The Effect of CustomTray Material Type and

Surface Treatment onthe Tensile Bond Strength

of an ImpressionMaterial/Adhesive System

Dnnng i . Diton, DMD, MA*Assistant Professor

Larry C. Breeding, DMD, MSEd'Associate Professor

Mary I, Bosser, DDS'"

Amir I, Nafso. DDS****Ceneral Practice Resident

The purpose of this investigation was to evaluate the tensilebond strength of one type of impression material adhesive tothree different custom tray materials: one autopolymerizing(Fastray) and two light-polymerizing (Triad and Extoral). Theeffect of different surface treatments was evaluated for eachof the materials. No significant difference in impressionmaterial adhesive mean tensile bond strengths was exhibitedfor any of the materials as the result of variations in thesurface treatment. It was observed that the Triad tray materialgroups, with different surface treatments, exhibitedsignificantly higher impression material adhesive meantensile bond strengths than the autopolymerizing tray resinand the Extoral light-polymerizing material. Intj Prosthodont1993:6:303-306.

P revious investigators have evaluated the bondstrengths of several impression materials tocustom and stock trays.' Because of health con-cerns regarding monomer inhalation, other typesof custom tray materials are receiving more atten-tion. In an effort to evaluate characteristics of analternative tray material, Hogans and Agar- com-pleted an investigation concerning elastomer trayadhesive bond strengths to thermoplastic andacrylic resin materials. However, investigations in-volving light-polymerizing materials in connectionwith impression material adhesion have not beenpublished. Tbe thermoplast ic and l ight-polymerizing materials avoid the risk of monomerinhalation; offer ease of tray fabrication; and, ac-

'Department of Restorative Dentistry, School of Dentistry,University of Alabama at Birmingham, Birmingham, Alabama.

"Department of Oral Health Practice, College of Dentistry,University of Kentucky, Lexington, Kentucky.

'"Lkewood. Colorado.""Detroit Receiving Hospital, Detroit, Michigan.

Reprint requests: Dr Donna L. Dixon, Department of RestorativeDentistry, School of Dentistry, University of Alabama al Birming-ham, 1919 7th Avenue South, Birmingham, Alabama 35294.

cording to manufacturers, provide immediate di-mensional stability upon completion of polymeri-zation. The purpose of this investigation was toevaluate the tensile bond strength of one impres-sion material/adhesive system to two types of light-polymerizing custom tray materials and comparethem to an autopolymerizing control group. An-other variable considered in this investigation wastray material surface treatment.

Materials and Methods

Perforated acrylic resin specimen holders(Orthodontic Resin, L.D. Caulk Co Div, Dentsply,Milford, DE] were fabricated for the tray materials(Figi) using a mold. Each tray material holder had aflaf square surface that measured 3.81 cm on eachside. A T-nut was incorporated in the holder so thatan eye-bolt could be threaded into it for attachmentduring tensile testing. The holders designated toretain the impression material were similar in de-sign, except small triangles of resin, 2 mm in thick-ness, were for med on all four corners of the surtaceto insure an even thickness of impression materialfor testing (Eig 2]. Eighteen specimens were fabri-cated using an autopolymerizing resin (Eastray,

6. Number3,1593 303 Journai of Pros 1 hod on lies

Custom Tray Material Type and Surface Treatment

Fig 1 Tray materiai specimen holder with Fastray materialattached.

Henry Bosworfh Co, Skokie, IL). This material wasmixed according to manufacfurer's insfructionsand rolled to a uniform thickness of 3 mm on aRollet Unit (Kerr Mtg, Romulus, Ml) coated withpetroleum jelly. The perforations in the holderwere filled with the resin, the holder was pressedonto the surface of the rolled resin, and the mate-rial was trimmed to the size of the holder using asharp scalpel. After the resin had polymerized, thesurfaces of nine specimens were cleaned with soapand water for 15 seconds, dried with a clean paperfowel, and allowed to set at room temperature for24 hours before testing.

