Final corrected 16-17 Operative (2)

OPERATIVE LEGENDTopic Cards Topic Cardsamalgam 1-22 miscellaneous 85-95bases/liners/cements 23-36 pins 96-99caries 37-43 rubber dam 100-102composite 44-57 sealants/fluoride 103-113gold 58-76 terms 114-124instruments/burs 77-84



amalgamAll Class III lesions should be filled with composite resin, because they areesthetically important.• Both the statement and the reason are correct and related• Both the statement and the reason are correct but not related• The statement is correct, but the reason is not• The statement is not correct, but the reason is correct• Neither the statement nor the reason is correct 1 copyright © 2016-2017 Dental DecksOPERATIVE

• Neither the statement nor the reason is correct*** Think closely, distolingual Class III lesions are relatively nonesthetic and NationalBoard questions consider the best material to be amalgam or direct gold.Composite resin is not recommended for Class III lesions on the distal-lingual aspect ofcanines (use either amalgam or direct gold). Composite material will not maintain themesiodistal dimension of the tooth. Note: This may not be entirely true today due to thefact that there are much better wear-resistant resins than in the past. However, for NationalBoard questions composite is not recommended for this situation.A lingual approach is made when preparing a Class III dental amalgam preparation for thedistal surface of a canine because a lingual approach preserves the esthetic value of thefacial surface.Remember: • A bite-wing radiograph is the best method to diagnose incipient carious lesions on the distal surface of canine teeth. • A diagnostic aid to be used as a last resort to confirm the presence of a carious lesion on the proximal surface of an anterior tooth is mechanical separation (usually with a wedge).Rule of thumb: When two teeth adjacent to each other have Class III lesions, you shouldprepare the larger one first and fill the smaller one first. Access to the preps and shadematching are easier when you do both at the same appointment.

amalgamWhat is the ideal depth of an amalgam preparation and dentin remaining foradequate pulpal insulation?• 1.0mm into dentin, 2.0mm dentin remaining• 2.0 mm into dentin, 1.0 mm dentin remaining• 0.5 mm into dentin, 2.0 mm dentin remaining• 2.0 mm into dentin, 0.5 mm dentin remaining 2 copyright © 2016-2017 Dental DecksOPERATIVE

• 0.5 mm into dentin, 2.0 mm dentin remaining*** Thermal insulator- resists the transfer of heat. Amalgam is a poor thermal insulator;this is why a base of either calcium hydroxide or zinc oxide-eugenol is placed under mostamalgam restorations (to provide thermal protection). Comparison of Restorative Materials Characteristic Direct Gold Amalgam Composite GoodClose adaptation to cavity walls Very good Good Poor PoorCoefficient of thermal expansion similar to tooth structure Very good Good Poor PoorChemically acceptable to hard and soft tissues Very good Good N/A GoodAbsence of irritation to gingival tissue Very good Good Fair FairHigh edge strength Very good Poor Fair PoorNon-corroding in oral fluids Very good Fair Poor Very goodInsolubility in oral fluids Excellent Excellent Very good GoodClinical longevity Very good GoodHigh abrasion resistance Good GoodPermanently restores M-D dimension Good Very goodWithstands masticatory forces Fair GoodVersatility in use Fair GoodImitates natural tooth color Fair PoorEase of manipulation and placement Poor GoodThermal and electrical insulator Poor Poor

amalgamA patient comes in claiming that their holistic doctor told him that he has anallergy to mercury and needs only white fillings. Your best response is:• There is no such thing as a mercury allergy; plus, there is no mercury in amalgam fillings• You might have mercury allergy, but that is very rare; plus, there is no mercury in amalgam fillings• There is no such thing as a mercury allergy; plus, with proper isolation and technique, your exposure will be minimal• You might have a mercury allergy, but that is very rare; plus, with proper isolation and technique, your exposure will be minimal 3 copyright © 2016-2017 Dental DecksOPERATIVE

