Konstantinos Michalakis

Serum Adiponectin Concentrations and Tissue Expression of Adiponectin Receptors Are Reduced in Patients with Prostate Cancer: A Case Control Study

Purpose: Adiponectin, an adipocyte-secreted hormone with insulin-sensitizing effects, has been inversely associated with several hormonally dependent malignancies, including breast, endometrial, and colorectal cancer. Few studies have examined serum adiponectin in relation to prostate cancer, and expression of adiponectin receptors has previously not been assessed in prostate tumors. Experimental Design: We collected plasma samples and covariate data in the context of a case-control study of 300 Greek men, including 75 prostate cancer cases, 75 patients with benign prostatic hyperplasia (BPH), and 150 healthy controls. Prostate tissue samples were taken from 72 cases and 27 noncases and examined for relative expression of adiponectin receptors AdipoR1 and AdipoR2 using immunohistochemistry. Results: Prostate cancer patients had significantly lower plasma adiponectin concentrations as compared with men with BPH and healthy controls (7.4 ± 5.0 versus 11.5 ± 6.4 and 12.8 ± 8.0 ng/mL, respectively). Men in the top two quartiles of adiponectin had a 71% to 73% reduced risk of prostate cancer as compared with men in the lowest quartile after adjusting for age, body mass index, and additional potential confounders. We found no similar relationship between adiponectin and risk of BPH. Results from immunohistochemistry experiments show weaker expression of adiponectin receptors AdipoR1 and AdipoR2 in cancerous versus healthy prostate tissue. Conclusions: Higher serum adiponectin is associated with a marked reduction in risk of prostate cancer, but not BPH, independently of other risk factors. Malignant prostate tissue samples have reduced expression of adiponectin receptors as compared with benign prostate tissue. These results support a role for adiponectin in the pathogenesis of prostate cancer. (Cancer Epidemiol Biomarkers Prev 2007;16(2):308–13)

Attachment systems for implant retained overdentures: a literature review.

This article presents a comparison between different attachment systems used to retain and support maxillary and mandibular overdentures in completely edentulous patients. A literature review based on a MEDLINE search limited to English-language articles published from 1988 to the present was performed, and a large number of attachments available in the dental market were reviewed with regard to several factors, including: (1) implant survival rate, (2) marginal bone loss, (3) soft tissue complications, (4) retention, (5) stress distri-bution, (6) space requirements, (7) maintenance complications, and (8) patient satisfaction. These factors are considered essential for the successful outcome and good long-term prognosis of the prostheses. Selection criteria previously published in the literature are discussed as well. Product names and manufacturers are mentioned only if related to attachment systems, as they are cited in the original articles.

Internal vs. external connections for abutments/reconstructions: a systematic review.

OBJECTIVES The objectives of the review were (1) to evaluate the accuracy of implant-level impressions in cases with internal and external connection abutments/reconstructions, and (2) to evaluate the incidence of technical complications of internal and external connection metal- or zirconia-based abutments and single-implant reconstructions. MATERIALS AND METHODS A MEDLINE electronic search was conducted to identify English language publications in dental journals related to each of the two topics by inserting the appropriate keywords. These electronic searches were complemented by a hand search of the January 2009 to January 2012 issues of the following journals: Clinical Oral Implants Research, The Journal of Prosthetic Dentistry, The International Journal of Prosthodontics, The International Journal of Periodontics and Restorative Dentistry, The International Journal of Oral Maxillofacial Implants, Clinical Implant Dentistry and Related Research. RESULTS Seven in vitro studies were included in the review to evaluate the accuracy of implant-level accuracy. No clinical study was found. There was no study that directly compared the influence of internal and external implant connections for abutments/reconstructions on the accuracy of implant-level impressions. All in vitro studies reported separately on the two connection designs and they did not use same protocol and, therefore, the data could not be compared. Fourteen clinical studies on metal-based abutments/reconstructions and five clinical studies on zirconia-based abutments/reconstructions satisfied the inclusion criteria and, therefore, were included in the review to evaluate the incidence of technical complications. The most frequent mechanical complication found in both implant connection design when employing metal abutments/reconstructions was screw loosening. CONCLUSIONS Implant-level impression accuracy may be influenced by a number of variables (implant connection type, connection design, disparallelism between multiple implants, impression material and technique employed). Implant divergence appears to affect negatively impression accuracy when using internal connection implants. Based on the sparse literature evaluating the incidence of technical complications of metal or zirconia abutments/reconstructions, it was concluded that: The incidence of fracture of metal-based and zirconia-based abutments and that of abutment screws does not seem to be influenced by the type of connection. Loosening of abutment screws was the most frequently occurring technical complication. The type of connection seems to have an influence on the incidence of the screw loosening: more loose screws were reported for externally connected implant systems for both types of materials. However, proper preload may decrease the incidence of such a complication.

