Bone, none disorders and arthritis Flashcards
What is bone
A form of specialised connective tissue with a calcified extracellular matrix
Describe the composition of bone
Mainly inorganic ions deposited in an organic proteinaecous matrix
Name the different cells that make up bone
- Osteocytes
- Osteoclasts
- Osteoprogenitor
What do osteoblasts do
They produce new bone by secreting collagen matrix AND calcium salts
What is the collagen matrix also referred to as
Osteoid
What happens to the osteoblasts as new bone is laid down
Osteoblasts get trapped in their own lacunae and their structure and functions change into that of osteocytes
What is the new layer of bone formed called
Lamellar bone
Where are osteoprogenitor cells found
Inside the bone marrow
What do osteoprogenitor cells do
They are where osteoblasts and osteocytes come from
Why are osteoprogenitor cells so important
As osteoblasts and osteocytes can’t divide do new one needs to come from stem cells
What is the turnover rate for healthy bone
10%
What do osteoclasts do
They are responsible fro bone resorption
Describe osteoclasts
Large, multinucleate cells
How do osteoclasts resorb bone
they secrete hydrochloric acid and proteolytic enzymes which metabolise bone
Where are osteoclasts derived from
White blood cell lineage mostly monocytes and macrophages
What are osteocytes formed from
Trapped osteoblasts
Why are osteocytes important
They secrete enzymes into the matrix to help maintain mature bone
How is the balance of bone secretion and absorption managed
Chemical messengers such as hormones
Which hormones are associated with bone resorption
- Vitamin D
- Parathyroid hormone
- Thyroid hormone
- Growth hormone
- High levels of circulatory calcium ions
Which hormones are associated with bone formation
- Oestrogen
- Calcitonin
- Androgens
What is the very first type of bone laid down referred to as
Woven or immature bone
What does woven (immature) bone get remodelled into
Secondary bone
What is secondary bone divided into
- Cortical or lamellar bone
2. Cancellous or trabecular bone (spongy bone)
What percentage of secondary bone is made up of cortical (lamellar) bone
80%
What percentage of secondary bone is made up of Cancellous or trabecular bone (spongy bone)
20%
What is cortical (lamellar) bone made up of
Concentric layers o bone
Describe cortical (lamellar) bone
Dense and compact
Has a central bone marrow
Where is cortical (lamellar) bone found
In long bones
It is the outermost layer or codec of many bones of the skeleton
Describe the appearance of Cancellous or trabecular bone (spongy bone)
appearance of a sponge
The voids are islands of marrow and the main structure is low density sheets of bone
How is lamellar bone arranged
In the Haversian canal system
What is another term for vitamin D
calcitriol
What is vitamin D a key component of
Bone metabolism
What does vitamin D do
Its presence increases the amount of calcium and phosphate circulating in the body
What is vitamin D synthesised from
Cholesterol in the skin upon exposure to sunlight (UVB)
OR
Obtained from the diet in o
What in your diet can contain vitamin D
- Oily fish
- Red meat
- Liver
- Egg yolk
- Fortified cereals
How is vitamin D metabolised
first by the liver then by the kidney to the metabolically active 1,25- dihydroxycholecalciferol
What action does vitamin D carry out
Increases the amount of free calcium in the circulation
How does vitamin D increased the amount of free calcium in the circulation
promotes uptake in the small intestines and postman osteoclastic activity to release calcium from the skeleton
What effect on bone will their be if there is a vitamin D deficiency
There will be a failure of osteoid to mineralise
What can vitamin D deficiency in children lead to
Rickets
What does childhood rickets cause
Bowing of the long bones
What can vitamin D deficiency in adults lead to
Osteomalacia
What does osteomalacia cause
Softening of the bone
How does osteomalacia present
With vague bone pains and aches
OR
Pathological fractures
What are pathological fractures
Break in the bone as a result of an underlying disease process not due to accident
What is found on the posterior surface of the thyroid
