A light microscopic study of the efficacy of the telescopic and the Giromatic preparation of root canals

Comparison of root canal preparation using reciprocating Safesiders stainless steel and Vortex nickel-titanium instruments

OBJECTIVE

The aim of the present study was to assess several parameters related to the clinical usage of 2 root canal preparation instruments: Vortex .06 rotary nickel-titanium instruments, and Safesiders reciprocating stainless steel instruments.

STUDY DESIGN

Fifty extracted mandibular molars with mesial root canal curvatures between 20° and 50° were divided into 2 groups and embedded in acrylic resin inside a modified Bramante muffle system. All root canals were prepared to ISO size 40 using either Vortex .06 rotary nickel-titanium-instruments in a low-torque motor or Safesiders stainless steel instruments in a proprietary reciprocating handpiece. The following parameters were evaluated: straightening of curved root canals, working safety issues (perforations, instrument breakages, canal blockages, loss of working length), postpreparation root canal cross-section, and working time.

RESULTS

The Vortex .06 instruments maintained canal curvatures well, with the mean degree of straightening recorded as 0.72°. Safesiders instruments demonstrated significantly more canal straightening, with the mean degree of straightening recorded as 15.5°. More than 90% of the root canals prepared with the Vortex .06 instruments resulted in a round or oval cross-section, whereas the Safesiders instruments produced round or oval cross-sections 60% of the time. Neither of the 2 instruments could effectively prepare 100% of the root canal circumference. The area of dentin removed and the remaining dentin thicknesses from each region were similar for the 2 groups. Six procedural incidents were recorded for the Vortex .06 group, compared with 19 for the Safesiders group. There were no instrument fractures recorded in either group. Mean working time was significantly shorter for Vortex .06 (279 s) than for Safesiders (324 s).

CONCLUSIONS

Vortex .06 maintained the original root canal curvatures well, whereas Safesiders instruments demonstrated significant straightening and irregular preparation shapes when used in sizes larger than ISO 20. Preparation of the complete circumference of the root canal was not possible with either system. Fewer procedural errors occurred with the Vortex instruments.

Effect of Er,Cr:YSGG laser irradiation on eruption of rat mandibular incisor after disturbance of the enamel organ in the pulp

To investigate the efficacy of Er,Cr:YSGG (erbium,chromium:yttrium scandium gallium garnet) laser irradiation in root canal preparation and to evaluate its effect on eruption of rat incisors after disturbance of the enamel organ in the pulp, 20 canals of lower left incisor teeth were prepared by K-files followed by Er,Cr:YSGG laser irradiation, and 20 canals of right incisors were subjected to K-files only (control). At 1 week after irradiation, both sides of incisors erupted at the same level from the gingival margin. Histological findings showed that laser irradiation produced a slightly larger damage in the pulp than that of control. Scanning electron microscope observation revealed that laser-treated surface revealed a rough, irregular, and very clean surface; there was almost no evidence of debris or smear layer, and dentinal tubules were opened. Adequate power of Er,Cr:YSGG laser irradiation is effective in root canal preparation without disturbance of the eruption.

Canal preparation with Hero 642 rotary Ni-Ti instruments compared with stainless steel hand K-file assessed using computed tomography

AIM

To compare ex vivo root canal preparation with conventional stainless steel K-files and Hero 642 rotary Ni-Ti instruments.

METHODOLOGY

Mesiobuccal canals of 20 maxillary first molars (with angles of curvature between 25 degrees and 35 degrees ) were used. After preparation with Hero 642 rotary instruments and stainless steel K-files, the amount of transportation that occurred was assessed using computed tomography. The teeth were scanned by computed tomography before instrumentation. One millimetre thick slices were prepared from the apical end point to the pulp chamber. The first two sections were 3 mm from the apical end of the root (apical level) and 3 mm below the orifice (coronal level). A further section (mid-root level) was recorded, dividing the distance between the sections of apical and coronal levels into two equal lengths. Ten teeth were instrumented using Hero 642 rotary instruments and another 10 teeth were instrumented using stainless steel K-files. Following the completion of the instrumentation, the teeth were again scanned and compared with the cross-sectional images taken prior to canal preparation. Amount of transportation and centreing ability was assessed. Student's t-test was used for statistical analysis.

