Foundations in Posts, Cores and Adhesives

By Partovi, Mahtab

A Peer-Reviewed Publication Educational Objectives

After completion of this course, the reader will be able to do the following:

1. Understand the role of adhesive bonding agents in conjunction with post placements and core build-ups

2. List the guidelines established to assess the necessity of posts based on the number of walls of remaining tooth structure

3. Understand the considerations in post materials and design

4. Understand the varying properties of core materials

Introduction

In recent years, more patients have been receiving endodontic treatment with an approximately 13% increase in these treatments between 1990 and 19M9.1 Following successful endodontic therapy, long-term success is directly correlated to the restoration provided.’1 Restorations are only as good as the toundations they are built on. Continued advancements in post, core and adhesive technologies enable the clinician to adopt new materials and techniques that offer improvements over traditional techniques, with the objective of increasing the longevity and success of final restorations. To achieve these objectives, careful consideration must be given to a number of factors related to the overall restorative design, post and core if required, and to adhesives.

Posts

Before the advent of bonding and bondable materials m dentistry, if there was insufficient coronal tooth structure to provide retention for a core and/or final restoration, a post was a necessity.3 With current adhesive technology and strong composite materials, this is no longer the case, and determinants include remaining tooth structure and the material chosen to build up or restore the tooth. Peroz et al. in 2005 developed guidelines from an in vitro study on the assessment of post requirement. These guidelines were based on the number of walls of remaining tooth structure. It was found that if at least two or three cavity walls remained that a post was not necessarily needed, and in the case of anterior teeth with proximal cavities, they would not benefit from receiving posts or crown restorations (for strength). If only one cavity wall remained, it was determined that a post would be required and that the choice of core material would have little or no effect on fracture resistance (Table \).4 With respect to Class III cavities in endodontically treated anterior teeth, Heydecke et al, also found that there was no advantage to cementing a post and that less catastrophic failures were found in teeth that did not receive endodontic posts.5

Crown Lengthening/Ferrule Effect

A ferrule is delined as a arcumterential area of axial dentin superior to the preparation bevel. A number of in vitro studies have been conducted on ferrule lengths, variously using preparations with pre-fabricated posts and composite cores, cast posts and cores, and fiber posts and composite cores. Isidor et al. investigated crowned preparations with prefabricated titanium posts and composite resin cores, with ferrule lengths of Omm, 1.25mm and 2.5mm; increasing the terrule length was found to increase fracture resistance.’1 A separate study assessing ferrule length with cast posts and cores found that a 2mm ferrule length offered more fracture resistance than a non-uniform ferrule varying from 0.5mm to 2mm or no ferrule.7 A third study compared ferrule lengths of Imm, 1.5mm and 2mm in preparations restored with four different post systems (glass fiber, glass fiber reintorced with zirconia, zirconia, and quartz fiber) followed by a composite core and cast crown. This study found that while there were differences in the response of different dowel preparations to fracture thresholds with ferrule increases, fracture thresholds for all four types of dowels were greater if the ferrule length was 2mm rather than 1 .Omm or 1.5mm.8 Earlier studies also suggest using a ferrule of at least 1.5mm and up to 2.5mm.9,10 Increasing ferrule length increases fracture resistance.11 If the remaining exposed tooth structure does not allow adequate ferrule preparation, results from in vitro testing have suggested that surgical crown lengthening should be considered to enable ferrule preparation and that this will result in a reduction of static load failure.12

Table 1. Determination of Post Requirement

Post Materials

The ideal post material would he biocompatible, corrosionresistant” and radiopaque: it would be able to be bonded, mimic the biomechanical properties of dentin,14 involve a onestep procedure and be inexpensive. Available post materials and options include indirect custom cast metallic posts/cores and direct prefabricated metallic posts or posts/cores as well as pre- fabricated fiber posts and reinforced fiber posts. None of these meets every requirement of an ideal post material.

Cast cores require two patient appointments. They are cast to the shape of the prepared canal post space and cemented into place. Prefabricated titanium alloy and stainless steel posts are available – beyond material selection, individual prefabricated posts are selected based upon the required shape and length, and are cemented in one visit; stainless steel posts have been shown to corrode. Non- threaded prefabricated posts are preferred to threaded prefabricated posts these can result in internal stresses and potentially root fracture as a result of the threading action during placement.1″ More recently, fiber and reinforced fiber posts have become available. These are available in a variety of shapes and lengths (parallel-sided, or parallel-sided with an apical taper, or tapered), are non-corrosive and can be bonded to dentin.

