Does root canal treatment in necrotic pulp or retreatment cases with periapical lesions require anaesthesia? An in vivo clinical study.

AIM: To examine whether local anaesthesia is required for treating teeth with necrotic pulps (TNP) and retreatment cases (RCs) associated with periapical lesions. METHODOLOGY: Root canal treatment was performed in TNP and RCs without the administration of local anaesthesia. Patients were assured that if they experienced pain, local anaesthesia would be provided. Eighty canals, 40 TNP and 40 RCs, were included in the study. Two length measurements were performed: one using an electronic apex locator (EAL), which was defined as the electronic length (EL), and the second, the length at which the patient first reported that a size 15 file was touching the periapical tissues, which was defined as the periodontal length (PL). The difference between these two measurements (Δ = PL - EL) was the parameter studied. Statistical analysis was conducted using two-way anova and paired t-tests. Working length (WL) was defined in this study as being 0.5 mm short of the EL. RESULTS: EL was shorter than PL in 96% of cases. The mean difference between measurements was 0.78 (±0.11) mm in the TNP group and 0.63 (±0.15) mm in the RC group; the difference was not significant. The distances between the WL and PL were thus 1.28 and 1.13 mm, respectively. In none of the 80 canals did the patient experience any pain, either during the measurements or during the instrumentation procedures. CONCLUSIONS: When EALs are used, local anaesthesia may not be required for root canal treatment in teeth with necrotic pulps and retreatment cases associated with periapical lesions.

The diagnosis and conservative treatment of a complex type 3 dens invaginatus using cone beam computed tomography (CBCT) and 3D plastic models.

AIM: To investigate the use of 3D plastic models, printed from cone beam computed tomography (CBCT) data, for accurate diagnosis and conservative treatment of a complex case of dens invaginatus. SUMMARY: A chronic apical abscess with a draining sinus tract was diagnosed during the treatment planning stage of orthodontic therapy. Radiographic examination revealed a large radiolucent area associated with an invaginated right maxillary central incisor, which was found to contain a vital pulp. The affected tooth was strategic in the dental arch. Conventional periapical radiographs provided only partial information about the invagination and its relationship with the main root canal and with the periapical tissues. A limited-volume CBCT scan of the maxilla did not show evidence of communication between the infected invagination and the pulp in the main root canal, which could explain the pulp vitality. A novel method was adopted to allow for instrumentation, disinfection and filling of the invagination, without compromising the vitality of the pulp in the complex root canal system. The CBCT data were used to produce precise 3D plastic models of the tooth. These models facilitated the treatment planning process and the trial of treatment approaches. This approach allowed the vitality of the pulp to be maintained in the complex root canal space of the main root canal whilst enabling the healing of the periapical tissues. KEY LEARNING POINTS: Even when extensive periapical pathosis is associated with a tooth with type III dens invaginatus, pulp sensibility tests should be performed. CBCT is a diagnostic tool that may allow for the management of such teeth with complex anatomy. 3D printed plastic models may be a valuable aid in the process of assessing and planning effective treatment modalities and practicing them ex vivo before actually performing the clinical procedure. Unconventional technological approaches may be required for detailed treatment planning of complex cases of dens invaginatus.

Residual bacteria in root apices removed by a diagonal root-end resection: a histopathological evaluation.

AIM: To assess bacteria in the apical portion of the root end after 45 degrees root-end resection in teeth with persistent periapical lesions. METHODOLOGY: The study included 27 apical root segments from patients with persistent periapical lesions. Histological sections of the coronal part of the amputated root segment were stained with Brown and Brenn to detect the presence of bacteria in the main root canal and/or in irregular root spaces and dentinal tubules. The quality of each root canal filling was evaluated using preoperative radiographs of filling, length of root filling as assessed from the distance between its apical end and the radiographic apex, diameter of apical preparation, and presence of apical perforations or deviations from the root canal. Two endodontists, blinded to the bacteriological results, independently evaluated the radiographs. RESULTS: Bacteria were present in 23 (85.2%) specimens: five in only the main canal (21.7%), 10 in only the dentinal tubules and irregular spaces (43.5%), and eight in both irregular spaces and dentinal tubules and in the main root canal (34.8%). No correlation was found between the technical quality of the root filling assessed radiographically and bacterial presence in the central canal or irregular areas. CONCLUSIONS: Infected irregular areas were found in the root tips of teeth with persistent periapical lesions. This was found regardless of the radiographic quality of the root filling. Diagonal, 45 degrees root-end resection may expose such contaminated irregularities to the periapical tissue.

