scholarly journals Chemo-mechanical characterization of carious dentine using Raman microscopy and Knoop microhardness

2020 ◽  
Vol 7 (5) ◽  
pp. 200404 ◽  
Author(s):  
M. Alturki ◽  
G. Koller ◽  
U. Almhöjd ◽  
A. Banerjee
Keyword(s):  
Raman Spectroscopy ◽  
Hardness Test ◽  
Operative Management ◽  
Knoop Hardness ◽  
Raman Microscopy ◽  
Permanent Teeth ◽  
Peak Ratio ◽  
Carious Dentine ◽  
Knoop Microhardness

One of the aims in the clinical operative management of dental carious lesions is to remove selectively the highly infected and structurally denatured dentine tissue, while retaining the deeper, repairable affected and intact, healthy tissues for long-term mechanical strength. The present study examined the correlation of chemical functional groups and the microhardness through the different depths of a carious lesion using Raman spectroscopy and Knoop microhardness testing. The null hypothesis investigated was that there was no correlation between Raman peak ratios (amide I : phosphate ν1 ) and equivalent Knoop microhardness measurements. Ten freshly extracted human permanent teeth with carious dentine lesions were sectioned and examined using high-resolution Raman microscopy. The ratio of absorbency at the amide I and phosphate bands were calculated from 139 scan points through the depth of the lesions and correlated with 139 juxtaposed Knoop microhardness indentations. The results indicated a high correlation ( p < 0.01) between the peak ratio and the equivalent Knoop hardness within carious dentine lesions. This study concluded that Raman spectroscopy can be used as a non-invasive analytical technology for in vitro studies to discriminate the hardness of carious dentine layers using the peak ratio as an alternative to the invasive, mechanical Knoop hardness test.

Effect of Zinc Sulfate on Human Primary Enamel Microhardness: An in vitro Study

2012 ◽  
Vol 36 (4) ◽  
pp. 369-371 ◽  
Author(s):  
M Mirkarimi ◽  
M Bargrizan ◽  
S Eskandarion ◽  
M Shahsavari
Keyword(s):  
Zinc Sulfate ◽  
Artificial Saliva ◽  
In Vitro Study ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Control Group ◽  
Expected Time ◽  
Rich Solution ◽  
The Mean

Objective: The aim of this study was to assess the effect of zinc sulfate on microhardness of human primary enamel. Method: Sixteen sound primary molars were sectioned mesiodistally. For each sample one of the sections was randomly immersed in artificial saliva (Biotene,USA) and the other was immersed in artificial saliva which was charged with 10 mg/5mL concentration of zinc sulfate supplement (Razak Company, Iran) daily. After 24 days (the expected time to use up one 120-mL bottle) the surface microhardness of enamel was measured by knoop hardness test (KH) with Knoop diamond under a 50-gram load for 10 seconds. Results: The mean (± SD) microhardness values (KHV) for the tested groups were 320 ± 49.45 and 357 ± 36.35, respectively. There were statistically significant differences between the groups as exhibited by independent t-test (P=0.023). Conclusion: Primary teeth immersed in a zinc sulfate rich solution for 24 days showed higher microhardness values in comparison with the control group.

Effects of Preheating and Precooling on the Hardness and Shrinkage of a Composite Resin Cured with QTH and LED

2013 ◽  
Vol 38 (3) ◽  
pp. E50-E57 ◽  
Author(s):  
FH Osternack ◽  
DBM Caldas ◽  
JB Almeida ◽  
EM Souza ◽  
RF Mazur
Keyword(s):  
Composite Resin ◽  
Light Emitting Diode ◽  
Resin Composite ◽  
Hardness Test ◽  
Optical Microscope ◽  
Knoop Hardness ◽  
Halogen Light ◽  
Different Temperatures ◽  
Composite Hardness

