Melbourne Dental School - Theses
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ItemThe effects of Nd:YAG laser irradiation on pressure transmission through dentine: in vitro( [1999])Even though laser applications for both soft and hard oral tissues have been investigated for a period of time, lasers have not been routinely used in restorative dentistry. It has been well documented that with adequate energy density of laser radiation, both dental hard and pulp tissues can be affected. Most previous studies have shown histological effects on enamel, dentine, or pulp tissues. Moreover, the studies revealed that laser irradiation may cause undesirable changes in pulpal tissues due to an increase in pulpal temperature and it has been hypothesised that this would result in an irreversible pulpitis or pulpal necrosis (Abt et al., 1992; von Fraunhofer and Allen, 1993). Other studies (Myers and Myers, 1985; White et al., 1993) have showed that laser treatment of enamel and dentine could be achieved without a significant increase in pulpal temperature. The effectiveness of the Nd:YAG laser, with its fiberoptic delivery system and pulsed emission, has been investigated and used in dentistry such as for removing caries, and reducing dentine hypersensitivity (Myers and Myers, 1985; Renton-Harper and Midda, 1992). However the effects of laser irradiation on pulpal pressure has not been investigated. Besides the importance of pulpal temperature, pulpal pressure is also a characteristic of pulpal physiology and can play a role in pulpal inflammation (Kim, 1990). Laser irradiation might influence the pulpal pressure. Thus, the purpose of this study was to investigate (in the laboratory) the effects of laser irradiation on pulpal pressure during lasing of dentine, and compare it with the effects of a high-speed dental handpiece with a diamond bur.
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ItemThe effects of tooth preparation on intrapulpal pressure: a laboratory study( 1998)The objective of this study was to determine intrapulpal pressure changes during tooth preparation with either diamond or tungsten carbide burs in a dental highspeed handpiece, in the laboratory. Twenty premolar teeth were collected and randomly assigned to two groups. Group 1 received preparation with diamond burs, Group 2 with tungsten carbide burs. The teeth were mounted on a pressure transducer and the pulp chambers filled with saline. A thickness of 0.1 mm of tooth tissue was removed from the proximal surface of each tooth, alternating dry and wet-cutting, until the pulp chamber was exposed. Pressure and temperature changes were recorded during tooth preparation. At the 0 - 1 mm depth of remaining dentine level, dry cutting with diamond and tungsten carbide burs generated a mean positive pulpal pressure of 11.64 kPa and 6.06 kPa respectively. Wet cutting under the same conditions produced 0.58 kPa and 0.15 kPa respectively. The difference between wet and dry cutting was highly significant (p<0.001). Diamond burs produced significantly higher pressure increases than carbide burs, at all levels, for both wet and dry techniques (p<0.05). When cutting greater than 2 mm from the pulp, tooth preparation created an average 0.09 kPa pressure increase, which was not influenced by either coolant use or bur type. The temperature change was minimal during wet cutting and only minor temperature increases were recorded during dry cutting. It is concluded that significant pressure changes occur in the pulp chamber during tooth preparation when the remaining dentine thickness is less than 2 mm.