Dental Anatomy and Occlusion Part 1.pdf

8/11/2019 Dental Anatomy and Occlusion Part 1.pdf

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NTAL ANATOMY OCCLUSION

Occl Ter

The

mandible functions as a

I

lever

lever

111

lever

1 1

opyright

Q 2012 2013

h t a l ecks

DENTALANATOMY OCCLUSION

Which of the following types of

or l

mucosa s ot

keratinized under normal conditions?

Buccal

mucosa

Vermillion border of

the lips

Hard

palate

Gingiva


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The cranium is fixed and the mandible is movable.

this system Class III):

Fulcrum

condyle

Force muscles

Workload teeth

a Class ever system the fulcnun is at one end he workload at the other end and

force (efiort) lies between the workload and the fulcrum

The pressure point of

support

on which a

rotates. Because all upward force

is

appliedbe

the

teeth

between

the

f i l m nd the teeth the

s

always under pressure

compression)

when

elevatormusclesconhact.This is a very

mportant

to understand as it affects both the TMJs and the

Exertion of power that starts or stops move

Can

result in compression

loading)

....or ten-

-with p mission mDamn Pcca8 ;

Funcrio~IOc

d n From W l o

mile

Design SL Louis 2007,

Mcaby.

three functional types of oral mucosa are masticatory lining and specialized mucosa. These

terms

functional descriptions of the oral mucosa in specific locations.

Masticatory mucosa: covers the gingiva and hard palate.

Epithelium: it has a keratinized or parakeratinized stratified squamous epithelium.

Lamina propria: has two layers: a thick papillary layer of loose connective tissue and a deep

reticular layer of dense connective tissue.

Lining mucosa: covers all of

soft

tissue of the oral cavity except the gingiva hard palate and dor-

sal surface of the tongue.

Epithelium: generally the epithelium of the lining mucosa is nonkeratinized.

On

the verrnillion

border of the lip however it is keratinized. If subject to unusual frictional stress the epithelium

may become parakeratinized or keratinized. Other cells found in the epitheliumof the lining mucosa

are Langerhans cells melanocytes and Merkel cells.

Lamina propria: under the epithelium of the lining mucosa a loose connective tissue with

t in

collagen fibers forms a papillary lamina propria that carries blood vessels lymphatic vessels and

nerves.

Submucosa:a distinct submucosa underlies the lining mucosa except on the inferior of the tongue.

The submucosa contains large bands of collagen and elastic fibers that bind the mucosa

to

the un-

derlying muscle. The submucosa also contains the larger nerves blood vessels and lymphatic ves-

sels that supply the neurovascular networks of the lamina propria throughout the oral cavity. In the

lips tongue and cheeks the submucosa contains many minor salivary glands.

Specialized mucosa: is restricted

to

the dorsal surface of the tongue and is characterized by the

presence of surface papillae of several types and by t ste buds in the epithelium. The epithelium is

keratinized.

All oral mucosa whether keratinized nonkeratinized or parakeratinized is of the strati-

squamous type of epithelium and the underlying central core of connectivetissue. Although the ep-

is predominantly cellular in nature the connectivetissue is less cellular and composed]nimady

collagen

fibers

and ground substance.


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ENT L N TOMY OCCLUSION

The principal fibers of th periodontal ligament are arrangedin four groups

The molecularconf~uratioa f collagen fibers in the periodontalligament

providesthem with a tensilestrengthgreaterfhan that

o

steel.

is true the second statement is false

ond statement is true the fmt statement is false

1 3

CopyrightQ 2012 2013 Wtal Decks

NT L N TOMY OCCLUSION

following is not one hose groups?

Circular group

Gingivodental group

Apical group

Transseptal group


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he second sta te me nt is true; th e f irst s ta teme nt s f a l ~

l r ~

~ U Mlllpult rlr

elemenrs or me

periodontal

llgament are the princ ipal fibers, which are col-

us and arranged in bundles and follow a wavy course when view ed in longitudinal section.

termed

y s fibers.

principal fibers of the periodontal ligament are arranged in six gr oup s that develop sequentially

eveloping root:

Tra nss ept al fibers: extend interproximally over the alveolar bone crest and are embedded in

the cementum o f adjacent teeth. These fibers keep all the teeth aligned they maintain the in-

tegrity o the dental arches). Note: These fibers may be considered as belonging to the gingiva

because they d o n ot have osseous attachment.

Alveolar cres t fi emextend obliquely

h r n

he cementum ust beneath the junctional epithe-

lium to the alveolar crest. These fibers prevent the extrusion of the tooth and resist lateral tooth

movements.

Ho rizo ntal fibers: extend at right angles to the long axis of the tooth from the cementum to

the alveolar bone.

Ob liq ue fibers: the largest group in the periodontal ligament, they extend from the cementum

in a coronal direction obliquely to the bon e. They bear the brunt of vertical masticatory stresses

and transform them into tension on the alveolar bone.

