Evaluation of the bioactivity of fluoride-enriched mineral trioxide aggregate on osteoblasts.

AIM: To investigate whether a combination of mineral trioxide aggregate (MTA) and fluoride compounds affects bone cells. METHODOLOGY: Mineral trioxide aggregate (MTA) discs (ProRoot® , Dentsply Sirona, Ballaigues, Switzerland) with and without the addition of 0.1%, 0.25% and 0.5% sodium fluoride were characterized for their surface roughness by laser scanning microscopy and for the adhesion of human alveolar osteoblasts by scanning electron microscopy. Using eluates from fluoride-enriched MTA discs, the cell proliferation was measured by monitoring the DNA incorporation of 5-bromo-2'-deoxyuridine. Further, gene expression was evaluated by qPCR arrays, extracellular matrix mineralization was quantified by absorption measurement of Alizarin red stains, and effects were calculated with repeated measures analysis and post hoc P-value adjustment. RESULTS: Irrespective of fluoride addition, cell adhesion was similar on MTA discs, of which the surface roughness was comparable. Control osteoblasts had a curvilinear proliferation pattern peaking at d5, which was levelled out by incubation with MTA. The addition of fluoride partly restored the MTA-related reduction in the cellular proliferation rate in a dose-dependent manner. At the mRNA level, both fluoride and MTA modulated a number of genes involved in osteogenesis, bone mineral metabolism and extracellular matrix formation. Although MTA significantly impaired extracellular matrix mineralization, the addition of fluoride supported the formation of mineralized nodules in a dose-dependent manner. CONCLUSION: The addition of fluoride modulated the biocompatibility of MTA in terms of supporting bone cell proliferation and hard tissue formation. Hence, fluoride enrichment is a trend-setting advancement for MTA-based endodontic therapies.

The effects of various mixing solutions on the biocompatibility of mineral trioxide aggregate.

AIM: To evaluate the effects of various mixing solutions on the biocompatibility of mineral trioxide aggregate (MTA). METHODOLOGY: Human alveolar osteoblasts (hOAs) were incubated with eluates of 24 h-set cement discs of MTA mixed with sterile H2 O, 3% sodium hypochlorite (NaOCl), 4% articaine (Ultracain(®) D-S), 0.9% NaCl, Ringer's solution or citrated blood, respectively. The cell proliferation in the presence of eluates was assessed by real-time cell analysis, and the expression of genes associated with proliferation (histone H3, HistH3), inflammation (interleukin-6, IL-6, matrix metalloproteinases 1 and 3, MMP1, MMP3) or apoptosis (caspase 3, Casp3) was analysed by qPCR after 24 and 72 h. The ultrastructure of cells grown on cement discs was visualized by scanning electron microscopy (SEM), whilst actin cytoskeleton was monitored by fluorescence staining in the presence of eluates after 7 and 14 days. A repeated-measure analysis was performed, and P-values were adjusted by Tukey. RESULTS: Whilst articaine-MTA sustained hOA proliferation patterns similar to H2 O-MTA, NaOCl-MTA reduced hOA proliferation and significantly increased the expression of MMP1 and MMP3. The addition of H2 O and articaine modulated the gene expression of Casp3 or Hist3H3. The use of NaCl, Ringer and blood induced mRNA levels comparable to matched controls. With the exception of NaOCl-MTA, SEM and FM revealed regular hOA morphology for all mixing solutions. CONCLUSIONS: NaOCl was highly cytotoxic for hOAs whilst all other mixing solutions can be considered as convenient biocompatible mixing solutions as alternatives to H2 O for clinical use.

Ultrasonic activation and chemical modification of photosensitizers enhances the effects of photodynamic therapy against Enterococcus faecalis root-canal isolates.

