A DFT and molecular docking study of xerantholide and its interaction with Neisseria gonorrhoeae carbonic anhydrase.

Xerantholide is a sesquiterpene lactone that has anti-gonorrhea and anti-plasmodium activities. We present gas-phase electronic structure calculations of the equilibrium geometry of xerantholide, its adiabatic electron affinity (AEA), adiabatic ionization energy (AIE) and the energy barrier (ΔE‡) connecting the lowest energy conformers of the sesquiterpene. The computations were performed with the B3LYP, M06-2X and ωB97xd variants of the density functional theory (DFT) in conjunction with large basis sets. With the inclusion of the vibrational zero point energy, the computed AEA range from 0.740 eV [B3LYP/Aug-CC-pVTZ] to 0.774 eV [B3LYP/6-311++G(d,p)], and the AIE is roughly 8.6 eV at all theoretical levels. At the B3LYP/Aug-CC-pVTZ level, the barrier (ΔE‡) connecting the two lowest energy conformers is predicted to be 13.9 kcal/mol. Based on the molecular docking analysis, xerantholide interacts with the active site of Neisseria gonorrhoeae carbonic anhydrase (NgCA) via hydrogen bonding, metal-acceptor interaction, and non-polar alkyl and pi-alkyl interactions. The predicted binding affinity of - 6.8 kcal/mol compares well with those obtained for standard NgCA inhibitors such as acetazolamide (-5.7 kcal/mol). A biomimetic model study involving xerantholide and zinc-tris imidazole ([ZnIm3]2+) ion was also carried out at different theoretical levels to estimate the interaction energy for the formation of the complex formed between the ligand and the active site model of NgCA. The binding free energy (ΔG) has been calculated to be - 28.5 kcal/mol at the B3LYP/6-311++G(d,p) level. The interaction mode observed in both the docking and the model calculations involves the lactone ring.

Oral hygiene in Namibia: A case of chewing sticks.

ETHNOPHARMACOLOGICAL RELEVANCE: Chewing sticks have served as the primary form of dental care for rural communities in resource-poor settings for millennia. They are one of the most important under-researched, non-timber forest products in Namibia. This review provides an overview of plants that are used as chewing sticks in Namibia and highlights pharmacological as well as phytochemical studies conducted on them. AIM OF THE STUDY: This review aims to present a summary of studies that have been done on the ethnomedicinal uses, phytochemistry, biological activity as well as evidence on the scientific validation and geographical distribution of chewing sticks in Namibia. It also highlights research gaps and provides an impetus for the scientific investigations of these plant species. MATERIAL AND METHODS: Literature searches using keywords including oral hygiene, chewing sticks, ethnomedicinal uses, phytochemistry, antimicrobial, antioxidants, anti-inflammatory activities and toxicity studies, chewing sticks, and distribution in Namibia on various electronic search engines was conducted. RESULTS: Of the 41 plant species identified, Cordia sinensis Lam., Faidherbia albida (Delile) A.Chev. and Harpagophytum zeyheri Decne. are used for both gargling and as mouthwash. The plant families Fabacae, Ebenaceae, and Burseraceae account for 22.0%, 12.2%, and 7.30% of plant species recorded as chewing sticks in Namibia respectively. This study revealed a significant relationship between plant family and scientific validation. Species belonging to Burseraceae, Apocynaceae, Montiniaceae, and Cucurbitaceae families have only been partially validated. The Kunene region, home to the Ovahimba ethnic group, had the highest proportion (87.8%) of chewing sticks species compared to other regions. CONCLUSION: This review revealed that most of the plants used as chewing sticks in Namibia require an in-depth pharmacological and phytochemical investigation as deduced from the paucity of literature on the therapeutic methods, mechanisms of action, efficacy, toxicity, and clinical relevance of these species.

In vitro evaluation of variances between real and declared concentration of hydrogen peroxide in various tooth-whitening products.

