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Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report

Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report Objective: To measure the long-term linear hygroscopic expansion (LHE) of several ma- terials using bulked and layered techniques. Materials and Methods: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for each material using layered and bulked techniques (each group comprises five specimens). The specimens were stored in distilled water at 37°C. The length of each specimen was meas- ured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used. Results: The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively. However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansion until six month, whereas bulked specimens reached the constant length at three months. Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except be- tween 24 hours and one year measurements. But in bulked specimens, the results at nine months and one year were significantly different from those obtained at three months and Corresponding author: before. H. Torabzadeh, Department of Conclusion: Fuji II showed no significant LHE and resin-modified glass ionomer cements Operative Dentistry, School of (RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in compar- Dentistry, Shahid Beheshti University of Medical Sciences, ison with RMGIC and composite resin. Tehran, Iran. 5htorabzadeh@gmail.com Key Words: Absorption; Water; Composite Resins; Glass Ionomer Cements; Compomers Received: 9 August 2010 Accepted: 24 November 2010 Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2011; Vol. 8, No.1) INTRODUCTION some relief from the curing shrinkage may The polymerization of a light-cured material arise from water uptake. The water that diffus- will result in shrinkage of the restoration. This es into the material causes a gradual expan- may lead to the formation of interfacial gaps. sion, up to a certain equilibrium value which These are believed to cause microleakage, will contribute to relaxation of shear stresses. postoperative sensitivity, recurrent caries and In contrast to the rather rapid polymerization eventual loss of the restorations [1,2]. contraction and stress development, the hygro- After exposure of the restoration to oral fluids, scopic relief will proceed slowly and might 2011; Vol. 8, No. 1 25 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. even take days [3,4]. Hygroscopic expansion modified composite resin and dual curing may compensate for the curing shrinkage composite, respectively; concluding that the thereby improving the marginal quality of the hygroscopic expansion of the polyacid- restoration and closing of the gap [5-7]. The modified composite resin material was signifi- rate and magnitude of hygroscopic expansion cantly greater than that of the composite resin of a resin material depends on several varia- tested [14]. bles such as the nature of the resin, the type of Investigations of linear hygroscopic expansion filler, filler loading, filler matrix adhesion and of the resin-modified GICs are limited, espe- the volumetric ratio between the filler and ma- cially regarding their long-term expansion. trix [8-10]. The aim of this study was to investigate the Results from a 7-day-study showed that the long-term linear hygroscopic expansion of hygroscopic expansion of composites reached resin-modified GICs in comparison with those equilibrium after approximately four to six of a conventional GIC, a polyacid-modified days depending on the materials investigated composite resin and two composite resins. The [8]. Whereas, in another study, an increased magnitude of the hygroscopic expansion of water absorption was observed during the first specimens which were made using bulk inser- month for all composite resins with a further tion techniques was also investigated. small increase up to six months [6]. The linear hygroscopic expansion of conven- MATERIALS AND METHODS tional and resin-modified GIC liners was The materials used in this study were Fuji Cap measured for up to one week [11]. It was ob- II, Fuji II LC, Photac-Fil Aplicap, Vitremer, served that the dimensions of the conventional Dyract, Tetric and Z 100 (Table 1). GICs did not show any significant change after The moulds (6×4 mm) used for specimen 30 minutes of immersion, while the resin- preparation were of the split-body type, con- modified cements exhibited changes up to 24 structed of stainless steel. Before use, a dry hours and remained constant for the next PTFE (Poly Tetra Fluoro-Ethylene) separating week. The resin modified GIC liners showed a film was utilized to facilitate removal of the significantly higher expansion than the con- specimens. The mould was placed on a clean ventional cements, a finding which was con- glass plate that had been coated with a PTFE firmed by other studies [12,13]. It was also film. The restorative material was mixed and reported that at six months, the mean change handled according to the respective manufac- in linear expansion was 0.16%, 0.66% and turer’s instructions. It was packed in three two- 0.32% for the microfilled composite, polyacid- milimeter thick increments. The mould was Table 1. Details of the materials used in this study. Time (seconds) P : L Name Description Manufacturer Batch No. Ratio Setting Working Curing Conventional GIC GC International, Tokyo, Japan Fuji Cap II 225 105 - E 911225 P:211212 Fuji II LC Resin-modified GIC GC International, Tokyo, Japan - 195 20 3.0/1.0 L: 29111 Photac-Fil Espe GMBH, Seefed/Oberbay Resin-modified GIC - 180 20 E 0003 Germany Aplicap Vitremer Resin-modified GIC 3M, Health Care, St Paul USA 240 180 40 2.5/1.0 19930520 Polyacid modified C. Dentsply/De Trey, Surrey England Dyract - - 40 - 921082 Tetric Fluoridated C. resin Vivadent, Schaan, Liechtensein - - 40 - 462284 C. resin 3M, Health Care, St. Paul USA Z 100 - - 40 - 19940413 P=Powder, L=Liquid, E=Encapsulated, C.