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Showing 11 results for Monzavi

A. Monzavi , R. Mosharaf ,
Volume 9, Issue 1 (8 1996)

Normal 0 false false false EN-US X-NONE AR-SA Lever is a solid part that can turn on a fulcrum. There are three types of fulcrums. The efficacy of a lever system is measured by mechanical advantage. The first type of lever has the most and third type has the least mechanical advantage. The situation of muscles attachments and direction of forces on teeth in mandible is similar to lever type 3 and therefore, the muscles, bones and teeth can bear occlusal forces. If a destructing contact develops, this lever system will change and cause damaging effects on stomatognathic structures.


A. Monzavi , R Mosharaf ,
Volume 10, Issue 2 (8 1997)

Normal 0 false false false EN-US X-NONE AR-SA  Teeth and periodontal ligaments can resist more efficiently opposing vertical forces parallel to their axial axis in comparison to horizontal forces. Thus, in designing dental prostheses and preserving interocclusal relationships we should notice to eliminate horizontal forces on teeth. A partial prosthesis can rotate in vertical, horizontal and Sagittal axis and by understanding levers and designing appropriate frameworks these rotations can be avoided.

A. Monzavi ,
Volume 13, Issue 3 (9 2000)

Dentists and dental professional are constantly in contact with round, sharp, hot, and rotating instruments such as burs, scalpel blades, files, etc., in daily practice. Gate Glidden is one of the mentioned instruments used for removing gutta percha from root canal- treated teeth. In this article, a rare case of penetration of a fractured Gate Gildden bur into a dentist's elbow is reported and precaution instructions are discussed.

A. Monzavi , Gh R. Farhang ,
Volume 13, Issue 3 (9 2000)

The geometric shape of dental arch (square, tapering, ovoid) is an important factor in stress distribution pattern around dental implant. The aim of this study was to evaluate the role of arch form and the amount of bone loss (normal, moderate, high) in stress distribution around dental implant by considering different load direction. Three arch forms square, ovoid, and tapering with three different stages of bone loss were designed. Models were divided into three-dimensional elements, which made 5500 nodes. The 143N load was applied at two angles (straight, oblique) at the last fixture, 8mm, and 16 mm from the center of implant on l!ie cantilever. The Sap90 software was used for analyzing the stress distribution in this study. 54 different conditions were evaluated. Results showed that stress concentration changed from support toward fixture due to distally changing the load in the square and ovoid arch forms with normal bone. In the tapering arch with normal bone stress concentration was around the fixture. The amount of stress in normal tapering arch was more than physiologic extend, therefore, application of cantilever in tapering arches is not recommended.

S. Nokar , A. Monzavi , F. Hashemi ,
Volume 15, Issue 2 (8 2002)

Retention, resistance and marginal integrity mostly depend on tooth preparation. An appropriate convergence angle fulfil this purpose, to high extent. In this study, a new method was used to measure the convergence angle of the teeth prepared for single crowns in Genera! practitioners" offices in Tehran. In order to do this. 325 dyes, prepared by General dentists in Tehran, were collected from 10 laboratories. All dyes wore trimmed at the area below the finishing line and then were scanned (Genius Color page- FIR 6) buccoiingualiy and mesiodistaily. Convergence angle of dyes were also measured with Adobe Photoshop (5.0) software. Data were analyzed by variance analysis test and 1- student bv the help of SPSS software. Results showed that the average convergence angle ranged from 16.18+8.34 to 35.1 8~10.38 which belonged to maxillary canine and mandibular molars, respectively, and the measured convergence angle is more than the ideal value of 10-16 degrees. Dyes of the madibular molars were ma"illar" convergent. These conclusions are helpful for professors, dentistry students and dentists, and arc an indicative of the practice quality of General practitioners in Tehran. Due to the fact that a convergence angle, more than the allowed limitation, endangers retention, resistance and marginal integrity of the restoration, paying attention to the principles of tooth preparation and proper application of instruments and dental cements, can progress fwed restorations quality.
A. Monzavi , S. Mir Mohammad Rezaei , H. Bajelan ,
Volume 15, Issue 2 (8 2002)

