A Comparative Study of Protaper and Twisted File Nickel Titanium Instruments in Curved Canals Preparation

Cleaning and shaping of the root canal are important steps to achieve success in endodontic treatment. These include disinfection and dentin removal from canal walls, maintaining the original shape of the root canal and creat­ ing continuously tapered preparation in order to receive an adequate obturation [1]. Due to variable root canal anatomy, mechanical instrumentation of curved canals may lead to procedural errors such as ledge, zip, elbow formation, canal transportation and perforation [2, 3]. Safe preparation techniques should eliminate or minimize these procedural errors. However, several instruments have been suggested for this purpose. Nickel titanium (NiTi) alloys for endodontic instru­ ments were first described in 1988 [4]. Since then, several rotary NiTi instruments of different tapers and designs have been introduced in root canal preparation. Due to their flexibility and elasticity there has been an improve­ ment in the quality of root canal shaping and less iatro­ genic damage even in severely curved root canals [5]. ProTaper (Dentsply/Maillefer, Ballaigues, Switzerland) and Twisted File (SybronEndo, Orange, CA, USA) are the two NiTi rotary systems used worldwide. ProTaper has 3 shaping files and 5 finishing files. Shaping files (S) have an increasing taper from the tip to the shaft that provides more flexibility in the middle region and at the tip. Fin­ ishing files (F) have decreasing taper, they are stiffer and produce greater taper in apical region. Their convex tri­ angular cross sectional design and grooves reduce raw material section on the rounded noncutting safety tip, and their flute design combines multiple tapers within the shaft [6, 7]. Twisted File system production is by proc­ ess of heating, cooling, and twisting NiTi alloy, providing superelasticity and cyclic fatigue resistance of the instru­ ments [8, 9]. These files have constant taper (.04, .06, .08, .10, and .12), triangular cross section, variable pitch and safe ended tip. Instrument design may also potentially influence instrumentation outcomes. Many rotary file manufacturers have incorporated different designs into their file systems to minimize apical transportation and achieve faster and more predictable preparations [10]. The A Comparative Study of Protaper and Twisted File Nickel Titanium Instruments in Curved Canals Preparation


INTRODUCTION
Cleaning and shaping of the root canal are important steps to achieve success in endodontic treatment.These include disinfection and dentin removal from canal walls, maintaining the original shape of the root canal and creat ing continuously tapered preparation in order to receive an adequate obturation [1].Due to variable root canal anatomy, mechanical instrumentation of curved canals may lead to procedural errors such as ledge, zip, elbow formation, canal transportation and perforation [2,3].Safe preparation techniques should eliminate or minimize these procedural errors.However, several instruments have been suggested for this purpose.
Nickel titanium (NiTi) alloys for endodontic instru ments were first described in 1988 [4].Since then, several rotary NiTi instruments of different tapers and designs have been introduced in root canal preparation.Due to their flexibility and elasticity there has been an improve ment in the quality of root canal shaping and less iatro genic damage even in severely curved root canals [5].
ProTaper (Dentsply/Maillefer, Ballaigues, Switzerland) and Twisted File (SybronEndo, Orange, CA, USA) are the two NiTi rotary systems used worldwide.ProTaper has 3 shaping files and 5 finishing files.Shaping files (S) have an increasing taper from the tip to the shaft that provides more flexibility in the middle region and at the tip.Fin ishing files (F) have decreasing taper, they are stiffer and produce greater taper in apical region.Their convex tri angular cross sectional design and grooves reduce raw material section on the rounded noncutting safety tip, and their flute design combines multiple tapers within the shaft [6,7].Twisted File system production is by proc ess of heating, cooling, and twisting NiTi alloy, providing superelasticity and cyclic fatigue resistance of the instru ments [8,9].These files have constant taper (.04, .06,.08,.10,and .12),triangular cross section, variable pitch and safe ended tip.Instrument design may also potentially influence instrumentation outcomes.Many rotary file manufacturers have incorporated different designs into their file systems to minimize apical transportation and achieve faster and more predictable preparations [10].The evaluation of the efficiency of instruments and techniques is very important before their introduction to the clinical practice.
The present study aimed to compare changes in root canal dentin caused by instrumentation with two nickel titanium rotary systems, ProTaper and Twisted File in curved canals.