RESULTS

Less transportation occurred with Hero 642 rotary instruments than stainless steel K-files at the mid-root and coronal levels (mid-root: P < 0.05 and coronal: P < 0.001). Hero 642 rotary instruments had better centreing ability than K-files at all three levels (apical: P < 0.05, mid-root: P < 0.05 and coronal: P < 0.001).

CONCLUSIONS

Hero 642 rotary instruments transported canals less, especially at the middle and coronal thirds of the root canals than stainless steel K-files. Hero 642 instruments had better centreing ability.

Cleaning efficiency of nickel-titanium GT and .04 rotary files when used in a torque-controlled rotary handpiece

This study determined if the cleaning efficiency of nickel-titanium rotary files in an endodontic electric handpiece using a no-torque control setting was superior to that obtained when using the torque-control feature. Fifty extracted human anterior teeth with straight canals were divided into two groups of 20 and two control groups of 5. Canals were instrumented with GT and .04 ProFile nickel-titanium files until a size 35 advanced to working length. Samples were sectioned and the apical 6 mm of the canal was photographed (x20) and projected onto a 3- x 4-foot grid with squares measuring 0.5 inches each. Total debris was the percentage of the number of squares containing debris versus the total number of squares. The teeth in the torque-controlled group showed an average of 24.99% debris versus 15.55% for the teeth in the no-torque group. The difference was not statistically significant; therefore, no difference can be said to exist between the two torque settings in terms of cleaning efficiency.

A scanning electron microscopic study of debris and smear layer remaining following use of GT rotary instruments

AIM

The aim of the present study was to assess debris and smear layer remaining following canal preparation with GT rotary instruments.

METHODOLOGY

Sixteen freshly extracted single-rooted premolar teeth were instrumented with GT rotary instruments using a crown-down preparation technique. All specimens were flushed with 2 mL of 5% NaOCl between each rotary instrument. At the end of instrumentation the following final irrigation sequence was repeated two times: 2 mL of EDTA + Cetrimide for 1 min (Largal Ultra, Septodont, France) and 2 mL of 5% NaOCl for 5 min. A final flush with saline solution was made to halt any chemical activity. Two other uninstrumented teeth that were not irrigated served as controls. All teeth were split longitudinally and prepared for SEM evaluation. The presence of debris and smear layer was evaluated from photomicrographs at x200 and x1000 magnification taken in the apical, middle and coronal thirds of the canals. Blind evaluation was performed by two trained observers and scores were compiled separately. A five category scoring system for debris and smear layer was used. Values obtained were tabulated and statistical analysis was carried out using a parametric chi-squared test.

RESULTS

Statistical analysis showed that there was no significant difference between the three regions of the root canals (P > 0.05) for debris. Comparison of the removal of the smear layer between the three regions showed that there was a statistically significant difference between all parts, especially between the coronal and apical thirds (P < 0.001). Overall, the coronal sections were cleaner than the middle and apical sections. The uninstrumented canals showed walls completely covered with tissue, confirming that specimen preparation alone did not remove tissue.

CONCLUSIONS

Under the conditions of the present study GT rotary instruments removed debris effectively, but left root canal walls covered with smear layer, particularly in the apical third.

Antibacterial effects of pulsed Nd:YAG laser radiation at different energy settings in root canals

The in vitro study aimed at the determination of the bacterial reduction in root canals used pulsed Nd:YAG laser radiation without a photosensitizing dye. In addition the temperature change in the root canals was determined during laser irradiation. The study sample was 114 root canals of extracted single-rooted human teeth that have been enlarged mechanically, sterilized, and randomly assigned to two experimental units. The source of radiation was a Nd:YAG laser device emitting pulsed infrared radiation at a wavelength of 1.064 microm, a pulse duration of 100 micros, and a pulse repetition rate of 20 pps. Samples of each experimental unit were inoculated with Escherichia coli (ATCC 25922) or Staphylococcus aureus (ATCC 25923), respectively, and divided into subgroups of 13 teeth each for irradiation for 20 s at 100 mJ or 200 mJ. One subgroup was left untreated as positive control and one subgroup was rinsed with 0.5 ml of sodium hypochloride. After laser treatment or rinsing with sodium hypochloride the number of bacteria in each root canal was determined using the surface spread plate technique. Statistical analysis of the results was performed with ANOVA and Scheffé test at a level of significance of 5% (p < 0.05). In case of E. coli the number of bacteria was reduced from 8.67 x 10(6) (+/-4.11 x 10(5)) colony-forming units (CFU)/ml to 4.39 x 10(4) (+/-1.72 x 10(4)) CFU/ml after laser radiation at 200 mJ. Regarding S. aureus the number of bacteria decreased from 1.44 x 10(6) (+/-1.59 x 10(5)) CFU/ml to 3.8 x 10(4) (+/-1.06 x 10(4)) CFU/ml at a radiation energy of 200 mJ. Rinsing with sodium hypochloride reduced the number of bacteria to 1.03 x 10(3) (+/-4.02 x 10(2)) CFU/ml regarding E. coli and to 1.84 x 10(3) (+/-7.4 x 10(2)) CFU/ml in case of S. aureus. The temperature increase at 100 mJ was 24.3 degrees C (+/-3.9) and that at 200 mJ was 61.8 degrees C (+/-4.2). The Nd:YAG laser radiation has antimicrobial effects in root canals even in the absence of photosensitizing dyes but also causes considerable temperature increase.

