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PubMed2005

Finite element analysis of stresses in endodontically treated, dowel-restored teeth.

STATEMENT OF PROBLEM: Endodontically-treated, dowel-restored teeth may experience fracture, but investigations of variables related to fracture are often inconclusive and occasionally contradictory. PURPOSE: The finite element method was used to analyze the stresses in dowel-restored teeth. The variables studied were material, shape, bonding, modulus of elasticity, diameter, and length of the dowel. MATERIAL AND METHODS: The model of the dowel-restored tooth involved dentin, ligament, cortical and trabecular bone, gingiva, and gutta-percha. The dowels were made of glass fiber, titanium, or zirconia and modeled as an approximation of the brands ParaPost Fiber White, ParaPost XH, and Cerapost, respectively. The dowel was cemented with zinc-phosphate cement or with bonded or nonbonded resin luting agents, and an approximation of the material properties of these 2 materials were used in the modeling. The restoration included a composite resin core and a gold crown. Other variables included taper versus parallel-sided posts, modulus of elasticity, diameter, and length of post. The model was axisymmetrical in 3 dimensions. A load of 100 N was applied to the crown at an angle of 45 degrees, and tensile, shear, and von Mises stresses were calculated. RESULTS: The generated stresses decreased with respect to the dowel material in the following order: glass fiber, titanium, and zirconia. Stresses were in general higher with tapered than with parallel-sided dowels. Stresses were reduced by bonding and with an increasing modulus of elasticity, increasing diameter, and increasing length of the dowel. CONCLUSIONS: Within the limitations of this study, it was found that all investigated dowel-related factors influenced the stress field generated in dowel-restored teeth.

Alveolar Process↗
PubMed2006

Treatment concepts for restoration of endodontically treated teeth: A nationwide survey of dentists in Germany.

STATEMENT OF PROBLEM: Opinions concerning proper restoration of endodontically treated teeth (ETT) vary. A variety of techniques and materials for post-and-core restorations are available. The rationale for post placement performed by German dentists was unknown. PURPOSE: The purpose of this study was to determine current opinions, applied techniques, and materials for the restoration of ETT in Germany. MATERIAL AND METHODS: A nationwide questionnaire-based survey containing 18 multiple choice questions regarding treatment philosophies, favored post type, and materials for core foundations was mailed to 36,500 German general dentists. A total of 6029 questionnaires (16.5%) were returned. Data were evaluated in terms of the dentists' occupational experience and the frequency of post placement. Descriptive statistics were used to analyze the data. RESULTS: Irrespective of their occupational experience, 52% of the surveyed dentists consider post placement for almost every postendodontic restoration of ETT. The majority of dentists (54%) believe that a post reinforces ETT. Cast posts and cores are used by 55% of all dentists, whereas 34% use prefabricated posts exclusively. Screw posts are the most popular prefabricated post type (47%). Composite resin (51%) is preferred for core foundation, followed by glass ionomer cements (GICs) (26%). Amalgam is seldom used (0.5%). Posts are placed primarily with zinc phosphate cement (51%), followed by GIC (38%). CONCLUSION: The treatment philosophy of German dentists is not in complete agreement with recommendations found in the literature. The belief that a post would reinforce an ETT might explain the high frequency of post placements. Due to the partially inconsistent responses, it is difficult to derive a generalized treatment concept.

Cementation↗
PubMed2004

Success rate of endodontic treatment of teeth with vital and nonvital pulps. A meta-analysis.

OBJECTIVE: The purpose of this study was to use meta-analysis statistics to determine the influence of factors such as apical limit (short vs. overextension), status of the pulp (vital vs. nonvital), and periapical status (presence or absence of radiolucency) on endodontic prognosis. Study design The study-list was obtained by using a MEDLINE search and Japana Centra Revuo Medicina search. Only those papers in which the criteria for success or failure was exactly described were accepted. RESULTS: The cumulative success rate of 82.8 +/- 1.19% (average +/-95% confidence interval) was obtained for vital pulp; and 78.9 +/- 1.05%, for nonvital ones. There was a significant difference between the 2 groups.The cumulative success rates with overextension, flush, and underextension in vital teeth were 70.8 +/- 1.44, 86.5 +/- 0.88, and 85.5 +/- 0.98% respectively. There was a significant difference between flush and overextension and between flush and underextension. The rates for nonvital pulp were similar to those for vital ones. CONCLUSION: The root canal should be filled to within 2 mm of the radiographic apex.

Adult↗
PubMed2004

Postoperative pain after endodontic retreatment: single- versus two-visit treatment.

