J Clin I'criodontol 1994: 21: 38^4Primed in Demnurk , All righi,-^ reserved

Copyright {C Mtink.''giicnd t994

cliniGal periodDiitolog]fISSN O.m3-6979

Effects of the Nd:YAG laser andcombined treatments on in vitrofibroblast attachment to rootsurfaces

Daniel Thomas\ John Rapley\Charles Cobb\ Paulette SpenceHand William Killo/'Department of Periodontics, University ofMissouri-Kansas City Schooi ol Dentistry;^Department of Pediatric Denlistry, Universityof Missouri-Kansas City Schooi of Dentistry,Kansas City, Mo 64108, USA

Thomas D. Raptey J, Cobb C. Spencer P and Killoy W: Effects of ttie Nd:YAGtaser and cornbined trecttments on in vitro fibroblast attachment to root .surfaces.J Ctin Periodontol 1994: 21: 38^4. C Munksgaard, 1994.

Abstract. The purpose of this in vitro study was to evaluate the effects of theNd:YAG laser either alone or in combination with root planing or air-powderabrasive treatment on fibroblast attachment to non-diseased root surfaces. 28,4x4 mm root specimens and four disc-shaped root specimens 6 mm in diameterwere obtained from unerupted 3rd molars. The root segments were randomlyassigned to 4 treatment groups: (1) control: (2) laser-only treated; (3) lasertreated followed by root planing; (4) laser treated followed by air-powder abrasivetreatmenl. Laser-treated root specitnens were exposed for I min with the NdiYAGlaser calibrated at an energy setting of 75 mJ at 20 pulses/s using a 320 /;mcontact fiber. The contact fiber was held parallel to the root segments and the rootsegments were kept moist with distilled water. Following the prescribed treat-ments, the root specimens were incubated with fibroblast cultures and then pre-pared for SEM examination. Results of cell counts of fibroblasts attached tospecimens within each treatment group yielded the following means and stan-dard deviations: control groups, 181,64 + 44,74; lased only, 78.57 + 21.35; lasedand root planed 125,35 + 26.13; and lased followed by an air-powder abrasive.177.28 + 55.71. Application of ANOVA followed by the Dunn Multiple Compari-son test revealed significant differences (/7<0,01) in the number of attachedcells between the control and laser-only treated grottps; and between the laser-only and laser/air-powder abrasive treated groups. The decreased fibrobiastattachment observed in the laser-only treated group suggests a laser-indueedbioincompatibiiity of the root surface. Several surface alterations includingablation of cementurn with exposure of dentinal tubules and crater formationwere observed. Increased numbers of fibroblasts were seen attached to the lasedroot segments after root planing or after exposure to an air-powder abrasive,indicating that the laser-induced bioincompatibiiity is reversible and most likely asurface phenomena, A pilot study using photoacoustic Fourier transform infraredspeclt-oscopy revealed reduetions in the intensity of the Amide II band between1500-1550 cm-1, suggesting the laser exposure denatures surface protein which,in turn, may contribute to inhibition of fibroblast attachment.

Key words: iasers; root; fibrobiasts; scaling/root pianmg; periodontai therapy.

Accepted for pubiication 8 February 1993

Cementum and dentin exposed to thepocket environment undergo alterationsthat render them biologically unaccept-able for fibroblast and epithehal attach-ments (Selvig 1966, Rubin & Shapiro1978). A basic objective of periodontaltherapy is the reattachment of gingival

tissues to previously-diseased root sur-faces. The ultimate goal of periodontaltherapy is to achieve predictable re-generation of Ihe periodontium at pre-viously-diseased sites (Stah! 1977).

Several modalities have been pro-posed for root preparation to render

them compatible for healthy connectivetissue and epithelial attachment. Thesetreattnent modalities include scaling androot planing by manual or ultrasonicinstruments, use of an air-powder abras-ive system, and most recently, theNd:YAG laser.