Low-dose doxycycline inhibits bone resorption associated with apical periodontitis.

AIM: To test the effect of low-dose doxycycline on bone resorption associated with apical periodontitis. METHODOLOGY: Apical periodontitis was induced by occlusal pulp exposure in the mandibular first molars of 36 rats. Animals were divided into three groups of 12: group A received doxycycline in drinking water at a dose of 5.85 mg day(-1); group B received a dose of 1.48 mg day(-1) (one-quarter of the original dose); and group C received no medicament and served as the control. A bioassay determined the doxycycline serum levels. After 21 days, the mandibles were removed, radiographed and the radiographs scanned to generate digital images. These images were analysed morphometrically and the total area of the periapical bone resorption of the mesial and distal roots of each tooth was determined and used to compare the groups. Statistical analysis was completed using anova with repeated measures. RESULTS: The mean doxycycline serum level in group A was 0.22(+/-0.03) microg mL(-1) and in group B below the detection level of the assay (<0.062 microg mL(-1)). The mean area of the periapical bone resorption in the control group C was 2.91(+/-0.61) mm(2). In animals treated with a low-dose doxycycline, the mean size of the bone resorption was significantly smaller at 1.59(+/-0.59) mm(2) (group A) and 1.72(+/-0.85) mm(2) (group B) (P = 0.001). No significant difference was found in the area of the bone resorption between these two groups A and B. CONCLUSIONS: Low-dose doxycycline reduced the area of bone resorption associated with apical periodontitis in the mandibular first molar teeth of rats.

["Flare-up" during endodontic treatment--etiology and management].

"Flare-ups" during or following endodontic treatment are not uncommon. A "Flare-up" refers to post-operative pain and/or swelling resulting from bacterial, mechanical or chemical irritation. Prompt diagnosis and treatment are essential for reducing patients' pain and discomfort. Prevention of bacterial, chemical or mechanical invasion to the periapical tissues is the best approach. Other treatment modalities which reduce the probability of periradicular tissue irritation should also be adopted. Etiology, prevention, diagnosis and treatment options of "flare-up" cases are discussed as well as indications for analgesics, in accordance with the severity of the pain.

Sensitivity of oral bacteria to 254 nm ultraviolet light.

AIM: To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. METHODOLOGY: The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer. RESULTS: Direct exposure to relatively low doses of UV light (2-7 mJ cm(-2)) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells microm(-2) were present in the light path, the UV light dose had to be increased by a factor of x10 to achieve 100% elimination of the bacteria in an inner layer. CONCLUSIONS: The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.

A virtual reality dental simulator predicts performance in an operative dentistry manikin course.

This study was designed to test the ability of a virtual reality dental simulator to predict the performance of students in a traditional operative dentistry manikin course. Twenty-six dental students were pre-tested on the simulator, prior to the course. They were briefly instructed and asked to prepare 12 class I cavities which were automatically graded by the simulator. The instructors in the manikin course that followed were unaware of the students' performances in the simulator pre-test. The scores achieved by each student in the last six simulator cavities were compared to their final comprehensive grades in the manikin course. Class standing of the students in the simulator pre-test positively correlated with their achievements in the manikin course with a correlation coefficient of 0.49 (P = 0.012). Eighty-nine percent of the students in the lower third of the class in the pre-test remained in the low performing half of the class in the manikin course. These results indicate that testing students in a dental simulator, prior to a manikin course, may be an efficient way to allow early identification of those who are likely to perform poorly. This in turn could enable early allocation of personal tutors to these students in order to improve their chances of success.

Improving the seal of amalgam cores with cemented dowels: a comparative in vitro radioactive tracer study.

Amalgam cores with cemented dowels are commonly used to restore endodontically treated teeth. These restorations were widely studied for their mechanical properties; however, less is known about their sealing ability. The effect of the cement type used for the dowel and that of a bonding agent application were studied in a radioactive tracer coronal leakage study. The sealing ability of posts and cores was also compared with that of 5 mm remaining root canal fillings. Composite luting cement provided a better seal than zinc phosphate cement. The seal provided by 5 mm root canal fillings was poorer than that provided by posts and cores. High variability in seal quality was found among all types of posts and cores studied. This may indicate that the seal provided by cemented dowels with amalgam cores is unpredictable. Because neither the remaining root canal filling nor the post and core may be trusted alone for a seal, each should be performed with the greatest care and both covered with a crown as soon as possible.

