NBDE Dental Boards Operative Dentistry-33

OPERATIVE DENTISTRY Part 1: Dental Caries Dental Caries -infectious bacterial disease caused by cariogenic plaque formation on tooth that results in demineralization of enamel at pH 5.5 or less, sometimes requiring restorative tx or even extraction -for caries to occur, three things must be present at same time: 1) cariogenic bacteria 2) susceptible tooth surface 3) foodstuffs to support bacterial growth Specific Plaque Hypothesis -not all of bacterial species in oral cavity cause caries; only the bacteria that generate plaque formation resulting in caries are considered cariogenic (not all plaque is cariogenic) -ex. Viridans streptococci cause plaque but much less virulent for caries formation Streptococcus Mutans -nonmotile, gram+ bacteria that is cariogenic (primary causative agent of initial caries formation) -adheres to enamel through glucosyltransferase enzyme, which causes formation of extracellular polysaccharide that allows it to stick to smooth tooth surfaces -converts sucrose into fructans and glucans, which extrude from bacteria and stick to tooth -produces and tolerates acid (metabolizes sucrose to lactic acid) -thrives in sucrose-rich environment -produces bacteriocins, which kill off competing organisms Enamel Caries -ion transfer continuously occurs at plaque-enamel surface -initial decalcification occurs at subsurface -may be 1-2 years before enough decalcification occurs to cause surface integrity loss a) Incipient caries: caries that have not progressed farther than enamel and are reversible/able to remineralize b) Frank caries: caries that have progress just into DEJ and not reversible Zones of Carious Enamel 1) Surface zone: outermost zone which seems unaffected by caries 2) Body zone: largest zone which represents demineralizing phase 3) Dark zone: represents remineralization; named b/c it can’t transmit polarized light 4) Translucent zone: deepest zone; named b/c of its absent appearance under polarized light -represents advancing front of enamel lesion Dentinal Caries -once enamel decalcification occurs, the underlying dentin has already been affected by progression of the destruction -Lactobacillus organism becomes a primary agent for further destruction of the dentin -Lactobacillus produces lexan instead of dextran -dentin is less resistant to caries and can progress rapidly through proteolysis of dentin -dentin is less mineralized than enamel and has tubular structures allowing for spread of acid destruction -caries appears V-shaped w/ base at DEJ and apex toward pulp -necrotic dentin appears soft, wet, and mushy 1) Infected dentin: tubules infected w/ cariogenic bacteria and proteolytic activity causes degradation 2) Affected dentin: bacteria present but in smaller amounts; demineralization occurs but can be reversed if infected layer removed and environment favorable

Zones of Carious Dentin (from innermost to outermost) 1) Normal dentin: deepest area; no bacteria or byproducts present 2) Subtransparent dentin: demineralization from acidogenesis but no bacteria found in tubules -capable of remineralization 3) Transparent dentin: softer than normal and has further demineralization; no bacteria here --capable of remineralization 4) Turbid dentin: zone of first encountered bacterial invasion w/ tubules filled w/ bacteria; zone must be removed 5) Infected dentin: outermost zone; consists of decomposed dentin and many bacteria found in this zone and must be removed -zones 1-3 are capable of remineralization -zones 2 and 3 (subtransparent and transparent) termed affected dentin and zones 4 and 5 (turbid, infected) are termed infected dentin Tertiary/Reparative Dentin -produced by secondary odontoblasts in response to irritants -if insult is strong enough, it will kill odontoblasts and form dead tracts, which calcify to form sclerotic dentin -other types of dentin: 1) Primary dentin: dentin forming initial shape of tooth and deposited before completion of apical foramen 2) Secondary dentin: dentin formed after completion of apical foramen Other Bacteria Involved in Caries 1) Actinomyces viscus: most common cariogenic bacteria in root surface caries and smooth surface caries 2) Streptococcus sanguis: earliest bacteria in dental plaque 3) Other cariogenic bacteria: Actinomyces naeslundi, Veillonella, Streptococcus salivarious Cyclic Process of Caries -as plaque is exposed to sucrose, the plaque metabolism produces acid which when less than pH 5.5, causes demineralization of tooth structure -as sucrose or plaque is removed, ions from saliva (Na, K, Ca) cause remineralization to occur, which attempt to restore ionic component of tooth structure -when fluoride is present, it is picked up by tooth and forms fluoroapatite in enamel, which is even more resistant to future demineralization than normal enamel Hydrodynamic Theory of Pain from Caries -when tooth is subjected to insult, fluid movement through tubules increases and greater flow deforms the nerve endings in pulp leading to pain response -cold conductivity increases both volume and flow in tubules resulting in pain stimulus Saliva -saliva is a major block barring the cariogenic bacteria -protective mechanisms: 1) Bacterial clearance: large carbohydrate-protein molecules in saliva cause some bacteria to agglutinate and then be removed by swallowing 2) Buffering action: saliva contains urea and other buffers to help dilute plaque acid 3) Antimicrobial actions: a variety of proteins and Ab in saliva discourage/kill bacterial growth a) Lysozyme: destroys bacterial cell walls and causes membrane permeability b) Lactoferrin: actively binds iron, which is important for bacterial enzyme production and fxn (may also destroy S. mutans) c) Lactoperoxidase: inactivates bacterial enzymes d) Type A secretory immunoglobulin: Ab in saliva which fights S. mutans attacks 4) Remineralization: Ca, K, PO4, and F ions in saliva assist w/ remineralization of enamel -some salivary proteins promote remineralization (statherin, cystatin, histatin, proline)

