Dental Indices

Definition

Dental indices provide a quantitative method for measuring, scoring, and analyzing dental conditions in individuals and groups. An index describes the status of individuals or groups with respect to the condition being measured.

Description

Oral health surveys depend on dental indices, as do researchers and clinicians, to help in understanding trends and patients' needs. In epidemiological oral health surveys, an index is used to show the prevalence and incidence of a particular condition, to provide baseline data, to assess the needs of a population, and to evaluate the effects and results of a community program. Researchers use indices to determine baseline data and to measure the effectiveness of specific agents, interventions, and mechanical devices. In private practice, index scores are used to educate, motivate, and evaluate the patient. By comparing scores from the initial exam during a follow-up exam, the patient can measure the effects of personal daily care.

The first dental index, developed by Schour and Massler, was known as a Papilla, Marginal gingiva and Attached gingiva (PMA) Index. Each of those areas was examined and scored from 0 to 5, depending on the severity of inflammation. The PMA Index, largely of historic interest now, was primarily used in surveys of acute gingivitis.

Today, dental indices are used to assess both individual and group oral health and disease status. They can be simple, measuring only the presence or absence of a condition, or they can be cumulative, measuring all evidence of a condition, past and present. Irreversible indices measure conditions that will not change, such as dental caries. A reversible index measures conditions that can be changed, such as the amount of bacterial plaque present.

The status of a patient's periodontal health or disease is commonly measured by an index in private practices. One of the most widely used is the Periodontal Screening and Recording (PSR) Index, adapted in 1992 from a system in use in Europe called the Community Periodontal Index of Treatment Needs. The PSR is an early detection system for periodontal disease. It is not intended to replace full periodontal charting, but to serve as a simple and convenient screening tool. (The PSR is more fully discussed in the entry on dental and periodontal charting.)

In addition to measuring a patient's periodontal status, dental indices can measure the amount of plaque and calculus present or not present in a patient's mouth, the amount of bleeding present in the gingiva, the amount of tooth mobility present at a given time, the amount of fluorosis present, and the number of decayed, missing, or filled teeth present. Some of the more widely known indices are:

Plaque index (PI)

The PI as developed by Silness and Loe assesses the thickness of plaque at the cervical margin of the tooth (closest to the gum). Four areas, distal, facial or buccal, mesial, and lingual, are examined.

Each tooth is dried and examined visually using a mirror, an explorer, and adequate light. The explorer is passed over the cervical third to test for the presence of plaque. A disclosing agent may be used to assist evaluation. Four different scores are possible. A zero indicates no plaque present; 1 indicates a film of plaque present on the tooth; 2 represents moderate accumulation of soft deposits in the gingival pocket or on the tooth that can be seen by the naked eye; 3 represents an abundance of soft matter within the pocket or on the tooth.

Each area of each tooth is assigned a score from 0 to 3. Scores for each tooth are totaled and divided by the four surfaces scored. To determine a total PI for an individual, the scores for each tooth are totaled and divided by the number of teeth examined. Four ratings may then be assigned: 0 = excellent, 0.1-0.9 = good, 1.0-1.9 = fair, 2.0-3.0 = poor.

Plaque control record

A similar system for measuring plaque is credited to O'Leary, Drake, and Naylor. This system measures plaque present, rather than plaque not present, but no attempt is made to differentiate in the quantity of plaque seen on each surface. The number of surfaces examined may be increased from four to six. When using six surfaces, they are facial (or buccal), mesio-facial, mesio-lingual, lingual, disto-lingual, and disto-facial.

To determine an individual's score, the clinician multiplies the number of surfaces with plaque by 100, and divides that by the number of tooth surfaces examined. For example, if an individual has 26 teeth, that equals 104 surfaces. If eight surfaces are found to have plaque, then 800 is divided by 104, leaving a plaque control index of 7.6%. A score under 10% is considered good.

Oral hygiene index (OHI)

The OHI, developed by Greene, Vermillion, and Waggener, has two components, the debris index and the calculus index, and is an indication of oral cleanliness. The scores may be used singly or in combination. For scoring, the clinician divides the dentition into sextants and selects the facial (or buccal) and lingual tooth surface in each sextant that is covered with the greatest amount of debris and calculus. Twelve surfaces, therefore, will be evaluated. For this index, a surface includes half the circumference of the tooth.

Greene and Vermillion have also developed a simplified OHI in which the clinician measures only one tooth surface in each sextant, equaling only six surfaces.

