Dental Research Journal
Volume:11 Issue: 4, Jul 2014

Control of hemorrhage is one of the challenging situations dentists confront during deep cavity preparation and before impressions or cementation of restorations. For the best bond and least contamination it is necessary to be familiar with the hemostatic agents available on the market and to be able to choose the appropriate one for specifi c situations. This review tries to introduce the commercially available hemostatic agents, discusses their components and their specifi c features. The most common chemical agents that are widely used in restorative and prosthodontic dentistry according to their components and mechanism of action as well as their special uses are introduced. PubMed and Google Scholar were searched for studies involving gingival retraction and hemostatic agents from 1970 to 2013. Key search words including: “gingival retraction techniques, impression technique, hemostasis and astringent” were searched. Based on the information available in the literature, in order to achieve better results with impression taking and using resin bonding techniques, common hemostatic agents might be recommended before or during acid etching; they should be rinsed off properly and it is recommended that they be used with etch and-rinse adhesive systems.

Tissue engineering represents very exciting advances in regenerative medicine; however, periodontal literature only contains few reports. Emdogain (EMD) consists of functional molecules that have shown many advantages in regenerative treatments. This study investigated EMD effect on gingival fi broblast adhesion to different membranes. Two dense polytetrafl uoroethylene membranes (GBR-200, TXT 200), Alloderm and a collagenous membrane (RTM Collagen) were used in this experimental study. Each membrane was cut into four pieces and placed at the bottom of a well in a 48-well plate. 10 μg/mL of EMD was added to two wells of each group.Two wells were left EMD free. Gingival fi broblasts were seeded to all the wells. Cell adhesion was evaluated by means of a Field Emission Scanning Electron Microscope after 24 hours incubation. Data was analyzed by independent t-test, one-way and two-way ANOVA and post hoc LSD test. P < 0.05 in independent t-test analysis and P < 0.001 in one-way ANOVA, two-way ANOVA and post hoc LSD analysis was considered statistically signifi cant. Alloderm had the highest cell adhesion capacity in EMD+ group and the difference was statistically signifi cant (P < 0.001). In EMD- group, cell adhesion to TXT-200 and Alloderm was signifi cantly higher than GBR-200 and collagenous membrane (P < 0.001). This study showed that EMD may decrease the cell adhesion effi cacy of GBR 200, TXT-200 and collagenous membrane but it can promote this effi cacy in Alloderm. It also showed the composition of biomaterials, their surface textures and internal structures can play an important role in their cell adhesion effi cacy.

The aim of this study was to evaluate the effect of local injection of human growth hormone (GH) in stimulating cartilage and bone formation in a rabbit model of temporomandibular joint (TMJ). In an experimental animal study, 16 male Albino New Zealand white rabbits aged 12 weeks were divided into two groups: In the fi rst group (7 rabbits) 2 mg/kg/1 ml human GH and in the control group (9 rabbits) 1 ml normal saline was administered locally in both mandibular condyles. Injections were employed under sedation and by single experienced person. Injections were made for 6 times with 3 injections a week in the all test and control samples. Rabbits were sacrifi ed at the 20th day from the beginning of study and TMJs were histologically examined. ANOVA (two-sided) with Dunnett post hoc test was used to compare data of bone and cartridge thickness while chi-square test was used to analyze hyperplasia and disk deformity data. P < 0.05 was considered as signifi cant. Cartilage layer thickness was greater in the GH-treated (0.413 ± 0.132) than the control group (0.287 ± 0.098) (P value = 0.02). Although bone thickness and condylar cartilage hyperplasia were greater in the GH-treated group, these differences were not statistically signifi cant (P value = 0.189 and 0.083, respectively). There was no statistically signifi cant difference between two groups regarding the disc deformity (P value = 0.46). Local injection of human GH in the TMJ is able to accelerate growth activity of condylar cartilage in rabbit.

