Back to Basics 1: Craniofacial growth and the pubertal growth spurt

Introduction

This is the first of a new series of blog posts. We intend to focus readers on the basics of orthodontics. This should be useful because it reminds us to remember our basic science, and we commonly forget this key area of orthodontics.  I managed to persuade Martyn Cobourne, who is Professor of Orthodontics at Kings College London (the beautiful South of England).  Martyn has a background in basic science and contemporary clinical trials.  Interestingly, we both grew up in a small village in the Worcestershire countryside.  I am a few years older than him, so our paths did not cross at school.

Craniofacial growth

There is a wide range of opinions about craniofacial growth and orthodontic treatment. We thought it might be interesting to briefly discuss the salient points – focusing on the fundamentals as concisely as possible. We realise this is a contentious subject area. However,  an overview of the essential theory might be helpful because the basic principles often get lost in the debate. These are based upon a short series currently available within the Evidence-Based Orthodontics Facebook group run by Martyn Cobourne and Andrew DiBiase.

Optimal treatment timing

In the UK, operators usually start functional appliance treatment in the late mixed dentition. We, ideally, complete any sagittal correction. Then allow settling before we do a phase of fixed appliance treatment coinciding with the establishment of the early permanent dentition. There is generally not much attempt to predict the growth status of these patients. As a result, they are usually started based on age and dental development (the more dentally advanced they are and the younger they are – the better). Still, we are aware that globally, many orthodontists believe that coinciding functional appliance treatment with the pubertal growth spurt yields better results. Therefore, they attempt to predict optimal timing.

There are 3 main aspects to this subject area:

1. Do the jaws grow more rapidly during the growth spurt?
2. Can we reliably predict the growth spurt if they do?
3. If we can predict it, do you get better results if you coincide your functional appliance treatment with the growth spurt?

This is a lot for one blog, so we thought it best to start with (1) and discuss (2) and (3) over the coming weeks.

Jaw growth during the growth spurt

We generally recognise that the facial region demonstrates variation in growth rates during development. In particular, the mandible can exhibit rapid growth in and around the pubertal growth spurt.

Several classic craniofacial growth studies have suggested that multiple linear dimensions in the cranial base and face undergo an increase in growth velocity during this time. Some of these measurements relate to maxillary and mandibular unit lengths. Naturally,  there has been considerable focus on the mandible. In addition, data from the Denver Child Research Council (Nanda, 1955), King’s College Hospital (Bhatia and Leighton, 1993), and Copenhagen growth studies (Björk, 1963; 1966), to name but a few, have suggested that facial growth can peak during the pubertal growth spurt.

Prediction?

This has encouraged some orthodontists to enthusiastically embrace the prediction of the pubertal growth spurt as part of their routine clinical practice – particularly for managing class II cases. However, it hasn’t proved easy to establish a precise correlation between condylar and somatic growth (Patcas et al., 2016). Indeed, some studies have found little or no correlation between standing height and mandibular growth (Bishara et al., 1981). Furthermore, the subject area is complicated by multiple issues relating to the methodology underlying some of these studies and the differences that have been found.

Points to remember

So, it is not necessarily that simple, and it is helpful to remember a few other points about facial growth and the growth spurt:

• Most data relating a peak in mandibular growth to peak height velocity are based upon relatively small samples of individuals derived from more extensive growth studies;
• Measuring conveniently identifiable linear distances on cephalometric radiographs is not wholly representative of the actual changes that take place with facial growth;
• Neither the maxilla nor the mandible grows in a simple linear direction, they have been shown to rotate, and the degree of rotation varies widely between individuals. These effects are not generally taken into account when correlating the linear growth velocity of the jaws with height, and this introduces inaccuracy (Hagg and Attström, 1992);
• Wide individual variation in the timing of growth exists amongst individuals. This compromises the relevance of calculated average changes from a sample and questions the validity of retrospective data;
• An exact correlation between peak height velocity and change in facial dimensions is lacking; indeed, peak change in facial dimensions may potentially lag peak height velocity (which might be a good thing?)
• Craniofacial growth does also continue beyond the period of peak height velocity.

Some food for thought – In the next “back to basics” post, we will discuss how successfully we can predict the pubertal growth spurt with the tools that we have at our disposal.