Digitization, analysis and processing of dental images during root canal preparation with Quantec Series 2000 instruments

AIM

The aim of this study was to determine the shaping ability of Quantec Series 2000 nickel-titanium instruments in the mesio-buccal roots of maxillary first molars and the mesial roots of mandibular first molars.

METHODOLOGY

A total of 20 canals were prepared with Quantec instruments, adopting the technique recommended by the manufacturer. Each canal was sectioned horizontally into four and the canal in each portion photographed before and after preparation. The images obtained were digitized and the increase in canal surface for each quadrant of the four sections was evaluated, along with the variation in centre of mass after instrumentation.

RESULTS

Mechanical instrumentation of the canals generated mean centre of mass displacements that did not vary between sections, except for the mid-apical section, which showed significant mesial displacement, i.e. toward the side opposite the furcation. Thus, overall, the widening of the canal was symmetrical.

CONCLUSIONS

Under the conditions of the study, the Quantec Series 2000 rotary system was simple and safe to use, and created good three-dimensional mechanical preparation of natural canals.

Shaping ability of Hero 642 rotary nickel-titanium instruments in simulated root canals: Part 1

AIM

To determine the general efficacy and shaping ability of Hero 642 nickel-titanium rotary instruments during the preparation of simulated canals. Part 1 of this two-part report describes the efficacy of the instruments in terms of three-dimensional canal form.

METHODOLOGY

A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared by Hero 642 instruments using a crown-down preparation sequence. The efficacy of the instruments was assessed in terms of preparation time, instrument failure, canal blockages and loss of canal length. Intra-canal impressions were taken of the prepared canals in order to assess three-dimensional canal form.

RESULTS

The mean time for canal preparation was 8.6 min and was influenced significantly (P < 0.05) by canal shape. Two instruments fractured and eight instruments deformed; significant differences were observed between canal shapes (P < 0.05). All of the canals remained patent. Fifteen canals (39.5%) maintained the correct working distance, 15 lost distance and eight canals gained length. Examination of intracanal impressions demonstrated that the majority of canals (79%) had apical stops; canal shape had a significant influence (P < 0.001) on the quality of apical stops. With one exception all canals had smooth canal walls and all of the canals showed good flow characteristics. Taper was poor in 30 canals (79%) and good in eight canals (21%).

CONCLUSIONS

Hero 642 rotary nickel-titanium instruments prepared simulated canals rapidly but with a three-dimensional form that lacked adequate taper.

Location of contact areas on rotary Profile instruments in relationship to the forces developed during mechanical preparation on extracted teeth

AIM

The aim of this study was to locate the areas of direct instrument contact with dentine in the root canal system during rotary preparation and to analyse the relationship between these areas and the vertical forces and torque developed during the preparation.

METHODOLOGY

Canal preparations were performed by endodontists either with the step-back (SB) or the crown-down (CD) technique. In order to locate the areas of contact, the instruments were coated with two layers of gold by electro-deposition. They were photographed before and after use, and a coding system, based on mm from the instrument tip, was devised to designate areas of gold removal or instrument wear due to friction. To standarise the conditions of instrument manipulation, the teeth were fixed in the Endographe holder, and this device was used to measure vertical forces and torque.

