Modern high powered led curing lights and their effect on pulp chamber temperature of bulk and incrementally cured composite resin.

Pulpal temperature changes induced by modern high powered light emitting diodes (LEDs) are of concern when used to cure composite resins. This study showed an increase in pulp chamber temperature with an increase in power density for all light cure units (LCU) when used to bulk cure composite resin. Amongst the three LEDs tested, the Elipar Freelight-2 recorded the highest temperature changes. Bulk curing recorded a significantly larger rise in pulp chamber temperature change than incrementally cured resin for all light types except for the Smartligh PS. Both the high powered LED and the conventional curing units can generate heat. Though this temperature rise may not be sufficient to cause irreversible pulpal damage, it would be safer to incrementally cure resins.

Teaching approaches in South African dental schools: direct restorative procedures.

INTRODUCTION: Worldwide the use of amalgam has declined and mercury-containing products are banned in several countries. National and international opinions on amalgam were recently discussed in journals. According to surveys, significant time is spent on the teaching of amalgam in American, Canadian, Irish and United Kingdom Dental Schools. AIMS AND OBJECTIVES: To i) investigate the teaching approaches on direct restorative techniques and materials in South African Dental Schools; ii) compare the teaching approaches of the dental schools in South Africa with each other as well as with the American, Canadian, Irish and United Kingdom schools; iii) use the information of this study as baseline data for future studies on teaching approaches. METHODS: A questionnaire regarding the teaching and training of direct restorations was e-mailed to the heads of Restorative Dentistry departments in four South African Dental Schools in 2007. RESULTS: Significant time is spent on teaching and training of amalgam as a restorative material. Teaching and training on direct restorations are very similar in all South African Dental Schools. CONCLUSION: Although there is a decline in the use of amalgam worldwide, significant time is spent on teaching of amalgam restorations in South African Dental Schools and this corresponds to the curriculums of American, Canadian, Ireland and United Kingdom Dental Schools.

Shear bond strength comparison of RelyX Unicem with six other orthodontic resin adhesive systems.

Orthodontic bracket adhesion involves multistep procedures which are technique sensitive to various factors within the oral environment. RelyX Unicem is a restorative/prosthodontic adhesive material which by virtue of its one step adhesion procedure may prove to be suitable for efficient orthodontic bonding. The objective of this study was to compare the SBS of RelyX Unicem with six other known orthodontic bonding materials. Seventy extracted human premolar teeth were divided into seven groups of 10 teeth each. On each group, metal orthodontic brackets were bonded using one of the seven bonding materials: (A) Transbond XT primer and Transbond XT luting cement (B) F2000 compomer primer/adhesive (C) Transbond Plus and Transbond XT luting cement (D) RelyX Unicem (E) Prime & Bond NT and Calibra cement (F) Xeno III and Calibra cement (G) NRC + Prime & Bond NT and Calibra cement. Shear bond strength evaluation of each tooth was tested and recorded using the Instron materials testing machine. The results show that the mean SBS for RelyX Unicem is 5.38 MPa and NRC is 4.70 MPa which rates weak compared to all the other materials where the means for the SBS are within the acceptable range of 5.9 to 7.8 MPa. It appears that by reducing the number steps followed for orthodontic bracket adhesion, the SBS of the orthodontic adhesive materials becomes significantly compromised to the extent where such materials can be rejected as suitable for orthodontic bracket adhesion. RelyX Unicem and NRC were found to be unsuitable for orthodontic bracket adhesion.

Microleakage of different amalgams bonded with dual cure resin cements.