Nd: YAG taser treated root surfaces 39

Complete removal of plaque and cal-culus appears impossible using the cus-tomary methods ol" instrumentation.Reasons for incomplete removal of rootaccretions include root anatomy, mor-phology of the periodontai pocket, andinadequate technique (Waerhaug 1978,Jones OXeary 1978, Rabbani et al,1981, Caffesse et al. 1986, Adriaens etal, 1988, Kepic et al. 1990), Severalstudies using ultrasonic instrumentshave concluded that they are an adjunctto root preparation and not a substitutefor hand instrumentation. Further,most studies agree to the presence ofresidual ealculus even with the eom-bined use of hand and ultrasonics in-struments (Nishimine & OXeary 1979,Thornton & Garnick 1982, Badersten etal, 1984, Gellin et al, 1986),

Depending on the length of exposure,air-powder abrasive systems are capableof removing both plaque and calculusand detoxifying areas difficult to accesswith hand instruments. Air-powderabrasive systems may have a positiveeffeet on root surface biocompatibilityas expressed through increased cellularattachment (Gilman & Maxey 1986).However, air-powder abrasive systemshave several disadvantages sueh as softtissue trauma, root surface abrasivity.damage to composite restorations, aero-sol production, and an unpleasant taste.The search for more effieient ways toachieve biocompatible root surface is acontinuous process and lasers have beenpromoted as having distinct advantagesin this regard.

Currently, predictable regenerationhas not been attainable with sonic,ultrasonic, airpowder abrasives, orhand instrumentatioti with or withoutsurgical access. The NdiYAG laser hasbeen purported to elirninate surgicalpain, alter the mieroflora, vapot"izeplaque and caicuius, coagulate blood,minimize root damage, and desensitizeroot surfaces (Myers 1989. 1991), If la-sers are capable of vaporizing bacteriaand calculus and detoxifying rool sur-faces, they could conceivably enhancetissue reattachrnent and/or t-egenera-tion. However, recent studies haveshown that the laser ean alter root sur-faces (Morlock et al, 1992, Trylovich etal, 1992), and inhibit fibroblast attach-ment (Trylovich et al. 1992, Spencer etai, 1992). Such root surface changes andbio-incompafibility may represent re-versible surface phenomena. Thus, thepurpose of this in vitro study was toevaluate the effects of the Nd:YAG la-

ser, either alone or in combination withroot planing or an air-powder abrasivetreatment on fibroblast attachment tonon-diseased rool surfaees. Further, anin vitro pilot study was performed toexamine any molecular changes on therool surface following use of theNd:YAG laser.

Materials and MethodsSpecimen acquisition and preparation

Root specimens were obtained from 32unerupled third molars using the fol-lowing criteria:(1) Root surfaces had not been exposed

to the oral cavity except at the timeof extraetion,

(2) Root surfaces were free of sofl andhard tissue debris,

(3) Surfaces appeat"ed smooth and un-altered by the extraetion procedure.

(4) The roots presented a broad and flatsurface area from which specimenscould be obtained.

All teelh were stored at 4 C in a solu-lion of triple distilled water containingpenicillin (100 units/ml), streptomycin(100 //g/ml), and amphotericin B (2,5//g/ml).

Twenty-eight root specimens approxi-mately 4 x 4 mm, and four disc-shapedspeeimens, approximately 6 mm in di-ameter, were cut from fiat root surfacesusing a (=557 earbide bur in a high speeddental handpieee with water eoolanl.The specimens were retnoved from areasat least 2 mm below the eemento-enameljunction. All root specimens were brief-ly treated with an air-powder abt"asivespray* to ensure retnoval of residualsurface debris and/or contaminants.The specimens were then randomly as-signed to four treatment groups. Groupp 1. control; Group i/'2, laser-onlytreated; Group r-'3, taser treated fol-lowed by root planing vvilh a Graeey1-2 curette for 15 strokes, and Group(̂4, laser treated followed by an air-pow-