• You might have a mercury allergy, but that is very rare; plus, with proper isolation and technique your exposure will be minimalThe amount of mercury remaining in a set amalgam restoration is related to how much ofthe mercury-rich matrix is left in the amalgam after condensation. The key is to minimizethe amount of matrix that forms during the reaction. By condensing the amalgammixture in the cavity preparation, the mercury-rich matrix will come to the surface and beremoved by subsequent condensing and carving. The final amalgam restoration will becomposed of mostly residual alloy and very little of the mercury-rich matrix.The amount of mercury remaining in dental amalgam after condensation directly affects:(1) the porosity of the restoration, (2) the compressive strength of the restoration, (3) thecorrosive resistance of the restoration, and (4) the surface finish of the restoration.Mercury is used to initiate the reaction with the alloy. Although an amalgam restorationis nontoxic, mercury is poisonous. Free mercury, in the form of vapor or liquid droplets,represents a significant health hazard in the dental office. The greatest potential hazard ofchronic mercury toxicity comes from inhalation of mercury vapor. The vaporization is mostlikely to occur during the condensation or removal of amalgam (always use high speedsuction). Note: Mercury hypersensitivity (allergy) is very rare (1 in 100 million).Controlled studies have shown there is no connection between amalgam and degenerativediseases, like Alzheimer's or the incidence of neuropsychological effects in children.According to the ADA, the removal of amalgam solely for the purpose of mercurydetoxification is an unethical practice. http://www.ada.org/1741.aspxImportant point concerning condensation pressure: The area of the condenser point andthe force exerted on it by the operator govern the condensation pressure. The smaller thecondenser point, the greater is the pressure exerted on the amalgam.

amalgamA patient presents to your office with interproximal caries involving #4 disto-occlusal. The decision is made to do a Class II Inlay instead of a traditionalamalgam restoration. The inlay preparation will include all of the followingfeatures EXCEPT one. Which one is the EXCEPTION?• Sharp Internal line angles• Slightly divergent walls occlusally• Proximal retentive grooves• Reverse bevel at the axial gingival line angle 4 copyright © 2016-2017 Dental DecksOPERATIVE

• Proximal retentive grooves***This is a characteristic of Class II amalgam preparationsComparison of Conservative Class II Amalgam and Inlay PreparationsCharacteristic Class II Inlay Class II AmalgamOcclusal isthmus width 1/3 intercuspal (max) 1/3 intercuspal (max)Inclination of walls with respect Diverge 2-5 degrees occlusally Buccal and lingual walls convergeto the occlusal surface approximately parallel to the external surfaceDepth into dentin 0.5 mm 0.5 mmInternal line angles Sharp RoundedAxio-pulpal line angle Beveled or rounded Beveled or roundedProximal retention form Rectangular box Retentive grooves Reverse bevelGingival wall Form a reverse bevel at the axial Gingivo-axial line angle slightly gingival line angle, into the rounded gingival wallImportant: The gingival margin should clear the contact area to allow for adequate fin-ishing of the enamel margins and placement of a matrix band.

amalgamYou would prefer your assistant overtriturate the amalgam rather thanundertriturate it.This is because an undertriturated amalgam has less strength, faster corrosion,and a rougher finished surface.• Both statements are true• Both statements are false• The first statement is true, the second is false• The first statement is false, the second is true 5 copyright © 2016-2017 Dental DecksOPERATIVE

• Both statements are trueThe longer the trituration time, the smaller the setting expansion. If the trituration iscarried to the extent that the amalgam appears shiny and wet, the strength will bemaximal and the smooth, carved surface will retain its luster long after polishing. Aproperly triturated amalgam appears shiny, wet, smooth, and homogeneous.Inadequate trituration results in an amalgam mix that has a low strength and a rough sur-face that will accelerate corrosion. An undertriturated amalgam mixture will appear dryand grainy. Condensing this mixture will result in poor adaptation to the walls of thepreparation, lacrimation between condensed increments, and reduced strength. Overtrituration can result in decreased working time, high final contraction, and increasedcreep.Remember: An overtriturated mix is preferable to an undertriturated mix.Notes 1. The discolored, corroded, superficial layer frequently seen on the surface of a dental amalgam restoration is most likely a sulfide. 2. When carving an amalgam restoration, be sure to trim the margins with a sharp instrument that rests on tooth structure (this will prevent \"ditching\" the margins). 3. If an amalgam \"chips\" when you are carving it, the reason for this is that the amalgam was condensed after its working time had elapsed.

amalgamClass V amalgam restorations rarely require retentive grooves, but if they areused, they are placed at the incisoaxial and gingivoaxial line angles.• Both statements are true• Both statements are false• The first statement is true, the second is false• The first statement is false, the second is true 6 copyright © 2016-2017 Dental DecksOPERATIVE

• The first statement is false, the second is true*** Class V amalgam restorations commonly require and utilize retention grooves.The retention form for a Class V amalgam preparation is provided by the gingivalretention groove placed along the gingivoaxial line angle and the incisal retention grooveplaced along the incisoaxial line angle.The outline form for the classical Class V amalgam preparation is a deformed trapezoid(sometimes called “kidney-shaped”). The outline form is determined by the location andsize of the carious area.The nonparallel mesial and distal walls of the preparation are straight and parallel to thetransitional line angles. The direction of these walls is determined by the direction of theenamel walls (as is the decay pattern).The occlusal and gingival walls of the preparation should be gently curved arcs asdetermined by the contour of the free margin of the gingival tissue. Note: These arcsshould be as parallel to each other as possible.Important points: 1. The occlusal arc will normally be the longer of the two. 2. The gingival margin will normally be at, or slightly below, the margin of the free gingiva. 3. For incipient lesions, the axial wall should be uniformly deep into dentin.

