Vojkan Lazic

Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

Restoring endodontically treated teeth with all-ceramic endo-crowns: Case report

The all-ceramic endocrowns are one piece restoration used in the therapy of endodontically treated teeth, usually, with a decreased vertical dimension of the tooth crown. The aim of this paper is to describe two techniques of the making of endocrowns using case studies and to present the advantages and disadvantages of both techniques by way of their comparison. Chair-side production with the Cerec CAD-CAM system and pressing of the ceramic with the Empres II system was used for the production of the endocrowns. Cerec CAD-CAM and Empres II systems yielded equally good results in the production of the endocrowns, in terms of their functionality, retention, aesthetic and duration. The basic difference between them is the length of the endocrown production procedure as the Cerec CAD-CAM system makes it possible to apply the treatment during a single visit using a wide range of materials….

Occlusal stabilization splint for patients with temporomandibular disorders: Meta-analysis of short and long term effects

Background Psychological discomfort, physical disability and functional limitations of the orofacial system have a major impact on everyday life of patients with temporomandibular disorders (TMDs). In this study we sought to determine short and long term effects of stabilization splint (SS) in treatment of TMDs, and to identify factors influencing its efficacy. Methods MEDLINE, Web of Science and EMBASE were searched for randomized controlled trials (RCTs) comparing SS to: non-occluding splint, occlusal oral appliances, physiotherapy, behavioral therapy, counseling and no treatment. Random effects method was used to summarize outcomes. The effect estimates were expressed as odds ratio (OR) or standardized mean difference (SMD) with 95% confidence interval. Subgroup analyses were carried out according to the use of Research Diagnostic Criteria (RDC/TMD) and TMDs origin. Strength of evidence was assessed by GRADE. Meta-regression was applied. Results Thirty three eligible RCTs were included in meta-analysis. In short term, SS presented positive overall effect on pain reduction (OR 2.08; p = 0.01) and pain intensity (SMD -0.33; p = 0.02). Subgroup analyses confirmed SS effect in studies used RDC/TMD and revealed its effect in patients with TMDs of muscular origin. Important decrease of muscle tenderness (OR 1.97; p = 0.03) and improvement of mouth opening (SMD -0.30; p = 0.04) were found. SS in comparison to oral appliances showed no difference (OR 0.74; p = 0.24). Meta-regression identified continuous use of SS during the day as a factor influencing efficacy (p = 0.01). Long term results showed no difference in observed outcomes between groups. Low quality of evidence was found for primary outcomes. Conclusion SS presented short term benefit for patients with TMDs. In long term follow up, the effect is equalized with other therapeutic modalities. Further studies based on appropriate use of standardized criteria for patient recruitment and outcomes under assessment are needed to better define SS effect persistence in long term.

Accuracy of optical scanning methods of the Cerec®3D system in the process of making ceramic inlays

BACKGROUND/AIM One of the results of many years of Cerec 3D CAD/CAM system technological development is implementation of one intraoral and two extraoral optical scanning methods which, depending on the current indications, are applied in making fixed restorations. The aim of this study was to determine the degree of precision of optical scanning methods by the use of the Cerec 3D CAD/CAM system in the process of making ceramic inlays. METHODS The study was conducted in three experimental groups of inlays prepared using the procedure of three methods of scanning Cerec 3D system. Ceramic inlays made by conventional methodology were the control group. The accuracy of optical scanning methods of the Cerec 3D system computer aided design-computer aided manufacturing (CAD/CAM) was indirectly examined by measuring a marginal gap size between inlays and demarcation preparation by scanning electron microscope (SEM). RESULTS The results of the study showed a difference in the accuracy of the existing methods of scanning dental CAD/CAM systems. The highest level of accuracy was achieved by the extraoral optical superficial scanning technique. The value of marginal gap size inlays made with the technique of extraoral optical superficial scanning was 32.97 +/- 13.17 mus. Techniques of intraoral optical superficial and extraoral point laser scanning showed a lower level of accuracy (40.29 +/- 21.46 mus for inlays of intraoral optical superficial scanning and 99.67 +/- 37.25 mus for inlays of extraoral point laser scanning). CONCLUSION Optical scanning methods in dental CAM/CAM technologies are precise methods of digitizing the spatial models; application of extraoral optical scanning methods provides the highest precision.

Assessment of Stability of Craniofacial Implants by Resonant Frequency Analysis

AbstractImplant stability is a principal precondition for the success of implant therapy. Extraoral implants (EO) are mainly used for anchoring of maxillofacial epithesis. However, assessment of implant stability is mostly based on principles derived from oral implants. The aim of this study was to investigate clinical stability of EO craniofacial disk implants (single, double, and triple) by resonance frequency analysis at different stages of the bones healing. Twenty patients with orbital (11), nasal (5), and auricular (4) defects with 50 EO implants placed for epithesis anchorage were included. Implant stability was measured 3 times; after implant placement, at 3 months and at least after 6 months. A significant increase in implant stability values was noted between all of the measurements, except for triple-disk implants between third and sixth months, and screw implants between 0 and third months. Disk implants showed lower implant stability quotient (ISQ) values compared with screw implants. Triple-disk implants showed better stability compared with single and double-disk implants. Based on resonance frequency analysis values, disk implants could be safely loaded when their ISQ values are 38 (single disks), 47 (double disks), and 48 (triple disks). According to resonance frequency analysis, disk implant stability increased over time, which showed good osseointegration and increasing mineralization. Although EO screw implants showed higher ISQ values than disk implants, disk-type implants can be safely loaded even if lower values of stability are measured.

Reliability of conventional shade guides in teeth color determination.

BACKGROUND/AIM Color matching in prosthodontic therapy is a very important task because it influences the esthetic value of dental restorations. Visual shade matching represents the most frequently applied method in clinical practice. Instrumental measurements provide objective and quantified data in color assessment of natural teeth and restorations. In instrumental shade analysis, the goal is to achieve the smallest deltaE value possible, indicating the most accurate shade match. The aim of this study was to evaluate the reliability of commercially available ceramic shade guides. METHODS VITA Easyshade spectrophotometer (VITA, Germany) was used for instrumental color determination. Utilizing this device, color samples of ten VITA Classical and ten VITA 3D - Master shade guides were analyzed. Each color sample from all shade guides was measured three times and the basic parameters of color quality were examined: deltaL, deltaC, deltaH, deltaE, deltaElc. Based on these parameters spectrophotometer marks the shade matching as good, fair or adjust. RESULTS After performing 1,248 measurements of ceramic color samples, frequency of evaluations adjust, fair and good were statistically significantly different between VITA Classical and VITA 3D Master shade guides (p = 0.002). There were 27.1% cases scored as adjust, 66.3% as fair and 6.7% as good. In VITA 3D - Master shade guides 30.9% cases were evaluated as adjust, 66.4% as fair and 2.7% cases as good. CONCLUSION Color samples from different shade guides, produced by the same manufacturer, show variability in basic color parameters, which once again proves the lack of precision and nonuniformity of the conventional method.

Characterisation of NiTi orthodontic archwires characteristic functional properties

The aim of this paper was to analyse the characteristic properties of different commercially available NiTi archwires (diameter 0.014”). Characteristic properties were determined by using DSC analysis for identification of phase temperatures and a tensile test for obtaining the mechanical properties, while semi-quantitative EDS analysis was used for their chemical composition. Analysis of phase temperatures showed that nickel- titanium orthodontic archwires, in the austenitic phase, were exhibiting superelastic effect in the oral environment (T= 37°C). The uniaxial stress-strain curves showed different values for the beginning and the end of loading due to the stress and transformation range. The investigation of the chemical composition showed an equiatomic NiTi alloy.

Implant Retained Orbital Prosthesis – Case Report/ Implantatno retinirana orbitalna proteza – prikaz slučaja

SUMMARY Orbital defects after tumor resection (exenteration of orbital content) have been traditionally reconstructed with adhesive-retained craniofacial prostheses, also known as epistheses. The breakthrough in rehabilitation of facial defects with implant-retained prostheses has come with development of modern silicones (vynilpolysiloxane) and bone anchorage called osseointegration. Craniofacial implant technology offers improved reconstructive options to patients. This paper describes therapeutical procedure on a patient who received craniofacial implant-retained orbital prosthesis after orbital exenteration. The patient reported excellent prosthesis handling and stability KRATAK SADRŽAJ Orbitalna oštećenja nastala resekcijom tumora (egzenteracija sadržaja orbite) se uglavnom rekonstruišu kraniofacijalnim protezama pričvršćenim adhezivima koji se nazivaju i epitezama. Izuzetne mogućnosti u rehabilitaciji defekata lica sa implantatno retiniranim protezama nastale su razvojem savremenih silikona (vinilpolisiloksana) i oseointegracijom implantata. Kraniofacijalna implantatna tehnologija danas pruža široke i poboljšane rekonstruktivne mogućnosti. U ovom radu je opisana terapijska procedura na pacijentu sa defektom orbite gde je izrađena implantatno retinirana orbitalna proteza. Pacijent je posle završene terapije bio zadovoljan zbog jednostavnog rukovanja i izuzetne stabilnosti proteze.

Implant Restoration in a Patient with Neurofibromatosis Type 1: A Case Report

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen’s disease, is a human genetic disorder. It is probably the most commonly inherited disorder caused by a single gene. This is a report of a 57-year-old man affected by NF1 who has severe atrophy of the jaws and extremely unsatisfactory anatomical conditions for conventional dental restauration. Radiographic and clinical evaluations showed inadequate quantity of bone for immediate implant rehabilitation. Delayed implant protocol was performed to obtain the correct bone volume and implants were inserted in the anterior parts of both jaws to support a prosthetic restoration.

Occlusal splints in reversible occlusal therapy of craniomandibular dysfunction

Craniomandibular dysfunction (CMD) is a set of structural and functional disorders of different etiology that affects temporomandibular joint (TMJ) and orofacial muscles. The most common etiologic factors are psychogenic, occlusal, trauma and congenital anomalies of craniofacial structures. About 75% of the examined population have mild symptoms of CMD while 3-4% have more severe symptoms which require medical attention. The main symptoms why people seek for medical attention are: facial pain which increases with chewing and irradiates in surrounding areas and pain in TMJ which irradiates in the ear canal, temporal area or neck. Painful restriction of mandible during mouth opening and eccentric movements is frequent as well as mandible deviation or deflection. Sound effects in TMJ such as popping or clicking during mouth opening are common. Initial and least invasive therapeutic procedure is reversible occlusal therapy using splints. There are two main types of occlusal splints: stabilization and relaxation. First type of splints works on condyle stabilization in orthopedically stable position; it is superoanterior condylar position in articular fossa with position of intercondylar discs between condyle and articular fossa when working cusps of the antagonists are in maximal contact with the splint. Another type of splint causes disocclussion of posterior teeth and eliminates negative effects of occlusal interference in the intercuspal position or during eccentric mandibular movements. During therapy, occlusal splint temporarily changes occlusal relationships as well as relations within TMJ, causing reduction of CMD symptoms. The best therapeutic effect for reduction of CMD symptoms is achieved by combination of physical therapy and medication.