Week 4 Lectures PDF

**[Week 4 Lectures]** **[Dr Pierce Lecture 1]** **Respiratory function and dentistry** - Need to monitor respiratory function when using sedation - Need to reduce risk of asthma attacks and know how to manage an attack **Respiratory system** 1. Pulmonary ventilation (breathing)- movem...

**[Week 4 Lectures]** **[Dr Pierce Lecture 1]** **Respiratory function and dentistry** - Need to monitor respiratory function when using sedation - Need to reduce risk of asthma attacks and know how to manage an attack **Respiratory system** 1. Pulmonary ventilation (breathing)- movement of air in and out of lungs 2. External respiration- diffusion of oxygen from lungs to blood and carbon dioxide from blood to the lungs 3. Gas transport- transport of oxygen from lungs to tissues and carbon dioxide from tissues to lungs via cardiovascular system 4. Internal respiration- diffusion of oxygen from blood to tissue cells and carbon dioxide from tissue cells to blood **Respiratory functions** Anatomical division - Upper respiratory tract- nose to larynx portion above vocal cords - Lower respiratory tract- larynx from vocal cords, trachea, bronchi, bronchioles and lungs Functional division - Conducting zone- nose to respiratory bronchioles; allows air to reach site of gas exchange; also cleanses and conditions air - Respiratory zone- respiratory bronchioles, alveolar ducts, and alveoli (all microscopic structures); actual site of gas exchange **Conducting zone** - Passage through nose- "air conditioning" and defense - Warms air to within 0.5 degrees of body temperature - Humidifies air to within 2-3% of complete saturation with water vapour - Removes small particles Tracheobronchial tree - Trachea divides into right and left main bronchi - Further division in a dichotomous manner into smaller and smaller tubes until respiratory surface of alveoli is reaches - 23 generations of airways arising form the trachea - Fractal branching tree for efficient air exchange: 1. Maximises surface area for gas exchange 2. Minmises distance between alveolar air and capillaries **Airway patency** Key problem- keep respiratory passageways open to allow easy passage of air  **Airway mucosa** - Mucus layer moistens surface of respiratory passages-first line of defense - Secreted by goblet cells in epithelial lining and small submucosal glands - Physical barrier to protect the lung with properties that help trap/disarm potentially infectious bacteria, fungi and viruses - Normal lung kept free from bacteria **Mucociliary clearance** 1. Mucociliary clearance- prevents respiratory infections such as pneumonia 2. Alveolar macrophages- clears particles from alveoli - "Power stroke" towards pharynx when mucous from respiratory passages - Pseudostratified ciliated columnar epithelium- removes mucus from respiratory passages - Mucosal epithelium thins as it changes from pseudostratified columnar to columnar and then to cuboidal in terminal bronchioles Alveolar macrophages- third cell type in alveoli, others type 1 and type 11 pneumocytes - Few mucous-producing cells and cilia in bronchioles - Most airborne debris at or below level of bronchioles removed by macrophages - Phagocytose foreign pathogens, but also apoptic and necrotic cells **Mechanics of pulmonary ventilation- key principles** 1. Air movement in and out of lungs dependant on pressure gradients between a. Atmospheric pressure b. Intra-alveolar pressure 2. Inverse relationship between volume and pressure (Boyle's law) **Pressure Gradient** - Gas molecules move down a pressure gradient - For air to move INTO lungs Palv\Patm - Pressure changes are achieved by varying lung volume **Boyles law** - Increase in lung volume causes a decrease in pressure - Palv\ i. Hard particulate fillers ii. Rubbery inclusions iii. Glass fibre reinforcement iv. Transformation toughening **Wear-** Destruction of surface of materials due to mechanical or chemical attack **Abrasive wear**- caused by indenting or scratching surface by abrasive toothpaste, incorrect brushing, food or foreign objects. Hardness test is often used to describe resistance of materials against abrasive wear **Hardness** - Resistance of a material against penetration of an indenter. - Depending on the shape of indenter, there are different methods of hardness - Tests include Vickers, knoop, brinnell, and rockwell **Fatigue wear** **Fatigue failure is characterized by:** - Crack initiation- a crack forms at some point of high stress concentration - Crack propagation- the crack advances incrementally with each stress cycle - Catastrophic failure- occurs very rapidly once the crack reaches a critical size **Fatigue failure** - The failure of structures at stresses well below the tensile strength of the material