[Comparing the effect of porcelain firing cycles on marginal adaptation of procera all-ceramic restorations with metal ceramics]

Although all-ceramic restorations are widely used, there is lack of information about how the fit is affected by fabrication procedures. This study evaluated the marginal gap of Pocera all-ceramic crowns before and after porcelain firing cycles. This was an experimental study, using ten standardized all-ceramic crown of Procera system that were fabricated on metal die crowns of the conventional metal-ceramic restorations served as control group. A device was used to retain specimen during measurement and to reposition them on the device after each manufacturing process. The specimens were not cemented and the gaps were measured on the metal die using stereo microscope. The crown systems were compared by using ANOVA and paired sample t-tests. The conventional metal ceramic [69.17 +/- 44.8 micro] and Procera crowns [61.35 +/- 43.79 micro] demonstated nearly identical marginal discrepancy values. Statistical analyses demonstrated no significant differences in the marginal discrepancy values of Procera and metal ceramic crowns. The findings indicate that the addition of porcelain to the copings of Procera did not cause significant change in marginal discrepancy values [P=0.7], although there were a significant difference in marginal discrepancy values of control group after firing cycles [P=0.001] Within the limitation of this study, it was concluded that Procera all ceramic crown system demonstrated an acceptable marginal fit. The porcelain firing cycle did not affect the marginal fit of this system

[Effect of impression tray on accuracy of implant position transferring in close tray method using polyvinyl siloxane]

Regarding the dependency of successful long-term treatment by implant based prostheses on passive adaptation and since failing to achieve this adaptability may have crucial biological and mechanical consequences and threats the future treatments, we conducted the present research with the aim of comparing dental implants transfer system by close tray impression technique when stock and special trays have been used. In this study, impression material was polyvinyl siloxane. During this experimental research, 10 impressions in each group and totally 30 impressions were prepared. A stainless steel model containing 4 implants to the diameter of 4 mm in the holes were presented and impression procedure was performed by providing 10 metal stock trays, 10 plastic trays and 10 light cure resin special trays using polyvinyl siloxane. Putty and light body impressions were used simultaneously with stock trays and medium body impression material were used with special trays. Then abutments were ried on analog by the use of ball top screws. Distances between ball top centers and third ball top as a reference inner point were measured in three dimensions. ANOVA one-directional test and Turkey multiple contrasts were also used for data analysis. The result of distance differences, out of using special tray and stock trays are meaningful. In dental implant impression technique using close method, metal trays have similar accuracy to that of special trays

[Immediate loading in dental implants [A literature review]]

The absolute advantages of immediate loading of dental implants, such as time saving, immediate function and patient satisfaction, increases the demand for this protocol. In this article we report the results of literature review on conditions under which necessary for successful immediate loading and discuss the predictable conditions as well. Search of relevant published articles was conducted for the period between 1970 to 2007 in Medline, PubMed, Embase, Blackwell Synergy, Sciencedirect, Scholar google, Google and Yahoo databases along with manual search to identify pertinent English text-books. The key words used for this search were dental implants, immediate loading, early loading, delayed loading, occlusal loading and primary stability. Factors that may influence the success of immediate implant loading, including patient selection, type of bone quality, required implant length, micro- and macrostructure of the implant, surgical skills, the need for achieving primary stability/control of occlusal forces, and prosthesis guidelines, were thoroughly reviewed and discussed. Immediate loading is predictable in the anterior section of the mandible, irrespective of implant type and surface topography [success rate 90% - 100%]. Limited evidence is available for edentulous maxilla and partially edentulous patients. Unfortunately most of the reviewed articles provided limited information due to study design and methodological shortcomings. Anatomical locations implant designs, and restricted prosthetic guidelines are a key to ensure successful outcomes. Future studies, preferably should be more of randomized control trials and prospective longitudinal studies are certainly needed before this approach can be widely used

[Introduction of a technique for fabrication of an implant-supported fixed temporary prosthesis]

In fully edentulous patients, reconstruction with implant-supported fixed prosthesis is a complicated treatment. In conventional technique, after the placement of the implants, fixed temporary prosthesis is fabricated with no consideration of the removable prosthesis that the patient has used yet. Therefore, the logical relation of the phases of treatment is lost and the points such as vertical dimension occlusion and centric relation are not recorded exactly. The purpose of this article is to introduce a technique in which a fixed temporary prosthesis is fabricated by use of patient's full denture. In this study, a 60-year-old patient with complete edentulous in the mandible was referred to Dental School. He has used a complete jaw denture in the mandible. The complete denture especially in the lower jaw has caused destructions to the remaining ridge. Due to the patient's condition and the existing circumstances, the treatment design of implant-supported fixed prosthesis was accepted by the treatment team. Prior to the surgery, assessments of the bone quality and quantity, force factors, the number of the implants, their lengths and angles were done and the complete denture was converted to implant-supported fixed temporary prosthesis. The fabrication of conversion prosthesis was introduced with implant-supported metal ceramic restoration

[Prefabricated posts: a literature review]

Restoring endodontically treated tooth with prefabricated post is a well accepted technique with a long history. This article reviews and classifies various prefabricated posts. Different types of prefabricated posts are available in the market now. These posts are different from each other in installation method, geometric form, surface configuration and material. Each type has it's own advantages and disadvantages. Previously, only metal prefabricated posts in different designs, shapes and surfaces were fabricated by manufacturers. With increasing demand for esthetic restorations, like all ceramic restorations and also for using bonding systems more and more, the need for nonmetallic posts is increased, pushing manufacturers to fabricate ceramic and fiber-reinforced resin posts. A dentist must know about characteristics, advantages and disadvantages of different posts and choose the most suitable type for each case

[Effect of smear layer on the retention of custom made posts luted with two different cements]

Post retention has a considerable effect on restorative treatments and is influenced by various factors. The purpose of this study was to evaluate the effect of dentinal smear layer on the retention of custom-made posts luted with composite resin and zinc phosphate cements. Forty single-rooted lower premolars were decoronated, filed and filled with gutta-percha and divided into 4 equal groups. Post spaces were prepared to a length of 8 mm. Direct post patterns were made with acrylic resin and castings were fabricated using Ni-cr alloy. In Groups A and C, the post spaces were rinsed with 2 ml of 0.9% normal saline. The specimens in Groups B and D were rinsed with 1 ml of 17% EDTA followed by 1 ml of 5.25% Naocl and 10 ml distilled water. After drying, ZPC [Dentsply] was used for cementation in groups A and B. The samples in Groups C and D were luted with Panavia F[2.0]. Retention was measured on a Universal Testing Machine at 0.5 m/min. Data were subjected to statistical analysis using ANOVA. The mean amount of retention was 19.66 +/- 1.98 kg, 19.72 +/- 2.08 kg, 20.99 +/- 2.08 kg and 22.17 +/- 3.66 kg in groups A, B, C and D, respectively. There was no significant difference between the groups, but the mean value was highest in group D. The use of resin cement provided greater retention for custom-made posts compared to ZPC. Removing dentinal smear layer did not significantly affect the retention of custom-made posts cemented with ZPC or Panavia F[2.0]