Tooth Microstructure and Dental Pulp Morphology Part I

Question 1

• Enamel - the highly mineralized tissue covering the anatomical crown of a tooth. It is the ____ tissue in the body.
• Inorganic salts ___%
• Organic matter _%
• Water ___%

Answer 1

• Enamel - the highly mineralized tissue covering the anatomical crown of a tooth. It is the hardest tissue in the body.
• Inorganic salts 95-97%
• Organic matter 1%
• Water 2-4%

Question 2

Enamel – Chemistry

•Inorganic matrix is composed of ;

–___

___

–__ ___

–___ ___

–___ ___

The calcium and phosphate join to form ___ ____ which makes up the majority of the matrix. Note: this means that calcium and phosphate make up the greatest percentage of the inorganic matrix.

Answer 2

•Inorganic matrix is composed of ;

–Calcium

–Phosphate

–Calcium Carbonate

–Magnesium Phosphate

–Calcium Fluoride

The calcium and phosphate join to form Calcium Hydroxyapatite which makes up the majority of the matrix. Note: this means that calcium and phosphate make up the greatest percentage of the inorganic matrix.

Question 3

Enamel – Formation

• Formation begins with the ____ secreting the ____ proteins in the embryonic tooth buds.
• Amelogenins form ____

–These 18-20 nanometer structures regulate the formation and organization of tooth enamel by controlling the crystalline growth

–Amelogenins also ___ ___ to form the ___ __ ____ within which the crystals of mineralization start to form

Answer 3

• Formation begins with the ameloblasts secreting the amelogenin proteins in the embryonic tooth buds.
• Amelogenins form Nanospheres

–These 18-20 nanometer structures regulate the formation and organization of tooth enamel by controlling the crystalline growth

–Amelogenins also self assemble to form the extra-cellular matrix within which the crystals of mineralization start to form

Question 4

Enamel – Formation

–The crystals are __ ____arranged at ___ angles to the ____ of the tooth

Answer 4

–The crystals are hexagonal prisms arranged at right angles to the surface of the tooth

Question 5

Enamel

• The hardness of enamel has been compared to that of a good ___ __ ___
• The hardness of enamel helps the tooth ___ ____
• Enamel’s hardness also makes it ____ resistant to decay than dentin or cementum.
• Compared to ___ and ___ ___ enamel ranks ___ on the hardness scale. When soft, one knows that enamel (or dentin) is ___

Answer 5

• The hardness of enamel has been compared to that of a good stainless steel alloy.
• The hardness of enamel helps the tooth resist wear.
• Enamel’s hardness also makes it more resistant to decay than dentin or cementum.
• Compared to diamond and tungsten carbide, enamel ranks eighth on the hardness scale. When soft, one knows that enamel (or dentin) is diseased.

Question 6

Enamel - Solubility

• The presence of ___ and___ are known to affect the solubility.
• ___, ___, and ____ decrease solubility.
• ____, such as lemon juice and vinegar, ___ the solubility. Note - many soft drinks are acidic. Years ago, auto mechanics used Coca Cola to clean deposits off the car battery posts and clamps.
• Nature tries to saturate the saliva with ___, ___ and ___e ions to help protect the teeth.

Answer 6

• The presence of alkalis and acids are known to affect the solubility.
• Sodium, calcium, and phosphates decrease solubility.
• Acids, such as lemon juice and vinegar, increase the solubility. Note - many soft drinks are acidic. Years ago, auto mechanics used Coca Cola to clean deposits off the car battery posts and clamps.
• Nature tries to saturate the saliva with sodium, calcium, and phosphate ions to help protect the teeth.

Question 7

Enamel

• As a general rule, enamel___ ___ repair itself.
• However, incipient caries of enamel can______ if the surface is not cavitated.
• The use of _____ varnishes, rinses, toothpastes and gels can be helpful if the patient has areas of enamel that are partially de-mineralized.
• Flouride ions enhance the precipitation o___ and ___e ions from the___ and make the re-mineralized enamel___ resistant to decay, i.e. ____ e as opposed to hydroxyapatite

Answer 7

• As a general rule, enamel does not repair itself.
• However, incipient caries of enamel can re-mineralize if the surface is not cavitated.
• The use of fluoride varnishes, rinses, toothpastes and gels can be helpful if the patient has areas of enamel that are partially de-mineralized.
• Flouride ions enhance the precipitation of calcium and phosphate ions from the saliva and make the re-mineralized enamel more resistant to decay, i.e. fluorapatite as opposed to hydroxyapatite

Question 8

Enamel - Arrested Lesions

• Arrested lesions can be observed clinically as ___t, but ____ spots.
• These spots are usually___ or ____. The change in color is believed due to trapped, ____ debris and/or ___ ions within the enamel.
• These arrested lesions are _____d and are ____ to subsequent caries.
• Arrested lesions occur mainly in ___ and ____. They may be restored for esthetic reasons.