OBJECTIVE: The purpose of this clinical study was to determine the effect of 1- or 2-visit root canal treatment on the postoperative pain in the retreatment cases. STUDY DESIGN: Two hundred eighteen cases that required retreatment were included in the study. Obturated and unfilled canal space and the status of periapical tissues were evaluated according to the PAI index. The patients were subcategorized in regard to the presence or the absence of preoperative pain. Approximately half of each category was treated in 1 appointment. After removing the previous root canal obturation materials and biomechanic preparation of root canals, the teeth in the 1-visit group were obturated at the first appointment by using AH 26 sealer and laterally compacted gutta-percha, and those in the 2-visit group were medicated with calcium hydroxide-chlorhexidine combination and then closed with a temporary filling material. One week after the initial appointment, patients were asked about the occurrence of postoperative pain. The level of discomfort was rated as no pain, mild pain, moderate pain, or severe pain (flare-up). Data were statistically analyzed using the chi-squared and Fischer exact tests. RESULTS: Eight patients from the 1-visit group and 2 patients from the 2-visit group had flare-ups. There was a statistical difference between the groups (P <.05). Two-visit root canal treatment was more effective in completely eliminating pain than 1-visit treatment of previously symptomatic teeth (P <.05). CONCLUSIONS: Two-visit endodontic treatment with intracanal medication was found to be effective in reducing postoperative pain of previously symptomatic teeth and decreased the number of flare-ups in all retreatment cases.

Bismuth↗
PubMed2005

A new quantitative method using glucose for analysis of endodontic leakage.

OBJECTIVE: The purpose of this study was to introduce a new method for quantitative testing of endodontic leakage. STUDY DESIGN: Eighty straight maxillary anterior teeth were divided randomly into 3 experimental groups of 20 samples each and 2 control groups. The experimental groups were prepared using the modified double-flared technique and obturated by lateral compaction of cold gutta-percha with Pulp Canal Sealer EWT, Sealapex, or AH Plus sealer. With the leakage test device, coronal 1 mol/L glucose solution was forced under a hydrostatic pressure of 1.5 kPa toward the apical part of the root. Leakage was measured by the concentration of leaked glucose in apical reservoir at 1, 2, 4, 7, 10, 15, 20, and 30 days with the enzymatic glucose oxidase method. RESULTS: No significant difference of sealing ability was found among 3 test groups at 1, 2, 4, and 7 days. From the tenth day, Pulp Canal Sealer EWT showed the highest leakage, and the leakage was not significantly different between Sealapex and AH Plus. CONCLUSIONS: The quantitative method is sensitive, nondestructive, and clinically relevant. Pulp Canal Sealer EWT showed more leakage than Sealapex and AH Plus in most observation time.

Calcium Hydroxide↗
PubMed2005

Molecular detection of Enterococcus species in root canals of therapy-resistant endodontic infections.

OBJECTIVES: The objectives were to identify Enterococcus spp in nonhealing endodontic cases using PCR amplification and molecular sequencing, and to determine if the prevalence of enterococci is increased in diabetic patients. STUDY DESIGN: Specimens from 40 cases undergoing retreatment were incubated in prereduced thioglycollate broth at 37 degrees C. Extracted DNA had PCR amplification using primers that target the tuf gene of 14 Enterococcus spp. PCR products were directly sequenced and identified phylogenetically. RESULTS: Three cases were eliminated because the patients were on antibiotics or the tooth did not have a periradicular radiolucency. The remaining 37 specimens included 6 from diabetic patients. Eight specimens were positive for Enterococcus spp. Of these, 6 (19%) were from nondiabetic and 2 (33%) from diabetic patients (odds ratio = 2.1; chi squared, P = .45). Phylogenetically, all sequences from positive specimens matched E faecalis V583 (AE016947). Conclusion E faecalis was the only enterococcal species detected, with an overall prevalence of 22%.

Adult↗
PubMed2005

Genotoxicity of antimicrobial endodontic compounds by single cell gel (comet) assay in Chinese hamster ovary (CHO) cells.

OBJECTIVE: In the current study, the potential DNA damage associated with exposure to a number of antimicrobial endodontic compounds was assessed by the single cell gel (comet) assay in vitro. STUDY DESIGN: Chinese hamster ovary (CHO) cells were exposed to formocresol, paramonochlorophenol, calcium hydroxide, or chlorhexidine at final concentration ranging from 0.01% to 1%. RESULTS: Formocresol, paramonochlorophenol, and calcium hydroxide, as well as chlorhexidine in all concentrations tested did not contribute to the DNA damage. CONCLUSION: These findings are clinically relevant since they represent an important contribution to the correct evaluation of the potential health risk associated with exposure to dental agents.

