Embryology PDF

Embryology Induction → competence → differentiation First branchial arch - muscle of mastication, ⅔ anterior tongue, trigeminal nerve, meckel's cartilage, maxillary and part of external carotid artery, subsequently forms maxillary process...

Embryology Induction → competence → differentiation First branchial arch - muscle of mastication, ⅔ anterior tongue, trigeminal nerve, meckel's cartilage, maxillary and part of external carotid artery, subsequently forms maxillary process Second branchial arch - muscles of facial expression, reichert’s cartilage, facial nerve (7th) Third branchial arch - glossopharyngeal nerve, ⅓ posterior tongue Wk 1 Zygote - morula - blastocyst (external trophoblast and embryoblast) Fertilisation, implantation Wk 2 1. Embryoblast differentiates and proliferates to form bilaminar disc (epiblast & hypoblast) Bilaminar disc 2. 2 cavities formed (amniotic cavity and secondary yolk sac) 3. Embryological axis established (prochordal plate thickens) Wk 3 1. Cells of amniotic cavity differentiates and burrow -> primitive streak forms trilaminar disc, neurulation, NCC 2. Epiblast moves towards hypoblast to form mesoderm migration; mesoderm formation 3. Ectoderm thickens and forms a neural plate - invaginates inwards - neural folds and groove forms - neural fold fuses and forms a neural tube (spinal cord and brain) 4. NCC develops from neuroectoderm and undergoes mesenchymal epithelial transformation - migrates from neural crest and folds to join mesoderm - mesenchyme - ectomesenchyme Wk 4 1. Expansion of neural tube - primitive forebrain Stomatodeum, forebrain, tongue 2. Rostral-caudal folding - primitive stomatodeum 3. Anterior ⅔ of tongue: Local proliferation of mesenchyme in the floor of the mouth (tuberculum impar and lingual swellings at first branchial arch, fuses with hypobranchial eminence) - innervated by mandibular branch of trigeminal nerve Wk 5 1. Localised thickening within ectoderm of frontal prominence (olfactory placode) Olfactory placode, nasal process 2. Proliferation from mesenchyme around olfactory placode - medial & lateral nasal process development, lower lip development 3. Apparent fusion of md processes (lower lip) Wk 6 1. Merkel’s cartilage acts as a scaffolding for intramembranous ossification - reabsorbed after - ossification occurs where IAN divides into Mandible formation mental and incisive branches Wk 7-9 1. Medial nasal process + frontonasal process fuses (middle lips + philtrum) Upper Lips (wk7), secondary palate Lateral aspect of medial nasal process + Anterior of maxillary process (lateral lips) 2. Nasal septum grows down from frontonasal process and fuses with palatine shelves from the maxillary processes By Wk 12 Final palate formed True fusion vs apparent fusion True fusion - Epithelial breakdown, continuous process, mesenchymal contact and true cellular integration Apparent fusion - No-epithelial breakdown, no continuous process, no true cellular integration, merely furrow elimination Genes Homeobox genes (acts on 3 levels) 1. Regulates genes that regulates other genes 2. Regulates effector genes that forms tissue, structures and organs (SOT) 3. Regulate cell division and adhesion, apoptosis and cell migration (DAAM) Growth factors 1. GFs activates hox genes - other effector genes that cause segments in developing embryo to differentiate 2. Creates positive and negative feedback loops, and morphogenetic fields 3. Creates discrete, localised biochemical signals leading to specific development of morphological structures or organs Hox genes 1. Determines basic structure and orientation of organism 2. Critical for proper placement of segmented structures during early embryology 3. Promotes cell division, adhesion, apoptosis and migration (DAAM) 4. Synthesises hox proteins Hox proteins Transcription factors that are capable of binding to specific nucleotide sequences on DNA - used to activate or suppress genes Factors causing CLP Mutation in genes 1. Transcription factors - MSX1, are important for the regulation of NCC development and migration -> needed for expression of BMP2 & BMP4 in palatal mesenchyme 2. Signalling pathways - BMP4, important for guidance and proliferation of NCC Environmental factors 1. Nutritional deficiencies - lack of folic acid is associated with neural tube defects 2. Heavy alcohol use during pregnancy - interfere with NCC migration What goes wrong for CLP to occur? Molecular - Mutation of key genes involved in normal development of lip and palate (MSX1 - NCC proliferation + migration, BMP2 BMP4 - palatal mesenchyme - Signalling pathways affected which affects subsequent proliferation of NCC Cellular - Failure of NCC proliferation and migration -> insufficient tissue formation of lip and palate - Dysregulation of cellular apoptosis - either excess cell death or insufficient cell removal leads to CLP Tissue - Cleft lip: Fusion failure of Mx process with medial nasal process (5-7th week gestation) - Clef palate: Fusion failure of palatal shelves (either failure to elevate or failure to fuse) with nasal septum (either failure to grow downwards or failure to fuse) (7-12th week gestation) Types of CLP Unilateral (1) : medial nasal process + max process Bilateral (2) : nasal process + 2 palatine shelves Median : 2 median nasal process Oblique cleft : lateral nasal process + max process Problems associated Dietary malnutrition Hearing problems: due to middle ear effusion and related infection (otitis media) Dental defect: hypodontia, supernumerary tooth, malformed and malposition Speech Psychological impacts * need to mention incompetent lips Dental defects Hypodontia: dental lamina falls to form due to the disruption of continuous band of dental lamina leading to gaps where tooth bud does not form Supernumerary tooth: disruption of normal signalling pathways - abnormal dental lamina - development of extra tooth buds Malformed teeth: disturbance of ameloblast and odontoblast secretion Malposition: cleft affects the alignment of developing tooth buds + abnormal development of jaw and surrounding structures - incorrect position of teeth Treatment - Orthodontic, prosthodontic Interventions or regular dental monitoring Food intake Buccal phase 1. Voluntary intake of food into the oral cavity, food is mechanically broken by the teeth and the tongue pushes the food against the hard palate forming a bolus 2. Tongue retacts and s/p elevates to seal nasopharynx Pharyngeal phase 1. Involuntary movement of food from pharynx to oesophagus 2. Bolus stimulates tactile receptors in the uvula and palatal arch - uvula and s/p elevates to seal nasopharynx 3. Motor commands are send from the medulla oblongata - contraction of pharyngeal muscles causes the elevation of larynx and epiglottis folds -> upper pharyngeal sphincter relax - bolus into oesophagus Oropharyngeal phase 1. Involuntary movement of food from oesophagus to stomach 2. Pharyngeal muscle contracts -> upper pharyngeal sphincter relax - bolus move through oesophagus by peristalsis 3. Lower pharyngeal sphincter relax -> bolus into stomach Liquid intake Buccal phase 1. Voluntary movement of liquid from bottle/breast to oral cavity 2. Muscle of lips contract around the nipple/bottle - generate negative pressure to draw liquid into the mouth Pharyngeal phase 1. Liquid is collected at the back of the mouth 2. Liquid stimulates tactile receptors in the uvula and palatal arch - uvula and s/p elevates to seal nasopharynx 3. As liquid reaches palatal arch the tongue elevates, vocal cords close and pharynx elevates and move anteriorly guides liquid towards the oesophagus 4. Upper esophageal sphincter relax allow liquid to enter oesophagus 5. swallowing reflex occurs Oropharyngeal phase 1. In the oesophagus liquid travels down by gravity 2. Lower esophageal sphincter relax -> liquid into stomach Hypothalamus Receives information from higher brain centres - major control for autonomic mediated functions (heart rate, body temp, bp, digestion) + hormone production, milk production, contraction of uterus, kidneys, growth and development Posterior pituitary Only stores hormones from hypothalamic neurons (ADH, Oxytocin) - ADH and Oxytocin ADH and Oxytocin is synthesised via hypothalamic neurons - packaged into vesicles - transported down axons - to posterior pituitary - stored in neuron terminals - activated by stimulus - released into extracellular space - capillaries - circulation Anterior pituitary Controlled by hypophysiotropic hormones (TSH, ACTH, FSH, LH, - TSH, ACTH, FSH, LH, Prolactin, GH Prolactin, GH) Thyroid - TSH is regulated by anterior