Journal of the Dental Association of South Africa, 35, 821-824 Experimental marginal leakage around Isocap® and Compocap S® restorations A Jodaikin and O Sparrius MRC/University of the Witwatersraiul Dental Research Institute, 1 Jan Smuts Avenue, Johannesburg, 2001. Keywords: resin restorations SUMMARY Experimental marginal leakage around IsoeapK and Compocap SR restorations placed with or without prior etching o f cavity margins was compared using a fluores­ cent dye technicpte. A ll o f the restorations examined leaked to some extent. No statistically significant differ­ ences were found between the marginal leakage o f the lsocapn and Compocap SR restorations. Statistically sig­ nificant differences in experimental marginal leakage were found between the etched and unetched prep­ arations. Restorations placed in conjunction with the etching technicpte displayed less experimental marginal leakage. OI’SOMMING 'n Rluoressercnde kleurstof is gebruik out eksuerimen- tele randlekkasie om Isoeap11 en Compocap''" herstel- lings met geeiste en ongeeiste kawiteitsrancle tc oncler- soelc. A l die herstellings het 'n mate van lekkasie getoon. Cecil statistics nocmenswaardige verskille is tussen die randlekkasie van die lsocapK en CompocapSK herstel­ lings gevind nie. Statistics nocmenswaardige verskille is wel tussen die geetste en ongeeiste preparate gevind. In gevalle waar die geetste tegniek gebruik is het herstellings minder eksperimentele randlekkasie getoon. INTRODUCTION Clinical marginal leakage may hasten the breakdown and dissolution of certain biomaterials and tooth sub­ stance and may cause tooth or restoration discolour­ ation, post-operative tooth sensitivity, pulpal inflamm­ ation and dental caries with their sequelae. However, the clinical significance of experimental marginal leak­ age remains speculative as it demonstrates a potential, but not a clinical reality (Roydhousc, l%S). This does not preclude the possibility that the best seal against an experimental penetrant may be the best seal against dinical marginal leakage (Swartz and Philips, 1962). Isositc* is a direct filling resin marketed as a hand- mixed, two paste system (IsopastR), an ultra-violet acti- ivation system (IsoluxR) and a normal (Isoeap — NR) mid a syringc-capsulated (IsocapR) system. Isosite, which is a microfill restorative material, contains or­ ganic submicron particles in a matrix based on a modi­ fied Bowen resin. Although microfill restorative ma­ terials can be polished to a higher gloss than the con­ ventional composites, they have a relatively high coeffi­ cient of thermal expansion (Braden, 1979 and Dogan, Van Lccuwen and Norris, 1980). Nelson, Wolcott and Paffenbarger (1952) have empha­ sized the importance of a material’s coefficient of ther­ mal expansion with respect to marginal percolation. However, Asmussen and Jorgensen (1978), have stated that, provided that a relatively small wall-to-wall poly­ merization contraction and adequate expansion due to water absorption occurs, temperature changes within realistic limits will not influence the marginal integrity. The manufacturers of Isosite (Technical Information 1977*) have claimed that the coefficient of thermal ex­ pansion of a dental material evaluated as an isolated factor docs not predict the marginal seal in a clinical sit­ uation. They also claimed that an essential factor in producing a marginal seal is the controlled water ab­ sorption of a dental restoration in relation to its poly­ merization shrinkage. In other words, if the water ab­ sorption ovcr-compcnsatcs for the polymerization shrinkage, as realised in lsopastR, the restorative ma­ terial will produce in the cavity an effect similar to a cork in a bottle-neck. The restoration is thus firmly re­ tained in the cavity because the over-compensating water absorption produces a tight marginal seal by ade­ quate expansion. The purpose of this study was to determine and to com­ pare the in vitro experimental marginal leakage of an Isosite syringc-capsulated system, IsocapR* (selected for case of mixing control) and a similar syringc-capsul­ ated conventional composite system, Compocap SR*. "VivjulciH. Scliaan. LcichtcmtcinVivailcnt. Scliaan. l.cidilcnstcin. Journnl o f the D .A .S .A . — December 1980 821 A Jodaikin and O Sparrius MATERIALS AND METHODS Unblemished, noil-carious, extracted human canine teeth were selected from a batch that had been stored for several months at - 5 °C. The teeth were examined under a binocular operating microscope** (at a mag­ nification of X 16) and the visible, fracture-free regions on the middle third of the labial surface in which the cavities could be prepared were outlined with pencil. Any teeth presenting fractures in the middle third of the buccal regions were discarded. Oval cavities (ap­ proximately 4 mm x V / 2 mm) with the bases in the outer third of the dentine and with bevelled margins (approximately 0.5 - 1,0 mm wide) were cut within the outlined labial regions using a water-cooled tungsten carbide fissure bur *** in an air turbine handpiece. The bur was changed after every 8 cavities to ensure that all cavities were cut with a sharp instrument. The