545 research outputs found

    Measurements for restorative dentistry: shrinkage and conversion degree of bulk-fill composites

    Get PDF
    The paper deals with a measuring approach based on Raman Spectroscopy and micro-CT imaging for correlating the degree of conversion of bulk-fill composites to the contraction shrinkage and consequently to the internal gap formation in high c-factor dental cavities. The developed study was performed on extracted molars in which a first-class cavity was prepared. A micro-CT scan was performed before and after composite lightcuring to tridimensionally measure the interfacial gap between the composite material and the cavity walls. After the complete polymerization of the composite, each sample was sectioned vertically to expose the lateral surface of the restorative material. Raman Spectroscopy measurements were performed along the cross-section of the cavity filled with the restorative material, every 0.5 mm from the occlusal surface. The obtained results showed a minimal gap opening after light-curing and a degree of conversion which was not affected by the bulk-fill composite thickness. Thanks to the 3D rendering, it should be observed that gaps were mostly concentrated at the cavity floor and despite the reduction in the degree of conversion detected in the deeper portions of the restoration, a three-dimensional opening of an interfacial gap was not observed. Therefore, it is possible to assume the presence of a correlation between the degree of conversion and the volumetric interfacial gap could. Further studies are actually in progress to compare these preliminary results with those obtained on other dental composite materials

    Comparison of postoperation bone defects healing of alveolar processes of maxilla and mandible with the use of Bio-Gen and Bio-Oss

    Get PDF
    Bone defects of mandible and maxilla alveolar processes have often iatrogenic origins, because they appear as a consequence of performed operations. Bone atrophy may be stopped by filling bone defects with augmentative biomaterial directly after an oral surgery procedure. To achieve this aim augmentative biomaterials are used. Many years of experimental studies confirmed xenogenic biomaterials as the most ef fective. The aim of this study was clinical assessment of bone lesions healing with the use of Bio-Gen and Bio-Oss materials. A comparison of radiological imaging of healed defects was performed, as well as histological analysis of biopsies obtained from the defect sites. The structure analysis of both materials was performed with the use of electron microscopy. Chemical ingredients of analyzed biomaterials were assessed with the use of X-ray microanalysis. Postoperation follow-up in all groups was done. Histological and radiological analysis of regeneration course were performed. Radiological analysis was performed with the use of Digora 2,1 system, which allows to asses optical density of images. Histopathologic regenerates were analyzed morfometrically. The results of this study confirmed effectiveness of Bio-Gen and Bio-Oss materials in regeneration of bone defects. Six month long follow-up period confirmed a significant increase of the optical density of regenerates augmented with Bio-Gen and Bio-Oss comparing to lesions healed without biomaterial augmentation

    Is alveolar ridge preservation an overtreatment?

    Get PDF
    The morphology and dimensions of the postextraction alveolar ridge are important for the surgical and restorative phases of implant treatment. Adequate new bone formation and preservation of alveolar ridge dimensions following extraction will facilitate installation of the implant in a restorative position, while preservation of soft tissue contour and volume is essential for an aesthetic and implant-supported restoration with healthy peri-implant tissues. Alveolar ridge preservation (ARP) refers to any procedure that aims to: (i) limit dimensional changes in the alveolar ridge after extraction facilitating implant placement without additional extensive bone and soft tissue augmentation procedures (ii) promote new bone formation in the healing alveolus, and (iii) promote soft tissue healing at the entrance of the alveolus and preserve the alveolar ridge contour. Although ARP is a clinically validated and safe approach, in certain clinical scenarios, the additional clinical benefit of ARP over unassisted socket healing has been debated and it appears that for some clinicians may represent an overtreatment. The aim of this critical review was to discuss the evidence pertaining to the four key objectives of ARP and to determine where ARP can lead to favorable outcomes when compared to unassisted socket healing

