4 Eqal. Characterization of a Glass fonomer Base/Iiner Material'r

Transcription

1 tt bortory Chrcteriztion of Glss fonomer Bse/iner Mteril'r E. Steven Duke, D.D.S., M.S.D. John \ry. Osborne, D.D.S., M.S.D. Brt Yn Meerbeek, D.D.S., Ph.D. inc Conn, D.D.S. Clinicl Reserch cility university of rexs Helth science center t sn ntonio 4 Eql

2 r. u.üsdjsisjt Esthetic restortive mterils often fil premturely due to mrginl stining or recurrent cries.l Such behvior my be linked to deteriortion t the interfce between the restortive mteril nd the remining tooth structure. Presenting s mrginl cries or stining, restortions my need to be replced within couple of yers of clinicl service.2 The development of dentin bonding gents, glss ionomer formultions, nd new dhesive clinicl techniques hve been focused t overcoming these deficiencies nd propose to improve the clinicl longevity of esthetic restortive mterils. The use of glss ionomer cement s bse or liner beneth composite resin restortion, referred to s the "sndwich" or "lminte" technique, hs recently been identified s the most relible esthetic dhesive procedure.3 The concept behind this restortion is bsed upon the predictble dhesion of glss ionomer cements mtched with the esthetics nd durbility of the composite resin. urthermore, the potentil benefits from continued fluoride relese my be of significnce in reducing the incidence of recurrent cries or my ssist with the tretment of high risk cries individuls.46 Reserch into the use of liners hs been limited to mostly lbortory studies involving microlekge behvior nd dhesive bond strengths to either the dentin or composite resin. Recently, Wtson7 hs shown the utility of imging glss ionomer liner using scnning confocl microscopy. Question ws rised reltive to the dpttion of new light cured glss ionomer which ws found to pull wy from the underling dentin. Such n exmintion with the confocl microscope hs llowed for nondestructive imging (in situ) tht my provide better understnding of the behvior of these new mterils. Without the introduction of preprtion rtifcts, greter confidence is gined with observed reserch results. urther, using specific fluorescence lbels, n understnding of the dhesive mechnisms my be possible. Such knowledge will ultimtely led to better understnding of current formultions nd provide insights towrds developing new nd more efficcious formultions.. Stridy Objectives The purpose of this lbortory study ws to evlute the behvior of light cured glss bse/liner mteril, onosit (DMG, Hmburg) when used

3 with composite resin. Specificlly, n understnding of the dhesive qulities nd.microbiologiil properties were exmined: Specific im 1: mge the glss ionomer/dentin interfce of onosit utilizing lser confocl microscopy. Specific im 2: Mesure the bility of onosit to inhibit the growth of Mutns streptococcus in cell culture tests.. Experimentl Design. Mteril Selection. The light cured glss ionomer onosit Bse/liner (DMG, Hmburg) ws be used with hybrid type direct composite resin (Universl Hybrid, DMG, Hmburg) restortive mteril. n ccepted liner mteril, Vitrebond (3M Dentl, St. Pul, MN) ws used s control mteril. B. Confocl Microscopy Phse Tooth Preprtion: Recently extrcted third molr humn teeth were prepred with Clss V type cvities for composite resin on the fcil nd lingul surfces. No. 556 plin tungsten crbide burs in high speed hndpiece equipped with n irlwter spry were used to cut the preprtions. New burs were frequently employed. The preprtions were rirde s uniform s possible with the pulpl floor plced t depth of 4 fril, s mesured in the centrl prt of the tooth. The preprtions were pproximtely 8 mm wide (mesildistl) by 4 mm in width (buccllingul). The preprtions were wshed with wter spy for 10 seconds nd dried with oil free cornpressed ir. mde with ll mrgins in enmel. totl of 20 preprtions were Restortion Plcement: The prepred teeth were restored with the so clled "lminte" or "sndwich" plcement technique. The incrementl technique for composite plcement ws used s well. inishing of the restortions ws ccomplished with the excess mteril removed with crbide burs. The finl finishing of the restortions ws ccomplished using fine grit composite finishing dimonds followed by lumin polishing pstes. Scnning Confocl Microscopy: To fcilitte fluorescence imging with the scnning confocl microscope, lbel ws plced into the glss ionomer liners prior to

4 plcement in the prepred teeth. n initil sturtion of hydroxyethyl methcrylte (HEM) ws ccomplished by slow titrtion of rhodomine B isothiocynte using n ultrsonic bth. When visible precipitte ws observed, the solution ws centrifuged nd the superntnt drwn off for incorportion into the glss ionomers. With the Vitrebond mteril, the liquid portion ws lbeled with the rhodomine B t rtio of 0.1 ml lbel to 6 ml glss ionomer liquid. With the onosit mteril. rtio of 0.1 ml of lbel ws incorported into 2 grms of glss ionomer liner. SCM smples were prepred by sectioning through the restortions using low speed dimond sw (Buehler, nc., Houston, Tx) coolnt (igure 1.). with wter The sections were then polished on Buehler Ecomet rotry polisher with 600 grit luminum oxide, 9um dimond pste, nd 3um dimond pste nd ultrsoniclly clened in distilled wter between ech step. The SCM evlution utilizes in situ specimens nd ws bsed upon the methods described by WtsonT. The smples were stored in n queous solution of slowdetm (Moleculr probes, nc., Eugene, or) under refrigertion until imged. Mny of the computerized fetures of the lser scnning microscope (Zeiss SM 10) were utilized in imging the specimens nd storge of the imge ws in digitl formt on floppy disk. Viewing nd mnipultion of the imges for presenttion were ccomplished on Mcintosh bsed system utilizing the NH mge 1.52 softwre pckge. dpttion of the liners to the dentin surfced ws ssessed long pulpl nd xil wlls. D. Microbiology Phse The onosit BseÄiner (DMG, Hmburg) nd Vitrebond liner (3M Dentl, St. Pul, MN) Streptococcus mutns. the inhibitory ctivities. were compred for their bility to inhibit the growth of n ntibiotic control disc ws utilized to vlidte composite resin ws used s negtive control. gr pltes were prepred by plcing 20 ml of tryptic soy gr into sterile petri dishes. Specimens of the glss ionomer mterils 6 mm in dimeter were prepred nd stored in sterile sline t 37 degrees C for 24 hours nd 7 dys. The gr pltes were inoculted with stndrdized colonies of Streptococcus muttrns #67t5. mmeditely fter inoculting the pltes, the mterils were plce on the gr surfces using sterile procedures. totl

5 of 10 pltes were prepred. ive pltes were used for exmintion,of specimens ged for 24 hours nd 5 pltes were used for specimens ged 7 dys. The pltes will be incubted overnight t 37 degrees C. nhibition zones were directly mesured on the pltes using dil cliper (see igure 7.). V. Results Results of the lser scnning confocl microscopy found the onosit liner to produce close dpttion to the dentin surfce with no evidence of gp formtion between the liner nd dentin. during imging of the Vitrebond liner specimens. n contrst, gps were observed observed mostly on the pulpl floors of the clss v cvities. These gps were consistent finding with the onosit liner specimens ws the development of n pprent morphous "rection zone" between the originl liner nd the dentin. ionomer nd the dentin surfce. imges re shown in igures 2. through igures 6. This zone ws distinct from the lbeled glss Representtive pulpl nd xil confocl Results of the microbiology testing re shown in Tble 1. seen, there ws greter inhibition compred to 7 dys. men inhibition zones for the two mterils. s cn be of growth for both liners t 24 hours There were no sttisticl differences between the Mteril Men Zone of nhibition (mm) 24 Hours 7 Dys Positive control Negtive control onosit iner Vitrebond r Tble 1. v. The dpttion to dentin cvities glss ionomer liner ws exmined microscopy nd stndrd gr overly nd ntimicrobil behvior of new in vitro. ser scnning confocl techniques were used. The confocl

6 6 imges clerly demonstrte excellent dpttion to the dentin surfces. This dpttion ppers to be the result of continued rection of the new liner beyond the initil light polymeriztion. The morphous lyer observed between the lbeled liner nd the dentin ws void of rhodomine B nd must hve developed subsequent to liner polymeriztion. mnufcturer suggests tht the single component onosit contins nhydrous crylic cid tht becomes hydrted from moisture in the dentin. This would suggest tht "drk" rection of the glss ionomer continues beyond the initil plcement nd would explin the unlbeled morphous zone found on pulpl nd xil wlls. This "fill in" of glss ionomer phse would fcilitte the polymeriztion shrinkge tht ccompnies resin reinforced glss ionomer cements. The microbiologic behvior of the onosit liner compres fvorbly with the Vitrebond liner tht hs previously demonstrted inhibition to plque producing orgnisms. reported previously. The The decrese in men zone over time hs not been This is most likely the result of less fluoride nd other ions leching out s function of specimen ge. inl vlidtion of the clinicl consequences of this new technology will require clinicl trils. However, initil lbortory results offer sound evidence for the use of onosit liner under composite resin restortions. The further dvntge of single component void of mixing step is n obvious clinicl dvntge over other commercil glss ionomer liners. vr. iterture Cited 1. Phillips, R.: New concepts in mterils used for m Dent ssoc 70:65266t, Wilson, E.G., Mndrdjieff, M. nd Brindock, posterior composite resin restortions. Dent Clin Mount, G.J.: Esthetics with glssionomer cements nd the "sndwich: technique. Quintessence nt 2:9301, wilson, nd Mclen, J. "Glss onomer Cement.", 1988, Quintessence, Chicgo, pp. l3l41. restortive dentistry. J T.: Controversies in North m 34:27 44,

7 5. Svnberg, M, Krsse, B nd Ornerfeldt, HO: Mutns streptococci in interproximl plque from mlgm nd glss ionomer restortions. Cries Res 24:133, Holtn, JR, Nystrom, GP, Dougls, WH nd Phelps, R2: Microlekge nd mrginl plcement of glssionomer liner. Quintessence nt 2l:ll7 122, Wtson T.. (1990): Confocl Microscopic Study of Some ctors ffecting dpttion of ightcured Glss onomer to Tooth Tissue, J Dent Res 69: ,

8 t 0.00 CE f, l.'l cg stl () '). *..? f, (). {i) u), t ( ; n.,/ u) c) ( t r\ tr n g rh \J fr 0 't fli fi.y t (.) t l fr t.r rt () li r T s d r.e r (t) { tr!1.lc0 l.

9 . r1 l l Ṯ (.l rh) () f,l tr () *) ll c N fi.ä0 v. l

10 o l ä l. Xt bu äo t4 l trl U s.!v li.rj ll c ( () rl bo k

11 l hu l. X,e bu 0 f.tv.) o : lrl \f () tr{ 0.l tr

12 T t.] T.r t +).cg rlt o+) ( tn tr bo.e f. l

13 = l!u,n X bu ä0, l.y ) f,l.tv r *)?l E E o \o r d. 00 tr

14 l o *).l.!l E E.T CH o. N ( r ) o!) l. Ā' tr.l E. r) s 6t lr rl o0 T.l!r) l l r oo f c) t, (n.!l n ' ti 00.l f. l t ri tsl.!l (h u) t l r\ v