amalgamDelayed expansion of amalgam restorations is associated with which twofactors?• Insufficient trituration and condensation• High residual mercury• The contamination of the amalgam by moisture during trituration and condensation• The failure to use a cavity varnish 7 copyright © 2016-2017 Dental DecksOPERATIVE

• Insufficient trituration and condensation • The contamination of the amalgam by moisture during trituration and condensation*** Important: The contamination of the amalgam by moisture during trituration and condensation isunquestionably the principal cause of failures.If moisture is incorporated into an alloy that contains zinc, the water reacts with the zinc to producehydrogen gas. The resulting pressure from the liberated gas produces severe expansion of the amalgam.This results in the following clinical manifestations: • The amalgam protrudes from the cavity preparation • Postoperative pain • Excessive corrosionImportant points to remember regarding amalgam: 1. The compressive strength is greatly reduced when amalgam is contaminated with moisture. The compressive strength of high-copper amalgam is similar to tooth structure. 2.The most important problem for amalgam restorations is that they have different coefficients of thermal expansion/contraction (amalgam = 25 ppm/°C) compared to tooth structure (10 ppm/°C). During reductions in intraoral temperature, there is a strong tendency at the margins for amalgam restorations to contract away from the margins and allow marginal leakage of intraoral fluids (percolation) that are later expelled when the temperature returns to normal. 3. The tensile strength of amalgam is about one-fifth to one-eighth of its compressive strength, that is why enamel is needed to support amalgam at the margins of restorations. Note: It is more abrasion- resistant than composite resin or unfilled resin. 4. Amalgam is brittle and has a low edge strength. 5. Amalgam is a high thermal conductor and a poor thermal insulator. 6. High-copper amalgams exhibit no clinically relevant creep or flow. 7. You need a minimum thickness of 0.75 mm (in axial areas) to 1.5 to 2 mm (in areas of occlusal contact) for adequate compressive strength.

amalgamProper condensation and carving makes an amalgam restoration strongerbecause it removes the mercury-rich gamma-two matrix.• Both the statement and the reason are correct and related• Both the statement and the reason are correct but not related• The statement is correct, but the reason is not• The statement is not correct, but the reason is correct• Neither the statement nor the reason is correct 8 copyright © 2016-2017 Dental DecksOPERATIVE

• Both the statement and the reason are correct and relatedThe most important consideration in the strength of the amalgam is the mercury content.If the mercury content exceeds 55%, a dramatic loss in strength results. Amalgamrestorations that contain mercury levels of about 55% exhibit a high incidence of marginalbreakdown, fracture,and corrosion, and the surface finish of the restoration is not good.Factors that influence the final mercury content of a restoration: • Original mercury-alloy ratio: specific to each product but generally less than 1:1 so that amalgam contains 43% to 50% mercury • Amount of trituration • Condensation pressure and time involved in carrying out condensationVery important: Removing the mercury-rich matrix by proper condensation andcarving produces a stronger and more corrosion-resistant amalgam because it minimizesthe formation of the matrix phases of amalgam, which are the least desirable parts of theset material.

amalgamA high-copper amalgam is preferred over a lower-copper amalgam due to theundesirable clinical properties that present in which phase of the reaction?• Gamma• Gamma-one• Gamma-two• Gamma-three 9 copyright © 2016-2017 Dental DecksOPERATIVE

