Self-Protective Features of the Dentition & Handout #3

• Primary function of the teeth: prepare food for swallowing

• Facilitate digestion

• Teeth have respective form to facilitate their function: incision, holding, tearing, grinding and trituration of the food.

• The shapes of the anterior and posterior teeth are related to to the function they perform.

• Aid in Speech

• Esthetics

Form & Function of the Permanent Dentition:

Each tooth has specific contours that has a functional role, and it is important to reproduce these contours to allow for proper function for mastication, phonetics, and esthetics.

Why is it important to preserve the shape of a tooth?

1. The nature of the biologic tissues themselves.

2. The shapes of the teeth.

3. The way the shapes of the teeth relate to one another.

Important features of teeth that help reserve their existence:

2mm

What is the approximate biological width?

CEJ

Identify the structure in the blue box

Biological width (2mm)

Identify the structure in the red box

Crest of bone

Identify the structure in the yellow box

Free gingival margin (marginal gingiva) - nonkeratinized

Identify the structure in the green box

Attached gingiva - keratinized

Identify the structure in the purple box

Trapezoidal (the long side is towards the occlusal or incisal and the short side of the trapezoid is towards the gingiva)

All crowns in the permanent dentition have a ___________ shape from a buccal or lingual view

B) They promote healthy interdental papillae

What is one function of properly formed proximal contacts?

A) They increase tooth enamel strength.

B) They promote healthy interdental papillae.

C) They reduce tooth sensitivity to hot and cold.

D) They increase the size of the interproximal spaces.

They prevent food from packing between teeth

Why are proximal contact areas important for oral health?

They stabilize the teeth in the arches

What role do proximal contacts play in dental arches?

interproximal contact area

The area of contact between two adjacent teeth where proximal surfaces meet.

interproximal contact area

serve to prevent food from lodging between the teeth

Proximal contact areas

Allows protection of the gingival tissue:

Proximal contact areas

Prevents build up of excessive bacteria, plaque, calculus:

Proximal contact areas

Offers support to adjacent and opposing teeth in the arches

Anterior teeth are more incisal versus posterior teeth are more cervical

How does the proximal contact area differ in anterior versus posterior teeth?

More centered

Slightly more buccal

Anterior teeth have contact areas that are normally ____________ in the faciolingual dimension versus posterior teeth have proximal contacts that are normally located ____________ in the faciolingual dimension.

Interdental papilla

- A triangle is formed on its base by the crestal bone of the alveolar bone and the sides by the interproximal surfaces of the adjacent teeth.

The interproximal space is a triangle space filled with the...

• Food impaction between teeth.

• Potentially increasing the risk of periodontal disease.

• Caries

• Tooth movement

• Halitosis due to retention of food that results from food decomposition

Improper contacts and interproximal spaces may result in:

embrasure

The V-shaped space around the contact area of two adjacent teeth

embrasure

serve as spillways for masticated food

embrasure

Integral part of the self cleansing process for teeth:

Four:

1. Incisal or Occlusal

2. Facial (Labial or Buccal)

3. Lingual

4. Gingival or Cervical (interproximal)

How many embrasures does each contact area have?

facial and lingual HOC

believed to protect and stimulate the gingival tissues during the mastication of food

Gingival/cervical

Identify the embrasure space in blue

Occlusal/incisal

Identify the embrasure space in red

Buccal/labial

Identify the embrasure space in yellow

Lingual/palatal

Identify the embrasure space in pink

The facial embrasure between the First and Second Maxillary Molars (1st molar converges buccally instead of lingually)

Lingual embrasures are larger than the facial embrasures because of lingual convergence of the crown, except for...

These facial embrasures are larger on the mesial and distal sides of the Maxillary First Molar

In the permanent maxillary first molars, where are the facial embrasures larger?

The embrasures are approximately the same size due to the symmetrical nature of this tooth

How do the Permanent Mandibular Central Incisors facial and lingual embrasures compare?

1 - Too closed (can cause food impaction)

2 - Perfect!

3 - Too open (can cause food impaction)

How do these three restorations compare?

Height of contour (Crest of curvature)

Greatest convexity or bulge on the crown of a tooth:

- Protect and stimulate gingival tissues during mastication of food.

- Prevents trauma to the gingiva by moving food away from the gingival collar.

- Prevention of food being forced into the gingival sulcus.

- Subtle enough to prevent food accumulation at the CEJ.

- Aids in the self-cleansing process.

Importance of Proper Contours:

under- stimulation of supporting tissues and will cause food stagnation- can lead to tooth decay

Over-contoured tooth deflects food

from gingiva and results in...

Soft tissue irritation and food impaction

Under-contour of tooth may result in...

adequate stimulation of supporting tissue, preserving healthy gingival tissue

Correct contours of a tooth permits...

Cervical third

The facial and lingual HOC of all permanent anterior teeth is in the...