pituitary hypophysiotropic hypothalamic hormones → TSH acts on thyroid follicle TSH initiates the synthesis of thyroglobulin -> active transport of iodine to thyroid follicle → tyrosine residue within thyroglobulin causes iodination and couple forming T3 & 4 - promotes cellular development, steroid like action, increase O2 consumption, increase CO, increase metabolic rate Calcium regulation PTH, Vit D - Calcitriol, Calcitonin (PTH, Vit D - Calcitriol, Calcitonin) Ca2+ levels important because decrease in Ca levels - increase membrane permeability of Na - leads to progressive depolarisation - ease of AP initiation - unwanted excitability of nerves - excessive/insufficient muscle contraction Bone reabsorption - PTH Bone integrity - Calcitonin & Vit D PTH - on - Secreted by chief cells of thyroid gland kidneys, on - K: conserves Ca in DT- prevents precipitation Ca3(PO4)2 + enhances VitD activation with hydroxylase bones , on enzyme bone fluid - Bones: PTH does not bind directly to osteoclast instead it binds to osteoblast receptor - increase RANKL decrease OPG - Increase RANKL binding to osteoclast precursor - differentiation of precursor to fully pledge osteoclast - bone resorption - BF: PTH stimulates rapid transfer of Ca from bone across osteoblast and osteocyte membrane - into canaliculi - into circulation Vit D - - Calcitriol binds to VitD receptor - translocated to nucleus & forms a heterodimer with X retinoid receptor - give Calcitriol rise to specific gene expressions - genes that are important for Ca movement across gut mucosal cells - Calcitriol increase expression of Ca channels + increase production of calbindin -> calbindin binds to Ca in enterocyte cytosol -> delivers Ca to basal lateral membrane - increase Ca-ATPase pump that actively pump Ca from cell into ECF against concentration gradient - Vit D stimulates osteoclast - increase Ca serum levels from bone reabsorption - also increase absorption of Ca from kidneys and intestine - net protective overall effect -> adequate or elevated levels of Ca for bone formation Calcitonin - Secreted by c cells of thyroid gland - Decreases osteoclast activity -> decreases Ca movement from labile pool - Decreases reabsorption of Ca in kidneys and intestine -> decreases plasma Ca and P - Protects skeletal integrity when there is high Ca2+ demand Stress Adrenaline, SNS, CRH-ACTH cortisol system Adrenaline - Stress activates SNS which sends signals to hypothalamus which travels down preganglionic sympathetic neurons in the spinal cord releasing Ach - Ach binds to receptor on chromaffin cells - release adrenaline - blood - targeted tissues CRH-ACTH - Stress activates SNS which sends signals to hypothalamus to release CRH to cortisol system median eminence - CRH taken up by hypophysiotropic hypothalamus portal system of blood vessels to anterior pituitary - CRH stimulates anterior pituitary to release ACTH into blood to adrenal cortex - zona fasciculata releases cortisol and zona glomerulosa to release aldosterone Cortisol - Secretion is regulated by circadian diurnal rhythm and ACTH -> Controls sleep/wake cycle - Increase cardiac function - Decrease immune function - Inhibits bone formation - Psychosocial - alters mood and behaviour Long term stress - With diabetes: antagonistic effects to insulin - Damage blood vessel - chronic BP - Allostatic overload - adrenaline acts on pancreas -> increase glucagon secretion - inhibit insulin - increase BGL and fatty acids GLUT-2 vs GLUT-4 Insulin 1. Glucose enters cells via the GLUT-2 pathway, becomes glucose-6-phosphate and undergoes glycolysis - increase in ATP production 2. Increased ATP levels - closes K+ channels, causing membrane depolarization 3. Which opens v-Ca channels leading to Ca2+ influx 4. Which stimulate insulin secretion 5. Which binds to tyrosine kinase receptors, facilitating entry of insulin into cells 6. An amplification cascade occurs and causes phosphorylation events 7. that translocate GLUT-4 receptors to the cell membrane, allowing glucose entry 8. Glucose influx activates anabolic pathways, promoting synthesis of fats and glycogen 9. Insulin presence inhibits catabolic pathways 10. Glycogen stored in muscle and liver cells Glucagon 1. Detection of low BGL by a-cells via GLUT-2 transporters, increase glucagon secretion 2. Promotes the breakdown of fat and glycogen in the liver and muscles, supplies energy during periods of stress or starvation 3. Increases glycolysis, leads to the production of acetyl-CoA that is converted into fats 4. Stimulates gluconeogenesis, crucial for maintaining BGL during prolonged fasting 5. Promotes lipolysis and the formation of ketones - alternative energy source for tissues 6. Protein metabolism is increased - to support glucose production and maintain BGL 7. When we need increased energy, glucagon stimulates the release of glucose & fat for energy 8. Glucagon secreted to mobilise energy reserves for metabolic needs Brain and ketones 1. Increase beta-oxidation of fat - produces excess acetyl-CoA - converted into ketone bodies 2. Released into the bloodstream and can be used for energy - the brain utilises ketones as an energy source Diabetes symptoms 1. Ketone/sweet breath 2. Unexplained weight loss 3. Increased urination 4. Increased infections 5. Blurred vision 6. Increased thirst and dehydration Type 1 Autoimmune destruction of b-cells, body cannot produce insulin - body is in a chronic fasted state and compromises glucose storage - ketogenesis occurs as the body thinks that there is insufficient BGL so it breaks down fatty acid instead to produce ketone for muscle and brain - decrease in production of new functional and structural proteins - paracrine suppression of a-cells lost of insulin - glucagon increase leading to ketoacidosis - diagnosed before 20 - insulin injection - Chronic hyperglycemia - glycation of haemoglobin - elevated levels of H1bA1c - Ketosis - Muscle wastage - decreased transport of amino acids into muscle and decreased protein synthesis - Rapid breathing -> excessive production of ketones that are not required - body is in a chronic fasted state -> excess ketones lowers blood pH - respiratory distress -> body trying to remove excess CO2 - Polyol pathway -> visual blurring, cataracts ~ Excess glucose converted into fructose and sorbitol via polyol pathway - sorbitol cannot cross cell membrane and accumulates - cause osmotic distress - higher extracellular sorbitol cause H2O to move into the cell - lysis + damage Periodontitis - Diabetes increases Advanced glycated end products (AGE’s) that signal cells to make Adipokines -> causing inflammation - Increase collagenase activity -> increases collagen degradation in gingival tissues - Increase RANKL production -> stimulates osteoclasts -> increase bone resorption -> increase in alveolar bone loss - AGEs dock on the macrophage receptors -> activate pro-inflammatory genes to increase production of cytokines like TNF-a and IL6 -> enhances tissue destruction & reduce tissue repair (immune dysfunction, narrowing of BV, decreases blood supply to gingiva and delivery of immunity cells) -> increased perio destruction Uncontrolled T1DM - Increase appetite, thirst, weight loss, polyuria, sudden vision changes, hyperglycemia and ketosis Type 2 Genetic influence Insulin resistance - insulin production is impaired - glucotoxicity = impair b cell function - lipotoxicity = excessive fatty acid can block GLUT 4 mobilisation - worsening insulin resistance - diagnose after 40 - common in sedentary or obese individual - lose weight, better diet - vascular damage, atherosclerotic plugs and increase risk of gingivitis and caries, more susceptible to develop infections and taste altered disorder - increase BGLs - glycosylation of blood proteins -> causes deficiency & compromise MSCs in PDL & pulp -> increase risk of caries and periodontitis To monitor Diabetes 1) H1bA1c are not damaged and can perform normal metabolic functions, levels are monitored for a period of 3 months - can give insight on BGL Normal - 4-5.6%, pre-diabetic 5.7- 6.4%, diabetes 6.5%, poorly controlled diabetes 7% 2) Glucometer blood glucose levels - taken with a glucometer at least 4 times a day  - T1DM (fasting levels): 4- 6 mmol/L - Pre meal BGLs: 4-8 mmol/L - Post meal BGLs: SNS withdrawal -> decrease noradrenaline -> increase in peripheral vasodilation to increase BF to other parts of the body -> increase in PSNS results decrease in HR and CO -> decrease in BP -> decreased blood flow to the heart and brain -> lack of oxygenated blood to the brain -> patient faints Metabolic syncope T1DM (insulin