MATERIAL AND METHODS
The study was approved by the Research Ethics Commit tee at the School of Dentstry, University of Pernambuco.Twenty five extracted human mandibular first molars were selected.Inclusion criteria were: intact pulp cham ber, fully formed roots, similar root lenghts (14.53±1.52 mm), two separated mesial root canals and canal curva tures between 20 and 40 degrees, measured according to Schneider's method [11].
After distal roots amputation, occlusal surfaces of the molars were leveled using a diamond disc (Vortex, São Paulo, SP) to provide a reference point for instrumenta tion.Mesial root canals of all teeth were accessed using a diamond coated bur (Dentsply/Maillefer) and negotiated with 10 K files (Dentsply/Maillefer) until the tip was vis ible beyond the apex.Working length was set to 1 mm shorter of the apical foramen.
Fifty canals (25 mesiobuccal and 25 mesiolingual) were randomly assigned into two groups: group 1 -ProTaper and group 2 -Twisted File.Each group consisted of the same number of mesiobuccal and mesiolingual canals.
Specimens were prepared using a technique described by Bramante et al. [12].Access cavities and apices were sealed with a small ball of utility red wax (Hygienic Cor poration, Akron, OH, USA).Roots were embedded up to cementoenamel junction in a cold polymerizing acrylic resin (VIPI, Pirassununga, SP, USA).After resin cure, hori zontal grooves were made on the models for subsequent segmentation.Roots were sectioned transversely at three levels: 1) 4 mm from the apical foramen, 2) middle third, and 3) coronal third of the root.A muffle system was built around each mold to ensure that, after segmenta tion, pieces seated in the same position.Each resin block was sectioned into four pieces using a low speed 0.15 mm stainless steel wafering blade.
Before root canal preparation, coronal side of the cross sections was scanned (HP Deskjet F4200 printer, Hewlett Packard, Palo Alto, CA, USA) at 1200 ppi and 100% scale.All digital images were analyzed using the appropriate software (Adobe Photoshop CS4 Extended, Adobe System Incorporated, San Jose, CA, USA).The conversion of pixels to millimeters was 1 pixel = 0.0211 mm.For each digital image, the canal cross sectional area was filled in black, and the center was marked in white.The cross sectional area and all distances from the center to the four walls (external, internal, mesial and distal) were measured and recorded.The buccal wall of mesiobuccal canals and the lingual wall of mesiolingual canals were classified as ex ternal walls, and the opposite walls, as internal.
The sections were reassembled and all canals instru mented by the same operator.All files were used with torque control engine, in crown down technique, and following the manufacturers' instructions.Canals were instrumented with files: group 1 -S1, SX, S2, F1, F2 and F3; group 2 -#25/.08,#25.06, #25.04 and #30/.06.Final instruments were F3 (group 1) and #30/.06 (group 2) to the working length.In both groups, 10 K file was intro duced after each file to ensure patency and irrigation was performed with 2 ml of 2.5% sodium hypochlorite after each instrument.Postoperative cross sections were digi tized and measured under the same conditions as during preoperative phase.Changes in dentin walls were meas ured in coronal, middle, and apical thirds of all canals and compared by superimposition of pre and post instrumen tation digital images using image analysis software.
Statistical analysis was performed using the Mann Whitney U test in the SPSS software (SPSS Inc, Chicago, IL, USA).The level of significance was set at p<0.05.

RESULTS
There was statistically significant greater difference in coronal and middle thirds cross sections before and after the preparation (p=0.040 and p=0.043) between group 1 and group 2 whereas there was no difference in the api cal third cross sections when the two systems were used (p=0.992)(Table 1).
Mean difference in distance from the center to the mesial wall in the cervical third was greater in the Pro Taper group and, statistically significant compared to the Twisted File group (p<0.05)(Table 2).Other walls, both in middle and apical thirds, did not have any statistically significant differences between the groups (p>0.05)(Ta ble 2).There was no statistically significant difference (p>0.05) between the two groups in cross sectional canal areas before preparation.

