Accuracy of Software-Based Three-Dimensional Root Canal Length Measurements Using Cone-Beam Computed Tomography.

OBJECTIVE: This study aims to evaluate the accuracy of three-dimensional root canal length measurements performed by dentists with different experience levels using a special software based on cone beam com-puted tomography (CBCT). METHODS: A CBCT scan of an artificial resin maxillary molar was used to train dentists (n=65) in using the software (3D Endo, DentsplySirona, Ballaigues, Switzerland) as part of a continuing education course. At the beginning, each participant completed a questionnaire on endodontic and CBCT experiences. After com-prehensive instructions, each participant performed an entire three-dimensional treatment plan by tracing the root canal anatomy between the apical foramen and the center of the canal orifice and simulating a straight-line access. The final root canal length was indicated after the virtual rubber stop of a simulated instrument was adapted to the adjoining cusp. To evaluate the individual accuracy in terms of trueness and precision, differences between the three-dimensional planning and the actual root canal length (ARCL) were calculated, and statistically analyzed. RESULTS: Mean absolute differences between the measurements with the 3D Endo™ software (n=260) and the ARCL were 0.30±0.22 mm. All measurements were within a limit of ±1 mm. The accuracy of root canal length measurements was significantly influenced by the type of root canal (p<0.0001). The smallest devia-tions were observed for the palatal root canal (0.18±0.13 mm), followed by the mesiobuccal (0.26±0.22 mm), the distobuccal (0.32±0.17 mm), and the second mesiobuccal root canal (0.46±0.24 mm). CONCLUSION: Within the limitations of this study, the 3D Endo software enables reproducible and accurate root canal length measurements as part of a three-dimensional endodontic treatment plan. However, mea-surements should always be clinically verified, as root canal morphology has a statistically significant influence.

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.

Comparative assessment of the incidence of vertical root fractures between conventional versus surgical endodontic retreatment.

OBJECTIVES: Vertical root fractures (VRFs) are a common cause of tooth loss. Little evidence exists though, relating the incidence of VRFs to the type of endodontic retreatment. This retrospective study aimed at evaluating the impact of conventional versus surgical endodontics on root canal-filled teeth with VRFs. MATERIALS AND METHODS: Over a period of 13 years, 200 endodontically retreated teeth from 192 patients with VRFs were extracted and further examined. VRFs were assessed in relation to age, gender, tooth group, clinical signs, extension on the root surface, patency, as well as type of endodontic retreatment and restoration. Statistical analysis was conducted using a Cox PH Model, Chi-squared, Wilcoxon rank-sum, and Log rank tests at a significance level of 5 %. RESULTS: The majority of teeth with VRFs (62.31 %) had undergone the combination of conventional root canal retreatment and apical surgery. Women (64.06 %) presented VRFs more frequently than men (35.94 %) at the mean age of 51.1 and 55.1 years, respectively. Maxillary first (17.5 %) and second (16.5 %) premolars, restored by a resin-based material without a post (56.28 %) were more susceptible to VRFs. Apically initiated (84.1 %) VRFs could be diagnosed more easily on radiographs. CONCLUSIONS: The type of endodontic treatment strongly correlated with VRFs. The prevalence of VRFs in teeth having undergone both conventional and surgical endodontic retreatment could be attributed, among others, to additive dentin damage related to the aforementioned endodontic procedures. CLINICAL RELEVANCE: The possible involvement of endodontic retreatment in the multifactorial etiology of VRFs needs to be taken into consideration in clinical practice.

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.

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.

Evaluation of the clinical success of Cerec 3D inlays.

The objective of the present study was to determine the clinical success of Cerec 3D inlays over a period of three years. Within the scope of the restorative dentistry course II, 62 Cerec ceramic inlays were inserted with Dual Cement (Ivoclar Vivadent) in combination with the Syntac Classic system (Ivoclar Vivadent). Regular follow-up examinations and assessments were performed by reference to modified US Public Health Service (USPHS) criteria. The baseline examination was performed one week after insertion and further follow-up examinations were performed at 6-month intervals. The survival rate of the Cerec 3D inlays was 95% after three years. Three inlays were assessed as failures because of loss of sensitivity, restoration fracture, and marginal gap formation. Six patients initially suffered from postoperative hypersensitivity, which vanished by the first follow-up examination. The results of this study show that dentists with little experience are able to achieve good clinical results and long-term success after short theoretical as well as practical training and an introductory course in the Cerec method.

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.

In vitro study assessing apical leakage of sealer-only backfills in root canals of primary teeth.