BACKGROUND: The aim of this study was to evaluate the effect of photodynamic therapy (PDT) on Enterococcus faecalis biofilms in artificially infected root canals using modified photosensitizers and passive ultrasonic activation. METHODS: Two hundred and seventy extracted human teeth with one root canal were instrumented utilizing ProTaper files, autoclaved, infected with E. faecalis T9 for 72 h and divided into different groups: irrigation with 3% sodium hypochlorite (NaOCl), 20% ethylenediaminetetraacetic acid (EDTA), or 20% citric acid, PDT without irrigation, PDT accompanied by irrigation with NaOCl, EDTA, or citric acid, PDT using an EDTA-based photosensitizer or a citric-acid-based photosensitizer and PDT with ultrasonic activation of the photosensitizer. A 15 mg/ml toluidine blue served as the photosensitizer, activated by a 100 mW LED light source. Sterile paper points were used for sampling the root canals and dentin chips were collected to assess the remaining contamination after treatment. Samples were cultured on blood agar plates and colony forming units were quantified. RESULTS: PDT alone achieved a reduction in E. faecalis counts by 92.7%, NaOCl irrigation alone and combined with PDT by 99.9%. The antibacterial effects increased by the combination of irrigation using EDTA or citric acid and PDT compared to irrigation alone. More than 99% of E. faecalis were killed using PDT with the modified photosensitizers and ultrasonic activation. CONCLUSIONS: NaOCl based disinfection achieved the highest antimicrobial effect. Using PDT with an EDTA-based or citric-acid-based phozosensitizer or activating the photosensitizer with ultrasound resulted in a significantly higher reduction in E. faecalis counts compared to conventional PDT.

Pre-clinical endodontic training with artificial instead of extracted human teeth: does the type of exercise have an influence on clinical endodontic outcomes?

AIM: To evaluate whether artificial resin teeth could replace extracted human teeth in pre-clinical endodontic training and if this teaching approach influences the outcome of root canal treatment on patients. METHODOLOGY: In a pre-clinical training course, students of group 1 (n = 44) performed simulated endodontic exercises on four plastic blocks and three extracted human teeth. Students of group 2 (n = 45) performed their exercises on plastic blocks and artificial resin teeth (Real-T Endo, Acadental, Lenexa, KS, USA). Both groups performed their first root canal treatments on patients in the following term. Radiographs taken during root canal treatment were used for the evaluation of treatment outcome. Distances between the master cone or the root filling and the radiographic apex as well as iatrogenic errors were assessed, and comparisons were made using Fischer's exact test. RESULTS: In the pre-clinical course root canal treatments performed by students of group 2 were more often classified as acceptable and a higher number of iatrogenic errors were observed in group 1. When root canal treatments were performed on patients for the first time, no significant difference was observed between the groups in terms of radiographic technical quality of root fillings. CONCLUSIONS: The application of artificial teeth instead of extracted human teeth had no effect on the technical quality of root fillings in terms of position in relation to the root apex or the creation of aberrations.

Supplementary sampling of obturation materials enhances microbial analysis of endodontic treatment failures: a proof of principle study.

OBJECTIVES: Root canal treatment failures often correlate with persistent biomaterial-associated endodontic infections. The aim of the present study was to assess the impact of endodontic obturation material sampling from root canals with posttreatment apical periodontitis on improving standard study protocols. MATERIALS AND METHODS: Samples from previously filled root canals and their corresponding endodontic filling materials were obtained from five root-filled teeth with posttreatment periradicular lesions. After cultivation, the isolated microorganisms were quantified and biochemically identified. Moreover, clone libraries were constructed after the amplification of bacterial 16S ribosomal DNA (rDNA) from the same samples. DNA from selected clones was sequenced to identify microbial species. Transmission electron microscopy (TEM) aided visualization of the detected bacteria. RESULTS: Overall, 22 taxa of the phyla Firmicutes, Actinobacteria, and Bacteroidetes were detected in both obturation and root canal samples by culture-dependent and culture-independent methods. Root canal fillings sheltered 17 species (3.30-7.50 × 10(3) CFU/ml). Of these, nine were detected solely in the retrieved obturation materials. The reinfected root canals harbored 13 taxa (3.48-7.36 × 10(3) CFU/ml). Obligate and facultative anaerobic bacteria prevailed. The number of different species ranged from 1 to 5 within a single sample. Fungi were not detected. CONCLUSIONS: Bacteria can colonize both root canals and endodontic fillings in vivo. CLINICAL RELEVANCE: Integrating the sampling of obturation materials with standard root canal sample collection offers a clearer insight into the actual microbial flora of reinfected root canals and improves the study protocols of secondary/persistent endodontic infections.

Determination of drugs of abuse in bovine dentin using liquid chromatography-electrospray ionization tandem mass spectrometry.