der abrasive for 10 s at a distance of 5

Laser treatmenl

A Nd:YAG** Laser was calibrated withan Energy Meter*** prior to lasing the

*Propliy-.Iel 30, Dentsply InternationalInc., P,0, Box 872, York. PA, USA,

**American Dentai Laser Inc.. Troy, MLUSA

***Sunrise Technologies Inc., Fremont,CA. USA,

24 root segments from Groups ^'2, ,^3,and ^4, A 320 micron diameter contactoplic fiber was used to deliver an aver-age energy of 75 mj at 20 pulses/s. Thefiber was held parallel to the rool speci-men and moved in a back and forthmotion in an atlempt lo cover the entireroot segment wilh overlapping strokesfor one minute. Distilled water was usedto moisten the root surface during treat-ment.

Root planing treatmenl

The root segments from Group .̂ '3 wereplaced in a customized holder made ofacrylic and kept moist with distilledwater. The specimens were ihen manu-ally rool planed using new Graeey 1-2curettes for 15 strokes eovering the en-tire surface.

Air-powder abrasive treatment

The ait"-powder abrasive was used for10 s at a controlled distance of 5 mmfrom the surface of specimens in Group=4, The specimens were placed in thecustomized acrylic holder which wasthen moved back and forlh under thestabilized handpieee, thereby insuringthe entire root surface was instru-mented.

Fibroblastic Culture Preparation andincubation

The 28 root specimens were randomlydistributed to four separate pelri dishes(60 mm diameter). Human gingivalfibroblasts in the fifth passage werecounted and added to each of the pelridishes at a concentralion of 2.5 x 10\The cells were then incubated for 8 h at37 C al 100% humidity in 5% carbondioxide in air. The incubation was ter-minated by gentle agitation of speci-metis to dislodge non-adherent cells fol-lowed by the addition of 2.5% glutar-aidehyde fixative prepared in 0,01 Mcacodylate buffer al pH 7,4,

Scanning eiectron microscope preparation

Specimens were prepared for SEMexaminalion by dehydration in a seriesof graded ethyl alcohol solutions(20-100%). Final dehydration was af-fected by immersion in hexamelhydisil-azane for 3 h followed by overnight dry-ing in a desiccator. All specimens weresputter-coated with 200 A of gold/pal-ladium and examined in a Phillips 515

40 Thotnas et al.

Ftg. I. Attached fibroblast with well-developed lameilopoda from a laser and root planedspecimen. This genera! morphologic appearance was typical of fibroblasts regardless oi" treat-men! group, Bar = O.I mm at an original magnification of 8IOx,

seanning electron microscope (SEM).Photomicrographs used for cell countswere taken at -1-15' angle and a magni-fication of 170. Three non-overlappingpholomicrographs were obtaitied atrandom points along an imaginary lineextending through diagonal corners.The 3 micrographs per root specimenconstiluled an examination field andwas assumed to be representative of thetotai surface area.

Studies were done to evaluate the dif-ferences between using 3 diagonalmicrographs, 5 micrographs coveringthe center and 4 corners of the ileld.and 7 micrographs covering the entirefield. No difference was found betweenthe patterns using a single factor ANO-VA, and for purposes of time and ex-pense, the three diagonal micrographswere used.

FTIR photoacoustic sample preparation

The 4 disc-shaped rool specimens werestored in a desiccator at 4 G for 48 hprior to and after speclroscopic analy-sis. Spectra were recorded using an Ana-lect RFX 65 FTIR Spectrometerequipped wilh an MTEC Model 200pholoacoustic cell. A spectrum was re-corded for each specimen before andafter treatmenl.