deficient) can have reduced sympathoadrenal response to hypoglycemia, with reduced awareness and defective glucose counterregulatory mechanisms - can lead to recurrent hypoglycemia - can result in TLOC Hypoglycemia (below 3.9mmol/L) leading to syncope (neuroglycopenia) -> inadequate BGL leads to TLOC as a protective mechanism to preserve cerebral blood flow by lowering metabolic demand on the brain during low BGL Orthostatic hypertension Blood distributed equally when lying down -> suddenly stand up -> blood pools to feet -> decreased cerebral perfusion -> syncope (baroreceptors cannot detect change in stretch fast enough to trigger SNS response to increase HR and contractility) Body’s reduced or inability to overcome gravitational shift causing syncope or symptoms associated with low BP - transient shift in autonomic response tends to trigger peripheral vasodilation and reduced CO - increased blood flow due to vasodilation -> reduced heart filling even if HR increases -> heart less full -> reduced CO -> cerebral hypoperfusion Collapse DRS ABCD 1) Danger: Check that the surrounding area is safe for both Pt and operator; remove any sharp instruments nearby. If conscious: let Pt sit comfortably to recover, check for signs of injury. If unconscious: lay Pt in supine position and elevate legs above heart level, loosen tight clothing (check for signs of injury simultaneously) → restore cerebral perfusion 2) Response: Check if there is any response from Pt by giving verbal cues or squeezing their shoulder. If there is a response → Pt is conscious. If no response, carry on with the rest of the first aid process 3) Send for help: Critical moment → reduce damage to Pt to get O2 as quickly as possible to the brain. Simultaneously ask another person (eg. DA) to call 000 for ambulance 4) Airway: Tilt head and lift chin → moves tongue away from pharynx → open and clears airway. Remove visible foreign objects to eliminate possible airway obstruction 5) Breathing: ‘Look, listen, feel’ → check if Pt is breathing. Look for chest rising and falling with breathing; listen for air movement near nose & mouth; feel for breath from Pt. If Pt is not breathing carry on to the next step 6) CPR: Start CPR - 30 chest compressions followed by 2 breaths → keeps oxygenated blood flowing until heart pumping can be restored Never stop CPR until help arrives 7) Defibrillation: Apply defibrillator if there is one and follow prompts given by machine → restore normal rhythm by sending electrical shock to heart. Post-incident: Pt sit in the waiting room for observation for 15 min. Complete SLS on SA Health. Do case notes. Follow-up If pt feels faint 1) seat the patient down 2) check BP - monitor for 15 min 3) give water 4) after observing for 15 min check BP again and if it is back to normal range (120/80), they can leave Periodontal Pristine periodontal health Total absence of clinical inflammation and no physiological immune surveillance on periodontium with normal support Clinical periodontal health Total absence or minimal presence of clinical inflammation and no physiological immune surveillance on periodontium with normal support Gingivitis Classification Risk factor: - a shift from Gram +ve to -ve 1. Intact periodontium Local risk - a reversible, destructive chronic inflammation caused by 2. Reduced periodontium that has not been treated for - plaque, biofilm retention, oral dryness periodontitis bacteria accumulation around the gingival margins 3. Reduced periodontium that has been treated for Systemic risk - loss of collagen periodontitis - smoking, diabetes, nutritional factor, drugs, sec hormones, - changes in OHH haematological conditions - localised BOP ≥10%, ≤ 30%, PPD ≤ 3mm - generalised BOP > 30%, PPD ≤ 3mm + CAL loss + possible bone loss First encounter 1. GCF and plasma factors (complement system and antibodies) Initial Periodontal Health 1. As biofilm accumulates 2. Bacteria produces LPS and metabolites - immune system recognises LPS and causes an inflammatory response 3. JE stimulated, secretes inflammatory mediators (cytokine IL-8) 4. In response to cytokines - free nerve endings produces neuropeptides and histamine 5. IL8 stimulates perivascular mast cells secrete histamine 6. Causes local vascular reaction - endothelium secretes IL-8 into blood vessels to attract PMNs -> PMNs follow IL-8 towards sulcus 7. Complement + antibodies support phagocytosis to decrease bacterial load Early Gingivitis (8-14days) 1. PMNs forms a dense layer over biofilm (palisade) - engulf and separate bacteria from sulcus 2. If PMN cannot control - proinflammatory cytokines and enzymes are released from macrophage activation 3. Lymphocyte infiltration in CT (mostly T cells, little plasma cells) 4. Increased vascular dilation + permeability (serum plasma protein influx) 5. Lateral proliferation of JE basal cells - act as mechanical barrier against plaque- thickening the JE 6. T-lymphocytes interact with fibroblasts - collagen degradation to make room for increasing immune cells Late gingivitis (~21days) 1. A shift from gram +ve to -ve 2. Intense PMN infiltration in JE/sulcus 3. As PMNs cannot control anymore, more lymphocytes, dominate infiltrate 4. Activated T cell releases many types of cytokines which helps B cell differentiate and convert into plasma cells 5. Plasma cells release antibodies and cytokines 6. Macrophages activates fibroblast to release MMP and TIMP instead of collagen - loss of collagen fibres provides space for expanding infiltrate 7. More lateral proliferation and apical migration of JE (pseudopocket) Necrotising gingivitis (use radiograph to differentiate between the 2) - fast progressive destruction - ulceration with central necrosis of interdental papilla form a crater (greyish, yellowish slush) - Limited to gingiva only - pain on probing, severe BOP, halitosis Treatment:  - Debridement under LA - OHI : chlorhexidine 0.2% 2 weeks - Antibiotic therapy metronidazole 400mg orally, every 12 hours, 3-5 days - Stress and smoking counselling - Analgesic (painkiller) - Review pt after 2-3 days Necrotising periodontitis: - destructive periodontal attachment and bone loss - gingival recession -> ct and epithelium destruction Periodontitis - an irreversible chronic inflammation and destruction of surrounding periodontal tissues (PDL & alveolar bone) - host immune system is responsible - genetic predisposition or from gingivitis Role of PMNs in maintaining periodontal health 1. Phagocytosis (IgG attaches to bacteria receptor, neutrophil forms pseudopodia and wraps around bacteria and phagocytoses, fuse with lysosome and digest) 2. Degranulation (Bacteria binds to PMN membrane, triggers release of antibacterial proteins via exocytosis) 3. NETosis (forms extracellular traps by uncoiling all its chromatin and releasing chromatin to trap pathogens) 4. Releases chemical signals (to recruit more PMNs) Recession - ‘an apical shift of gingival margin associated with CAL and exposure of root surface’ - clinical significance: aesthetic, dentine hypersensitivity, non-carious lesions, impaired OH, caries - aetiology: periodontal disease, gingiva phenotype, biofilm, fenestrations, dehiscence, frenal attachment, trauma, post-periodontal treatment Types of recession Stillman’s cleft - first sign of rapidly progressing recession Mccall’s Festoon - remaining attached gingiva becomes thickened and rolled Classification Type 1: no loss of interproximal attachment + buccal attachment loss Type 2: loss of interproximal attachment + ≤ buccal attachment loss Type 3: loss of interproximal attachment + > buccal attachment loss Treatment Monitor, Orthodontics, mucogingival surgery How does biofilm turn bad? - early pioneer bacteria attaches to pellicle via 1) initial reversible binding (weak non-covalent bond), 2) irreversible adhesion-receptor interactions - adhesins on these bacteria binds to more bacteria and those with compatible receptors - poor OH and cariogenic diet -> bacteria accumulates -> biofilm matures -> ecological succession - filament bacteria are introduced - diversity and bacteria increases - fusobacterium nucleatum - bridging organism with a lot of adhesins - causes a change in environment from aerobic to anaerobic - climax community - state of microbial homeostasis - where multiple species are able to coexist w the host - can cause gingivitis Why is there BOP when probing? biofilm accumulation around the gingival margin, bacteria LPS causes an host inflammatory response - blood vessels dilates - increase blood flow - allows immune cells to migrate to the site to kill the bacteria clinical signs of