The in vitro effect of different implant angulations and cyclic dislodgement on the retentive properties of an overdenture attachment system.

STATEMENT OF PROBLEM The retentive capacity of ball attachments may be altered by a change in implant angulations. PURPOSE The purpose of this in vitro study was to investigate the effect of cyclic dislodgement on the retention of an overdenture attachment system when 2 implants were placed at angulations of 0, 5, 10, 15, and 20 degrees. MATERIAL AND METHODS Twelve acrylic resin blocks were fabricated and divided into 6 groups of 2 pairs each. In each of the 6 groups, 1 acrylic resin block was used to house the implants (block A), while the other (block B) was used to house the overdenture attachments. Two implants positioned at 0/0 degrees, with a standard plastic component(white) designed for 0-degree angulations, served as a control (CTRL), while the other 5 pairs of implants were placed in 5 different angulations: 0D: 0/0 degrees, 5D: 5/5 degrees, 10D: 10/10 degrees, 15D: 15/15 degrees, 20D: 20/20degrees (n=5). The extended range (green color) attachment was used for all groups except the control group. Implants(4.3 mm x 13 mm, internally hexed) were placed in blocks B. All angled implants were mesially tilted. Thirty pairs of attachments (Locator) were used. Dislodging cycles were applied to the overdenture attachment system. The initial retentive forces among the groups were not identical. The cycles required for the retentive forces of the attachments to decrease from the initial values to 60 N, and then to 40 N and 20 N, were recorded for standardization purposes.One-way ANOVA and Tukey HSD tests were used to analyze the difference in retention loss among the 6 groups(alpha=.05). A regression analysis (alpha=.05) was also performed to investigate the relationship between the implant angulation,the retentive force, and the logarithm of the number of cycles required for ball attachment retention decrease. RESULTS The 1-way ANOVA and the Tukey HSD tests revealed significant differences for the number of cycles required by different implant angulation groups for the initial retentive values to decrease to 60 N, 40 N, and 20 N (P<.001).The 0D and 5D groups required the longest time for retention loss, while 20D and CTRL groups demonstrated the shortest time for retention loss. The results of the regression analysis of the logarithmic number of cycles on retentive force and implant angulation demonstrated a significant effect (P<.001). CONCLUSIONS Implant angulations negatively affect attachment retention longevity. (J Prosthet Dent 2009;102:140-147)

New Ti-Alloys and Surface Modifications to Improve the Mechanical Properties and the Biological Response to Orthopedic and Dental Implants: A Review

Titanium implants are widely used in the orthopedic and dentistry fields for many decades, for joint arthroplasties, spinal and maxillofacial reconstructions, and dental prostheses. However, despite the quite satisfactory survival rates failures still exist. New Ti-alloys and surface treatments have been developed, in an attempt to overcome those failures. This review provides information about new Ti-alloys that provide better mechanical properties to the implants, such as superelasticity, mechanical strength, and corrosion resistance. Furthermore, in vitro and in vivo studies, which investigate the biocompatibility and cytotoxicity of these new biomaterials, are introduced. In addition, data regarding the bioactivity of new surface treatments and surface topographies on Ti-implants is provided. The aim of this paper is to discuss the current trends, advantages, and disadvantages of new titanium-based biomaterials, fabricated to enhance the quality of life of many patients around the world.