A significant number of in vitro and retrospective studies have been conducted on the use of various post materials. A recent in vitro study comparing teeth with prefabricated stainless steel posts and fiber posts found that a significantly lower load was required for failure with stainless steel posts due to the modulus of elasticity being significantly different lrom that of dentin.’” The modulus of elasticity measures rigidity; if two materials are adjacent to one another, the material that is more rigid will have a tendency to transfer functional stress to the other material,17 causing it to fail first (Table 2). As an example, a material such as titanium, with a higher modulus of elasticity, would be more rigid and transfer stress to dcntin.

Table 2. Modulus of Elasticity

Cormier et al. compared a number of fiber posts with conventional cast posts and concluded that the fiber posts resulted in fewer irretrievable fractures ot posts and roots.18 In addition, teeth with stainless steel posts exhibited lower failure load in a separate study, as post diameter increased for stainless steel posts but not for fiber posts.19 In vitro studies of tiber posts have shown more variability in fracture resistance; however, fiber posts have been found in testing to result in more retrievable/repairable fractures compared to other posts.20,21,22 They can also be removed trom roots more easily.23 A further study found root fractures occurring with cast posts but not fiber posts, 4 and another lound that tapered cast posts resulted in more failures than serrated pre- tabricated posts.-1 Yet another found a higher load resistance with cast posts than with fiber-reinforced composite posts and the lowest load resistance with ceramic posts, but again found more retrievable fractures and failures with the fiber posts.26 Another found the lowest failure rate with ceramic posts.27

Clearly there are a number of studies with conflicting results. Cast posts require extra visits and are more expensive, and generally seem to offer little benefit over prefabricated posts. Fiber posts offer the option of using adhesive technology to bond them to teeth, have the closest modulus of elasticity to teeth and are more easily retrieved if they fracture.

Post Design and Length

Tapered-post failure has been found to be 15% more common than parallel-sided post failure.-”Tapered cemented posts are less retentive, and in vitro research in the 1970′s indicated that a parallel shape was more retentive than a tapered shape.-1′ Tapered metal posts also sometimes behave like “wedges,” predisposing the root to splitting.30

Parallel posts do not mimic the shape of the root, therefore either a shorter post is used to avoid removing dentin more apical 1 y in the canal or more dentin is removed, weakening the remaining tooth structure. In addition, use of a parallel post results in a gap at the root-crown interface that must be filled and sealed. Cemented parallel-sided posts with serrations are more retentive than smooth ones.31

A very short root length and poor crown-to-root ratio are unfavorable for restoration. Typically, the length of a post should extend two-thirds down the length of the root. Crown-to-root ratio should be at least 1:1.32-33 However, the use of bonded fiber posts has enabled restoration with retention of shorter posts than was previously achievable. One study comparing fracture resistance with varying post and ferrule lengths found that increasing post length did not decrease fracture resistance (post lengths assessed were 5mm, 7.5mm und 10mm).34

Post Fixation

Post fixation can be achieved using luting cements or adhesive bonding technology, depending on the post used. Cast posts are cemented into the root canal, commonly with zinc phosphate cements. Since the introduction of pre-fabricated posts and advanced adhesive technology, it is now possible to bond fiber-reinforced composite posts to the dentin. One study comparing the use of zinc phosphate cement or composite bonding on pre-fabricated parallel-sided posts found significantly less root fracture with use of bonding,” and a separate study found that bonding resulted in significantly higher tensile strengths.36 Core Materials

Historically, cast alloys (post and core) and direct core materials have been used for core build-ups. Direct core materials consist of amalgam, composite resin and glass ionomers (GI). The GI category can be further broken down into resin-modified glass ionomers (RMGI), metal-modified glass ionomers (MMGI), compomers and ceramets.’ Ceramets have metal particles sintered to the glass particles, Metal-modified (Hs have metal powders added to the glass ionomer particles. The ideal core material should have the following characteristics: biocompatibility, a coefficient of thermal expansion similar to dentin, appropriate compressional and flexural strength, ability to bond to the tooth and luting agent, cariostatic capability, compatibility with temporary cements, dimensional stability and ability to add-on additional material as well as easy mixing and placing, It should be esthetic, non-allergic and radiopaque and have a short setting time, a long shelf life and low thermal diifusivity.38 The ideal core material does not exist (Table 3).

