epidemiology 3

7/30/2019 Epidemiology 3

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Note: this lecture includes what is mentioned in the lecture

summarized by your group and the handouts

METHODS OF MEASURING DENTAL CARIES

Dental caries = a microbial process (infection)

characterized by demineralization of inorganic matter

followed by destruction of the organic matter

If we want to measure dental caries among certain

population then we can do it in more than one way:

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1. We can measure the number of members having dental

caries and divide it by the total number of the population

studied

2. We can measure the number of decayed teeth and

divide it by the total number of teeth examined

History of dental caries measurement:

- Measurements of the intensity of dental caries in the

early 20th century by:

The proportion of first molars lost through caries

The percentage of permanent teeth affectedBoth of these methods were useful when there was little

information of any kind about the disease, but they were

not sensitive

- Bodeckers' index, described in 1931, was sensitive but

complicated

- Dean and his colleagues used a systematic approach to

counting the numbers of teeth in the mouth visibly

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affected by caries in their studies of the caries - fluoride

relationship

- The first description of what is now known as the DMF

index is usually attributed to Klein, Palmer, and Knutson

in their studies of dental caries in the 1930s

Since then, the DMF index has received practically

universal acceptance and is probably the best known of

all dental indexes

DMF INDEX:

The DMF is an irreversible index DMF index is applied only to permanent teeth

DMF index can be used for an individual or for a

population at larger

DMF index counts number of teeth in the mouth

with history of dental caries

DMF index indicates oral hygiene of the patient

D is for decayed teeth, M is teeth missing due

to caries and F is for teeth that had been previously

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filled assuming that these filled teeth were carious

prior to restoration

DMF index counts teeth missing as missing

due to caries although they might be missing for

something else other than caries such as trauma,

periodontal disease, developmental anomaly and

this overestimates the caries risk of the

individual

DMF index counts teeth filled as being filled

due to caries although they might be filled just for

cosmetic reasons or for prevention and this again

overestimates the caries risk of the individual

The DMF score for any one individual can range

from 0 to 32

The DMF score for one individual is expressed in

whole number integral number "

"

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A mean DMF score for a group is

calculated by dividing the total of individual values by

the number of subjects examined

DMF score mean of a group can have

fractional values

The DMF index applied towhole teeth

is

designated as (DMFT)

The DMF index applied to surfaces of teeth is

designated as (DMFS)

We have 32 teeth, each has 5 surfaces, so 32 teeth

have 160 surfaces

DMFT counts one tooth as one surface BUT

DMFS counts one tooth as five surfaces, thus

DMFS is more sensitive than DMFT

Modifications can be made to the DMF index

to include other situations than those included already

in the index, such as: teeth that have been filled and

have redecayed secondary caries, crowned teeth,

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bridge pontics, and any other particular attribute

required for a study

To save time in a large survey, DMF can be

applied to half mouth or applied to one

quadrants and the score is doubled or multiplied

by four an approach that assumes the bilateral

nature of caries

When we have a patient with DMF of 10, then we

cant tell what has composed this 10 how many teeth

with caries?!, how many teeth missing due to caries?!,

how many teeth filled due to caries?!

We cant actually know!!

The DMF index for permanent teeth is always

signified by uppercase letters

The equivalent index for the primary dentition is

the defthat is always signified by lowercase letters

In the def, d stood for decayed teeth, e stood

for indicated for extraction, and f stood for filled

teeth

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It is def BUT NOT dmf , why?!

In the def index, teeth missing due to caries are

not recorded because of the frequent difficulty

of distinguishing between extracted primary

teeth due to caries and naturally exfoliated

primary teeth

Modifications of the def index are :

A. dmffor use in children before ages of

exfoliation before 5-6 years old it is supposed

that if any tooth is lost before normal age of teeth

exfoliation might be due to caries, and thats why

dmf is used and the letter m indicates missing due

to caries

B. dmfapplied only to the primary molar teeth

primary molar teeth usually last very long in the arch

before exfoliation, so if they are lost sooner than

normal, it is supposed that they are lost due to

caries and thats why dmf is used and the letter m

indicates missing due to caries

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C. dfindex in which missing teeth are ignored

because we are NOT sure if this missing tooth

has normally shed or lost due to caries

Values for df and defshould be numerically

the same since neither index counts missing

teeth

Both def and dfmay therefore underestimate

the true extent of the carious attackalthough

sometimes ignoring missing teeth is often seen

as a net benefit

Grainger's hierarchy = an ordinal scale

designed to simplify the recording of the caries

status of a population

This scale which uses five zones of severity of the

carious attack

It has been shown to be valid, but has received little

further use, probably because oflow sensitivity

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Limitation of the DMF index

No index is perfect and even the DMF index has its

limitations. The principal ones are these:

1. DMF values are NOT related to the

number of teeth at risk

A DMF score for an individual is a simple count of

those teeth that in the examiner's judgment

have been affected by caries and it has nodenominator

A DMF score thus does not directly give an

indication of the intensity of the attack in

any one individual

- DMF score of 3.0

Without knowing the age of the patient

and the total number of teeth this patient has

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we may think that this DMF value is small and

not important

If this patient is 7 years old only and has 9

permanent teeth in the mouth then this DMF

value indicates that one third of these teeth

have already been attacked by caries in a short

space of time

- DMF score of 8.0

If this patient is 30 years old and has a full

set of 32 teeth then this DMF value indicates

that one quarter of the teeth have been

affected over a longer period of time

DMF scores therefore have little meaning

unless age and total number of teeth at risk

is also stated

2. The DMF index can be invalid in older

adults because teeth can become lost for

reasons other than caries

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Although caries appears to be the greatest single

