Influence of cervical preflaring on apical file size determination - An in vitro study

Transcription

1 Original Research Influence of cervical preflaring on apical file size determination - An in vitro study VASUNDHARA SHIVANNA * DEEPALI AGARWAL ** ABSTRACT Aim: To investigate the influence of cervical preflaring on apical file size determination using 4 different rotary instruments. Methodology: Forty extracted human maxillary central incisors were used for the study. Access opening was done and the working length was established. Teeth were randomly divided into 4 groups namely, no preflaring (Control), Gates Glidden drills, Protaper instruments and LA Axxess burs. After apical file size determination for each tooth IAF were fixed at the WL. Teeth were sectioned transversally 1mm from the apex, with the binding file in position, analyzed & root canal & file maximum diameters were recorded for each sample. Results: LA Axxess burs produced the smallest differences between anatomical diameter & first file to bind. The major discrepancy was found in group 1, where no cervical preflaring was performed. Protaper instruments were ranked second & Gates Glidden Drills third with statistically significant results (p< 0.01). Conclusion: Cervical preflaring helps to gauge the apical diameter better and LA Axxess burs are more effective for preflaring compared to other rotary instruments. Keywords: Apical File Size Determination, Initial Apical File, Coronal Flaring, Instrument Type, Working length(wl). INTRODUCTION Endodontic therapy is traditionally divided into two main objectives. Cleaning & shaping & three dimensional obturation of the root canal system (Contreras 2001). Although cleaning & shaping accurately describes the mechanical procedures, it should be emphasized that shaping & cleaning more correctly reflects the fact that enlarged canals direct & facilitate the cleaning action of irrigants & removal of infected dentin (Cohen). Effective canal debridement relies on the accurate determination of WL & adequate apical canal enlargement. Detection of the apical constriction & determination of the first file that binds at the working length are based on the operator s tactile sensitivity. This premise relies on the assumptions that the root canal is narrowest in the apical third & that the file would pass without interference until reaching this constriction, which offers resistance to further penetration (Ibelli 2007). However, it has been advocated that continuous & progressive dentin formation on pulp chamber floor creates dentin projections that narrow the canal diameter, especially at the cervical third. Because of these interferences, determination * Professor & Head, ** PG Student, Department Of Conservative Dentistry & Endodontics, College of Dental Sciences, Davangere. 75

2 VASUNDHARA SHIVANNA, DEEPALI AGARWAL of the first file that binds at the apical region as a manner of establishing the final instrument size required for a complete apical enlargement does not provide a reliably predictable method. Thus, the concept of cleaning the apical canal to three sizes larger than the first file to bind is not based on scientific evidence (Wu et al 2002). The importance of cervical preflaring prior to initial apical file determination has been confirmed by different studies. Preflaring can be done with either manual or rotary instruments. One of the commonly used rotary instruments is a Gates Glidden drill. However, newer instruments like Protaper SX & Titanium nitrite treated stainless steel LA Axxess Burs, seem to be more promising for cervical preflaring (Schmitz 2008). The present study aims to evaluate the influence of cervical preflaring using different rotary instruments on apical file size determination. MATERIALS AND METHODS Forty human maxillary central incisors with complete root formation were collected. The teeth were kept in 0.1% thymol solution at 9 o C & were placed under running water to eliminate the traces of thymol 24 hrs prior to use. Standard access to the pulp was performed &the pulp tissue was removed with a barbed broach, avoiding contact with the root canal walls. The root canal of each tooth was explored using a 08 K file until the apical foramen was reached & the tip of the file was visible. The actual length for each tooth was determined & the WL was established by deducting 1 mm. Forty maxillary central incisors were then divided into 4 groups of 10 teeth each: Group I: (Control) Received the Initial apical instrument without previous preflaring of the root canal. Group II: Gates Glidden Drills of sizes 090, 110, 130 (Mani) were used to preflare the cervical & middle thirds of the root canal. The length of this preflaring was determined by the resistance felt in the middle portion of the root canal. Group III: Cervical portion of root canals were enlarged with Protaper SX (Dentsply) rotary files using endodontic electronic torque control Motor X- SMART (Dentsply), 3 mm short of the WL. Group IV: Titanium nitrite treated, stainless steel, LA Axxess burs (Sybron Endo) sizes 20/.06, 35/.06 & 45/.06 were used for preflaring the cervical & middle portions of the root canal, 3 mm short of the WL. During the preflaring of all the canals, copious irrigation with 10 ml of 1% sodium hypochlorite was performed. Each canal was sized using manual K files, starting with size 08 files until the WL was reached. File size were increased until a binding sensation was felt at the WL & the instrument size was recorded for each tooth. After apical file size determination for each tooth, the first K files which were binding at the WL were fixed with methylcyanacrylate. Teeth were sectioned transversally 1mm from the apex, with the binding file in position. The sections were then observed under a Stereoscopic magnifier (Olympus, SZX12 Japan) at 45X magnification & Images recorded digitally. The analysis of the images obtained were performed using Image ProPlus Software (USA). 76

