Upper & Lower jaws Development Flashcards
Bones from endochondral ossification are ……
Bones of the base of the skull
- Ethmoid
- Inf. concha
- Body, lesser wing, base of greater wing, lateral pterygoid plate of the sphenoid; petrosal of temporal bone
- Basilar, lateral, and squamous part of occipital
Bones from intramembranous ossification are ….
- frontal, parietal bones
- squamous & tympanic parts of temporal
- part of greater wing, and medial pterygoid plate of sphenoid
- upper part of squamous portion of occipital
All bones of upper face develop by ……
intramembranous ossification
The mandible develops by …..
intramembranous ossification (lateral to Meckel's cartilage) * The condyle develops from endochondral ossification
The Maxilla is derived from two bones …. &…..
maxilla proper & premaxilla
* Maxilla grows downward & forward by appositional growth at the sutures
The mandible is first seen in …….
the sixth week of life as two bones
- At one year, the bones fuse at the symphysis
- The mandible grows downward & forward due to appositional growth at posterior border of the ramus
First sign of tooth development is at ……
six weeks of embryonic life
* The embryo is 11 mm
An epithelial thickening, forming a band at the outline of future arches is …….
dental lamina
Bulb like thickening in the dental lamina indicates ……..
the future tooth buds
* They are 20 in number
The tooth bud consists of …….
- Enamel organ (from ectoderm)
- Dental papilla (from mesenchyme. Forms pulp & dentin)
- Dental sac (from mesoderm. Forms cementum & PDL)
Cap stage follows ………
It is characterized by ……….
Bud stage
- There is expansion of the whole tooth bud
1. Enamel organ: outer cuboidal cells & inner columnar cells (on the concavity). Separated by stellate reticulum
2. Enamel knot: in the center of the enamel organ
3. Dental papilla and dental sac: more proliferation
The Bell stage is characterized by ……..
- Inner enamel epi. becomes ameloblasts
- Stratum intermedium: develops between inner enamel epi. & stellate reticulum
- Stellate reticulum: more expansion
- Dental lamina: forms of new tooth buds for permanent teeth (not for molars though)
- Outer enamel epi: cells flatten
- Dental papilla: becomes odontoblasts
- Dental sac: shows circular arrangement of fibers. resembling a capsule
Vestibular lamina is ………
epithelial thickening labial to the dental lamina
It forms the vestibule
Ameloblasts will release a factor that will affect ……
the dental papilla, and start the transformation into odontoblasts, and formation of predentin
* Odontoblasts will release a reciprocal factor that affects ameloblasts to form enamelin
Root formation starts when …..
enamel and dentin formation reach the CEJ
* Enamel organ plays an important role in root formation
Hertwig root sheath is ……
the part of the enamel organ, where the inner & outer layers are fused, with no stellate reticulum or stratum intermedium
* It initiates root formation (molding the shape of the root)
After Hertwig’s sheath initiates root dentin formation, it ……..
degenerates, leaving the Epithelial rest of Malassez (which is found in the PDL)
Cementoblasts form after ………. come into contact with ……
the primitive cells of the PDL
root dentin
* This is after Hertwig’s root sheath is broken
Cementoblasts lays down ……
cementoid
* calcifies later into cementum
The term “cellular cementum” refers to ……
cementoblasts in the apical third of the root, which are trapped into their own secretion
* Acellular cementum is found in the occlusal two thirds of root
Enamel prisms and the interprismatic substance are composed of ……
96% inorganic (hydroxyapatite)
1% organic
3% water
Dentin is much more bone-like than enamel. T/F??
True
- Dentin is harder than compact bone, but softer than enamel
- The most bone like dental tissue is cementum
Enamel rods are arranged in …….
a perpendicular fashion on every point of the enamel surface in the crown
- It starts with a wavy course, close to dentin
- Every rode runs the entire thickness of enamel
Hunter-Schreger bands appear when ……
there is a change in the arrangement of the enamel prisms
A cross section of enamel shows concentric lines of brown color with …….. & colorless with ………
These are …….
transmitted light
reflected light
Lines of Retizus (run obliquely in longitudinal section)
* They are growth rings
Enamel spindles are ……..
extension of the dentin into the enamel (short tubules)
Perikymata are ……
transverse, wavy grooves on the enamel, extension of Lines of Retizus
- Parallel to each other and to the CEJ
- Disappears with aging
Tomes processes are ……..
the projection of the ameloblasts into the enamel
* Ameloblasts long axis is not parallel to the long axis of the rods they produce
Enamel lamellae are ……….
hypomineralized structures. extend from enamel surface to DEJ or deeper
* No clinical significance
Enamel tufts are ……
hypocalcified enamel rods extending from the DEJ into the enamel
* Resembles cracks
Enamel tufts differ from enamel lamellae by …
- they are non linear (branched - optical illusion)
- extend from DEJ outwards
* Both are caused by disturbance in enamel formation
Dentin is composed of ……
70% inorganic
30% organic & water
Dentinal tubules start at ……
right angles to the pulp, then follow and S shape wavy path
Tomes fibers refers to ……
odontoblastic process extending into the dentinal tubules
Peritubular dentin is …..
dentin surrounding the odontoblast process
* Stain darkly, highly mineralized
Intertubular dentin is …..
forms the main bulk of dentin. Less mineralized than peritubular
* More collagenous fibers in ground substance
Imbrication lines or ………, are …….
