Fracture resistance of human roots filled with mineral trioxide aggregate mixed with phosphate-buffered saline, with and without calcium hydroxide pre-medication.

AIM: To compare the fracture strength of extracted human roots with apical plugs of mineral trioxide aggregate (MTA) mixed with either Ca- and Mg-free phosphate-buffered saline (PBS) or water, with and without calcium hydroxide (CH) canal pre-medication. METHODOLOGY: A total of 180 single-rooted human teeth were prepared to resemble immature roots and divided into groups (n = 20). The negative control received canal irrigation only, and the positive control received intracanal treatment with CH for either two or twelve weeks. MTA mixed with water was used in Group 1: (i) without CH pre-medication - MTA(W); (ii) after 2 weeks CH pre-medication - 2/52CH + MTA(W); and (iii) after 12-week CH pre-medication - 12/52 CH + MTA(W). MTA mixed with PBS was used in Group 2: (i) without CH pre-medication - MTA(PBS); (ii) after 2-week CH pre-medication - 2/52CH + MTA(PBS); and (iii) after 12-week CH pre-medication - 12/52 CH + MTA(PBS). A compressive force was applied to each root until the point of fracture. The results were analysed by the Kruskal-Wallis and Dunn's multiple comparisons tests (P < 0.05). RESULTS: There was no significant difference between groups MTA(W), MTA(PBS) and 2/52CH + MTA(PBS), and all three groups were significantly (P < 0.01, P < 0.05 and P < 0.05, respectively) more resistant to fracture than the negative control. Within Group 1, the samples that received two- (P < 0.01) and twelve-week (P < 0.001) CH pre-treatment were more prone to fracture than those which did not. No difference was found amongst the control groups. The roots of the MTA(PBS) group had a higher dependability (P < 0.05) than the MTA(W) group when compared by the Weibull modulus. The difference was also present when a 2-week CH pre-medication was used. CONCLUSIONS: Mineral trioxide aggregate mixed with Ca- and Mg-free phosphate-buffered saline had a significant strengthening effect on the fracture resistance of structurally weak roots, even when short-term calcium hydroxide pre-medication had been used. MTA mixed with water lost its strengthening effect on human roots when 2- or 12-week CH pre-treatment had been used. Use of CH dressing for up to 12 weeks had no negative effect on fracture resistance of human roots.

Prevalence of periradicular periodontitis in a Scottish subpopulation found on CBCT images.

AIM: To investigate the prevalence of periradicular periodontitis (PRP) using cone-beam computed tomography (CBCT) scans in a retrospective cross-sectional epidemiological study in a Scottish subpopulation. METHODOLOGY: Of the 319 CBCT scans performed at Dundee Dental Hospital between November 2009 and July 2012, 245 dentate scans of patients over 18 years of age were included and 3595 teeth examined. Odds ratios were calculated, and the association between root filling and posts with PRP was determined. RESULTS: Radiological signs of PRP were detected in 209 teeth (5.8%) in 96 patients (male = 53, female = 43) of which 145 (69.4%) were measurable and 64 (30.6%) appeared as periapical widening. Most lesions were seen in the 46-55-year age group and in maxillary anterior teeth (35.4%); 47.4% (n = 81) of the total root filled teeth (n = 171) had PRP. Of the root filled teeth with lesions, approximately half (50.6%) had an inadequate root filling. Teeth with crowns, but not root filled, accounted for 17.7% of PRP. Periapical changes were detected on a high proportion of teeth with post-retained crowns (70.7%). The presence of a root filling was significantly associated with PRP (z = 17.689 P < 0.0001; odds ratio 16.36 < 23.17 < 32.83, 95% CI) and the presence of a post (z = 10.901 P < 0.0001; odds ratio 21.36 < 41.8021 < 81.78, 95% CI). CONCLUSIONS: The prevalence of PRP in a Scottish subpopulation was 5.8%. The presence of a root filling or a post-retained crown was significantly associated with the presence of PRP as determined by CBCT scans. The prevalence of periradicular disease in root filled teeth remains high in the Scottish population.