Common Drugs Causing Xerostomia 1) Anticholinergics (atropine) 2) Diuretics (hydrochlorothiazide) 3) Local anesthetics 4) Antipsychotics 5) Beta blockers (atenolol) 6) Benzodiazepines (alprazolam) 7) Antihistamines Identification of High-Risk Caries Patients -no exact mechanism for determination, but some factors that predispose to caries: 1) high S. mutans count 5) large number of restorations 9) oral appliances 2) 2 or more active lesions 6) poor oral hygiene 10) deep pits/fissures 3) poor diet 7) suboptimal fluoride 11) exposed roots 4) low salivary flow 8) unusual tooth morphology 12) drug use Fluoride -is bactericidal and provides fluoride ion for remineralization -sources: 1) water fluoridation systems 4) varnishes 2) rinses 5) toothpaste 3) gels Prevention of Dental Caries 1) Decrease S. mutans activity and educate pt that repairing carious lesion doesn’t cure caries problem 2) Intense antimicrobial application on short-term basis 3) Fluoride 4) Saliva -alter salivary-reducing meds if possible -use saliva stimulants (gum, paraffin wax, saliva substitutes, diet high in protein and vegetables) 5) Decrease sucrose in diet (better to decrease FREQUENCY than QUANTITY) -single exposure to sucrose for caries-active mouth can result in pH reduction below 5.5 for sustained period of time b/c of rapid metabolism by S. mutans 6) Xylitol (natural sugar from birch trees that keeps sucrose from binding w/ S. mutans) -S. mutans can’t ferment xylitol 7) Enforce good oral hygiene (disrupts plaque formation) 8) Sealants (removes habitat for S. mutans) 9) Restorations Treatment of Carious Lesions 1) Restorations: when cavitated lesions present, they must be restored (Cavitated lesions > Restore) -use of antimicrobials must wait until after cavitated lesion is restored, or the antimicrobial will disrupt the normal flora and allow virulent organisms in protected, cavitated area to flourish on now-unprotected surfaces -restorations remove large nidi of infectious organisms as well as remove habitats for more bacterial adherence -restorations alone don’t cure caries problems, need better preventive strategies 2) Sealants -sealants should be applied simultaneously to at-risk molars and premolars as well as ditched restoration margins (etch enamel and microabrade amalgam) 3) Intense, short-term use of agents -Chlorhexidine -Fluoride varnishes 4) Xylitol products 5) Fluoride rinses (OTC) -use after Chlorhexidine is finished and use at difft. times than for brushing 2x/day 6) 3-month recalls after Chlorhexidine/fluoride varnish application

Part 2: Clinical Exam Clinical Exam for Caries 1) Visual changes in tooth surface texture or color 5) DIAGNOdent 2) Tactile sensation w/ explorer 6) DIFOTI (digital imaging fiberoptic transillum.) 3) Radiographs 7) Quantitative light-induced fluorescence (QLF) 4) Transillumination 8) Electronic caries monitor -no single test is completely accurate, so can’t rely solely on one test Caries Indicating Solution -colored dye in organic base adheres to denatured collagen, which distinguishes btw infected and affected dentin Occlusal Pits and Fissures -caries is most prevalent in faulty pits and fissures on occlusal surfaces where developmental lobes have failed to coalesce -occlusal grooves/fossae are smooth, valleys indicating region of complete coalescence of developmental grooves (not susceptible to caries normally b/c not prone to plaque formation) -occlusal fissures and pits are deep, tight crevices in enamel where lobes fail to coalesce -use of an explorer in diagnosing caries is strongly discouraged b/c injudicious use of explorer may actually cause fracture of surface enamel that was weakened by carious destruction beneath it -occlusal surface should be examined visually and radiographically -visual exam done by drying tooth and using illumination to look for chalkiness, brown-gray coloration or softening/cavitation in fissure/pit -radiographic diagnosis made by BW radiographs, looking for radiolucency beneath enamel surface at DEJ (narrow at enamel surface and spreads wide at DEJ (inverted V) -actual lesion much larger than clinically presentable -lesion progresses parallel to enamel rods -carious pits and fissures also occur on occlusal 2/3 of facial and lingual surfaces of posterior teeth and on lingual surface of max. incisors -pit/fissure caries mostly caused by Strep. Sanguis and other Strep species -prevented by fissurotomy or sealants Cusp Tip Caries -pre-carious or carious pits are occasionally found on cusp tips -these are result of developmental enamel defects Proximal Surface Caries -form of smooth surface caries located btw teeth -diagnosed radiographically most often, but may be detected visually w/ tooth separation or fiberoptic transillumination -starts wide at surface and converges toward DEJ (V-shape) -DEJ provides least resistance to caries and allows repaid spread once reached -proximal caries in anterior teeth may also be detected by explorer probing -located just gingival to IP contact -progresses much slower than pit/fissure caries Brown Spots -brown spots on intact, hard proximal surfaces adjacent to and gingival to contact area often seen in older pts who have low caries activity -are result of extrinsic staining during earlier caries demineralizing episodes that were remineralized -spots are no longer carious and usually more resistant to caries, so restorative tx not indicated