Table 3: Comparison of Core Material Properties38

Traditionally, the ability of glass ionomers to bond to enamel and dcntin and to release fluoride was the reason clinicians favored these over amalgam. Problems associated with their use included interior tensile strength and the role of water in the setting reaction. Recently, conventional glass ionomers have been improved by a higher powder-to-liquid ratio, thereby requiring less water. Glass particle sizes are also smaller, resulting in higher viscosity.

Figure 1. Composite core build-up

Direct resin composite materials allow the clinician to perform core build-up and crown preparation procedures in one visit (Figure 1). Their case of use and rapid curing have resulted in a dramatic growth in their use.” A study performed in the United States showed that by 1995 48% of clinicians were using composites for direct core build-ups and 25% were using amalgam. One-visit core build-ups seemed tobe the number-one reason composites were being used more frequently,40 and they offered bond strength to dentin when used with appropriate adhesive agents. When selecting a composite resin tor core build-ups, considerations include the polymerization depth, curing, handling (stickiness), mixing, viscosity (high viscosity resins allow for packing and condensing), insertion technique and ability to release fluoride. Composite resins have excellent compressive strength similar to amalgam, and superior tensile and flexural strength. Purely from the point of view of strength, it has been found that the strength of the core material is of greater importance than post material or size.41 It is important to understand that the dimensional stability of both resin composite and glass ionomer core materials is affected by polymerization shrinkage, thermal contraction and expansion, and interaction with an aqueous environment. The interaction between resin composites and water causes two opposing phenomena. In some resin composites, water will leach out uncreated monomers and other species.42 This change contributes to shrinkage, loss in weight and reduction of mechanical properties. Conversely, water sorption leads to a swelling of the material and an increase in weight43,44,45,46

It has been found that teeth restored with core build-ups are best prepared for crowns within one month of placement, especially if the core build-up is subjected to direct occlusal loading. The consequences of delaying crown preparation with core build-ups of these material could include bulk fracture.47

Adhesive systems

Advances in composite materials have also led to advancements in dentin bonding technology. It has been shown that use of dentin bonding agents can increase the fracture resistance of endodontically-treated teeth and help prevent fracture at the core build-up to dentin junction.4″ Dentin adhesive systems are available as one-, two- and three-step procedures depending on how etching, priming and bonding are incorporated into the formulation. The newest generation of self-etch adhesive products combines these into one step. By eliminating separate acid etching and rinsing procedures, the risk of contamination and poor bonding between the tooth and the composite is reduced. Single-step products have increased in popularity and studies have shown that both overwetting and overdrying the dentin can negatively impact bond strength.49,50,51 Comparison studies between different adhesive systems for the reconstruction of root canal-treated prcmolars with MOD cavities have shown that these dentin-bonding systems stabilize teeth particularly well and have shown that their fracture resistance was comparable to that of intact teeth.52

Single-step adhesive products function by having an acidic adhesive dissolve the smear layer, which is then incorporated into the mixture. This then demmeralizes the superficial dentin and hardens after curing light exposure. The rationale is to reduce discrepancies between the depth of demineralization and the depth of resin infiltration, since both processes occur simultaneously.51 Bond strengths of these products have been found to vary. A study performed by the University of North Carolina’s Department of Operative Dentistry evaluated the microtensile bond strength (mTBS) of dentin, and failure mode pattern of five one-step self-etching adhesives, on 25 freshly extracted bovine teeth (Table 4). An in vitro study at a separate site examined bonding agents on human enamel and dentin that had been stored for 24 hours in water and thermocycled (Table 5).54

Table 4. Microtensile bond strength

Table 5. Bonding agents on human enamel and dentin

In determining which adhesive system to use, it is important to ensure the system is compatible with the restorative material being used. Some believe that bonding agents recommended by the manufacturer oi the core material should be used, because some sell- cured composite core materials are incompatible with some light- cured bonding agents.1′ It is advisable, il there is uncertainty about compatibility, to contact the manufacturer of the composite core material selected and check on its compatibility with the adhesive system you are proposing to use.

Summary

With an abundance of posts, cores and adhesive materials, selection is based on a number of factors that include ease of use, location, root canal configurations, strength, biocompatibility, retentive ability and personal preference. Recent developments have given the clinician more advanced materials that enable placement of materials that can be bonded and more closely approach the biomechanical properties of dentin.