3 INFLUENCE OF CERVICAL PREFLARING ON APICAL FILE SIZE DETERMINATION - AN IN VITRO STUDY Root canal & file maximum diameters were recorded for each sample. The differences between these measures was evaluated statistically for multiple comparison by one variable test (ANOVA) followed by Tukey s post test. RESULTS Results of present study ( Table 1& Graph 1) showed that the major discrepancy was found in group 1, where no cervical preflaring was performed (0.06 mm average). The LA Axxess burs produced the smallest differences between anatomical diameter & first file to bind (0.01mm average). Protaper instruments were ranked second & Gates glidden drills third with statistically significant results (0.03mm & 0.05mmrespectively). The ANOVA test showed a statistically significant difference (p <0.01) amongst groups, concerning the discrepancy between anatomical diameter at WL & the first file to bind in the canal. Tukey s post test was used to elucidate which groups were different. TABLE 1 Discrepancies measured between canal diameter at working length & binding file with different preflaring techniques. GROUPS 1. No preflaring 2. Gates Glidden drills 3. Protaper instrument 4. LA Axxess burs RANGE MEAN ± SD 0.06 ± ± ± ± One way ANOVA, F= 201.3, p <.01, Significant F- ANOVA Index GRAPH 1 Comparison of discrepancies (mm) between the diameters of the binding files and canals at the working length Instruments Used For Cervical Preflaring section at 1 mm when no preflaring is done section at 1mm preflared with protaper section at 1 mm when preflaring is done with GG drills section at when 1mm when preflared with LA Axxess burs DISCUSSION The biomechanical preparation of the apical region is an essential & critical operative step of the endodontic therapy. Research has shown that mechanical instrumentation greatly reduces the number of microorganisms remaining in the root canal system. To what extend the canal is supposed to be prepared has been a myth in the endodontic field. Grossman stated that the canal should be enlarged at least three sizes greater than its original diameter to remove bacteria and their substrates, dead pulpal tissue, to increase the capacity of the root canal to retain a larger amount of sterilizing agent; and to 77

4 VASUNDHARA SHIVANNA, DEEPALI AGARWAL prepare the tooth to receive the canal filling. On the other hand, it should not be so wide that it unnecessarily weakens the root & increases the risk of fracture. Apical access by cervical preflaring has been increasingly investigated. The increase in file size after flaring can be explained by realizing that, within a canal, irregularities & curvatures produce contacts with the file & interfere with its progression towards the apex. Early flaring, regardless of the method used, removes these contacts, opens the space & reduces file contact, thus a file progresses more easily toward the apex & comes to a stop only when the diameter of the canal begins to apply pressure against the instrument. This better sense of apical diameter provides information that should result in better biomechanical preparation. The findings of the present study showed that the removal of cervical interferences by canal preflaring with Gates Glidden drills (Group 2), Protaper (Group 3), LA Axxess burs (Group 4) allowed determining the IAF at the WL 1mm short of the apical foramen with K- files of larger sizes than those used in Group 1( no cervical preflaring). The ANOVA test showed a statistically significant difference amongst groups. The non flared group presented the greatest discrepancies between the canal size & the IAF diameter at the WL, compared to the other experimental groups (Contreras et al 2001, Wu et al 2002, Tan & Messer 2002 & Sreenivasa et al 2008). From all the specimens evaluated, the root canals preflared with LA Axxess system presented the least discrepancies between the canal size & the diameter of the first file that bound at the WL (Pecora et al 2005, Ibelli et al 2007 & Schmitz et al 2008). This may possibly be attributed to characteristics of the LA Axxess system, which includes: The configuration of LA Axxess burs, metal alloy properties, mode of operation & additionally, the taper (0.06), safe- end and flute design of LA Axxess instruments have been shown to yield complete removal of cervical interferences without occurrence of deviation or perforation. The groups preflared with Protaper & Gates Glidden drills were ranked second & third respectively ( Barroso et al 2005 & Vanni et al 2005). The performance of Protaper files is due to their modified design that provides optimal cutting efficiency and also to the multiple tapers along the active tip of the files, which allows for greater removal of interferences in the cervical third. The Gates Glidden drills straightened the coronal two- thirds of the root canals in an attempt to reduce binding in the coronal region. This provided direct access to both the cervical and middle thirds of root canals, reducing the contact area of the instrument in these regions. When used adequately GG instruments are inexpensive, safe and clinically beneficial tools. Nevertheless, these instruments did not allow for accurate determination of the initial apical file. Taking into account that the major purpose of the endodontic therapy is the cleaning and shaping of root canals, and considering that the first shortcoming to be overcome is performing an accurate determination of the file from which on the canal should be instrumented, it is important that the current concepts and techniques in Endodontics are reviewed to widen the scopes in root canal treatment and offer new perspectives and parameters that make these goals achievable. It seems consensual that cervical preflaring should be performed prior to determination of the size of the file that first fit at the WL. The results of the present study showed that, although cervical preflaring prior to IAF determination provided smaller discrepancy between the IAF & the smallest root canal diameter but in most cases, it did not 78

