A comparison of physical characteristics of six hard denture reline materials

REMOVABLE SECTION

PROSTHODONTICS

EDITORS

LOUIS BLATTERFEIN

S. HOWARD

PAYNE

A comparison of physical characteristics of six hard denture reline materials C. C. L. Wyatt, D.M.D.,* T. J. Harrop, L.D.S., D.D.S., M.S., Ph.D,** and M. I. MacEntee, L.D.S.*** University

of British

Columbia,

Faculty

of Dentistry,

Vancouver,

R

igid autopolymerizing acrylic resin is used to reline dentures directly in the mouth. The resin is polymerized by mixing a powder of poly(methy1 methacrylate) with a liquid of methyl methacrylate and using peroxides, amines, and plasticizers to control the chemical process. The effects of this chemical reaction on the oral mucosa are unknown; however, many patients find the procedure uncomfortable and distasteful. The purpose of this investigation was to explore selected physical properties of six commercially available reline materials. Studies were conducted to determine (1) the temperature and consistency changesof the setting acrylic resin, (2) the surface texture of the hardened acrylic resin, and (3) the detail reproduction of each material. In addition, the cost of the material necessary to reline one complete denture was calculated for each product.

MATERIAL

Table I. Tested materials Material

Supported by a Youth Employment Program grant from the University of British Columbia. ‘Graduate student, Department of Restorative Dentistry. **Professor, Department of Restorative Dentistry l **Associaw Professor, Department of Restorative Dentistry. OF PROSTHETIC

DENTISTRY

Manufacturer Coe Laboratories Chicago, Ill. Lang Dental Mfg. Chicago, 111. Coe Laboratories Hygienic Dental Akron, Ohio Stratford-Cookson Newnan, Ga. Harry J. Bosworth Skokie, III.

&erect Flexacryl Kooliner Perm Total Truliner

Inc. Co. Inc. Inc. Mfg. Co. Co. Co.

Table II. Cost of package and the cost of relining one maxillary denture base with each material Number of

AND METHODS

The six products chosen were available on the Canadian market (Table I). Each product was mixed according to the manufacturer’s instructions to produce a quantity of material sufficient to reline one maxillary complete denture. The recommended mixing proportions for one product (Perm) were reduced by half because the manufacturer’s recommendations produced a quantity of resin that was at least double that of the other products. The surface temperature of the acrylic resin was monitored during polymerization. The materials were mixed and poured into 35 mm diameter petri dishes to a depth of 2 mm. A thermocouple with constantan and copper electrodes was used to measure the surface temperature of the setting resin to an accuracy of kO.25” C. With the probe placed on the surface of the polymerizing resin, the temperature was monitored at l-minute intervals in a controlled environment until the maximum temperature was recorded. Five samples of each product were monitored. An analysis of variance was used to test

THE JOURNAL

B.C.. Canada

Material &erect Flexacryl Kooliner Perm Total Truliner

relines/ Ppc~S~ 34 24 11 44 I8 25

cost*

Single reline cost*

28.28 37.07 14.70 34.23 17.71 29.37

0.83 1.55 1.30 0.77t 0.97 1.16

Package

*U.S. dollars. tCosc of this material is that of half the amount recommended by the manufacturer.

for significant differences among setting time and temperatures for the six products. Three samples of each product were prepared for visual, light microscopic, and scanning electron microscopic @EM) observations by pouring acrylic resin into 40 mm diameter petri dishes to a depth of 3 mm. The resin was allowed to polymerize at room temperature (24 f 2” C) for 2 hours before examination. The SEM samples were cooled with liquid nitrogen, fractured, cleaned ultrasonically, and coated with metal ions. A 0.25 mm2 area of the surface exposed to air was chosen randomly on each sample, and the number of Gable pores were counted to estimate the relative porosity of the material. Cost of relining a maxillary complete denture was 343

WYATT,

80

HARRUP,

AND

MAcENTE

I

Perm

01 0

’

’

4

’

’

8

’ Time

’

12

’

’

16

’

’

20

0 5

(min)

Fig. 1. Surface temperature of setting acrylic resins.

Setting

IO time

15

20

(min]

Fig. 2. Average peak temperatures and setting times.

