Orofacial Anatomy Ch 5

Tooth germs

Tiny tooth buds that begin to form before birth around the 6th week of fetal life

Crypts

Cavities within the alveolar process

Primary dentin

The type of dentin formed at an early age; forms before root completion

Secondary dentin

Dentin that is continually formed within the tooth throughout one's entire lifetime; secondary dentin is laid down as protection for the pulp from irritation caries or trauma

Odontoblasts

Form dentin

6th week of embryonic life

Earliest evidence of tooth formation; dental lamina begins to form

Calcification

The hardening of the tooth tissues by the deposition of mineral salts within these tissues

Last area of the tooth to become calcified?

Apex of the root

Developmental lobes

Growth centers from which teeth develop; each tooth begins to develop from four or more developmental lobes

Coalescence

The fusion of developmental lobes

How many lobes do all anterior teeth form from?

FOUR (4; 3 labial and one lingual)

Mamelons

The incisal ridges of three labial developmental lobes

How many lobes do maxillary premolars have?

FOUR; 3 facial and one lingual; the three facial lobes of maxillary premolars form one high buccal cusp instead of an incisal ridge and the single lingual cusp forms a large lingual ridge rather than a cingulum

How many lobes do mandibular first premolars have?

FOUR; 3 facial and 1 lingual same as the maxillary premolars. The arrangement is also the same. The lingual cusp of the mandibular first premolars is smaller than its maxillary counterpart

The mandibular second premolars have how many cusps?

It varies; some have two and some have three cusps; this is why the term premolars is preferred over the term bicuspid

Molars have how many lobes?

Four; two facial and two lingual lobes; Except the first molars usually have a fifth minor (smaller) lobe located at the distolingual cusp. maxillary first molars also have a rudimentary lobe or small cusp like elevation called the cusp of Carabelli located on the mesiolingual surface

Where is the cusp of Carabelli located?

On the maxillary first molars on the lingual of the mesiolingual cusp

Do maxillary second molars have a cusp of Carabelli?

No, not usually

Are first or second molars proportionately bigger?

First molars

Which cusp of first and second molars is generally the smallest in proportion?

The distolingual cusp

T/F the minor cusp becomes smaller as the location becomes more posterior?

True

Which teeth are the most unpredictable of all the teeth?

The third molars; they can be well or poorly developed, can have from three to eight cusps; they are likely to deviate in form or be completely missing

When have all deciduous teeth began to develop?

By the end of the sixth fetal month

Which part of the tooth calcifys first

The crown

What are the general rules regarding eruption?

The individual mandibular teeth usually precede the maxillary teeth; Teeth in both jaws erupt in pairs; permanent teeth (not deciduous) usually erupt slightly earlier in girls than boys.

Which teeth are usually first to appear in the mouth?

Deciduous mandibular central incisors; 6.5 to 7 months of age; the maxillary central incisors usually erupt about 1 month later

At what age have all deciduous teeth usually erupted?

2.5 years

Which teeth in the permanent dentition are usually first to erupt?

The mandibular first molars followed by the maxillary first molars within a few weeks; they are usually called the 6 year molars because they erupt at around the age of 6; first molars erupt around 6-7 years

Mesial drift

The tendency of the permanent molars to have an eruptive force toward the midline; this force causes the spaces between deciduous teeth to close up. if a tooth is lost prematurely it will cause the permanent first molar to be placed in the wrong position

When do the permanent central incisors erupt?

Mandibular permanent central incisors - 6-7years

Maxillary permanent central incisors - 7-8 years

Exfoliation

The process by which the roots of a baby tooth are resorbed and dissolved until so little root remains that the baby tooth falls out

Resorption

The removal of tissues or body products such as the destrution of the roots of deciduous teeth by osteoclastic cells or the destruction of the alveolar process after the loss of the permanent teeth

Osteoclasts

Bone destroying cells

When do the lateral incisors erupt?

7-9 years of age;

Mandibular 7-8 years of age

Maxillary 8-9 years of age

When do the canines erupt?

Mandibular canines erupt at 9-10 years of age; the maxillary canines do not erupt at this time. Maxillary canines erupt 11-12 years

When do the first premolars erupt?