• Gamma-twoThe reaction that occurs between the alloy particles and the mercury can be summarized as follows:Silver-tin alloy + Mercury ® Silver-tin alloy + Silver-mercury + Tin-mercuryAg3Sn Hg Ag3Sn Ag2Hg3 Sn8Hg (gamma)(gamma) (gamma-one) (gamma-two)Gamma is the unreacted alloy. It is the strongest, and corrodes the least, and forms 30% of volumeof set amalgam. Gamma-one is the matrix for unreacted alloy and is the second strongest phase.It Forms 60% of volume of set amalgam. Gamma-two is the weakest and softest phase. It is alsothe most susceptible to corrosion in the mouth and forms 10% of the volume of the set amalgam.The volume of the gamma-two phase decreases with time due to corrosion.The key difference between the low-copper and the high-copper amalgams is that the low-copperamalgams contain the gamma-two phase, which is not present in the high-copper amalgams.Instead, the high-copper amalgams contain the Cu6Sn5 phase. Since the gamma-two phasecorrodes faster than the Cu6Sn5 phase, the gamma-two phase containing low-copper amalgamsdevelops micro- porosities due to corrosion faster than the high-copper amalgams. Theseporosities weaken the amalgam margins and explain why marginal defects (chipped margins) aremore often seen around low-copper amalgams. This explains why high-copper amalgams shouldbe used rather than the low-copper amalgams.Notes 1. Smaller particle size results in higher strength, lower flow, and better carvability. 2. Spherical amalgams high in copper usually have the best tensile and compressive characteristics. 3. Copper contents over 6% (\"high-copper\" alloys) eliminate the gamma-two phase by forming a copper-tin (Cu6Sn5) phase resulting in superior properties. 4. Amalgam has a coefficient of thermal expansion approximately twice that of tooth structure. 5.The tensile strength of amalgam is about one-fifth to one-eighth of its compressive strength.

amalgamWhich of the following properties would not be beneficial to the retention andresistance of a Class II amalgam preparation?• Occlusal dovetail• Convergent buccal and lingual walls• Retentive proximal grooves• Axio-Gingival line angle greater than 90 degrees 10 copyright © 2016-2017 Dental DecksOPERATIVE

• Axio-Gingival line angle greater than 90 degreesGeneral properties of Class II amalgam preparations: • All walls should meet the surface of the tooth at a 90o angle (butt joint) • Occlusal dovetail: provides resistance to proximal displacement • Pulpal floor should be flat same as Class I • The buccal and lingual walls of the proximal section should converge occlusally — the extension of these walls is determined primarily by the position of the adjacent teeth in relation to the tooth being restored • The buccal, lingual, and gingival walls should be extended into the embrasures enough to allow easy cleaning — areas of lessened caries susceptibility • The axiopulpal line angle is beveled to reduce concentration of stresses — resistance form • Retention grooves are placed in the axiobuccal and axiolingual line angles and extended to the height of the axial wall — resistance to dislodgement • Lingually, it is often necessary to create a reverse curve in the outline. A reverse curve is a curve put into the buccal or lingual wall so the wall meets the external surface of the tooth at a 90o angle.Note: Class II amalgam preps have independent retention and resistance form for both theproximal box and occlusal portion of the preparation.Important: When caries is extensive, reduction of one or more of the cusps for capping maybe indicated. When the facial (or lingual) extension is two-thirds from the primary groovetoward the cusp tip, reduction of the cusp(s) for amalgam capping is mandatory for thedevelopment of adequate resistance form. Note: The final restoration has to have restoredcusps with a minimal thickness of 2 mm of amalgam for functional cusps and 1.5 mm ofamalgam for nonfunctional cusps.

amalgamBeveling the gingival cavosurface margin of the proximal box of a Class IIamalgam preparation on a permanent tooth:• Should result in a long bevel• Is contraindicated because of the low edge strength of amalgam• Should remove unsupported enamel that may fracture• Is unnecessary since the tooth structure in this area is strong 11 copyright © 2016-2017 Dental DecksOPERATIVE

• Should remove unsupported enamel which may fracture*** The gingival cavosurface margin is beveled only if it is in the enamel. Beveling is notnecessary if the gingival margin is within cementum.The gingival cavosurface margin should be beveled to remove any unsupported enamel.The bevel is usually placed with a gingival margin trimmer. This gingival margin must bebelow any existing contact with the adjacent tooth in order to allow proper finishing of thegingival margin.Notes 1. The bevel is no steeper than necessary to ensure full-length enamel rods forming the gingival margin and is no wider than the enamel. 2. Remember: Enamel rods in the gingival third of the primary teeth extend occlusally from the DEJ, eliminating the need in Class II preparations for the gingival bevel that is required in permanent teeth. 3. Primary molar teeth have marked cervical constriction. Therefore, when preparing the proximal portion of a Class II cavity prep, a satisfactory gingival seat may be difficult to obtain if the prep extends too deeply gingivally.

amalgamWhich tooth requires special attention when preparing the occlusal aspect for arestoration?• Mandibular first bicuspid• Mandibular second bicuspid• Maxillary first molar• Maxillary first bicuspid 12 copyright © 2016-2017 Dental DecksOPERATIVE

• Mandibular first bicuspidThe key to this question is the angulation of the preparation. The bur should be tiltedlingually to prevent encroachment on the facial pulp horn and also to maintain dentinalsupport of the lingual cusp. The pulpal floor should be parallel to the occlusal plane of thetooth faciolingually.Note: Pulpal floor slopes to coincide with the slope (height) of the cusps.Remember: Anesthesia is necessary for restorative preps that involve or extend past theDEJ, as sensitivity will be present.