Smooth Surface Caries on Facial/Lingual Surfaces -mostly in gingival areas that are less accessible for cleaning -earliest evidence is incipient caries which shows as white spot that is visually difft. from adjacent translucent enamel and disappears when wetted (drying will cause it to reappear) -should promote remineralization of these incipient lesions -enamel hypocalcification does not disappear when wet -presence of several facial/lingual smooth surface lesions indicated high caries rate, so should always check facial/lingual areas of posterior teeth b/c these areas are at even more risk -advanced smooth surface caries will feel soft to explorer penetration and discolored (white to dark brown) -w/ slowly progressing caries, darkening occurs due to demineralization-remineralization cycle, resulting in hardened, arrested lesion -restoration not indicated, except for esthetics -dentin in an arrested lesion is termed eburnated or sclerotic Root Surface Caries (Senile Caries) -early on, root caries appears as well-defined discolored area adjacent to gingival margin near CEJ -softer than adjacent tissue and spreads laterally around CEJ -thin cementum layer provides little resistance to attack and results in rapid progression (progresses more rapidly than enamel and dentin caries) -progresses more laterally along surface than in depth -pathway of initial demineralization is along Sharpey’s fibers -no clinical criteria universally accepted for diagnosing root caries, it is agreed though that softened tooth structure compared to surrounding structure is characteristic -active root caries detected by softening and cavitation -may be detected radiographically, but careful clinical exam is crucial b/c root caries and cervical burnout are similar in appearance -vertical BW best for diagnosing root caries -appears as cupped-out/crater-shaped radiolucency just below CEJ -often occurs in elderly due to gingival recession (xerostomia and lack of hygiene play role also) -cementum is rougher than enamel and more likely to acquire plaque -often remineralize due to shallow nature -often asymptomatic and difficult to restore -best restored w/ glass ionomer Other Forms of Caries 1) Residual caries: infected tooth structure remaining after attempted removal in a complete cavity prep 2) Recurrent caries (secondary caries): decay that remains in completed cavity or forms around existing restoration -radiolucent bases/liners may be mistaken for recurrent decay on radiograph 3) Rampant caries (acute caries): rapidly progressing wide-spread caries; usually acute onset and painful -assoc. w/ poor hygiene, drug use, radiation, high sugar diet, xerostomia 4) Arrested caries (chronic caries): lesions that have remineralized -hard, black, and asymptomatic -should be completely removed if found in enamel or close to DEJ

Clinical Exam of Amalgam Restorations -involves visual observation, tactile sense w/ explorer, dental floss, radiographs, and knowledge of probabilities that given tooth or restoration is at risk for further breakdown -problems that can arise w/ amalgam restorations include: 1) Amalgam “blues”: discolored enamel resulting from leaching of corrosion products of amalgam into dentinal tubules or from color of underlying amalgam seen through thin, translucent enamel (unsupported) -does not indicate failing restoration/caries and no re-tx needed, unless for esthetics 2) Proximal overhangs: diagnosed visually, tactilely, and radiographically 3) Marginal gap/ditching: shallow ditching of amalgam margin less than 0.5mm usually not reason for retxt b/c it looks worse than it really is -eventual seal-sealing property of amalgam allows restoration to survive as long as it can be cleaned -if ditch is too deep to be cleaned or jeopardizes restoration/tooth structure, it should be replaced 4) Voids: accessible small voids in areas where enamel is thick may be corrected by recontouring or repairing w/ small restoration 5) Fracture lines: detected by clinical exam 6) Line indicating interface btw abutted restorations: acceptable and better than a small intervening strip of enamel 7) Improper anatomic contours: amalgams should mimic normal anatomic contours of teeth -restorations that impinge on soft tissue, have inadequate embrasure form, bad contact, or prevent use of floss should be replaced or recontoured 8) Marginal ridge incompatibility: marginal ridge of amalgam should be compatible w/ adjacent marginal ridge of tooth or restoration -should both be at about same level and display correct occlusal embrasure for passage of food to facial/lingual surfaces and proper contact area -if ridges aren’t compatible, have poor tissue health, food impaction, or can’t floss, should be replaced or recontoured 9) Improper proximal contacts: there should be closed and proper contact btw restoration and adjacent tooth -checked w/ floss or through illumination and mirror inspection (must be dry!) 10) Recurrent caries: detected visually, tactilely, and radiographically 11) Inadequate occlusal contacts: can cause improper occlusal fxning, and tooth movement Part 3: Treatment Planning Treatment Plan Sequencing 1) Urgent/Emergency phase 2) Disease control phase 3) Re-evaluation phase 4) Definitive phase 5) Maintenance phase Restoration of Incipient Lesions -incipient lesions are contained entirely within enamel and haven’t yet spread to dentin -two options to treat: 1) Targeted remineralization and monitoring: first and preferred approach for incipient lesions -incipient lesions do not progress rapidly -changing oral environment combined w/ fluoride varnish and home fluoride can remineralize these lesions 2) Restorative txt: last resort for incipient lesions -be as conservative as possible Criteria for Restoring 1) Poor oral hygiene 2) Low frequency of routine dental care 3) Hx of caries or numerous restorations 4) Cavitation or defect present

