@article{George2007b,

title = {Photophysical, photochemical, and photobiological characterization of methylene blue formulations for light-activated root canal disinfection},

author = {Saji George and Anil Kishen},

doi = {10.1117/1.2745982},

issn = {1083-3668},

year  = {2007},

date = {2007-01-01},

journal = {Journal of Biomedical Optics},

volume = {12},

issue = {3},

pages = {34029},

abstract = {Tissue-specific modification of treatment strategy is proposed to increase the antimicrobial activity of light-activated therapy (LAT) for root canal disinfection. Methylene blue (MB) dissolved in different formulations: water, 70% glycerol, 70% poly ethylene glycol (PEG), and a mixture of glycerol:ethanol:water (30:20:50) (MIX), is analyzed for photophysical, photochemical, and photobiological characteristics. Aggregation of MB molecules, as evident from monomer to dimer ratio, depends on the molar concentrations of MB, which is significantly higher in water compared to other formulations. MIX-based MB formulation effectively penetrates the dentinal tubules. Although, the affinity of MB for Enterococcus faecalis (gram positive) and Actinomycetes actinomycetemcomitans (gram negative) was found to be high in the water-based formulation, followed by MIX, the MIX-based formulation significantly enhanced the model substrate photooxidation and singlet oxygen generation compared to MB dissolved in other formulations. Finally, the efficacy of LAT is evaluated on biofilms produced by both organisms under in vitro and ex vivo conditions. A dual-stage approach that applies a photosensitization medium and an irradiation medium separately is tested. The MIX-based photosensitization medium in combination with dual-stage approach demonstrates thorough disinfection of the root canal with bacterial biofilms. This method will have potential application for root canal disinfection.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{George2007c,

title = {Effect of tissue fluids on hydrophobicity and adherence of Enterococcus faecalis to dentin},

author = {Saji George and Anil Kishen},

doi = {10.1016/j.joen.2007.07.035},

issn = {0099-2399},

year  = {2007},

date = {2007-01-01},

journal = {Journal of Endodontics},

volume = {33},

issue = {12},

pages = {1421-1425},

abstract = {This in vitro study was carried out to determine (1) the hydrophobicity of selected oral bacteria, (2) the influence of growth media (saliva and serum) and mode of growth (planktonic or biofilm) on the hydrophobicity of Enterococcus faecalis, and (3) the influence of growth media and conditioning fluids on the adherence of E. faecalis to dentin. The ability to bind to a hydrocarbon phase (xylene) was used as an index of relative hydrophobicity of cells. Fluorescent microscopy-based technique was used to assay the bacterial adherence to dentin. Results showed that bacteria involved in the primary stage of oral biofilm formation such as Streptococcus mutans, Fusobacterium nucleatum, and Porphyromonas gingivalis are relatively more hydrophobic than E. faecalis. The hydrophobicity of E. faecalis was significantly increased during starvation and biofilm mode of growth (p .05). The adherence of E. faecalis to dentin was appreciably increased after starvation and when dentin was conditioned with saliva. It was observed that surface conditioning of dentin with saliva and starvation can enhance the adherence of E. faecalis to dentin. The findings from this study indicated that the coronal leakage of saliva and the physiologic state of microbes might play an important role in the adherence and biofilm formation of bacteria to root canal dentin.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2006,

title = {Enterococcus faecalis-mediated biomineralized biofilm formation on root canal dentine in vitro},

