Dental diagnosis
Tooth decay (dental caries) is caused by streptococcus mutans bacteria.

Figure 1: A scanning electron micrograph of a colony of Streptococcus mutans bacteria, such as those found in the fuzzy plaque on teeth. These are the bacteria responsible for the vast majority of tooth decay. (Image from, used with permission).

Dental caries is a bacterial illness believed to be caused by a single strain of bacteria known as Streptococcus mutans, although Lactobacillus may also be involved. These bacteria use sugars from the food and drinks we eat, to produce acids and enzymes that attack tooth enamel.

Tooth decay (also called dental caries, or cavities.)

A sugary diet and poor oral hygiene results in tooth decay (caries).

Directly consumed acids, such as phosphoric acid found in many soft drinks, can also attack tooth enamel, resulting in a hole (cavity) in the tooth. Food and drink containing citric acid (for example, lemons) should be consumed in moderation.

Dental caries can devastate teeth, even with all that is known about its causes, and all of the excellent preventive measures available to stop the disease. Proper nutrition and excellent oral hygiene are the keys to avoidance of dental caries.

How is this dental diagnosis established?

Traditionally, dentists have detected tooth cavities in one of three ways: visual and tactile examination; and X-ray images.

Visual/Tactile Exam

Sectioned tooth shows fissure smaller than single toothbrush bristle, making it difficult to clean.

Pits and fissures in teeth may be too deep and narrow to allow access for even one toothbrush bristle, as illustrated by this cross section of a tooth.

Some cavities are obvious from looking; others develop in the deep pits and fissures of teeth (some studies suggest as many as 80% of cavities begin in pits and fissures).

A dental explorer on a tooth.

Dental explorers have been used for many years to detect early decay of teeth.

Dentists typically use an instrument called a dental explorer, a sharp, wiry instrument for probing the depths of the pits and fissures. If the base of the pit or fissure is softened by decay, the instrument will stick in the tooth.

X-ray Images

A dental periapical X-ray (radiograph) showing tooth decay (caries).

Tooth decay has occurred where an impacted wisdom tooth (third molar) has been leaning against a second molar tooth (See arrow). Without the X-ray, the decay would have gone undetected.

Decayed areas of teeth are visible as dark areas of the tooth on X-rays (radiographs). Dentists use X-rays to evaluate teeth for decay where visual/tactile examination is not possible, most notably between the teeth.

Laser Cavity Detection

Laser caries detection enables tooth decay to be diagnosed without using X-rays.

An artist’s rendering of the tip of a laser fluorescence caries detection meter emits a focused beam of 655nm wavelength light into the pits and fissures, causing fluorescence of decayed tooth structure. The amount of fluorescence is directly related to the size of the cavity. Healthy tooth enamel does not fluoresce.

A more recent and extremely sensitive diagnostic tool for determining whether the pits and fissures in teeth have begun to decay at their base is the laser fluorescence caries detection device, the tip of which is shown in the photograph below.

Healthy teeth do not fluoresce, and decayed teeth fluoresce in proportion to the amount of bacteria present in the tooth. This device measures the fluorescence pattern of teeth, and produces a reading on a meter which is recorded by the dentist.

Diagnosis of pit and fissure cavities is most effective when a combination of visual/tactile examination, appropriate use of laser fluorescence caries detection devices, and X-ray images are used.

Treatment options

Depending on the severity of the decay, restoring teeth with caries may involve fillings, inlays, onlays, crowns or tooth extraction. Decay that reaches the inner pulp of the tooth may require root canal therapy to eliminate the bacteria. Sometimes early decay can be arrested by applying topical fluoride to the affected site. Photographs and radiographs (dental X-rays) are useful for monitoring such areas for progression of the carious lesion.

