International Journal of Medical Dentistry 155 HYPODONTIA OF PERMANENT TEETH IN A GROUP OF YOUNG PATIENTS FROM THE NORTH‑EASTERN REGION OF ROMANIA Abstract The present study deals with the statistical evaluation of the number of congenitally missing teeth, of the affected dental groups, of the clinical forms and of hypodontia topography, performed on a group of patients from the North‑Eastern region of Romania, examined in the Ambu‑ latory of the “Sf. Spiridon” Universitary Emergency Hos‑ pital of Iaşi, between 1990‑2012. 111 patients (51 boys and 60 girls), with ages between 5 and 28 years, have been dia‑ gnosed with hypodontia of the permanent teeth (third molars excepted), by interview and by clinical and orto‑ pantomographic examinations. Statistical analysis made use of a SPSS 20.0 software. Four categories of hypodontia were discovered on the congenitally missing teeth, a high prevalence of the premolar (mandibular and maxillary) and maxillary incisor groups, as well as the predominant presence of the mono‑ and unidental clinical forms of hypodontia. Hypodontia was localized both unilaterally and bilaterally, on the four dental quadrants. Statistically signiicant correlations have been established among the number of teeth, the dental groups with agenesis and the clinical forms of hypodontia (p=0.000). Keywords: agenesis, hypodontia, orthopantomography, bootstrapping method, Chi‑square test. INTRODUCTION Development of human dentition is a complex process, initiated very early, in the prenatal period, through cell proliferation from the oral epidermis and the subadjacent mezenchyma derived from the cells of the neural crest [1–3]. Regulation of the dental pattern is generated by the combined expression of the HOX genes from the mezenchyma of the neural crest cells [4,5]. Genetic studies attempted at explaining the mutation of the genes involved in dental agen‑ esis, yet no unanimoulsy‑accepted conclusion could be reached [6,7]. Mutation of Msx1, Msx2 and Pax9 genes was associated to agenesis, as well as to other congenital anomalies [8,9]. HYPODONTIA OF PERMANENT TEETH IN A GROUP OF YOUNG PATIENTS FROM THE NORTH‑EASTERN REGION OF ROMANIA Georgeta ZEGAN 1 , Cristina Gena DASCĂLU 2 , R.B. MAVRU 3 1. Assist. Prof., PhD, Dept. Orthodontics, Faculty of Dental Medicine, “Grigore T. Popa” UMPh of Iasi, Romania 2. Lecturer, PhD, Dept. Preventive Medicine and Interdisciplinarity, Faculty of Dental Medicine, ”Grigore T. Popa” UMPh of Iasi, Romania 3. PhD student, Dept. Pedodontics, Faculty of Dental Medicine, “Grigore T. Popa” UMPh of Iasi, Romania Contact person: Georgeta Zegan – georgetazegan@yahoo.com The literature provides several terms for this dental anomaly. Agenesis represents the absence of all dental buds. Anodontia represents the con‑ genital absence of all teeth. Oligodontia repre‑ sents the congenital absence of more than 6 teeth. Hypodontia represents the congenital absence of 1–6 teeth (third molars excepted) [10,11]. Populational studies on the normal evolution of human permanent dentition considered hypo‑ dontia as the most common development anom‑ aly. According to the population under study, the global prevalence reported for hypodontia was between 2.6–11.3% [12,13], while the value recorded for the European population ranged between 4.6 and 6.3% [14]. The variable expression of hypodontia in dif‑ ferent populations generated two questions on its genetic origin – still not elucidated – and on the normal numeric evolution of human perma‑ nent dentition, as a relection of the contempo‑ rary world. In this respect, the present investigation aims at elucidating the statistical aspects of permanent teeth hypodontia, with the exception of third molars, on a group of young patients from the North‑Eastern region of Roma‑ nia. Hypodontia is evaluated by the parameters which deine the number of congenitally missing teeth, the affected dental groups, the clinical forms and the topography on groups of patients and also on sexes, comparatively with previous studies performed on other populations. MATERIALS AND METHOD The experimental group was formed of 111 patients with ages between 5 and 28 years (mean Orthodontics