Many studies on removable retainers have focused on retention efficacy and characteristics. However, studies on plaque accumulation, periodontal health, breakages, and patient compliance are still lacking. Thus, in this study, we aimed at evaluating these parameters in 2 groups of young patients wearing Essix or Hawley retainers for a 6-month period.
Seventy subjects were included. Periodontal health was investigated by measuring the plaque, gingival, calculus, and bleeding on probing indexes. Evaluations were performed at 1, 3, and 6 months of wearing. Accumulation of plaque on the retainers was also evaluated. Furthermore, compliance on wearing retainers and breakage data were collected by specific questionnaires.
Subjects wearing Essix retainers had significantly higher levels of plaque, gingival, and calculus indexes and increased percentages of bleeding sites, compared with subjects wearing Hawley retainers. The Essix group also had increased accumulations of plaque and calculus on the retainers. Nonetheless, subjects of the Essix group had better overall experiences, self-perceptions, and comfort compared with those of the Hawley group. Essix retainers had higher incidences of little and serious breakages compared with Hawley retainers.
Our results suggest that Essix retainers are well accepted by patients for their esthetic and oral comfort characteristics. However, Essix retainers may cause greater accumulations of plaque on both teeth and retainers, presumably because of inhibition of the cleaning effect of saliva caused by the thermoplastic material or the reduced opportunity for good hygiene on the retainer.
Subjects wearing Essix retainers had higher levels of plaque and gingival indexes.
Subjects wearing Essix retainers had increased percentages of bleeding sites.
Essix retainers had increased accumulations of plaque and calculus.
Subjects wearing Essix retainers had better experience, self-perception, and comfort.
The Essix group had higher incidences of little and serious breakages.
Removable or fixed retainers are widely used after an orthodontic treatment to maintain teeth in corrected positions and prevent relapse. Relapse is a major concern since teeth have the tendency to move back toward their original positions because of periodontal, gingival, occlusal, and growth-related factors.
Long-term studies have shown that relapse occurs in approximately 70% of patients. Thus, the successive phase of retention after orthodontic treatment is crucial and is considered by some authors an essential part of active orthodontic treatment.
The retention phase may last a year or longer, making the use of retainers particularly important during the first year after the orthodontic treatment. Retainers can be fixed or removable. Each kind has advantages and disadvantages. Fixed retainers are effective and do not need the patient’s cooperation, but they have been criticized for their potential to compromise the periodontal status, due to the accumulation of plaque and calculus on the retainer. Thus, removable retainers have become more common for a number of reasons, including lower costs, better esthetics, and less time consumed in the laboratory, and they can be removed from the mouth and cleaned by the patient.
Nonetheless, some important issues have emerged. First, removable retainers require the patient’s cooperation and discipline to follow the instructions, especially during the first year after the orthodontic treatment. Patients need to be extremely motivated, and their compliance in wearing the retainers is crucial. Patient cooperation, however, may be doubtful, and some authors have introduced microsensors during the period of wearing.
Another issue is related to oral hygiene during wearing. To reduce the risk of relapse, retainers must be worn for a long period. Different authors have recommended full-time (nearly 24 hours per day) or part-time use (night), or a combination of these. The prolonged contact of the appliance with tooth surfaces, especially during the first 3 months, might promote plaque accumulation, enamel demineralization, and caries because of the decreased cleaning effects of saliva and tongue. This happens particularly at night, when there is a reduction in the activity of saliva, even if the device is properly cleaned. This risk is also related to the retainer design, the surface roughness, and the physical properties of the material. Therefore, the choice of retainer is important because different designs or materials can cause accumulation of bacterial plaque on the device.
Among removable retainers, the most used is the Hawley retainer. Another common type is the Essix retainer, which is a vacuum-formed thermoplastic retainer, manufactured with polypropylene or polyvinylchloride material. It generally fits over the entire arch of teeth, covering their chewing surfaces, and is esthetic because of its transparency.