Related diagnoses

There are other bacterial illnesses of the mouth, other conditions that can have the appearance of dental caries, and other conditions that may increase the likelihood a patient will get cavities. Recurrent caries is decay that occurs under an existing tooth restoration (filling, etc.). The biologic processes that cause it, and the treatment for it are the same as for new cavities, except recurrent caries means more of an already-restored tooth is being destroyed, and fixing the tooth may be more involved. Only a dentist can properly diagnose these conditions. Sometimes plaque and bacteria get into teeth via poorly contoured dental restorations, failing restorations, or cracked teeth, leading to tooth decay. Chronic dry mouth (xerostomia) can also predispose a person to dental caries.

Author: Thomas J. Greany, D.D.S.
Editor: Ken Lambrecht
This page was reviewed by members of our review board.

This page was last updated on June 1, 2016.

ToothIQ for dentists
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For dentists and dental school students

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Background information

Fractional Urinary Fluoride Excretion of Young Female Adults During the Diurnal and Nocturnal Periods
Villa A., et al.
Caries Research
2008 42 (4): 275-281

Viability of Streptococcus mutans on Toothbrush Bristles
Saravia, Marta Estela, et al.
Journal of Dentistry for Children
2008 75 (1): 29-32

Caries Prior to Age 3 and Breastfeeding: A Survey of La Leche League Members
Weber-Gasparoni, Karin, et al.
Journal of Dentistry for Children
2007 74 (1): 52-61

Effect of Addition of Citric Acid and Casein Phosphopeptide-Amorphous Calcium Phosphate to a Sugar-Free Chewing Gum on Enamel Remineralization in situ
Cai, F., et al.
Caries Research
2007 (41): 377-383

Methamphetamine Use and Dental Disease: Results of a Pilot Study
Cretzmeyer, Margaret, et al.
Journal of Dentistry for Children
2007 74 (2): 85-92

The Efficacy of Chlorhexidine Spray vs Mouthwash in the Microbial Contamination of Child Toothbrushes
Aysegul, Olmez, et al.
Journal of Dentistry for Children
2007 74 (3): 177-181

The use of sorbitol- and xylitol-sweetened chewing gum in caries control
Burt, Brian A., BDS, MPH, PhD
The Journal of the American Dental Association
2006 137 (2): 190-196

Assessing the accuracy of caries diagnosis via radiograph—Film versus print
Otis, Linda L., DDS and Sherman, Robert G., DMD
The Journal of the American Dental Association
2005 136 (3): 323-330

Filmless Imaging—The uses of digital radiography in dental practice
Van Der Stelt, Paul F., DDS, PhD
The Journal of the American Dental Association
2005 136 (10): 1379-1387

Imaging of occlusal dental caries (decay) with near-IR light at 1310nm
Buhler, Christopher,
Optics Express: The International Electronic Journal of Optics
2005 13 (2): 573-582

The advantages of minimally invasive dentistry
Christensen, Gordon J., DDS, MSD, PhD
The Journal of the American Dental Association
2005 136: 1563-1565

A Caries Vaccine? The State of the Science of Immunization Against Dental Caries
Russel, Michael W., et al.
Caries Research
2004 38: 230-235

Minimally invasive dentistry
Murdoch-Kinch, Carol Anne, DDS, PhD, and McLean, Mary Ellen, DDS
The Journal of the American Dental Association
2003 134: 87-95

Artificial Salivas
The Journal of the American Dental Association
2001 132 (12): 1720-1721
Editor’s notes: Published in the “Dental Product Spotlight” column of the Journal

Diagnosis of Occlusal Caries: Part I. Conventional Methods
McComb, Dorothy, BDS, MScD, FRCD(C), and Tam, Laura E., DDS, MSc
Journal of the Canadian Dental Association
2001 67 (8): 454-457

Diagnosis of Occlusal Caries: Part II. Recent Diagnostic Technologies
McComb, Dorothy, BDS, MScD, FRCD(C), and Tam, Laura E., DDS, MSc
Journal of the Canadian Dental Association
2001 67 (8): 459-463

Protective Immunity to Streptococcus mutans Induced by Nasal Vaccination with Surface Protein Antigen and Mutant Cholera Toxin Adjuvant
Saito, Masayuki, et al.
The Journal of Infectious Diseases
2001 183: 823-826