AIM: To assess the sealing ability of zinc oxide-eugenol (ZOE), Apexit, and Sealapex used as sealer-only backfills in root canals of primary teeth using the high-pressure replica technique. METHODOLOGY: Two hundred and seventy root canals of deciduous molars as well as primary anterior teeth were randomly assigned to three groups (n=90). Root canals were prepared to size 35 and filled with either zinc oxide-eugenol (ZOE), Apexit, or Sealapex using a lentulo filler. Twenty-four hours after setting of the materials the roots were nail-varnished (except for the apical tip), and half of the specimens (n=45) were penetrated by a coloured (rhodamine B) epoxy resin. The resin was infiltated into the pores and cavities of the teeth in a high-pressure vessel. The remaining groups (n=45) were stored in 100% humidity, and infiltration of the resin followed after 40d. Apical leakage was assessed by means of a grinding technique using eight steps of 0.5mm each. RESULTS: ZOE and Apexit failed to seal the root canals in both subgroups. This was significantly different from the root canals filled with Sealapex where in both subgroups some 30% of the specimens revealed a tight seal up to a distance of 2.9mm of the apex. CONCLUSIONS: Under the conditions of this study it can be concluded that Sealapex shows less leakage than ZOE and Apexit. With regard to the three materials tested, Sealapex should be a viable alternative for sealer-only obturation of pulpectomized primary teeth. The high-pressure replica technique seems to be suitable for assessing leakage of root canal filling materials.

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.

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.

Effectiveness of hand and rotary instrumentation for removing a new synthetic polymer-based root canal obturation material (Epiphany) during retreatment.

AIM: To evaluate the effectiveness of hand and rotary instrumentation for removal of vertically compacted Epiphany and gutta-percha during retreatment. METHODOLOGY: Sixty extracted single-rooted maxillary central incisors were enlarged to size 40 using FlexMaster instruments. The teeth were randomly divided into four groups of 15 specimens each. The canals of two groups were obturated using vertically compacted Epiphany. The others were filled with vertically compacted gutta-percha and AH Plus sealer. One Epiphany group and one gutta-percha group was reinstrumented with Gates Glidden burs and Hedström files. In the other two groups, obturation material was removed using Gates Glidden burs and RaCe rotary instruments. After clearing the roots, the area of remaining obturation material on the root canal wall was measured using a computer image analysis program. Statistical analysis was performed using Repeated Measures Analysis of Variance and anova. RESULTS: Retreatment of specimens obturated with gutta-percha showed significantly more remaining obturation material than specimens filled with Epiphany (P < 0.05). No difference was found between the removal with Hedström files and with RaCe instruments (P > 0.05). Regarding the mean time of retreatment and time required for reaching the working length, Hedström files were significantly faster than RaCe instruments (P < 0.05). The times did not depend on the kind of obturation material (P > 0.05). CONCLUSIONS: Vertically compacted Epiphany in combination with Epiphany Root Canal Sealant was removed more effectively than gutta-percha and AH Plus sealer. Hedström files were more rapid than RaCe rotary instruments.

Effects of additional teaching of final-year dental students on their radiographic diagnosis of caries.

The aim of this study was to evaluate whether the skills of final-year dental students in the diagnostic interpretation of bitewing radiographs could be improved by additional didactic instruction. 6 consecutive classes of students in the same stage of education (last semester in the Department of Operative Dentistry) took part in the investigation from 1995 to 1998. At the beginning of each semester, the same in vivo made bitewing radiograph was demonstrated in a separate radiology revision lecture and interpreted with the students. The intensification of the training in the diagnosis of bitewing radiographs was made when the 4th class of students started. At the end of each semester, each student of the 6 consecutive classes was asked to evaluate the same bitewing radiograph, which had been demonstrated at the start of the semester. The students were not told that they had already diagnosed from this radiograph before. The results of the radiographic diagnosis were then analyzed using an evaluation system paying special attention to the treatment decision. True positive and true negative diagnoses were scored as correct and false positives and false negatives as incorrect. There was no significant difference (ANOVA) in the ability to diagnose from bitewing radiographs between the groups of students who received, and those who did not receive, additional training. The benefits of this type of additional instruction in the last semester in the Department of Operative Dentistry seem only to be important in some individual cases.

An in situ study on the comparison of fluoride uptake and bond strength of composite resin on fluoridated enamel.