The other nine Fastray specimens were cleanedwith 90% isopropyl alcohol for 15 seconds prior tocleaning with soap and water and drying as de-scribed above. Next, two light-polymerizing ma-terials (Triad, Dentsply, York, PA, and Extoral,Pro-Den Systems, Portland, OR) were used to fabri-cate 36 additional specimens (18 of each type).These were attached to the holders by first fillingthe perforations and then placing the holder ontothe sheet of material and removing the excess. AirBarrier Coating (Dentsply) was applied to all of theTriad specimens and nine of the Fxtoral specimens.The 36 Triad and Fxtoral specimens were placedin a Triad light-polymerizing unit (Model 2000,Dentsply) for 5 minutes.

After polymerization, the 18 Extoral specimenswere cleaned with 90% isopropyl alcohol for 15seconds followed by a 15-second cleaning withsoap and water. Nine of fhe polymerized Triadspecimens were cleaned with only soap and waterfor 15 seconds; and nine were cleaned for 15 sec-onds using isopropyl alcohol, followed by another15-second soap and water cleaning. All specimenswere dried with a paper towel and allowed to set atroom temperature for24 hours before testing.

One coat of the adhesive (Caulk Tray Adhesive,L.D. Caulk Corp Div) was applied to each tray speci-

Fig 2 Impression material specimen holder

men and to each vinyl(poly siloxane) impressionmaterial (Reprosil Heavy Body Impression Material,L.D. Caulk Corp Div) holder. After the adhesive haddried for 10 minutes at room temperature, equallengths of the impression material base and catalystwere hand mixed with a spatula for 1 minute andapplied to the specimen holder. The tray materialand mixed impression material were placed in evencontact with each other and allowed to set under aconstant 6-kg load for 10 minufes. Impression ma-terial that had been expressed beyond the sides ofthe approximated specimen holders was removedusing a sharp scalpel blade. A summary of speci-men group treatments is presented in Table 1. Fachspecimen was placed in a testing machine (InstronUniversal, Instron Corp, Canton, MA) (Fig3). Usinga500-kg load cell with a crosshead speed of 0.5 cm/min, a tensile force was applied, and fhe forcenecessary to separate the impression materiai sidefrom the tray materiai side of each specimen wasrecorded. Following compilation of dafa, appropri-ate statistical analyses were conducted.

Results

Adhesive failure was observed to occur both atthe impression material adhesive/tray maferial in-terface and at the adhesive/impression materialinterface in all of the specimens studied (Fig 4). Thecalculated adhesive tensile bond strengths for thetray material groups tested are displayed in Table 2.Both kg/cm- and Ib/in- values are listed in this tableto allow comparison of the results from fhis investi-gafion to the results from previously publishedstudies involving autopolymerizing tray resins,'Thedata in Table 2 were then compared using a one-wayanalysis of variance (P < .05). A significant diffeT-ence was shown to exist among the groups (Table3). To determine between which groups the differ-ences existed, a Scheffe F test was completed

Tiie Internationa i of Prosthodontii 304

CStorr Tray Malerial Type and Surface Treatment

Fig 3 Specimen placed in the Instron machine for fensiietesting.

Fig 4 Mode ct failure observed tcr all specimens

Table 1 Summary o( Experirrental Conditions

Material

Triad

Triad

Extorai

El to ral

Pa strayPa Stray

Polymerizationconditions

Air Barrier Coatingapplied

Air Barrier Coatingapplied

No Air Barner Coating

Air Barrier Coatingapplied

Wifh petroleum jellyWith petroleum jelly

Cleaningmethods

t5 s alcohol15 s soap'watert 5s soap'water

15 s alcohol15 s soap.'water15 s alcchol15 s soap.'water15 s soap/water15 s alcohol15 s soap/water

Storage time betreadhesive addition (h]

24

24

24

24

2424

Adhesivedrying time (mm)

10

10

10

10

1010

Table 2 Calculated Data for Tray Material Groups Measured in kg/cm=

Group Mean SD SEM CV

Triad (aicotiol]Triad (no alcohoi]Extoral (no air barner)Exforal (air barrier)Fastray (aicohoi]Fa stray (no alcohoi]

5.11 (72.71)4.35(61.89)3.16(44.99)3.05 (43.43)2.36 (33.58)2.16(30.66)

0.30 (4.26)0.76 (10,36)0.70 (9.99)0.35 (4.9B)1.18(16.75)0.58 (8.30)

