In a retrospective multicentre study, the success rate and efficiency of activator treatment were analysed. All patients from two University clinics (Giessen, Germany and Berne, Switzerland) that fulfilled the selection criteria (Class II division 1 malocclusion, activator treatment, no aplasia, no extraction of permanent teeth, no syndromes, no previous orthodontic treatment except transverse maxillary expansion, full available records) were included in the study. The subject material amounted to 222 patients with a mean age of 10.6 years. Patient records, lateral head films, and dental casts were evaluated. Treatment was classified as successful if the molar relationship improved by at least half to three-fourths cusp width depending on whether or not the leeway space was used during treatment. Group comparisons were carried out using Wilcoxon two-sample and Kruskal-Wallis tests. For discrete data, chi-square analysis was used and Fisher's exact test when the sample size was small. Stepwise logistic regression was also employed. The success rate was 64 per cent in Giessen and 66 per cent in Berne. The only factor that significantly (P¡0:001) influenced treatment success was the level of co-operation. In approximately 27 per cent of the patients at both centres, the post-treatment occlusion was an ideal Class I. In an additional 38 per cent of the patients, marked improvements in occlusal relationships were found. In subjects with Class II division 1 malocclusions, in which orthodontic treatment is performed by means of activators, a marked improvement of the Class II dental arch relationships can be expected in approximately 65% of subjects. Activator treatment is more efficient in the late than in the early mixed dentition.

Before performing any procedure or initiating early intervention on children in lacteal dentition, it is crucial to closely investigate a few key elements of the cranial base of the child. A first step of diagnostics is needed - the classification of the dysharmony ie its squelettal and/or functional element - before we prescribe a major orthopedic treatment or just stop dysfunctions using simple functional appliances. To confront these constraints of diagnostic, a set of 243 children in the lacteal dentition was examined. Our clinical expertise made it possible to select cephalometric measurements that would be supposedly linked with the type of skeletal dysharmony (based on cranial and facial osseous landmarks located on the profile-view of a digital tele-X-ray). The occlusal classification takes into account occlusal criteria and the design of the masticatory function. Statistical analysis (namely linear discriminant analysis of cephalometric variables) indicates that in lacteal dentition, some cranial architectural features have preferred links with specific occlusions. We noticed that the amplitude of basicranial "flexure" (hence the sphenoidal angle) is influenced by the occipital remodeling: the ontogenic process of flexion of the base and the amplitude of closure of the sphenoid angle are under controlled by the remodeling of the occipital bone in three main modalities. Correlations exist between these groups and the facial equilibrium, like a forward or backward position of the chin. The important clinical deduction is that the masticatory function in lacteal dentition is organized by architectural constraints that arise from the remodeling of the cranial base; the squelettal effect of dysfunctions is certainly specific to each type of dysfunction, nonetheless it also depends on the architectural uniqueness of the cranial base.

Temporomandibular disorders are described in children from the age of 4. Their prevalence and severity increase strongly during the second decade, which corresponds to the period of orthodontic treatments. At this age the most common symptoms are joint clicking sounds (more than 70% of the cases), sometimes accompanied by episodes of intermittent locking. They would be favored by oral parafunctional activities (gum chewing, biting habits, bruxism...), ligamentous hyperlaxity and modification of the intra-articular space relations during growth. The questioning of the patient and his parents and clinical examination (muscular, articular and occlusal) are essential and very often sufficient for establishing the diagnosis. Even more than in the adult, the therapeutic attitude must rely on conservative and non-irreversible methods (explanations, suppression of the parafunctions, occlusal splints in the case of severe bruxism). These considerations are illustrated by the presentation of two representative clinical cases of temporomandibular disorders frequently encountered in children and adolescents.

The debate concerning the optimal timing for beginning treatment of maxillo-facial dysmorphia is far from over. The possible choices are very early treatment in the primary dentition, early treatment only during a period of time when the mixed dentition is stable or waiting until complete adult dentition is present, at the end of, or close to the end of, the growth period. Opting for early treatment is problematic because it is difficult to make a very early diagnosis (and sometimes impossible to make when there are no strong developmental signs for dysmorphia present), long-term prognosis can always be inaccurate, patients may not yet be psychologically mature enough, there is insufficient anchorage available, ultimately a two-stage treatment is required and hence a longer process, the feeling that this is "experimental therapy", that, in case of failure, leads to disappointment and a loss of confidence. Opting for later treatment reassures both orthodontist and patient; however, these delayed treatments might represent a lost opportunity for some patients who must a priori undergo more extractions and additional surgical procedures. The presentation of a case of hyperdivergent class III occlusion, where the orthodontist hesitates to treat at various stages of growth, and finally ends up performing a late surgical treatment, illustrates quite well the problem we face in choosing a timeframe for treatment.

After a first article [5] written to present the published evidence based facts concerning early treatment of class III malocclusions, the authors present, in this second article, their reasons why they think our routine early treatment of these dysmorphia is useful. When orthodontists clearly present all the elements involved in this therapeutic choice to patients and their parents, they usually decide on early treatment. A clear time frame and simple therapeutic procedures that young patients accept easily, makes it possible to achieve significantly good results. This approach requires the cooperation of the children and their parents and beyond the orthodontic sphere, of pediatricians and otolaryngologists. They will use three clinical cases to illustrate the therapeutic concepts that support their opinions.

The goal of this article is to present some evidence based facts in order to answer the following questions: 1) Is early treatment of class III malocclusions effective? 2) Which therapeutic device is the most effective? 3) Are the results lasting? The positions of Jean Delaire and the author regarding the usefulness of routine early treatment for these dysmorphia will be discussed in a second article [4].

Should treatment of a Class II div. 1 malocclusion begin in the early, in mixed dentition or later in the adolescent dentition? In a Cochrane review, the authors conclude: "The evidence suggests that providing early orthodontic treatment for children with prominent upper front teeth is no more effective than providing one course of orthodontic treatment when the child is in early adolescence." So, should you wait to treat ? Certainly not ! Many arguments in favor of early treatment are: reduction of the risk of fracture of prominent incisors, esthetic factors, increase in patient self-esteem and reduction of negative social experiences, reduction of the length of fixed appliance therapy thereby reducing possible iatrogenic effects, creating an environment more favorable to harmonious growth and development, without forgetting the legal concept of loss of opportunity. These elements will be developed in a literature review and illustrated by a clinical case.

Chance is the probability that a particular event may or may not occur and, in this sense, a loss of chance∗∗ can be defined as the missed opportunities resulting from the loss of the possibility that a favorable event will occur (a contrario, the failure to take risks)∗∗∗. This is a self-imposed liability that should be distinguished from the final damage. Moral damage is a notion that is very close to loss of chance although it is based on indemnification from the final damage of an affliction or malady.