amalgamAll of the following correctly describe the ideal preparation for a Class oneamalgam EXCEPT one. Which one is the EXCEPTION?• Convergent Buccal and Lingual walls• Pulpal floor extending 0.5mm into dentin• Divergent mesial and distal walls 1mm away from proximal surfaces• Rounded internal line angles 13 copyright © 2016-2017 Dental DecksOPERATIVE

• Divergent mesial and distal walls 1 mm away from proximal surfaces***Mesial and distal walls should be at least 1.6 mm away from proximal surfaces onpremolars and 2.0 mm away on molars to prevent marginal ridge fracture.Important: • Only two walls of a Class I amalgam preparation should diverge, the mesial and distal. The buccal and lingual walls of a Class I amalgam preparation should be convergent. • The reason is still true because there are only two marginal ridges per tooth: mesial and distal DIVERGING CONVERGING (Correct) (Incorrect)*** This slight occlusal divergence prevents undermining the marginal ridges of theirdentin support.Notes 1. This divergence of the mesial and distal walls holds true for Class I preparations for direct filling gold and gold inlays as well. 2. For premolars, the distance from the margin of the mesial and distal wall to the proximal surface must not be less than 1.6 mm. For molars this minimal distance is 2 mm. Violation of this distance can increase the likelihood of future marginal ridge fracture.

amalgamThe matrix band should be removed after condensation of the amalgam but priorto the final carving of the restoration. This is because the wedge compensates forthe thickness of the matrix band.• Both the statement and the reason are correct and related• Both the statement and the reason are correct but not related• The statement is correct, but the reason is not• The statement is not correct, but the reason is correct• Neither the statement nor the reason is correct 14 copyright © 2016-2017 Dental DecksOPERATIVE

• Both the statement and the reason are correct but not relatedAlthough the wedge is used to compensate for the thickness of the matrix band, the true reason forcarving after the removal of the band is to gain proper access to all margins of the amalgamrestoration.Important points to remember regarding matrix bands: • The reason for placing the matrix for a Class II amalgam restoration to protrude above the cavity preparation is to allow for overfilling, thus enhancing adequate cavosurface coverage. • Contact areas are always carefully restored in all restorations to protect the gingival tissue. The matrix band should be burnished into contact with adjacent teeth, this will help ensure contact. • One of the most difficult teeth to adapt the matrix band to is the mesial of a maxillary first premolar due to its developmental depression (concavity in the cervical third of the mesial surface of the crown).Important: The wedging action between the teeth should provide enough separation to compen-sate for the thickness of the matrix band. This will ensure a positive contact relationship after thematrix is removed following the condensation and initial carving of the amalgam.Common problems associated with amalgam restorations: • Postoperative sensitivity: - May be caused by inadequate condensation, or lack of proper dentinal sealing • Marginal voids: - May be caused by inadequate condensation, or amalgam breaking away from margins when carving • Marginal ridge fractures: may be caused by any of the following: - Not rounding the axiopulpal line angle in Class II tooth preparations - Marginal ridge left too high - Improper occlusal embrasure form - Improper removal of matrix band - Overzealous carving of the restoration

amalgamThe diagonal slot opening on the Tofflemire matrix retainer (also called theUniversal matrix system) is always placed facing the gingiva. This:• Permits easy separation of the retainer from the band in an occlusal direction• Allows for better contour of band to tooth• Allows for easier wedge placement• Is less harmful on the gingiva 15 copyright © 2016-2017 Dental DecksOPERATIVE

• Permits easy separation of the retainer from the band in an occlusal directionIn addition, the larger circumference of the matrix band is always placed toward theocclusal surface of the tooth. This accommodates for the larger tooth circumference atthe contact level.The primary function of the matrix band is to restore anatomical contours and contactareas. Other functions include providing a rigid wall to condense filling material against,preventing excess filling material from going subgingivally, and to some extent, limitingmoisture contamination during condensation. A properly placed wedge will also protectthe gingival tissue and help reduce moisture leakage into the cavity preparation.Wedges are inserted from the facial or lingual embrasure, whichever is larger, slightlygingival to the gingival margin. The wedging action between the teeth should provideenough separation to compensate for the thickness of the matrix band.Important: When placing a matrix band for a Class II amalgam restoration, the gingivo-occlusal width of the band should be trimmed to be at least 1 mm greater than theexpected marginal ridge height.