0.10(1.42)0.25 (3.62)0.23 (3.33)013(1.66)0 39(5.99)0 19(2.77)

5.86 (5,86)17.54(17 55]22 20 (22.20)11 54(11.46)49.91 (49,89)27.12(27,08)

Table 3 Analysis of Variance Comparison of the Tensile Bond Strengths lor the TrayMaterial Groups

Sum ofsquares

Meansquare

ModelErrorCorrelation total

59.7024,1583.85

11.940.50

A significant difference exists at P < ,05

: 6, Number 3,1993 305 The International lournal of Prosthodontics

Custom Tray Material Type and Surface Treatment

(Table 4). Results from this test indicated that bothTriad groups (with and without alcohol) exhibitedsignificantly higher impression material adhesivemean tensile bond strengths than the other traymaterial groups (5.11 kg/cm- and 4.35 kg/cm-, re-spectively], and these values were found to besimilar. The impression material adhesive meantensile bond strengths of the Extoral specimengroups were shown to be similar to the mean ten-sile bond strengths of the Fastray groups.

Table 4 Scheffe F Test for Tray Material GroupsGroup Mean (kg/om^Triad (alcohol)Triad (no aloohoi)Extorai (no air barrier)rxtorai (air barrier)=astray (alcohol)=astray (no alcohol)

999999

5.114.353.t63.052.362.16

Vertical lines opn groups thai are not significantly difterenl at P < .05.

Discussion

The light-polymerizing tray material, under theconditions of this investigation, exhibited higherimpression material adhesive mean tensile bondstrengths than the autopolymerizing groups. TheExtoral material manufacturer does not recom-mend the use of Air Barrier Coating during lightpolymerization, although the removal of the air-inhibited unpolymerized surface layer using iso-propyl alcohol is recommended.

The Extoral specimens on which the Air BarrierCoating was used exhibited a nonsignificant de-crease in bond strength compared to the speci-mens cleaned with isopropyl alcohol. Therefore,theadditionai procedureof applying the Air BarrierCoating to the Extoral material is unnecessary. TheExtoral material, with and without the Air BarrierCoating, exhibited tensile bond strengths that weresignificantly lower than those of the Triad groupson which the coating was used during light poly-merization. The use of an alcohol surface cleaningtreatment did not significantly improve the bondstrength with the Triad material. The addition of analcohol cleaning procedure during the preparationof the Fastray specimens resulted in a nonsignifi-cant increase in the adhesive tensile bond strength.

When using a custom tray and a stiff impressionmaterial such as vinyKpoly siioxane), the force nec-essary to remove the impression from the oral cav-ity can be greatly increased by the presence of; (1)large undercuts around pontics in existing pros-theses; (2) long clinical crowns with open gingivalinterproximal spaces; or (3) dental implant impres-

sion copings that may be divergent. Isolated bondfailure of the impression material to the tray isdifficult to detect. Such bond failure may result ininaccurate casts and, therefore, inaccurate pros-theses. The use of an impression material adhesive/tray material system that exhibits a high tensilebond strength is indicated under the intraoral con-ditions mentioned above to minimize the occur-rence of such inaccuracies.

Conclusion

The results from this investigation suggest thefollowing conclusions:

1. The Triad tray material groups exhibited signifi-cantly greater impression material adhesivemean tensile bond strengths than the Extoraland Fastray groups.

2. The use of an alcohol surface-cleaning treat-ment resulted in a nonsignificant increase in theimpression material adhesive mean tensile bondstrength for both the Triad and Fastray resins.

3. The use of Air Barrier Coating with the Extorairesin resulted in a nonsignificant decrease in theimpression material adhesive mean tensile bondstrength.

References

1. Chai JY, Jameson LM, Moser |B, IHesby RA. Adhesive proper-ties of several impression material systems: Part I. | ProsthetDenM991;6S:201-20'i.

2. Hogans WR, Agar |R. The bond strength of elastomer trayadhesives to Ihermoplastic and acrylic resin Iray materials. |Proslhet Dent 1992 ; 67:541-.3.

Tile Internationai lournai of Prosthodontics 306