Scanning Electronic Microscopy Analysis of the Apical Surface After of Root-End Resection With Different Methods

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1 SCANNING VOL. 37, (2015) Wiley Periodicals, Inc. Scanning Electronic Microscopy Analysis of the Apical Surface After of Root-End Resection With Different Methods RICARDO AFFONSO BERNARDES, 1,2 MARCO ANTONIO HÚNGARO DUARTE, 2 RODRIGO RICCI VIVAN, 2 JARCIO VBALDI, 1 BRUNO CVASCONCELOS, 3 AND CLÓVIS MONTEIRO BRAMANTE 2 1 Department of Dentistry, Endodontics and Dentistry Material, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil 2 Brazilian Dental Association, Taguatinga, Federal District, Brazil 3 School of Dentistry of Sobral, Federal University of Ceara, Campus Sobral, Sobral, Ceara, Brazil Summary: To compare the time dispensed and the surface characteristics when a root-end resection was performed with a surgical ultrasonic device (VarioSurg, NSK, Japan) or with a Zekrya bur. Forty distal roots of freshly extracted mandibular molars were selected and divided into four different groups: (G1) stainless steel insert with ultrasound; (G2) diamond insert with ultrasound; (G3) stainless steel and diamond inserts with ultrasound, and (G4) Zekrya burs. The time required for the root-end resection was timed and the surface characteristics were evaluated via scanning electronic microscopy. The median times for the root-end resections were: s for G1, s for G2, s for G3, and 7.44 s for G4, the latter presented a smoother root-end surface. There was no statistically significant difference in the comparisons between G3 group and G4 group (Zekrya burs). The other groups where the root-end resections were with ultrasonic devices proportioned a prolonged time to resection with irregular surfaces. SCANNING 37: , Wiley Periodicals, Inc. Key words: root-end resection, ultrasound, Zekrya bur Introduction The aim of endodontic therapy is the prevention or elimination of apical periodontitis in order to achieve Contract grant sponsor: FAPESP; Contract grant number: 2012/ Address for reprints: Ricardo Bernardes, Department of Dentistry, Endodontics and Dentistry Material, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil dr.ricardoaffonso@uol.com.br Received 13 October 2014; revised 22 December 2014; Accepted with revision 29 December 2014 DOI: /sca Published online 4 February 2015 in Wiley Online Library (wileyonlinelibrary.com). adequate healing and success. Endodontic surgery may be indicated in cases with persistent or refractory periradicular pathosis that does not heal after nonsurgical retreatment (Setzer et al.,2012). In the last decades, new technologies were introduced into endodontic surgery, such as the use of the microscope, micro-instruments, ultrasonic tips, and more biologically acceptable root-end filling materials. These modern techniques increased the success rates, with outcomes for all microsurgical approaches of approximately 90% (Kim et al., 2008). The endodontic surgery modalities include curettage, root-end resection, surgery with simultaneous root canal filling, and rootend filling (Bernardes et al., 2009). The root-end resection technique is a critical step in endodontic surgery. According to some authors it must be done in such a way as to achieve a uniform cut and smooth surface (Gutman and Harrison, 91). A smooth surface is important because it can decrease the number of exposed dentinal tubules at the resected root surface and minimizes apical leakage (Del Fabro et al., 2010). The #57 Lindeman or Zekrya burs with and without refinement with multi-fluted carbide burs produced more regular and smooth surfaces with the least shattering (Morgan and Marshall, 98). The introduction of ultrasonic activation represents an important advancement in endodontic surgery because bone-tissue management and the root-end cavity preparation can be performed with this device, thus reducing the risk of damage to the soft tissues (Richman, 57; Neilsen et al., 55). A study compared the time required for the root-end resection and the root-end surface characteristics by scanning electron microscopy between the ultrasonic chemical vapor deposition (CVD)-coated tip (#FG700L) with high-speed and (#699) low-speed carbide burs (Bernardes et al., 2009). The results showed that the carbide burs produced more regular root-end surfaces, and the crosscut tapered flat end