A oval shaped glans which contains 4 parathyroid glands
What do the parathyroid glands secrete
Parathyroid hormone
What does the parathyroid hormone do
Acts to raise the circulation concentration of calcium in the blood
How does the parathyroid hormone raise calcium circulation
Promotes the kidneys to make vitamin D and resorbs calcium in the renal tubules to minimise loss in the urine
Other than calcium what else does the parathyroid hormone effect and how
Encourages lOSS of phosphate
What can happen if phosphate concentration in the blood is too high
Can lead to pathological bone resorption
What can a person with malfunctioning parathyroid gland have
- Primary hyperthyroidism
2. Secondary hyperparathyroidism
What is primary hyperthyroidism due to
Often due to adenoma of one of the parathyroid glands
What happens in patients with primary hyperthyroidism
- Increase in parathyroid hormone levels
- Hypercalcaemia results
- Bone resorptive state is promoted
In whom is secondary hyperthyroidism seen in
In patients with chronic renal disease
Why do some patients with chronic renal disease develop secondary hyperthyroidism
They have an inappropriate calciuria and to compensate the parathyroid glands secrete more parathyroid hormone
What can happen in secondary hyperthyroidism
- Increased resorption of bone
2. Renal osteodystrophy
What is renal osteodystrophy
Failure of the kidneys to maintain calcium and phosphate levels and decline in kidney function
How can hyperparathyroidism present in the jaw
As a central giant cell granuloma
If you find a patient has a central giant cell granuloma in their jaw what should do
Refer them to have bone profile blood s to confirm diagnosis
Name the different stages of bone healing following fracture
- Early inflammatory stage
- Repair stage
- Remodelling stage
What happens in the early inflammatory stage of bone healing
- Bleeding occurs at the fracture sire with formation of a haemotoma
- Inflammatory cells and fibroblasts infiltrate the clot
- Blood vessel ingress into the haemotoma and granulation tissue forms
what can delay fracture healing in the early inflammatory stage
If the fracture site is not adequately immobilised during this period
Name some inflammatory meditar present in the early inflammatory stage of bone healing
- PDGF
- TNF- alpha
- TGF- beta
- IL- 1, 6, 10, 12
When does the early inflammatory stage of bone healing occur
in the first 2 weeks post fracture
What happens in the repair stage of bone healing
- The granulation tissue turns to callus
- Primary callus turns into secondary callus
- Osteoid is secreted it not eh area forming new weak bone
- Proteases degrade the extra cellular matrix
- cartilaginous calcification takes place
- Collagen fibres ingress into the area
- Formal new woven bone is created at fracture site
Name the process that turns primary callus into secondary callus
endochondral ossification
What can happen if the fracture site is not adequately immobilised during the repair stage of bone healing
A fibrous union may form in place of the solid bone formation
How long does the repair stage take
Typically 4 weeks in adults but much less in children
What does the remodellignstage allow fro
Redistribution of the proportion of compact and woven bone
What co ordinate the remodelling phase
Organised osteoblastic and osteoclastic activity
How long does the remodelling stage last
Many weeks of months
What factors can impact fracture healing
- Blood supply to the fracture site
- Infections
- underlying bone pathologies
- Whether fracture is closed or compound
- Degree of tissue loss
- Comorbid conditions eg diabetes
- Use of NSAIDs
- Tobacco smoking and high alcohol intake
- Nutritional status of patient
- Risk of further falls
Name some specific bone disease we should be aware of
- Osteogenesis imperfecta
- Osteopetrosis
- Osteopenia
- Osteoporosis
- Paget’s disease
- Osteoarthritis
- Rheumatoid arthritis
- Ankylosing spondylitis
What is osteogenesis imperfecta
A collection of familial inherited defects of collagen
What does osteogenesis imperfecta result in
Failure of normal biomineralisation of bone
In dentistry we should be aware of osteogenesis imperfecta caused by what?