Multi-specie biofi lms are highly resistant to antimicrobials due to cellular interactions found in them. The purpose of this study was to evaluate, by confocal laser scanning microscopy, the biofi lm dissolution effectiveness of different irrigant solutions on biofi lms developed on infected dentin in situ. A total of 120 bovine dentin specimens infected intraorally (/group) were treated by the following solutions: 2% of chlorhexidine digluconate, 1%, 2.5% and 5.25% of sodium hypochlorite (NaOCl). The solutions were utilized for 5, 15 and 30 min with 2 experimental volumes 500 μL and 1 mL. All the samples were stained using an acridine orange and the biofi lm thickness before (control group) and after the experiments were evaluated, utilizing a confocal microscope at ×40. The Mann-Whitney U and the nom-parametric Kruskal-Wallis Dunns tests were utilized to determine the infl uence of the volume and to perform the comparisons among the groups respectively. The signifi cance level was set at P < 0.05. Statistical differences were not found among the control and the 2% chlorhexidine digluconate groups at any experimental period (P > 0.05). The biofi lm dissolution treated with 1% NaOCl was directly proportional to the exposure time (P < 0.05). The higher values of biofi lm dissolution were found in 2.5% and 5.25% NaOCl groups (P > 0.05). The higher exposure times and concentrations of NaOCl were not suffi cient to dissolve 100% of the biofi lm. However, all NaOCl solutions were more effective than 2% chlorhexidine digluconate to dissolve organic matter.

Primary stability is an important factor for the clinical success of orthodontic mini-screws. The present study made an attempt to evaluate the effect of insertion angle changes on the maximum insertion and removal torque of orthodontic mini-screws. In this experimental study, 72 mini-screws (Dual Top Anchor System, Jeil, 1.6 mm diameter, 8 mm length) were used. They were randomly divided into four equal groups and inserted in poly-carbonate plates with 3 mm thickness. Then, their maximum insertion torque (MIT) and maximum removal torque (MRT) were recorded using a digital torque tester/screwdriver. Each group had a different insertion angle (90o, 75o, 60o and 45o). The data were analyzed by SPSS software (version 18) using one-way ANOVA and post-hoc Tukey’s tests. The level of signifi cance was set at 0.05. The maximum MIT was observed in 45o insertion angle (14.84 Ncm) and the minimum MIT was reported in 75o insertion angle (12.66 Ncm). The maximum MRT was observed in 4 o insertion angle (23.21 Ncm) and the minimum MRT was reported in the 90o insertion angle (17.43 Ncm). Oblique insertion of the mini-screws results in higher insertion and removal torques and probably more primary stability compared to the vertical insertion.

The accelerating effect of plasma rich in growth factors (PRGFs) in the healing of extraction sockets has been demonstrated by some studies. The aim of the present study was to histologically and histomorphometrically evaluate whether bone formation would increase by the combined use of PRGF and demineralized freeze-dried bone allograft (DFDBA). In four female dogs, the distal root of the second, third and fourth lower premolars were extracted bilaterally and the mesial roots were preserved. The extraction sockets were randomly divided into DFDBA + PRGF, DFDBA + saline or control groups. Two dogs were sacrifi ced after 2 weeks and two dogs were sacrifi ced after 6 weeks. The extraction sockets were evaluated from both histological and histomorphometrical aspects. The data were analyzed by Mann-Whitney followed by Kruskal-Wallis tests using the Statistical Package for the Social Sciences version 20 (SPSS Inc., Chicago, IL, USA). Signifi cant levels were set at 0.05. The least decrease in socket height was observed in the DFDBA + PRGF group (0.73 ± 0.42 mm). The least decrease in the coronal portion was observed in the DFDBA + PRGF group (1.38 ± 1.35 mm²). The least decrease in the middle surface was observed in the DFDBA group (0.61 ± 0.80 mm²). The least decrease in the apical portion was observed in the DFDBA group 0.34 ± 0.39 mm²). The present study showed better socket preservation subsequent to the application of DFDBA and PRGF combination in comparison with the two other groups. However, the difference was not statistically signifi cant.

The aim of this ex vivo study was to compare the antimicrobial effect of triantibiotic paste, 0.2% chlorhexidine gel, Propolis and Aloe vera on Enterococcus faecalis in deep dentin. Ninety fresh extracted single-rooted teeth were used in a dentin block model. Seventy-fi ve teeth were infected with E. faecalis and divided into four experimental groups (n = 15). Experimental groups were treated with triantibiotic mixture with distilled water, 0.2% chlorhexidine gel, 70% ethanol + Propolis and Aloe vera. Fifteen teeth treated with distilled water as the positive control and 15 samples, free of bacterial contamination, were considered as the negative control. Gates- Glidden drill #4 was used for removal of surface dentin and Gates-Glidden drill #5 was used to collect samples of deep dentin. The samples were prepared and colony-forming units were counted. Data were analyzed by one-way ANOVA and post hoc Tukey tests. Statistical signifi cance was defi ned at P < 0.05. Triantibiotic mixture group exhibited the least bacterial growth. However, the rate of bacterial growth showed no signifi cant differences between chlorhexidine and Propolis groups (P > 0.05). Aloe vera had antibacterial effects on E. faecalis, but in comparison with other medicaments, it was less effective (P < 0.05). This experimental study showed that triantibiotic mixture, 0.2% chlorhexidine gel, Propolis and Aleo vera were relatively effective against E. faecalis. All the intracanal medicements had similar effects on E. faecalis in deep dentin except for Aloe vera.

