Calcium metabolism

post graduate student at dashmesh institute of research and dental sciences, faridkot à dashmesh institute of research and dental sciences, faridkot
29 Jan 2015

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Calcium metabolism

  1. Guided by- Dr. Akshey Sharma Dr. Rajesh Bhanot Dr. Pardeep Bansal Dr. Gagan Chahal Presented by- Dr. Swati Mittal PG student 1st year Deptt of Prosthodontics
  2. As dentists, it is vital for us to have a complete understanding of the general metabolism of calcium as it helps in the formation and maintenance of the teeth and their supporting bony structure.
  3. Approximately 99% of the total body weight of calcium is present in the skeleton.  The remaining 1% is found in the cell membranes and extracellular fluid.  It is this small percentage of calcium that is vital to all life processes.
  4. 1. Contributes to hardness of bone and is a major component of teeth. 2. Stabilises the cell membrane and their permeability. 3. Maintenance of excitability of nerve and muscles. 4. Normal skeletal and cardiac muscle contraction. 5. Blood coagulation – Ca++ is required for the conversion of many inactive enzymes in the coagulation process.
  5. Infants (< 1 year) = 300-500 mg/ day Children (1 – 18 years) = 0.8-1.2 g/day Adult men and women = 800 mg/day Pregnancy and lactation = 1.0-2gm/day
  6.  Milk is a good source for calcium. Calcium content of cow milk is about 100mg/100ml.  Egg, fish & vegetables are medium source for calcium.  Cereals (wheat, rice) contains small amount of calcium. But cereals are the staple diet in India. Therefore, cereals form the major source of calcium in Indian diet.
  7.  Several different kinds of calcium compounds are used in calcium supplements. Each compound contains varying amounts of the mineral calcium.  Common calcium supplements may be labeled as:  Calcium carbonate - Tums® and Caltrate®  Calcium citrate- Citracal® and Solgar®
  8.  If the calcium in diet and from supplements exceeds the tolerable upper limit, you could increase your risk of health problems, such as:  Kidney stones  Prostate cancer  Constipation  Calcium buildup in your blood vessels  Impaired absorption of iron and zinc
  9.  Calcium absorption in the small intestine occurs by both active & passive diffusion.  Uptake of calcium by active transport predominates in: duodenum jejunum;  Simple diffusion predominates in: ileum  Most of the ingested calcium is normally eliminated in the feces, although the kidneys have the capacity to excrete large amounts by reducing tubular reabsorption of calcium
  10.  VitaminD –Calcitriol induces the synthesis of the carrier protein (Calbindin) in the intestinal epithelial cells & so facilitates the absorption of calcium.  Parathyroid hormones increases calcium transport from the intestinal cells.  Amino acids, especially lysine & arginine increase absorption.  Lactose : enhance passive Ca uptake; its effect is valuable because of it presence in milk.
  11.  Phytates — Phytates are substances found in some plant foods that can bind calcium in the intestine and decrease its absorption.  Oxalates are present in some leafy vegetables which cause formation of insoluble calcium oxalates .  In malabsorption syndromes , fatty acid is not absorbed , causing formation of insoluble calcium salt of fatty acid .  High phosphate content will cause precipitation as calcium phosphate.  Absorption is also decreased with increase intake of protein & fiber in diet.
  12.  This term is used to describe the amount of Ca++ either stored or lost by the body over a specific period of time.  When the assimilation of calcium from dietary sources is less than the metabolic requirements and the obligatory losses , then calcium is withdrawn from the skeleton to maintain the critical concentration of the element in the blood and tissue fluids.
  13.  Calcium homeostasis is the mechanism by which the body maintains adequate calcium levels. Positive Ca2+ balance  Is seen in growing children, where intestinal Ca2+ absorption exceeds urinary excretion and the difference is deposited in the growing bones.
  14. Negative Ca2+ balance  Is seen in women during pregnancy or lactation, where intestinal Ca2+ absorption is less than urinary excretion and the difference comes from the maternal bones.
  15.  The primary source of available calcium is trabecular bone, not cortical bone.  The sites of trabecular bone which supply mobile calcium are the jaws, ribs, bodies of the vertebrae, and the ends of the long bones.