amalgamWhich of the following are true statements regarding the polishing of amalgam?Select all that apply.• It reduces marginal discrepancy• It should be done about 10 minutes after placement• Occlusion should not be checked prior to polishing• It prevents tarnishing of the restoration• It improves the appearance of the restoration• It should be done with a dry polishing powder 16 copyright © 2016-2017 Dental DecksOPERATIVE

• It reduces marginal discrepancy • It prevents tarnishing of the restoration • It improves the appearance of the restorationThe final finish of the amalgam restoration should not be done until after the amalgam is fullyset. It should be delayed for at least 24 hours after condensation and preferably longer (24-48hours). By waiting, you can be ensured that the reactions between the alloy and mercury willhave been completed and a more corrosion-resistant surface will be created.Amalgam restorations should be finished and polished for three major reasons: (1) to reducemarginal discrepancies and to create a more hygienic restoration, (2) to reduce marginal break-down, which will reduce the chance of recurrent decay, and (3) to prevent tarnishing and toimprove the appearance of the restoration.Heat generation must be avoided. The use of dry polishing powders and discs caneasily raise the surface temperature above the 60°C (140°F) danger point. Thus, a wetabrasive powder in a paste form is the agent of choice. Note: Heat will not only damage thepulp but also draws mercury to the surface of the restoration and an inferior restoration willresult.Final polishing may be accomplished using a rubber cup with flour of pumice followed by ahigh-luster agent, such as tin oxide.Remember: When checking the occlusion on a newly condensed amalgam restoration, themarks left by the articulating paper should be of the same intensity as other markings in thesame quadrant.

amalgamAll of the following are true concerning a Class V amalgam preparationEXCEPT one. Which one is the EXCEPTION?• The outline form is determined primarily by the location of the free gingival margin• The mesial, distal, gingival, and incisal walls of the cavity preparation diverge outward• The retention form is provided by the gingival retention groove along the gingivo- axial line angle and an incisal retention groove along the incisoaxial line angle• A cervical clamp is usually necessary to retract gingival tissues 17 copyright © 2016-2017 Dental DecksOPERATIVE

• The outline form is determined primarily by the location of the free gingival margin*** This is false; the outline form is determined primarily by the location and size of thecarious lesion.Notes 1. Care must be taken to distinguish the active root-surface carious lesion from the root-surface lesion that was active but has become inactive (arrested). The arrested lesion shows eburnated dentin (sclerotic dentin) that has darkened from extrinsic staining and is firm to the touch of an explorer. 2. The Class V amalgam restoration is used to restore lesions from caries, erosion, and abrasion. 3. Care should be taken not to \"ditch\" the cementum when finishing and polishing. 4. Occasionally, you will notice that the gingival tissue has receded apically from the gingival margin of a Class V restoration that was previously polished. This may be related to irreversible tissue changes caused by inadvertently traumatizing the tissue when the restoration was being polished. Key point: Be careful.Remember: Incipient carious lesions that are contained entirely within enamel and havenot spread to the underlying dentin. The two options for treatment are: 1. Promote remineralization: with fluoride varnish and self-administered fluoride, followed by regular monitoring. Note: Incipient carious lesions usually do not progress rapidly. 2. Place a restoration: be as conservative as possible.

amalgamIn regard to the selection and placement of amalgam restorations, all of thefollowing are true EXCEPT one. Which one is the EXCEPTION?• High-copper amalgams are preferred over low-copper amalgams due to elimination of the gamma two phase• Increased trituration time will increase compressive strength and decrease setting expansion compared to decreased trituration time• Ideal mercury content should range between 55%-60%• Tensile strength is 1/5-1/8 the compressive strength of set amalgam• The smaller the particle size the less expansion 18 copyright © 2016-2017 Dental DecksOPERATIVE

• Ideal mercury content should range between 55%-60%Dimensional change Setting Expansion: - Most amalgam restorations show slight setting expansion, but not of clinical significance. - The more free mercury, the more setting expansion (and vice versa). • The greater the time of trituration, the less the expansion • The greater the pressure used in condensation, the less the expansion • The smaller the particle size, the less the expansion Strength: - Amalgam is brittle but possesses good compressive strength. The most important consideration in the strength of the amalgam is the mercury content. Mercury content above 55% will cause a marked decrease in strength (should be within 45- 53% by weight). • Higher condensation pressure increases strength • The smaller the particle, the more strength • The longer the trituration time, the more strength • The fewer voids, the more strength

amalgamAmalgam restorations require an obtuse cavosurface margin because amalgamis a brittle material.• Both the statement and the reason are correct and related• Both the statement and the reason are correct but not related• The statement is correct, but the reason is not• The statement is not correct, but the reason is correct• Neither the statement nor the reason is correct 19 copyright © 2016-2017 Dental DecksOPERATIVE