inflammation, redness, heat, oedema - Redness - increase blood flow increase RBC with haem which is red - Heat - increase blood flow - increase water in that area (blood is 90% water) - water has heat capacity - Oedema - Mast cells releases histamine that causes dilation that increase blood flow + increases gaps in epithelial surface of lining -> plasma leaks into IST via oncotic pressure and increase ISF -> increase in ISF causes oedema -> bleeding on probing is due to the increased number of dilated blood vessels in the inflamed gingiva which easily ruptures with probing due to small trauma Microbiology MS vs SM - M. Step : group of bacteria species - S. Mutans : specific species of bacteria that are linked to caries (Gram + - which thick peptidoglycan layer) Most common bacteria Mutans streptococci and lactobacili at later stages present in caries Indicators of high risk - MS (>10^6/ml) caries - Lactobacilli (>10^5/ml) - high cariogenic potential, active lesions might be present - Salivary flow rate ( not vulnerable Ways sucrose is used by 1. Glucan & mutans formation via glucosyltransferases (GTFs) S. Mutans → SM uses GTFs to break down sucrose into glucose & fructose → glucose forms glucans (soluble), which contributes to plaque bulk, bacterial cell (HIgh concentration) aggregation, creates water channels in plaque for nutrients and waste exchange and attachment to tooth surface (stabilising biofilm) → fructose is metabolised in glycolysis to form ATP 2. Fructan formation via fructosyltransferase (FTFs) → SM uses FTFs to break down sucrose into glucose and fructose → fructose joins together to form fructan → used as emergency fuel or help with bacterial adhesion. Fructans are broken down by fructanase into fructose to be used in glycolysis 3. Energy production via glycolysis → both fructose & glucose enters glycolysis - generating ATP for bacterial metabolism Ways sucrose is used by - Glucans and mutans are broken down by dextranses into glucose S. Mutans - Fructans are broken down by fructanase into fructose (Low concentration) → both used in glycolysis to form ATP for bacteria metabolism Role of glucans & GTFs Glucans : contributes to plaque bulk, bacterial cell aggregation, creates water channels in plaque for nutrients and waste exchange and attachment to tooth surface (stabilising biofilm) GTFs : are released by SM are found freely in saliva can bind to pellicle, where they form glucans & help bind bacteria to tooth surfaces, enhancing bacteria aggregation → promoting biofilm formation SM matining its - SM uses membrane-bound ATPase to pump out H+ → helping maintain a stable cytoplasmic pH even in acidic environment cytoplasmic pH in acidic → ↓ Sucrose PTS system, ↑ multi-sugar TS environment → in highly acidic conditions, SM shifts towards homo-fermentative metabolism, producing only lactic acid & synthesising stress proteins to withstand environmental stresses Surcose and oral health - High sugar consumption promotes a shift in bacterial composition of plaque from non-cariogenic to cariogenic species like SM, which thrives in acidic environments - Frequent sugar intake → prolonged acid exposure, during progression of dental caries by demineralising enamel and dentine ↳ pH 5.5-6 (snacking) favours demin of HA, ↑ sucrose = ↑ bacteria growth = ↓ pH = ↑ caries formation ↳ pH 6.5-6.6 (normal 3 meals a day) Immunocompromised - can impair the host's ability to control bacterial growth, allowing opportunistic pathogens to flourish individuals (ILA) - chronic inflammation can alter the local environment, making it more conducive for pathogenic bacteria to establish and persist Caries into dentine (ILA) (1) Recognition of Pathogens and Signal Transmission - Bacteria in carious lesions express PAMPs that are recognized by PRRs on host cells → TLRs and NLRs are expressed in dental pulp detects bacterial invasion → initiate immune response (2) Odontoblasts express TLRs and NLRs to recognize bacteria, secrete antimicrobial peptides & proinflammatory cytokines (3) Pulp fibroblasts produce proinflammatory cytokines, chemokines and activates components of complement system, enhances the inflammatory response, aids in eliminating bacteria and regenerating tissue (4) Inflammatory signalling molecules and Immune Cell Accumulation - IL-6, IL-10, nitric oxide (5) Tertiary Dentine Formation - protective mechanism - forms a barrier between the pulp and the advancing bacterial infection (6) Vascular and Neuronal Networks - Vasodilation and increased vascular permeability, allowing immune cells to move to the infection site → activation → nerve fibre sprouting → neuropeptides released to help mediate immune response and contribute to the formation of tertiary dentine (7) Odontoblasts secrete signalling molecules, and become embedded in the dentine matrix. When caries progress and demin occurs, these molecules are released and activated, triggering immune responses and tissue repair mechanisms Public health initiative Fluoride in public water supply → has reduced 50% of caries incidence to decrease caries - Optimal concentration ~1 ppm  prevalence Host factors in - oral hygiene controlling caries - enamel type (fluorapatite vs hydroxyapatite) - salivary flow rate and composition( buffering capacity & calcium levels) F vs MS Fluoride has anti-microbial action: (1) Reduces glycolysis which Inhibits enolase (2) PEP/PTS system inhibited, ↓ sugar uptake during low sugar conditions (eg. at night) (3) Acidifies bacterial cytoplasm by increasing membrane permeability to hydronium ions → Inhibition of cellular enzymes & interferes with membrane function (4) Reduces IPS synthesis- affects cells during famine conditions MS are particularly sensitive to Fluoride at low pH → pH fall expt with plaque – in the presence of F – MS =1% without =18% MS can develop resistance to Fluoride- less cariogenic as resistance is accompanied by reduced acidogenicity and aciduric environment In clinic Chlorhexidine, Essential oils CHx is both bactericidal and bacteriostatic - targets broad spectrum, bactericidal ~ 5 hrs in saliva (damages bacteria membrane), MS very susceptible to CHx & able to suppress MS levels for long periods - Does not upset oral microbial ecology ☆ Antagonistic effect when used with F- (must use separately), F- is negatively charged, CHx is positively charged Alcohol sugars - are non-cariogenic, does not contribute to caries formation as they are not easily metabolised by oral bacteria (mannitol & sorbitol) in - Unlike xylitol, these alcohol sugar do not induce a futile cycle in cariogenic bacteria reducing caries - Sorbitol are slow fermentation, slight acid production but still less than sucrose - Mannitol have lesser fermentation than sorbitol Xylitol effectiveness - Induces futiles cycle in MS, where ATP is used each time xylitol is transported across cell membrane → ATP reserve depletes of stress proteins that against MS are crucial for aciduricity (tolerating highly acidic environment) → affecting their ability to produce acid and adhere to tooth surfaces - decreases capacity to cause caries x Xylitol is expensive to make and has bad GI effects (diarrhoea & gas) when consumed in large amounts Cell injury and death Cell injury and death What causes cell injury 1. Oxygen deprivation - ↓ blood flow, inadequate blood oxygenation = ↓ O2 carry ability = ↓ cellular aerobic oxidative respiration and death? 