=Composite 2011; Vol. 8, No. 1 26 Emamieh et al. Hygroscopic Expansion of Restorative Materials overfilled with the restorative material and the percentage change in the length of the ma- another glass plate was placed over it with terials. firm pressure. Each layer of the material was The specimens were removed from the water light cured separately using the Visilux 2 (3M, after 24 hours, one week, one month, three USA) curing unit for the recommended time. months, six months, nine months and one year Fuji Cap II was inserted into the mould in one following preparation and dried using tissue bulk and the specimens were left for 10 paper. The length of the specimens was again minutes at 37°C and 100% humidity. Five measured as mentioned above and the linear specimens were made for each material. To expansion of the materials was presented as assess the effect of a bulk insertion technique the percentage of change of the specimens in on the expansion of the light-cured materials, relation to the baseline measurement. The five more specimens were made for each of mean hygroscopic expansion and standard these materials. To prepare these specimens, deviation (SD) were calculated for each mate- the material was applied in bulk until the rial at various time intervals. Repeated meas- mould was overfilled and light-cured from ure analysis was used to determine the effect both sides simultaneously using two light- of variables. P value lower than 0.05 was re- curing units Visilux II and Caulk Max; L.D. garded as statistically significant. Paired sam- (Dentsply, Germany). ple t-test with Bonferroni correction was em- After curing, any flash of excess material was ployed to assess the difference between the removed so that the surfaces of the specimen means of the two groups. were flush with the surfaces of the mould and were perpendicular to the long axis of the RESULTS specimen. This was achieved by lapping the The results obtained are presented in Tables 2 mould containing the test specimen on 1000- and 3. Results indicated that material had a grit paper. Lapping was carried out in as short significant effect on the expansion (P<0.001). a time as possible without using water to elim- Therefore, the results were further subjected to inate the effect of hydration. After lapping, the Tukey HSD test. Significant differences be- specimen was removed and stored in a sepa- tween all materials were revealed. Photac-Fil rate plastic bottle containing distilled water at Aplicap showed the highest expansion values 37°C for up to one year. Prior to storage, the followed by Fuji II LC and Vitremer; whereas, length of each specimen was measured three Fuji Cap II exhibited the least expansion. Bulk times using a digital micrometer (Mitutoyo, inserted specimens showed higher expansion Mitutoyo Corporation, Japan) and the mean of than layered specimens (P<0.001) except for the three readings was used for calculation of Z100. Table 2. The linear hygroscopic expansion (%) of layered specimens in different time intervals. Photac-Fil Fuji Cap II Fuji II LC Vitremer Dyract Tetric Z100 Aplicap Time Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 24 hours 0.047 0.088 1.483 0.122 2.548 0.068 1.339 0.155 0.057 0.164 0.001 0.036 0.037 0.038 1 week 0.111 0.071 1.766 0.117 2.815 0.074 1.471 0.151 0.168 0.053 0.108 0.019 0.174 0.033 1 month 0.084 0.063 1.952 0.118 2.980 0.050 1.617 0.134 0.363 0.034 0.209 0.054 0.325 0.009 3 months 0.010 0.086 1.966 0.123 2.963 0.053 1.600 0.145 0.551 0.066 0.229 0.033 0.385 0.023 6 months 0.017 0.027 2.032 0.070 3.052 0.054 1.631 0.142 0.783 0.053 0.259 0.051 0.429 0.009 0.014 0.060 2.124 0.107 3.126 0.077 1.698 0.147 0.870 0.044 0.333 0.036 0.449 0.037 9 months 1 year 0.037 0.047 2.111 0.139 3.149 0.073 1.688 0.158 0.867 0.070 0.336 0.057 0.473 0.025 2011; Vol. 8, No. 1 27 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. 3.5 Fuji Cap II 2.5 Fuji II LC Photac-Fil Aplicap Vitremer 1.5 Dyract Tetric 0.5 Z100 24 hours 1 week 1 month 3 months 6 months 9 months 1 year Fig 1. The linear hygroscopic expansion of layered technique in different time intervals. The interaction between material and method respectively). However, the interaction be- of preparation was significant (P<0.01). This tween time and material was significant could be explained by the fact that Z100 was (P<0.001), which could be elucidated by the the only material that exhibited similar expan- difference in the hygroscopic expansion slope sion for both layered and bulk inserted speci- of materials (Fig 1). mens (0.325 vs 0.330). Results also indicated that all materials had DISCUSSION significant expansion during the test period. Dimensional changes of restorative materials Paired sample t-test showed that the time to caused by hygroscopic expansion may be de- reach a constant level differs for each material. termined by a variety of equipment and test For instance, Fuji Cap II, Fuji II LC and Tetric methods such as hydrostatic or Archimede’s achieved the constant length at three months, principle [12,15,16]; model cavities cut in while this time was six months for Photac-Fil brass, in which the hygroscopic expansion of Aplicap and Z100 and nine months for the material was expressed by the displace- Vitremer and Dyract. ment force generated due to water sorption The interaction between time, material and [6,17]; the ability of materials in reducing the method of preparation as well as the interac- marginal gap [5]; measuring the relaxation of tion between time and method of preparation setting shrinkage shear stress [18]; measuring was not significant (P=0.330 and P=0.151, the length of specimens by means of an elec- Table 3. The linear hygroscopic expansion (%) of bulk specimens in different time intervals. Photac-Fil Fuji II LC Vitremer Dyract Tetric Z100 Aplicap Time Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 24 hours 1.319 0.094 2.349 0.076 1.135 0.095 0.104 0.040 0.057 0.035 0.037 0.036 1 week 1.601 0.117 2.621 0.042 1.202 0.116 0.047 0.047 0.024 0.044 0.181 0.042 1 month 1.709 0.106 2.709 0.035 1.304 0.121 0.245 0.040 0.117 0.043 0.339 0.040 3 months 1.793 0.121 92.806 0.052 1.382 0.133 0.446 0.040 0.198 0.055 0.389 0.028 6 months 1.874 0.134 92.830 0.037 1.385 0.098 0.650 0.035 0.218 0.042 0.443 0.038 1.961 0.128 92.853 0.020 1.493 0.105 0.683 0.026 0.228 0.039 0.439 0.014 9 months 1 year 1.965 0.131 92.894 0.060 1.476 0.100 0.714 0.053 0.231 0.033 0.479 0.026 2011; Vol. 8, No. 1 28 Emamieh et al. Hygroscopic Expansion of Restorative Materials