A comparison of root surfaces following apical root resection with various burs: scanning electron microscopic evaluation

Topography of root-end surface after freehand and three-dimensional-guided apicoectomy procedure: A scanning electron microscope study

Background

Dentinal microcracks formed during apical resection may lead to increased susceptibility to root fracture and improper sealing of apical preparation that may negatively influence the outcome of endodontic microsurgery.

Aims

This study was performed to analyze the root-end surface for dentinal microcracks using a scanning electron microscope (SEM) after resection with high-speed bur and trephine drill.

Materials and Methods

Thirty extracted single-rooted maxillary premolar teeth were selected and randomly distributed into two groups (n = 15). Working length was established using a #15 K-type file. Canals were prepared with a rotary Ni-Ti system to size 30/0.06 using endomotor, irrigated with 3% sodium hypochlorite, dried with paper points, and obturated with gutta-percha cones using a single-cone technique. All samples were mounted on preformed molds and poured using a mixture of sawdust and gypsum. In Group A; tungsten carbide bur was used to perform a freehand apicoectomy. In Group B; a trephine drill was used with a three-dimensional guide to perform 3 mm of root resection. Apicoectomy was performed in both groups under a dental operating microscope. Resected root ends were inspected for microcracks using SEM. The Shapiro-Wilk and Mann-Whitney U-test were used for statistical analysis.

Results

Microcracks were observed in all samples in both study groups. Trephine drill produced more microcracks on the resected root surface compared to the use of high-speed tungsten carbide bur with a statistically significant difference (P < 0.05).

Conclusions

The trephine drill used during targeted endodontic microsurgery produced more microcracks on the resected root dentine surface compared to the high-speed tungsten carbide bur used during freehand apicoectomy.

Effect of Endo-Z bur or Bladesonic ultrasonic tip on the adaptation of filling material. A micro-CT study

This study aimed to evaluate the effect of apicoectomy performed with a bur or an ultrasonic tip on the adaptation of the filling material to root canal dentin. Twenty human mandibular incisors were selected and prepared with a ProDesign Logic system up to diameter 40/.05. The root canals were filled with Bio-C Sealer (Angelus, PR, Brazil) using the single cone technique and were stored at 37ºC and 95% relative humidity for 7 days. After this period, the apicoectomy of the 3 millimeters of the root apex was performed using Endo-Z bur (Dentsply Sirona) or Bladesonic ultrasonic tip (Helse Ultrasonic, Santa Rosa de Viterbo, Brazil) (n=10). The specimens were scanned by micro-computed tomography (micro-CT; SkyScan 1176) with a voxel size of 8.74 µm after obturation and after apicoectomy. The percentage of voids at the interface between the filling material and the root canal wall was evaluated in the apical 4 mm of the root after apicoectomy, besides the time cutting to both devices. The data obtained were submitted to paired and unpaired t-tests (α = 0.05). Endo-Z and Bladesonic increased the percentage of voids between the filling material and the dentin after apicectomy (p<0.05), and they were similar (p>0.05). Endo-Z has a shorter time to perform apicoectomy compared to Bladesonic (p<0.05). Apicectomies with Endo-Z or Bladesonic could harm the material/dentin interface, while the Endo-Z bur was faster than the Bladesonic ultrasonic tip.

Evaluation of surface roughness after root resection: An optical profilometer study

The aim of this study was to evaluate the roughness of the apical surface after apical resection performed by six different methods with an optical profilometer. Sixty human single root premolar teeth were used in this in vitro study. After root canal preparation, root canals were filled with gutta-percha and AH Plus root canal sealers by lateral condensation technique. The teeth were randomly divided into six groups according to the apical resection method: steel fissure bur, tungsten carbide fissure bur, Lindeman bur, diamond fissure bur, laser, and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex and at a 90° angle. The time required for apicectomy was recorded for each group. After apical resection, the root surfaces were analyzed by an optical profilometer. The Kruskal-Wallis method was used to analyze the differences between groups. The significance level was set at 5%. The roughest surfaces were obtained by laser (25.54 ± 9.01 μm) and Lindeman bur (17.35 ± 6.03 μm), respectively. The longest mean resection times were recorded in piezosurgery and laser surgery (57 ± 14.39 s and 50.9 ± 16.86 s), respectively. Although the diamond-tipped piezo surgical cutting time is long, it has the best results in terms of surface roughness (5.50 ± 1.73 μm). The optical profilometer is a more convenient tool for evaluating the surface after apical surgery, as it provides an opportunity to evaluate objectively with both visual and numerical data.