Question 9

Enamel

• Tensile strength - causes enamel to be___ and require ____ support.
• Restorative preparations must be extended to areas of dentinal support. This means leaving little____ ____ .
• Reduced salivary flow may lead to tooth____ problems due to lack of natural cleansing and lack of available calcium and phosphate ions for ____

Answer 9

• Tensile strength - causes enamel to be brittle and require dentinal support.
• Restorative preparations must be extended to areas of dentinal support. This means leaving little unsupported enamel.
• Reduced salivary flow may lead to tooth decay problems due to lack of natural cleansing and lack of available calcium and phosphate ions for re-mineralization.

Question 10

Enamel

• Enamel is generally a ___ ___e, but at times appears yellowish due to the reflection of the color of the underlying ____
• The smooth enamel surface is very helpful in the ___ of ___. This smoothness makes enamel somewhat ___ ___ and helps prevent food from ___ to its surface.

Answer 10

• Enamel is generally a translucent white, but at times appears yellowish due to the reflection of the color of the underlying dentin.
• The smooth enamel surface is very helpful in the flow of food. This smoothness makes enamel somewhat self-cleansing and helps prevent food from sticking to its surface.

Question 11

Enamel -Translucency

• Translucency - the ability of ___ to)___ ____ an object.
• The reproduction of the “enamel” can be very important when making esthetic restorations.
• Dentists sometimes wait to take the__ ___ for a crown until___ the preparation is finished.

Answer 11

• Translucency - the ability of light to pass through an object.
• The reproduction of the “enamel” can be very important when making esthetic restorations.
• Dentists sometimes wait to take the dentin shade for a crown until after the preparation is finished.

Question 12

Enamel

•The enamel is thickest on the___ and ___ surfaces of the permanent teeth.

Answer 12

•The enamel is thickest on the incisal and occlusal surfaces of the permanent teeth.

Question 13

Dentin - Physical Properties

•Dentin is significantly ___ than enamel, but it is harder than ___ or ___.

Dentin becomes ___ with increasing age.

• The hardness of dentin averages about __ ___that of enamel.
• Inorganic salts ___%
• Organic matter ___%
• Water __%

Answer 13

• Dentin is significantly softer than enamel, but it is harder than cementum or bone. Dentin becomes harder with increasing age.
• The hardness of dentin averages about one fifth that of enamel.
• Inorganic salts 65-75%
• Organic matter 20-30%
• Water 5%

Question 14

Dentin

• Dentin - the hard tissue which forms the ___ __ of the tooth. It surrounds the ___ ___.
• It is covered by the enamel in the ___ crown and by cementum in th -___ root.
• Dentin ___ repair itself.

Answer 14

• Dentin - the hard tissue which forms the main body of the tooth. It surrounds the pulp cavity.
• It is covered by the enamel in the anatomical crown and by cementum in the anatomical root.
• Dentin may repair itself.

Question 15

Functions of Dentin

• Supports the ____ - loss of underlying dentin requires special consideration in preparation design.
• Poor t___ ____y - reduces trauma from normal thermal stimuli. Dentin provides a fairly thick wall of____n around the pulp.
• Note - excessive heat from dental procedures has killed many teeth.
• Transmits -__ ____ n - the fibers within the__ ___s are responsible for the conduction of stimuli.

Answer 15

• Supports the enamel - loss of underlying dentin requires special consideration in preparation design.
• Poor thermal conductivity - reduces trauma from normal thermal stimuli. Dentin provides a fairly thick wall of insulation around the pulp.
• Note - excessive heat from dental procedures has killed many teeth.
• Transmits sensory information - the fibers within the dentinal tubules are responsible for the conduction of stimuli.

Question 16

Thermal Conductivity

• All materials conduct heat and cold.
• Ideally, a material of very ___ thermal conductivity would be highly desirable.
• This would ____ the pulpal cells from too much heat or cold.
• On a large or deep preparations, the dentist should place a _____ to help protect the patient from sensitivity to heat and cold.

Answer 16

• All materials conduct heat and cold.
• Ideally, a material of very low thermal conductivity would be highly desirable.
• This would protect the pulpal cells from too much heat or cold.
• On a large or deep preparations, the dentist should place a base/liner to help protect the patient from sensitivity to heat and cold.