Data coilection and analysis

The number of attached fibroblasts ob-served in each SEM mierograph was

recorded separalely. Micrographs werere-examined 10 days laler and fibro-blasts recounted by the same investi-gator. Inlra-examiner reliability wasanalyzed using both a Pearson corre-lalion coefficient and a correlated Mest.The cell count data was analyzed usinga one-factor analysis of variance (ANO-VA) to determine ihe error term for usewith the Dunn multiple comparisontechnique.

Results

Intra-examiner reliability between thetwo separate cell counts indicated a higheorrelation, i.e., /• = 0,998, The mean dif-ference of 3.0 cells (.Yi = i39.21; .v.-142,21) between the two cell counts wasstatistically significant (/?<0,01). Thetwo cell counts varied by 2.3%i, with 36percent within+1 and 68%i within+4.The greatest difference between countswas twelve and there was a reasonabledegree of intraexatniner reliability.

Attached fibroblasls with well-de-veloped lameilopoda (Eig, 1) were ob-served on all root specimens regardlessof treatment group. However, a signifi-cant varianee in the total numbers offibroblasts was observed among treat-ment groups (Eig. 2), A summary of ihestatistical data, i.e,, mean and standarddeviation, for each group is presentedin Table 1,

The control group exhibited thegreatest number of attached cells witha mean and standard deviation of181,64+44.74 cells per examinafionfield. This was followed by the laser atidair-powder abrasive treated specirnenswith a mean and standard devialion of177,28 + 55,71 cells per field. The lasertreated and root planed group had amean and standard deviation of125,35 + 26,13 cells per field; and ihelaser only treated specimens a mean andstandard devialion of 78.57 + 21.35 cells

Eig, 2. Composite photograph demonstrating the variations in and relative densities of cellularattachment between e,\perimentai groups. As shown in 2A, a monolayer of cells approachiagconfiuency was representative of control specimens; 2B representing laser-only .specimensexhibits considerably fewer attached cells; 2C and 2D representing la.ser-air-powder abrasiveand la,ser-root planed treated specimens, both sow numerous attached cells but comparativelyfewer than t;ontrol specimens.

Tahte I. Statisticai analysis of the attached fibroblasLs counted Tor each treatment group

meanstandard deviation

Control

181,6444,74

Table 2. Mean difference between pairs

Treatment

lasedlased root planedlascd/air powder abrasive treatment

Lased

78,5721,35

of treatment

Control(181,64)

103,07*56,294,35

Lased/root planedabrasive treated

125,3526.13

groups^'

Lased /air-powderabrasive treated

(177,28)

98,71*51,92

Lased /air powder

177,2855,71

Lasedroot planed

(125.35)

46,79

"Statistical significance determined by the Dunn Multiple Comparison Technique.0OI

per field. The data was analyzed with aone-factor analysis of variance to deter-mine the error term for use wilh theDunn tnulliple comparison technique,Dunn comparisons between pairs ofgroups (Table 2) revealed a significantdifference {p<0.0\} in the number offibroblasts between the control and la-ser only treated groups; and betweenthe laser oniy and laser and air-powderabrasive treated groups,

SEM evaluation of the laser-onlytreated specimens revealed several sur-face alterations that included charring,tracking, cementum meltdown withspheres of t"esolidified mineral, craterformation, and ablation of eernentumwith exposure of dentinal tubules (Eigs.

3, 4), The laser treated root surface ap-peared lo be incompatible with cellularattachment as the mean number of at-tached fibroblasts was considerably re-duced. Further, only one specimen ex-hibited fibroblastic attachment within alaser induced crater,

A pilot study using Eourier Trans-fomi Infrared (FTIR) PhotoacousticSpeetroseopy revealed signifieant reduc-tions in the intensity of the Amide IIband between 1500-1550 cm ' in thelaser treated root segments (Fig. 5). Thisobservation suggests a la.ser induceddegradation of matrix protein on theroot surface which in turn may be as-sociated in some manner with the reduc-tion in fibroblast atlachment.

