The Role of Cements in Dental Implant Success, Part 2

Continuing Education Course Number: 162 The Role of Cements in Dental Implant Success, Part 2 Authored by Chandur P. K. Wadhwani, BDS, MSD, and Kwok-...
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Continuing Education Course Number: 162

The Role of Cements in Dental Implant Success, Part 2 Authored by Chandur P. K. Wadhwani, BDS, MSD, and Kwok-Hung (Albert) Chung, DDS, MS, PhD Upon successful completion of this CE activity 2 CE credit hours may be awarded

A Peer-Reviewed CE Activity by

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Continuing Education

The Role of Cements in Dental Implant Success, Part 2 Effective Date: 6/1/2013

San Antonio. He was appointed by the University of Washington as a full professor of the restorative dentistry department in 2006. Dr. Chung is a Fellow of Academy of Dental Materials, has published more than 90 articles in peer-reviewed journals, and has lectured internationally. He can be reached at (206) 543-5948 or via e-mail at [email protected].

Expiration Date: 6/1/2016

This is part 2 of a 2-part article series. Part 1 of this series was published in the April 2013 issue of Dentistry Today and can be found within the Online Courses listing of the dentalcetoday.com Web site.

Disclosure: Dr. Chung reports no disclosures.

INTRODUCTION LEARNING OBJECTIVES

Cementation as a means of attaching a restoration such as an inlay, onlay, crown, or bridge to a natural tooth has been used for close to 100 years. The process serves to unite components of the same or different materials together. The cementing media used can result in a union that is primarily frictional (eg, zinc phosphate cement) where some form of mechanical or micromechanical interlocking occurs, or adhesive in nature where a chemical bond unites the structures (eg, self-etching resin systems and dentine), or both, depending on the materials joined. With the advent of dental implants and the subsequent introduction of the cement-retained implant restoration has come the emergence of new issues that are not commonly observed when restoring teeth.1-4 The cement-retained implant restoration may be more vulnerable to the effects of cement entering the soft tissues and residual excess cement on the implant restoration when compared to a tooth.5 Although there are tens of thousands of articles written on cements, highlighting compressive, tensile, and shear strengths, their properties, and clinical applications, very little is reported about the way in which cements flow during the cementation process, how to optimize their application, or the amount of cement required to achieve the ideal cementation results. The occlusion of the cemented crown can be altered by the quality and quantity of cement applied to the internal aspect of the crown. This has been reported by several authors who have studied cement application techniques with respect to vertical displacement.6-8 Having a sealed restorative margin is considered a prerequisite for a tooth to eliminate ingress of bacteria that could cause subsequent caries.9 With implant restorations, a

After participating in this CE activity, the individual will learn: • The fluid mechanics and flow involved with implant luting cements so that flow can be manipulated and controlled effectively, and • How the abutment can be used as a repository for excess cement to reduce the amount extruded out through the restorative margin.

ABOUT THE AUTHORS Dr. Wadhwani received his specialty certificate in prosthodontics with a master’s degree from the University of Washington School of Dentistry. He is currently in private practice in Bellevue, Wash, and is past president of the Washington State Society of Prosthodontics. He is an affiliate instructor at the University of Washington department of restorative dentistry. He has authored several technique and research papers on the subject of implants and is involved in numerous research projects. He can be reached via e-mail at [email protected]. Disclosure: Dr. Wadhwani reports no disclosures. Dr. Chung graduated from the National Defense Medical Center, Taiwan, with a DDS degree. He received his PhD degree in biomaterials from the Northwestern University at Chicago and a certificate in advanced prosthodontics from the University of Texas Health Science Center at 1

