Progressive bilateral enophthalmos associated with cerebrospinal shunting

A 22-year-old woman was examined for a complaint of bilateral progressive enophthalmos that had begun after the cerebrospinal fluid shunting procedure 9 years ago. Photographs and CT scans taken before surgery proved that the position of her eyes was normal before surgery. The enophthalmos was so severe that it induced a poor eyelid-globe apposition with trichiasis and superficial keratopathy. CT of the orbits showed that both orbital roofs were arched and displaced toward the anterior cranial fossa. The placement of porous polyethylene sheets on the orbital roofs through a coronal approach corrected the eye position. A literature review indicated that cerebrospinal shuntings are plagued by a variety of complications including bone changes and craniosynostosis. We believe that enophthalmos associated with cerebrospinal fluid shunting results from a rare acquired bony orbital anomaly.

Palpebral fissure changes after monobloc frontofacial advancement in faciocraniosynostosis

There is virtually no literature on the effect of correction of syndromal faciocraniosynostosis with monobloc advancement on the palpebral fissure shape. Using image processing software, we measured the effect of monobloc advancement on the position of the upper and lower eyelids as well as the palpebral fissure slant in a series of 18 patients with syndromal faciocraniosynostosis who had undergone surgery for correction of orbital and midface hypoplasia. For both eyed of each patient, 3 variables were measured on the pre- and postoperative photographs: the linear distances between the upper and lower eyelid margins, the pupil center and the angle between the inner and outer canthi. The globe protrusion was also measured on axial computed tomography scans before and after surgery. The results indicate that the exorbitism reduction induced by monobloc advancement is accompanied by a diminution of the distance between both eyelids and the pupil center. However, the downward slant of the palpebral fissure is increased after surgery. The data suggest that the lower and upper eyelid retraction seen preoperatively in the majority of patients with faciocraniosynostosis tend to be corrected when the frontofacial region is advanced by the monobloc. On the other hand, the surgery tends to lower the outer canthus, increasing the negative slant of the fissure. The postoperative changes induced by the frontofacial monobloc advancement need to be taken into account when the surgery is going to be performed.

Mechanical behavior of prosthesis in Toucan beak (Ramphastos toco)

The purpose of this study is to characterize the structure of the beak of Toco Toucan (Ramphastos toco) and to investigate means for arresting fractures in the rhinotheca using acrylic resin. The structure of the rhamphastid bill has been described as a sandwich structured composite having a thin exterior comprised of keratin and a thick foam core constructed of mineralized collagenous rods (trabeculae). The keratinous rhamphotheca consists of superposed polygonal scales (approximately 50 pm in diameter and 1 mu m in thickness). In order to simulate the orientation of loading to which the beak is subjected during exertion of bite force, for example, we conducted flexure tests on the dorso-ventral axis of the maxilla. The initially intact (without induced fracture) beak fractured in the central portion when subjected to a force of 270 N, at a displacement of 23 mm. The location of this fracture served as a reference for the fractures induced in other beaks tested. The second beak was fractured and repaired by applying resin on both lateral surfaces. The repaired maxilla sustained a force of 70 N with 6.5 mm deflection. The third maxilla was repaired similarly except that it was conditioned in acid for 60s prior to fixation with resin. It resisted a force of up to 63 N at 6 mm of deflection. The experimental results were compared with finite element calculations for unfractured beak in bending configuration. The repaired specimens were found to have strength equal to only one third of the intact beak. Finite element simulations allow visualization of how the beak system (sandwich shell and cellular core) sustains high flexural strength. (C) 2010 Elsevier B.V. All rights reserved.

Arthrodesis of the equine proximal interphalangeal joint: a biomechanical comparison of 3-Hole 4.5 mm locking compression plate and 3-hole 4.5 mm narrow dynamic compression plate, with two transarticular 5.5 mm cortex screws

Objectives To compare the biomechanical characteristics of 2 arthrodesis techniques for the equine proximal interphalangeal joint (PIP) using either a 3-hole 4.5 mm locking compression plate (LCP) or 3-hole 4.5 mm narrow dynamic compression plate (DCP), both with 2 transarticular 5.5 mm cortex screws. Study Design Experimental. Sample Population Cadaveric adult equine forelimbs (*n=6 pairs). Methods For each forelimb pair, 1 limb was randomly assigned to 1 of 2 treatment groups and the contralateral limb by default to the other treatment group. Construct stiffness, gap formation across the PIP joint, and rotation about the PIP joint were determined for each construct before cyclic axial loading and after each of four, 5000 cycle loading regimens. After the 20,000 cycle axial loading regimen, each construct was loaded to failure. Results There were no significant differences in construct stiffness, gap formation, or sagittal plane rotation between the LCP and DCP treatment groups at any of the measured time points. Conclusion Biomechanically, fixation of the equine PIP joint with a 3-hole 4.5 mm LCP is equivalent to fixation with a 3-hole 4.5 mm narrow DCP under the test conditions used.

