Micro-computed tomographic evaluation of two single rotary glide path systems.

AIM: To compare (i) canal-centring ability and transportation of K-files, ProGlider and One-G files after glide path preparation in curved root canals; (ii) changes in canal volume after glide path preparation, using micro-computed tomography. METHODOLOGY: A total of 135 mesiobuccal root canals of maxillary molars were randomly divided into three glide path groups: (i) pre-curved sizes 10-15-20 K-files (n = 45); (ii) size 10 K-file followed by One-G (n = 45); and (iii) size 10 K-file followed by ProGlider (n = 45). Micro-CT was used to scan teeth before and after glide path preparation; the isotropic voxel size of the micro-CT scans was 22 µm. Centring ratio values and canal transportation values were compared between the three glide path preparation groups at the apical, midroot and coronal levels. Changes in canal volume were compared for all glide path groups. The results were analysed statistically using a one-way anova and Kruskal-Wallis H tests. RESULTS: One-G and ProGlider displayed significantly greater mean centring ratio values than K-files at all levels examined (P < 0.05). Apical canal transportation values after glide path preparation were significantly higher for the K-files (P < 0.05). At the midroot and coronal levels, canal transportation results were statistically similar for all glide path groups (P > 0.05). Changes in canal volume were statistically similar for the three glide path groups (P > 0.05). CONCLUSION: One-G and ProGlider were significantly more centred at the apical, midroot and coronal levels than K-files. Apical canal transportation ratio values after glide path enlargement were significantly higher for K-files than for One-G and ProGlider. All groups resulted in similar canal volume changes.

The influence of glide path preparation on the failure rate of WaveOne reciprocating instruments.

INTRODUCTION: The aim of this study was to determine the influence of two different glide path preparation methods on the fracture rate of the Primary 25/08 WaveOne reciprocating instrument. Preparation times for different glide path methods and total time for root canal preparation, with and without prior glide path preparation, were also calculated. MATERIALS AND METHODS: ISO 15, 0.02 taper Endo-Training-Blocks (n = 300) were selected and randomly divided into three main groups (n = 100): Group 1: no glide path (control); Group 2: glide path preparation with stainless-steel hand files; and Group 3: glide path preparation with rotary PathFiles. The time taken to prepare each glide path was recorded. The specimens in each main group were then randomly assigned into five subgroups (n=20). New Primary 25/08 WaveOne files were used for canal preparation in each subgroup. The outcome was measured by recording how many simulated canals could be shaped with one WaveOne reciprocating file in each subgroup before instrument breakage occurred. The average time it took to prepare each of the simulated canals was calculated and recorded. The data were collected and statistically analysed using the ANOVA / Bonferroni test. RESULTS: Glide path preparation with PathFiles was significantly faster than with hand files (P<0.001). After the glide path preparation had been performed with PathFiles, a greater number of simulated canals could be prepared before failure of the WaveOne file (P<0.001). Root canal preparation time was significantly shorter (P<0.001) when an initial glide path had been prepared with PathFiles.

A comparative study of student vs supervisor diagnoses of anatomical abnormalities affecting the TMJ.

INTRODUCTION: The use of modern teaching methods and learning tools by educators to ensure competent graduates has been encouraged. At the Department of Odontology, University of Pretoria, School of Dentistry, four diagnostic screening tests were tested as learning tools and their efficacy in teaching undergraduate dental students to diagnose abnormalities affecting the osseous components and associated muscles of mastication of the temporomandibular joint (TMJ). These screening tests are known as joint play, end feel, static pain and dynamic pain. OBJECTIVES: The aim of this study was to determine if dental students would be able to diagnose abnormalities affecting the osseous components and associated muscles of mastication of the TMJ using these four screening tests, as well as to compare their diagnoses with the diagnosis of a prosthodontist. METHODS: One hundred joints were randomly examined for abnormalities by 50 dental students and a prosthodontist. The diagnoses were recorded on a diagnostic form and entered into an electronic Microsoft Excel database. RESULTS: Of the 100 joints examined, 78 of the diagnoses made by the students were in agreement with that of the prosthodontist, which is highly significant (p < 0.001). CONCLUSION: The tests were used successfully by the majority of the students to make a correct diagnosis.

Antibacterial properties of five bonding agents.