2. Physical agents - mechanical trauma, temperature extremes and radiation 3. Chemical agents - too acidic/alkaline 4. Infectious agents - bacteria, virus, fungi & parasites - toxins, invasion or immune response 5. Immunological reaction - ‘collateral’ damage from immune responses, autoimmune reaction can attack healthy cells 6. Genetic changes - mutation or inherited defects → deficiency / become more susceptible to disease or injury 7. Nutritional imbalances - starvation or nutritional excess (i.e. cholesterol) → dysfunction and cell injury Mechanism of cell injury Mitochondrial damage - Leads to ATP depletion & formation of reactive oxygen species (ROS) → reduced & abnormal oxidative phosphorylation Depletion of ATP - Caused by ↓ supply of oxygen and nutrients / mitochondrial damage - Consequences: failure of Na & Ca pumps, ↑ anaerobic glycolysis → lactic acid build up, protein synthesis impaired Accumulation of ROS - Damages protein, lipids & DNA, generated by metabolic processes, inflammation, radiation & toxins Loss of calcium homeostasis - When cells experience ischaemia or toxins, releases Ca2+ from intracellular stores (mitochondria and ER) → this increases the movement of Ca2+ across plasma membranes → increase Ca2+ intracellular levels ↳ cell injury: activation of degradation enzymes, ↑ mitochondrial permeability, generation of ROS  Defects in membrane permeability - Damage to mitochondrial, plasma (loss of osmotic balance & cellular contents) or lysosomal damage → loss of cell integrity & enzyme leakage (RNAses, DNAses, Proteases…) Removal of free radicals - Spontaneous decay - Antioxidants (e.g. vitamins E and A, ascorbic acid) - Enzymes neutralises free radicals Catalase (present peroxisomes, decomposes H2O2) Superoxide dismutases Glutathione peroxidases Morphological cellular (1) Hydrophobic changes (cellular swelling) changes due to cell - Cells cannot maintain ionic & fluid homeostasis → water accumulation death or injury (2) Fatty changes - Accumulation of lipids in cells due to metabolic injury → seen in hepatocytes in liver Histology (1) Hydrophobic changes (2) Fatty changes Apoptosis vs Necrosis - Apoptosis (programmed cell death) ↳ Activation of intracellular enzymes that degrades nuclear DNA & cytoplasmic proteins ↳ Causes: embryogenesis, hormonal withdrawal, protection against autoimmune diseases, resolution of immune disease ↳ Morphological changes: (1) cell shrinkage (2) nuclear changes - condensation of chromatin (3) formation of apoptotic bodies (4) no inflammation - clean process - Necrosis (unregulated, irreversible cell injury) ↳ Denaturing of intracellular proteins, enzymatic digestion & loss of membrane integrity - leakage of intracellular contents ↳ Causes: ischemia, toxins, infections & trauma ↳ Histology changes: increased eosinophilia (more pink because of protein denaturation), nuclear changes (karyolysis, karyorrhexis) - Patterns of necrosis: (1) Coagulative necrosis - caused by ischemia or hypoxia ↳ basic structure of tissue preserved for a few days despite cell death - cells appear eosinophilic and anualated → before removal by phagocytosis  loss of shape and increase eosinophilia of cytoplasm (2) Liquefactive necrosis - caused by bacterial/fungal infection ↳ enzymatic digestion of dead cells → liquid liquefaction → formation of pus a lot of neutrophils (3) Caseous necrosis - cheese like ↳ seen in tuberculosis pt ↳ collection of fragmented necrotic cells, surrounding granulomatous inflammation complete breakdown of cells (4) Gangrenous necrosis ↳ body tissue dies from ischemia or bacteria infection Necrosis in kidney Healing and repair (1) Granulation tissue (2) Granulation tissue function - to act as healing tissue (3) Blood vessels, myofibroblasts, fibroblasts, macrophages Clinical examples Pathological terms (1) Growth - multiplicative growth (hyperplasia) : ↑ cell number - auxetic growth (hypertrophy) : ↑ cell size - accretionary growth : ↑ intercellular tissue compartment - combined patterns of growth (2) Differentiation - cells acquire specialised function of morphology (3) Atrophy - cause by ↓ function, loss of innervation, blood supply, poor nutrition or endocrine stimulation (4) Metaplasia - reversible change where one mature tissue type is replaced by another ↳ in response to altered cellular environment eg. by chronic irritation or injury (5) Dysplasia - abnormal, disorganised growth with changes in cell size, shape and loss of differentiation ⛤ pre-neoplastic condition - can reverse in early stages → can progress to cancer (6) Neoplasia - uncontrolled abnormal cell proliferation that persist after removal of stimulus ↳ genetic alteration influence behaviour of cells → excessive & uncoordinated growth Atrophy Mouth: alveolar bone - after extraction, loading on the bone becomes lesser and atrophy occurs Brain: sulci are wider and shrinks - ageing, neurodegenerative disorder, pathological or physiological disturbance Changes in oral cavity (1) Linea alba (hypoplasia) - a benign white line lesion on buccal mucosa caused by cheek biting (local mechanical trauma) ↳ thicken prickle layer, hyperkeratosis  (2) Fibroepithelial hyperplasia (polyp) - occurs at sites prone to trauma (cheek biting, irritation from broken teeth/resto, ill-fitting dentures) ↳ hyperplastic or atrophic epithelium - with dense collagenous fibrous CT + chronic inflammation - Exophytic localised lesion (sessile - no neck, broadest area of lesion is the base | pedunculated - have neck) (3) Smoker’s keratosis - usually in elderly male pts - a diffuse, white thickening of the palate from smoking, small red dots may be present (inflamed salivary ducts) Neoplasia - Refers to the abnormal, uncontrolled growth of cells or tissues that results from genetic mutations. It persists even after the initial stimulus that triggered it has been removed, forming a lump/mass called a neoplasm, consist of 2 key components ↳ Parenchymal cells, which define the type of tumour (whether benign or malignant) ↳ Tumour stroma, the supporting tissue that provides nutrients, influencing the tumour's growth and spread - Irreversible and permanent Benign vs. Malignant Neoplasms Benign neoplasms No metastasis Remain localised (typically well-circumscribed or encapsulated, remaining in their original site) Slow growth rate Usually close histological resemblance to tissue of origin (well differentiated) - suffix “oma” e.g. adenoma, osteoma etc Malignant neoplasms Metastatic potential Localised invasion of surrounding tissues - capable of destroying adjacent tissues Rapid growth rate Variable histological resemblance to tissue of origin (variable differentiation) Characteristics of Progressive: Neoplastic growth continue to grow regardless of requirements of the body neoplasia Purposeless: The mass serves no useful function. Parasitic: It draws nutrients from the body without providing any benefits. Process of neoplasia 1. Initiation: A genetic event that alters the genome causing permanent damage to DNA - mutations. 2. Promotion: Further mutations occur as cells proliferate, driven by various promoting factors. 3. Progression: More genetic alterations lead to subclones of neoplastic cells, resulting in an increasingly aggressive tumour - Double hit model (2 alleles per gene - if one it hit and one is functional, function will not be affected) ⇢ If a hit is inherited, increase susceptibility to developing specific types of cancer - usually involves genes that regulate cell growth, DNA repair or apoptosis ⇢ Inherited mutations often lead to the development of tumours at a younger age compared to sporadic cases, because of hit allele present - Eg. Multiple endocrine neoplasia syndrome, Xeroderma pigmentosum, Familial polyposis coli, Retinoblastoma or Familial breast carcinoma Genetic Alterations in Genetic alterations leads to alteration in normal cell proliferations (unregulated and excessive, limitless replicative potential , sustained angiogenesis, evade Neoplasia apoptosis, self-sufficiency in growth signals, insensitive to anti-growth signals, tissue invasion and metastasis) Oncogenes: Mutations convert normal regulatory genes (proto-oncogenes) into oncogenes, leading to uncontrolled cell proliferation - Promote cell growth without external stimuli, reduce cell cohesiveness, leading to increased invasiveness, immortalization of cells, abnormal cellular orientation and increased motility Tumor suppressor genes: Inactivation of P53 genes removes the brakes on cell division, leading to unchecked growth, allowing damaged cells to divide - Normally activated in response to DNA damage, arresting the cell cycle to allow for repair before S phase or inducing apoptosis if the damage is irreparable Telomerase reactivation: Reactivated in neoplastic cells and maintains length, allows for limitless replication Bcl-2 gene: Overexpression of this gene prevents apoptosis, enabling cancer cells to survive longer than normal cells (observed in certain lymphomas) Anaplasia lack of differentiation of tumour cells, however often equated with poor differentiation at a tissue level  Anaplastic tumour = poorly differentiated tumour Invasion and Metastasis Invasion: - Important feature of malignancy, characterised by the ability of neoplastic cells to breach the basement membrane and infiltrate surrounding tissues. This is often facilitated by enzymes like matrix metalloproteinases, which degrade the extracellular matrix and basement membrane Metastasis: - spread of cancer cells from the primary tumour to distant sites via the lymphatic system, blood vessels, or nerves. This process involves a series of steps, including local invasion, intravasation, circulation, extravasation, and colonisation at a distant site Abnormal vs Normal Carcinogenesis the transformation of a normal cell