Ortho module 1 Flashcards
What are the distribution measures seen in variability of growth?
The range is from smallest to the largest value
The mean is the arithmetic average
The standard deviation is calculated from a mathematical formula as a way to describe the variance within the distribution
What is the difference between growth and development?
Growth, most of the time, will refer to a change, almost always an increase, in size or number, generally with an anatomic reference. Occasionally, however, it will be used to indicate more of an increase in complexity than size.
Development will be used primarily to refer to an increase in complexity—especially when this carries with it an overtone of specialization and loss of potential.
Why should a dentist know growth/development?
2 important reasons:
It is important to know normal patterns of growth and development in order to work with children and know what changes are normal and what changes aren’t.
It is important to understand growth in order to understand how to manipulate growth to treat developmental problems in children.
What does growth pattern describe?
Growth of objects follow proportional relationship to the overall growth of a structure. (eg article of clothing becoming larger means logo grows all around in a proportional way)
What does the cephalocaudal gradient of growth describe?
The proportion of total body size contributed by the head and face steadily decreases after the 3rd month of fetal life. By the time of birth, greater growth of the trunk and limbs has reduced the head to 25% of the entire body. This pattern continues, so that the head and face contribute proportionally less and less to the total body length. This relative reduction in head and face size is because the craniofacial structures developed earlier. In later growth, structures away from the head grow more to catch up. This is called the cephalocaudal gradient of growth, and it’s an important part of the growth pattern that you need to always keep in mind.
What is the sample size effect?
Normal variation leads to a bell shaped curve in the distribution of individuals within a group. Most individuals cluster at the midpoint of the distribution and few are around the extremes. The bigger the group the more obvious the clustering near the mean.
What does it mean if there is no bell-shaped curve?
The distribution is not a normal distribution and the rules that apply to normal distributions don’t apply to this.
What is the range mean and SD?
Range is from smallest to largest value
Mean is arithmetic average
SD is calculated from mathematical formula describing the variability
What do growth charts tell us?
Growth charts, expressed in percentiles, often are used to show how a patient compares to his or her peers in height and weight, and how that changes over time.
Lines tell us the percentiles. x-axis is time and y-axis is height or weight.
What do percentiles of growth charts tell us?
Normal growth follows the percentiles consistently (a 20 percentile child may be small but if he consistently plots at 20 percentile he is healthy)
Crossing the percentiles, particularly crossing several of them, usually indicates abnormal growth and some problem. In this respect, height is a more sensitive indicator than weight.
What does timing of growth/growth spurts tell us?
Boys and girls get bigger over time, of course, but differences between individuals of the same age and gender, and differences between the sexes, are most notable near adolescence. That is because sexual maturation leads to an adolescent growth spurt. This happens at a different time in girls and boys and happens at different times in individuals of the same gender. On the average, girls have their adolescent growth spurt 2 years ahead of boys. That doesn’t mean that all girls mature faster than all boys–there’s too much individual variation for that to be true.
What does crossing the percentiles during adolescence tell us?
It shouldn’t be considered a problem especially if the plot for the early or late maturing person returns to normal.
How can biological age be measured?
It can be measured in terms of progression towards certain developmental markers.
For dentists and orthodontists, a good way to do this is to use the stages in maturation of cervical vertebrae, which are seen in the cephalometric radiographs that are obtained for most orthodontic patients.
What is used for calculation of biological age?
Many different types of maturation, not just the skeletal age calculated from vertebrae or other skeletal indicators, can be determined and quantified in biologic terms. Dentists use dental age all the time, judging the state of development of the dentition against the usual chronologic markers.
What are the types of growth data obtained?
Cross-sectional study data (groups of 9 10 11 year olds)
Longitudinal study data (Following the same individuals over a long period of time)
How can the problem of timing be avoided when measuring growth patterns?
The effect of plotting the individual data can be done with menarche as a base. Using biologic age in that way with cross-sectional data can make it easier to avoid distortions due to different timing in different individuals.
How do other transformations of data besides velocity and growth curves tell us more about foetal growth?
Various other mathematical transformations of data can make it easier to understand what is occurring during growth. In image 1, the graph showing the increase in weight of early embryos, you can see that there is an exponential acceleration in weight with increasing time.
In image 2, the same data are plotted after a logarithmic transformation. This shows a straight line, indicating that the rate of multiplication of individual cells remains almost constant. It’s not that cells are dividing faster as the embryo gets older, it’s that increasingly there are more cells to divide.
What are the 4 basic methods for measuring physical growth?
Craniometry
Anthropometry
Cephalometric radiography
3D radiography (CT)
What is craniometry?
The scientific measurement of skulls, especially in relation to craniology.
What is anthropometry?
Anthropometry refers to measurements on living individuals. Various landmarks on the skull were established by investigators studying skeletal material, and the soft tissue points overlying those landmarks (or other soft tissue points that can be found repeatedly) can be used to study living individuals.