Fracture Resistance of Metal Ceramic Restorations with Two Different Margin Designs After Exposure to Masticatory Simulation

STATEMENT OF PROBLEM Although the esthetic outcome of a collarless metal ceramic restoration is superior to that of a restoration with a metal margin, its mechanical strength has not been evaluated. PURPOSE The purpose of this study was to evaluate and compare the fracture resistance of metal ceramic restorations with metal margins to that of metal ceramic restorations with circumferential porcelain margins, after exposure to masticatory simulation. MATERIAL AND METHODS Twenty-four metal ceramic restorations were fabricated and paired with 24 cobalt-chrome tooth analogs. Twelve of the specimens had metal margins, while the remainder had circumferential porcelain margins. The restorations were cemented on the metal tooth analogs with a resin-modified glass ionomer luting agent (FujiCEM). All specimens were subjected to cyclic loading by a texture analyzer. A total of 600,000 loading cycles in an aqueous environment was performed, with a minimum load of 0 N and a maximum load of 200 N. Controlled loads were then applied to the teeth until fracture, using a stainless steel rod with a 2-mm-wide, rounded end, mounted in a universal testing machine. The specimens were examined under a stereomicroscope to determine failure mode. Descriptive statistics and the independent t test (alpha=.05) were used to determine the effect of failure loads among the tested groups. RESULTS The independent t test revealed statistically significant differences among the 2 tested groups (P<.001). The 2 groups presented different failure modes. Metal ceramic restorations with metal margins presented cohesive failures starting from the point of load application. Metal ceramic restorations with circumferential porcelain margins demonstrated a combination of adhesive and cohesive failures, starting from the point of load application and extending to the highest point of the proximal margins. CONCLUSIONS Metal ceramic restorations with metal margins required significantly greater loads (P<.001) to fracture than metal ceramic restorations with circumferential porcelain margins. (J Prosthet Dent 2009;102:172-178).

Body mass index vis-à-vis total sperm count in attendees of a single andrology clinic

In this large series of 349 unselected men, no significant relationship between body mass index and total sperm count was found. Thus, the association of body mass index and sperm count reported in some studies was not confirmed.

An Experimental Study on Particular Physical Properties of Several Interocclusal Recording Media. Part I: Consistency Prior to Setting

PURPOSE To evaluate the consistency prior to the setting of 5 elastomeric interocclusal recording materials in comparison with a wax and a zinc oxide-eugenol paste. This property is related to the viscosity as well as to the working and setting times of these materials. MATERIALS AND METHODS Testing of consistency was performed following a modification of the method described in ADA Specification No. 19, for elastomeric impression materials. Each one of the tested materials was mixed for 20 seconds and was then loaded into a 0.5 mL syringe. The material was syringed onto a 10 x 10 x 0.5 cm glass plate. A second 575 g glass plate was placed on top of the unset interocclusal registration material. A total of 10 samples were tested for each material. The surface area covered by the materials was measured with the help of a scanner and the use of appropriate computer software. RESULTS One-way ANOVA revealed significant differences among the materials (F = 889.493, p < 0.0005). According to Tukeys honest significant difference test, all materials were significantly different (p < 0.05) from one another. All polyvinylsiloxanes occupied a smaller area than that of the polyether and of the zinc oxide-eugenol paste. CONCLUSIONS Zinc oxide-eugenol paste was the most fluid of all materials tested. Polyvinylsiloxanes displayed less flow properties than polyether.