The unpredictability of seal after post space preparation: a fluid transport study.

A root canal filling remaining after post space preparation is commonly expected to provide adequate seal. Coronal leakage of 30 endodontically treated teeth was measured before post space preparation using a fluid transport assay. In 10 of these teeth post space was prepared, using a two-step procedure, first to a remaining filling of 6 mm and then to 3 mm, with the leakage studied after each step. In 10 teeth the removal was done in one step to a remaining length of 3 mm. The other 10 teeth, with intact root canal fillings, served as controls and were tested twice for leakage. A significant difference was found between the sealing ability of intact fillings and that of partially removed ones (p < 0.05). The difference between the sealing ability of 3 and 6 mm remaining length group was not statistically significant. The lack of statistical differences between the 6 mm and 3 mm fillings was due to a great variability which existed among the 3 mm remaining fillings. These results suggest that 3 to 6 mm fillings provided a seal inferior to that of intact root canal fillings. Reduction of the fillings to 3 mm resulted in an unpredictable seal.

Calcium hydroxide retention in wide root canals with flaring apices.

Calcium hydroxide (CH) is used to induce apexification in immature, pulpless teeth with wide root canals and flaring apices. Three placement methods of CH were compared in vitro, for their ability to enhance CH retention in the canal. Barium sulfate (BS), added as radiopacifier, was studied for its effects on the radiographic follow up of CH retention, as well as on the ability to detect voids in the CH. Calcium hydroxide filled teeth were kept in phosphate buffered saline-containing tubes in a shaker water bath. Radiographs were taken weekly to follow the retention or loss of the material; they were scanned and stored as digitized images. Quantitative evaluations were done on these images, using a computerized gray scale. Condensed CH was better retained in root canals than either lentulo-placed paste or commercial injected paste. Barium sulfate in the CH paste enabled better detection of voids in the paste filling the canal, however, it obscured the disappearance of CH from the canal, due to a residual radiopacity effect. The results supported (a) condensation of calcium hydroxide as a preferred method that improves its retention in wide root canals, and (b) discontinuing the use of barium sulfate as a radiopacifier in apexification procedures.

Kinetics of coaggregation of Porphyromonas gingivalis with Fusobacterium nucleatum using an automated microtiter plate assay.

Coaggregation between Porphyromonas gingivalis and Fusobacterium nucleatum strains was previously studied using either a semi-quantitative macroscopic assay or radioactive tracer assays. A new automated microtiter plate assay is introduced, in which the plate reader (Vmax) was adapted to allow quantitative evaluation of the kinetics of coaggregation. F nucleatum PK 1594 coaggregated with P. gingivalis HG 405 with a maximal coaggregation rate of 1.05 mOD/min, which occurred at a P. gingivalis to F. nucleatum cell ratio of 1 to 2. F. nucleatum PK 1594 failed to do so with P. gingivalis strains A 7436 or ATCC 33277. Galactose inhibition of this coaggregation could be quantitatively measured over a wide range of concentrations to demonstrate its dose-dependent manner. P. gingivalis HG 405 failed to coaggregate with F. nucleatum strains ATCC 25586 and ATCC 49256. The assay used in the present study is a sensitive and efficient quantitative automated tool to study coaggregation and may replace tedious radioactive tracer assays.

Effect of repeated vertical loads on microleakage of IRM and calcium sulfate-based temporary fillings.

Temporary fillings are commonly used to seal endodontic access cavities between visits. IRM and Cavidentin were selected to represent two widely used groups of temporary filling materials. The first is a reinforced zinc oxide-eugenol preparation that is mixed at chairside, whereas the second is a ready-to-use calcium sulfate-based material that gained popularity due to its convenience of application. The seal provided by the aforementioned materials was studied using a radioactive tracer quantitative assay. When compared as passive temporary filling, the two provided a similar quality of seal. However, when subjected to repetitive "occlusal" cyclic loading of 4 kg, IRM was clearly superior to the calcium sulfate-based material. Whereas IRM maintained a reasonable seal, the calcium sulfate-based fillings deteriorated and lost the ability to seal. These results suggest that even though calcium sulfate-based materials may be useful when not subjected to any occlusal forces, IRM should be preferred whenever occlusal loads may be applied. Furthermore it is demonstrated that testing such materials for microleakage with no reference to mastication forces may be of limited value.