5) Lesion extends to DEJ 6) High degree of caries susceptibility 7) Patient age 8) Esthetic txt

Treatment of Abrasion, Erosion, and Attrition -areas of significant attrition that are worn into dentin and are sensitive or annoying should be restored -before cast restorations are used, a complete occlusal analysis and in-depth interview w/ pt regarding etiology should be done to reduce contributing factors -biteguard therapy should be considered also -abrasion or erosion should be considered for restoration if: 1) area is carious 2) defect s deep enough to compromise structural integrity of tooth 3) intolerable sensitivity exists and is unresponsive to desensitizing measures 4) defect contributes to perio problem 5) area to be involved in RPD 6) depth of defect close to pulp 7) pt wants esthetic improvement Treatment of Root Surface Caries -must use caution to only correct active root carious lesions, not areas that are arrested (discolored, but hard to explorer) Treatment of Root Surface Sensitivity -theory for cause of sensitivity is hydrodynamic theory which states the pain results from indirect innervation caused by dentinal fluid movement in tubules that stimulates mechanoreceptors near predentin -cause of fluid shift includes temp. change, air drying, and osmotic pressure -any tx that can reduce fluid shifts by occluding tubules may help reduce sensitivity -dentin hypersensitivity is problem in pts following perio surgery that exposes root surface -tx used to provide relief include topical fluoride, fluoride rinses, oxalate solutions, dentin bonding agents, sealants, iontophoresis, and desensitizing toothpastes -dentin bonding agents work best -when these methods don’t provide relief, restorative tx is indicated Indications for Indirect Tooth-Colored Restorations -may be indicated for class I and II restorations due to esthetics, strength, and other bonding benefits -b/c of potential for bonded restorations to strengthen remaining tooth structure, indirect restorations may be indicated for conservative restoration of weakened posterior teeth in esthetic areas -indirect tooth-colored restorations include: 1) Processed composite: have better wear resistance over direct composites -used mainly in conservative class I and II restorations in low-moderate stress areas 2) Feldspathic porcelain: used for inlays and onlays for class I and II restorations b/c highly esthetic -suffer from high incidence of fracture, especially under heavy occlusal forces -porcelain can also wear opposing tooth structure 3) Cast ceramic: inlays and onlays for class I and II preps have great marginal fit, low abrasion to opposing tooth structure, and superior strength compared to processed composite or Feldspathic -are excellent esthetic alternative to cast metal restorations 4) Computer-generated (CAD/CAM): better physical characteristics than processed composite, are also more expensive due to expense of equipment needed -advantage is they are fabricated chairside, so only one appt needed -do have high strength, low abrasiveness, and highly esthetic Part 4: Hand Instruments Hand Instrument Materials -hand instruments are made from two materials: carbon steel and stainless steel -some made w/ carbide inserts to provide more durable cutting edges (is more brittle though) -carbon steel is harder than stainless steel but will corrode easier -stainless steel will lose its keen edge quicker than carbon steel