Drugs deposited in human teeth are well preserved; the spectrum of toxicological investigations may therefore be supplemented by an analysis method for drugs in teeth. A liquid chromatography-electrospray ionization tandem mass spectrometry assay for the detection and quantification of basic drugs of abuse in bovine dentin samples was developed and validated. The drugs and metabolites amphetamine, methamphetamine, methylenedioxymethylamphetamine, methylenedioxyethylamphetamine, codeine, morphine, cocaine and benzoylecgonine were extracted from 50 mg ground dentin powder by ultrasonication for 60 min in methanol 3 times. The extracts were analyzed on a triple-quadrupole mass-spectrometer in multiple reaction monitoring mode. The method was validated and proved to be accurate, precise, selective, specific and stable with good linearity within the calibration range and a lower limit of quantification of 10 to 20 pg/mg. To artificially load bovine dentin samples with drugs, the natural process of de- and remineralization in the oral cavity was mimicked by a pH-cycling experiment. The artificially drug-loaded dentin samples showed drug concentrations of 20 to 80 pg/mg. The method can be applied in further in vitro experiments as well as in post-mortem cases, especially where limited sample tissue is available.

Evaluation of an improved endodontic teaching model: do preclinical exercises have an influence on the technical quality of root canal treatments?

AIM: To investigate whether the preclinical application of an electronic root canal length measurement device (ERCLMD) leads to more accurate working length (WL) determinations in a preclinical endodontic course and if this exercise effects the technical quality of root canal procedures when treatments are performed on patients for the first time. METHODOLOGY: Root canal treatments performed by two consecutive groups of third year students (group 1: n = 39, group 2: n = 44) were compared in the preclinical course and when root canal treatments were performed on patients in the following term. Two different teaching models were applied in the preclinical endodontic course. WL in group 1 was determined with radiographs only. The teaching model applied in group 2 allowed the application of an ERCLMD. When treatments were performed on patients, both groups used the same technique to determine WL. It was first determined using an ERCLMD and verified radiographically. Master cone and root filling lengths were evaluated using radiographs, and comparisons between both groups were made using Fischer's exact test. RESULTS: Root fillings performed by students of group 2 were more often classified as acceptable. This observation was made in the preclinical endodontic course and when treatments were performed on patients. CONCLUSIONS: The application of an ERCLMD in combination with radiographs is more accurate to determine WL than radiographs alone. Students practiced the use of ERCLMDs with the new model and benefited from this experience when performing their first root canal treatments on patients.

The use of cone beam computed tomography to predetermine root canal lengths in molar teeth: a comparison between two-dimensional and three-dimensional measurements.

OBJECTIVES: The aim of this study was to evaluate the accuracy of two-dimensional (2D) and three-dimensional (3D) root canal length measurements in molar teeth using cone beam computed tomography (CBCT). MATERIALS AND METHODS: Root canal lengths of twenty molar teeth were measured with two different CBCT approaches. After adjusting the CBCT images, 2D measurements were performed within the sagittal plane between the apical foramen and the coronal reference (cusp). The 3D approach measured centrically in axial planes. A linear mixed model with random intercepts was fitted to compare differences between methods (2D and 3D). The correlation between CBCT measurements and the actual root canal length was evaluated using the Pearson correlation coefficient. RESULTS: Differences between 3D measurements and the actual root canal lengths were significantly smaller compared to the 2D approach (p < 0.001). Mean differences were 0.32 and 0.58 mm, respectively. A high correlation was found between the actual root canal length and 3D measurements (Pearson correlation coefficient = 0.97). Compared to the actual root canal length, 80 % of the 3D measurements were within the limits of ±0.5 mm. CONCLUSIONS: 3D measurements of root canals in molar teeth are more accurate than simple 2D measurements and show a high correlation to the actual lengths. CLINICAL RELEVANCE: In cases where a CBCT is already available, root canal lengths in molar teeth can be accurately predetermined using a standardized 3D approach.

Antimicrobial photodynamic therapy using visible light plus water-filtered infrared-A (wIRA).

The aim of this study was to investigate the effectiveness of antimicrobial photodynamic therapy (APDT) using visible light together with water-filtered infrared-A (VIS+wIRA) to eradicate single species of planktonic bacteria and micro-organisms during initial oral bacterial colonization in situ. A broadband VIS+wIRA radiator with a water-filtered spectrum in the range 580-1400 nm was used for irradiation. Toluidine blue (TB) was utilized as a photosensitizer at concentrations of 5, 10, 25 and 50 µg ml(-1). The unweighted (absolute) irradiance was 200 mW cm(-2) and it was applied for 1 min. Planktonic cultures of Streptococcus mutans and Enterococcus faecalis were treated with APDT. Salivary bacteria harvested by centrifugation of native human saliva were also tested. In addition, initial bacterial colonization of bovine enamel slabs carried in the mouths of six healthy volunteers was treated in the same way. Up to 2 log(10) of S. mutans and E. faecalis were killed by APDT. Salivary bacteria were eliminated to a higher extent of 3.7-5 log(10). All TB concentrations tested proved to be highly effective. The killing rate of bacteria in the initial oral bacterial colonization was significant (P=0.004) at all tested TB concentrations, despite the interindividual variations found among study participants. This study has shown that APDT in combination with TB and VIS+wIRA is a promising method for killing bacteria during initial oral colonization. Taking the healing effects of wIRA on human tissue into consideration, this technique could be helpful in the treatment of peri-implantitis and periodontitis.

