Journal of Dental Medicine
Year:2002 | Volume:15 | Issue:3 (32)|Papers Count:9

Dentin bonding agents create stronger bonding between dental composites and dentin. But, none of them can prevent the microleakage. The important factors of progressing microleakage are the stress of polymerization shrinkage of resin composite and removal of smear layer in total-etch technique. The aim of this study was the evaluation of the effect of experimental method (modifying smear layer and etching of enamel margin) and comparison with the total-etch technique. In this experimental method, 60 extracted human molar teeth were disinfected. Then, class 5 cavities were prepared on the buccal surface and 1 mm above CEJ. The specimens were divided randomly to 6 groups with 10 samples in each group. The specimens groups were: 1- Scotchbond Multi- Purpose Plus Adhesive System (S.B.M.P.P) +Tetric composite2- S.B.M.P.P + Ariston composite3- Ariston liner + Ariston composite4- S.B.M.P.P without enamel and dentin etching + Tetric composite + rebonding with Flowable Tetric 5- S.B.M.P.P without enamel and dentin etching + Ariston composite + rebonding with Flowable Tetric 6- S.B.M.P.P without enamel and dentin etching + Tetric compositeAfter finishing and polishing, the specimens were termocycled, stained with fushin, sectioned within the specimens and evaluated for dye penetration with stereomicroscope. Wilcoxon Sign and Kruskal Wallis tests were used for statistical analysis.Results showed that group 3 had microleakage more than groups of 1, 2 and 5 (P<0.0 5) and this difference was significant. There was no significant difference among the other groups.

Nowadays, different materials have been used for regeneration of interosseous defects and Neo-Os is one of them. The objective of this study was to evaluate histologically the influence of Neo-Os® particles on bone regeneration using rabbit calvarias defects with and without protection of Gore-Tex® barrier membrane. A cutaneous- periosteal incision and flap was made on the forehead of 12 rabbits exposing the top of the skull. A standardized trans-osseous skull defect (8 mm diameter) was made in each of the parietal bone with rotating round bur. In half of the rabbits, one defect was filled with the Neo-Os® particles without any type of the barrier membrane. The other defect was left empty. In the other half of the rabbits, one defect was filled with Neo-Os® and two flat expanded polytetrafluoroethylene (Gore-tex®) membranes. For the other defect, only the Gore-tex membrane protected the defect. After 8 and 16 weeks, the specimens were processed using standard, decalcified, hard tissue histology techniques. Rabbit calvarias defects treated with Neo-Os® particles and polytetrafluoroethylene (Gore-tex®) membrane, healed by in growth of woven bone from the defect margins and by formation of bony islands within the defect area. Finally, the defects were treated with woven and lamellar bone.

One of the most important characteristics of denture base is thermal conductivity. This property has a major role in secretions of salivary glands and their enzymes, taste of the food and gustatory response. Polymethyl methacrylate used in prosthodontics is relatively an insulator. Different materials such as metal fillers and ceramics have been used to solve this problem. The aim of this study was the evaluation of Al2O3 effect on thermal conductivity of heat-cured acrylic resin. Acrylic resin was mixed with Al2O3 in two different weight rates (15 and 20 % of weight). So, group 1 and 2 were divided on this basis. Samples with pure acrylic resin were considered as control group. 18 cylindrical patterns were made in 9 9 mm dimensions and thermocouple wires embedded in each sample to act as conductor. The specimens were put in water with 70±1°C thermal range for 10 minutes. Then, thermal conductivity was measured. The results were analyzed with variance analysis and Dunken test. There was significant difference between thermal conductivity of all groups in all period times. It the first seconds, thermal conductivity in groups 1 and 2 were more than control group. Therefore, for developing of thermal conductivity of acrylic resin, Al2O3 can be used. Certainly, other characteristic of new resin should be evaluated.

Recently, inductive materials have been used for accelerating pulp cells and differentiation of odontoblast cells for regenerating secondary dentin. Bone Morphogenic Protein (BMP) is one of these materials. Endochondral Bone Matrix Gelatin (Ec BMG) has been used less than others. This study was designed to evaluate dentin formation by Ec BMG in rabbit. Ec BMG was prepared from tibia and femur of 4 Deutsche-Poland rabbits with average ages of 4-6 months. In this research, 12 rabbits were divided randomly to two groups (8 and 4 rabbits, respectively). In the first group, incisive tooth in one side was considered as experimental group and in other side as control group. In experimental group, pulp was exposed and Ec BMG was put in it. But, in control group, after exposing the pulp, tooth was dressed. In the second group, the rabbits were kept like the first group. They were killed in 28 and 60 days period time and their natural dentin was used for comparison of their calcium and phosphor with the first group. The light microscope and scanning electron microscopic study were performed on days of 28 and 60 after operation. Also, new secreted matrix was analyzed for measuring calcium and phosphor on all groups. The histological results on day 28 showed secondary dentin and osteodentin formation in experimental group. The scanning electron microscopic observation on 60th days after operation in experimental group showed mineralized mass on site of Ec BMG implantation. In contrast, in control and second groups, no mineralized mass was observed. Analyzing of new secreted matrix in experimental group showed the high deposition of calcium and phosphate on Ec BMG implantation site. But, the amount of calcium and phosphate in experimental group was the same as the second group. Results of present investigation indicated that, implantation of Ec BMG in pulp cavity could induce pulp cells, secondary dentin and osteodentin in rabbit. So, Ec BMG can be effective in repairing of dentin related defects.

