Magister Scientiae Dentium - MSc(Dent) / Resin composite is one of the most commonly used materials in restorative dentistry. However, it has undergone continuous developments like changes in the fillers and initiators. One such improvement is the new bulk-fill composites which are materials intended for bulk placement up to 4mm. However, an optimum polymerization to the full depth of the restoration i.e. complete depth of cure is of utmost importance in order to obtain proper mechanical and physical properties of resin composites. Aim: The aim of this study was to measure the surface hardness of the top and bottom surfaces of the composites and to determine the depth of cure of bulk-fill composites using two different types of light curing units. Material and methods: A total of 160 specimens were used in this study: four bulk-fill composite were used of which two were conventional viscosity bulk-fill composites namely, Tetric N Ceram (Ivoclar Vivadent) and SureFil bulk-fill composite (Densply Caulk) and two were low viscosity flowable bulk-fill composites namely, SDR flowable (Densply Caulk) and Filtek bulk-fill flowable restorative (3M ESPE). Two different curing light were used namely, LED (Elipar Freelight, 3M ESPE) at 1500mW/cm2 and a Quartz Tungsten Halogen (QTH) curing unit (Megalux CS, Megadenta, Germany) at 600 mW/cm2. To evaluate micro-hardness, Vickers hardness at top and bottom of each sample was measured immediately after light curing and after 24 hours post curing using a Zwick micro-hardness machine load 300g/15 seconds. The mean hardness values obtained from the top and the bottom surface of each material were used to compare the micro-hardness of the various materials. The mean values obtained from the bottom surface were compared to the respective values of the top surface of each material (bottom/top ratio) and used to calculate the depth of cure. Results: The micro-hardness test showed a significant difference between the four materials (ANOVA, p<0.05) immediately after curing and after 24 hours post curing. The material with the greatest micro-hardness was SureFil followed by Tetric N Ceram, Filtek bulk-fill flowable and SDR flowable respectively. The material with the greatest depth of cure was Filtek bulk-fill flowable followed by SDR flowable, Tetric N Ceram and SureFil. When the curing lights were compared the Light Emitting Diode Curing Unit (LED) obtained significantly better depth of cure compared to Quartz Tungsten Halogen Light Curing Units. The LED curing light showed greater micro-hardness values than the QTH curing light except for Tetric N Ceram where the QTH curing showed more hardness values than the LED curing light. For all materials, the surface hardness and depth of cure values increased when tested 24hrs after light curing. Conclusion: There was a difference in the micro-hardness values between the four materials where the conventional viscosity materials showed greater surface hardness values than the low viscosity materials but the depth of cure compared to the bulk-fill flowable LED curing lights showed higher hardness values than QTH curing light except for Tetric N Ceram. Depth of cure ratios were found to be lower than 0.80 for all composite types, however the flowable bulk-fill materials showed higher depth of cure than the conventional viscosity bulk-fills. In general LED curing light produced better hardness and depth of cure values than QTH curing light. The low micro-hardness values for the bulk-fill flowable composites and the inadequate polymerization raises a concern regarding placing these materials in bulk. In such cases, the flowable bulk-fills should be protected with a conventional composite "covering or capping" especially in posterior teeth and in deeper cavities. Furthermore, bulk-fill composites should be used in layering incremental technique to ensure sufficient depth of cure.