• The statement is not correct, but the reason is correctRemember for the boards: (when this is the answer) A. The statement is NOT correct B. Therefore, the reason is obviously not related C. So, you need to evaluate the reason independently thus: • Amalgam restorations require a 90° cavosurface margin • Amalgam is a brittle materialClinical experience has established that this butt joint margin of enamel and amalgam isthe strongest. Amalgam is a brittle material with low edge strength and tends to chip underocclusal stress if its angle at the margins is less than 80° to 90°.Comparison of the Cavosurface Margins for a Conservative Class II Amalgam and an Inlay PreparationCharacteristic Class II Inlay Class II AmalgamOcclusal cavosurface margin Beveled to result in 40 degree 90 degrees with the external surface marginal metalProximal cavosurface margins Outer planes carried into cleansable 90 degree angle with external surface area (provides access for finishing margins). Beveled to result in 40 degree marginal metalGingival cavosurface margin Beveled to result in 40 degree 90 degree angle with external surface marginal metal

amalgamHigh copper amalgams reduce gamma-two formation and marginal breakdownUnreacted AgSn gamma phase is the strongest and prevalent in trituratedamalgam.• Both statements are true• Both statements are false• The first statement is true, the second is false• The first statement is false, the second is true 20 copyright © 2016-2017 Dental DecksOPERATIVE

• Both statements are trueConstituents in Amalgam:Basic constituents:• Silver (Ag) (40-70%) • Tin (Sn) 25-27% Note: Influences the amalgam in an - increases strength - decreases expansion opposite manner to silver. - increases expansion - decreased strength - increases setting time• Copper (Cu) 6% or more: Note: New alloys called \"high copper\" contain 9-- ties up tin: reducing gamma-2 formation 30% copper. These alloys have less marginal break-- increases strength down and are less likely to corrode.- reduces tarnish and corrosion- reduces creep: reduces marginal deterioration• Mercury (Hg):- activates reaction- only pure metal that is liquid- spherical alloys - admixed alloys • require more mercury • require less mercury - smaller surface area easier to wet - lathe-cut particles more difficult to wet - 45% to 50% Hg - 40% to 45% HgOther constituents:• Zinc (Zn) 1% or less: used in manufacturing, decreases oxidation of other elements (sacrificialanode)- Provides better clinical performance: less marginal breakdown- Causes delayed expansion with low Cu alloys if contaminated with moisture during condensation• Palladium (Pd) 1% or less: reduced corrosion, greater luster• Indium (In) 1% or less:- decreases surface tension - reduces creep and marginal breakdown• reduces amount of mercury necessary - increases strength• reduces emitted mercury vapor - must be used in admixed alloys

amalgamWhich of the following statements are true regarding creep?Select all that apply.• Creep is a process that happens over time• Creep gradually increases the marginal integrity of an amalgam restoration• Undertrituration tends to increase the creep rate• Overtrituration tends to decrease the creep rate• Increasing the condensation pressure decreases the creep rate 21 copyright © 2016-2017 Dental DecksOPERATIVE

• Creep is a process that happens over time • Undertrituration tends to increase the creep rate • Increasing the condensation pressure decreases the creepCreep (time-dependent deformation or strain relaxation) is the deformation with time inresponse to a constant stress. It has been implicated as one of the main causes formarginal fracture of amalgam restorations. 1. The higher the creep, the greater the degree of marginal deterioration. Notes 2. Creep is time-dependent.High copper and low mercury content of an amalgam restoration will tend to decreasecreep. Altering the trituration time and condensation pressure can change the creep rateof an amalgam restoration: • Both undertrituration and overtrituration tend to increase the creep rate • If there is a delay between trituration and condensation, the creep rate increases • Increasing the condensation pressure decreases the creep rate (this will also decrease the final mercury content of the restoration)The marginal leakage of an amalgam restoration decreases as the restoration ages.Corrosion products are helpful in reducing marginal leakage around amalgamrestorations. These corrosion products, such as tin oxide and tin sulfide, accumulate inthe gap between the restoration and the tooth, thus providing an excellent seal.

amalgamThere is no free mercury in triturated amalgam because trituration causes thealloy to dissolve in the mercury.• Both the statement and the reason are correct and related• Both the statement and the reason are correct but not related• The statement is correct, but the reason is not• The statement is not correct, but the reason is correct• Neither the statement nor the reason is correct 22 copyright © 2016-2017 Dental DecksOPERATIVE

