Flexural strengths of conventional and nanofilled fiber-reinforced composites: a three-point bending test

Effects of aligner activation and power arm length and material on canine displacement and periodontal ligament stress: a finite element analysis

BACKGROUND

This study aimed to assess the impact of aligner activation and power arm length and material on canine and aligner displacement, von Mises stress in the power arm, and principal stress in the periodontal ligament (PDL) during canine tooth distalization using finite element analysis (FEA). The effects of aligner activation and power arm length were primary outcomes, while the effect of the power arm material was a secondary outcome.

METHODS

Aligner activation (0.1 mm or 0.2 mm) was applied without using a power arm in two models. The effects of aligner activation, power arm length (12, 13, or 14 mm) and power arm material (stainless steel [SS] or fiber-reinforced composite [FRC]) on canine distalization were investigated in 12 models by evaluating displacement and stress via ALTAIR OptiStruct analysis.

RESULTS

Greater canine displacement was observed in all models with 0.2 mm than 0.1 mm of aligner activation. When models with the same aligner activation were compared, reduced mesiodistal tipping, increased palatal tipping, and increased extrusion of the canine cusp were observed with increasing power arm length. Moreover, the von Mises stress increased as the power arm length increased. Increasing the aligner activation and power arm length increased the maximum principal stress in the PDL. Power arms of the same length in both materials showed the same results in terms of canine displacement, clear aligner displacement, and maximum principal stress in the PDL. However, under conditions of equal length and aligner activation, the von Mises stress of the SS power arm was higher than that of the FRC power arm.

CONCLUSION

Using a power arm in canine distalization reduced mesiodistal tipping but increased palatal tipping and extrusion of the canine cusp. Aligner activation and additional force increased tooth movement and principal stress in the canine PDL. FRC power arms exhibited less von Mises stress than SS power arms.

Development of Light-Polymerized Dental Composite Resin Reinforced with Electrospun Polyamide Layers

As the mechanical properties of resin-based dental composite materials are highly relevant in clinical practice, diverse strategies for their potential enhancement have been proposed in the extant literature, aiming to facilitate their reliable use in dental medicine. In this context, the focus is primarily given to the mechanical properties with the greatest influence on clinical success, i.e., the longevity of the filling in the patient's mouth and its ability to withstand very strong masticatory forces. Guided by these objectives, the goal of the present study was to ascertain whether the reinforcement of dental composite resins with electrospun polyamide (PA) nanofibers would improve the mechanical strength of dental restoration materials. For this purpose, light-cure dental composite resins were interspersed with one and two layers comprising PA nanofibers in order to investigate the influence of such reinforcement on the mechanical properties of the resulting hybrid resins. One set of the obtained samples was investigated as prepared, while another set was immersed in artificial saliva for 14 days and was subsequently subjected to the same set of analyses, namely Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Findings yielded by the FTIR analysis confirmed the structure of the produced dental composite resin material. They also provided evidence that, while the presence of PA nanofibers did not influence the curing process, it strengthened the dental composite resin. Moreover, flexural strength measurements revealed that the inclusion of a 16 μm-thick PA nanolayer enabled the dental composite resin to withstand a load of 3.2 MPa. These findings were supported by the SEM results, which further indicated that immersing the resin in saline solution resulted in a more compact composite material structure. Finally, DSC results indicated that as-prepared as well as saline-treated reinforced samples had a lower glass transition temperature (Tg) compared to pure resin. Specifically, while pure resin had a Tg of 61.6 °C, each additional PA nanolayer decreased the Tg by about 2 °C, while the further reduction was obtained when samples were immersed in saline for 14 days. These results show that electrospinning is a facile method for producing different nanofibers that can be incorporated into resin-based dental composite materials to modify their mechanical properties. Moreover, while their inclusion strengthens the resin-based dental composite materials, it does not affect the course and outcome of the polymerization reaction, which is an important factor for their use in clinical practice.

