Biomechanical interactions between bone and metal-ceramic bridges composed of different types of non-noble alloys under vertical loading conditions

The purpose of this study was to compare the mechanical properties of three metal-ceramic bridges of different types of dental alloys and to present and evaluate the possible biomechanical interactions between a marginal bone and metal-ceramic bridges during vertical loading. The research was done as an experimental study. A mandible with an intact anterior region was used. The preparation of the remaining teeth for receiving three types of porcelain-fused-to-metal (PFM) restorations was performed. Vita VMK 95 was used for all three metal-ceramic restorations. These three metal-ceramic bridges composed of different alloys, nickel and non-nickel, served as different models: the Niadur-nickelferous model, the Wiron 99-nickel model and the Wirobond C-cobalt-chrome model. The maximum compressive strain of 5% for all three virtual models is observed in the region of central incisors. The Niadur model has the lowest mean strain (2.62%) in comparison with the other two models. The mean strain of Wiron 99 is lower, by 0.10%, than the mean strain of the Wirobond model. Biomechanical behavior of the presented models caused by the vertical-loading conditions is explained as an interaction between the marginal bone and the metal-ceramic bridges. All of them, nickel and non-nickel models, indicate a similar strain (deformation) distribution; however, from the biomechanical perspective, Niadur is more favorable than the other two materials

Analiza deformacija donje vilice optičkom metrologijom

Background/Aim. New optical stereometric methods based on both contact and noncontact mechanisms for displacement measurement have become common methods in biomechanical behavior research of biomaterials, bone and soft tissue. The aim of this study was to register and measure possible deformations of the lower jaw (mandible) with the intact dental arch using optical metrology method. Methods. The system for full field measurement of deformations (strains) comprised of two digital cameras for a synchronized stereoview of the specimen, and the Aramis software. Results. The maximum mandibular bone strains were measured in the regions of the lower first premolar and the lower second molar. In the action force of 500 N simulated in the region of the first lower premolar the intensity of deformation was 86 μm. The value of maximum strain in the bone around the molars was 24 μm for the force of 500 N acting on the second lower molar. When it comes to premolars, 3-5 times stronger deformation was observed in the region of the first lower premolar, compared to the deformation values of the second lower premolar area. Conclusion. Under loading of the applied forces the measured strains were in the elastic deformation area, meanning that the dependence of force and deformity is linear. The highest values of strain measurements obtained by the optical method were found in the jaw bone tissue around the loading teeth, and the bony regions of the triangle and mental region. According to the obtained results from the Aramis processing software it can be concluded that this method is applicable in a variety of biomedical research.Uvod/Cilj. Nove optičke stereometrijske metode koje se zasnivaju na kontaktnim i nekontaktnim mehanizmima za merenje zapremine postaju uobičajene metode u istraživanju biomehaničkog ponašanja biomaterijala, koštanog i mekog tkiva. Cilj ove studije bio je da se optičkom metodom merenja registruju i izmere eventualne deformacije koštanog fundamenta donje vilice sa intaktnim zubnim nizom i da se, ujedno, prikažu mogućnosti primene optičke metrologije u istraživanjima u stomatologiji. Metode. Sistem za merenje deformacija ispitivane donje vilice sa intaktnim zubnim lukom obuhvatio je dve digitalne kamere koje obezbeđuju stereosinhronizovani prikaz primerka, i softver Aramis. Rezultati. Najveće deformacije koštanog tkiva donje vilice izmerene su u regionu donjeg prvog premolara i donjeg drugog molara. Pri delovanju sila od 500 N za region prvog donjeg premolara veličina deformacije bila je 86 μm. Vrednost maksimalne srednje deformacije u koštanom sistemu oko molara iznosila je 24 μm pri delovanju sile od 500 N na drugi donji molar. Kada su u pitanju premolari, 3-5 puta jače deformacije uočene su u regionu prvog donjeg premolara, nego u predelu drugog donjeg premolara. Zaključak. Prilikom delovanja primenjenih sila deformacije se nalaze u elastičnom deformacionom polju, a međusobna zavisnost sile i deformacije ima linearan karakter. Najveće vrednosti deformacija dobijene optičkom metodom merenja registruju se u koštanom tkivu donje vilice koja je u neposrednom kontaktu sa zubima koji se opterećuju, kao i u koštanim regionima zakutnjačkog trougla i bradnog (mentalnog) otvora. Na osnovu analize rezultata dobijenih primenom softvera Aramis može se reći da postoje mogućnosti primene ove metode u različitim biomedicinskim istraživanjima

