A comparison between two root end preparation techniques in human cadavers

Comparison of the sealing ability amongst orthograde apical plugs of mineral trioxide aggregate plus, mineral trioxide aggregate repair HP, and Biodentine after root resection: a bacterial leakage study

This study aimed to analyse the effect of root-end resection on the sealing ability of orthograde apical plugs of three root-end filling materials (MTA Repair HP, Biodentine, MTA Plus) using the bacterial leakage method and compare it with the retrograde root-end filling technique. Eighty-four extracted mandibular premolar teeth with single root and single straight canals were selected and randomly divided into two main experimental groups (n = 36) depending on the apical plug placement technique and a control: Group I: orthograde technique, followed by root-end resection; Group II: retrograde root-end filling technique; one control Group III (n = 12): obturation with gutta-percha, followed by root-end resection. Experimental groups were further subdivided into three subgroups A, B, and C (n = 12) depending on the three different root-end filling materials used. An apical plug of 3 mm thickness was obtained in both the experimental groups. The apical sealing ability was evaluated with the dual-chamber bacterial leakage method. Statistical analysis was performed using the Kaplan-Meier survival analysis test. By the end of 30 days, the occurrence of turbidity indicating bacterial leakage was 75% in MTA Repair HP, 83.3% in Biodentine, and 91.7% in MTA Plus samples. This trend of turbidity was similar in both orthograde and retrograde technique. The control group showed turbidity in all the samples (100%). More MTA Repair HP samples (25%) survived the 30 days observation period with no bacterial leakage compared to Biodentine (16.7%) and MTA Plus (8.3%). The sealing ability of already set root-end filling materials placed through the orthograde technique did not deteriorate after root-end resection. Also among three root-end filling materials, MTA Repair HP presented the lowest bacterial microleakage followed by Biodentine and MTA Plus, respectively.

Magnification in endodontics: A review of its application and acceptance among dental practitioners

The application of magnification devices in endodontics is mainly meant for visual enhancement and improved ergonomics. This is crucial especially when long hours are spent in a narrow operating space to treat obscure microanatomy. Nevertheless, application of magnification in endodontics has yet to be introduced into the mainstream practice due to various influences in behavioral patterns. By conducting an extensive literature search in the PubMed database, this narrative review paper depicts the present state of magnification devices, their applications within the endodontic practice, factors that influence their usage, the advantages, and shortcomings, as well as the significances of magnification in the field of endodontics. This review paper will encourage clinicians to employ magnification in their practice for improved outcome.

Clinical Evaluation of Root End Resection Bevel in Periapical Surgery

Root end resections play an important role in the success of periapical surgery. Beveling of the root end resections can vary significantly depending on the surgical technique, the root and canal morphology. The intention of this article was to clinically assess the root resections bevels and to estimate their relation to applied periapical surgeries. A prospective clinical study consisted of sixty periapical surgeries performed on teeth with chronic periapical lesions. Thirty periapical surgeries were performed in a conventional manner, while thirty were contemporary ultrasonic surgeries. Following the completion of strictly planned and performed intraoperative procedures, the resection bevels were assessed. To obtain the real bevel angles a compass was used. Root resections were significantly less beveled in all teeth operated with contemporary ultrasonic surgery, with mean values between 2.1° to 7.8°. The number of roots and their dilacerations didn't influence the root resection bevel. For comparison, root resections were significantly beveled in all conventionally operated teeth, with mean values of 46°. Due to the technical limitations of the conventional periapical surgery, mandibular premolars were exclusively operated with ultrasonic periapical surgery, with mean values of resection bevel not exceeding 20.7°. Significantly lesser resection bevel associated with ultrasonic periapical surgery contributes to root preservation and favorable surgical outcome.

