BIOLOGY OF TOOTH
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Periodontium ď Ž
ď Ž ď Ž
Periodontium is a connective tissue organ covered by epithelium , that attaches the teeth to the bones of the jaws and provides a continually adapting apparatus for support of teeth during function. 4 connective tissues Two mineralized -Cementum -Alveolar bone Two fibrous -Periodontal ligament -Lamina propria of the gingiva.
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Cells
Progenitor cells Synthetic cells a) Osteoblasts b) Fibroblasts c) Cementoblasts Resorptive cells A) Osteoclasts B) Fibroblasts C) Cementoclasts www.indiandentalacademy.com
Extra cellular elements ď Ž
Fibres -Collagen -Oxytalan Ground Substance -Proteoglycans -Glycoproteins
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Principle Fibres of the Periodontal Ligament(Collagen Fibres) 1. 2. 3. 4. 5.
Alveolar crest group Horizontal group Oblique group Apical group Interradicular group
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GINGIVAL FIBRES 1. 2. 3. 4. 5.
Circular Alveologingival Dentoperiosteal Dentogingival Transseptal fibres(Accesory fibres)
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Alveolar bone 1. 2.
Two parts Alveolar bone proper Supporting alveolar bone A.- Cortical Plate B.- Spongy Bone Alveolar process is formed by intramembranous ossification. They can be remodelled owing to the structure.
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Active stabilization of teeth against forces of low magnitude
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Response to normal function: Forces applied on the teeth are1-2 kgs when soft Upto 50 kgs against harder food
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Tooth movementVanarsdall
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Peridontally Compromised Teeth
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Historical Perspective 1. 2. 3. 4. 5. 6.
Celsus Reitan Openheim Norton Burstone Davidovitch www.indiandentalacademy.com
TOOTH MOVEMENTď Ž
Application of orthodontic force – tooth movement on account of resorption on the pressure side and deposition on the tension side.
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Cascade of activitiesTooth movement (Norton)
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Classification of orthodontic forces- Schwartz
Four degrees of biologic efficiency. 1st –Below threshold stimulus. 2nd-Most favourable 15-20 gms per square cm.Less than the blood pressure. 3rd-Medium strength.They stop the blood. flow.Tissues are not crushed. 4th –Forces are so high that the tissues are crushed. Irrepairable damage may be caused to the tissues involved.
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Theories of orthodontic tooth movement 1) Bioelectric theory -electric signals produced when alveolar bone flexes and bends. Also called the piezoelectric theory. 2) Pressure tension theory(Schwartz1932)-related to cellular changes produced by chemical messengers. Bien Hydrodynamic damping of tooth movement, J. D. 1966. ď Ž
Theories are mutually dependent. www.indiandentalacademy.com
Bioelectric theory ď Ž 1. 2.
2 unusual characteristics-quick decay rate -equivalent signal opposite direction
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Bioelectric theory
Crystal deformation-electrons migrate due to distortion of cross linkages between the collagen fibres in the bones. Electropositive response (convexity) –resorption Electronegetive (concavity) -deposition Ions in fluids bathe the bone and cause “streaming potential”. Similar but not the same. No place in natural control of body.
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Bioelectric theory
Stress generated signals importantastronauts.(can also be explained OB differentiation) Chewing /orthodontic forces. Bioelectric signals-active growth, not exactly known. Exogenous signals – modify tooth movement-lag phase before tooth movement. www.indiandentalacademy.com
Effect of Pulsed Electromagnetic Field on Tooth Movement- Stark and Sinclair Ajo - 1987 Feb Simple non invasive pulsed electromagnetic (25-Hz) field can cause an effect on the rate and amount of tooth movement. 20-experimental,20-control Guinea pigs
AFTER 10 DAYS Tooth movement Osteoclast cell count
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Observations1.
Protein metabolism indicated by creatinine ,craetinine phosphokinase, uric acid.
2.
Na Ca K which are postulated to be the effect of pulsed electromagnetic stimulation on the cell membrane are not increased.
3.
Exciting possibily for future consideration - Ability to initiate and enhance the bone deposition-use with functional appliances.
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Effect of Pulsed Electromagnetic Field on Tooth Movement- Stark and Sinclair Ajo - 1987 Feb PRE AND POST EXPERIMENT
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CONTROL AND EXPERIMENTAL GROUP
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INCREMENTAL MOVEMENT www.indiandentalacademy.com
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Structure of the bone
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Pressure -Tension Theory ď Ž
Relies on chemical signals and not electrical signals for cellular differentiation and tooth movement.
