[Discrepancy measurements of copings prepared by three casting methods and two different alloys, on ITI implants]

An important criterion of success assessment of implant-supported prostheses is marginal fit. Vertical and horizontal discrepancy can result in loosing of the prosthetic screw, crestal bone resorption, peri-implantitis and loss of osseointegration. Despite careful attention to waxing, investing, and casting, marginal discrepancies are inevitable. The aim of this study was to evaluate the marginal gap and overhang in three casting methods with two different alloys in ITI implants. In this experimental in vitro study 48 analog abutments were randomly divided into six groups as follows: 1] burn out cap + BegoStar, 2] impression cap+ BegoStar, 3] conventional wax up + BegoStar, 4] burn out cap + Vearbpond2, 5] impression cap + Verabpond2, 6] conventional wax up+ Verabond2. Waxing was done in 0.7 mm thickness verified by a digital gauge and a putty index was made for all groups. Reamer was used for correction of the finish line after casting in all groups. Castings were seated on analog abutments and embedded in acrylic resin. Specimens were sectioned by isomet instrument and polished and cleaned by ultrasonic cleaner for 10 min. The marginal gap and overextended margins of castings were examined under a Scanning Electron Microscope [SEM] [X200]. The mean gap and margin overextension were calculated for each group. Data were analyzed by multivariate analysis and Bonferroni post-hoc test with p<0.05 as the level of significance. No significant difference in gap size was observed among the three casting methods with two alloys [P=0.56]. The marginal gap was not different in the studied casting methods [P=0.092]. Gold alloy crowns showed lower marginal gaps compared to base metal alloy crown [P<0.001]. No significant difference in overhang size was observed among casting methods with two alloys [P=0.093]. Base metal alloy crowns showed less overhang compared to gold alloy crowns [P<0.001]. There was a significant correlation between overhang and use of impression cap in base metal alloys [P<0.001]. Based on the results of this study, vertical discrepancy of frameworks made with gold alloy were less than those made with base metal alloy. Base metal alloy demonstrated less overhang. Conventional wax up or using burn out caps reduced less horizontal discrepancy

[Photography in dentistry: part IV [object + photography]]

Object photography in dentistry including dental instruments, models, teeth and gross specimens has some special features and needs special consideration. These objects are usually very small, highly usually reflective and often with very bright surfaces. They need special lighting and other accessories for acceptable results. On the other hand, in laboratories and dental clinics we haven't enough time for taking photographs. The purpose of this article is to introduce the principles of object photography in dentistry

[ survival rate of fiber-reinforced composite inlay bridges after two million load cycles: an in vitro study]

Fiber reinforced composite [FRC] inlay bridges have become popular for being conservative, simple and relatively inexpensive. The aim of this in vitro study was to determine the survival rate of FRC inlay bridges replacing missing maxillary lateral incisors, after being subjected to a cyclic mechanical load of 2 million cycles with a force of 30 N at a frequency of 2 Hz. In this experimental study, 30 anterior bovine teeth were used as abutments to make 15 anterior FRC inlay bridges. Fifteen acrylic resin blocks were fabricated utilizing a dentoform. The teeth were mounted in the resin blocks while trying to simulate normal tooth angulations, PDL and biologic width. Pontics were made indirectly and bridges were directly fabricated in 2x2x2 mm prepared cavities using Nulite F fiber- reinforced composite resin and polyethylene fiber based braids [NSI, Australia]. The specimens were thermocycled for 2000 cycles between 5°C and 55°C and were then exposed to two million load cycles [30 N, 2 Hz] at 130°C to the long axis of the pontics [3mm under the incisal edge] in a cyclic loading machine. Three specimens were excluded due to experimental mishandling. All 12 remaining bridges [%100] survived the applied loads. Based on the results of this study, it may be concluded that FRC bridges can tolerate more than 2 million normal masticatory forces which is equivalent to 7-9 years of clinical service

Photography in dentistry: Part II [Intraoral photography]

In addition to the camera, other accessories such as retractors and mirrors are necessary for intraoral photography. They enable directly inaccessible subjects, to be viewed and photographed easily. Gaining adequate view, by suitable retractors and mirrors, is the most important step, requiring skill and patient cooperation to achieve successful results. Composition, visualization of the final photograph and a carefully controlled clinical technique must be practiced in order to produce rapid, precise and reproducible clinical photographs. There are many procedures to be followed and precautions to be taken in order to obtain good quality, reproducible dental photographs. Failures can be avoided by following a distinct procedure. This article focuses on clinical equipments such as retractors, mirrors and intraoral photography

Photography in dentistry: Part III [Dental portraits]

Dental portraits are predominantly used for orthodontics, orthognathic surgery and prosthetic dentistry. If these images are to be used for documentation, then the patient must be positioned in accordance with strict guidelines for further references. If the images are to be used to present an aesthetic impression of dental treatment there is more flexibility in positioning the patient. Dental photography is used to make pictures of teeth and surrounding tissues, radiographs, casts and other objects. In this section, standard principles for portrait pictures are explained