tric or a computer-controlled laser micrometer This is in agreement with the results of the or a microscope [8,11,14,19,20]. In the present present study. study, a micrometer with an accuracy of one The higher linear expansion for the resin- micron was used to measure the change in the modified GICs observed in the present study is length of cylindrical specimens (6×4 mm). The in agreement with the result of recent investi- procedure proved to be uncomplicated and the gations [11]. Irie et al [20] reported that the equipment was inexpensive. In addition, the resin-modified GIC liners showed significantly advantages of using specimens with the above higher linear expansion than the conventional dimensions were that they simulated relatively cements, the magnitude of which was in the large dental restorations. range of 2.4% - 6.3%. In Kimishima et al’s In this study, unlike the conventional GIC, the [21], Vitremer showed slightly less expansion resin-modified cements showed significant (4.98%) than Fuji II LC (5.44%), which is in expansion. The pattern of such expansion dif- line with the results of the present study. fered according to the material tested. As men- This high linear expansion of resin-modified tioned earlier Fuji Cap II, Fuji II LC and Tetric GICs could be attributed to the presence of reached a constant length after about three hydrophilic resin HEMA in resin-modified months while more time was necessary for cements. The higher linear expansion associat- Photac-Fil Aplicap and Z100 (six months). ed with Dyract, in comparison with that of Dyract and Vitremerl required nine months to composite resins, could also be explained by reach a constant length. the fact that this material also contained some The finding that a relatively long time was hydrophilic monomers [22,23]. It was reported required for the composite materials to reach a that at six months, Dyract showed a linear ex- constant length is in agreement with that of pansion (0.66%) greater than that of either a Momoi and McCabe [6], who observed an light-cured composite (0.16%) or a dual-cured increase in the displacement force due to water composite resin (0.32%) [14]. In addition, it uptake during the six-month test period. They was shown that Fuji II LC produced the great- suggested that such an increase indicated that est (38 MPa) and most rapid rise in lateral there were regions within the specimens that stress brought about by hygroscopic expan- were not fully saturated [6]. In another study, sion. Z100 and Tetric produced a linear rise up however, after seven days of storage in water to six and four MPa, respectively. Dyract pro- at 37°C, all composite materials showed sig- duced 7 MPa stress by one month [17]. These nificant hygroscopic expansion that did not findings are congruent with the results of the significantly increase further until the 30-day present study where Dyract showed a hygro- storage [7]. scopic expansion intermediate to that of the It was observed that the dimensions of conven- resin-modified GICs and composite resins. tional GICs did not show any significant The results currently recorded for Fuji Cap II change after 30 minutes of immersion in wa- must be viewed with caution. In the present ter, while the resin modified cements exhibited study, the specimens made from Fuji Cap II changes up to 24 hours and remained constant were maintained at 37°C and 100% relative for the next week. The composite resin used humidity for 10 minutes. Therefore, the first demonstrated a significantly continuous in- measurement was performed approximately 20 crease during the period of the study (one minutes after mixing (taking into account the week). These results indicate that composite time required for lapping). Since conventional resins require a longer time than the resin- GICs undergo setting shrinkage immediately modified GICs to reach a constant length [11]. after setting, this delay in measurement might 2011; Vol. 8, No. 1 29 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. have had an effect on the results. For all other that the hygroscopic expansion of composite materials which were all of the light-curing resins during a 6-month study resulted in pres- type, the measurements were carried out with- sure values of 3.3 to 14.5 MPa dependent on in 5 minutes after curing. the material. They suggested that positive Except for Z100, the difference between the pressure of a similar magnitude pushing linear hygroscopic expansion of the layered against the cavity walls may be capable of and bulk inserted specimens was generally putting the supporting tooth tissues under con- significant, with the bulk inserted specimens siderable stress [6]. showing less expansion. This finding is in Using the results of this study and the modulus agreement with that of Bowen et al [19], who of material elasticity provided by another reported that when a composite resin was study, the magnitude of the pressure generated placed in bulk it had more shrinkage, less hy- from the expansion of the materials tested may groscopic expansion and some degree of re- be calculated from the following equation: sidual shrinkage. The higher shrinkage of a Stress=Strain×E, where E is the modulus of material placed in bulk; therefore, might ac- elasticity of a material and strain is the expan- count for the lower hygroscopic expansion sion (%) of the material at a given time [26]. observed in this study. However, it is known Such calculations gave pressure values of that restorations that are inserted in bulk show 124.55 MPa for Photac-Fil Aplicap, 111.33 wider marginal gaps and more microleakage MPa for Vitremer, 103.41 MPa for Fuji II LC, [24]. 