    Strain Mapping in Teeth with Variable Remaining Tooth Structure

    Get PDF
    Problem: The effect of remaining tooth structure on strain in compromised teeth is not fully understood. Different remaining tooth quantities may affect stress and strain concentration within the remaining structure and potentially the longevity of the related restoration. Objectives: The aim of this project was to map and evaluate tooth strain levels at different stages and areas of structural tooth loss created by dental preparation (simulating caries created lesions) or soft drink demineralisation (simulating external acid erosion lesions), before and after restoration, and to evaluate and compare different strain measurement techniques: strain gauges (SG), the surface displacement field measured using digital image correlation (DIC), electronic speckle pattern interferometry (ESPI), and finite element analysis (FEA). In addition, testing teeth affected by erosion required testing and verifying different acid demineralisation protocols. Material and methods: Part I: Enamel samples (sound, polished) were subjected to extended 25 hours (hr) soft drink immersion protocols (accelerated, prolonged) with different salivary protection conditions (no saliva, artificial saliva, and natural saliva) to compare enamel surface loss. Moreover, enamel surface loss of extended erosion periods simulating different levels of clinical erosion lesions was calculated by different imaging methodologies. Microscopic analysis was performed to compare subsurface changes of early and extended erosion protocols. Part II: Strain under static loading was compared in teeth with different stages of unrestored occlusal and buccal accelerated soft drink demineralisation lesions and after restoration using different techniques (strain gauges, electronic speckle pattern interferometry, and finite element analysis). Part III: Strain under static loading was compared in prepared teeth with different remaining tooth dimensions and different restorations using strain gauges and digital image correlation techniques. Results: Part I: No statistical significance was detected in enamel thickness loss between sound and polished enamel samples in the accelerated erosion groups under all salivary conditions or between early and extended erosion groups tested. Part II: All testing methodologies measured an increased strain reading after 1 day in occlusal erosion group followed by gradual decrease, while, continuous increase in strain was observed with buccal erosion progression. For both groups, all restorative materials used were able to restore strain close to pre-treatment level. However, strain distribution pattern was more favourable in ceramic and gold occlusal onlays than composite onlays. Part III: for both strain gauges and digital image correlation, remaining tooth height ≥ 3 mm and width of 1 to 1.5 mm of the remaining tooth structure had a positive effect on strain. Tooth compositions of enamel and dentine resisted strain better than dentine counterparts at all dimensions. Both core restorations (with and without cuspal coverage) were found to support the remaining tooth structure and reduce strain. However, only cuspal coverage recorded significantly lower strain than their unrestored counterparts. Conclusion: Restorations bonded to advanced erosion induced lesions restored strain levels to pre-treatment condition and produced a more favourable strain distribution pattern highlighting the role of adhesion in reducing strain. Remaining tooth structure suffers less strain under loading when enamel is part of the structure and when the minimum dimension of 3 mm in height and 1.5 mm in width is preserved. Bonding of core restoration or cusp coverage aids in reducing strain under loading. All strain measuring methodologies were comparable, where similar strain behaviour was recorded. Remineralisation of enamel and dentine is effective in the management of initial erosion

    Monolithic zirconium dioxide as a full contour restorative material: With special emphasis on the optical and mechanical properties