used when it has been subjected to repeated stress cycles - Fatigue failure occurs at low loads with no outward signs of a problem **Corrosion wear** - In an oral environment, most of the time combination of mechanical and chemical attacks cause wear (abrasion-erosion lesion) **Creep** - Permanent deformation of materials when subjected to a constant or cyclic load for a period of time - Factors influencing creep are 1. Applied load 2. Temperature 3. Time **Surface contact angle** **Elastic and plastic behaviour** Elastic behaviour- instantaneous and full recovery occurs after removal of load. The deformation and recovery are fast and is not time dependent Plastic (viscous) behaviour- material retains deformation after removal of load **Viscoeleastic behaviour** - The deformation (strain and relaxation) of materials especially polymers under certain conditions can be time-dependent - The recovery after loading can be complete (elastic) or incomplete (viscose) **Stress relaxation** - Reduction of stress in the material when subjected to a constant strain - Stress relaxation rate is important in orthodontic elastic bands - Latex bands have a constant stress relaxation compared to plastic bands **Example of viscoelastic rules in dental materials** - This type of behaviour is important when elastic impression material is removed from undercuts - Permanent distortion that happens on the removal of an impression depends on magnitude of force and the time for which the force is applied - The magnitude of the force is dictated by elastic modulus and thickness of material and depth of undercut - Distortion-time x force **Rheological properties** - Deformation behaviour of material under stress - Explained by elasticity and viscoelasticity theory in the case of sold and elastomers - In the case of liquid and paste, the rheological behaviour is explained by viscosity, which is the - resistance of a fluid to flow **Rheological behaviour and shear rate** - **dilatant**- viscosity increases with increasing shear rate (shear thickening) - **Newtonian**- shear stress is directly proportional to shear rate and the viscosity of the material is constant and independent of shear rate - **Pseudoplastic**- viscosity decreased with increasing shear rate (shear thinning) **Rheological behaviour of dental materials** - Increasing temp generally reduces viscosity of non-setting materials, but increases viscosity of setting materials - Once the initial material starts chemically setting, the viscosity will increase until the manipulation becomes impossible - The time taken (from mixing) to reach that point is working time - The setting reaction is continued to a finite level which the intended initial properties are achieved - The total time (from mixing) to reach this point is setting time **[Dr Dabas Lecture 1]** **Damage to teeth** **Carious** **Non-carious** - tooth wear - developmental defects - trauma **Caries-** preventable, chronic and biofilm mediated disease modulated by diet. - Multifactorial, oral disease caused primarily by an imbalance of oral flora (biofilm) due to the presence of fermentable dietary carbs on tooth over time **Non-Carious damage** - Irreversible loss of surface of dental hard tissue caused by factors other than caries or trauma - Erosion- Erosion is the irreversible loss of tooth substance brought about by a chemical process that does not involve bacterial action 1. Most common denominator in multifactorial tooth wear - Attrition- tooth-tooth contact - Abrasion- tooth to non-tooth contact - Abfraction- cervical v shaped enamel-dentin defect with no history of abrasion (masticatory forces like bruxism/multifactorial) **Causes/acid sources of erosion** - Intrinsic acid (gastric acid)- involuntary Extrinsic acid (dietary-acid food and drinks) - Environmental (acid fumes, inhalation) **Mechanical wear due to tooth-to-tooth contact** - Functional - Parafunctional - Proximal wear due to physiological tooth movements **Abrasion** - Mechanical/frictional wear due to tooth to non-tooth contact - Tooth brushing using coarse abrasives (smooth notch V shaped at neck of teeth) - Habits- pin, pen, pipe holding, teeth, nail biting, bottle opening, stripping wire - Chewing on abrasive materials/food regularly Abfraction - Cervical wedge-shaped sharp enamel or dentine tooth wear, understood to be microfractures or abfractures due to masticatory stresses concentrated over cervical area - Most likely multifactorial tooth wear with erosion and toothbrush abrasion as predisposing factors **Schema of pathodynamic mechanisms of tooth surface lesions**  **Non carious damage** - Accidental - Non-accidental (violence) - Hereditory developmental defects i. Generalized conditions: a. Amelogenesis imperfecta- defective