Development and growth of the facial skeleton in individual skeletal classes in the human population. Literature review

Studies regarding development of the facial skeleton and understanding of morphogenetic background of various types of skeletal classes are important not only from a cognitive point of view, but also from a clinical one, in relation to treatment of patients according to a personal phenotype.

Introduction
This paper aimed to present a review of literature regarding development and growth of the facial skeleton in the aspect of skeletal classes.

Material and methods
A review of the literature from the years 2001–2016 was conducted using the PubMed database. Key words used to search for articles included: skeletal class development, skeletal class malocclusion development. Inclusion criteria were based on selection of original papers regarding development and growth of facial skeleton in the prenatal and postnatal period. Exclusion criteria included review papers and case reports.

Results
Articles selected based on inclusion criteria indicate there are many reasons affecting a direction of morphogenesis of the facial skeleton and mutual correlations during development. It is possible to understand these processes as a result of distinguishing between growth and physical development in the prenatal and postnatal period. Important factors present in the prenatal period include, among others, the following: interactions of the Frontonasal Ectodermal Zone, shh proteins, fgf8 proteins and BMP signalling. Factors present in the postnatal period depend on structural, functional, anatomical, genetic and growth patterns interactions. The following factors affecting development of skeletal classes were analysed: sexual dimorphism, effects of masticatory muscles, permanent tooth eruption, and quality of the respiratory tract.

Conclusions
Studies regarding development of the facial skeleton and morphogenetic background of various types of skeletal classes contribute to improvement of clinical aspects of treatment, according to a personal phenotype and any dysfunctions associated with the skeletal structure.