Fixed retention: pitfalls and complications

Three-dimensional analysis of posttreatment tooth movements despite bonded retainers: part I-upper jaw

PURPOSE

Adverse side effects of fixed retainers in terms of unwanted tooth movements have been described for both the upper and lower jaw, but data about the extent and movement patterns for the maxilla are scarce. The purpose of the present retrospective case-control study was to analyze the amount and direction of unwanted tooth movements despite upper bonded retainers as well as to analyze possible predisposing pretreatment- and treatment-related factors.

METHODS

Plaster casts of 1026 patients who completed orthodontic treatment and a subsequent retention phase of 2 years were screened for unintentional tooth movements. The study group comprised 57 patients with visually obvious tooth movements in the upper jaw, while 57 randomly selected patients without visible tooth movements served as control group. For all patients, plaster casts after debonding of multibracket appliance (T1) and after supervised retention (T2) were digitized, and superimposed digitally using a stable palatal reference area. Thereafter, translational and rotational movements were measured in all three planes of space. Pretreatment- and treatment-related factors of the study and control groups were compared by χ2 test, exact Fisher test, Mann-Whitney U test, and the T‑test for independent samples.

RESULTS

The mean translational movements ranged between 0 and 0.6 mm and the average rotational movements between 0 and 1.3°. Large individual movements up to 2.7 mm translation and 15.9° rotation were seen. A movement pattern around the Y‑ and Z‑axis with an opposite rotational peak at the canines ("upper twist effect") was identified. Compared to the control group, patients of the study group showed a significantly smaller intercanine width pretreatment. Also, study group patients presented a larger intercanine expansion and a slightly larger overjet reduction during treatment, and were more often affected by retainer bonding site detachments and wire fractures, but without reaching statistically significance.

CONCLUSION

Upper bonded retainers show a similar unwanted movement pattern ("twist effect") like the one described for mandibular retainers.

Assessment of the unwanted tooth movement associated with an extended maxillary fixed retainer (3D analysis)

BACKGROUND

Posttreatment changes after orthodontic treatment are challenging. One of the main reasons for such a phenomenon is the lack of patient compliance with removable retainers especially in the maxillary arch, due to palatal coverage, deterioration of speech, decreased masticatory efficiency, and loss of retainers. Fixed retainers have been introduced to overcome patient compliance and provide longer stable results. However, teeth still show movements when a six-unit fixed retainer is in place. Thus, in this study, an eight-unit fixed retainer was evaluated in an attempt to eliminate unwanted movements. THE AIM OF THIS RESEARCH: was to assess short-term positional changes associated with an eight-unit extended maxillary fixed retainer.

MATERIALS AND METHODS

A single-arm clinical trial was conducted to address the aim of the study. This research was approved by the institutional review board of the Faculty of Dentistry, Alexandria University (IORG:0008839, No-0479-8/2022). The registration date of this study was 5/06/2023. Twenty-eight patients (19.8 ± 4.5 years) who had finished the active orthodontic phase and started retention had an eight-unit extended maxillary fixed retainer that was bonded to the palatal surface of the maxillary incisors, canines, and the first premolars or the second premolars. Pre-retention and one-year post-retention intra-oral scans were made to produce STL files that were superimposed to determine the amount of tooth change. Additionally, analysis of digital casts and lateral cephalometric radiographs was performed.

RESULTS

Statistically significant changes in all planes and the rotation of teeth after one year of retention were found. The upper right lateral incisor exhibited the most evident change in the vertical plane, while the upper right central incisor exhibited the greatest change overall. Minimal changes in the cast measurements were observed. Lateral cephalometric measurements showed minimal changes after one year of retention, and these changes were not statistically significant except in the interincisal angle and the angle between the upper incisor and the line connecting the A-point to the pogonion.

CONCLUSION

Increasing the extension of maxillary fixed retainers did not eliminate unwanted tooth movement in the first year of retention.