Delayed linear dimensional changes of five high strength gypsum products used for the fabrication of definitive casts

STATEMENT OF PROBLEM Prolonged storage of definitive casts made from Type IV and Type V gypsum products, especially in an environment of increased temperature and low humidity, may result in contraction. PURPOSE The purpose of this study was to evaluate the linear dimensional changes of 5 different high strength stones after exposing them to 2 different storage conditions over a period of 3 weeks. MATERIAL AND METHODS Three Type IV dental stones (Fujirock, Vel-Mix, Suprastone) and 2 Type V dental stones (Hard Rock, Jade Stone) were tested in this study. A circular conical stainless steel die with a diameter of 66 mm and a height of 10 mm was made. Two V-shaped grooves, 38 mm apart, were scribed on the surface of the die for the purposes of measurement. A conical stainless steel ring with a bottom inner diameter of 68 mm and a top inner diameter of 65 mm was also fabricated to fit precisely around the stainless steel die. The dental stone was mixed with water under vacuum and poured under vibration onto the stainless steel die, which was surrounded by the ring. The specimens (n=20) were separated from the stainless steel die 1 hour after pouring. Half of these specimens (control) were stored in a room at 22 ±1°C with relative humidity of 50 ±5%, while the rest of the specimens were placed in a temperature regulating incubator at 40 ±1°C and relative humidity of <20%. The linear dimensional changes were recorded at designated time intervals with a traveling microscope over a 3 week period. Collected data were subjected to a 2-way repeated-measures analysis of variance (ANOVA) (α=.05). RESULTS The highest expansion values for the specimens in the control group were recorded between 72 and 96 hours. A contraction was noticed thereafter for all specimens, in both groups. No difference in the measurements was registered between the second and third week. ANOVA revealed significant differences (P<.001) among different Type IV and V dental stone products, time, and storage conditions. CONCLUSIONS The highest expansion values for all specimens in the control group were recorded between 72 and 96 hours. The highest expansion values for all specimens in the experimental group were recorded at 24 hours. For all specimens, contraction was noticed up to the 2-week measurements. All factors examined (dental stone, time, storage condition) significantly affected the linear dimensional changes.

Delayed setting and hygroscopic linear expansion of three gypsum products used for cast articulation

STATEMENT OF PROBLEM Wetting of the set gypsum product used for cast articulation may result in additional expansion. PURPOSE The purpose of this study was to evaluate the linear expansion of 2 type II and 1 type III gypsum products with and without addition of water after setting, over a time period of 120 hours. MATERIAL AND METHODS The gypsum products tested in this study were Model Plaster, Lab Plaster, and Mounting Stone. All materials were hand mixed for 5 seconds and mechanically mixed under vacuum for another 15 seconds. The mixes were poured into a linear expansion-measuring instrument (n=20). Half of the specimens were wet with 25 ml of water immediately after the setting time recommended by the manufacturer, and at all time intervals, immediately after data collection. No treatment was performed on the remainder of the specimens. The expansion values were recorded with an expansion-measuring device over a period of 120 hours. Collected data were subjected to a 2-way repeated-measures analysis of variance (ANOVA) (alpha=.05). RESULTS The highest expansion values for all gypsum products were recorded at 96 and 120 hours. No significant difference in setting expansion values was recorded between these 2 time intervals for any of the materials and treatment conditions (dry vs. wet). Mean expansion values ranged between 0.08% +/-0.06% for dry Mounting Stone specimens at 15 minutes, to 0.57% +/- 0.02% for wet Lab Plaster specimens at 96 and 120 hours. Significant differences (P<.001) between different mounting gypsum products and time were identified. A significant difference between wet and dry specimens was not observed. CONCLUSIONS The expansion of all gypsum products used for articulation purposes was complete at 96 hours. The type III gypsum product demonstrated lower mean expansion values than type II products. Time and material were more important factors than the dry/wet condition when measuring total expansion values. Type II gypsum products demonstrated 80% or more of the total expansion values in the first 45 minutes, while type III stone demonstrated the same expansion after 24 hours.