Objectives
• After this session you should be able to• 1- Understand the different types of bone density
tests,
• 2- Recognize the results of a bone density test "T"
and "Z" scores,
• 3- Identify the bone quality groups,
• 4- Evaluate the densitometry before implant
placement.
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STRUCTURE OF A NORMAL BONE
MOLECULAR STRUCTURE :
• The majority of bone is made of the matrix.
• Difference between matrix of bone and that of
other cells is that the matrix of bone is hard.
• It has inorganic and organic parts.
INORGANIC
MATRIX
ORGANIC
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• The inorganic part/bone mineral consists of
calcium hydroxyapatite (Ca10(PO4)6(OH)2).
• The organic part of matrix is mainly composed of
Type I collagen.
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STRUCTURE OF BONE
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PATHOGENESIS OF OSTEOPENIA AND
OSTEOPOROSIS
• In osteopenia and osteoporosis, there is an
imbalance between osteoblastic and osteoclastic
activity. Existing bone is reabsorbed faster than
new bone is made.
• As this occurs, the bones lose minerals, heaviness
(mass) and structure, making them less dense,
weaker and increasing the risk of fractures.
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What is a Bone Mineral Density
(BMD) test?
• A bone mineral density test is an easy, reliable
test that measures the density or thickness of
bones.
• It measures the amount of mineral (calcium)
in a specific area of the bone.
• The more mineral in the bone measured, the
greater is the bone density or bone mass.
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What is bone density testing used for?
Doctors do bone density testing for 2 reasons:
1- To see if a person has osteoporosis or is at risk for the
disorder
2- To see if treatments for osteoporosis are working
Who should get bone density testing?
All women age 65 and older should have bone density testing at least once.
women who are younger than 65 but who have gone through menopause.
check bone density in people who they are at high risk of breaking a bone. Such as:
Having already broken a bone as an adult
Taking medicines called steroids for a long time
Weighing less than 58 kilgrams
Having rheumatoid arthritis
Having a parent who broke a hip after a minor injury
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Are there different types of bone
density tests?
• Dual-energy X-ray absorptiometry (DXA) – This is the
most useful and reliable bone density test. It is a
special kind of X-ray that gives off very little radiation.
DXA gives reliable measures of bone density in
different parts of the body, such as the spine, hip, and
wrist.
• Quantitative computerized tomography (CT) – It gives
reliable measurements of bone density in the spine.
• Ultrasound testing – Measure the bone density of the
heel. This test can help find out a person’s risk of
breaking a bone.
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DEXA SCANNER
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INDICATIONS FOR BMD TEST
BMD is done in :
• All women aged 65 or older and men over 70
years of age regardless of risk factors
• Postmenopausal women under age 65 and
men in the age group of 50 – 70 years who
have one or more risk factors
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WHAT DOES THE DEXA TEST DO?
• A DEXA test measures the bone mineral density
and compares it to that of an established standard .
• The results of the test are usually reported as a "T
score" and "Z score."
• In either score, a negative number means you have
thinner bones than the standard.
• The more negative the number, the higher your risk
of a bone fracture.
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T-SCORE
• The T score compares your bone density with that
of healthy young adult.
• A score of 0 means your BMD is equal to the
standard for a healthy young adult.
• Differences between your BMD and that of the
healthy young adult standard are measured in units
called standard deviations (SDs). The more standard
deviations below 0, indicated as negative numbers,
the lower your BMD and the higher your risk of
fracture.
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Osteopenia
• Osteopenia refers to bone mineral density that is
lower than normal peak BMD (i.e, between -1.0 and
-2.5) but not low enough to be classified as
osteoporosis.
• It is a sign of normal ageing, in contrast
to osteoporosis which is a sign of pathologic ageing.
• It occurs more frequently in post-menopausal
women, can be exacerbated by lifestyle factors such
as lack of exercise, alcoholism, smoking or
prolonged use of glucocorticoid medications for
asthma.
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Osteoporosis
• Osteoporosis = "porous bones."
• Osteoporosis is defined by the WHO as a bone
mineral density that is 2.5 standard deviations or
more below the mean bone mass (average of
young, healthy adults).
• The underlying mechanism in osteoporosis is an
imbalance between bone resorption and bone
formation.
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Bone quality
• Type I: Homogeneous cortical bone;
• Type II: Thick cortical bone with marrow cavity;
• Type III: Thin cortical bone with dense trabecular
bone of good strength;
• Type IV: Very thin cortical bone with low density
trabecular bone of poor strength.