Fig. 3, Laser-induced tracking (arrow) which appears to inhibit normal spreading of cells.Note how cell "fold-up" at tiieir periphery and do not enter the tracking area. Bar = 0.1 mmat an original magnification of 745 x ,

Nd: YAG laser treated root surfaees 41

Discussion

The fibroblasl is the predominanl celltype found in gingival lamina propriaand mediates altachmenl lo healthyroot surfaces via the periodontal andgingiva] fiber ligaments. Numerousauthors (Gilman & Maxey 1986, Trylo-vich et al. 1992, Aleo et al, 1975) haveused fibroblast aliachmeni as an indi-cator of biocompalibility. The com-bined resulls of SEM and the ETIRPhotoacoustic Speclrocopy demon-strate that use of the Nd:YAG laser re-sulted in rool surface changes thai sig-nificantly inhibited fibroblast attach-ment. Tryiovich et al. also foundminimal fibroblast attachment afterNd:YAG use on root specimens withmany of the cells exhibiting an abnor-mal morphology. By comparison, theincreased fibroblasl allaehment notedin this study may be attributed lo vari-ations in treatment procedures:

(1) The energy level was slightly (3%)lower and was chosen since clin-icians are more likely to select a set-ting of reduced wattage wilh morerepetitions for purposes of comfortlo the paiient,

(2) The contact optic fiber was orientedparallel to the root surface insteadof perpendicular to simulate theclinical appliealion,

(3) The root segments were kept moist.Even with these modifications, laser-

induced surface alterations were still ob-served. Root surface alterations in-cluded charring, tracking, eementummeltdown with spheres of resolidifiedmineral, ablation of the cementuni withexposure of the denlinal tubules, andcrater formation.

Charring is caused by intense, local-ized heat produced when the lasercomes into contact with surface debris,organic material, or a pigmented sur-face. This charred layer can be easilyretnoved by wiping the surface, a pro-eedure not easily accomphshed in vivo.Tracking is a fiber-induced smear layerresulting from a super-heated contaclfiber as it moves along the rool surface.The laser mells rool mineral which, ascooling occurs, results in resolidifiedspheres of inorganic material thai havea lava-like appearance. Because the la-ser is pulsed, there at"e periodic peaks orbursts of energy. These "energy peaks"may damage the root surface, as indi-cated by crater formation, Resolidifi-cation of the mineral phase ("moltenlava") was frequently noted on the erat-

42 Thomas et al.

Fig. 4. Split image photograph of a laser-only specimen showing few attached cells (arrows)and crater formation containing resolidified rool mineral. Bar = 50 //m at magnification ofI56x (left photo) and 25 ptn at magnification of 1,325 x (right photo).

Absorbance (cm-')F'lg. 5, FTIR. Photoacoustic spectra of root surface prior to (a) and after (b) laser treatment(80 mJ at 20 pps for 1 min). Note reduction in the Amide Ii peak. Other peaks labeled arewater (OH), carbonate (CO3) and phosphate (P04),

cr walls, Simiiar surface changes athigher energy settings have been notedby others (Myers 1991, Morlock et al,1992, Trylovich et al. 1992, Dederich etal. !984, Hess 1990).

The FTIR photoacoustic spee-troseopy pilot study revealed significantreduclions in the intensity of the AmideII band between 1500-1550 cm"' in thelaser treated root segments. This sug-

gests the Nd:YAG laser denatured rootsurface proteins which may be erueialin deereasing fibroblast attaehment.Trylovich et al, (1992) described thepresence of ammonia on a laser-treatedroot specimen ihal was lased at 80 mJand 10 pulses/s for 2 and 4 min. FTIRphotoacoustic speetroseopy demon-strated alleralions in the phosphate tocarbonate ratio. It was suggested that

the amtnonia present resulted from heatdegradation of the collagen matrixwhieh in turn, affected fibroblastattachment.