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The Role of Cements in Dental Implant Success, Part 2 bacterial marginal seal provided Group 1 Group 2 Group 3 by cement lute may not be a great concern, especially when one considers the success that screwretained restorations have, where no seal exists.10 Marginal adaptation of an implant crown has not been shown to be problematic. Jemt11 found no issue with the exposed set cement that filled marginal space between the implant abutment and crown. However, marginal seal may be important with respect to cement lute washout during luting (contamination from crevicular fluids), and after luting (dissolution of the Gross Application Brush Application Rim Application cement) the restoration. Residual excess cement extrusion from Figure 1. Actual examples of loading patterns and site of cement from a survey of more than 400 dentists on how they place cement for an implant crown. around the margin of the cemented restoration of implants is a problem and has also been consensus on the most appropriate site or technique when 12 described in the literature. considering cementation of implant crowns. A second part of the survey13 involved weighing the The purpose of this article is to provide an overview of how cement flows within an implant abutment crown amount of cement placed into the crowns and comparing it system and how this may be altered to reduce the to the ideal amount required such that the crown completely possibility of peri-implant disease. The discussion focuses seated with complete cement lute space filled with cement on cement application and how to manage the flow patterns and no excess. This was determined to be 3% of the total in relation to implant restorations. A visual reference as to crown volume. What was of significant interest was the how cement may be affected by the site placed, amount range of cement placed within the crowns. Some surveyed applied, and modifications to the abutment is described. dentists loaded the crowns with greater than 50 times the Part 1 of this article reviewed differences between teeth and amount of cement required. Others placed only one quarter implants with regard to cement selection. of the ideal amount needed (Figures 2a and 2b). The clinical significance of the cement application and HOW MUCH CEMENT SHOULD WE USE? volume data indicates a large variation in thought processes, A recent survey of more than 400 dentists evaluated with very few dentists able to provide the appropriate volume cement application techniques specifically for implant of cement. Too little cement and the crown may not stay in crowns.13 The data revealed a large difference in place; too much cement may result in cement extrusion into application technique and site. Most dentists (55%) applied the tissues and result in peri-implant disease.1 It should be cement on the internal surface with a brush; 28% of those understood that the laboratories fabricating the restorations surveyed applied cement arbitrarily by loading the inside of provide the clinician with a limited finite volume for cement, the crown; and a smaller proportion (17%) preferentially usually in some form of relief such as a die spacer, either loaded the internal margin of the crown (Figure 1). The painted onto the abutment if fabricated by conventional study13 concluded that there appeared to be little dental techniques, or “built in” with CAD/CAM technology. 2

Continuing Education

The Role of Cements in Dental Implant Success, Part 2 This usually equates to about 20 µm to 50 µm of space, or as thick as a one to 2 layers of nail varnish.

a

b

CEMENTS AS LIQUIDS Clinicians should be aware of how materials such as liquids behave. While this is beyond the scope of this text, a very brief summary will be given. Cements vary in Figures 2a and 2b. (a) This group of dentists overfilled the crowns with cement—some their physical nature, predominantly de- placed more than 50 times the ideal amount required. (b) This group underfilled the crowns pendent upon their chemical composition, with insufficient cement to fill the lute space. but in general, cements are considered a b viscous fluids. Fluids can be loosely defined by their behavior when exposed to an applied force. Many liquids, including water, have Newtonian fluid properties. Regardless of the forces acting on such a fluid, the viscosity remains unchanged, so the fluid will flow, taking up the shape of the container it is in (Figure 3a). In dentistry, most polymers (many Figures 3a and 3b. (a) This body of water has Newtonian properties. It fills this container and will flow according to Newtonian laws when a force is applied to it. (b) This liquid does not cements are polymers) are considered non- follow Newtonian laws. It does not flow into the container and will behave differently than Newtonian fluids; although they may appear water when force is applied. as liquids, they have unusual flow properties. Their viscosities change with the applied strain rate. Fluids may not flow into containers as does water (Figure 3b), thus they are considered non-Newtonian in nature. Figure 4. Typical form of a posterior implant abutment: flat top cone, circular in cross section, occlusal convergence taper 6º to 10º.

MODELING CEMENT FLOW: A SIMPLE DEMONSTRATION The closed solid abutment onto which a restoration is subsequently cemented frequently has a simple form, usually circular in cross section, and similar to a flat top cone with an occlusal convergence taper of approximately 6° to 10° (Figure 4). Cement flow can be easily modeled to demonstrate the influence of placement site, amount used, and abutment modifications. To do this, the model system should allow the cement flow to be visualized—in other words, the model system should ideally be transparent. The 2 model structure should conform to the shape of a crown and the implant abutment. One simple model system is to use clear plastic drinking beakers (Figures 5a to 5c). For demonstration purposes,

the cement and flow behavior can be mimicked by using shaving cream. One documented method for loading cement into a crown prior to seating onto an implant abutment is to arbitrarily or gross fill the restoration, and then seat it onto the abutment. The amount loaded is usually far in excess of what is required to ideally fill the cement space provided for the clinician during crown fabrication.13 Often, the crown is further seated by the application of a seating force of approximately 5 kg (the patient bites on a wood stick or cotton wool, holding the restoration as the cement set 3