Fig. 3. SEMs of air-exposed surfaces of acrylic resin. A, Total. B, Coerect. estimated by dividing the package cost by the number of relines obtainable from each package. The cost of the packages was based on the normal retail value on the Canadian market in 1983. RBSULTS The package cost for the products ranged from $14.70 to $37.95 (U.S.) and the cost of relining one maxillary denture base is presented in Table II. The surface temperature of the samples plotted against time are shown in Fig. 1. Three product groups had setting times that were diffennt (p > .Ol), and two product groups attained different (p > .Ol) average m&mum temperatures (Fig. 2). AlI surfprocessed against the petri dishes had a smmth~apparance whereas the surfaces e to the air hitd either a glossy or matte appearanoc. The d-y stufaas occurred with qual clarity. The surface characteristics of the three samples of 344

each produet shamed little variation. The number of surface pores per square millimeter associated with each product is presented in Table III with an exam+ of the most and least porous materials’ displayed in I?& 3. A cross-section of each sample under the SW reveal& two distinct layers; a solid uniform mass of acrylic resin below and a thinner layer of porous material on the surface (Fig. 4). The outer layer varied in tbicksess from a 0.25 mm thickness to a total la& of poru&y (Figs. 5 and 6). DISEU-N The sections tested for temperature m dtiag polymerizing were comparable to the thickaebs ti ~JHW materials used clinically. Although thin s&ons WiH lose heat quickly in the mouth,’ the mean VW p!e.+ of57”CislaighandcouldbumttKoral~~F~~fl/is reason the manufaetufGrs of FlmMwryl, atid, aal Pm recommend removing their products from the mouth as MARCH

1986

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PHYSICAL

CHARACTERISTICS

OF RELINE

MATERIALS

Fig. 4. SEM cross-section. A = Porous surface layer; B = solid uniform mass of acrylic resin; and C = plastic container.

Fig. 5. SEM cross-section of porous resin. A = Porous surface layer; B = solid uniform mass of acrylic resin. the temperature rises. The effect of removing the incompletely cured resin from the mouth on the final fit of the denture was not tested in this study. Of note, the manufacturers of Truliner did not recommend removing their reline material from the mouth despite a mean peak temperature of 70” C attained by their product. Patients may find such high temperatures intolerable. The layer of porosity on the air-exposed surface of each sample produced with &erect and Truliner suggests that they may accumulate microbial plaque more readily than the pore-free products2 A study of the critical surface tension of wetting on teeth demonstrated that an organic film or pellicle brought teeth in different THE JOURNAL

OF PROSTHETIC

DENTISTRY

parts of the mouth and in different subjects to a common state of bioadhesiveness.) This pellicle could explain why Skjorland et al.’ found that bacterial adhesion to composite resin fillings was not influenced by the relative porosity of the materials tested. However, since it is unclear what combination of factors is needed to induce denture stomatitis, it may be prudent for dentists to avoid porous products in any patient, particularly those who may be susceptible to this disease.5

SUMMARY Six rigid autopolymerizing acrylic resins were examined to determine and compare the cost per reline, the 345

WYATT,

Fig. 6. SEM cross-section resin.

Table III. Surface porosity materials

of denture

of nonporous

reline

&erect TrIlll”er Kooliner Perm

6672 2856 2560 2208 756 512

Flexacryl Total

780 312 392 88 52 140

2 3. 4.

5

curing temperatures,

the setting times, and the porosity

of each material. The cost per reline ranged from SO.63 to $1.55. Three product groups had significantly different mean setting times, and two groups had significantly different mean setting temperatures. SEM cross-sections of each product revealed an apparently porous-free solid mass of acrylic resin, which in two products was overlayed by a thin porous surface layer. The physical characteristics of any one product did not indicate clinical superiority.

I

New JOURNALpolicy

A = Air-exposed

surface;

AND

MAcENTEI

B = acrylic

REFERENCES I

Surface pores/mm’ No. SD

Material

resin.

HARROP.

Braurr SM. Whltc EL Burns (:I,. Wcwllcl JB- I)cnturc rellncrs-lI)lrccr. hard. self-turlng resin. J .\m Den! 4s~~ 59270. l9i9 \‘a” Rcencn JF: blicrobiologlc studws un drnturr swmalit~s. J I’IO~HET DEm %49X 1970 Jcndrcscn MD. Glantz PO: (Aimcat adhcslvct~crs 01 the t(wh surfaw Acrn Odontol Sand 38~379. 1980 Sktortdnd KK. Hcnsrcn-Prtterccn A. Oruwk D. Swlcrholm K-J Tooth colored drntal rworatwc materials. Pwosirics and surface wpographu III relalion 10 hwcri;l/ adhrsron. .4na OdonId Scdnd 4&i t 3. 1982. ~claRudtz-Jorgenwn E. Thcilade L rhciladc J: Quantitauw swmati~wnship hr~ween yeasts and bactc*ri.c in denture-induced 11s Sand J Dcnc Rcs 91:lS4. 1983

for il lushUmw

I

in fztdoc

The $225 charge to authors for each page of color illustrations will be eliminated for all manuscripts received in the JOURNAL office after January 1, 1986. High-quality 35 mm color transparencies must be submittal, and manuscript lcng!h capnot exceed 10 to 12 double-spaced typewritten pages. The Editor and his r&men have final autharity to determine whether color illustrations afford the most efktive presentation. I

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