Dental dilemmas: endodontics or dental implants?

This narrative review explores treatment planning options in restorative dentistry. The growth of dental implants, as an accessible and predictable treatment option, gives practitioners a useful tool for managing the missing tooth or teeth with a hopeless prognosis. Traditionally, endodontics and fixed prosthodontics have been used to restore teeth and spaces where the outlook for such treatment appears reasonable. Practitioners may, however, question the predictability and cost effectiveness of such an approach where, at times, it might appear that replacement of a compromised tooth with a dental implant could be a more predictable option. The evidence base for these treatment options is explored and discussed, and suggestions are made for future management strategies.

Assessment of vascularity as an index of angiogenesis in periradicular granulomas. Comparison with oral carcinomas and normal tissue counterparts.

AIM: To quantify vascularity in periradicular granulomas using different endothelial markers, and assess its value as an index of angiogenesis by comparing granulomas with healthy periodontal ligament (PDL). To use oral tumours, compared with adjacent normal mucosa, as positive controls. METHODOLOGY: Paraffin-embedded sections were stained with antibodies to von Willebrand factor (vWF), a pan-endothelial marker, and CD105, a putative marker for angiogenic vessels. Vascularity was quantified by different methods reflecting vessel volume and density. RESULTS: Irrespective of the marker or method used, vascularity values were similar in periradicular granuloma and PDL. Both tissues were highly vascularized, with levels similar to those found in oral squamous cell carcinoma. Vascularity was significantly higher in the latter than in normal mucosa. Fewer vessels were positive for CD105 than for vWF in the normal mucosa, whereas similar numbers were found in the other tissues examined. CONCLUSIONS: A comparison of vascularity in oral tumours and normal oral mucosa provided evidence of angiogenesis in the former. Staining with CD105 added limited value to staining with vWF in these tissues. In contrast, a comparison of periradicular granuloma and PDL failed to demonstrate evidence of angiogenesis in the granuloma. As all vessels were similarly stained with vWF and CD105 in granuloma and PDL, a possible hypothesis is that all vessels are newly formed in these tissues. A more plausible alternative is that CD105 expression may reflect the metabolic activity or intrinsic characteristics of the tissues, rather than the presence of angiogenic vessels.

Detection of bacteraemias during non-surgicalroot canal treatment.

UNLABELLED: Some dental procedures initiate a bacteraemia. In certain compromised patients, this bacteraemia may lead to distant site infections, most notably infective endocarditis. OBJECTIVE: To investigate whether a detectable bacteraemia was produced during non-surgical root canal therapy. METHODS: Thirty patients receiving non-surgical root canal therapy were studied. Three blood samples were taken per patient: pre-operatively, peri-operatively and post-operatively. In addition, a paper point sample was collected from the root canal. The blood samples were cultured by pour plate and blood bottle methods. The isolated organisms were identified by standard techniques. Blood samples were analysed for the presence of bacterial DNA by the polymerase chain reaction (PCR). In two cases where the same species of organism was identified in the root canal and the bloodstream, the isolates were typed by pulsed field gel electrophoresis (PFGE). RESULTS: By conventional culturing, a detectable bacteraemia was present in 9 (30%) of the 30 patients who had no positive pre-operative control blood sample. In 7 (23.3%) patients, the same species of organism was identified in both the bloodstream and in the paper point sample from the root canal system. Overall, PCR gave lower detection rates compared with conventional culture, with 10 of 90 (11%) of the blood samples displaying bacterial DNA. PFGE typing was undertaken for two pairs of culture isolates from blood and paper points; these were found to be genetically identical. CONCLUSIONS: Non-surgical root canal treatment may invoke a detectable bacteraemia.

Influence of smear layer on the coronal leakage of Thermafil and laterally condensed gutta-percha root fillings with a glass ionomer sealer.

The effect that two methods of root canal obturation, combined with removal of the smear layer, had on coronal leakage was studied in vitro. Single-rooted teeth with mature apices were prepared chemomechanically and divided into two groups of 72 teeth each. One of the groups was treated with 40% citric acid and 2% sodium hypochlorite to remove the smear layer. The teeth were then subdivided and obturated using the glass ionomer sealer, Ketac Endo and either lateral condensation or Thermafil. After storage for 7 days or 4 months, the specimens were evaluated for coronal leakage using Indian ink. After 90 h, each root was split longitudinally and the maximum extent of leakage was measured using a stereomicroscope at x6 magnification. After 7 days, there was significantly less leakage in those teeth obturated with Thermafil without smear layer compared with the other groups (p < 0.05). After 4 months, there was no significant difference in leakage between the groups (p > 0.05).

Comparison of three instruments in the preparation of the curved root canal using the modified double-flared technique.

Fifty-one extracted intact human first molar teeth with mature root apices were radiographed in a standardized way; their root curvature was determined and they were divided into three groups. One root canal in the mesial root of the mandibular molars, or the major mesiobuccal root in maxillary molars, was prepared with the modified double-flared technique, in one of three ways. The modified double-flared technique involves coronal flaring followed by working length determination and apical preparation. In group 1, unmodified tipped instruments (Flexofile) were manipulated with a balanced force technique. In groups 2 and 3, Flexogates files and Canal Master U files were operated in the manner recommended by the manufacturers. After preparation, the teeth were radiographed. The processed images of the root canals were traced using an image analysis computer software package. Comparisons were made between the preoperative and postoperative shapes of each root canal. A low viscosity polyvinyl siloxane was injected into the prepared root canals and the specimens were demineralized, dehydrated, and cleared. The preparation was evaluated subjectively according to desirable or undesirable criteria. The overall quality of preparation was rated. Statistical analysis showed that there was no significant difference in the overall change of area between the three groups (p = 0.994). There was a significant proportional increase in mesiodistal width in the coronal part of the canals in the Canal Master U group and more of the instruments in this group fractured.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of noncutting tipped instruments on the quality of root canal preparation using a modified double-flared technique.

Fifty-one extracted human first molar teeth with intact crowns and mature root apices were divided into three groups. Root curvature was determined. One of the root canals in the mesial root of lower molars, or the mesiobuccal root in maxillary molars, was prepared in one of three ways. In group 1 the root canals were instrumented using a modified double-flared technique with noncutting tipped files (Flex R); in group 2 the same files were used with a step-back technique. Group 3 was prepared with conventionally tipped files (K-Flex) using the step-back technique. A low viscosity polyvinyl siloxane impression material was injected into the prepared root canals and the specimens were decalcified, dehydrated, and cleared. The preparation was evaluated subjectively according to various desirable or undesirable criteria. A rating for overall quality of preparation was given. Statistical analysis showed that the teeth in group 1 had better overall preparation than those in group 3 (p < 0.05). There were no other statistically significant differences between the groups. The mean time required for each preparation technique was not statistically significantly different (p > 0.1). The use of a modified double-flared technique with non-cutting tipped files was shown to be an effective method for the preparation of curved root canals.

Coronal leakage of obturated root canals after long-term storage using a polymicrobial marker.

This in vitro study investigated the effect of long-term storage on the coronal leakage of a microbial marker on teeth root filled with lateral condensation of cold gutta-percha and one of two sealers. Sixty single-rooted teeth were prepared chemomechanically to a size 40 master apical file. The teeth were divided into two groups of 20 teeth each and obturated with gutta-percha using either Apexit or Tubliseal EWT sealer. The teeth were stored for 6 months in artificial saliva and tested for leakage using a marker consisting of S. sanguis and P. intermedia. The teeth were checked for bacterial leakage daily for 90 days. All positive control teeth leaked after 24 h, while the negative control teeth remained uncontaminated throughout the test period. Leakage reached the apex through the experimental teeth at the earliest at 17 days and at latest at 88 days. Fifty percent and 70% of the specimens of the Apexit and Tubliseal EWT groups respectively showed leakage at 90 days. There was no statistically significant difference (p > 0.05) between the two groups.