44.66 MPa for Dyract, 34.95 MPa for Z100, As discussed earlier, the setting shrinkage of 11.04 MPa for Tetric and 0.52 MPa for Fuji restorative materials results in marginal gap Cap II; each calculation was made using the formation, microleakage and probably recur- values obtained at the time when the material rent caries. Hygroscopic expansion may com- reached its constant length. These values are pensate for this shrinkage and close the mar- much higher than those reported by Momoi ginal gap. Since the expansion occurs some- and McCabe [6], Watts et al [17]. time after the shrinkage has taken place, the The reason might be due to the test methods expansion will not lead to the re-establishment employed. These studies employed a model of any broken adhesive bonds and perfect clo- cavity design, in which the materials were in- sure. serted in a brass mould and the pressure re- During its earliest stages, expansion may quired to displace the specimens was calculat- simply cause a closing up of the contraction ed. The presence of such close contact be- gaps caused by setting shrinkage. Continued tween the brass and test material might have expansion, however, may cause development led to a lesser water absorption, hence less of an outward pressure against the cavity hygroscopic expansion than that recorded in walls. Estimation of the magnitude of this the present study [6,17]. pressure may enable its clinical significance to be inferred. Feilzer et al [25] suggested that in CONCLUSION the clinical situation, a slight positive stress is 1. Fuji Cap II showed the least linear hygro- preferable to a tensile stress as it may improve scopic expansion during the study. The resin- the marginal integrity of a restoration. They modified GICs exhibited the highest linear found that when the experiments ended after hygroscopic expansion among the materials 15 hours, a further build-up of compressive tested. Photac-Fil Aplicap showed the highest stress was observed with the resin-modified hygroscopic expansion between the resin- GICs [25]. Momoi and McCabe [6] reported modified cements. 2011; Vol. 8, No. 1 30 Emamieh et al. Hygroscopic Expansion of Restorative Materials 2. The time to reach a constant level was var- characteristics of composites for use in posterior ied, acquiring three to nine months depending teeth. J Dent Res 1986 Nov;65(11):1315-8. on the material tested. 10- Floyd CJ, Dickens SH. Network structure of 3. The initial linear expansion of Dyract was Bis-GMA and UDMA-based resin systems. Dent similar to that observed with composite resins. Mater 2006 Dec;22(12):1143-9. At one year, however, its linear expansion was 11- Irie M, Nakai H. Effect of immersion in water significantly higher than the composite resins. on linear expansion and strength of three base/liner materials. Dent Mater J 1995 Jun;14(1):70-7. ACKNOWLEDGMENTS 12- Attin T, Buchalla W, Kielbassa AM, Helwig E. We thank Dr. S. Mohammad Reza Safavi head Curing shrinkage and volumetric changes of resin- of Dental Research Center of Shahid Beheshti modified glass ionomer restorative materials. Dent University of Medical Sciences for providing Mater 1995 Nov;11(6):359-62. the opportunity to prepare the manuscript and 13- Pospiech P, Rammelsberg P, Tichy H, Gernet Dr. Alireza Akbarzadeh Baghban for his help W. The suitability of compomers as a core- in statistics. material: investigation on the volume stability. J Dent Res1995;74:475. REFERENCES 14- Martin RS, Jedynakiewicz NM. Measurement 1- Brannstrom M. Infection beneath composite of hygroscopic expansion of composite restora- resin restorations: can it be avoided? Oper Dent tives. J Dent Res 1995;74:462. 1978 Autumn;12(4):158-63. 15- Chutinan S, Platt JA, Cochran MA, Moore BK. 2- Phillips RW. Bonding agents and adhesives. Adv Volumetric dimensional change of six direct core Dent Res1988 Aug;2(1):150-4. materials. Dent Mater 2004 May;20(4):345-51. 3- van Noort R. What’s in a number? Todays Den- 16- Watts DC, Kisumbi BK, Toworfe GK. Dimen- tist 1988;1:1-5. sional changes of resin/ionomer restoratives in 4- Yap AU, Wang HB, Siow KS, Gan LM. aqueous and neutral media. Dent Mater 2000 Polymerization shrinkage of visible-light-cured Mar;16(2):89-96. composites. Oper Dent 2000 Mar-Apr;25(2):98- 17- Watts DC, el-Hejazi AA, AL-Hindi A. Hygro- 103. scopic-stress-development of resin-based restora- 5- Asmussen E, Jorgensen KD. A microscopic in- tives in situ. J Dent Res 1995;74:462. vestigation of the adaptation of some plastic filling 18- Feilzer AJ, de Gee AJ, Davidson CL. Relaxa- materials to dental cavity walls. Acta Odontol tion of polymerization contraction shear stress by Scand 1972 Mar;30(1):3-21. hygroscopic expansion. J Dent Res 1990 Jan;69(1): 6- Momoi Y, McCabe JF. Hygroscopic expansion 36-9. of resin based composites during 6 months of wa- 19- Bowen RL, Rapson JE, Dickson G. Hardening ter storage. Br Dent J 1994 Feb;176(3):91-6. shrinkage and hygroscopic expansion of composite 7- Ruttermann S, Kruger S, Raab WH, Janda R. resins. J Dent Res 1982 May;61(5):654-8. Polymerization shrinkage and hygroscopic expan- 20- Irie M, Nakai H, Hirota K. Marginal gap of sion of contemporary posterior resin-based filling light-activated glass-ionomer: effect of hygroscop- materials—a comparative study. J Dent 2007 Oct; ic expansion. J Dent Res 1992;71:633. 35(10):806-13. 21- Kimishima T, Shibaoka N, Enomoto H. Water 8- Hirasawa T, Hirano S, Hirabayashi S, Harashima expansion and microleakage of glass ionomer ce- I, Aizawa M. Initial dimensional change of compo- ments. J Dent Res 1996;75:73. sites in dry and wet conditions. J Dent Res 1983 22- Kanchanavasita W, Pearson GJ, Anstice HM. Jan;62(1):28-31. Influence of humidity on dimensional stability of a 9- Øysæd H, Ruyter IE. Water sorption and filler range of ion-leachable cements. Biomaterials 1995 2011; Vol. 8, No. 1 31 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. Aug;16(12):921-9. 25- Feilzer AJ, Kakaboura AI, de Gee AJ, Da- 23- Toldano M, Osorio R, Fuentes V, Prati C, Gar- vidson CL. The influence of water sorption on the cia-Godoy F. Sorption and solubility of resin-based development of setting shrinkage stress in tradi- restorative dental materials. J Dent 2003 Jan;31(1): tional and resin-modified glass ionomer cements. 43-50. Dent Mater 1995 May;11(3):186-90. 24- Koenigsberg S, Fuks A, Grajower R. The effect 26- Torabzadeh H. Laboratory and clinical investi- of three filling techniques on marginal leakage gations into resin-modified glass-ionomer cements around Class II composite resin restorations in and related materials. Ph.D. thesis, Bristol: Univer- vitro. Quintessence Int 1989 Feb;20(2):117-21. sity of Bristol. 1996. 2011; Vol. 8, No. 1 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Dentistry (Tehran, Iran) Pubmed Central

Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report

Journal of Dentistry (Tehran, Iran) , Volume 8 (1) – Mar 31, 2011

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Abstract

Objective: To measure the long-term linear hygroscopic expansion (LHE) of several ma- terials using bulked and layered techniques. Materials and Methods: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for each material using layered and bulked techniques (each group comprises five specimens). The specimens were stored in distilled water at 37°C. The length of each specimen was meas- ured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used. Results: The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively. However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansion until six month, whereas bulked specimens reached the constant length at three months. Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except be- tween 24 hours and one year measurements. But in bulked specimens, the results at nine months and one year were significantly different from those obtained at three months and Corresponding author: before. H. Torabzadeh, Department of Conclusion: Fuji II showed no significant LHE and resin-modified glass ionomer cements Operative Dentistry, School of (RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in compar- Dentistry, Shahid Beheshti University of Medical Sciences, ison with RMGIC and composite resin. Tehran, Iran. 5htorabzadeh@gmail.com Key Words: Absorption; Water; Composite Resins; Glass Ionomer Cements; Compomers Received: 9 August 2010 Accepted: 24 November 2010 Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2011; Vol. 8, No.1) INTRODUCTION some relief from the curing shrinkage may The polymerization of a light-cured material arise from water uptake. The water that diffus- will result in shrinkage of the restoration. This es into the material causes a gradual expan- may lead to the formation of interfacial gaps. sion, up to a certain equilibrium value which These are believed to cause microleakage, will contribute to relaxation of shear stresses. postoperative sensitivity, recurrent caries and In contrast to the rather rapid polymerization eventual loss of the restorations [1,2]. contraction and stress development, the hygro- After exposure of the restoration to oral fluids, scopic relief will proceed slowly and might 2011; Vol. 8, No. 1 25 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. even take days [3,4]. Hygroscopic expansion modified composite resin and dual curing may compensate for the curing shrinkage composite, respectively; concluding that the thereby improving the marginal quality of the hygroscopic expansion of the polyacid- restoration and closing of the gap [5-7]. The modified composite resin material was signifi- rate and magnitude of hygroscopic expansion cantly greater than that of the composite resin of a resin material depends on several varia- tested [14]. bles such as the nature of the resin, the type of Investigations of linear hygroscopic expansion filler, filler loading, filler matrix adhesion and of the resin-modified GICs are limited, espe- the volumetric ratio between the filler and ma- cially regarding their long-term expansion. trix [8-10]. The aim of this study was to investigate the Results from a 7-day-study showed that the long-term linear hygroscopic expansion of hygroscopic expansion of composites reached resin-modified GICs in comparison with those equilibrium after approximately four to six of a conventional GIC, a polyacid-modified days depending on the materials investigated composite resin and two composite resins. The [8]. Whereas, in another study, an increased magnitude of the hygroscopic expansion of water absorption was observed during the first specimens which were made using bulk inser- month for all composite resins with a further tion techniques was also investigated. small increase up to six months [6]. The linear hygroscopic expansion of conven- MATERIALS AND METHODS tional and resin-modified GIC liners was The materials used in this study were Fuji Cap measured for up to one week [11]. It was ob- II, Fuji II LC, Photac-Fil Aplicap, Vitremer, served that the dimensions of the conventional Dyract, Tetric and Z 100 (Table 1). GICs did not show any significant change after The moulds (6×4 mm) used for specimen 30 minutes of immersion, while the resin- preparation were of the split-body type, con- modified cements exhibited changes up to 24 structed of stainless steel. Before use, a dry hours and remained constant for the next PTFE (Poly Tetra Fluoro-Ethylene) separating week. The resin modified GIC liners showed a film was utilized to facilitate removal of the significantly higher expansion than the con- specimens. The mould was placed on a clean ventional cements, a finding which was con- glass plate that had been coated with a PTFE firmed by other studies [12,13]. It was also film. The restorative material was mixed and reported that at six months, the mean change handled according to the respective manufac- in linear expansion was 0.16%, 0.66% and turer’s instructions. It was packed in three two- 0.32% for the microfilled composite, polyacid- milimeter thick increments. The mould was Table 1. Details of the materials used in this study. Time (seconds) P : L Name Description Manufacturer Batch No. Ratio Setting Working Curing Conventional GIC GC International, Tokyo, Japan Fuji Cap II 225 105 - E 911225 P:211212 Fuji II LC Resin-modified GIC GC International, Tokyo, Japan - 195 20 3.0/1.0 L: 29111 Photac-Fil Espe GMBH, Seefed/Oberbay Resin-modified GIC - 180 20 E 0003 Germany Aplicap Vitremer Resin-modified GIC 3M, Health Care, St Paul USA 240 180 40 2.5/1.0 19930520 Polyacid modified C. Dentsply/De Trey, Surrey England Dyract - - 40 - 921082 Tetric Fluoridated C. resin Vivadent, Schaan, Liechtensein - - 40 - 462284 C. resin 3M, Health Care, St. Paul USA Z 100 - - 40 - 19940413 P=Powder, L=Liquid, E=Encapsulated, C.