• The statement is correct, but the reason is not*** There is no free mercury in triturated amalgam because trituration coats the alloyparticles with mercury.The object of trituration is to bring about an amalgamation of the mercury and alloy. Eachindividual alloy particle is coated with a slight film of oxide that prevents penetration by themercury. During trituration, this film is rubbed off, and the clean metal is then readily attackedby the mercury.Silver Alloys for Dental Amalgams: Low copper alloys: 4% to 6% or less, traditional alloy • Comminuted (irregular, filing, or lathe-cut) • Spherical particles High copper alloys: 9% to 30% most common, corrosive resistant • Spherical: sets faster and attains final mechanical properties more rapidly • Comminuted can have zinc or be zinc-free and also can be fine-cut or microcut • Combination (admix) mixture of spherical and comminuted particlesDispersed-phase alloy was the original admix alloy, mixture of comminuted traditionalsilver alloy and spherical particles of silver-copper eutectic alloy. Most commonly used alloytoday.Eutectic alloy is an alloy in which the elements are completely soluble in liquid solution butseparate into distinct areas on solidification.Note: Once amalgamation occurs, no free (unreacted) mercury is associated with the amalgamrestoration. The restoration has no toxic properties. However, if the amalgam is heatedbeyond 80°C, liquid mercury can form on the surface of the amalgam, and its vapor presentsa health hazard.

bases/liners/cementsPlease rank the following in order of application thickness and consider whichwould be used to replace a large amount of dentin that has been destroyed.• Cement• Cavity Liner• Base 23 copyright © 2016-2017 Dental DecksOPERATIVE

• Cavity liner, cement, baseA base would be appropriate (application thickness 1-2mm) when a large amount of dentin hasbeen destroyed.The most important consideration for pulp protection in restorative techniques is the thickness ofthe remaining dentin.In general, cements that are thicker than 2 mm are termed bases and, as such, function to replacelost dentin structure beneath restorations. A base may be used to provide thermal protection undermetallic restorations, to increase the resistance to the forces of condensation of amalgam, or toblock out undercuts when taking impressions for cast restorations.The only distinction between a base, a cement, and a cavity liner is their final application thick-ness: 1. Cements for luting have a desired final film thickness of approximately 15 to 25 microns. 2. Cavity liners (either solution or suspension liners). Liners are materials that are placed as a thin coating ( have a desired final film thickness of approximately 5 microns) on the surface of a cavity preparation. Although they provide a barrier to chemical irritants, they are not used for thermal insulation or to add bulk to a cavity preparation. Furthermore, these materials do not have sufficient hardness or strength to be used alone in a deep cavity. 3. Bases have a final application thickness of approximately 1 mm to 2 mm (they may be thicker depending on the amount of dentin that has been destroyed). Bases can be considered as restorative substitutes for the dentin that was removed by caries and/or the cavity preparation. They act as a barrier against chemical irritation, provide thermal insulation, and can resist the condensation forces on a tooth when placing a restoration. Also, the clinician can shape and contour base materials after placement into the cavity preparation. Important: A base should not be used unnecessarily.Remember: Calcium hydroxide is very effective in promoting the formation of secondary dentin,which is an important aid in the repair of the pulp.Note: The selection of appropriate bases and liners to restore the axial wall of a Class IIrestorations depends on the biological effect required and the thickness of the remaining dentin.

bases/liners/cementsWhich of the following statements are true regarding glass ionomer cements?Select all that apply.• Release fluoride• Good chemical adhesion• Good thermal insulator• Thermal expansion similar to tooth• High solubility after initial setting 24 copyright © 2016-2017 Dental DecksOPERATIVE

• Release fluoride • Good chemical adhesion • Good thermal insulator • Thermal expansion similar to tooth*** Glass ionomer cements have low solubility, lower than zinc phosphates (which arelower than zinc polycarboxylates).Glass ionomer cements are hybrids of silicate and polycarboxylate cements designed tocombine the fluoride releasing properties of silicate particles with the chemicallyadhesive and more biocompatible characteristics of the polyacrylic acid matrixcompared to the extremely acidic matrix of silicate cement.Advantageous physical properties of glass ionomer cements: • Release of fluoride: anticariogenic • Chemical adhesion to the prepared tooth and certain metals. Micromechanical bond to composite resins. Important: Chelation of calcium ions on tooth structure by ionized polyacrylic acid side-groups is the principal mechanism of chemical adhesion to tooth structure. • Biocompatibility is high, thus with enough dentin remaining (0.5-1 mm,) no pulpal protective agent (calcium hydroxide) is required • Good thermal insulators: equal to that of natural dentin • Thermal expansion is similar to that of tooth structure • After initial setting, they have low solubility in the mouthNote: Its disadvantage as a cement is that it has a higher cement film thickness than zincphosphate cements.Remember: No lab test of cement has correlated solubility with clinical retention.