DISCUSSION
Root canal preparations are frequently evaluated using extracted human teeth or plastic blocks with simulated curved root canals [13,14].Simulated canals have stand ardized canal diameter, length and curve radius, but do not simulate the coinciding bucco lingual and mesio distal curvatures often found in natural teeth [15].Furthermore, root dentin hardness and abrasion rates may not be iden tical and do not reproduce the instrument stress during canal instrumentation.
Several methods have been suggested to evaluate root canal preparation such as comparative analysis of radiographic images, resin blocks, silicone impressions and microcomputed tomography [2,16,17,18].The present study used the method developed by Bramante et al. [12] because it is an established method and allows comparison of the samples before, during, and after the instrumentation [13,19,20].This methodology is easy to perform and of low cost [20].Disadvantage of such recon structive technique is that lateral movements of cutting disc may result in some loss of material [21].Comparison of digital images acquired before and after instrumenta tion using image analysis software may be an alternative to evaluate canal preparation [13,20,21].
Curved canals present a challenge in endodontic treat ment.Mesial canals in mandibular molars are narrow and flattened making instrumentation difficult [22,23].In this study, both groups had the same number of specimens, and the instruments were used alternately in the buccal and lingual canals of consecutive specimens to com pensate possible differences in canal morphology.Both mesiobuccal and mesiolingual canals were included and equally distributed between groups.The mean differences between areas before and after preparation were greater in the ProTaper group in all thirds, furthermore, this difference was statistically sig nificant in cervical and middle thirds when compared to the Twisted File group (p<0.05).These findings are simi lar to results from other studies [24,25].
In the present study, ProTaper removed significantly more dentin than Twisted File on mesial wall in coronal sections.Greater dentin removal may be assigned to the S shape of ProTaper instruments.According to the manu facturer's instructions, these instruments should be used without applying apical pressure, but should work laterally on the wall with the thickest dentin, in our case, mesial walls, using brushing movements [25].Excessive dentin removal in this region may result in contact with peri odontium and weakening tooth structure, which may lead to root fracture.The distal wall is the thinnest in mesial canals, and this is explained by the concavity of the distal wall of mesial roots in mandibular molars [26].Preparing curved canals with anticurvature method might protect root against perforation and optimize access to the apical portion of canal [3].
The analysis of changes in dentin wall thickness re vealed that the two types of instruments did not cut dentin uniformly in all reference points, but differences were not significant, except for the mesial wall in cervical third.Other studies found symmetrical instrumentation using ProTaper system particularly in the apical third [21,27].However, radiographic method used in these stud ies might failed to detect dentin removal as accurately as analysis of cross sectional areas, as in Bramante method used in our study.
In both groups, some specimens showed areas not touched by instruments in all thirds, particularly in the internal walls of isthmuses.This finding is in agreement with the study of Hülsmann et al. [28].We believe that combination of instrumentation techniques should be evaluated in future studies in order to provide better shap ing of root canals [29,30].

CONCLUSION
ProTaper removed more dentin than Twisted File during canal instrumentation in coronal and middle thirds of root canals.Also, ProTaper eliminated more dentin than Twisted File on the mesial wall in the coronal sections.Furthermore, ProTaper system caused greater cross sec tional changes of root canals before and after instrumen tation compared to Twisted File system.

UVOD
Či šće nje i ob li ko va nje ka na la ko re na zu ba je va žan ko rak u en do dont skoj te ra pi ji.Ova fa za uklju ču je dez in fek ci ju i ukla nja nje de la den ti na sa zi do va uz odr ža va nje iz vor nog ob li ka ka na la i po sti za nje kon ti nu i ra nog ko nu sa, ka ko bi se do bi la od go va ra ju ća op tu ra ci ja [1].Zbog pro men lji vo sti ana to mi je ka na la ko re na, in stru men ta ci ja za kri vlje nih ka na la mo že do ve sti do na sta ja nja pro ce du ral nih gre ša ka, kao što su ste pe nik, zip ping, el bow, tran spor ta ci je i per fo ra ci je ka na la [2,3].Si gur ne teh ni ke pre pa ra ci je ka na la ko re na bi tre ba lo da eli mi ni šu ili ma kar sma nje ove pro ce du ral ne gre ške.Ne ko li ko si ste ma in stru me na ta je pred lo že no da bi se po sti gao ovaj cilj.Niklti ta ni jum ske (Ni Ti) le gu re za en do dont ske in stru men te su pr vi put opi sa ne 1988.go di ne [4].Ota da je u en do don ci ju uve de no ne ko li ko ma šin skih Ni Ti si ste ma in stru me na ta raz li či tih ko nu sa i di zaj na.Zbog nji ho ve flek si bil no sti i ela stič no sti po bolj šao se kva li tet pre pa ra ci je ka na la ko re na, a ja tro ge na ošte će nja ve o ma za kri vlje nih ka na la ko re na su po sta la re đa [5].