Physico-Mechanical Properties and Bonding Performance of Graphene-Added Orthodontic Adhesives

This study aimed to assess the key physico-mechanical properties and bonding performance of orthodontic adhesives with graphene addition for bonding a fixed retainer. Transbond LR (3M) and Transbond LV (3M) with no graphene were set as the control groups. Graphene was added into LR and LV at concentrations of 0.01 wt%, 0.05 wt% and 0.1 wt%. The stickiness of the uncured samples (n = 5) and real-time degree of conversion (DC) of the samples (n = 3) were measured over a 24-h period using Fourier-transform infrared spectroscopy. The hardness and other mechanical parameters, including the Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT) and creep (CIT), were measured (n = 5). To measure the shear bond strength (SBS), adhesive composites were applied using a mold to bond the retainer wire to the lingual surfaces of bovine incisors (n = 10). Fracture modes subsequent to the SBS test were examined under light microscopy. Statistical analysis was conducted using ANOVA and Tukey tests (α = 0.05). In the LR groups, the LR + 0.01 showed the highest SBS (12.6 ± 2.0 MPa) and HM (539.4 ± 17.9 N/mm2), while the LV + 0.05 (7.7 ± 1.1 MPa) had the highest SBS and the LV + 0.1 had the highest HM (312.4 ± 17.8 N/mm2) among the LV groups. The most frequent failure mode observed was adhesive fracture followed by mixed fracture. No statistical difference was found between the graphene-added groups and the control groups in terms of the EIT, ηIT and CIT, except that the CIT was significantly lower in the LR + 0.01 than in the control group. Graphene addition had no significant adverse effect on the stickiness and DC of both LR and LV.

The Micromechanical Properties and Surface Roughness of Orthodontic Retainer Wires-An In Vitro Analysis

BACKGROUND

Despite the large variety of retainer wires available, no studies could be found comparing the micromechanical properties and surface roughness of different retainer wires. Such characteristics affect the survival of the fixed retainer in terms of both fracture resistance and resistance to debonding from the tooth. Therefore, the aim of the present study was to examine and compare those characteristics in popular retainer wires.

METHODS

six different popular orthodontic retainer wires were subjected to instrumental indentation based on the Oliver and Pharr method. The geometric surface structure was analysed using a non-contact profilometer.

RESULTS

stainless steel wires had a higher hardness and a higher elastic modulus compared to titanium wires and white gold chain. The titanium wire and the white gold chain showed much more roughness than other wires.

CONCLUSIONS

stainless steel wires are the most resistant, considering both the shape retention capacity and the ability to resist abrasive wear. The titanium wire showed the lowest hardness and, thus, the highest susceptibility to deformation. Bond-a-braid, Retainium and Orthoflex white gold are more resistant to fracture than other steel wires. Titanium wire and chain retainer wires have more roughness, which is a great advantage in terms of mechanical adhesion to composite materials.

Keeping the teeth in line: Exploring the necessity of bonded retainers in orthodontics: A narrative review

In most recent studies, long-term retention after orthodontic treatment has been hypothesized that may be necessary to maintain the stability of the dentition and avoid post-treatment changes. The bonded fixed retainer is characterized by its clinical effectiveness, patient acceptance, and lack of patient complaints as compared with a removable retainer. An electronic database (such as PubMed, PubMed Central, Web of Science, Science Direct, Cochrane Library, Scopus, and ResearchGate) has been collected using specific keywords. Of the 152 articles, only randomized clinical trials that investigated different types of fixed retainers or compared fixed with removable retainers were illustrated in tables and included in this review. The present review has gone some way towards enhancing our understanding of the bonded fixed retainer, types, material, bonding methods, and how to improve its the success rate, besides the importance of new technology in fixed orthodontic retention.

Blanket or tailored prescription of retainers in orthodontics: a questionnaire-based study

OBJECTIVE

To explore retainer protocols and how they are influenced by orthodontic presentation and the nature of occlusal correction.

MATERIALS AND METHODS

A prepiloted 45-item online questionnaire targeting orthodontists was developed. The questionnaire covered clinical preferences in terms of retainer type, fabrication, and follow-up during retention; the clinical indications for adjunctive surgical procedures; and the use of active designs to mitigate relapse in specific malocclusions.