into a neoplastic cell by causing permanent genetic alterations occurs through a series of mutations - abnormal proliferation - ability to break down basement membranes and extracellular matrix (able to invade surrounding structures) - ability to metastasise (cancer cells spread from the primary tumour to distant sites in the body, forming secondary tumours Agents of Carcinogenesis: - Chemical: Polycyclic aromatic hydrocarbons (lung/skin cancer), aromatic amines (bladder), nitrosamines (gut), and azo dyes (bladder/liver). - Viral: Human papillomavirus, Epstein-Barr virus, and hepatitis B virus - Physical: Ionizing radiation (leukemia, thyroid malignancies), UV radiation (skin/lip cancer), asbestos Viral carcinogenesis Certain viruses contribute to the development of cancer, via integration of viral genome into host DNA or viral proteins lead to interference with host normal cellular processes, leading to cell damage and regeneration - increasing chances of genetic mutations Eg. HPV – cervical carcinoma, oropharyngeal carcinoma EBV – lymphomas, nasopharyngeal carcinoma HBV - hepatocellular carcinoma Common clinical symptoms Actinic cheilitis (pre-cancerous) Skin and vermillion border are blended Clinically - dry, looks white/pale pink and may lose elasticity With more exposure can eventually lead to a malignant lesion Squamous cell Non-healing ulcer with a rolled border and carcinoma can be crusted or ulcerated Lesions may appear erythematous or white Dysplasia and cellular Dysplasia refers to disordered growth and maturation of tissues, often seen as a precursor to cancer, but not yet malignant. features of cancers - Epithelial atypia: Abnormal cellular features indicative of potential progression to cancer - Carcinoma in situ: A pre-invasive stage where dysplasia involves the entire thickness of the epithelium but does not invade the basement membrane Severity of dysplasia is determined by: (1) How many features of epithelial atypia are present (2) How much of the epithelial thickness is atypical Mild Dysplasia: Limited to the lower third of the epithelium Moderate Dysplasia: Extends into the middle third of the epithelium Severe Dysplasia: Involves more than two-thirds of the epithelial thickness but does not invade the basement membrane Normal vs neoplastic Normal: regulated proliferation, cells under apoptosis, contact inhibition, limited lifespan cells Neoplastic: unregulated proliferation, evasion of apoptosis, loss of contact inhibition, limitless replication Histology Epithelial atypia:  Dropped shaped rete pegs Irregular stratification Suprabasal mitotic figures Increased mitotic figures Histology Cellular changes: Cellular and nuclear pleomorphism/ Increased nuclear-cytoplasmic ratio Cellular and nuclear pleomorphism Loss of cohesion Clinical Effects of Benign neoplasms grow slowly, have infrequent mitoses, and often resemble normal tissue histologically. They do not invade or metastasize, epcapsulated or Benign and Malignant circumscribed borders Neoplasms Malignant neoplasms grow rapidly, have frequent and atypical mitoses, variable histological resemblance to normal tissue, and invade surrounding tissues. They can metastasize and have poorly defined borders, mostly occurring on mucosal surfaces Clinical Appearance of Early stage: leukoplakia (white patches) or erythroplakia (red patches) - painless, papillary lesions (small-wart like growth) Oral Cancer Advance stage: non-healing ulcers with raised borders, lesion may become bigger - noticeable deformities, bleeding, necrosis-tissue break down (foul smelling) Recognise and describe Oral cancer, particularly squamous cell carcinoma (SCC), presents with various clinical features depending on the stage. Early signs may include painless the clinical appearance white patches, papillary lesions, leukoplakia, or erythroplakia. Advanced signs include ulceration, necrosis, and tissue destruction of oral cancer Histological Features of Histologically, SCC varies in differentiation from well-differentiated to anaplastic Oral Squamous Cell Features such as keratin pearls, abnormal mitoses, dyskeratosis, and depth of invasion are important prognostic Carcinoma (SCC) indicators Management of Oral Management involves early diagnosis through clinical suspicion and biopsy. Cancer Treatment modalities include surgery, radiotherapy, chemotherapy, or combinations based on clinical staging (TNM system). follow-up and maintenance are crucial post-treatment Inflammation Protective process that deals with infection and injury but causes damage to surrounding tissues ↳ acute (reversible), chronic (based on pathology) Causes Infection, hypersensitivity reactions, physical/chemical injury, necrosis 5 cardinal signs of inflammation Redness, Heat, Swelling, Mast cells, histamine → increase in epithelial spaces → increased in lumen size from vasodilation → increased blood flow → Pain, Loss of function increase in gaps of endothelial lining → plasma leaks into IST because of oncotic pressure→ increases ISF → causes oedema Mast cells, histamine → increase in epithelial spaces → increased in lumen size from vasodilation → increased blood flow → RBC contains haem from haemoglobin that is red in colour Mast cells, histamine → increase in epithelial spaces → increased in lumen size from vasodilation → increased blood flow → increase in gaps of endothelial lining → plasma leaks into IST because of oncotic pressure → increases ISF → blood is made of 55% of blood volume, plasma is 90% water → water have heat capacity Mast cells, histamine → increase in epithelial spaces → increased in lumen size from vasodilation → increased blood flow → increase in gaps of endothelial lining → plasma leaks into IST → increases ISF → increase pressure from oedema and ISF volume, compresses nerve ending= nociceptors stimulated , prostaglandins lower AP threshold = pain threshold → AP is processed in CNS leading to the perception of pain Changes in vessel calibre (a) ↑ vascular permeability: allows protein (immunoglobulins, complement & coagulation factors - fibrinogen) to escape into EVS, promotes more fluid to leave vessel → accumulation = fluid exudate = oedema (b) Formation of cellular exudate : neutrophils are the first immune cells to response to injury or infection 1. Neutrophils migrate to get closer to endothelial cells 2. Increase adhesion via ELAM-1 & integrins 3. Pavementing of neutrophils 4. Emigration - neutrophils pass between endothelial cells → through plasma membrane into EVS 5. Diapedesis - neutrophils pass through basement membrane into CT (EVS) (c) Chemotaxis of neutrophils: once in EVS, chemical gradients attracts neutrophil to site of injury → facilitated by chemical mediators such as complement components & cytokines → neutrophils then phagocytose & engulf pathogens, dead cells & debris Key mediators 1. Macrophages - produce medical mediators (IL-1 & TNF) 2. Mast cells & histamine - vasodilation, ↑ vascular permeability → oedema 3. Neutrophils - phagocytosis & release of lysosomal enzymes (proteases) 4. Lymphatics - draining inflammatory exudate Clinical features & - Usually 5 clinical signs & pus microscopic features of - Granulomatous inflammation (collection of macrophages) inflammation - Accumulation of macrophages, surrounding lymphocytes and fibroblasts, when they are unable to eliminate more macrophages are recruited and fusion of macrophages occurs → Langhan’s giant cells, nuclei distributed around periphery of cytoplasm and becomes very eosinophilic and look like epithelial cells → epithelioid cells - Central necrosis – “caseous” cheesy appearance macroscopically Example in dental practices Pulp response : - Inflammation -> reparative dentine formation (pulp canal obliteration + sclerosis of tubules) - Fibrosis and reduced cellularity - Granulation tissue formation (pulp must have sufficient blood supply and time) Limitation: - Limited capacity for drainage - Limited access for repair - Limited space for swelling - Concentrated stimulus - Limitations of materials to treat Pulpitis Periapical abscess: - Untreated pulp necrosis, acute inflammation in periapical tissues ↳ Severe pain, Neutrophil infiltration, dilation of blood vessels, Tissue necrosis, Pus formation, Spread of pus, Draining sinus - Histology: localised collection of pus (proteinaceous exudate, neutrophils, necrotic tissue) surrounded by acutely inflamed tissue - Spread of an abscess: spread through buccal cortical bone or gingival tissue – sinus formation or cellulitis formation or periapical granuloma formation Periapical granuloma: - Chronic inflammation in