Vol 4, No 1 (2007)
Proceeding Abstracts
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Objective: The aim of this study was to compare subepithelial connective tissue grafts (SCTG) and coronally advanced flaps (CAF) with the addition of Emdogain in the treatment of gingival recession.
Materials and Methods: This interventional randomized controlled clinical trial involved eleven patients and 31 teeth demonstrating facial recessions of > 2 mm identified as Miller's class I or II. Recession depth (RD), recession width (RW), probing depth (PD), clinical attachment level (CAL), and keratinized tissue (KT), were measured at baseline and at 4, 12 and 24 weeks postoperation. Before surgery the samples were randomized to receive either a CAF with Emdogain (test group) or a connective tissue graft (control group). Data were analyzed using independent t-test and univariate analysis of variance.
Results: Twenty-four weeks after therapy, the mean root coverage in the test and control cases was 50.24% and 65.82%, respectively. There was no significant difference between the two groups (P=0.759). Within the 24-week follow-up period both procedures resulted in statistically significant improvement in RD, RW and CAL, but not in PD. KT increased 0.7 mm in the SCTG group while it decreased 0.5 mm in the Emdogain group (P<0.05).
Conclusion: The SCTG procedure provided better results in comparison to CAF with Emdogain. However the later method is easier and less technique-sensitive. Therefore it can be considered as a possible substitute for the treatment of gingival recessions, especially when increasing KT is not required. -
Objective: The purpose of this study was to evaluate the dental movements of the labial segmentand the canines during leveling and alignment using pre-adjustedappliances and light forces with the MBT technique.The effect of lacebacks on the horizontal movement of the first molars was also assessed.
Materials and Methods: Fourteen patients with a mean age of 14.08 years were selected for this before-after clinical study. Dental casts were prepared for each subject at the onset of the study followed by banding and bonding using preadjusted brackets. A lateral cephalogram was taken with the appliances in place (T0). All patients underwent exraction of the four first premolars and treatment started using the MBT technique. A second set of casts and another cephalogram was obtained after 8 weeks (T1).
Results: All contact point displacements decreased between T1 and T2 with the mean (SD) of -7.65 (4.16) mm in the upper arch; -7.07(3.28) mm in the lower arch. Retroclination was observed in the maxillary and mandibular incisors with the mean value of -0.021 (1.696) mm and -0.021 (1.515) mm during the study period respectively. The lower first molars showed 0.0207 (0.9657) mm displacementand the upper first molars showed 0.665 (1.296) mm mesial movementin the horizontal plane. The upper and lower canines moved distally and were uprighted, respectively. A significant increase was found in the mandibular intercanine width (P= 0.004).Conclusion: The results of this study are in favor of using preadjusted brackets for orthodontic treatment. In premolar-extraction, cases receiving preadjusted edgewise appliances; the lower labialsegment does not procline during the leveling stage.
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Objective: This study was designed to compare the stress produced at the PDL of abutment teeth with two angles of cervical convergence, in otherwise similar settings.
Materials and Methods: Two finite element models were designed for a second premolar and a removable partial denture frame containing an I-bar clasp. Maximum Principal Stress (S1) and Von Mises Stress (SEQV) were assessed along a cervico-apical path of nodes in the PDL.
Results: Output data for S1 and SEQV were the same regarding the height of contour. A gradual decrease in both models was observed. A larger decrease was found in the model with the higher angle of cervical convergence.Conclusion: I-bars placed on teeth with lower angles of cervical convergence produce a higher stress to the PDL of abutments.
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Objective: Different ceramic repair systems have been reported for fractured ceramics. However, limited information is available concerning the bond strength of these systems especially after thermocycling. The aim of this in-vitro study was to determine the effect of thermocycling on the shear bond strength of composite-resin to feldspathic porcelain with and without silane pretreatment.
Materials and Methods: In this experimental study, forty porcelain blocks were prepared and randomly divided into four groups (n=10). All porcelain surfaces were etched with 9.6% hydrofluoric acid, rinsed and air dried. In groups 1 and 3, silane pretreatment was applied using Adper Scotchbond Multipurpose Plus (ASMP). Small-particle composite-resin was subsequently added on the ceramic surfaces, and light-cured. Specimens of groups 3 and 4 then subjected to 1000 thermal cycles. Shear bond strength was determined on a universal testing machine at a crosshead speed of 1mm/min. Two-way ANOVA test (a=0.05) was used to analyze the bond strength.
Results: There were statistically significant differences between study groups (P<0.05). Thermocycling caused a decrease in the shear bond strength for both silanized and non-silanized groups.