In addition, this study investigatedthe effect of rool planing or air-powderabrasive treatments on lased root seg-ments, SEM and statistical analysis ofmean ceil counls showed an increasein fibroblast attachment on these rootsurfaces indicating increased biocom-patibility as compared lo laser-onlytreated specimens. Root planing and theair-powder abrasive removed altered ee-menlum but the exact amount is unde-termined and variable. Cementum re-moval is dependent on the mode of ac-tion, Ihe operator force, and thesharpness and angulation of the instru-ment. Berkstein et al, (1987) rneasuredthe rool diameter after a singie curettestroke and approximately tht"ee seeondsof air-powder abrasive exposure. Theloss of root substance was 27 /̂ m withthe curette and 10,64 /(m with the air-powder abrasive. Extrapolation of thisdata due lo this study's instrutnenlationwould conclude that a considerableamount of root surface was removed.Although nol significant, the laser androot planed specimens exhibited fewerattached cells than the laser and air-powder abrasive treated groups(125.35 + 26,13 versus 177.28± 55,71).This difference may be a result of thesmear layer produced by hand instru-menlalion (Eick et al. 1970. Pashley1984), The smear layer is eotnprised oforganic and mineralized debris and isthought to serve as a physical barrierbetween the periodonlal tissues and Iherool surface (Poison et al. 1984), Proteinfragments resulting from subsurfacethermal damage may have been incor-porated in the smear layer and possiblymay be responsible for the depressedfibroblast attachtnent noted in the laserand root planed specimens.

A significant increase in fibrobiaslattachment, similar to the control, wasobserved when the lased t"ool specirnenswere treated by an air-powder abrasiveas compared to laser only Irealed speci-mens. This suggests that the air-powderabrasive may aller surface chemisiry inaddition lo the removal of root struc-ture. The air-powder abrasive spraycontains sodiutn bicarbonate and trical-cium phosphate; both are basic in na-ture, and may produce surface pHchanges more favorable lo cellularatlachment. Further studies are neededto determine if, in fact, sueh chemical

Nd: YAG laser treated root surfaees 43

interactions can alter or enhance fibro-blast attachment. The air-powder abras-ive provides an exceptionally smoothroot surface. It rernoves rool structureuniformly and can even eliminate minorsurface irregularilies. The comparalivelack of exposed dentinal tubules on theroot surface treated with the air-powderabrasive may play a significani role clin-ically in decreasing rool sensitivity, Fut"-thermore, the instrument is faster andiess stressful to the clinician than rootplaning. However, since the air-powderabrasive cannot treat tased root surfaeeswithout surgical fiap reflection, ils clin-ical application as an adjunct to rootplaning is severely litniled.

The NdiYAG laser is nol a self-ealib-raling instrutnent and this inherent de-fect affects its use and may inadver-tently cause injury lo soft and hardtissues. The laser used in this study hadto be frequently calibrated with a ModelEIVI 22 Energy Meter since there wereconstant energy fiuctuations, A secondNd:YAG laser, which was availablecould not be used due to gross energyfluctuations. The practitioner who doesnot calibrate the Nd:Y.A,G laser period-ically or is unaware of the need to cali-brate, may be treating patients with in-appropriate energy levels and thus caus-ing irreversible damage.

In consideration of the inherent limi-tations of this in vitro study design, thefollowing conclusions may be made:(1) The laser-only treated root speci-

mens exhibited a significantly de-creased fibt"oblasl attachment com-pared to the control, laser/rootplaned, and laser/air-powder abras-ive irealed root segments,

(2) The increased fibroblast attachmentto the laser/root planed and laser/air-powder abrasive treated rootsegments suggests that the laser-pro-duced surface alterations are revers-ible and are therefore a surfacephenomena.

(3) Laser-treated root segments dis-played surface alterations includingcharring, tracking, resolidifiedspheres of root mineral, ablation otcemenlum with exposure of the den-tinal tubules, and crater formation.