5 INFLUENCE OF CERVICAL PREFLARING ON APICAL FILE SIZE DETERMINATION - AN IN VITRO STUDY accurately reflect the real canal diameter 1 mm short of the apex. Hence, Apical shaping is easy when early flaring is used because only the apical one third remains unshaped. One can speculate that early flaring would be advantageous for all teeth, & it is recommended no matter the tooth type, because interfering contacts can exist in any canal. Endodontic research should further develop instruments and techniques for root canal preparation that are able to determine the real dimension of the root canals, while respecting the complexity of the apical anatomy. This is expected to provide a more effective cleaning of the root canal system with no risk of causing canal deformations during instrumentation and minimizing the difficulty in the lateral extension of the canal enlargement. It is mandatory to change clinical decisions guided by empiric personal experiences into clinical approaches supported by scientific evidence. CONCLUSION 1. The instrument binding technique for determining the anatomical diameter at WL is not precise; 2. The non flared group had the greatest discrepancy between the IAF diameter and canal diameter at the WL, regardless of the type of instrument; 3. Preflaring of the cervical and middle thirds of the root canal improves the determination of the anatomical diameter; 4. The instrument used for preflaring may play a role in determining the anatomical diameter at the working length. Canals preflared with LA Axxess burs presented the lowest discrepancy values between the file size and anatomical diameter. REFERENCES 1. Barroso JM, Guerisoli DMZ, Capelli A. Influence of cervical preflaring on determination of apical file size in maxillary premolars: SEM analysis. Braz Dent J 2005 ; 16 : Baugh D, Wallace J. the role of apical instrumentation in root canal treatment: A review of literature. J Endod 2005 ; 31(5) : Contreras MAL, Zinman EH, Kaplan SK. Comparison of the first file that fits at the apex, before and after early flaring. J. Endod 2001; 27(2) : Ibelli GS, Barroso JM, Capelli A. Influence of cervical preflaring on apical file size determination in maxillary lateral incisors. Braz Dent J 2007; 18(2) Ribeirao Preto 5. Leeb J. Canal orifice enlargement as related to biomechanical preparation. J Endod 1983 ; 9(11) : Pecora JD, Capelli A, Guerisoli DMZ. Influence of cervical preflaring on apical file size determination. Int Endod J 2005 ; 38 : Schmitz MS, Santos R, Capelli A. influence of cervical preflaring on determination of apical file size in mandibular molars: SEM analysis. Braz Dent J 2008,19(3) Ribeirao Preto 8. Spangberg LS. Comparison in vivo of the first tapered and non tapered instruments that bind at the apical constriction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod ; 102: Sreenivasa Murthy BV, George JV, Kumar M. Influence of coronal preflaring using gates glidden and protaper instruments on the first apical file size determination- A comparative in vitro study. Endodontology 2008 : Stephen Cohen, Kenneth M Hargreaves. Pathways of the Pulp 9 th Edition. 11. Tan BT, Messer HH. The quality of apical canal preparation using hand and rotary instruments with specific criteria for enlargement based on initial apical file size. J Endod 2002 ; 28 (9) : Tan BT & Messer HH. The effect of instrument type & preflaring on apical file size determination. Int Endod J 2002 ; 35 : Vanni JR, Santos R, Limongi O. Influence of cervical preflaring on determination of apical file size in maxillary molars: SEM analysis. Braz Dent J 2005 ; 16 (3) : Wu MK, Barkis D, Roris A & Wesselink PR. Does the first file to bind correspond to the diameter of the canal in the apical region? Int Endod J 2002 ; 35: