Towards Enhancing the Efficiency of Nonlinear Optical Generation

The chapter dwells on two novel approaches towards enhancing the efficiency of nonlinear optical generation. The former is to enable the unabsorbed pump beam to pass through the crystal repeatedly. Integration of an unstable cavity containing the crystal with the stable pump cavity made this possible. The Q of the unstable cavity could be maintained high as the output coupler of the pump laser, itself served as the entrance mirror of this cavity. The unstable nature of the cavity kept the crystal from being exposed to high flux while ensuring longer interaction length. Although this scheme demonstrated in mid-IR region its advantage should persist across UV, visible, and near-IR regions too. The enhancement of conversion efficiency is effected in the second scheme by way of illuminating the crystal with alternate high and low regions of intensity along its length as against the uniform illumination case maintaining the same average intensity as in the conventional operation. The advantage is attributed to the square dependence of the second harmonic on the intensity of the pump. A simple modification of the existing experimental setup involving integration of an additional optical element with the pump cavity allowed exploitation of interference effect to realise such a non-uniform illumination condition

Effectiveness of new vibration delivery system on pain associated with injection of local anesthesia in children

Aim: Pain is highly subjective and it is neurologically proven that stimulation of larger diameter fibers - e.g., using appropriate coldness, warmth, rubbing, pressure or vibration - can close the neural "gate" so that the central perception of itch and pain is reduced. This fact is based upon "gate control" theory of Melzack and Wall. The present study was carried out to investigate the effects of vibration stimuli on pain experienced during local anesthetic injections. Materials and Methods: Thirty patients aged 6-12 years old of both the genders with Frankel′s behavior rating scale as positive and definitely positive requiring bilateral local anesthesia injections for dental treatment were included in the split-mouth cross over design. Universal pain assessment tool was used to assess the pain with and without vibration during the administration of local anesthesia and the results obtained were tabulated and statistically analyzed. Results: Local anesthetic administration with vibration resulted in significantly less pain (P = 0.001) compared to the injections without the use of vibe. Conclusion: The results suggest that vibration can be used as an effective method to decrease pain during dental local anesthetic administration

Oral manifestations of gastroesophageal reflux disease in children: A preliminary observational study

Aims: This study aimed to document the prevalence of oral manifestations seen among pediatric gastroesophageal reflux disease (GERD) patients in Chennai, Tamil Nadu, India. Methodology: This study was performed at various children's hospitals in Chennai. Fifty-one GERD patients who were assessed by endoscopy and 24 h pH-metry, 31 (60.78%) males and 20 (39.21%) females, aged 2–12 years (mean age, 7.43 years), comprised the study group. All patients answered a detailed frequency questionnaire related to regurgitation and acidic foods and participated in a clinical dental examination. Statistical Analysis Used: Data were analyzed using the SPSS statistical software package version 19. Results: Among the GERD patients, 42 (82.35%) had dental erosion. A total of 668 (57.98%) deciduous teeth and 484 (42.02%) permanent teeth were examined, of which dental erosion was detected in 248 (21.52%) and 171 (14.84%) teeth, respectively. The most commonly affected primary tooth was the occlusal surface of the maxillary posteriors and commonly affected permanent tooth was occlusal surface of the mandibular molars. Conclusions: There may be a positive correlation between GERD and dental erosion. According to this study, presence of erosion, especially in posterior teeth, could be a key to diagnose GERD and refer the child to the gastroenterologist

Efficacy of three-tone disclosing agent as an adjunct in caries risk assessment

Background: Today, most approaches to caries viewed that catastrophic change in normal plaque biofilm is responsible for the disease. The behavior and composition of the biofilm are a reflection of the oral environment; the caries is a reflection of adverse changes occurring in that environment. Thus, it is important to identify the pathogenicity of the plaque biofilm so as to predict the caries risk. The recently developed three-tone plaque disclosing agent was used to test its ability in identifying the pathogenicity of plaque. Aim: To assess the efficacy of three-tone plaque disclosing agent in identifying the plaque pathogenicity and correlate with the clinical caries status and microbiological findings. Materials and Methods: Sixty children of 6-13 years age group of both sexes were clinically examined for caries and plaque scores, and then disclosing agent was applied; the color stained plaque samples were collected and cultured for microbiological assessment, and the data were analyzed based on the caries status of the children. Results: There was a significant difference between the pathological plaque of caries active and caries free group (P < 0.05). The pathological plaque scores and the total colony counts, Streptococcus counts and mutans streptococci counts increased with the increase in caries. Conclusion: Three-tone plaque disclosing agent was effective in identifying pathological plaque and can be used as one of the chairside adjuvants in caries risk assessment

Comparative evaluation of shear bond strength and microleakage of tricalcium silicate-based restorative material and radioopaque posterior glass ionomer restorative cement in primary and permanent teeth: An in vitro study

Background: Restoration of carious primary molars is still a major concern while treating the young children that too in deep carious lesion which extends below the cemento-enamel junction (CEJ) where pulp protection and achieving adequate marginal seal are very important to prevent secondary caries. The needs were met with the development of new materials. One such of new bioactive material is tricalcium silicate-based restorative material (Biodentine), recommended for restoring deep lesions. Aim: To evaluate and compare shear bond strength and microleakage of tricalcium silicate-based restorative material (Biodentine) and glass ionomer cement (Fuji IX GP) in primary and permanent teeth. Materials and Methods: Occlusal surface of crowns were ground flat. PVC molds were stabilized over flat dentin surface and filled with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained. Shear bond strength was evaluated using universal testing machine (INSTRON). Standardized Class II cavities were prepared on both primary and permanent teeth, and then restored with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained, over which composite resin material was restored using an open sandwich technique. Microleakage was assessed using dye penetration. Microleakage was examined using a stereomicroscope. Results: Results showed that glass ionomer cement (Fuji IX GP) exhibited better shear bond strength than tricalcium silicate-based restorative material (Biodentine). Mean microleakage score for glass ionomer cement (Fuji IX GP) in permanent teeth was 1.52 and for primary teeth was 1.56. The mean microleakage for tricalcium silicate-based restorative material (Biodentine) in permanent teeth was 0.76 and for primary teeth was 0.60. Glass ionomer cement (Fuji IX GP) exhibited more microleakage than tricalcium silicate-based restorative material (Biodentine), which was statistically significant both in permanent (P = 0.02) and primary (P = 0.006) teeth. Conclusion: Shear bond strength of glass ionomer cement (Fuji IX GP) is greater than tricalcium silicate-based restorative material (Biodentine) in both primary and permanent teeth. Tricalcium silicate-based restorative material (Biodentine) exhibited less microleakage compared to glass ionomer cement (Fuji IX GP) in both primary and permanent molars

Enhancement of photorefractive two wave mixing gain with a Bessel pump beam

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal