Temporary CementRemnants as an Adhesion

Inhibiting Factor in theInterface Between Resin

Cements and Bovine Dentin

Elisete Kazumi Watanabe, DDS'

Atsushi Yamashita, DOS, PhD''

Makoto Imai, DDS, PhD'

Hirofumi Yatani, DDS, PhD''

Kazuomi Suzuki, BE, DDSc"

This study investigated the effect of temporary cement remnants on freshlyprepared dentin in the adhesion of resin cements. The tensiie bond strengthof three types of resin cements to dentin were measured in a control groupand after the application of (wo types of temporary cement. Scanningelectron microscopy and energy dispersive x-ray spectroscopy were used toconfirm the presence of temporary cement remnants. Overall results suggestthai temporary cement application significantly decreased the tensile bondstrength in all adhesive systems (P= 0.0001, analysis of variance). Scanningelectron micrographs presented granular elements on the dentin surfacestreated with temporary cement even after preconditioning. Energy dispersivex-ray spectroscopy results showed the presence of zinc peaks in thespecimens that was not present in the control, Int i Prosthodont1997;IO:440-A52.

Adhesive materials are often used in restorativedentistry, and the adhesive is an important fac-

tor in the prognosis of a restoration or prosthetictreatment,' Recently, research on new surface con-ditioners and bonding agents has been conducted,and a great number of quality adhesive resin ce-ments have been produced and released. How-ever, the experimental data derived from studies ofthese products cannot always be used in clinicalsituations. For example, adhesive strength is influ-enced by environmental conditions such as thetype and age of the teeth, type of cavity, dryness,or cleanliness.

'Doctoral student. Department of Fixed Prosthodontici.''Professor, Department of Fixed Prosthodontics.'Assistant Professor, Department of Fixed Prosthodontics.''Associate Professor, Department of Fixed Prosthodontics."Professor, Department of Dental Materials.

Reprint requests: Dr Elisete Kazunii Walanabe, Department ofFixed Proslhodontics, Okayama University Dental School, 2-5-1Shikala-cho, Okayama 700, Japan,

The bond strength of adhesive resin cements todentin surfaces after temporary cement (TC) appli-cation, the type of TC used, and materials remain-ing on the tooth surface are a matter of concern.Previous studies have indicated a vertical raising ofthe crown and infiltration of TC components intodeep zones of the abutment tooth when TC wasused before final cementation,^ Microleakage ofresin-luted restorations after pretreatment with TC^indicated a hypothetical inhibitory action of TCson adhesion. While some reports concluded thatre-etching is sufficient to provide the expectedbond strength,"t other reports found that TC in-creased the contact angles of distilled water andthat etching did not remove all traces of cement,therefore only slightly improving wettability,^

The purposes of this study were (1¡ to analyzetooth surface structure after TC application and re-moval of the remaining TC by both physical andchemical methods, and to clarify the mechanism ofthe adhesion inhibiting elements; and (2) to investi-gate a method for the maintenance or improve-

The International lournal of Prosthodontiti 440 • to . Numbers, 1997

WatanabE et al

ment of the adhesive's original qualities. Scanningelectron microscopy (SEM) and energy dispersivex-ray spectrosccpy lEDS), were used to assess theefficacy of TC elimination. From the SEM images ofthe interfacial layer, the presence or absence of thehybrid layer was interpreted as explained byNakabayashi*" and Nakabayashi et al"'^ to evaluatethe influence of TCs on the impregnation of resincements into the dentin.

Materials and Methods

Surface Preparation

The radicular portion of bovine mandibular incisors,frozen immediately after extraction, was cut, thepulp was removed, and the vestibular area of thecoronal portion was ground by a diamond disk toexpose the dentin. The obtained area was polishedflat to 600-grit using a silicon carbide waterproofabrasive paper under running water. An acr^'lic resinplate (Unifast II, GC) measuring 1 0 X 5 x 2 mmwas then cemented to the dentin surface with HY-Bond Temporary Cement (Shoful for the HB groupand with Freegenol Temporary Pack (GO for the FGgroup. Both were mixed according to the manufac-turer's instructions. After 10 minutes, the specimenswere immersed in distilled water at 37°C for 1week. The acrylic resin plates were then removed,and the temporary cement remaining on the dentalsurface was removed using an excavator. In the con-trol group (C), exposed dentin surfaces were pre-pared and stored in the same manner, but speci-mens received no temporary cement treatment.

Tensile Bond Strength Measurement

A 4-mm-diameter stainless steel rod (SUS-304) wasairborne particle abraded using 50 pm aluminumoxide and cemented on the dentin surfaces of the C,HB, and FG groups with three types of resin cement;(1) Panavia 21 (Kuraray]; (2) Super Bond C&B {SunMedicall; and (3) Bistite (Tokuyama), according tothe manufacturers' instructions. The materials and re-spective abbreviations are shown in Table 1. Thespecimens were placed in water at 37°C for 24hours. The Autograph testing machine (DCS-2000,Shimazul, running at a cross-head speed of 2 mmper minute, was used to obtain the tensile bondstrength measurements of eight specimens in eachgroup. Means and standard deviations were com-piled, and a two-way factorial analysis of variance(ANOVAl was used to analyze the effect of the tem-porary cement application and adhesive resin ce-ment difference on tensile bond strengths.

an Adhesion-Inhibiting Factor

Table 1 Materials and Abbreviations Used

'^a'erial Abbreviation

Adhesive resin cementsPanauia 21 P2iSuper Bond CSB SBBistite BT

Temporary CementstSY-Bona Temporary Cement HBFreegenol Temporary Pack FG

Control c

SEM Observations of the Adhesive Interface

The same dentin treatment for the tensile bondstrength samples was carried out for the C, HB, andFG groups, and an acrylic resin plate {Unifast II)measuring 1 0 x 5 X 2 mm was cemented to thesurfaces with P21, SB, and BT, according to themanufacturers' instructions. Samples were then em-bedded in slow-polymerizing epoxy resin (Epofix,Struers) and sectioned along the long axis of thetooth using a diamond cutter (Isomet, Buehler). Thesurface obtained was highly polished using siliconcarbide paper (< î l .000, Nihon Kenshi) and treatedwith 37% HjPO^ for 7 seconds and with sodiumhypochlorlte solution (NeoCleaner, Neo Pharma-ceuticl for 10 minutes to remove the organic com-pound on the interfacial layer.

SEM Observations of the Preconditioned Surfacesof tbe Dentin

The same dentin treatment for the tensile bondstrength samples was carried out for the C, HB, andFG groups. Fach group was then treated with: (1) EDPrimer (P21f for 60 seconds; (2) etching agent (SB)for 10 seconds; Í.3) conditioner {BT) for 10 seconds;and (4) conditioner IBT) for 10 seconds and primer(BT) for 30 seconds. All samples were then washedunder running water for 10 seconds after applicationof the primers (contrary to the manufacturers' in-structions). After drying with an air blower (Three-way syringe WS-9, Morlta), the samples were gold-plated in the ion coater {IB-5, Eiko Engineering) forSEM lDS-720, Topcon) observation.

EDS Analysis of tbe Dentin Surface

The dentin surfaces of the C, HB, and FC groups thatwere observed by the SEM were then carbon coated(Polaron CC7650 Carbon Coater, Fisons Instruments)and analyzed using energy dispersive x-ray spec-troscopy (Voyager, Noran Instruments) for the pres-ence of zinc at an accelerating voltage of 15 keV, amagnification of x 1000, and an acquisition time of300 seconds.

Voiume 10, Number 5, 1997 441 Journal of PrOílhodonlits

Cemeni Remnants .IB an Adhosion-lnliitiiiirB Factor

Fig 1 Tensile bond strength vaiues of adhesive resin ce-ments to dentin, 'PS 0.05; " P < 0.005;'•*P< 0,0001.

Results

Tensile Bond Strength

The mean and standard deviation for the tensilebond strengths obtained are shown in Fig 1.

Two-way factorial analysis of variance (ANOVA)was performed on the tensile bond Strength valuesand revealed that TC application significantly de-creased the tensile bond strength between resin ce-ments and dentin (P = 0,0001), Least mean squareanalysis demonstrated a significant mean differencebetween C-SB and H8-SB (P = 0.0027), C-SB andFG-SB (P = 0,0001 ), C-BT and HB-BT (P = 0,0243),and C-BT and FC-BT (P = 0,0367), These findingsdemonstrate that there was no significant mean dif-ferences in tensile bond strengths between HB andFC, There was no significant mean difference be-tween C-P21 and Hß-P21 (P = 0,7157), C-P21 andFC-P21 (P= 0-3561), or between HB-P21 and FG-P21 (P= 0,5870), HB-SB and FG-SB (P = 0,1779),and HB-BT and FG-BT (P= 0,8628), There was alsoa strong effect regarding adhesive resin cement dif-ference (P = 0,0001) in the tensile bond strengths,and there was no interaction between TC applica-tion and adhesive resin cement difference (P =0,1221), This indicates that tensile bond strengths ofSB were higher than that of P21 and BT for any TC,

SEM Images of the Adhesive Interface

Figure 2 shows the adhesive interface between thedentin and the adhesive resin cements in group C,Resin tags that infiltrated and polymerized in the

dentinal tubules were observed. In the higher mag-nification of this intertubular dentin region, a hy-brid layer about 0,5 (jm thick for P21 and BT, andabout 3 pm thick for SB, indicated by the arrows,was evident.

