caries

Copyright © 2005 by Elsevier Inc. All rights reserved.
Dental Caries
Chapter 13

“The mouth is the gateway to the rest of the
body, a mirror of our overall well-being.”
Harold C. Slavkin, D.D.S.
Former Director of the National Institute of Dental and Craniofacial Research, and
Dean of the University of Southern California School of Dentistry

Everyday in the United States, millions of
people including children, working families,
and the elderly live in constant pain as a result
of oral disease or injury to the mouth.

Introduction
Dental caries is an infectious bacterial disease
that has plagued humans since the beginning
of recorded history. What is dental caries?
Simply stated, it is tooth decay.
Today, because of scientific advances and new
technologies, dentistry is developing new
strategies for managing dental caries.
These strategies emphasize prevention
and early intervention.

You cannot be healthy without oral health.
Oral health and general health should not
be interpreted as separate entities.
Oral health is a critical component of health.

Dental Caries: A Bacterial Infection
• There are two specific groups of bacteria
found in the mouth that are responsible for
dental caries:
– Mutans streptococci (Streptococcus mutans)
– Lactobacilli
• They are found in relatively large numbers
in the dental plaque.
• The presence of lactobacilli in the mouth
indicates a high sugar intake.

Transmission of Caries Causing Bacteria
• Mutans streptococci are transmitted through saliva,
most frequently the mother’s, to the infant.
• When mothers have high counts of mutans
streptococci in their mouths, the babies also have
high counts of the same bacteria in their mouth.
• Women should be certain their own mouths are
healthy.
• When the number of caries causing bacteria in the
mouth increases, the risk for developing dental
caries also increases.

Dental Plaque
• Dental plaque is a colorless, soft, sticky
coating that adheres to the teeth.
• Plaque remains attached to the tooth despite
movements of the tongue, water rinsing,
water spray, or less than thorough brushing.
• Formation of plaque on a tooth concentrates
millions of microorganisms on that tooth.

Fig. 13-1 Dental plaque made visible with disclosing agent

Structure of Enamel
• Enamel is the most highly mineralized tissue
in the body.
• Enamel is stronger than bone.
• Enamel consists of microscopic crystals of
hydroxapatite arranged in structural layers or rods,
also known as prisms.
• The enamel crystals are surrounded by water.
• The water and protein components in the tooth are
important because that is how the acids travel into
the tooth and the minerals travel out and the tooth
structure dissolves.

Fig. 13-2 Dental caries

The Caries Process
• For caries to develop, three factors must
occur at the same time:
– A susceptible tooth
– Diet rich in fermentable carbohydrates
– Specific bacteria (regardless of other factors,
caries cannot occur without bacteria)

Fig. 13-3 Dental caries
(Courtesy Ivoclar, Vivadent, Amhurst, NY.)

Areas for Development of Caries
• Pit and fissure caries occurs primarily on the
occlusal surfaces and buccal and lingual grooves
of posterior teeth, as well as in lingual pits of the
maxillary incisors.
• Smooth surface caries occurs on intact enamel
other than pits and fissures.
• Root surface caries occurs on any surface of
the root.
• Secondary, or recurrent, caries occurs on the
tooth surrounding a restoration.

Stages of Caries Development
• It usually takes a period of time, from months to years,
for a carious lesion to develop.
• It is an ongoing process, characterized by alternating
periods of demineralization and remineralization.
– Demineralization is the dissolving of the calcium and
phosphate from the hydroxyapatite crystals.
– Remineralization is the calcium and phosphate being
redeposited in previously demineralized areas.
• It is possible to have the processes of demineralization
and remineralization occur without any loss of tooth
structure.

Stages of Caries Development-cont’d
• Incipient lesion develops in the earliest stages
when caries begins to demineralize the enamel.
• Overt, or frank, lesion is characterized by
cavitation (the development of a cavity or hole
in the tooth).
• Rampant: The time between the onset of the
incipient lesion and the development of the
cavity is rapid and there are multiple lesions
throughout the mouth.