Micro-CT analysis of filling ability and porosity of root-end filling materials

Abstract Introduction Filling ability of retrograde cavity and porosity are important properties for root-end filling materials and may be evaluated by using microcomputed tomography (micro-CT). Objective To evaluate filling ability and porosity of root-end filling materials using microcomputed tomography (micro-CT). Material and method Cavities with 1 mm internal diameter and 3 mm depth were prepared in bovine dentin sections by using ultrasonic tips (CVD No. 6.1107-6), and filled by Mineral Trioxide Aggregate (MTA); Sealer 26 (S26) and zinc oxide and eugenol cement (ZOE). Before and after filling, cavities were scanned by using micro-CT (SkyScan 1176). Filling and porosity were analyzed by using CTAn software. Filling ability was calculated based on volumetric percentage of the filled cavity. The number and percentage of closed pores were measured throughout entire extension of the filled cavity (total) and in each third (cervical, middle and apical), by using bi and tridimensional analyses. The filling data were submitted to ANOVA and Tukey statistical tests, and porosity data to Kruskall-Wallis and Dunn tests, at a 5% significance level. Result S26 and ZOE presented higher filling ability than MTA (p<0.05). S26 showed the highest total porosity (number and percentage) (p<0.05). In all thirds after 2D and 3D analyses, porosity was higher for S26 in comparison to MTA and ZOE (p<0.05). Conclusion Although Sealer 26 presented more porosity, the material was associated with a great filling ability. Micro-CT analysis showed no correlation between filling ability and porosity.

The Effect of Thickness on the Sealing Ability of CEM Cement as a Root-end Filling Material

Background and aims. Different materials have been used for root-end filling during surgical endodontic treatment. The aim of this in vitro study was to evaluate the dye penetration in different thicknesses of calcium enriched mixture (CEM) cement as root-end filling material. Materials and methods. Following root canal filling in 70 extracted human single-rooted premolar teeth, the apical 3 mm of their root-ends was resected; the root-end cavities with depths of 1, 2 and 3 mm were prepared by ultrasonic retrotips and filled with CEM cement. After setting of cement, the roots were immersed in 2% Rhodamine B and the dye leakage was measured under stereomicroscope (×16) using Image J software. The data were analyzed by one-way ANOVA and Bonferroni post hoc tests at 5% significance level. Results. The means and standard deviations of dye penetration in the 1, 2, and 3 mm groups were 3395.5±1893.4, 3410.4±1440.5, and 2581.6±1852.9 μm, respectively. The one-way ANOVA analysis indicated significant differences (P < 0.001); however, the Bonferroni post hoc test revealed that only the positive control group differed significantly from the experimental groups (P < 0.001). Conclusion. The findings demonstrated CEM cement to have an adequate root-end sealing ability in 3-mm thickness.

Application and development of ultrasonics in dentistry

Since the 1950s, dentistry's ultrasonic instruments have developed rapidly. Because of better visualization, operative convenience, and precise cutting ability, ultrasonic instruments are widely and efficiently applied in the dental field. This article describes the development and improvement of ultrasonic instruments in several dental fields. Although some issues still need clarification, the results of previous studies indicate that ultrasonic instruments have a high potential to become convenient and efficient dental tools and deserve further development.

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.

Endoscopic periradicular surgery: A prospective clinical study

We did apicectomies of 30 teeth with periradicular lesions in 23 patients, using a 3 mm endoscope. Two patients failed to attend for postoperative assessment and of the remaining 21 patients who had 28 teeth treated the operation was judged after 1 year to be a success in 26 (93%).

Evaluation of Apical Cavity Preparation With a New Type of Ultrasonic Diamond Tip

This study evaluated the time, occurrence of fracture, and quality of apical cavity preparation with three different ultrasonic diamond tips: Satelec, Trinity, and a new type, CVD (chemical vapor deposition), using scanning electron microscopy (SEM) analysis. Thirty human single-rooted premolars were selected, submitted to apicectomy, and prepared with ultrasonic tips; impressions were then obtained. The presence of fractures was evaluated on the impressions, and the quality of preparation was evaluated by SEM analysis of teeth and scoring by two examiners. The group prepared with the CVD tips exhibited the shorter preparation time and did not present fractures. There was no statistically significant difference in the quality of preparation for the three tips. The three brands of ultrasonic tips produced adequate grinding without altering the morphology of the apical foramen.

