Shear modulus of 5 flowable composites to the EverStick Ortho fiber-reinforced composite retainer: An in-vitro study

Evaluation of Bond Strength and Adhesive Remnant Index of Different Lingual Retainers in Human Incisor Teeth

Objective

This study aimed to evaluate and compare the bond strengths of four different lingual retainers and assess the adhesive remnant index (ARI) to determine their effectiveness in orthodontic retention.

Methodology

Eighty human incisor teeth were divided into four groups, with each group bonded using a different retainer: Group 1 (E-Glass retainer), Group 2 (0.017" Co-axial stainless steel wire), Group 3 (Splint C.T. fiber mesh), and Group 4 (0.010" stainless steel ligature wire). Bond strength was measured using a universal testing machine, and ARI scores were recorded to assess bond failure types.

Results

Group 1 (E-Glass retainer) demonstrated the highest bond strength, followed by Group 3 (Splint C.T. fiber mesh), Group 2 (Co-axial stainless steel wire), and Group 4 (stainless steel ligature wire). Cohesive bond failures were observed in most groups, except for the co-axial stainless steel wire group, which exhibited adhesive failures.

Conclusion

E-Glass fiber-reinforced retainers showed the highest bond strength, making them a promising alternative to conventional stainless steel wires for orthodontic retention, especially in patients with esthetic concerns or nickel hypersensitivity. Stainless steel retainer groups exhibited lower bond strengths, and cohesive bond failures were prevalent. Further research is needed to validate these findings in clinical settings and evaluate the long-term effectiveness of different lingual retainers.

Comparison of the different retention appliances produced using CAD/CAM and conventional methods and different surface roughening methods

The purposes of this study are to conduct an in vitro comparison of the shear bond strength, breakage mode, and wire deformation of three different types of retainers and to compare the subsequent enamel surface changes. Two hundred seventy intact lower incisor teeth were embedded in acrylic blocks in pairs. Dead wire and CAD/CAM-fabricated and fiber-reinforced wires were applied to the teeth roughened with acid and Er:YAG or Er,Cr:YSGG laser. The surface roughness was observed by scanning electron and atomic force microscopy. The samples were analyzed for shear bonds. The dead wire and acid group were found to have the highest bonding strength and the strengths for all groups in which acid was used as an agent were found to be higher than others. Deformation of retainers was most noted in the dead wire-acid group. Among all the groups, the CAD/CAM-fabricated wire group showed the least deformation, with no deformation observed. In this study, it was determined that there is a significant correlation between ARI scores and agents. Consequently, acid etching was found to create more enamel surface roughness than laser groups. It was also seen that the combined use of the acid method and dead soft wire had the highest bond strength, even though it was not statistically significant. It was concluded that CAD/CAM-fabricated wire provides the opportunity for reuse in clinical applications due to its lack of deformation, being more conservative for the patient, and being more advantageous for the clinician in terms of session time, considering the residual adhesive amount left on the enamel surface.

Covering of fiber-reinforced composite bars by adhesive materials, is it necessary to improve the bond strength of lingual retainers?

Objectives:

The objectives were to evaluate the shear bond strength (SBS) of fiber-reinforced composite (FRC) retainers when bonding them to teeth with and without covering the FRC bars using two different adhesive systems.

Materials and Methods:

Hundred and twenty extracted human maxillary premolars were randomly divided into eight groups (n = 15). FRC bars (4 mm length, Everstick Ortho^®, Stick Tech, Oy, Turku, Finland) were bonded to the proximal (distal) surfaces of the teeth using two different adhesives (Tetric Flow [TF, Ivoclar Vivadent, Switzerland] and resin-modified glass ionomer cement [RMGIC, ODP, Vista, CA, USA]) with and without covering with the same adhesive. Specimens were exposed to thermocycling (625 cycles per day [5–55°C, intervals: 30 s] for 8 days). The SBS test was then performed using the universal testing machine (Zwick, GMBH, Ulm, Germany). After debonding, the remaining adhesive on the teeth was recorded by the adhesive remnant index (0–3).