author = {A Kishen and S George and R Kumar},

doi = {10.1002/jbm.a.30622},

issn = {1549-3296},

year  = {2006},

date = {2006-01-01},

journal = {Journal of Biomedical Materials Research. Part A},

volume = {77},

issue = {2},

pages = {406-415},

abstract = {Enterococcus faecalis is the most predominant bacteria in teeth with failed root canal therapy and is found to survive harsh conditions prevailing in the root canals of endodontically treated teeth. This study aims to investigate the interaction between E. faecalis and root canal dentine substrate. Towards this end, tooth specimens were prepared and divided into two groups. The tooth specimens in group 1 were incubated with E. faecalis for periods of 2-, 4-, and 6-week intervals and the chemical composition of the biofilm was determined using X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy. The tooth specimens in group 2 were incubated with E. faecalis for a period of 6 weeks and the topography and ultrastructure of the biofilm were examined using scanning electron microscopy (SEM), light microscopy, and laser confocal scanning microscopy. The sediments formed from the bacterial interaction on the dentine (in group 1) were also examined by SEM and FTIR. These experiments highlighted different stages in the interaction of E. faecalis with root canal dentine. Further, a bacterial-induced apatite reprecipitation on mature biofilm was also observed. This ability of E. faecalis to form such calcified biofilm on root canal dentine may be a factor that contributes to their persistence after endodontic treatment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2006b,

title = {Investigations on the dynamics of water in the macrostructural dentine},

author = {Anil Kishen and Adeela Rafique},

doi = {10.1117/1.2360257},

issn = {1083-3668},

year  = {2006},

date = {2006-01-01},

journal = {Journal of Biomedical Optics},

volume = {11},

issue = {5},

pages = {54018},

abstract = {The purpose of this study was twofold: (1) to investigate the nature and degree of water loss at 21 degrees C, 60% relative humidity (dehydration) and at 105 degrees 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 moire interferometry (DMI) was used to study the strain distribution pattern during dehydration and rehydration at 21 degrees 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 degrees 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 degrees C.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{George2005,

title = {The role of environmental changes on monospecies biofilm formation on root canal wall by Enterococcus faecalis},

author = {S George and A Kishen and K P Song},

doi = {10.1097/01.don.0000164855.98346.fc},

issn = {0099-2399},

year  = {2005},

date = {2005-01-01},

journal = {Journal of Endodontics},

volume = {31},

issue = {12},

pages = {867-872},

abstract = {Biofilm mode of growth is a strategy in microorganisms to survive harsh growth conditions. Although previous studies have established the ability of Enterococcus faecalis to survive postendodontic environmental conditions, the effect of such conditions on the ultrastructural and physiochemical features of E. faecalis biofilm has received less attention. This study aims to evaluate the effect of different growth conditions on the characteristics of E. faecalis biofilm on root canal, and the penetration of E. faecalis into dentinal tubules. Forty-five intact noncarious human maxillary molars were experimented under nutrient-rich, nutrient-deprived, aerobic, and anaerobic conditions for a period of 21 days. Scanning Electron Microscopy with Energy Dispersive X-ray microanalysis, Laser Confocal Scanning Microscopy and Light microscopic examinations were carried out. The microscopic analysis highlighted a distinct variation in the ultrastructure of the biofilms formed under different experimental conditions. The EDX microanalysis showed a significant increase in the levels of Calcium (Ca) in the biofilm structures formed under anaerobic nutrient-deprived condition (p 0.001). The depth of bacterial penetration was significantly greater in nutrient-rich condition (p 0.001). This study demonstrated distinct ultrastructural and physiochemical properties of the biofilms formed and dentinal tubular penetration of E. faecalis under different conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2005,

title = {Experimental investigation on the role of water in the mechanical behavior of structural dentine},

author = {A Kishen and A Asundi},

doi = {10.1002/jbm.a.30288},

issn = {1549-3296},

year  = {2005},

date = {2005-01-01},

journal = {Journal of Biomedical Materials Research. Part A},

volume = {73},

issue = {2},

pages = {192-200},

abstract = {Dentine is a porous hydrated composite structure that forms the major bulk of the human tooth. The aim of this study was to investigate the role of free water on the in-plane, mechanical strain response in dentine structure. A digital moire interferometry was used for this purpose. It was observed from this experiment that structural dentine demonstrated distinct strain gradients in the axial (perpendicular to the dentinal tubules) and lateral (parallel to the dentinal tubules) directions. The hydrated dentine displayed significant increase in strain with stress in the direction perpendicular to the dentinal tubules, and this response was characteristic of a tough material. On the contrary, the dehydrated dentine, which was dehydrated at 24 degrees C, 55% relative humidity for 72 h showed a strain response characteristic of a brittle material. The strains formed in the direction parallel to the dentinal tubules for hydrated dentine were consistent and did not vary much with increase in applied loads. Upon dehydration, the outer dentine experienced higher strains, and the difference between the outer and inner dentine became more conspicuous with increase in loads. This experiment highlights hydration-induced, distinct in-plane strain gradients in the directions perpendicular and parallel to the dentinal tubules in the dentine structure.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2005b,

