Abstract: Aims: The purpose of this study is to evaluate the effect of 2% formaldehyde on compressive strength of dental stone (type IV), and to evaluate its antibacterial effect. Materials and methods: To study the effect of 2% formaldehyde on compressive strength of dental stone (type IV), ten samples of stone were prepared in cylindrical blocks and divided into two groups, each group contain of (5) samples. First group composed of stone and distilled water as (control group) and the second group composed of stone and (2%) formaldehyde solution. after (1h) the samples were tested for compressive strength using digital compression machine(ALFA Company, Turkey).To study the bacterial effect of formaldehyde 60 stone discs prepared and mixed with formaldehyde 2% divided into 12 group (each group consist of 5 discs) and stored for different intervals between 1-12 days, antibacterial effect against salivary sample for each interval day using disc diffusion test. Results: The statistical analysis of data by analysis of t-test reveals significant different in compressive strength between control group and stone-2% formaldehyde group at (P<0.05). The result showed that second group which contains 2%formaldehydehad higher values compared with control group. Also the results showed that the antibacterial effect of stone-formaldehyde discs continued till 12thday. Conclusions: Adding 2% formaldehyde as chemical disinfectant to dental stone increase the compressive strength in addition of the antibacterial activity of stone - formaldehyde disc continued till 12th day.

Abstract: Aims: To evaluate the accuracy of two different impression materials and to evaluate the effect of time of pouring on the accuracy of impression. Materials and Methods: Four parallel implant placed in foam arch to obtain study model. Medium body addition silicone and medium body polyether are used. 20 impressions of study model were taken under monophase technique, 10 by addition silicone and 10 by polyether by closed tray technique, half of them were pour after one hour and another half of the impressions were poured after 24 hours by die stone to obtain casts. By using Traveling microscope three linear measurements were measured between 4 implants and comparsime was made between distances on the model and on the casts to assess the dimensional changes of impression materials. Results: Statistical analysis of data by paired sample T-test at (p≤0.05) reveals no significant difference in the accuracy of each material after one and 24 hours and the results analyzed by independent samples T-test reveals no significant difference between materials after one and 24 hours under closed tray technique (dimensional change don’t exceed 1%). Conclusions: The results appeared that there is no difference in the accuracy between addition silicone and polyether and there is no effect of time (1h-24h) on the accuracy of impression, also results showed the high dimensional stability of two materials.

Abstract: Aims: To determine the real not radio graphical proximity of mandibular third molar tooth to the inferior dental canal (IDC) using panoramic radiograph. Materials and Methods: 144 mandibular third molars were evaluated by panoramic radiography. The teeth were grouped into erupted vs. un erupted further subdivided by tooth angulations. The real distance from the most inferior aspect of the mandibular third molar tooth to the superior border of the inferior alveolar canal (IAC) was calculated regarding to the reference object used. Descriptive statistics were performed as well as a t test was performed to compare erupted and unerupted teeth, and ANOVA was used to determine a significant difference where exists based upon tooth angulations. In addition, intra observer analysis was done to ensure the standardization of the radiologist interpretation. Results: The mean distance from erupted mandibular third molar teeth to the inferior alveolar canal was 0.23mm. This distance was significantly different from unerupted teeth (P = .000). The mean values for unerupted teeth were negative values which indicated that the apices of all teeth measured was below the superior border of the canal –1.26 mm and as follows: Mesioangular–1.32 mm, vertical – 1.34 mm and –1.04mm for horizontal impactions. Statistically there was no significant positional difference between the impaction groups (P = .835). In general there was a significant difference in third molar position between those age equal and less than 22 years old and those equal and over 23 years old. Conclusions: Unerupted mandibular third molar teeth (mostly vertical impaction) are closer to the inferior alveolar canal than erupted teeth and persons in general of an age equal or less than 23 years old have a closer lower third molar to mandibular canal than other ages and there is no significant relation between this age group and any of impaction types.