enamel in formation/development or calcification b. Dentinogenesis imperfecta- dentin is defective causing early loss of overlying enamel - Non-hereditary developmental defects i. Hypoplasia a. Lack in amount of enamel/quantitative defect b. Can be generalized or localized ii. Hypomineralisation a. Lack in mineral content of enamel-qualitative **Caries can be described according to:** - Location- pit and fissure, smooth surface, root surface, residual, secondary - Direction of progression- forward/backward caries - Zone- enamel/dentine caries - Extent- incipient/reversible or cavitated/irreversible - Progression rate- acute/rampant or chronic/arrested **Caries- location- pit and fissure** - Detection of these are important as a small caries in enamel can transverse and spread into large lesion underneath **Plaque and caries process** - Requires 4 factors: 1. Plaque microorganisms 2. Substrate 3. Time 4. Host and teeth **Dental plaque/cariogenic biofilm** - Plaque is a firmly adherent biofilm attached to teeth and is the prime etiological agent of caries and periodontal disease - Careful observation of distribution of plaque in mouth reveals that it forms most readily only at certain sites, namely, molar fissures, the gingival crevice and on those surfaces between adjacent teeth apical to the contact area **Plaque initiation** Sticking to surface has benefits for many microorganisms - They maintain their position in the environment - They can exploit the organic and inorganic molecules which adsorb to surfaces - can interact with other bacteria in cooperative consortia to maximize potential - mature plaque needs to be present for caries to establish and develop **2 ways by which caries can be arrested or if early enough, reversed:** 1. regularly disrupt the biofilm 2. remove the biofilm energy/food source From an operative dentistry point of view - open access for improved hygiene or seal the caries under a bio-active restoration which acts as a fluoride reservoir - Gum-margin plaque can develop to the point where it begins to overgrow the smooth areas of teeth in the direction of the crown - Often referred to as smooth surface plaque. - Ability of plaque to grow over smooth areas speaks volumes for the tenacity of its adhesive and cohesive properties **Stephans curve** - Depicts sudden decrease in plaque pH following glucose rince, which returns normal after 30-60 minutes - Net demineralization of dental hard tissues occurs below the critical pH (5.5) - Mature plaque metabolizes then readily fermentable carbohydrates as an energy source, creating acid **Progression of caries/caries balance** A diagram of a process Description automatically generated **Rampant caries** - Accelerated rate of caries with multiple carious lesions. Usually occurs in: 1. Infants- nursing bottle caries (frequent or prolonged bottle with sweet milk/juice) 2. Teenager/youth- with high cariogenic diet/recreational drugs 3. Adults- with dry mouth (xerostomia) due to medications or medical conditions e.g. sjogren's syndrome **Arrested caries** - Lesions that have stopped progressing and are inactive - Enamel- white lesions in enamel-incipient or initial ones can be arrested/reversed with equilibrium of net mineral gain - Dentine- process can be arrested but not reversed as proteolytic destruction of organic collagen matrix has occurred (surface is not intact anymore/cavitated) **Enamel caries** - Subsurface demineralization causes enamel prism porosities (white spot lesions) which can heal with regular effective removal of biofilm by patient and demineralizing medium (solutions/toothpastes) - Note- avoid latrogenic damage of WSL with sharp probes) - Progresses microscopically as inverted cone towards until DEJ - Active WSL is initially smooth, frosty white/opaque and non-cavitated - If arrested result in heard smooth shiny surfaces of arrested lesions - As porous they can easily get stained to create brown spot lesions - Can be detected by drying the lesion for few seconds - Eventually get rough/micro-cavitated and can be detected with rounded ball end probe **Caries at DEJ (ADJ)** - Histologically caries reaches DEJ even before cavitation - Defense reaction of dentin pulp are stimulated with evidence of translucent dentin zone at the advancing lesion and tertiary dentin at pulp interface - Lesion extends laterally (subject to progression of caries and then starts penetrating the dentinal tubules) **Caries in Dentine** - Once in Dentine, often cavitate creating visible gray shadow/opacity - Acute pulpal response (pulpitis) to hot/cold/sweet and is poorly localized - The demin/remin process is still active but irreversible damage has occurred - Active caries- dentine appears moist and matte, rough, soft, wet/leathery