Apic al fibers : radiate in a rather irregular manner from the cemen tum to the bone at the api-

cal region of the socket. They d o not occur on incompletely formed roots.

Inte rrad icul ar fibers: fan out from the cementum to the tooth in the furcation areas of mul-

tirooted teeth.

Small collagen fibers associated with the larger principal collagen fibers have been found .

l directions, forming a plexus called the indiffe ren t fib er plexus.

po r ta nt: The molecular configuration of collagen f ibers provides them with

a

tensile

the tissues.

arginal gingiva is densely collagenous, containing

a

prominent sys-

fiber bundles called the gingival fibers. They consist of typ e I collagen. The gin-

functions:

1. To brace the m arginal gingiva firmly against the tooth.

2.

To provide the rigidity necessary to withstand the forces o f mastication without being de-

flected away from the tooth su rface.

3.

To unite the free marginal gingiva with the cem entum of the root and the adjacent attached

gingiva.

he gingival fibers are arranged in three groups:

Ging ivode ntal gro up: these fibers are those on the facial, lingual, and interproximal surfaces.

They are embedd ed in the cementum just b eneath the epithelium at the base of the gingival sul-

cus.

C ir cu la r group: these fibers course through the connective tissue of the marginal and inter-

dental gingivae and encircle the tooth in ringlike fashion . They resist rotational forces.

Tra nss ept al grou p: these fibers are located interproximally and form horizontal bundles that

extend between the cementum of app roximating teeth into which they are embed ded. They lie

in the area between the epithelium at the base of the gingival sulcus and the crest of the inter-

dental bone. They are som etimes classified with the principal fibers of the

PDL.

. The a ttachment ap paratus is a term used to describe these gingival fibers and the

epithelial attachment.

2. Some studies have also described two more gingival fiber groups:

(1)

a group of

semicircular fibers and

2)

a group of transgingiv al fibers

3.

Tra ctio nal forces in the extracellular matrix produced by fibroblasts are believed to

be the forces responsible for generating tension in the collagen. This keeps the teeth

tightly bound to each o ther and to the alveolar bone.


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N TOMY OCCLUSION

Thejunctional epitheliumconsistsof a collar likebandof

stratified squamons nunkeratinid epithelium.

he

reducedenamelepithelium

is

not essential for

its

formation.

is true; the first statement is false

1 5

Coppight

012 2013 Dental Decks

NT L

N TOMY

OCCLUSION

Bone consistsof

thirds organic matter and one third inorganicm trix

third organic matter and two thirds inorganic matrix

half organic matter and one half inorganic matrix

thirds inorganic matter and one third organic matrix


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Both statements are true

junctional epithelium consists of a collar-like band of stratified squamous nonkera-

epithelium. It is three to four layers thick in early life but the number of layers in-

with age to 10or even 20 layers.Also the junctional epithelium tapers fiom its coronal

which may be 10 to

29

cells wide to one or two cells at its apical termination located at

CEJ in healthy tissue. These cells can be grouped in two strata; the basal layer facing the

tissue and the suprabasal layer extending to the tooth surface. Note: The length of

junctional epithelium ranges fiom

0 25

to 1 35 rnm average~ .97 mm .

unctional epithelium is formed by the confluence of the oral epithelium and the reduced

epithelium

during tooth eruption. However the reduced enamel epithelium

is not es-

for its formation; in fact the junctional epithelium is completely restored after pocket

or surgery and it forms around an implant.

junctional epithelium is attached to the tooth surface (epithelialattachment)by means of

internal basal lamina. It is attached to the gingival connective tissue by an external basal

The internal basal lamina consists of a lamina densa adjacentto the enamel) and a

lucida to which hemidesmommes are attached. Hemidesmosomes have a decisive

in the firm attachment of the cells to the internal basal lamina on the tooth surface.

order for a new attachment to form after periodontal treatment the followingmust occur:

1

Complete removal of calculus altered cementum diseased junctional epithelium and

pocket epithelium

2. Need undifferentiated mesenchymal cells

The junctional epithelium

in disease

whichis

referre

to

s

a longjunctionalep-

is different fiom the junctional epithelium in health. In disease migration of the

epithelium occurs along with degeneration in the connective tissue under the at-

as the junctional epithelium proliferates along the root surface gets longer) the

portion detaches. Barrier membranes which are often used to treat bony defects help

prevent this long junctional epithelium from forming.

m

T~vo- th irdsnorganic matter and one-third organic matrix

The a lveolar process is the portion of the m axilla and mandible that forms and supports the tooth

sockets alveoli).It forms when the tooth erupts to provide the osseous attachment to the forming

PDL; it disappears gradually after the tooth is lost. The alveolar process consists of the following:

An external plate of cortical bone formed by haversian bone and compacted bone lamellae.

The inner socket wall of thin compact bone called the alveolar bone proper which is seen as

the lamina dura in radiographs. Histologically it contains a series of openings cribrifonn plate)

through which neurovascular bundles link the PDL with the central component of the alveolar

bone the cancellous bone.

