Dental Anatomy Lecture 2: Incisors

Incisors

The front 4 teeth

Central-lateral

Mesial surface of right central incisor contacts the mesial surface of the left central incisor unless there is a space.

Why do we need to learn about each tooth morphology, shape, and function?

To restore and manage the oral health of the patient

What tooth numbers are the central maxillary incisors?

8 and 9

What tooth numbers are the lateral maxillary incisors?

7 and 10

What tooth numbers are the central mandibular incisors?

24 and 25

What tooth numbers are the lateral mandibular incisors?

23 and 26

Functions of incisors

Cut food

Enable/articulate speech

Lip support and esthetic

Guide the mandible posteriorly

How many lobes do the class traits develop from?

4

How many facial developmental lobes?

3

How many lingual developmental lobes?

1 (cingulum)

Three Mamelons

From 3 labial developmental lobes before they wear down, like the little grooves on the incisal edge of newly erupted incisors

What are the two incisal elevations?

Mamelons and Perikymata

What is Perikymata?

Numerous horizontal ridges on the enamel of newly erupted permanent teeth

What shape is the incisal edge from the facial view of the maxillary central incisors?

Straight or slightly curved

What shape is the crown from the facial view of the maxillary central incisors?

Rectangular

Longer incisogingivally

Which direction does the incisal crown taper from the facial view of the maxillary central incisors?

From the widest area/proximal contacts to the cervical third

Which set of incisors have the longest crowns?

Maxillary central incisor

Are crowns more convex distally or mesially in the facial view of the maxillary central incisors?

Distal, the contact point is more cervical because of this

How are the mesioincisal angles shaped from the facial view of the maxillary central incisors?

Acute, sharp

Which direction do the incisal edges slope in the facial view of the maxillary central incisors?

Cervically towards the distal

What does incisogingivally mean?

From the incisal edge to the gingival edge

What teeth are the exception to most of the morphology in this lecture? Why?

Mandibular central incisors

They are extremely symmetrical

Which direction does the cervical line curve in the facial view of the maxillary central incisors?

Towards the apex, in the middle of the facial surface

How do the contact points differ mesially and distally in the facial view of the maxillary central incisors?

The contact points are more cervical on the distal surface than the mesial

How do the roots taper in the proximal view of the central incisors?

From the cervical line to the apex

Which direction and at what place in the root can it bend in the proximal view of the maxillary central incisors?

More often towards the distal, bending at the apical third

Which is longer, roots or crowns, in central incisors?

Roots

Where are the mesial and distal marginal ridges located at on the maxillary central incisors? Where do they converge?

Located on the lingual side of the tooth, converging towards the lingual cingulum

Where is the lingual fossa located on the maxillary central incisors?

Between the marginal ridges

From the proximal view, what shape is the crown of the maxillary central incisors?

Wedge-shaped, triangular

Where on the crown is the facial outline most convex when looking proximally at the maxillary central incisors?

In the cervical third

The crest of curvature is here both facially and lingually

Is the lingual cervical third concave or convex when looking proximally at the crown of the maxillary central incisors? What about the middle and incisal thirds?

Lingual: Convex

Middle: Concave

Incisal: Concave

What shape is the lingual outline of the crown on the maxillary central incisors?

S-shaped

Which direction does the cervical line curve in the proximal view of the maxillary central incisors?

Towards the incisal edge

On which proximal side is the cervical line curve greater?

Mesial side

Is the lingual fossa concave or convex in the incisal view of the maxillary central incisors?

Concave

What is the incisal ridge?

The edge of the tooth at the biting surface

Which has a longer and wider crown: Maxillary central or lateral incisor?

Central, lateral is more narrow mesiodistally

Which incisor is often missing or peg-shaped?

Maxillary lateral

Which has a deeper pit and larger cingulum: Central or lateral maxillary incisor?

Laterals

What surface is narrower on incisors, lingual or facial?

Lingual

If you take a transverse cross section, it is almost triangle shaped

Where do the marginal ridges converge at on the incisors?

The cingulum

Which incisors are smoother, maxillary or mandibular?

Mandibular

From the proximal view, what is considered the class trait for the lingual outline shape of most incisors?

S-shaped

On which side of the maxillary lateral incisors is the marginal ridge shorter?

Distal

This is due to greater slope of incisal edge shorter towards distal, and distal placement of cingulum

Which direction do roots typically curve in maxillary incisors?

Towards the distal

Are incisal lingual root surfaces concave or convex?