OBJECTIVES: The aim of this in vitro study was to analyze the real hydrogen peroxide (HP) concentration in various commercially available tooth-whitening products containing HP and/or carbamide peroxide (CP). MATERIALS AND METHODS: Sixteen commercially available tooth-whitening products containing various concentrations of CP or HP were investigated. The products were divided into four groups: dentist-supervised home bleaching products (Group 1, n = 5), in-office bleaching products (Group 2, n = 4), over-the-counter bleaching products (Group 3, n = 3) and whitening toothpastes and rinses (Group 4, n = 4). The peroxide concentration was determined using the oxy-reduction titration method. All the reagents used in the study were of analytic grade and freshly prepared before the experiment. RESULTS: The HP concentration in various dentist-supervised home bleaching products and in-office bleaching products ranged from 3.02-37.08% (expected range = 3-38%). The HP concentration of over-the-counter whitening products ranged from 1.24-5.57% (expected range cannot be estimated as no concentration of active ingredient was provided). Among whitening toothpastes and rinses, Colgate Plax whitening rinse showed more than 1% HP concentration, whereas it was lower than 0.05% in other whitening toothpastes and oral rinses (expected range cannot be estimated as no active ingredient was mentioned). CONCLUSIONS: HP concentration of most of the professional tooth-whitening products was different from the expected concentrations, although the deviations were small and most of the products were close to the expected concentration. No concentration of active ingredient was provided for over-the-counter whitening products and no active ingredient was mentioned for whitening toothpastes and rinses.

A clinical study of the effectiveness of two different 10% carbamide peroxide bleaching products: a 6-month followup.

The purpose of this study was to evaluate the efficacy of two different 10% carbamide peroxide bleaching products just after treatment and after a 6-month follow-up period. Methods. Two 10% carbamide peroxide products (Opalescence PF and Nite White ACP) were applied nightly for 14 days, according to the manufacturers' instructions. The color of teeth 11 and 21 of thirty-four subjects having A2 or darker teeth were measured with a spectrophotometer (L(∗); a(∗); b(∗)) before treatment, just after treatment (14 days) and after 6 months. Results and Conclusions. Both products produced significant whitening of teeth with total color change (ΔE(ab) (∗)) of approximately 5.20 units. There was a significant improvement in all 3 color coordinates (L*, a*, and b(∗)) for up to 6 months postbleaching (P < .05). Nite White showed a higher degree of relapse (27%) than Opalescence (18%) over the 6-month period. It is suggested that rebleaching after 6 months is not necessary.

Effect of four over-the-counter tooth-whitening products on enamel microhardness.

OBJECTIVES: This in vitro study evaluated the effect of four over-the-counter tooth-whitening products on enamel microhardness. METHODS: Fifty enamel blocks were prepared from extracted human molar teeth. The enamel surfaces were polished up to 1200 grit fineness and the specimens randomly divided into five groups. Enamel blocks were exposed to: Rapid White (n=10); Absolute White (n=10); Speed White (n=10) and White Glo (n=10) whitening products, according to the manufacturers' instructions. As control, ten enamel blocks were kept in artificial saliva at 37 degrees C without any treatment. Microhardness values were obtained before exposure (baseline) and after 1, 7 and 14-day treatment periods using a digital hardness tester with a Vickers diamond indenter. Data were analysed using Wilcoxon Signed Rank Sum Test, one-way ANOVA and Tukey-Kramer Multiple Comparison Test (p<0.05). RESULTS: Both Rapid White and Absolute White reduced enamel microhardness. Speed White increased the microhardness of enamel, while White Glo and artificial saliva had no effect on hardness. CONCLUSIONS: Over-the-counter tooth-whitening products might decrease enamel microhardness depending on the type of product.

The pH of various tooth-whitening products on the South African market.