DEBRIS INDEX (DI). For this index, debris is defined as soft, foreign matter consisting of bacterial plaque and food debris. The criteria include 0, no debris or stain present; 1, debris covering not more than one-third of the tooth surface or extrinsic stain without debris; 2, debris covering between one- and two-thirds of the tooth surface; and 3, debris covering more than two-thirds of the tooth surface.

CALCULUS INDEX (CI). Calculus, a hard calcified deposit of inorganic salts, is scored for this index with four criteria. They are 0, no calculus present; 1, supragingival calculus present covering not more than one third of the tooth surface; 2, supragingival calculus covering between one- and two-thirds of the tooth surface, or scattered subgingival calculus; and 3, supragingival calculus covering more than two-thirds of the tooth surface, or a continuous heavy band of subgingival calculus around the tooth.

To arrive at an OHI score, one first calculates the DI and CI scores by dividing the total scores for each tooth by the number of sextants. The DI and CI scores are then added to determine an OHI score. A perfect score would be 0, and the worst score possible is 12. In the simplified OHI, the worst score possible is 6.

Gingival index (GI)

Also attributed to Loe and Silness, the GI assesses the severity of gingivitis based on color, consistency, and bleeding on probing. Each tooth is examined at the mesial, lingual, distal, and facial (or buccal) surface. A probe is used to press on the gingiva to determine its degree of firmness, and to run along the soft tissue wall adjacent to the entrance to the gingival sulcus. Four criteria are possible: 0, normal gingiva; 1, mild inflammation but no bleeding on probing; 2, moderate inflammation and bleeding on probing; 3, severe inflammation and ulceration, with a tendency for spontaneous bleeding.

Each surface is given a score, then the scores are totaled and divided by four. That number is divided by the number of teeth examined to determine the GI. Ratings are 0 = excellent; 0.1-1.0 = good; 1.1-2.0 = fair; 2.1-3.0 = poor.

Periodontal index (PI)

Developed by Russell, the PI determines the periodontal disease status of populations in epidemiologic studies. Each tooth is scored according to the condition of the surrounding tissues. On examination, each tooth is assigned a score using the following criteria:

• 0: Negative. Neither overt inflammation nor loss of function caused by the destruction of supporting tissue is noted.
• 1: Mild gingivitis. Overt inflammation in the free gingiva is present, but does not circumscribe the tooth.
• 2: Gingivitis. Inflammation surrounds the tooth, but there is no apparent break in the epithelial attachment.
• 6: Gingivitis with pocket formation. The epithelial attachment of gum to tooth is broken. There is no interference with normal function. The tooth is not loose or drifting.
• 8: Advanced destruction with loss of function. The tooth may be loose or drifting. It may sound dull on percussion and may be depressible in the socket.

Scores for each tooth are added, and the total divided by the number of teeth examined. Scores can be interpreted as follows:

• 0-0.2: clinically normal supportive tissues
• 0.3-0.9: simple gingivitis
• 0.7-1.9: beginning destructive periodontal disease
• 1.6-5.0: established destructive periodontal disease
• 3.8-8.0: terminal periodontal disease

Gingival bleeding index (GBI)

Unwaxed dental floss is used to measure a GBI, developed by Carter and Barnes. A full complement of teeth has 28 proximal areas to be examined. Floss is passed interproximally, first on one side of the dental papilla, then on the other. The clinician curves the floss around each tooth and passes it below the gingival margin, taking care not to lacerate the gingiva. Any bleeding noted indicates the presence of disease. The numbers of bleeding areas versus proximal areas scored is recorded and used for patient motivation.

Mobility index

The mobility index, developed by Grace and Smales, can be useful to track the amount of mobility in teeth over a period of time. Grade 0 indicates no apparent mobility. Grade 1 is assigned to a tooth in which mobility is perceptible, but less than 1mm buccolingually. Grade 2 mobility is between 1 and 2 mm, and grade 3 mobility exceeds 2 mm buccolingually or vertically.

Dean's Dental Fluorosis Index

Dean's is used to score the amount of dental fluorosis (discoloration due to excess fluoride) present on teeth. Fluorosis generally appears as a horizontal striated pattern across a tooth. Molars and bicuspids are most frequently affected, followed by upper incisors. The mandibular incisors are usually least affected. Fluorosis tends to be bilaterally symmetrical. Defects may appear as fine white or frosted lines or patches near the incisal edges or cusp tips.