Animals↗
PubMed2005

Accuracy of film-based, digital, and enhanced digital images for endodontic length determination.

OBJECTIVE: This study compared the accuracy of D- and F-speed intraoral radiographs and digital and enhanced digital radiographic images for endodontic file length determination. STUDY DESIGN: Size 15 K-files were bonded in 51 canals of 34 human cadaver teeth. The distance from file tip to root apex was measured on D- and F-speed film and on unenhanced and enhanced digital images. The quality of the images was rated by the observers. Overlying cadaver bone and root structure were subsequently removed to expose the file tip for actual measurement to the apex. The distance measured on each image was compared with the actual measurement. ANOVA, Kruskal-Wallis, sign test, and Pearson correlation statistical analyses were applied. RESULTS: There were no significant differences in measurement accuracy among the 4 image types (P < or = .05). Subjective ratings showed a preference for the quality of enhanced digital images. Conclusion All 4 image types were similar in accuracy of file measurement. The image quality of enhanced digital images was subjectively superior to the others.

Analysis of Variance↗
PubMed2005

In vitro assessment of the immediate and prolonged antimicrobial action of chlorhexidine gel as an endodontic irrigant against Enterococcus faecalis.

OBJECTIVE: The aim of this study was to assess in vitro the antimicrobial activity of 2% chlorhexidine gel against Enterococcus faecalis , comparing it to other endodontic irrigants (2% chlorhexidine liquid and 5.25% sodium hypochlorite). STUDY DESIGN: Eighty roots of human mandibular premolars were prepared by serial instrumentation technique, autoclaved, and contaminated for 7 days with E faecalis monocultures. The roots were then divided into 5 groups according to the irrigant substance used during the standardized biomechanical preparation. In order to evaluate the antimicrobial action of the irrigant substances, 3 microbial samples were taken: initial (before the biomechanical preparation); post-treatment (immediately after the biomechanical preparation), and final (7 days after the biomechanical preparation). The microbiological samples were plated to count the colony-forming units (CFU). RESULTS: The 2% chlorhexidine gel and 2% chlorhexidine liquid significantly reduced the E faecalis CFU in the post-treatment and final microbiological samples. The 5.25% sodium hypochlorite also reduced the E faecalis CFU immediately after the root canal instrumentation, but it was not able to keep the root canal free of detectable E faecalis in the final sample. CONCLUSIONS: The 2% chlorhexidine gluconate (gel and liquid) antimicrobial ability was more effective than 5.25% sodium hypochlorite in keeping low CFU of E faecalis for 7 days after the biomechanical preparation.

Anti-Infective Agents, Local↗
PubMed2004

Denaturing gradient gel electrophoresis analysis of bacterial communities associated with failed endodontic treatment.

OBJECTIVE: A great deal of evidence indicates that persistent infections of the root canal of human teeth play an important role in the failure of the root canal treatment. The present study was undertaken to apply the PCR-DGGE fingerprinting approach to examine the structure of the bacterial population infecting previously treated root canals of humans associated with persistent periradicular lesions. STUDY DESIGN: Samples were taken from 14 filled root canals, DNA was extracted, and part of the 16S rDNA of all bacteria was amplified by PCR and separated by DGGE, generating banding patterns representative of the community structure. Species-specific PCR for the detection of Enterococcus faecalis was also performed. RESULTS: The mean number of bands detected in the 16S rDNA community profiles was about 6, ranging from 1 to 26 bands. Each sample showed a unique structure of the microbial community. The species-specific PCR assay revealed the presence of E. faecalis in 10 of 14 samples, but DGGE analysis revealed it was not the dominant species. CONCLUSIONS: Results revealed that the intraradicular bacterial community associated with failed endodontic treatment significantly varied in composition from teeth to teeth. Persistent intraradicular infections were present in all root-filled teeth.

Adult↗
PubMed2005

A comparative prospective randomized clinical study of MTA and IRM as root-end filling materials in single-rooted teeth in endodontic surgery.

OBJECTIVE: Randomized clinical prospective study to evaluate the application of MTA and IRM as retrograde sealers in surgical endodontics. STUDY DESIGN: One hundred single-rooted teeth were surgically treated. After randomization, MTA or IRM was used as a retrosealer. Radiographs were taken 1 week, 3 months, and 1 year postoperatively. Assessment was performed by 2 independent assessors 1 year after surgery. Both treatment groups were homogeneous in their composition, and clinical features and radiographic findings were classified according to Rud's classification. RESULTS: Complete healing was observed in 64% of the MTA-treated teeth vs 50% of the IRM-treated teeth. Incomplete healing was seen in 28% (MTA) vs 36% (IRM), and unsatisfactory in 6% (MTA) vs 14% (IRM). Only 1 failure was seen (MTA). No statistically significant differences were found between the 2 retrofilling materials. CONCLUSION: As root-end filling materials in this clinical prospective randomized design on single rooted teeth, MTA and IRM had the same clinical effectiveness.

