Monopoly study Y. Asian,

coating D.M.D.,

on acrylic

M.S., Ph.D.,*

resin

and M. Avci, D.M.D.,

surfaces:

A bacteriologic

M.S., Ph.D.**

University of Hacettepe, Faculty of Dentistry, Ankara, Turkey In an open bulb of a buccal flange obturator, it is almost impossible to polish the inner surface of the bulb. Because it cannot be cleaned easily, oral and nasal secretions lead to odors. To obtain a smoother surface, it is suggested that monopoly be painted on the unpolished surface of the open bulb. In this study, the effect of a monopoly coating on bacteria retention and washability of acrylic resin surfaces was investigated. Coated and uncoated acrylic resin samples were prepared and both were contaminated with Escherichia coli. After standard washing, the remaining viable E. coli colonies were counted. The statistical results showed that the difference in the number of E. coli colonies between coated and uncoated groups was highly significant (p < 0.001). It was suggested that monopoly should be applied to the acrylic resin surfaces where mechanical polishing cannot be done. (J PROSTAET DENT 1990;63:478-81.)

A

cquired hard palate defects may be restored with hollow-bulb obturators or buccal-flange obturators. They are equally effective in eliminating speechprob1ems.lAlthough the buccal flange obturator is easierto make, it is mechanically almost impossibleto polish the inner surface of the openbulb of the buccal flange obturator.2 To obtain a smoother surface, it was suggestedthat monopoly (a mixture of monomerand polymer) be painted on the unpolished inner surface of the open bulb.3 Even though

*Professor, Department of Prosthodontics. **Assistant Professor, Department of Prosthodontics. 10/l/17596

preparation and applications of monopoly are well described in the literature,4 the effect of the monopoly coating has not been documented. This study determined the effect of the monopoly coating on bacteria retention and/or washability of the acrylic resin surfaces.

METHODS

AND

MATERIAL

Standard acrylic resin sampleswere prepared by means of a metal mold. For each sample,1.5 gm of autopolymerizing acrylic resinwasprepared and condensedfor 13 minutes at 18’ C. The condensedacrylic resin waspacked into the metal mold and kept under 2 atm pressurefor 15 minutes. Faulty sampleswereexcluded from the study. Surface

Fig. 1. Coated and uncoated groups of samples.

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Fig. 2. Simultaneous and even washing of samples of pair. Fig. 3. Petri dishes containing colonies of E. coli belong to coated and uncoated samples of pair.

polish was broken with sandpaper. Each sample was tied with a ligature wire and 40 samples were divided into two groups by random selection (Fig. 1). Ail of the samples of one group were coated with monopoly and all of the samples of both groups were stored for 10 days at room temperature and humidity. One coated and one uncoated sample was subjected to the following procedures. 1. Each pair of samples was sterilized at 120” C for 2 hours. 2. Escherichia coli was inoculated into a I.75 cc broth culture with a wire loop. The first pair of samples were dipped into the broth culture, which was covered with a petri dish and incubated at 37’ C for 18 hours. 3, Each sample pair was dipped into a 200 cc sterile saline solution three times by moving it up and down to provide even washing (to imitate the rinsing of an obturator) (Fig. 2). 4. Each sample was dropped into a glass balloon vessel confining 175 cc sterile saline solution. The two glass balloons were shaken for 15 minutes with a mechanical flask shaker simultaneously. 5. Next, 0.1 cc of solution was removed from each glass balloon and was added to 9.9 cc sterile saline solution in two separate sterile tubes. These solutions were stirred thoroughly with sterile pipettes. 6. Then 0.1 cc was taken out of 10W2diluted solutions obtained as a result of the previously mentioned procedure and was inoculated into a selective medium (Eosin-meth-

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ylene blue agar, D&o, Detroit, lvIich.1 in petri dishes with a sterile loop. 7. Petri dishes were kept in the incubator at 37” C for 24 hours. E. Coli colonies in petri dishes from the coated and uncoated samples were counted and recorded. 8. Since two samples, one coated and one uncoated, were tested one at a time, the previously mentioned experiment was repeated for 15 pairs. 9. The last five pairs were the control group and the mentioned procedure was applied to the control group without inoculation with E. coli.

