In vitro comparison of flexural strength and elastic modulus of three provisional crown materials used in fixed prosthodontics

Objectives: To evaluate and compare the flexural strength and the elastic moduli of three provisional crown materials (methyl methacrylate based autopolymerized resin, bis acryl composite based autopolymerized resin and urethane dimethacrylate based light polymerized resin) after storing in artificial saliva and testing at intervals of 24 hours and 7 days. Study design: A metal master mould with four slots of dimensions 25x2x2 mm was fabricated to obtain samples of standard dimensions. A total of 135 specimens were thus obtained with 45 each of three provisional materials. Further 15 samples of each group were tested after storing for one hour at room temperature and again at intervals of 24 hours and 7 days after storing in artificial saliva. Three point flexural tests were carried out in the universal testing machine to calculate the flexural strength and the elastic modulus. The changes were calculated and data was analyzed with Fisher's test and ANOVA. Results: The flexural strength of the methyl methacrylate resin reduced significantly while bis-acrylic composite resin showed a significant increase in its flexural strength after storing in artificial saliva for 24 hours and the values of both remained constant thereafter. Contrary to these findings, light polymerized resin showed a significant decrease in flexural strength after storing in artificial saliva for 24 hours and then significantly increased in flexural strength after 7 days. However the changes in the values for elastic modulus of respective materials were statistically insignificant. Conclusion: Methacrylate based autopolymerizing resin showed the highest flexural strength and elastic moduli after fabrication and after storing in artificial saliva and for 24 hours and 7 days. Bis-acrylic composite resin showed the least flexural strength and elastic moduli

Interplay of polarizations in a cascade EIT system in the presence of vortex coupling light in 87Rb atomic vapor medium

We investigate both experimentally and theoretically the cascade electromagnetically induced transparency (EIT) in $5S_{1/2}-5P_{3/2}-5D_{5/2}$ configuration in ^87 Rb atomic vapor medium in the presence of vortex coupling Laguerre Gaussian (LG) light. We demonstrated Doppler free double resonance EIT structure in cascade configuration and observed transmission spectra for $\vert H\rangle-\vert H\rangle$ and $\sigma^+-\sigma^+$ polarized probe and coupling lights. We demonstrate that the double resonance structure can be identified by two photon transition probabilities and it is found to be $F^{^{\prime\prime}} = 2$ and $F^{^{\prime\prime}} = 3$ . By considering coupling LG light, several polarization combinations are taken into account, and their effects on amplifying and diminishing the EIT resonances are demonstrated experimentally. In order to understand the polarization effects of vortex coupling light on EIT spectrum in a degenerate multilevel atomic system, a theoretical model is developed by considering a simplified double hut level structure. Semi-classical density matrix analysis is used to understand the dynamics and also to establish the enhancement and reduction of EIT peak height with coupling light polarizations. The impact of two photon transition probabilities, polarization combinations and relative orientations of probe and coupling lights in degenerate multilevel atomic systems leads to modification of EIT resonances significantly. We establish quantitative agreement between our theory and experimental results

OVERLAY DENTURES: A REVIEW AND REPORT OF FOUR CASES

Patients with ectodermal dysplasia or having under‑ gone cleft surgery with anodontia or hypodontia, hypo‑ plastic conical teeth and patients with severely worn dentition are difficult to treat because of the poor remaining tooth structure. These patients often exhibit loss of vertical dimension of occlusion and aesthetic problems and usually need complex prosthetic treatments. Financial constraints or other priorities often restrict one from choosing the most desirable treatment. The overlay removable denture is a covering prosthesis partially supported by natural teeth, tooth roots, or dental implants, providing an efficient alter‑ native of treatment. Clinical reports describe the various applications of overlay dentures

LASERS : A BOON IN THE MANAGEMENT OF TEMPOROMANDIBULAR DISORDERS

Temporomandibular disorders have been identified as the most important cause of pain in the facial region. Pain relief and reestablishment of normal masticatory function are the main goals of conservative management of Temporomandibular Disorders (TMD). Laser therapy is a part of the treatment modality that have demonstrated to have an analgesic, anti-inflammatory and biostimulating effect. The LLLT is a non invasive , quick and safe, non pharmacological intervention that may be beneficial for patient with TMDs. This review article projects the use of LLLT for management of temporomandibular disorders ,its mode of action and also gives a review on various studies conducted to assess its efficacy on pain management

Nasomaxillary complex in size, position and orientation in surgically treated and untreated individuals with cleft lip and palate: A cephalometric overview

Background: This cross-sectional retrospective cephalometric study was designed to clarify whether the maxillary deficiency seen in surgically treated individuals with non-syndromic complete unilateral cleft lip and palate (UCLP) is due to inherent growth potential or iatrogenicity. Materials and Methods: 72 adult individuals were randomly selected in the age range of 12-20 years, and were divided into two groups. Group I had 47 untreated individuals. Group II consisted of 25 surgically treated individuals. Lateral and frontal cephalograms of the selected individuals were taken and analysed using Nemoceph software. Results: Group II showed a marked reduction in the cranial base angle, maxillary base length, anterior and posterior maxillary positions, palatal plane angle, maxillary width, maxillary height, occlusal plane height, nasal width and nasal height. Conclusion: Surgical intervention does interfere with growth in the facial region. This could be attributed to the scar tissue in lip and palate region, which has a restraining effect on growth in the facial region. These altered functional matrices play a significant role in determining the growth of facial structures