R J Rossouw’s research while affiliated with University of the Western Cape and other places

Tooth bleaching (whitening) is one of the most common and inexpensive method for treating discolouration of teeth. Dental aesthetics, especially tooth colour, is of great importance to majority of the people; and discolouration of even a single tooth can negatively influence the quality of life. Therefore, a review of the literature was carried out (limited to aesthetic tooth-bleaching) to provide a broad overview of the efficacy and adverse effects of various tooth whitening products on soft and hard oral tissues.

To clinically evaluate the effectiveness of Nite White 10% carbamide peroxide with amorphous calcium phosphate, potassium nitrate and fluoride over a 6-month follow-up period. Nite White was applied nightly for 14 days, according to the manufacturer’s instructions. The color of teeth 11 and 21 of twenty one subjects was measured with a spectrophotometer (L*; a*; b*). Subjects were instructed to take note of any tooth sensitivity and gingival irritation. For all three components (L*, a* and b*) statistical significant differences (p<0.05) in the values between base-line (pre-bleaching) and; after treatment, after 1-month, after 3-months as well as after 6-months were found (Wilcoxon Signed Rank Sum Test). Significant differences were also found amongst the ΔE*ab (0-14days) values and; ΔE*ab (0-1 month), ΔE*ab (0-3 months) and ΔE*ab (0-6 months). However, no significant differences were found between pairs of ΔE*ab (0-1 month), ΔE*ab (0-3 months) and ΔE*ab (0-6months). The decrease in ΔE*ab was the highest after 1 month (~30%). The highest decrease in L* was about 58% after 1 month. Over the 14-day treatment period tooth sensitivity was 24.5%. Conclusions: Nite White ACP demonstrated significant tooth-whitening (unit increase = 5.29) with a low tooth sensitivity (25%) probably due to the presence of amorphous calcium phosphate, potassium nitrate, and fluoride. The whitening effect decreased the most after one month and then maintained well even after a 6 month period (units 3.89). Clinical implications The product is a good tooth whitener with a color increase of about 5 units accompanied with a low sensitivity.

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.

Bruxism is the oral parafunctional habit of clenching and grinding the teeth. It occurs mainly unconsciously, diurnally and/or nocturnally. It is considered an important contributory factor in the aetiology of myofascial pain and temporomandibular joint disorders and derangements. The aetiology of bruxism is considered to be multifactorial, involving both physiological and psychological factors. The aim of the study was to examine the relationship between the sub-threshold symptoms of anxiety and bruxism, using a spectrum model. Firstly, levels of anxiety were determined using the Spielberger State Trait Anxiety Inventory (STAI) and the Kessler-10 (K-10). Secondly, a tooth-wear score was determined by means of a clinical examination and dental casts. Thirdly, bruxism was rated on an ordinal scale according to specified criteria. A dualistic trend in the relationship between sub-threshold symptoms of anxiety and bruxism was observed in the results. In approximately half of the subjects with higher than average anxiety scores, bruxistic behaviour was found. This indicates the possibility of two groups with separate relationships. The dentist could play a role in recognizing that a patient may be experiencing anxiety, expressed through bruxism behaviour, and refer the patient for therapy or counselling. An understanding of the psychological factors involved in the aetiology of bruxism could foster a more holistic approach to the treatment of patients with signs of bruxism.

This field study included the whole population of children aged 10-15 years (77 from a 0.19 mg/L F area; 89 from a 3.00 mg/L F area), with similar nutritional, dietary habits and similar ethnic and socioeconomic status. The fluoride concentration in the drinking water, the bone mineral content, the bone density and the degree of dental fluorosis were determined. The left radius was measured for bone width, bone mineral content, and bone mineral density. The mean fluorosis score was 1.3 in the low fluoride area and 3,6 in the high fluoride area. More than half the children in the low fluoride area had no fluorosis (scores 0 and 1) while only 5% in the high fluoride area had none. Severe fluorosis (30%) was only observed in the high fluoride area. The Wilcoxon Rank Sum Test indicated that fluorosis levels differed significantly (p < 0.05) between the two areas. No relationships were found between dental fluorosis and bone width or between fluorosis and bone mineral density in the two areas (Spearment Rank correlations). A significant increase in bone width was found with age but no differences amongst and boys and girls. A significant positive correlation was found in the high fluoride area between bone mineral density over age. In the 12-13 and 13-14 year age groups in the high fluoride area, girls had higher bone mineral densities. However, a significant negative correlation (p<0.02) was found for the low fluoride area (0.19 mg/L F) over age.

The purpose was to evaluate the effect of various Opalescence tooth-whitening products on enamel. 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. 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). 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).

This study investigated the microleakage, etching ability, and dentin-restorative interface of 2 different single-step self-etching bonding agents with compomers as restoratives. Fifteen extracted noncarious human premolars were used for each dental material system. The bonding agent Xeno III was used with their compomer Dyract AP (Dentsply) and Adper Prompt L-Pop with their compomer Z2000 (3M Espe). Cylindrical cavities were prepared in enamel and dentin on the buccal surface at the cementoenamel junction and restored. The specimens were thermocycled and cut into slices, and the depth of dye penetration scored. The dentine-restorative interface was examined through a confocal scanning laser microscope. Microleakages between the enamel and dentin sides differed significantly for Xeno (Wilcoxon rank sum test; P = .0058) as well as for Prompt (P = .0106), while the microleakages between the dentin sides of Xeno and Prompt did not differ significantly. However, between the enamel sides, a significant difference was found (P = .000), with the highest value for Prompt. The confocal laser studies showed tag formation, penetration of the bonding agents deep into the tubules, and hybrid layer formation for both bonding agents. It can be concluded that both adhesives gave microleakage values for dentin that are on the lower side. However, careful inspection of the enamel side indicated that both cannot be recommended for enamel sealing.

Unlabelled: This study compared the microleakages in enamel and dentine of newly developed bonding systems from different manufacturers. Fifteen or more extracted non-carious human premolars were used for each dental material system. The bonding systems were used with their respective composites. Cylindrical cavities were prepared in enamel (scored as a separate entity 0-3) and cementum/dentine (scored 0-4) on the buccal surface at the cemento-enamel junction and restored. The specimens were thermocycled, cut into slices and the depth of dye penetration scored. For enamel, the microleakage values of Clearfil Protect Bond (CPB; median = 1.0) and Xeno III (2.3) did not differ statistically (p > 0.05, Chi-square test), while the microleakage of CPB (1.0) was significantly better than that of GC Unifil Bond (GC; 3.0), Prime & Bond XP (P & B; 3.0) and Adper Prompt L-Pop (APL; 3.0), p < 0.05. At the cementum/dentine side significantly (p < 0.05) more microleakage for CPB (2.0) was found than for GC (0.0), P&B (0.5), APL (0.5), and Xeno III (0.5). Conclusion: Enamel was most effectively sealed by CPB and cementum/dentine by GC, P&B, APL and Xeno III. The chemical composition perse did not seem to determine the amount and location of microleakage.

Saliva contamination is a major clinical problem during restorative dental treatment. Restorative systems must possess sufficient marginal sealing ability to avoid microleakage. The purpose of this study was to investigate the effect of saliva contamination on the microleakage of cavities restored with Prime & Bond NT and Dyract-AP. Cavities were prepared with occlusal margins in enamel and gingival margins in dentine on the buccal surfaces of extracted human permanent premolar teeth. The cavities were etched with phosphoric acid or a non rinse conditioner (NRC). Preparations were distributed randomly into 4 treatment groups (N = 18) consisting of two respective etching methods (phosphoric acid/NRC), each with and without saliva contamination. After the restorative process the samples were thermocycled in dye, sectioned, and scored for microleakage. Contamination with saliva had no significant effect on microleakage on the enamel or dentine sides where phosphoric acid was used as conditioner. Where NRC was used, significantly more microleakage was observed at the enamel sides, but significantly less at the dentine sides.

Polymerisation shrinkage is a critical limitation of dental resins and may contribute to micro leakage. The purpose of this study is to record and compare volumetric changes of various dental composites and compomers, exposed for 40 seconds to a commercial halogen light source. Eleven light-polymerised composites and compomers were evaluated using a dilatometer that recorded the polymerisation shrinkage every 0.5 second. The mercury column pressure was measured electronically with a pressure-sensitive transducer, and the data recorded and stored in a computer. The computer also recorded the temperature, controlled the light-source and displayed the data in graphic format. Every material was tested ten times. The data were analysed by means of an ANOVA (P < 0.05). A high rate of shrinkage occurred for all materials in the first ten seconds of polymerisation. Surefil showed the lowest rate while TPH displayed the highest. Of the higher filled materials, Surefil (0.96%) showed the least shrinkage, followed by Z250 (0.99%), Dyract AP (1.18%), Herculite (1.27%), Compoglass (1.32%), Amelogen (1.34%) and TPH-Spectrum (1.6%). Overall, the flowable materials exhibited significantly more shrinkage (P < 0.05). For this group Compoglass Flow (2.3%) showed the least shrinkage followed by Filtec Flow (2.31%). Permaflo (3.6%) exhibited the most shrinkage followed by Dyract Flow (3%). Within the limitations of this study, it is concluded that significant differences exist among the polymerisation shrinkage of the most resins tested. An increase in the filler content of a material significantly lessens the polymerisation shrinkage while an increase in the monomer concentration causes significantly more polymerisation shrinkage. The more flowable a composite material becomes, the more the restoration will shrink. Clinicians should take this into account when they decide on cavity design and materials to use.