Attachment of Fusobacterium nucleatum PK1594 to mammalian cells and its coaggregation with periodontopathogenic bacteria are mediated by the same galactose-binding adhesin.

It has been shown that Fusobacterium nucleatum PK1594 coaggregates with Prophyromonas gingivalis PK1924 through a galactose-binding adhesin. In the present study, attachment of F. nucleatum PK1594 to a variety of mammalian cells was characterized. F. nucleatum PK1594 attached to all eukaryotic cells tested, including human buccal epithelial cells, gingival and periodontal ligament fibroblasts, HeLa cells and murine lymphocytes, macrophages, and polymorphonuclear leukocytes. These attachments were (i) inhibited by galactose, lactose and N-acetylgalactosamine and (ii) inhibited by monoclonal antibody specific for the galactose-binding adhesin of F. nucleatum PK1594. In addition, a coaggregation-defective mutant of F. nucleatum PK1594 (PK2172), which does not exhibit galactose binding activity, did not attach to the mammalian cells. Coaggregation of F. nucleatum PK1594 with P. gingivalis PK 1924 and Actinobacillus actinomycetemcomitans JP2, but not with other bacteria, showed a similar pattern with sugars, monoclonal antibody, and the adhesin-deficient mutant. The results suggest that the attachment of F. nucleatum PK1594 to mammalian cells and its coaggregation with periodontal pathogens are mediated by the same galactose-binding adhesin.

Macrophages in periapical lesions.

Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen-specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T-lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone-resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.

Gutta-percha softening: "Hemo-De" as a xylene substitute.

The putative hazardous nature of chloroform and xylene implies that safer substitutes should be considered. Standard cylindrical gutta-percha samples were immersed in Hemo-De, a xylene substitute, for 60 s at 37 degrees C. Weight loss of a sample, after drying, was used as a measure of its solubility. Master and accessory cone gutta-percha of three brands were compared. The highest solubility of all kinds of gutta-percha was in chloroform, which served as a positive control. The average solubility of all samples in xylene and Hemo-De was 61% and 52% of that in chloroform, respectively. DMS gutta-percha was more soluble than of Hygienic and DeTrey. Master cone gutta-percha of all brands was more soluble than that of their accessory cones. These results indicate that (a) large differences exist in the solubility of gutta-percha and (b) Hemo-De dissolved gutta-percha in a range similar to that of xylene and may be considered as a potential substitute for this organic solvent.

The effect of immediate vs. delayed post space preparation on the apical seal of a root canal filling: a study in an increased-sensitivity pressure-driven system.

A 5 mm remaining length of root canal filling, after post space preparation, is commonly assumed to maintain sealing ability similar to that of the intact filling. Post spaces were prepared either immediately using hot pluggers, or later, using drills. The sealing ability of the fillings, 5 mm remaining length, were compared with each other and with an intact root canal filling control, using radioactive tracer in a pressure-driven system. When no pressure was applied, no differences could be detected between either of the groups and the control. When a pressure of 120 mm Hg was applied to the same teeth, the control group clearly maintained a better seal than each of the experimental groups, which did not significantly differ from each other. These results suggest that (a) the pressure-driven system was more sensitive than the passive leakage assay that failed to detect differences even at 14 days; (b) a remaining root canal filling of 5 mm was inferior to the intact root canal filling; and (c) the immediate post space preparation with hot pluggers did not differ from a delayed preparation with drills.

Sealing furcation perforations with silver glass ionomer cement: an in vitro evaluation.

Furcation perforations sealed with silver glass ionomer cement (Chelon Silver) were evaluated in vitro compared with amalgam. Access cavities were prepared in 25 extracted human molar teeth. The coronal orifices of the root canals were sealed with amalgam and varnish. Naturally occurring coronal leakage through the intact pulp chamber floor was determined quantitatively for each tooth, using a modified fluid transport model, under pressure of 1.2 Atm. Each tooth was then disconnected from the system, perforated at the furcation, and the perforation sealed with either Chelon Silver (10 teeth) or amalgam (10 teeth); five remaining teeth served as a negative control. After incubation for 24 h at 37 degrees C in 100% humidity, teeth were reconnected to the modified fluid transport system, and coronal leakage under pressure was evaluated at 1, 2, 6, 15, and 24 h. Leakage through each tooth was compared with that of its own intact pulp chamber floor before perforation and the groups compared with each other. No significant difference was found between the mean leakage of the intact pulp chamber floors of the two groups. Chelon Silver had a significantly better sealing ability than amalgam (p < 0.01): leakage rate of 0.007 and 0.017 microliter/min, respectively. It is concluded that Chelon Silver could be an adequate sealer for furcation perforations.

