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Introduction/Objective The study was conducted to identify the maximum strain generated in the samples composed of poly-methyl-methacrylate, Straumann® implants, and three types of ceramic systems. Methods Three types of experimental models were used, loaded by external load of 100 N, 300 N, and 500 N and analyzed using the digital image correlation method. The models were composed of yttriastabilized zirconia, e.max lithium disilicate, and Vita Enamic® hybrid ceramics, placed on the Straumann® cylindrical dental implant systems (4 × 10 mm) with straight abutments. Results Significant differences in strain values between samples with different crown material groups were detected (p = 0.000). This suggests that strain values were dependent on the type of crown material. Strain values were also affected by the region of interest (p = 0.000). Application of two-way ANOVA enabled testing of the interaction effect between two independent variables, crown material and region of interest, where a significant difference was also found (p = 0.046). This indicates that strain values were also influenced by different combinations of material type and region of interest. The highest strain values were found for Z (0.383 ± 0.015) in the apical region, and the lowest for E (0.303 ± 0.015) in the middle region. Conclusion The study shows maximum strain in the apical and marginal directions. When considered various all-ceramics, we noticed the minimum strain below Vita Enamics®, while the maximum strain was found in samples with yttria-stabilized zirconia crown., Uvod/Cilj Studija je sprovedena da identifikuje maksimalnu deformaciju proizvedenu u uzorcima sastavljenim od polimetilmetakrilata, Štrauman® implantata i tri vrste keramičkih sistema. Metode Korišćene su tri vrste eksperimentalnih modela izloženih spoljašnjem opterećenju od 100 N, 300 N i 500 N i analiziranih uz pomoć metoda korelacije digitalnih slika. Modeli su bili sastavljeni od itrijum-cirkonije, e. maks. litijum disilikatne i hibridnih keramika Vita enamik®, postavljenih na cilindrične dentalne implantantne sisteme Štrauman® (4 × 10 mm) sa abatmentima pod pravim uglom. Rezultati Značajne razlike su otkrivene u vrednostima deformacija između uzoraka sa različitim keramičkim krunicama (p = 0,000). Ovo podrazumeva da su vrednosti deformacija zavisne od tipa keramičkog materijala. Vrednosti deformacija su zavisne i od regiona interesa (p = 0,000). Primena ANOVA testa je omogućila da se uoči interakcija između nezavisnih varijabli, meterijala keramičkih kruna i regiona od interesa, gde je takođe nađena statistički značajna razlika (p = 0,046). Ova činjenica ukazuje na to da vrednosti deformacija zavise od različite kombinacije tipa keramičkog materijala i regiona interesa. Najveće vrednosti deformacija su nađene na modelu Z (0,383 ± 0,015) u apikalnom regionu, dok su najmanje vrednosti deformacija nađene na modelu E (0,303 ± 0,015) u regionu srednje trećine. Zaključak Izveštaj je pokazao maksimalne deformacije u apikalnim i marginalnim pravcima. Kada se razmatraju različite vrste keramika, najmanje deformacije su primećene ispod kruna Vita enamik®, dok je najveća deformacija pronađena u uzorcima sa krunama itrijum-cirkonija.

Introduction/Objective Current biomechanical analyses can provide full view of the strain induced by loading of various replacements to be used for prosthetic rehabilitation. The aim of this study was to analyze strain distribution of supporting tissues beneath two different types of removable partial dentures, commonly indicated in the conventional rehabilitation of partially edentulous patients. Methods This in vitro study included two groups of experimental models composed of the mandibles (Kenedy Class 1) and two types of removable partial dentures. These models were exposed to occlusal loading and the digital image correlation method was used for strain visualization and strain measurement. Results The highest strain was measured beneath the removable partial dentures, on the surfaces of bone adjacent to distal abutments and in the anatomical structure called the retromolar area. Strain values in the experimental models with clasp removable partial dentures ranged 0-10%. Strain values in the experimental models with attachment - removable partial dentures ranged 0-2.3%. Conclusion The findings showed that the attachment retaining removable partial dentures induced lower strain in the residual alveolar ridges. However, higher strain was detected in the marginal bone next to the abutment teeth., Uvod/Cilj Savremene biomehaničke analize omogućavaju kompletnu vizuelizaciju deformacija od opterećivanja različitih zubnih nadoknada u protetskoj rehabilitaciji. Cilj ove studije je bio da analiza distribucije deformacija unutar potpornih tkiva ispod dva različita tipa najčešće korišćenih parcijalnih skeletiranih proteza. Metode In vitro studija je obuhvatila dve grupe eksperimentalnih modela donjih vilica (Kenedi 1 klasa krezubosti) i dva tipa parcijalnih skeletiranih proteza. Modeli su bili izloženi okluzalnim silama, a za prikaz i merenje deformacija je korišćena metoda digitalne korelacije slika. Rezultati Najveća deformacija je izmerena ispod parcijalnih proteza, na površinama kosti koja okružuje distalne zube nosače i u retromolarnoj regiji. Vrednosti deformacija u eksperimentalnim modelima sa protezama retiniranim livenim kukicama su bile 0-10%. Vrednosti deformacija u eksperimentalnim modelima sa protezama retiniranim atečmenima su bile 0-2,3%. Zaključak Parcijalne skeletirane proteze sa atečmenima indukovale su manje deformacije rezidualnog alveolarnog grebena. Veće deformacije su uočene u marginalnoj kosti koja je u neposrednom kontaktu sa zubima nosačima.

