Text versus Numerical Methods to Describe Periodontal Health Status
by John Martin, D.D.S.
Periodontal health status can be described using one of the following five diagnoses, listed in order of increasing disease severity:
These diagnoses assume that a single entity, like a tooth, quadrant or mouth is being described. Generally a periodontal diagnosis describes the condition of the mouth using a quadrant as the basic diagnostic unit. Four quadrants allow the concept of extent of disease to be used along with severity. Disease extent is based on the number of quadrants affected. The terms localized and generalized are used to describe disease extent. For example 1 and 2 quadrants are classified as localized and 3 and 4 quadrants are classified as generalized. Combining 5 stages of disease severity with 2 categories of disease extent gives 9 unique descriptions. (Localized health is not possible.)
These 9 text descriptions are too few to adequately describe the diagnosis for a 4quadrant mouth as there are 625 diagnostic combinations using 5 diagnoses for 4 quadrants. This number is arrived at by multiplying 5, the number of possible diagnoses for each quadrant, by 5 by 5 by 5, (5 x 5 x 5 x 5 = 625). One possible situation is 1 quadrant has gingivitis, 1 has beginning periodontitis, 1 has moderate periodontitis, and 1 has severe periodontitis. While a text description is possible, it is too long to be useful. 625 diagnostic combinations is a worst case example as the calculation assumes that the order of diagnoses is important. To describe this effect assume that the diagnosis for the mouth is determined by the diagnosis for the lower jaw and the upper jaw. The tables below use H to designate health, G for gingivitis, B for beginning periodontitis, M for moderate periodontitis, and S for severe periodontitis.

Upper jaw diagnosis

H

G

B

M

S

Lower
jaw
diagnosis

H

HH

HG

HB

HM

HS

G

GH

GG

GB

GM

GS

B

BM

BG

BB

BM

BS

M

MH

MG

MB

MM

MS

S

SH

SG

SB

SM

SS

This example results in 25 combinations. But it assumes that the order of diagnosis for each jaw is important. By eliminating this restriction the number of combinations is reduced to 15, identified by the grey background.

Upper jaw diagnosis

H

G

B

M

S

Lower
jaw
diagnosis

H

HH

HG

HB

HM

HS

G

GH

GG

GB

GM

GS

B

BH

BG

BB

BM

BS

M

MH

MG

MB

MM

MS

S

SH

SG

SB

SM

SS

These 15 combinations can be correlated with the following text descriptions:
HH Health
HG Localized gingivitis
HB Localized beginning periodontitis
HM Localized moderate periodontitis
HS Localized severe periodontitis
GG Generalized gingivitis
GB Localized gingivitis and localized beginning periodontitis
GM Localized gingivitis and localized moderate periodontitis
GS Localized gingivitis and localized severe periodontitis
BB Generalized beginning periodontitis
BM Localized beginning and localized moderate periodontitis
BS Localized beginning and localized severe periodontitis
MM Generalized moderate periodontitis
MS Localized moderate and severe periodontitis
SS Generalized severe periodontitis
Now assume that the mouth is divided into three segments. This example would require a 3dimensional cube to diagram as shown above. This is too complex to be done here. Instead this is a partial list of diagnostic combinations.
HHH
HHG
HHB
HHM
HHS
HGH
HBH
HMH
HSH
HGG
HGB
HGM
HGS
HBG and so on until all 5 x 5 x 5 = 125 combinations are listed.
Again, these represent combinations where the order is important. When the order is not important then the combinations is reduced to 35. This can be done by counting the number of segments with the same diagnosis. In this manner HBH = HHB = BHH = 2 healthy and 1 beginning periodontitis, which could be described as localized beginning periodontitis. The same text diagnosis, however, could correspond to the situations BBH = BHB = HBB = 1 healthy and 2 beginning periodontitis. Alternatively if BBH is called generalized beginning periodontitis, then this inadequately distinguishes it from BBB. Similarly there is no short and simple text description for BMS. The task of assigning text diagnoses worsens when four quadrants or six sextants are used to determine a whole mouth diagnosis, where the number of combinations is 70 and 210 respectively.
There is a solution.
It is possible to use the method of counting sextants with a specific diagnosis to generate a number and correlating this number to a score that ranges from 1 for health to 100 for the most severe and extensive disease condition. Internal consistency can be accommodated, meaning that a score of 36 corresponds to every sextant having a diagnosis of generalized moderate periodontitis, regardless of how many sextants have teeth. In other words, the patient who has only lower anterior teeth that have moderate periodontitis will have the same score of 36 as the patient who has only lower teeth with each of the 3 sextants having moderate periodontitis, and the patient who is missing the upper anterior teeth with each of the 5 sextants having moderate periodontitis.
The correlation of the numeric score with the text diagnosis groupings might seem unusual as the range is not uniform.
Score

Diagnosis Group

1

Health

23

Gingivitis

410

Beginning Periodontitis

1136

Moderate Periodontitis

37100

Severe Periodontitis

The explanation of why there is a large variance in scores for diagnosis groups can be explained by referring back to the 9item list of diagnoses for severity and extent and the lower jaw  upper jaw diagnosis example. The number of combinations, listed in the rightmost column includes in its count the most severe stage of disease. Hence GB counts as beginning periodontitis; not as gingivitis. The 15 possible combinations correlate with 9 text descriptions and 5 diagnosis groups in an unequal distribution amongst diagnostic groups.
Text

Combinations

Diagnostic
Group

# of combinations

Health

HH

Health

1

Localized gingivitis

HG

Gingivitis

2

Generalized gingivitis

GG

Localized beginning periodontitis

HB, GB

Beginning periodontitis

3

Generalized beginning periodontitis

BB

Localized moderate periodontitis

HM, GM, BM

Moderate periodontitis

4

Generalized moderate periodontitis

MM

Localized severe periodontitis

HS, GS, BS, MS

Severe periodontitis

5

Generalized severe periodontitis

SS

The unequal distribution of scores for a diagnosis group is a result of an increased number of possible combinations as disease severity increases. When 6 sextants are used the total number of combinations is 210. 126 of these have 1 or more sextants with a diagnosis of severe periodontitis, 56 have 1 or more sextants with a diagnosis of moderate periodontitis, 21 have beginning periodontitis, 6 gingivitis, and 1 health.
Seventeen text diagnoses can be correlated with the 1 to 100 score range.
Score

Diagnosis Group

Text Diagnosis

1

Health

Health

23

Gingivitis

Gingivitis

410

Beginning Periodontitis

Localized Beginning Periodontitis
Generalized Beginning Periodontitis

1136

Moderate Periodontitis

Localized Beginning and Moderate Periodontitis
Localized Moderate Periodontitis
Generalized Beginning to Moderate Periodontitis
Generalized Beginning and Localized Moderate Periodontitis
Generalized Moderate Periodontitis

37100

Severe Periodontitis

Localized Beginning and Severe Periodontitis
Localized Moderate and Severe Periodontitis
Localized Severe Periodontitis
Generalized Beginning to Severe Periodontitis
Generalized Beginning and Localized Severe Periodontitis
Generalized Moderate to Severe Periodontitis
Generalized Moderate and Localized Severe Periodontitis
Generalized Severe Periodontitis

Text descriptions for diagnosis are more complicated, less descriptive, and hence, less useful than an internally consistent numeric score. For example an improvement in health is more likely to be captured in the numeric score.
