Comparative analysis of biofilm formation on materials used for the fabrication of implant-supported prostheses

Abstract The purpose of this study was to compare biofilm formation on materials used for the fabrication of implant-supported dental prostheses. Twenty discs (D=15 mm, H=3 mm) were fabricated from one of the following restorative materials: yttria tetragonal zirconia polycrystal (Y-TZP); commercially pure titanium (CP-Ti); or heat-cured polymethyl methacrylate (PMMA). Specimens were polished following standard protocols. A non-contact profilometer (NPFLEX, Bruker, UK) was used to assess the surface roughness of each disk; results were reported as Ra (µm). Five strains of Gram-negative bacteria frequently associated with peri-implantitis, Aggregatibacter actinomycetemcomitans, Candida. albicans, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia, were cultured on hand-polished discs fabricated from heat-cured PMMA, Y-TZP, or CP-Ti to compare biofilm formation on each type of material. The results were reported as colony-forming units per milliliter (CFU/mL). One-way ANOVA and post hoc tests were used to compare surface roughness and bacterial colonization on the respective materials. Statistical significance was set at a = 0.05. Discs fabricated from Y-TZP had a significantly higher Ra value (350 ± 30 µm) than either PMMA, or CP-Ti discs. Discs fabricated from either Y-TZP and CP-Ti may exhibit less colonization by bacteria associated with peri-mucositis and peri-implantitis. Y-TZP and CP-Ti are suggested materials for fabrication of implant-supported prostheses, considering biofilm formation.

Resumo O objetivo deste estudo foi comparar a formação de biofilme em materiais utilizados na confecção de próteses dentárias implantossuportadas. Vinte discos (D = 15 mm, H = 3 mm) foram confeccionados com um dos seguintes materiais restauradores: zircônia tetragonal policristalina estabilizada por ítrio (Y-TZP); titânio comercialmente puro (CP-Ti); ou polimetilmetacrilato (PMMA). As amostras foram polidas seguindo protocolos padrão. Um perfilômetro sem contato (NPFLEX, Bruker, UK) foi usado para avaliar a rugosidade da superfície de cada disco; os resultados foram relatados como Ra (µm). Cinco cepas de bactérias Gram-negativas freqüentemente associadas a peri-implantite, Aggregatibacter actinomycetemcomitans, Candida. albicans, Porphyromonas gingivalis, Prevotella intermedia e Tannerella forsythia, foram cultivadas em discos polidos à mão feitos de PMMA, Y-TZP ou CP-Ti para comparar a formação de biofilme em cada tipo de material. Os resultados foram relatados como unidades formadoras de colônias por mililitro (UFC/mL). Análise de variância a um fator e testes post hoc foram usados ​​para comparar a rugosidade da superfície e a colonização bacteriana nos respectivos materiais. A significância estatística foi estabelecida em a=0,05. Os discos feitos de Y-TZP tiveram um valor Ra significativamente mais alto (350 ± 30 µm) do que os discos de PMMA ou CP-Ti. Os discos fabricados com Y-TZP e CP-Ti podem apresentar menor colonização por bactérias associadas à perimucosite e peri-implantite. Considerando O Y-TZP e CP-Ti são materiais indicados para a confecção de próteses implantossuportadas, considerando a formação de biofilme

Evaluation and comparison of different polymerization techniques, curing cycles, and thicknesses of two denture base materials

Purpose: The study aimed to compare the effect of different materials, thicknesses, and polymerization methods and cycles, on the surface porosity of acrylic denture base resins. Materials and Methods: Conventional heat-polymerized polymethyl methacrylate (PMMA) and specially designed acrylic resin (Acron MC) were used to make 84 rectangular samples. They were divided into three groups to evaluate and compare the polymerization techniques, curing cycles, and thicknesses of the two denture base materials (28 samples each). Group A contained PMMA samples polymerized using water bath method (control group); Group B contained Acron MC samples polymerized by microwave method, and Group C contained PMMA samples polymerized by microwave method. Each group was further divided based on sample thickness and polymerization cycles. Each sample was scanned for surface porosity and area of each pore was measured using optical microscope. Data was analyzed using ANOVA, Bonferroni, and student t-tests. Unpaired student t-test was performed to compare the means of surface porosity with polymerization cycles and thicknesses among the groups. The power of study was kept at 80%. Results: Group C showed highest mean % of porosity depending on method of polymerization, different polymerization cycles (short and long) and polymerization cycles within the group. Group B showed the highest mean % of porosity depending on thickness and thickness within the groups. Conclusions: Microwavable acrylic resin polymerized by microwave energy exhibited statistically insignificant increase in porosity when compared to conventional heat cured acrylic resin by water bath method. Conventional acrylic resin polymerized by microwave energy exhibited high statistically significant porosity irrespective of sample thickness. There was statistically insignificant increase in porosity depending on sample thickness irrespective of material and method of polymerization.

Effects of incorporation of 2.5 and 5 wt% TiO₂ nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA)

PURPOSE: The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO2) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. MATERIALS AND METHODS: TiO2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO2:PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. RESULTS: SEM images of n-TiO2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO2 represented the anatase crystal phase of TiO2. Moderate to very strong significant positive correlations were observed between the concentration of n-TiO2 and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO2 were significantly higher than those of control (P≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO2 (but not those of 2.5% n-TiO2) was higher than control (P=.002). CONCLUSION: Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

Complicaciones en craneoplastias: hueso autólogo criopreservado vs. polimetilmetacrilato. Análisis retrospectivo de 63 pacientes / Complications in cranioplasties: autologous bone cryopreserved vs. Polymethylmethacrylate. Retrospective analysis of 63 patients

Introducción: se define como craneoplastia a la reparación quirúrgica de los defectos óseos craneanos. En nuestro medio el material utilizado mayormente es el hueso autólogo criopreservado (HACp) y, en caso de no contar con dicho tejido, el Polimetilmetacrilato (PMMA) es de elección. Objetivo: Se plantea un estudio retrospectivo observacional a fin de analizar y comparar complicaciones en pacientes sometidos a craneoplastias con HACp en comparación a un grupo de pacientes a los que se les realizó craneoplastia con PMMA. Materiales y métodos: Se incluyeron pacientes que fueron sometidos a craneopatías durante un periodo de 5 años (2008-2013). El seguimiento delos pacientes fue de al menos 12 meses. Se analizaron variables relacionadas a complicaciones tempranas y tardías. Resultados: 63 pacientes recibieron craneoplastia con HACp (31 pacientes, 52%) o polimetilmetacrilato (31 pacientes, 49%). La tasa de complicación global fue del 36,6%. Doce pacientes (19,04%) requirieron tratamiento quirúrgico. Las complicaciones más frecuentes fueron las colecciones subcutáneas no infectadas (19%), seguidas por las infecciones de heridas (17%). No existen diferencias estadísticamente significativas en cuanto a para complicaciones, tanto globales como en las distintas categorías (p>0,05), para ambas técnicas quirúrgicas. Conclusión: Las craneoplastias tanto con HACp como aquellas con PMMA presentan una alta tasa de complicaciones. En nuestra serie no se hallaron diferencias entre ambos grupos estudiados.

Introduction: cranioplasty is defined as the surgical procedure to cover a skull bone defect. In our institution, we mainly use cryopreserved autologous bone graft (HACp), and if it is not available, polymethylmethacrylate is chosen (PMMA). Objective: We performed an observational retrospective study to assess complications in both groups of patients. Materials and Methods: Patients who underwent cranioplasty between 2008 and 2013 were included. Minimum follow up was 12 months. Variables related with early and late complications were analyzed. Results: 63 patients received cranioplasty consisting of autologous bone graft (32 patients, 52%) or PMMA (31 patients, 48%). The global complications rate was 36.6%. 12 patients (19.04%) required surgical treatment for these complications. The most common complications were sterile persistent subcutaneous fluid collection (19%) and wound infection (17%). No differences in complications rates were found between both groups (p>0.05). Conclusions: Cranioplasty following craniectomy is associated with a high complication rate. In our series, both groups showed no differences in complications rates.

Bone cement injection for the treatment of thoracolumbar osteoporotic fractures：Common problems in the mature technology / 中国组织工程研究

10.3969/j.issn.2095-4344.2013.26.022