Failure Rates of Orthodontic Fixed Lingual Retainers bonded with Two Flowable Light-cured Adhesives: A Comparative Prospective Clinical Trial

Failure frequency of fixed mandibular retainers after pre-treatment of the enamel surface with pumice versus sandblasting-a randomized controlled trial

BACKGROUND/OBJECTIVES

To compare retainer survival, periodontal health, and caries implications of fixed lower retainers bonded after pre-treatment of the enamel surface with either pumice or sandblasting.

TRIAL DESIGN

Two-arm parallel-group, two-center randomized controlled clinical trial.

METHODS

One hundred sixty patients (101 females, 59 males, mean age: 17.9) requiring mandibular retainers were consecutively recruited. Patients were randomly allocated to have pre-treatment of the enamel surface with either pumice (n = 80) or sandblasting (n = 80). The primary outcome was retainer survival at 3 (T1) and 12 months (T2) control. Secondary outcomes were carious lesions and periodontal health: plaque index (PI), gingival index (GI), calculus index (CI), and probing depth (PD). The randomization sequence was generated using an online randomization and allocation concealment was secured by contacting the sequence generator for treatment assignment. Blinding was not possible at T0 due to the nature of the intervention. Statistical analyses were carried out using the t-test, Fisher's exact test, repeated measure analysis of variance, and log rank test.

RESULTS

Overall, the risk of bonding failure at T1 was 6.7 per cent and at T2 6.9 per cent. There were no statistically significant differences in failure rate between the two groups, neither at T1 (P = 1.000) nor at T2 (P = 0.360). No statistically significant differences were found for the intercanine periodontal indices GI, PI, CI, PD, and caries between the two groups at T0 and T1. At T2, significantly more gingivitis and plaque were seen in the sandblasting group (P = 0.05 and P = 0.047, respectively) compared with the pumice group. Calculus increased during the follow-up period in both groups (P ≤ 0.001) as well as plaque levels (P ≤ 0.001 and P = 0.025, respectively). No harm was reported.

CONCLUSIONS

Enamel sandblasting prior to bonding mandibular retainers is not better at preventing bonding failure.

REGISTRATION

275767 (https://www.researchweb.org/is/sverige).

Universal Adhesive for Fixed Retainer Bonding: In Vitro Evaluation and Randomized Clinical Trial

This study aims to assess the efficacy of a universal adhesive (Scotchbond Universal, 3M ESPE) (SB) in total-etch mode, compared to a traditional orthodontic primer (Transbond XT Primer, 3M ESPE) (XT Primer), to perform bonding of orthodontic fixed retainers along with the Transbond XT Light Cure Adhesive Paste (3M ESPE). For the in vitro study, a round section wire (Ortosmail Krugg) was bonded using XT Primer for 20 bovine incisors (Group 1) and SB for other 20 (Group 2). Samples were debonded in a universal testing machine applying a tangential force to specimens (crosshead speed of 1 millimeter per minute). Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. For the in vivo study, 100 patients needing upper and lower canine-to-canine fixed retainers after orthodontic treatment were randomly assigned to two groups of 50 participants each, i.e., group 1 (retainer bonding with XT Primer) and group 2 (retainer bonding with SB). Over two years, examinations were carried out monthly, and detachments were registered by considering the teeth and arches affected. In vitro, no statistically significant differences in SBS and ARI scores were demonstrated between the two groups, both showing a mean bond strength of about 12 MPa and major frequency of ARI "2" (>50% remnant adhesive on the enamel). Conversely, a significantly lower failure rate over 2 years was assessed clinically for group 2 in both arches. Independently of the adhesive and arch, incisors reported a significantly higher failure rate than canines. Scotchbond Universal used in total-etch mode could be a valid alternative to the traditional orthodontic Transbond XT Primer.

Antibacterial activity and debonding force of different lingual retainers bonded with conventional composite and nanoparticle containing composite: An in vitro study

BACKGROUND

To evaluate the antibacterial activity and debonding force of retainers bonded with conventional and nanoparticle (TiO₂) containing composite.

METHODOLOGY

Antibacterial activity was tested against Streptococcus mutans and Lactobacillus acidophilus using disk agar diffusion, biofilm inhibition, and eluted components tests. For the eluted components test, colony counts of bacteria were tested on 0, 3, and 30 days. Three different retainers were bonded to the lingual surface of extracted lower incisors using conventional and 1% TiO₂ composite. Samples were divided as follows: Group 1: 1a, stainless steel retainer (Bond-a-Braid) with conventional composite, and 1b, stainless steel retainer with nanoparticle composite; Group 2: 2a, titanium retainer with conventional composite, and 2b, titanium retainer with nanoparticle composite; Group 3: 3a, fiber-reinforced retainer (Interlig) with conventional composite, and 3b, fiber-reinforced retainer with nanoparticle composite. The Instron stereomicroscope was used to test debonding force and failure sites respectively.

RESULTS

In the disk agar diffusion test, TiO₂ composite has shown more inhibition zones. Biofilm inhibition test showed a significant decrease in colony counts of both organisms in the TiO₂ group. The eluted component test showed a significant decrease in colony counts from day 0 to day 30 in the TiO₂ group compared with the control group. The highest debonding force was observed in stainless steel retainers with conventional composite, and lowest in fiber-reinforced composite retainers with TiO2 composite, with no significant difference in Adhesive Remnant Index scores.

CONCLUSION

The TiO₂ composite group showed greater antibacterial activity without compromising the bond strength, which was statistically significant. Compared with other groups, stainless steel wires bonded with conventional composite showed the highest debonding force.