Effect of retrograde cavity preparations on root apexes

Comparison of crack formation induced by ultrasonic tips and burs during root-end preparation: a systematic review and meta-analysis

Introduction The main objective of root canal treatment is to achieve apical seal. Crack formation during root-end preparation promotes bacterial penetration, thereby leading to failure. This systematic review aims to examine the literature and summarise studies that compare the crack formation induced by ultrasonic tips and burs during root-end preparation.Methods This systematic review and meta-analysis were reported and conducted according to the PRISMA guidelines. The online databases PubMed, Scopus, and Google Scholar were used for data search. In vitro and ex vivo studies conducted up to March 2021 in the English language were included in the review. The risk of bias in the present study was assessed using a customised tool. A random-effects model was used for meta-analysis, χ² values and I² values were used to assess statistical heterogeneity. Meta-analysis was performed using RevMan software Version 5.4.Results A total of 317 records were found from all of the databases and one article was added following hand-searching. Twelve articles were included in the study after the application of the eligibility criteria of which ten articles were included for the meta-analysis. Nine studies showed a medium risk of bias while three studies showed a high risk of bias. The analysis of the crack formation showed a statistically significant difference between the ultrasonic tip and the bur (P = 0.0002). The odds ratio was 2.72 (1.60, 4.65) with a confidence interval of 95% suggesting higher odds of crack formation in the ultrasonic group.Conclusion This review concludes that ultrasonic root-end preparation resulted in higher crack formation than burs.

Present Status and Future Directions - Surgical Endodontics

Endodontic surgery encompasses several procedures for the treatment of teeth with a history of failed root canal treatment, such as root-end surgery, crown- and root resections, surgical perforation repair, and intentional replantation. Endodontic microsurgery is the evolution of the traditional apicoectomy techniques and incorporates high magnification, ultrasonic root-end preparation and root-end filling with biocompatible filling materials. Modern endodontic surgery uses the dental operating microscope, incorporates cone-beam computed tomography (CBCT) for preoperative diagnosis and treatment planning, and has adopted piezoelectric approaches to osteotomy and root manipulation. Crown- and root resection techniques have benefitted from the same technological advances. This review focuses on the current state of root-end surgery by comparing the techniques and materials applied during endodontic microsurgery to the most widely used earlier methods and materials. The most recent additions to the clinical protocol and technical improvements are discussed, and an outlook on future directions is given. While non-surgical retreatment remains the first choice to address most cases with a history of endodontic failure, modern endodontic microsurgery has become a predictable and minimally invasive alternative for the retention of natural teeth.

Evaluation of Root-End Preparation with Two Different Endodontic Microsurgery Ultrasonic Tips

The aim of this study is to compare root-end preparation performed with two different ultrasonic tips-CVDentus and NSK-and respective time requirements. After root-end resection, 32 teeth were randomly divided in two groups, according to the ultrasonic tip used for root-end preparation. Preparation time was recorded. Photomicrographs were taken to assess the following parameters: root surface microcracking, marginal integrity and presence of debris. One ultrasonic tip from each group was analyzed through scanning electron microscopy before and after root-end preparation. The significance level was set at α = 0.05. Incidence of microcracks in both groups was 12.5%. Solely intracanal microcracking was found, consistently positioned within the widest side of the remaining dentine. No statistically significant differences were verified between both experimental groups regarding marginal integrity (p = 0.102) and preparation time (p = 0.780), whereas statistical differences (p = 0.003) were found concerning the presence of debris (the minimum registered score was mostly verified in CVDentus group). NSK tips showed major morphological changes, with extensive surface wear and noticeable loss of particles, which was not verified on CVDentus tips. Our findings suggest significant differences regarding root-end preparation walls quality, with CVDentus tips showing better results. Concerning microcracking, as well as preparation time and marginal integrity, both ultrasonic tips showed similar results. Qualitative analysis exposed NSK tips major morphological changes and wear after use, which was not verified on CVDentus tips.

Effects of Dimensions of Root-End Fillings and Peripheral Root Dentine on the Healing Outcome of Apical Surgery

Objective:

The objective of this study was to assess dimensions of root-end fillings (REFs), as well as peripheral root dentine (PRD) and their effects on the healing outcome of apical surgery.

