Cytotoxicity of seven recent dentine bonding agents on mouse 3T3 fibroblast cells

Today it is generally accepted that most bonding agents are cytotoxic. In this study the relative cyto-toxicity of seven recent dentine bonding agents on mouse 3T3 fibroblast cells were investigated. Materials and Methods. Near-confluent mouse 3T3 fibro- blast cells were exposed to Dulbecco Modified Eagle’s Medium containing extractions from the seven different bonding agents. The cell survival rate was then determined using the standard MTT assay. Results. The cell survival rate ranking is: iBond (94%) < Gbond (78%) < Xeno V (71%) < Adper Easy Bond (63%) < Xeno V+ (61%) < Adper Scotchbond SE (33%) < XP Bond (32%). Part A of Adper Scotchbond SE had a survival rate of 35% and part B 38%. These two parts did not differ significantly. Adper Scotchbond SE and XP Bond do not differ significantly. While Xeno V+, Xeno V and Adper Easy Bond do not differ. (p < 5%; Tukey-Kramer Multiple-Comparison Test). Conclusion. All of the tested adhesive bonding agents were cytotoxic with survival rate of 3T3 cells between 94% to 31%. Of the 7 bonding agents tested iBond was found to be only slightly toxic and by far the least toxic. The two bonding agents (XP Bond and Adper Scotchbond SE) containing UDMA plus TEGDMA plus HEMA plus camphorquinone were found to be the most toxic

Volumetric change of flowable composite resins due to polymerization as measured with an electronic mercury dilatometer

BACKGROUND: To determine the total volumetric change and the relative speed of shrinkage of bulk fill flowable composites during polymerization. MATERIALS AND METHODS: A specially designed electronic mercury dilatometer was used to determine the volumetric change. The light intensity was 500mW/cm2. The mercury dilatometer measured the volumetric change every 0.5 seconds during the 35 second irradiation exposure time. The materials tested were Z250 as standard and control. Four bulk fill flowable composites were tested. RESULTS: The sequence of total volumetric change was found to be: Z250 < Filtek bulk fill < Xtra-Base bulk fill < SDR < Venus bulk fill. The speed of shrinkage of the bulk fill flowables was faster than that of Z250, while the 2 flowables with the highest shrinkage speed (SDR and Venus) also had the highest total volumetric change. Of the different materials tested the volumetric change of Z250 (1.13%) was the lowest and significantly less (p<0.05) than that of SDR (1.55%) and Venus (1.72%). The material with the highest filler content (Z250) also showed the lowest shrinkage (1.13%) but this effect could not be seen in the flowables. In general, it was found that a 35 second irradiation period (with a light intensity of 500mW/cm2) was satisfactory for complete polymerization of the resins. CONCLUSIONS: The volumetric changes and speed of shrinkage were higher for all 4 bulk fill flowable composites than for Z250. SDR and Venus flowables had the fastest and highest volumetric shrinkage. Clinical significance: The manufacturers of bulk fill flowable composites advocate filling layers of 4mm. However, because of the high shrinkage values found in this study it should be suggested that the standard 2mm layer increments still be used.It was partly supported by the IADR and the C. H. Pameijer Fellowship 2012.Web of Scienc

Comparison of colour components between maxillary central incisors - an in vivo study

Objectives: The purpose of this study was to determine the relationship of colour in the CIE L a b scale between the maxillary central incisors. Methods: The colour of the maxillary central incisors of 83 patients was measured (in vivo) using a spectrophotometer. Three measurements (6 mm diameter) at the centre of the crown of each of the maxillary central incisors were performed. Results: The total colour difference (?E ab) showed wide variability with the average ?E ab = 1.79. The Wilcoxon Signed Rank Test showed statistically significant differences (p < 0.05) between maxillary right (11) and left central incisors (21) in both the L and b colour components. In the a scale no significant difference was noted. Conclusion: Small colour differences exist between the maxillary central incisors in the same individual when evaluated with a spectrophotometer. Clinical significance: As there is often a difference between the colours of the two central incisors in the same patient, the colour of both the central incisors should be taken into consideration when shade matching anterior teeth.DHE

Insights into the clinical effectiveness of whitening products - Part 1: Dentist-supervised-at-home bleaching product

This section of the report is about the success of a dentist-supervised-at home tooth whitener, giving the results of a clinical study. Opalescence PF 10% was applied for 14 days and the colour change followed over a 14 month period. It could be concluded that: a) Opalescence is a good tooth whitener, b) the time of re-bleaching should actually depend on the colour choice expressed by the patient. Overall re-bleaching should only be done after six months and not on a monthly basis, otherwise enamel damage may become a problem. Remember that peroxide, which is responsible for the bleaching process, is a strong oxidizing agent. Furthermore, A2 and darker teeth showed more aesthetically observable colour changes.DHE

Insights into the clinical effectiveness of whitening products. Dentist-supervised-at-home bleaching product (Opalescence PF). Whitening of darker teeth in contrast to the effects on relatively whiter teeth

This study evaluated the success of the whitening of darker teeth by comparing the results of a tooth whitening programme in two groups, subjects with darker (A2 and darker) teeth and patients with whiter teeth. Opalescence PF 10% was applied for 14 days (nightly for 6-8 hours) and the colour changes followed over a six month period. The overall effect (∆E*ab) showed a much higher improvement (p<1%) in the whitening of darker teeth (~40%) relative to teeth which at the outset had been whiter than A2. Overall (∆E*ab) a deterioration of about 19% for darker teeth and ~9% for whiter teeth was seen after six months, but a significant improvement in colour was still evident. Conclusion: The effect of Opalescence PF 10% treatment was significantly better in all components (L*, a*, b* and ∆E*ab) for A2 and darker teeth relative to whiter teeth. Despite a significant colour relapse after a six-month period, there was still an improvement compared with before treatment. Thus, it can be expected that bleaching treatment of darker teeth would result in more aesthetic observable colour changes. The significant loss of the whitening effect found after six months may suggest the recommendation to re-bleach