on gentle probing - Arrested/inactive caries- shiny hard and scratchy on gentle probing **Caries in dentine**  **Soft dentin/infected dentin** - Outer carious, soft (infected) dentin - Bacterial contamination (referred to as necrotic and contaminated) - Low mineral content, and irreversibly denatured collagen - Soft dentin typically does not self-repair - Clinically, soft dentin lacks structure and can be easily excavated with hand and rotary instrumentation **Firm Dentin/affected dentin** - Inner carious dentin, characterized by demineralization of intertubular dentin and of initial formation of intratubular fine crystals at the advancing front of caries lesion - Transparent appearance - Softer than hard, normal dentin - Organic contents of dentin, the collagen cross-linking remains intact in this zone and can serve as a template for remineralization of intertubular dentin - Clinically, firm dentin is resistant to hand excavation and can only be removed by exerting pressure - Transition between soft and firm dentin can have a leathery texture - Does not deform upon pressure from an instrument but can be excavated with hand instruments such as spoons and curette without much pressure **Hard dentin** - Deepest zone of a caries lesion-assuming the lesion has not yet reached the pulp- and may include sound normal dentin - Clinically this dentin is hard, cannot be easily penetrated with a blunt explorer and can only be removed by a bur or a sharp cutting instrument **Minimal invasive dentistry** - Concerned with the first occurrence, early detection and earliest possible cure of damaged and defect tooth structure on a micro level following by minimally invasive treatment in order to repair irreversible damages caused by the disease - Restorative treatment does not cure caries process - Instead identifying and managing the risk factors must be primary focus in addition to restorative treatment caused by caries **ICDAS 11 codes and criteria** A screenshot of a computer Description automatically generated  **Caries detection and diagnostic aids** Visual and clinical methods - Mirror and probe - Magnification - (loupes and headlight) can help prevent missing due to visual errors - Wet/dry field - Clean dry field plays essential role in diagnosing white spot lesions - Caries detecting dyes Radiographs - Intraoral (Bitewing/periapical x-rays) - Extraoral (OPG (not always reliable due to resolution, higher radiation dose)) Optical/trans illumination - Intraoral cameras/LED cams - FOTI, laser, QLF systems Tooth separators **Principles of caries management in MID** - Disease control by reduction in cariogenic bacteria - Remineralization of early lesions - Avoid removal of tooth structure in excess to absolutely required to restore to their normal conditions - Use of dental material to conserve biological cost of tooth structure **ICCMS risk factors** **Risk status of the patient**  **Caries treatment** - Non-invasive (OHI, Topical, FI, varnish etc.) - Micro-invasive (Pit and fissure sealants) - Selectively invasive (partial caries removal to minimize biological cost) - Invasive (conventional preps and restorations) Prevention - Non-invasive and preventative modalities - Traditionally using fluoride - Acts as a catalyst for enamel surface remineralization - Casein phosho peptipe-amorphous calcium phosphate - CPP-ACP has been proven superior to fluoride products for the depth of remineralization - xylitol products have been proven to starce out the cariogenic bacteria and promote proliferation of good bacteria - Dental ozone **Dental ozone** - Indications for the use of dental ozone - Primary root carious lesions and primary pit and fissure carious lesions - Advantages of ozone: 1. Kills \99% of microorganisms in carious lesions at a concentration 2200ppm 2. Oxidizes caries and speeds up remineralization 3. Potentially whitens discoloured caries 4. Decreased treatment time 5. Treatment painless and noiseless 6. Does not cause any allergy reaction 7. Helps remove organic debris on lesion 8. Microorganisms do not develop resistance to ozone - Contraindication for use of ozone (highly irritating to eyes and lungs) **MID** - Application of engine/turbine driven rotary instruments in operative treatment of carious lesions has resulted in removal of considerable tooth structure (invasive) - There can be used a stand-alone or an adjunct to rotary instrument e.g. 1. Air abrasion 2. Hardt issue laser 3. Chemo-mechanical caries removal - Remove hard substance by impacting abrasive particles in a stream of air or air water - Air prophylaxis units use non-abrasive powder designed to remove plaque and staining without any damage to tooth structure - Does not work on soft structure very well (soft tissue