Glossary of Terms

Compressive strength: the capacity of a material to withstand axially directed pushing forces. When the limit of compressivc strength is reached, materials are crushed.

Elastic modulus: the relative stillness of the material within the elastic range.

Tensile strength: the resistance of a material to a force tending to tear it apart determines the maximum tension the material can withstand without tearing.

Flexural strength: the ability of a material to withstand bending beture reaching the breaking point, usually measured in psi.

Flexural modulus: a measurement that determines how much a sample will bend when a given load is applied. In general, more flexible materials will have a lower flexural modulus, and stilfer materials a higher one.

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Questions

1. Between 1990 and 1999, the increase in the number of endodontic treatments was:

a. Approximately S%

b. Approximately ID’%

c. Approximately 1.1%

d. Approximately 17%

2. Early core materials relied mainly on what type of retention?

a. Mechanical

b. Chemical

c. Thermal

d. Covalent bonding

3. Based on Peroz’s guidelines for (he indications of post s based un the number oi walls of a remaining tooth, which oi the following is true?

a. With one remaining cavity wall, a post is not necessary

b. With four remaining cavity walls, a post is necessary

c. With no remaining cavity walls, a post is necessary to provide retention for the core material

d. With two or three remaining cavity walls, a post is never needed

4. In endodonlically treated teeth with Class 111 cavities, Hcydccke et al. found that:

a. There was no advantage to cementing a post

b. Less catastrophic failures were found in teeth that did not receive posts

c. It was advantageous to place a cast post and core

d. Both a and b

5. With respect to ferrules, il has been found that a (lmin ferrule length is associated wilh less fracture resistance than n 2mm ferrule length.

a. True

b. False

c. Historically, which of the following have been used for core build-ups?

a. Dental amalgam

b. Resin composites

c. Glass ionomers

d. All of the above

7. Based on a 1995 study by Christensen in the United States, what percentage of practitioners were using composites for direct core build-ups?

a- 26%

b. 32%

c. 87%

d 4fi%

8. Based on the results shown in Table 2, which material has the least eompressive strength?

a. Glass ionomer

b. Composite

c. Amalgam

d. Metal-modified glass ionomers

9. Properties to look for in composite resins include:

a. Polymerization depth

b, Curing

c. Viscosity (slumping)

d Mlnf the above

10. Polymerization contraction affects the dimensional stability of resin composite materials.

a. True

b. False

11. It has been suggested that if there is insufficient exposed Ioolh structure to create a ferrule: a. A ferrule is not needed

b. Surgical crown lengthening should be considered

c. A longer post will serve as an alternative to having a ferrule

d. None of the above

12._____is a measurement that determines him much a sample will hcnd when a given load is applied. In general, more flexible materials will have a lower flexural modulus, and stiller materials a higher one.

a. Tensile strength

b. Flexural modulus

c. Elastic modulus

d. Compressive strength

13. The interaction between resin composites and water causes two opposing phenomena. In some resin composites, water will leach out unereated monomers and other species,

a. The first statement is true; the second statement is true.

b. The first statement is false: the second statement is false.

c. The first statement is true; the second statement is false.

d. The first statement is false; the second statement is true.

14. Teeth restored with core build-ups are best prepared fur crowns within _____ mimthfs) of placement, especially if the core huild-up is subjected to direct occlusal loading.

a. Three

b. Two

c. One

d. Four

15. Non-threaded prc-fabricatcd posts are preferred over threaded pre-fabricated posts, as:

a. Placement of threaded posts can result in internal stresses

b. Threaded posts are more expensive

c. Non-threaded posts provide a more esthetic result

d. All of the above

16. The new generation ol adhesive products function by having an acidic adhesive dissolve the smear layer, which is then _____into the mixture; this then ____ the superficial dcntin, then ____ after curing.

a. Incorporated, demineralizes, hardens

b. Extracted, demineralizes, softens

c. Incorporated, remineralizes. hardens

d. Extracted, remineralizes, softens

17. Based on a study pertormed by the University of North Carolina, the two products with the highest mierotcnsile bond strength (mTBS) in dcntin were:

a. Prompt L-Popandi-Bond

b. Xeno IV and Brush & Bund

c. XenoIVandClearfiISEBond

d. i-BondandBrush&Bond

18. Since both processes occur simultaneously, the reduction of discrepancies hciwccn the depth ul dcmincrali/aiion and thedcinincrali/aiion nt .superficial dentin are the rationale behind the self-etching primer adhesixes.