Maxillary 10-11 years

Mandibular 10-12

When do the second premolars erupt?

10-12 years of age; the eruption of the maxillary premolars often precede the eruption of the mandibular. This is the most common exceptional the rule ofmandibularteeth preceeding the maxillary;

Maxillary 10-12

Mandibular 11-12

When do the second molars emerge?

"12 year molars"; 12-13 years of age

When do third molars emerge?

Around age 17-22 years

Which teeth are most likely to be impacted?

Third molars (mandibular most likely; maxillary second most likely)

Impacted

Teeth that do not completely erupt but remain embedded in bone or soft tissue.

What are the most common teeth to be congenitally missing?

The maxillary and mandibular third molars are most likely to be congenitally missing followed by the maxillary lateral incisors

Congenitally missing tooth

A tooth that never formed because a tooth bud was never produced; this can be a hereditary trait.

Attrition

The wearing away of the tooth through contact of its functioning surfaces

Occlusal plane

Side view of the occlusal (biting) surfaces of teeth; The curved line along the area where teeth meet teeth in the opposing arch

The first primary tooth erupts when?

About 6-7 months after birth

T/F when the first permanent molar erupts, the period of primary dentition ends.

True

Mixed dentition

The period when both primary and permanent teeth are present simultaneously. This period begins at about 6 years of age when the first permanent molar erupts and ends when the last deciduous tooth is exfoliated and only permanent teeth remain

Permanent dentition

Begins when the last primary tooth is lost and ends when the last permanent tooth is lost; usually begins at about the age of 12 and is hope to never end.

Endentulous

No teeth

Which hard tissue of the tooth forms last?

Cementum

What does the term coalescence mean?

The joining of two lobes of a tooth

What do developmental grooves or lines separate

Developmental lobes of a tooth

From what lobe does the cingulum of anterior teeth form?

lingual lobe

What is a rudimentary lobe of the maxillary first molar called?

Cusp of Carabelli or Lobe of Carabelli

Which teeth erupt first, the deciduous first molars or the canines?

deciduous first molars

Which of the following statements are usually true about eruption:

a. girls' teeth erupt earlier than boys' teeth

b. Maxillary teeth erupt before their mandibular counterparts

c. Teeth in both jaws do not erupt in pairs

d. The erosion sequence varies little from person to person

a. girls' teeth erupt earlier than boys' teeth

Name the first permanent teeth to erupt in the oral cavity.

Permanent MANDIBULAR first molars (6 year molars). The central incisors sometimes erupt before the first molars but more often do not.

Of the following, which is the only acceptable dental term?

a. bicuspid

b. premolar

c. milk teeth

d. baby teeth

b. premolar

Explain all of the various problems associated with premature loss of a deciduous molar

If a deciduous molar is lost, especially a second molar, the permanent first molar will move mesially into the space once occupied by the deciduous tooth. Thus less space is left for the eruption of the permanent second premolar. The second premolar could then erupt out of alignment or be blocked out entirely.

With which teeth does the phenomenon of mesial drift occur and what does it do?

All permanent molars; the molars tend to be pushed in a mesial direction (toward the midline) closing up gaps in between

Which teeth are the most likely to be congenitally missing?

Mandibular and maxillary third molars; second most likely are maxillary lateral incisors

Name the structures now worn off that used to be present on the incisal ridge of fig. 5-9

mammelons

How many lobes are present in the mandibular premolar in figure Fig. 5-10? (Hint: it has three cusps.)

5 lobes

What are the periods of dentition for a 12 year old boy? Give two possible reasons for each period of dentition.

Mixed dentition with the deciduous mandibular second molars and/or maxillary canines still present; or permanent dentition with all the deciduous teeth replaced by their succedaneous replacements and first molars and possibly second molars present.

When does the period of primary dentition end?

When the first permanent tooth erupts in the oral cavity; this usually is a first permanent molar or sometimes a central incisor

What deciduous teeth might an 11 year old still have?

deciduous mandibular canines and fist and second molars; deciduous maxillary canines and first and second molars

An orthodontist asks you to refer a patient back when the patient is out of mixed dentition. When would you send the patient to the orthodontist? What marks the end of the period of mixed dentition?

When the last primary/deciduous tooth has been lost and only permanent teeth remain in the oral cavity.

