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ORAL ANATOMY

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ORAL ANATOMY

• Deciduous teeth are also called “primary” or “baby” teeth.

• Humans have 20 deciduous teeth

• They usually begin erupting at 6 months of age and eruption is usually complete by 2-3 years of age.

• Deciduous teeth consist of incisors, cuspids and molars

• Deciduous enamel is thin so be cautious when polishing.

Deciduous Teeth

• Humans have 32 permanent teeth including incisors, cuspids, premolars and molars.

• Permanent teeth that replace primary teeth are called “succedaneous” teeth.

• Permanent incisors and cuspids replace primary incisors and cuspids so are “succedaneous”

• Permanent premolars replace primary molars and are also succedaneous.

Permanent Teeth

“Nonsuccedaneous”

• Permanent molars are “nonsuccedaneous” because they come in behind primary molars.

• The first permanent teeth to erupt are usually the mandibular first molars.

Terminology Review

• The part of a tooth covered by enamel, the hardest substance in the body, is called the “anatomic” crown of the tooth.

• The roots of a tooth are covered by cementum, a material much softer than enamel.

• The “clinical” crown is that part of the tooth showing in the mouth.

• Sometimes the “clinical” crown may include some of the root if there is recession.

• Do not polish the exposed root with the same pressure as enamel. Cementum covering the roots will be destroyed!

Beware !!

• The “clinical” crown may also be just part of a newly erupting tooth.

• Polish it very gently. It takes some time for the enamel to attain its full hardness.

Terminology Review

• The anatomic crown is separated from the roots by the “cementoenamel junction” (CEJ)

• The inside of the crown and the roots is composed of dentin which contains live tissue.

• In some patients, the tooth’s dentin is exposed at the CEJ causing sensitivity.

• Ask your patients if they have any sensitive areas before polishing and avoid those areas if possible.

CEJ

• The crown of a tooth has three parts, an incisal 1/3, a middle 1/3 and a gingival 1/3.

• The gingival 1/3 of a crown usually has the most plaque, so be sure to polish that area thoroughly.

Gingival 1/3

Middle 1/3

Incisal 1/3

• If a patient’s gingiva is healthy, it attaches to the tooth at the CEJ.

• This attachment is at the bottom of the trough or “sulcus” that circles the tooth.

• In a healthy patient, the sulcus is 1 – 3 millimeters deep.

Keratin • Tissue in the mouth that is constantly

rubbed builds up “keratin”, a material much like a callous.

• Examples of “keratinized” tissue include the hard palate, the top of the tongue and the gingiva.

• “Nonkeratinized” tissue includes the floor of the mouth and the lining of the sulcus.

• When polishing, be sure the rubber cup goes gently into the sulcus.

• Be careful, the tissue lining the sulcus is nonkeratinized, and the attachment at the bottom of the sulcus is fragile.

Other terminology • Tooth surfaces facing the cheek are

called buccal surfaces.

• Tooth surfaces facing the tongue are called lingual surfaces.

• Tooth surfaces facing the front of the mouth are called mesial surfaces.

• Tooth surfaces facing the back of the mouth are called distal surfaces.

• Occlusal surfaces are the chewing surfaces of posterior teeth

• Incisal surfaces are biting surfaces of anterior teeth.

lingual buccal

distal

mesial

distal

mesial

mesial

distal

• Two tooth surfaces that contact each other (mesial and distal) are called “proximal” surfaces.

• The triangular space on either side of the contact formed by the two proximal surfaces is called the “embrasure”.

lingual buccal

distal

mesial

distal

mesial

mesial

distal

embrasure

• The imaginary line that separates two of a tooth’s surfaces (say, mesial from buccal) is called a “line angle”.

• When polishing, it is important to “roll” the rubber cup around the line angle into the embrasure so the proximal surface is polished.

occlusal

mesial Line angle

• The purpose of flossing your patient during coronal polishing is to remove plaque and excess polishing paste from the proximal surfaces.

• If contacts are tight, be careful! Floss could injure the papilla.

More Terminology

• The indentation on the lingual surface of maxillary incisors is called the “lingual fossa”.

• It is sometimes difficult to polish so spend a little more time on these teeth.

• Occlusal and lingual pits and grooves are also difficult to polish with a rubber cup.

• Use a toothbrush, if necessary, to clean these areas, but you can’t use a rotating brush Occlusal pits

and grooves Lingual Groove

Coronoid process

• When opening wide, a patient’s coronoid process interferes with polishing buccal surfaces of maxillary molars.

• When polishing these surfaces, have the patient close slightly, so the coronoid process is out of the way.

Coronoid process