a. True

b. False

19. Overwriting and overdrying the dentin can result in:

a. Decreased bond strength

b. Increased bond strength

c. No effect on bond strength

d. Either increased or decreased bond strength

20. The newest generation ol’adhesives contains:

a. Primer and bonding agent

b. Primer and etch

c. Bonding agent and etch

d. Primer, bonding agent and etch

21. With ihr use of iht- newest adhesive systems, onr IKI longer needs the separate slcp of usinf; phosphoric acid to etch the denlin.

a. True

b. False

22. Some believe that bunding agents iruni the manufacturer of the core material should be used because:

a. Some self-cured composite core materials are incompatible with some light-cured bonding agents

b. Some light-cured composite core materials are incompatible with some self-cure bonding agents

c, Some dual-cured composite materials are incompatible with dual- cure bonding agents

d. Some light-cure composite materials are incompatible with some light-cured bonding agents

23. Compared Io other posts, fiber posts:

a. Are the least resistant to fracture

b. Are more easily retrieved if they fracture

c. Are impossible to see on a radiograph

d. Alloftheabove

24. Several bonding agents release nitrites.

a. True

b. False

25. Smaller glass-size particles in glass ionomer lead to:

a. A higher viscosity

b. A lower viscosity

c. An increase in toughness

d. A decrease in toughness

26. Which of the following post designs is least retentive?

a. Cementedparallel-sidedwithserrations

b. Cemented parallel-sided smooth

c. Tapered cemented

d, Noneoftheabove

27. Typically, I lie length of a post should extend down the length of the root:

a. Two-thirds

b, One-half

c. Three-quarters

d To the apex

28. Ceramets contain:

a. Ground limestone

b. Metal particles sintered Io glass particles

c. Metal particles sintered to sand

d. None of the above

29. According to this course, restorations are only as good as the foundations they are built on.

a True

b. False

30. The appeal of composite resins fteems to be warranted due to their:

a. Esthetics

b. Single visit placement

c. Bond strengths to dentin when used with appropriate bonding agents

d. All of the above

References

1 American Dental Association. The 1999 Survey of Dental Services Rendered. 2002.

2 Morgano SM, Rodrigues AH, Sabrosa CE. Restoration of endodontically treated teeth. Dent Clin North Am. 2004;48(2):vi. 397- 416.

3 Peroz I, Biankenstein F, Lange K P1 Nauinann M. Restoring endodontically treated teeth with posts and cores A review. Quintessence Int. 2005;36:737 746.

4 Ibid.

5 Heydecke G, Butz F1 Strub JR. Fracture strength and survival rate of endodontically treated maxillary incisors with approximal cavities after restoration with different post and core systems: an in vitro study. JDent. 2001;29(6):427 433.

6 Isidor F. Brondurn K, Ravnholt G. The influence ot post length and crown Ierrule length on the resistance to cyclic loading ol bovine teeth with prefabricated titanium posts. Int J Prosthodont.l999;12:78 82.

7 Tan PL, Aquilino SA. Grattun DC!, Stanford CM. Tan SC, Johnson WT, Dawson D. In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations. J Prosthet Dent. 2005;93(4):331 336.

8 Akkayan B. An in vitro study evaluating the effect of ferrule length on fracture resistance of endodontically treated teeth restored with fiberreinforced ami zirconia dowel systems. J Prosthet Dent. 2004;92(2): 155 162.

9 Sorensen JA, Engelman MJ. Ferrule design and fracture resistance of t’ndodontically treated teeth. J Prosthet Dent. 1990;63:529-536.

10 Assil’D. Bitenski A, PiIo R, Oren E. Effect of post design on resistance to fracture of” endodontically treated leeth with complete crowns. J Prosthet Dent. 1993;69:36-40.

11 Isidor F, Brondum K, Ravnholt G. The influence ol post length and crown ferrule length on the resistance to cyclic loading of bovine teeth with prefabricated titanium posts. IntJProsthodont. 1999;28:78-82.

12 Gegauff AG. Effect ol crown lengthening and Ierrule placement on static load failure of cemented cast post-cores and crowns. J Prosthet Dent.2000;84:169-179.

