Influence of Ozone onOxidation of Dental Alloys

Tetsuya Suzuki. DDS.Makoto Oizumi, DDS,¡unicbi Furuya, DDS'^Yugo Okamoto. DDS'Stephen F, Rosenstiel. BDS.

Purpose; The purpose of this study was to examine the influence of ozone on the surfaceot removable partial denture (RPD) alloys to determine its usefuiness as a cleaningmethod for RPDs, since ozone has powerful sterilizing and deodorizing properties.Materials and Methods: Two types of ozone cleaning were used. The quantities of ozonegenerated by both methods were the sanie (20 mg/hi. In method A, ozonewas generated for 10 minutes every 12 hours and in method B, ozone was generatedover 24 hours a day. Test specimens of 3 types of dental alloy (Co-Cr, Au-Ag-Pt, andAu-Cu-Ag-Pd) were subjected to different cleaning methods for 7 days and measured Interms of reflectance, surface roughness, and weight. Five difierent cleaning solutions(three commercial denture cleaners, acid-electro I y zed water with a pH of 2.4, and purewater! vvere used for comparison with the ozone treatments. Results: No significantchanges were detected after treatment of the Co-Cr and Au-Ag-Pi alloys with ozone.Ozone caused a slight change in the Au-Cu-Ag-Pd alloy in terms of retiectance, but thechanges were significantly less than those caused by acid-electrolyzed water and oneof the commercial denture cleaners. Conclusion: Ozone had little influence on theoxidation of dental alloys, lot] Prosthodont 1999:12:179-183-

'Associate Professor, Department of Geriatric Dentistry, Toi<yoMedicai and Dentai University Facuity of Dentistry, Tokyo,¡apan.'•Research Associate, Department of Geriatric Dentistry, TokyoMedical and Oentai University Facuity of Dentistry. Tokyo,Japan.'^Graduate Student, Department of Geriatric Dentistry, TokyoMedical and Dental University Faculty of Dentistry, Tokyo,japan.''Professor and Chairman, Section of Restorative Dentistry,Prosthodontics, and Endodontics, The Ohio 5tate UniversityCoiiege of Dentistry. Columbus, Ohio.

Reprint requests: Dr Tetsuya Suzuki. Department of GeriatricDentistry, Faculty of Dentistry, Tokyo Medical and DentalUniversity, 1-5-45 Yushima, 8unkyou-ku, Tokyo 113-8549.Japan. Fa>c: ^SI-3-5803-0208- e-mail: t.suzuki.geroS-denr.tmd.ac.jp

This paper was presented at the 27th Annual Meeting of theAmerican Association for Dentai Research, Minneapolis,Minnesota, 4-7 March 1998.

Regular and efficient bygiene procedures are im-portant for the iong-term success of removable

prosthodontic treatment. If a patienfs denture be-comes unsanitary, the consequences may be badbreath, poor esthetics, and occasionally denturestomatitis and angular cheilitis.'- Furthermore, el-derly hospital patients are reported to run a risk ofcontracting pneumonia from bacteria that adhereto their dentures through the inhaiation of organ-isms during mastication.^ Therefore, it is beneficialto establish a technique by wbich dentures can besteriiized effectiveiy and efficientiy.

Ozone has powerfui steriiizing. bleaching, anddeodorizing properties, and it has been used indus-triaily in sucb fieids as dermatology, water purefi-cat ion, agricuiture, and food processing.•'"^Recentiy, an apparatus that can safeiy generateozone has been applied to the cieaning of den-tures.^' The authors have previousiy reported that

Volume 12, Number 2, 1999 1 7 9 The Inlemalional loumal of Prosthodontii

Intkiente of Ozone on ONirlalior of Dental Alloys

Table 1 Composition {wt%) of Dental Alloys

Suzuki et

Alloy

Au-Cu-Ag-PdAu-Ag-PtCo-Cr

Manufacturer

Casl we IIPGA-2Lebochrome

Ag

469

Au

1268

Cu

2015

Pd

202

Pt

5

Co

63

Cr

27

Table 2 Cleaning Solutions

Cleaning solution

OzoneMettiod A (ESC-100, 20 mg/h]tulettiod B (OZSD-3000, 20 mg/h)

Commarcial denture cleanerPika (enzymes)Polident (neutral peroxide witfi

enzymes]Sunny Lite (neutral peroxide)

Acid-electrolyzed water (SuperoxideLab, pH 2.4]

Pure water (control)

Manufacturer

EbaraEbara

Rhoto PharmaceuticalBlock Drug

GCShionogi

ozone is effective in steriiizing the bacteria that at-tach to dentures and are ciaimed to piay a majorrole in oral infection," iHowever, ozone aiso has apowerfui oxidation effect, causing concern that thecieaning may adversely affect tbe metal framewori<of removabie partial dentures.

