Developmental dental hard tissues disorders are rarely diagnosed both in children and adults, and their treatment is a problem for dentist. Despite the fact that molecular genetics studies allow to discriminate some dentine disorders, pathogenesis of radicular dentin dysplasia is still obscure. Type I dentin dysplasia is characterized by normal or slightly coloured crowns with no roots or only rudimentary roots, reduced pulp space in permanent teeth and incomplete or total obliteration of the pulp chambers, and periapical radiolucent areas or cysts which might result in premature loss of tooth. Fortunately, teeth demonstrate higher resistance to caries than normal teeth do.
 Dentin dysplasia type II is characterized by yellow, brown, grey, translucent primary teeth with complete pulpal obliteration. Permanent teeth are normal or might be slightly coloured. Roots are normal in size, but pulp chamber has pulp stones. A third type of dentine dysplasia or focal odontoblastic dysplasia has radiographic aspects of the other two types of disease.
 Also dentine dysplasia type I has subtypes Ia, Ib, Ic and Id. Dentine dysplasia Ia is characterized by complete obliteration of the pulp, disorder of root development, and many periapical radiolucent areas. A single small horizontally oriented and half-moon shaped pulp is presented in case of dentine dysplasia Ib, roots have a few millimetres length and frequent periapical radiolucencies. Dentine dysplasia Ic is characterized by the presence of two horizontal or vertical semicircle-shaped pulpal remnants which surround dentine in pulp chamber. Also teeth have shortened roots and variable periapical radiolucencies. Dentine dysplasia Id is characterized by the distinct pulp chambers with pulp stones in the coronal third of the root canal; periapical radiolucencies are possible as well. Aim of this study was to analyse clinical case of dentine dysplasia in 8,5-year-old boy.
 A 8,5-year old boy patient with parents came to a dental office due to caries cavity in tooth 62. Shape of tooth crowns was not changed and teeth with no signs of mobility; white lines and spots on teeth are were detected. Based on age, the decision of orthopantomogram was made to evaluate status of primary and permanent teeth. The image showed almost obliterated pulp chamber in both erupted and developing teeth and considerably shortened, blunted and malformed roots without a visible lumen of root canals in primary teeth. Periapical lesions were found about roots of primary molars and follicles of teeth 12 and 14 without caries lesions.
 Patient's medical history revealed no disturbance in general health. Clinical examination of the patient's mother did not show dental hard tissues disorders, but radiograph examination revealed such disorder in the orthopantomogram. Thus, history, clinical and radiographic findings revealed this case as dentine dysplasia type I subtype 1c inherited from mother.
 Oral rehabilitation of patients with dentine dysplasia type I require effective prevention and a complex approach. Thus, meticulous oral hygiene measures and dietary instructions, regular check-ups twice a year were established for this patient; orthodontic consultation was recommended. Varnish «Ftoplen-LC» was applied on the permanent teeth 3 times. To prevent early exfoliation, plan of preventive measures was developed included application of fluoride varnish twice a year and fissure sealing in the premolars in 9-10 years and in the second premolars in 12-13 years.
 Treatment of dentine dysplasia I type that depends on patient age and severity of disease may include also filling of carious teeth, orthodontic, surgical and orthodontic treatment. In this regard, dentist has to know developmental dental hard tissues disorders and select measures to prolong the retention of affected teeth maintaining them as long as possible.