prep­ arations were then examined with the operating micro­ scope at a magnification of X16 and specimens with fractures associated with the cavity margins were dis­ carded. Each of two operators produced 40 satisfactory cavities in this manner. The 80 prepared teeth were pooled and stored at room temperature in a screw top jar on cotton wool saturated with distilled water containing a few granules of thymol disinfectant. Fifty teeth were rand­ omly selected, thoroughly washed and dried with an air and water syringe before being etched for 60 seconds. Equal numbers of etched cavities were thoroughly washed and dried and alternately filled according to the manufacturer’s instructions with Compocap SR and Iso­ cap1*. The remaining 30 specimens were thoroughly washed and dried and their cavities alternately filled with the two restorative materials, without any prior etching. A primer (contact resin) was not applied to any of the preparations. All the specimens were then stored at room temperature for 24 hours in distilled water containing a few granules of thymol, before being polished with a recommended polishing kit*. The polished specimens were then placed in a thermal cycling machine**** and subjected to cyclic tempera­ ture changes by alternate immersions in water at 15 °C and 45 °C employing immersion times of 45 seconds. There were 24 runs of thermal cycling and each spec­ imen was exposed to a mean of 2 408 immersions (S.D. 116). After each thermal cycling run, the batch of specimens was dried with compressed air and the tooth surfaces around the restorations painted with two applications of varnish, leaving only the restorations and an area of about 1 mm width around their margins free of varnish. The specimens were then immersed in an aqueous fluorescent dye * for 24 hours at room temperature. Alter removal from the dye solution, the specimens were thoroughly washed in running water and the tooth crowns then scraped clean of varnish. The specimens were thereafter embedded in clear polyester** resin for subsequent sectioning. Two transverse parallel sections ** Carl Zeiss. Oberkochcn. Germany. *** Juia Carbide Balirer Burs, i-‘ruses Fieasas CTG2I 014. ****Mcdu|uip Hngincering. P.O. Box 5b.V»0. Pinegowrie. Kamllnirg. R.S.A. + Black Ray. Ultra-Violet Products. Inc. San Gabriel. California. U S.A. + + Jacksons Fibreglass (Ptv) Limited. Johannesburg. R.S.A. were cut at 100pm intervals at the junction of the middle and outer thirds of the restorations, using a water-cooled, lowspecd saw***. The sections were mounted in glycerine and examined by transmitted ultra-violet fluorescent microscopy**** Damaged sections were discarded. Each investigator independently graded the observed marginal leakage according to the following scoring system (Fig. 1.): Score 0 Score 1 Score 2 Material Fluorescent Dyc□ Enamel Restorative Dentine. l-'ii;. / Experimental Marginal leakage scoring system. 0 = No experimental marginal leakage — no dye pen­ etration between the restoration and cavity wall. 1 = Moderate marginal leakage — no dye penetration beyond the dentino-enamel junction. 2 = Severe marginal leakage — dye penetration beyond the dentino-enamel junction. The scoring system was applied to two sections per tooth specimen, and the highest score obtained from each specimen was adopted as the degree of marginal leakage. Inter- and intra-examiner variations were as­ sessed after 50 per cent of the specimens had been re­ examined. No statistically significant differences were found. RESULTS A total of 13 specimens were discarded because the specimens were unsuitable for examination owing to sectioning errors. On examination, the remaining 67 re­ storations all showed dye penetration, indicating leak­ age. Thus none of them displayed scores of zero. The results tire tabulated in Table 1 and were subjected to statistical analysis using the Fisher exact probability test and the Chi square test where applicable. A p value of < 0,01 was selected as the level of statistical signific­ ance. The number of restorations exhibiting moderate marginal leakage (Score 1) was compared against the number of restorations demonstrating severe marginal leakage (Score 2). No statistically significant differ­ ences were found between the experimental marginal + + + Isomcl. Bueliler l.lil. 2I2H Greenwood Street. Lv.instou. Illinois. U.S.A. + + + + Univar. Reichert. Vienna. Austria. Tydskrif vir die T. V.S. A. — Desembcr 1980 822 Experimental marginal leakage Tqble 1 Results of experimental marginal leakage around etched and unctchcd Compocap S® and Isocap® restorations. SCORE: 0 1 2 Material Etched or unctchcd n % n % n % Compocap SR etched 0 0 13 62 8 38 unctchcd 0 0 1 9 10 91 Isocap1' etched 0 0 9 43 12 57 unctchcd 0 0 1 7 13 93 leakage around the IsocapK and Compocap1* rcstora- tions. However, statistically significant differences were found between the etched and unetched specimens. Restorations placed in conjunction with the etching lechnic]uc displayed less marginal leakage. DISCUSSION Enamel fractures, (Fig. 2) possibly produced during mechanical cavity preparation, thermal stressing (As- niusscn 1974), polymerization shrinkage or