A score is given based on the two teeth most affected. If the teeth are not equal in appearance, the less affected tooth is the one scored.

Scores used in Dean's Index are as follows:

• Normal (0): The enamel is smooth, glossy and translucent, usually a pale creamy-white color.
• Questionable (1): There are slight aberrations from the translucency of normal enamel. Lesions may range from a few white flecks to occasional spots.
• Very mild (2): Opaque paper-white areas are visible, involving less than 25% of the facial or buccal tooth surface.
• Mild (3): White opacity of the enamel is more apparent than for code 2, but still covers less than 50% of the surface.
• Moderate (4): Marked wear and brown stain, frequently disfiguring, is visible.
• Severe (5): Hypoplasia is so marked that the general form of the tooth may be altered. Pitted or worn areas and brown stain are widespread. Teeth often have a corroded appearance.
• Excluded (8): Used for crowned teeth.
• Not recorded (9): Used for missing teeth or teeth that cannot be scored.

Decayed, missing, and filled teeth (DMFT) index

To assess dental caries in a population, a DMFT index is used. During a systematic examination with a mirror and explorer that includes the crown and exposed root of every primary and permanent tooth, each crown and root are assigned a number based on the result of that exam. The numbers are recorded in boxes corresponding to each tooth to provide a DMFT chart. It is recommended that care be taken to record all tooth-colored fillings, which may be difficult to detect.

Number are assigned as follows:

• 0: A zero indicates a sound crown or root, showing no evidence of either treated or untreated caries. A crown may have defects and still be recorded as 0. Defects that can be disregarded include white or chalky spots; discolored or rough spots that are not soft; stained enamel pits or fissures; dark, shiny, hard, pitted areas of moderate to severe fluorosis; or abraded areas.
• 1: One indicates a tooth with caries. A tooth or root with a definite cavity, undermined enamel, or detectably softened or leathery area of enamel or cementum can be designated a 1. A tooth with a temporary filling, and teeth that are sealed but decayed, are also termed 1. A 1 is not assigned to any tooth in which caries is only suspected. In cases where the crown of a tooth is entirely decayed, leaving only the root, a 1 is assigned to both crown and root. Where only the root is decayed, only the root is termed a 1. In cases where both the crown and root are involved with decay, whichever site is judged the site of origin is recorded as a 1. These criteria apply to all numbers.
• 2: Filled teeth, with additional decay, are termed 2. No distinction is made between primary caries which is not associated with a previous filling, and secondary caries, adjacent to an existing restoration.
• 3: A 3 indicates a filled tooth with no decay. If a tooth has been crowned because of previous decay, that tooth is judged a 3. When a tooth has been crowned for another reason such as aesthetics or for use as a bridge abutment, a 7 is used.
• 4: A 4 indicates a tooth that is missing as a result of caries. Only crowns are given 4 status. Roots of teeth that have been scored as 4 are recorded as 7 or 9. When primary teeth are missing, the score should be used only if the tooth is missing prematurely. Primary teeth missing because of normal exfoliation need no recording.
• 5: A permanent tooth missing for any other reason than decay is given a 5. Examples are teeth extracted for orthodontia or because of periodontal disease, teeth that are congenitally missing, or teeth missing because of trauma. The 5 is assigned to the crown, the root is given a 7 or 9. Knowledge of tooth eruption patterns is helpful to determine whether teeth are missing or not yet erupted. Clues to help in the determination include appearance of the alveolar ridge in the area in question, and caries status of other teeth in the mouth.
• 6: A 6 is assigned to teeth on which sealants have been placed. Teeth on which the occlusal fissure has been enlarged and a composite material placed should also be termed 6.
• 7: A 7 is used to indicate that the tooth is part of a fixed bridge. When a tooth has been crowned for a reason other than decay, this code is also used. Teeth that have veneers or laminates covering the facial surface are also termed 7 when there is no evidence of caries or restoration. A 7 is also used to indicate a root replaced by an implant. Teeth that have been replaced by bridge pontics are scored 4 or 5; their roots are scored 9.
• 8: This code is used for a space with an unerupted permanent tooth where no primary tooth is present. The category does not include missing teeth. Code 8 teeth are excluded from calculations of caries. When applied to a root, an 8 indicates the root surface is not visible in the mouth.
• 9: Erupted teeth that cannot be examined—because of orthodontic bands, for example—are scored a 9. When applied to a root, a 9 indicates the tooth has been extracted. The crown of that tooth would be scored a 4 or 5.
• T: Indicating trauma, a T is used when a crown is fractured, with some of its surface missing but there is no evidence of decay.