the periapical tissues Long-term, abscess may develop into a “granuloma” - Histology: granulation tissue and fibrous tissue Inflammatory cells (macrophages, lymphocytes, plasma cells and neutrophils) R/L around roots are indicators of PG Oral ulceration: - From trauma, infections, neoplasia or aphthous ulceration are all characterised by loss of epithelium and inflammation loss of continuous epithelium Beneficial/harmful effects of acute inflammation  Beneficial Harmful - Dilution of toxins - Destruction of normal tissues - Entry of antibodies - Swelling - Transport of drugs - Inappropriate inflammatory response - Fibrin formation - Delivery of nutrients and oxygen - Stimulation of the immune response Inflammation triggers Regeneration healing - replacement of dead or injured cells with identical types of cells ↳ Labile cells (skin, lining epithelium) constantly divide and regenerate easily ↳ Stable cells (glandular organs) divide when necessary to replace lost cells ↳ Permanent cells (nerves, muscle) cannot regenerate and rely on repair mechanisms Repair - Replacement of dead or damaged tissue with fibrous CT (scar tissue) Primary vs. Secondary Primary intention: Intention Healing - occurs in small, clean wounds with minimal tissue loss. Edges are approximated, and healing results in minimal scarring. Secondary intention: - Involves larger wounds with significant tissue loss.This process forms larger blood clots, involves more inflammation, and results in wound contraction and greater scarring as the area is replaced with dense fibrous connective tissue Granulation Tissue and Granulation tissue: a type of healing tissue that forms at the site of an injury Angiogenesis - consists of new blood vessels, fibroblasts, and macrophages - provides a framework for tissue regeneration Angiogenesis: - formation of new blood vessels from pre-existing (damaged) ones that migrates toward stimulus activated via growth factors (VEGF) - provide oxygen and nutrients to regenerating tissues Timeline of Secondary 0 hours: Intention Healing - Blood vessels rupture, leading to tissue loss - A blood clot forms to stop the bleeding and protect the injured area 24 hours: - Exudate forms, haemorrhage and blood clot formation continue - Inflammation occurs to eliminate dead cells, bacteria, and debris, initiating the healing process. 2-7 days: - The blood clot is invaded by granulation tissue, which helps repair the tissue - Inflammation decreases in intensity as damaged tissue is removed and healing begins. 2 weeks: - Granulation tissue decreases in volume, and collagen production increases, strengthening the healing tissue. - Inflammation continues to decrease. - Epithelial regeneration begins beneath the scab as the new tissue grows to cover the wound. - The scab falls off, usually within a few weeks. 2 months: - The tissue undergoes organisation and maturation. - There is a reduction in vascularity and collagen matures and the wound contracts, making the area stronger and reducing its size. Factors Affecting Wound Healing Systemic Age (generally the older the person is, the longer the healing time) Nutrition A. Protein deficiency B. Vitamin C deficiency C. Zinc deficiency Local Infection Metabolic disorders (Diabetes) Inadequacy of blood supply → less nutrients available for cells → slower healing Foreign bodies Type of tissue involved Bone Fracture Healing By secondary intention + bone regeneration Process 0 hours: Fracture, cell and tissue lost and blood vessel rupture causes a hematoma to form at the site + inflammation 1-7 days: Granulation tissue invades the clot, initiating bone resorption and repair 1-3 weeks: A procallus forms, composed of immature bone (woven bone) and granulation tissue, providing stability  3-4 weeks: The procallus becomes rigid (becomes callus) as more bone forms, increasing its stability. 1-2 months: The callus remodels into mature bone, restoring normal function and appearance Factors Affecting Bone Healing General Nutritional status (adequate intake of calcium, phosphorus, and vitamins) Metabolic disorders (Paget’s disease or rickets impair bone quality and regeneration) Local Blood supply (nutrients and oxygen) Type of fracture - complete, incomplete, closed, (comminuted or compound fractures take longer to heal due to greater tissue damage) Infection - delays healing Mobility: excess movement at the fracture site can delay healing and result in fibrous union or false joints Tooth Socket Healing Process similar to healing of any bone wound Secondary intention with bone regeneration - After extraction, a blood clot forms, followed by granulation tissue invasion → the bone regenerates to fill the bony defect left by the extraction Immunology Allergy - Systemic disease in the immune system ↳ immunological sensitivity ↳ Mechanism (1) Genetic disposition, (2) Adequate antigen exposure, (3) abnormal immune response Importance of atopy 1. Medical history - atopy runs in the family → history of allergic reaction can help identify patterns & potential triggers (early identification) 2. Diagnosis - identifying allergens distinguishing between allergic vs non-allergic reaction 3. Treatment planning - knowledge allows for tailored treatment 4. Long-term management Hygiene hypothesis Atopic diseases are prevented by infections in early childhood → contact with siblings & prenatal exposure by mother infected by children Innate vs acquired immunity Innate immunity Acquired immunity Naturally occurring Develops over lifetime Non-specific, no memory cells Specific memory cells Rapid response (neutrophils, basophils, macrophages) Delayed on first response → faster response on subsequent exposure → ↑ Recognises PAMPs effectiveness (B cells - plasma cells, antibodies | T Cells - T helper(CD4+), Does not increase in potency with subsequent exposure Treg (CD4+, CD25+), CD8+ Cytotoxic (killing)) - B cells (Humoral immunity), T cells (Cell-mediated immunity) Does not recognise PAMPs ↑ in potency with subsequent exposure Complement system: secretion of cytokines, polypeptides & other cells reacts with antigens → activation of complement system (macrophage) → opsonization, degranulation & NETosis Humoral vs cell-mediated immunity Humoral immunity Cell-mediated immunity B lymphocyte → antibodies secreted T helper cell → activates macrophages to kill phagocytose microbes ↳ blocks interactions & eliminates extracellular microbes Cytotoxic T cell - kills infected cells & eliminates reservoir of infection (in infected cells) BCR vs TCR All immune cells derived from hematopoietic stem cells in the bone marrow Both B and T cells undergo both positive and negative selection in the primary lymphoid organs ↳ B lymphocytes : will remain in the bone marrow to be educated by being exposed to self-antigens - Immature B cells express IgM on their surface & during maturation they also express IgD, Non-self reactive B cells mature & express IgM+ & IgD+, leave the bone marrow → into circulation → migrate to secondary lymphoid organs (spleen or lymph nodes) ↳ T lymphocytes : undergoes positive selection - recognise self MHC are selected - T cell receptors are inserted into cell membrane (a:B chains further divides into T helper-CD4+, Cytotoxic-CD8+ → occurs in immature after T cell receptor  genes have been assembled - Activation requires successful binding of antigen receptor to epitope & additional signals ↳ (1) stimulation of cell to leave G0 & enter cell cycle ↳ (2) repeated mitosis, producing a large number of daughter cells with the same antigen receptor (identical specificity to the same epitope) ⛤ Genes for TCR and BCR are contained int heir germ line & each individual lymphocyte is determined through V, C, J, D segments which are rearranged Variable region genes, Constant region genes, Joining & diversity genes, Diversity regions (VCJD) ↳ BCR able to isotype switch (eg. IgA to IgG) via constant region genes (C) → without altering antigen specificity to the antibody - regulated by cytokine environment & important for pt with serious anaphylactic allergy Subsets to T cells Th only applies for T helper cell and the type of cytokines it produce Th0 - undifferentiated CD4+/CD8+ cells, no cytokines produced at all (naive T cell - T helper cell not activated and has successfully undergone positive and negative selection) Th1 - subsets of CD4+, produced during cell mediated response (parasites, virus and bacteria) → cytokines (IFNy, IL-2) Th2 - subsets of CD4+, produced during allergic response → Th2 \cells produces cytokines (IL-4, 5, 13), activates & differentiates B cells into plasma cells