=Composite 2011; Vol. 8, No. 1 26 Emamieh et al. Hygroscopic Expansion of Restorative Materials overfilled with the restorative material and the percentage change in the length of the ma- another glass plate was placed over it with terials. firm pressure. Each layer of the material was The specimens were removed from the water light cured separately using the Visilux 2 (3M, after 24 hours, one week, one month, three USA) curing unit for the recommended time. months, six months, nine months and one year Fuji Cap II was inserted into the mould in one following preparation and dried using tissue bulk and the specimens were left for 10 paper. The length of the specimens was again minutes at 37°C and 100% humidity. Five measured as mentioned above and the linear specimens were made for each material. To expansion of the materials was presented as assess the effect of a bulk insertion technique the percentage of change of the specimens in on the expansion of the light-cured materials, relation to the baseline measurement. The five more specimens were made for each of mean hygroscopic expansion and standard these materials. To prepare these specimens, deviation (SD) were calculated for each mate- the material was applied in bulk until the rial at various time intervals. Repeated meas- mould was overfilled and light-cured from ure analysis was used to determine the effect both sides simultaneously using two light- of variables. P value lower than 0.05 was re- curing units Visilux II and Caulk Max; L.D. garded as statistically significant. Paired sam- (Dentsply, Germany). ple t-test with Bonferroni correction was em- After curing, any flash of excess material was ployed to assess the difference between the removed so that the surfaces of the specimen means of the two groups. were flush with the surfaces of the mould and were perpendicular to the long axis of the RESULTS specimen. This was achieved by lapping the The results obtained are presented in Tables 2 mould containing the test specimen on 1000- and 3. Results indicated that material had a grit paper. Lapping was carried out in as short significant effect on the expansion (P<0.001). a time as possible without using water to elim- Therefore, the results were further subjected to inate the effect of hydration. After lapping, the Tukey HSD test. Significant differences be- specimen was removed and stored in a sepa- tween all materials were revealed. Photac-Fil rate plastic bottle containing distilled water at Aplicap showed the highest expansion values 37°C for up to one year. Prior to storage, the followed by Fuji II LC and Vitremer; whereas, length of each specimen was measured three Fuji Cap II exhibited the least expansion. Bulk times using a digital micrometer (Mitutoyo, inserted specimens showed higher expansion Mitutoyo Corporation, Japan) and the mean of than layered specimens (P<0.001) except for the three readings was used for calculation of Z100. Table 2. The linear hygroscopic expansion (%) of layered specimens in different time intervals. Photac-Fil Fuji Cap II Fuji II LC Vitremer Dyract Tetric Z100 Aplicap Time Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 24 hours 0.047 0.088 1.483 0.122 2.548 0.068 1.339 0.155 0.057 0.164 0.001 0.036 0.037 0.038 1 week 0.111 0.071 1.766 0.117 2.815 0.074 1.471 0.151 0.168 0.053 0.108 0.019 0.174 0.033 1 month 0.084 0.063 1.952 0.118 2.980 0.050 1.617 0.134 0.363 0.034 0.209 0.054 0.325 0.009 3 months 0.010 0.086 1.966 0.123 2.963 0.053 1.600 0.145 0.551 0.066 0.229 0.033 0.385 0.023 6 months 0.017 0.027 2.032 0.070 3.052 0.054 1.631 0.142 0.783 0.053 0.259 0.051 0.429 0.009 0.014 0.060 2.124 0.107 3.126 0.077 1.698 0.147 0.870 0.044 0.333 0.036 0.449 0.037 9 months 1 year 0.037 0.047 2.111 0.139 3.149 0.073 1.688 0.158 0.867 0.070 0.336 0.057 0.473 0.025 2011; Vol. 8, No. 1 27 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. 3.5 Fuji Cap II 2.5 Fuji II LC Photac-Fil Aplicap Vitremer 1.5 Dyract Tetric 0.5 Z100 24 hours 1 week 1 month 3 months 6 months 9 months 1 year Fig 1. The linear hygroscopic expansion of layered technique in different time intervals. The interaction between material and method respectively). However, the interaction be- of preparation was significant (P<0.01). This tween time and material was significant could be explained by the fact that Z100 was (P<0.001), which could be elucidated by the the only material that exhibited similar expan- difference in the hygroscopic expansion slope sion for both layered and bulk inserted speci- of materials (Fig 1). mens (0.325 vs 0.330). Results also indicated that all materials had DISCUSSION significant expansion during the test period. Dimensional changes of restorative materials Paired sample t-test showed that the time to caused by hygroscopic expansion may be de- reach a constant level differs for each material. termined by a variety of equipment and test For instance, Fuji Cap II, Fuji II LC and Tetric methods such as hydrostatic or Archimede’s achieved the constant length at three months, principle [12,15,16]; model cavities cut in while this time was six months for Photac-Fil brass, in which the hygroscopic expansion of Aplicap and Z100 and nine months for the material was expressed by the displace- Vitremer and Dyract. ment force generated due to water sorption The interaction between time, material and [6,17]; the ability of materials in reducing the method of preparation as well as the interac- marginal gap [5]; measuring the relaxation of tion between time and method of preparation setting shrinkage shear stress [18]; measuring was not significant (P=0.330 and P=0.151, the length of specimens by means of an elec- Table 3. The linear hygroscopic expansion (%) of bulk specimens in different time intervals. Photac-Fil Fuji II LC Vitremer Dyract Tetric Z100 Aplicap Time Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 24 hours 1.319 0.094 2.349 0.076 1.135 0.095 0.104 0.040 0.057 0.035 0.037 0.036 1 week 1.601 0.117 2.621 0.042 1.202 0.116 0.047 0.047 0.024 0.044 0.181 0.042 1 month 1.709 0.106 2.709 0.035 1.304 0.121 0.245 0.040 0.117 0.043 0.339 0.040 3 months 1.793 0.121 92.806 0.052 1.382 0.133 0.446 0.040 0.198 0.055 0.389 0.028 6 months 1.874 0.134 92.830 0.037 1.385 0.098 0.650 0.035 0.218 0.042 0.443 0.038 1.961 0.128 92.853 0.020 1.493 0.105 0.683 0.026 0.228 0.039 0.439 0.014 9 months 1 year 1.965 0.131 92.894 0.060 1.476 0.100 0.714 0.053 0.231 0.033 0.479 0.026 2011; Vol. 8, No. 1 28 Emamieh et al. Hygroscopic Expansion of Restorative Materials