Abstract: Aims: This study investigated the effect of polishing times (immediately, 1 hour and 24 hour after light curing) and staining solutions on the color stability of two composite resins. Materials and Methods: Nanocomposite (Filtek Z350) and microhybrid composite (Valux plus) were used. Sixty discs (8mm diameter×2mm height) were made for each composite, and divided into four groups: the first group was polished immediately after light curing; second group was polished after 1 h; third group was polished after 24 h of curing; and the fourth group was the control. Color was measured with spectrophotometer. After baseline color measurements, the specimens of each group divided into three subgroups; specimens of first subgroup were immersed in coffee; specimens of second subgroup were immersed in orange juice; specimens of third subgroup were immersed in distilled water, after 7 day of immersion, the color was measured again and ΔE were calculated. Statistical analysis: Two-way ANOVA, Duncan's Multiple Range test and t-test. Results: The influence of polishing times and staining solutions on color change was significant. Polishing 24 hours after curing presented lowest ΔE value. Coffee promoted more color change than orange juice and distilled water, Filtek Z350 showed lower ΔE than Valux plus. Conclusions: Immediate polishing negatively affect the color stability of composite resins, coffee had a significant influence on discoloration of composite resins. The nanocomposite showed higher color stability than microhybrid composite.

Abstract: ABSTRACT Aims: The thickness of Co-Cr metal beneath the ceramic in the metalo-ceramic system can affect the color parameters. This study investigated the effect of different thicknesses of Co-Cr plate on the color parameters. Materials and method: Thirty square Co-Cr samples were made (10x10)mm length, width, respectively with varying thickness (0.3, 0.5, 1)mm, two shades (A1, A3.5) of ceramic build on the metal squares five of each thickness, and they were tested by colorimeter to measure the color parameters. Results: Mean L*value of 0.3mm metal thickness of both shades have shown a significant increase on expense of other thicknesses at (P>0.05). Conclusions: L* values were increased with the decrease in the metal thickness to a value near the opaque layer thickness, and decreased with the increase of metal thickness up to five folds of opaque layer thickness, metal thickness had no effect on the means of a*b* values.

Abstract: Aims:To investigate the efficacy of dried gamma-irradiated amniotic membrane dressing for the healing of full-thickness skin wounds, using a rabbit model. Materials and Methods: This study was performed in the Oral and Maxillofacial sugery Department, College of Dentistry, University of Mosul, Iraq. Twenty, locally bred, six to eight months old male rabbits were planned to conduct the study. Bilateral full-thickness circular segments approximately 10 mm in diameter and nearly (3-4)mm in thickness were excised from the the back of each rabbit ( near to the mid-dorsum area) with a surgical blade; one dorsal skin wounding was performed lateral to the midline on right side, the other wound was performed lateral to the midline on left side. The right wound was used as an experimental wound and covered with dried amniotic membrane whereas the left wound was considered as a control wound. All wounds were covered with non adherent moist occlusive gauze. Animals were divided into four groups according to sacrificing date ( 3, 7, 14, 30) days. Skin specimens were collected after sacrificing the rabbits. The specimens were placed in formaldehyde and sent for histopathological examination and scoring for wound healing. Results: The histopathological findings of this study revealed that there was a significant difference of reepithelialization between the two groups at two weeks period, at p-value < 0.05, while there was no significant difference at 3 days, one week, and one month. Conclusions: This study concluded that amniotic membrane can be used as a safe dressing, promoting epithelialization on secondary wounds.

Abstract: Aims : The objective of this study is to evaluate the effects of 5-fluorouracil (5-FU) on the liver tissue of rabbits, as well as the effect of folic acid on the effectiveness of 5-FU on the rabbit's liver. Materials and Methods: In this study nine adult male rabbits ,aged about 3 months were used and divided into three main groups .Group 1 : served as a control group and received normal saline only.Group 2 : treated by 5fluorouracil , 10 mg / kg intraperitonealy twice weekly for 8 weeks. Group 3 : treated by 5-fluorouracil , 10 mg / kg intraperitonealy twice weekly for 8 weeks with 5mg of folic acid orally twice weekly for 8 weeks .The animals were sacrificed and livers were excised and processed for histological study. Results: The liver of the treated group 2 shows disturbance in the architecture of hepatic lobule , swelling and vacuolation of the hepatocytes ,with ballooning degeneration and areas of necrosis. Congestion in the portal blood vessels and congestion in the central vein , together with congestion and dilatation of the sinusoids. Infiltration of mononuclear inflammatory cells in the portal area and around the central vein .While liver sections of group 3 show slight disturbance in hepatic cords architecture , hepatocytes showed no swelling and few vacuolation in their cytoplasm ,mononuclear cells infilitration mainly in the portal area and in lesser degree than that found in group 2 ,necrosis were not present. Conclusion:Toxic effect of 5-FU was observed on the liver tissue of rabbits , and an effective drugs must be applied with anticancer agents to improve liver function .

