Inherited risk for common disease

Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007.Includes bibliographical references (leaves 149-151).Linkage disequilibrium studies have discovered few gene-disease associations for common diseases. The explanation has been offered that complex modes of inheritance govern risk for cancers, cardiovascular and cerebrovascular diseases, and diabetes. Such studies, however, depended on the untested assumption of monoallelic risk. My research advisor and I set out to investigate whether simple forms of inherited risk, monoallelic or multiallelic, could be excluded by analysis of familial risk for a common disease, such as colorectal cancer (CRC). First, we derived formulae that describe the risk for monogenic, multigenic, and polygenic possibilities of Mendelian inheritance. Next, we obtained an estimate of minimum lifetime risk for CRC of >0.26. Then, we examined the case of late-onset CRC, using the Swedish Family Cancer Database (1958-2002) to estimate the familial relative risk for CRC diagnosis at age 50 or older, and obtained an estimated range of 1.5 to 3.0. We compared this range of actual values to the ranges of expected values for monogenic, multigenic, and polygenic modes of inheritance.(cont.) We delimited bounds that can be placed on the conditions for various modes of inheritance. The key observation is that monogenic risk for CRC is included among various possibilities, and cannot be eliminated by existing observations. The arguments herein indicate that further efforts can and should be made to obtain more precise estimates of familial risk for CRC and other common forms of cancer.by Helen Banava.Ph.D

Histological Evaluation of Single and Double-visit Direct Pulp Capping with Different Materials on Sound Human Premolars: A Randomized Controlled Clinical Trial

Introduction: The aim of this study was to evaluate the clinical and histological status of the pulp in sound human premolars after direct pulp capping (DPC) with four different DPC methods/materials. Methods and Materials: This study was conducted on eight volunteers who had to extract four first premolars due to orthodontic treatment. Subsequent to tooth isolation, standardized class I occlusal cavities were prepared and the buccal pulp horns were exposed. Then four different protocols of DPC were applied randomly: group A (control); calcium hydroxide lining paste (Dycal), group B; ProRoot MTA (standard double-visit method), group C; ProRoot MTA (single-visit method) and group D; calcium hydroxide injectable paste (Multi-Cal). The cavities were then restored and the patients were put on a six-week clinical follow-up and by the end of this period the teeth were extracted for histological evaluation. Data were analyzed with the Kruskal Wallis test and the level of significance was set at 0.05. Results: In terms of clinical symptoms and formation of hard tissue bridge (HTB), no significant differences were found between groups A, B and C (P>0.05); however, group D’s results were significantly different as they exhibited minimal HTB formation and excessive sensitivity (P<0.05). Inflammation was significantly lower in group B (P>0.05). Conclusion: Application of MTA during a single-visit protocol of DPC was clinically and histologically as successful as the standard double-visit method but the routine use of Multi-Cal as pulp capping material is questionable and should be reconsidered

Effect of pH on compressive strength of some modification of mineral trioxide aggregate

Objectives: Recently, it was shown that NanoMTA improved the setting time and promoted a better hydration process which prevents washout and the dislodgment of this novel biomaterial in comparison with WTMA. This study analyzed the compressive strength of ProRoot WMTA (Dentsply), a NanoWMTA (Kamal Asgar Research Center), and Bioaggregate (Innovative Bioceramix) after its exposure to a range of environmental pH conditions during hydration. Study Design: After mixing the cements under aseptic condition and based on the manufacturers' recommendations, the cements were condensed with moderate force using plugger into 9 × 6 mm split molds. Each type of cement was then randomly divided into three groups (n=10). Specimens were exposed to environments with pH values of 4.4, 7.4, or 10.4 for 3 days. Cement pellets were compressed by using an Instron testing machine. Values were recorded and compared. Data were analyzed by using one-way analysis of variance and a post hoc Tukey's test. Results: After 3 days, the samples were solid when probed with an explorer before removing them from the molds. The greatest mean compressive strength 133.19±11.14 MPa was observed after exposure to a pH value of 10.4 for NanoWMTA. The values decreased to 111.41±8.26 MPa after exposure to a pH value of 4.4. Increasing of pH had a significant effect on the compressive strength of the groups (p<0.001). The mean compressive strength for the NanoWMTA was statistically higher than for ProRoot WMTA and Bioaggregate (p<0.001). Moreover, increasing of pH values had a significant effect on compressive strength of the experimental groups (p<0.001). Conclusion: The compressive strength of NanoWMTA was significantly higher than WMTA and Bioaggregate; the more acidic the environmental pH, the lower was the compressive strength