Correlation between remaining length of root canal fillings after immediate post space preparation and coronal leakage.

The seal provided by root canal fillings after post space preparation was studied using a pressure-driven radioactive tracer assay. The coronal part of root canal fillings was immediately removed, using a hot plugger, to a remaining length of either 3, 5, 7, or 9 mm. Intact root canal fillings of 14 mm served as control. Application of air pressure of 130 mm Hg to the tracer solution drove it through the fillings and into phosphate-buffered saline surrounding the apex. Leakage gradually increased for 28 days, and differences in the leakage through 3 to 9 mm fillings were demonstrated. In a passive system by which an additional group of teeth were tested none of these differences could be detected. It was concluded that: (a) root canal fillings of 3, 5, and 7 mm have an inferior seal, compared with that of an intact filling; (b) the sealing is proportional to the length of the remaining filling; and (c) a passive system is unable to detect these differences, even when conducted for as long as 28 days.

Endodontic complications of root canal therapy performed by dental students with stainless-steel K-files and nickel-titanium hand files.

Straightening of curved canals is one of the most common procedural errors in endodontic instrumentation. This problem is commonly encountered when dental students perform molar endodontics. The purpose of this study was to compare the effect of the type of instrument used by these students on the extent of straightening and on the incidence of other endodontic procedural errors. Nickel-titanium 0.02 taper hand files were compared with traditional stainless-steel 0.02 taper K-files. Sixty molar teeth comprised of maxillary and mandibular first and second molars were treated by senior dental students. Instrumentation was with either nickel-titanium hand files or stainless-steel K-files. Preoperative and postoperative radiographs of each tooth were taken using an XCP precision instrument with a customized bite block to ensure accurate reproduction of radiographic angulation. The radiographs were scanned and the images stored as TIFF files. By superimposing tracings from the preoperative over the postoperative radiographs, the degree of deviation of the apical third of the root canal filling from the original canal was measured. The presence of other errors, such as strip perforation and instrument breakage, was established by examining the radiographs. In curved canals instrumented by stainless-steel K-files, the average deviation of the apical third of the canals was 14.44 degrees (+/- 10.33 degrees). The deviation was significantly reduced when nickel-titanium hand files were used to an average of 4.39 degrees (+/- 4.53 degrees). The incidence of other procedural errors was also significantly reduced by the use of nickel-titanium hand files.

Local dexamethasone improves periodontal healing of replanted dogs' teeth.

The purpose of the present investigation was to evaluate histologically the effect of dexamethasone on root resorption in stored and replanted dogs' teeth. Twenty-nine roots from three beagle dogs were endodontically treated to prevent subsequent inflammatory root resorption of pulpal origin. The teeth were extracted and randomly assigned to three groups for 48-h storage. Group 1: control group teeth (n = 13) were stored in vials containing ViaSpan only; Group 2: topical treatment teeth (n = 10) were stored in vials containing ViaSpan and dexamethasone (16 micrograms/ml); and Group 3: systemic treatment teeth (n = 6) were stored in vials containing ViaSpan without any additives. Dexamethasone was administered intramuscularly (0.5 mg/kg body weight) 2 days prior to, on the day of, and every other day after extraction and replantation for two administrations. After 12 weeks, the dogs were sacrificed, and the teeth histologically prepared and evaluated according to the analysis of Andreasen. Significant differences were found for complete healing (P = 0.0583) and inflammatory root resorption (P = 0.0568) but not for replacement resorption (P = 0.1952). In addition, comparing local to systemic administration of dexamethasone (Group 2 vs. Group 3), statistically significant differences were found for healing, 85% (Group 2) vs. 67% (Group 3) (P = 0.0125) and inflammatory root resorption, 13% (Group 2) vs. 28% (Group 3) (P = 0.0126). This study indicated that topical use of dexamethasone enhances healing and results in fewer resorption complications.