The significant increase in the prevalence of malocclusions between the primary and mixed dentition--distoclusion and lateral crossbite, and the impairment of vertical occlusal relationships in the mixed dentition in particular--reveal the need for orthodontic prevention. They highlight the absence of applied interceptive and early treatment measures in orthodontics. The indication system in current use for early orthodontic treatment here in Germany fails to fulfill the requirements for prevention-oriented dental care.

Habitual open mouth posture (expressing hypotonia in the perioral muscles) and a visceral swallowing pattern become established during the primary dentition and are increasingly carried over into the mixed dentition period. Both criteria, along with assessment of occlusal relationships, are appropriate parameters with which to identify "children at risk for orthodontic treatment".

The need for preventive orthodontic therapy and for the intensified application of interceptive and early treatment measures is stressed in view of the high number of malalignments and malocclusions in the deciduous and mixed dentition and the tendency for some forms of malocclusion to deteriorate as the dentition develops.

The purpose of this epidemiological cross-sectional study was to determine the prevalence of malocclusion and caries in children and to investigate whether a relationship exists between prevalence of caries and studied malocclusion. The study consisted of 8,864 preschool and schoolchildren with primary dentitions (mean age 4.5 years) and mixed dentitions (mean age 8.9 years). 1997 WHO dental caries criteria were applied to both groups. The existence of an increased caries risk was deducted from the dmft and DMFT indices related to age. Malocclusion in primary and mixed dentitions was classified into seven types. Fifty-seven percent of all children had some form of malocclusion. Prevalence of malocclusion increased and was significantly greater in the mixed dentition sample (p < 0.001) than in the primary dentition sample. Seventy-four percent of children with primary dentitions and 23% of children with mixed dentitions had zero dmft and DMFT scores. Mean dmft indices in subjects with primary and mixed dentitions were 1.02 and 1.53, respectively. No positive correlation between prevalence of caries and malocclusion could be established in the sub sample with primary teeth only. However, statistically significant parallelism in prevalence of malocclusion and caries were found for posterior cross-bite (p= 0.050) and mandibular overjet (p= 0.013) in children with mixed dentitions.

These findings support the hypothesis that clefting is part of a complex malformation associated with other dental anomalies resulting from disturbed development of the dentition. Patients with clefts are also likely to present other deficiencies of dental development and tooth eruption in both dentitions, even in regions not affected by the cleft.

Our results enable us to prognosticate which children risk future orthodontic problems. Any child presenting one of the four occlusal disorders plus one static or two dynamic dysfunctions is a child more likely to develop orthodontic problems later on. Orthodontic prevention and early treatment must include functional rehabilitation so as to eliminate or at least diminish those factors causing undesirable developments.

These findings support the hypothesis that clefting is part of a complex malformation associated with other dental anomalies resulting from disturbed development of the dentition. Patients with clefts are also likely to present other deficiencies of dental development and tooth eruption in both dentitions, even in regions not affected by the cleft.

Delayed eruption and false direction of eruption of the upper 6-year molars may-already at an early stage-raise the likelihood of problems during later dental arch development, such as crowding in the sagittal and transverse directions or Class III developments.