RESULTS

A total of 206 responses were obtained. The majority of the respondents prescribed maxillary removable and mandibular fixed retainers, with almost half (49.1%) reviewing patients for more than 1 year primarily in person (95.1%). The majority prescribed vacuum-formed (69.6%) 1-mm-thick (44.3%) retainers. Only 37.3% were aware of the type of material used, with polyethylene terephthalate glycol copolymer, followed by polypropylene, being the most common. Hawley retainers were preferred following nonsurgical maxillary expansion and with suboptimal interdigitation. A preference for clear retainers and/or fixed retainers was found in open-bite cases and deep-bite cases. Supracrestal fiberotomy was prescribed commonly (61.1%) for rotations greater than 90°. No retainer was rarely prescribed except after the correction of an anterior crossbite.

CONCLUSIONS

Blanket prescription of orthodontic retention is common, with limited awareness of clear plastic retainer materials. Future trials evaluating the effectiveness of approaches for retainer prescription based on the presenting malocclusion would be timely.

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.

Bonded lingual retainer adhesives and discoloration : An in vitro study

PURPOSE

This in vitro study was conducted to compare the discoloration of a flowable self-adhesive composite, a highly filled composite adhesive, and a liquid polish applied highly filled composite adhesive for bonded lingual retainers.

METHODS

Thirty composite discs were fabricated and divided into three groups: group 1, flowable self-adhesive (GC Ortho Connect™ Flow [GCO], GC Orthodontics, Tokyo, Japan); group 2, highly filled composite adhesive (Transbond™ LR [TLR], 3M Unitek, Monrovia, CA, USA); and group 3, highly filled composite adhesive with liquid polish (TLR and BisCover LV™ [TLRB], BISCO Inc, Schaumburg, IL, USA). L*a*b* values were measured by spectrophotometer prior to (T0) and following (T1) immersion in coffee. T1 - T0 differences were calculated as ∆L*, ∆a*, ∆b*, and ∆E*ab values. The Shapiro-Wilk test was performed to determine whether the data were normally distributed. The values that did not fit the normal distribution were evaluated with the Kruskal-Wallis one-way analysis of variance (ANOVA), and Dunn's test was used for multiple comparisons. The level of significance was p < 0.05.

RESULTS

The difference between the TLR and TLRB groups was statistically significant for ∆E*ab (P = 0.007). ∆E*ab value of TLR group was greater than ∆E*ab value of TLRB group. The differences between the GCO and TLR groups (p = 0.001) and the TLR and TLRB groups (p = 0.010) were statistically significant for ∆a*. ∆a* values of GCO and TLRB groups were greater than ∆a* value of TLR group. The difference between the TLR and TLRB groups was statistically significant (p = 0.003) for ∆b*. ∆b* value of TLR group was greater than ∆b* value of TLRB group.

CONCLUSIONS

Using a Transbond LR polished with BisCover LV or only GC Ortho Connect Flow for lingual retainer bonding reduces coffee-induced discoloration.

The dark side of fixed retainers: Case series

This article focuses on on the presentation and management 9 adult patients who experienced complications because of their maxillary or mandibular fixed retainers 5-33 years after orthodontic treatment. Such complications include the development of an anterior crossbite, open bite, incisal cant, and twist- and x-effects. The detrimental effects on periodontal health were highlighted, especially in the mandibular canines. A range of fixed retainer types was identified, including flexible spiral wire bonded to 4 maxillary or 6 mandibular anterior teeth, rigid wire bonded to mandibular canines only and fiber-reinforced composite fixed retainer. Orthodontic retreatment was necessary in all patients using fixed appliances or clear aligners. Radiographic findings from cone-beam computed tomography or orthopantomogram before and after retreatment are presented when available. Despite the improvement of teeth position clinically, the cone-beam computed tomography scans taken directly after the completion of orthodontic retreatment did not show notable improvement with regards to root proximity to the cortical plates. The prevention of further complications was highlighted, including the use of dual retention, remote monitoring, frequent follow-up appointments and the importance of developing clear guidelines for monitoring patients in retention for treating clinicians and general dentists to promote early detection of adverse changes.

