Risk factors for orthodontic fixed retention failure: A retrospective controlled study

Objective

: To investigate the potential correlation between fixed orthodontic retention failure and several patient- and treatment-related factors.

Methods

: Patients finishing treatment with fixed appliances between 2016 and 2017 were retrospectively included in this study. Those not showing fixed retention failure were considered as control group. Patients with fixed retention failure were considered as the experimental group. Additionally, patients with failure of fixed retainers in the period of June 2019 to March 2021 were prospectively identified and included in the experimental group. The location of the first retention failure, sex, pretreatment dental occlusion, facial characteristics, posttreatment dental occlusion, treatment approach and presence of oral habits were compared between groups before and after treatment separately by using a Fisher exact test and a Mann-Whitney U test.

Results

: 206 patients with fixed retention failure were included, 169 in the mandibular and 74 in the maxillary jaws. Significant correlations were observed between retention failure in the mandibular jaws and mandibular arch length discrepancy (P = 0.010), post-treatment growth pattern (P = 0.041), nail biting (P < 0.001) and abnormal tongue function (P = 0.002). Retention failure in the maxillary jaws was more frequent in patients with IPR in the mandibular jaws (P = 0.005) and abnormal tongue function (P = 0.021).

Conclusions

: This study suggests a correlation between fixed retention failure and parafunctional habits, such as nail biting and abnormal tongue function. Prospective studies with larger study populations could further confirm these results.

Preclinical in vitro study of streptococcus mutans accumulation in three fixed retainer designs: Microbiological assay

The use of fixed retainers in the lower arch is frequent; however, its presence increases the accumulation of biofilm and dental calculus. The objective of this research was to evaluate, in vitro, the accumulation of Streptococcus mutans (S. mutans) in 3 designs of fixed retainers. Nine models were reproduced in heat-cured acrylic resin and divided into groups: straight retainer (SR), retainer with vertical strap (RVS), retainer with horizontal strap (RHS). The accumulation of S. mutans was assessed using the MTT assay (3-4,5-dimethyl-thiazol-2-yl-2,5-diphenyltetrazolium bromide) and then measured using an automated reader. The RHS group showed less biofilm accumulation compared to the other groups (p<0.05). The distance between the tooth surface and the retainer showed a strong negative correlation with biofilm accumulation (rs=-0.79, p=0.00037). The RHS showed significantly less accumulation of S. mutans due to the distance between the retainer and the tooth surface. This research provides relevant data for a future randomized clinical trial.

Antimicrobial efficacy, optical properties and flexural strength following antimicrobial photodynamic therapy over vacuum-formed orthodontic retainers

BACKGROUND AND AIMS

Vacuum-formed retainers (VFRs) are widely used in dental practices because of their superior esthetics. However, simultaneous maintenance of their hygiene, mechanical and optical properties is challenging. This study aimed to evaluate and compare the disinfection efficacy of antimicrobial photodynamic therapy (aPDT), chlorhexidine (CHX), sodium hypochlorite (NaOCl) and water over VFRs specimens, along with their effect on flexural strength and color stability.

MATERIALS AND METHODS

Fabricated VFRs of thicknesses 1 mm and 2 mm were contaminated with S. mutans and C. albicans. Brain Heart Infusion agar was used to seed Streptococcus Mutans whereas Candida Albicans was seeded in Sabourand Dextrose Agar. The contaminated retainers were divided into four groups and decontaminated using four different treatment protocols: aPDT, CHX, NaOCl and water, with 10 specimens per group. Microbial viability following decontamination, was assayed using MTT. To assess the color stability, pre and post decontamination color difference of 10 specimens was recorded using a spectrophotometer by blinding technique. The flexural strength of 10 specimens was measured using a universal testing machine by a standardized 3-point flexural strength (FS) test.

RESULT

aPDT showed the highest reduction in the viability of S. mutans (28%) and C. albicans (20%) species in 1 mm thickness group while the second highest reduction following disinfection with CHX (40%) in followed by NaOCl disinfection (50%). On comparison between 1 mm and 2 mm, a statistically significant difference was noted for S. mutans in aPDT (p = 0.033) and NaOCl (p = 0.028) groups, and for C. albicans, a significant difference was noted within NaOCl (p = 0.001) and CHX (p = 0.043) groups. For FS, a statistically significant difference (p < 0.05) was observed between aPDT and the rest of the groups, whereas there was no statistically significant difference in the flexural strength between the CHX, NaOCl and water groups (p > 0.05) in both 1 mm and 2 mm specimens. Between 1 mm and 2 mm specimens, no statistically significant difference in the mean color difference was noted after any disinfection protocol (p > 0.05).

CONCLUSION

Antimicrobial photodynamic therapy showed a remarkable reduction in candidal and bacterial viability over VFRs. aPDT treated VFR specimens showed increased flexural strength and a higher color difference post treatment compared to other reagents.

Influence of a bleaching agent on surface and mechanical properties of orthodontic thermoplastic retainer materials : An in vitro study

OBJECTIVE

To investigate the effect of a tooth whitening agent on surface roughness, surface hardness, and force delivery properties of polyethylene terephthalate glycol (PETG) thermoplastic retainer materials of two different thicknesses.

METHODS

PETG sheets (1 mm and 1.5 mm) were thermoformed over a 30 × 60 × 10 mm³ rectangular stone model. Surface hardness, surface roughness, and results of a three-point bending test were evaluated before and after treatment (5 h daily for 14 days) with a 15% carbamide peroxide home bleaching agent. Data were analyzed using an independent sample t‑test.