Nowadays, application of implants as a new method for replacing extracted teeth has been improved. So, many researches have been performed for improving the characteristics of implants. The aim of this study was to design and produce a desired coating in order to obtaining two goals including; improvement of the corrosion behavior of metallic endodontic implant and the bone osseointegration simultaneously. Stainless steel 316L (SS), cobalt-chromium alloy (Vit) and commercial pure titanium (cpTi) were chosen as metallic substrates and hydroxyapatite coating (HAC) were performed by plasma-spraying (PS) process on three different substrates. A novel double layer Hydroxyapatite/Titanium (HA/Ti) composite coating composed of a HA top layer and a Ti under layer was prepared using PS and physical vapor deposition (PVD) process respectively on SS. Structural characterization techniques including XRD, SEM and EDX were utilized to investigate the microstructure, morpholgy and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens behavior as an indication of biocompatibility. Results indicated that the cpTi possesses the highest and SS the lowest corrosion resistance (highest corrosion current density) between uncoated substrates. This trend was independent to the type of physiological environment. The HA coating decreased the corrosion current density of HA coated metallic implants but did not change that trend. HAC acted as a mechanical barrier on the metallic substrate but could not prevent the interaction between metallic substrate and environment completely. The HA/Ti composite coating improved the corrosion behavior of SS. The corrosion current density of HA/Ti coated SS decreased and was exactly similar to single HA coated cpTi in physiological solutions. The results indicated that HA/Ti composite coated SS could be used as an endodontic implant and two goals including improvement of corrosion resistance (biocompatibility) and bone osseointegration could be obtained simultaneously.

There are many researches evaluation different methods for covering the root surface. In the most of these studies, type I and II of Miller treatment had been searched. The purpose of this study was a comparison between connective tissue graft (CTG) and guided tissue regeneration (GTR) with a collagen membrane in the treatment of gingival recession defects (Miller class III). Six patients, each contributing a pair of Miller class III buccal gingival recessions, were treated. The clinical measurements were obtained at baseline and 1, 2, 4, 6, 12, 18 months after surgery. Statistical analysis were performed using paired t-test between periods (baseline versus 6 months and baseline versus 18 months) within each treatment group and also between treatment groups before treatment and 6, 12 and 18 months after the treatment. The treatments were compared by a triple analysis of variance along the time (treatment, patient, time). Both CTG and GTR with a bioabsorbable membrane demonstrated significant clinical and esthetic improvement for gingival recession coverage. The CTG and GTR procedures had mean root coverage of 55% and 47.5% respectively, in the end of study. The CTG group was statistically better than GTR for recession depth, recession width and keratinized tissue width. Also, passing the time (18 months) as a distinct factor of treatment procedures was effective in increasing of clinical attachment level and keratinized tissue width.

The major activity for vice chancellor for research at Tehran University of Medical Sciences (TUMS) is to monitor research projects undertaken by the academic staff. Sometimes projects have been failed in meeting their objectives. The aim of this project was the evaluation of the failure of the research projects at TUMS from the establishment date to 1999. A case-control survey was designed and 70 failed projects with 71 successfully completed projects were considered and compared. Results showed that type of study, location of administration, methodology, qualification of executive and duration of project were the factors of failure of the projects. Number of executives, experienced in research projects and executive position were not the effective factors. The most important reason for failure was unsustainably of executive. So, university research council (URC) should pay attention on forecast of time and budget of projects and realization of mentioned matters, besides of attention to methodology of project.

This review was focused on investigations in the relationship between human leukocyte antigens and periodontal disease. Several studies have looked for relationship between HLA phenotypes and early onset periodontitis (EOP). There have also been reports on both positive and negative relationship between specific HLA antigens and periodontal disease. Positive relationship has been reported among HLA-A1, A9, A24, A28, A33, B15, B22, B35, B44, C4, DR2, DR4, DR7, DR53, DRB1, DQ3 and DQB1 antigens and different forms of EOP. Several studies have reported negative relationship with HLA-A2, A5, A10, A28, A68, B5, DR2 and DR6. Two antigens that appear to be more related to EOP are HLA-A9 and DR4. Evidence suggests that genes in this area are not genes with major effect for early-onset periodontal diseases. It is possible that genes in the MHC region of chromosome 6 may function as modifying genes that affect clinical expression of periodontal disease. However, additional documents are needed to evaluate the relationship of HLA antigens with periodontal disease. These documents should have adequate controls, which account for racial differences in HLA type and well-defined patient groups whose state of disease is described.

Diagnosis and treatment of patients with periodontitis as a manifestation of systemic diseases is of especial concern to the periodontist, especially those associated with genetic disorders, which have poor prognosis. With aggressive progression of periodontal bone and attachment loss, a patient could be a partial or total edentulous early in life.The aim of this article was to report a case of Papillon-Lefevre syndrome (PLS) with generalized prepubertal periodontitis (GPPP). A ten-year old boy for whom active periodontal treatment and subsequent maintenance recalls was performed for five years since the diagnosis of PLS. Treatment procedures included: precise mechanical instrumentation at several visits, periodontal surgery, adjunctive serial systemic antibiotic therapy, professional irrigation of pockets with 0/2% chlorhexidine solution and periodic maintenance recall visits. In spite of all of these, progressive course of the disease continued until the patient was fifteen and edentulous. Unfortunately association of GPPP with systemic unmanageable condition or diseases has caused refractory periodontitis, which yet has no proven and reliable treatment protocol. Besides, this article has discussed more successful treatment modalities for PLS with GPPP and the genetic aspects of host susceptibility, which is a complicated and challenging field.