DH119-2NDEXAM-2NDPPT

Enamel is

hard, calcified tissue that covers dentin of crown

enamel can only be removed by a

rotary instrument except decay/trauma reasons

enamel has NO nerves termed?

avascular

enamel can undergo mineralization changes which means that its

NOT static

enamel is the

hardest tissue in the body

the enamel composition crystalline structure is (IMPORTANT)

96% inorganic material (calcium hydroxyapatite)

1% organic material (protein)

2-3% water

enamel provides a hard surface for

speech mastication

enamel provides the "whiteness" for our smile, however underlying dentin isn't white so it turns the enamel into what color?

yellowish white color

primary teeth are referred as milk teeth because the cyrstalline form more

opaque, teeth look whiter

During the apposition of enamel, Amelogenesis is the process of

enamel matrix formation (important) only in the crown portion of the tooth

During the apposition of enamel, Ameloblasts are cells that produce the

enamel matrix only in the crown portion of the tooth

Each ameloblast has a

Tome's process which is located on the surface of the ameloblast

Tome's process secretes the

enamel matrix and faces the DEJ

Tomes process is responsible for the way the enamel matrix is

laid down ( important)

•As Tome's secrete the matrix, the ameloblasts pump

calcium hydroxyapatite into the enamel matrix

In the tomes process, which portion of the future crown is laid down first?

•Incisal/occlusal

In the tomes process, each layer is formed and

overlaps the previous layer (important)

The tomes process moves from the

incisal edge to the CEJ area until crown is covered

enamel mineralization involves 2 stages:

mineralzation and maturation stage

in the mineralization stage, there are

enamel rod calcifications and its also called the Apposition stage

Maturation stage is the

2nd stage of calcifiation where crystals grow until tightly packed together

in the enamel maturation stage, ameloblasts pump

calcium hydroxyapatite into the partially mineralized enamel matrix

In the enamel maturation stage, the ameloblast is responsible for the

maturation of enamel into matrix (IMPORTANT)

After these 2 stages, theres disintegration during tooth eruption and all the ameloblasts are

lost forever

Post eruption maturation is due to minerals of

floride and calicium from saliva

components of mature enamel include

rod sheath, enamel rods, DEJ, imbrication lines, perikymata, and lines of retzius (aka Straie of Retzius)

Imbrication lines is a

line or ridge on surface of tooth

Perikymata is a

groove

Straie of retzius are

incremental growth lines of mineralization

The rod sheath outlines the rod that contains most of the

fibrous organic substance that has rods stacked in rows

in the rod sheath, the head to tail is

interlocking and the tail is between 2 heads

enamel rods are

crystalline unit of enamel and extend from from the DEJ to outer enamel

Longer rods are located on the

incisal/occlusal where enamel is thickest while shorter rods are in the CEJ

the shape of the enamel rod is determined by the

tomes process of ameloblast

rod shape is

cylindrical and have a fish scale shape, head, and tail

rods are how many micrometers in diameter (IMPORTANT)

4

how many ameloblasts are needed to form 1 rod?

4 (important)

the head portion has how many ameloblast

1 (important)

the tail portion has how many ameloblast?

3 (important)

the dentinoenamel junction (DEJ) is a ridge between 2 tissues of dentin and enamel and adds

strength during mastication

Straie of retzius are the incremental lines of enamel rods that curve

outwardly/occlusally from the DEJ

on the 4th day during the 2nd stage of maturation in the striae of retzius, there is a change in the (IMPORTANT)

rod and a brownish line develops in the enamel

the imbrication line and perikymata are found on

non-masticatory surfaces of SOME teeth, they represent work/rest pattern of ameloblasts, and can indicate metabolic activity or nutritional deficieny

what is attrition?

wearing away of tooth from tooth to tooth contact

what is abfraction?

pressure from grinding causing tooth flexure which flakes teeth of enamel at the neck of the tooth on the buccal side near the gingiva marjin where enamel is the weakest

abrasion is?

using hard toothbrush or abrasive toothpaste

erosion is?

enamel wore off due to chemicals (gerd, energy drinks, bulimia)

clinical considerations with enamel structure are

pit and fissures

•During apposition/maturation stage, ameloblasts "back into each other" and cut off each others

nutrition causing incomplete maturation of the enamel matrix, making the tooth weak in that area

Bacterial plaque produces

acids that demineralize the weak area of the tooth creating DECAY!

the 1st clinical indicator is a

white spot lesion where enamel appears whiter and rougher from demineralization. this STAGE IS WHERE ENAMEL IS AFFECTED.

does decay in enamel hurt?