The aim of this in situ study was to compare the fluoride uptake and composite resin bond strength on enamel fluoridated with Duraphat (2.26 wt% fluoride). Six enamel specimens were prepared from the labial surfaces of 39 bovine incisors. The enamel samples were embedded into epoxy resin, and ground flat (800 grit). One specimen served as negative control (no fluoride treatment). The other samples were fluoridated with Duraphat for 24 hours under moist conditions, and one of them served as positive control. The remaining four samples were inserted in both buccal aspects (with a total of 12 samples originating from 3 teeth) of 13 intraoral mandibular appliances. The appliances were worn by 13 persons for a period of 6 days, 24 hours per day. The samples were also brushed twice a day, in situ, with a fluoride-free toothpaste. During meals, the appliances were stored in saline. After in situ periods of 36, 72, 108, and 144 hours, three samples each were remounted. One specimen was used for analysis of both alkali-soluble and acquired fluoride. The other two specimens served for shear bond strength testing of a light-cured composite resin. While the KOH-soluble fluoride increased significantly (p < 0.001, ANOVA) after application of the fluoride lacquer and decreased slowly with time, both the acquired fluoride and bond strengths of the composite resin did not differ significantly from the non- and fluoridated controls. The application of highly concentrated fluoride lacquers results in an increase of alkali-soluble fluoride, but does not adversely affect enamel bond strength of composite resin.

Correlation of transversal microradiography and microhardness on in situ-induced demineralization in irradiated and nonirradiated human dental enamel.

The objective was to evaluate whether a correlation exists between microhardness (MH) and transversal microradiographical (TMR) data for in situ-induced caries lesions in irradiated and nonirradiated human enamel. Enamel specimens were prepared from the lingual and buccal surfaces of 20 freshly extracted, caries-free third molars. The surfaces were polished (4000 grit). Either the lingual or the buccal specimen of each tooth was irradiated with 60 Gy; the other sample was not irradiated. Two irradiated and two nonirradiated specimens were inserted into both buccal aspects of each of five intraoral mandibular appliances. The appliances were worn by five persons for 6 weeks day and night. One side was brushed daily with a fluoride-free toothpaste; on the other side, dental plaque was allowed to grow. Individual oral hygiene was performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. Then the enamel specimens were cut perpendicular to their oral surface. The cut surface was polished (4000 grit) and the Knoop hardness number (KHN) was measured across the lesions, at 25, 50 and 75 microm from the oral surface. After MH testing the samples were polished again, thereby reducing the surface by about 10 microm. Subsequently, the slabs were ground to a thickness of 90 microm, and studied by means of TMR. Mineral loss was calculated with dedicated software at the locations corresponding to the MH testing. A total of 120 paired data was submitted to linear-regression analysis. Neither MH nor TMR showed significant differences between irradiated and nonirradiated enamel lesions. A linear relation was found between square root of KHN and the mineral volume percent. In naturally induced caries lesions, MH values can be converted to mineral volume percent using the equation [21.19 + 3.66 x square root of KHN]. This equation fits the data with a reliable correlation coefficient (r2=0.915).

Initial tensile bond strength of resin-modified glass ionomers and polyacid-modified resins on perfused primary dentin.

The objective of this study was to evaluate the initial tensile bond strength of a resin-modified glass ionomer (Photac-Fil) and two polyacid-modified composite resins (Compoglass, Dyract) to primary dentin. A hybrid composite resin (Tetric) and two chemical cured glass ionomers (BaseLine, Hi-Dense) served as controls. Ninety caries-free dentinal discs were ground flat and perfused with Ringer's solution. Dentinal surfaces were conditioned (except for Base Line). From each material, fifteen standardized specimens were attached to the dentin. Light-curing of the respective materials followed (1 min), and adhesion was tested with a universal testing machine 15 min after application. The highest initial bond strength was observed with Tetric (5.17 MPa). Closed test procedure (Kruskal-Wallis) showed significant differences between all materials (P < 0.05), except for Compoglass (1.82 MPa) vs. Dyract (2.35 MPa), and BaseLine (0.37 MPa) vs. Photac-Fil (0.42 MPa). The condensable glass ionomer Hi-Dense revealed a mean tensile bond strength of 0.79 MPa. Adhesion of (polyacid-modified) composite resins is superior to the other tested glass ionomer materials, when applied to perfused primary dentin.

Microscopic studies of accessory canals in primary molar furcations.

The purpose of this study was to evaluate the incidence of accessory canals in the furcation region of human primary second molars. Forty freshly extracted teeth were radectomized and furcations were separated. The severed pulp chamber floors were decalcified and dehydrated. Paraffin embedding followed and cross-cut serial sections were taken from the specimens. Microscopic examination of each section followed. Sixteen out of twenty (80 percent) of the maxillary and fifteen out of twenty (75 percent) of the mandibular primary second molars demonstrated accessory foramina in the furcation area. 17.3 percent of the accessory foramina were found in the pulp chamber floor and 82. 7 percent were observed interradicular, close to the periodontal ligament. Thirty percent of the primary second molars demonstrated accessory canals, running from the pulp chamber to the periodontal ligament. Within the limitations of a microscopic investigation it is assumed that accessory furcation canals might be responsible for interradicular bone pathology in case of pulpal inflammation or necrosis.