Type 1 collagen mutation
What happens in osteogenesis imperfecta caused by type 1 collagen mutations
Can result in partial or complete absence of collagen giving a varying clinical phenotype
What can patients with osteogenesis imperfecta caused by type 1 collagen mutations have an increased number
Patients sustain multiple fractures due to low impact trues as their bones are more brittle and easy to break
What is osteogenesis imperfecta also referred to as
Brittle bone disease
What can patients with osteogenesis imperfecta caused by type 1 collagen mutations present with
- Grey blue discolouration to the sclera
- Shortened or bowed long bone shapes
- hyper mobility of joints
- Varying degree of bone pain
- Deafness
- dentinogenesis imperfecta
What are the oral features of osteogenesis imperfecta
- Skeletal class iii abnormality
- Anterior open bite
- Impacted first or seconds permanent molar teeth
- Thin greyish brown enamel
- Defective or premature eruption
- Defective dentinal development or opalescent dentine
When does osteopetrosis occur
Where osteoclasts fail to resorb bone leading to increased bone formation
Describe bones affected by osteopetrosis
They are harder, more marble like and have less ability to flex and elastically recoil
How do bones affected by osteopetrosis look on radiograph
Denser so more opaque
What can happen as a result of increased inorganic component in bone affected by osteopetrosis
Can lead to haematopoietic insufficiency by the bone marrow effectively being walled off by the pathologically thicker bone
What can patients with osteopetrosis come in with
- Delayed tooth eruption
- Growth imaprimetns
- Nerve entrapment syndrome
What is Osteopenia
Where bones have thinned to a mild degree (may not result in pathological fracture)
How are patients with Osteopenia diagnosed
DEXA scan
What does a DEXA scan of a patient with Osteopenia show
A T score between -1 and -2.5
What does a T score of less than -2.5 indicate
Osteoporosis
What does DEXA stand for
Dual Energy X-ray Absorptiometry
What does a DEXA score measure
How dense your bones are in comparison to the average healthy adult of 30 years of age
What happens to bone density as we get older
Bone density declines
How many people are affected by Osteoporosis
3 MILLION in the uK
Name the most common fractures caused by Osteoporosis
- Neck of femur (NOF)
- Wrist (Colles fracture)
- Vertebral bodies (compression or wedge fractures)
What is a fragility fracture
One occurring due to a fall from standing height or less
List some lifestyle factors that can accelerate bone loss
- High caffeine intake
- High salt intake
- Low BMI
- High levels of alcohol consumption
- Smoking tobacco
- Long period of prolonged immobility
What can we eat to help prevent bone loss
- Increased calcium
- Dairy
- Vitamins and minerals
- Tofu
- Nuts
- Whole fish
List some genetic factors that can accelerate bone loss
- Female gender (due to menopause)
2. Family history of osteoporosis
List some endocrine factors that can accelerate bone loss
- Early menopause
- Oophrectomy
- Postmenopausal hormonal changes
- Amenorrhoea (Loss of period for extended period of time)
List some diseases that can accelerate bone loss
- Cushings syndrome
- Hyperthyroidism
- Hyperparathyroidism
List some DRUGS that can accelerate bone loss
- Glucocorticoids (aka corticosteroids)
- Thyroxine
- Heparin
- Diuretics e.g. furosemide
- Cytotoxic drugs
How do we manage a patent with osteoporosis
- Patent education and lifestyle modifications
- Pain relief
- Physiotherapy
- Occupational therapy
- Physical aids eg walking stick
- Medication to prevent further loss of bone mass
- Active fall prevention
- Surgery
What medications can be prescribed to prevent further loss of bone
- Vitamin D or calcium supplements
- Bisphosphonates
- Selective Oestrogen receptor modulators (SERMs)
- Parathyroid replacement Treatment
- Hormone replacement therapy (HRT)
- Testosterone Treatment
What happens in Pagets disease
Increased resorption by overactive osteoclasts leading to overactivity and destruction of bone
How does the body try to counteract the increased resorption by osteoclasts in pagets disease
Osteoblasts come highly active however the bone they secrete is larger and weaker than healthy bone
What can happen to bone in pagets disease
Bone becomes weakened, tends to deform and fracture in some cases
Name some of the commonly affected sites in pagets disease
Pelvis and spine
What does pagets disease lead to
Constant dull bone pain
Sometimes cranial nerve deficits
What are the oral presentations of pagets disease
- Enlargement of the maxillae/ mandible
2. Hypercementosis which can make dental extraction more difficult
How can we treat pagets disease
- Bisphosphonates to regulate abnormal bone turnover
- Analgesia
- Physiotherapy
- Surgery
What is osteoarthritis
A wear and tear degeneration of the joints accompanied with low levels of chronic inflammation of the joints
Which sites are most affected by osteoarthritis
Affects large weight bearing joints eg the hip and knee
What does primary osteoarthritis result in
- Synovial softening
- Tearing of articular cartilage
- Development of subchondral bone cysts
- Development of bony spurs or osteophytes in the joints
What does secondary osteoarthritis occur following
Following trauma
How do we manage osteoarthritis
- patent education and self management programmes
- Weight loss fro obese patients
- Physiotherapy and occupational therapy plus any required walking aides
- Analgesia
- Intra articular corticosteroid injections f
- Intramuscular corticosteroids infections
- Supplements with glucosamine and/or chondroitin sulphate
- Surgery