tric or a computer-controlled laser micrometer This is in agreement with the results of the or a microscope [8,11,14,19,20]. In the present present study. study, a micrometer with an accuracy of one The higher linear expansion for the resin- micron was used to measure the change in the modified GICs observed in the present study is length of cylindrical specimens (6×4 mm). The in agreement with the result of recent investi- procedure proved to be uncomplicated and the gations [11]. Irie et al [20] reported that the equipment was inexpensive. In addition, the resin-modified GIC liners showed significantly advantages of using specimens with the above higher linear expansion than the conventional dimensions were that they simulated relatively cements, the magnitude of which was in the large dental restorations. range of 2.4% - 6.3%. In Kimishima et al’s In this study, unlike the conventional GIC, the [21], Vitremer showed slightly less expansion resin-modified cements showed significant (4.98%) than Fuji II LC (5.44%), which is in expansion. The pattern of such expansion dif- line with the results of the present study. fered according to the material tested. As men- This high linear expansion of resin-modified tioned earlier Fuji Cap II, Fuji II LC and Tetric GICs could be attributed to the presence of reached a constant length after about three hydrophilic resin HEMA in resin-modified months while more time was necessary for cements. The higher linear expansion associat- Photac-Fil Aplicap and Z100 (six months). ed with Dyract, in comparison with that of Dyract and Vitremerl required nine months to composite resins, could also be explained by reach a constant length. the fact that this material also contained some The finding that a relatively long time was hydrophilic monomers [22,23]. It was reported required for the composite materials to reach a that at six months, Dyract showed a linear ex- constant length is in agreement with that of pansion (0.66%) greater than that of either a Momoi and McCabe [6], who observed an light-cured composite (0.16%) or a dual-cured increase in the displacement force due to water composite resin (0.32%) [14]. In addition, it uptake during the six-month test period. They was shown that Fuji II LC produced the great- suggested that such an increase indicated that est (38 MPa) and most rapid rise in lateral there were regions within the specimens that stress brought about by hygroscopic expan- were not fully saturated [6]. In another study, sion. Z100 and Tetric produced a linear rise up however, after seven days of storage in water to six and four MPa, respectively. Dyract pro- at 37°C, all composite materials showed sig- duced 7 MPa stress by one month [17]. These nificant hygroscopic expansion that did not findings are congruent with the results of the significantly increase further until the 30-day present study where Dyract showed a hygro- storage [7]. scopic expansion intermediate to that of the It was observed that the dimensions of conven- resin-modified GICs and composite resins. tional GICs did not show any significant The results currently recorded for Fuji Cap II change after 30 minutes of immersion in wa- must be viewed with caution. In the present ter, while the resin modified cements exhibited study, the specimens made from Fuji Cap II changes up to 24 hours and remained constant were maintained at 37°C and 100% relative for the next week. The composite resin used humidity for 10 minutes. Therefore, the first demonstrated a significantly continuous in- measurement was performed approximately 20 crease during the period of the study (one minutes after mixing (taking into account the week). These results indicate that composite time required for lapping). Since conventional resins require a longer time than the resin- GICs undergo setting shrinkage immediately modified GICs to reach a constant length [11]. after setting, this delay in measurement might 2011; Vol. 8, No. 1 29 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. have had an effect on the results. For all other that the hygroscopic expansion of composite materials which were all of the light-curing resins during a 6-month study resulted in pres- type, the measurements were carried out with- sure values of 3.3 to 14.5 MPa dependent on in 5 minutes after curing. the material. They suggested that positive Except for Z100, the difference between the pressure of a similar magnitude pushing linear hygroscopic expansion of the layered against the cavity walls may be capable of and bulk inserted specimens was generally putting the supporting tooth tissues under con- significant, with the bulk inserted specimens siderable stress [6]. showing less expansion. This finding is in Using the results of this study and the modulus agreement with that of Bowen et al [19], who of material elasticity provided by another reported that when a composite resin was study, the magnitude of the pressure generated placed in bulk it had more shrinkage, less hy- from the expansion of the materials tested may groscopic expansion and some degree of re- be calculated from the following equation: sidual shrinkage. The higher shrinkage of a Stress=Strain×E, where E is the modulus of material placed in bulk; therefore, might ac- elasticity of a material and strain is the expan- count for the lower hygroscopic expansion sion (%) of the material at a given time [26]. observed in this study. However, it is known Such calculations gave pressure values of that restorations that are inserted in bulk show 124.55 MPa for Photac-Fil Aplicap, 111.33 wider marginal gaps and more microleakage MPa for Vitremer, 103.41 MPa for Fuji II LC, [24]. 