trauma if uncontrolled) - Can be quite messy if not properly evacuated **Hard tissue laser** - Used for accessing enamel/dentin caries - Required skills and precision hand control **Chemo-mechanical caries removal** - Idea of chemo-mechanical caries removal was developed in the 1970s by an endodontist who was using sodium hypochlorite to remove organic materials in the root canals and incidentally also dissolved the carious dentine as well **Pit and fissure sealants and why it happens** A comparison of a white and red body Description automatically generated with medium confidence 1. Plaque and cariogenic microbiota accumulate in narrow pits and fissures 2. Evan a single bristle of a toothbrush is too large to reach or clean it - Sealants are defined as low viscosity, plastic material that can flow into, conform and occlude the pit and fissure system of a tooth, as a preventative measure against the development or progression of dental caries **Functions of pit and fissure sealants** 1. Physical barrier- occlude the pit and fissures, stopping food and bacteria being stuck in there 2. Eliminate environment- forming a barrier to the substance that is needed for caries process 3. Cleansibility- providing an easily accessible area for natural cleansing by saliva flow and the chewing action and during toothbrushing 4. Chemically releasing fluoride and in the case of GICs, can act as a fluoride reservoir Pit and fissures are classified on the basis of curing (self, auto, chemical or light) Composition can be: - Composite (with or without fluoride) - GIC - Can be clear/opaque/coloured **Penetration coefficient** - Property to be able to flow into narrow pits and fissures - Penetration into deep pits and fissures is a function of both capillary action and viscosity - The sealant material will adapt more closely to enamel surface if it has a high coefficient of penetration, high surface tension and low viscosity - Fluoride releasing P/F sealants- which teeth/age group **Priority** - Primary molars, 1^st^ permanent molars only if they have deep fissures - If there is a history of caries- premolars and 2^nd^ permanent molars as well - Permanent upper incisors with lingual pits **Assess caries risk- if high risk- potential sealant benefits- P/F seal advised** - In any tooth with a non-self-cleansable pit or fissure - Including primary teeth of children and permanent teeth - At any group of children and adults **Benefits** - Over a 15-year period, non-sealed teeth are 7.5x more likely to develop caries - Children treated with P/F sealants are less likely to require permanent restoration - There is a longer period between placement of sealants and placing permanent restoration and that these restorations were less extensive **Procedure** - Only prep required on the tooth surface to remove pellicle or plaque Techniques to achieve cleaned surface before restoration - Pumice-water and a bristle brush - Prophylaxis paste and bristle brush - Dry bristle brush and probe - Tooth brushing, wet or dry - Air polishing using prophy jet etc. (sodium bicarbonate) - Air abrasion using aluminum oxide- not recommended- abrasive - Minimum tooth preparation with a bur- not recommended- invasive **GIC based P/F sealants** - Combined with fluoride - Adhere under moist conditions - Low retention rate compared to composite resins - (25% partially or totally lost in 4 months resin modified GIC, 38% loss over 2 years, compared to 10% for resin based) - Should be considered in cases where moisture control is not possible such as partially erupted molars - Indicated as a transitional sealant or in the field where conditions are not optimal Resin sealants - Currently vast number of composite sealants are available with fluoride releasing properties and able to flow and adhere better than GIC, and can comparatively withstand shearing masticatory forces better when in thin layer **Clear vs opaque** - White makes it easier for the operator to see how much sealer has been placed - White is much easier to see when reviewing sealants - White is generally filled as opposed to the unfilled clear - Clear was marketed so that the clinician could detect recurrent caries **Steps in P/F restoration** 1. Acid etch clean enamel surface- removes plaque- etch with 35% phosphoric acid 15 secs. Fluorosed and deciduous teeth need 30 secs 2. Avoid saliva contamination- saliva contamination causes sealnt failure. Field isolation is crucial for majority of resin sealants and can be obtained by: 1. Cotton wool rolls/absorbent cheek pads 2. Loads of suction 3. Pit and fissure prep not needed- complete occlusion of fissure system achieved 4. Complete seal is important- incomplete is at same risk of caries as an untreated tooth. Most sealant failures occur in the first six months. Important to follow up to assess filling 5. Less is more- do not overfill. Bulky over-contoured sealants fail quickly. Bulk of sealant to the minimum so that it just barely fills up the valleys and grooves is crucial **Light cured resin sealant clinical procedure** 1. Pumice or prohylaxis paste/rinse/dry 2. 