A new drug has been developed. It is a good drug with a bad side effect. This side effect is that this drug can discolor teeth if taken during the period of tooth development.

a. What age of patient should therefore avoid this drug to protect permanent dentition?

b. If this drug passes the placental barrier and affects the unborn fetus, then at what ages and what period of fetal development should it be avoided.

a. from birth to 16 years

b. from the third or fourth month of fetal life to birth (Tetracycline is such a drug and its package insert states such a warning precaution.)

T/F Only primary teeth begin to develop in utero (during fetal life)

False

If a child has spaces between the deciduous teeth at 5 years of age, these spaces will always remain, even after the permanent teeth have erupted.

False

Permanent teeth show no evidence of development until the sixth month after birth.

False

Deciduous teeth begin to calcify as early as the fourth month of fetal life.

True

Deciduous teeth become fully formed somewhere around 3.5 years after birth.

True

Permanent teeth contiune to calcify until age 21 to 25.

True

The dentin that begins to form in the alveolar crypt is primary dentition.

True

The cingulum eventually develops into a lingual cusp on posterior teeth.

False; there is no cingulum on posterior teeth

Lobes are centers of formation that develop into teeth.

True

Premolars are considered to be bicuspids because they all have two cusps.

False; a mandibular second premolar can have three cusps therefore it is not a bicuspid.

Third molars show great variation in in size and shape.

True

Permanent teeth begin to calcify at birth.

True

Maxillary first molars erupt before mandibular first molars.

False; mandibular teeth usually erupt first

Permanent mandibular first molars erupt before permanent central incisors.

True

Permanent maxillary canines erupt before maxillary first premolars.

False; maxillary canines erupt about one year after the maxillary premolar erupts.

Teeth erupt in right and left pairs.

True

The permanent maxillary central incisors erupt at 7-8 years.

True

Deciduous canines erupt after deciduous first molars

True

Deciduous tooth germs begin to grow and develop by what age:

a. The sixth week of fetal life

b. The sixth month of fetal life

c. birth

d. six weeks of age

a. the sixth week of fetal life

Deciduous root calcification is completed by what age?

a. 3 months

b. 6 months

c. 2.5 years

d. 3-4 years

d. 3-4 years

All of the following refer to clinical signs of lobe fusion except:

a. coalescence

b. developmental grooves

c. root bifurcation

d. mamelons

c. root bifurcation

Which molar usually has a cusp of Carabelli?

a. mandibular first

b. mandibular second

c. maxillary first

d. maxillary second

c. Maxillary first

A 20-month-old child would have all of the following deciduous teeth except:

a. mandibular lateral incisors

b. maxillary canines

c. maxillary first molars

d. mandibular second molars

d. mandibular second molars

A 10-year-old child would have all of the following except:

a. deciduous second molars

b. deciduous maxillary canine

c. permanent maxillary lateral incisors

d. permanent maxillary first molars

e. they would have all of the above

e. all of the above

Which of the following is not a factor in causing tooth movement?

a. mesial drift

b. curve of spee

c. eruption

d. lingual forces of the tongue

b. curve of spee

Which of the following could occur when parents do not have the proper knowledge of their child's eruption patterns?

a. a five year old with no primate space

b. an eight year old with missing permanent molars

c. a 10 year old with crowded mandibular incisors

d. a 13-year-old with unerupted molars

b. an 8-year-old with missing permanent molars

Root resorption of deciduous teeth begins:

a. immediately after eruption

b. soon after eruption

c. 1 year after root completion

d. 1 or 2 years before exfoliation

d. 1 or 2 years before exfoliation

A seven year old enters the office with only six permanent teeth. Which of the following is probably true?

a. Four of the permanent teeth are incisors.

b. The child has delayed eruption.

c. Two permanent teeth have been extracted

d. Four of the permanent teeth are first molars

e. Three of the permanent teeth are maxillary, three are mandibular

d. Four of the permanent teeth are first molars

Where is the height of contour on the facial of all teeth?

The cervical third

Where is the height of contour on anterior teeth facial and lingual?

facial: cervical third

lingual: cervical third

Where is the height of contour on posterior teeth facial and lingual?

Facial: cervical third

Lingual: middle third