The purpose of this study was twofold: (1) to investigate the nature and degree of water loss at 21°C, 60% relative humidity (dehydration) and at 105°C (desiccation), and to relate these findings with (2) the strains produced in the dentine structure during dehydration and rehydration processes. In stage 1, digital moiré interferometry (DMI) was used to study the strain distribution pattern during dehydration and rehydration at 21°C. In stage 2, the nature and degree of water loss was determined using gravimetric analysis and nuclear magnetic resonance spectroscopy. DMI showed that dehydration produced strains in the dentine structure after an initial latent period. Gravimetric analysis showed that dentine exhibited an initial rapid water-loss phase followed by a slow and steady water-loss phase. Though the major portion of water loss occurred in the initial 2 h of dehydration (rapid water-loss phase), no obvious strains were produced during this period. Rehydration lead to the major reversal of dehydration-induced water loss and strains in dentine. Heating at 105°C resulted in further substantial loss of water from dentine. These experiments highlighted that the free water in the dentine surface, porosities and tubules are lost rapidly and constitute the major water lost when dehydrated at 21°C.
The aim of this study was two fold: (1) to investigate the nature and degree of water loss at 21°C (dehydration) and relate these findings with (2) strains produced in dentine structure during water loss and regain. The nature and degree of water loss was investigated using Nuclear-Magnetic Resonance Spectroscopy and gravimetric analysis. Digital Moire Interferometry (DMI) was used to study the patterns of strain distribution during water-loss (dehydration) and water-regain (rehydration) at 21°C. The gravimetric analysis showed that dentine exhibited a biphasic response in water-loss. An initial rapid phase followed by a gradual and steady phase. DMI showed that dehydration induced strains were formed within dentine in three phases. These experiments highlighted that the major portion of free water from dentine was lost rapidly from the surface and the dentinal tubules, as soon as they are exposed to 21°C (55% RH). DMI showed that dehydration produced strains in the dentine structure after an initial latent period. Rehydration caused almost complete reversal of the dehydration induced water-loss and strains.
The purpose of this study is to monitor structural response in intact teeth and teeth with structural loss using a noninvasive fiber optic microbend (FOMB) sensor. In this study a miniature fiber optic microbend sensor is fabricated and tested on intact tooth specimens, tooth specimens in which one-third crown structure was removed, tooth specimens in which access cavity was prepared and tooth specimens in which access cavity and root canal were prepared. The microbend sensor displayed a direct relationship between the applied load and the output light intensity. The rate of change in light intensity with increase in loads corresponded with the structural response of the tooth. This experiment highlights the potential of FOMB sensor technology to quantitatively monitor tooth structural loss during post endodontic restorations.