title = {Periapical biomechanics and the role of cyclic biting force in apical retrograde fluid movement},

author = {A Kishen},

doi = {10.1111/j.1365-2591.2005.00986.x},

issn = {0143-2885},

year  = {2005},

date = {2005-01-01},

journal = {International Endodontic Journal},

volume = {38},

issue = {9},

pages = {597-603},

abstract = {AIM: To investigate the stress distribution pattern in the periapical region caused by biting forces and to study the role of cyclic biting loads on periapical fluid movement. 

METHODOLOGY: In the first part, a digital photoelastic experiment was conducted to study stress distribution in the periapical region. In the second, 20 maxillary central incisors were selected and divided into three main groups: normal intact teeth (group 1), tooth specimens in which the root canal was enlarged and maintained wet (group 2), and tooth specimens in which the root canal was enlarged and maintained dry (group 3). The tooth specimens were placed in a polycarbonate support with a cavity filled with a sponge soaked in methylene blue solution to simulate a periapical defect with exudate. During testing, the specimens were placed in a water bath at 37 degrees C, and were loaded cyclically with a load of 20 N, at a rate of 72 cycles min(-1), to a maximum of 20,000 cycles. The specimens were then sectioned and evaluated for retrograde fluid movement using light microscopy. The data were analysed using one-way anova (post hoc tests). 

RESULTS: Digital photoelastic experiments showed that the compression of teeth produced bending stresses in the periapical region. Testing with cyclic loads demonstrated retrograde fluid movement into the apical portion of the root canal and extraradicular region in all groups. There was a significant difference amongst the apical retrograde fluid movement displayed by different groups (0.01). Group 2, in which the root canal was enlarged and maintained wet showed maximum retrograde fluid movement, whilst group 3, in which the root canal was enlarged and maintained dry showed the least retrograde fluid movement. 

CONCLUSIONS: Biting forces would cause bending of the periapical bone and cyclic biting forces would contribute to retrograde fluid movement into the root canal space and extraradicular region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2005c,

title = {Photomechanical investigations on the stress-strain relationship in dentine macrostructure},

author = {A Kishen and A Asundi},

doi = {10.1117/1.1924688},

issn = {1083-3668},

year  = {2005},

date = {2005-01-01},

journal = {Journal of Biomedical Optics},

volume = {10},

issue = {3},

pages = {34010},

abstract = {In this study photomechanical experiments were carried out to examine the relationship between macroscopic mechanical stress and strain gradients within the root dentine structure. Three-dimensional digital photoelasticity was used to study the stress distribution patterns in tooth models, while digital moire interferometry was used to study the strain gradients within the natural teeth. The stress analysis showed a distinct bending stress distribution, along faciolingual plane in the coronal and cervical regions of the tooth. There was a reduction in bending towards the apical third of the tooth model. The strain analysis displayed strain gradients in the axial (along the long axis of the tooth) and lateral (perpendicular to the long axis of the tooth) directions in dentine. There was a conspicuous reduction in strains from the cervical to the apical third of the root dentine. The root dentine displayed uniform distribution of normal strains. Although there was a steep increase in stresses from the inner core region to the outer surface of an isotropic tooth model, there were more uniform strain gradients in the natural dentine structure. It is apparent from these observations that complex organization of material properties facilitated distinct strain gradients in dentine structure during mechanical functions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2004,

title = {Stress-strain response in human dentine: rethinking fracture predilection in postcore restored teeth},