Figure 3 represents the adhesive border betweendentin treated with HB (eliminated with an excava-tor) and the adhesive resin cements. The resin tagsand hybrid layer seen in Fig 2 were present for SBand BT, but absent for P21,

Figure 4 represents the adhesive border betweendentin treated with FC (eliminated with an excava-tor) and the adhesive resin cements. The imageswere similar to those found in Fig 3.

SEM Images of tbe Dentin Surface

Dentin Surfaces Without Preconditioning. The SFMimages of the dentin surfaces of the C, HB, and FGgroups are shown in Fig 5, A smear layer was ob-served in the C group. In the HB and FG groups, TCresidue was not observed macroscopically after useof an excavator, but excavator scratches, the TCsubstrate, and granules derived from the remainingsubstrate were present in the SEM images. In addi-tion, cement remnants were present as cracks,

Dentin Surfaces With P21 Preconditioning, TheSFM images of the dentin surfaces of the C, HB,and FC groups after ED Primer (P21) treatment for60 seconds are shown in Fig 6, In the controlgroup, the smear layer was eliminated and thetubule positions could be defined. Nevertheless, asubstrate suspected to be a part of the smear layeror a substance resulting from a reaction betweenprimer and dentin was observed. In addition,under low magnification group C presented asmear resulting from silicon carbide polishing overthe whole surface, and under higher magnification,the tubule apertures were poorly defined and inone part dentinal plugs were observed. In the TCgroups, few dentinal tubules were observed andgranular substances different from those observedin SB and BT were present on the dentin surface.These substances were thought to have originatedfrom the TC remnants or residues dissolved by theprimer that then recrystallized or recombined.

Dentin Surfaces With SB Preconditioning. TheSEM images of the dentin surfaces of the C, HB,and FC groups affer etching (SB) treatment for 10seconds are shown in Fig 7, In the C group thesmear layer was eliminated and the dentinaltubules were opened. In the TC groups, althoughthe dentinal tubules could be observed, all the sur-faces presented granular substances thought tooriginate from tbe temporary cement remnants.

Journal of Pros[hodonti( 442 • IÜ, Numbers, 1997

an Adhc5ion-lnliibii¡ng Fa c lor

Fig 2 Scanning electron micrographs ot the interfacial layer between dentin and adhesive resin oements in the control (C) group.Arrows delinéale the hybrid layer. Original magnitication x 2,000 (left) and x 10,000 (right).

O, Number 5, 1997 443 The Iniemalional Journal ûf Prosthodontics

Cement Remriiinls as an Aclliesior-lnhil:iitins Factor WatjnabtM

Fig 3 Scanning electron micrographs of the interfaciai iayer between dentin and adhesive resin cements in the Hy-Bond tempo-rary cement (HB) group. Arrows deiineate the hybrid layer. Original magnification x 2,000 íleñ)atiú x 10,000 ¡right).

loumal cifProsLhodontk 444 •ID, Numbers, 1997

Watanabe el al nis ai ,in Adheíion,lnliibitiiig Factor

Rg 4 Scanning electron micrographs of the intertacial layer between dentin and adhesive resin ce-ments in the Freegenol temporary cement (FG) group. Arrows delineate the hybrid iayer. Originalmagnification x 2.000 (left) and x 10,000 (righf).

VoiumelO, Numbers, 1997 445 The Internalionsi tournai of Prosthodontlcs

Cement Remnanlí ni an Atlliesiun-lnhitiiling Factor Watanabe et al

Fig 5 Scanning electron micrograptis of the dentin surfaces ot the C (top). HB (widöte), and FG (bottom) groups. Original magnifi-cation X 2.000 (len)anä x 10,000 (right).

The Intern a tiOíiaí lournal of Prosthodonlii 446 Volurre 10, Number S, 1997

Watdnabe el ,i[ Cemeni Remnants ,is an Aclhesl,m.|nliiÍ3iting Facloi

Fig 6 Scanning electron micrographs of the dentin surfaces of the C (top). HB (middle), and FG (bottom) groups after ED Primer(P21) treatment, Originai magniticalion x 2,000 (/efl; and x 10,000 (nghi).