The purpose of this study was to examine the in-fluence of ozone on the oxidation of dentai aiioysto determine whether it can be safeiy used to cieanremovabie partial dentures in ciinicai practice.

Materials and Methods

Three representative dentai aiioys were chosen forthe study (Table 1 ). Each was cast according to themanufacturer's instructions into 10 mm X 10 mmX 1 mm test specimens. These were ground with Í100Ü emery paper and poiished with 0.06-[jm aiu-mina. A total of 63 sampies were prepared (n = 3for each cleaning soiution).

Two ozone cieaning techniques were used. Inmethod A, an ESC-100 commerciai ozone cieanerlEbara) was operated according to the manufac-turer's instructions for a 10-minute cycie that wasrepeated at 12-hour intervais for the 7 days of thestudy, in method B, an OZSD-3000 variable ozonegenerator (Ebara) produced the same concentrationof ozone (20 mg/h) as the ESC-100, but continu-ously over 24 hours a day for 7 days. Five differentsolutions (three commerciai denture cieaners, acidelectrolyzed water with a pH of 2.4, and pure

water) were used for comparison with ozone(Tabie 2). Fresh soiutions were prepared every 12hours foiiowing the manufacturers' instructions.The test specimens were suspended with thread in200 mL of solution for a total of 7 days; they wereremoved periodicaily for anaiysis.

Ail specimens were analyzed for refiectance,surface roughness, and weight. The measurementswere taken before the treatment, and again afterbeing suspended in the solution for 1, 3, and 7days, Refiectance of the aiioys was measured witha CM-26DS gioss meter (Muracami Color ResearchLab) according to American Society for Testing andMateriais standard E 167.^ The angle of incidencewas 20 degrees. Each test specimen was anaiyzedin 5 different positions because ofthe variabiiity ofmeasurement caused by surface defects. The arith-metic mean of surface roughness (Ra), described ininternational Standards Organization documentiSO 4287^° and Japanese Standards Associationdocument B0601," was measured with a Surfcomroughness meter (Toi<yo Seimitsu). Measurementspeed was 0.3 mm/scc, measurement iength was 2mm, diameter of the styius tip was 0.05 \>m, andcutoff iength was 0.8 mm. Weight was measuredwith an AE240 analytic balance (Mettler Toiedo)with an accuracy of ± 0.01 mg. Muitipie compari-son anaiysis software (Stat View version 4.54,Abacus Concepts) was used for the statisticalanalysis, appiying Scheffe's method. Whenever sta-tistical tests were performed, P vaiues less than0.05 were considered statisticaiiy significant.

Results

No significant changes of refiectance, surfaceroughness, or weight were shown in any of thetests for the Co-Cr alioy (Tabie 3 and Fig 1). Eor theAu-Ag-Pt aiioy, significant changes of refiectance,surface roughness, and weight were seen in aiitests with acid-electrolyzed water oniy (Tabie 3and Eig 2). For the Au-Cu-Ag-Pd alioy, significantreflectance changes were shown with ozonemethod B, Sunny Life {CC) treatment, and acid-eiectrolyzed water treatment (Table 3 and Eig 3).Significant weight changes were seen with SunnyLife and acid-electroiyzed water treatment.Significant surface roughness changes were seenwith acid-eiectroiyzed water. Reflectance of theAu-Cu-Ag-Pd ailoy on day 7 was 29% iower aftermethod B treatment, 36% iower after Sunny Lifetreatment, and 54% iower after acid-eiectroiyzedwater treatment. The change of refiectance aftermethod B treatment was significantly iess than that

Tiie In lerna tmna 180 Volume 12, Number 2, 1999

Suzuki et al Influence of Ozone on Oxidation of Dental Alloys

Table 3 Mean (+ SD) of Measurements After 7 Days of Treatment

Cleaning solution

Oione methtjd AOzone method BPikaPolidentSunny LifeAcid-electro lyzed

waterPure water (contnji)