Effect of Long-Term Brushing on Deflection, Maximum Load, and Wear of Stainless Steel Wires and Conventional and Spot Bonded Fiber-Reinforced Composites

Fiber-reinforced composite (FRC) retainers are an aesthetic alternative to conventional Stainless Steel splints. They are generally used with a full bonded technique, but some studies demonstrated that they could be managed with a spot bonding technique to significantly decrease their rigidity. In order to propose this FRC spot bonding technique for clinical use, the aim of this study was to evaluate mechanical properties and surface wear of fibers left uncovered. Tests were made by simulating tooth brushing, comparing FRC spot bonding technique splints with stainless steel and FRC traditional technique splints. Specimens were tested both at 0.1 mm of deflection and at maximum load, showing higher values of rigidity for the FRC full bonded technique. After tooth brushing, no significant reduction in values at 0.1 mm deflection was reported, while we found a similar reduction in these values for the Stainless Steel and FRC spot bonding technique at maximum load, and no significant variation for the FRC full bonded technique. SEM images after tooth brushing showed wear for FRC fibers left uncovered, while no relevant wear signs in metal and conventional FRC fibers were noticed. Results showed that FRC spot bonding technique has advantages in mechanical properties when compared to the FRC traditional full bonding technique, also after tooth brushing. However, the surface wear after tooth brushing in the FRC spot bonding technique is considerable and other tests must be performed before promoting this technique for routine clinical use.

CUSTOMIZED POST-AND-CORE DESIGN AND STRESS ANALYSIS FOR POSTERIOR TOOTH PROSTHESIS

A post-and-core crown is widely used in prosthetic dentistry; however, in clinical treatment, it easily causes root fracture and tooth penetration. To address these problems, this study aimed to present a customized post-and-core design for the posterior tooth implant. First, a residual tooth and its root canal were reconstructed. Then, the root canal surface was extracted, the surface curvature and length parameters were defined, and the customized post-and-core design was developed. Finally, the tooth, root canal, and post-and-core with different implant lengths in five masticatory directions were analyzed using finite element analysis to evaluate the stress distribution. The results showed that, with the similar shape of the post-and-core structure and the root canal, the tooth stress trend was uniform. When the length of the post-and-core structure [Formula: see text] was 0[Formula: see text]mm, that is, it was two thirds of the root canal length, the root canal stress was minimum. Therefore, the customized design of the post-and-core structure could well adapt to any kind of root canal, and the length of the post-and-core structure [Formula: see text] provided guidance for the post-and-core crown prosthesis in clinic.

Effect of fiberglass orientation on flexural properties of fiberglass-reinforced composite resin block for CAD/CAM

A fiberglass-reinforced composite resin (FRP) block using a plain woven fiberglass sheet for CAD/CAM has been introduced in dental practice. The aim of the present study was to evaluate the effects of the fiberglass sheet orientation on the flexural properties of an FRP block. The flexural properties of five types of fiberglass sheet-assigned specimens were examined using a three-point bending test. A one-way analysis of variance revealed that the orientation of fiberglass sheet significantly influenced the flexural strength, 0.2% yield strength, and flexural modulus. The values of the flexural properties of the FRP were the largest when the fiberglass sheets were perpendicular to the applied force, and the smallest when the fiberglass was parallel to the same. The flexural properties of the FRP block were anisotropic and they were significantly influenced by the orientation of fiberglass sheet.

Experimental synthesis of size-controlled TiO2 nanofillers and their possible use as composites in restorative dentistry

The aim of this work was to obtain an efficient protocol with a green, fast and facile way to synthesize TiO2 NPs and its application as fillers for enhancement of desired dental properties of light curing dental composites. A comparative study comprised the fabrication of light curing restorative composite materials with incorporating different fillers with varying wt%, varying resin material composition, to determine optimal dental restoration by focusing on the physical properties of dental materials. It was observed that the as-prepared green synthesized TiO2 nanohybrid particles contributed to the improvement in physical properties, thus promoting the green and rapid synthesis of nanohybrid fillers. In addition, mechanical values for experimental cured resin materials with bare and surface modified fillers were obtained. The experimental light curing nanocomposites with 5 wt% (wt%) nanohybrid surface modified filler particles with BisGMA (60 wt%), TEGDMA (20 wt%) and UDMA (20 wt%) resin composition provided increased physical strength and durability with higher compressive stress 195.56 MPa and flexural stress 83.30 MPa. Furthermore, the dental property, such as polymerization shrinkage (PS) obtained from volumetric method was decreased up to 3.4% by the addition of nano-hybrid fillers. In addition to this, the biocompatible and antimicrobial nature of TiO2 and its aesthetics properties such as tooth-like color makes TiO2 favorable to use as fillers. This study presents a green and facile method for the synthesis of TiO2 nanohybrid particles that can be successfully used as fillers in an experimental light curing resin matrix for enhancing its dental properties. This describes the potential of the green synthesized TiO2 nanohybrid particles to use as fillers in restorative dentistry.