Results:

The lowest mean SBS (standard deviation) was found in the TF group without covering with adhesive (12.6 [2.11] MPa), and the highest bond strength was in the TF group with covering with adhesive (16.01 [1.09] MPa). Overall, the uncovered RMGIC (15.65 [3.57] MPa) provided a higher SBS compared to the uncovered TF. Covering of FRC with TF led to a significant increase in SBS (P = 0.001), but this was not true for RMGIC (P = 0.807). Thermal cycling did not significantly change the SBS values (P = 0.537). Overall, eight groups were statistically different (ANOVA test, F = 3.32, P = 0.034), but no significant differences in bond failure locations were found between the groups (Fisher's exact tests, P = 0.92).

Conclusions:

The present findings showed no significant differences between SBS of FRC bars with and without covering by RMGIC. However, when using TF, there was a significant difference in SBS measurements between covering and noncovering groups. Therefore, the use of RMGIC without covering FRC bars can be suggested, which can be validated with in vivo studies.

Evaluation of the cytotoxicity of fiber reinforced composite bonded retainers and flexible spiral wires retainers in simulated high and low cariogenic environments

OBJECTIVES

The aim of this study was to evaluate the cytotoxic effects of fiber reinforced composite bonded retainers in comparison with flexible spiral wires (FSWs) under high and low cariogenic-simulated environments using human oral fibroblasts.

MATERIALS AND METHODS

Four types of bonded retainers were evaluated: (1) reinforced with glass fibers: Interlig (Angelus), (2) reinforced with polyethylene fibers: Connect (Kerr), (3) reinforced with quartz fibers: Quartz Splint UD (RTD), and (4) FSW. Twenty specimens of each sample group were prepared with the same surface area and halved. Next, half of them were placed in a high cariogenic environment 60 min in 10% lactic acid 3 times a day and remained in Fusayama Meyer artificial saliva for the rest of the day) and the other half were placed in a low cariogenic environment 20 min in 10% lactic acid 3 times a day and remained in Fusayama Meyer artificial saliva for the rest of the day) for 1, 7 and 30 days. Cell viability was assessed by MTT assay. Data were analyzed using SPSS software (α =0.05).

RESULTS

During the 1(st) month, cytotoxicity reduced gradually. In the low cariogenic-simulated environment, the cytotoxicity of all of the groups were reported to be mild at day 30 and the difference between them was significant (P = 0.016). In the same period in the high cariogenic-simulated environment, the cytotoxicity of Connect and Quartz Splint was mild, and they had lower cytotoxicity than the other groups. Meanwhile, Interlig had moderate (52%) and FSW had severe cytotoxicity (22%) and the difference between the groups was also significant (P = 0.000).

CONCLUSIONS

FSW retainers are not recommended in those at high-risk for dental caries. However, in those at low-risk, there is no difference from the standpoint of cytotoxicity.

Failure evaluation after a 6-year retention period: a comparison between glass fiber-reinforced (GFR) and multistranded bonded retainers

OBJECTIVES

The aim of this study was to compare bond failure and breakage rates of two types of bonded lingual orthodontic retainers (GFR and .0175" multistranded stainless steel wire [MST]) after a 6-year retention period.

SUBJECTS AND METHODS

Eighty-five young adults were randomly divided into two groups: 40 subjects received 48 GFR retainers (14 maxillary and 34 mandibular retainers), and 45 subjects received 50 MST retainers (18 maxillary and 32 mandibular retainers). A Fisher's exact test was performed in order to identify significant differences in the percentage of detachment and breakage of the retainers between the groups.

RESULTS

The maxillary detachment rates were 21.42% for the GFR group and 22.22% for the MST group; the mandibular detachment rates were 11.76% for the GFR group and 15.62% for the MST group. The maxillary breakage rates were 7.14% for the GFR group and 16.66% for the MST group; the mandibular breakage rates were 8.82% for the GFR group and 15.62% for the MST group. The differences were not statistically significant.

CONCLUSION

GFR and multistranded stainless steel retainers showed similar results in terms of bond failure and breakage after 6 years of retention. The use of GFR retainers as a retention strategy should not be discouraged and could be considered a viable esthetic alternative to stainless steel wire retainers.