Au-Cu-Ag.Pd alloy

Reflectance(%)

55,60 ±1,1226.14±2,86t54.34 ± 3,4850 36 + 4 89ia.io + o.2iT

46,45 * 4.09

Surface Change otroughness

(Ijm)-

0,000,06 ±0.04

0.000.00

0,05 * 0.022.71 ± 0 89T

0,00

weight(%)

-0.01-0.18

0-0.02-1.36t

0.62'

-0,01

Au-Ag-P1 alloy

Réflectance(%)

59,06 ±1,6553,81 ±4.9756,54 * 1,9358 82 ± 2.0154.09 + 3.51

0.02 ± 0,04'

55.92 ± 2,08

Surfaceroughness

(|jm]-

0,000,000.000.000-00

1,23±0,38t

0,00

Change otweight

("•'o)

0-0 01

0-0,02

0-2,33'

0

Co-Cr alloy

Reflectance i(%]

62.16-^0.4982.33-^1.3584,00 ± 2,6459,9313,3262,35 ±0-9460,74 ±4.17

62.83 ± 0,42

Surfaceroughness

(lim)'

0,000,000.000,000,000.00

0,00

Change ofweight

|%|

-0,02-0.05-0,06-0,05-0.04-0,04

-0.03

•Initial surface roughness lor all measurements - Û.00.

SD = standard deviation.

F i g lalloy.

Reflectance ot tfie Co-Cr

100-1

90-

8 0 -

7 0 -

i 50-

1 40-

30-

20

10

1 1 1D 1

Day

= If—*— Method A—•— Method B—*— Pika

X Pûlident—©— Sunny Life—a— Acid-electrolyzed water—A— Conlrol

7

Fig 2 Refleotance of the Au-Ag-Pt alloy.

100

9 0 .

8 0 .

7 0 ,

^ 60,

1 50,

= 40-ir

30

2 0 -

10

0

Ê = 3 = 1

\

\\

f 1 ^] 1

i

Day

-•— Method A- •— Method B- 4 — Piks-ht— Polidenl- e — Sunny Life- H — Acid-elecirolyzed water— i — Control

-- 1

7

Volume12,Numb€r2,l999 181 ^^ Journal of Prosthodontio

Intiuence ol Oïone on Oxidalioji of Dental Alloys Suzuki et al

Fig 3 Réflectance ot the Au-Cu-Ag-Pd alloy.

after Sunny Life and acid-electroiyzed water treat-ments. The weight of the Au-Cu-Ag-Pd alloy after7 days of treatment with Sunny Life significantlydecreased by 1,4%, The weight of the same alloywith acid-eiectrolyzed water significantly in-creased by 0,6%. Surface roughness (Ra) of theAu-Cu-Ag-Pd alloy after 7 days of treatment withacid-electrolyzed water was 2,71 pm.

Discussion

Ozone exerts a powerful sterilizing effect by directlydestroying cell walls and bacterial membranes,^Oizumi et ai^ studied thecleaningeffect of ozone onbacteria with the same commercial ozone cleaner.The number of Streptococcus mutans, Staphylo-coccus aureus, and Candida aibicans organisms de-creased by a factor of 10^ after 1 minute of cleaningand was below the detection limit by the end of 3minutes of cleaning. We believe that a cleaningcycle of "10 minutes with the ozone cieaner lESC-100} would be sufficient to sterilize a denture.Method B was the same as the ESC-lOO operated for144 cycles a day for 7 days. This test may be very in-tensive. For comparison, it takes at least 2 hours tosterilize dentures with typical commercial denturecleaners and it is generally recommended to leavethe dentures in the solution overnight,'^-'^ The cur-rent period of investigation, 7 days, was not unrealis-tically short for the ozone cleaner, but on the otherhand, it was clearly much too short for commercialdenture cleaner assessment. Nevertheless, the com-merciai cleaner Sunny Life caused some reflectanceand weight changes in the Au-Cu-Ag-Pd alloys.