OBJECTIVES: The purpose of this in vitro study was to investigate the pH of 21 commercially available tooth-whitening products. METHODS: Tooth-whitening products were divided into four categories: dentist supervised-home bleaching products (n = 5); in-office bleaching products (n = 5); over-the-counter bleaching products (n = 4) and whitening toothpastes and rinses (n = 7). The pH of three samples of each product was measured using an Orion Expandable Ion Analyzer EA940 with a Sure-Flow, Epoxy-body combination pH electrode. The group data were analysed using one way ANOVA (significant at p < 0.05). RESULTS: The five dentist supervised-home bleaching products had a mean pH of 6.21 +/- 0.76 and ranged from 4.88 to 6.81. The five in-office bleaching products had a mean pH of 6.26 +/- 1.19 and ranged from 5.30 to 7.85. The four over-the-counter whitening products had a mean pH of 5.07 +/- 1.74 and ranged from 3.76 to 8.03 and the seven whitening toothpastes had a mean pH of 7.66 +/- 1.19 and ranged from 6.61 to 9.68. The pH of the over-the-counter category was significantly lower (more acidic) than all other categories (p < 0.05). The whitening gel of Rapid-White had the lowest acidic pH of 3.76 and Colgate Advanced Whitening toothpaste showed the highest alkaline pH of 9.68. CONCLUSIONS: The pH of all tooth-whitening products showed a wide range from 3.76 (highly acidic) to 9.68 (highly alkaline). Over-the-counter whitening products showed the lowest pH levels and in general these can be expected to damage enamel more than the other products. Dentists should be vigilant with regards to products used outside their surgeries and should warn their patients accordingly. CLINICAL IMPLICATIONS: The acidic pH of many of the whitening products other than in-office bleaching products is of concern and the general public should be better informed by the dental professionals of the dangers of these products.

Spectrophotometric assessment of the effectiveness of Opalescence PF 10%: a 14-month clinical study.

OBJECTIVES: To evaluate the effectiveness of Opalescence PF 10% just after treatment, at 6-month follow-up and at a 14-month follow-up period. METHODS: Opalescence PF 10% was applied nightly for 14 days. The color of teeth 11 and 21 of 17 subjects were measured with a spectrophotometer (L*; a*; b*) before treatment, just after treatment (14 days), after 6 months and after 14 months. Subjects were instructed to take note of any tooth sensitivity. RESULTS: For all three components (L*, a* and b*) statistical significant differences (p<0.05) in the values between base-line, after treatment (14 days later), after 6 months and after 14 months were found (Wilcoxon Signed Rank Sum Test). The decrease in L* was about 20% after 6 months and about 50% after 14 months. The a* value decreased approximately 14% after 6 months but was worse after 14 months than at the beginning. The b* value decreased the least with about 9% after 6 months and about 8% after 14 months. The decrease in DeltaE(ab)(*) was approximately 20% after 14 months. Less than 20% of the subjects experienced mild tooth sensitivity just after treatment. CONCLUSION: Significantly whiter teeth were found after treatment as well as after a 6-month follow-up period. The whiteness/brightness (L*) decreased with approximately 50% after 14 months and the a* value with approximately 50% after 7 months, while the yellowness (b* value) remained even after 14 months. CLINICAL IMPLICATIONS: The product is an effective tooth whitener resulting in only low tooth sensitivity. Re-bleaching could be done at about 14 months.

Effect of various tooth-whitening products on enamel microhardness.