The effectiveness of various disinfectants used as endodontic intracanal medications: an in vitro study.

The purpose of this study was to compare in vitro the suitability of four disinfectants as intracanal medications: calcium hydroxide, chlorhexidine gel, chlorhexidine in the form of a controlled-release delivery system (PerioChip), and the combination of chlorhexidine gel with calcium hydroxide. Saline was used as the control. The disinfectants were tested at three different time periods (3, 8, and 14 days) by using human tooth specimens that had been previously contaminated with Enterococcus faecalis. Calcium hydroxide worked very efficiently in killing E. faecalis in the 3-day group and 8-day group. It was not as effective in the 14-day group. The different chlorhexidine formulations were also found to be effective for all time periods. More specifically, the combination of chlorhexidine gel with calcium hydroxide and the chlorhexidine gel worked slightly better than the PerioChip, but there was no significant difference among the medications.

Marginal microleakage of resin-retained bridges in association with existing resin composite and amalgam restorations.

The aim of this study was to determine the microleakage associated with resin-retained bridge retainers cemented over amalgam and resin composite restorations. Cavities prepared on the labial surfaces of bovine incisors were restored with either amalgam or a posterior resin composite. Non-precious nickel-chromium alloy frameworks were then attached to the teeth by use of one of four cements: Conclude, ABC, Panavia Ex, and Superbond. The specimens were then stored for two weeks or six months, thermocycled, and tested for microleakage by use of a radioactive tracer and an autoradiographic technique. The results showed that more leakage was associated with the amalgam restorations than with the teeth filled with resin composite. Leakage scores increased with time with both the amalgam and composite restorations, except for the Panavia Ex and ABC materials, respectively.

The plane of fracture and shear bond strength of three composite inlay systems.

Composite inlays have been introduced to overcome some of the problems encountered with direct placement techniques. However, some doubt has been expressed about the strength of the bond between the inlay surface and the composite luting cement due to the decreased number of C = C bonds remaining following supercuring of the inlay. This study investigated the bond strength of three composite inlay systems to etched bovine enamel and recorded the plane of fracture of the samples. The bond strength of one system was significantly greater than that of the other groups and was increased by the application of an unfilled resin enamel bonding agent. Unfilled resin application did not significantly alter the other systems tested. In only one of the systems tested was the inlay/composite cement bond found to be the weak link in the bonding procedure. In this group, the application of the manufacturer's specially formulated bond enhancer did not lead to an increase in bond strength.

Predicting ozone-induced soybean losses: sensitivity to model form and inputs.

In this study, alternative dose-response equations for assessing the effects of O3 on soybeans (Glycine max (L.) Merr.) were established. For each of three soybean cultivars, three models (linear, quadratic, and Weibull) were fitted to relate different measures of O3 dose, during the soybean flowering maturity period, to the soybean yield. The dose measures were 7-h (9:00 a.m. to 4:00 p.m.) and 12-h (7:00 a.m. to 7:00 p.m.) means, 7-h and 12-h total doses, and the 90th and 75th percentile O3 concentrations. Using data for primarily rural and small city O3 monitoring sites, county-level O3 doses were calculated, and soybean losses due to O3 were predicted for Illinois, Kentucky, and Virginia. The sensitivity of O3-induced soybean loss predictions to model forms and inputs was determined with regard to: (1) inter-year differences in ambient O3, (2) differences among the six dose measures, (3) differences among the three different model forms, (4) the impact of the agricultural practice of double-cropped soybean production, and (5) variance in response to O3 among three different soybean cultivars.