SUMMARY The aim of this study was to evaluate in vitro the hardness and shrinkage of a pre-cooled or preheated hybrid composite resin cured by a quartz-tungsten-halogen light (QTH) and light-emitting diode (LED) curing units. The temperature on the tip of the devices was also investigated. Specimens of Charisma resin composite were produced with a metal mold kept under 37°C. The syringes were submitted to 4°C, 23°C, and 60°C (n=20) before light-curing, which was carried out with the Optilux 501 VCL and Elipar FreeLight 2 units for 20 seconds. The specimens were kept under 37°C in a high humidity condition and darkness for 48 hours. The Knoop hardness test was carried out with a 50 gram-force (gf) load for 10 seconds, and the measurement of the shrinkage gap was carried out using an optical microscope. The data were subjected to analysis of variance and the Games-Howell test (α=0.05). The mean hardness of the groups were similar, irrespective of the temperatures (p&gt;0.05). For 4°C and 60°C, the top surface light-cured by LED presented significantly reduced shrinkage when compared with the bottom and to both surfaces cured by QTH (p&lt;0.05). It was concluded that the hardness was not affected by pre-cooling or preheating. However, polymerization shrinkage was slightly affected by different pre-polymerization temperatures. The QTH-curing generated greater shrinkage than LED-curing only when the composite was preheated. Different temperatures did not affect the composite hardness and shrinkage when cured by a LED curing unit.

scholarly journals Is It Possible to induce Artificial Caries-affected Dentin using the Same Protocol to Primary and Permanent Teeth?

2015 ◽  
Vol 16 (8) ◽  
pp. 638-642
Author(s):  
Tathiane Larissa Lenzi ◽  
Fabio Zovico Maxnuck Soares ◽  
Tamara Kerber Tedesco ◽  
Rachel de Oliveira Rocha
Keyword(s):  
Repeated Measures ◽  
Permanent Teeth ◽  
Control Group ◽  
Dentin Caries ◽  
Ph Cycling ◽  
Knoop Microhardness ◽  
Caries Lesions ◽  
Experimental Group ◽  
Mineral Loss

ABSTRACT Aim This in vitro study compared the mineral loss of natural and artificially-created caries-affected dentin in primary and permanent teeth using the same protocol to induce caries lesions. Materials and methods Twenty molars presenting natural occlusal dentin caries lesions (10 primary–PriC and 10 permanent– PermC; control group), and 20 sound molars (10 primary – PripH and 10 permanent–PermpH; experimental group), were selected. Occlusal cavities were prepared in teeth of the experimental group that were submitted to pH-cycling for 14 days to simulate caries-affected dentin. All specimens were longitudinally sectioned and prepared in order to obtain Knoop microhardness values from 15 to 250 ìm depth, starting in bottom of center of natural lesions or cavities. The microhardness (KHN) data were submitted to three-way repeated measures analysis of variance (ANOVA) and Tukey's tests (α = 0.05). Results Considering all depths, there was no statistically significant differences (p > 0.05) between the mineral loss of the control (PriC = 30.9 ± 6.4 and PermC = 40.8 ± 8.6) and experimental (PripH = 27.3 ± 11.1 and PermpH = 35.5 ± 14.0) groups, neither between primary and permanent teeth. Conclusion The mineral loss of the artificially-created cariesaffected dentin is similar to that from naturally developed dentin caries lesions. Clinical significance The pH-cycling model may be a suitable method to simulate caries-affected dentin in both permanent and primary teeth. How to cite this article Lenzi TL, Soares FZM, Tedesco TK, de Oliveira Rocha R. Is It Possible to induce Artificial Caries-affected Dentin using the Same Protocol to Primary and Permanent Teeth? J Contemp Dent Pract 2015;16(8):638-642.