44.66 MPa for Dyract, 34.95 MPa for Z100, As discussed earlier, the setting shrinkage of 11.04 MPa for Tetric and 0.52 MPa for Fuji restorative materials results in marginal gap Cap II; each calculation was made using the formation, microleakage and probably recur- values obtained at the time when the material rent caries. Hygroscopic expansion may com- reached its constant length. These values are pensate for this shrinkage and close the mar- much higher than those reported by Momoi ginal gap. Since the expansion occurs some- and McCabe [6], Watts et al [17]. time after the shrinkage has taken place, the The reason might be due to the test methods expansion will not lead to the re-establishment employed. These studies employed a model of any broken adhesive bonds and perfect clo- cavity design, in which the materials were in- sure. serted in a brass mould and the pressure re- During its earliest stages, expansion may quired to displace the specimens was calculat- simply cause a closing up of the contraction ed. The presence of such close contact be- gaps caused by setting shrinkage. Continued tween the brass and test material might have expansion, however, may cause development led to a lesser water absorption, hence less of an outward pressure against the cavity hygroscopic expansion than that recorded in walls. Estimation of the magnitude of this the present study [6,17]. pressure may enable its clinical significance to be inferred. Feilzer et al [25] suggested that in CONCLUSION the clinical situation, a slight positive stress is 1. Fuji Cap II showed the least linear hygro- preferable to a tensile stress as it may improve scopic expansion during the study. The resin- the marginal integrity of a restoration. They modified GICs exhibited the highest linear found that when the experiments ended after hygroscopic expansion among the materials 15 hours, a further build-up of compressive tested. Photac-Fil Aplicap showed the highest stress was observed with the resin-modified hygroscopic expansion between the resin- GICs [25]. Momoi and McCabe [6] reported modified cements. 2011; Vol. 8, No. 1 30 Emamieh et al. Hygroscopic Expansion of Restorative Materials 2. The time to reach a constant level was var- characteristics of composites for use in posterior ied, acquiring three to nine months depending teeth. J Dent Res 1986 Nov;65(11):1315-8. on the material tested. 10- Floyd CJ, Dickens SH. Network structure of 3. The initial linear expansion of Dyract was Bis-GMA and UDMA-based resin systems. Dent similar to that observed with composite resins. Mater 2006 Dec;22(12):1143-9. At one year, however, its linear expansion was 11- Irie M, Nakai H. Effect of immersion in water significantly higher than the composite resins. on linear expansion and strength of three base/liner materials. Dent Mater J 1995 Jun;14(1):70-7. ACKNOWLEDGMENTS 12- Attin T, Buchalla W, Kielbassa AM, Helwig E. We thank Dr. S. Mohammad Reza Safavi head Curing shrinkage and volumetric changes of resin- of Dental Research Center of Shahid Beheshti modified glass ionomer restorative materials. Dent University of Medical Sciences for providing Mater 1995 Nov;11(6):359-62. the opportunity to prepare the manuscript and 13- Pospiech P, Rammelsberg P, Tichy H, Gernet Dr. Alireza Akbarzadeh Baghban for his help W. The suitability of compomers as a core- in statistics. material: investigation on the volume stability. J Dent Res1995;74:475. REFERENCES 14- Martin RS, Jedynakiewicz NM. Measurement 1- Brannstrom M. Infection beneath composite of hygroscopic expansion of composite restora- resin restorations: can it be avoided? Oper Dent tives. J Dent Res 1995;74:462. 1978 Autumn;12(4):158-63. 15- Chutinan S, Platt JA, Cochran MA, Moore BK. 2- Phillips RW. Bonding agents and adhesives. Adv Volumetric dimensional change of six direct core Dent Res1988 Aug;2(1):150-4. materials. Dent Mater 2004 May;20(4):345-51. 3- van Noort R. What’s in a number? Todays Den- 16- Watts DC, Kisumbi BK, Toworfe GK. Dimen- tist 1988;1:1-5. sional changes of resin/ionomer restoratives in 4- Yap AU, Wang HB, Siow KS, Gan LM. aqueous and neutral media. Dent Mater 2000 Polymerization shrinkage of visible-light-cured Mar;16(2):89-96. composites. Oper Dent 2000 Mar-Apr;25(2):98- 17- Watts DC, el-Hejazi AA, AL-Hindi A. Hygro- 103. scopic-stress-development of resin-based restora- 5- Asmussen E, Jorgensen KD. A microscopic in- tives in situ. J Dent Res 1995;74:462. vestigation of the adaptation of some plastic filling 18- Feilzer AJ, de Gee AJ, Davidson CL. Relaxa- materials to dental cavity walls. Acta Odontol tion of polymerization contraction shear stress by Scand 1972 Mar;30(1):3-21. hygroscopic expansion. J Dent Res 1990 Jan;69(1): 6- Momoi Y, McCabe JF. Hygroscopic expansion 36-9. of resin based composites during 6 months of wa- 19- Bowen RL, Rapson JE, Dickson G. Hardening ter storage. Br Dent J 1994 Feb;176(3):91-6. shrinkage and hygroscopic expansion of composite 7- Ruttermann S, Kruger S, Raab WH, Janda R. resins. J Dent Res 1982 May;61(5):654-8. Polymerization shrinkage and hygroscopic expan- 20- Irie M, Nakai H, Hirota K. Marginal gap of sion of contemporary posterior resin-based filling light-activated glass-ionomer: effect of hygroscop- materials—a comparative study. J Dent 2007 Oct; ic expansion. J Dent Res 1992;71:633. 35(10):806-13. 21- Kimishima T, Shibaoka N, Enomoto H. Water 8- Hirasawa T, Hirano S, Hirabayashi S, Harashima expansion and microleakage of glass ionomer ce- I, Aizawa M. Initial dimensional change of compo- ments. J Dent Res 1996;75:73. sites in dry and wet conditions. J Dent Res 1983 22- Kanchanavasita W, Pearson GJ, Anstice HM. Jan;62(1):28-31. Influence of humidity on dimensional stability of a 9- Øysæd H, Ruyter IE. Water sorption and filler range of ion-leachable cements. Biomaterials 1995 2011; Vol. 8, No. 1 31 Journal of Dentistry, Tehran University of Medical Sciences Emamieh et al. Aug;16(12):921-9. 25- Feilzer AJ, Kakaboura AI, de Gee AJ, Da- 23- Toldano M, Osorio R, Fuentes V, Prati C, Gar- vidson CL. The influence of water sorption on the cia-Godoy F. Sorption and solubility of resin-based development of setting shrinkage stress in tradi- restorative dental materials. J Dent 2003 Jan;31(1): tional and resin-modified glass ionomer cements. 43-50. Dent Mater 1995 May;11(3):186-90. 24- Koenigsberg S, Fuks A, Grajower R. The effect 26- Torabzadeh H. Laboratory and clinical investi- of three filling techniques on marginal leakage gations into resin-modified glass-ionomer cements around Class II composite resin restorations in and related materials. Ph.D. thesis, Bristol: Univer- vitro. Quintessence Int 1989 Feb;20(2):117-21. sity of Bristol. 1996. 2011; Vol. 8, No. 1

Journal

Journal of Dentistry (Tehran, Iran)Pubmed Central

Published: Mar 31, 2011

References