PURPOSE: This study compared antibacterial properties of five bonding agents with that of a control, Chlorhexidine (2.5%). Products evaluated were the self-etch primers (-P) and adhesives (-A) of Clearfil SE Bond (SE-P; SE-A) [Kuraray Dental], Clearfil Protect Bond (PB-P; PB-A) [Kuraray Dental], Optibond Solo Self-etch (OS-P; OS-A) [Kerr] and the one-bottle products, self-etch Clearfil Tri-S Bond (3S) [Kuraray Dental] and total-etch Adper Scotchbond 1 XT (XT) [3M ESPE]. METHODS: Spread plates of three different bacteria (Streptococcus mutans, Lactobacillus paracasei and Actinomyces naeslundii) were prepared on Casein-peptone-Soymeal-peptone Agar (CASO-Agar). Controls, Primers, Adhesives, and Primer & Adhesive combinations were placed on standardized, sterilized filtration paper or composite disks and then placed on the inoculated agar and incubated at 37 degrees C for 48 hours. Inhibition zones were measured and data was statistically analyzed using the Student t-test. An additional test was performed by which growth inhibiting of 1/10 and 1/100 dilutions of the test suspensions were measured spectrophotometrically as turbidity at 600 nm and expressed as percentage growth (%). RESULTS: Compared to the controls, the only cured product which produced significant inhibition was Scotchbond 1 XT (XT), and that for Actinomyces naeslundii only. The primer of Clearfil Protect Bond (PB-P) showed statistically significant growth inhibition for all three test bacteria, the primer of SE Bond (SE-P) had significant inhibitive properties against Streptoccocus mutans and Actinomyces naeslundii and the primer of Optibond Solo Self-etch (OS-P) inhibited growth of Actinomyces naeslundii significantly. CONCLUSIONS: The primers of Clearfil Protect Bond, Clearfil SE Bond, Optibond Solo Self-etch and the product Adper Scotchbond 1 XT may be beneficial in eliminating remaining bacteria after cavity preparation, but further research on a possible long-term antibacterial benefit of these products needs to be undertaken.

Self-etching bonding systems: in-vitro micro-leakage evaluation.

The purpose of this in vitro study was to compare dentine and enamel micro-leakage values of six self-etching bonding agents to that of a total etch dentine bonding agent (used as a control). Products evaluated were Scotchbond Multipurpose Plus (3M/ESPE), Xeno III (Dentsply), Clearfil SE Bond (Kuraray), ABF (Kuraray), Optibond Solo Self-Etch (Kerr), OneCoatSE Bond (Colténe Whaledent), and iBond (Heraeus-Kulzer). Using a medium sized Cerana bur (Nordiska Dental) a standard, cylindrical preparation was made at the cemento-enamel junction (CEJ) of human third molars. The teeth were randomly divided into 7 groups of ten teeth each. The bonding agents were applied and light cured strictly according to the manufacturer's instructions and the cavities then filled in two increments, using Z100 composite (3M/ESPE). The restored teeth were imbedded in acrylic resin and thermocycled between 5 degrees - 60 degrees C (+/- 2 degrees C) for 250 cycles with a dwell time of 20 seconds. All seven groups were then placed in a 5% basic Fuchsin solution for 12 hours at 37 degrees C. The embedded teeth were removed from the basic Fuchsin, rinsed well, imbedded in acrylic and cut longitudinally through the centre of each restoration using an Accutom-2 cutting machine. Each tooth was then evaluated at the occlusal enamel margin and at the cervical dentine margin for micro-leakage using a light microscope at 50x magnification. The data obtained was analysed using the Kruskal-Wallis test, with Fisher's least significant difference method used for comparison of specific groups (p<0.05). When compared to the control (Scotchbond Multipurpose Plus), results for microleakage at the occlusal enamel margins as well as the cervical dentine margins indicated that only SE Bond and ABF (Protect Bond) showed values as low as the control. It can be concluded that, as far as micro-leakage is concerned, Clearfil SE Bond and ABF (Protect Bond) self-etching bonding agents could be clinically acceptable alternatives to the clinically proven Scotch-bond Multipurpose. The other products showed more microleakage.

Self-etching bonding systems: in-vitro shear bond strength evaluation.