Extensive evolution of glass ionomer cements (GIC) has marked a significant shift in the practice of luting indirect dental restorations limiting the use of zinc-phosphate and zinc-polycarboxylate cements to a few indications. GIC are now one of the materials of choice for cementation of all ceramics, fiber reinforced composite posts and veneers. GICs are determined by unique properties like chemical adhesion to tooth and base metals, low thermal expansion coefficients similar to dentin and minimal microleakage at the tooth-enamel interface due to low shrinkage. Shrinkage strain is identified as the cause, and the associated stress as the mechanism for the loss of marginal adaption and cohesive fracture within the material. The aim of this study is to measure the strain and displacement field in a conventional GIC (Riva Luting, SDI, Australia) related to different cement diameter, using 3D Digital Image Correlation (DIC) method. The experiment is done for samples with thickness of 1 mm combined with diameters of 4 mm (Group I) and 3 mm (Group II). The strain field is measured using 3D 11optical system Aramis 2M (GOM, Braunschweig, Germany). This study provides valuable data about strain behaviour and displacement as a possible failure factor in GIC, Riva Luting. Visible differences between Group I and Group II were observed.

The study showed an application of the 3 D Digital Image Correlation Method (3 D-DIC) for detection of von Mises strain in samples of the self-etch, self-adhesive resin based cement (RBC). The aim was to determine and compare strain in the self-cured and light-cured Maxcem Elite, furthermore to investigate the hardness of these two cement-types. The experiment was carried out using two groups of Maxcem Elite (Kerr, Orange, CA, USA) samples; each tested group includes five (o5 x 2 mm sized) samples, for both self-curing and light-curing mode. All samples were prepared by filling teflon ring-type molds. In addition, Vickers micro-hardness was measured for all samples. Maxcem Elite showed similar maximum strain values from 10% to 12% for both groups. Besides the maximum strain value, the 3 D-DIC method also enabled monitoring the change of strain field even after the recommended polymerization time. This method has shown that the polymerization shrinkage continues even after 10 min which disagreed with manufacturer's suggestion. Group II showed maximum strain values of 12% in the peripheral zone after 10 min, in the last Stage (Stage 60). Statistically significant difference was not found in the overall strain between self- and light-cured Maxcem Elite neither peripherally (p = 0.118) nor centrally (p = 0.879). However, statistical significance was found in strain regarding central and peripheral zone in both, self-cured (p = 0.020) and light-cured (p = 0.002) Maxcem Elite. The mean von Mises strain values in the periphery of the samples (Section 0) were significantly higher compared to strain values in the center of the samples (for Section 1 and 2). The last stage (Stage 60) of the light-cured Maxcem Elite polymerization showed significantly higher values of von Mises strain compared to initial stage (Stage 0). Higher values of micro-hardness were noticed on the surfaces directly exposed to LED lamp after performing measurements of micro-hardness on light-cured sampl

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.

Dental-implant overload can cause bone resorption. Load-transfer characteristics of dental implants are affected by their macro-design parameters. The goal of this study was to experimentally analyse the load-transfer characteristics of different dental implants, using polymethyl-methacrylate blocks. Three polymethyl-methacrylate blocks were created, with dimensions of (68 x 25 x 9) mm. Three dental implants, Nobel empty set3.5 mm x 15 mm, Strauman empty set4.1 mm x 10 mm and Strauman empty set4.8 mm x 12 mm. were placed in separate blocks. The samples were supported by a three-point-bending set-up and loaded with an axial force of 600 N. The 3D digital image correlation method was employed for strain and displacement measurements. The highest displacement and von Mises strain values were found for Strauman empty set4.1 mm x 10 mm (p lt 0.05), 0.186 mm and 0.596 %, respectively. The sample of Nobel empty set3.5 mm x 15 mm showed the lowest strain values. The sample of Strauman empty set4.8 mm x 12 mm (p > 0.05) had similar strain values as Nobel empty set3.5 mm x 15 mm. The load transfer during axial loading was primarily affected by the size of the implant contact surface. The displacement and strain values in the implant vicinity may provide an insight into the effect of dental-implant design on the load transfer.