Adolescent↗
PubMed2005

Influence of simulated clinical use on the torsional behavior of nickel-titanium rotary endodontic instruments.

OBJECTIVE: The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion. STUDY DESIGN: Thirty sets of 0.04 and 0.06 ProFile instruments in sizes #20, #25, and #30 were randomly divided into 3 groups: 1 contained 10 sets of new files, torsion tested to failure, while the other 2 groups, with 10 sets each, were first submitted to fatigue tests of up to one half and three fourths of their fatigue life, respectively, in geometrical conditions similar to those of the clinical practice and then torsion tested for rupture. RESULTS: Statistical analysis of the values obtained for the torque to failure and maximum angular deflection, using the Student t test at the 95% confidence level, showed that the cyclic deformation of instruments of up to one half and three fourths of their fatigue life gives rise to a significant reduction in these parameters. CONCLUSIONS: The simulated clinical use of ProFile instruments for shaping curved canals adversely affects their torsional properties.

Dental Alloys↗
PubMed2005

Effectiveness of a calcium hydroxide and chlorhexidine digluconate mixture as disinfectant during retreatment of failed endodontic cases.

OBJECTIVE: The purpose of this in vivo investigation is to compare the effect of a slurry of Ca(OH)2 mixed in aqueous 2% chlorhexidine (CHX) versus aqueous Ca(OH)2 slurry alone on the disinfection of the pulp space of failed root-filled teeth during endodontic retreatment. STUDY DESIGN: Forty single-rooted previously root-filled teeth with associated periradicular lesions were included. The teeth were nonsurgically retreated and medicated over 3 treatment visits with 7-10-day intervals with either Ca(OH)2 in water or Ca(OH)2 in 2% aqueous CHX. Root canal cultures were collected in fluid thioglycollate, and bacterial growth was assessed by turbidity daily for 1 week, then weekly for an additional 3 weeks. The presence of enterococci in the root canals at the initial treatment session was determined. RESULTS: Of the total sample population, 12 of 40 (30%) were positive for bacteria before root filling. The control medication disinfected 12 of 20 (60%) teeth including 2 of 4 teeth originally diagnosed with enterococci. The experimental medication resulted in disinfected 16 of 20 (80%) teeth at the beginning of the third appointment. None of the teeth originally containing enterococci showed remaining growth. This difference between the overall positive cultures was not statistically significant (P > .05). CONCLUSIONS: Canal dressing with a mixture of 2% CHX and Ca(OH)2 slurry is as efficacious as aqueous Ca(OH)2 on the disinfection of failed root-filled teeth.

Adult↗
PubMed2005

Digital imaging analysis with mathematical morphology and fractal dimension for evaluation of periapical lesions following endodontic treatment.

OBJECTIVE: To see if a method for digitizing trabecular pattern of bone could be used to quantitatively evaluate changes in bone pattern following endodontic treatment of teeth with periapical osteolytic lesions. STUDY DESIGN: Periapical radiographs were digitized and further processed with mathematical morphology operations known as skeletonization. The trabecular patterns resulting from this skeletonization process were further analyzed with fractal dimension analysis using box-counting. RESULTS: The periapical area in digitized radiographic images showed fractal behavior. Twenty-five of 27 patients showed increase of the fractal dimension after root canal treatment. Significant changes of the box-counting could be noted 3 months after root canal treatment (P < .05). CONCLUSIONS: Mathematical morphology operation and box-counting might be helpful in early detection of changes of periapical trabecular pattern after root canal treatment.

Adult↗
PubMed2005

Radiographic evaluation of periapical status and prevalence of endodontic treatment in an adult Japanese population.

OBJECTIVES: To determine the prevalence of periapical radiolucencies and endodontic treatment in an adult Japanese population. STUDY DESIGN: Periapical status and length of root fillings of 672 adult patients attending Okayama University Hospital of Dentistry were evaluated using full mouth intraoral radiographs. RESULTS: Overall, 87% of the subjects had root-filled teeth, and 70% exhibited an apical radiolucency. Of the 16,232 teeth examined, 21% had been root-filled, and, of these, 40% exhibited an apical radiolucency. Root-filled teeth that were overfilled or that were mandibular incisors had the highest prevalence of apical radiolucencies. CONCLUSIONS: The prevalence of root-filled teeth appears higher in this Japanese population than in Europe or America; however, the ratio of teeth with an apical radiolucency to root-filled teeth was within the range of that reported for other countries. Overfilled teeth and mandibular incisors are most likely to exhibit apical radiolucencies.