13 Cohen S, Bums CF. Pathways of the Pulp. Nth Kd. St. Louis; Mosby Yearbook. 2002:777.

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17 Turbjorner A, Karlsson S1 Syverud M, Hensten-Pettersen A. Carbon fiber reinforced root canal posts: mechanical and cytotoxic properties. Eur J Oral Sci. 1996:104: 605-611.

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20 Cormier CJ, Bums DR. Moon P. In vitro comparison oi the lracture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration. J Prosthodont. 2001;10:26 36.

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22 Sirimai S, Riis DN, Morgano SM. An in vitro study of the fracture resistance and the incidence of vertical root fracture ot pulpless teeth restored with six post-and-core systems. J Prosthet Dent. 1449;Sl(3);2b2 269.

23 de Rijk WCi. Removal of fiber posts from endodontically treated teeth. Am J Dent. 2000;13:19B 21B.

24 Ferrari M, Vichi A1 Garcia-Godoy F. Clinical evaluation of fiberreinlbrced epoxy resin posts and cast post and cores. Am J Dent. 2000;13:15B 18B.

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31 Ingle JI. Endodontics. BC Decker. 2002:418 114.

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34 Isidor F. Brondum K, Ravnholt G. The influence oi post length and crown ferrule length on the resistance to cyclic loading of bovine teeth with prefabricated titanium posts. Int J Prosthodont. 1994;12:78 82.

35 Mendoza DB, Eakle WS, Kahl EA. Ho R. Root reinforcement with a resin-bonded prelonnfd post. J Prosthet Dent. I447;78:10 14. 36 Utter JD, Wring BH, Miller BH. The effect of cementing procedures on retention of prefabricated metal posts. J Am Dent Assoc. 1997;128:1123 1127.

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38 Craig RG. Direct esthetic restorative materials. In Restorative Dental Materials, 10th ed. St Louis: Mosby, 1447:244 280.

39 Chutinan S, Platt JA. Cochran MA, Moore BK. Volumetric dimensional change of six direct core materials. Dent Mater. 2004; 20(4):345 351.

40 Christensen CiJ, Christensen RP. Product use survey l(‘l>5. CRA newsletter 1995:19:3.

41 DarcndclY. Stress Distribution of Post-Core Applications in Maxillary Central Incisors. J Biomater App. 2004; 18(3):163 177.

42 Braden M, Pearson GJ. Analysis of”aqueous extract from lilled resins. J Dent. 1981;9:141-143.

43 Fan PL, Edahl A1 Leung RG, Stanford JW. Alternative interpretations of water sorptiun values of composite resins. J Dent Res.ll)85;64: 7S SU.

44 Hirasawa T, Hiranu S, Hirabayshi S, Harishima I1 Aizawa M. Initial dimensional changes of composite in wet and dry conditions. J Dent Res. I98.1;62:2R 31.

45 Oysaed H, Ruler IE. Water sorption and filler characteristics of composites for use in posterior teeth. J Dent Res. 1986;G5:1315 1318.

4b Momoi Y1 McCabe JK Hygroscopic expansion of resin based composites during (j months of water storage. Br Dent J. 1994:176: 91 96.

47 Combe EC, Shaglouf AM, Watts DC, Wilson NH. Mechanical properties of direct core build-up materials. Dent Mater. 1999;15(3):158 165.

48 Aykent F, Kalkan M, Yucel MT, Ozyesil ACi. Effect of dentin bonding and ferrule preparation on the fracture strength of crowned teeth restored with dowels and amalgam cores. J I’rosthet Dent. 2006;95(4):297 301.

49 Kanca J. Improved bond strength through acid etching of dentm and bonding to wet dentin surfaces. J Am Dent Assoc. 1492; 123:35 43.

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54 Reference on file.

55 Craig RCi, C,V. Restorative Denial Materials, Moaby 2004.

Written by Mahtab Partovi, DDS

Author Profile

Mahtab Partovi, DDS

Dr. Partovi received her dental degree from New York University College of Dentistry. Dr. Partovi is presently managing two clinical orthodontic studies. She has been accepted as a resident at Jacksonville University. School of Orthodontics, and is a member of the American Dental Association and the California Dental Association.

Disclaimer

The author of this course has no commercial ties with the sponsors or the providers of the unrestricted educational grant for this course.

Copyright PennWell Publishing Company Jul 2007

(c) 2007 Dental Economics. Provided by ProQuest Information and Learning. All rights Reserved.