Uvod/Cilj Studija je sprovedena da identifikuje maksimalnu deformaciju proizvedenu u uzorcima sastavljenim od polimetilmetakrilata, Štrauman® implantata i tri vrste keramičkih sistema. Metode Korišćene su tri vrste eksperimentalnih modela izloženih spoljašnjem opterećenju od 100 N, 300 N i 500 N i analiziranih uz pomoć metoda korelacije digitalnih slika. Modeli su bili sastavljeni od itrijum-cirkonije, e. maks. litijum disilikatne i hibridnih keramika Vita enamik®, postavljenih na cilindrične dentalne implantantne sisteme Štrauman® (4 × 10 mm) sa abatmentima pod pravim uglom. Rezultati Značajne razlike su otkrivene u vrednostima deformacija između uzoraka sa različitim keramičkim krunicama (p = 0,000). Ovo podrazumeva da su vrednosti deformacija zavisne od tipa keramičkog materijala. Vrednosti deformacija su zavisne i od regiona interesa (p = 0,000). Primena ANOVA testa je omogućila da se uoči interakcija između nezavisnih varijabli, meterijala keramičkih kruna i regiona od interesa, gde je takođe nađena statistički značajna razlika (p = 0,046). Ova činjenica ukazuje na to da vrednosti deformacija zavise od različite kombinacije tipa keramičkog materijala i regiona interesa. Najveće vrednosti deformacija su nađene na modelu Z (0,383 ± 0,015) u apikalnom regionu, dok su najmanje vrednosti deformacija nađene na modelu E (0,303 ± 0,015) u regionu srednje trećine. Zaključak Izveštaj je pokazao maksimalne deformacije u apikalnim i marginalnim pravcima. Kada se razmatraju različite vrste keramika, najmanje deformacije su primećene ispod kruna Vita enamik®, dok je najveća deformacija pronađena u uzorcima sa krunama itrijum-cirkonija., Introduction/Objective The study was conducted to identify the maximum strain generated in the samples composed of poly-methyl-methacrylate, Straumann® implants, and three types of ceramic systems. Methods Three types of experimental models were used, loaded by external load of 100 N, 300 N, and 500 N and analyzed using the digital image correlation method. The models were composed of yttriastabilized zirconia, e.max lithium disilicate, and Vita Enamic® hybrid ceramics, placed on the Straumann® cylindrical dental implant systems (4 × 10 mm) with straight abutments. Results Significant differences in strain values between samples with different crown material groups were detected (p = 0.000). This suggests that strain values were dependent on the type of crown material. Strain values were also affected by the region of interest (p = 0.000). Application of two-way ANOVA enabled testing of the interaction effect between two independent variables, crown material and region of interest, where a significant difference was also found (p = 0.046). This indicates that strain values were also influenced by different combinations of material type and region of interest. The highest strain values were found for Z (0.383 ± 0.015) in the apical region, and the lowest for E (0.303 ± 0.015) in the middle region. Conclusion The study shows maximum strain in the apical and marginal directions. When considered various all-ceramics, we noticed the minimum strain below Vita Enamics®, while the maximum strain was found in samples with yttria-stabilized zirconia crown.

The purpose of this study was to investigate the influence of the abutment angulation upon the strain distribution pattern for the vertical loading situation by means of the digital image correlation (DIC) method. In addition, to find the correlation between acrylic-layer thickness around implant body and surfaces strain induced by vertical loads. Two types of samples consisted of the Straumann (R) cylindrical dental implant system (4x10mm) with the SLActive (R) surface and the poly-methyl-methacrylate were used in this study. For strain analysis, the DIC system was used, manufacturer GOM. The optical deformation measurement system consists of special set of stereo cameras and lenses, and ARAMIS software (6.2.0, Braunschweig, Germany). Maximum von Mises strain was 0.30% in the sample with the straight abutment and 0.50% in the sample with the angled abutment. Minimum strain measured by Aramis was 0.01%, detected in the 6mm surface layer of the sample with straight abutment. According to results obtained by Aramis data processing, the 4mm surface layer indicated greater overall strain in apical direction with the strains of 0.18-0.50%, depending on the force intensity. Higher strain was noticed in the thinner surface layers. The angulated abutment induced higher strain in both surface layers than the straight abutment did.

Purpose: The aim of this study was to find the correlation between the number, type, and placement of symmetric functional tooth units and the nutritional status using body mass index (BMI) and Mini Nutritional Assessment (MNA) in patients with both maxillary and mandibular removable partial dentures. Materials and Methods: A randomized study was conducted at the Clinic for Prosthodontics, School of Dentistry, University of Belgrade, Serbia, followed by determination of number of functional tooth units. After insertion of the prostheses, the nutritional status was assessed, using BMI and MNA form. Nutritional status was reviewed 12 months after prosthetic treatment. Number of teeth and age were analyzed using analysis of variance and t test. For other variables such as BMI baseline, BMI follow-up, MNA baseline, MNA follow-up, change in BMI, and change in MNA, Kruskal-Wallis Test or Mann-Whitney Test were used. Results: The results on the MNA changes showed that patients with symmetric natural functional tooth units had significantly higher values (2.9 +/- 0.8) compared with patients without natural functional tooth units (1.9 +/- 0.6) or with asymmetric natural functional tooth units (1.6 +/- 0.4). Patients with asymmetric artificial functional tooth units had significantly lower change in MNA (1.9 +/- 0.4) than those with symmetric artificial functional tooth units (2.6 +/- 0.9). Conclusion: The findings of this study suggest that adequate rehabilitation with symmetric positioning of the functional tooth units can improve the nutritional status of partially edentulous patients.

Purpose: This study was conducted to identify the prevalence of partially edentulous individuals in Serbia and to identify prosthodontic treatment used for their rehabilitation as well as to compare prosthodontic treatment concepts among Serbian elderly participants who answered closed-format questionnaires. Materials and Methods: The study was conducted at the Clinic for Dental Prosthetics, University of Belgrade, Military Medical Academy and the Department of Prosthodontics of Home Centre Belgrade; the study consisted of 120 participants. A questionnaire with closed-format questions regarding the influence of applied therapy concepts for participants with Kennedy Class I partial edentulism was created. Statistical software SPSS 11.5 was used for data analysis. Chi-square tests were performed, and p-values were calculated for each parameter. Results: A total of 1081 people were examined; 730 participants were partially edentulous in at least one jaw. Five hundred forty-one participants wore Kennedy Class I maxillary or mandibular removable partial dentures (RPDs). Ninety percent of the patients were restored with RPDs; 60% of participants were unrestored, had shortened dental arches, and requested alternative therapeutic solutions. Significantly lower needs for new treatments were identified in participants with fixed dental prostheses (7.5%). Conclusions: Kennedy Class I was the most common type of partial edentulism among Serbian elderly, usually treated with RPDs. Elderly participants with the applied shortened dental arch and RPD therapy concepts requested alternative therapeutic solutions more often than those rehabilitated with fixed partial dentures.

Dizajn dentalnih implanata utiče na vrednosti deformacija koje nastaju u njihovoj okolini, i ako se pređe granična vrednost od 0.3 %, može doći do resorpcije kosti. Cilj ove studije je da predstavi novi eksperimentalni pristup za analizu uticaja geometrije dentalnih implanata na deformacije okolne strukture. Model kosti, sa dimenzijama od 68h25h9 mm, je napravljen od polimetil-metakrilata. Kalup za model koji je napravljen pomoću tehnike 3D štampe, je takođe služio i kao fiksator položaja za vertikalno postavljeni implant Štrauman ø4.0x12 mm. Uzorak je opterećen na savijanje u tri tačke. Aksijalna sila od 600 N je primenjena na dentalni implant. Za merenje deformacija i pomeraja je korišćena metoda Digitalne korelacije slika. Najveće vrednosti Von Mizesovih deformacija od 0.7 % su izmerene u području vrata implanta. Maksimalne vrednosti pomeraja u pravcu opterećenja su iznosile 0.466 mm. Površinska deformacija i pomeraji su povezani sa geometrijom implanata. Ova eksperimentalna metodologija se može koristiti u cilju određivanja karakteristika prenosa opterećenja dentalnih., Deformations in the vicinity of dental implants are affected by their design and if threshold level of 0.3 % is surpassed, bone resorption could occur. The goal of this study is to present a novel experimental approch for the analysis of effect od dental implant geometry on the surrounding structure strain values. A bone block model, with dimensions of 68x25x9 mm, was made from polymethyl-methacrylate. 3D printed block mold also provided a fixture for vertically placed Strauman ø4.0x12 mm. The sample was loaded in a three-point bending setup. The axial force of 600 N was applied on the dental implant. The Digital Image Correlation method was used for strain and displacement measurement. The highest von Mises strain of 0.7 % is located in the area of implant neck. The maximum displacement value in loading direction was 0.466 mm. Surface strain and displacement are correlated with implant geometry. This experimental methodology can be utilized to estimate dental implant load transfer characteristics.