Guidelines for the selection of tooth whitening products amongst those available on the market

Background: Several tooth whiteners are available on the market, and the ideal choice should be determined by ef­ ficacy and optimal clinical results. Objectives: The purpose of this study was to compare the reported clinical success rates of different tooth whitening products. Search strategy: The relevant literature (1998 - 2011) was studied, using as sources the databases: Google Scholar, Science Direct, Medline and Pubmed. Selection criteria: The material was clearly identified, the manufacturers' instructions were respected and the sample size stated. Results and conclusions: This descriptive report on 49 papers focuses on the total colour change, measured with a calibrated shade guide and also numerically {colourime­ ter, chromameter or spectrophotometer), the relapse of the colour change and tooth sensitivity. In general, the dentist­ supervised at-home bleaching and the in-office treatment gave approximately the same initial percentage improvement of tooth whitening. However,the relapse after a four week or longer period was significantly higher for the in-office treat­ ment. The treatment of choice should be a dentist super­ vised at-home bleaching product which generally contains -1096 carbamide peroxide applied over about 14 days for about eight hours per night. Tooth sensitivity should not be a general problem although some subjects might choose to discontinue treatment as a result of sensitivity.Department of HE and Training approved lis

A comparative study to determine the shock absorption ability of two popular mouth guards available on the South African market

It is expected that most mouth guards will provide some level of protection to teeth. In this study a device was developed to measure the relative impact absorption of two different mouth guards (Proform, Type III vacuum-formed and Max, Type IV pressure laminate). Seven of each of the two types of mouth guards were made and each batch was exposed to between six and 10 impact trials.DHE

The whitening effect of four different commercial denture cleansers on stained acrylic resin

Denture hygiene and denture cleansers are very important for their antimicrobial effect and also in removing stain from the dentures. The purpose of this study was to determine the effectiveness of Steradent, Corega, Dentalmate and Fitty Dent in improving the colour of stained, polished-and unpolished, acrylic specimens and to determine which colour component should be the visual impression factor. Samples of stained acrylic specimens were severally exposed once to one or other of the denture cleansers. The colour components (L*, a* and b*) of the specimens were measured with a spectrophotometer before and after exposure to one of the four products. In general there was only a slight non-significant improvement (p>0.05) in the yellowness (a*) and redness (b*) of the acrylic samples as a result of a single treatment with any of the four stain removal products. However, the L* value was mainly negatively influenced. The differences (ΔE*ab; ΔL*; Δa* and Δb*) between before and after treatment for any one of the four products were also not statistically significant on a 5% level (Kruskal Wallis nonparametric test). Conclusion: A small improvement of the yellowness and redness could be seen even after a single treatment. This was found for all four commercially available denture cleansers on polished and on non-polished specimens. From the relative magnitudes of L*, a* and b* which contribute to the overall colour value (ΔE*ab) it was statistically confirmed that the brightness/lightness component (L*) should be the visual impression factor.Department of HE and Training approved lis

Prevalence of Post COVID-19 Condition among Healthcare Workers: Self-Reported Online Survey in Four African Countries, December 2021–January 2022

The impact of Post COVID-19 Condition (PCC) is ongoing despite the declaration that the 2019 COVID-19 pandemic has ended. In this study, we explore the prevalence of PCC among healthcare workers (HCWs) in four African Countries and its influence on their professional performance. This study was conducted as an online cross-sectional survey of healthcare workers from four African countries (Cameroon, Egypt, Nigeria, and Somalia) between the 20th of December 2021 to 12th of January 2022. We determined the prevalence of PCC based on the WHO case definition and assessed variables associated with a higher prevalence of PCC in these countries using univariable and multivariable logistic regression analyses. A total of 706 HCWs from four African countries were included in this survey. Most of the HCWs were aged between 18–34 years (75.8%, n = 535). Our findings showed that 19.5% (n = 138) of the HCWs had tested positive for SARS-CoV-2. However, 8.4% (n = 59) were symptomatic for COVID-19 but tested negative or were never tested. Two-thirds of the HCWs (66.4%, n = 469) have received a COVID-19 vaccine and 80.6% (n = 378) of those vaccinated had been fully vaccinated. The self-reported awareness rate of PCC among the HCWs was 16.1% (n = 114/706) whereas the awareness rate of PCC among COVID-19-positive HCWs was 55.3% (n = 109/197). The prevalence of PCC among HCWs was 58.8% (n = 116). These changes include the self-reported symptoms of PCC which included headache (58.4%, n = 115), fatigue (58.8%, n = 116), and muscle pain (39.6%, n = 78). Similarly, 30% (n = 59) and 20.8% (n = 41) of the HCWs reported the loss of smell and loss of taste long after their COVID-19 infection, respectively. Some HCWs (42%, n = 83) believed that their work performance has been affected by their ongoing symptoms of PCC. There was no significant difference in the prevalence of PCC among the vaccinated and unvaccinated HCWs (p > 0.05). Of the socio-demographic variables, age (older HCWs between 45–54 years; OR:1.7; 95% CI: 1.06, 10.59; p = 0.001) and location (Egypt; OR:14.57; 95% CI: 2.62, 26.76; p = 0.001) were more likely to have experienced PCC than other age groups and countries respectively. The study revealed a low prevalence of PCC among the surveyed HCWs. In addition, it observed the need for adequate medical and psychological support to HCWs with PCC and improved mass advocacy campaigns on PCC