Endoscopic Evaluation of Cut Root Faces and Histologic Analysis of Removed Apices Following Root Resection: A Clinical Study

Objective:

To evaluate the resection plane after root-end resection during apical surgery using endoscopy.

Methods:

Following apicectomy of 69 roots, the cut root faces were inspected with a rigid endoscope for the presence of unfilled areas of the root canal space, gaps between the obturated root canal and dentinal wall, isthmi, ‘opaque’ dentine and cracks. Endoscopic pictures were captured and assessed using a 12-sectorn transparent grid for determination of location of the studied elements. Furthermore, the removed apices were examined histologically (n=47). The surfaces of the removed apices opposite the cut root faces were histologically analysed for the same outcome measures.

Results:

Endoscopy revealed the following findings: opaque dentine in 84.1%, unfilled parts of the root canal system in 59.4%, gaps between the existing root canal filling and dentinal walls in 49.3%, and cracks in 10.1% of cases. With regard to isthmi, histology of the removed apices demonstrated an isthmus in two-thirds of those seen with endoscopy at the root end. Ramifications were histologically observed only in 6 root apices.

Conclusion:

The studied elements may cause failure of the root canal treatment, and conventional root canal retreatment or apical surgery may be indicated. The clinical significance of opaque dentine with regard to tooth prognosis after apical surgery remains unclear and warrants further research.

Scanning electronic microscopy analysis of the apical surface after of root-end resection with different methods

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: 115.9 s for G1, 249.8 s for G2, 112.7 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.

Temperature variation during apicectomy with Er:YAG laser

OBJECTIVE

The purpose of this in vitro study was to evaluate the generated temperature of the Er:YAG laser, with three different pulse durations for apicectomy, compared with tungsten bur and surgical saw.

BACKGROUND DATA

Apicectomy is an endodontic surgery performed to remove the root apex and curette adjacent periapical tissue because of lesions of the apical area that are not healing properly.

METHODS

Sixty single-rooted extracted human teeth were resected by three cutting methods: tungsten bur, surgical saw, and Er:YAG laser irradiation with three different pulse durations; pulse duration 50 μs, pulse duration 100 μs, and pulse duration 300 μs. Teflon-insulated, type K thermocouples were used to measure temperature changes during the apicectomy process. Data were analyzed using the general linear models procedure of the SPSS statistical software program.

RESULTS

Although there was no statistically significant difference for the mean values of temperature changes at 1 mm away to the cutting site of teeth, there was statistically significant difference among groups for the mean values of temperature changes at 3 mm away to the cutting site of teeth. Additionally, there was statistically significant difference among groups for the total time required for apicectomy.

CONCLUSIONS

The laser irradiation with pulse duration 50 μs appears to have the lowest temperature rise and the shortest time required for apicectomy of the three pulse durations. However, Er:YAG laser for apicectomy in all pulse durations could be used safely for resection in endodontics in the presence of sufficient water.

Apical surgery: A review of current techniques and outcome

Apical surgery is considered a standard oral surgical procedure. It is often a last resort to surgically maintain a tooth with a periapical lesion that cannot be managed with conventional endodontic (re-)treatment. The main goal of apical surgery is to prevent bacterial leakage from the root-canal system into the periradicular tissues by placing a tight root-end filling following root-end resection. Clinicians are advised to utilize a surgical microscope to perform apical surgery to benefit from magnification and illumination. In addition, the application of microsurgical techniques in apical surgery, i.e., gentle incision and flap elevation, production of a small osteotomy, and the use of sonic- or ultrasonic driven microtips, will result in less trauma to the patient and faster postsurgical healing. A major step in apical surgery is to identify possible leakage areas at the cut root face and subsequently to ensure adequate root-end filling. Only a tight and persistent apical obturation will allow periapical healing with good long-term prognosis. The present paper describes current indications, techniques and outcome of apical surgery.