Methods:

Cone beam computed tomography (CBCT) scans were utilized to measure the REF length and width and the PRD thickness in 61 roots of 53 teeth 1 year after apical surgery. Measurements were taken in the mesio-distal as well as bucco-lingual directions. The REF alignment with respect to the root axis was also evaluated. In addition, the dimensions of REF and PRD were assessed for possible correlations with the healing outcome. Criteria for determining the healing outcome included clinical and radiographic parameters.

Results:

The mean REF length was 2.02±0.52 mm. No significant differences were observed with regard to tooth groups, but one-canal roots had a significantly longer mean REF than two-canal roots (P=0.006). The mean REF widths were 1.14±0.24 mm mesio-distally and 2.61±1.24 mm bucco-lingually. Roots with two canals presented a significantly wider REF (P<0.001) in the bucco-lingual dimension but had a significantly narrower REF in the mesio-distal direction (P<0.001) compared to roots with single canals. PRD measured on average 1.19±0.23 mm at the resection level and 1.44±0.27 mm at the coronal end of the REF. Almost all REFs were perfectly aligned with the longitudinal axis of the roots. With regard to healing outcomes, no correlations were found with REF and PRD values, respectively.

Conclusion:

The mean REF length was 2.02 mm. On average, a thickness >1 mm of peripheral root dentine was maintained. The REF or PRD dimensions had no statistical effect on the healing outcome.

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.

Cutting efficiency of apical preparation using ultrasonic tips with microprojections: confocal laser scanning microscopy study

Objectives

The purpose of this study was to compare the cutting efficiency of a newly developed microprojection tip and a diamond-coated tip under two different engine powers.

Materials and Methods

The apical 3-mm of each root was resected, and root-end preparation was performed with upward and downward pressure using one of the ultrasonic tips, KIS-1D (Obtura Spartan) or JT-5B (B&L Biotech Ltd.). The ultrasonic engine was set to power-1 or -4. Forty teeth were randomly divided into four groups: K1 (KIS-1D / Power-1), J1 (JT-5B / Power-1), K4 (KIS-1D / Power-4), and J4 (JT-5B / Power-4). The total time required for root-end preparation was recorded. All teeth were resected and the apical parts were evaluated for the number and length of cracks using a confocal scanning micrscope. The size of the root-end cavity and the width of the remaining dentin were recorded. The data were statistically analyzed using two-way analysis of variance and a Mann-Whitney test.

Results

There was no significant difference in the time required between the instrument groups, but the power-4 groups showed reduced preparation time for both instrument groups (p < 0.05). The K4 and J4 groups with a power-4 showed a significantly higher crack formation and a longer crack irrespective of the instruments. There was no significant difference in the remaining dentin thickness or any of the parameters after preparation.

Conclusions

Ultrasonic tips with microprojections would be an option to substitute for the conventional ultrasonic tips with a diamond coating with the same clinical efficiency.

Effects of ultrasonic root-end cavity preparation with different surgical-tips and at different power-settings on glucose-leakage of root-end filling material

Aim:

The aim of this in vitro study was to evaluate the effects of different ultrasonic surgical-tips and power-settings on micro-leakage of root-end filling material.

Materials and Methods:

The root canals were instrumented using rotary-files and were filled with tapered gutta-percha and root canal sealer using a single-cone technique. The apical 3 mm of each root was resected and the roots were divided into six experimental groups; negative and positive control groups. Root-end cavities were prepared with diamond-coated, zirconum-nitride-coated and stainless-steel ultrasonic retro-tips at half-power and high-power settings. The time required to prepare the root-end cavities for each group was recorded. Root-end cavities were filled with Super-EBA. Leakage values of all samples evaluated with glucose penetration method on 7, 14, 21 and 28^th days. The results were statistically analyzed with Kruskal-Wallis and Hollander-Wolfe tests.

Results:

The mean time required to prepare retro cavities using diamond-coated surgical tip at high-power setting was significantly less than other groups (P < 0.01). There were no statistically significant differences in the glucose penetration between the groups at first and second weeks (P > 0.01). Diamond-coated surgical tip showed the least leakage at high-power setting at 3^rd and 4^th weeks (P < 0.01).

Conclusions:

Under the conditions of this study, cavity preparation time was the shortest and the leakage of the root-end filling was the least when diamond-coated retro-tip used at high-power setting.