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The Role of Cements in Dental Implant Success, Part 2 commences).14 To simulate the cement flow a c b when this technique is used, the crown component of the model system is half filled with the shaving foam, then seated onto the beaker, representing the implant abutment. The “crown” has to be forced down to overcome the hydrostatic pressure resistance from the occlusal cement layer that traps between the 2 horizontal surfaces. Liquids (cements prior to setting) are resistant to compression, unlike water. Once the applied force is great enough to overcome this compression, the cement Figures 5a to 5c. (a) The model system: Clear drinking beakers—note total occlusal flows down onto the axial walls of the convergence recorded with a protractor (10º total); (b) beakers designed to “fit” directly to one “abutment,” and the excess cement will another similar to a crown and an abutment; and (c) shaving foam represents the cement. eventually be extruded out of the crown/abutment margin a b under great pressure (Figures 6a and 6b). The pressure may be so great that the vulnerable soft-tissue hemidesmosomal attachment to the implant may be damaged and even detached, which could allow cement to flow well beneath the tissues.5 In this demonstration, note the excess and the blanching of the fingers indicating the amount of force required to seat the “crown.” Large amounts of excess cement are extruded out through the margin of the crown/abutment because the amount of cement loaded into the crown is poorly controlled. Some studies6,7 have suggested that the axial wall of the abutment, near to but not including the occlusal surface itself, should have cement applied to it (Figures 7a to 7c). Figures 6a and 6b. Cement applied in the form of gross application. When this is modeled, as the crown component is seated, Two effects are noted: (a) The occlusal cement is in compression and the applied force, which is provided by seating pressure, resists seating forces, propping the “crown” up. (b) The cement extruded is under great force; this may damage the soft tissue attaching to the works to shear the cement. The result is that the cement is implant surface. The crown is on average 50% filled with cement; only about 3% is actually required, so too much is used and most of it must forced down the abutment axial walls, leaving a void near be extruded out of the system. the occlusal aspect of the abutment.7 Less excess cement extrusion is seen at the margin when compared to the gross (Figures 8a to 8c). The cement appears to flow against the application technique due to less cement material applied direction of the seating force. In effect, it flows “up.” As the in the first instance. However, the incomplete fill of the crown is seated, the cement contacts the axial walls of the cement space makes this process potentially problematic, abutment. The seating force acts to compress the cement with potential reduction of retentive force capabilities. against the axial walls, which are round and tapered. This When the cement is applied to the internal aspect of the compression forces the cement to flow up, until the occlusal crown near to, but not including the crown margin, then table is reached. At this point, the vector of force no longer seated onto the abutment, a different effect is seen15 acts as it lies perpendicular to the seating force. The 4

Continuing Education

The Role of Cements in Dental Implant Success, Part 2 remainder of the cement is forced down toward the margins, with much less extrusion outward than compared with either of the 2 former techniques. The cement fill is also more ideal.

a

b

c

OCCLUSAL VENTING EFFECT AND THE INTERNAL VENTED ABUTMENT The cement flow toward the occlusal surface (Figure 9) is of interest especially where implant restorations are involved. It is considered common practice to close an abutment screw access before the crown is Figures 7a to 7c. Application of cement to the axial wall, near but not on the occlusal cemented; in fact, all of the US dental schools surface, results in cement flow in the same direction as the applied seating force. The occlusal aspect remains unfilled; considerably less excess extrusion is noted when compared advocate this16 (Figure 10). One concept to the gross application. recently developed is to leave the screw a c b access chamber open and not seal it off.17 This provides a reservoir for excess cement to be retained within the crown abutment system, rather than have excess cement be extruded out of the crown margin. This is beneficial from several aspects: 1. Less cement extrusion may reduce the potential for cement induced periimplant disease. 2. Cleanup of a reduced amount of cement is considered easier and faster. 3. There is the ability to improve Figures 8a to 8c. Application of the cement near the inner crown margin results in a flow retentive capabilities as the surface area of pattern that forces cement occlusally initially, then as the model crown seats, the cement the cement contact area with the abutment flows down toward the margin, with small amounts of excess cement. is increased. Using the abutment screw chamber as a reservoir has been studied and proven to reduce the amount of cement extruded out of the crown abutment margin as well as change the retention capabilities of the cement used. One Figure 9. The occlusal surface is partially filled other feature that has also been investigated is modifying as a result of compression forces vectoring the the abutment by placing vent holes internally.17 The internal cement upward against vent abutment (IVA) (Figure 11) has 2 holes, 180° apart the taper of the abutment. approximately 3 mm below the occlusal surface. It has the added advantage of changing the way cement flows to be modified simply, which can also increase the retentive enhance the amount of cement kept within the abutment capabilities of a given cement18 and reduce residual compared to keeping the chamber open (Figures 12a and cement extrusion when compared to closing off the 12b). With such modifications as the IVA, cement flow can abutment, or leaving it open (Tables 1 and 2). 5