Instrument Categories 1) Cutting: excavators, chisels, margin trimmers 2) Noncutting: condensers, mirrors, explorers, probes Instrument Design -most hand instrument have 3 parts: 1) Handle: part operator holds 2) Shank: connects handle to blade 3) Blade: working end of instrument -noncutting instruments have a nib instead of a blade -the end of the nib (working surface) is call the face Cutting Instrument Formulas 1) First number: width of blade in tenths of mm 2) Second number: primary cutting edge angle (always exceeds 50) -if edge is perpendicular to blade, this number omitted, resulting in 3 number formula 3) Third number (2nd number of 3-number code): blade length in mm 4) Fourth number (3rd number in 3-number code): blade angle (always 50 or less) Classification of Hand Instruments 1) Order: describes purpose of instrument 2) Suborder: describes position and technique 3) Class: describes form and shape (chisel or hatchet) 4) Subclass: describes angle of shank (straight, mono, bin, triple angles) Cutting Instrument Applications 1) Excavators: used for removal of caries and refinement of prep 2) Chisels: used for cutting enamel Excavators -four subdivisions: 1) Hatchets: has cutting edge of blade in same plane as long axis of handle -is bi-beveled -used primarily on anterior teeth for preparing retentive areas and sharpening internal line angles 2) Hoes: has cutting edge of blade perpendicular to axis of handle -used for planing tooth prep walls and forming line angles -commonly used in class III and V preps for gold 3) Angle-formers: is a mono-angle instrument w/ cutting edge at angle other than 90 degrees to blade -used primarily for sharpening line angles and creating retentive features in dentin -can also be used to place bevel in enamel margins -like a combo of chisel and gingival margin trimmer 4) Spoons: blades are slightly curved and cutting edges are circular (discoid) or claw-like (cleoid) -used for removing caries and carving amalgam and wax patterns Chisels 1) Straight chisel: cutting edge perpendicular to axis of handle and has bevel on only one side -force used is mainly straight thrust -used to plane/cleave enamel 2) Enamel hatchet: used for cutting and planing enamel surfaces 3) Gingival margin trimmer: designed to produce a proper bevel on gingival margins of proximo-occlusal preps and bevels on axiopulpal line angle in class II preps -blade is curved and cutting edge at angle other than perpendicular to axis of blade

Other Cutting Instruments 1) Knives (finishing knives, amalgam knives, gold knives): have thin, knife-like blade used to trim excess restorative material on gingival, facial, or lingual margins on proximal or class V preps 2) Files: also used to trim excess material, particularly at gingival margins 3) Discoid-Cleoid: used mainly to carve occlusal anatomy in unset amalgam -may be used to trim or burnish inlay-onlay margins -working ends larger than spoon excavator Using Hand Instruments -modified pen grasp has greatest intricacy of touch and is most common -palm and thumb grasp is most powerful grasp Part 5: Power Cutting Instruments Rotary Speed Ranges -rotational speed of power instruments measured in revolutions per minute (rpm) -3 speeds: 1) Low/Slow speed: < 12,000 rpm 2) Medium speed: 12,000 to 200,000 rpm 3) High speed: > 200,000 rpm -crucial factor is velocity at which edges of cutting instrument pass across surface being cut, which is proportional to: 1) rotational speed 2) diameter of instrument (large instruments have higher surface speeds) Laser Equipment -primarily used for soft tissue applications or hard tissue modifications -not used generally for tooth preparation b/c it is difficult to get a defined margin Carbide Dental Burs -rotary cutting burs that have bladed cutting heads -greater number of cutting blades, less efficient but smoother surface will result (polishing burs) -lesser number of cutting blades, more efficient but rougher surface will be (fissure burs) -includes burs for finishing metal restorations and surgical removal of bone, as well as tooth preps -there are also steel burs, which are used for finishing procedures Parts of Bur 1) Shank: part that fits into handpiece -straight, latch-type, and friction-grip 2) Neck: intermediate portion that connect head and shank -transmits rotational and translational forces to head 3) Head: working part of bur Sides of Bur Blade 1) Rake face: surface of blade which makes contact w/ tooth surface and daces in direction of bur rotation 2) Clearance face: surface of blade that faces away from direction of bur rotation Angles of Bur Blade 1) Rake angle: angle btw line connecting edge of blade to axis of bur and rake face -most impt part of bur blade -carbide burs for cutting tooth/amalgam have negative rake angle -burs used to cut acrylic/soft materials have positive rake angle 2) Edge angle: angle formed btw rake face and clearance face 3) Clearance angle: angle formed btw clearance face and tangent to path of rotation -eliminates friction (higher clearance angle, less friction) Round Burs -used for initial entry into tooth, preparation extension, preparing retentive features, and caries removal