Evaluation of two different root-end cavity preparation techniques: A scanning electron microscope study

OBJECTIVE

In this study, we aimed to evaluate and compare the dentinal walls of root-end cavities for the presence of cracks after cavity preparation using US retrotips and Er: YAG laser.

MATERIALS AND METHODS

Fifty single-rooted teeth were prepared by Protaper NiTi rotary system and obturated by lateral condensation. Three milimeters of root-end was resected. Twenty teeth were prepared with US retrotip (Group 1), 20 teeth with Er: YAG laser (Group 2), and 10 teeth without retropreparation (control group). The root-end surfaces were examined under a scanning electron microscope (SEM). Then the cracks of the resected root surfaces were evaluated on microphotographs.

RESULTS

No statistically significant difference was detected between US Group and Laser Group for complete, incomplete, intradentinal, and total number of cracks (P = 0.47, P = 0.80, P = 0.69, P = 0.869, respectively).

CONCLUSION

Statistical analysis revealed no significant effect of retropreparation technique on the development of apical cracks (P > 0.05).

Evaluation of apical preparations performed with ultrasonic diamond and stainless steel tips at different intensities using a scanning electron microscope in endodontic surgery

Objective: The objective of our study is to analyse (with the help of scanning electron microscopes) the quality of the dental root surface and the appearance of dental cracks after performing apical preparations using two diffe-rent types of ultrasonic tips. Study design: We used 32 single-rooted teeth that underwent a root canal and apical resection. Afterwards, the teeth were divided into 4 groups of 8 teeth each, with preparations of the apical cavities in the following manner: Group 1: stainless steel ultrasonic tip at 33KHz. Group 2: stainless steel ultrasonic tip at 30KHz. Group 3: diamond ultrasonic tip at 30KHz. Group 4: diamond ultrasonic tip at 33 KHz. The quality of the root surface and the presence of cracks were evaluated by one single observer using a scanning electron microscope. Results: All of the teeth in our study had cracks after the apical preparations. The mean number of cracks per tooth ranged between 6.1±1.9 (group 1) and 3.5±2.4 (group 4), with a significantly higher number found in the groups that used stainless steel tips (P=.03). The types of cracks produced involved: 8 complete cracks (4.5%), 167 incomplete cracks (94.4%), and 2 intradentinal cracks (1.1%), with no significant differences observed between the different frequencies used for each group. Conclusions: Stainless steel ultrasonic tips provoked a larger number of cracks than diamond tips. The frequency of vibration used did not have any effect on the number of cracks found.

Key words:Apicoectomy, scanning electron microscope, therapeutic ultrasound, endodontic surgery, dentinal crack.

Ultrasonic root-end preparation in apical surgery: a prospective randomized study

OBJECTIVE

The purpose of this study was to evaluate the potential benefit of an ultrasonic device in apical surgery on the outcome of treatment.

STUDY DESIGN

A randomized prospective design was used in a standardized treatment protocol. Patients were allocated to treatment with an ultrasonic device (P-Max Newtron) or treatment with a bur in an otherwise similar protocol. One year after treatment the results were evaluated by 2 oral and maxillofacial surgeons who were blinded for the therapy.

RESULTS

Out of a total group of 399 patients who were included in the study, adequate follow-up could be obtained in 290 patients. The overall success rate in the ultrasonic group was 80.5% and in the group treated with a bur 70.9% (P = .056). In molars, the difference in success rate was significant (P = .02).

CONCLUSION

The use of an ultrasonic device in apical surgery improved the outcome of treatment. In molars this effect was significant.

Ex vivo microscopic assessment of factors affecting the quality of apical seal created by root-end fillings

AIM

(i) To evaluate the incidence of microcracks around root-end preparations completed with ultrasonic tips and their relationship with the root filling technique and thickness of surrounding dentine. (ii) To investigate the effect of rapid exposure to a water-soluble dye of Intermediate Restorative Material (IRM), Super Ethoxybenzoic Acid (sEBA) and Mineral Trioxide Aggregate (MTA), on the marginal adaptation and microleakage of root-end fillings. (iii) To describe the microstructure of the surface of root-end filling materials.