Comparison between round multi-strand wire and rectangular wire bonded retainers: a randomized clinical trial

OBJECTIVE

The primary objective was to compare round multi-strand wire and Ortho-Flex-Tech™ rectangular wire retainers in terms of gingival health. The secondary objectives were to assess plaque/calculus accumulation, and to determine the effectiveness of these retainers in maintaining tooth alignment and their failure rate.

MATERIAL AND METHODS

This single-center study was a two-arm parallel randomized clinical trial and was conducted at the Orthodontic clinics in Dental Teaching Center/Jordan University of Science and Technology. Sixty patients, with bonded retention for the mandibular anterior segment after fixed orthodontic treatment, were randomly selected. The sample comprised Caucasian patients with mild to moderate pretreatment crowding in the mandibular anterior region, Class I relationship, treated without extraction of mandibular anterior tooth. In addition, only patients presenting normal overjet and overbite after treatment were included.

INTERVENTION

One group received round multi-strand wire retainer (30 patients, average age: 19.7 ± 3.8 years), while the other group received Ortho-Flex-Tech™ retainer (30 patients; average age: 19.3 ± 3.2 years). In both groups, the retainers were bonded to all mandibular anterior teeth from canine to canine. All patients were recalled one year after bracket debonding. Randomization sequence was created using Excel 2010, with a 1:1 allocation, using random block size 4. The allocation sequence was concealed in sequentially numbered, opaque and sealed envelopes. Only participants were blinded to the type of bonded retainer used. The primary outcome was to compare the gingival condition between the two groups. The secondary outcomes were to assess plaque/calculus indices, irregularity index of the mandibular anterior teeth and retainers' failure rate. Comparisons were conducted using Mann-Whitney U test or chi-square test. Statistical significance was predetermined at the p≤ 0.05 level for all tests.

RESULTS

Complete data were collected for 46 patients (round multi-strand wire retainer group, n=24 patients; rectangular Ortho-Flex-Tech™ retainer group, n=22 patients). No significant differences were found in the gingival health parameters between the two groups (p>0.05). Ortho-Flex-Tech™ retainers maintained the alignment of mandibular anterior teeth more than multi-strand retainer (p<0.05). No significant difference was found in the failure rate between the two groups (p>0.05).

CONCLUSIONS

Gingival health parameters and failure rate were not different in both groups. However, Ortho-Flex-Tech™ retainers were more efficient to retain the mandibular incisors than the multi-strand retainers; nevertheless, the difference was not clinically significant.

Tooth loss as a result of a bonded retainer: a case report

To reduce the risk of unwanted post-treatment changes following orthodontic treatment, use of bonded retainers is gaining popularity. Despite their efficacy and popularity with patients, it has been widely reported that there are significant risks with bonded retainers if they are not maintained and monitored. This case report demonstrates how unwanted tooth movement caused by a bonded retainer can lead to catastrophic failure and ultimately, tooth loss. The importance of active and regular monitoring of bonded retainers is highlighted and recommendations are made to the wider dental community on how to monitor such retainers in clinical practice.

CAD/CAM nitinol bonded retainer versus a chairside rectangular-chain bonded retainer: A multicentre randomised controlled trial

BACKGROUND

Bonded retainers are widely used to maintain the positions of anterior teeth after orthodontic treatment. Various types of bonded retainer exist however, there is a lack of evidence to indicate which type is superior.

AIM

To compare upper and lower CAD/CAM nitinol bonded retainers (Memotain^®) with upper and lower chairside rectangular-chain bonded retainers (Ortho-FlexTech™), in terms of stability, retainer failures and patient satisfaction.

TRIAL DESIGN

Multi-centre, two-arm, parallel-group, randomised controlled clinical trial with 1:1 allocation.

SETTING

Three trial centres: University Teaching Hospital; District General Hospital; and Specialist Orthodontic Practice. All treatment was provided free as part of a state-funded healthcare system.

MATERIALS AND METHODS

A total of 68 patients were randomly allocated to receive either upper and lower Memotain^® bonded retainers or upper and lower Ortho-FlexTech™ bonded retainers. Ten trained operators placed and reviewed the bonded retainers. Measurements were carried out on study models taken at debond and after six months. Patient satisfaction questionnaires were completed at six months following debond.