Inverted Cone Bur (#34) -rapidly tapered cone wider at apex and tapers toward neck of bur -good for preparing undercuts into preparations Pear-Shaped Bur (#330) -more slightly tapered bur widest at apex and tapers toward neck of bur -end of bur is either continuously rounded or flat w/ rounded corners -used especially in Class I preps for gold foil as well as amalgam preps Straight Fissure Bur (#56) -elongated cylinder used for amalgam preps Tapered Fissure Bur (#169) -slightly tapered bur w/ narrowest part at apex and widest part at neck of bur -used for preps for indirect restorations that can’t have undercuts Diamond Abrasive Instruments -involves abrasive cutting instead of blade cutting -based on small, angular particles of a hard substance held in a matrix of softer material -cutting occurs at a large number of points where individual hard particles protrude from the matrix rather than along a continuous blade edge -diamond burs consist of a metal blank, the powdered diamond abrasive, and a metallic bonding material that holds diamond powder onto the blank Diamond Particle Factors -performance depends on size, spacing, uniformity, exposure, and bonding of diamond particles -increased pressure causes particles to dig into surface more deeply, leaving deeper scratches and removing more tooth structure -particles size categorized as coarse, medium, fine, and very fine, which corresponds to standard sieve sizes which separate diamond particles -larger particles means number of particles is decreased, so more force is applied to each particle -diamond finishing burs use even finer diamonds to produce smooth surfaces for final polishing Cutting Mechanisms -requirements for effective cutting include handpiece, air-water spray for cooling, high operating speed (>200,000 rpm), light pressure, and bur -carbide burs are better for end-cutting, produce lower heat, and have more blade edges per diameter -used for punch cuts to enter tooth structure, intracoronal tooth prep, amalgam removal, small preps, and secondary retentive features -diamond instruments have greater hardness and very high cutting effectiveness -more effective than burs for both intracoronal and extracoronal tooth preps, beveling enamel margins, and enameloplasty Hazards with Cutting Instruments 1) Pulpal precautions: cutting instruments can harm pulp by mechanical vibration, heat generation, dessication and loss of dentinal tubule fluid, and transection of odontoblastic processes -as thickness of dentin decreases, pulpal insult increases 2) Soft-tissue precautions: should isolate operating field from soft tissue by rubber dam, suction/assistant, cotton roll, mirror, etc. 3) Eye precautions: wear glasses w/ eye shields (dentist more likely to have eye injury than assistant) -if eye is injured, it should be covered w/ gauze until medical attention received 4) Ear precautions: high-pitch from high speed handpiece may cause hearing loss 5) Inhalation precautions: aerosols of tooth structure, restoration debris, microorganisms, etc. should be avoided by using intraoral evacuation when cutting -rubber dams can prevent inhalation by patient, but operators should use face masks (filter out bacteria and fine particulate matter, but not mercury or monomer vapors from restorations)

Part 6: Tooth Preparation Emphasis on Conserving Tooth Structure in Tooth Preps 1) Supragingival margins 2) Minimal pulpal depth 3) Minimal B-L width 4) Rounded internal line angles Principles of Tooth Preparation 1) All prepped walls and internal line angles should be placed in dentin that is free of infection, hard, and can’t be flaked away 2) Prepped cavity should be extended to include all decay and provide convenience for restoring and finishing 3) Enough depth and width should be prepped to prevent fracture of tooth and restoration a) about 1/5 distance btw buccal and lingual cusps b) at least 0.5mm into dentin c) pulpal floor should be flat and parallel to occlusal surface -should ideally be at least 2mm of dentin btw amalgam and pulpal floor -pulpal floor should be tilted lingually in mand 1st PM due to high buccal pulp horn d) line angles should be rounded and defined (sharp line angles increase risk of fracture) Cavity Classification by Number of Surfaces Involved 1) Simple cavity: lesion confined to one surface 2) Compound cavity: lesion involves two surfaces 3) Complex cavity: lesion involves three or more surfaces G.V. Black Cavity Classification 1) Class I: involves pit/fissure caries -occlusal surface of posterior teeth and lingual surface of anterior teeth -mesial/distal walls should diverge occlusally; buccal/lingual walls parallel -if width of marginal ridge less than 1.6mm, should be converted to class II -difficult to see radiographically 2) Class II: involves proximal surfaces on posterior teeth -occlusal outline at proximal segment dictated by position of proximal contact and extent of caries -proximal walls are divergent occluso-gingivally -gingival floor should parallel the enamel rods 3) Class III: on proximal surfaces of anterior teeth that don’t include incisal angle -for esthetic reasons, unsupported enamel may be left intact -composite is preferred material (distal of canine may be restored in amalgam) 4) Class IV: cavities of proximal surfaces of anterior teeth that involve incisal angle 5) Class V: cervical caries in gingival 1/3 of buccal or lingual surfaces -dictated by extent of caries -mesial and distal walls parallel enamel rods -occlusal wall is longer than cervical/gingival wall in ideal preps, giving trapezoidal shape 6) Class VI: on incisal edges of anterior teeth or on occlusal cusp heights of posterior teeth Initial Tooth Preparation 1) Outline form 2) Resistance form