The management of Sjogren’s syndrome in dental practice
Al-Hashimi, Ibtisam, BDS, MS, PhD
The Journal of the American Dental Association
2001 132 (10): 1409-1417

Caries-Detector Dyes — How Accurate and How Useful Are They?
McComb, BDS, M.Sc.D., FRCD( C )
Journal of the Canadian Dental Association
2000 66: 1995-1998

Determination of endotoxins in caries: association with pulpal pain
Khabbaz, M.G., et al.
International Endodontic Journal
2000 33 (2): 132-137

The science and practice of caries prevention
Featherstone, John D.B., MSc, PhD
The Journal of the American Dental Association
2000 131 (7): 887-899

Digital enhancement of radiographs: Can it improve caries diagnosis?
Shrout, Michael K., DMD, et al.
The Journal of the American Dental Association
1996 127 (4): 469-473

Prevention of colonization of Streptococcus mutans by topical application of monoclonal antibodies in human subjects
Ma, J.K., and Lehner, T.
Archives of Oral Biology
1990 35
Notes: Supplement: 115S-122S. Dept. of Immunology, United Medical School, Guy’s Hospital, London, England.

Topical Fluoride Therapy: Discussion of Some Aspects of Toxicology, Safety, and Efficacy (PDF, 665K)
Newbrun, E.
Journal of Dental Research
1987 66: 1084-1086

Pathogenesis of pulpitis resulting from dental caries
Trowbridge, Henry O., DDS, PhD; Journal of Endodontics
Journal of Endodontics
1981 7 (2): 52-60

Caries Vaccine
HealthMantra web site
Last viewed: 9/23/2010
Editor’s notes: An untitled article summarizing various international research projects aimed at developing a caries vaccine. Summary discusses progress 1990–1999.

Comparison of Conventional Caries Detection and Caries Detector Dye
Zavareh, F. Arbabzadeh, et al.
International Association for Dental Research web site
Last viewed: 9/23/2010
Editor’s notes: Originally presented at the International Association for Dental Research/American Association for Dental Research/Canadian Association for Dental Research, 83rd General Session, March 9–12, 2005.

Dental Fluorosis (Mottled Teeth)
Meiers, Peter
Fluoride-History web site
Last viewed: 9/23/2010
Editor’s notes: Personal web site cataloging various personalities, milestones, and volatile issues associated with fluoride.

Making Cavity-Causing Bacteria Self-Destruct
Greg Williams, University of Rochester Medical Center
Medical News Today web site
Last viewed: 9/24/2010

Methamphetamine use and oral health
ADA Division of Communications in cooperation with JADA and the ADA Division of Scientific Affairs
The Journal of the American Dental Association

More U.S. Teeth Susceptible to Silent Enamel Eating Syndrome
Not specified
Medical News Today web site
Last viewed: 9/23/2010

More U.S. Teeth Susceptible to Silent Enamel Eating Syndrome
Not specified
Medical News Today web site
Last viewed: 9/23/2010

Protecting Oral Health Throughout Your Life
American Academy of Periodontology web site
Last viewed: 9/23/2010
Editor’s notes: Article addresses gender-specific oral health concerns of women.

Quantum Detection of Tooth Decay
Hamilton, Tyler
MIT Technology Review

Researchers seek to make cavity-causing bacteria self-destruct web site
Last viewed: 9/24/2010

Tooth Decay, Open Wide—Oral Health Training for Health Professionals
National Maternal and Child Oral Health Resource Center web site

Last viewed: 9/23/2010

Vaccine prevents cavities—ready for tests on tots
Cromie, William J.
Harvard University Gazette
Notes: Published October 4, 2001

Information you may wish to read before making a decision on treatment

A review of the current literature on the management of halitosis
ven den Broek, AMWT, et al.
Oral Diseases
2008 14 (1): 30-39

Effects of Natural Cross-Linkers on the Stability of Dentin Collagen and the Inhibition of Root Caries in vitro
Walter, R., et al.
Caries Research
2008 42 (4): 263-268

Preformed metal crowns for decayed primary molar teeth
Innes, NPT, et al.
Cochrane Database of Systematic Reviews
2008 1