elastic hys­ teresis (Jyfrgcnsen, Asmusscn and Shimokobe, 1975) may account for the fact that all the restorations leaked. The results appear to advocate the use of an etching technique as a significant difference (p < 0,01) was found between resolutions placed in etched and mi­ ddled preparations. This conclusion is supported by numerous studies including those of Relief (1973), Ba- harloo and Moore (1974), Eliasson and Mill (1977) and Dogan et al (1980). Unetched cavity preparations filled with either type of restorative material permitted more leakage than restorations placed in conjunction with the etch technique. Another technique advocated in order to limit marginal leakage, other than acid etching, is the use of a primer resin (also referred to as an intermediary resin). Al­ though the acid etch technique is widely accepted, the use of a primer resin is controversial. Recent exper­ imental marginal leakage studies on microfill restora- :ivc materials have however supported the use of a 'rimer rosin (Dogan et al 1980; Valcke and Austin 3/80). Although Eliasson and Mill (1977) staled that the des­ igns of cavosurface margins have little influence on marginal leakage patterns, the use of a bevel has been advocated (Bjorvatin, 1975; Erikscn and Buonocor. 1976; Soekwell 1976). A bevel may increase the enamel surface area which comes into contact with the restora­ tive material that mechanically bonds to it. The use of a restorativc-fcathcr-cdge technique (Buonoeore, Sheyk- holcslam and Glena, 1973) may also provide an in­ creased enamel surface area whilst also sealing frac­ tures associated with the cavity preparation. Although the bevelled preparation and/or rcsloralive-feathcr- jedge technique appear to be theoretically sound, there lire practical limitations especially on the cervical mar­ gins of restorations where the tooth enamel is thin (if still present) and the gingival tissue is close to the prep- liy .2 Experiment;)! Marginal leakage of fluorescent live (I-) between a restoration (R) anil enamel (It). The fluorescent dye lias also penetrated into an enamel fracture, x 50. aration. 0 ilo and Jorgensen (1977) showed that be­ velled margins display a reduced number of restora­ tions with fractures in enamel. Thus bevels may not only increase enamel — restorative material interlace areas, but in some tooth legions may reduce the number of fractures which result along the cavity mar­ gins. Isoeapu which has a relatively high coefficient of ther­ mal expansion has performed satisfactorily in clinical studies (Bryant, Rees and Ross, 1979 and Christensen and Christensen, 1980). 'This may be due to the low thermal diffusity of this resin which reduces the effects of thermal stresses (McLean, 1979; Braden, 1979), the sufficient expansion due to water absorption (Bryant et al 1979) and /or other manipulation and clinical factors. A C K N O W L LDG EM ENTS We would like to thank Professors P.E. Clcaton-Joncs, and C.F. Valcke, Dr. J.C. Austin, Miss E. Vieira and Mrs. E. Pain for their guidance and assistance and Mrs. J. Parker for typing this manuscript. REFERENCES Asmusscn. IT (197*1) The effect of temperature changes on ailapt- ution of resin fillings I . Ada. (Jdontoloyica Scandinavica, 32, 161- 171. Asmusscn, E. & J/rgenscn, K.D. (I97. & Jorgensen, K.D. (1977) Effect of bevelling on the occur- ance of fractures in the enamel surrounding composite resin fill­ ings. Journal o f Oral Rehabilitation, 4, 305-309. Retief, D.ll. (1973) Effect on conditioning the enamel surface with Phosphoric Acid. Journal o f Dental Research. 52. 333-341. Roydhouse, R.I I.. (1908) Penetration around the margins of restora­ tions: 2. Nature and significance. Journal o f the Canadian Dental Association, 34, 21-28. Sockwell. C.L. (1970) Clinical evaluation of anterior restorative ma­ terials. The Dental Clinics o f North America, 20, 403-422. Swartz. M.L. & Phillips. R.W. (1902) Influence of manipulative var­ iables on the marginal adaptation of certain restorative materials. Journal o f Prosthetic Dentistry, 12, 172-181. Valcke. CM', it Austin. J.C. (1980) The Effectiveness of a Primer (contact resin) in Diminishing the Marginal Leakage of a Direct Filling Resin (Isopast). Journal o f the Dental Association of South Africa, in press. ANDREW JODAIKIN is a graduate of the University of the Witwatersrand (1978). After a short period in general practice he joined the Dental Research Insti­ tute at his alma-mater where he was involved in various research projects as well as an MSc. He is at present in the Department of Conservative Dentistry where he is responsible' for the undergraduate dental materials course whilst continuing his research and MSc. OTTO SPARRIUS also qualified at the University of the Witwatersrand in 1978, since when he has been in private practice in Johannesburg. Dr Sparrius has shown a keen interest in computers and has attended the Wits Technikon to further his knowledge. During his undergraduate days he was chairman of the Wits Fencing Club and a member of the Protea touring team (drawn from a number of South African Universities) which toured Europe in 1974! Tydskrif vir die T.V.S.A. — Dcsember 1980 824