    Get PDF
    Full contour monolithic zirconia restorations have shown an increased popularity in the dental field over the recent years, owing to its mechanical and acceptable optical properties. However, many features of the restoration are yet to be researched and supported by clinical studies to confirm its place among the other indirect restorative materials This series of in vitro studies aimed at evaluating and comparing the optical and mechanical properties, light cure irradiance, and cement polymerization of multiple monolithic zirconia material at variable thicknesses, environments, treatments, and stabilization. Five different monolithic zirconia materials, four of which were partially stabilized and one fully stabilized were investigated. The optical properties in terms of surface gloss, translucency parameter, and contrast ratio were determined via a reflection spectrophotometer at variable thicknesses, coloring, sintering method, and after immersion in an acidic environment. Light cure irradiance and radiant exposure were quantified through the specimens at variable thicknesses and the degree of conversion of two dual-cure cements was determined via Fourier Transform Infrared spectroscopy. Bi-axial flexural strength was evaluated to compare between the partially and fully stabilized zirconia prepared using different coloring and sintering methods. Surface characterization was performed using a scanning electron microscope and a spinning disk confocal microscope. The surface gloss and translucency of the zirconia investigated were brand and thickness dependent with the translucency values decreasing as the thickness increased. Staining decreased the translucency of the zirconia and enhanced surface gloss as well as the flexural strength of the fully stabilized zirconia but had no effect on partially stabilized zirconia. Immersion in a corrosive acid increased surface gloss and decreased the translucency of some zirconia brands. Zirconia thickness was inversely related to the amount of light irradiance, radiant exposure, and degree of monomer conversion. Type of sintering furnace had no effect on the optical and mechanical properties of zirconia. Monolithic zirconia maybe classified as a semi-translucent material that is well influenced by the thickness, limiting its use in the esthetic zones. Conventional acid-base reaction, autopolymerizing and dual-cure cements are recommended for its cementation. Its desirable mechanical properties give it a high potential as a restoration for posterior teeth. However, close monitoring with controlled clinical studies must be determined before any definite clinical recommendations can be drawn.Monoliittinen zirkonium dioksidi anatomiseen muotoon tehtyjen restauraatioiden materiaalina: kokeellisia tutkimuksia materiaalin optisista ja mekaanisista ominaisuuksista. Zirkonian suosio on kasvanut viime vuosina lopulliseen muotoonsa valmistetuissa hammasproteettisissa rakenteissa materiaalin optisten ja mekaanisten ominaisuuksien parannuttua. Zirkoniarakenteet vaativat kuitenkin lisää materiaalitutkimuksia sekä kliinisistä kokemuksista saatavaa näyttöä ennen kuin materiaali vahvistaa paikkansa muiden epäsuorissa restauraatioissa käytettyjen materiaalien joukossa. Näiden tutkimusten tavoitteena on ollut verrata erilaisten monoliittisten zirkonia materiaalien optisia ja mekaanisia ominaisuuksia ja valokovetuksen toimivuutta sekä selvittää materiaalin paksuuden, pintakäsittelyn ja stabilointiasteen vaikutusta niihin. Tutkimukseen valittiin neljä osittain stabiloitua ja yksi kokonaan stabiloitu zirkonia materiaali. Optiset ominaisuudet arvioitiin materiaalin pinnan kiillon, läpikuultavuuden ja kontrastisuhteen perusteella. Analyysit tehtiin heijastus spektrofotometrilla ottaen huomioon tutkittavan materiaalin paksuus, värjäys, sintrausmenetelmä sekä happoaltistuksen vaikutus. Kahden zirkoniarakenteiden kiinnittämiseen käytettävän kaksoiskovetteisen kiinnityssementtien toimivuus testattiin eripaksuisilla testikappaleilla määrittämällä kovetusvalon irradianssi ja säteilyn läpäisevyys sekä sementin kovettumisaste. Mittaukset suoritettiin FTIR spektroskopiaa käyttämällä. Biaksiaalista taivutusluu-juusmittausta käytettiin selvittämään värjäyksen ja erilaisten sintrausmenetelmien vaikutus osittain tai kokonaan stabiloitujen zirkonia materiaalien mekaanisiin ominaisuuksiin. Materiaalien pintarakenteet arvioitiin pyyhkäisyelektroni ja konfokaali mikroskopiaa käyttämällä. Tutkittavien materiaalien pintakiilto ja läpikuultavuus riippuivat materiaalityypistä ja paksuudesta, joka oli kääntäen verrannollinen läpikuultavuuteen. Materiaalin värjäys vähensi zirkonian läpikuultavuutta, mutta paransi kokonaan stabiloidun zirkonian pintakiiltoa ja mekaanista lujuutta. Vastaavaa vaikutusta ei todettu osittain stabiloidulla zirkonialla. Altistaminen syövyttävälle hapolle lisäsi joidenkin tutkittavien materiaalien pinnan kiiltoa, mutta vähensi niiden läpikuultavuutta. Zirkoniamateriaalin paksuus oli käänteisesti verrannollinen valon irradinassiin, säteilyn läpäisevyyteen ja sementin kovettumisasteeseen. Sintrausmenetelmällä ei todettu olevan vaikutusta materiaalien optisiin tai mekaanisiin ominaisuuksiin. Monoliittiset zirkoniamateriaalit voidaan luokitella osittain läpikuultaviksi materiaaleiksi, mikä rajoittaa niiden käyttöä esteettisesti vaativilla alueilla. Perinteisiä ja kaksoiskovetteisia sementtejä voidaan suositella zirkoniarakenteiden kiinnittämiseen. Hyvien mekaanisten ominaisuuksiensa ansiosta lopulliseen anatomiseen muotoon tehtyjä zirkonia rakenteita voidaan käyttää takahammasalueiden restauroinneissa. Kontrolloituja kliinisiä tutkimuksia kuitenkin tarvitaan ennen kuin lopullisia johtopäätöksiä zirkonian käyttäytymisestä voidaan esittää.Siirretty Doriast

    TEETH DEHYDRATION/ REHYDRATION AND THE EFFECT OF TIME ON TOOTH SHADE SELECTION

    Get PDF
    ABSTRACT Sama A. Suliman: Teeth Dehydration/Rehydration and the effect of time on tooth shade selection (Under the direction of Harald H. Heymann) Objective: The purpose of this clinical study is to estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. Materials and Methods: Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. Measurements were made at baseline, and then after isolation using a lip retractor at 1, 2, 3, 5, 7, 10 and 15 minute intervals to determine tooth dehydration time. After mouth rinsing for 5 minutes measurements were again made at the same interval time to determine tooth rehydration time. The values obtained were used to calculate CIEDE2000 values for color change between the baseline recordings and all intervals. The data were compared to the 50:50% perceptibility and acceptability thresholds and analyzed for the color change over time using ANOVA and Tukey test was used for multiple comparisons. Result: There was a perceivable change in tooth color within the first minute of tooth dehydration (P>0.0001). After the first minute, 87% of the teeth were beyond the ∆E00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ∆E00 acceptability threshold (1.8). After 15 minutes of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold. The original shade was not restored for the tested teeth even after 15 minutes of rehydration time. Conclusions: Shade selection procedures should be carried out within the first minute and before the teeth are exposed to dehydration by means of isolation. Teeth do not rehydrate within 15 minutes after rehydration.Master of Scienc