3) Retention form

4) Convenience form

Outline Form -Def: Extension of the prep walls to sound tooth structure in all directions except pulpally. -shape or form of cavity on surface of tooth -margins placed in areas of lessened caries susceptibility (extension for prevention) -all undermined enamel must be removed -extension to sound, finishable tooth structure at initial depth of 0.2 to 0.75 mm into dentin 1) Principles: a) place margins where finishable b) remove unsupported, weakened tooth structure c) include all faults 2) Dictated by: caries, old material, defect size, occlusion, marginal configuration, and adjacent tooth contour 3) Features: a) Preserve cuspal strength d) Connect two close preps (within 0.5mm) b) Preserve marginal ridge strength e) Restrict depth to 0.2-0.75mm into dentin c) Keep B-L width narrow f) Use enameloplasty 4) Pit and fissure preps: extend to all of the fissure that is not eliminated by enameloplasty 5) Smooth surface preparations a) extend until no friable enamel remains b) don’t stop margins on cusp heights or ridge crests c) extend gingival margin/floor to get 0.5mm clearance d) extend facial and lingual proximal walls to clearance 6) For class V preps, outline is governed only by extent of lesion, except pulpally 7) Enameloplasty: removal of defect by recontouring enamel when defect is no deeper than ¼ thickness of enamel -when defect is greater than 1/3 thickness of enamel, the wall must be extended Resistance Form -prevention of tooth OR restoration fracture from occlusal forces along long axis of tooth 1) Factors: a) occlusal contacts b) amount of remaining tooth structure c) type of restorative material 2) Features: a) flat floors (pulpal and gingival) e) remove weakened tooth structure b) box shape f) cap cusps if needed c) preserve marginal ridges g) round internal line angles d) preserve cuspal strength h) adequate thickness of material Preserving Marginal Ridges -mesial and distal walls in class I prep should be divergent to prevent undermining of marginal ridges -for premolars, distance from margin of prep to proximal surface should be at least 1.6mm -for molars, distance from margin of prep to proximal surface should be at least 2mm Rule for Cusp Capping 1) If extension from a primary groove toward the cusp tip is no more than half the distance, no cusp capping needed 2) If extension is ½ to 2/3 of the distance, consider cusp capping 3) If extension is more than 2/3 the distance, usually cap the cusp Retention Form -prevention of dislodgement of restoration -preparation should have some undercuts for retention, or other retentive features if can’t use undercuts -should have sufficient height to have bulk of material Convenience Form -alterations made to prep to improve access and visibility for preparing and restoring the cavity

-aids operator in preparing, placing, and finishing restoration Final Tooth Preparations 1) Remove remaining caries 2) Secondary resistance/retention forms 3) Finishing external walls Removal of Remaining Caries -initial prep may remove all of caries, but additional removal may be needed -if have deep excavation and questionable dentin near pulp, can use indirect pulp cap (leave dentin, CaOH, GI base, restoration) Pulp Exposure 1) Indirect pulp cap indicated if: a) small exposure (1mm) b) symptomatic tooth c) area contaminated (saliva, debris) d) purulent exudate Pulp Protection 1) Sealers: seal dentinal tubules -is desirable for ALL restorations 2) Liners: used when cavity prep is within 0.5mm from pulp -ex. CaOH (stimulates formation of reparative dentin) a) placed in 0.5mm thickness b) Provides minimal thermal and mechanical protection c) provides some chemical protection 3) Bases: provide bulk for thermal and mechanical protection (need approximately 2mm bulk between pulp and metallic restorative material) -glass ionomer is typical base choice -other bases are zinc phosphate and polycarboxylate cement Secondary Resistance and Retention Features 1) Mechanical/Preparation Features a) retentive locks, grooves, coves (mainly for metallic restorations) b) groove extensions c) skirts (for cast restorations) d) beveled enamel margins (cast and composite restorations) e) pins, slots, steps, amalgam pins (mainly for amalgams) 2) Surface treatment of prepared walls a) Enamel wall: etching for bonded restorations b) Dentin wall: etching and priming for bonded restorations 3) Cement (for cast restorations)

Finishing of External Walls -establishing the design and smoothness of cavosurface margin 1) Objectives: a) get best seal btw tooth and restoration b) have smooth junction btw tooth and restoration c) maximum strength for tooth and restoration 2) Features a) bevels b) butt joints 3) Considerations a) direction of enamel rods b) support of enamel rods c) type of material d) location of margin e) degree of smoothness required Tooth Preparation Features: Amalgam vs Composite Amalgam Includes adjacent suspicious Outline form areas Pulpal depth uniform 1.5mm Axial depth uniform .2-.5mm inside DEJ Cavosurface margin 90 degree amalgam margin Bevels only gingival Texture of prepped walls smooth Cutting Instrument burs Primary retention form convergence occlusally Secondary grooves, slots, locks, pins, retention form bonding Resistance flat floors, rounded angles, form box-shaped floors Base need 2mm btw pulp and indications amalgam Liner indications CaOH Sealer used when not bonding

Composite Does not include adjacent suspicious areas remove fault (not usually uniform) remove fault (not usually uniform) 90 or greater degrees included for esthetic and seal rough diamonds none needed (bonded) bonding similar for large preps; no special form for small restorations not needed CaOH sealed by bonding system