METHODOLOGY

Ninety-two single-rooted teeth were divided into two groups (n = 46) according to the root canal instrumentation/filling techniques. Group 1 consisted of specimens in which canal preparation was completed using a crown-down technique and then filled with the Thermafil system (TF group); Group 2 consisted of specimens in which canal preparation was completed using a step-back technique and lateral condensation (LC group). Following root-end resection and ultrasonic cavity preparation, the samples were further divided into three subgroups (n = 24) for root-end filling with IRM, sEBA or MTA. The ultrasonic preparation time was recorded. Eight teeth were kept as positive and 12 as negative controls. Following immersion in Indian ink for 7 days, all resected root surfaces were evaluated for the presence of microcracks and the cross-sectional area of root-end surface and root-end filling were measured to evaluate the thickness of the dentinal walls. Thereafter, the samples were sectioned longitudinally so as to assess the depth of dye penetration and marginal adaptation of root-end fillings. Negative controls longitudinally sectioned were used to describe microstructural characteristics of the root-end filling materials using scanning electron microscopic (SEM) techniques.

RESULTS

Although the thickness of dentinal walls between groups 1 and 2 was similar, the ultrasonic preparation time and number of microcracks were significantly higher (P < 0.001) in the TF group. Both groups had a significant correlation between microcracks and ultrasonic preparation time (P < 0.001). sEBA and IRM had better adaptation and less leakage compared with MTA. A SEM analysis displayed microstructural differences between the root-end filling materials.

CONCLUSION

Microcracks can occur independently of the thickness of dentinal walls and may be associated with the prolonged ultrasonic preparation time required for the removal of the root filling during root-end cavity preparation. Although sEBA and IRM had better behaviour than MTA regarding microleakage and marginal adaptation, it is possible that exposure of MTA to a water-soluble dye before achieving full set and its porous microstructure contributed to the results.

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.

SEM analysis of the integrity of resected root apices of cadaver and extracted teeth after ultrasonic root-end preparation at different intensities

AIM

To compare the integrity of root apices of cadaver and extracted teeth after resection, ultrasonic root-end cavity preparation at medium and low ultrasonic power settings and retrieval.

METHODOLOGY

Root canal treatment, perpendicular root-end resection and root-end preparation were performed on single-rooted anterior and premolar teeth (49 teeth in situ in maxillary and mandibular jaws from cadavers and 45 extracted teeth). Apical root-end cavities were prepared with the S12/90 degrees D tip and the Suni-Max ultrasonic unit (Satelec, Merignac, France) at the intensity prescribed by the manufacturer (power 7 at power mode S) (34 cadaver teeth, 30 extracted teeth) and at a lower intensity (power 4 at power mode S) (15 cadaver teeth, 15 extracted teeth). After ultrasonic preparation the cadaver teeth were retrieved from the jaws. Exaflex impressions (GC Corporation, Tokyo, Japan) were made of the root apices after resection, root-end preparation and retrieval. These impressions were processed for SEM analysis, and the recordings evaluated for cracks and marginal chipping.

RESULTS

In general, extracted teeth showed significantly more cracks and chipping than cadaver teeth. Lowering the ultrasonic power from medium to low intensity resulted in equal scores for cracks on extracted teeth and for chipping on cadaver teeth, in higher scores for cracks on cadavers and in lower scores for chipping on extracted teeth. Complete cracks and cracks originating from the root surface occurred only in extracted teeth.

CONCLUSIONS

The number of cracks and degree of chipping caused by ultrasonic root-end preparation was higher on extracted teeth than on cadaver teeth. Lowering the ultrasonic power from medium to low intensity cannot be recommended as it resulted in more cracks and equal chipping on cadaver teeth. Investigation of techniques and materials should be conducted in situ and not on extracted teeth.

Effects of ultrasonic root end preparation on resected root surfaces: SEM evaluation

OBJECTIVE

The purpose of this study was to investigate the in vitro effect of ultrasonic retrotips on root end surfaces.

STUDY DESIGN

Root end resection was performed on 45 single-root teeth endodontically treated after extraction. Setting the ultrasonic device at full power, a retrograde cavity was made by a stainless steel tip in 9 specimens (SS-FP). In another 9 samples a diamond tip was used (D-FP). Setting the intensity of the ultrasonic device at half power, 9 specimens were treated using stainless steel tips (SS-HP) and 9 using diamond tip (D-HP). Nine teeth were only apically resected and used as controls. Histologic serial sections were examined by scanning electron microsope to assess the number of root-face cracking, the marginal quality, and the crack type.