Many studies have focused on the efficacy, retention, and cleaning characteristics of these retainers. However, other factors may influence oral health status and the outcome of the treatment. Oral hygiene during wearing is an important issue, since the presence of the device in the oral cavity changes the oral environment and alters the microbiota. The biofilm formation may affect patients’ oral and general health. It has been demonstrated that patients who used Essix retainers were more susceptible to caries because the retainer prevented salivary flow over the tooth surfaces and provided a protective cover for bacteria. Positioning of the retainers in the arches may also influence oral status. For example, it has been shown that plaque and calculus are more prone to accumulate in the mandible, compared with the maxilla.
These studies indicate that data on plaque accumulation, periodontal health, positioning of the retainer (maxillary or mandibular arch), technical complications, and patient compliance while wearing these 2 types of removable retainers may be relevant.
Thus, in this study, we aimed to evaluate these parameters in 2 groups of young patients wearing Essix or Hawley retainers for a 6-month period. Periodontal health was investigated by measuring various parameters in accordance with other studies. These parameters included the Loe plaque index (PI), Loe and Silness gingival index (GI), Greene and Vermillion calculus index (CI), and bleeding on probing index (BOP). Evaluations were performed at 1, 3, and 6 months of wearing on subjects having Essix retainers on their maxillary teeth and Hawley retainers on their mandibular teeth at the same time and vice versa. Accumulations of plaque on the retainers were also evaluated. Compliance on wearing retainers and breakage data were collected in specific questionnaires.
Material and methods
Seventy subjects, 35 girls and 35 boys (ages, 13-17 years) who completed fixed orthodontic treatment, were enrolled in this prospective cohort study. Demographic characteristics are reported in Table I . Written informed consent signed by the parent or legal guardian was obtained before the study.
|Total patients (n)||70|
|Age (y)||14.87 ± 1.37|
|Sex||35 M/35 F|
|Group A (n)||35|
|Age (y)||14.83 ± 1.36|
|Sex||17 M/18 F|
|Group B (n)||35|
|Age (y)||14.79 ± 1.40|
|Sex||18 M/17 F|
Exclusion criteria were the following: patients over 18 years of age, or having craniofacial or dentofacial syndromes, diabetes, habit of smoking, or poor dental hygiene during the observation period.
Two types of removable retainers were used in this study.
The Essix (copolyester plastic, 0.8 mm thick; Erkodent, Pfatzgrafenweiler, Germany) is a vacuum-formed retainer made of polypropylene or polyvinylchloride material produced with the thermoforming technique.
The Hawley retainer consists of a metal wire that typically surrounds the 6 anterior teeth and keeps them in place. Hawley retainers (DDS Dental Lab, Tampa, Florida) were manufactured with self-curing resin (monomer-based on methyl methacrylate; Vertex-Dental B.V., The Netherlands), Stainless Steel Adams clasps, and fitted with a labial bow of acrylic material to improve tooth contact from mandibular left second premolar to,right second premolar with adjustment loops.
After the fixed orthodontic treatment and debonding, all patients had professional hygiene treatment and were randomly divided into 2 groups.
In group A, an Essix retainer for the maxillary teeth and a Hawley retainer for the mandibular teeth were given to each patient. In group B, a Hawley retainer for the maxillary teeth and an Essix retainer for the mandibular teeth ( Table I ) were given.
The subjects were instructed to wear the retainers full time for the first 3 months after debonding. Full time was defined as wearing the retainer all the time, except for eating, toothbrushing, and contact sports.
After the first 3 months, the subjects were instructed to wear the retainers only at night for the next 3 months.
The subjects were also instructed to clean their teeth and retainers 3 times a day after meals for 30 seconds, using bristles of average hardness with the dentifrice, to enhance the brushing effect.
Disinfecting mouth rinsing solutions were avoided so as not to influence the measurements.
The patients were evaluated at 1 month, 3 months, and 6 months after the delivery of the retainers. The evaluation included measurements of periodontal health and administration of questionnaires to evaluate their compliance while wearing the retainers. All evaluations were performed by 2 dentists (L.M., E.R.) and an orthodontist (A.B.) previously trained and calibrated with a periodontist.
