Process of Maturation and Growth

Process of maturation and growth

Prediction

Charles J. Burstone, DDS, MS

Chairman, Dept. of orthodontics, Indiana University

Presented at AAO meeting 1963

Am. J. Orthodontics, December 1963, Vol 49, no.12, p907-919

Abstract by Don McGann: 1/2011

This is a ‘must read’ article for any orthodontist and is really where the whole concept of growth prediction started. Yes, there were those before this, as you would see in the ‘reference’ section, including Nanda and Ricketts, but this presentation + article clearly lays out the issues associated with growth prediction.

The overall concepts:

some think growth can be ignored in treatment planning, just place the teeth where they belong. If favorable growth, better result. McGann: I can see this especially in a group of general dentists.
Dramatic changes between the maxilla and mandible can happen during treatment as the skull enlarges.
Mandibular growth occurs horizontally at a faster rate than the maxilla, this differential improves treatment of class II division 1 cases and improves the profile.
The horizontal growth improves the profile, reducing facial convexity as the mandible grows faster than the maxilla.
Reduction in the deep overbite is from the vertical mandibular growth.
Reduction in the class II results from the horizontal differential of maxilla vs. mandible rather than tooth movement itself.
The diagrams below are commonly seen in the treatment during periods of growth.

The orthodontist would like to know how much of these changes are due to growth, but this is difficult due to the wide variation between patients.
It is necessary for the orthodontist to make some kind of growth prediction before starting treatment. This is important not only in the treatment planning, but also determining the prognosis during retention and post-retention.
Every orthodontist consciously or subconsciously makes an estimate of the growth potential of a his patient.
The specialty cannot declare a moratorium on treatment until more is known about growth prediction. (McGann: nearly 50 years later, still trying to find it!!)
The starting point of a growth prediction is the normal growth process. Any prediction must consider the maturation level and the rate of maturation.

Concept of Maturation:

The level of maturation refers to the status of an individual (patient) relative to completion of growth.
The rate of growth or growth velocity is measured in millimeters or degrees per year.
Prepubertal stage = 6-12 years
Pubertal stage = growth spurt, or rapid acceleration of growth
Postpubertal stage = following peak velocity, a desceleration
The optimal time for treatment is logically the circum-pubertal growth spurt, around the time of peak velocity. This would minimize the amount of tooth movement to correct class II (disto-occlusion) or deep bite.
There are other reasons than peak growth to consider when evaluating the best time to start treatment.
Then an estimation of growth after treatment is important to determine the prognosis. For example, a class III case completed before peak velocity will have a poor prognosis relative to another that was finished after the peak velocity.

Rate of Maturation

there is considerable variation in the magnitude and time of peak velocity in the population.
Average maturer: reaches peak velocity at the same time as the average is his age group
Early Maturer: reaches peak velocity at an earlier age
Late Maturer: reaches peak velocity at a later age
There are NO discrete catagories here, just a general blend.
Peak velocity of stature (height) is a guide to peak velocity of the face. This is approximately 11.5 years in girls and 14 years in boys, with a range of approximately +/-2 years. .
Chronological age is NOT a good guide.
Early maturers (height) tend to have increased RATE of growth and late maturers have decreased rates of growth at puberty.
Orthodontists have a difficult time making a determination of the level of development and the rate of maturation with less than full records of the past.

Dental Age

the correlation between dental and skeletal age is very low.
Using the time of full eruption to determine the best time to start treatment is a mistake, but of course has advantages mechanically
Eruption of the 7s before starting orthodontic treatment may also be a mistake since most of these are already past the peak velocity, especially in girls.
Treatment planning a class II correction becomes more difficult if the patient gets their teeth late…with skeletal maturation already passing before the full occlusion is present.

Skeletal age

Different bones of the body may have different rates of maturation
Skeletal age evaluated by a wrist x-ray may be one of the most useful and accurate adjucts to evaluate maturation.

Gender

Girls tend to mature earlier than boys
Girls typically have a peak velocity 2 years before the boys.
The magnitude of the peak velocity is much greater in boys than girls
A boy teenager will show more favorable response to class II treatment than the typical girl teenager.
It may be better to start ortho treatment earlier on girls than boys. But NOT all treatment of boys need to wait until peak velocity.

Sexual Development

It is important to recognize and understand the changes associated with puberty, as this relates to the stage of maturation and optimal time to start treatment
Rapid changes in stature (height)
Mandible is rapidly increasing in size
Male: voice and beard changes, but these are difficult to evaluate
Female: breast changes signal changes in the reproductive system.
Development of these secondary sex characteristics generally means the peak velocity at puberty has passed.
Female time of Menarche is very important. Early maturers start menarche earlier than late maturers, but notice that all are on the descending slope of the growth curve. The early maturer will experience more growth before menarche than the late maturer.

Body Type

generally girls and boys that are particularly tall for their age are early maturers and those that are short for their age or late maturers

Height and Facial growth

Peak velocity of height and facial growth come at nearly the same time (according to Nanda)
Information of height changes is helpful in predicting when the peak velocity is coming. The family commonly keeps these records, or even the schools. Most important is the ‘rate’ of growth, changes between 2 time periods

Genetic factors:

There is a strong genetic basis for the morphology of the bones of the skull
With Height, there is a similar tendency between siblings and parents of the SAME sex.
Observation of family members may give a hint of the rate of maturation coming for a starting orthodontic patient.

Discussion

cephalometric analysis is ONLY meaningful if they are correlated with the overall physiologic changes occurring in the child.
The orthodontist not only needs to measure the head, but also look at the entire body.

McGann commentary,

This paper and presentation in 1963, nearly 50 years ago, is often cited as the start of growth prediction, the foundation. I can see this as Burstone clearly states what a growth prediction is, how it can be used, and the various other factors that influence a prediction. It is the starting point, and this is why every graduate student studying to be an orthodontist will have this paper on their “reading list”.

This shows you the basis for the orthodontist ‘secret’ understanding of growth that the general dentists ignore. Therefore this paper, or at least my abstract summary, needs to be read and applied by every POS student studying to compete on the same level as the specialist.

Burstone states EXACTLY what I am proposing with “differential horizontal growth”. The concept Is NOT knew and unknown, as this proves that it has been known since at least 1963. What is new is the A point overlay, defining what actually happened between the maxilla and mandible in finished cases, forming the basis to predict this difference.

When should we be taking a hand-wrist x-ray? Evaluating the ranges of maturation, Girls age 10-13 years and boys 12-15 should get a wrist x-ray to help us to better define the stage of maturation (stage 2-3-4). Keep in mind that some object to the additional radiation, and so the benefit should outweigh the risks.

Burstone lays out the reasoning for a growth prediction system, telling us why McGann is asking you to measure the height of growing patients, take wrist x-rays, and have a growth interview to determine the stage of growth, especially if you are adding growth to your diagnosis (correction of class II).

In regards to genetic factors, it is generally believed, and I believe it also, that the mandible is genetically determined. McGann noticed that the upper teeth must follow the growth of the mandible, generally keeping the teeth together in the same relationship as the mandible grows more than the maxilla. Otherwise all class I cases would become class III.

Study this, learn it, and break out into the lead.