Introduction/Objective The absence of functional loading due to molar loss might cause changes to the microstructure of the bone. Therefore we investigated and visualized deformation and strain pattern distribution of the mandibule with full arch dentition (FDA) and shortened dental arches (SDA) during occlusion. Methods A 3D model of an adult cadaveric dentate mandible, without pathological and traumatic damages, was developed based on CT scan images, set to 0.7 mm slice thickness. The scanned slices were imported into software where the bone and teeth were identified and modelled separately based on image density thresholding. Using the software and based on the grey-scale analysis of the slices initial meshes for the cortical, cancellous bone and teeth were generated. Results Highest stress/strain values were registered in the structures adjacent to molars i.e. molar region of processus alveolaris assigned by blue color in FDA model. Similar to FDA, the SDA models exibited deformation with evident highest strain (9.33%) at the processus coronoideus and mandibular angle. The highest overall stress (5 MPa) and strain (6.67%) was found in the mandibular intercanine segment of the SDA model, considering the mandibular body. Conclusion Finite element method can be employed as a powerfull tool for visualization of the stress and strain of the loaded mandible models with full and shortened dental arches. It was registered that molar support loss caused higher stress and strain in SDAs compared to FDA model., Uvod/Cilj Odsustvo funkcionalnog opterećenja usled gubitka molara može izazvati promene u mikrostrukturi kosti. Cilj ovog istraživanja je bio da se ispitaju i vizuelizuju naponi i deformacije u mandibulama sa intaktnim zubnim lukom (IZL) i skraćenim zubnim lukom (SZL) u toku okluzije. Metod 3D model kadaverske donje vilice odrasle osobe (procenjena vizuelnim pregledom bez patoloških i traumatskih oštećenja) razvijen je na osnovu KT slike, debljine sloja od 0,7 mm. Skenirani preseci su uneti u softver gde su identifikovana i modelirana tvrda tkiva kosti i zubi pojedinačno na osnovu segmentacije slike. Početne mreže za kortikalnu kost, spongioznu kost i zube su proizvedene korišćenjem softvera i na osnovu analize sive skale preseka. Rezultati Najveće vrednosti napona i deformacija su registrovane u strukturama donje vilice neposredno uz molare u tzv. molarnom regionu alveolarnog nastavka, što je označeno plavom bojom na IZL modelu. Slično IZL, i SZL modeli su pokazali najveće vrednosti deformacija (9,33%) u koronoidnom nastavku i mandibularnom uglu. Najveći napon (5 MPa) i deformacija (6,67%) pronađeni su u interkaninom regionu SZL modela, ukoliko se razmatra telo donje vilice. Zaključak Metodom konačnih elemenata su vizuelizovane slike napona i deformacija modela donje vilice sa punim i skraćenim zubnim lukovima. Uočeno je da gubitak molarne potpore izaziva jače napone i deformacije u SZL modelima u poređenju sa IZL modelom.

Deformations in the vicinity of dental implants are affected by their design and if threshold level of 0.3 % is surpassed, bone resorption could occur. The goal of this study is to present a novel experimental approch for the analysis of effect od dental implant geometry on the surrounding structure strain values. A bone block model, with dimensions of 68x25x9 mm, was made from polymethyl-methacrylate. 3D printed block mold also provided a fixture for vertically placed Strauman ø4.0x12 mm. The sample was loaded in a three-point bending setup. The axial force of 600 N was applied on the dental implant. The Digital Image Correlation method was used for strain and displacement measurement. The highest von Mises strain of 0.7 % is located in the area of implant neck. The maximum displacement value in loading direction was 0.466 mm. Surface strain and displacement are correlated with implant geometry. This experimental methodology can be utilized to estimate dental implant load transfer characteristics., Dizajn dentalnih implanata utiče na vrednosti deformacija koje nastaju u njihovoj okolini, i ako se pređe granična vrednost od 0.3 %, može doći do resorpcije kosti. Cilj ove studije je da predstavi novi eksperimentalni pristup za analizu uticaja geometrije dentalnih implanata na deformacije okolne strukture. Model kosti, sa dimenzijama od 68h25h9 mm, je napravljen od polimetil-metakrilata. Kalup za model koji je napravljen pomoću tehnike 3D štampe, je takođe služio i kao fiksator položaja za vertikalno postavljeni implant Štrauman ø4.0x12 mm. Uzorak je opterećen na savijanje u tri tačke. Aksijalna sila od 600 N je primenjena na dentalni implant. Za merenje deformacija i pomeraja je korišćena metoda Digitalne korelacije slika. Najveće vrednosti Von Mizesovih deformacija od 0.7 % su izmerene u području vrata implanta. Maksimalne vrednosti pomeraja u pravcu opterećenja su iznosile 0.466 mm. Površinska deformacija i pomeraji su povezani sa geometrijom implanata. Ova eksperimentalna metodologija se može koristiti u cilju određivanja karakteristika prenosa opterećenja dentalnih.

Introduction/Objective In an attempt to simplify dental procedures, a new group of resin cements, self-adhesive resin cements (SARCs), have been introduced. Performance of SARCs can widely vary. One of the main reasons of adhesion failure is polymerization shrinkage. The aim of this study was to determine, evaluate, and measure strain field of self-adhesive dual cure resin cement during polymerization in self-cure mode using 3D digital image correlation (DIC) method. Methods The self-adhesive Maxcem Elite (Kerr, Orange, CA, USA) cement was tested in five cylindrical samples (5 mm in diameter and 2 mm in thickness) prepared by filling plastic ring-type molds. Digital images were recorded immediately after sample preparation. Results Non-uniform strain distribution was found in resin cement with higher strain values along the periphery (up to 15%) and lower strain values in central parts (around 4%) of each sample. Conclusion It can be concluded that DIC is a powerful tool for full-field strain measurements in material characterization., Uvod/Cilj U nastojanju da se pojednostave stomatološke procedure uvedene su nove grupe kompozitnih cemenata - samoadhezivni, dvojnovezujući kompozitni cementi. Svojstva ovih cemenata mogu da variraju u velikoj meri. Jedan od glavnih razloga narušavanja adhezionih svojstava kompozitnih cemenata je polimerizacijska kontrakcija. Cilj ovog rada je da se odredi i izmeri deformaciono polje samoadhezivnog dvojnovezujućeg kompozitnog cementa tokom hemijske polimerizacije korišćenjem eksperimentalne tehnike - metode 3D korelacije digitalnih slika. Metode Samoadhezivni kompozitni cement Maxcem Elite (Kerr, Orange, SAD) ispitivan je na pet uzoraka prečnika 5 mm, debljine 2 mm, koji su pripremljeni punjenjem plastičnih kalupa prstenastog oblika. Digitalne slike su zabeležene neposredno posle pripreme uzoraka. Rezultati Neuniformno deformaciono polje je pokazalo veće vrednosti deformacija na periferiji uzoraka (do 15%) i manje vrednosti deformacija u centralnim delovima uzoraka (oko 4%). Zaključak Može se zaključiti da je 3D korelacija digitalnih slika precizna i pouzdana metoda za merenje deformacionih polja u oblasti karakterizacije materijala.

This study analyzed the influence of platform switching on the stress/strain distribution of vertically loaded implants. Employing finite element analysis, the aim of this study was to determine the distribution of stresses and strains generated by a simulated vertical load on different implant models positioned in the molar region with respect to changes of implant design and biomechanics. Two different implant designs, one with and one without platform switching, with the same length (11.5 mm) and diameter of (3.80 mm) were analyzed. Both virtual implant-bone models were subjected to a load of 500 N. The results showed that the maximum stress/strain in implant-bone samples was located in the area of the implant neck, with stress/strain values decreasing in the apical direction. It was found that the implant design with platform switching developed lower stresses and strains than the implant design without platform switching.

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.

The aim of this in vitro study was to investigate the strain distribution of the compressed mandible bone under the applied restoration-removable partial denture and to compare with the same but unrestored mandible under vertical (occlusal) load and to find out whether removable partial denture-restored or unrestored mandible causes greater strain effect on supporting tissue. Four mandible models were tested during loading for the purpose of strain measuring. Digital image correlation system (GOM - German Optical Measuring, Braunschweig, Germany), used for measuring strain consists of two digital cameras and software ARAMIS (6.2.0, Braunschweig, Germany). Remaining teeth suffer from greater strain in the mandible model without removable partial denture (7.5-10%). On the contrary, mandible with removable partial denture shows the maximum strain below the denture saddle (3.5%). However, it can be noticed that the marginal bone of the second lower praemolar in both experimental models is deformed whether the mandible model has (2.8%) or has not (10%) replacement. Within the limitations of this study the higher strain is observed in mandible model without replacement and the strain is limited locally, in the bone region that surrounds remaining teeth and mental foramen.

The aim of this study was to register and measure any deformation of mandible models under load. The method for full field measurement of strain is done by using the ARAMIS three-dimensional image correlation system. The system uses two digital cameras that provide a synchronized stereo view of the specimen and the results show the complete strain field during the tests. The biggest deformation values were just under the working force of the biggest intensity 500 N, and for the region of the lower second premolar the deformation is 625 mu m. The following study is presented that highlight the use of stereometric measuring system for modern research. It is shown that this measuring methodology can capture the trends of the experiments.

It was the purpose of this study to determine and analyse strains in the bone of posterior mandible below the removable and fixed partial dentures using Digital Image Correlation Method. Dried mandible with shortened dental arch (Kennedy Class 1) was used in the experiment. The mandible model was prepared for accepting two types of restorations for bilaterally missing molars conventional therapy, and removable and fixed partial dentures were manufactured following standard prosthetic protocol. The models with prosthetic restorations placed in situ were subjected to loading of 50-300 N, and photographed using two digital cameras as part of the digital image correlation method equipment. Afterwards, the obtained data for strains within restored mandible during loading ciclus were analysed in the software Aramis and graphically presented. Percentage size of the mandible strains within the line section are from 0.14 to 0.19% for the removable partial denture experimental model and 0-0.14% for the fixed partial denture experimental model. The study has demonstrated that Digital Image Correlation method can be used to measure strain on the mandible surface and replacements during loading and that from biomechanical perspective both therapeutic modalities can be equally useful for the restoration of the mandible with bilaterally distal edentulous spaces.

Recently, resin based cements have become very popular in dental practice for cementation of dental restorations, especially considering all-ceramics, due to improved adhesion features. The aim of this study was to visualize and compare strain in the self-cured and dual-cured MaxCem Elite and to investigate hardness of these two curing modes of the same cement. Strain field was measured using 3D optical system Aramis 2M (GOM, Braunschweig, Germany) based on digital image correlation method. Ten, 5 × 2 mm sized samples of the self-cured and dual-cured Maxcem Elite (Kerr, Orange, CA, USA) were prepared by filling plastic ring-type molds. Analysis of the strain fields was done using sections and stage points created by software. The distribution of the overall strain was found to be more expressive and uniform in the self-cured samples. Overall shrinkage strain ranged from 0 to 12%. Samples with dual-curing mode showed higher strain peripherally, compared to self-cured samples where the overall strain was distributed all over the sample surface. The Vickers measurements could not be carried out on self-cured samples due to incomplete chemical polymerization. The values of hardness were relatively equal in dual-cured Maxcem Elite due to hardness is interpreted as a statistical magnitude practically depends on the composition of the tested structure. Additionally, closeness between cements layers and led lamp was a factor for increasing hardness values in dual–cured Maxcem Elite. The study provided valuable data about strain behavior of Maxcem Elite during polymerization and highlighted dual-cured over self-cured mode.