  16.  A significant finding from animal experimentation is that, when skeletal depletion of calcium occurs as a result of stimulation of the parathyroid gland, alveolar bone is affected first, the ribs and the vertebrae are affected second, and the long bones third.  Prolonged depletion results in disorganization and loss of trabeculae, followed by cortical remodeling or structural failure.
  17.  A complex set of interlocking mechanisms takes place in order to allow man to survive major dietary Ca intake fluctuations. These mechanisms are mainly controlled by the endocrine systems.  Three main hormones acting at 3 different sites are responsible for Ca metabolism. 1. Vit. D3 - Bone. 2. Parathormone - Kidney 3. Calcitonin - Intestine
  18.  Physiologically active form of vitamin D is a hormone called calcitriol or 1,25 – dihydroxycholecalciferol (1,25 – DHCC).  It stimulates Ca uptake by osteoblasts of the bone and promotes calcification or mineralization and remodelling , thus increasing the blood calcium levels.
  19.  The prime function is to elevate the serum calcium levels.  Action on kidney – increases Ca reabsorption by kidney tubules.  Action on bone – decalcification or demineralization of bone – increase blood Ca levels.
  20.  Promotes calcification by increasing activity of osteoblasts.  Decreases bone resorption.  Increases excretion of Ca in urine. Thus, has a decreasing influence on blood Ca.
  21.  Estrogen is a hormone that plays an important role in helping increase calcium absorption.  After menopause, estrogen levels drop and so may calcium absorption.  Hormone replacement therapy has been shown to increase the production of vitamin D thus increasing calcium absorption.
  22.  Hypercalcemia - Increased level of Ca in the blood.  Symptoms - Tiredeness - Loss of appetite. - Nausea, vomitting. - Constipation.  Conditions in which it occurs - Hyperparathyroidism. - Acute osteoporosis. - Vit. D intoxication. - Thyrotoxicosis. - Polyuria. - Dehydration. - Loss of muscle tone. - Decreased excitability of muscles and nerves.
  23.  Hypocalcemia - Decreased levels of Ca in the blood.  Below 8.8mg/dl mild tremors  Less than 7.5mg/dl tetany  Symptoms - Tetany (Carpopedal spasm).  This occurs in cases of – - Insufficient Ca in the diet. - Hypoparathyroidism. - Insufficient vit. D in the diet. - Increase in calcitonin levels.
  24.  Osteoporosis is the most common of all bone diseases in adults, especially in old age.  It results from diminished organic bone matrix rather than from poor bone calcification.  In osteoporosis the osteoblastic activity in the bone usually is less than normal, and consequently the rate of bone osteoid deposition is depressed.
  25.  Characterized by demineralization of bone resulting in progressive loss of bone mass.  Elderly persons (>60 years) of both sexes are at risk.  More predominantly in postmenopausal women.  Etiology – ability to produce calcitriol from vitamin D is reduced with age.  Results in frequent bone fractures – major cause of disability.
  26.  The spine, hips, ribs, and wrists are common areas of bone fractures from osteoporosis although osteoporosis-related fractures can occur in almost any skeletal bone.  Osteoporosis can be present without any symptoms for decades because osteoporosis doesn't cause symptoms until bone fractures.
  27.  Therefore, patients may not be aware of their osteoporosis until they suffer a painful fracture.  The symptom associated with osteoporotic fractures usually is pain; the location of the pain depends on the location of the fracture.  Repeated spinal fractures can lead to chronic lower back pain as well as loss of height and/or curving of the spine due to collapse of the vertebrae.
  28.  Osteoporosis can be described as a lack of bone density or poverty of bone tissue.  Many patients exhibit continuing bone resorption under well-made dental prostheses.  These patients return with complaints of discomfort and inability to tolerate their prostheses, showing rapid, inexplicable bone loss.  Most of these patients are postmenopausal women.
  29.  There are many systemic factors which contribute to alveolar bone loss and decreased ability to tolerate dental prostheses.  Osteoporosis should always be considered as a possibility.  The condition of osteoporosis results in bone loss in the maxillae and mandible as well as in other bones of the body.
  30.  Studies have shown that nutritional supplementation can yield impressive results.  Albanese used a supplement of 750 mg of calcium per day over a 3-year period and found that the supplemented patients showed cessation of bone loss or an increase of up to 12% in bone density when compared to a test group showing continued bone loss.