Convex, the triangle shape

Which direction do incisal roots taper narrower?

Towards the lingual, triangle shaped

What slight feature do maxillary central incisors sometimes have on the incisal edge?

A distolingual twist

On which side does the CEJ curve more incisally on all anterior teeth?

Mesial

Where is the largest proximal CEJ curve for all teeth?

On the mesial surface of the maxillary central incisors

Which half of an incisor has a narrower mesiodistal width, lingual or facial?

Lingual, the triangle shape

Are laterals or centrals more uniformly tapered?

Laterals

In which proximal outline, lingual or facial, are the maxillary central roots flatter in the cervical third before they taper?

Lingual

In which direction are ALL maxillary incisors wider, mesiodistally or faciolingually?

Mesiodistally

Which maxillary incisors are closer to equal lengths mesiodistally and faciolingually?

Lateral incisors

Which maxillary incisor has a triangular crown outline from the incisal view?

Central

Why do maxillary central incisors have a triangular crown outline from the incisal view?

Because the facial surface is flatter

Which maxillary incisors have a more round/oval outline from the incisal view?

Lateral, it has more labial curvature than centrals

Which incisor has the widest crown?

Maxillary central

Which tooth has the longest anatomical crown?

Maxillary central incisors

Which tooth has the smallest root to crown ratio?

Maxillary central incisors

For which tooth is the mesioincisal angle close to 90 degrees?

Maxillary central incisors

Is the lingual anatomy more prominent in maxillary or mandibular incisors?

Maxillary

Where is the cingulum at relative to the root on maxillary central incisors (mesial, centered, distal)?

Distal

Where is the incisal ridge located relative to the root on maxillary central incisors (facial, centered, lingual)?

Centered

Where does tooth wear occur for maxillary central incisors in Class I occlusion?

In the lingual surface

Is the maxillary lateral incisor crown smaller or larger than the central?

Smaller, it has a longer and more slender look

Are mamelons more prominent on the central or lateral maxillary incisors?

Central

Which incisors have the most prominent lingual anatomy?

Maxillary lateral

Do maxillary lateral incisors have a smaller or larger lingual fossa than centrals?

Smaller

Is the cingulum medial, distal, or centered on maxillary lateral incisors?

Centered

Which incisors are likely to have a pit in the deep fossa?

Maxillary lateral

Is the incisal ridge lingual, centered, or facial on maxillary lateral incisors?

Centered

Are mandibular central incisors smaller or larger than other incisors?

Smaller

What are the most symmetrical teeth in the mouth?

Mandibular central incisors

Where are the contact areas on mandibular central incisor? Are they the same medially and distally?

Closer to the incisal ridge

Yes

Do mandibular central incisors have more or less prominent lingual anatomy than maxillary?

Less

There is a smoother lingual surface

Is the root/crown proportion of mandibular central incisors smaller or larger than maxillary?

Larger, the root is much longer compared to the crown

Where is the cingulum on mandibular central incisors (mesial, distal, centered)?

Centered

Are mandibular central incisors wider faciolingually or mesiodistally?

Faciolingually

On mandibular central incisors, is the incisal ridge curved or straight?

Straight

On what surface does tooth wear occur in mandibular central incisors, lingual or facial?

Facial

In mandibular central incisors, is the incisal ridge curved more facially, lingually, or centered?

Lingually

Are mandibular lateral incisors wider or narrower than central?

Slightly wider

Where is the cingulum located on mandibular lateral incisors (central, medial, distal)?

Distal

On mandibular lateral incisors, is the mesial marginal ridge longer or shorter than the distal?

Longer

What is the incisal ridge curve direction of mandibular lateral incisors?

Distolingual twist

On mandibular lateral incisors, is the distoincisal angle the same as mesioincisal?

No, distoincisal is more rounded (like maxillary centrals)

Which direction does the root tip more commonly bend in mandibular incisors?

Distally

Do mandibular incisors have marginal ridges and fossas?

Yes, but very minimal compared to maxillary incisors

Do mandibular incisors have root depressions?

YES, both mesial and distal

More prominent than in maxillary

On which side does the CEJ curve more incisally on mandibular incisors from the proximal view?

Mesial

On which side is CEJ curvature in the mandibular arch central incisors?

Mesial

Are mandibular roots wider faciolingually or mesiodistally?

Faciolingually

Which root depression, mesial or distal, is deeper in mandibular incisors?

Distal

Which mandibular incisor is number 1? Number 2?

1: central

2: lateral