2 (#699) carbide bur at a low speed had a better performance than the plain tapered fissure (#170L) carbide bur at a high speed. Similar results were found by other authors (Duarte et al., 2007). In dentistry the surgical ultrasonic device is used for osteotomies, sinus lifts, bone splitting, extractions, and implants because the cutting is precise and the width varies between 60 and 200 mm, depending on the insert. Surgical ultrasound offers two types of tips, stainless steel and diamond, both with varied designs (Del Fabro et al., 2010). However, the literature is scarce in studies regarding scanning electronic microscopy analysis of the apical surface after a root-end resection with different methods. This study compared the time required and the root-end surface characteristics when the use of surgical ultrasound with diamond and/or stainless steel inserts with Zekrya burs on the root-end resections. The null hypothesis tested was that the root-end resection with surgical ultrasound with stainless steel and/or diamond inserts requires the same time and produces similar surface characteristics of that of the Zekrya bur. R. Bernardes et al.: SEM Analysis of the Apical Surface After Resection 127 Material and Methods Forty distal roots with single root canals of freshly extracted mandibular molars were selected and stored in 10% formalin solution for a maximum time of 3 months until use in the study. The roots were divided into four groups according to the root-end resection methods: (G1) with a SG1 stainless steel insert (NSK, JAPAN) with a mm thickness blade; (G2) with a SG6D diamond insert (NSK) with a mm thickness; (G3) with a SG1 stainless steel insert and refined with a SG6D diamond insert; (G4) with Zekrya burs (KG Sorensen, São Paulo, SP, Brazil) (Fig. 1). For G1, G2, and G3, the inserts were utilized in a surgical ultrasonic device (VarioSurg, NSK,Tokyo, Japan) in surgical function and 100% potency. For the G4 group, the Zekrya bur was utilized at high speed with 350,000 rpm. The teeth were positioned in a clamp with the apex turned upward during the root end section. The 2 mm of the apical portion of the root were sectioned at a 90 angle with the root long axis using the following instruments under copious water irrigation. The total Fig. 1. (a) Stainless steel insert SG1 (NSK, JAPAN) and SEM. (b) Diamond insert SG6D (NSK) and SEM. (c) #170L fissure multipurpose Zekrya burs (KG Sorensen, São Paulo, SP, Brazil) and SEM.

3 128 SCANNING VOL. 37, 2 (2015) time required for the root-end resection was recorded for each root. The resected roots were dried at room temperature during 24 h and then mounted on metallic stubs, sputtercoatedwithgold(hammervisputtering System; Anatech Ltd, Alexandria, VA) at 10 a, 120 V, f ¼ 50/60 hz and examined with a Scanning Electron Microscope (JSMT220A, Jeol, Tokyo, Japan). Electromicrographs were taken at 35 and 350 magnification for analysis of the surface roughness. Two calibrated examiners, using a scoring method (0 3) as described by Duarte et al. (2007): 0 smooth surface, 1-surface with slight roughness, 2 surface with moderate roughness, and 3 surface with severe roughness. After the analyses by scanning electron microscopy, the data were tabulated and submitted to analysis by the Kappa test to evaluate the concordance between examiners. The comparison between the groups for the time spent to the root end section and the superficial roughness were performed using the Kruskall Wallis and Dunn tests. The significance level was established at 5%. Results The Kappa test showed a value of 0.89 which demonstrated a great concordance among the examiners in the evaluations of the electromicrographs. The time for the root-end resection was s for the SG1 stainless steel insert (G1), s for the SG6D diamond insert (G2), s for the SG1 stainless steel insert, refined with a SG6D diamond insert (G3), and 7.44 s for the Zekrya burs (G4) as shown in Table I. At the statistical comparison of the time required for the root-end resection, no significant statistical differences (p > 0.05) were found among the groups 1 and 3. Statistical significant differences (p < 0.05) occurred in the other comparisons. For the roughness analysis, there was no statistically significant difference between the G3 (SG1 stainless steel insert and refined with a SG6D diamond insert) and G4 (Zekrya burs) (Table II). Significant statistical differences (p < 0.05) occurred in the comparisons among the group 4 with groups 1 and 2. Figures 2 and 3 show the representative images of scores used. Mean, standard deviation (SD) and statistical comparison of the time (seconds) required by each group at the realization of the apicoectomy TABLE I Groups Mean SD G a G b G a G c 1.97 Different letters show significant statistical differences (p < 0.05) Median, minimum and maximum of the score values and statistical comparison of the roughness analysis TABLE II Groups Median Minimum Maximum G1 2 a 1 3 G2 2 a 1 3 G3 1 ab 0 2 G4 0 b 0 1 Different letters show significant statistical differences (p < 0.05) Discussion This study evaluated the null hypothesis that the rootend resection with surgical ultrasound with stainless steel and/or diamond inserts requires the same time and produces similar surface characteristics of that of the Zekrya bur. The null hypothesis was rejected. Many studies have attempted use of the burs at high and low speeds (Bernardes et al., 2009; Duarte et al., 2007), laser (Bramante and Arellano, 2003), and ultrasonic (Setzer et al., 2012) methods but there are few studies utilizing surgical ultrasonic methods (Del Fabro et al., 2010). This method is mainly utilized for surgical dentistry involving bone surgery and implants. When utilized in bone surgery, it has demonstrated greater safety with minor accidental occurrences during surgery (Angiero et al., 2011). The alteration of the intraosseous temperature changes during the use of stainless steel surgical ultrasonic inserts with three, four and five cutting blades is low, showing that the correct use of the method does not give rise to prolonged temperature increases over 47 C and does not cause any irreversible thermal damage in the bone (Schutz et al., 2012). Endodontic surgery outcomes improved in recent years because of the adaption of microsurgical instruments which permit a better management of the root end. It is important exists methods for minimizing the adverse effects, such as angled root-end resections, cracks, marginal quality of the retrograde cavity, and smoothness of the resected apical surface should be considered to reach the healing (Kim and Kratchman, 2006). In relation to the power setting utilized, the potency of the ultrasonic device did not affect quality of the results, which was similar to other studies (Morgan and Marshall, 98; Frank et al. 96; Layton et al., 96; Gilheany et al. 94; Taschieri et al., 2004). In the present work, a surgical ultrasonic instrument with a stainless steel insert with five cutting blades or a diamond insert was utilized in constant vibration mode and 100% potency. The use of the constant vibration mode for the retrograde preparation with the ultrasonic surgery instrument has been recommended (Del Fabro et al., 2010). The correct angulation in root-end resection is important because an angle less than 90, in relation