Modern Endodontic Surgery Concepts and Practice: A Review

Endodontic surgery has now evolved into endodontic microsurgery. By using state-of-the-art equipment, instruments and materials that match biological concepts with clinical practice, we believe that microsurgical approaches produce predictable outcomes in the healing of lesions of endodontic origin. In this review we attempted to provide the most current concepts, techniques, instruments and materials with the aim of demonstrating how far we have come. Our ultimate goal is to assertively teach the future generation of graduate students and also train our colleagues to incorporate these techniques and concepts into everyday practice.

Endodontic Surgery Using 2 Different Magnification Devices: Preliminary Results of a Randomized Controlled Study

PURPOSE

The introduction of microsurgical instruments and magnification devices has brought advantages in root-end management and the application of root-end filling materials. The main purpose of this prospective clinical study was to monitor the outcome of ultrasonic root-end preparation using magnification loupes or an endoscope. Tooth location and the presence of post restoration were also examined as potentially affecting the outcome.

MATERIALS AND METHODS

Teeth treated surgically showed a periradicular lesion of strictly endodontic origin. A total of 59 patients were included in the study, according to specific selection criteria. Following the reflection of a full mucoperiosteal tissue flap, residual soft tissues were curetted, root ends were resected, and root-end cavities were prepared ultrasonically with a zirconium nitrate tip, and zinc oxide EBA-reinforced cement root-end fillings were placed. Thirty-two root-end management procedures were performed using magnification loupes and 39 using an endoscope. All cases followed for a period of 1 year were classified into 3 groups (success, uncertain healing, and failure) according to radiographic and clinical criteria.

RESULTS

Of the 71 teeth evaluated at 1-year follow-up, 67 teeth (92.95%) successfully healed, 3 teeth had uncertain healing, and 2 failed. In the group using endoscopy, 94.9% of successful healing was achieved, while for the other group, 90.6% was recorded. We found no statistically significant differences in treatment results related to the arch (P = .20), post restoration (P = .21), or type of magnification device (P = .08).

CONCLUSIONS

In the present study, adherence to a strict endodontic surgical protocol and the use of modern surgical endodontic procedures, together with visual magnifications, resulted in an overall high success rate.

Erbium: YAG Laser versus Ultrasonic in Preparation of Root-End Cavities

The aim of this in vitro study was to compare the sealing effectiveness of the Erbium:YAG laser to the sealing effectiveness of an ultrasonic device in the preparation of similar retrograde cavities using different retrograde filling materials. After root-canal instrumentation and filling, apices of 60 single-rooted teeth were resected. Retrograde class I cavities 3 mm deep were prepared using an ultrasonic device (group A) and Er:YAG laser (group B). An ultrasonic unit was used with CT-5 retrotip at the frequency of 32 KHz. Laser beam parameters were a pulse of very short duration (100 micros), energy of 280 mJ, and repetition rate of 10 Hz. Cavities of each group of 10 samples were filled with mineral trioxide aggregate (MTA), Super-EBA, and IRM. Microleakage was measured using a fluid transport model. The results showed that cavities prepared with Er:YAG laser have significantly lower microleakage for all tested materials.

Endodontic surgery with ultrasonic retrotips: One-year follow-up

OBJECTIVE

The purpose of this prospective clinical study was to monitor the outcome of ultrasonic root-end preparation, in relation to tooth type and location, presence of post restoration and type of retrotip.

STUDY DESIGN

Teeth treated surgically showed a periradicular lesion of strictly endodontic origin. Fifty teeth were included in the study, according to specific selection criteria. Cases were followed for a period of 1 year and then classified in 3 groups (success, uncertain healing, and failure) according to radiographic and clinical criteria.

RESULTS

Of the 46 teeth evaluated at 1-year follow-up, 42 teeth (91.3%) successfully healed, 1 tooth had uncertain healing, and 3 failed. We found no statistically significant differences in treatment results related to the type of tooth, tooth location, post restoration, and type of retrotip.

CONCLUSION

Adherence to a strict endodontic surgical protocol and the use of contemporary techniques and materials can lead to a predictable outcome.

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.

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.

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.

