Journal of Dental Medicine

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Normal 0 false false false EN-US X-NONE AR-SA Palatal lift appliances are used when the soft palate is anatomically normal but dysfunctional and patients suffer from speech problems while surgical correction is not possible. The aim of these prostheses is lifting soft palate to its normal level in order to achieve palatopharyngeal competence. The prostheses are designed based on maximum retention to keep soft palate in new position without prosthesis displacement. Various methods of constructing these appliances are mentioned and discussed in this article.

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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.

 

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Normal 0 false false false EN-US X-NONE AR-SA Although a full denture cab  replace the teeth and their supporting structures , it commonly develops temporary speech problems that are resolved after a while. In this study, 70 patients were recruited from Prosthodontics department of Tehran and Isfahan dental schools. The patients were analyzed via special questionnaires and oral interview by gender, previous prosthesis and  in 3 phases of edentulous, immediately after denture delivery and a week after delivery. Following data gathering and statistical analysis, it was found that "sh", "s"," Ch" sounds are the most and " m" is the least difficult sound to  pronounce. The study results showed significant difference between 3 stages of denture usage. Also, the effect of previous prosthesis on speech was concluded while gender had not any relation with speech problems.

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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.

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Statement of Problem:Iranian product, Acropars autopolymerizing acrylic resin is nowadays widely used in dental prostheses. Dimensional change is a common problem among Iranian made acrylic resins in making custom trays and record bases, seems to be more than the similar foreign products. In order to achieve a technique for making a record base with minimum dimensional changes, more research is necessary.
Purpose: The aim of the present study was to determine a curing technique for Iranian autopolymerizing acrylic resins leading to the least polymerization shrinkage and the most adaptation between record bases and stone casts.
Materials and Methods: In this experimental study, 40 stone casts were divided into four 10- member group. For each group, polymerization shrinkage was determined at three points with one of the following techniques: Bench curing, Curing under a coat of petroleum jelly , Curing in a monomer saturated atmosphere, Curing in boiled water. Adaptation between bases and stone casts were measured at three points (the right and left crests of the ridge and the midpalatal region) with a light-measuring microscope. To analyze
the data, Variance analysis was used.
Results: The monomer atmosphere technique showed the minimum dimensional changes and the samples in boiled water group had the maximum dimensional changes. No statistical differences were observed between other groups.
Conclusion: More adaptation between record bases and stone casts was observed in monomer atmosphere polymerization technique. The differences between bench curing and curing under a coat of petroleum jelly techniques with this method were not statistically significant. Therefore, it is suggested for making base records with maximum adaptation.

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Background and Aims: Using the conservative adhesive resin restoration (CAR) in uncooperative children lead to numerous problems because of being time consuming. The purpose of this study was to compare the microleakage of conservative adhesive resin restoration under separate curing and co-curing.

Materials and Methods: In this experimental study, 120 intact premolar teeth were collected and 120 vertical grooves were prepared on them. Then the teeth were divided into four groups: group 1, separated curing of bonding agent, flowable composite and sealant group 2, co-curing of all materials for 60 seconds group 3,
co-curing of all materials for 40 seconds and group 4, co-curing of all materials for 20 seconds. Then the specimens were thermocycled and immersed in basic fuchsin solution. The teeth were sectioned horizontally and dye penetration was evaluated with stereomicroscope. Date were analyzed using one-way ANOVA and Scheffe test.

Results: Mean value of dye penetration in groups 1, 2, 3, and 4 was 1.53±0.6, 2.06±0.6, 2.5±0.7 and 3.53±0.6, respectively. There was a statistically significant difference between group 1 and the other groups (P=0.0001).

Conclusion: Considering the problems caused by microleakage in conservative resin adhesive restorations, co-curing method should not be used. In the case of using co-curing method, 60 second curing time is suggested for sufficient polymerization.