Abstract: Aims: The purpose of this study was to estimate the bactericidal effect of erbium,chromium:yttrium scandium gallium garnet 2,780nm (Er, Cr:YSGG) on contaminated sand-blasted, large grit, acid-etched (SLA) dental implant and determine the parameter that effectively detoxify the surface of implant ailed with periimplantitis before regenerative therapy of the area. Material and Methods: Implants (3.4*10mm) with SLA surfaces fixed with Enterococcus faecalis and irradiated with Er,Cr:YSGG lasers. After laser treatments, the number of remaining colony-forming units (CFUs) counted. The entire implant surface exposed uniformly in constant time and different energies. six powers were used ( 0.25, 0.5, 0.75, 1, 1.25, 1.5watt ) at 20 Hz, water 20%, air 40% with movable motions on each thread for 30 second and in non contact mode at 2 mm distance between MZ10 tip and target with H mode. Results: laser showed total bacteria reduction on the implants irradiated with 1.5W. Significant differences between measurements in the different groups at (P<0.05) were observed, depending on the used power. Conclusions: Er,Cr:YSGGlaser can be used at above parameter safelyon implant surface as disinfection tool in treatment of peri-implantitis

Abstract: Aims :evaluate the effect of abutment angulation on fracture strength of pre-fabricated zircon implant abutment supported CADCAM zircon crown. Material and methods: Ten analog with 3.75×14mm were placed into resin blocks divided in to 2 groups: group A (n=5) parallel to long axis and group B (n= 5) fixed at angulation (17°) to long axis. Then ten abutments were tightened to 25 N/cm2. Ten full anatomic zircon (CAD/CAM) crowns constructed as upper right central incisor: 5 on each group. After luting all crowns with dual cure resin-based luting, all samples passed to artificial aging using thermocycling machine, 500 cycles at (5 to 55 C°±2) degree. Then the load was applied by universal testing machine at 30 degree to the long axis until fracture occurred. Results: Statistical analysis showed that the implant abutment angulations significantly (p < 0.05) reduced the fracture resistance of zircon implant abutment. Conclusions: Within the limitation of this in vitro study it may be concluded that: the fracture strength of zircon implant abutment supported CADCAM zircon crown is significantly reduced in respect to the angulation fromstraight to angulated (17°) zircon abutment.

Abstract: Aims: The present study aims to estimate the effect of maxillary canine displacement on the arch measurements including ( inter 1st premolar width, inter1st molar width, inter2nd molar width, arch length, and arch perimeter). Materials and Methods: Maxillary dental study casts of 105 patients attending the orthodontic department of dentistry college, University of Mosul. The casts were photocopied and then all the measurements accomplished with the aid of AutoCAD 2010 software program (Automatic Computer Aided Design). The statistical analysis were done using software package (SPSS 11.5). Results and Discussion: The results showed significant difference among the variables at (p < 0.001, p < 0.05 ), the maxillary transverse dimensions were greater in the control group than in the canine displacement group and this may be attributed to that the displaced canine subjects have narrower dental arch than that for the normal subjects, also the results show that the mesiodistal dimensions of maxillary teeth in the canine displacement group were wider in comparison to the control group. Conclusion: The displaced canine position affect the arch width resulting in a narrow transverse arch measurement. In addition, the results of the arch perimeters indicate wider teeth for displaced canine group compared to control group.