Cancellous trabeculae between these two compact layers which act as supporting alveolar

bone. The interdental septum consists of cancellous supporting bone enclosed within a com-

pact border.

In addition the bones of the jaw include the basal bone which is the portion of the jaw located api-

cally but unrelated to the teeth.

Most of the facial and lingual portions of the sockets are formed by compact bone alone; cancel-

lous bone surrounds the lamina dura in apical apicolingual and interradicular areas.

Osteoblasts the cells that produce the organic matrix of bone are differentiated fiom pluripotent

follicle cells. Alveolar bone is formed during fetal growth by intramembranous ossiJicationand con-

sists of a ca lcified matrix with o steocytes enclosed within spaces called lacunae.

Bone consists of two-thirds inorganic matter and one-third organic matrix. The inorganic matrix

is composed principally of the minerals calcium and phosphate along with hydroxyl carbonate cit-

rate and trace amounts of other ions such

as

sodium magnesium and fluoride. The mineral salts

are in the form of hydroxyapatitecrystals and constitute approximately two thirds of the bone

structure.

The

organic

matrix consists mainly of

collagen type

I

(90 ),

with small amounts of noncollage-

nous proteins such as osteocalcin osteonectin bone morphogene tic protein phosphoproteins and

roteo l cans.


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The periodontal space is diminished around teeth that are not in function and in unempted

but it is increased in teeth subjected to hyperfunction.

eriodontal ligament is composed of a co mplex vascular and highly cellular connective tissue

surrounds the tooth root and connects it to the inner wall of the alveolar bone. It is continuous

ctive tissue of the gingiva and com munica tes with the marrow sp aces through vas-

periodontal ligamen t is abund antly supplied with sensory nerve fibers capa ble of transmitting

le, pressure, and pain se nsations by the trigem inal pathways. Nerve b undles pass into the pe-

area and through cha nnels from the alveolar bone that fol-

mately lose their myelin shea ths and end in one o f four types of neu ral termination:

1 Fre e endings, which have a tree-like configuration and carry pain sen sation.

. Ruffini-like mecha noreceptors, located primarily in the apical area.

3. Coiled Meissner's corpuscles, also mechanoreceptors, found mainly in the midroot region.

Spindle-like p res sur e an d vibra tion endings, which are surrounded by a fibrous capsule

and located mainly in the apex.

Orthodo ntic treatment is possible because the PDL continuously responds and changes

as

a

l requireme nts imposed upon it by e xternally applied forces.

and its hard tissue anchorage in terms of resisting occlusal force:

1. An terio r teeth have slight or no contact in the intercuspal position.

2. The occlusal table is less than

60

of the overall faciolingua l width of the tooth.

3. The occlusa l ta ble of the tooth is generally at right angles to the long axis of the tooth.

4.

Crowns of m andib ular molars are inclined about

15-20

toward the lingual. For this reas-

on, the root apices of mandibular molars are positioned more facially and the crow ns are pos-

itioned more lingually.

Con nec tive tissu e cells: fibroblasts, ceme ntoblasts, and osteoblasts. Fibroblasts are the most

common cells, they synthesize collagen and possess the capacity to phagoc ytose old collagen

fibers. Note: Cem entoclasts and osteo clasts are also seen in the cementa1 and osseou s surfaces

of the PDL.

Epith elial r est cells: the epithelial rests of M alassez form a latticework in the periodontal lig-

ament and are co nsidered remnants of Hertwig's root sheath, which disintegrates during root

development. They are distributed close to thc cementum throughout the PDL of most teeth and

are most numero us in the apical and cervical areas.

Defen se cells: include neutrophils, lympho cytes, macrophages, mast cells, and eosinophils.

These cells, as w ell as those asso ciated with neurova scular elements, are siniilar to the cells in

other conn ective tissues.

he fu nctions of the periodontal ligament are categ orized into:

Physical: attachment of the tooth to the bone via principal fibers and the absorption of occlusal

forces.

Form ative: formation of conne ctive tissue compo nents by activities of connective tissue cells

cementoblasts, ?hroblnsts and osteoblasts).

Rem odeling: by activities of conne ctive tissue ce lls that are able to form a s well as resorb ce-

mentum cementoblasts or cementoclasts), the periodontal ligament Cfibroblasts orfibroclasts),

and the alveo lar bone osteoblasts or osteoclasts).

Nu tritive: through blood vessels that maintain the vitality of its various cells.

Sensory: carried by the trigeminal nerve, proprioceptive and tactile sensitivity is imparted

through PDL

sensation of contact between teeth).

Note: The periodontal ligament also contains a large proportion of ground substance, filling the

paces between the fibers and cells.

t

consists of two main components: glycosaminoglycans,

uch as hyaluronic acid and proteoglycans, and glycoproteins, such as fibronectin and laminin.

he PDL may also contain calcified masses called cem enticles, which are adherent to or detached

from the root surfa ces. These deve lop from calcified epithelial rests.


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Dental Anatomy and Occlusion Part 1.pdf

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