RESULTS

The results showed that the first series of instruments used for the CD technique (taper 0.06) left 2 +/- 1 mm of the tip with the gold intact, indicating that these instruments and this step of the CD technique are the safest part of the preparation. For all other instruments (taper 0.04 series), the areas of gold removal involved the 3 mm around the tip and this finding was independent of the order of instrument use and preparation technique (SB or CD). The differences between the two techniques were significant in terms of the mean area of decolouration and the mean force and torque values. For the SB and CD techniques, the contact areas were, respectively, 10 +/- 3 and 7 +/- 2 mm. The forces and torque values were correspondingly higher for SB vs. CD; the mean values were, respectively, 19 and 21 N for vertical forces and 16 10(5) and 13 10(5) Nm for torque.

CONCLUSIONS

The recorded torque values and the location on the instruments of the areas of contact with dentine during this development of torque i.e. at or near the tip, indicate that great caution should be used with the rotary technique, particularly with the taper 0.04 instruments, regardless of preparation technique.

Bactericidal action of 308 nm excimer-laser radiation: an in vitro investigation

The aim of the present study was to investigate the influence of 308 nm excimer-laser radiation on bacterial growth. Six different bacterial strains (Staphylococcus aureus, Escherichia coli, Streptococcus faecalis, Lactococcis lactis, Salmonella typhimurium, and Deinococcus radiodurans) were exposed in vitro to various doses and energy densities of laser radiation. To exclude bacterial killing by supraphysiological heating, the temperature change in the samples during irradiation was measured. Extended antimicrobial effects of XeCl excimer-laser radiation depending on the time of radiation, the energy density of the laser beam, and the irradiated bacterial strain were observed. Reduction of bacterial growth is independent of temperature and not linked to any ablative tissue removal. In almost all cases, a 99.9% reduction of bacteria was reached by total radiation times < 100 ms. The proven antimicrobial effects of 308 nm excimer-laser radiation may be of significant clinical importance in endodontics and periodontology in the future.

Study of the Nd:YAP laser. Effect on canal cleanliness

The aim of this study was to evaluate the canal cleanliness achieved by five different preparation techniques, including use of the laser. By randomization, the palatal roots of 50 maxillary molars were assigned to one of five groups. During all preparations, a sodium hypochlorite irrigant was used. The following techniques were studied: (A) manual instrumentation (serial preparation), (B) laser preparation (Nd:YAP laser), (C) manual preparation with laser as adjunct, (D) manual preparation with a subsonic device as adjunct (MM 3000 with shapers), and (E) manual instrumentation with a subsonic device and laser as adjuncts (MM 3000 with shapers, Nd:YAP laser). The canal wall surfaces were examined under a scanning electron microscope at all levels with a new method using grid incrustation on the microscope screen. Techniques A and C differed from each other only by the size of the debris particles, which were smaller for the C preparation. For laser preparation (B) there was little increase in canal diameter increase, and a substantial amount of debris was present. The differences between techniques A, C, and D were not significant. The use of the subsonic device and laser together as adjuncts (E) showed the cleanest preparation with very little debris, opened tubules, and very small particle size. This result suggests that the laser has a potential in ensuring optimal canal cleanliness.

Root canal cleanliness after preparation with different endodontic handpieces and hand instruments: a comparative SEM investigation

The root canals of 150 extracted mandibular incisors were prepared to ISO 30 using eight different automated devices and hand instruments. The automated devices investigated were: Endoplaner, Excalibur, Ultrasonics (Piezon Master 400) with H2O2 (5%), or NaOCl (1%) as irrigants, Giromatic, Intra-Endo 3-LDSY, Canal Finder System, Canal Leader 2000, and Endolift. Hand instrumentation was performed using reamers and Hedstroem files. Fifteen teeth were instrumented with each device, cracked longitudinally, and investigated under the scanning electron microscope using five category scoring systems based on reference photographs for debris and smear layer. No preparation system or technique resulted in complete removal of smear layer and debris. The ultrasonic unit performed best followed by the Canal Leader 2000 and hand instrumentation, whereas the use of the Giromatic, the Endolift, the Canal Finder System, and the Intra-Endo-3-LDSY-handpiece resulted in insufficiently cleaned root canal walls.