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Cells causing remodeling of bone
2.
OB OC
ď Ž
ORIGIN OF THE CELLS
1.
1)
OB-Neural crest cells(OB)- Pre Osteoblasts
a)
Contact inhibition.
b)
G1,G2 blocked cells. www.indiandentalacademy.com
Differentiation of cells under mechanical influence
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Differentiation of cells under mechanical influence
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Differentiation of cells under mechanical influence
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Cells causing remodeling of bone 2) ď Ž ď Ž
OC- Hematogenous in origin Monocytes have been suggested to be the predecessors. Progenitors ??? Blocked cells local preosteoclasts & circulating preosteoclasts.
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Differentiation of cells under mechanical influence-OB & OC
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Vit D metabolites ď Ž
They are known to effect bone formation and deposition via the differentiation of the comitted progenitor cells into mature cells.
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OSTEOBLASTS
RESORPTIVE FUNCTION 1) OB-Physical barrier-layer of cells on the bone surface. If these cells are stimulated by PTH they change shape (round) thus exposing the underlying mineral of the tooth – only affects already differentiated cells.
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Shape change in cells: mechanism for the transduction of mechanical forces ( SandyBdj;1992)
Relationship exists bw cell shape and metabolic activity. Flattened cells synthesize more DNA than rounded cells. PG and PTH induce change in shape. Suggested – in pressure sites the cells are rounded and have catabolic effects-tension sites the cells are flattened and in a synthetic mode. www.indiandentalacademy.com
OSTEOBLASTS
RESORPTIVE FUNCTION 2) Release certain mediators –cytokines-Bring about osteoclastic resorption. They are defined as short range soluble mediators,released from the cells which modulate the activity of other cells - ( Bone remodeling- Sajeda Meghji 1992; Bdj ) - lymphokines.
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Cytokines:Mediators of bone remodeling( -SandyBdj;1992 -Biology of tooth movement- Norton and Burstone)
ď Ž
Osteoclasts don’t work independently -signal transmitted to the osteoclast by an Osteoblast Cytokine.
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Cytokines:Mediators of bone remodeling ( SandyBdj;1992,-Biology of tooth movement- Norton and Burstone)
RESORPTIVE FUNCTION
3)Osteiod layer covering the bone is removed by OB - secrete collagenase.
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P TIMP TIMP-TISSUE TIMP-TISSUEINHIBITOR INHIBITOROF OF METTALOPROTEINASES METTALOPROTEINASES www.indiandentalacademy.com
OSTEOBLASTS FORMATIVEď Ž ď Ž
a) b) c) d)
1)Pressure 2)Production of first messenger( physical/ chemical) Deformation may lead to ca influx Hormones(PTH) They Theybind bindto tothe thecell cell Prostaglandins( macrophages ) surface surfacereceptors. receptors. Neurotransmitters(SP)
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OSTEOBLASTS
a. b. c.
3)Second messengers c AMP c GMP Ca
4)Increased bone activity
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Trans membrane signaling pathway
PHOSPHOINOITIDASE PHOSPHOINOITIDASE INOSITOL INOSITOL TRIPHOSOHATE TRIPHOSOHATE
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Role of Prostaglandins (Tooth eruption and orthodontic movement:Sandy-Bdj,1992)
Discovered by VON Phospholipids EULER –1934 phopholipase Prostate gland Arachidonic acids Yamasaki –injection of c AMP exogenous PG increased osteoclast numbers. Prostaglandin's Ca+2
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ARACHIDONIC ACID METABOLISM
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ď Ž
Leukotrienes and HETE (Leucocytes) (Hydroxyeicosatetraenoic Acid) , produced from the same substrate.
ď Ž
Since PGs do not fully account for bone remodeling associated with tooth movement , lipoxygenase products may be involved.
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OSTEOCLASTS ď Ž
Resorptive action PTH- systemic factor Cytokines Mechanical Ruffled border Lysosomal enzymes
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Osteocytes ď Ž
Osteocytes – cytoplasmic processes which help to gauge the pressure changes and signal the OB.
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Events during bone remodelling
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PDL and bone response to sustained forces on pressure side1.
Undermining resorption
2.