no because enamel has NO nerves which means theres no pain, however pain will happen if dentin and pulp involved

fluoride affects teeth in 2 different ways:

systemically (preeruptive) and topically (posteruptive) (IMPORTANT)

in the systemically-preeruptive, fluoride enters enamel thru

blood supply of developing tooth and enters thru crystalline formation of enamel matrix

systemically preeruptive fluoride produces

calcium hydroxyapatite (IMPORTANT) which prevents demineralization

ex. fluoride tablets

in the topically post eruptive, fluoride contacts tooth

directly and increases minerals in demineralized area

ex. fluoride gel

fluoride produces more

caries-resistant teeth w/fewer shallow grooves/pits

excess fluoride causes

enamel dysplasia/fluorosis and occurs systemically during tooth development with intrinsic staining

causes of fluorosis can be from

Geography: water contains too much fluoride

Mishandling of fluoride prescriptions

Excess of sweetened fluroide toothpaste swallowed habitually

dentin forms the

BULK of the tooth, yellowish in color, and is less mineralized and softer than enamel

Dentin is (IMPORTANT)

70% inorganic hydroxyapatite crystal

30% organic (collagen, water, and mucopolysaccharide ground substance)

dentin is more radiolucent than enamel and more radiopaque than pulp thats covered by enamel and covered by

cementum in the root of tooth

dentin is in 3 distinct areas

dentinal tubule, peritubular dentin, and inter-tubular dentin

dentinal tubule is a

long tube, running from the DEJ (or DEC-dentincemental junction) to pulp containing an ODONTOBLASTIC PROCESS

PERITUBULAR DENTIN has higher

crystalline content surrounding dentinal tubules

inter-tubular dentin is the

bulk of the dentinal material

CLINICALLY, dentin appears

solid

initally, formation occurs during

apposition/maturation stage of tooth development

in dentinogeneis, odontoblasts lay down

4 MICROMETERS OF DENTIN DAILY

(IMPORTANT)

apposition/maturation of dentin occurs thruout life of tooth unlike

enamel

Odontoblasts don't disappear after initial dentin formation, but

ameloblasts do

Odontoblasts live along the

outer pulpal wall at the junction of the dentin and pulp

components of mature dentin are

dental tubules and imbrication lines of Von Ebner

dental tubules are long tubes in the dentin that extend from

DEJ or DCJ to the outer wall of pulp and is AVASCULAR

in the dental tubules, nutrition comes from blood vessels located in the

pulp tissue

the dental tubules provide

communication from pulp to dentin

Imbrication lines of Von Ebner are similar to growth rings and represent

dentin apposition/maturation in increments

the Imbrication Lines of Von Ebner involves the formation of dentin that's

deposited causing hesitation in activity

Imbrication Lines of Von Ebner is the period where

odontoblasts work/rest

there are 3 types of dentin

primary, secondary, tertiary

primary dentin is when

all dentin formed PRIOR/BEFORE to root/apical foramen completion

secondary dentin is when all dentin

produced AFTER root/apical foramen completion thats NOT due to any trauma and continues thurout life

tertiary dentin is all

REPARATIVE dentin which can be regular or irregular (protective feature)

Types of dentin is categorized by WHEN

dentin is formed (National board)

primary dentin is formed until tooth has reached

occlusion and is functional-erupts into oral cavity

AND

makes up BULK of tooth

secondary dentin forms more slowly than

primary dentin and is PRODUCED by odontoblastic layer that lines junction of dentin and pulp

in secondary dentin, as tooth comes into occlusion, it signals the dentin to

slow down

tertiary dentin forms quickly in localized areas and responds to localized injuries in the

Occlusal (force)

Mechanical (cavity prep)

Chemical(acid)

tertiary dentin ia formed

underneath to protect pulp

tubules act as a

entryway for cariogenic microrganisms for decay to move quickly from enamel to dentin

when dentin is exposed, the open end of the tubules becomes painful due to dentinal hypersensitivity causing

decay, recession, attrition, aggressive hand scaling

enamel and cementum don't meet at the CEJ

10% of the time (IMPORTANT)

dentinal hypersensitivity can come from

thermal changes (cold water/cold-hot drinks)

mechanical irritation (handpiece vibrations)

chemical exposure (sweet/salty/sour foods0

dentinal hypersensitivity can be relieved with

OTC/RX toothpaste

sensodyne

sealants

pulp is the

innermost tissue of tooth inside dentin and occurs during ODONTOGENESIS when dentin is formed

types of pulp are

1. coronal (located in crown and resembles shape of crown)

2. radicular

pulp horns are

extension of pulp tissue into thin point of pulp chamber in tooth crown

pulp horns are also

protrusions of pulp that extend into cusps of teeth AND diminishes with age

number of pulp horns equal to number of

cusps tooth has

Secondary dentin lays down

dentin DAILY (odontoblast cells in pulpal wall form more dentin)