Shaping ability of ProFile.04 Taper Series 29 rotary nickel-titanium instruments in simulated root canals. Part 1

The aim of this study was to determine the shaping ability of ProFile.04 Taper Series 29 nickel-titanium instruments in simulated canals. A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared by ProFile instruments using a step-down approach. Part 1 of this two-part report describes the efficacy of the instruments in terms of preparation time, instrument failure, canal blockages, loss of canal length and three-dimensional canal form. The time necessary for canal preparation was not influenced significantly by canal shape. No instrument fractures occurred but a total of 52 instruments deformed. Size 6 instruments deformed the most followed by sizes 5, 3 and 4. Canal shape did not influence significantly instrument deformation. None of the canals became blocked with debris and loss of working distance was on average 0.5 mm or less. Intracanal impressions of canal form demonstrated that most canals had definite apical stops, smooth canal walls and good flow and taper. Under the conditions of this study, ProFile.04 Taper Series 29 rotary nickel-titanium instruments prepared simulated canals rapidly and created good three-dimensional form. A substantial number of instruments deformed but it was not possible to determine whether this phenomenon occurred because of the nature of the experimental model or through an inherent design weakness in the instruments.

Effectiveness of apical clearing: histological and radiographical evaluation

Preparation of the apical one-third in curved canals is difficult both in debridement and maintaining canal shape. A technique of final apical preparation, "apical clearing," attempted to debride and increase the apical size without transportation. Apical clearing is defined as: following cleaning and shaping, sequentially rotating files two to four sizes larger than the initial (master) apical file at working length, then rotating the largest apical file again after a final irrigation and drying. This study evaluated histologically and radiographically the quality of apical preparation with or without apical clearing. Examined were (a) extent of transportation and (b) debris accumulation in the apical third. Fifty-four extracted teeth with vital pulps and curved canals were divided into two groups. After step-back preparation, 29 had apical clearing and 25 did not. Pre- and postpreparation double-exposed radiographs evaluated canal deviation. The apical one-third of the canals was examined histologically and ranked, based on remaining tissue, predentin, dentin shavings, other debris, and canal walls planed. Radiographically, the apically cleared group showed slight deviation of the canal during preparation. Histologically, canals in the apically cleared group had significantly less remaining tissue, predentin and debris, as well as more canal walls planed. This experiment showed that apically the apical clearing technique resulted in better debridement, with minimal increase in apical transportation.

An in vitro comparison of incomplete root fractures associated with three obturation techniques

This study compared the incidence of incomplete root fractures among five groups of mandibular incisors (20/group). The groups were: (a) no canal preparation, (b) canal preparation, (c) canal preparation and obturation with laterally condensed gutta-percha, (d) canal preparation and obturation with thermoplasticized gutta-percha on a central carrier (Thermafil), and (e) canal preparation and obturation with thermoplasticized injectable gutta-percha (Ultrafil). Following experimental manipulation, all teeth were stained, transversely sectioned, and evaluated for the presence of root fracture. No complete root fractures were noted. The lowest incidence of stained incomplete fracture was found in the no canal preparation group. The canal preparation, lateral condensation, Ultrafil, and Thermafil groups had more incomplete fractures than the no canal preparation group. The incidence of stained fracture in the three obturation groups was not significantly different from the incidence in the group which had only canal preparation.

Comparison of root canal preparation using different automated devices and hand instrumentation

The pre- and postinstrumentation degree of curvatures in curved mesial root canals of mandibular molars were compared after preparation with eight automated devices and hand instrumentation. The straightening of the root canal was measured before preparation and after preparation to size 25 and 35. Procedural mistakes such as loss of working length or file fractures were also recorded. Following preparation to ISO 25, only the Endoplaner and the Canal Finder system showed significantly more straightening than hand instrumentation. After preparation to ISO 35, the Endoplaner and the Intra-Endo 3-LDSY showed significantly more straightening than hand instrumentation. Mecasonic, Excalibur, and the Canal Finder system also straightened the root canal more than hand instruments, but the results did not differ significantly. The best results with only moderate straightening and few cases of loss of working length were obtained by the Endolift and Giromatic handpieces, which both were comparable to hand instrumentation.

