Concepts of occlusion in prosthodontics: A literature review,part I

Occlusion and its relationship to the function of the stomatognathic system have been widely studied in dentistry since many decades. This series of articles describe about occlusion in the complete denture, fixed partial denture, and implants. Part I and II of this articles series describe concepts and philosophies of occlusion in complete denture. So far, available research has not concluded a superior tooth form or occlusal scheme to satisfy the requirements of completely edentulous patients with respect to comfort, mastication, phonetics, and esthetics. Since then, several balanced and nonbalanced articulation concepts were proposed in the literature. A balanced articulation appears to be most appropriate because of tooth contacts observed during nonfunctional activities of patients. This article discusses about evolution of different concepts of occlusion and occlusal schemes in complete denture occlusion.Key Words: Articulation, complete denture, occlusion     

Mechanical and Tribological Behavior of Mechanically Alloyed Ni-TiC Composites Processed via Spark Plasma Sintering

Titanium carbide (TiC) reinforced nickel (Ni) matrix composites were processed via mechanical alloying (MA) followed by spark plasma sintering (SPS) process. Mechanical alloying has gained special attention as a powerful non-equilibrium process for fabricating amorphous and nanocrystalline materials, whereas spark plasma sintering (SPS) is a unique technique for processing dense and near net shape bulk alloys with homogenous microstructure. TiC reinforcement varied from 5 to 50 wt.% into nickel matrix to investigate its effect on the microstructure and mechanical behavior of Ni-TiC composites. All Ni-TiC composites powder was mechanically alloyed using planetary high energy ball mill with 400 rpm and ball to powder ratio (BPR) 15:1 for 24 h. Bulk Ni-TiC composites were then sintered via SPS process at 50 MPa pressure and 900–1200 °C temperature. All Ni-TiC composites exhibited higher microhardness and compressive strength than pure nickel due to the presence of homogeneously distributed TiC particles within the nickel matrix, matrix grain refinement, and excellent interfacial bonding between nickel and TiC reinforcement. There is an increase in Ni-TiC composites microhardness with an increase in TiC reinforcement from 5 to 50 wt.%, and it reaches the maximum value of 900 HV for Ni-50TiC composites.     

Relationship of Quality of Life with Disability Grade in Obsessive Compulsive Disorder and Dysthymic Disorder

Background:

There is paucity of information on the relationship of quality of life (QOL) in obsessive compulsive disorder (OCD) and dysthymic disorder (DD) with disability grade in India.

Aim:

To assess the relation of QOL with disability level in OCD and DD.

Materials and Methods:

This hospital based study was conducted in a medical institution in Davanagere, Karnataka, India. Data was collected by using Diagnostic and Statistical Manual IV Text Revision (DSM IV TR) criteria, WHO QOL BREF and IDEAS. Relationship between disability grade and QOL was assessed by independent sample t test.

Results:

Mild disabled OCD patients had a significantly better QOL in the Q1 domain i.e. perception on quality of life as compared to moderately disabled patients (P < 0.05), while in other domains of QOL, there was no statistically significant difference (P > 0.05). But, QOL score in physical domain showed significant difference across disability grades (56.00, SD = 6.89; 48.50, SD = 12.28) in DD, but not in other domains.

Conclusion:

Perception of QOL is better in those with mild disability in OCD, but in DD, physical domain of QOL score is more in mild disability compared to moderate disability.     

Self-assembled pearl-necklace patterned upconverting nanocrystals with highly efficient blue and ultraviolet emission: femtosecond laser based upconversion properties

This work reports new findings on the formation of a pearl-necklace pattern in self-assembled upconverting nanocrystals (UCN-PNs) which exhibit strong upconversion emission under an NIR excitation source of a femtosecond laser (Fs-laser). Each nano-necklace consists of several upconversion nanoparticles (UCNPs) having a size ca. 10 ± 1 nm. UCN-PNs are arranged in a self-organized manner to form necklace type chains with an average length of 140 nm of a single row of nanoparticles. Furthermore, UCN-PNs are comprised of UCNPs with an average interparticle separation of ca. 4 nm in each of the nanonecklace chains. Interestingly, these UCN-PNs exhibit high energy upconversion especially in the UV region on interaction with a 140 Fs-laser pulse duration at 80 MHz repetition rate and intense blue emission at 450 nm on interaction with a 900 nm excitation source is obtained. The preparation of self-assembled UCNPs is easy and they are very stable for a longer period of time. The emission (fluorescence/luminescence) intensity is very high which can make them unique in innumerable industrial and bio-applications such as for disease diagnosis and therapeutic applications by targeting the infected cells with enhanced efficiency.