where IgE is produced (particularly against parasites) Role of TCR & MHC - TCR: antigen recognition, TCR binds to specific MHC complex → initiating signalling cascade for T-cell activation class 1 or 2 in - MHC class 1: nucleated cell presents peptide to CD8+ cells T-helper activation - MHC class 2: APCs presents peptide to CD4+ cells ↳ both leads to the activation if TCR recognises Immune response is 1. Response via TCR & BCR achieved via 2. Unresponsive to self-antigens, constant generation of lymphocytes that recognise self 3. Unresponsive to harmless external antigens/commensal organisms Central vs Central peripheral tolerance - In the thymus & bone marrow immature lymphocytes undergoes negative selection for self-reactive cells before leaving primary lymphoid organs & enter peripheral circulation ↳ are deleted, apoptosis, change in specificity (receptor editing → change their antigen), self reactive CD4+ cells may differentiate to Treg → important for immune tolerance Peripheral tolerance - After T cell exits thymus / B cell exits bone marrow → limits the activation of mature self-reactive T cells by anergy (inactive), deletion or immunological ignorance (ignore self-antigens) ↳ controlled by Treg, B cells & other leukocytes - Molecules like CTLA-4 & PD-1 on T cells dampens immune response & maintain tolerance to self-antigens Apoptosis Induced by pro-apoptotic proteins - antigen recognition induces: - pro-apoptotic protein production -> causes mitochondrial proteins to leak -> activates cytosolic enzymes (caspases), absence of co-stimulation - co-expression of death receptors, signals via death receptor, pro-apoptotic protein production Clonal anergy Functionally unresponsive - self-antigen recognition - absence of adequate co-stimulation - absence of adequate by the TCR complex, inhibitory signals from receptors other than the TCR complex - Enzyme activation (ubiquitin ligases) - signalling proteins modified -> causes intracellular signalling protein destruction or inhibitory proteins stimulated - Cytotoxic T cell antigen or programmed cell death protein Suppression - Treg development program - Lymphocyte subsets may act as suppressors or regulators of T & B cell activation recognition of self antigens Regulatory T cells develop suppress the activation lymphocytes specific for these self antigens CD4+ T regulatory cells (Treg) - suppression of several autoimmune diseases CD8+ T suppressors (Ts) - suppression of graft rejection Apoptosis Induced by pro-apoptotic proteins - antigen recognition induces: - pro-apoptotic protein production -> causes mitochondrial proteins to leak -> activates cytosolic enzymes (caspases), absence of co-stimulation - co-expression of death receptors, signals via death receptor, pro-apoptotic protein production Autoimmunity - may arise from (1) loss of tolerance, (2) formation of new epitopes, (3) exposure of hidden epitopes, (4) epitope sharing ↳ severity & development depends on genetic makeup ↳ Genetic - formation of forbidden clones (self-reactive) ↳ Environmental triggers - infection (viral/bacterial) - autoantibodies present can help with diagnosis - cell mediated response 1. non-self reactive lymphocytes → may be active 2. Innate immune system can activate mature lymphocytes → adaptive immune response that cause damage to body’s own tissue Disorders Systemic lupus erythematosus (chronic autoimmune disease) - body attacks CT affecting heart, joints, skin, lungs, blood vessel, liver, kidney & nervous system → unpredictable flares ↳ Medications: immunosuppressant ↳ Symptoms: butterfly facial rash ↳ Oral: predisposition for infection (pain and swelling) Rheumatic arthritis (chronic systemic inflammatory disorder) - immune system attacks joint synovium causes thickening & the inflammatory destroys cartilage & joins ↳ Also affects the lung, heart, pericardium, vessels, pleura, sclera, neurological, skin lesions ↳ HLA-DRA allotypes of MHC class II, this gene are more susceptible to RA autoantibodies directed to IgEFc are used to diagnose RA Diabetes mellitus - type 1 (genetics) - Inflammation of islet of langerhans destruction of pancreatic beta cell (insulin impacted) ↳ normal secretion of glucagon, somatostatin & pancreatic polypeptide - large number of mononuclear cells & CD8+ T cells (targets beta cells) Pemphigus vulgaris - autoimmune process targeting skin & oral mucosa desmosomes ↳ immune system produce autoantibodies against desmoglein-3 (cells fail to adhere to each other) ↳ clinical signs: ulcerations and slough of buccal mucosa and ulceration of gingiva  Benign mucous membrane pemphigoid - production of autoantibodies directed against basement membrane of the oral mucosa ↳ clinical signs: red inflamed gingiva, subepithelial clefting Sjogren’s syndrome (autoimmune disorder) - (1) primary sjogren’s - exocrine glands - (2) secondary sjogren’s - CT and RA ↳ Autoantigens in salivary & lacrimal glands are recognised as foreign → CD4+ & B cells are activated → activated lymphocytes release cytokines & CAMPs over expression of proliferation & cloning → leading to chronic inflammation & tissue damage → targets & destroys salivary ducts, acinar cells (produce saliva) ↳ Oral: Lacrimal gland - epithelial cell death & disintegration → dry eyes, photosensitivity, foreign body sensation Salivary gland (xerostomia) → speech difficulties, chewing, swallowing, altered taste, pain, burning, cracked dry desquamative lips, dry fissures Gland swelling, rampant caries, occlusal wear, mucositis, chronic candidiasis Treatment plan: (1) relieve symptoms, (2) replace secretions - insulin, thyroid hormone, synthetic tears, saliva replacement (3) suppress immune system - immunosuppressants, anti-inflammatory medications, chemotherapy, anti- TNF Immunodeficiency = immunocompromised → impacts health & oral health (oral candidiasis) → recurrent infections (ID) Primary ID - born with, defects in immune system Secondary ID - mostly acquired from external factors (injections, malnutrition or medication) ↳ prevent rejection of transplanted tissues, immunosuppressive drugs are taken to suppress immune system → prevents rejection ↳ environmental (eg. drugs, virus, exposure to chemical, diet) On world health - pt with immunodeficiencies ↳ treatment/therapies (organ & bone marrow transplantation, cancer therapy, autoimmune diseases), acquired immunodeficiency syndrome (CD4+/8+ taken out of circulation causes immunodeficiency) ↳ Malnutrition (↓ protein), suppresses antimicrobial production (antibacterial proteins, immunoglobulins & complement proteins) Immunodeficiency - ↑ disease susceptibility = ↑ metabolic demand in children ↳ impairs growth, ↓ thymic development (↓ T cell store/supply) = affects innate & acquired immunity because insufficient a.a. for antimicrobial proteins & Ig ⛤ ultimately impacts reduced energy & education → propagates a poverty cycle that cycles to produce more malnutrition Types of ID (1) Primary ID - Mutation or deficiency (T cell, B cell or phagocytes), will show up in health of oral mucosa (2) T cell defects - more vulnerable to fungi, virus & parasites ↳ B cells are still activated by antigen but lower response → does not have high levels of antibody production compared to T cell activation ⛤ molecules are not recognised by MHC complex - antigen presentation is altered causing ID & B cells are not activated, compromising immune response - pt highly susceptible to recurrent bacterial & viral sinopulmonary infections - Oral complications: candida albicans, herpes & opportunistic pathogens Another kind of T cell defects (CD40 ligand deficiency) - T helper cells cannot dock with B cells, B cells are not stimulated and cannot differentiate or mature into plasma cells to produce antibodies. B cells restricted & only produce IgM - causes elevated levels of IgM (hyper IgM syndrome), plasma cells not able to produce IgA, that is important for mucosal immunity & long term protection - Oral complications: candida albicans, opportunistic pathogens, viral infections, respiratory infections, pneumonia & increased susceptibility (3) B cell defects - leads to reduce antibodies production (hypogammaglobulinemia), ↑ risk of autoimmune diseases, sinus infection & lung infection - Oral complications: ↓ resistance to oral infections, sepsis from odontogenic infections, apthae like ulcerations in mouth (pearlised kind) (4) Neutrophils/phagocytes defects - ↑ risk of systemic infections from fungi & bacteria - Oral complications: recurrent bacterial infection (mucosal candidiasis, septicemia & other fungal infections) Serious periodontal changes (severe