Fig. 13-4 A, The earliest sign of decay is decalcification
(Courtesy Dr. John Featherstone, University of California, San Francisco, School of Dentistry.)

Fig. 13-4 B, Dental caries
(Courtesy Dr. Frank Hodges, Santa Rosa, CA.)

Fig. 13-4 C, Dental caries
(Courtesy Dr. Frank Hodges, Santa Rosa, CA.)

Fig. 13-5 Severely decayed molar on a child

Fig. 13-6 Decay on the lingual of a maxillary lateral incisor

Root Caries
• Root caries is becoming more prevalent and is a
concern for the elderly population who often have
gingival recession exposing the root surfaces.
• People are living longer and keeping their teeth
longer. Older people are often taking medications
known to reduce salivary flow.
• Carious lesions form more quickly on root surfaces
than coronal caries because the cementum on the
root surface is softer than enamel and dentin.
• Like coronal caries, root caries has periods of
demineralization and remineralization.

Fig. 13-7 Root caries
(Courtesy Dr. John Featherstone, University of California, San Francisco, School of Dentistry.)

Secondary, or Recurrent, Caries
• Secondary, or recurrent, caries starts to form in the small
spaces or gaps between the tooth and the margins of a
restoration.
• Bacteria are able to thrive in these areas.
• When dental restorations need to be replaced, it is
because there is recurrent caries under the existing
restoration.
• New restorative materials that are bonded to the tooth
structure eliminate the gap between tooth and filling
where microleakage can occur. Restorative materials that
slowly release fluoride help to prevent secondary caries.

Fig. 13-8 Recurrent caries under an amalgam restoration

The Role of Saliva
• Physical protection provides a cleansing effect. Thick, or
viscous, saliva is less effective than a more watery saliva in
clearing carbohydrates.
• Chemical protection contains calcium, phosphate, and
fluoride. It keeps calcium there ready to be used during
remineralization. It includes buffers, bicarbonate, phosphate,
and small proteins that neutralize the acids after we ingest
fermentable carbohydrates.
• Antibacterial substances in saliva work against the bacteria.
• If salivary function is reduced for any reason, such as from
illness or medications or due to radiation therapy, the teeth
are at increased risk for decay.

Diagnosis of Dental Caries
• Detectable explorer “stick”
• Radiographs
• Visual
• Laser caries detector

Laser Caries Detector
• The laser caries detector is used to
diagnose caries and reveal bacterial
activity under the enamel surface.
• Carious tooth structure is less
dense and gives off a higher reading
than non- carious tooth structure.

Fig. 13-10 Visual and radiographic appearance
of seemingly intact molar

Fig. 13-11 Cross section of molar showing decay

Methods of Caries Intervention
• Fluoride: A variety of types are available to
strengthen the tooth against solubility to acid.
• Antibacterial therapy: Products such as
chlorhexidine rinses are effective.
• Fermentable carbohydrates: Reduce the amount
and frequency of ingestion.
• Salivary flow can be increased by chewing
sugarless gum, for example, those with a non-
sugar sweetener such as xylitol.

Fig. 13-12 Preventive measures against caries.
A, Fluoride rinse. B, Chlorhexidine rinse. C, Xylitol gum.

Risk Assessment for Dental Caries
• If the patient’s risk for developing dental caries can
be determined, it is possible to prevent the caries
from developing by beginning appropriate preventive
treatment.
• Caries risk assessment tests are based on the
amount of mutans streptococci and lactobacilli
present in the saliva.
• High bacterial counts indicate a high caries risk, low
counts indicate a low risk for caries. If the preventive
measures are not provided, carious lesions are likely
to develop.

Indication for Using a Caries Risk Test
• New patients with signs of caries activity
• Pregnant patients
• Patients experiencing sudden increase
in incidence of caries
• Individuals taking medications that may
affect the flow of saliva
• Xerostomic patients

Indication for Using a Caries Risk Test-cont’d
• Patients about to undergo chemotherapy
• Patients who consume fermentable
carbohydrates frequently
• Patients suffering from diseases of the
autoimmune system

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