Johanna Tanner

Flexural properties of fiber reinforced root canal posts

OBJECTIVES Fiber-reinforced composite (FRC) root canal posts have been introduced to be used instead of metal alloys and ceramics. The aim of this study was to investigate the flexural properties of different types of FRC posts and compare those values with a novel FRC material for dental applications. METHODS Seventeen different FRC posts of various brands (Snowpost, Carbopost, Parapost, C-post, Glassix, Carbonite) and diameters, (1.0-2.1 mm) and a continuous unidirectional E-glass FRC polymerized by light activation to a cylindrical form (everStick, diameter 1.5 mm) as a control material were tested. The posts (n=5) were stored at rooms humidity or thermocycled (12.000 x, 5 degrees C/55 degrees C) and stored in water for 2 weeks before testing. A three-point bending test (span=10 mm) was used to measure the flexural strength and modulus of FRC post specimens. RESULTS Analysis of ANOVA revealed that thermocycling, brand of material and diameter of specimen had a significant effect (p<0.001) on the fracture load and flexural strength. The highest flexural strength was obtained with the control material (everStick, 1144.9+/-99.9 MPa). There was a linear relationship between fracture load and diameter of posts for both glass fiber and carbon fiber posts. Thermocycling decreased the flexural modulus of the tested specimens by approximately 10%. Strength and fracture load decreased approximately 18% as a result of thermocycling. SIGNIFICANCE Considerable variation can be found in the calculated strength values of the studied post brands. Commercial prefabricated FRC posts showed lower flexural properties than an individually polymerised FRC material.

Five-year survival of 3-unit fiber-reinforced composite fixed partial dentures in the anterior area

OBJECTIVES The purpose of this clinical study was to evaluate the long-term outcome of 3-unit anterior fixed partial dentures (FPDs) made of fiber-reinforced resin composite (FRC), and to identify design factors influencing the survival rate. METHODS 52 patients (26 females, 26 males) received 60 indirectly made FRC FPDs, using pre-impregnated unidirectional glass fibers, requiring manual wetting, as framework material. FPDs were surface (n=48) or hybrid (n=12) retained and mainly located in the upper jaw. Hybrid FPDs had a combination of retainers; i.e. crown at one and surface retention at the other abutment tooth. Surface FPDs were either purely adhesively retained (n=29) or with additional mechanical retention (n=19). Follow-up period was at minimum 5 years, with check-ups every 1-2 years. Six operators were involved, in three centers in the Netherlands, Finland and Sweden. Survival rates, including repairable defects of FPDs, and success rates were determined. RESULTS Kaplan-Meier survival rate at 5 years was 64% (SE 7%). For the level of success, values were 45% (SE 7%) and the estimated median survival time 58 (SE 10.1) months. For surface FPDs, additional mechanical retention did not improve survival significantly. There was a trend towards better survival of surface FPDs over hybrid FPDs, but differences were not significant. Main failure modes were fracture of the FPD and delamination of veneering composite. SIGNIFICANCE A success rate of 45% and a survival rate of 64% after 5 years was found. Fracture of the framework and delamination are the most prevalent failure modes, especially for surface FPDs.

Adherence of Streptococcus mutans to an E-glass fiber-reinforced composite and conventional restorative materials used in prosthetic dentistry

The adherence of Streptococcus mutans to E-glass used in fiber-reinforced composites, denture base polymer, and four other restoratives was investigated. The materials were studied with and without a parotid saliva and serum pellicle. Specimens of the studied materials (E-glass, denture base polymer, titanium, cobalt-chromium alloy, gold alloy, and grained feldspar ceramic) were incubated in a suspension of S. mutans, allowing initial adhesion to occur. The degree of bacterial adhesion was studied using scanning electron microscopy (SEM). The studied uncoated materials showed rather similar adhesion of S. mutans. Saliva coating resulted in a decrease of adherence to all materials except glass. With a saliva pellicle E-glass showed the strongest ability to bind S. mutans, and it differed significantly from the other studied materials. Serum coating markedly decreased adhesion to all materials, and only minor differences among the studied materials were observed. The results of this study suggest that the studied restoratives are rather similar with respect to S. mutans adhesion and that a saliva pellicle may promote adhesion of S. mutans to glass fibers.

Restoration of myofiber continuity after transection injury in the rat soleus.

In a shearing type of muscle injury, scar formation prevents restoration of myofiber continuity and the transected myofibers may become permanently divided into two separate myofibers. We have analysed whether the injured myofiber stumps can fuse and continuity of the transected fibers be re-established, if the stumps are surgically closely apposed immediately after injury. 55 rat soleus muscles were transected, after which the epimysium was carefully sutured and the leg was immobilised for seven days. The animals were sacrificed at 2, 5, 7, 10, 14 and 25 days after surgery. All muscles were analysed by light and electron microscopy as well as by immunohistochemistry. Mechanical strength was also measured at day 10 and 25. We observed that suturing reduced the extent of the intervening scar and accelerated healing. More importantly our results indicate that fusion of the stumps and thus restoration of myofiber continuity, is possible after myofiber transection injury.

Effect of water storage of E-glass fiber-reinforced composite on adhesion of Streptococcus mutans

This study investigated the effect of water storage of fiber-reinforced composite on the adhesion of Streptococcus mutans (S. mutans) and its ability to stay adhered and multiply on the FRC. The materials (E-glass fibers and denture base polymer) were stored in water for 14 or 30 days or left dry. Water contact angles of the materials before and after water storage were determined. Test specimens, with or without parotid saliva or serum pellicle, were incubated in a suspension of S. mutans allowing initial adhesion to occur. Bacterial adhesion and multiplication was studied using scanning electron microscopy. Contact angles of both materials were significantly reduced after water storage indicating an increase in surface free energy. When studied without a surface pellicle, water storage significantly increased adhesion of S. mutans to both glass and polymer. Saliva coating of the materials resulted in higher degree of adhesion to glass fibers in comparison with polymer and after 14 days water storage glass bound over twice as much S. mutans cells than the polymer matrix. Bacterial growth and biofilm formation occurred equally on both materials. The results of this in vitro study suggest that in order to avoid the possible increase in S. mutans adhesion, the reinforcing glass fibers should be covered with the matrix polymer of the composite.

Preliminary Clinical Evaluation of Short Fiber-Reinforced Composite Resin in Posterior Teeth: 12-Months Report

This preliminary clinical trial evaluated 12 month clinical performance of novel filling composite resin system which combines short fiber-reinforced composite resin and conventional particulate filler composite resin in high stress bearing applications. A total of 37 class I and II restorations (compound and complex type) were placed in 6 premolars and 31 molars. The restorations were reviewed clinically at 6 months (baseline) and 12 months using modified USPHS codes change criteria for marginal adaptation, post-operative sensitivity, pulpal pain and secondary caries criteria. Photographs and x-rays were obtained for restorative analysis. Results of 12 months evaluation showed 5 restorations having little marginal leakage (B score) and 1 patient had minor pulpal symptom and post-operative sensitivity (B score). No secondary caries or bulk fracture was detected. The majority of restorations exhibited A scores of the evaluated criteria. After 12 months, restorations combining base of short fiber reinforced composite resin as substructure and surface layer of hybrid composite resin displayed promising performance in high load bearing areas.

Adherence of Streptococcus mutans to Fiber-Reinforced Filling Composite and Conventional Restorative Materials.

Objectives. The aim was to investigate the adhesion of Streptococcus mutans (S. mutans) to a short glass fibers reinforced semi-IPN polymer matrix composite resin. The effect of surface roughness on adhesion was also studied. For comparison, different commercial restorative materials were also evaluated. Materials and Methods. Experimental composite FC resin was prepared by mixing 22.5 wt% of short E-glass fibers, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using high speed mixing machine. Three direct composite resins (Z250, Grandio and Nulite), resin-modified glass ionomers (Fuji II LC), amalgam (ANA 2000), fiber-reinforced composite (FRC) (everStick and Ribbond), and pre-fabricated ceramic filling insert (Cerana class 1) were tested in this study. Enamel and dentin were used as controls. The specimens (n=3/group) with or without saliva were incubated in a suspension of S. mutans allowing initial adhesion to occur. For the enumeration of cells on the disc surfaces as colony forming units (CFU) the vials with the microbe samples were thoroughly Vortex-treated and after serial dilutions grown anaerobically for 2 days at +37°C on Mitis salivarius agars (Difco) containing bacitracin. Bacterial adhesion was also evaluated by using scanning electron microscopy. Surface roughness (Ra) of the materials was also determined using a surface profilometer. All results were statistically analyzed with one-way analysis of variance (ANOVA). Results. Composite FC resin and other commercial restorative materials showed similar adhesion of S. mutans, while adhesion to dentin and enamel was significantly higher (p<0.05). Surface roughness had no effect on bacterial adhesion. Saliva coating significantly decreased the adhesion for all materials (p<0.05). Composite FC resin had a significantly higher Ra value than control groups (p<0.05). Conclusions. Short fiber-reinforced composite with semi-IPN polymer matrix revealed similar S. mutans adhesion than commercial restorative materials.

Root canal anchoring systems

Abstract Endodontically treated teeth with a substantial coronal loss of dentin may require additional support to retain the coronal restoration. The use of posts has decreased along with the development of adhesive techniques and materials. Yet, when remaining coronal tissue is scarce, additional bonding surface, retention, and support from the root canal is needed especially in anterior teeth and premolars.

Fiber-Reinforced Dental Materials in the Restoration of Root-Canal Treated Teeth

Fiber-reinforced composites (FRC) are a group of lightweight metal-free dental materials characterized by their anisotropic nature. They are relatively low-cost, tooth-colored materials that are compatible with the use of adhesive and direct restorative techniques. Contemporary dental FRCs are predominantly based on glass fibers and dimethacrylate resins. For optimal clinical performance, it is crucial that the properties and behavior of these composite materials are well understood. In an FRC, the fibers provide strength and stiffness, while the matrix polymer binds the fibers together, forming a continuous phase around the reinforcement. For optimal mechanical properties, the fibers must be well adhered to and well impregnated by the matrix polymer. Other factors influencing the mechanical, optical, and bonding properties of FRCs include the type of fiber and matrix polymer, quantity, positioning, and orientation of fibers. Contemporary dental FRCs can be based on either unidirectional or multidirectional long continuous fibers or short discontinuous fibers. FRCs offer several benefits in restoring root-canal treated (RCT) teeth. Elastic modulus close to that of natural dentin, high tensile strength, and the suitability for cost-effective chairside techniques make fiber-reinforced composites well suited in the restoration of structurally compromised RCT teeth.

Clinical Evaluation of Fiber-Reinforced Composite Restorations in Posterior Teeth - Results of 2.5 Year Follow-up

Objectives: The aim of this study was to evaluate the clinical performance of posterior composite restorations reinforced by bulk base of short-fiber composite (everX Posterior, GC Corporation). Methods: Thirty-six short fiber-reinforced composite restorations were placed in premolar and molar teeth of 33 patients. Eight of the teeth were vital and 28 were non-vital. Average follow up time of the restorations was 30.6 months (2.5 years), ranging from 16.2 to 51.3 months (1.3 - 4.3 years). Results: One restoration failed during the follow-up period due to secondary caries, at time point 39.5 months. Three fillings had minor fractures during the follow-up. The overall survival rate of the restorations was 97.2% and success rate (no maintenance needed) was 88.9%, respectively. Conclusion: Posterior composite restorations with a bulk base of short-fiber composite showed good clinical performance in the short term evaluation.