Volume 10, Numbers, 1997 447

s an Aclhcsion.lnliihilmg Factor

Fig 7 Scanning electron micrographs ot the dentin surtaces ot the C (top), HB (middle), and FG(bottom) groups after etching agent (SB) treatment. Original magnification x 2,000 (ieft) and x10,000 (rigfit).

alof Proslhodcnlii 448 ; 10, Number 5, 1997

Watanahe el .il Cement Remnanls ai an Adliesroii-lfihiliilin!; Faclor

Fig 8 Scanning electron micrographs of the dentin surfaces ot the C (top), HB (middle), and FG(bottom) groups after conditioner (BT) treatment. Original magnification x 2,000 (left) and x 10,000(right).

Dentin Surfaces With BT Acid Etching. TheSEM images of the dentin surfaces of the C, HB,and FG groups after conditioner {BT) treatment for

10 seconds are shown in Fig 8. In the C group thesmear layer was eliminated and the dentinaltubules were opened. In the TC groups, although

449 The Irtematioral Jojfnal of Prosrhodonlicî

nts as n Adiiraior-lrtiibiiing r.n-

1.4/im

F¡9 9 Scanning electron micrographs of the dentin surfaces of the C (top), HB (middle), and FG (botiom) groups atter conditionerand primer (BT) treatment. Original magnification x 2,000 (left) aod x 10,000 (right).

the dentinal tubules could be observed, all thesurfaces presented granular substances thought tooriginate from the TC remnant,

Dentin Surfaces Wilh BT Etching and PrimerConditioning, The SEM Images of the dentin sur-faces of the C, HB, and FG groups after treatmentwith a conditioner (BT| for 10 seconds and primer(BT) for 30 seconds are shown in Fig 9. The result-

ing images were similar to those in Fig 8, but thegranules appeared to be covered by the primers.

£DS Results

The EDS resulis presented a peak of Zn remainingon the surface after TC elimination with an excava-lor which was not present in the C group {Fig 10),

The International loumal r>i 4 5 0 VolumciO, Number 5, 1997

Discussion

Temporary restoration and cementation on dentinsurfaces are important procedures for restorationprosthesis retention to avoid pain and infectionand to restore function and esthetics. However, ifthe materials used at the preliminary stage remainon the dental surface, they may be adhesive-inhibiting factors during final cementation.

After temporary cement removal using an exca-vator the dentin surface remained covered on allsurfaces by cracked cement substrate. HY-BondTemporary Cement is composed of zinc oxide, anaqueous solution of polyacrylic acid, and HY com-pound (tannin, ZnF,, SrF,, and ZnO mixture! andpresents a high level of h ardness and an adhesivestrength that may limit the mechanical eliminationusing an excavator. Consequently, these propertiesmay lead to insufficient temporary cement re-moval. This was shown by the FDS results.Furthermore, the HY compound presents proper-ties of dentinal tubules closure and dental substratehardness that permit a relatively long-term provi-sional cementation or restoration {2 weeks to 1month). Freegenol Temporary Pack contains oleiacid and polymer-fatty acid that seem to have amild etching effect. The carboxylic acid present inthese substances might improve the adhesion tothe dental surface, and cement may therefore re-main on the surface.

For dentin surface analysis, the samples withprimer substance application were washed, con-trary to the manufacturer's instructions, becausethe surface was covered by the primer, which hidits effect on the dentin surface.^

Although some remnants of temporary cementwere observed on the dentin surface after the pre-conditioning procedures of the resin cement sys-tems, the SEM images of the interfacial layer weresimilar to the controls, except for the specimenstreated with Panavia 21. When FD Primer was ap-plied to the dental sud aces treated with temporarycements, morphologic changes in the remainingsubstances were observed, although these remainingsurfaces were not removed and the dentinal tubuleswere closed. The 10-methacryloyloxydecyl dihydro-gen phosphate ¡MDP¡/water present In the FDPrimer composition had an etching effect, and elim-inated the smear layer, dissolved the surface sub-strate, and opened the dentinal tubules. However, ifcomposites such as zinc oxide and HY substancesare present on the dental surface, the MDP reactswith them, the acid effect disappears, and the etch-ing effect of the dentin substrate is lost. The primercannot act, and the monomer present in the resin

Ctmen

1100

1000

900

800

700f 600

Cou

400

300200

100Q

1000

900

800

700

^ 600

1 500" 400

300

200

100

0

1100

1000

900

800

700§ 600

Q 500

400

300200

1000 1-

Remnanl.

