[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

[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

Influence of abutment surface roughness on retention of implant supported crowns luted with different provisional cements

Easy retrieval is the main advantage of using provisional luting agents for cementation of cemented type implant supported prosthesis. However, adequate retention is also required. The purpose of this study was to compare the retention status of implant supported single restorations with different combinations of implant abutment surface conditions and provisional luting agents. This experimental study was conducted using twenty prepable titanium implant abutments [Biohorizons] 8mm in height. They were placed in implant analogs and torqued to 30 Ncm. Implant analogs were mounted in self cured acrylic resin blocks using surveyor. After fabrication of crowns for each abutment, provisional luting agents, such as TempBond, Dycal and TempBond NE were used to secure the crowns over the respective abutments. All specimens were stored in 100% humidity for 48 hours at 37 C prior to testing. Each crowns was pulled from the abutment with a 500 kg load cell in a universal testing machine at a crosshead speed of 0.5 cm/minute, and tensile strength was recorded [N]. The specimens were then divided into 2 groups. Ten samples were abraded with [um] aluminum oxide and the other 10 were roughened by using a medium roughness diamond rotary cutting instrument. Temporary cements were used and tensile strength tests were performed similarly for all samples. Data were analyzed using paired T-Test and two-way ANOVA. Tensile strength was significantly higher for Dycal [26.01 +/- 3.53] than TempBond NE and TempBond. The result of the two-way ANOVA indicated that a significant interaction existed between the provisional luting agents and the surface conditions. TempBond and TempBond NE showed significantly higher tensile strength when combined with airborne particle abraded surface or roughened surface with diamond burs. However no difference was detected in tensile strength for Dycal in different combinations. The surface modification of an implant abutment by airborne particle abrasion or diamond rotary cutting instrument may be an effective method to increase the retention of a crown when TempBond NE or TempBond was used. However, this process did not improve the retention of crown which was secured with Dycal