How is anthropology done in a way to avoid reliance on cross-sectional data and instead on longitudinal data?
Varying soft tissue thickness introduces a source of error if the goal is to measure growth of the facial skeleton, but it is highly advantageous to follow the growth of an individual directly, making the same measurement repeatedly at different times
Anthropometric measurements are still important in clinical examination of orthodontic patients. They are used now primarily to establish facial proportions–which are important in planning orthodontic treatment.
What is cephamometric radiology?
The third important measurement technique is cephalometric radiology. Using x-ray pictures of the head and face provides a way to combine the advantages of crainometry and anthropometry.
It allows direct measurement of the skeleton because the soft tissue thickness can be ignored—but the soft tissues also are imaged and can be measured if desired.
Proper positioning of the subject in a head holder is necessary, so that repeated x-rays can be made with the head positioned exactly the same. This allows longitudinal study of growth (or treatment) changes in an individual.
What are the disadvantages of using cephalometric radiology?
Exposure to X-rays is required
2D image instead of 3D
Some measurements are not possible and others distorted
What are the advantages to cephalometric images?
Cephalometric radiographs give an excellent view of many skeletal and dental structures that aren’t accessible for anthropometric study,
These radiolographs are used routinely in dentistry to monitor growth and treatment of patients
What are the disadvantages of using axial CT scans for imaging?
It is expensive
It delivers a large radiation dose
How are CB-CT images used to measure changes over time?
For growth studies, images of CB-CT from before and after are superimposed.
How is superimposition of CB-CT different to cephalometric radiographs?
With cephalometric radiographs, tracings based on identification of landmarks typically are used.
That doesn’t work with 3-D images, but now it is possible to superimpose on surface contours, and changes between sequential 3-D images can be discerned by color maps. This allows you to look at the amount of change at thousands of points that can be viewed from any orientation, instead of being limited to tens of points seen from one orientation in a cephalometric radiograph.
What are the experimental methods used in the study of growth?
Vital staining
Autoradiography
Cephalometric superimposition on implants
Molecular biology
What is vital staining?
Dyes that are incorporated into bone are injected and this allows amount of growth to be seen.
It shows both the site of growth and the rate of growth. The sites of growth are the areas where new bone is being formed, or removed by the remodeling that accompanies bone growth. The rate of growth is shown by the distance between bands of color that were deposited at known times when the dye was injected.
What is autoradiography?
It is based on tissues taking their own pictures by using radioactively labelled substances.
Radioactive labels injected -> Tissue specimens prepared -> photographic film is put over the tissue and the location of these materials can be located via silver grains being activated in the film.
How is implant radiology used to visualize changes in bone structure/size?
Implant radiology is based on visualizing metal pins placed in the skeleton. Perhaps you know that when bones are fractured, metal pins often are placed to hold them while they heal, and often the pins are left in place. A long time after the fracture has healed, the pin will still be visible on x-rays as a marker of the fracture site. It is possible experimentally to place small metallic implants in bones anywhere in the skeleton, including the face and jaws, as permanent markers.
How can molecular techniques be used to analyse growth?
It also is possible to use the techniques of molecular biology to study growth, and this holds great promise for the near future. An example of such methods is diagrammed on this slide. Genetic information carried by plasmids can be injected into the nucleus of a mouse egg, which is then implanted into a pseudopregnant mouse.
Summary:
In studies of growth and development:
Growth (increase in size) and development (increase in complexity with specialization and loss of potential) are different concepts
Growth pattern refers to predictable changes in proportions with growth
Children outside the 3rd and 97th percentiles on standard growth charts may be beyond normal variation
The timing of adolescence is a major contributor to variability in growth
Biologic ages based on physiologic events can be used to reduce variation related to timing
Important measurement techniques to know:
Craniometry
Anthropometry
Cephalometric radiology
Cone-beam CT
Remember: the timing of adolescence is a major contributor to variability in growth
Cross-sectional growth studies:
Quicker, less expensive, less precise in detecting typical timing fluctuations
Longitudinal growth studies:
slow, expensive and hard to maintain, very efficient and excellent in showing details
Experimental marker techniques to know:
Vital staining
Autoradiography
Implant superimposition
Molecular biology techniques: The way of the future in growth studies.
What does calcification of extracellular material lead to?
Leads to a critical distinction between soft or non-calcified tissues and the hard calcified tissues.
What kinds of tissues are considered “hard tissues and which are considered soft?
Hard tissues: Bone, teeth, and sometimes cartilages.
Soft tissues everything else including some cartilages.
How does soft tissue grow?
By a combination of hypertrophy and hyperplasia. Within tissues it can occur resulting in interstitial growth. Secretion of extracellular material can also accompant interstitial growth by hyperplasia (primary) and hypertrophy (secondary)