An improved model for teaching use of electronic apex locators.

AIM: To develop a simple, practical and inexpensive model, which enables the use of electronic apex locators (EALs) during pre-clinical and continuing education. METHODOLOGY: Extracted teeth were placed in a mould and embedded in acrylic resin. The resin was applied in two consecutive steps to form a cavity around the root apices. A closable plastic tube serves as a valve, and a steel wire connects to the EAL. RESULTS: With its semi-closed reservoir for conductive fluids surrounding the root apices, the new model enables working length measurements of root canals using EALs. CONCLUSIONS: The model simulates the clinical situation for endodontic teaching purposes, as it allows working length determination of root canals as recommended. The measuring results of the EAL can be verified by radiography. At the same time, the roots are not directly visible and accessible to the user, allowing a precise evaluation and grading of the treatment.

[Paradigm shift in conservative dentistry: from a mechanistic to a prevention-oriented perception]. / Paradigmenwechsel in der Zahnerhaltung : Von einer mechanistischen zu einer präventionsorientierten Sichtweise.

The application of different preventive measures has resulted in a decline of clinically detectable carious lesions in children and adolescents. Not only have caries symptoms changed significantly, but the number of extracted teeth in adults has decreased. Due to these epidemiological facts, modern conservative dentistry is based on a careful risk analysis and caries diagnosis, which also takes into consideration biological and psychosocial components of caries etiology. Conservative dentistry will fail if the dentists are only interested in repairing defects. Simultaneous with the positive outcome of prevention, some unanswered problems have arisen, for which there are no adequate solutions. In young children, caries prevalence is still high and the restorative care of these primary teeth should be improved. For adolescents, early detection of carious lesions should be improved and polarization of caries prevalence should be eliminated. In older adults, evidence-based therapy options for treatment of erosions, abrasions, and root caries are lacking. For seniors needing general care, preventive and restorative concepts should be established.

Cerec3D endocrowns--two-year clinical examination of CAD/CAM crowns for restoring endodontically treated molars.

The present clinical study evaluates the clinical prognosis of Cerec3D endocrowns over an observation period of two years. Twenty Cerec endocrowns (VITABLOCS Mark II, Vita Zahnfabirk, Bad Säckingen, Germany) were placed with PanaviaTM F 2.0, a dual-curing bonding composite. The control examinations took place semi-annually and the restorations were evaluated based on modified US Public Health Service criteria (USPHS). The two-year survival rate of the Cerec endocrowns was 90%. Two out of 20 endocrowns were assessed as failure because of fractures. The first fracture was observed after 12 months and the second fracture after 18 months. No recurrent caries was diagnosed during the entire examination period. Slight percussion symptoms were found on three restorations in the first weeks after placement. The results of the present study show that good esthetic and functional results similar to those of other restoration types can be achieved with endocrowns and that CAD/CAM-fabricated crowns represent a very promising treatment alternative for endodontically treated molars.

Efficacy of enzymatic toothpastes for immobilisation of protective enzymes in the in situ pellicle.

AIM: Different enzyme-containing toothpastes are available on the market. The aim of the present in situ study was to investigate their efficacy for immobilisation of protective enzymes in the pellicle layer. METHODS: Pellicle formation took place in situ on bovine enamel slabs fixed to individual upper jaw splints carried by 6 subjects. After pellicle formation for 1 min, brushing was performed for 3 min with the commercially available toothpastes Enzycal, biotène and BioXtra, respectively. Before as well as 0, 20 and 40 min after brushing, samples were removed from the splints and tested for lysozyme, peroxidase and glucoseoxidase activity. The assays for the respective enzyme activities were based on fluorogenic substrates. Separate experiments were conducted for the different enzymes and toothpastes. RESULTS: Brushing with the toothpastes caused an extensive increase of glucoseoxidase activity in the pellicle, but it was of low tenacity whereas peroxidase activity was enhanced considerably. However, targeted accumulation of lysozyme in the pellicle was not very pronounced. Brushing without toothpaste had no effect on enzyme activities in the acquired pellicle. CONCLUSION: Targeted immobilisation of enzymes in the in situ pellicle can be achieved with toothpastes.