Root-end fracture during retropreparation: a comparison between zirconium nitride-coated and stainless steel microsurgical ultrasonic instruments

The purpose of this study was to evaluate a stainless steel (CT-5) and zirconium nitride coated (KiS) microsurgical ultrasonic instrument with regard to possible root-end fracture production during retropreparation. Forty extracted human central incisors were prepared in a crown-down fashion. Canals were obturated with gutta-percha by lateral condensation. Root-ends were resected. Teeth were placed in methylene blue for 48 h and evaluated by three independent evaluators under microscope. Teeth with existing fractures were eliminated from the study. The remaining teeth were randomly divided into two equal groups. Group A was prepared with the CT-5 tip and Group B with the KiS tip. Preparation time was recorded for all roots. The teeth were again immersed in methylene blue for 48 h and reevaluated. No root-end fractures were produced by either the KiS or CT-5 microsurgical ultrasonic instruments.

Periradicular surgery of molars: a prospective clinical study with a one-year follow-up

AIM

The purpose of this prospective clinical study was to evaluate the outcome of periradicular surgery of molars after one year.

METHODOLOGY

The material consisted of 25 molars with 39 roots demonstrating periradicular lesions of endodontic origin. Surgical treatment included root-end resection, root-end preparation with sonic microtips, and root-end filling with Super-EBA cement. At the one-year follow-up examination, healing was evaluated clinically and radiographically. Healing was assigned to three categories: (i) success (ii) improvement, and (iii) failure using well defined criteria.

RESULTS

Eighty-eight per cent of the surgically treated molars showed successful healing. In 8%, the healing was rated as improved and only 4% were failures.

CONCLUSIONS

The outcome of the present study and data of recently published studies show that periradicular surgery may result in a predictable treatment outcome in molars with persistent periradicular lesions.

An in vitro study comparing root-end cavities prepared by diamond-coated and stainless steel ultrasonic retrotips

AIM

This study compared the appearance of root-end cavity preparations and the time required to prepare them using prototype ultrasonic diamond-coated (DC) and stainless-steel (SS) retrotips.

METHODOLOGY

In 12 maxillary and 12 mandibular molar teeth 48 root-end cavities were prepared ultrasonically in the palatal, mesio-buccal, distal and mesial root-ends using DC and SS retrotips, alternately. Replicas of the resected root tips and the root-end cavities were examined under a scanning electron microscope (SEM), recording (i) incidence and extent of dentine cracks (ii) minimum remaining thickness of the dentine walls and (iii) surface quality of the resected root-ends. The time taken to complete the preparation was also recorded. Means of these parameters were compared for both types of retrotips using nonparametric tests.

RESULTS

No resected root-ends had cracks before preparation. However, after preparation one root-end cavity shaped by an SS retrotip had a microcrack visible at 23x magnification. Four and seven other root-ends had crazed surfaces in the DC and SS groups, respectively (P > 0.05). Remaining minimum dentine thickness was 0.56 +/- 0.28 mm and 0.71 +/- 0.24 for the DC and SS groups, respectively, and this difference was significant (P < 0.05). A root-end cavity in one specimen in the DC group was perforated. Preparation times ranged from 25 s to 361 s and were significantly lower for DC tips (P < 0.01) than the SS tips. The time required to prepare root-end cavities also differed between roots; root-end preparation in mandibular molars was more time consuming.

CONCLUSIONS

A better quality surface was produced by the prototype diamond-coated retrotips, in less time than the SS retrotips, which in turn caused fewer cracks than previously reported. DC retrotips removed more dentine than SS retrotips and should therefore be used with care to avoid overpreparation or perforation.

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.

Ultrasonic root-end preparation with smooth and diamond-coated tips

The purpose of this study was to compare the effects of smooth and diamond-coated ultrasonic retrotips on the external and internal surfaces of root-end preparations with the aid of a scanning electron microscope (SEM). Forty-four mesial roots of human mandibular molars were selected. The canals were cleaned, shaped and obturated using gutta-percha and sealer. The apical portions were resected at a 45 degrees-angle bevel exposing both mesial canals and the isthmus area. The roots were then divided into two groups according to the type of root-end preparation: Group A--performed with smooth retrotips (S) and Group B--performed with diamond-coated retrotips (DC). The specimens were coded and prepared for SEM evaluation. Observations of the external surface preparation showed that the S and DC retrotips produced very well-centered cavities involving both canals and isthmus area with minimal deviations and no perforative defects. When the internal surface of the root-end preparations was evaluated, it was evident that the use of S retrotips resulted in clean canal walls with little superficial debris and smear layer. Internal canal surfaces done with DC retrotips were irregular showing patent grooves, in contrast with the more uniform, regular and smoother surfaces when S retrotips were employed.