OBJECTIVES: The purpose of this in vitro study was to evaluate the effect of various tooth-whitening products containing carbamide peroxide (CP) or hydrogen peroxide (HP), on enamel microhardness. METHODS: Enamel blocks were exposed to: Nite White ACP 10% CP (Group 2, n=10); Yotuel Patient 10% CP (Group 3, n=10); Opalescence PF 10% CP (Group 4, n=10); Opalescence PF 20% CP (Group 5, n=10); Opalescence Treswhite Supreme 10% HP (Group 6, n=10); Yotuel 10 Minutes 30% CP (Group 7, n=10); Opalescence Quick 45% CP (Group 8, n=10), Yotuel Special 35% HP (Group 9, n=10), Opalescence Boost 38% HP (Group 10, n=10) according to the instructions of the manufacturers. The control (Group 1, n=10) was enamel blocks kept in artificial saliva at 37 degrees C without any treatment. The microhardness values were obtained before exposure and after a 14-day treatment period. Specimens were kept in artificial saliva at 37 degrees C between treatments. Data were analysed using Kruskal-Wallis one-way ANOVA and Tukey-Kramer Multiple Comparison Test. Indent marks on the enamel blocks were also examined under the Scanning Electron Microscope. RESULTS: All whitening products decreased enamel microhardness except group 10 but only Groups 2, 3, 4, 5 and 7 showed significant decrease in enamel microhardness as compared to the control group (p < 0.05). Groups 2, 3 and 7 differed significantly from all the other groups (p < 0.05). The highest damage was recorded for Group 2 (Nite White ACP 10% CP), which differed significantly from Groups 3 and 7. SEM images also showed damage to enamel. CONCLUSIONS: All products tested in this study decreased enamel microhardness except Opalescence Boost 38% HP. The products containing carbamide peroxide were more damaging to enamel because of the longer application times. Nite White ACP 10% CP showed the highest reduction in enamel microhardness as compared to other products tested.

Effect of four different opalescence tooth-whitening products on enamel microhardness.

OBJECTIVES: The purpose was to evaluate the effect of various Opalescence tooth-whitening products on enamel. METHODS AND MATERIALS: Enamel blocks were exposed to Opalescence PF 10% Carbamide Peroxide (n = 10), Opalescence PF 20% Carbamide Peroxide (n = 10), Opalescence Trèswhite Supreme 10% Hydrogen Peroxide (n = 10) and Opalescence Quick PF 45% Carbamide Peroxide (n = 10) according to the manufacturer's instructions. The control group was enamel blocks (n = 10) kept in artificial saliva. The values were obtained before exposure and after the 14-days treatment period. Enamel blocks were kept in saliva between treatments. Indent marks on enamel blocks were examined using the scanning electron microscope for treatment effects. RESULTS: All four different Opalescence products damaged enamel. The most damage was done when treated for a long period (112 hours). SEM images also showed damage to enamel by all 4 products. Opalescence with 10% and with 20% Carbamide Peroxide showed the highest damage, which also differed significantly (p < 0.05) from the saliva control group (p < 0.05; Tukey-Kramer Multiple comparison test). CONCLUSION: All 4 Opalescence products damaged enamel. Higher damage was done by the 10% carbamide peroxide and 20% carbamide peroxide products because of the much longer exposure period (112 hours in comparison to 7 hours).

Quality assurance, benchmarking, assessment and mutual international recognition of qualifications.

The aim of this report is to provide guidance to assist in the international convergence of quality assurance, benchmarking and assessment systems to improve dental education. Proposals are developed for mutual recognition of qualifications, to aid international movement and exchange of staff and students including and supporting developing countries. Quality assurance is the responsibility of all staff involved in dental education and involves three levels: internal, institutional and external. Benchmarking information provides a subject framework. Benchmarks are useful for a variety of purposes including design and validation of programmes, examination and review; they can also strengthen the accreditation process undertaken by professional and statutory bodies. Benchmark information can be used by institutions as part of their programme approval process, to set degree standards. The standards should be developed by the dental academic community through formal groups of experts. Assessment outcomes of student learning are a measure of the quality of the learning programme. The goal of an effective assessment strategy should be that it provides the starting point for students to adopt a positive approach to effective and competent practice, reflective and lifelong learning. All assessment methods should be evidence based or based upon research. Mutual recognition of professional qualifications means that qualifications gained in one country (the home country) are recognized in another country (the host country). It empowers movement of skilled workers, which can help resolve skills shortages within participating countries. These proposals are not intended to be either exhaustive or prescriptive; they are purely for guidance and derived from the identification of what is perceived to be 'best practice'.

Gender and race distribution of dental graduates (1985-2004) and first year dental students (2000-2005) in South Africa.