Effect of fatigue upon the interfacial bond strength of repaired composite resins.

A comparative study of the fatigue limits of repaired samples of three composite resins was undertaken using the staircase technique. Following storage in water for 21 days at 23 degrees C the surfaces of the specimens to be bonded were ground with a fine Soflex disc, washed and dried. The surface was treated with either Scotchbond or a silane coupling agent, or left untreated, and a composite repair of the same material added. The specimens were thermally cycled and tested sequentially for 5000 cycles at different stress instruments using a transverse impact load. A statistically valid value for mean fatigue limit was determined for each design. This showed that resistance to fatigue forces was lower in repaired specimens than in complete specimens. The use of Scotchbond Dual Cure bonding agent gave the strongest repair.

Resin bonded bridgework: a review.

The use of resin bonded bridgework has become accepted as a routine procedure in restorative dentistry. The aim of this paper is to assess the performance of this type of restoration based upon the evidence of published studies. The opening section describes the evolution of the various designs of framework for this type of bridge. The use of in vitro testing to determine possible clinical effects is then discussed. Clinical aspects of the use of resin bonded bridgework are described including abutment tooth preparation and the use of cementing resins, as well as the chemically adhesive materials. Factors influencing the retention of resin bonded bridgework are also discussed. Finally, the clinical performance of these bridges is considered.

Effect of impression tray design upon the accuracy of stone casts produced from a single-phase medium-bodied polyvinyl siloxane impression material.

The study examined the accuracy of stone casts produced from impressions taken in stock polycarbonate trays, some of which had been strengthened with autopolymerizing polymethyl methacrylate resin and four designs of custom-made trays. Impressions of an acrylic master model of the mandibular arch on which two extracoronal crown preparations and one intracoronal inlay preparation had been carried out were taken using a medium-bodied polyvinyl siloxane material. Each preparation had been intended with a reference point for later measurement. Five impressions were taken for each type of tray and these were cast in die-stone after 24 h. The distances between the points were measured with a reflex microscope and the means determined for each design of tray. The mean difference between casts produced from the various tray designs and the acrylic master model were determined for each of the distances between the three measuring points. Statistical analysis showed that, with the stock trays, there were no significant differences between any of the modifications, or between them and the acrylic model, for any of the three distances (P greater than 0.1). When the results from the custom-made trays were analysed there were statistical differences between the acrylic model and the casts from the unperforated tray with no stops (P = 0.02), and between the unperforated tray with no stops and the perforated with stops for the distance A-B (P less than 0.01). There were no other significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of impression tray design and impression technique upon the accuracy of stone casts produced from a putty-wash polyvinyl siloxane impression material.

This study examined the accuracy of stone casts produced from impressions taken in stock polycarbonate trays, some of which had been strengthened with autopolymerizing polymethyl methacrylate resin. Three techniques were used to make the impression of an acrylic master model of the mandibular arch on which two extracoronal preparations for bridgework and one intracoronal inlay preparation had been carried out. Each preparation had been indented with a reference point for later measurement. The impression material was a putty-wash polyvinyl siloxane material. Five impressions were taken for each type of tray for each impression technique and these were cast in die-stone after 24 h. The distances between the points were measured with a reflex microscope and the means determined for each design of tray. The mean difference between casts produced from the various tray designs and the acrylic master model were determined for each of the distances between the three measuring points for the various impression techniques. Statistical analysis showed that, with the polycarbonate stock trays, there were significant differences between some of the modifications and between them and the acrylic model, for the three distances (P less than 0.05). These differences were limited to one measurement for one design of tray for each of the two-stage impression methods. With the one-stage technique the unreinforced tray and those reinforced with acrylic, over the heels and anteriorly, and the barred design were statistically significantly different from the acrylic model for measurement A-B.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of human enamel wear against four dental ceramics and gold.