The aim of this study was to present the possibility for digital image correlation (DIC) and finite element analysis (FEA) investigation of ceramic crowns placed on angulated and non angulated implants. Additionally, to determine strain in models composed of all-ceramics supported by angulated and non angulated implants with or without platform switching. Three-dimensional finite element (FE) and the digital (DIC) models of the Strauman cylindrical dental implant systems (4 x 12 mm; Straumann, Basel, Switzerland) placed in the polyurethane resin (F16, Axson Technologies, France) block with an inclination of the vertical axis in interval of +1, -1 and -3 degrees were created. Additionally, control FEA and DIC models with straight implants (one for each analyzing system) were created to support results obtained for models with inclined implants. Height of the block was 14.5 mm and length 11.5 mm. The width of the sample was 13 mm. The implants were placed so that their outer diameter surface was 2 mm away from the surface of interest, measured in the straight orientation (0˚). The strain was observed at two locations i.e. modes – “block implant” interface (cross section), and in the area of interest. Solid modeling for the implant and block model was performed in Ansys 13.0 APDL Multyphysics in Windows 7 OS. Finite Element analysis was performed in Ansys 13.0 by Sparsesolver. Solidworks 2015 Academia (Dassault Systemes) was used for creating block mold models. Overall von Mises strain for every sample was calculated by averaging strain values in cervical, middle and apical region. Increase of the angle of inclination increased overall strain in the apical region of the DIC and FEA models. DIC mode confirmed findings supported by FEA modes, so FEA models validate DIC models.

Mostly, mechanical properties such as elastic modulus, flexural strength and fracture toughness were assessed under static loading conditions for the initial characterization of materials. During this course authors presented the digital image correlation technique as possible method for biomechanical investigations of all-ceramics under vertical loading conditions using standard tensile testing machine and several samples of all-ceramics’ blocks: E-max lithium disilicate glass-ceramics, Vita enamic, Feldsphatic ceramic and Yttria-stabilized zirconia polycrystal ceramic. Lithium disilicate glass-ceramics has a needle like crystal structure that offers excellent strength and durability as well as outstanding optical properties. For the lithium disilicate ceramics, the amount of glass phase is determinant in their fatigue behavior. Vita enamic is the first hybrid dental ceramic with a dual-network structure. Feldsphatic is a glass material with an amorphous (non-crystalline) structure. Yttria-stabilized zirconia polycrystal is a high-strength ceramic with high values of flexular strength and fracture toughness. Zirconia, the strongest and toughest of all dental ceramics meets the mechanical requirements for high stress-bearing posterior restorations. All of these blocks were subjected to load in the tensile testing machine and the obtained strain was visualized using cameras and Aramis software. Findings provide that the highest strain was detected in Feldspathic, E-max and Zirconia all-ceramic blocks, respectively. Vita enamic was found to be the lowest strained due to polymer infiltrated its structure. This fact has significance for clinicians due to application of all’ceramic system in patients with decreased vertical occlusion and abrasion. Additionally, the hardness and elastic modulus of Vita enamic was found to be similar to those of the dental tissue values which makes this material a good choice for restoring posterior areas with inlays.

Strain fields in the vicinity of the dental implant varies depending of several factors, among which is the implant geometry. This study investigates new experimental methodology for analysis of effect of implant geometry on the load transfer during axial loading of dental implant. Two dental implants, Strauman 4.8 x 14 mm and Strauman 4.0 x 12 mm, were placed in individual blocks of polymethyl methacrylate with dimensions of 68 x 25 x 9 mm. Samples were placed in the three point bending support. Axial load was applied on the implant, with maximum intensity of 600 N. 3D Digital Image Correlation method was used for strain measuring. Two FE models were developed according experimental models. Von Mises strains were presented and compared. Results show the greatest values of Von Mises strain values in the neck region of the implant, in the upper part of the block. Experimental results show Von Mises strain in the range of 0.4 – 0.8 %. Numerical models show Von Mises strains in the range of 0.4–0.6 %. Experimental and numerical models show tendency of deformation decrease in the apical region of the implant. Lower strain values in experimental and numerical analysis were observed for Strauman 4.8 x 14 mm. This coincides with reports in the literature where it is reported that implants with greater contact surface transfer lower strain values. This study shows that this methodology could be used in preliminary analysis in effect of dental implant geometry on the strains in their vicinity during axial loading.