(4) Rool treatmenl wilh root planing orair-powder abrasive would appearessential following laser treatmentin order lo render the root surfacebiocotnpalible.

Acknowledgments

The authors wish lo acknowledge theRoy ,1, Rineharl Educational Eounda-

tion of the University of Missouri-Kan-sas City for the support of ihis investi-gation. We are indebted to Ms. EileenRoach, Mr, Scott Robinson and Mr,Hsien Lin for their expert technical as-sistance and to Ms. Diane Millush forpreparation of the manuscripl,

Zusammenfassung

Die Wirkung der Nd:YAG La.sertherapie. so-wie von Kombinatton.sbehandlungen auj das Fi-brohtastenattachment an Wurzetoberfldehen invitroMit der vorliegenden Arbeit wurde beabsich-tigt, die Wirkungen des Nd;YAG Laser • so-wohl als allehiige Therapie als auch in Verbin-dung mit Wurzelgiattung oder mit abrasiverLufi/Pulverstrahl Behandlung - auf das At-tachment von Fibrablasten an gesundenWurzel oberflachen zu beurteilen, Nichtdurchgebrochenen dritten Molaren wurden28 Wurzelsegmente (4 mm x 4 mm) und 4scheibchenformige Wurzel praparato miteinem Durchme,sser von 6 mm eninommen.Die Segmente und Praparate wurden nachdem Zufailsprinzip den 4 folgenden Behand-lungsgruppen zugeteilt: (I) Kontroligruppe:

(2) ausschiieBlich mit dem Laser behandelt;(3) Laserbehandlung mit anschlieBenderWurzelglattnng; (4) Laserbehandlung mit an-schtieBender Luft/Pulverstrahl Behandlung,Mittels einer Kontaktfa.ser (320 /(m) wurdendie mi: Laser zu behandelnden Wurzelpriipa-rate. bei einer Energieeinstellung von 75 mjund 20 Puisen pro Sekunde, eine Minute langdem Nd:YAG Laserstrahl ausgesetzt. DieKoniaktfaser wurde parallel zu den, mit de-stiliicriem Wasser feucht gehaltenen, Wurzel-segmenien eingestellt, Nach den vorgesehe-nen Behandlimgen wurden die Praparate mitFibroblastenkulturen inkubiert und danachfiir die SEM-Untersuchung vorbereitet. Fol-gende Auszahlungsresultate wurden bei deneinzelnen Behandlungsgruppen fiir die. anden Praparaten haftenden Fi-broblasten festgestellt (Mittel werte undStandardabweichungen); KontrollgrnppenISL64-^44,74: nur bestrahlt, 78.57-1-21.35:bestrahh imd Wurzelglattung 125,35-^26,13und bestrahlt mit anschlieBender abrasiverLiift/Pulver Behandlung 177,28 + 55,71, Hin-sichtHch der Anzahl haftender Zellen (Zelien-attachment). machlc die .ANOVA-Analysemit dem anschlieBenden miiltiplen Ver-gleichstest nach Dunn, signifikante Unter-schiede iyj<0,01) deutlich und zwar zwischenden Kontrollgruppen und den nur mit demLaser behandelten. wie auch zwischen den"nur mit dem La.ser" behandelten und denmit Laser/abrasivem Luft-Pnlverstrahl be-handelten Gruppen, Das bei den "nur-mitdem Laser" behandelten Gruppen beobach-tete, herabgesetzte Fibroblastenattachment,laBt eine Laser-induzierte Bioinkompatibili-tat der Wurzeloberiiache vermiiten, Weiter-hin wurden verschiedenartige OberOaehen-veranderungen, einschlieClich Zementverlustmit Freilegung von Dentintubuli und Krater-