Cervical third

The Facial HOC for all posterior teeth is in the...

incisal third

mesial contact area for maxillary central incisors:

junction of incisal and middle third

distal contact area for maxillary central incisors:

junction of incisal and middle third

mesial contact area for maxillary lateral incisors:

middle third

distal contact area for maxillary lateral incisors:

junction of incisal and middle third

mesial contact area for maxillary canine:

middle third

distal contact area for maxillary canine:

maxillary lateral incisor &

maxillary canine

the largest incisal embrasure is between:

mandibular lateral incisor &

mandibular canine

the second largest incisal embrasure is between:

maxillary central incisor &

maxillary lateral incisor

the third largest incisal embrasure is between:

mandibular central incisors

the smallest incisal embrasure is between:

mandibular central incisor &

mandibular lateral incisor

the second smallest incisal embrasure is between:

maxillary central incisors

the third smallest incisal embrasure is between:

Maxillary canine & maxillary premolar

Largest occlusal embrasure between

middle third

From an incisive view, the facio-lingual locations of interproximal contacts for all anterior teeth are in the _______ of the crown

mesial surface of maxillary and mandibular 1st molars

the occluso-gingival location of interproximal contacts for all posterior teeth are located in the middle third of the crown EXCEPT:

junction of middle and occlusal third

location of mesial interproximal contacts for maxillary and mandibular 1st molars is located :

lingual

generally, which embrasures are larger: lingual or facial?

mesial and distal embrasures of maxillary first molars &

mandibular central incisors and the mesial of the mandibular lateral incisors

lingual embrasures are larger than facial embrasures for all teeth EXCEPT:

mandibular central incisors &

mesial of the mandibular lateral incisors

which teeth have a lingual and facial embrasures that are approximately equal in size.

cervical third

The buccal HOC for maxillary posterior teeth is in the...

Middle third

The lingual HOC for maxillary posterior teeth is in the...

Cervical third

Buccal HOC for mandibular posterior teeth

Middle third

Lingual HOC for mandibular posterior teeth except for mandibular 1st premolar and mandibular 2nd premolar

Middle third but approaches occlusal third

Lingual HOC for mandibular 1st premolar

Occlusal third

Lingual HOC for mandibular 2nd premolar

Mandibular Anterior teeth, which can be as little as 0.5mm

Teeth with the least degree of Facial/Lingual HOC

Mandibular molars, which can be as great as 1mm

Teeth with the greatest degree of facial/lingual HOC

Contact areas

The mesial and distal HOC are normally located at the...

A little more facially

Mesial surfaces of First Molars have their Facio-lingual contacts located

Junction of middle and occlusal thirds of crowns

Mesial surface of First molars have their occlusal gingival contacted located at the

True

T/F: Mesial and Distal embrasures of Permanent Maxillary First possess larger Facial/Buccal embrasures, due to the unique morphology of this tooth

True

T/F: The Permanent Mandibular Centrals and the Mesial of the Mandibular Lateral Incisors possess Facial and Lingual embrasures that are approximately the same size or are equal in size

True, except for Maxillary first molars and Mandibular Central/Lateral Inscisors

T/F: generally, lingual embrasures are larger than facial embrasures for all teeth

middle third

generally, the lingual heights of contour of maxillary and mandibular posterior teeth are in the ______ of the crowns, but there are exceptions.

mandibular second premolar

what tooth's lingual height of contour is in the occlusal third of the crown (this is the only posterior tooth with this characteristic)

mandibular molars

The teeth with the greatest degree of facial/buccal or lingual heights of contour are the:

mandibular anterior teeth

The teeth with the least degree of facial/buccal or lingual height of contour are the:

mesial surface of maxillary 1st premolar (deep) and distal surface of maxillary 1st molar which have concavities

Mesial and distal contours of the crowns of all permanent teeth are either flat or convex, except for what two teeth that have concavities?

Their contours are concave

What is unique about the mesial surface of maxillary 1st premolar and distal surface of maxillary 1st molar?

greater

The more anterior the tooth, the ______ is the curve of the cervical line.

less

The more posterior the tooth, the ________ the curve of the cervical line.

greater

Generally, the mesial surface of a tooth has a ________ curvature than the distal

greater

The curvature of the cervical line for any tooth type (e.g., Central Incisors) is _______ on the Maxillary tooth when compared to the same surface of the same tooth type of the Mandibular arch

trapezoidal

All permanent tooth crowns, when viewed from the facial or lingual, are_________ in shape

wedge (or triangular)

All permanent anterior crowns, when viewed from the interproximal, are ______ in shape

trapezoidal

All maxillary posterior permanent tooth crowns, when viewed interproximally, are _______ in shape

rhomboidal

All Mandibular Posterior Permanent tooth crowns, when viewed from the interproximal, are ________ in shape

triangular

from an incisal view, maxillary and mandibular anterior teeth are ______ in shape

hexagonal

from an occlusal view, maxillary premolars are ______ in shape

rhomboidal

from an occlusal view, maxillary molars are ______ in shape

diamond

from an occlusal view, mandibular 1st premolars are ______ in shape

round (2-cusp type) or square (3-cusp type)

from an occlusal view, mandibular 2nd premolars are ______ in shape

hexagonal

from an occlusal view, mandibular 1st molars are ______ in shape

rectangular

from an occlusal view, mandibular 2nd molars are ______ in shape

Anterior teeth

Do anterior or posterior teeth have a greater CEJ curvature?

Maxillary

Do mandibular or maxillary teeth have a greater CEJ curvature?

Permanent

Do permanent or primary teeth have a greater CEJ curvature?

Mesial

Generally, does the mesial side of a tooth or distal side have a greater CEJ curvature?