Apical sealing quality of in vitro apicectomy procedures after using both Er:YAG and Nd:YAG

The aim of this study was to evaluate the apical sealing of dentinal tubules after root-end surface cutting by using Er:YAG and Nd:YAG lasers. After root-canal instrumentation and filling, apices of 50 extracted maxillary canine human teeth were resected by Er:YAG with 400 mJ, 10 Hz, for 30 sec. The samples were randomly assigned to five groups (n = 10): (GI) treated without root-end cavity, but with Nd:YAG (1.0 W, 10 Hz, 20 sec) for dentinal tubules sealing; (GII) treated with root-end cavity without the use of Nd:YAG; (GIII) treated with root-end cavity and Nd:YAG application; (GIV) treated with root-end cavity made by Er:YAG with no focus and without Nd:YAG application; and (GV) treated without root-end cavity and without Nd:YAG application. The root-end cavities were performed by using Er:YAG at 300 mJ, 10 Hz, for 20 sec. Subsequently, all teeth were waterproofed and immersed in 2% methylene blue for 48 h in a vacuum environment. The samples were longitudinally sectioned, and microleakage was measured. ANOVA and the Fisher LSD test showed that GIV was less susceptible to microleakage than were the other groups (p < 0.05). Interestingly, the use of the Er:YAG with no focus showed superior dentinal tubule sealing in comparison with the other groups, even with or without root-end cavity and Nd:YAG application.

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 surfaces

This study compared ultrasonic chemical vapor deposition (CVD)-coated tip (CVDentus #8.1117-1; Clorovale Diamantes Ind. e Com. Ltda Epp, São José dos Campos, SP, Brazil) versus high-speed (#FG700L) and low-speed (#699) carbide burs for apicoectomy, evaluating the time required for resection and analyzing the root-end surfaces by scanning electron microscopy. Thirty extracted human premolars had the canals instrumented and obturated and were randomly assigned to 3 groups (n = 10), according to the instrument used for root-end resection. The time required for resection of the apical 2 mm of each root was recorded. The resected apical segments were dried, sputter coated with gold, and examined with a scanning electron microscope at x350 magnification. A four-point (0-3) scoring system was used to evaluate the apical surface smoothness. The results were analyzed statistically by the Kruskal-Wallis test, and two-by-two comparisons analyses were performed using the Miller test. The significance level was set at 5%. Root-end resection with the high-speed bur was significantly faster (p < 0.05) compared with the low-speed bur and CVD tip. The carbide burs produced significantly smoother root-end surfaces than the CVD tip (p < 0.05). The low-speed bur produced the smoothest root-end surfaces, whereas the roughest and most irregular root ends (p < 0.05) were obtained with the CVD tip. However, no statistically significant difference (p > 0.05) was found between the high- and low-speed burs regarding the surface roughness of the resected root ends (p > 0.05). In conclusion, under the tested conditions, ultrasonic root-end resection took a longer time and resulted in rougher surfaces compared with the use of carbide burs at both high and low speed.

Evaluation of apical surface roughness after root resection: a scanning electron microscopic study

OBJECTIVES

The objective of this study was to compare, by scanning electron microscopy, the smoothness of the resected apical root surface after preparation with high-speed #699 bur, #699 bur plus Shofu finishing and Zekrya bur, and with an erbium:YAG laser.

STUDY DESIGN

Thirty-nine extracted human premolars were instrumented and obturated and their root apices were resected. The roots were divided into 4 groups according to the root resection method. The teeth were dried, metallized, and analyzed at x400 by scanning electron microscopy. Scores ranging from 0 to 3 were attributed to surface smoothness. The data were analyzed by the Kruskal-Wallis test for overall comparison, and by Dunn's test for individual comparisons.

RESULTS

Smoother surfaces were observed for the groups treated with the #699 bur and the #699 bur plus Shofu point finishing, while rougher surfaces were obtained with the laser, which differed significantly from the other 2 methods (P < .05).

CONCLUSIONS

Treatment with the #699 bur plus Shofu finishing yielded better results in terms of surface smoothness, whereas the laser treatment produced more irregular and rougher surfaces after root resection.

Effect of Waterlase laser retrograde root-end cavity preparation on the integrity of root apices of extracted teeth as demonstrated by light microscopy

Most endodontists use ultrasonic instruments for retrograde root-end cavity preparations even though they have been found to produce cracks. In this laboratory study, thirty-six randomly chosen roots had root-end cavity preparations made with the Waterlase laser and only one questionable intra-canal crack was found. It was concluded that the Waterlase laser when used to make endodontic root-end cavity preparations produces either no cracks, or a very low percentage (2.8%) of cracks.

Apicectomy with the Er:YAG laser or bur, followed by retrograde root filling with zinc oxide/eugenol or sealer 26

OBJECTIVE

This study evaluated the influence of root resection, by means of the use of erbium:YAG laser in sealing two different materials, OZE and Sealer 26, in retrograde obturations.

BACKGROUND DATA

Few studies with sufficient data have been conducted in this area.

METHODS

Forty uniradicular teeth were used. They were biomechanically prepared using the step-back technique and obturated using the lateral condensation technique. The teeth were divided into two groups of 20 teeth, one group using the erbium:YAG laser (350 mJ and 6 Hz) for the resection process and the other using the Zekrya Drill, in high rotation. Then, the retrograde cavities were prepared using a micro counter-angle with a number 2 spherical bur. After preparing the cavities, the teeth were impermeabilized and divided into two subgroups. One subgroup used the retrograde obturation technique with Sealer 26 cement, and the other subgroup used OZE. After completing the retrograde obturation, the teeth were immersed in 2% methylene blue for a 7-day period. Teeth were then removed from the dye, washed, scraped, and sectioned in the vestibule-lingual direction.

RESULTS

The results were analyzed with the aid of a magnifying lens, and scores were attributed based on the magnitude of infiltration. The data were then submitted to statistical analysis.

CONCLUSIONS

No statistical difference was noticed regarding the root resection methods; however, in comparing materials, Sealer 26 was statistically superior to OZE. In the subgroup comparison, a significant difference was noticed in the Laser and Sealer 26 and the Laser and OZE and bur and OZE.

Finishing of glass ionomer retroseals

Various techniques have been suggested for the finishing of retrosealing materials. By measuring marginal leakage and by the use of scanning electronic microscopy, this study evaluated the use of bone files, burnishers, and Shofu points for the finishing of 60 retrosealings done with glass ionomer. With each of the three finishing agents, one group of teeth was polished with movements directed from the palatal toward the buccal, and in another group it was done from the center of the retroseal toward the margins of the cavity. ANOVA showed significant differences among the groups according to the way the finishing was done. The use of instruments from the center to the margins of the cavity rather than in just one direction always caused less leakage. The Shofu stone and the burnisher caused equivalent leakage which was significantly less than that caused by bone files. Scanning electron microscopic photos show that the use of the instrument in only one direction caused the material to shift away from the palatal side. This shift always led to greater leakage of dyes on that side.

A comparison in vitro of fibroblast attachment to resected root-ends

AIM

The aim of this study was to investigate the effect of surface morphology of root ends resected with various bur configurations on fibroblast attachment.

METHODOLOGY

Seventy-two human single-rooted teeth were collected and decoronated. The root canals were instrumented, and then obturated with thermoplasticized gutta-percha using AH-26 as the sealer. The roots were randomly divided into eight different groups, and apical root-end resections were performed using eight different instruments, which included high and low speed burs and a scalpel blade. After each root was resected, the surface area of the root end was measured. Cultured human periodontal ligament fibroblasts were radiolabelled and then allowed to attach, in vitro, to the root-ends. Cell attachment to the resected root-ends was determined by counting in a liquid scintillation system and expressed as the number of decays per min/mm2 (DPM/mm2) of root surface.

RESULTS

There was no significant difference in fibroblast attachment to the root-ends prepared with various instruments.

CONCLUSIONS

These findings indicate that the choice of instrument for root-end resection has little influence on the initial attachment of fibroblasts, and thus may have little effect on healing following root-end resection.

A scanning electron microscopic evaluation of root surfaces and the gutta-percha interface following root-end resection in vitro

AIM

The aim of this study was to evaluate the effects that various commonly used instruments have on root surface morphology, the obturating material, and the interface between the obturation and the root canal walls following root-end resection in vitro.

METHODOLOGY

Sixty human single-rooted teeth with fully formed apices were collected and decoronated. The root canals were instrumented, and then obturated with thermoplasticized gutta-percha using AH-26 as the sealer. The roots were randomly divided into 12 different groups, and apical root-end resections were performed using eight different instrument configurations, and two different directions in which the bur moved across the root face in relation to its direction of rotation. Epoxy resin replicas of the resected root ends were examined using scanning electron microscopy.

RESULTS

Each instrument produced a characteristic surface finish on the resected root end that mirrored its cutting profile. Irrespective of the design of the bur used, smearing and shredding of the gutta-percha across the root face occurred only when the handpiece was moved across the root face in reverse direction in relation to the direction of rotation of the bur.

CONCLUSIONS

To ensure minimal disruption and distortion of the root filling and to prevent shredding of the gutta-percha interface, care should be taken to ensure that the final pass of the bur across the root canal is in the correct direction in relation to its direction of rotation.