Monogenic, multigenic, and polygenic determinants of cancer risk

Thesis (S.M. in Toxicology)--Massachusetts Institute of Technology, Biological Engineering Division, 2002.Includes bibliographical references (leaf 23, 1st group).A formal series of conditions of lifetime genetic risk of cancer is explored, and algebra is provided for applications in human population genetics. Risks are considered in terms of alleles necessary and/or sufficient for carcinogenesis. Alleles are first classified with respect to their effects on reproductive fitness, and then in terms of their potential effects on carcinogenic pathways. The algebraic formulations for a series of genetic possibilities: monogenic, multigenic, and polygenic, are provided. It is expected that technology will be developed to identify and enumerate rare inherited alleles in large general and cancer proband populations.by Helen Banava.S.M.in Toxicolog

The effect of casein phosphopeptide amorphous calcium phosphate fluoride paste (CPP-ACPF) on oral and salivary conditions of patients undergoing chemotherapy: A randomized controlled clinical trial

Background: Oral and saliva conditions of patients undergoing chemotherapy is often affected by the medication they receive. Up to now, no appropriate medication that possesses the positive effects of chemotherapy without presenting oral complications has been introduced. Objective: The aim of this study was to assess the clinical effects of CPP-ACPF paste on the oral and salivary status of patients undergoing chemotherapy. Methods: From October 2013 to April 2014, 20 patients in chemotherapy treatment plans and who met the inclusion criteria enrolled in this randomized parallel single-blind controlled clinical trial in Shohada-e-Tajrish Hospital in Tehran, Iran. Patients were divided into two groups: 1) patients received their daily medication of cancer therapy center (group 1, control); 2) patients applied CPP-ACPF Crème (MI paste plus, GC USA) twice a day as instructed (group 2). The baseline status of oral conditions of patients (mucositis, dry mouth, infection, diminished tasting sense, difficulty in food intake, burning sensation of mucosa, saliva and dental plaque pH, rest and stimulated saliva, buffering capacity of saliva) were recorded and reevaluated after 21 and 42 days. The data were analyzed with a Mann-Whitney U-test. Results: A total of 20 patients were allocated randomly to groups 1 and 2. The Mann-Whitney U-test showed that application of CPP-ACPF paste twice daily did not cause any significant difference in oral complication of the subject group compared with the control group (p>0.05). Among salivary signs, resting and stimulated saliva rates and saliva buffering capacity had significantly altered in the CPP-ACPF group in day 21 and 42 in comparison with those of the control group (p<0.05). Conclusion: Application of CPP-ACPF paste before and during chemotherapy can improve the salivary status of patients undergoing this treatment. Trial registration: The trial is registered at the U.S. National Institutes of Health (https://www.clinicaltrials.gov) with the identification number NCT01737307. Funding: The authors received no financial support for the research, authorship, and/or publication of this articl

In vitro Comparative Study of Compressive Strength of DifferentTypes of Composite Resins in Different Periods of Time: Deposition of nano-crystalline fluorhydroxyapatite coatings on titanium substrates via sol-gel method

To evaluate the ultimate compressive strength of five composite resins after 1 hour,24 hours, 7 days and 1 month. Twenty four cylindrical 4 mm×8mm specimens ofeach commonly used composite resins in posterior region (Nulite-F , Z250 , P60,Biscore, Tetric ceram HB) were prepared. Each group of composite resins weredivided into four time groups of 1 h, 24 h, 7 days and 1 month. All of specimensstored in an incubator with 37 °C. After each period of time all of the specimenswere tested by Zwick/Roell Z020 (Germany) for ultimate compressive strength atcross head speed of 0.5 cm/min. Results were analyzed by ANOVAand Scheffe test.P60 and Z250 had the highest and Nulite-F and Tetric ceram HB had the lowestcompressive strength at all the times. The difference between these two groups wasstatistically significant (p&lt;0.05). The results of the Biscore was steady among theother groups. It is suggested to use Z250 or P60 in posterior restorations instead ofthe other composite resins tested

Enamel Erosion by 15% and 18% Hydrochloric Acid Gels after Different Application Times

Background and Aim: Discolored teeth are among the most common reasons behind seeking esthetic dental treatments. Resin infiltration is a new technique for treatment of white spot lesions (WSLs). In this technique, 15% hydrochloric acid (HCl) is used to cause surface erosion. The aim of this study was to compare the enamel erosion caused by 15% and 18% HCl gels after different application times. Materials and Methods: In this experimental study, sixty sound enamel surfaces were randomly divided into six groups of 10 (G1-G6). G1 specimens were subjected to 15% HCl gel for 75 seconds. G2 and G3 samples were subjected to 15% HCl for 90 and 120 seconds, respectively. G4, G5, and G6 specimens were subjected to 18% HCl for 75, 90, and 120 seconds, respectively. The specimens were then evaluated under a scanning electron microscope (SEM), and the depth of erosion was recorded. Data were analyzed by using one-way analysis of variance (ANOVA) and Tukey’s post-hoc test with a 95% confidence interval. Results: The depth of erosion in 18% HCl groups was greater than that in 15% HCl groups after the same application times (P0.05). Conclusion: The results of this study showed that the application of 18% HCl for 75 seconds is a suitable alternative to the application of 15% HCl for 120 seconds in the resin infiltration technique