Indiana University-Purdue University Indianapolis (IUPUI) / Objectives: To investigate the effect of bulk-fill resin based composite materials on cuspal deflection in large slot mesio-occlusal-distal cavities (MOD) in premolar teeth. Methodology: Thirty-two sound maxillary premolar teeth with large slot MOD cavities were distributed to four groups (n=8). Three groups were restored with bulk-fill resin composite materials (Tetric EvoCeram, x-tra fil, and Sonic Fill, respectively) in a single increment. The conventional composite group, Filtek Z100, was used to restore the cavities in 2mm increments. Cusp deflection was recorded post irradiation using a Nikon measurescope UM-2 (Nikon, Tokyo, Japan), by measuring the changes in the bucco-palatal width of the premolar teeth at 5 minutes, 24 hours, and 48 hours after completion of the restoration. The cuspal deflection was obtained by recording the difference between the baseline measurements and the other measurements for each tooth. Results: Cuspal deflection was significantly higher in Conventional Composite than in Tetric EvoCeram Bulk Fill (p=0.0031), x-tra Fil Bulk (p=0.0029), and SonicFill Bulk (p=0.0002). There was no significant difference in cuspal deflection for Tetric EvoCeram Bulk, X-tra Fil Bulk, and SonicFill Bulk Composites. Conclusions: All the investigated bulk-fill resin composites exhibited cuspal deflection lower than conventional resin composite. One of the aims of research and studies on the resin composite materials is improving their clinical longevity, and simplifying their use. For that purpose bulk-fill materials are considered promising materials and further clinical studies should be conducted.

Magister Scientiae Dentium - MSc(Dent) / Resin filled dental composite materials has been introduced into dental practice since mid-1960s as an aesthetic restorative material for anterior teeth (Bowen, 1962 cited in Peutzfeldt, 1997). Since then, they have undergone several developments in order to enhance the longevity and performance of these materials. Resin filled dental composites consist of three main components namely, organic resin matrix which consists of a monomer, an initiator system and a stabilizer system, inorganic filler such as quartz, silica, etc. and coupling agent such as organo-silane coupling agent that chemically bonds the inorganic fillers to the organic resin matrix (Phillips, 1973). The properties and the performance of the resin filled dental composites are basically dependent upon the components of the materials. Some properties are related to the resin matrix, whereas others are related to the inorganic fillers and coupling agent. Furthermore, properties such as polymerization shrinkage and water sorption are dependent on both the inorganic fillers and the organic resin matrix (Asmussen, 1975; Hashinger and Fairhust, 1984; Munksgaard et al., 1987). Aim and objectives: The aim and the objectives of this study was to compare the water sorption and solubility of four bulk-fill dental resin composite materials namely, two conventional viscosity bulk-fill (Surefil bulk fill composite and Tetric N Ceram Bulk Fill) and two low viscosity bulk-fill flowable dental composite materials (Filtek Bulk Fill flowable restorative and Surefil SDR Flow). Materials and methods: Four types of bulk-fill composite restorative materials (2 bulk-fill conventional viscosity (Surefil bulk fill composite and Tetric N Ceram Bulk Fill) and 2 bulk-fill flowable low viscosity (Filtek Bulk Fill flowable restorative and Surefil SDR Flow) were used to analyse the water sorption and solubility for each resin composite type. Thirty specimens for each type of material were prepared, giving the total number of specimens to be 120 (n=120). To standardize this study Vita shade A2 was used for all the material types. All specimens were prepared in a Teflon mould with internal diameter of 15±1mm and thickness of 1±0.1mm in accordance with ISO 4049. The light curing unit used for all specimens was Elipar™ S10, (3M ESPE, Germany) at an output of 1200 mW/cm2 and used according to the manufacturer’s instructions. Prior to curing, the intensity of the light was checked using Cure Rite visible curing light meter (Caulk, USA) to ensure light output consistency between specimens and was found to be 1200 mW/cm2 . All the specimens were first removed from the Teflon mould as prepared and described previously and placed in an oven at 37 ºC until their weights were constant and these weights were recorded as m1 by using an analytic balance (OHAUS, TS400D, USA). Ten specimens of each type of resin filled composite were then immersed individually in glass containers filled with 10 ml distilled water and placed in the oven at 37±1 ºC for 24 hours, 7 days, 14 days respectively. The specimens were removed; surface water was blotted with tissue paper until free from visible moisture and weighed using the analytic balance (OHAUS, TS400D, USA). The resultant weights were recorded as m2. The specimens were then placed in a desiccator containing silica gel (Associated Chemical Enterprises, ZA) and freshly dried for two hours in an oven at 58 ºC and then weighted to obtain m3. According to Oysaed and Ruyter formula (Oysaed and Ruyter, 1986), the water sorption and solubility was calculated using the following equation: i.Water sorption (SP) = m2 -m3 / v., ii.Water solubility (SI) = m1 -m3 / v - where v is the volume of the specimen. For monomer leakage high performance liquid chromatography (HPLC) was used to identify monomers. The water that contained stored specimens was transferred to a refrigerator immediately after the specimens were removed until HPLC analysis was carried out to determine the amount of monomers that leached out of the cured composite specimens. Results: A significant difference between the materials (p<0.05, ANOVA Analysis of Variance) showed that Surefil SDR Flow composite had the lowest overall mean water sorption values (10.191) over the three time intervals (24 hrs, 7 days and 14 days) which was significantly smaller than the other means, followed by Filtek Bulk Fill flowable restorative composite (11.135) and Tetric N Ceram Bulk Fill composite (16.419). The highest water sorption mean value was recorded for Surefil bulk fill composite (21.515). The overall means of water solubility for the two bulk-fill flowables i.e. Filtek Bulk Fill flowable restorative and Surefil SDR Flow were smaller than bulk-fill conventional viscosity Surefil bulk fill and Tetric N Ceram Bulk Fill. However, all the test materials displayed no statistically significant increase in water solubility over the time period (p > 0.05 two way ANOVA test). The amounts of eluted monomers from bulk-fill conventional viscosity materials (Surefil bulk fill and Tetric N Ceram Bulk Fill) were higher than bulk-fill flowable materials (Surefil SDR Flow and Filtek Bulk Fill flowable restorative). Of all the monomers tested UDMA eluted more than Bis-GMA and TEGDMA. Overall UDMA monomer eluted the most, followed by Bis-GMA and the TEGDMA. Conclusion: Within the limitation of this study, the results of this study did not support the null hypothesis that there is no significant difference in the water sorption. The bulk-fill low viscosity flowables showed lower water sorption than the conventional viscosity bulk-fills. Surefil SDR Flow was significantly lower than the other materials followed by Filtek Bulk Fill flowable restorative and Tetric N-Ceram Bulk Fill and the highest overall means were recorded for Surefil bulk fill. For water solubility the overall means for the flowables of Filtek and SDR were smaller than Surefil and Tetric N-Ceram. For monomer elution three monomers were detected of which UDMA monomer eluted the most, followed by Bis-GMA and the TEGDMA. With regards to the elution of monomers, it was found that 3 monomers named UDMA eluted more than Bis-GMA and TEGDMA.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais / O tratamento endodôntico associado à restauração direta com resina composta tem sido utilizado para restaurar molares severamente destruídos em pacientes jovens. O objetivo deste estudo foi avaliar o efeito de diferentes níveis de perda de estrutura dentária antes e após a realização de tratamento endodôntico e restauração com resina composta bulk fill na distribuição de tensões e magnitude da força de mordida. Foram selecionados três pacientes jovens (9, 10 and 12 anos de idade) com primeiros molares com cárie extensa e envolvimento pulpar com diferentes níveis de perdas de estrutura dentária: PI, manutenção das duas cristas marginais e de todas as cúspides; PII, manutenção de pelo menos uma crista marginal e perda mínima de uma cúspide; e PIII, perda de ambas as cristas marginais, mantendo apenas as cúspides vestibulares. Os molares foram tratados endodonticamente utilizando técnica de instrumentação rotatória e obturados com guta-percha e cimento AHPlus (Dentsply) e em seguida foram restaurados com Filtek Bulk Fill Posterior (3M ESPE). A força de mordida em Newtons (N) foi mensurada antes e após a intervenção endodôntica e restauradora na posição habitual de oclusal usando aparelho de força de mordida por meio de uma célula de carga (Kratos). Tomografias computadorizadas cone beam foram realizadas antes e após o procedimento endodôntico/restaurador, e arquivos DICOM (.dcm) foram exportados para o software Mimics, 3-Matic (Materialize) e Patran (MSC Software) para criação dos modelos específicos dos pacientes nos dois momentos experimentais. A aplicação de carga foi simulada por contato oclusal dos dentes antagonistas nas cargas mensuradas clinicamente em cada momento. Nos modelos que representam as condições iniciais foram aplicados tanto os valores de força de mordida (N) mensurados no momento inicial quanto após o procedimento reabilitador: PI. 30,1/136,6; PII. 34,3/133,4 e PIII. 47,9/124,1 e para os modelos que representam a condição final foram utilizados os valores obtidos após a intervenção endodôntica e restauradora: PI. 136,6; PII. 133,4 e PIII. 124,1. As restaurações foram avaliadas após 2 anos. Após intervenção endodôntica e restauradora a força de mordida aumentou em 260% (de 36,7±11,6 para 12 131,9±17,8). Antes da intervenção endodôntica e restauradora, as tensões se concentraram na estrutura coronal e, após a reabilitação foram transferidas de forma homogênea para a dentina radicular, independente do nível de perda de estrutura dentária. Quando a carga final foi aplicada nos modelos de condições iniciais, evidenciou-se elevada concentração de tensão em áreas enfraquecidas e na região de furca. As restaurações apresentaram desempenho adequado após 2 anos. A presença de cárie extensa com envolvimento pulpar afetou negativamente a carga de mordida e aumentou a concentração de tensão na estrutura frágil o que pode favorecer à ocorrência de fratura dental. O tratamento endodôntico associado à restauração direta em resina composta bulk fill demonstrou ser um método eficiente para restabelecer o desempenho mastigatório e a eficiência biomecânica dos molares jovens com comprometimento severo da estrutura coronária. / Endodontic treatment (ETT) followed by direct composite resin restoration has been used for rehabilitating the severely damage molar teeth in young patients. The aim of this study was to evaluate the effect of the molar teeth with different levels of the dental structure loss before and after the ETT and direct restoration with bulk fill resin composite on the stress distribution and the bite force magnitude. Three young patients (with 9, 10 and 12 years old), with the first mandibular molar teeth with deep occlusal caries with pulp involvement were selected attending with different levels of the dental structure loss: PI, both marginal ridge and all cusps; PII, maintenance of one marginal ridge and loss of one cusp; and PIII, loss of both marginal ridge, maintaining only buccal cusps. ETT was restored using Filtek Bulk Fill Posterior (3M ESPE). The bite forces in Newtons were measured initially and postoperatively for all teeth in habitual bite force using a miniload cell. Cone-beam tomography imaging was performed, and the Digital Imaging and Communication in Medice (.dcm) files were exported to Mimics, 3-Matic (Materialise) and Patran (MSC Software) software to create a patient-specific FEA models. Bite load was carry out using contact load applied by antagonist teeth in two moments: without ETT and restoration: PI. 30.1/136.6; PII. 34.3/133.4 and PIII. 47.9/124.1; and after restorative procedure: PI. 136.6; PII. 133.4 and PIII. 124.1 N. Performing ETT and bulk fill resin composite restoration the bite load increased 260% (36.7±11.6) to 131.9±17.8). The restorations were evaluated after 2 years. Before rehabilitation the stresses concentrated on weakened coronal dental structure and after rehabilitation they were homogeneously transferred to root dentin, irrespective of the level of the tooth structure loss. When the postoperatively bite load was applied on nontreated tooth models, high stress concentration on weakened areas was verified. The restorations performed perfectly after 2 years. The extensive caries with pulp involvement affected negatively the bite load and increased the stress concentration on weakened areas and at furcation favoring the tooth fracture. The ETT and bulk fill resin composite restoration showed to be an efficient method for rehabilitate the biomechanical performance of molar teeth of young patients severely compromised structurally. / Dissertação (Mestrado)