Flexural Properties and Elastic Modulus of Different Esthetic Restorative Materials: Evaluation after Exposure to Acidic Drink

Background

Acidic beverages, such as soft drinks, can produce erosion of resin composites. The purpose of the present study was to investigate mechanical properties of different esthetic restorative materials after exposure to acidic drink.

Methods

Nine different composites were tested: nanofilled (Filtek Supreme XTE, 3M ESPE), microfilled hybrid (G-ænial, GC Corporation), nanohybrid Ormocer (Admira Fusion, Voco), microfilled (Gradia Direct, GC Corporation), microfilled hybrid (Essentia, GC Corporation), nanoceramic (Ceram.X Universal, Dentsply De Trey), supranano spherical hybrid (Estelite Asteria, Tokuyama Dental Corporation), flowable microfilled hybrid (Gradia Direct Flo, GC Corporation), and bulk fill flowable (SureFil SDR flow, Dentsply De Trey). Thirty specimens of each esthetic restorative material were divided into 3 subgroups (n=10): specimens of subgroup 1 were used as control, specimens of subgroup 2 were immersed in 50 ml of Coca Cola for 1 week, and specimens of subgroup 3 were immersed in 50 ml of Coca Cola for 1 month. Flexural strength and elastic modulus were measured for each material with an Instron Universal Testing Machine. Data were submitted to statistical analysis.

Results

After distilled water immersion, nanofilled composite showed the highest value of both flexural strength and elastic modulus, but its flexural values decreased after acidic drink immersion. No significant differences were reported between distilled water and acidic drink immersion for all other materials tested both for flexural and for elastic modulus values.

Conclusions

Even if nanofilled composite showed highest results, acidic drink immersion significantly reduced flexural values.

Travel beyond Clinical Uses of Fiber Reinforced Composites (FRCs) in Dentistry: A Review of Past Employments, Present Applications, and Future Perspectives

The reinforcement of resins with short or long fibers has multiple applications in various engineering and biomedical fields. The use of fiber reinforced composites (FRCs) in dentistry has been described in the literature from more than 40 years. In vitro studies evaluated mechanical properties such as flexural strength, fatigue resistance, fracture strength, layer thickness, bacterial adhesion, bonding characteristics with long fibers, woven fibers, and FRC posts. Also, multiple clinical applications such as replacement of missing teeth by resin-bonded adhesive fixed dental prostheses of various kinds, reinforcement elements of dentures or pontics, and direct construction of posts and cores have been investigated. In orthodontics, FRCs have been used also for active and passive orthodontic applications, such as anchorage units, en-masse movement units, and postorthodontic tooth retention. FRCs have been extensively tested in the literature, but today the advances in new technologies involving the introduction of nanofillers or new fibers along with understanding the design principles of FRC devices open new fields of research for these materials both in vitro and in vivo. The present review describes past and present applications of FRCs and introduces some future perspectives on the use of these materials.

Reliability of Orthodontic Miniscrews: Bending and Maximum Load of Different Ti-6Al-4V Titanium and Stainless Steel Temporary Anchorage Devices (TADs)

Temporary anchorage devices (TADs) have been introduced into orthodontic clinical practice in order to allow tooth movements while avoiding strain on adjacent teeth. Miniscrews are available in the market with different diameters and materials. Accordingly, the purpose of the present report was to measure and compare the forces to bend and fracture different mini implants. Ti-6Al-4V titanium and stainless steel TADs of different manufacturers (Spider ScrewHDC; Mini Implants⁻Leone; Benefit⁻Orteam; Storm⁻Kristal) were evaluated. Two different diameters (1.5 mm and 2.0 mm) were tested. The sample included 10 unused specimens for each group, blocked in an Instron Universal Testing Machine, and a shear load was applied at the neck of the miniscrew. The force to bend the miniscrew was measured at 0.1 mm and 0.2 mm deflections. Also, the maximum force before screw fracture was recorded. Data were submitted for statistical analysis. Results showed significantly higher forces for 2.0 mm than 1.5 mm screws, both at 0.1 mm and 0.2 mm deflections and at maximum load. Moreover, no significant differences were reported between titanium and stainless steel miniscrews of equal diameters.