author = {Anil Kishen and Ganesh V Kumar and Nah-Nah Chen},

doi = {10.1111/j.1600-4469.2004.00250.x},

issn = {1600-4469},

year  = {2004},

date = {2004-01-01},

journal = {Dental Traumatology: Official Publication of International Association for Dental Traumatology},

volume = {20},

issue = {2},

pages = {90-100},

abstract = {In this study, the biomechanical perspective of fracture predilection in post-core restored teeth is investigated using computational, experimental, and fractographic analyses. The computational finite element analysis and the experimental tensile testing are used to evaluate the stress-strain response in structural dentine. The fractographic evaluations are conducted using laser scanning confocal microscopy and scanning electron microscopy to examine the topography of dentine from experimentally fractured specimens, and clinically fractured post-core restored teeth specimens. These experiments aided in correlating the stress-strain response in structural dentine with cracks and catastrophic fractures in post-core restored teeth. It was observed from these experiments that the inner dentine displayed distinctly high strains (deformations), while the outer dentine demonstrated high stresses during tensile loading. This implies that the energy fed into the material as it is extended will be spread throughout the inner dentine, and there is less possibility of local increase in stress at the outer dentine, which can lead to the failure of dentine structure. During post-endodontic restoration with increase in loss of inner dentine, the fracture resistance factor contributed by the inner dentine is compromised, and this in turn predisposes the tooth to catastrophic fracture.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2004b,

title = {Chairside sensor for rapid monitoring of Enterococcus faecalis activity},

author = {A Kishen and N N Chen and L Tan and A Asundi},

doi = {10.1097/01.don.0000129038.97791.8a},

issn = {0099-2399},

year  = {2004},

date = {2004-01-01},

journal = {Journal of Endodontics},

volume = {30},

issue = {12},

pages = {872-875},

abstract = {In this study, optical spectroscopy was used to monitor a chromogenic, enzyme-substrate reaction for the rapid identification of Enterococcus faecalis. The detection system, comprising a miniature spectrophotometer and an accompanying data acquisition system, was placed in an incubator. During testing, a 3-ml test sample was placed in a cuvette within the spectrophotometer. This permitted online, real-time, and remote analysis of spectral signature needed to monitor the bacteria. It was observed that the absorption peak intensity increased conspicuously 3.5 h after inoculation and through the entire period of testing. A linear-regression analysis demonstrated a significant correlation between the increase in absorption peak intensity at 610 nm (r = 0.9389) and 653 nm (r = 0.9387) with the formation of colony-forming units. Optical spectroscopy-based sensing systems can pave the way for rapid, nonlaboratory-based approaches to monitor microbial status quantitatively and qualitatively from clinical samples.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Griggs2003,

title = {Effect of hydrolyzed surface layer on the cytotoxicity and chemical resistance of a low fusing porcelain},

author = {Jason A Griggs and John C Wataha and Anil Kishen},

doi = {10.1016/s0109-5641(02)00066-0},

issn = {0109-5641},

year  = {2003},

date = {2003-01-01},

journal = {Dental Materials: Official Publication of the Academy of Dental Materials},

volume = {19},

issue = {5},

pages = {353-358},

abstract = {OBJECTIVE: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC and to determine its effect on the cytotoxicity of the porcelain as measured by cellular activity and concentrations of leached ionic species. 

METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique. Half of the specimens underwent accelerated aging by subjecting them to the standard test for hydrolytic resistance (ISO 6872). Fibroblast cell cultures were placed in direct contact with specimens. Cell viability was assessed using succinic dehydrogenase activity. Chemical resistance was determined by leaching specimens with a continuous flow of deionized water and measuring the concentrations of soluble ions in the leachates. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to detect the composition of the surface layer. 