American Dental Association high noble alloysmust have a noble metal content of > 50 wt% anda gold content of > 40 wt%,''' The alloy used forthis study, which is often used in Japan for remov-able partial denture frameworks, had a gold con-tent of only 12 wt%, with a copper content of 20wt% and a palladium content of 20 wt%. There-fore, this alloy could be expected to be less resis-tant to oxidation than the typical high noble alloys.Method B also caused significant changes in theAu-Cu-Ag-Pd alloy in terms of reflectance bLJt notin terms of weight. Because method B has muchless influence on oxidation of this alloy than SunnyLife, the weight did not change significantly.Commercial denture cleaners are used at home ona daily basis, whereas ozone cleaning will only bedone in dental offices approximately 2 to 4 times ayear. Considering the frequency of cleaning witheach method, ozone would have little or no influ-ence on the oxidation of dental alloys.

Acid-electrolyzed water also has a powerfulsterilizing effect, and it has been used for debrid-ing periodontal pockets and for cleaning severaldental appliances.'^ Acid-electrolyzed watercaused significant changes not only in the Au-Cu-Ag-Pd alloy, but also in the Au-Ag-Pt alloy afteronly 1 day. The oxidation of the Au-Cu-Ag-Pdalloy with acid-electrolyzed water was the mostsignificant finding of all of the tests. The increasein the weight was probably due to oxides formedby the acid-electrolyzed water treatment, whichbuilt up on the surface of the Au-Cu-Ag-Pd alloy,Tbe use of acid-electrolyzed water for intraoralcleaning in a patient with prostheses made of this

The International lournal of Pro;thodonti( 182 Volume 12, Number 2, 1999

Suzuki et al

alloy would eventuaily cause accelerated oxida-tion.

Ozone itself quickly decomposes into oxygen

with a halt-life of 12 minutes at pH 7.'̂ Thus, there

is no possibility of significant concentrations of

ozone remaining on the denture after cleaning.

Cleaning dentures with ozone is safer than cleaning

with some denture cleaners or acid-electrolyzed

water where there is a possibility of acids or alkalis

remaining and being ingested.

Judging from these findings, the powerful steril-

izing effect of ozone would make it beneficial for

treatment of Au-Ag-Pt and Co-Cr alloy metal

framework removable partial dentures in clinical

practice. It will be necessary to study the influence

of ozone on the oxidation of several dirferent com-

positions of the Au-Cu-Ag-Pd alloy for a longer pe-

riod of time.

Conclusions

This study evaluated the influence of ozone on oxi-

dation of three dental alloys. Five different clean-

ing solutions were used for comparison with

ozone. Within the limitations of this experimental

design, the following conclusions can be made;

1. Ozone had no influence on oxidation of the

Au-Ag-Pt and Co-Cr alloys.

2. Ozone caused a slight change in the Au-Cu-

Ag-Pd alloy in terms of reflectance, but the

change was significantly less than those caused

by acid-electrolyzed water and Sunny Life.

Influence of Ozone on Onidation ot Dental Alloys

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Literature Abstract -̂

Complications and primaty failures related to fixed metal ceramic bridge

prostheses made by dental students.

Tbe aim of this study was to evaluate complications and primary faiiures of metal-ceramic fixed

partial dentures (FPD) made by dentai students. Files from 61 patients in the age range of 2B to

73 years were studied for data from preprostbetic treatment to 6 months after completion of the

prosthodontic treatment. The material comprised 82 FPDs with 221 abutments, 136 pontics, and

47 cast cores. Seven teeth had to be extracted because of complication or failure reiated to en-

dodontio treatment and root canal perforation during preparation Two teetfi fractured al tbe re-

moval of the old crown. Four f̂ PDs bad to be remade and firing ot porcelain had to be renewed

on seven FPDs The cohclusion was that most failures occur during preprosthetic endodontic

treatmerrt and during root cahal preparation of abutment teeth. Long-temi follow-up studies to

evaluate t ie total success rate of fixed prosthodontics should therefore also include the prepros-

thetic part of fhe treatment.

Raustia AM, Näpänkangas R, Salonen MAM. J Oral BeHaM 1998:25:677-680. References: 14.Reprints; Prol Aune M. Rausta. Department of Prosthetic Dentistry and Stomatognathic Physrology,institute of Dentistry, University of Ouiu, AapisUe 3, FiN-90220 Oulu, Finland-AW

Volume 12, Number 2, 1999 183 The Iniematronal lojmal of Prosthodontics