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The Role of Cements in Dental Implant Success, Part 2 When considering the IVA, the vent holes should only be placed in materials that are not weakened by the inclusions, and therefore, are not recommended for zirconia or ceramic abutment materials. The number and sites of the vents required is currently being evaluated; presently it is considered adequate to have 2 vents, 180° apart, with Figure 10. Examples of abutments that have one at the mesial aspect of the implant, one closed off abutment screw access holes, as advocated by US dental schools. at the distal, and 3 mm from the occlusal surface. Further study may be required to optimize their position. The screw head should always be protected by a spacer to prevent cement getting into the screwdriver engagement site; currently the recommended material is polytetrafluoroethylene Figure 11. The open screw access chamber tape.19 This material can be sterilized, is easy and the internal vented abutment (IVA). Both provide a space for excess cement to flow to manipulate, is radiopaque, and is less within. The addition of the vent holes in the associated with malodor when retrieved. IVA improve both the amount of cement kept inside the system as well as the retentive Some abutments do not contain a screw tensile strength of the cemented crown. access chamber (eg, Straumann Solid abutment). For these abutments, other a b forms of selectively applying cement have been described.8 This involves loading the crown then seating it onto an analog outside of the mouth to pre-extrude excess cement and coat the inside of the crown with a layer of cement. One technique suggests the use of the laboratory analog that is used to fabricate the crown.20 However, the clinician should be aware that the laboratory analog is actually larger than the abutment that is used for the patient; the laboratory abutment has die spacer built into it. This would likely leave a layer of cement that is inadequate for cementation needs. A more Figures 12a and 12b. Cement flow was improved in the IVA compared to the open screw appropriate technique is to either use a access (OA) abutment, indicating more excess cement would be extruded out from the OA copy abutment of the identical size,8 or an system. appropriately smaller sized abutment than the one used for almost exactly the correct amount of cement lute and can 21 the patient. Making a copy Blu-mousse abutment also be used for multiple abutments for a bridge or (Parkell) as a pre-extrusion device appears to provide conjoined implant restoration.

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Continuing Education

The Role of Cements in Dental Implant Success, Part 2 Table 1. Comparison of the Amount of Cement Retained Internally in Each System; In All Cases the Same Amount of Cement Was Used Initially

0.14 Cement Weight (g)

Simple modeling systems can be used to demonstrate how cement flows, helping with the understanding of how luting cements work as liquids, knowledge of how much is required, application techniques, and how simple modifications to abutment design can be of benefit to the implant restoring dentist.

0.12

E X C E S S

0.10 0.08 0.06 0.04

E X C E S S

E X C E S S

0.02 0 CLOSED

OPEN

INTERNAL VENT

Table 2. Comparison of Abutment Modification and Tensile Retentive Force to Remove Cemented Crown; Closed Was Approximately Half the Value of the IVA