Finite Element Modeling for Development and Optimization of a Bone Plate for Mandibular Fracture in Dogs

This study aimed to develop a plate to treat fractures of the mandibular body in dogs and to validate the project using finite elements and biomechanical essays. Mandible prototypes were produced with 10 oblique ventrorostral fractures (favorable) and 10 oblique ventrocaudal fractures (unfavorable). Three groups were established for each fracture type. Osteosynthesis with a pure titanium plate of double-arch geometry and blocked monocortical screws offree angulanon were used. The mechanical resistance of the prototype with unfavorable fracture was lower than that of the fcworable fracture. In both fractures, the deflection increased and the relative stiffness decreased proportionally to the diminishing screw number The finite element analysis validated this plate study, since the maximum tension concentration observed on the plate was lower than the resistance limit tension admitted by the titanium. In conclusion, the double-arch geometry plate fixed with blocked monocortical screws has sufficient resistance to stabilize oblique,fractures, without compromising mandibular dental or neurovascular structures. J Vet Dent 24 (7); 212 - 221, 2010

Oral Myiasis in a Captive Hippopotamus

Causes of dental infections can be related to failed dental eruption, malocclusion, abrasion, fractures with or without exposure of the dental pulp, and periodontal disease. Reports of oral myiasis in megavertebrates in captivity air infrequent, perhaps due to the difficulty in observing the oral cavity in such species. This report describes a case of oral myiasis in an adult male hippopotamus in the gingival area and alveolar mucosa of the left mandibular canine tooth. J Vet Dent 26 (3); 168 170,2009

Healing of displaced condylar process fracture in rats submitted to protein undernutrition

Introduction: This study evaluated the healing of mandibular condylar fracture in rats submitted to experimental and protein undernutrition (8% of protein) by means of histological analysis. Material: Forty-five adult Wistar rats were divided into three groups of 15 animals: a fracture group, who were submitted to condylar fracture with no changes in diet; an undernourished fracture group, who were submitted to a low protein diet and condylar fracture: an undernourished group, kept until the end of experiment, without condylar fracture. Displaced fractures of the right condyle were created under general anaesthesia. The histological study comprised fracture site and temporomandibular joint evaluations. Results: The undernourished fracture group showed significant weight loss. There was a marked decrease in the values of serum proteins and albumin in the undernourished fracture group. Histological analysis showed that protein undernutrition lead to atrophy of the condylar fibrocartilage. Fractures in undernutrition presented a delay in callus formation due to more extensive devitalized bone areas, and after 3 months there were still bone formation areas, while fibrous ankylosis occurred in the articular space. Conclusion: It was concluded that mandibular condyle fractures in rats with protein undernutrition had impaired callus formation, as well as fibrous ankylosis into the temporomandibular joint. (C) 2010 European Association for Cranio-Maxillo-Facial Surgery.

Influence of laser irradiation on fiber post retention

The purpose of this in vitro study was to compare the bond strength between fiber post and laser-treated root canals. Forty single-rooted bovine teeth were endodontically treated and randomly divided into four groups of equal size according to the root canal treatment: group 1 conventional treatment (without laser irradiation); group 2 Nd:YAG laser (1.5 W, 10 Hz, 100 mJ); group 3 Er,Cr:YSGG laser (0.75 W, 20 Hz); and group 4 Nd:YAG + Er,Cr:YSGG lasers. The fiber posts were cemented with an adhesive system + resin cement, in accordance with the manufacturer`s instructions. A mini acrylic pipe was fixed on the coronal section of the post using a light-polymerized resin. Specimens were mounted on an acrylic pipe with a self-polymerized resin. Retention forces were determined using a universal testing machine (0.5 mm/min). Data were analyzed using one-way ANOVA and Tukey tests (p < 0.05). The post retention force in group 2 was found to be lower than that in the other experimental groups. Fractures were observed at the interface between the dentin and the resin in all groups. High-intensity lasers can be used in conventional endodontic treatment; however, root canal surface irradiation using the Nd:YAG laser was shown to negatively affect the post retention force.