RESULTS

No significant difference between diamond and stainless steel groups was found at a given power setting. Significant differences were found between SS-FP and SS-HP group for both the number of cracks and the marginal quality.

Identification of Resected Root-End Dentinal Cracks: A Comparative Study of Transillumination and Dyes

The dilemma of diagnosing and possibly treating dentinal cracks continues to present a challenge in endodontics. The purpose of this in vitro study was to compare the effectiveness of transillumination and dyes in identifying root-end dentinal cracks. Fifty maxillary central incisors were decoronated, and the canals were instrumented to an ISO size 50 at the working length. The apical 3 mm of the roots was resected, and cracks were artificially created in the apical dentin. Four independent examiners evaluated the root ends at x8 magnification with a surgical operating microscope using transillumination (group 1), sodium fluorescein dye (group 2), caries detect dye (group 3), methylene blue dye (group 4), and methylene blue plus transillumination (group 5). The examiners' ability to identify root ends correctly with and without cracks was analyzed by comparing the data with the predetermined standard (cracked and noncracked) using logistic regression analysis. All techniques used were shown to be more effective than random chance at diagnosing cracks. The areas under the curve of the different techniques were as follows: transillumination, 0.81 (95% confidence interval [CI], 0.69-0.93); sodium fluorescein, 0.72 (95% CI, 0.58-0.86); caries detector, 0.76 (95% CI, 0.63-0.89); methylene blue, 0.70 (95% CI, 0.55-0.84); and methylene blue plus transillumination, 0.82 (95% CI, 0.70-0.94). Thus, the crack assessment techniques that gave the best discrimination between cracked and noncracked specimens, regardless of rater, was methylene blue plus transillumination. This study emphasizes the usefulness of transillumination along with magnification in detecting dentinal cracks.

Evaluation of different methods for the root-end cavity preparation

OBJECTIVE

The dentinal walls of root-end cavities were examined for the presence of cracks and debris in correlation with the area of the root surfaces that remained after the resection.

STUDY DESIGN

One hundred extracted single-rooted teeth were endodontically treated, mounted in acrylic resin blocks, and the apical 2 mm of the root-apex was resected. According to the resected root surface area the teeth were divided into 2 groups having large (>2 mm(2)) or small (<2 mm(2)) surface area. For retrograde cavity preparation 4 devices were used: slow-speed handpiece, diamond coated stainless steel ultrasonic tip, smooth stainless steel ultrasonic tips, and sonic diamond-coated tips. Teeth were examined under a videomicroscope for the presence of fractures, dentin chips, and gutta-percha remnants on cavity walls. Preparation time was also recorded.

RESULTS

Preparation with smooth stainless steel ultrasonic tips produced few intradentin cracks. Dentin debris was more frequently seen in rotary preparations whereas gutta-percha remnants were seen mainly at ultrasonically prepared teeth.

CONCLUSIONS

Sonic and ultrasonic devices produced cleaner, well-centered, and more conservative root-end cavities than the rotary instrumentation. Cracks do not correlate directly with the surface area of the root-end surfaces but rather with the type of retrotip used to prepare the root-end cavity.

Diagnostic accuracy of endoscopy in periradicular surgery - a comparison with scanning electron microscopy

AIM

To compare the accuracy of endoscopic diagnostics with the scanning electron microscope (SEM) in evaluating elements of periradicular surgery.

METHODOLOGY

The material consisted of 22 extracted human molars, which were subjected to the following treatments: orthograde root-canal obturation, root-end resection and root-end cavity preparation with diamond-coated sonic microtips. After each step, the cut root face was inspected with an endoscope, and subsequently, the roots were duplicated for SEM evaluation. Endoscope findings were compared to those obtained with SEM serving as the 'gold standard' with a blinded observer. The presence of the following structures was assessed including specificity and sensitivity: isthmuses, accessory canals, obturation gaps, microfractures and chipping of cavity margins.

RESULTS

The specificity and sensitivity of the identification of isthmuses or accessory canals was 100% each for the endoscope compared to SEM. The sensitivity of identification of obturation gaps, crack formation or chipping ranged between 73 and 95% (except intradentine cracks with only 36% sensitivity). The specificity of the same parameters ranged between 77 and 100% for the endoscope compared to SEM.

CONCLUSIONS

With the exception of intradentine cracks, the endoscope accurately identified microstructures following root-end resection and root-end preparation. The endoscope could be considered for use during intraoperative diagnostics in periradicular surgery.

Evaluation of root-end cavity preparation using ultrasonic retrotips

AIM

To evaluate and compare the efficiency of root-end preparations using ultrasonic retrotips coated with diamond and zirconium nitride.

METHODOLOGY

Eighty-five extracted single-rooted teeth were root filled, and then resected 3 mm from their apices. Root-end cavities were prepared with KiS (zirconium nitride-coated retrotip), CT-5 (stainless steel tip) or diamond-coated (DC) ultrasonic retrotips, and 10 teeth served as controls. Thirty teeth were used for evaluation of the time required to prepare the root-end cavity, the number of microcracks produced on the resected surface and the number of dentinal tubule openings on the root-canal wall using scanning electron microscope (SEM) images. A further 55 teeth were used for evaluation of dye penetration following filling of the root-end cavities with Super EBA. The degree of dye penetration in millimetres was measured under the microscope after 7 days of immersion in India ink. Statistical analyses were performed using the one-way ANOVA and Scheffe's F-test as the post hoc test.

RESULTS

There was no significant difference in the number of microcracks and dentinal tubule openings present in the root apices prepared by the three retrotips. The time required for root-end cavity preparation using the DC retrotip was significantly less than that using the other groups (P<0.01). Positive controls showed dye penetration throughout the length of the root-end cavity, and negative controls showed no dye penetration. There was no significant difference between the three experimental groups in dye penetration.

CONCLUSIONS

In this laboratory study, the time required to prepare root-end cavities using KiS retrotips was the same as that using CT-5 retrotips, and longer than that using DC retrotips. There was no significant difference in the number of microcracks or dye penetration between the three kinds of retrotips.

Effect of sonic and ultrasonic retrograde cavity preparation on the integrity of root apices of freshly extracted human teeth: scanning electron microscopy analysis

Sonic and ultrasonic root-end preparation devices permit the preparation of conservative and straight cavities. However, microfractures and marginal chipping can occur due to the vibratory action of such instruments. The purpose of this study was to evaluate the effect of retrograde preparations by using sonic and ultrasonic tips on the integrity of root-end surfaces. Eighty, human anterior teeth were grouped according to size and treated as follows: treatment 1: root-end resection (RR) and root-end cavity preparation (RP) with KIS ultrasonic retrotip; treatment 2: RR and RP with Satelec S12/90 (no diamond coating) ultrasonic retrotip; treatment 3: RR and RP with a diamond-coated retrotip attached to a sonic device (Sonics); treatment 4: RR and RP with Satelec S12/90D (diamond coated) ultrasonic retrotip. The root-end surface topographies were assayed by means of polyvinylsiloxane impressions and epoxy resin replicas. SEM pictures of each sample were taken before and after preparation, and the images were evaluated by using an image processing and analysis system. The parameters evaluated were shape quality, presence of cracks, and marginal chipping. The results showed no statistically significant differences among anatomic groups, treatments, or tooth sizes (p > 0.05). Because treatment 3 removed more dental structure than the others did, its use on small teeth is inadvisable.

Occlusal loading of EBA and MTA root-end fillings in a computer-controlled masticator: a scanning electron microscopic study

AIM

The aim of this investigation was to assess the marginal adaptation of Super-EBA (EBA) and Pro Root MTA (MTA) root-end fillings and the occurrence of microcracks in resected root-ends of extracted teeth before and after occlusal loading for a five-year equivalent period in a computer-controlled masticator.

METHODOLOGY

Twenty-four molar teeth were root-filled using lateral condensation and their root-ends resected. Root-end cavities were prepared and either EBA or MTA root-end fillings were placed. All surgical procedures were completed in vitro under an operating microscope. Replicas taken of the root-end fillings and resected root-ends were examined using an SEM before and after they were subjected to in vitro chewing cycles in a computer-controlled chewing simulator for the equivalent of 5 years. Marginal adaptation and integrity of the two root-end filling materials were evaluated and the presence of microcracks recorded.