RESULTS: Hydrolyzation treatment created a smooth texture on the porcelain surfaces but did not result in a hydrolyzed surface layer with increased hydroxyl content. There was a decreased alkali ion content in the surface layer of hydrolyzed specimens. Mean cellular SDH activities for non-hydrolyzed and hydrolyzed porcelain were 75+/-7 and 80+/-5% of Teflon controls, respectively. Only sodium ions were present in significant concentrations in collected leachates. The sodium concentration decreased over the initial 4.5h of leaching. 

SIGNIFICANCE: The changes in surface layer texture and composition as the result of the aging treatment had little effect on the cytotoxicity and chemical resistance of Duceram LFC. The results suggest that Duceram LFC would pose no biocompatibility risk even after extended exposure to the oral environment. These data also provide baseline material properties to be used in future studies of the effects of porcelain additives.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Preejith2003,

title = {Total protein measurement using a fiber-optic evanescent wave-based biosensor},

author = {P V Preejith and C S Lim and A Kishen and M S John and A Asundi},

doi = {10.1023/a:1021955032291},

issn = {0141-5492},

year  = {2003},

date = {2003-01-01},

journal = {Biotechnology Letters},

volume = {25},

issue = {2},

pages = {105-110},

abstract = {A novel method and instrumental system to determine the total protein concentration in a liquid sample is described. It uses a fiber optic total protein sensor (FOPS) based on the principles of fiber optic evanescent wave spectroscopy. The FOPS applies a dye-immobilized porous glass coating on a multi-mode optical fiber. The evanescent waves at the fiber optic core-cladding interface are used to monitor the protein-induced changes in the sensor element. The FOPS offers a single-step method for quantifying protein concentrations without destroying the sample. The response time and reusability of the FOPS are evaluated. This unique sensing method presents a sensitive and accurate platform for the quantification of protein.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2003,

title = {A fiber optic biosensor (FOBS) to monitor mutans streptococci in human saliva},

author = {A Kishen and M S John and C S Lim and A Asundi},

doi = {10.1016/s0956-5663(03)00081-2},

issn = {0956-5663},

year  = {2003},

date = {2003-01-01},

journal = {Biosensors \& Bioelectronics},

volume = {18},

issue = {11},

pages = {1371-1378},

abstract = {A fiber optic biosensor (FOBS) to monitor mutans streptococci activity in human saliva is developed. The biosensor utilizes e fiber optic evanescent wave spectroscopy to monitor a bacterial mediated biochemical reaction. To achieve this, a short length of the cladding is removed; the fiber core surface is treated and coated with a thin film of porous glass medium using sol-gel technique. The mutans streptococci mediated reaction with sucrose is monitored using a photosensitive indicator, which is immobilized within the porous glass coating. Spectroscopic analysis shows that the transmitted intensity at 597 nm increases conspicuously when monitored for 120 min. Two distinct phases are observed, one from 0 to 60 min and the other from 60 to 120 min. A negative correlation coefficient between the rate of increase in absorption peak intensity recorded by the FOBS and the decrease in pH measured using the pH meter, was calculated to be rho=-0.994. This investigation highlights the potential benefits of this sensor to monitor mutans streptococci activity in saliva.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Griggs2003b,

title = {Mechanism of strength increase for a hydrothermal porcelain},

author = {Jason A Griggs and Anil Kishen and Kim Nga Le},

doi = {10.1016/s0109-5641(03)00005-8},

issn = {0109-5641},

year  = {2003},

date = {2003-01-01},

journal = {Dental Materials: Official Publication of the Academy of Dental Materials},

volume = {19},

issue = {7},

pages = {625-631},

abstract = {OBJECTIVES: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC, to determine the effects of such a layer on mechanical material properties, and to identify a specific mechanism responsible for any strength increase observed. 

METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique and were prepared to have either blunt or sharp surface flaws. Half of the specimens underwent accelerated aging. Specimens were fractured in three-point flexure to measure their strength, and fractographic analysis was used to determine fracture toughness and residual surface stress. Surface hardness and elastic modulus were measured using a microindentation method. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to determine the composition of the surface layer. 