Self-assembled pearl necklace patterned-upconverting nanoparticles and their femtosecond laser based upconversion properties.     

Approximation of the expected value of the harmonic mean and some applications

Although the harmonic mean (HM) is mentioned in textbooks along with the arithmetic mean (AM) and the geometric mean (GM) as three possible ways of summarizing the information in a set of observations, its appropriateness in some statistical applications is not mentioned in textbooks. During the last 10 y a number of papers were published giving some statistical applications where HM is appropriate and provides a better performance than AM. In the present paper some additional applications of HM are considered. The key result is to find a good approximation to E(H_n), the expectation of the harmonic mean of n observations from a probability distribution. In this paper a second-order approximation to E(H_n) is derived and applied to a number of problems.The harmonic mean H_n of n observations Z₁, …, Z_n drawn from a population is defined byHn=n∑i=1n1Zi.[1]There have been a number of applications of the harmonic mean in recent papers. A more general version of H_n with weights w₁, …, w_n isHn(w)=∑i=1nwi∑i=1nwiZi.[2]where w = (w₁,…,w_n)^T. The harmonic mean H_n is used to provide the average rate in physics and to measure the price ratio in finance as well as the program execution rate in computer engineering. Some statistical applications of the harmonic mean are given in refs. 1–4, among others. H_n(w) has been used in evaluation of the portfolio price-to-earnings ratio value (ref. 5, p. 339) and the signal-to-interference-and-noise ratio (6) among others. The asymptotic properties of H_n including the asymptotic expansion of E(H_n) are investigated in refs. 7 and 8 by either assuming that some moments of 1/Z_i are finite or that Z_i s follow the Poisson distribution. It is noted that recent papers (9, 10) enable one to use saddle-point approximation to give the asymptotic expansion of E(H_n) to any given order of 1/n for some constants c₀, c₁, c₂, …, i.e.,E(Hn)=c0+c1n+c2n2+⋯.[3]However, such methods are not applicable for obtaining the asymptotic expansion of H_n when the first moment of 1/Z_i is infinite. In ref. 3, Z_i s are assumed to follow a uniform distribution in the interval (0,1), i.e., U(0,1), motivated by learning theory. Using the property that the inverse of H_n converges to the stable law, ref. 3 showed thatE(Hn)∼1log(n),[4]where the symbol “∼” means asymptotic equivalence as n → ∞. Our interest in this paper is to determine the second term in the asymptotic expansion of E(H_n) or the general version E(H_n(w)) under more general assumptions on distributions of Z_i s. We show that under mild assumptions,E(Hn)∼1log(n){1+c1log(n)},[5]where the constant c₁ will be given. In addition, we use the approach for obtaining [5] to the case that the first moment of 1/Z_i is finite, motivated by evaluation of the marginal likelihood in ref. 11.     

Cyclooxygenase‐2 in epilepsy

Epilepsy is one of the more prevalent neurologic disorders in the world, affecting approximately 50 million people of different ages and backgrounds. Epileptic seizures propagating through both lobes of the forebrain can have permanent debilitating effects on a patient's cognitive and somatosensory brain functions. Epilepsy, defined by the sporadic occurrence of spontaneous recurrent seizures (SRS), is often accompanied by inflammation of the brain. Pronounced increases in the expression of key inflammatory mediators (e.g., interleukin ‐1β [IL‐1β], tumor necrosis factor alpha [TNFα], cyclooxygenase‐2 [COX‐2], and C‐X‐C motif chemokine 10 [CXCL10]) after seizures may cause secondary damage in the brain and increase the likelihood of repetitive seizures. The COX‐2 enzyme is induced rapidly during seizures. The increased level of COX‐2 in specific areas of the epileptic brain can help to identify regions of seizure‐induced brain inflammation. A good deal of effort has been expended to determine whether COX‐2 inhibition might be neuroprotective and represent an adjunct therapeutic strategy along with antiepileptic drugs used to treat epilepsy. However, the effectiveness of COX‐2 inhibitors on epilepsy animal models appears to depend on the timing of administration. With all of the effort placed on making use of COX‐2 inhibitors as therapeutic agents for the treatment of epilepsy, inflammation, and neurodegenerative diseases there has yet to be a selective and potent COX‐2 inhibitor that has shown a clear therapeutic outcome with acceptable side effects.