Evaluation of a new caries detecting dye for primary and permanent carious dentin
Hosoya, Y., et al.
Journal of Dentistry
2007 35 (2): 137-143

Noninvasive Control of Dental Caries in Children with Active Initial Lesions- A Randomized Clinical Trial
Hausen, H., et al.
Caries Research
2007 (41): 384-391

A novel technique using preformed metal crowns for managing carious primary molars in general practice – A retrospective analysis
Innes, N.P.T., et al.
British Dental Journal
2006 200 (8): 451-454

Minimally invasive operative techniques using high tech dentistry (PDF, 148K)
Brostek, Andrew M. Dr., et al.
Dental Practice
2006: 106-106
Editor’s notes: Online publication date September/October 2006.

Pit and fissure sealants versus fluoride varnishes for preventing dental decay in children and adolescents
Ahovuo-Saloranta, Hiiri A., et al.
Cochrane Database of Systematic Reviews
2006 4
Notes: Art. No.: CD003067

A systematic review of the performance of a laser fluorescence device for detecting caries
Bader, James D., DDS, MPH and Shugars, Dan A., DDS, PhD
The Journal of the American Dental Association
2004 135 (10): 1413-1426

Caries detection using laser fluorescence
Croll T.P., Tyma M.S.
Compendium of Continuing Education in Dentistry
2001 22 (10): 838-842, 844

A technique for repairing bridge abutments damaged by caries
Liftig, Rick, DMD
The Journal of the American Dental Association
1996 127 (10)

Addressing the caries dilemma: detection and intervention with a disclosing agent
Styner, D. et al.
General Dentistry
1996 44 (5): 446-449

The use of caries detector dye in diagnosis of occlusal carious lesions
al-Sahaibany, F., et al.
Journal of Clinical Pediatric Dentistry
1996 20 (4): 293-298

Cranberries contain possible anti-caries/anti-plaque agents web site
Last viewed: 9/23/2010
Editor’s notes: Correspondence with the IADR showed that this research was presented at the annual meeting of the IADR in Brisbane, Australia, June 29, 2006 by Koo, H, et al. Dr. Koo’s group has published two articles on the subject.

Endocarditis Prophylaxis Information
American Heart Association web site
Last viewed: 9/23/2010

FDA says mercury-based fillings not harmful—Critics say agency playing politics, seek ban on their use in pregnant women web site
Last viewed: 9/23/2010
Notes: Associated Press—September 1, 2006

In Battle Against Tooth Decay Simple Push Fillings Preferred Over Crowns
Charlotte Webber, BioMed Central
Medical News Today web site
Last viewed: 9/24/2010

Innovative New Treatments Take Fear Out of Dentist’s Chair
No author specified
Medical News Today web site
Last viewed: 8/27/2008

JAMA Publishes Dental Amalgam Studies (PDF, 96K)
Illinois State Dental Society web site
Last viewed: 9/23/2010
Notes: American Medical Association issues statement in support of the use of dental amalgam—April 19, 2006

Letter to U.S. Representative Ron Paul stating the USFDA’s position on use of dental amalgam (PDF, 416K)
U.S. Food and Drug Administration web site
Last viewed: 9/23/2010
Notes: A letter from an FDA spokesperson to US Representative Ron Paul (TX), describing the current position of the US Food and Drug Administration on Dental Amalgam Fillings, August 5, 2002.

Microdentistry Fundamentals
No author specified
National Center for Biotechnology Information web site
Last viewed: 9/23/2010

Sealant Success (Letter)
The Journal of the American Dental Association
Editor’s notes: Editorial comment by Robert J. Feigal, DDS, PhD, re: Dr. Leinfelder’s recommended use of dentin bonding agents to reduce the effects of moisture contamination in sealant placement.

The Fissurotomy® Bur: a conservative solution to suspect fissures.
SS White Burs, Inc. web site
Last viewed: 9/23/2010
Editor’s notes: Manufacturer’s web site. Discusses of the use of a fissurotomy bur.