Pro Ta per (Dentsply/Ma il le fer, Bal la i gu es, Švaj car ska) i Twi sted Fi les (Sybro nEn do, Oran ge, CA, SAD) su dva Ni Ti si ste ma in stru me na ta ko ja se ko ri ste ši rom sve ta.Pro Ta per je si stem ko ji se sa sto ji od tri in stru men ta za ob li ko va nje ka na la i pet in stru me na ta za za vr šnu ob ra du ka na la.In stru men ti za ob li ko va nje ka na la (S) ima ju ras tu ći ko nus od vr ha do vra ta in stru men ta, ko ji omo gu ća va bo lju flek si bil nost u sre di šnjoj i api kal noj re gi ji.In stru men ti za za vr šnu ob ra du (F) ima ju ma nji ko nus, kru ći su i pro iz vo de ve ći ko nus u api kal ni re gi ji.In stru men ti Pro Ta per ima ju po pre čan pre sek kon vek snog tro u gla stog ob li ka, ko ji ukla nja ma nje den ti na, kao i za o bljen vrh.Di zajn žle bo va ovih in stru me na ta je ta kav da kom bi nu je pro men lji vu ve li či nu ko nu sa duž in stru men ta [6,7].Si stem Twi sted Fi les je pro iz ve den na spe ci fi čan na čin ta ko što je Ni Ti le gu ra za gre ja na, hla đe na, a po tom uvr nu ta, da ju ći in stru men tu su per e la stič nost i ot por nost na ci klič ki za mor [8,9].Ovi in stru men ti ima ju ne pro men ljiv ko nus (0,04, 0,06, 0,08, 0,10, 0,12), na po preč nom pre se ku su tro u gla stog ob li ka, ima ju pro men ljiv broj se či va po je di ni ci du ži ne in stru me na ta i za tu pljen, ne ak ti van vrh.Di zajn in stru men ta je va žan za to što mo že uti ca ti na is hod te ra pi je.Mno gi pro iz vo đa či uklju ču ju raz li čit di zajn u svo je si ste me in stru me na ta da bi sma nji li api kal nu tran spor ta ci ju ka na la i po sti gli si gur ni ju pre pa ra ci ju ka na la [10].Pro ce na efi ka sno sti in stru me na ta i teh ni ka pre pa ra ci je je ve o ma va žna pre nji ho vog uvo đe nja u kli nič ku prak su.
Cilj ove stu di je bio je da upo re di pro me ne na zi du ka na la ko re na na sta le ob ra dom za kri vlje nih ka na la ko re na po mo ću dva Ni Ti si ste ma ma šin skih in stru me na ta -Pro Ta per i Twi sted Fi les.

MATERIJAL I METODE RADA
Iz vo đe nje stu di je odo brio je Etič ki ko mi tet Sto ma to lo škog fa kul te ta Uni ver zi te ta u Per nam bu ku.Za eks pe ri ment je upo tre blje no 25 eks tra ho va nih man di bu lar nih pr vih mo la ra.Kri te ri ju mi za oda bir zu ba bi li su: in takt na ko mo ra pul pe, pot pu no for mi ran ko ren, ko re ni slič ne du ži ne (14,53±1,52 mm), dva odvo je na me zi jal na ka na la i za kri vlje nost ko re na od 20 do 40 ste pe ni me re no pre ma me to di Šnaj de ra (Schne i der) [11].
Na kon am pu ta ci je dis tal nog ko re na, oklu zal ne po vr ši ne mo la ra su po rav na te po mo ću di ja mant skog di ska (Vor tex, São Pa u lo, SP) da bi se do bi la re fe rent na tač ka to kom in stru men ta ci je ka na la.Za pri stup ka na li ma upo tre blje na su di ja mant ska svr dla (Dentsply/Ma il le fer), a za pro ve ru pro hod no sti ka na la ko ri šćen je 10K in stru ment (Dentsply/Ma il le fer) dok ni je po stao vi dljiv pre ko vr ha ko re na.Rad na du ži na je od re đe na 1 mm kra će od api kal nog fo ra me na.
