Dental Caries Chapter 13 Copyright 2005 by Elsevier

“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 Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -1 Dental plaque made visible with disclosing agent Copyright © 2005 by

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -2 Dental caries Copyright © 2005 by Elsevier Inc. All rights reserved.

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) Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -3 Dental caries (Courtesy Ivoclar, Vivadent, Amhurst, NY. ) Copyright © 2005

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -4 A, The earliest sign of decay is decalcification (Courtesy Dr. John Featherstone, University of California, San Francisco, School of Dentistry. ) Copyright © 2005 by Elsevier Inc. All rights reserved.

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 Copyright © 2005 by Elsevier

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

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -8 Recurrent caries under an amalgam restoration Copyright © 2005 by Elsevier

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

Fig. 13 -10 Visual and radiographic appearance of seemingly intact molar Copyright © 2005

Fig. 13 -11 Cross section of molar showing decay Copyright © 2005 by Elsevier

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 nonsugar sweetener such as xylitol. Copyright © 2005 by Elsevier Inc. All rights reserved.

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

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. Copyright © 2005 by Elsevier Inc. All rights reserved.

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 Copyright © 2005 by Elsevier Inc. All rights reserved.

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 Copyright © 2005 by Elsevier Inc. All rights reserved.