OBJECTIVES: This in vitro study compared the wear of enamel against aluminous porcelin, bonded porcelain, low fusing hydrothermal ceramic, feldspathic machinable ceramic, and cast gold. METHODS: Fifty pairs of tooth-material specimens were tested in a dental wear machine, under a standard load (40 N), rate (80 cycles min-1) and for 25,000 cycles in distilled water. The amount of wear was determined by measuring the height loss of the tooth, and the depth of wear track of the restorative materials. RESULTS: There was a significant difference in wear among the groups for both enamel and materials (p < 0.001). Follow-up comparisons (95% CI significance level) showed that gold caused significantly less enamel wear than all ceramics tested. The amount of enamel wear in the aluminous and bonded porcelain groups was significantly higher than with the hydrothermal and machinable ceramic groups. There was no significant difference between the amount of enamel wear produced by the aluminous and bonded porcelains nor between that produced by the hydrothermal and machinable ceramics. Furthermore, the wear of the aluminous and bonded porcelains was significantly greater than that of the hydrothermal ceramic, the machinable ceramics and gold. No significant difference in wear was found between aluminous and bonded porcelains, hydrothermal and machinable ceramics, or between machinable ceramic and gold. However, the hydrothermal ceramic had significantly greater wear than gold. CONCLUSIONS: It was concluded that the hydrothermal and the machinable ceramics were significantly less abrasive and more resistant to wear than the conventional aluminous and bonded porcelains. Gold was the least abrasive material and most resistant to wear, although the difference in wear between the machinable ceramic and gold was not statistically significant.

The effect of a resin-modified glass ionomer restorative material on artificially demineralised dentine caries in vitro.

OBJECTIVES: Recurrent caries is one of the most common reasons for the replacement of restorations. One method of reducing the frequency of this problem may be by using fluoride-releasing restorative materials. The aim of this in vitro study was to evaluate the progression of artificial lesions around resin-modified glass ionomer (Vitremer) restorations placed in root surfaces. Class V cavities were prepared on the mesial and distal surfaces of 28 human premolar teeth. Artificial carious wall lesions were created in all cavities. The root of each tooth was then hemisected through the middle of the two cavities, before being restored with either the glass ionomer or amalgam, while the opposing cavities on the same root portion were varnished as negative controls. Forty-eight specimens were pH-cycled in remineralising and demineralising solutions for 20 h and 4 h, respectively, each day for 4 weeks, whilst in a smaller control group of eight specimens, the demineralising solution was replaced with deionised water. Mineral changes in the carious lesions were evaluated using contact microradiography. RESULTS: Results showed that varying degrees of subsurface demineralisation and remineralisation were evident, with a laminated appearance in lesions adjacent to the glass ionomer. There was higher remineralisation in the glass ionomer-filled cavities compared with the amalgam-filled cavities. In the water-cycled group, glass ionomer showed an increase in mineral content (p < 0.05), while no changes were observed in the amalgam-filled cavities. CONCLUSIONS: This model has shown that glass ionomer has a greater potential than amalgam for remineralisation of artificially created wall lesions within an acidic environment.

A clinical study of pulsed Nd: YAG laser-induced pulpal analgesia.

The pulsed Nd: YAG laser is advocated as an alternative means of providing analgesia during routine dental procedures. Since the evidence to support this claim is mainly anecdotal, a clinical trial was carried out using an electric pulp tester (EPT) to measure the extent and duration of any analgesic effect induced by pulsed Nd: YAG laser treatment. A double-blind crossover experiment involving laser and sham treatments was used on 21 subjects. A small (3.6 arbitrary units) but statistically significant increase was observed in the mean responses measured 5 min after laser treatment with 113 mJ pulses at 15 pulses s-1 (pps) for 3 min. The pain thresholds returned to baseline values after 60 min. No statistically significant changes in threshold were found with the sham treatment. The order in which laser and sham treatment was received made no difference to the results.