Part 7: Moisture Control Goals of Isolation 1) Moisture control 2) Retraction and access 3) Harm prevention 4) Local Anesthesia Rubber Dam -isolates working field, prevents moisture and contamination, retracts soft tissue, and saves time 1) Advantages a) increased access and visibility d) protects pt and operator g) impr. mater. properties b) isolates area e) retracts soft tissue c) keeps area dry f) preserves and protects materials 2) Disadvantages a) some pts object c) partially erupted teeth e) time consuming b) some situations don’t work d) extremely malpositioned teeth f) asthma -alternatives to rubber dam for moisture control include cotton roll isolation and cellulose wafers (dry angle) Five Fxns of Rubber Dam 1) Retracts soft tissue 2) Provides clean, dry field 3) Protects pt and dentist 4) Provides for maximum physical properties of materials 5) Can save time for multiple preps Problems w/ Rubber Dam 1) Wrinkling of rubber dam btw teeth: holes punched too far apart 2) Papillae protrude from beneath dam: holes punched too close together Clamping -for clamp to be stable, all four points of jaws of clamp must contact tooth gingival to HOC -points of clamp must not extend beyond line angles to prevent impinging on papillae and interference w/ wedge Rubber Dam Frames 1) Young’s frame: most popular; U-shaped metal frame 2) Woodbury’s frame: provides most retraction of soft tissues Part 8: Liners, Bases, and Cements Liners -the only use of liner is to effect a pulpal response to lay down reparative dentin as used for direct or near pulpal exposure -traditional liner used is CaOH -glass ionomer liners may be used in conjunction w/ composite restorations as stress breaker in class I composites and on root surface of class II composite -should have thickness of 5 microns -should differentiate btw liners and varnishes 1) Liners: suspensions of CaOH in water (DyCal); may contain fluoride -liners are thicker than varnishes 2) Varnishes: solution liners of resin in liquid (Copalite) -varnishes shouldn’t be used under composites b/c disrupt monomer -varnishes under amalgam serve to reduce microleakage and seals tubules -do not act as thermal barriers

Bases -additional bulk from base affords mechanical and thermal protection (low thermal conductivity) to pulp under metal (amalgam/gold) restorations -termed base when 2mm or thicker which fxn to replace missing dentin structure 1) Glass ionomer: has been recommended as base to overly any CaOH liner -protects liner from amalgam condensation or dissolution of liner from etchant application for composite -used for posterior composites, porcelain/composite inlays or onlays, and amalgam -considered near ideal base b/c adheres to tooth structure, snap set when light-cured, anticariogenic (fluoride-releasing), and can bond to composite 2) Zinc phosphate/zinc polycarboxylate: used under gold restorations -must use varnish before zinc phosphate application 3) Secondary bases: zinc phosphate cement over CaOH base over pulp exposure (direct pulp cap) Thermal Insulation Capacity of Base Dependent On: 1) Thickness of base 2) Thermal conductivity of base 3) Density of base Base Use w/ Amalgam Restorations 1) Shallow excavations: if 2+mm dentin remains after prep, only sealer needed (Gluma Desensitizer or Copalite) 2) Moderately deep excavations: if btw .5 and 2mm of dentin remains, GI base can be placed to build total thickness from pulp to 2mm then sealer 3) Deep excavation: if less than 0.5mm or small pulp exposure encountered, place CaOH liner and 2mm GI base then sealer Base Use w/ Composite Restorations 1) Shallow excavations: if 2+mm dentin remains, no varnish, liner or base needed (GI cement may be placed) 2) Moderately deep excavations: if btw 0.5mm-2mm dentin remains, GI base can be placed to fill 3) Deep excavations: if dentin=composite 2) Tensile strength: forces applied opposite and away from each other (pulling) -dentin>amalgam>composite>enamel 3) Shear strength: forces applied opposite and toward each other but at difft. positions (sliding) Dimensional Change -is the percent of expansion or contraction of a material -when thermal expansion of tooth does not equal that of restoration, the differing expansions result in leakage of fluids btw the two -percolation refers to intermittent inlet and outlet of fluid leakage and can result in marginal decay -coefficient of thermal expansion: measures per unit length expansion if a material is heated by 1 degree C -composite>amalgam>gold=tooth Thermal Conductivity -quantity of heat transferred per second across an area and length when temp. difference is 1 degree C/cm -gold>amalgam>composite=tooth Stress -force per unit area -stress=force/area -the smaller the area the force is applied, the greater stress experienced -a small area of contact on restoration has more stress than broad area of contact Strain -change in deformation per unit length of material subjected to stress -rubber has greater deformation (strain) than gold Elastic Modulus -measure of stiffness/rigidity of material -higher elastic modulus=more rigid material -elastic limit: greatest stress an object can be subjected to in which it can return to its original dimension once force is removed -material loaded beyond elastic limit results in both elastic and plastic deformation -gold>enamel>amalgam>composite>dentin

Proportionate Limit -stress at which material no longer fxns as elastic (greatest stress that can be produced before permt. deformation exists) -greatest stress produced such that stress is directly proportional to strain -yield strength: arbitrary stress point immediately higher than proportionate limit and defines point at which permt. deformation begins -gold>enamel>amalgam>composite>dentin -brittleness is measure of material’s likeliness to fracture at its proportional limit -brittle material has high compressive strength and low tensile strength Coefficient of Thermal Expansion -measure of tendency of material to change shape when subjected to temp. change -possible break in marginal seal of restoration becomes imminent when there is marked difference in CTE btw tooth and restoration -one of consequences of thermal expansion and contraction is percolation which is cyclic ingress/egress of fluids at restoration margins -possibility of recurrent decay increases w/ increased percolation -ranks of CTE: tooth