  31.  Jowsey suggests calcium supplementation of 1,000 mg/day.  Wical and Brussee treated patients with 750 mg of calcium per day for 1 year. When compared to a similar nonsupplemented group, the reduction of bone loss was an impressive 34% in the maxillae and 39% in the mandible.  In contrast, several studies reported no benefit to bone density from daily calcium supplementation.
  32. Calcium metabolism and osteoporotic ridge resorption R. P. Blank, H. A. Diehl, G. T. Ballard, and R. C. Melendez (JPD NOV 1987)  Osteoporosis may be defined simply as a condition of insufficient bone.  This deficiency undermines skeletal strength, resulting in fractures that occur with minimal stress in the spine, distal radius and ulna, and in the femoral neck.  Of the 190,000 hip fractures occurring annually, 80% are in postmenopausal women.
  33.  The relationship of osteoporosis to alveolar and residual ridge resportion is of justifiable concern to the dental profession.  Although generalized bone loss is characteristic of osteoporosis, the first sign may be alveolar bone loss, followed by loss in the vertebrae and long bones.  It may be difficult to treat edentulous patients who manifest the excessive residual ridge resorption often associated with osteoporosis.
  34.  By the time osteoporosis is generally diagnosed, 50% to 75% of the original bone material has been lost from the skeleton.  Increasing calcium intake by means of dairy foods and supplementation is the method most practiced in the prevention and treatment of osteoporosis to optimize calcium balance.
  35.  Studies indicate protection against age-related bone loss in the hand bones and residual ridge bone with increased calcium intake.  In contrast, several studies reported no benefit to bone density from daily calcium supplementation.  This variance in reported data helps to explain the wide range in recommended dietary calcium intake from various health organizations.
  36.  The current recommended dietary allowance (RDA) is 800 mg of calcium/day,  The most recent National Institutes of Health (NIH) proposal calls for 1000 to 1500 mg of daily calcium.  The World Health Organization (WHO) recommendation is only 400 to 500 mg of calcium/day.  Calcium intake in most populations around the world is 300 to 500 mg/day without any evidence of osteoporosis.
  37.  Bone resorption of residual ridges is common. The rate of resorption varies among different individuals and within the same individual at different times.  Factors related to the rate of resorption are divided into anatomic, metabolic, functional, and prosthetic factors.
  38.  Anatomic factors include the size, shape, and density of ridges, the thickness and character of the mucosa covering, and the ridge relationships.  Metabolic factors include all of the multiple nutritional, hormonal, and other metabolic factors which influence the relative cellular activity of the boneforming cells (osteoblasts) and the bone resorbing cells (osteoclasts).
  39.  Functional factors include the frequency, intensity, duration, and direction of forces applied to bone which are translated into cellular activity, resulting in either bone formation or bone resorption.  Prosthetic factors include the myriad of techniques, materials, concepts, principles, and practices which are incorporated into the prostheses. Although the various factors can be divided into these four groups for academic purposes, they are all interrelated.
  40.  The diets of subjects with minimal bone resorption were compared with the diets of subjects with severe alveolar destruction.  The results indicate a positive correlation among low calcium intake, and severe ridge resorption.
  41.  Emphasis was placed on the importance of considering dietary factors in the diagnosis and treatment of prosthodontic problems which arise from the excessive resorption of residual ridges.  It was concluded that systemic conditions are important in the etiology of residual ridge resorption. The resistance of bone to mechanical stresses depends on its physiologic state.
  42.  Of the many systemic influences which affect the bone responses of patients, dietary factors may be subject to the dentist’s control just as are factors of denture construction.  Nutritional deficiencies and imbalances, as well as mechanical factors, should receive consideration in diagnosis and treatment planning for prosthodontic patients.
  43.  Biochemistry U. Satyanarayan  Sheldon Winkler ,A.I.T.B.S. Publishers , Essentials of complete denture Prosthodontics,2nd edition  Relationship of osteoporosis to excessive residual ridge resorption ; J. Crystal Baxter (JPD July 1974)  Calcium metabolism and osteoporotic ridge resorption R. P. Blank, H. A. Diehl, G. T. Ballard, and R. C. Melendez (JPD Nov 1987)
  44.  Some clinical factors related to rate of resorption of residual ridges ; Atwood (JPD Aug 2001)  Studies of residual ridge resorption. The relationship of dietary calcium and phosphorus to residual ridge resorption ; Wical and Swoope (JPD July 1974)