Von Ebner lines, are lines run at right angle to the dentinal tubules in cross section. Sign of incremental apposition
* resembles lines of Retizus in enamel
Contour line of Owen is …..
an exaggeration of the Von Ebner incremental lines
- due to disturbance in mineralization process
- If due to trauma, it is called neonatal lines
Predentin is non mineralized. T/F??
true
The first sign of predentin mineralization is formation of ……
Failure of fusion of the globules in the dentin will form ……
Korff fibers (fan like arrangement of collagen fibers), which forms globules that fuse later, forming a regular dentin * interglobular dentin (poorly mineralized dentin between the globules)
Interglobular dentin subjacent to cementum is called ……
Tomes granular layer
* Note that: Dentin is considered a vital tissue
Secondary dentin is characterized by ……
- separated from early dentin by dark line
2. less tubules, but more wavy
In response to injury, odontoblasts may …… or ……….
- degenerate, and replaced by undifferentiated cells from the pulp, which form hard reparative dentin
- continue to produce dentin to protect the pulp
The reparative dentin have ……
less tubules, which are twisted
Scelrotic dentin is ……..
seen in elderly people, where calcium salts may obliterate the dentinal tubules
* It is transparent dentin
Cementum is composed of …….
65% inorganic
35% organic & water
Cementocytes in the root apical third have …….
processes that branch & anastomose in canaliculi
If damage occurs to the cementum, ……
PDL cells differentiate into cemetoblasts, which form secondary cementum
* Secondary cementum resembles cellular cementum, and reabsorbs more easily (but less than bone)
Secondary & cellular cementum are similar to bone by …….
contain cells in lacunae, have canaliculi, & can be reabsorbed (though not under normal condition)
* Note that: cementum doesn’t have a Haversian system like bone
Cementum can compensate for tooth structure loss. T/F??
true
Hypercementosis occurs in ……
chronic inflammation in the periapical area
* May also occur due to hypofunction of a tooth
The primary function of the pulp is ……
the production of dentin Also: 1. Nutrition 2. Sensory: GVE (pain only) and sympathetic (for the blood vessels) 3. Defensive
Describe the embryonic pulp tissue.
argyrophilic, and lacks vessels & collagen fibers
* Adult pulp has cells, fibroblasts, and intercellular substance (argyrophilic fibers, collagen fibers & ground substance). There is no elastic fibers. Histiocytes are present
Pulp vessels communicate with the PDL vessels via ……..
accessory canals
* Lymph vessels also found in the pulp
What are the types of nerve fibers in the pulp?
- Myelinated: mediate pain
2. Unmyelinated; sympathetic
What is the pulp stones? and what are the types?
Pulp stones (denticles) are normal finding in the adult pulp
- True: has real dentin structure with tubules
- False: calcified mass
* Denticles could be free (surrounded by pulp), attached, or embeded
TMJ is …….
a sliding hinge joint (diarthrosis) between articular eminence of the temporal and the condyle of the mandible.
* An articular disc is interimposed between the two bones
The articular surface of the eminence is ……..
The condyle is ……..
concave in its posterior portion & convex anteriorly
* arc shaped with its axis placed medially & posteriorly
The articulating surface of TMJ is covered by ……
fibrous CT (not hyaline cartilage like the rest of the body)
TMJ blood supply is from
superficial temporal branch of the external carotid artery
The condyle is …….
cancellous bone covered by thin layer of compact bone. Filled with bone marrow or fat (in older age)
* Same for the articular eminence
The glenoid fossa is composed of …….
a thin layer of compact bone. May get perforated by the condyles in severe trauma
Articular disc center is made of ………
very dense connective tissue, with no blood vessels. Resemble an erythrocyte
* The posterior border of the disc is connected to the capsule by loose CT
Articular capsule is ……
a fibrous sac, lined by synovial membrane. attached to the circumference of the mandibular fossa (superiorly), the eminence (anteriorly), & the condylar neck inferiorly
- Laterally strengthened by the temporomandibular ligament
- Capsule has numerous blood vessels
The temporomandibular ligament is …….
composed of two short fibrous ligaments
1. one from the zygomatic arch
2. one from the eminence
both attach to the lateral of the condylar neck
Some fibers of the lateral pterygoid muscle attach to ……..
anterior border of the disc
The synovial membrane of the capsule is originated from ……
mesothelium. Secrete hyaluronic acid synovial fluid
* Lines the upper and lower space of TMJ
All muscles of the tongue are innervated by hypoglossal nerve except ……
palatoglossus, innervated by CN X from the pharyngeal plexus