The purpose of this in vitro study was to compare the dentine shear bond strength of five self-etching bonding agents with that of a total-etch dentine bonding agent (used as control). Sixty recently extracted third molar teeth were mounted in acrylic resin and the occlusal surfaces ground to expose superficial dentine. A standardised smear layer was created by polishing with wet 600-grit SiC paper. Products evaluated were Xeno III (XIII), Clearfil SE Bond (SE), ABF (ABF), Optibond Solo Self-etch (OS), Adper Prompt-L-Pop (PLP) and the control, Scotchbond Multipurpose Plus (SBMP). Resin stubs were bonded to the dentine using the bonding agents according to manufacturer's instructions. Composite stubs were manufactured using an Ultradent jig and two increments of Z100, A1 shade composite. The bonds were subsequently stressed to failure with an Instron testing machine, operating at a crosshead speed of 0.5 mm/min. The data was statistically analysed using ANOVA (alpha < or = 0.05). The mean SBS (MPa) were: SBMP (Control) = 24.1 +/- 7.6; XIII = 17.3 +/- 4.1; SE = 26.2 +/- 7.8; ABF = 25.9 +/- 4.3; OS = 21.9 +/- 3.9 and PLP = 15.4 +/- 3.1. The shear bond strengths of both XIII and PLP to dentine were significantly lower than the control SBMP (p < 0.05). The remaining three products (SE, ABF and OS) displayed bond strengths comparable to the control (p > 0.05). Further research into cut (ground) and un-cut (un-ground) enamel shear bond strength and micro-leakage using these bonding agents are needed.

Shear bond strength of five porcelain repair systems on cerec porcelain.

The purpose of this in vitro investigation was to evaluate the shear bond strength of composite resin bonded to Cerec Vitablocs Mark II porcelain with four different porcelain repair systems. The systems evaluated in this study were Scotchbond/ RelyX Primer (S/ 3M), Ultradent Porcelain Repair Kit (U, Ultradent), Vivadent Ceramic Repair Kit (V, Vivadent) and Prime & Bond NT/ Calibra Silane Coupling Agent (P, Dentsply). Seventy five Cerec Vitablocks Mark II porcelain were embedded in metal rings, leaving 7 mm of porcelain exposed above the ring surface. Samples were ground wet on 400 grit SiC paper to roughen the surface and then screened for surface defects. The five porcelain repair agents were applied according to manufacturers' instructions and matching composite stubbs, then bonded onto 15 treated porcelain surfaces, using an Ultradent mould with a diameter of 2,38 mm. All samples were stored in distilled water for 24 hours at 37 degrees C before the bonds were stressed to failure, using a shear load in a Texture Analyser (TAXT2i) (Stable Micro Systems) Data was analyzed statistically (ANOVA). The effects of the pretreatments on the porcelain surfaces after treatment with the different systems were examined in a Scanning Electron Microscope (SEM), and the modes of fracture were assessed under a light microscope. The mean SBS (MPa) for the products in descending order were: U = 26.6 1.7; V = 20.9 3.4; C = 19.4 5.3; S = 18.0 2.0 and P = 15.9 2.1. The Student-t Test revealed a statistical significant difference (p < 0.05) between the mean shear bond strengths of P and U. There was also a statistical significant difference (p < 0.05) between the mean shear bond strengths of P and V. Most debonded specimens showed cohesive fractures in the porcelain. Significant shear bond strength differences were observed for the different repair systems. All the systems tested can probably be used to repair Cerec Vitablocs Mark II porcelain, with some systems providing higher bond strengths.

Resin-infiltrated-dentine--a FE-ESEM microscopy investigation.

The formation of a hybrid layer is essential for bonding of dental composites to dentine. The objective of this study was to examine the effects of various etchants/conditioners and dentine bonding systems on dentine surfaces utilising a Field Emission Environmental SEM (FE-ESEM). Twenty one, freshly extracted human molar teeth were utilised. Dentine without resin application was initially observed both wet and dried in the following conditions: (1) fractured surface, (2) smear layer, and (3) smear layer removed with 37% phosphoric acid. Resin infiltration into dentine was then studied after applying Scotchbond 1, Optibond Solo, Prime & Bond NT, or Prompt L-Pop systems. Scotchbond 1, Optibond Solo, and Prime & Bond NT resins penetrated the dentine tubules and created hybrid layers; although, in some cases Prime & Bond NT only created a partially filled hybrid layer. No polymerised resin or hybrid layer was observed for Prompt L-Pop. The FE-ESEM permitted observation of specimens at near in-vivo wet conditions.

Anti-bacterial efficacy of new self-etching dentine bonding agent.