Evaluation of diamond-coated ultrasonic instruments for root-end preparation

Ultrasonic instrumentation has been associated with cracking of the dentin in the area of the root-end preparation. The purpose of this study was to evaluate root-end preparations for cracking and to describe cavosurface morphology after the use of diamond-coated instruments. Forty teeth were inspected for intradentin cracks, incomplete canal cracks, and complete canal cracks before and after preparation with a stainless steel CT-5 ultrasonic instrument and again after root-end preparation with an S12D/90 degrees diamond-coated instrument. Six teeth had polyvinylsiloxane impressions taken of the root ends after preparation with the CT-5 and again after preparation with the diamond-coated instrument. Replicas were made, split, sputter-coated, and inspected using the scanning electron microscope. This study indicates that use of the diamond-coated instrument for root-end preparation does not result in significant root-end cracking and that it can remove cracks created by a prior instrument's use. The use of the diamond-coated instrument resulted in a heavily abraded, debris-covered cavosurface that may affect the apical seal.

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.

Response of periradicular tissues to growth factors introduced into the surgical site in the root-end filling material

AIM

The objective of this study was to evaluate the healing of the periradicular tissues when exogenous growth factors were delivered to the respected root-end. The healing response was compared with that when Diaket was used as a control.

METHODOLOGY

Non-surgical root canal treatment was performed on mandibular teeth in mongrel dogs. Surgical treatment followed and included root-end resection and root-end cavity preparation. Insulin-like growth factor in combination with platelet-derived growth factor, or fibroblast growth factor alone, were then placed in the root-end preparations on a polylactic acid carrier (Atrisorb) with or without the incorporation of the carrier tetracalcium phosphate. The healing was evaluated at 60 days with regard to presence of inflammatory response, bone regeneration, periodontal ligament formation and cementum formation.

RESULTS

Osseous regeneration in the excisional would and periodontal formation were significantly greater when Diaket was used as the root-end filling material. Likewise, cementum deposition occurred significantly more frequently in the Diaket group (P < 0.05). The polylactic carrier Atrisorb remained in the surgical sites for the duration of the study.

CONCLUSIONS

The use of specific growth factors, FGF and a combination of IGF/PDGF, delivered to the prepared root end in a collagen carrier did not initiate the desired periradicular tissue response of regeneration. Diaket, as used in this study, did stimulate a periradicular tissue response compatible with regeneration.

The quality of ultrasonic root-end preparation: a quantitative study

Ultrasonic root-end preparation techniques have recently been introduced and revolutionized the field of endodontic surgery. The purpose of this study was to compare quantitatively the quality of root-end preparation techniques prepared by a specially designed ultrasonic retrotip with those prepared in a traditional manner by a microhandpiece bur. Twenty roots with two canals and an isthmus from extracted maxillary human molars were selected for this study. After instrumentation, obturation, and root-end resection, root-end preparations were made using either an ultrasonic retrotip or a conventional microhandpiece bur. With the aid of the image processing and analysis system, the specimens were inspected under a stereomicroscope for further evaluation of the quality of the shape and size of preparation. The results of this investigation showed that the ultrasonic root-end preparations produced more conservative and less perforated cavities than those made with conventional microhandpiece bur preparations.

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.