The "D" of DMFT refers to all teeth with codes 1 and 2. The "M" applies to teeth scored 4 in subjects under age 30, and teeth scored 4 or 5 in subjects over age 30. The "F" refers to teeth with code 3. Those teeth coded 6, 7, 8, 9, or T are not included in DMFT calculations.

To arrive at a DMFT score for an individual patient's mouth, three values must be determined: the number of teeth with carious lesions, the number of extracted teeth, and the number of teeth with fillings or crowns. A patient who has two areas of decay, six missing teeth and 11 filled or crowned teeth for example, has a DMFT score of 19. Teeth that include both decay and fillings or crowns, are only given one point, a D. Thirteen teeth (based on a full dentition of 32) remain intact.

It is also possible to determine more detailed DMFS (decayed, missing, or filled surface) scores. As anterior teeth have four surfaces and posterior teeth have five, a full dentition of 32 teeth includes 128 surfaces. A patient with seven decayed surfaces, 20 surfaces from which teeth are missing, and 42 surfaces either filled or included in a crown, the DMFS score is 69. Fifty-nine surfaces are intact.

For primary dentition, scoring is referred to as "deft" or "defs" (decayed, extracted, or filled).

Significant caries index

In 2000, the World Health Organization developed the Significant Caries Index (SiC) to be used when studying DMFT scores on a global basis. A single population may include a number of individuals with low DMFT scores, as well as those with high scores. A mean DMFT value would not accurately reflect the status of the population. The SiC index isolates and highlights those individuals with the highest caries values in a particular population.

To calculate a SiC index, individuals are sorted according to DMFT values. The third of the population with highest caries scores is isolated, and a mean DMFT for this subgroup is calculated. The resulting value is the SiC index.

Viewpoints

Researchers all over the world develop dental indices to suit their particular needs, resulting in some duplication. There are at least six indices that measure the presence or absence of plaque. Indices have become flexible, able to be adapted, modernized, or simplified to fit different needs. They will continue to develop as those needs change again.

Professional implications

Dental professionals from the private practice clinician to the researcher use indices to benefit their patients. A dentist or hygienist might use a PI to impress upon a patient the need for better oral hygiene. A World Health Organization researcher might use the same index to assess the home care practices of a population. Indices will continue to be important and necessary tools for dental professionals.

KEY TERMS

Buccal— Surface of a posterior tooth closest to the cheek.

Caries— Tooth decay.

Cementum— Outer surface of the tooth root.

Disclosing agent— Tablet or liquid containing a red dye that is used to color and reveal plaque in a patient's mouth.

Distal— Surface of a tooth farthest from the midline.

Edentulous— Without teeth.

Facial— Surface of an anterior tooth closest to the lips.

Fixed bridge— Two or more prosthetic crowns covering teeth on either side of a missing tooth. A pontic, or artificial tooth, is suspended between the crowns to fill the space.

Fluorosis— Mottled discoloration of tooth enamel due to excessive systemic ingestion of fluoride during tooth development.

Hypoplasia— Incomplete or defective development of the enamel of a tooth.

Lingual— Surface of a tooth closest to the tongue.

Mandibular— Pertaining to the lower jaw.

Maxillary— Pertaining to the upper jaw.

Mesial— Surface of a tooth closest to the midline.

Papilla— Triangular pad of gum tissue filling the space between the proximal surfaces of two adjacent teeth.

Pontic— Artificial tooth suspended between two prosthetic crowns to fill a space left by a missing tooth.

Sealant— Composite resin applied to pits and fissures of teeth to prevent decay.

Sulcus— Groove between the surface of a tooth and the epithelium lining the free gingiva.

Resources

BOOKS

Collins, W.J.N., et al. A Handbook for Dental Hygienists. 4th ed. Woburn, MA: John Wright, 1999.

Wilkins, Esther M. Clinical Practice of the Dental Hygienist. 7th ed. Philadelphia: Williams and Wilkins, 1994.

ORGANIZATIONS

American Dental Association, 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. 〈http://www.ada.org〉.

OTHER

"Oral Health Methods and Indices." WHO Oral Health Country/Area Profile Programme, 1997. 〈http://www.whocollab.od.mah.se/expl/methods.html〉.