INTRODUCTION: To reduce microleakage in high-copper amalgam restorations, bonding of amalgam was introduced. AIM: This study compared the microleakage of admixed and spherical amalgams when bonded with different bonding intermediates under thermo- and non-thermocycling conditions. METHOD AND MATERIALS: Class II butt-joint cavities were prepared in 200 extracted human molar teeth, and randomly divided into 5 groups. Calibra, Duo Cement Plus, RelyX ARC and Amalgambond Plus were applied to 4 of these groups. The fifth group was left untreated. The groups were further divided and restored with either Dispersalloy or Oralloy Magicap S. Ten specimens of each group were thermocycled between 5 degrees C and 55 degrees C, placed in basic fuchsin for 8 hours, sectioned and evaluated for dye penetration under 40X magnification. The mean microleakage scores were analysed using the chi-squared test at a confidence level of 95%. RESULTS: Microleakage of the non-bonded amalgams was significantly higher (p < 0.0001) than for the bonded amalgams (thermocycled and non-thermocycled). The microleakage of the different intermediates bonded to Dispersalloy (thermocycled and non-thermocycled) was not significantly different (p > 0.05). The microleakage of the different intermediates was not significant different except for Duo Cement compared to Calibra (p < 0.0001), RelyX (p < 0.0001) and Amalgambond (p = 0.0433) and Amalgambond compared to Calibra (p = 0.0433) and RelyX (p = 0.0433). The microleakage of the bonded amalgams was not significantly increased by thermocycling (p > 0.05). The microleakage of the two amalgams when bonded with the same resin cements (thermocycled and non-thermocycled) was not significantly different except for Duo Cement (thermocycled) (p = 0.0051) and RelyX (non-thermocycled) (p = 0.0356). CONCLUSIONS: Bonding amalgam restorations to tooth structure in butt-joint cavities will reduce microleakage of both admixed and spherical amalgam restorations. Thermal stress does not affect the bond adversely.

Effect of woven glass fibre reinforcement on the flexural strength of composites.

To measure and compare the flexural strength of composites reinforced with fibres, four groups of specimens (N = 10) were prepared from the combinations: Filtek Flow/Filtek Z250 and Esthet-X flow/Esthet-X dental composite. One group from each combination was reinforced with woven glass fibre (everStick net) and all the specimens subjected to three-point bend flexural testing. The mean and standard deviations for each test group were calculated and compared using one-way analysis of variance (ANOVA) followed by pairwise Bonferroni T-tests at a preset alpha of p < 0.05. It was found that fibre reinforcement significantly (p < 0.001) increased the flexural strength of both types of composites. As the inclusion of only one layer of glass fibre net produced an increase of approximately 30% in the flexural strength of the composite samples, it can be speculated that multiple layers would increase it even more. The use of fibre-reinforcement to strengthen directly placed composite crowns and bridges will enable the clinician to provide a more cost effective service as well as aesthetic dentistry to more patients.

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.

The bonding effectiveness of five luting resin cements to the IPS Empress 2 all ceramic system.

BACKGROUND: Variolink II is the only resin cement used for bonding IPS (Ivoclar Porcelain System) Empress 2 ceramic restorations. Alternative luting resin cements need to be investigated for their bonding effectiveness with the IPS Empress 2 ceramic. OBJECTIVES: To determine the shear bond strength (SBS) and the effect of thermocycling, on the bonding effectiveness, of five resin cements to IPS Empress 2 ceramic. MATERIALS AND METHODS: The projecting surfaces of one hundred ceramic discs were ground wet on silicone carbide paper. The specimens were divided into 5 groups of 20. The resin cements were bonded to the prepared ceramic surfaces, in the form of a stub. The specimens were stored under distilled water at 37 degrees C in an oven for 24 hours. Ten specimens in each group were thermocycled for 300 cycles between 5 degrees C and 55 degrees C. All the specimens were stressed to failure in an Instron Materials Testing Machine. RESULTS: The results were subjected to a one-way analysis of variance (ANOVA). Statistically similar mean SBS values were grouped using the Bonferroni (Dunn) multiple comparison test. The means for the non-thermocycled group were: 26.21, 19.41, 17.69, 17.43, and 15.76. The means for the thermocycled group were: 22.90, 15.72, 14.34, 13.96 and 13.45. The differences between the means were highly significant (p < 0.0125). CONCLUSIONS: The shear bond strength of Variolink II and Rely XARC to IPS Empress 2 ceramic was effective. Thermocycling had a significant effect on the mean SBS values of Calibra. Thermocycling had no significant effect on the mean SBS values of the other resin cements.