Stem Cells Derived from Human Exfoliated Deciduous teeth [shed] in Neuronal Disorders: A Review

2020 ◽  
Vol 16 ◽  
Author(s):  
Minu Anoop ◽  
Indrani Datta
Keyword(s):  
Stem Cells ◽  
Neurodegenerative Diseases ◽  
Dental Pulp ◽  
Therapeutic Potential ◽  
Permanent Teeth ◽  
Deciduous Teeth ◽  
Proliferative Potential ◽  
Pulp Tissue ◽  
Human Exfoliated Deciduous Teeth

: Most conventional treatments for neurodegenerative diseases fail due to their focus on neuroprotection rather than neurorestoration. Stem cell‐based therapies are becoming a potential treatment option for neurodegenerative diseases as they can home in, engraft, differentiate and produce factors for CNS recovery. Stem cells derived from human dental pulp tissue differ from other sources of mesenchymal stem cells due to their embryonic neural crest origin and neurotrophic property. These include both dental pulp stem cells [DPSCs] from dental pulp tissues of human permanent teeth and stem cells from human exfoliated deciduous teeth [SHED]. SHED offer many advantages over other types of MSCs such as good proliferative potential, minimal invasive procurement, neuronal differentiation and neurotrophic capacity, and negligible ethical concerns. The therapeutic potential of SHED is attributed to the paracrine action of extracellularly released secreted factors, specifically the secretome, of which exosomes is a key component. SHED and its conditioned media can be effective in neurodegeneration through multiple mechanisms, including cell replacement, paracrine effects, angiogenesis, synaptogenesis, immunomodulation, and apoptosis inhibition, and SHED exosomes offer an ideal refined bed-to-bench formulation in neurodegenerative disorders. However, in spite of these advantages, there are still some limitations of SHED exosome therapy, such as the effectiveness of long-term storage of SHED and their exosomes, the development of a robust GMP-grade manufacturing protocol, optimization of the route of administration, and evaluation of the efficacy and safety in humans. In this review, we have addressed the isolation, collection and properties of SHED along with its therapeutic potential on in vitro and in vivo neuronal disorder models as evident from the published literature.

scholarly journals Impact of refrigeration on the surface hardness of hybrid and microfilled composite resins

2009 ◽  
Vol 20 (1) ◽  
pp. 42-47 ◽  
Author(s):  
Fernando Henrique Ruppel Osternack ◽  
Danilo Biazzetto de Menezes Caldas ◽  
Rodrigo Nunes Rached ◽  
Sérgio Vieira ◽  
Jeffrey A. Platt ◽  
...  
Keyword(s):  
Room Temperature ◽  
Surface Hardness ◽  
In Vitro Study ◽  
Knoop Hardness ◽  
Composite Resins ◽  
Bottom Surface ◽  
Steel Mold ◽  
Polymerization Condition ◽  
Post Hoc

This in vitro study evaluated the Knoop hardness of the composite resins Charisma® (C) and Durafill VS® (D) polymerized in 3 different conditions: at room temperature (A) (23 ± 1°C); refrigerated at 4 ± 1°C and immediately photo-activated after removal from the refrigerator (0); and, refrigerated at 4 ± 1°C and photo-activated after a bench time of 15 min at room temperature (15). One hundred and twenty specimens (4 mm diameter and 2 mm depth) were made using a stainless steel mold and following manufacturer's instructions. All specimens were tested immediately after polymerization (I) and after 7 days of water storage in the dark at room temperature (7d). The data were subjected to ANOVA and post-hoc Tukey's test (a=0.05). On the top surface, CAI was statistically similar to C15I and DAI to D15I (p>0.05). On the bottom surface, CAI presented higher hardness values when compared to COI and C15I (p<0.05). The D groups showed no significant differences (p>0.05) on the bottom surfaces for any tested polymerization condition. After 7 days of storage, the Knoop hardness decreased significantly (p<0.05) for groups C7d and D7d except for C07d, which was not different from COI at either surface (p>0.05). D07d showed higher Knoop hardness (p<0.05) values on the top surface when compared to the other groups.

scholarly journals Effect of microwave disinfection on physical and mechanical properties of acrylic resins

2008 ◽  
Vol 19 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Rafael Leonardo Xediek Consant ◽  
Erica Brenoe Vieira ◽  
Marcelo Ferraz Mesquita ◽  
Wilson Batista Mendes ◽  
João Neudenir Arioli-Filho
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Physical And Mechanical Properties ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Microwave Energy ◽  
Bending Test ◽  
Acrylic Resins ◽  
Strength Tests ◽  
The Impact

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (?=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.

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