Microleakage of super-EBA with and without finishing as determined by the fluid filtration method

Super-EBA (SEBA) has been used as a root-end filling material because of its superior sealing properties and clinical success. The purpose of this study was to evaluate whether finishing SEBA after it had set would affect the apical seal. Sixty-five extracted maxillary anterior teeth were instrumented and obturated with a single gutta-percha master cone. The root end was resected, and a 3 mm deep root-end preparation was made using ultrasonic tips. Teeth were randomly divided into three groups. Group 1 received SEBA and was finished with a 30-flute high-speed finishing bur. Group 2 received SEBA, which was cold-burnished with a ball burnisher. Temporary Endodontic Restorative Material was used as the negative control in group 3. Microleakage (microliter/min) was measured under 10 psi using the fluid filtration method at days 1, 7, 30, 90, and 180. SEBA/finished exhibited significant microleakage at day 1 when compared with the burnished group. The differences in leakage were not significant at any other time period.

The topography of root ends resected with fissure burs and refined with two types of finishing burs

OBJECTIVES

This study compared the surface topography of roots resected with #57, Lindeman, and Multi-purpose burs. Further comparisons were made after refinements with either a multifluted carbide or an ultrafine diamond finishing bur.

STUDY DESIGN

Three groups of single-rooted human teeth were resected with each resection bur, and resin replicas of the root ends were made. Root ends from each resection bur group were finished with either a multifluted carbide or an ultrafine diamond finishing bur, and the root ends were replicated. All replicas were evaluated at a magnification of x20 for smoothness and surface irregularities. Data analysis was done with the Wilcoxon signed rank test and the chi-square test at a significance level of p < 0.05.

RESULTS

The Multi-purpose bur produced a smoother and more uniplanar surface than the #57 bur and caused less damage to the root than either the #57 or the Lindeman bur. The multifluted carbide finishing bur tended to improve the smoothness of the root end, while the ultrafine diamond tended to roughen the surface.

CONCLUSIONS

The Multi-purpose bur produced the smoothest and most uniplanar resected root-end surface with the least root shattering. The multifluted carbide finishing bur produced a smoother surface than the ultrafine diamond bur.

Evaluation of cracks associated with ultrasonic root-end preparation

The purpose of this study was to evaluate the integrity of resected root-end surfaces of extracted human teeth after using ultrasonic tips at low or high frequencies for root-end preparation. Thirty bilaterally matched pairs of single-rooted human teeth had root-end resections using a low-speed diamond saw and were examined for root-end cracks. The matched pairs of teeth were then divided into two experimental groups, with one member of each pair being placed in each group. In group 1, root-end preparations were made with an ultrasonic tip on the lowest frequency setting. The preparations in group 2 were done on the highest power setting. Two investigators again examined the resected root-ends using a stereomicroscope at x20 to x63 and recorded the numbers, types, and location of the cracks. Three types of cracks were observed: canal cracks, intradentin cracks, and cemental cracks. There were significantly more root-ends with cracks after ultrasonic root-end preparation than after root-end resection only. In root-ends that had any cracks, significantly more canal cracks per root occurred when the ultrasonic tip was used on the high-frequency setting for root-end preparation than when the ultrasonic tip was used on the low power setting.

Preventing root tip loss in the maxillary sinus during endodontic surgery

Exclusion of infected root tips, dentinal debris, and inflammatory tissue from the maxillary sinus during endodontic surgery is imperative. A simple technique for preventing accidental root tip intrusion into the maxillary sinus using a 6-0 suture and needle and a hole prepared in the root tip with a #2 round bur prior to apicoectomy is presented.

The present status of dental rotary cutting performance tests

Appropriate methods of assessing the cutting ability of handpiece and rotary cutting instrument combinations are needed for research into the processes involved in dental cutting. They are also required for the development of improved devices and recommendations on operation as well as for equipment specification and standards testing. In reviewing the literature on dental rotary cutting performance testing to evaluate available methods, the factors which may influence clinical cutting behaviour are identified as those related to characteristics of the operator, handpiece, rotary cutting instrument, coolant/lubricant used and workpiece material. Existing industrial cutting theory is of limited help in understanding dental cutting in view of the differences between the control of relevant variables in the two cases. Consideration is given to the ways in which the important variables have (or have not) been controlled in past studies of dental cutting and thus the clinical relevance of available methods evaluated. Serious problems such as the lack of suitable test workpiece materials, as well as deficiencies in current knowledge of operator behaviour, handpiece characteristics and effects of coolant/lubricant application are noted. It is concluded that before improved, clinically relevant tests can be developed, further fundamental research in these areas is essential and that until this is done, further work under arbitrary experimental conditions would be of little value.