Advances in light curing units and curing techniques: a literature review.

There exists a constant need for a dental curing light that works reliably and conveniently in the general practitioner's office and can be used effectively for all the different curing procedures. Due to the need for improved physical properties of resin based composites (RBCs) and less stress at the marginal interface, light curing units (LCUs) experienced significant advances in the past years. The dental industry has focused on reducing the curing time by developing higher intensity curing lights and by altering the resin composition and photo-initiator concentration. As a result the dentist can now choose from a vast variety of curing lights, light intensities and curing methods. This article presents a review of the advances in light curing units and curing techniques, as well as the scientific principles that guided past developments and that will influence future advances.

Development of bioconjugated dye-doped poly(styrene-co-maleimide) nanoparticles as a new bioprobe.

Fluorescent dye-doped poly(styrene-co-maleimide) nanoparticles were synthesised and functionalized with amine groups and avidin and the dye-loading was varied. The nanoparticles showed great potential as bioprobes when conjugated with biotinylated antibodies.

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.

Shear bond strength of one-bottle dentine bonding systems.

The purpose of this in vitro study was to determine the shear bond strength (SBS) of composite resin to human, buccal dentine, using four one-bottle dentine bonding systems. Eighty recently extracted human molar teeth were embedded in metal rings by means of self-curing acrylic resin. The projecting buccal surfaces were ground wet on 600 grit silicone carbide paper in order to expose superficial dentine. The teeth were randomly divided into four groups (N=20): 1=Prime&tBond 2.1 (PB, Dentsply); 2=Scotchbond 1 (SB, 3M); 3=Optibond Solo (OS, Kerr) and 4=Syntac Single Component (SY, Vivadent). The dentine surfaces were etched, treated with one of the four dentine bonding systems, and cylinders of matching composites were then bonded to the surfaces by means of a silicone rubber split mould. All specimens were stored for 24 hours under water at 37 degrees C. The bonds were then stressed to failure with an Instron testing machine, operating at a crosshead speed of 0.5 mm/min. The data were statistically analysed (Kruskall-Wallis). The mean SBS (MPa) were: PB = 12.5 +/- 2.0; SB = 16.2 +/- 1.9; OS = 17.4 +/- 3.1 and SY= 8.1 +/- 1.9. There was a statistically significant difference (P = 0.0001) between the mean of SY and the other 3 groups, and also between PB and the other groups. There was no statistically significant difference (P = 0.244) between the SBS of OS and SB. SY demonstrated the lowest SBS.

New sputum metabolite markers implicating adaptations of the host to Mycobacterium tuberculosis, and vice versa.

In this study, a metabolomics research approach was used to identify new tuberculosis (TB) markers from sputum, in an attempt to better characterise the disease as well as the metabolic response of the host to Mycobacterium tuberculosis infection. After GCxGC-TOFMS analyses, various multivariate and univariate statistical methods were implemented to identify those compounds best describing the variation between the TB-positive and TB-negative patient groups. The interpretation of these new metabolite markers led to a number of new hypotheses, including: 1) support of the previously proposed citramalate cycle in M. tuberculosis; 2) the interaction of this cycle with an up-regulated glyoxylate cycle during pulmonary M. tuberculosis infection; 3) the increased utilisation of fatty acids and glutamate as alternative carbon sources by M. tuberculosis during pulmonary infection; 4) an alternative mechanism by which the host produces hydrogen peroxide via glucose oxidation, in order to eliminate the bacterial infection; 5) inhibition of the ETC due to pronounced oxidative stress during an active TB disease state, resulting in increased concentrations of various neurotransmitters and other metabolites previously associated with an inborn error of metabolism (MADD/GA type II); and 6) elevated concentrations of neurotransmitters associated with a number of previously described symptoms of TB.