bildung beobachtet. Nach Wurzeigiattungoder nach Behandlung mit abrasivem Luft/Pulverstrahl wurde an ausschlieRlich mit La-ser behandelten Wurzelsegmenten eine hohe-re Aozahl haftender Fibroblasten gesehen,was andeutet, daB die durch den Laserstrahlinduzierte Bioinkompatibilitiit reversibel istund es sich wahrscheinlich um ein Oberfia-chenphanomen handelt. Eine Pilotstudie mitphotoakustisch nach Fourier transformierterInfrarotspektroskopie machte Reduktionender Intensitiit im Amide II Band zwischen1500-1550 cm ' deutiich. was vermuten laBt,daB die Lasereinwirkung das Oberfiiichen-protein denaturiert. was dann zur Inhibi-tion des Fibroblastenattachments beitragenkonnte.

Resume

Ejjets du LASER Nd: YAG et des traitemmtseomhines sur I'attactie in vitro de jibroblastessur les .surjaces radiculairesLe but de cette etude in vitro a ete d'evaluerles effets du LASER Nd:YAG soit seu! soitavec lissage radiculaire ou traitement parpoudre et air abrasifs sur ["attache du fibro-blaste au niveau de surfaces radiculaires nonatieintes, 28 echantillons radiculaires de 4 x 4mm et 4 echantillons radiculaires en formede disque de 6 mm de diametre ont etc prepa-res a partir de dents dc sagesse inclu.ses, Lessegments radiculaires ont ete repartis au ha-sard dans les 4 groupes de traitement sui-vants: I controle. 2- laser, 3-laser puis iissageradiculaire, 4- laser puis traitement par pou-dre abrasive, Les specimens radiculaires trai-tes par laser ont etc exposes durant une minavec le laser "NdiYAG calibre a une energiede 75 mJ a 20 pulsions/s en utiiisant une fibrede contact de 320 /(m. La fibre de contact aete piacee parallelement aux segments radicu-laires qui ont ete maintenus humides grace ade l'eau distiliee. Suite a ces divers traiie-ments. ies specimens radiculaires ont ete incu-bes avec des cultures de tibroblasies puis pre-parees pour l'examen au microscope electro-nique a baiayage, Les resultats des comptagescellulaires de fibioblastes attaches aux echan-tillons dans chaque groupe de traitement ontdonne les moyennes et ecarts types suivants:groupe 1:18.64 ( + 44,74): groupe 2: 78,57 (±21,35): groupe 3: 125.35 ( + 26,13) et groupe4: 177,28 ( + 55.71), Lanaiyse des donneespar ANOVA suivie du test de comparaisonmultiple de Dunn ont revele des differencessignificatives (/)<0,01) dans ie nombre de cel-lules attachees entre le groupe controle etceu\ ou le laser avait ete utilise, et entre celuioil le laser seul avait ete utilise et eelui oilil y avait une combinaison laser - poudreabrasive. La faibie attache des fibroblastesobservee dans le groupe traite uniquementpar laser suggere la formation d'une bio-in-compatibilite induite par le laser au niveaude la surface radiculaire. Differentes altera-tions de surface comprenant I'ablation du ce-ment avec mise a nu des tubules dentinaireset la formation de crateres ont ete observees,Davantage de Obroblastes ont ete aper^us

Thomas et al.

attaches aux surfaces radiculaires ou ie laseravait ete utilise avec lissage radiculaire ouutilisation de poudre abrasive, indiquant quecette bio-incompatibiiite induite par Ie laserest reversible et n'est vraisemblablementqu"un phenomene de surface. Une etude pilo-te itlilisant la spectroscopie infra-rougephoto-aceoustique a revele des reductionsdans Fintensite de la bande Amide II entre1500 et 1550 cm"' suggerant que le laser de-nature la proteine de surface qui. a son tour,peut contribuer a Finhibition de I'attache dufibroblaste.

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Address:

John RapleyDepartment oj FeriodonticsUniversity of Mi.ssouri-Kansas CitySchool of DentistryEast 25th StreetKansas City. MO 64108USA