RESULTS

The trial was terminated due to the high number of failures (50%) of the upper Memotain® retainers within six months. Memotain^® retainers were three times more likely to fail (unadjusted hazard ratio = 2.82, 95% confidence interval = 1.00-7.99) than Ortho-FlexTech™ retainers at six months in the upper arch. Patients were satisfied with both types of retainer.

LIMITATIONS

Early termination of the trial means that the a priori sample size was not reached, so outcomes should be interpreted with caution.

CONCLUSION

The trial was terminated early due to the high failure rate of upper Memotain^® bonded retainers. They had a higher risk of failure in the maxillary arch when compared to upper Ortho-FlexTech™ bonded retainers after six months.

Survival of conventionally bonded mandibular retainers with or without enamel sandblasting in orthodontic patients over a 12-month period. A single-centre, split-mouth randomized clinical trial

BACKGROUND

The aim of this trial was to assess the effect of enamel sandblasting in addition to the acid-etch technique in reducing first-time failures of fixed mandibular retainers placed over a 12-month period.

MATERIALS AND METHODS

Ethical approval was obtained. Participants were recruited in a single private practice. The primary outcome of this study was any first-time failure of the mandibular fixed retainer assessed at three timepoints over a 12-month period. Three consecutive teeth either on the left or right side (from lower canine-lower central incisor) were randomly allocated to the intervention (sandblasting) and the control (non-sandblasted). Randomization was performed using a centralized randomization service. The patients were randomized in blocks of four and eight with allocation concealment secured by contacting the sequence generator for group assignment. Blinding of either the patient or clinicians was not possible at time of placement of the mandibular retainer.

RESULTS

One hundred and ninety-seven participants were randomized to receive enamel sandblasting (intervention) and non-sandblasting (control) in the region of the six anterior mandibular teeth in a split-mouth fashion. Participants were recruited between December 2018 to October 2020. The data for all participants were analysed resulting in 394 observations. Overall, the risk of first-time failure was 11.4%. No difference in first-time failures was observed between the intervention (sandblasting) and control (non-sandblasting) groups [hazard ratio (HR), 1.05; 95% confidence interval (CI), 0.59, 1.88, P = 0.88]. Males had a higher instant probability of first-time failures (HR, 3.18; 95% CI, 1.65-6.14; P < 0.01). Participants with a fair level of co-operation had a lower instant probability of first-time failures (HR, 0.37; 95% CI, 0.16-0.86; P = 0.02). There were no harms reported to either the participant or their dentition.

CONCLUSIONS

No difference in the first-time failures of mandibular bonded retainers placed with conventional etch-bond technique with or without enamel sandblasting was observed. The overall risk of first-time failure was 11.4%.

REGISTRATION

This trial was not registered prior to trial commencement.

Orthodontic Fixed Retainer and Unwanted Movements of Lower Anterior Teeth: A Case Report

The use of fixed retainers at the end of an orthodontic treatment has become a standard practice. Nonetheless, orthodontic relapse can still occur, requiring retreatment in the most severe cases. This case report describes a patient with a mandibular canine to canine fixed retainer presenting uncontrolled torque on all lower anterior teeth, probably due to tongue thrust and/or activation of the wire. Multibracket orthodontic treatment was performed, and an orthodontic lingual sectional was used to control (reposition) the root movement of the lower right cuspid. This case highlights the need for clinicians and patients to be aware of the potential problems associated with bonded retainers. In addition, patients with an orthodontic fixed retainer need regular short-term observation by an orthodontist in order to detect any adverse movements and long-term control by a general dentist.