RESULTS: The aging treatment modified the porcelain surface topography but did not create a layer with increased hydroxyl ion content. Porcelain strength increased upon aging, and the increase was proportional to initial flaw severity. The apparent fracture toughness of sharp flaw specimens increased to match that for specimens containing blunt flaws upon aging. Surface hardness and elastic modulus decreased upon aging. 

SIGNIFICANCE: Previous studies on the strength increase of hydrothermal porcelain were contradictory because a variety of specimen preparation procedures were used. This study resolves the apparent contradiction by determining the effect of specimen preparation on material strength.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2002,

title = {Approaching biomimetics in dental restorations via photonics},

author = {A Kishen and A Asundi},

issn = {0895-3996},

year  = {2002},

date = {2002-01-01},

journal = {Journal of X-Ray Science and Technology},

volume = {10},

issue = {3},

pages = {153-166},

abstract = {It is established that a natural system balances functional requirements with the anatomical optimizations it has achieved. Though such process of functional adaptation is recognized in bone tissue, any mode of functional adaptation in dental tissue is yet to be understood. In this study a three-dimensional digital photoelasticity is conducted to evaluate the nature of stress distribution in the sagittal aspect and the cross-sections of the dentine structure. Later, a fluoroscopic X-ray microscopic analysis and a microindentation experiments, are performed on different sections obtained from the sagittal and cross-sections of the dentine. These experiments aided in correlating the multi-plane pattern of mineralization and the spatial gradients in elastic modulus in the original dentine structure with the three-dimensional stress distribution in photoelastic models. This study highlights dentine structure as a biologically graded structure to functional loads.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2002b,

title = {Photomechanical investigations on post endodontically rehabilitated teeth},

author = {A Kishen and A Asundi},

doi = {10.1117/1.1463046},

issn = {1083-3668},

year  = {2002},

date = {2002-01-01},

journal = {Journal of Biomedical Optics},

volume = {7},

issue = {2},

pages = {262-270},

abstract = {An investigation of the stress distribution patterns in post-core restored teeth and the behavior of dentin material to fracture propagation was conducted using experimental techniques such as digital photoelasticity (on photoelastic models), mechanical testing and scanning electron microscopy (SEM) (on extracted teeth). Digital photoelastic experiments showed that endodontic post-core restoration resulted in regions of high tensile stress and of stress concentrations in the remaining dentin structure. It was observed from mechanical testing that the fracture resistance in post-core restored teeth is significantly lower (p0.0001) than that in intact tooth. There was a significant correspondence between the plane of stress concentrations identified in the photoelastic models and in those of the plane of fracture exhibited by the rehabilitated tooth specimens. While the fracture of post-core rehabilitated teeth was consistent, that of control teeth was not as distinct. The SEM highlighted varying dentin response to fracture propagation at the inner core and the outer regions. The fractographs showed brittle and ductile response to fracture propagation in the outer and inner core dentin, respectively. These photomechanical studies highlighted that the stress concentrations, high tensile stress and loss of inner ductile dentin associated with post endodontic rehabilitation diminished their resistance to fracture.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kumar2002,

title = {Scanning electron microscopic and energy dispersive spectrometric investigations on the effect of XeCl excimer laser on human dentin with smear layer},

author = {A R Pradeep Kumar and C V Subba Rao and A Parameswaran and A Kishen and C S Lim},

