116 research outputs found
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 optiÄkom 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 Ī¼m. The value of maximum strain in the bone around the molars was 24 Ī¼m 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 optiÄke stereometrijske metode koje se zasnivaju na kontaktnim i nekontaktnim mehanizmima za merenje zapremine postaju uobiÄajene metode u istraživanju biomehaniÄkog ponaÅ”anja biomaterijala, koÅ”tanog i mekog tkiva. Cilj ove studije bio je da se optiÄkom metodom merenja registruju i izmere eventualne deformacije koÅ”tanog fundamenta donje vilice sa intaktnim zubnim nizom i da se, ujedno, prikažu moguÄnosti primene optiÄke metrologije u istraživanjima u stomatologiji. Metode. Sistem za merenje deformacija ispitivane donje vilice sa intaktnim zubnim lukom obuhvatio je dve digitalne kamere koje obezbeÄuju stereosinhronizovani prikaz primerka, i softver Aramis. Rezultati. NajveÄe deformacije koÅ”tanog 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 veliÄina deformacije bila je 86 Ī¼m. Vrednost maksimalne srednje deformacije u koÅ”tanom sistemu oko molara iznosila je 24 Ī¼m pri delovanju sile od 500 N na drugi donji molar. Kada su u pitanju premolari, 3-5 puta jaÄe deformacije uoÄene su u regionu prvog donjeg premolara, nego u predelu drugog donjeg premolara. ZakljuÄak. Prilikom delovanja primenjenih sila deformacije se nalaze u elastiÄnom deformacionom polju, a meÄusobna zavisnost sile i deformacije ima linearan karakter. NajveÄe vrednosti deformacija dobijene optiÄkom metodom merenja registruju se u koÅ”tanom tkivu donje vilice koja je u neposrednom kontaktu sa zubima koji se optereÄuju, kao i u koÅ”tanim regionima zakutnjaÄkog trougla i bradnog (mentalnog) otvora. Na osnovu analize rezultata dobijenih primenom softvera Aramis može se reÄi da postoje moguÄnosti primene ove metode u razliÄitim biomedicinskim istraživanjima
Anatomsko 3D modeliranje specifiÄnih bioloÅ”kih 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.MehaniÄko ponaÅ”anje bioloÅ”kih struktura je vrlo Äest predmet nauÄnih istraživanja. Rezultati takvih istraživanja pružaju precizne podatke o biomehaniÄkim karakteristikama bioloÅ”kih struktura i kao takvi su korisni za predviÄanje ponaÅ”anja struktura kada su izložene optereÄenjima. Iako su za sprovoÄenje takvih istraživanja Äesto koriÅ”Äene ekesperimentalne životinje, u novije vreme sve su ÄeÅ”Äa takva istraživanja na matematiÄkim modelima. Pri tome primat ima metoda konaÄnih elemenata. Da bi se sprovelo istraživanje metodom konaÄnih elemenata potrebno je napraviti digitalni model strukture koja je predmet istraživanja. Jednom napravljen matematiÄki digitalni model omoguÄuje primenom raÄunara beskonaÄan broj promena oblika pojedinih elemenata i struktura, ali takoÄe i bezbroj simulacija aplikacija sila. Cilj ovog rada bio je prikazati naÄin dobijanja trodimezionalnog modela zuba potrebnog za sprovoÄenje analiza ponaÅ”anja zuba nakon okluzalnog optereÄenja metodom konaÄnih elemenata kao i proceniti moguÄnost primene ove metode u biomehaniÄkim istraživanjima u veterinarskoj nauci. Na osnovu podataka iz literature, analizom morfologije ekstrahovanih zuba i plastiÄnih zuba u odgovarajuÄim kompjuterskim programima izvrÅ”eno je kreiranje sopstvenog modela intaktnog zuba. Posebno treba istaÄi da je MKE vrlo efikasan istraživaÄki alat koji je preuzet iz inžinjerskih oblasti i ima potencijala za Å”iru primenu u veterinarskoj nauci, posebno stomatologiji.
UÄestalost 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 UtvrÄivanje uÄestalosti i kvaliteta punjenja kanala zuba jeste naÄin da se procene potrebe za endodontskim leÄenjem i stepen uspeha primenjenih endodontskih procedura. Cilj rada Cilj ovog rada je bio da se odrede uÄestalost i kvalitet punjenja kanala korena zuba, kao i uÄestalost apeksnih parodontitisa endodontski leÄenih zuba kod odraslih pacijenata u Srbiji. Metode rada Radi utvrÄivanja postojanja i kvaliteta punjenja kanala korena i uÄestalosti rasvetljenja u periapeksu endodontski leÄenih zuba, analizirano je 3.526 zuba na ortopantomogramima 153 odrasle osobe. Rezultati Ukupno je endodontski leÄeno 12,5% pregledanih zuba, od kojih je 51,8% imalo radiografske znake apeksnih parodontitisa. Analiza kvaliteta punjenja kanala pokazala je da je bilo viÅ”e neadekvatnih punjenja (55,9%). UÄestalost apeksnih parodontitisa je bila znaÄajno veÄa kod zuba s neodgovarajuÄim kanalnim opturacijama (72,2%) u odnosu na one s odgovarajuÄim punjenjem kanala korena (25,9%). ZakljuÄak Kod ispitanih pacijenata utvrÄena je visoka uÄestalost apeksnih parodontitisa zuba s punjenim kanalima korena, Å”to ukazuje na slabu uspeÅ”nost primenjenih endodontskih zahvata, kao i na potrebu za ponovljenim endodontskim leÄenjem
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 gleÄno tkivo zuba maÄke oÅ”teÄenog 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 maÄaka pominju se razliÄiti etioloÅ”ki faktori kao Å”to su oboljenja parodontalnih tkiva, faktori naÄina ishrane, mehaniÄko optereÄenje, defekti nastali u toku razvoja zuba i virusna oboljenja. Ni za jedan od navedenih faktora do sada nije potvrÄeno da je direktan uzroÄnik lezija. Nedavno je objavljeno da je gleÄ u maÄaka na gleÄno-cementnoj granici znaÄajno tanja od ostale gleÄi, kao i da su gleÄ i dentin tog podruÄja mnogo manje mineralizovani nego na ostalim delovima zuba. Ipak nije potvrÄeno da li postoje i posebni anatomski delovi zuba koji imaju predispoziciju za nastajanje resorptivnih lezija i Å”ta je inicijalni faktor za kasnije aktiviranje odontoklasta. Istraživanje je sprovedeno sa ciljem da se ispita distribucija i transport organskih molekula intaktne gleÄi zuba maÄke i gleÄi koja je zahvaÄena resorptivnim procesom. Rezultati istraživanja prikazuju da je oÅ”teÄena gleÄ podložnija intenzivnijem bilateralnom procesu difuzije, koja dovodi do kontinualnog oÅ”teÄivanja strukture gleÄi. Zubi koji su izloženi okluzalnom optereÄenju su takoÄe pod veÄim rizikom od propadanja jer mikropukotine koje nastaju usled koncentracije napona uzrokuju poremeÄaj homeostaze dentalnih tkiva. UtvrÄivanje povezanosti faktora difuzije i mehaniÄkog optereÄenja zahteva dodatna istraživanja
Kompjutersko modeliranje specifiÄnih bioloÅ”ko-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.BiomehaniÄka eksperimentalna istraživanja pružaju potpuni uvid u kompleksno ponaÅ”anje bioloÅ”kih struktura pod optereÄenjem, vizualizuju potencijalna slaba mesta u samom materijalu i analiziraju da li mehaniÄko optereÄenje igra ulogu u nastajanju pojedinih patoloÅ”kih lezija. Primena MKE omoguÄuje istraživaÄima da napuste istraživanja na eksperimentalnim životinjama, i da se fokusiraju na kompjuterske modele i analizu distribucije napona i deformacija koji su pokazatelji biomehaniÄkog ponaÅ”anja strukture. Cilj ovog rada je bio da se prikaže ponaÅ”anje kompjuterskog modela intaktnog zuba nakon optereÄenja 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 optereÄenja u odnosu na vertikalno mogu se pripisati jednostavnom mehaniÄkom principu poluge, koji kaže da se sile koncentriÅ”u na mestu oslanjanja. Kada je zub izložen lateralnim silama, on se ponaÅ”a kao jednostavna poluga Äiji je oslonac u cervikalnom delu. Ovaj rad unosi novi pristup u istraživanjima u veterinarskoj stomatologiji. Jednom izraÄen model, omoguÄava da se menjanjem parametara ispituju i analiziraju razliÄite kliniÄke situacije. Sa narastajuÄom popularnoÅ”Äu veterinarske stomatologije analize MKE mogu postati veoma koristan alat u biomehaniÄkim istraživanjima, posebno zbog svoje neinvazivnosti
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 werenāt 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 < 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
BiomehaniÄki aspekt nastajanja dentalnih resorptivnih lezija u maÄaka
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 maÄaka su vrlo Äest nalaz, i mogu se uoÄiti u viÅ”e od jedne treÄine domaÄih maÄaka. 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 mehaniÄka trauma veoma znaÄajan faktor u inicijaciji dentalnih resorptivnih lezija u maÄaka i da postoji veza izmeÄu nastajanja lezija i postojanja okluzalne traume. Cilj ove studije je da se analizira distribucija napona i deformacija unutar bilo kog zuba maÄke tokom okluzalnog optereÄenja, kako bi se potvrdila ili odbacila hipoteza da je okluzalna trauma moguÄi etioloÅ”ki faktor u nastajanju dentalnih resorptivnih lezija u maÄaka. Za sprovoÄenje ovog istraživanja bilo je potrebno krerirati matematiÄki model bilo kog zuba maÄke. Osnovna ideja je bila analizirati distribuciju napona i pomeranja tokom okluzalnog optereÄenja pomoÄu metode konaÄnih elemenata. Rezultati ove studije daju doprinos teoriji da okluzalno preoptereÄenje može biti etioloÅ”ki faktor nastajanja dentalnih resorptivnih lezija u maÄaka. NaizmeniÄno smenjivanje zateznog i kompresionog napona u strukturama zuba tokom mastikacije može imati uticaja u patogenezi dentalnih resorptivnih lezija u maÄaka
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
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