The aims of the study are as following : First, define and clarify the role and function of the dental hygienist. Second, based on thai definition, present an improved dental hygienist curriculum, improving their special competence. This study seeks to present a way for promoting role of dental hygienists as independent specialists, rather than as auxiliaries, contributing to better dental service in the process. The research was pursued by surveying by questionnaire those directly related to dental hygiene. They are 58 professors of dental hygiene, 164 dentists, 253 dental hygienists and 496 dental hygiene students, selected by the method of simple random sampling. Due to the small size of the sample, professors' group was analysed only through frequency and probabilities. For groups with larger samples(dentists, dental hygienists, dental hygiene students), methods of chi square(${\chi}^2$) tests, frequency analysis and one-way ANOVA were used in their analysis. Conclusions of the study are as following : First, role and function of the dental hygienist was defined and clarified. According to the analysis of the survey, main role of the dental hygienists as perceived by 62.9% of dentists was supporting treatments and managing patients and facility. This perception by dentists differs significantly to perception of other groups, which saw main role of dental hygienists as preventive dental treatment and dental hygiene education. Also, only 20.2% of dental hygienists perceived patients and facility management as their main role. This divergence of perception between groups weakens speciality competence of dental hygienists. To strengthen dental hygienists' speciality competence, preventive dental treatment and dental hygiene education must be defined as main role of dental hygienists. Furthermore, role of dental hygienists can be categorized into cooperative and auxiliary role. Second, in order to strengthen speciality competence of dental hygienists, their education must be augmented with curriculum emphasizing cooperative role. Specifically, courses on preventive dental treatment, dental hygiene education and dental X-ray photography must become compulsory, as well as becoming more comprehensive and organized. Also, training in schools and hospitals must be focused on those subjects. In addition, courses concerning auxiliary role must be incorporated into optional courses and more pedagogical courses are needed to widen students' career choices. Third, practical relevance of national dental hygienist certification examination must be heightened. In the survey, all groups gave negative response to questions concerning practical relevance of national dental hygienist certification test. Specifically, contents of the tests must be changed to test participants' competence in the cooperative area. Also, the test itself must be strengthened by adding practical examination to the certification scheme, as well as having more difficult examinations.