    Dentistry on the bridge to Nanoscience and Nanotechnology

    Get PDF
    Dentistry is the area of medical sciences that is most resistant to the introduction of the novel methods arisen from the development of nanoscience and nanotechnology in the last 20 years. Without moving on to science fiction like views pointing to times far ahead in the future, we show that the available nanoscale devices and processes of current science and technology, partly inherited from the areas of microscopy and microelectronics, have already proven to be useful for research and development in different fields of dental research. To this goal, we review some results obtained in the last few years at our Institute in the area of dental materials and their characterization, which showed successful application of our background in microscopy and nanoengineering

    Finite Element Analysis in Dental Medicine

    Get PDF

    Shear Bond Strength Comparison of Bioceramics to Root Dentin.

    Get PDF
    Introduction: The purpose of this study is to compare the push-out bond strength of four bioceramic materials to root dentin that are used during regenerative endodontics. The bioceramics being tested are: 1. Biodentine®(Septodont); 2. EndoSequence BC Putty Fast Set® (Brasseler); 3. NeoPutty® (Avalon Biomed); and 4. ProRoot MTA White® (Dentsply). A high bond strength of a bioceramic material to root dentin will provide excellent seal. An improved seal may correlate with less potential for contamination of the pulp space that is undergoing regenerative activity. This in turn will lead to long-term clinical success. The null hypothesis is that there is no difference in the mean bond strength of the four Bioceramic materials to dentin. The alternative hypothesis is that there is a significant difference among the mean push-out bond strength among the four materials investigated. Methods: One hundred 2.0 mm thick dentin slices from human teeth were created using a 0.3 mm thick diamond cut-off wheel. For standardization, the canal space of each slice was prepared to a diameter of 1.5 mm. The cavity preparations were conditioned with 1.5% NaOCl, 17% EDTA, and saline. The slices were randomly separated into four groups: Biodentine® (n = 20); EndoSequence BC Putty Fast Set® (n=20); NeoMTA Plus® (n=20); and ProRoot MTA White® (n=20). Portland cement was used as the positive control (n=10). Cavit®, with no significant bond strength to dentin was used as the negative control (n=10). The push-out bond strength values were measured using a universal testing machine. A load was delivered to the cement surface by applying downward pressure with a 1.2 mm diameter cylindrical stainless-steel plunger at a crosshead speed of 0.5 mm/min. The nature of bond failure was inspected under a surgical microscope at 6.4x magnification. Failure pattern were categorize as adhesive failure, cohesive failure, or mixed failure. R software was used for all statistical analyses. The data were analyzed using a robust linear mixed- effects model to compare the mean fracture resistance of the samples. Statistical significance was defined as a p \u3c 0.05. Results: The mean push-out bond strength ± standard deviation in MPa values of EndoSequence BC Putty Fast Set®; ProRoot MTA®; Biodentine®; NeoPutty®; Cavit®; and Portland Cement were 16.03 ± 4.05, 10.69 ± 3.00, 8.63 ± 3.73, 7.29 ± 2.27, 1.07 ± 0.53, and 10.71 ± 3.47 respectively. The push-out bond strength of the EndoSequence BC Putty Fast Set® was significantly greater than the other experimental and control groups (p \u3c 0.05). Inspection of the samples revealed the bond failure of the bioceramics to be predominantly cohesive failure. Conclusion: Bond strength of a material plays an important role in clinical practice. The proper adhesion of bioceramics with dentin is critical. It is crucial to understand how bioceramics adapt and bond to dentin as the majority of endodontic failures are related to bacteria and their toxins entering the periapical tissues due to microleakage. The findings of the present study imply that the push-out bond strength of EndoSequence BC Putty Fast Set® was statistically greater when compared to Biodentine®, NeoPutty®, ProRoot MTA®, Cavit®, and Portland Cement. The majority of bioceramic showed cohesive bond failure, while the positive and negative control groups exhibited majority adhesive bond failure
    corecore