Anatomsko 3D modeliranje specifičnih bioloških struktura

Mechanical behavior of biological structures is a common subject of scientific research. The results of such investigations offer the precise insight into the biomechanical properties of biological structures and are usefull for predicting their behavior when subjected to loading. Although, such biomechanical investigations were conducted on experimental animals nowadays are very popular investigations concerning mathematical experimental models. The most common is the finite element method analysis. A digital model of a structure of interest has to be created for an investigation with the finite element method. Once the digital model is created with the use of computer technology numerous changes of elements and structures are possible, with different applications of the simulated load. The aim of this paper was to to present the development of our own three-dimensional tooth model created for finite element analyses of intact tooth behavior under functional loading. Also, the idea was to evaluate the possibility for using finite element analysis in veterinary biomechanical research. Our own 3D model was created using computer software according to available literature data, and facts gained from freshly extracted intact teeth and plaster models. It is necessary to emphasize that FEM is an effective tool that has been adapted from the engineering arena to biomechanic research and has the potential to contribute to the growing scientific basis of knowledge in veterinary dentistry.Mehaničko ponašanje bioloških struktura je vrlo čest predmet naučnih istraživanja. Rezultati takvih istraživanja pružaju precizne podatke o biomehaničkim karakteristikama bioloških struktura i kao takvi su korisni za predviđanje ponašanja struktura kada su izložene opterećenjima. Iako su za sprovođenje takvih istraživanja često korišćene ekesperimentalne životinje, u novije vreme sve su češća takva istraživanja na matematičkim modelima. Pri tome primat ima metoda konačnih elemenata. Da bi se sprovelo istraživanje metodom konačnih elemenata potrebno je napraviti digitalni model strukture koja je predmet istraživanja. Jednom napravljen matematički digitalni model omogućuje primenom računara beskonačan broj promena oblika pojedinih elemenata i struktura, ali takođe i bezbroj simulacija aplikacija sila. Cilj ovog rada bio je prikazati način dobijanja trodimezionalnog modela zuba potrebnog za sprovođenje analiza ponašanja zuba nakon okluzalnog opterećenja metodom konačnih elemenata kao i proceniti mogućnost primene ove metode u biomehaničkim istraživanjima u veterinarskoj nauci. Na osnovu podataka iz literature, analizom morfologije ekstrahovanih zuba i plastičnih zuba u odgovarajućim kompjuterskim programima izvršeno je kreiranje sopstvenog modela intaktnog zuba. Posebno treba istaći da je MKE vrlo efikasan istraživački alat koji je preuzet iz inžinjerskih oblasti i ima potencijala za širu primenu u veterinarskoj nauci, posebno stomatologiji.

Učestalost i kvalitet punjenja kanala korena zuba kod odraslih osoba u Srbiji

Introduction Estimation of frequency and quality of root canal fillings is the way to evaluate endodontic treatment needs and success/failure rates of performed endodontic procedures. Objective The aim of this study was to determine the frequency and quality of root canal fillings and the frequency of apical periodontitis on endodontically treated teeth in a group of adult patients from Serbia. Methods In order to analyze the presence and quality of root canal fillings and the frequency of periapical radiolucencies on endodontically treated teeth, 3526 teeth were examined on orthopantomograms of 153 adult patients. Results Overall, 12.5% of examined teeth were root filled, and 51.8% of them had radiographic signs of apical periodontitis. The analysis of root fillings quality revealed the presence of more inadequate ones (55.9%). The frequency of apical periodontitis was significantly higher in teeth with inadequate than in those having adequate root canal obturation (72.2% and 25.9%, respectively). Conclusion The frequency of apical periodontitis on root-filled teeth in this group of patients was high, indicating a low success rate of performed endodotic procedures and high endodontic retreatment needs.Uvod Utvrđivanje učestalosti i kvaliteta punjenja kanala zuba jeste način da se procene potrebe za endodontskim lečenjem i stepen uspeha primenjenih endodontskih procedura. Cilj rada Cilj ovog rada je bio da se odrede učestalost i kvalitet punjenja kanala korena zuba, kao i učestalost apeksnih parodontitisa endodontski lečenih zuba kod odraslih pacijenata u Srbiji. Metode rada Radi utvrđivanja postojanja i kvaliteta punjenja kanala korena i učestalosti rasvetljenja u periapeksu endodontski lečenih zuba, analizirano je 3.526 zuba na ortopantomogramima 153 odrasle osobe. Rezultati Ukupno je endodontski lečeno 12,5% pregledanih zuba, od kojih je 51,8% imalo radiografske znake apeksnih parodontitisa. Analiza kvaliteta punjenja kanala pokazala je da je bilo više neadekvatnih punjenja (55,9%). Učestalost apeksnih parodontitisa je bila značajno veća kod zuba s neodgovarajućim kanalnim opturacijama (72,2%) u odnosu na one s odgovarajućim punjenjem kanala korena (25,9%). Zaključak Kod ispitanih pacijenata utvrđena je visoka učestalost apeksnih parodontitisa zuba s punjenim kanalima korena, što ukazuje na slabu uspešnost primenjenih endodontskih zahvata, kao i na potrebu za ponovljenim endodontskim lečenjem

Treatment of obstructive sleep apnea patients using oral appliances: Our experiences

Background/Aim. Obstructive sleep apnea (OSA) is one of the most prevalent sleep disorders. It is recognized as a serious risk factor for car and workplace accidents due to daytime sleepiness, and factor for coronary heart diseases and stroke. The aim of this study was to examine the effectiveness of oral appliances for mandibular advance in treating mild to moderate OSA. Methods. A total of 15 patients were included in this study, all diagnosed with mild or moderate OSA. Oral appliances were custom made for each patient in protrusive position at 50% of maximum mandibular advancement. The patients were given instructions not to sleep on their backs and avoid alcohol consumption during the study as these are the factors that can contribute to symptoms progression. Results. Complete and partial treatment success was achieve in 14 of the patients. Apnea-hypopnea index values were significantly lower (p < 0.05) at the end of a 6-month observation period compared to those at the treatment beginning. A great improvement in symptoms was observed, with daytime sleepiness index values significantly reduced already within the first month of the treatment. Conclusion. Treatment of obstructive sleep apnea with oral appliances has proven successful. Patients were comfortable using oral appliances and were ready to wear them for prolonged period of time. Use of oral appliances is very common in the world and should not be discarded. They are also very comfortable, practical and affordable comparing to continuous positive airway pressure (CPAP) apparatus, not to mention surgery. Use of oral appliances is safe and very well tolerated, and ought to be offered to patients with OSA

Identifikovanje karakteristika difuzije kroz gleđno tkivo zuba mačke oštećenog resorptivnim procesom

Various factors have been suggested in the pathogenesis of feline resorptive lesions, such as periodontal disease, dietary factors, mechanical stress, developmental tooth defects, breed and viral disease, although none of these factors have been definitively proven to be the direct cause. It was recently published that normally enamel in cats is significantly thinner at the cemento-enamel junction, and both enamel and dentine are significantly less mineralized than elsewhere on the tooth. However, it is still unclear what anatomical features of the tooth surface are associated with a predisposition for resorptive lesions, and what is the initiating cause for the clastic activity afterwards. The present study was undertaken with the aim to describe enamel properties of transport and distribution of organic molecules in intact feline teeth and teeth affected with resorptive lesions. The results indicate that damaged enamel is prone to a greater bilateral diffusion process, leading to continuous disruption of the enamel structure. Also, teeth that are subjected to occlusal stress are at greater risk of destruction because micro fractures produce disarrangements in feline dental tissue diffusion homeostasis. The relationship between these features with feline dental resorptive lesions requires further studies.U patogenezi dentalnih resorptivnih lezija u mačaka pominju se različiti etiološki faktori kao što su oboljenja parodontalnih tkiva, faktori načina ishrane, mehaničko opterećenje, defekti nastali u toku razvoja zuba i virusna oboljenja. Ni za jedan od navedenih faktora do sada nije potvrđeno da je direktan uzročnik lezija. Nedavno je objavljeno da je gleđ u mačaka na gleđno-cementnoj granici značajno tanja od ostale gleđi, kao i da su gleđ i dentin tog područja mnogo manje mineralizovani nego na ostalim delovima zuba. Ipak nije potvrđeno da li postoje i posebni anatomski delovi zuba koji imaju predispoziciju za nastajanje resorptivnih lezija i šta je inicijalni faktor za kasnije aktiviranje odontoklasta. Istraživanje je sprovedeno sa ciljem da se ispita distribucija i transport organskih molekula intaktne gleđi zuba mačke i gleđi koja je zahvaćena resorptivnim procesom. Rezultati istraživanja prikazuju da je oštećena gleđ podložnija intenzivnijem bilateralnom procesu difuzije, koja dovodi do kontinualnog oštećivanja strukture gleđi. Zubi koji su izloženi okluzalnom opterećenju su takođe pod većim rizikom od propadanja jer mikropukotine koje nastaju usled koncentracije napona uzrokuju poremećaj homeostaze dentalnih tkiva. Utvrđivanje povezanosti faktora difuzije i mehaničkog opterećenja zahteva dodatna istraživanja

Kompjutersko modeliranje specifičnih biološko-strukturnih odlika zuba

Biomechanical experimental studies are often a subject of interest to many researchers. The results of such investigations give a full insight of complex structural behavior under loading, visualize potential material weaknesses and evaluate if mechanical factors play a substantial role in the pathogenesis of the lesions of the investigated biological structure. The use of FEM enables most of the researchers to abandon the experimental animal models and expand the investigation on computational models, analyzing stress and strain distribution as an indicator of structural biomechanical behavior. The aim of this paper was to present computational modeling of any (human or animal) intact tooth behavior under loading and evaluate the intact tooth stress and strain distribution pattern. For the investigation to be carried out a mathematical model of an intact tooth had to be created. The difference in stress concentration, when masticatory forces are acting lateraly comparing to the ones acting vertically, can be attributed to the basic mechanical principle of leverage which states that forces concentrate at or near the fulcrum. When subjected to lateral loading, tooth with its root acts as a simple lever that fulcrums near the cervical region. This paper offers the new approach in veterinary dental scientific research. Once when a mathematical model is made, it is possible by changing the parameters to investigate different clinical situations. With increasing popularity of veterinary dentistry, the FEM/computational analyses could became a useful tool in biomechanical veterinary dental research due to its noninvasiveness.Biomehanička eksperimentalna istraživanja pružaju potpuni uvid u kompleksno ponašanje bioloških struktura pod opterećenjem, vizualizuju potencijalna slaba mesta u samom materijalu i analiziraju da li mehaničko opterećenje igra ulogu u nastajanju pojedinih patoloških lezija. Primena MKE omogućuje istraživačima da napuste istraživanja na eksperimentalnim životinjama, i da se fokusiraju na kompjuterske modele i analizu distribucije napona i deformacija koji su pokazatelji biomehaničkog ponašanja strukture. Cilj ovog rada je bio da se prikaže ponašanje kompjuterskog modela intaktnog zuba nakon opterećenja i evaluira distribucija napona i deformacija. Da bi se sprovelo ovo istraživanje bilo je potrebno kreirati digitalni model bilo kog zuba (ljudskog ili životinjskog). Razlike u distribuciji napona kod lateralnog opterećenja u odnosu na vertikalno mogu se pripisati jednostavnom mehaničkom principu poluge, koji kaže da se sile koncentrišu na mestu oslanjanja. Kada je zub izložen lateralnim silama, on se ponaša kao jednostavna poluga čiji je oslonac u cervikalnom delu. Ovaj rad unosi novi pristup u istraživanjima u veterinarskoj stomatologiji. Jednom izrađen model, omogućava da se menjanjem parametara ispituju i analiziraju različite kliničke situacije. Sa narastajućom popularnošću veterinarske stomatologije analize MKE mogu postati veoma koristan alat u biomehaničkim istraživanjima, posebno zbog svoje neinvazivnosti