RESULTS

Exposure of PETG specimens to the bleaching agent for 14 days significantly reduced surface hardness and increased surface roughness of samples of both thicknesses. The magnitude of force at different deflection points decreased significantly in the 1.5 mm thickness specimens treated with the bleaching agent, but no significant change was observed in the specimens with 1 mm thickness.

CONCLUSION

Use of a home bleaching agent could have adverse effects on surface roughness and hardness of PETG materials leading to reduced survival time of thermoplastic orthodontic retainers.

[Magnets in orthodontics : which indications, which effects ? A review of the literature]

The first publication on the use of magnets in dentistry for stabilizing prosthetics on implants dates back to 1953. Clinical development in orthodontics, without having experienced a real boom, has increased over the past ten years, in parallel with the improvement of the device. The objective of this review of the literature is to synthesize clinical applications and reported iatrogenic effects. A systematic review of the international literature from the Pubmed and Cochrane databases from 1999 to July 2018 was conducted which resulted in 36 articles. The factors studied are the indications and contraindications, the means or procedure, as well as the iatrogenic effects. Original cases are presented. The correction of infraclusions is the main indication, followed by the correction of anteroposterior malocclusions and then the correction of over-erupted teeth. Traction of an impacted teeth and diastema closure have not been found in recent publications probably because of the low benefit-risk ratio. The future no longer seems to be buried magnets or left in the long term in the mouth considering there seems to be concerns in terms of toxicity (or even the risk in terms of vital prognosis). The magnets could offer interesting perspectives to manage the current limits of the aligners, the movements of anterior egression, rotation and previous torque being still problematic...

Approaches of Turkish Dentists in Cases of Orthodontic Lingual Retainer Failures

OBJECTIVE

This study aimed to investigate the approaches of Turkish dentists in cases of orthodontic lingual retainer failures.

METHODS

A self-administered questionnaire was used to quantify dentists' approaches to lingual retainer failures. The first part of the study investigated the demographic characteristics. In the second part, dentists' approaches to cases of failed retainers were assessed. The third part had questions related to the type of retainers bonded solely to the canines or to all the 6 anterior teeth. Descriptive statistics were done with Pearson's χ2 test, and Mann-Whitney U test was used.

RESULTS

A total of 320 Turkish dentists participated in the survey. Experienced and public dentists preferred to advise the patients whose retainers had failed to contact their orthodontist more frequently (p<0.05). Regarding their approach to patients who requested removal of the bonded retainer, inexperienced dentists more frequently preferred to refer the patients to an orthodontist (p<0.05). With regard to factors affecting the choice to remove a bonded retainer, the most and the least importance were attributed to the orthodontist's opinion and the patient's demand, respectively.

CONCLUSION

Turkish dentists prefer referring their patients to orthodontists rather than performing procedures in cases of failure associated with bonded retainers. Different demographic characteristics seem to have an impact on these approaches.

The effects of fixed and removable orthodontic retainers: a systematic review

OBJECTIVE

In the view of the widespread acceptance of indefinite retention, it is important to determine the effects of fixed and removable orthodontic retainers on periodontal health, survival and failure rates of retainers, cost-effectiveness, and impact of orthodontic retainers on patient-reported outcomes.

METHODS

A comprehensive literature search was undertaken based on a defined electronic and gray literature search strategy (

PROSPERO

CRD42015029169). The following databases were searched (up to October 2015); MEDLINE via OVID, PubMed, the Cochrane Central Register of Controlled Trials, LILACS, BBO, ClinicalTrials.gov, the National Research Register, and ProQuest Dissertation and Thesis database. Randomized and non-randomized controlled clinical trials, prospective cohort studies, and case series (minimum sample size of 20) with minimum follow-up periods of 6 months reporting periodontal health, survival and failure rates of retainers, cost-effectiveness, and impact of orthodontic retainers on patient-reported outcomes were identified. The Cochrane Collaboration's Risk of Bias tool and Newcastle-Ottawa Scale were used to assess the quality of included trials.

RESULTS

Twenty-four studies were identified, 18 randomized controlled trials and 6 prospective cohort studies. Of these, only 16 were deemed to be of high quality. Meta-analysis was unfeasible due to considerable clinical heterogeneity and variations in outcome measures. The mean failure risk for mandibular stainless steel fixed retainers bonded from canine to canine was 0.29 (95 % confidence interval [CI] 0.26, 0.33) and for those bonded to canines only was 0.25 (95 % CI: 0.16, 0.33). A meta-regression suggested that failure of fixed stainless steel mandibular retainers was not directly related to the period elapsed since placement (P = 0.938).

CONCLUSION

Further well-designed prospective studies are needed to elucidate the benefits and potential harms associated with orthodontic retainers.

Bonded orthodontic retainer and fixed partial denture made with fiber reinforced composite resin

Retention is the phase of orthodontic treatment which maintains teeth in their orthodontically corrected positions, following the cessation of active orthodontic tooth movement. Development of resin-impregnated, fiber-reinforced composite materials has provided the potential to develop new approaches for stabilizing teeth and replacing teeth conservatively. This case report describes the rehabilitation of a patient with orthodontic and prosthetic problems. The long-term behavior of glass fibers splint must be evaluated in clinical studies.