The Importance of Adhesive Area Delimitation in a Microshear Bond Strength Experimental Design

Purpose: The purpose of this study was to assess the influence of adhesive area delimitation on the microshear bond strength of different adhesives to dentin. Materials and Methods: Eighteen bovine incisors were sectioned and the exposed dentin surfaces were prepared with 600-grit SIC paper. These teeth were randomly divided into three groups, according to the adhesive to be applied: two-step etch-and-rinse Adper Single Bond 2 (3M ESPE), two-step self-etching Clearfil SE Bond (Kuraray), and one-step Clearfil S(3) Bond (Kuraray). On each dentin surface, 4 samples were built up with the composite resin Z100 (3M ESPE); on 2 of these, a suggested area delimitation technique was employed. After 24 h of storage in water at 37 degrees C, samples were subjected to the microshear bond strength test, and the failure modes were evaluated under optical and scanning electron microscopes. The obtained results were statistical analyzed using two-way ANOVA and Tukey`s test. Results: Groups without area delimitation presented significantly higher bond strength results (p < 0.05) and a higher incidence of cohesive failures. In these groups, fractures tended to occur beyond the limits of the actual adhesive area, while the area restriction technique succeeded in avoiding this phenomenon. The three adhesives performed similarly when area delimitation was employed (p > 0.05), but Clearfil S(3) Bond showed significantly higher bond strength results when no area delimitation was taken into account (p < 0.05). Conclusion: The extension of the adhesive area beyond the limits of the composite cylinder may play an important role in the results of microshear bond strength tests, while the suggested area delimitation technique may lead to less questionable outcomes.

Detection of Horizontal Root Fracture with Small-volume Cone-Beam Computed Tomography in the Presence and Absence of Intracanal Metallic Post

Introduction: The aim of the present study was to test the accuracy of small-volume cone-beam computed tomography (CBCT) scanning in the detection of horizontal root fractures and to assess the influence of a metallic post. Methods: Forty teeth were divided into four groups based on the presence of metallic posts and horizontal root fracture. The teeth were examined by small-volume CBCT scanning at 0.2-mm voxel resolution. Three observers analyzed the samples for the presence of a horizontal root fracture. Sensitivity and specificity were calculated. Results: High values for accuracy (73%-88%) were obtained in the groups without a metallic post, and statistically significant differences were found when the group with a metallic post has been observed (55%-70%). Intraobserver agreement also showed statistically significant differences in the groups with a metallic post. Conclusions: Small-volume CBCT scanning showed high accuracy in detecting horizontal root fracture without a metallic post. However, the presence of a metallic post significantly reduced the specificity and sensitivity of this examination. (J Endod 2011;37:1456-1459)

Fatigue life and failure modes of crowns systems with a modified framework design

Objectives: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. Methods: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n = 10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n = 10 each). Fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300 N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. Results: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups, whereas ICAs presented bulk fracture and ICAm failed mainly through the veneer. Y-TZP crowns failed through chipping within the veneer, without core fractures. Conclusions: Framework design modification did not improve the fatigue life of the crown systems investigated. Y-TZPm crowns showed comparable fatigue life to MC groups. Failure mode varied according to crown system. (C) 2010 Elsevier Ltd. All rights reserved.

Mechanical Testing of Indirect Composite Materials Directly Applied on Implant Abutments

Purpose: To test the strength to failure and fracture mode of three indirect composite materials directly applied onto Ti-6Al-4V implant abutments vs cemented standard porcelain-fused-to-metal (PFM) crowns. Materials and Methods: Sixty-four locking taper abutments were randomly allocated to four groups and were cleaned in ethanol in an ultrasonic bath for 5 min. After drying under ambient conditions, the abutments were grit blasted and a custom 4-cusp molar crown mold was utilized to produce identical crowns (n = 16 per group) of Tescera (Bisco), Ceramage (Shofu), and Diamond Crown (DRM) according to the manufacturer`s instructions. The porcelain-fused-to-metal crowns were fabricated by conventional means involving the construction and a wax pattern and casting of a metallic coping followed by sintering of increasing layers of porcelain. All crowns were loaded to failure by an indenter placed at one of the cusp tips at a 1 mm/min rate. Subsequently, fracture analysis was performed by means of stereomicroscopy and scanning electron microscopy. One-way ANOVA at 95% level of significance was utilized for statistical analysis. Results: The single load to failure (+/- SD) results were: Tescera (1130 +/- 239 N), Ceramage (1099 +/- 257 N), Diamond Crown (1155 +/- 284 N), and PFM (1081 +/- 243 N). Stereomicroscopy analysis showed two distinct failure modes, where the loaded cusp failed either with or without abutment/metallic coping exposure. SEM analysis of the fractures showed multiple crack propagation towards the cervical region of the crown below a region of plastic deformation at the indenter contact region. Conclusion: The three indirect composites and PFM systems fractured at loads higher than those typically associated with normal occlusal function. Although each material had a different composition and handling technique, no significant differences were found concerning their single load to fracture resistance among composite systems and PFM.