Reliability of Orthodontic Miniscrews: Bending and Maximum Load of Different Ti-6Al-4V Titanium and Stainless Steel Temporary Anchorage Devices (TADs)

Temporary anchorage devices (TADs) have been introduced into orthodontic clinical practice in order to allow tooth movements while avoiding strain on adjacent teeth. Miniscrews are available in the market with different diameters and materials. Accordingly, the purpose of the present report was to measure and compare the forces to bend and fracture different mini implants. Ti-6Al-4V titanium and stainless steel TADs of different manufacturers (Spider ScrewHDC; Mini Implants⁻Leone; Benefit⁻Orteam; Storm⁻Kristal) were evaluated. Two different diameters (1.5 mm and 2.0 mm) were tested. The sample included 10 unused specimens for each group, blocked in an Instron Universal Testing Machine, and a shear load was applied at the neck of the miniscrew. The force to bend the miniscrew was measured at 0.1 mm and 0.2 mm deflections. Also, the maximum force before screw fracture was recorded. Data were submitted for statistical analysis. Results showed significantly higher forces for 2.0 mm than 1.5 mm screws, both at 0.1 mm and 0.2 mm deflections and at maximum load. Moreover, no significant differences were reported between titanium and stainless steel miniscrews of equal diameters.

Magnesium Oxide Nanoparticles: Dielectric Properties, Surface Functionalization and Improvement of Epoxy-Based Composites Insulating Properties

Composite insulation materials are an inseparable part of numerous electrical devices because of synergy effect between their individual parts. One of the main aims of the presented study is an introduction of the dielectric properties of nanoscale magnesium oxide powder via Broadband Dielectric Spectroscopy (BDS). These unique results present the behavior of relative permittivity and loss factor in frequency and temperature range. Following the current trends in the application of inorganic nanofillers, this article is complemented by the study of dielectric properties (dielectric strength, volume resistivity, dissipation factor and relative permittivity) of epoxy-based composites depending on the filler amount (0, 0.5, 0.75, 1 and 1.25 weight percent). These parameters are the most important for the design and development of the insulation systems. The X-ray diffraction patterns are presented for pure resin and resin with optimal filler amount (1 wt %), which was estimated according to measurement results. Magnesium oxide nanoparticles were also treated by addition of silane coupling agent ( γ -Glycidoxypropyltrimethoxysilane), in the case of optimal filler loading (1 wt %) as well. Besides previously mentioned parameters, the effects of surface functionalization have been observed by two unique measurement and evaluation techniques which have never been used for this evaluation, i.e., reduced resorption curves (RRCs) and voltage response method (VR). These methods (developed in our departments), extend the possibilities of measurement of composite dielectric responses related to DC voltage application, allow the facile comparability of different materials and could be used for dispersion level evaluation. This fact has been confirmed by X-ray diffraction analyses.

Evaluation of the Flexural Strength of Submicron Hybrid Composite using Different Fabrication Methods: An in vitro Study

AIM

The aim of this study is to perform three-point bend test on submicron hybrid composite fabricated with direct and indirect veneer technique.

MATERIALS AND METHODS

A total of 20 maxillary anterior teeth were selected, and labial reduction of 0.5 to 0.75 mm with a chamfered finish line for veneer preparation was done. Teeth were divided into two groups depending on fabrication technique being used: group I-veneers fabricated with light and group II-veneers fabricated with light and heat (PHOTOPOL). Specimens were tested under universal testing machine (UTM) where load was applied at a crosshead speed of 1 mm/min with a pointer of 1 mm diameter. Data were statistically analyzed.

RESULTS

The results showed highly significant difference between the two groups with the mean value of group I (246.7 ± 2.285 N) and group II (531.1 ± 4.411 N).

CONCLUSION

The curing mechanism involving light and heat increases the fracture resistance of the veneers.

CLINICAL SIGNIFICANCE

Within the limitations of this study, the results led to the conclusion that the association of common composites with a simple postcure heat treatment may be an alternative for current indirect composite systems, although more studies are needed to assess other properties of the composites for this application.

Load-bearing capacity and fracture behavior of glass fiber-reinforced composite cranioplasty implants

BACKGROUND

Glass fiber-reinforced composites (FRCs) have been adapted for routine clinical use in various dental restorations and are presently also used in cranial implants. The aim of this study was to measure the load-bearing capacity and failure type of glass FRC implants during static loading with and without interconnective bars and with different fixation modes.

METHODS

Load-bearing capacities of 2 types of FRC implants with 4 different fixation modes were experimentally tested. The sandwich-like FRC implants were made of 2 sheets of woven FRC fabric, which consisted of silanized, woven E-glass fiber fabrics impregnated in BisGMA-TEGDMA monomer resin matrix. The space between the outer and inner surfaces was filled with glass particles. All FRC implants were tested up to a 10-mm deflection with load-bearing capacity determined at 6-mm deflection. The experimental groups were compared using nonparametric Kruskal-Wallis analysis with Steel-Dwass post hoc test.

RESULTS

FRC implants underwent elastic and plastic deformation until 6-mm deflection. The loading test did not demonstrate any protrusions of glass fibers or cut fiber even at 10-mm deflection. An elastic and plastic deformation of the implant occurred until the FRC sheets were separated from each other. In the cases of the free-standing setup (no fixation) and the fixation with 6 screws, the FRC implants with 2 interconnective bars showed a significantly higher load-bearing capacity compared with the implant without interconnective bars.

CONCLUSIONS

FRC implants used in this study showed a load-bearing capacity which may provide protection for the brain after cranial bone defect reconstruction.

Bending Properties of Fiber-Reinforced Composites Retainers Bonded with Spot-Composite Coverage

Orthodontic and periodontal splints are prepared with round or flat metallic wires. As these devices cannot be used in patients with allergy to metals or with aesthetic demands, fiber-reinforced composite (FRC) retainers have been introduced. Stiffness of FRC materials could reduce physiologic tooth movement. In order to lower rigidity of conventional FRC retainers, a modified construction technique that provided a partial (spot) composite coverage of the fiber has been tested and compared with metallic splints and full-bonded FRCs. Flat (Bond-a-Braid, Reliance Orthodontic Products) and round (Penta-one 0155, Masel Orthodontics) stainless steel splints, conventional FRC splints, and experimental spot-bonded FRC retainers (Everstick Ortho, StickTech) were investigated. The strength to bend the retainers at 0.1 mm deflection and at maximum load was measured with a modified Frasaco model. No significant differences were reported among load values of stainless steel wires and experimental spot-bonded FRC retainers at 0.1 mm deflection. Higher strength values were recoded for conventional full-bonded FRCs. At maximum load no significant differences were reported between metallic splints (flat and round) and experimental spot-bonded FRCs, and no significant differences were reported between spot- and full-bonded FRC splints. These results encourage further tests in order to evaluate clinical applications of experimental spot-bonded FRC retainers.

Spot-Bonding and Full-Bonding Techniques for Fiber Reinforced Composite (FRC) and Metallic Retainers

Fiber reinforced Composite (FRC) retainers have been introduced as an aesthetic alternative to conventional metallic splints, but present high rigidity. The purpose of the present investigation was to evaluate bending and fracture loads of FRC splints bonded with conventional full-coverage of the FRC with a composite compared with an experimental bonding technique with a partial (spot-) resin composite cover. Stainless steel rectangular flat, stainless steel round, and FRC retainers were tested at 0.2 and 0.3 mm deflections and at a maximum load. Both at 0.2 and 0.3 mm deflections, the lowest load required to bend the retainer was recorded for spot-bonded stainless steel flat and round wires and for spot-bonded FRCs, and no significant differences were identified among them. Higher force levels were reported for full-bonded metallic flat and round splints and the highest loads were recorded for full-bonded FRCs. At the maximum load, no significant differences were reported among spot- and full-bonded metallic splints and spot-bonded FRCs. The highest loads were reported for full bonded FRCs. The significant decrease in the rigidity of spot-bonded FRC splints if compared with full-bonded retainers suggests further tests in order to propose this technique for clinical use, as they allow physiologic tooth movement, thus presumably reducing the risk of ankylosis.

Shear bond strength of different surface treatments in bulk fill, microhybrid, and nanoparticle repair resins

Objectives

The purpose of this study was to evaluate the influence of surface treatment and different types of composite resin on the microshear bond strength of repairs.

Materials and methods

Seventy-two specimens (n=72) were prepared using a nanoparticle resin and stored in artificial saliva at 37 ± 1°C for 24 h. After this period, the specimens (n=24) were restored with microhybrid resin P60 (3M ESPE), nanoparticle resin Filtek Z350 (3M ESPE), and Bulk Fill Surefil SDR Flow (Dentsply) composite resins. Previously, the surfaces of the samples were treated, forming the following subgroups (n=12): (A) conditioned with 37% phosphoric acid for 30 s, and (B) abrasioned with a diamond tip for 3 s and conditioned with 37% phosphoric acid. In all groups, before insertion of the composite resin, the adhesive system Adper Single Bond 2 was actively applied and photopolymerized for 20 s.

Results

The microshear test was executed to assess bond strength. Kruskal–Wallis (p<0.05) and Mann–Whitney statistical tests showed significant statistical difference considering that the bulk-fill resin turned out to have a lower bond strength than the conventional nanoparticle and microhybrid composites. With regard to the technique, the roughening with diamond bur followed by the application of phosphoric acid exhibited values higher than the exclusive use of acid.

Conclusion

The microshear bond strength of the composite resin repairs varies in accordance with the type of composite resin utilized, and roughening the surface increased the bond strength of these materials.

The effect of silica nanoparticles on the mechanical properties of fiber-reinforced composite resins

Background. Nanotechnology has introduced many nanoparticles in recent years, which can be incorporated for mechanical improvement of dental materials. However, the existing data are widely sparse. This study investigated the reinforcing effect of silica nanoparticles when incorporated into the matrix phase of an experimental dental fiber-reinforced compositeresin (FRC) through evaluation of its flexural properties.

Methods. In this experimental study FRC samples were divided into two main groups (containing two or three bundles),either of whic consisted of five subgroups with 0, 0.2, 0.5, 2 and 5 wt% of silica nanoparticles in the matrix resin (n=10 in each subgroup); a commercial FRC (Angelus, Brazil) was used as the control group (n=10). Three-point bending test was performed to evaluate the flexural strength and modulus. Thereafter, the microstructure of the fractured samples was evalu-ated using scanning electron microscopy (SEM). The results were analyzed with one-way ANOVA and HSD Tukey tests (α = 0.05).

Results. The results revealed that the silica nanoparticles had a significant and positive effect on the flexural strength and modulus of FRCs (P<0.05), with no significant differences from 0.2 to 5 wt% of nanoparticles (P > 0.05) in either group with two or three bundles of fibers.

Conclusion. Incorporating silica nanoparticles into the FRC resin phase resulted in improved flexural strength and modulus of the final product.

Effects of nanofillers on mechanical properties of fiber-reinforced composites polymerized with light-curing and additional postcuring

BACKGROUND

The purpose of the present study was to evaluate the effect of nanofillers on the mechanical properties of 2 sizes (diameters 0.6 and 0.9 mm) of conventional and nanofilled fiber-reinforced composites (FRCs) polymerized with conventional light-curing and additional postcuring.

METHODS

The FRCs samples were divided into 8 groups (10 specimens each). Conventional FRCs with glass fibers preimpregnated with polymethyl methacrylate (groups 1, 2, 3 and 4) and FRCs with impregnating solution containing 32% nanofilled resin (groups 5, 6, 7 and 8) were tested in 2 different sections (0.6 and 0.9 mm in diameter). Two different polymerizations were analyzed: hand light-curing for 40 seconds with an halogen light, and additional postcuring for 25 minutes in a light-curing oven. Each sample was evaluated with a 3-point bending test on a universal testing machine, after 48 hours of dry storage. All of the data were statistically analyzed.

RESULTS

After oven postcuring, nanofilled FRCs exhibited significantly higher load values than conventional FRCs. No significant differences were found when comparing conventional and nanofilled FRCs after hand light-curing. Moreover, 0.6-mm FRCs showed significantly lower load values than 0.9-mm FRCs, both for conventional and nanofilled FRCs.

CONCLUSIONS

Nanofilled FRCs showed higher load values after additional oven postcuring.

Clinical evaluation of bond failures and survival between mandibular canine-to-canine retainers made of flexible spiral wire and fiber-reinforced composite

OBJECTIVES

The purpose of this longitudinal prospective randomized study was to evaluate the clinical reliability of two different types of postorthodontic treatment retainers: a silanised-treated glass fibers-reinforced resin composite (FRC) and a directly bonded multistranded stainless steel wire. The hypothesis of the study was to assess if significant differences are present between failure rates of the two retainers.

STUDY DESIGN

This prospective study was based on an assessment of 87 patients (35 men and 52 women),with an average age of 24 years who required a lower arch fixed retainer after orthodontic treatment. Patients were divided in two groups. Assignment was carried out with random tables. A follow-up examination was carried out once a month. The number, cause, and date of single bond adhesive failures were recorded for both retainers over 12 months. Teeth that were rebonded after failure were not included in the success analysis. Statistical analysis was performed by means of a Fisher's exact test, Kaplan-Meier survival estimates, and log rank test.

RESULTS

Bond failure rate was significantly higher (P=0.0392) for multistranded metallic wire than for FRC.

CONCLUSIONS

Glass fiber-reinforced resin composite retainers and multistranded metallic wires showed no significant difference in single bond failure rates over a one-year follow up. Key words:Fiber reinforced composite, fixed retention, multistranded wire, orthodontics, retainer, splint.