Comparison of ultrasonic and high-speed-bur root-end preparations using bilaterally matched teeth

The purpose of this study was to compare ultrasonic and high-speed-bur root-end preparations. Seventy-six roots from 29 bilaterally matched pairs of human teeth in cadavers were used in this study. In group 1 ultrasonic preparations were made in 38 roots and filled with amalgam. In group 2 high-speed bur preparations were made in 38 roots and filled with amalgam. The size of the bony crypt was measured and the teeth were extracted and radiographed mesial-distally and buccal-lingually. None of the root-end preparations resulted in root perforation. The mean mesial-distal minimum depth of ultrasonic and high-speed bur preparations were 2.11 mm and 1.39 mm, respectively. The mean buccal-lingual minimum depth of preparation was 2.51 mm for the ultrasonic and 2.05 mm for the high-speed bur preparations. The depth of the ultrasonic preparations was significantly greater for both measurements. A significantly greater bevel angle was associated with the bur preparations, 35.1 degrees versus 16.0 degrees for the ultrasonic preparations. The incidence of ultrasonic root-end preparations deviating from the uninstrumented canal spaces was found to be 2.6%. All bur root-end preparations were at an acute angle to the long axis of the root. The bony crypt size for bur preparations was significantly greater than that for ultrasonic preparations.

Incidence of root face alteration after ultrasonic retrograde cavity preparation

PROBLEM

Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation.

OBJECTIVES

The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy.

STUDY DESIGN

The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face.

RESULTS

Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.

Root-end cavity preparation using the MicroMega Sonic Retro-prep Tip. SEM analysis

The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.

Root end filling materials: a review

When non-surgical attempts prove unsuccessful or are contraindicated, surgical endodontic therapy is needed to save the tooth. The procedure usually consists of exposure of the involved area, root end resection, root end preparation and insertion of a root end filling material. Numerous materials have been suggested as root end filling materials. This article is a review of the literature on the suitability of various root end filling materials based on their leakage assessment, marginal adaptation, cytotoxicity, and usage test in experimental animals and humans.

Effect of retrograde cavity preparations on root apexes

Ultrasonic cavity preparations in endodontic surgery has become a popular procedure with several advantages noted: Smaller cavities, deeper and cleaner preparations, less removal of surrounding bone needed for instrumentation and less removal of root apex dentin. Concern has been raised that lines of infraction have appeared in some instances when the ultrasonic instruments have been used. We wished to examine the result of cavity preparations in root apexes using five different methods: high and slow speed handpieces, sonic instruments, and ultrasonic instruments at two power settings, medium and high levels, respectively. The results showed that all the methods produced some infractions; the high power ultrasonics produced the most infractions while the lowest numbers were associated with the slow speed handpiece and ultrasonic instruments at the medium power setting.

Cutting characteristics of a sonic root-end preparation instrument

The aim of this study was to investigate the cutting ability of retro tips powered by a sonic handpiece (MM 1500, Micro Mega, Prodonta, Geneva, Switzerland). Two levels of the following variables were evaluated in this study: a) power setting with the an inlet ring half or fully open, b) orientation of tip perpendicular or parallel to the long axis of the handpiece, c) length of tip 2 or 3 min, d) loading of 25 or 50 grams, e) tip size 35 or 55. The substrate used was 1 mm thick sections of bovine bone and load was controlled by using a load cell interfaced with a transducer meter. Instrumentation time was fixed at 10 seconds with water irrigation. A 2(5) full factorial analysis was performed with two replications making a total of 64 experimental units. The resultant depth of cut was measured using a stereo microscope at x50 magnification. Analysis of the data indicated that all variables had a significant effect on cutting (ANOVA p < 0.05). The most significant factor was power, followed by tip length tip orientation, width and load. An increase in loading resulted in tip constraint and a reduction of cutting at the lower power setting. In conclusion sonically activated retro tips were found to cut satisfactorily with instrument air inlet ring opening/power having the main effect.

Effects of ultrasonic root-end cavity preparation on the root apex

This study determined the effect of bur and ultrasonic preparation on the root apex. After cleaning, shaping, and obturation of root canals of 47 single-rooted teeth and resection of their apexes were done, 24 root-end cavities were prepared with a bur, and the rest were prepared with ultrasonic tips attached to two different ultrasonic units. After photographs of the prepared root ends were taken, their resin replicas were prepared and examined with a scanning electron microscope. Photographs and scanning electron microscope photomicrographs were examined for the presence or absence of cracks. The results showed a significantly higher incidence of crack formation in the walls of root-end cavities prepared by ultrasonic tips compared with those made by the bur.