This is the first study providing epidemiologic data on occlusal characteristics of preschool children in Greece. Thus, it is useful in understanding normal occlusion and various types of malocclusion of the primary dentition of Greek children. Moreover, results on occlusion combined with the results on children’s non-nutritive oral habits, may support the development of effective primary and secondary prevention programs to achieve the goal of occlusal harmony and function in the permanent dentition.
Our results presented no sex differences in either the sagittal relationships of second primary molars and primary canines, or overjet, overbite, crossbite and spacing in accordance with previous studies [15–17]. The present study showed that the majority of the children in the sample (44.8%) had a bilateral ‘flush terminal plane’ molar relationship, an observation consistent with that reported in several other populations [1, 18, 19]. However, much higher percentages have also been reported [5]. In our study population, bilateral mesial and distal step molar relationship present almost equal percentages in accordance with previous studies [4], while in other populations mesial step is reported in much higher percentages than distal step [16, 17, 20], and even predominate in several other studies [16, 21]. Such differences between populations may be attributed to ethnic predilection, as has been previously suggested [22, 23].
52% of children in our study, had a bilateral Class I canine relationship while almost 20% presented asymmetry, in accordance with the studies of Bervian at al [1] and Abu Alhaija and Qudeimat [16], in Brazilian and Jordanian schoolchildren respectively. Nevertheless, most previous studies reported higher prevalence of Class I canine relationship at least over 75% [4, 18, 19, 24].
Discussing other occlusal parameters, the prevalence of increased overjet was found to be 37.8% rather higher than what previous studies reported [4, 16, 18, 19]. Moreover, increased overbite has also been detected in high prevalence (40%) in our study population in accordance with the study of Talebi et al [24], while other studies reported lower prevalence of increased overbite [4, 18]. Both observations may be attributed to different methodology since in our study increased overjet was defined as over 2mm while in the other studies over 3mm.The anterior crossbite prevalence in the present study was found to be 4.8% much higher than previously reported in other study populations [4, 18, 19]. Regarding posterior crossbite, 8.8% of children presented a unilateral posterior crossbite while 1.2% of them on both sides. Results on posterior crossbite in other populations vary from zero to 13% [4, 7, 16, 18, 23].
Spacing in the present study was reported in 71% and 56.4% of the children, for the maxilla and mandible respectively. In more detail, 56.2% of children presented spacing in both arches. Our results coincide with the results of Hegde et al [19], while other studies reported higher prevalence of spacing [7, 16].
Malocclusion is a developmental condition. In most of the cases it is caused by moderate distortions of normal development and it results through a complex interaction among multiple factors that influence growth and development [25]. Transition to discrepancies from primary to permanent dentition has led to an increased awareness of the role of primary dentition characteristics in the establishment of permanent occlusion (Khan). Regarding Greek population, recent published data [26] regarding 12- and 15-years-old children, acquired in the same National Pathfinder survey of 2014, revealed a high prevalence of increased overjet (41.5% and 30.3% for 12- and 15-years old respectively) and overbite (48% and 33.2% for 12- and 15-years old respectively) as well, in accordance with our results for 5-years old children, a finding maybe indicating a prevalent occlusion pattern for Greek children. Another finding is that about 50% of 12-years-old were recorded with a class I Angle classification in Mylopoulou study [26] which is in accordance with our results where over 60% of children demonstrated a flush terminal plane or a bilateral mesial step for second primary molars and also over 50% of them, a class I primary canine relationship which consist favorable characteristics to develop a class I relation in permanent occlusion [2, 3].
Sucking behaviors are considered normal in infants and young children and derive mainly from the physiologic need for nutrients. They include nutritive sucking behaviors, consisting of breast- and bottle-feeding, and non-nutritive sucking, such as pacifier or finger sucking. Although such behaviors are considered normal in infants, the longer duration of the habit is associated to certain consequences on occlusion characteristics [27]. In the primary dentition, pacifier and digit sucking both present varying risks of developing features of malocclusions. In our study the prevalence of finger sucking and use of pacifier was 8.4% and 3.5% respectively, independent of gender, in a relevant agreement with equivalent studies in other populations [27, 28]. Moreover, we observed a correlation between father and mother educational level and prolonged use of pacifier. There is limited published research regarding who and what influences a mother’s decision to give a pacifier to her child but the association between lower mother education level and pacifier use is supported by previous studies [29, 30]. The above arise the need for better comprehension of the etiology of finger sucking and prolonged use of pacifiers through well designed studies. Moreover, educational programs and support for parents are necessary to diminish the side effects of such behaviors. Several studies have reported the association between non-nutritive oral habits and malocclusion, although most of them associated habits to malocclusions on mixed or permanent dentitions. Our results indicated that finger sucking and the use of pacifier significantly increased bilateral distal step molar relationship and open bite, while finger sucking also significantly increased Class II canine relationship and overjet, in accordance with previous studies [8–10, 31].