Conclusion: According to the results of this study, shear bond strength after thermocy-cling reduced considerably in ASMP system. In addition, silane treatment of porcelain was critical for achieving durable bond strength between composite-resin and porcelain. -
Objective: The purpose of this study was to evaluate and compare the effect of storage time and conditions on dimensional stability of acrylic patterns.
Materials and Methods: In this in vitro study, a cylindrical shaped metallic post-core was fabricated. Impressions were made from this metallic model and 30 samples were prepared with Duralay acrylic resin. The specimens were divided into three groups of ten. Groups A, B and C were stored in dry atmosphere at 25°C; 100% humidity at 25°C; and water placed in the refrigerator at 4°C, respectively. In each sample post length, post diameter and core diameter were measured at baseline, 24 hours and 48 hours after storage. All measurements were performed in an optical measurement device. Data were analyzed using the Rank regression test.
Results: The type of dimensional changes seen in this study was shrinkage. A significant difference in post diameter was found between group B and the other two groups (P=0.001). Storing time significantly affected post diameter (P<0.001), but not post length and core diameter.Conclusion: Within the limitation of this study, the best condition for storing Duralay post core patterns was found to be 100% humidity at 25°C for 24 hours. Storage time was also shown to have a negative effect on dimensional stability of Duralay post core patterns, in all three groups.
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Objective: Microleakage in the gingival floor of class II composite restorations can compromise the marginal adaptation of the filling material to the cavity edges. The aim of this study was to evaluate the effect of light conducting cylindrical inserts in decreasing the microleakage of the gingival floor in cavities 1mm below the CEJ.
Materials and Methods: Eighty maxillary first molars were randomly divided into eight groups according to use of glass inserts, type of resin (Coltene unfilled resin versus Scotchbond multi purpose) and filling technique (one-unit versus incremental). Proximal class II cavities were prepared in all samples with the gingival floor one millimeter below the CEJ. Etched and silan-treated glass inserts were made from 2mm cylindrical bioglass material and cavities were restored according to research protocol. The samples were subjected to 2500 thermal cycles (5-55oC), immersed in 0.5% basic fuchsin solution, embedded in epoxy resin and cut centrally and laterally (buccally or lingually) in a mesiodistal direction. Microleakage was scored and collected data were statistically analyzed using Chi-Square, Kruskal-Wallis and Mann-Whitney tests.
Results: Minimal dye penetration was observed in the group that employed the incre-mental technique along with Scotchbond, with or without glass inserts. A significant difference was observed between the eight groups. In addition the use of the incremental technique and glass inserts had a significant effect on the microleakage of lateral and central sections, respectively. Application of dentin bonding agent signifi-cantly affected both sections.
Conclusion: Glass inserts were effective in decreasing cervical microleakage of class II cavities restored with composite resin.
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Objective: The aim of the present study was to estimate crude and age-standardized incidence rates for oral and pharyngeal nonsquamous cell malignant tumors in Kerman province over a period of 11 years.
Materials and Methods: The data used in this retrospective population-based study were extracted from the records registered in all pathology centers of Kerman province from 1991 to 2001. All confirmed cases of oral and pharyngeal nonsquamous cell malignant tumors were included in the study. The crude and age-standardized incidence rates per 1 million populations were calculated based on the 1996 census data and the population growth rate.
Results: The total number of new nonsquamous cell cancers was 61, representing 18.2% of all oral and pharyngeal cancers in Kerman province. The average annual age-adjusted incidence rate per 1,000,000 population was 3.45 for both oral and pharyngeal tumors. The temporal variations in the annual incidence of oral and pharyngeal nonsquamous cell cancers was statistically significant (p=0.015). The most common types of nonsquamous cell malignant tumors in the oral cavity and pharynx were minor salivary tumors and lymphomas, respectively. The age-adjusted incidence was 0.74 for malignant salivary gland tumors, 0.66 for malignant melanomas, 0.4 for different types of sarcomas, and 1.65 for lymphomas.
Conclusion: It can be concluded that the incidence rate and other features of nonsquamous cell malignant tumors of the oral cavity and pharynx in residents of Kerman province are similar to those reported by other investigators. -
Oral malignant melanoma (OMM) accounts for 5% of all oral malignancies. It is a rare aggressive neoplasm usually found on the hard palate and gingiva. The etiology is unknown, but tobacco and chronic irritation are suggested as probable causative factors. Over 30% of the cases have been reported to arise from pre-existing pigmented lesions. A biopsy is required to establish the diagnosis and the treatment of choice is surgery which may be affected by several factors such as size of the lesion and anatomic location. Despite aggressive resection and adjuvant treatments such as chemotherapy and immunotherapy, the five-year survival rate of this malignancy is poor.