Question 17

Dentin - Clinical Significance

• Caries - dentin is ___ densely calcified than enamel and is ___ susceptible to the carious process than ___ or ___
• Inflammation of the pulp involves swelling , which cannot occur within the rigid dentinal ___. As a result, __ ___s may occur.

___ ___ - permits the placement and retention of restorations in the teeth. Restorations that are placed in __ ___ may not be retained (unless bonded).

Answer 17

• Caries - dentin is less densely calcified than enamel and is more susceptible to the carious process than enamel or cementum.
• Inflammation of the pulp involves swelling , which cannot occur within the rigid dentinal walls. As a result, pressure necrosis may occur.
• Plastic adaptability - permits the placement and retention of restorations in the teeth. Restorations that are placed in enamel only may not be retained (unless bonded).

Question 18

Thermal Expansion & Contraction

• All materials expand and contract with changes in the temperature.
• The measurement of this property is known as the ___ of ___ ___
• A dental material that expands too much will cause
• A dental material that does not expand enough will

Answer 18

• All materials expand and contract with changes in the temperature.
• The measurement of this property is known as the coefficient of thermal expansion.
• A dental material that expands too much will cause teeth to crack.
• A dental material that does not expand enough will leave a space between the filling and tooth structure.

Question 19

Physical Properties - Cementum

• Cementum - the layer of___, ___e tissue which covers the anatomical root of a tooth.
• Inorganic salts __
• Organic matter ++
• Water __
• The cementum is joined to the __ by the ____

•

Answer 19

• Cementum - the layer of hard, bonelike tissue which covers the anatomical root of a tooth.
• Inorganic salts 55%
• Organic matter 30-35%
• Water 15%
• The cementum is joined to the bone by the periodontal ligament.

•

Question 20

Cementum

•Cementum provides a ___ ___to the dentin of the anatomical root.

Answer 20

•Cementum provides a protective covering to the dentin of the anatomical root.

Question 21

Cementum

• Cementum has a ____h color.
• The layer of cementum on the root is relatively ___. The cementum is very thin next to the ___ ___ (about the thickness of a page of paper or 50-100 micrometers thick).
• Cementum is ___ than both enamel and dentin.

Answer 21

• Cementum has a yellowish color.
• The layer of cementum on the root is relatively thin. The cementum is very thin next to the cervical line (about the thickness of a page of paper or 50-100 micrometers thick).
• Cementum is softer than both enamel and dentin.

Question 22

Cervical Line

• A - the cementum overlaps the enamel in ___% of the cases.
• B - in _0% of the cases, the cementum meets the enamel at a ____ junction.
• C - in the remaining _0% of the cases, the enamel and cementum do not meet, leaving the dentin ___ at the cervical line.

Answer 22

• A - the cementum overlaps the enamel in 60% of the cases.
• B - in 30% of the cases, the cementum meets the enamel at a sharp junction.
• C - in the remaining 10% of the cases, the enamel and cementum do not meet, leaving the dentin exposed at the cervical line.

Question 23

Pulp Tissue

•The __ ___ __ found in the central portion of the tooth entirely surrounded by ___

Answer 23

•The soft connective tissue found in the central portion of the tooth entirely surrounded by dentin.

Question 24

Pulp

• Pulp - the ___ soft tissue that occupies the pulp cavity. The pulp cavity is surrounded by dentin.
• It contains the tooth’s ___t supply in the form of __ ___, as well as the ___ supply.
• The pulp transmits ___ ___
• The walls of the pulp cavity are lined with ___ which are responsible for ___ formation.

Answer 24

• Pulp - the living soft tissue that occupies the pulp cavity. The pulp cavity is surrounded by dentin.
• It contains the tooth’s nutrient supply in the form of blood vessels, as well as the nerve supply.
• The pulp transmits sensory stimuli.
• The walls of the pulp cavity are lined with odontoblasts, which are responsible for dentin formation.

Question 25

Pulp

• The pulp can be removed by ____ procedures.
• The pulp is subject to___ (pain, abscess, death). The inflammation may be ___ or ____

Answer 25

• The pulp can be removed by endodontic procedures.
• The pulp is subject to inflammation (pain, abscess, death). The inflammation may be reversible or irreversible.

Question 26

Pulp

•On badly broken down teeth, ___ or ___ ____ may be seated in a ___ ___ (after root canal therapy) to help __ __p the tooth to normal ___

•

Answer 26

•On badly broken down teeth, cast or prefabricated posts may be seated in a pulp canal (after root canal therapy) to help build up the tooth to normal contours.

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