This paper, written at the close of a decade of democracy in South Africa, sets out to analyse the demographic profile of dental graduates from 1985-2004 at the five Faculties/Schools of Dentistry in South Africa. A comparison of the profiles for the pre-democracy (1985-1994) and post-apartheid (1995-2004) periods has been made. The demographic profile of first year dental students from 2000-2005 is also presented. From 1985-1994, most dental graduates were male (79%), but this changed substantially from 1995-2004, with females comprising 46% of those graduating. In the pre-democracy period, more than three-quarters of all graduates were White (78%), decreasing to 46% in the post-apartheid period under review. Black graduates increased from 6% to 24% across the two study periods. Amongst the first year dental student intake from 2000-2005, females comprised 57%. There was an almost equal distribution across the White, Black and Asian groups. Dental faculties/schools have made important strides in transforming the demographic profile of their students. The percentage of Black graduates, however, needs to be significantly increased if it is to reflect the national population. Faculties/schools must further ensure that able students from working class background are identified and considered for acceptance into the undergraduate dental programme, and should then be offered the necessary academic and mentoring support to enable success.

Global trends in dental fluorosis from 1980 to 2000: a systematic review.

AIM: To determine trends in fluorosis prevalence at water fluoride levels <0.3, >0.3 to <0.7, and >0.7 to 1.4 ppm from 1980 to 2000. METHODS: A systematic review of 55 published articles identified in a Medline search for peer-reviewed articles on fluorosis published from 1 January 1980 to 31 December 2000. The prevalence recorded with any fluorosis index was pooled and the trends over time were determined in the three water concentration categories. RESULTS: The fluorosis prevalence for the three fluoride categories were 16.7, 27.4 and 32.2 percent, respectively. A 16-fold and a 2-fold increase in fluorosis prevalence compared with reported rates in the 1940s was seen in non-fluoridated (= 0.3 ppm F) and fluoridated (>0.7 to = 1.4 ppm F) areas, respectively. There has been an increase in fluorosis prevalence over time in the three fluoride water concentration categories but linear regression analysis showed that none are significantly different from zero. CONCLUSION: This systematic review concurs with recent reports of an increase in fluorosis prevalence in fluoridated and non-fluoridated communities.

Fluoridation in South Africa.

The issues on fluoridation, fluorosis and fluorides in South Africa have been reported for the last 50 years. Efforts to implement water fluoridation between 1960 and 1980 failed partly due to lack of government action and a strong anti-fluoride lobby. The political change in South Africa since 1994 has given new support from the Ministry of Health for enabling legislation to implement water fluoridation in metropolitan areas where the technical support and some 55 per cent of the population reside. Fluoridation also addresses the equitable distribution of resources and access to a known benefit.

Seroprevalence of hepatitis B surface antibody in South African dental personnel.

Because there are no data available on the seroprevalence of hepatitis B in dental personnel in South Africa, a study was performed to assess the antibody status to hepatitis B surface antigen among 129 dental (preclinical) students and 62 dental hygienists at the Western Cape Dental School of South Africa. A total of 11 dental students and nine hygienists were positive to hepatitis B surface antibody, indicating a seroprevalence of 8.5% and 14.5%, respectively. These results, reported for the first time in dental personnel in South Africa, imply that dental students and hygienists in this part of the world are exposed to a significant risk of contracting hepatitis B.

Prevalence of dental caries in preschool and primary school children in Mamre.

In order to plan and implement a comprehensive dental preventive health programme for the children of Mamre, the prevalence of dental disease was determined for the children attending the preschool and the primary school in the village. The prevalence of dental caries is reported in this article. A high prevalence of caries in the primary dentition was found, 26.4% of all primary teeth present in the under-5.5-year age group, 41.0% of those in the 6-year age group, and 41.4% of those in the 9-year age group being decayed. The prevalence of dental caries in the permanent dentition was low but increased with age: 3.8% of all permanent teeth present in the 6-year age group, 3.7% of those in the 9-year age group, 6.3% of those in the 12-year age group and 7.2% of those in the 14-year age group being decayed.