doi = {10.1046/j.1365-2842.2002.00973.x},

issn = {0305-182X},

year  = {2002},

date = {2002-01-01},

journal = {Journal of Oral Rehabilitation},

volume = {29},

issue = {10},

pages = {1003-1009},

abstract = {The purpose of this study was to study the effect of XeCl excimer laser on smear layer covered dentine of extracted human teeth. Twenty-four freshly extracted human molar teeth were collected and randomly divided into one control group and three experimental groups of six teeth each (groups A-D). The teeth in the experimental groups were irradiated with XeCl 308-nm excimer laser at a fluence of 0.4 J cm-2 and a constant pulse repetition rate of 25 Hz. Group A was used as the control, while groups B, C and D were irradiated at different exposure times of 3, 5 and 7 s, respectively. Subsequently these teeth specimens were subjected to scanning electron microscopic (SEM) examination and energy dispersive X-ray (EDX) spectrometric analysis. The SEM examination revealed melting of the smear layer covered dentin to conceal the underlying dentinal tubules. At a longer exposure time (7 s), dentin melted to form large grains and this resulted in non-uniform closure of underlying dentinal tubules. Under the conditions of this study, it is concluded that the pulsed XeCl 308-nm excimer laser at a fluence of 0.4 J cm-2, with an exposure time of 5 s uniformly occluded exposed smear layer covered dentine with no conspicuous variation in chemical structure.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{John2002,

title = {Determination of bacterial activity by use of an evanescent-wave fiber-optic sensor},

author = {M Shelly John and Anil Kishen and Lim Chu Sing and Anand Asundi},

doi = {10.1364/ao.41.007334},

issn = {1559-128X},

year  = {2002},

date = {2002-01-01},

journal = {Applied Optics},

volume = {41},

issue = {34},

pages = {7334-7338},

abstract = {A novel technique based on fiber-optic evanescent-wave spectroscopy is proposed for the detection of bacterial activity in human saliva. The sensor determines th e specific concentration of Streptococcus mutans in saliva, which is a major causative factor in dental caries. In this design, one prepares the fiber-optic bacterial sensor by replacing a portion of the cladding region of a multimode fiber with a dye-encapsulated xerogel, using the solgel technique. The exponential decay of the evanescent wave at the core-cladding interface of a multimode fiber is utilized for the determination of bacterial activity in saliva. The acidogenic profile of Streptococcus mutans is estimated by use of evanescent-waveabsorption spectra at various levels of bacterial activity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asundi2001,

title = {Advanced digital photoelastic investigations on the tooth-bone interface},

author = {A Asundi and A Kishen},

doi = {10.1117/1.1344587},

issn = {1083-3668},

year  = {2001},

date = {2001-01-01},

journal = {Journal of Biomedical Optics},

volume = {6},

issue = {2},

pages = {224-230},

abstract = {The purpose of this study was to investigate the behavior of the tooth-bone interface on the nature of stress distribution in the tooth and its supporting alveolar bone for various occlusal loads using an advanced digital photoelastic technique. A digital image processing system coupled with a circular polariscope was used for the stress analysis. The phase shift technique and a phase unwrapping algorithm was utilized for fringe processing. This aids in obtaining qualitative and quantitative information on the nature of stress distribution within the dento-osseous structures. The experiments revealed bending stresses within dento-osseous structures. However, the compressive stress magnitude was larger than the tensile stress. Zero stress regions were also identified within the dento-osseous structures. The results suggest that the geometry of the dento-osseous structures and the structural gradients at the tooth-bone interface play a significant role in the distribution of stresses without stress concentrations. Further, the application of an advanced image-processing system with the circular polariscope showed notable advantages and could be applied in other biomechanical investigations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kishen2001,

title = {Investigations of thermal property gradients in the human dentine},

author = {A Kishen and A Asundi},

doi = {10.1002/1097-4636(200104)55:1\<121::aid-jbm160\>3.0.co;2-5},

issn = {0021-9304},

year  = {2001},

date = {2001-01-01},

journal = {Journal of Biomedical Materials Research},

volume = {55},

issue = {1},

pages = {121-130},

abstract = {An investigation of the adaptation of dentine to temperature variation was conducted with the aid of digital moir\'{e} interferometry and thermomechanical analysis. The moir\'{e} interferometric patterns provided direct evidence of two major phases of thermally involved deformation in dentine. An initial phase of expansion was followed by contraction at higher temperatures. Significant gradients in thermal strain and the coefficient of thermal expansion were identified. Close agreement was found between the response of dentine to thermal changes as observed by moir\'{e} interferometry and that detected by thermomechanical analysis. This study highlights the biological adaptation of dentine to thermal variations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}