Minimally invasive caries removal using bio-active glass air-abrasion.

OBJECTIVES: Alumina air-abrasion has been used to clean teeth and shown to over-prepare access cavity preparation to caries. This study investigated the working hypothesis that bio-active glass air-abrasion is more self-limiting than alumina for minimally invasive caries removal. METHODS: Human extracted molars were scored visually using ICDAS II criteria, divided into sound and carious groups and air-abraded with alumina (n=10) and bio-active glass (n=10) in each group, using identical operating parameters. The amount of enamel removed was semi-quantitatively assessed using scanning electron microscopy. Operating time was recorded. RESULTS: Bio-active glass abrasion removed extrinsic stain and substantial quantities of enamel from all carious fissures but not from sound, where only minimal microscopic surface modifications were observed. Alumina air-abrasion resulted in faster extrinsic stain and clinically substantial enamel removal in both sound and carious groups equally. CONCLUSIONS: Bio-active glass air-abrasion appeared to show a significant self-limiting tendency towards demineralised enamel and extrinsic stain removal but was slower in comparison to alumina air-abrasion. Self-limiting bio-active glass air-abrasion could be used clinically to clean teeth, detect caries and minimally prepare carious enamel as part of MI caries access or placing a sealant restoration.

An in vitro investigation of the effect and retention of bioactive glass air-abrasive on sound and carious dentine.

OBJECTIVES: To examine the removal rate of sound and carious dentine using bioactive glass air-abrasion and investigate abrasive particle retention of alumina and bioactive glass on abraded dentine. METHODS: Crushed bioactive glass was investigated as an alternative air-abrasive to alumina at air pressures of 138, 413 and 689 kPa in the presence or absence of water. The correlation coefficient between the amount of dentine removed using bioactive glass air-abrasion and the Knoop Hardness Number of dentine was calculated. The comparative retention of bioactive glass (BG) and alumina (AL) abrasive on human dentine blocks were calculated as atomic ratios acquired by spectral analysis between air-abrasive tracers (Si for bioactive glass, and Al for alumina) and Ca. A total of 60 dentine blocks were abraded using Al or BG in 12 groups of 5 using three different pressures in using wet and dry air-abrasion. RESULTS: The amount of dentine removed using bioactive glass air-abrasion had a Somers'D coefficient of 0.65 for the Knoop hardness. Wet air-abrasion caused a significant (p 0.05) decrease in the amount of abrasive retained on the surface for Al air-abrasion at 138 and 413 kPa and BG air-abrasion at 413 and 689 kPa. CONCLUSION: There was a negative correlation between propellant pressure and abrasive retained. Bioglass removed healthy dentine at a higher rate than carious dentine - the difference however, being less than with equivalent alumina air-abrasion, thus making it a potentially more selective instrument for clinical caries excavation.

The effects of surface machining on heat cured acrylic resin and two soft denture base materials: a scanning electron microscope and confocal microscope evaluation.

STATEMENT OF PROBLEM: Rough surfaces promote the adhesion and colonization of denture plaque, therefore it is important to know the character of the surface left by rotary instruments on denture base materials. As a single microscopic technique can introduce artifact, complementary microscope techniques need to be used. PURPOSE: This study investigated the surface characteristics of the machined surfaces of heat-cured acrylic resin, Molloplast B and Novus. MATERIAL AND METHODS: Scanning electron microscopy and confocal microscopy were used to investigate surfaces that had been prepared with appropriate clinical rotary instruments. Thirty samples of each material were prepared with steel and tungsten carbide burs, Molloplast stones, and Arbor bands. An analysis of variance, with the Scheffe multiple comparison of means test, was used to compare average surface roughness of the individual surfaces. RESULTS: The tungsten carbide bur produced a smoother nongrooved surface than the steel bur on acrylic resin. The roughest surfaces were produced on the soft lining materials by the Arbor band and Molloplast stone. CONCLUSIONS: The confocal microscope is a valuable complementary instrument to scanning electron microscopy and provides surface roughness data by using a noncontact method. Each type of rotary instrument produces its own characteristic surface on denture base materials.

Determining the dental origins of foreign bodies in foodstuffs: applications of a new microscopic technique.

The use of confocal optical microscopes is reported as a method for histologically identifying foreign bodies, alleged to be of dental origin, found in foodstuffs. This technique offers the advantages of allowing rapid evaluation of a sample, without causing its destruction due to the production of thin sections which are normally required for conventional histology. The system has been used to identify fragments of dental origin, allegedly found by customers in foodstuffs which are marketed by a major retail chain.

Field accumulation of aflatoxin in cottonseed as influenced by irrigation termination dates and pink bollworm infestation.

Aflatoxin accumulation in Deltapine 16 cottonseed, grown in Yuma, Ariz., in a 3-year study, was significantly influenced by the timing of irrigation terminations and by level of pink bollworm infestations. In 1971 and 1972, termination of irrigations by early August resulted in significantly less aflatoxin than in plots where two additional irrigations were applied. Significantly less aflatoxin also was found in the 1971 and 1973 plots where low levels of pink bollworm infestations were maintained.