15 second 35% phosphoric acid etch 3. Rinse and dry 4. Place sealant material without trapping air 5. 20 second light cure for each sealant 6. Check the set, the edges and the occlusion **Restoring caries** - When caries starts to cavitate/destruct the tooth structure- it needs to be restored to - Prevent further damage by caries progression - Restore its form - Restore function - Restorations could be of 2 types 1. Direct restoration i. When a cavity/tooth structure is restored directly by the clinician by entirely fabricating the restoration directly in the mouth either by bonding or mechanical retention ii. Mostly done in single appointment. Inserted on to the tooth in their plastic state in the patients mouth iii. Materials most used are amalgam, composite, GIC etc. 2. Indirect restoration - They are restorations that are not fabricated directly on to the tooth - Usually, a prep is made on to the tooth and impressions taken of the prep which then is fabricated in the lab or on computer assisted milling machine in the clinic - They overcome many shortfalls of direct restorations as long as the patient is able to wait for the result - Improved strength, aesthetics and form/anatomy relative to direct restorations - Possibly 2 separate visits (can be singles with modern CAD-CAM in clinics) - Lab made (CAD CAM based), in office in a clinic equipped with onsite CAD-CAM machine - A specially trained lab technician is sent the impressions according to dentists detailed prescription is sent the impressions or model sent to study the prep and models to further fabricate the restoration - Which is then tried on patients prep tooth by the dentist and if satisfactory cemented on to restore - The process takes above 2 appointments depending on complexity of procedure **Types of indirect restorations** - Based on extent of the coverage of a single tooth indirect restoration can be - Intra-coronal 1. Inlays 2. Intra/extra-coronal 3. Onlays 4. Overlays 5. Extra-coronal 6. Crowns 7. Veneers **Bridge** - It is a multiunit restoration to replace a missing tooth - It can be an extra-coronal/combination restoration - Types of bridge - Conventional bridge 1. Traditional bridge supported by teeth either side of missing tooth e.g. 3 unit bridge. Cantilever bridge 2. Support from one side 2-unit bridge. Maryland. Partial prep/support of adjacent tooth/teeth e.g. wing bridge **Prep for indirect restorations** - ask for consent - tooth prep- remove tooth decay or weakened hard tooth structure, restore the core and prep of the cavity with no undercuts or over taper - create impressions which make precise duplication of the shape of the treated tooth and cavity. This duplication process allows technician to make restoration - temporization- placement of temporary restoration Types of preps include: 1. Convergent- lines come together (extra-coronal prep) 2. Divergent- lines go apart (intra-coronal prep) 3. Parallel- long axis of the prep **Preps and angulations** - Total occlusal convergence of partial fixed dental prosthesis abutment is defined as the convergence of two opposing external wall of a tooth prep as viewed in given plane - The taper is defined as the angle between a single prep wall and the long axis of the tooth prep - TOC= taper x 2 (provided that the taper symmetrically convergent) - TOC 0-15=good retention of crown - TOC\>15= poor retention **Steps for indirect restoration procedure** - Local anesthesia if required - Removal of temporary restoration and clean up temporary cement residue - Trial fit the restoration-assessment and patient approval - Cementation of the final restoration - Check final occlusion **Advantages of indirect restoration** - Fabricated outside the mouth-more patient comfort and less chair time restoring - Increased access/visibility and time for fabrication - Better produced anatomical morphology - Stronger-may be subjected to intense heat and curing pressures to create restorations many folds stronger than direct restorations **Disadvantages of indirect restorations** - Much higher biological cost of tooth (invasive prep) - Fabricated outside the mouth- more patient appointments and requires availability - Done in stages- and patient has to rely on a good temporary in the meanwhile - Gold crowns can create galvanization if opposing to amalgam fillings - Ceramic crowns can be much harder than natural teeth and can cause significant tooth wear