F

C

D

Hg

1 2

F

O

Zn

1C Í1

1 2

O

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1 2

as an AdI esion-lnhiijiling Faclor

Ca

C

Ca01 [Í

3 4 5 6 7 8 9 10Energy (keV)

Oa

[

HB

^3

L.3 4 5 6 7 6 9 10

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Ca

3 4 5 6 7 0 9 10Energy (keV)

Fig 10 Energy dispersive x-ray spectroscopy results of thedentin surfaces ot the C (top). HB (middle), and FG (tiottom)groups.

cement cannot infiltrate into the dentin. This wassupported by the absence of resin tags in the denti-nal tubules and hybrid layer in the ¡ntertubulardentin of the samples prepared with temporary ce-ments that were present in the control. This findingwas also suggested by Tetsuka's experiment^" con-cerning the coloring permeability to dentin after theapplication of temporary cements.

All the temporary cement groups showed a de-crease in tensile bond strengths compared to thecontrols, especially for Super Bond C&B and

re 10. Number 5, 1997 451 The Internaiional Jojinal of Proslhodoniics

r t Rem riants as iir Atihesion-lniiibiting F.iclor

Bistite, which suggests a difference in the quality ofthe hybrid layer. The aforementioned possible in-fluence of temporary cements in the ED Primertreatment might decrease the adhesive strength val-ues; however, the low values of the control mightmake it more difficult to verify differences relativeto the groups treated using temporary cements.

In summary, it was observed that Zn remnantsremain even after preconditioning, and that the ap-plication of temporary cements decreased the ten-sile bond Strengths, This phenomenon might becommon in other available adhesive resin systems.The authors are now studying new surface treat-ment strategies, including an appropriate methodof cleaning in preparation for adhesive use.

Conclusions

This study, evaluating the effect of HY-BondTemporary Cement and Freegenol Temporary Packon dentin surfaces, the bond strengths of Panavia21, Super Bond C&B, and Bistite to dentin, andtheir adhesive interfaces, resulted in the followingconclusions:

1. The mean tensile bond strengths between theadhesive resin cements and dentin surfaceswere lower for surfaces treated with temporarycements.

2. The temporary cements could not be mechani-cally removed by an excavator, and remainedon the dentin surface. Even when precondition-ers of the adhesive resin cement systems wereapplied, the temporary cements could not becompletely eliminated.

3, The resin tags in the dentinal tubules and thehybrid layer in the intertubular dentin observedin the adhesive interfaces of the groups withouttemporary cement treatment were also presentin the those treated with temporary cement, ex-cept in surfaces treated using for Panavia 21,

References

1. Yamasliita A. Atlas: New Adhesive Technique in Dentistry—For Restorative and Prosthodortic Treatment, ed ] , Toi<yo:ishiyaku Publishers, 1994:1-5,

2. Fujii K. Study of prelreatmenl of abutment tooth before iinalcementation—Influence of temporary cement and the methodof cleaning, | |pn Prosthodont Soc 1988;32:668-678

3. Woody TL, Davis RD, The effect of eugenol-coniaining andeugenoi-free ¡empcrary cements on microieakage in resinbonded restorations. Oper Dent 1992;17: l75-t80.

4. Xie I; Powers JM, McGuckin RS, In viiro bond strength o¡ twoadhesivas to enamel and dentin under normal and contami-naieri conditions. Dent Mater t993;9:295-299,

5. Terata R. Characterization of enamel and dentin surfaces alterremoval of temporary cemeni—Study on removai of (empo-raiy cement. Dent Mater | 1993;12:18-28,

6. Nakabayashi N, Resin reinforced denlin due to infiltralion olmonomers into the dentin at the adhesive interface, | |pn SocDent Maler Devices 1982;1:78-81,

7. Nakabayashi N, Ashizawa M, Nakamura M, Identification ofa resin-dentin hybrid layer in vital hijman dentin created invivo: Durable bonding to vital dantin. Quintessence Int1992;23:I35-141.

8. Nakabayashi N, Walarabe A, Ikeda W, Intraoral bonding of4-META/MMA-TBB resin lo vital human dentin. Am J Denl

9, Watartabe EK, Suzuki K, Yamashíta A, Shigela N, Imai M, YataníH, el al. Influence of temporary cement on the adhesiveness ofresin cement to dentin, | DenlMaier 1996;! 5:187-191,

10, Telsuka N. Influence of temporary cemeni on denlin perme-abiiity IJapanese], |pn I Conserv Dem 1993;36(3):822-828,

Tiie Iniernational loumai oí ProsthodontK 452 Volume 10, Niimbei 5, 1997