250 Retentive force (N)

SUMMARY

200 150 100 50

X

1.5X

2X

CLOSED

OPEN

IVA

0

7

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The Role of Cements in Dental Implant Success, Part 2 13. Wadhwani C, Hess T, Piñeyro A, Opler R, Chung KH. Cement application techniques in luting implantsupported crowns: a quantitative and qualitative survey. Int J Oral Maxillofac Implants. 2012;27:859-864. 14. Jorgensen KD, Petersen GF. The grain size of zinc phosphate cements. Acta Odontol Scand. 1963;21:255-270. 15. Assif D, Azoulay S, Gorfil C. The degree of zinc phosphate cement coverage of complete crown preparations and its effect on crown retention. J Prosthet Dent. 1992;68:275-278. 16. Tarica DY, Alvarado VM, Truong ST. Survey of United States dental schools on cementation protocols for implant crown restorations. J Prosthet Dent. 2010;103:68-79. 17. Wadhwani C, Piñeyro A, Hess T, Zhang H, Chung KH. Effect of implant abutment modification on the extrusion of excess cement at the crown-abutment margin for cement-retained implant restorations. Int J Oral Maxillofac Implants. 2011;26:1241-1246. 18. Wadhwani C, Hess T, Piñeyro A, Chung KH. Effects of abutment and screw access channel modification on dislodgement of cement-retained implant-supported restorations. Int J Prosthodont. 2013;26:54-56. 19. Moráguez OD, Belser UC. The use of polytetrafluoroethylene tape for the management of screw access channels in implant-supported prostheses. J Prosthet Dent. 2010;103:189-191. 20. Dumbrigue HB, Abanomi AA, Cheng LL. Techniques to minimize excess luting agent in cement-retained implant restorations. J Prosthet Dent. 2002;87:112-114. 21. Wadhwani C, Piñeyro A. Technique for controlling the cement for an implant crown. J Prosthet Dent. 2009;102:57-58.

REFERENCES 1. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: a prospective clinical endoscopic study. J Periodontol. 2009;80:1388-1392. 2. Pauletto N, Lahiffe BJ, Walton JN. Complications associated with excess cement around crowns on osseointegrated implants: a clinical report. Int J Oral Maxillofac Implants. 1999;14:865-868. 3. Gapski R, Neugeboren N, Pomeranz AZ, Reissner MW. Endosseous implant failure influenced by crown cementation: a clinical case report. Int J Oral Maxillofac Implants. 2008;23:943-946. 4. Callan DP, Cobb CM. Excess cement and peri-implant disease. Journal of Implant & Advanced Clinical Dentistry. 2009;1:61-68. 5. Wadhwani CP, Piñeyro AF. Implant cementation: clinical problems and solutions. Dent Today. 2012;31:56-63. 6. Assif D, Rimer Y, Aviv I. The flow of zinc phosphate cement under a full-coverage restoration and its effect on marginal adaptation according to the location of cement application. Quintessence Int. 1987;18:765-774. 7. Cardoso M, Torres MF, Rego MR, Santiago LC. Influence of application site of provisional cement on the marginal adaptation of provisional crowns. J Appl Oral Sci. 2008;16:214-218. 8. Santosa RE, Martin W, Morton D. Effects of a cementing technique in addition to luting agent on the uniaxial retention force of a single-tooth implantsupported restoration: an in vitro study. Int J Oral Maxillofac Implants. 2010;25:1145-1152. 9. Goodacre CJ, Bernal G, Rungcharassaeng K, et al. Clinical complications in fixed prosthodontics. J Prosthet Dent. 2003;90:31-41. 10. Weber HP, Kim DM, Ng MW, Hwang JW, Fiorellini JP. Peri-implant soft-tissue health surrounding cementand screw-retained implant restorations: a multi-center, 3-year prospective study. Clin Oral Implants Res. 2006;17:375-379. 11. Jemt T. Cemented CeraOne and porcelain fused to TiAdapt abutment single-implant crown restorations: a 10-year comparative follow-up study. Clin Implant Dent Relat Res. 2009;11:303-310. 12. Wadhwani C, Rapoport D, La Rosa S, Hess T, Kretschmar S. Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: a clinical report. J Prosthet Dent. 2012;107:151-157.

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The Role of Cements in Dental Implant Success, Part 2 2. During the fabrication of cemented restorations, dental laboratories usually provide some form of relief, often in the form of die spacer, to allow for:

POST EXAMINATION INFORMATION To receive continuing education credit for participation in this educational activity you must complete the program post examination and receive a score of 70% or better.

a. b. c. d.

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3. Relief is commonly built into conventional and CAD/CAM restorations providing a space between the crown/bridge and the abutment of ____ µm. a. b. c. d.