Biomehanički aspekt nastajanja dentalnih resorptivnih lezija u mačaka

Feline dental resorptive lesions affect more than one third of all adult domestic cats and continue to be an enigma in the veterinary dental science although different theories about the pathogenesis of these lesions have been proposed. Recently, a hypothesis was introduced that local mechanical trauma could be an important factor in the initiation of feline dental resorptive lesions and that there is a correlation between the occurrence of resorptive lesions and occlusal trauma in cats. The aim of this study was to analyze stress distribution in feline tooth during occlusal loading in order to accept or reject the hypothesis that dental resorptive lesions in cats might be caused by occlusal trauma. A solid model of feline tooth had to be created in order to perform the investigation. The idea was to gain data for tooth displacement (deformation) and stress and strain distribution under loading generally for any feline tooth using the finite element method. The results of the study contribute to the theory that occlusal overload might be one of the causes in multifactorial resorptive lesions in cats. Succession of tensile and compressive stresses and tooth displacement during occlusal loading might be a contributive factor in the pathogenesis of feline resorptive lesions. However, further research is required to confirm this statement.Dentalne resorptivne lezije kod mačaka su vrlo čest nalaz, i mogu se uočiti u više od jedne trećine domaćih mačaka. One su i dalje enigma u veterinarskoj stomatologiji iako je do sada postavljeno mnogo teorija o njihovom nastanku. Nedavno je predložena hipoteza da je lokalna mehanička trauma veoma značajan faktor u inicijaciji dentalnih resorptivnih lezija u mačaka i da postoji veza između nastajanja lezija i postojanja okluzalne traume. Cilj ove studije je da se analizira distribucija napona i deformacija unutar bilo kog zuba mačke tokom okluzalnog opterećenja, kako bi se potvrdila ili odbacila hipoteza da je okluzalna trauma mogući etiološki faktor u nastajanju dentalnih resorptivnih lezija u mačaka. Za sprovođenje ovog istraživanja bilo je potrebno krerirati matematički model bilo kog zuba mačke. Osnovna ideja je bila analizirati distribuciju napona i pomeranja tokom okluzalnog opterećenja pomoću metode konačnih elemenata. Rezultati ove studije daju doprinos teoriji da okluzalno preopterećenje može biti etiološki faktor nastajanja dentalnih resorptivnih lezija u mačaka. Naizmenično smenjivanje zateznog i kompresionog napona u strukturama zuba tokom mastikacije može imati uticaja u patogenezi dentalnih resorptivnih lezija u mačaka

Perioperative blood loss and diclofenac in major arthroplastic surgery

Introduction: Contemporary literature indicates precaution over the perioperative use of non-steroidal anti-inflammatory drugs, since they can potentially increase perioperative blood loss related to their mechanism of action. The aim of this study was to assess the influence of non-steroidal anti-inflammatory drugs on perioperative blood loss undergoing hip arthroplasty and its correlation with general and regional anesthesia.Methods: This prospective study included 120 patients who had undergone elective unilateral total hip arthroplasty. Patients were allocated into four groups. Groups 1 and 2 were pretreated with diclofenac and operated in general and regional anesthesia. Group 3 and 4 weren’t pretreated with any non-steroidal anti-inflammatory drug and were, as well, operated in general and regional anesthesia. Diclofenac was administered orally two times a day 75 mg (total 150 mg) and also as intramuscular injection (75 mg) preoperatively and 12 hours later on a day of surgery.Results: The perioperative blood loss in the rst 24 hours showed an increase of 29.4% in the diclofenac group operated in general anesthesia and increase of 26.8% in patients operated in regional anesthesia (P &lt; 0.05) compared to control group. Statistical data evaluation of patients operated in general anesthesia compared to regional anesthesia, the overall blood loss in the rst 24 h after surgery, showed an increase of 6.4% in the diclofenac group and increase of 3.6% in placebo group. This was not statistically significant.Conclusion: Pretreatment with non-steroidal anti-inflammatory drugs (diclofenac) before elective unilateral total hip arthroplasty increases the perioperative blood loss signficantly. Early discontinuation of non-selective non-steroidal anti-inflammatory drugs is advised

Structural adaptation of Salsola soda L. (Chenopodiaceae) from inland and maritime saline area

The microscopic analysis of leaf and stem in two populations of Salsola soda was carried out in order to examine mechanism of anatomical adaptations to environmental condition on saline habitats and to determine if there exists a morpho-anatomical differentiation between populations from maritime and inland saline area. Analysis included 26 quantitative characters of leaf and stem. The results showed that both populations exhibited halomorphic and xeromorphic adaptations, which refered to ecological plasticity and adaptations of plants to their habitats. Our research also showed that S. soda had quite a stable morphoanatomical structure, since only quantitative changes were recorded. [Projekat Ministarstva nauke Republike Srbije, br. 173002