RESULTS

Before loading, a continuous margin was observed with 99.4 +/- 2.4% of EBA and 99.2 +/- 1.6% of MTA root-end fillings. After loading, the percentage of continuous margin decreased to 93.1 +/- 6.6% and 98.9 +/- 3.2% for EBA and MTA, respectively. After occlusal loading, 39.5% of the EBA root-end fillings were overfilled, whilst 52.6% of the MTA root-end fillings were underfilled. In total, 12.5% of the resected root-end surfaces showed microcracking before loading and 25% after occlusal loading.

CONCLUSIONS

Both EBA and MTA displayed excellent marginal adaptation before masticatory loading. After loading, the amount of continuous margin for both root-end filling materials decreased slightly but was still high.

Quality of root-end preparations using ultrasonic and rotary instrumentation in cadavers

Prior investigations have demonstrated dentinal cracking and chipping during ultrasonic preparation of the root-end. This study compared the frequency of cracking and chipping in two groups, cadaver and extracted teeth, using an indirect resin technique. Preparations were performed using either a 33 1/2 inverted cone bur in a high-speed handpiece, or with ultrasonics using a CT-2 tip at either high or low intensity. After replication of the root-end in epoxy resin, all teeth were evaluated for cracking and chipping under scanning electron microscopy. Statistical analysis using a general contingency table or ANOVA with Scheffé post-hoc analysis (p = 0.05) revealed no significant difference between all groups in terms of root-end cracking. In extracted teeth (n = 15), rotary instrumentation produced less chipping than either ultrasonic technique. Varying the intensity was not significant. There was no significant difference between any instrumentation group in cadaver teeth (n = 10) related to the amount of chipping.

Root deformation during root-end preparation

Ultrasonic root-end preparation techniques have recently been introduced and revolutionized the field of endodontic surgery. However, several reports claimed that there was an increasing incidence of crack formation after ultrasonic root-end preparation. As yet, little work has focused on the root deformation during root-end preparation. Thus, the purpose of this investigation was to measure the amount of root deformation during root-end preparation with the use of microhandpiece and ultrasonic systems by using strain gauge methods, and simultaneously to detect any cracks with the aid of the stereomicroscope, stain, and an image processing system. The results demonstrated the ultrasonic instrumentation produced significantly greater strain on average than that generated with the microhandpiece system. From the viewpoint of fracture, any technique that could diminish the strain on the root would decrease the likelihood of fracture; however, no crack was observed on any resected surface of roots in this study.

Root-end cavity preparation after apicoectomy using a new type of sonic and diamond-surfaced retrotip: a 1-year follow-up study

PURPOSE

This study evaluated the outcome of periradicular surgery using a new set of retrotips for root-end cavity preparation.

PATIENTS AND METHODS

Forty-three patients who had 50 consecutively treated teeth with periradicular pathology were enrolled in this prospective study. After apicoectomy, root-end cavity preparation was performed, using diamond-surfaced retrotips driven by a sonic handpiece; EBA-cement was used as the root-end filling material. Healing assessment was based on clinical and radiographic criteria.

RESULTS

At the 1-year follow-up, 82% of the reexamined surgical cases presented with successful healing. Fourteen percent of the treated teeth were deemed as improved (partial healing), and 4% were classified as failures.

CONCLUSION

The new retrotips were found to be ideal for root-end cavity preparation. They simplify the surgical approach to root ends where the working space is limited by restricted access. Root-ends prepared with this new sonoabrasive technique yielded excellent results at the 1-year follow-up examination.

Ultrasonic root end cavity preparation assessed by an in situ impression technique

PROBLEM

In vitro studies have demonstrated microfractures in resected roots after root end cavity preparation with ultrasonic tips. Such microfractures are of concern; however, they may be artifacts.

OBJECTIVES

To assess the incidence of microfractures after ultrasonic root end cavity preparation in situ.

STUDY DESIGN

Fifty-two roots in two cadavers were endodontically treated, the soft tissues excised, and the root ends exposed and resected. The resected root surfaces were replicated with polyvinylsiloxane impressions. Root end cavities were prepared with ultrasonic tips, then impressed a second time. The roots were retrieved; 25 were processed for direct SEM examination as were both the impressions of each root. The specimens were examined by stereomicroscope and scanning electron microscope.

RESULTS

In the impressions, the resected and prepared surfaces appeared irregular, but none demonstrated microfractures. In contrast, 15 retrieved roots showed microfractures.

CONCLUSIONS

Ultrasonic root end cavity preparation in situ did not cause root microfractures, and the impression technique could be clinically usable with minor modifications.