Since a perfect seal is not easily achieved during bonding procedures, any product which will limit or delay bacterial proliferation in the resulting micro-leakage spaces should extend the life span of bonded restorations. This study compared the antibacterial properties of an experimental, self-etching, fluoride-releasing, antibacterial bonding system (ABF) with two standard bonding systems (SE Bond and Scotchbond MP). Spread plates of three different bacteria (Streptococcus mutans, Lactobacillus paracasei and Actinomyces naeslundii) were prepared on Brain-Heart Infusion agar. Standardised, sterilised filtration paper disks were infiltrated with 20 microl of primer and then placed on the inoculated agar and incubated at 37 degrees C for 48 hours. The extent of the inhibition zones were measured at different positions and data were analysed using the Student t-test to determine significant differences. All three primers showed zones of inhibition for all three bacteria tested. Inhibition zones for ABF primer against S. mutans were significantly larger (p<0.05) compared to that of Scotchbond MP and SE Bond. In general the antibacterial activity of the three primers against the three bacteria tested varied, and the inhibitory effect for the experimental primer was significantly superior against S. mutans only.

Flexural properties of denture-base polymer reinforced with glass-fibre polysulphone composite.

The aim of this study was to determine the effect of glass-fibre composite reinforcement on the flexural strength and flexural modulus poly-methyl methacrylate (PMMA). Prefabricated electrical glass-fibre polysulphone composite rods (GF/PSu), 3mm in diameter, were incorporated in cylindrical, heat polymerizing PMMA specimens with diameters of 4, 5 and 6mm respectively (n = 10). These specimens were compared with PMMA control groups of similar dimension. A three point loading test was performed in air after storage of specimens in water at 37 degrees C for 8 weeks. The following variables were measured : Flexural Strength (FS) and Flexural Modulus (FM). The data were analyzed using one way analysis of variance (ANOVA). After testing, the fracture zone was evaluated using a scanning electron microscope (SEM). The glass-fibre reinforcement used in this study significantly enhanced both the FM and FS values of PMMA. This enhancement was, however, progressively reduced in relation to an increase in cross-sectional dimension of the specimens. SEM evaluation revealed delamination and fracture of the glass-fibres in the polymer matrix.

Effect of biological contamination on dentine bond strength of adhesive resins.

The purpose of this in vitro study was to determine the effect of saliva (S) and blood (B) contamination on the dentine bond strength of two single-component dentine bonding systems. The occlusal thirds of 120 recently extracted, human molars were removed with a low speed saw and subsequently embedded in Bencor rings by means of self-curing, acrylic resin. The occlusal surfaces were ground wet on 600-grit silicone carbide paper in a polishing machine to expose superficial dentine and to create a smear layer. The teeth were randomly divided into 12 groups (n = 10). All the dentine surfaces were etched with 34% phosphoric acid for 15 seconds rinsed with water, air-dried for 3 seconds, leaving the surfaces visibly moist. For the control groups (C) the etched dentine surfaces were treated with either, Scotchbond 1 (SB1, 3M) or Prime & Bond NT (PBNT, Dentsply) according to the manufacturer's instructions. In the contaminated groups, the saliva or blood was applied by means of a disposable brush, left undisturbed for 1 minute, and the excess then thinned by air spray. The dentine bonding systems were then applied, also according to manufacturer's instructions. Composite (Z250 and TPH) and Compomer (F2000 and Dyract AP (D-AP)) stubs were packed and cured incrementally to the corresponding pretreated dentine surfaces. All specimens were stored for 24 hours under water at 37 degrees C. The bonds were then stressed to failure with a Zwick testing machine, operating at a crosshead speed of 0.5 mm/min. Fractured samples were examined in a Scanning Electron Microscope. The data were statistically analysed (Student-t test). The mean SBS (MPa) were. SB1 with Z250: C = 19.1 +/- 4.4; S = 17.3 +/- 3.5; B = 2.6 +/- 0.9; SB1 with F2000: C = 11.8 +/- 3.3; S = 9.7 +/- 1.8; B = 4.7 +/- 1.6. PBNT with TPH: C = 9.2 +/- 3.2; S = 6.5 +/- 3.0; B = 4.3 +/- 1.5; PBNT with D-AP: C = 10.2 +/- 3.6; S = 9.3 +/- 2.9 and B = 7.3 +/- 2.5. There was no statistical significant difference in shear bond strengths between the control and the saliva-contaminated samples for both systems. There was, however, a significant difference in bond strengths between the control and the blood-contaminated samples. Blood contamination negatively influenced bond strength of bonding systems to dentine.

Dental materials used by general dental practitioners.

As a follow-up to previous surveys regarding materials used by dentists a total of 1500 questionnaires were distributed to general dental practitioners in private practice. A response rate of 11.8% was achieved. The most popular products used during 1999 were identified. Changes in the choices of materials were observed when compared to previous surveys. This may be attributed to the development of various new products.