Failure modes of Y-TZP crowns at different cusp inclines

Objectives To compare the reliability of the disto-facial (DF) and mesio-lingual (ML) cusps of an anatomically correct zirconia (Y-TZP) crown system The research hypotheses tested were (1) fatigue reliability and failure mode are similar for the ML and DF cusps, (2) failure mode of one cusp does not affect the failure of the other Methods The average dimensions of a mandibular first molar crown were imported into CAD software, a tooth preparation was modelled by 1 5 mm marginal high reduction of proximal walls and occlusal surface by 2 0 mm The CAD-based tooth preparation was milled and used as a die to fabricate crowns (n = 14) with porcelain veneer on a 0 5 mm Y-TZP core. Crowns were cemented on composite reproductions of the tooth preparation The crowns were step-stress mouth motion fatigued with sliding (0 7 mm) a tungsten-carbide indenter of 6 25 mm diameter down on the inclines of either the DF or ML cusps Use level probability Weibull curve with use stress of 200 N and the reliability for completion of a mission of 50,000 cycles at 200 N load were calculated Results Reliability for a 200 N at 50,000 cycles mission was not different between tested cusps SEM imaging showed large cohesive failures within the veneer for the ML and smaller for the DF Fractures originated from the contact area regardless of the cusp loaded Conclusion No significant difference on fatigue reliability was observed between the DF compared to the ML cusp Fracture of one cusp did not affect the other (c) 2010 Elsevier Ltd All rights reserved

On the Hopf bifurcation in control systems with a bounded nonlinearity asymptotically homogeneous at infinity

The paper studies existence, uniqueness, and stability of large-amplitude periodic cycles arising in Hopf bifurcation at infinity of autonomous control systems with bounded nonlinear feedback. We consider systems with functional nonlinearities of Landesman-Lazer type and a class of systems with hysteresis nonlinearities. The method is based on the technique of parameter functionalization and methods of monotone concave and convex operators. (C) 2001 Academic Press.

Fatigue and damage accumulation of veneer porcelain pressed on Y-TZP

Objectives: This study compared the reliability and fracture patterns of zirconia cores veneered with pressable porcelain submitted to either axial or off-axis sliding contact fatigue. Methods: Forty-two Y-TZP plates (12 mm x 12 mm x 0.5 mm) veneered with pressable porcelain (12 mm x 12 mm x 1.2 mm) and adhesively luted to water aged composite resin blocks (12 mm x 12 mm x 4 mm) were stored in water at least 7 days prior to testing. Profiles for step-stress fatigue (ratio 3:2:1) were determined from single load to fracture tests (n = 3). Fatigue loading was delivered on specimen either on axial (n = 18) or off-axis 30 degrees angulation (n = 18) to simulate posterior tooth cusp inclination creating a 0.7 mm slide. Single load and fatigue tests utilized a 6.25 mm diameter WC indenter. Specimens were inspected by means of polarized-light microscope and SEM. Use level probability Weibull curves were plotted with 2-sided 90% confidence bounds (CB) and reliability for missions of 50,000 cycles at 200 N (90% CB) were calculated. Results: The calculated Weibull Beta was 3.34 and 2.47 for axial and off-axis groups, respectively, indicating that fatigue accelerated failure in both loading modes. The reliability data for a mission of 50,000 cycles at 200 N load with 90% CB indicates no difference between loading groups. Deep penetrating cone cracks reaching the core-veneer interface were observed in both groups. Partial cones due to the sliding component were observed along with the cone cracking for the off-axis group. No Y-TZP core fractures were observed. Conclusions: Reliability was not significantly different between axial and off-axis mouth-motion fatigued pressed over Y-TZP cores, but incorporation of sliding resulted in more aggressive damage on the veneer. (C) 2009 Elsevier Ltd. All rights reserved.