global reason for tooth loss, many teeth are also

extracted for other reasons

This is especially the case in adults aged 60 or

older, among whom the M component of a DMF

score is NOT a valid reflection of teeth lost

because of caries

3. The DMF index can be misleading in

children whose teeth have been extracted for

orthodontic reasons

In some child populations there is heavy loss of

premolars in the course of orthodontic

treatment

In young adults population there is heavy

extraction of 3rd molars especially if they are

symptomatic

The inclusion of these teeth in the M

component of the DMF score would obviously

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be invalid reflection of teeth lost because of

caries

4. The DMF index can overestimate caries

experience in teeth with "preventive

restorations" or where treatment services

are intense

Some dentists place restorations in teeth that are

not carious yet but they think they might get

carious in the future

In an epidemiological survey, such teeth must be

included in the F component of DMF although

they had not been filled due to caries and so DMF

scores will be overestimating the condition

5. DMF can NOT be used for root caries

Root cariesbegin below the cementoenamel

junction following recession of the gingivae

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Root caries needs to be measured separately

from coronal caries for two reasons:

a. Root caries occurs at a different period of life

from most coronal caries

b.Teeth with root lesions often already have

coronal lesions

The intensity of root caries is measured by dividing

the number of lesions already present by the

number of root surfaces at riskroot surfaces

exposed to the oral environment and might get

carious in the future, rather than using the

number of teeth present

6. DMF can NOT account for sealed teeth

Sealants and composite restorations for

cosmetic reasons are not included in the

description of the index

Sealants and other composite restorations

for cosmetic purposes have to be dealt with

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separately and to be placed in a category by

themselves

Criteria for Diagnosing Coronal Caries

There are NO globally accepted criteria for

diagnosing dental caries

There is a tradition about defining the carious

lesion in the gray area when it is difficult to tell

whether the disease is irreversibly established or not

It is known that by the time caries can be

clinically detected by either visual orradiographic methods, a lesion is histologically

well established

Diagnosis of a sound tooth is not difficult,

nor is diagnosis of an obvious lesion

The disease process in between requires

carefully defined criteria and an examiner who

can adhere to them during many examinations

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Criteria for diagnosis of caries used in North

America, Britain, and the other English-speaking

countries tend toward the dichotomous (yes

present/no absent") variety

Following these criteria means caries is either present

or absent theres nothing in between

Criteria for diagnosis of caries used in Europe are

much stricter in which grades of carious lesions are

diagnosed

Following these criteria means caries is subclassified

into many grades according to its extension and

severity

The European criteria should give a more

accurate estimate of disease progression, BUT:

a. Use of the European criteria requires a longer,

more meticulous survey examination and couldlead to a greater degree of examiner inconsistency

greater demands on examiner standardization

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because of the increased number of diagnostic

decisions that have to be made

b. Additional risk of inconsistency is also added if

the use of radiographs is being considered in a

caries study

Radiographs provide us with greater diagnostic

sensitivity but at the same time they need another

set of diagnostic decisions that require their own

criteria

Root Caries

DMF index is not designed for use with root

caries

Most root caries lesions occur on exposed

root surfaces after gingival rescission although

some lesions have been found on teeth withoutgingival rescission!!

The most teeth affected by gingival

rescission are:

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a. Labial surfaces of upper molars

b. Lingual surfaces of lower anterior teeth

The criteria most frequently used to diagnose root

caries were first described by Banting and his

colleagues

Criteria for diagnosing root surface caries:

1. There is a discrete , well-defined,

and discolored soft area

2. The explorer enters easily and displays

some resistance to withdrawal

3. The lesion is located either at the

cementoenamel junction or wholly on the root

surface

4. Restored root lesions are counted only if

it is obvious that the lesion originates at the

cementoenamel junction or is confined to the root

surface completely

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Root lesions are becoming increasingly

difficult to detect because:

a. Root caries lesions are more commonly found

as small, discrete lesions on a single root

surface rather than circumscribing a root

b. Inability to sometimes detect the

cementoenamel junction either because of

obliteration by restorations or calculus adds to the

difficulties of identifying root caries

Root Caries Index (RCI)

This index was intended to make the simple

prevalence measures of root caries lesions more

specific by including the concept ofteeth at riskin

contrast to the DMF usage

A tooth is considered to be at risk of root

caries ifenough gingival recession has occurred

to expose part of the cemental surface to the

oral environment

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The RCI is measured by scoring root lesions and

restorations and noting teeth with gingival recession,

according to the following formula:

Root surfaces: (decayed + filled) 100Root surfaces: (decayed + filled + sound)

The index can be measured for an individual or for

a population at large

RCI of 7% means = of all teeth with gingival

recession, 7% were decayed or filled on the root

surfaces

In the RCI there is chance ofunderestimation

brought on by gingival overgrowth subsequent to

the loss of periodontal attachment

Caries Treatment Needs

Assessment of caries treatment needs byepidemiological survey seems simple enough. In fact,

it becomes more complicated because:

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1. The criteria used to diagnose caries in a survey are

not necessarily those used by practitioners when

examining their patients

2. Perceived needs, dental awareness, and ability or

willingness to pay all influence treatment carried

out

3. A practitioner has to look at a patient's long-term

needs, whereas a survey does not

4. Treatment philosophy can change quite rapidly with

expanding knowledge and technological

developments

Because surveys are usually conducted under less

than ideal conditions relative to the dental office, it

would be expected that sur veys detect fewer

treatment needs than practitioners do

Which assessment is correct? Survey or

practitioner?!

Surveys can miss incipient lesions early enamel

lesions but practitioners can also over diagnose. In

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addition, treatment plans for the same patients have

been shown to vary drastically from dentist to dentist

epidemiology 3

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