Specimens from the four dental examination glove types investigated (Microtouch latex, Microtouch nitrile, Nitratouch nitrile and Safeskin nitrile) of 12 cm length and 1.5 cm breadth were removed from the sections marked in . Both sides of the glove were used and smooth edges were ensured using a razor blade and scalpel. The apparatus, identified in was used to clamp both ends of the glove specimen to an Instron tensile testing machine (Instron Model 5544, Buckinghamshire, England). The upper push fit bracket screwed into the moving arm of the machine and the lower push fit bracket was clamped to the base plate. The glove specimen was held to the upper and lower bracket using a steel bar, such that 1 cm of each end was fixed to the bracket using a push fit mechanism. The tensile testing machine cross-head speed was fixed at 100 mm min-1 and the gauge length, namely the distance between the brackets, was set to 10 cm. The force required to elongate the specimen by 10 cm (100% of the original length) was recorded and the modulus at this point, known as M100 was calculated. M100 was evaluated using Equation 1 from BS 903-A2: 1995 for the physical testing of rubber.
The GLM univariate method of analysis was used at the 95% significance level to compare all data obtained using dental injection needles as the pentrometer. The analysis technique reported an overall increase in the puncture resistance of dental examination gloves when aged ( = 0.004). When considering all aged and non-aged data, each glove type was assessed to be significantly different ( tests highlighting three homogenous subsets containing statistically similar groups (; ). The first group included specimens from the palm region only, the second group included the little, ring and index finger regions as well as the thumb region with the final subset or group comprising specimens from the middle and ring finger regions ().
The dental examination glove samples were also aged to investigate whether puncture resistance varied with aging in an attempt to mimic the clinical situation more closely. Aging was carried out according to ISO 188, at 70°C for 7 days in an air-circulating oven prior to testing. The puncture resistance experiments outlined above were repeated using both the steel puncture probe and the sterile dental injection needles as the pentrometer.
In the current study, when the steel puncture probe was used, each glove region was assessed to be equally puncture resistant. However differences were observed when the dental injection needle was used as a pentrometer. As outlined in , the palm regions were evaluated to have a significantly lower puncture resistance followed by the little, ring and index finger regions and the thumb region. The index and middle finger regions were assessed to have a significantly higher puncture resistance than the other regions. However, this may be less relevant in the dental surgery since clinically the fingers come most into contact with sharp instruments that may cause punctures. Murray . suggested that punctures in used dental examination gloves occurred principally in the upper portions of fingers and along the whole length of the thumb. The findings of the current study suggest that the index and middle finger regions were the most puncture resistant, however, as previously reported these regions, along with the thumb region, were assessed to be the most common location for punctures.