Cleanliness of dentinal tubules following gutta-percha removal with and without solvents: a scanning electron microscopic study.

AIM: To determine the influence of solvents on gutta-percha and sealer remaining on root canal walls and in dentinal tubules. METHODOLOGY: The root canals of 70 teeth were prepared chemomechanically to apical size 40. In group 1 (n = 10; control group), the canals remained unfilled. In groups 2-4 (n = 20 each), the canals were filled using lateral compaction with gutta-percha and sealer. Removal of root fillings was undertaken after 2 weeks using Gates Glidden burs and hand files without solvent (group 2), with eucalyptol (60 microL; group 3) and with chloroform (60 microL; group 4) to size 50. After further irrigation using sodium hypochlorite and ethylenediaminetetraacetic acid, the roots were split, photographed and scanning electron microscopy (SEM) was performed. The number of filled dentinal tubules (SEM) and the surface covered by root filling remnants (photographs) were evaluated for the coronal, middle and apical third of each root half. Statistical analysis was performed via mixed model for clustered data followed by Tukey's test. RESULTS: After pooling the results of all thirds of the canal, open tubules were more prevalent in the control group, followed by the nonsolvent group, the eucalyptol group and the chloroform group (P < 0.05 between all groups). Less surface was covered by root filling remnants in the nonsolvent group than in the eucalyptol group and the chloroform group (P < 0.05); again, fewer remnants were found in the control group than in all other groups (P < 0.05). CONCLUSIONS: Solvents led to more gutta-percha and sealer remnants on root canal walls and inside dentinal tubules.

Combination of apex locator and endodontic motor for continuous length control during root canal treatment.

AIM: To compare ex vivo an experimental setup consisting of an electronic apex locator (EAL) and endodontic motor with an established product (Tri Auto ZX) for accuracy of length control during root canal treatment with three different types of files. METHODOLOGY: An experimental setup consisting of porous spongy material and an electrolyte was used. Sixty anterior teeth were randomly assigned to six groups. Access cavities were prepared. During root canal treatment, constant length monitoring was performed either with the Tri Auto ZX or the Raypex5 apex locator attached to an endodontic motor (Endo IT professional) using ProTaper, M(two) or FlexMaster files. After root canal preparation the distances between file tip and major apical foramen and file tip and minor apical foramen were measured using a microscope and analysed using two-way anova to evaluate the accuracy of the two systems. RESULTS: Distances between the file tip and the major apical foramen were not significantly different between the file systems and the two EALs. In cases treated with FlexMaster significantly larger distances between file tip and minor apical foramen were found compared to M(two) and ProTaper. No significant differences were observed between the two EALs. After preparation of the root canals with the Tri Auto ZX, multiple minor apical foramina were mechanically widened. CONCLUSION: With the limitation of this laboratory study the combination of EAL and endodontic motor was as accurate as the Tri Auto ZX system in terms of length control during root canal preparation.

Fluoride uptake and remineralisation of enamel lesions after weekly application of differently concentrated fluoride gels.

There is only little information on the remineralising capability of regularly applied highly concentrated fluoride gels. The aim of this in situ study was to test the hypothesis that weekly application of a 1.25% fluoride gel results in a significantly higher fluoride uptake and a significantly higher mineral gain compared to a 0.5% fluoride or a placebo gel, respectively. Thirty-six subjects were included in this double-blind, three-way, crossover, placebo-controlled study and randomly assigned to a treatment scheme. Two weeks before the study, between treatment periods as well as during the study periods, subjects were instructed to abstain from any fluoride source other than the study medication. At the beginning of each of three 4-week periods specimen holders, each containing 10 bovine enamel slabs, were placed in the subjects' mouths. During the experimental periods the volunteers brushed the specimens with placebo gel, 0.5% fluoride gel or 1.25% fluoride gel once a week. Fluoride uptake was significantly higher after treatment with the 1.25% fluoride gel than after treatment with the 0.5% fluoride gel (p = 0.007) or the placebo gel (p < 0.001). Treatment with 0.5% fluoride gel led to a significantly higher fluoride uptake compared to placebo treatment (p < 0.001). Changes in mineral gain and lesion depth were not statistically significantly different between the three groups. Under the present experimental conditions repeated application of highly concentrated fluoride gels did not promote remineralisation significantly.

Bond strength between fibre posts and composite resin cores: effect of post surface silanization.

AIM: To evaluate the tensile bond strength between two different composite resin cores and (Clearfil Core, MultiCore Flow) and fibre posts (DT Light Post), with and without silanization of the post surface. METHODOLOGY: Forty fibre posts were shortened to a length of 15 mm. Specimens were then produced by covering the upper 3 mm of the posts with standardized composite core build-ups. The bonding surfaces of twenty posts were treated with silane coupling agent (Monobond-S). Four experimental groups were formed: G1: Clearfil Core; G2: Monobond-S + Clearfil Core; G3: MultiCore Flow; G4: Monobond-S + MultiCore Flow. Each post was positioned upright in a post centric device with moulds to ensure standardized shapes of the abutments. After tensile bond strength testing, the type of failure at the interface was determined. The results obtained were compared using an unpaired sample t-test. RESULTS: The mean tensile bond strengths and standard deviations were [MPa] 10.08 +/- 0.92 for Clearfil Core, 10.47 +/- 1.05 for Clearfil Core + silane; 6.65 +/- 0.79 for MultiCore Flow and 6.91 +/- 0.83 for MultiCore Flow + silane. Statistical analysis revealed that Clearfil Core achieved significantly higher bond strengths than MultiCore Flow (P < 0.0001). Post silanization had no significant effect. All tested specimens had an adhesive failure mode. CONCLUSION: Type of composite had a significant effect on tensile bond strength. Silanization of fibre post surfaces had no effect on core retention.

Effects of various forms of calcium added to chewing gum on initial enamel carious lesions in situ.

The purpose of this randomized, cross-over in situ study was to determine the effects of 4 chewing gums on artificial caries-like subsurface lesions. Two chewing gums (1 with zinc citrate and 1 without) contained dicalcium phosphate (3.9%), calcium gluconate (1.8%) and calcium lactate (0.45%), 1 chewing gum contained casein phosphopeptide-amorphous calcium phosphate nanocomplexes (0.7%), and another one contained no calcium. Fifteen subjects without current caries activity (7 male, 8 female; mean age: 27.5 +/- 2.5 years) wore removable buccal appliances in the lower jaw with 4 bovine enamel slabs with subsurface lesions. The appliances were inserted immediately before gum chewing for 20 min and then retained for an additional 20 min. This was performed 4 times per day. Every subject chewed 4 different chewing gums over 4 periods of 14 days each. During a fifth period (control) the subjects only wore the appliances without chewing gum. At completion of each period the enamel slabs were embedded, sectioned and subjected to transversal microradiography. With regard to change of mineral loss and of lesion depth no significant differences could be found between chewing gums containing calcium and calcium-free chewing gums. Moreover, the chewing gum groups and the control group did not differ significantly if adjustments were made for baseline values (p > 0.05; ANCOVA). Under the conditions of the present study it may be concluded that the use of chewing gum offers no additional remineralizing benefit to buccal tooth surfaces, even if the chewing gum contains calcium compounds.

In vivo comparison of working length determination with two electronic apex locators.

AIM: To compare the accuracy of two electronic apex locators (EALs) in the same teeth in vivo. METHODOLOGY: The working lengths in 20 teeth with a single canal were determined with two different EALs (Root ZX; J. Morita Corporation, Tokyo, Japan and Raypex 5 VDW, Munich, Germany) before extraction. When the first EAL was used the files were advanced until the display indicated the 'apical constriction'. The files were then fixed in removable and replaceable light curing composite patterns. The procedure was repeated in the same tooth with the second EAL and a different file. The teeth were then extracted and the apical 4 mm of the root canals were exposed. After that the apical parts with the repositioned files in the canals were digitally photographed under a light microscope. On the images the minor diameter and the major foramen of each sample were marked and the respective distances of the file tips from these positions were measured with a computer program. Subsequently the values of the two groups of EALs were compared using a paired sample t-test. RESULTS: The minor foramen was located within the limits of +/-0.5 mm in 75% of the cases with the Root ZX and in 80% of the cases with Raypex 5. The paired sample t-test showed no significant difference between the EALs regarding determination of the minor foramen. CONCLUSION: The use of EALs is a reliable method for determining working length. The differences between the two EALs were not statistically significant.