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5 to 10. 10 to 20. 20 to 50. 50 to 70.

4. The average amount of cement required to ideally fill the space between abutment and restoration is in the order of about ____ of the total volume of the restoration. a. b. c. d.

1%. 2%. 3%. 5%.

5. A survey of dentists found very little differences in cement application technique for implant crowns. The survey concluded that there is major consensus regarding the most appropriate cementation technique. a. b. c. d.

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The first statement is true, the second is false. The first statement is false, the second is true. Both statements are true. Both statements are false.

6. Most dental cements are considered non-Newtonian liquids. Although they may appear as liquids they have unusual flow properties.

POST EXAMINATION QUESTIONS

a. b. c. d.

1. A recent survey of dentists revealed a large difference in cement application techniques for implant restorations. Most dentists applied cement on the internal surface with a brush. a. b. c. d.

Rotation of the restoration. Space for cement. Air space so the model does not get damaged. Easier alignment.

The first statement is true, the second is false. The first statement is false, the second is true. 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. Both statements are true. Both statements are false.

7. Water as a liquid is considered to have Newtonian properties because: a. When a force is applied to water, its viscosity changes.

9

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The Role of Cements in Dental Implant Success, Part 2 c. Less cement is extruded out through the abutment crown margin. d. All of the above.

b. Water follows Newton’s laws and flows into the vessel containing it and takes up the shape. c. When a force is applied to water, its viscosity remains unchanged. d. Both b and c.

13. Internal venting is only useful with metal abutments that are not weakened by the inclusions. Internal venting is not recommended for zirconia or ceramic abutments.

8. How much force is usually applied to seating of a cemented restoration when a patient bites on a wood stick or cotton wool? a. b. c. d.

a. b. c. d.

0.5 kg. 5.0 kg. 50 kg. 500 kg.

14. For internal vent abutments the following is/are considered adequate:

9. Leaving the screw access channel open for a cemented implant abutment:

a. b. c. d.

a. Provides a hole that must be sealed. b. Provides a potential reservoir for cement to be kept within the abutment. c. Should not be done. d. Increases the chance of screw loosening.

Two vents. Vents 180º apart. Vents 3 mm from the occlusal surface. All of the above.

15. For abutments that have no screw access channel, a useful means of controlling the amount of cement used is:

10. For a cement-retained implant-supported restoration, when a definite amount of cement is used studies show:

a. Paint a layer of cement on the inside of the crown— studies have shown this is a predictable way to apply the ideal amount required. b. Use the laboratory abutment to pre-extrude cement— it is the same size as the actual abutment for the crown. c. Use a copy abutment that is appropriately smaller in size than the actual abutment to pre-extrude cement prior to seating the restoration. d. There are no such abutments—the solid abutment does not exist.

a. The more cement that stays inside the system, proportionally more will be extruded outside of the margin. b. The more cement that stays inside the system, proportionally less will be extruded out of the system. c. All cement always stays inside the abutment. d. All cement always is extruded out of the system. 11. Cements prior to setting are resistant to compression. In this regard, cements are the same as Newtonian fluids, which are also resistant to compression. a. b. c. d.

The first statement is true, the second is false. The first statement is false, the second is true. Both statements are true. Both statements are false.

16. Polytetrafluoroethylene tape is now being used as a spacer material on top of the screw head to prevent cement getting into the screwdriver engagement site because it is:

The first statement is true, the second is false. The first statement is false, the second is true. Both statements are true. Both statements are false.

a. b. c. d.

12. Abutment modifications can change the way cement flows, which can be of benefit for the following reason(s): a. Improves retention of the restoration. b. More cement can be retained within the abutment.

10

Easy to manipulate. Radiopaque. Can be sterilized. All of the above.

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Illustrations and photographs were clear and relevant. Written presentation was informative and concise. Approved PACE Program Provider FAGD/MAGD Credit Approval does not imply acceptance by a state or provincial board of dentistry or AGD endorsement. June 1, 2012 to May 31, 2015 AGD PACE approval number: 309062

Dentistry Today, Inc, is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in indentifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Concerns or complaints about a CE provider may be directed to the provider or to ADA CERP at ada.org/goto/cerp.

How much time did you spend reading the activity and completing the test? What aspect of this course was most helpful and why? What topics interest you for future Dentistry Today CE courses? 11

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