Relapse and inadvertent tooth movement post orthodontic treatment in individuals with fixed retainers: A review

Orthodontists must fully inform patients about the implications of orthodontic treatment and the subsequent need for retention. This review provides an update on relapse, unwanted movements and different factors that can cause loss of stability following orthodontic treatment. Since it is difficult to predict which patients will present some degree of loss of stability after treatment, it is important that they be treated as if they have a high potential for relapse. The present review included a bibliographic search in the main sources of scientific review including Medline via PubMed, Scopus and the Cochrane library. The search strategy was carried out until May 5, 2022. Only 34 studies fulfilling the selection criteria. Our results showed that maintaining teeth in the correct position following orthodontic treatment is a great challenge for orthodontists. The etiology of relapse is complex and not yet clearly established. Its origin is attributed to factors such as the time of gingival and periodontal tissue reorganization and changes produced by growth, compromising the stability of the results achieved with orthodontic treatment. The retention phase is necessary after orthodontic treatment to avoid relapse or loss of the occlusion results obtained. However, fixed retainers may induce unwanted tooth movement that may occur despite these retainers being attached and intact. There is currently no consensus among orthodontists regarding the ideal type of wire for fixed containment. We concluded that post-orthodontic treatment relapse is the result of a regression towards the original malocclusion. However, changes in the position of the teeth can also occur, which are considered as unwanted movements and have a multifactorial origin.

“Wire Syndrome” Following Bonded Orthodontic Retainers: A Systematic Review of the Literature

(1) Background and objective: Tooth movements described as unexplained, aberrant, unexpected, unwanted, or undesirable can occur in the presence of an intact orthodontic retention wire, without detachment or fracture. This iatrogenic phenomenon, known little or not by many practitioners, responsible for significant dental and periodontal complications, both functional and aesthetic, is called “Wire Syndrome” (WS). It is therefore considered an undesirable event of bonded orthodontic retainers, which must be differentiated from an orthodontic relapse. The objective was to perform, for the first time, a systematic review of the literature in order to define the prevalence of WS and to study its associated clinical characteristics. (2) Methods: A systematic review of the literature was performed following the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and recommendations using an electronic search strategy on four databases complemented by a manual search. All the prospective and retrospective clinical studies, including case reports and series, written in English or French, clearly mentioning the description, detection, or management of WS were included. Three independent blinding review authors were involved in study selection, data extraction, and bias assessment using the Mixed Methods Appraisal Tool (MMAT). (3) Results: Of 1891 results, 20 articles published between 2007 and 2021 fulfilled the inclusion criteria, with a globally high risk of bias since 16 articles were case report/series. The analysis of each article allowed the highlighting of WS through 13 categories, as follows: prevalence, apparition delay, patient characteristics, arch and tooth involved, families of movements, dental and periodontal consequences, type of wire, risk factors, etiologies, treatment, and preventive approach. (4) Conclusion: This systematic review of the literature elaborated a synthesis on WS, allowing general practitioners, periodontists, and orthodontists to understand this adverse event, to facilitate the diagnostic approach, and to underline preventive measures against WS. This review was registered in the International Prospective Register of Systematic Reviews (PROSPERO; number CRD42021269297).

Orthodontic treatment of an adolescent with cerebral palsy - A case report

Cerebral palsy is a common cause of chronic motor neuron impairment. A constant prevalence of 2 to 3/1000 births in industrialized countries has been described. This case report describes the treatment of a 9 year old boy presenting this form of motor neuron impairment and class II malocclusion with an overjet of 14 mm, hyperdivergent growth pattern and various habits. Orthodontic treatment consisted mainly of a two-phase treatment. The first phase was treated with removable appliances and followed by a phase with fixed appliances. Treatment duration with removable appliances was 4 years and 5 months and for the fixed appliance phase, 1 year and 7 months. A class I occlusion could be achieved in this case by removable and fixed orthodontic appliances combined with adjunctive treatment for the hypotonic orofacial musculature.

Orthodontic retention protocols: an evidence-based overview

In view of the diversity of orthodontic presentations, a single optimal retention protocol does not exist, with approaches tailored based on pre-treatment characteristics, treatment-induced changes and general patient characteristics. However, orthodontic practitioners should be responsive to the best available evidence to formulate optimal retention protocols in terms of appliance type, design and regimen, in particular. Based on a comprehensive search strategy, we discuss fundamental aspects concerning orthodontic retention of particular interest both to orthodontists and general dentists. These include stability and periodontal outcomes, cost-effectiveness, patient experiences, survival and failure rates of retainers, and the duration of retention.