Fontal resorption
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Oteoclast differentiation
2 waves -1st wave –local cell population. -2nd wave-blood flow. Optimal force-frontal resoption on pressure side Excess force would cause –undermining resorption. www.indiandentalacademy.com
Pattern of bone deposition and resorption
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Tooth movement
Tooth movement may be divide into (Graber .Vanarsdall) - Initial –Undermining resorption - Secondary period-Frontal resorption
Initial phase- 3 main stages
1.
Degeneration
2.
Elimination of destroyed tissue
3.
Establishment of new attachment www.indiandentalacademy.com
Tooth movement
1.Degeneration
1.
Blood flow Degradation of vessel walls Cellular changes
2. 3.
-Swelling of mitochondria -Rupture of cytoplasmic membrane leaving only isolated nuclei between the fibrous elements
The source of cells which differentiate into osteoclasts is lost. Area is cell free. Glassy appearing sterile necrotic area caused due to excessive pressure application -HYALINIZATION www.indiandentalacademy.com
Tooth movement 2.Elimination of destroyed tissue
Adjacent undamaged areas give rise to the osteoclasts (multinucleated giant cells) which cause remodeling of the bone on the peripheral areas.
Invasion of the hyalinized areas by the cellular elements.
Adjacent alveolar bone-undermining resorption
3.Establishment of new attachment
Synthesis of new tissue once the hyalinized tissue is removed - Fibroblasts. www.indiandentalacademy.com
Macrophages adjacent to hyalinized areas
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Tooth movement ď Ž
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In secondary phase Osteoclasts differentiate and cause frontal resorption. Osteoblasts deposit on the tension surface. On the tension side resorption occurs on the spongiosa surface of the alveolar bone. On pressure apposition takes place on the spongiosa surface. Remodelling also takes place on the on the periosteal surface of the bone - helps to maintain the thickness of the alveoar bone. www.indiandentalacademy.com
Differential Time Course Bw Frontal and Undermining Resorption
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Differential Time Course Bw Frontal and Undermining Resorption ď Ž
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Initial loading leads to some amount of tooth movement- movement increases with time-light forces. Movement takes place in a stepwise fashion with heavy forces.
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Effects of Tooth Movement and Force Distribution ď Ž
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Distribution of forces and tooth movement differ depending upon the type of tooth movement. Tipping -Forces used to tip the teeth must be kept low 50gms. www.indiandentalacademy.com
Effects of Tooth Movement and Force Distribution ď Ž ď Ž
Tipping-hyalinization Caution -alveolar crest.
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Effects of Tooth Movement and Force Distribution ď Ž
Bodily tooth movement-uniform loading of the teeth is seen.
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Effects of Tooth Movement and Force Distribution Bodily tooth movement Slight tipping due to the hyalinized zone formed and resorption adjacent to it. Further tipping prevented by the stretch of the fibres.
ď Ž
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Effects of Tooth Movement and Force Distribution Rotation
Practically impossible to bring about pure rotation tipping is the actual mechanism 2 pressure sites and 2 tention sites.usually 1 side shows frontal and other undermining resorption.After 3-4 weeks frontal resorption prevails. Supracrestal fibres-gingival fibres, trans gingival fibres. Long retention period, supracrestal fibrotomy. www.indiandentalacademy.com
TRANSSEPTAL FIBRES
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Effects of Tooth Movement and Force Distribution
Intrusion –light forces are actually needed for intrusion as the
forces are highly concentrated over a very small area. If bone compact as in adults-interrupted force maybe better. allows time for cell proliferation. Gingival fibres are relaxed - cause formation of bony spicules - crestal areas.
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Effects of Tooth Movement and Force Ditribution(Proffit) 1. 2. 3. 4. 5. 6.
Tipping –35-60gms Bodily –70-120gms Uprighting –50-100gms Rotation –35-60gms Extrusion –10-20gms Intrusion-10-20gms
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Effects of force duration and decay 1. 2. 3.