To evaluate periodontal health, we examined 14 teeth in each dental arch (all teeth except third molars) at 1, 3, and 6 months after the delivery of the retainers. Each tooth was examined according to the protocol of Silness and Löe : buccal, lingual, mesial, and distal surfaces.
The following indexes were recorded.
The PI index for the assessment of plaque according to the following scale: 0, no plaque; 1, a film of plaque adhering to the free gingival margin of the tooth that cannot be seen with the naked eye but only by using disclosing solution or a standard blunt probe; 2, moderate accumulation of plaque on the gingival area of the tooth that can be seen with the naked eye; and 3, abundance of plaque on the gingival margin, tooth surface, and interdental area. For each patient, a score (total score/number of surfaces examined) for both arches was obtained.
The GI index for the assessment of the gingival condition and to record qualitative changes in the gingiva according to the following scale: 0, no inflammation; 1, mild inflammation, slight change in color, slight edema, no bleeding on probing; 2, moderate inflammation, glazing, redness, or bleeding on probing; and 3, severe inflammation, marked redness and hypertrophy, ulceration, and tendency to spontaneous bleeding. Bleeding was assessed by probing gently along the wall of soft tissue of the gingival sulcus using a standard blunt probe with 2-mm increments.
The CI index for the assessment of calculus on 2 tooth surfaces (lingual and buccal) according to the following scale: 0, no calculus; 1, supragingival calculus covering one third of the tooth surface; 2, supragingival calculus covering between one third and two thirds of the tooth surface or discontinuous subgingival calculus presence; and 3, supragingival calculus covering more than two thirds of the tooth surface or continuous subgingival calculus presence.
The BOP test was used to diagnose gingival inflammation. A Florida probe was inserted into the gingival crevice along the gingival sulcus with pressure of 25 g measured with a computerized periodontal probing system. Bleeding was registered after 15 seconds and recorded as yes or no. Data for each patient were expressed as percentages of bleeding sites (number of bleeding sites/total number of sites examined × 100).
Plaque and calculus accumulation on or in the retainer. The surface of the retainer was divided into 10 zones to simplify the denture hygiene index used for dentures. After the retainer was washed with water and gently air dried, every zone was checked for plaque accumulation by 2 dentists (visual evaluation after staining with erythrosine) equipped with a 330-mm, 2.5-binocular Galileo frame loupe magnifier glasses (Univet-Optical Technology, Rezzato, Brescia, Italy) calibrated before the study. Plaque accumulation was scored with the 4-stage evaluation scheme used by Gohlke-Wehrße et al : 1, plaque free; 2, plaque shown by staining; 3, visible soft removable plaque; and 4, calculus accumulation.
The compliance of patients wearing Essix and Hawley retainers was evaluated in questionnaires. The questionnaires and answers are reported in Tables II and III . Data on wearing retention according to the instructions ( Table II ) were recorded from 35 boys and 35 girls. In Table III , data on overall experience, comfort, and self-perception during wearing the retainers are reported. These data were collected because of the importance of self and social perceptions of orthodontic retainer design and appearance among young patients.
|Retainer||Sex||No time||10%||Less than 50%||More than 50 %||All the time|
|Chi-square P value||0.7385|
|Absolutely negative||Neutral||Positive||Absolutely positive|
|Chi-square P value||0.0036|
|Chi-square P value||<0.0001|
|Chi-square P value||0.0047|
Data on breakages of retainers are reported in Table IV . We registered the number of little and serious breakages of the retainers after 1, 3, and 6 months of wearing. Little breakage was defined as a breakage of the retainer that did not compromise tooth retention. Serious breakage was a severe breakage that did not allow tooth retention by the retainer.
|Time||1 month||3 months||6 months|
|Breakage||None||Little breakage||Serious breakage||None||Little breakage||Serious breakage||None||Little breakage||Serious breakage|
|Chi-square P value||0.0008||<0.0001||<0.0001|