Materials used by dental technicians in South Africa.

In order to determine the choice of materials used by dental technicians, questionnaires were sent to 400 registered South African dental laboratories. The response rate was 30.5 per cent. The most frequently used brands were identified. The relationship between usage of materials and demographic variables is discussed.

Continuing education for dental practitioners.

Attendance of continuing education courses by dentists is important for the practitioner, the profession and the patient. This survey was undertaken to determine the attendance pattern and discipline preferences for such courses during the period 1985 to 1989. A total of 2674 questionnaires were sent to dentists and 706 (26.4 per cent) were returned. Courses were attended by 88.5 per cent of the respondents. The most popular disciplines were Operative Dentistry, Aesthetic Dentistry and Fixed Prosthodontics.

Shear bond strength of a composite resin to differently silicoated base metal alloys.

This study was undertaken to determine the shear bond strength of Charisma composite resin to both thermal and pyrogenic silicoated base metal alloys namely, Duracast MS, Rexillium V and Wironit extra-hard. The bonded specimens were subjected to three stress treatments prior to shear bond testing. The results indicated that both silicoating techniques significantly improved shear bond strengths to sandblasted alloys, whereas wet heat and thermocycling treatments reduced the bond strengths, except for pyrogenic silicoated Wironit. Thermocycling was more detrimental to thermal than to pyrogenic silicoated Rexillium nad Wironit specimens.

[Attitude of South African dentists and final year dental students to advertising]. / Die houding van Suid-Afrikaanse tandartse en finale-jaar tandheelkundige studente teenoor adverternsie.

Advertising or promotion comprises two aspects: the advertising message and the advertising medium. Since both aspects are viewed differently by various professions, including the dental profession, the current investigation was carried out to ascertain the attitude of South African dental practitioners. Although it was found that the majority of dentists were against the advertising of new practices and re-advertising of existing practices, the majority of the final year dental students of 1986 were in favour. Both groups, however, were against unlimited advertising and also preferred professional cards to press, radio and television as the medium of communication.

[Attitude of a group of South Africans toward advertising by dentists in private practice]. / Die houding van'n groep Suid-Afrikaners teenoor advertensie deur tandartse in die privaatpraktyk.

The advertising of dental services in South Africa is controlled by rules and regulations of the South African Medical and Dental Council. According to these, advertising is not permissible with the exception of specified professional information which may be made known only by means of a nameplate and an entry in a telephone directory. Questionnaires were sent to a randomised sample of 2,100 persons in order to determine the attitude of South Africans towards advertising by private practitioners. According to information obtained from this study there is a strong indication that consumers of dental services prefer a freer form of advertising by dentists in the private practice.

The effect of placement technique on marginal adaptation of posterior resins.

Polymerization shrinkage of posterior resin restorations leads to margins that pull away from the tooth, or to cracks in the material itself. The purpose of this study was to determine the effect of three different placement techniques on the marginal adaptation (or in effect the amount of polymerization shrinkage) of posterior resin restorative materials. Three posterior resin materials, namely, Distalite, Heliomolar and P30 were included in this study. Each of these materials were placed by means of three different placement techniques (Bulk pack, Horizontal layering and Vertical layering) into class II cavities in extracted human molars. No dentine bonding agents were used. The samples were light cured, the teeth sectioned longitudinally and stored dry before examination in a Scanning Electron Microscope. Results showed polymerization shrinkage with all three techniques, with the poorest the bulk pack technique where large marginal discrepancies were visible. No significant differences were detected between the horizontal and vertical placement techniques, but the two microfilled resins Heliomolar and Distalite showed significantly poorer marginal adaptation than the small particle conventional resin, P30. All three materials had better adaptation on the occlusal margins than on the margins situated along the floor of the cavity or the gingival margins of the proximal box of the cavity. It can be concluded that the bulk pack technique should be avoided as this leads to large contraction gaps at most of the margins of the restoration.