Zinc (Zn) is an essential nutrient that is required in humans and animals for the growth, development, and maintenance of healthy bones. The aim of this study is to investigate the effects of zinc-defi cient nutrition on the dental, mandibular, maxillary, and cranial dimensions of rats. This experimental study was carried out on 14 male Wistar rats. The rats were randomly divided into two groups. Group I rats were fed with a Zn-defi cient (ZD) diet, and Group II rats with a Zn-containing (ZC) diet. All the rats on the experimental diet were killed at the end of the fourth week and their blood samples were taken. The serum Zn levels were measured by an atomic absorption spectrophotometer. Radiographic assessment of the jaw bone density was done at the end of the study. Subsequently, the fi nal measurements were made on the dry skulls, the mandibles, and teeth in both the groups. Statistical evaluation was performed by the student’s t-test and repeated measures analysis. The difference between the groups was considered statistically signifi cant if P < 0.05. The ZD group showed a signifi cantly lower value in body weight (P < 0.05), serum level of zinc (P < 0.0001), and radiographic bone density of the mandible (P = 0.02). With regard to the craniofacial parameters, a signifi cant difference was observed only in the length of the clinical crowns of the teeth (L13), which were longer in group II as compared to group I (P = 0.03). This study confi rmed that changes in zinc intake could not affect the growth of craniofacial structures. Also, it might change the radiographic bone density of the mandible.

Low-intensity laser therapy (LILT) can be utilized for different treatments in the fi eld of orthodontics and dentofacial orthopedics. The aim of the present study was to evaluate the effi cacy of LILT on (1) the rate of canine movement during canine retraction phase and 2) evaluate the radiographic changes occurring during LILT around the irradiated area. A total of 10 patients of both genders were included for this study. One quadrant of the upper arch was considered control group (CG) and received mechanical activation of the canine teeth with 150 g. The opposite quadrant received the same mechanical activation and was also irradiated with a diode emitting light (gallium-arsenide laser) at 904 nm, for 10 s at 12 mW, at 4.2 J/cm2. Laser application was done on 1st day, 3rd, 7th, 14th, 21th, 2 th, 35th, 42nd, 49th, 56th day respectively during the canine retraction phase. Distance was measured on 1st day, 35th day and 63rd day and appliance activation was done on 1st and 35th day. Results were analyzed using t-test with the signifi cance level set at P < 0.01. Mean value obtained from 1st to 63rd day was 3.30 ± 2.36 mm for CG and 3.53 ± 2.30 mm for laser group (LG). There was no statistically signifi cant difference in the rate of tooth movement during canine retraction between the LG and the CG. There was no evidence of any pathologic changes in the radiograph following LILT.

The success of dental implants depends on the manner in which stresses are transferred to the surrounding bone. An important consideration is to design an implant with a geometry that will minimize the peak bone stresses caused by standard loading. The aim of this study was to assess the infl uence of implant thread geometry on biomechanical load transfer and to compare the difference between two different thread designs. A three-dimensional fi nite element model of D2 bone representing mandibular premolar region was constructed. Two implants of differing thread geometries, 13-mm length, and 4-mm diameter along with superstructures were simulated. One design featured fourfold microthread of 0.4-mm pitch, 0.25-mm depth in the crestal one-third; 0.8-mm pitch, 0.5 mm depth in the apical two-third. The other design had a single-pitch microthread of 0.8-mm pitch, 0.25-mm depth in the crestal one-third; 0.8-mm pitch, 0.5-mm depth in the apical two-third. A static axial load of 100-N was applied to the occlusal surface of the prosthesis. ANSYS CLASSIC 9.0 (PA,USA) software was used for stress analysis as von Mises stresses. A comparison of von Mises stresses between two thread designs revealed that fourfold microthread allows better stress distribution within the implant body by 43.85%, abutment by 15.68%, its superstructure by 39.70% and 36.30% within cancellous bone as compared to single pitch microthread. The effective stress transfer to the cortical bone is lowered by 60.47% with single-pitch microthread. Single-pitch microthread dissipates lesser stresses to cortical bone while the implant body, abutment, and superstructure absorb more stress. This will have a positive infl uence on the boneimplant contact and contribute to preservation of crestal bone. Implant with single pitch microthread will thus be preferable to be used in areas where the amount of cortical bone available is less.