The OHI was developed to measure :
The Oral Hygiene Index (OHI) was developed in 1960 by John C. Greene and Jack R. Vermillion to classify and assess oral hygiene status. 
This index was developed to study variations in gingival inflammation in relation to the degree of mental retardation in children. It was depicted as a sensitive, simple and rapid method for assessing group or individual oral hygiene quantitatively. 
The papillary - marginal - attachment index (PMA index) was developed by Maury Massler and Schour I. in 1944. 
The basic philosophy used in the development of the PMA index was very similar to the DMF index, i.e, the number of gingival units affected were counted rather than the severity of the inflammation. 
The Marginal Line Calculus Index (MLCI) was developed by Muhlemann H.R. and Villa R in 1967. MLCI, is another index that is frequently used in short-term clinical trials (i.e less than 6 weeks) of anticalculus agents. 
This index was developed to assess the accumulation of supra gingival calculus on the gingival third of the tooth or, more specifically, supragingival calculus along the margin of the gingiva. 
The Glass Index system was developed by Glass R.L. in 1965. This index assesses the presence and extent of debris accumulation, for evaluating tooth-brushing efficacy.
The variations in gingival inflammation in relation to the degree of mental retardation in children.
The number of gingival units affected rather than the severity of the inflammation.
The accumulation of supra gingival calculus on the gingival third of the tooth or, more specifically, supragingival calculus along the margin of the gingiva.
The presence and extent of debris accumulation, for evaluating tooth-brushing efficacy.