Histologic evaluation of three endodontic instrument/preparation techniques

33 curved canals were prepared to quantify both the increase in canal area and predentin removal in the apical region. Compared were three different file designs/instrumentation techniques, that is "stepback" with K-flex file, "balanced force" with Flex-R file, and the Canal Master system. Following canal preparation and histological processing, cross-sections at 1 and 3 mm levels were examined using the Bioquant image analysis system. Results showed that, at the 3 mm leve, the mean increase in canal area and predentin removal showed no statistically significant difference (p > 0.05) between the techniques. At 1 mm, the step-back technique (with K-flex files) resulted in a significant increase in canal area and greater predentin removal than did the "balanced forces" (with Flex-R files) or the Canal Master system. However, although there were statistical differences, the actual differences were small; these may not translate to clinically significant differences in the 3 techniques.

Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

The purpose of this study was to develop methods and criteria for the testing of the biocompatibility of endodontic materials. One hundred twenty-one teeth from 12 baboons (Papio anubis) were used to test three sealers: AH26, Kerr pulp canal sealer, and Kloroperka N.O. Gutta-percha cones were used as solid core in all cases. Under disinfected conditions, access preparation was performed, and with working length approximately 1.0 mm short of the foramen, the instrumentation of the root canal was started, using sodium hypochlorite (1%) for irrigation. After the root canals were cleaned and shaped, they were obturated with gutta-percha cones and the sealer, and by lateral condensation technique. Histologic periapical reactions were evaluated at 1, 7, 30, 365, 730, and 1095 days. The methods and criteria used were adequate for ranking of the biocompatibility of the tested materials in the short and long periods. At short observation periods (1 to 7 days) AH26 caused severe reactions, and Kerr pulp canal sealer and Kloroperka N.O., moderate and mild reactions, respectively. At 2- and 3-year observation periods the ranking was AH26, mild; Kerr pulp canal sealer, moderate; and Kloropercha N.O., severe.

Clinical factors associated with ledged canals in maxillary and mandibular molars

No clinical studies have been done to explore the relationship of ledging to the clinical practice of endodontics. The purpose of this study was to examine 171 cases completed by third-year dental students and to identify variables that were associated with ledging. A total of 336 canals were examined and tooth number, canal location, working length, the master apical file size, and root canal curvature were recorded. Of 336 canals, 46% were found to have been ledged. Analysis of variance revealed that No. 15 had a significantly higher incidence of ledging. Working lengths and master apical file sizes were not found to be significant variables. The main factor consistently related to the presence of ledges was canal curvature. The number of ledged canals increased significantly after 20 degrees and surpassed the number not ledged after 30 degrees. Multiple regression with the use of the five categories as the dependent variables and ledging as the independent variable resulted in an r = 0.397 and F = 12.216, p less than 0.0001. Curvature was found to have the highest significant t value (7.412) followed by "teeth" (2.471), whereas no other categories were identified as being significant. All the determinants for ledging were not identified with this study, and further research is indicated.

Scanning electron microscope observation of canal cleanliness

The aim of this study was to evaluate the cleansing efficiency of three root canal preparation techniques. The distal root canals of mandibular molars, divided into three groups of four teeth each, were prepared according to the following techniques: manual (serial), ultrasonic (Cavi-Endo), and automated (Canal Finder). The canal wall surfaces were examined under a scanning electron microscope at three levels. No preparation technique was found to result in any characteristic microscopic features that distinguished it from the other techniques. The lack of such differences makes it impossible to establish objective criteria for comparing these techniques in terms of root canal cleanliness. It was established that even canals that appeared to be clean included areas coated with smear layer and having uninstrumented areas and even pulpal tissue debris.

Paste technique re-treatment study: a clinical, histopathologic, and radiographic evaluation of 50 cases

This study correlated clinical, radiographic, and histopathologic aspects of 50 endodontic failures involving the paste technique. All clinical and radiographic findings were recorded. The teeth were re-treated with gutta-percha/Kloroperka and lateral condensation. Subsequently, periapical surgery, including retrograde amalgam filling, was performed for the removal of material in the periapical tissue. The resulting biopsy specimens were processed for histologic evaluation. Although neutrophilic leukocytes predominated in some cases, all types of inflammatory cells were present. Macrophages and foreign body cells contained paste particles. The blood pigment distinguished hemorrhage due to surgery from pathologic circulatory changes. There was resorption/apposition of bone and root fragments. Epithelial strands and parts of cyst walls were observed. There was a correlation between a periapical radiolucency and inflammation but no correlation between amounts and types of inflammatory cells and pain. Paste placed beyond the foramen caused tissue damage and reduced prognosis.