Duration – the second messenger produced only after 4 hours. Forces – Continuous Interrupted light and heavy Intermittent
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Force Duration and Decay Ideal to have light continuous forces but heavier forces can be allowed if a period of regeneration and repair is allowed. ď Ž 4 week appointment cycle. ď Ž
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Force Magnitude(Heavy pressure)
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Force Magnitude(Light pressure)
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AJO-DO 1985 Step Reassessment of force magnitude - Quinn and Yoshikawa
Modifying the force magnitude as suggested by Storey and Smith www.indiandentalacademy.com
Pressure Versus Response
pressure - movement Platue Decline at the end Optimum forcelightest force producing maximum or near maximum movement www.indiandentalacademy.com
Pressure Versus Response ď Ž ď Ž
A1-anchor teeth M1- teeth to be moved
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Stationary anchorage ď Ž
ď Ž
Bodily versus tipping movement- anchor teeth would move less but if the force is really high enough to bring posterior teeth into optimum movement rage they would move the same amount. Large forces
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Drug Effect on the Response of Orthodontic Forces 1. 2.
3.
+ve effect PG -ve effect Bisphosphanates-act as specific inhibitors of osteoclast mediated bone resorption. PG inhibitors –NSAIDS, indomethacin , tricyclic antidepressants,anti arrhythmic agents,anti malarial drugs, methyl xanthines. Corticosteroids (reduce the inflamation) www.indiandentalacademy.com
Drug Effect on the Response of Orthodontic Forces Phospholipids Corticosteroids
phopholipase
Arachidonic acids NSAIDS Prostaglandins
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The effect of acetaminophen on tooth movement in rabbits -1997 Angle Orthodontist John J. Roche et al It is a weak prostaglandin inhibitor - recommended for use to relieve pain during orthodontic tooth movement. 14 rabbits were used. Lower first molar and incisor teeth on one side were prepared with a perforation hole buccolingually. Maxilla was excluded from the study-21-day period. Over the 21 day period, each rabbit was force-fed 1000 mgs of Tylenol (10 ml of solution) per day
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The effect of acetaminophen on tooth movement in rabbits -1997 Angle Orthodontist John J. Roche, George J. Cisneros, George Acs.
On day 21, the rabbits were sacrificed Impressions of the final interdental distance were obtained and poured in stone for future examination.
Acetaminophen does not seem to retard orthodontic tooth movement, related to its lack of anti-inflammatory properties
Concentrated in the central nervous system
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The effect of acetaminophen on tooth movement in rabbits -1997 Angle Orthodontist John J. Roche, George . Cisneros, George Acs.
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Role Of Prostaglandins In Orthodontic Tooth Movement- Dr Anand Patil
1microgram (µgm) / injection (inj) of PG-E1 along with lignocaine as a vehicle was injected on three different days in the vestibular region distal to the right upper canine in 15 Patients.
The left side was the controlled side with injection of vehicle alone.
Occlusograms of pre and 60 days post canine retraction was obtained and distal canine movement was calculated by using stable land marks such as 1st rugae area .
The results showed statistically significant 57% increase in orthodontic distal canine tooth movement on prostaglandin injected side as compared with matched controlled left side. www.indiandentalacademy.com
Pre & post Retraction Occlusograms www.indiandentalacademy.com
AJO-DO 1983 Jan (62-75): Histochemistry of enzymes associated with tissue degradation incident to orthodontic tooth movement - Lilja, Lindskog, and Hamm
Acid phosphatase LDH as indicators of bone activity.
Activity of prostaglandin synthetase since some prostaglandins - important local activators of bone resorption.
The maxillary right first molar in each rat was moved in a buccal direction. www.indiandentalacademy.com
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AJO-DO 1983 Jan (62-75): Histochemistry of enzymes associated with tissue degradation incident to orthodontic tooth movement - Lilja, Lindskog, and Hamm ď Ž
A tipping movement had been produced by the orthodontic forces, and thus two pressure zonesbuccal and lingual.
ď Ž
Acid phosphatase activity Cells randomly distributed along the bone surface in the alveoli in non treated cases.
ď Ž
Prostaglandin synthetase - found exclusively in the bone marrow-not in PDM. www.indiandentalacademy.com
AJO-DO 1983 Jan (62-75): Histochemistry of enzymes associated with tissue degradation incident to orthodontic tooth movement - Lilja, Lindskog, and Hamm
Low force - rapid redistribution to the pressure zones of cells with a high acid phosphatase activity.
Accompanied by a high enzyme activity in the adjacent osteocytes.
Low forces caused no change in the distribution and activity of LDH at any time during the treatment.
After 1 day of high force a zone devoid of LDH activity developed in the buccal pressure zone
No change in the activity of this enzyme was found in the bone marrow during the treatment www.indiandentalacademy.com
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Pressure areas
Tension areas
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