RESULTS E. coti colonies inoculated in petri dishes containing coated and uncoated samples (Fig. 3) were counted and recorded. The difference in the number of colonies between the coated and uncoated groups was analyzed statistically by using the t-test for paired groups. Table I and Fig. 4 represent the number of colonies for both groups and the statistical results. There was no bacterial growth in the petri dishes of the last five pairs, which were the control groups.

DISCUSSION An open bulb tends to accumulate oral and nasal secretions and liquids seeping from the oral cavity, leading to odor and added weight.4*5 It was suggested that a small diagonal opening may be made between the inferior-lateral

479

ASLAN

AND

AVCI

90. 80, 70. m ei ..

60.

z 0 0

503 40.

c 0 30. i D

E 3 c

20. 10,

123456~69 83 amplesr

I coated Fig. 4. Number of colonies in each coated and uncoated acrylic resin pairs.

I. Number of colonies of E. co& in each acrylic resin sampleand statistical results Table

Sample numbers of acrylic pairs

Uncoated

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Mean error

of

differences

= 3.4; t = 14.07

78 83 75 76 48 55 51 51 61 71 71 65 69 76 66 = 48.26;

standard

Coated

Difference

15 16 28 30 16 18 16 9 8 9 6 13 9 38 41 deviation

63 67 47 46 32 37 35 42 53 62 65 52 60 38 25 = 13.28;

standard

(p< 0.01).

samples.The resultsshowedthat the coating hasa positive and statistically significant (p < 0.001) effect on bacteria retention and/or washability of the acrylic resin surfaces. A possiblebacteriostatic effect from the residual monomer may have beengreater in the coatedsamples.To avoid this possibility, the sampleswere stored for 10 days after the coating. In addition, the sterilizing processof the samples (2 hours at 120” C) before inoculation may have reduced the effect of the residual monomer. Coated and uncoated pairs of sampleswere compared with each other. Differences between pairs should be considerednormal becauseE. Coli concentration and washing proceduresmay causevariations between pairs. Since the acrylic resin wasnot sterile when it wasremoved from the glassballoon after shaking,it is impossibleto determinethe total number of E. coli in the glass balloon with this method. Our purposewasto comparethe number of viable E. coli that were not detachedwith a simplewashing,but were detached with strong shaking, from coated and uncoated samples. SUMMARY

floor of the bulb through to the cheek surface of the obturator for drainage.4However, this doesnot eliminate the need of a polished inner surface. In this study, monopoly was painted on the unpolished surfaces of acrylic resin

480

AND

CONCLUSION

The effect of a monopoly coat on sandpaperedacrylic resin surfaceswas tested for contamination, washability, and retention of viable E. coli. A standard microbiologic method was used. It was found that monopoly-coated samplesharbor fewer E. coli. It is suggestedthat monop-

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oly should be applied to acrylic resin surfaces where mechanical polishing can not be accomplished (for example, the inner surface of the bulb of a buccal flange obturator). The next step is to find evidence that this amount of reduction of colonies will produce a meaningful clinical difference. Further studies such as retention of monopoly coat on acrylic resin surfaces and the amount of residual monomer in comparison to application time of monopoly coat would also be beneficial.

3. Oral K. Construction

of a buccal flange obturator.

J PROSTHET

DENT

1979;41:193-7.

4. Beumer J III, Curtis TA, Firtell DN. Maxillofacial rehabilitation. St Louis: CV Mosby Co, 1979;210-8. 5. Zaki HS. Modified bypass in maxillary hollow-bulb obturators. J PROSTHET DENT

Reprint

requests

1980;43:320-1.

to:

DR. YAWZ ASAN HACE~TEPE UNIVERSITESI DISHEKIMLICI FAK. PROTEZ BOL. 06100 ANKARA TURKEY

REFERENCES 1. Oral K, Aramany MA, McWilliams BJ. Speech intelligibility buccal flange obturator. J PROSTHET DENT 1979;41:323-7.

2. Coffin F. Cancer and the dental surgeon.

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Br Dent J 1964;116:243-53.

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Monopoly coating on acrylic resin surfaces: a bacteriologic study.

In an open bulb of a buccal flange obturator, it is almost impossible to polish the inner surface of the bulb. Because it cannot be cleaned easily, or...
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