Adult↗
PubMed2006

Radiographic features of vertically fractured endodontically treated mesial roots of mandibular molars.

OBJECTIVE: The purpose of this study was to evaluate the most frequent radiographic appearance of bony lesions around endodontically treated vertically fractured mesial roots of mandibular molars. STUDY DESIGN: For the study, 49 extracted mesial roots with vertical fractures (study group) were evaluated and compared to 52 extracted roots without fractures (control). RESULTS: The "halo" (36.7%) and "periodontal" (28.6%) type radiolucencies were the most typical appearances of periradicular areas around the mesial roots of mandibular molars with vertical root fractures. By itself, bifurcation radiolucency was statistically insignificant (6.1%), however in conjunction with other areas of radiolucency, it was significant (63.3%, P < .0378). No radiolucency (38.5%) and periapical radiolucency (32.7%) were predominant features in the control (nonfractured roots). Amalgam dowel in the coronal part (1-2 mm) of the root was found in 67.3% of the vertically fractured roots (P < .0006). Defined but not corticated (57.2%) or diffuse (32.6%) borders were typical for vertically fractured mesial roots. CONCLUSIONS: The use of significant variables, such as "periodontal" and "halo" bony radiolucencies, bifurcation involvement, and the presence of amalgam dowel, has prediction sensitivity of 77.6% (VRF group) and specificity of 82.7% (nonfractured roots).

Alveolar Bone Loss↗
PubMed2006

Antimicrobial endodontic compounds do not modulate alkylation-induced genotoxicity and oxidative stress in vitro.

OBJECTIVE: To investigate if formocresol, paramonochlorophenol, or calcium hydroxide modulate the genotoxic effects induced by the oxidatively damaging agent hydrogen peroxide (H2O2) or the alkylating agent methyl methanesulfonate (MMS) in vitro by using single cell gel (comet) assay. STUDY DESIGN: Chinese hamster ovary (CHO) cells in culture were exposed directly to formocresol, paramonochlorophenol, or calcium hydroxide (adjusted to 100 microg/mL) for 1 hour at 37 degrees C. Subsequently the cultures were incubated with increasing concentrations (0-10 micromol/L) of MMS in phosphate-buffered solution (PBS) for 15 minutes at 37 degrees C or of H2O2 at increasing concentrations (0-100 micromol/L) in distilled water for 5 minutes on ice. The negative control cells were treated with PBS for 1 hour at 37 degrees C. The parameter from the comet assay (tail moment) was assessed by the Kruskal-Wallis nonparametric test followed by a post hoc analysis (Dunn test). RESULTS: Clear concentration-related effects were observed for the genotoxin-exposed CHO cells. Increase of MMS-induced DNA damage was not significantly altered by the presence of the compounds tested. Similarly, no significant changes were observed when hydrogen peroxide was used with the endodontic compounds evaluated. CONCLUSION: Formocresol, paramonochlorophenol, and calcium hydroxide are not able to modulate alkylation-induced genotoxicity or oxidative DNA damage as depicted by the single cell gel (comet) assay.

Alkylating Agents↗
PubMed2006

Cyclic fatigue of different nickel-titanium endodontic rotary instruments.

OBJECTIVE: A comparative study of the fatigue resistance of rotary nickel-titanium endodontic instruments was performed with the aim of assessing the influence of both instrument design and surface treatment on flexural fracture. STUDY DESIGN: To evaluate fatigue resistance of different rotary instruments, a total of 120 instruments were tested; these came from different sources: ProFile, RaCe, K3, Hero, and Mtwo. To compare the effect of electro-polishing procedures on fatigue resistance, a group of RaCe instruments (which are normally electro-polished) without surface treatment was used. A scanning electron microscope (SEM) study for each instrument was performed before and after fatigue study to determine the mode of fracture and the aspect of tips and cross-sectional surface areas. RESULTS: ProFile instruments gave the best values for fatigue resistance. It was seen that for RaCe instruments the surface treatment reduces the presence of micro-cracks, surface debris, and machining damage. CONCLUSIONS: This study shows that the instrument design often proves to be an important factor in the fatigue resistance of NiTi rotary instruments. In RaCe instruments the electro-polishing surface treatment increases the fracture-related fatigue resistance.

Analysis of Variance↗