Waxes have a lot of applications in dentistry. Such materials are of thermoplastic type that undergoes deformation in different temperatures. Two important properties of base plate waxes are flow and their coefficient of linear thermal expansion. Recently, different institutions, inside the country, produce dentistry waxes, while they have not been standardized. Consequently, consumers' dissatisfaction are observed. In this research, the two above- mentioned factors were compared between three kinds of Iranian waxes with Cavex that is foreign production, based on test number 24 of ADA. To measure the flow rate in the temperatures of 23, 37 and 45°c, Wilcoxon statistical analysis was used. The results showed that in 23°c, the flow rate of Cavex and Azardent waxes met ADA standards however, it was not true for two others types. In 37°c, the flow of none of the waxes was standardized and in 45°c their flow was acceptable, moreover, thermal expansion coefficient, for Cavex and Azardent types, was based on ADA standard.
A.  monzavi , Sh. Lavvaf ,
Volume 17, Issue 1 (7 2004)

Statement of Problem: Nowadays economical issues on high gold alloys have changed the practice of metal-ceramic restorations toward base-metal alloys. Minalux is one of the base-metal alloys produced in Iran. Marginal fitness is of high importance to be evaluated in dental alloys.
Purpose: The aim of the present study was to compare the marginal adaptation of two base-metal alloys, Minalux (Mavadkaran Co. Iran) and VeraBond2 (Aibadent Co. USA ) during firing cycles of porcelain.

 Materials and Methods: In an experimental study 24 standard brass dies, with 135° chamfer finishing line were fabricated by Computer Numeric Controlled (CNC) milling machine. The samples were randomly divided in two groups, A and B, 12 in each. Following wax-up, the samples were equally cast with two mentioned alloys. In each group, there were 4 controlled samples, which proceeded to firing cycle without veneering porcelain. Scanning electron microscope (SEM) measurements of marginal gap from buccal and lingual aspects were performed after 4 stages of casting, degassing, porcelain application and glazing. The data were analyzed using Four-way ANOVA and multiple comparative test based on Tukey criteria.

 Results: The findings of this study revealed that there was no significant difference in the marginal gap of Minalux (31.10±7.8u.m) and VeraBond2 (30.27±6.96u.m) with confidence level at 0.95 (P=0.43). For both alloys the greatest gap was observed after degassing stage (P<0.05). Porcelain and porcelain veneering proximity caused significant changes in the marginal gap of Minalux castings (P<0.05), however, such changes did not occur in VeraBond2 (PO.05).
Conclusion: Based on the findings of this study, the marginal gaps of two base metal alloys, Minalux and VeraBond2, were proved to be identical and that of the Minalux alloy existed in the range of acceptable clinical application. It was also concluded that Minalux dental alloys could provide proper marginal adaptation.

A. Monzavi , S. Zarati , T. Jafarzadeh , Mh. Amini ,
Volume 19, Issue 3 (4 2006)

Background and Aim: Use of provisional restorations is one of the important phases in the treatment of patients who need fixed prosthesis. Some physical properties are required for these materials. The purpose of this study was the comparison of some physical properties of 4 kinds of resins: Trim, Tempron, Duralay (Aria Dent) and Acropars TRII.

Materials and Methods: In this experimental study, transverse-strength (TS), setting time (ST), polymerization shrinkage (PS) and temperature rise (TR) during polymerization were tested. In transverse strength test, 5 samples of each resin were made. TS testing was done with an Instron testing machine. ST testing (5 samples in each group) was done with Gilmore needle. In PS test, 11 cylindric samples were prepared from each resin and the shrinkage was examined with digital micrometer (up to 24 hours). In TR test, after mixing the powder and liquid of resins (8 samples in each group), the temperature rise was recorded with 10 seconds interval (up to 15 minutes). Data were analyzed with one-way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance.

Results: In TS test, all samples of Trim were bent and no fracture was observed, while Tempron and Duralay showed no significant difference. Both Tempron and Duralay revealed high significant difference with Acropars TRII (P <0.01). In ST test, the difference between groups was significant (P<0.01). The lowest ST was observed in Acropars TRII (7 min), and the highest in Tempron (9.53 min). In PS test, significant difference was observed between Trim and Acropars TRII (P<0.01). PS was completed after 120 min in Tempron and Trim groups. However, PS continued to increase in other groups. In TR test, the difference between groups was significant (P<0.05). Duralay showed the highest TR and the lowest was seen in Trim.

