RESUMO
BACKGROUND: A common problem faced by prosthodontists is achieving adequate retention and stability in the mandibular dentures. Recording the lateral throat form (LTF) correctly can aid in the retention and stability. Till date, Neil's classification has been considered as the gold standard in measuring the depth of the LTF. This is a subjective classification and varies among different operators. In this study, a customized tool was used to measure the depth of the LTF, and a classification was proposed according to the measured depths. OBJECTIVES: The objective of this study is to measure the exact depth of LTF using customized gauge and to propose a classification based on the measured depth. MATERIALS AND METHODS: A customized gauge was made to measure the depth of the LTF. Two different observers classified the LTFs according to Neil's classification and according to the proposed classification in a total group of 50 patients. The customized gauge was inserted into the alveolo-lingual sulcus to measure the depth. The Pearson's correlation statistics was carried out to observe the inter-observer relationships of sulcus depth using this customized gauge. ANOVA test was used to compare the mean depth of the sulcus as measured by observers 1 and 2. RESULTS: There was more inter-observer variability when Neil's classification was used as compared to the one with the proposed classification using the gauge. The inter-observer agreement for the proposed new classification was assessed by Cohen's kappa value, with P < 0.001. The mean depth of the sulcus as calculated by observers 1 and 2 was compared with ANOVA test and found to be significant with P < 0.001. CONCLUSION: The proposed new classification for LTF gave consistent results and was easier to use with less variability when compared to the Neil's classification.
RESUMO
A key factor for the success or failure of a dental implant is the manner in which stresses are transferred to the surrounding bone. This depends on the type of loading, bone-implant interface, the shape and characteristics of the implant surface and the quality and quantity of the surrounding bone. This study was done to evaluate the pattern of stress distribution with two different implant designs in four different densities of bone using 3D finite element analysis. Graphic pre-processing software Ansys version 10 was used for creating the geometric configuration of a section of the mandible with a missing first molar. Eight 3D models of this section restored with implant-supported all ceramic crowns were created. Four of these models were created to simulate a single threaded implant placed in four different densities of bone (D1, D2, D3 and D4). The other four models were created to simulate a single cylindrical implant placed in four different densities of bone (D1, D2, D3, and D4). The Poisson's ratio (µ) and Young's modulus (E) of elasticity of the material were incorporated into the model. An average vertical load of 400 N was applied on the occlusal surface of the first molar between the buccal cusp, central fossa and the marginal ridge. Maximum Von Mises stresses in all the eight models were observed at the crestal region or neck of the implant. The stresses observed were more for the threaded implants in all the four densities of bone when compared to that of the cylindrical implants. The study concluded that the cylindrical implant design was more favorable in softer bone than the threaded implant design.
RESUMO
Implant dentistry is the latest developing field in terms of clinical techniques, research, material science and oral rehabilitation. Extensive work is being done to improve the designing of implants in order to achieve better esthetics and function. The main drawback with respect to implant restoration is achieving good osseointegration along with satisfactory stress distribution, which in turn will improve the prognosis of implant prosthesis by reducing the crestal bone loss. Many concepts have been developed with reference to surface coating of implants, surgical techniques for implant placement, immediate and delayed loading, platform switching concept, etc. This article has made an attempt to review the concept of platform switching was in fact revealed accidentally due to the nonavailability of the abutment appropriate to the size of the implant placed. A few aspect of platform switching, an upcoming idea to reduce crestal bone loss have been covered. The various methods used for locating and preparing the data were done through textbooks, Google search and related articles.
Assuntos
Implantes Dentários , Humanos , OsseointegraçãoRESUMO
BACKGROUND AND OBJECTIVES: This in-vitro study was conducted to evaluate the strength and properties of Type III and Type IV gypsum mixed with disinfectant solutions. MATERIALS AND METHODS: Type III and Type IV gypsum were used for the study. Three different mixing solutions namely waterqueous solutions of 0.525% sodium hypochlorite and 2% glutaraldehyde were used. Gypsum materials were subjected to further modification by adding a mixture of 1.0% gum arabic and 0.132% calcium hydroxide before mixing with the disinfectant solutions, at two different liquid/powder (L/P) ratios for each. Both, the unmodified and the modified gypsum were tested for compressive and tensile strength after one hour and one week from the start of the mix. The crystalline configuration of the fracture fragments of the unmodified and modified set gypsum were studied under the scanning electron microscope. RESULTS: The disinfectant solutions reduced the strength of both Type III and Type IV gypsum. Water showed higher-strength, which was followed by 0.525% sodium hypochlorite and 2% glutaraldehyde. The modified Type III and Type IV gypsum with reduced L/P ratio also showed strength values less than that of the control groups. INTERPRETATION AND CONCLUSION: Chemical disinfectants reduced the strength of gypsum when used as water substitutes. Gum Arabic and calcium hydroxide additives permitted lower L/P ratio, however, there was still excess water retained in the set gypsum that lowered the strength values of Type III and Type IV gypsum. Hence, further reduction of L/P ratio may increase the properties of the modified Type III and Type IV gypsum.