striations in the cementum layer
and the lamellar organization of the bone. (Courtesy P. Tambasco de Oliveira.)
Figure 105 Acellular extrinsic fiber cementum (AEFC). Some histologic stains
allow visualization of both a longitudinal layering (successive layers of
cementum) and a fibrous fringe at the surface of the cementum.
Figure 106 Appositional growth lines in cellular intrinsic fiber cementum
(CIFC).
Figure 107 Histologic section stained to highlight the fibrous component of the
periodontal ligament.
Figure 108 Specially prepared section to demonstrate oxytalan fibers in the
periodontal ligament.
Figure 109 Histologic preparation of alveolar bone examined by transmitted
light microscopy. Periodontal ligament fiber bundles insert into the bone lining
the alveolar socket, giving it the name bundle bone. The inserted fibers are
referred to as Sharpey’s fibers. (Courtesy P. Tambasco De Oliveira.)
Figure 110 Root resorption. The lost dentin has essentially been replaced by
cellular cementum, on top of which acellular cementum has formed.
Figure 111 Periodontium. The surface of the alveolar bone shows many
osteoclasts, indicating that it is undergoing remodeling.
Figure 112 The transseptal ligament (part of the gingival ligament) is situated
just below the junctional epithelium and extends from the cementum of one tooth,
over the alveolar crest, to the cementum of an adjacent tooth.
Figure 113 Micrograph of the globular organization of salivary glands.
Figure 114 Lobule of a salivary gland showing the presence of both serous and
mucous acini.
Figure 115 Salivary gland section stained to demonstrate mucous acini.
Figure 116 Seromucous demilunes capping mucous acini in the sublingual gland.
Figure 117 Salivary gland immunostained to demonstrate actin in the contractile
myoepithelial cells.
Figure 118 Parotid gland. Connective tissue septae divide the serous acini into
lobules.
Figure 119 Higher-magnification view of parotid gland lobule.
Figure 120 Submandibular gland. This mixed gland contains both serous and some
mucous acini.
Figure 121 Higher magnification of the submandibular gland in Figure 120.
Striated ducts and mucous acini with serous demilunes can be seen.
Figure 122 Monkey mandible in sagittal section showing the two primary molars
in function and the partially erupted first molar. Note the position of the
permanent premolar tooth germs between the resorbing roots of the deciduous
molars.
Figure 123 The gubernacular canal overlying the crypt of an erupting permanent
incisor. The canal is filled with soft connective tissue and an epithelial
strand, which is the remnant of the dental lamina.
Figure 124 Odontoclasts resorbing dentin.
Figure 125 Erupting molar. Both the reduced dental epithelium, overlying the
enamel space in this demineralized section, and the oral epithelium have begun
to proliferate into the intervening connective tissue as it breaks down.
Figure 126 Erupting tooth. The reduced dental organ and overlying tissues
reorganize as the tooth is about to protrude into the oral cavity.
Figure 127 Erupting molar. Fusion of the reduced dental epithelium and the oral
epithelium has occurred to form the beginning of an epithelial-lined canal.
Figure 128 The mucogingival junction (arrows) can be readily seen in a healthy
dentition.
Figure 129 The junctional epithelium attaches the gingiva to the tooth surface.
Figure 130 The dentogingival junction. Junctional, sulcular, and keratinized
gingival epithelium can all be distinguished.
Figure 131 Higher magnification of the gingiva. Note the various fiber groups
in the gingival ligament.
Figure 132 Free gingiva. The sulcular epithelium is not keratinized, whereas
that of the exposed gingival surface is keratinized.
Figure 133 The interdental papilla is the part of the gingiva that fills the
space between two adjacent teeth.
Figure 134 Attached gingiva. Note the thick layer of keratin.
Figure 135 Mucogingival junction. Keratinized gingiva (right) and
nonkeratinized mucosa (left) are shown.
Figure 136 Masticatory mucosa covering the hard palate.
Figure 137 Attached gingiva. This masticatory mucosa has no distinct submucosa.
The collagen fibers of the lamina propria attach directly and firmly to the
periosteum of the alveolar bone.
Figure 138 Palate. The lamina propria consists of a dense connective tissue.
Fat can be found in some regions of the submucosa.
Figure 139 Sagittal section through the tongue. The dorsal surface is covered
by a specialized keratinized and nonkeratinized mucosa, whereas the ventral
surface shows a thinner, nonkeratinized epithelium. Filiform papillae cover the
entire anterior part of the tongue.
Figure 140 Specialized mucosa of the tongue. Filiform papillae cover the
anterior dorsal portion of the tongue.
Figure 141 Low-power view of a circumvallate papilla. The papilla is
surrounded by a deep circular groove into which open the ducts of minor salivary
glands.
Figure 142 Taste buds line the lateral walls of circumvallate papillae.
Figure 143 Specialized mucosa. Taste bud at the junction of the hard and soft
palates.
Figure 144 Keratinized epithelium of the skin just below the vermillion zone of
the lip. Sebaceous glands and hair follicles are present within the dermis.
Figure 145 Block dissection of a human temporomandibular joint.
Figure 146 Section through the rat temporomandibular articulation.
Figure 147 Temporomandibular articulation. The condylar cartilage undergoes
typical endochondral ossification.
Figure 148 Lateral view of bones of the temporomandibular joint. (From Liebgott
B: The anatomical basis of dentistry, ed 2, St. Louis, 2001, Mosby.)
Figure 149 Mandibular fossa and articular eminence of temporal bone. A,Lateral
aspect. B,Inferior aspect of the base of the skull. (From Liebgott B: The
anatomical basis of dentistry, ed 2, St. Louis, 2001, Mosby.)
Figure 150 Internal features of the temporomandibular joint. A,Sagittal
section. B,Coronal section. (From Liebgott B: The anatomical basis of dentistry,
ed 2, St. Louis, 2001, Mosby.)