Conclusion: In this study, Trim showed better properties than other studied groups. Acropars TRII had the lowest strength. The highest temperature rise was recorded for Duralay and Tempron, respectively.

M. Alikhasi, H. Siadat, A Monzavi, M. Naseri, S. Sheikhzadeh, F. Taghavi,
Volume 24, Issue 3 (21 2011)

Background and Aims: The bond strength between veneer ceramics and zirconia frameworks is the weakest component in the layered ceramics. Due to the possible effect of adding pigments to the core materials on the bond strength between core and veneer as well as the introduction of new ceramic materials in dentistry, the aim of this study was to compare the zirconia core-veneer microtensile bond strength using two ceramic veneers with or without coloring the core.
Materials and Methods: In this experimental study, 12 disc-shaped specimens were fabricated using a manually aided design- manually aided manufactured (MAD/MAM) zirconia core (Zirkonzahn). Two veneering ceramics of Ceram Kiss and Zirkonzahn ICE were also used to veneer the specimens. Half of the Zirkonzahn discs were remained white and the others were colored by shade A2.Then, the discs were cut into microbars (30 for each group) and the microtensile bond strength of the core-veneer was calculated. The specimens were assessed using scanning electron microscopy (SEM) and the data were analyzed using two-way ANOVA and Student's t-test.
Results: Significant differences with respect to veneer layer were found (P<0.001). No significant differences were seen among colored and uncolored cores (P=0.69).
Conclusion: According to the apparent effect of veneering ceramics on the core-veneer bond strength, careful selection of these agents is essential to achieve adequate bond strength between core and veneer to prevent delaminating and chipping failures of zirconia veneered restorations.

Marziyeh Alikhasi, Abbas Monzavi, Hakimeh Siadat, Bita Fathi,
Volume 25, Issue 2 (9 2012)

Background and Aims: Accurate recording of implant location is required to achieve passive fit and have the implants without stress concentration. The aim of this in-vitro study was to evaluate the dimensional and angular accuracy of open-tray and closed-tray impression techniques using polyether impression material and also to assess the surface detail reproduction of the tooth while impression making.

Materials and Methods: One reference metal model with 2 implants (Implantium) on the position of the maxillary second premolar and first molar and one molar tooth for evaluation of surface details was prepared. 27 polyether impressions of these models were made (9 using open-tray, 9 using closed-tray techniques and 9 were made just of the surface of the teeth without any implants). Impressions were poured with ADA type IV stone. Coordinate Measuring Machine was used for measuring the dimensional accuracy and video measuring machine for surface detail reproduction. All of these measurements were compared with the measurements on the reference model. Data were analyzed by and compared by T-test and One-way ANOVA.

Results: There was a significant statistical difference between open-tray and closed-tray techniques (P<0.001). There was no significant difference in the surface detail reproduction of open-tray and Closed-tray techniques and impression making with or without the implants (P>0.05).

Conclusion: The accuracy of open-tray impression technique was more than closed-tray technique. The surface detail reproduction of the tooth was not affected by impression technique.

Abbas Monzavi, Reza Shabanpoor, Marzieh Alikhasi, Ghasem Omati Shabestari,
Volume 25, Issue 4 (9 2013)

Background and Aims: One of the decisive factors on the final esthetic results of implant treatment is the abutment material. Ceramic abutments are nowadays very popular in this regard. The purpose of this study was to compare the fracture resistance of three zirconia abutments with titanium abutment.

Materials and Methods: Four groups of abutments (five specimens in each) were prepared. The abutments were prefabricated titanium, prefabricated zirconia, zirconia-metal, and copy-milled zirconia abutment. After securing the abutments to the implant using a torque of 24 Ncm, they were mounted into a mounting jig using the 30º tilt. The force was applied on the assembly till the failure occured. Facture resistance and mode of failure were recorded for each specimen. The data were analyzed using One-way ANOVA.

Results: The mean values recorded for fracture resistance of different zirconia abutments varied between 426 to 688 N however, there was no significant differences among the groups (P=0.14). Body fracture was observed only in prefabricated zirconia abutments. Screw fracture and screw bending were the common failures observed in other groups.

Conclusion: Zirconia abutments of any type could be successfully used in regular plateform implants.

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