Type I
Type II
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Type III
Type IV
Mish Classify bone density in all
regions of the jaws.
D1
• Homogeneous, dense ,
• Is more often found in anterior mandibles with
moderate to severe resorption,
• Greater strength than any other type. Has fewer
blood vessels than the other three types, and
therefore it is more dependent on the periosteum
for its nutrient.
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Mish Classify bone density in all
regions of the jaws.
D2
• Is a combination of dense-to-porous cortical bone on the
crest and trabecular bone.
• Trabeculae are 40% to 60% stronger than D3 trabeculae.
• This bone type occurs most frequently in the anterior
mandible, followed by the posterior mandible. On occasion it
is observed in the anterior maxilla, especially for a single
missing tooth.
• Provides excellent implant interface healing, and
osseointegration is very predictable.
• The intrabony blood supply allows bleeding during the
osteotomy, which helps control overheating during
preparation and is most beneficial for bone-implant interface
healing.
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Mish Classify bone density in all
regions of the jaws.
D3
• Composed of thinner porous cortical bone on the crest
and fine trabecular bone within the ridge.
• The trabecula are approximately 50% weaker than
those in D2 bone.
• Is found most often in the anterior maxilla and
posterior regions of the mouth in either arch.
• The D3 anterior maxilla is usually of less width than its
mandibular D3 counterpart.
• The D3 bone is not only 50% weaker than D2 bone, the
bone-implant contact is also less favorable in D3 bone.
The additive factors can increase the risk of implant
failure.
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Mish Classify bone density in all
regions of the jaws.
D4
• Has very little density and little or no cortical cristal
bone.
• It is the opposite spectrum of D1 (dense cortical bone).
• The most common locations for this type of bone are
the posterior region of the maxilla. It is rarely observed
in mandible.
• The bone trabeculae may be up to 10 times weaker
than the cortical bone of D1.
• The bone-implant contact after initial loading is often
less than 25%. Bone trabeculae are sparse and, as a
result, initial fixation of any implant design presents a
surgical challenge
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Identify the bone type and density
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‫‪Session 2‬‬
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Computer Assisted Densitometric Image Analysis
(CADIA)
• Is one form of radiography that allows the
investigator to quantify changes by comparing the
radiographic density in a predetermined region of
interest (ROI) between baseline and follow up
radiographs. In this system, a video camera, which
interfaced with an image processor, and a computer
that allow the storage and mathematical
manipulation of the images, measures the light
transmitted through a radiograph, and the signals
from the camera are converted into grey-levels.
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•
•
•
•
•
•
Many Step wedges of different material and
consistency have been used:
1- an aluminium SW
2- copper SW
3- nickel SW
4- or some solutions like CaCl2 which simulate bone
density, ethanol simulating fat and water simulating
soft-tissue equivalent.
• Dental radiographs, standardized by this method,
could provide measures of the relative amounts of
bone mineral content.
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• Densitometric evaluation is based on intensity of gray shadows,
which is predetermined on a scale varying from 0 (zero=black) to
255 (white) for intra-oral and panoramic radiographs.
• using a copper SW composed of 5 steps on dental Panoramic X-ray,
to compare two different images of the same patient through the
Grey Level, optical densities (OD) for each point of measurement
• were calculated as follows:
• OD = -log Ii/255
• OD - optical density and
• Ii - measured intensity of GL.
• Recent CT scan devices can distinguish up to 4000 different gray
shadows and therefore are far more precise, objective and reliable
in comparison with periapical and panoramic images.
• Gray shadows determined by CT machines and its software
programs are called Houndsfield Units (HU) representing a
radiation attenuation for every pixel of the computer slice image.
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• The most common method in standardizing
densitometric technique is by using a copper calibrating
stepwedge which consists of 5 layers, with the first layer
presented by 0,1 in width and visible on a particular
and predetermined site of the image. Copper is chosen
due to its effective atomic number which is similar to
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bone.
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Pixels per inch (PPI) or pixels
per centimeter (PPCM) is a
measurement of the pixel
density (resolution) of an
electronic image device.
Dots per inch (DPI, or dpi) is a
measure of spatial printing or
video dot density, in particular
the number of individual dots
that can be placed in a line
within the span of 1 inch (2.54
cm).
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