4 R. Bernardes et al.: SEM Analysis of the Apical Surface After Resection 129 Fig. 2. SEM examples of apicoectomy with: Stainless steel insert SG1 (NSK, JAPAN) a ¼ 35 and b ¼ 350 (score 3 surface with severe roughness); c¼ 35 and d ¼ 350 with diamond insert SG6D (NSK) (score 2 surface with moderate roughness). Fig. 3. SEM examples of apicoectomy with: Stainless steel insert SG1 associated with diamond insert, a ¼ 35 and b ¼ 350 (score 1 surface with slight roughness); c ¼ 35 and d ¼ 350 with multipurpose Zekrya burs (KG Sorensen, São Paulo, SP Brazil) (score 0 smooth surface).

5 130 SCANNING VOL. 37, 2 (2015) the root long axis, exposes more dentinal tubules, which can increase the surface roughness and risk of bacterial contamination. In the present study, a 90 angle was utilized for all groups, with an extension of 3 mm from the apices, in accordance with a previous study (Vercellotti et al., 2001). The results of this study showed that the surface resected with the Zekrya burs (G4) presented the smoothest surface when compared to the stainless steel (G1) and diamond inserts (G2). When the two inserts were associated (G3), the results were similar to the Zekrya group (G4). It is, however, recommended that the use of a diamond insert be made in association with the stainless steel insert for the refinement (G3) of the resected root end. These results are in accordance with those of previous studies (Morgan and Marshall, 98; Bernardes et al., 2009). The presence of irregularities and rough surfaces may serve as irritants, accumulate debris, and stimulate the resorption during the reparation (Kim and Kratchman, 2006). In relation to the time dispensed for the root-end resection, the Zekrya bur (G4) was significantly faster when compared with both surgical ultrasonic inserts (G1, G2, and G3). The faster time dispensed for the root end resection favored a shorter surgical time (Bernardes et al., 2009; Morgan and Marshall, 98). Further in vivo studies are needed to evaluate the effect of a root-end resection utilizing surgical ultrasound in the apical repair. Conclusion In conclusion, under the tested conditions, The rootend resection with the surgical ultrasonic devices required a longer time than the root-end resection with bur. There was no statistically significant difference between the G3 group (stainless steel and diamond inserts with ultrasound) and the G4 group (Zekrya bur). For the other groups which utilized the ultrasonic device for the root-end resection were required a significant prolonged time and proportioned more rough surfaces than the use of the Zekrya bur group. Further studies are necessary, especially in vivo investigations, to determine the influence of root-end section technique on the apical healing after endodontic surgery. References Angiero F, Benedicenti S, Signore A, Parker S, Crippa R Apicoectomies with the erbium laser: a complementary technique for retrograde endodontic treatment. Photomed Laser Surg 29: Bernardes RA, Souza Jr JV, Duarte MAH, Moraes IG, Bramante CM Ultrasonic chemical vapor deposition-coated tip versus high and low speed carbide burs for apicoectomy: time required for resection and scanning electron microscopy analysis of the root end surface. J Endod 35: Bramante CM, Arellano MA Analisis en microscopia de barrido de la superficie apical en apicectomias realizadas usando fresa y laser. 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