Pe de set ka na la (25 me zi o bu kal nih i 25 me zi o lin gval nih) je na su mič no svr sta no u dve gru pe.U gru pi 1 pri me njen je si stem Pro Ta per, a u gru pi 2 si stem Twi sted Fi les.Sva ka gru pa se sa sto ja la od istog bro ja me zi o bu kal nih i me zi o lin gval nih ka na la.
Uzor ci su pri pre mlje ni pri me nom teh ni ke ko ju je opi sao Bra man te (Bramante) sa sa rad ni ci ma [12].Pri stup ni ka vi te ti i apek si su za tvo re ni po mo ću cr ve nog vo ska (Hygi e nic Cor po ra tion, Akron, OH, SAD).Ko re ni su uto plje ni u hlad no po li me ri zu ju ću akril nu smo lu (VI PI, Pi ras su nun ga, SP, SAD) do gleđ no ce ment nog spo ja.Na kon po li me ri za ci je smo le na pra vlje ni su ho ri zon tal ni žle bo vi, da bi se do bi la tri de la na sva kom ko re nu, i to: 4 mm od api kal nog fo ra me na, u sred njoj i ko ro nar noj tre ći na ko re na.Oko sva kog ka lu pa je na pra vljen do dat ni sloj, ka ko bi se omo gu ći lo vra ća nje svih de lo va ko re na u pr vo bit nu po zi ci ju na kon se če nja.Sva ki blok smo le je pre se čen na če ti ri de la po mo ću oštri ce od ner đa ju ćeg če li ka de blji ne 0,15 mm pri ma loj br zi ni.
Pre pre pa ra ci je ka na la ko re na ko ro nar na stra na sva kog de la je ske ni ra na (HP De skjet F4200 prin ter, Hew lett Pac kard, Pa lo Al to, CA, SAD) ko ri ste ći 1200 ppi i ve li či nu 100%.Sve di gi tal ne fo to gra fi je su ana li zi ra ne po mo ću od go va ra ju ćeg soft ve ra (Ado be Pho tos hop CS4 Ex ten ded, Ado be System In cor po ra ted, San Jo se, CA, SAD).Je dan pik sel je pre tvo ren u 0,0211 mm.Na sva koj di gi tal noj fo to gra fi ji po preč ni pre sek ka na la je bio obo jen cr no, a cen tar je ozna čen be lom bo jom.Po tom su iz me re ni po vr ši na po preč nog pre se ka i uda lje nost zi do va (spo lja šnjeg, unu tra šnjeg, me zi jal nog i dis tal nog) od cen tra ka na la.Bu kal ni zid me zi o bu kal nog ka na la i lin gval ni zid me zi o lin gval nog ka na la su kla si fi ko va ni kao spo lja šnji zi do vi, a na spram ni kao unu tra šnji zi do vi.
Pre se ci zu ba su na kon opi sa nog me re nja po no vo sa sta vlje ni i je dan sto ma to log je iz veo pre pa ra ci je svih ka na la mo to rom s kon tro li sa nim obrt nim mo men tom i pri me nom teh ni ke crown down pre ma pre po ru ci pro iz vo đa ča.Ka na li su ob ra đe ni na sle de ći na čin: gru pa 1 -S1, SX, S2, F1, F2 i F3; gru pa 2 -25/0,08, 25,06, 25,04 i 30/0,06.Zad nji in stru men ti su bi li F3 (gru pa 1) i 30/0,06 (gru pa 2) do rad ne du ži ne.U sva koj gru pi pri me njen je 10K in stru ment da bi se osi gu ra la pro hod nost ka na la, a za iri ga ci ju je ko ri šće no 2 ml dvo i po pro cent nog na tri jumhi po hlo ri ta na kon sva kog in stru men ta.Me re nje istih pa ra me ta ra pod istim okol no sti ma kao i pre pre pa ra ci je vr še no je i na po sto pe ra ci o nim pre se ci ma ko re na.Pro me na u de blji ni zi do va ka na la pre i po sle pre pa ra ci je do bi je na je su per im po zi ci jom fo to gra fi ja po preč nog pre se ka u ko ro nar noj, sred njoj i api kal noj tre ći ni pre i po sle pre pa ra ci je.

REZULTATI
Po sto ja la je sta ti stič ki zna čaj no ve ća raz li ka po preč nih pre se ka u ko ro nar noj i sred njoj tre ći ni pre i po sle pre pa ra ci je ka na la ko re na zu ba (p=0,040 i p=0,043) iz me đu gru pe 1 i 2, dok raz li ke ni je bi lo iz me đu pre se ka u api kal noj tre ći ni na kon ko ri šće nja si ste ma Pro Ta per i Twi sted Fi les (p=0,992) (Ta be la 1).
Sred nja uda lje nost od cen tra ka na la do me zi jal nog zi da u ko ro nar nom de lu bi la je ve ća u gru pi uzo ra ka gde je ko ri šćen Pro Ta per i sta ti stič ki zna čaj no raz li či ta u od no su na gru pu u ko joj je pri me njen si stem Twi sted Fi les (p>0,05) (Ta be la 2).Uda lje nost osta lih zi do va u ko ro nar noj tre ći ni, kao i svih zi do va u sred njoj i api kal noj tre ći ni, ni je bi la sta ti stič ki zna čaj no raz li či ta u gru pi 1 u od no su na gru pu 2 (p>0,05) (Ta be la 2).Sta ti stič ki zna čaj ne raz li ke iz me đu ove dve gru pe ni je bi lo (p>0,05) ni u po preč nim pre se ci ma ka na la pre pre pa ra ci je.

DISKUSIJA
Pre pa ra ci ja ka na la ko re na se če sto pro ce nju je ko ri šće njem eks tra ho va nih zu ba ili pla stič nih blo ko va sa si mu li ra nim za kri vlje nim ka na li ma [13,14].Si mu li ra ni ka na li ima ju stan dard ni preč nik, du ži nu i ste pen za kri vlje nja, ali ne opo na ša ju do bro kri vi nu ko ja po sto ji u bu ko lin gval nom i me zi o di stal nom prav cu kod pri rod nih zu ba [15].Osim to ga, ni je mo gu će si mu li ra ti tvr do ću i abra zi ju den ti na, ni ti stres ko ji pre tr pi in stru ment to kom pre pa ra ci je ka na la.
Pred lo že no je ne ko li ko me to da za pro ce nu pre pa ra ci je ka na la ko re na, kao što su upo red na ana li za ra di o graf skih sni ma ka, blo ko vi od smo le, si li kon ski oti sci i mi kro kom pju te ri zo va na to mo gra fi ja [2,16,17,18].U na šoj stu di ji je ko ri šće na me to da ko ju su raz vi li Bra man te i sa rad ni ci [12], jer je to pro ve re na me to do lo gi ja ko ja omo gu ća va po re đe nje uzo ra ka pre, to kom i na kon in stru men ta ci je ka na la [13,19,20].Ta ko đe, la ko se iz vo di i ni je sku pa [20].Ne do sta tak ove me to de je u to me da to kom re za nja zu ba la te ral ni po kre ti di ska mo gu do ve sti do gu bit ka ma te ri ja la [21].Po re đe nje di gi tal nih fo to gra fi ja na pra vlje nih pre i po sle ob ra de ka na la po mo ću pro gra ma za ana li zu sli ka mo že bi ti al ter na ti va u pro ce ni pre pa ra ci je ka na la [13,20,21].
Za kri vlje ni ka na li su pro blem u en do dont skom le če nju.Me zi jal ni ka na li man di bu lar nih mo la ra su uski i spljo šte ni, što ote ža va ob ra du ka na la [22,23].U na šoj stu di ji obe gru pe su ima le isti broj uzo ra ka, a in stru men ti su ko ri šće ni na iz me nič no u bu kal nim i lin gval nim ka na li ma da bi se na do me sti le even tu al ne raz li ke u mor fo lo škom iz gle du ka na la.Me zi o bu kal ni i me zi o lin gval ni ka na li su bi li pod jed na ko ras po re đe ni u obe gru pe.
Sred nje raz li ke iz me đu po vr ši na ka na la pre i po sle ob ra de ka na la bi le su ve će u gru pi 1 (Pro Ta per) u svim tre ći na ma; ta raz li ka je bi la sta ti stič ki zna čaj na (p<0,05) u ko ro nar noj i sred njoj tre ći ni u od no su na gru pu 2 (Twi sted Fi les).Ovi re zul ta ti su u sa gla sno sti s na la zi ma slič nih stu di ja [24,25].
U na šoj stu di ji Pro Ta per je uklo nio znat no vi še den ti na ne go si stem Twi sted Fi les na me zi jal nom zi du u ko ro nar nom de lu ka na la.Ukla nja nje ve će ko li či ne den ti na mo že bi ti zbog ob li ka Pro Ta per in stru me na ta, ko ji su u vi du slo va S. Pre ma uput stvi ma pro iz vo đa ča, ovi in stru men ti se ko ri ste bez api kal nog pri ti ska, ali sa la te ral nim po kre ti ma čet ka nja uz zi do ve ka na la, na ro či to onog gde je den tin naj de blji -u na šom eks pe ri men tu to je bio me zi jal ni zid [25].Pre ko mer no ukla nja nje den ti na u ovoj re gi ji mo že do ve sti do kon tak ta s pa ro don ci ju mom ili sla blje nja zub nog tki va, što po ve ća va ri zik od pre lo ma ko re na.Dis tal ni zid je naj ta nji zid kod me zi jal nih ka na la zbog za stu plje nog kon ka vi te ta na dis tal nom zi du me zi jal nog ko re na man di bu lar nih mo la ra [26].Ob ra da za kri vlje nih ka na la me to dom an ti cur va tu re mo že spre či ti per fo ra ci ju ko re na i omo gu ći ti pri stup api kal nom de lu ka na la [3].
Ana li za pro me na u de blji ni zi da den ti na je po ka za la da dve vr ste in stru me na ta ne ukla nja ju den tin pod jed na ko u svim re fe rent nim tač ka ma; ipak, raz li ke ni su bi le sta ti stič ki zna čaj ne, osim za me zi jal ni zid u ko ro nar noj tre ći ni.Dru ge stu di je su uoči le si me trič no ukla nja nje den ti na sa svih zi do va ka na la to kom pri me ne si ste ma in stru men ta Pro Ta per, na ro či to u api kal noj tre ći ni [21,27].Mo gu će je da ra di o graf ska me to da ko ri šće na u ovim stu di ja ma ni je tač no iz me ri la uklo nje ni den tin, kao što je to mo gu će ana li zom po preč nog pre se ka ka na la u Bra man te o voj me to di, pri me nje noj u na šoj stu di ji.
U obe gru pe je bi lo ka na la sa de lo vi ma zi do va u svim tre ći na ma ko ji ni su do tak nu ti in stru men ti ma, na ro či to u unu tra šnjim zi do vi ma ist mu sa.Ovaj na laz je u skla du s re zul ta ti ma stu di je Hils ma na (Hülsmann) i sa rad ni ka [28].Tre ba lo bi oba vi ti is tra ži va nja o to me ka kav efe kat ima ju kom bi na ci je me to da pre pa ra ci je na ob li ko va nje ka na la ko re na [29,30].

ZAKLJUČAK
Po mo ću si ste ma Pro Ta per je to kom pre pa ra ci je ka na la ko re na zu ba uklo nje no vi še den ti na u ko ro nar noj i sred njoj tre ći ni ka na la ne go pri me nom Twi sted Fi les.Ta ko đe, Pro Ta per je uklo nio vi še den ti na ne go si stem Twi sted Fi les sa me zi jal nog zi da u ko ro nar noj tre ći ni.Pro Ta per do vo di do na stan ka ve ćih pro me na po preč nog pre se ka ka na la ko re na pre i po sle in stru men ta ci je ne go si stem Twi sted Fi les.

Komparativna studija nikl-titanijumskih sistema instrumenata ProTaper i Twisted Files u preparaciji zakrivljenih kanala korena zuba
26. Machado MEL, Sapia LAB, Cai S, Martins GHR, Nabeshima CK.Comparison of two rotary systems in root canal preparation regarding disinfection.J Endod.2010; 36:1238-40.27.Setzer FC, Kwon TK, Karabucak B. Comparison of apical transportation between two rotary file systems and two hybrid rotary instrumentations sequences.J Endod.2010; 36:1226-9.28.Hülsmann M, Gressmann G, Schäfers F. A comparative study of root canal preparation using FlexMaster and Hero 642 rotary Ni-Ti instruments.Int Endod J. 2003; 36:358-66.29.Loizides AL, Kakavetsos VD, Tzanetakis GN, Kontakiotis EG, Eliades G.A comparative study of the effects of two nickel-titanium preparation techniques on root canal geometry assessed by microcomputed tomography.J Endod.2007; 33:1455-9.30.Farid H, Khan FR, Rahman M. ProTaper rotary instrument fracture during root canal preparation: a comparison between rotary and hybrid techniques.Oral Health Dent Manag.2013; 12:50-5.Žoze Rodolfo de Lima Dias 1 , Žizel Nevares 1 , Felipe Šavijer 1 , Lusijana Feraz Gominjo 2 , Dijana Santana de Albukerke 1 Svr ha pre pa ra ci je ka na la ko re na zu ba je či šće nje i ob li ko va nje ka na la ko re na uz što je mo gu će ve će oču va nje iz vor nog anatom skog iz gle da.Me đu tim, ovaj pri stup kod za kri vlje nih ka na la mo že do ve sti do pre ve li kog ukla nja nja den ti na sa zi do va ka na la i tran spor ta ci je ka na la.Cilj ove stu di je bio je da oce ni pro me ne u ob li ku ka na la na sta le upo tre bom dva nikl-ti ta ni jum ska si ste ma ro ti ra ju ćih in stru me na ta, Pro Ta per i Twi sted Fi les, u za kri vlje nim ka na li ma.Ma te ri jal i me to de ra da U stu di ji je ko ri šće no 25 eks tra ho va nih man di bu lar nih pr vih mo la ra ko ji su ima li dva odvo je na ka na la u me zi jal nom ko re nu.Dis tal ni ko re ni su am pu ti ra ni, a 50 me zi jal nih ka na la (25 me zi o bu kal nih i 25 me zi o lin gval nih) na su mič no su po de lje ni u dve gru pe: u gru pi 1 pri me nje ni su in stru men ti Pro Ta per, a u gru pi 2 Twi sted Fi les.In stru men ti su ko ri šće ni pre ma uput stvu pro iz vo đa ča.Kao kraj nji in stru ment ko ri šćen je F3 u gru pi 1, od no sno 30/0,06 u gru pi 2. For mi ra ni su pre se ci na tri ni voa ko re na (ko ro nar nom, sred njem i api kal nom) pre i po sle za hva ta.Pro me ne u de blji ni den tin skog zi da su me re ne i vred no va ne Braman te o vom (Bra man te) me to dom i po mo ću soft ve ra za ob ra du di gi tal nih fo to gra fi ja.Za sta ti stič ku ana li zu ko ri šćen je Man-Vit ni jev (Mann-Whit ney) U-test (p<0,05).Re zul ta ti Ko li či na den ti na ko ja je uklo nje na po mo ću si ste ma Pro Ta per u ko ro nar noj i sred njoj tre ći ni ka na la bi la je zna čaj no ve ća ne go u gru pi u ko joj je pri me njen si stem Twi sted Fi les (p=0,040 i p=0,043).Po mo ću si ste ma Pro Ta per je ta ko đe uklo nje na ve ća ko liči na den ti na sa me zi jal nog zi da u ko ro nar nom de lu ka na la ne go po mo ću si ste ma Twi sted Fi les (p=0,039).Iz me đu dve gru pe uzo ra ka ni je bi lo sta ti stič ki zna čaj ne raz li ke u uda lje no sti cen tra ka na la od svih zi do va u sred njoj i api kal noj tre ći ni (p>0,05).Za klju čak Si stem Pro Ta per iza zi va ve će pro me ne u po vr ši ni po preč nog pre se ka ka na la ko re na ne go si stem Twi sted Fi les.Ključ ne re či: pre pa ra ci ja ka na la ko re na; Pro Ta per; Twi sted Fi les; za kri vlje ni ka na li