To standardize sign language, for example in a specific country, it was necessary to set prescribed and definite guidelines to give correct meaning and interpretation to each idea. This also necessitates to preserve each idea uniformly over time for references, and there written sign language is accomplished.

This has open the way for any individual, hearing or deaf, to study and get acquainted with a recognizable sign language of his or her choice. The horizons of the deaf has expanded in that it become possible to study in subjects previously closed for there was no effective medium to convey the vast information collected in the past of such subject and the deaf was mostly excluded from practice e.g. dentistry.

To be able in a complex subject, to compete on the open market therefore the Deaf also had to be able to adjust to its hearing clientèle, for only to rely on Deaf customers are not always preferable. Deaf dentists need other forms of expression to communicate with hearing patients who does not sign. Normally, personnel (dental assistants) may interpret although I could never understand why a patient had to speak with his mouth full of equipment. :)

Whether under normal circumstances, on the market plain using written sign language in ones dealings is debatable, but surely to study sign language, text is necessary. Those who have used sign language over many years as their only means of communication tend to write sign as second nature.