This paper contains the results of a research focused on the determination of the influence of an implant inclination on the strain state throughout the acrylic block with implant. The aim of the presented research is to qualitatively determine the regions with the greatest strain fields on the models. The finite element models of implant and acrylic block are developed for predefined implant inclinations in order to analyze the influence of implant inclination on deformations on the outer surface of acrylic block. The comparative contour plots of stress and strain state of analyzed models, as well as the comparative diagrams with obtained results, are presented. The conclusions about the inclination angle which leads to the higher strains in the block-implant are explained. Obtained results could be applied for the planning of future experimental studies which could utilize this and similar models to determine their load transfer characteristics, and could be included in the planning of dental implant position, and prediction of successful dental therapy.

Programmable Graphics Processing Units (GPUs) have recently become the most pervasitheve massively parallel processors. They have come a long way, from fixed function ASICs designed to accelerate graphics tasks to a programmable architecture that can also execute general-purpose computations. Because of their performance and efficiency, an increasing amount of software is relying on them to accelerate data parallel and computationally intensive sections of code. They have earned a place in many systems, from low power mobile devices to the biggest data centers in the world. However, GPUs are still plagued by the fact that they essentially have no multiprogramming support, resulting in low system performance if the GPU is shared among multiple programs. In this dissertation we set to provide the rich GPU multiprogramming support by improving the multitasking capabilities and increasing the virtual memory functionality and performance. The main issue hindering the multitasking support in GPUs is the nonpreemptive execution of GPU kernels. Here we propose two preemption mechanisms with dierent design philosophies, that can be used by a scheduler to preempt execution on GPU cores and make room for some other process. We also argue for the spatial sharing of the GPU and propose a concrete hardware scheduler implementation that dynamically partitions the GPU cores among running kernels, according to their set priorities. Opposing the assumptions made in the related work, we demonstrate that preemptive execution is feasible and the desired approach to GPU multitasking. We further show improved system fairness and responsiveness with our scheduling policy. We also pinpoint that at the core of the insufficient virtual memory support lies the exceptions handling mechanism used by modern GPUs. Currently, GPUs offload the actual exception handling work to the CPU, while the faulting instruction is stalled in the GPU core. This stall-on-fault model prevents some of the virtual m, Las Unidades de Procesamiento de Gráficos Programables (GPU, por sus siglas en inglés) se han convertido recientemente en los procesadores masivamente paralelos más difundidos. Han recorrido un largo camino desde ASICs de función fija diseñados para acelerar tareas gráficas, hasta una arquitectura programable que también puede ejecutar cálculos de propósito general. Debido a su rendimiento y eficiencia, una cantidad creciente de software se basa en ellas para acelerar las secciones de código computacionalmente intensivas que disponen de paralelismo de datos. Se han ganado un lugar en muchos sistemas, desde dispositivos móviles de baja potencia hasta los centros de datos más grandes del mundo. Sin embargo, las GPUs siguen plagadas por el hecho de que esencialmente no tienen soporte de multiprogramación, lo que resulta en un bajo rendimiento del sistema si la GPU se comparte entre múltiples programas. En esta disertación nos centramos en proporcionar soporte de multiprogramación para GPUs mediante la mejora de las capacidades de multitarea y del soporte de memoria virtual. El principal problema que dificulta el soporte multitarea en las GPUs es la ejecución no apropiativa de los núcleos de la GPU. Proponemos dos mecanismos de apropiación con diferentes filosofías de diseño, que pueden ser utilizados por un planificador para apropiarse de los núcleos de la GPU y asignarlos a otros procesos. También abogamos por la división espacial de la GPU y proponemos una implementación concreta de un planificador hardware que divide dinámicamente los núcleos de la GPU entre los kernels en ejecución, de acuerdo con sus prioridades establecidas. Oponiéndose a las suposiciones hechas por otros en trabajos relacionados, demostramos que la ejecución apropiativa es factible y el enfoque deseado para la multitarea en GPUs. Además, mostramos una mayor equidad y capacidad de respuesta del sistema con nuestra política de asignación de núcleos de la GPU. También señalamos que la causa princip, Postprint (published version)

Strain analysis in the vicinity of the dental implants were the subject of many research papers. In this study, new experimental method was employed for strain determination in the surrounding area of the axially loaded dental implant, which was embedded in the resin block. This studies can improve understanding of strain distribution, and its possible effects on the surrounding structure. Dental Implant Branemark with dimensions of 14 x 3.75 mm was immersed into rectangular block of polymethil methacrylate in vertical position. Implant was distanced 2 mm and 4 mm from the block sides, and they were named as the surface 1 and surface 2, respectively. Axial load, in the range of 0 - 500 N, was applied using Universal testing machine Tinius Olsen. Digital Image Correlation method was used for measuring deformation. Results were presented in the form of horizontal and vertical strains. Horizontal strains were mostly tensile, with maximum value of 0.3 % on the bottom of the surface 1. This values decreased in the upper area of the block side. Vertical compressive strain were 2-3 times higher on the surface 1, when compared to the surface 2, with maximum values of 0.7 % located on the bottom of the surface 1, and 0.3 % on the bottom of the surface 2. Resin block models could be used for determination of strain distribution under axially loaded implants. Greatest strain concentration were located under the implants apex, in the bottom area of the block. It was concluded that, in this region, strain values decreased linearly with increase of distance from the implants surface.