The clinical fabrication of polyolefin mouthguards formed over fixed orthodontic appliances
Article Category: research-article
Online veröffentlicht: 13. Dez. 2021
Seitenbereich: 362 - 366
DOI: https://doi.org/10.21307/aoj-2021.042
© 2021 Bill Westerman., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.
It is widely accepted that mouthguards are a valuable safeguard for reducing injuries to oral tissues during contact sports.1,2 Over time, mouthguard development and improvement has seen the original primitive rubber blocks change to the current multi-laminar, hard-inclusions, air-inclusions, multi-colour, custom fitted appliances. The increased complexity of fabrication of the newer mouthguards has been accompanied by increases in the cost to the consumer and the clinician. The costs include the time taken for fabrication as well as the cost of the equipment necessary for manufacture. The costs of impressions and models are included in the costs associated with custom-made mouthguards.
A polyolefin of polypropylene and polyethylene (MG21 Molten Corporation, Tokyo, Japan) provides a new material for mouthguard fabrication3. The material is an alternative to ethylene vinyl acetate (EVA) which has been universally used for mouthguard manufacture for more than thirty years. Polyolefin is used extensively in food wrapping and packaging as well as the manufacture of chewable baby toys. The advantage of the material is that it is a thermoplastic compound that can be heated in a microwave oven. Heating produces plasticity which is necessary for moulding around intraoral structures while cooling stabilises the polyolefin into an elastic phase. Although it appears counter-intuitive, the mouthguard blank is cooled before insertion into the mouth for moulding. The product has similar qualities to those outlined on the Australian Dental Association website and is cost effective for all parties. The end-product provides the properties of fit and retention similar to other custom-made mouthguards and can be routinely fabricated over fixed orthodontic appliances. Grewal et al.4 in 2014 concluded that, without requiring laboratory fabrication, self-adapting polyolefin mouthguards fulfil similar protection requirements as custom-made mouthguards if properly chairside fitted by a dentist. Using the material, a total fabrication time of less than 6 minutes is possible.
The present study aims to demonstrate that polyolefin mouthguards can be fabricated efficiently and effectively over fixed orthodontic appliances and to suggest that their manufacture provides a useful addition to the range of services provided by orthodontists.
Patients undergoing an initial examination and briefing before orthodontic treatment were offered a sporting mouthguard if they participated in contact sports such as rugby or hockey. The importance of maintenance of the dentition during and after orthodontic treatment was stressed at the interview. All patients who were offered a mouthguard, accepted. The gender distribution of the subjects is outlined in Figure 1, the age distribution in Figure 2 and sport distribution in Figure 3.
Figure 1.
Distribution of patient gender.
Figure 2.
Distribution of patient age.
Figure 3.
Distribution of sports.
The polyolefin mouthguard blank was wrapped in a paper towel, submerged in room temperature water before being placed in a microwave oven (Bellini BMW18, 900 W) and heated on high for 3 min. The blank was then cooled under cold running water for 15 sec before being placed in the patient’s mouth over the maxillary teeth. The blank was adapted for 2 min to the upper arch with thumb pressure on the posterior teeth and finger pressure on the anterior teeth. The moulding was performed over fixed orthodontic appliances without any special preparation such as orthodontic wax or bumper tube to remove undercuts. The patients were then instructed to suck on the mouthguard for 30 sec, following which the mouthguard was removed and allowed to stabilise into its elastic phase at room temperature.
Retention and bulk/smoothness acceptance of the fabricated mouthguards were assessed by the patient and the clinician. All assessments used a sliding scale of 4 grades defined as 4—very good/excellent; 3—good but minor issues; 2—average; 1—poor not suitable for use in contact sports. Figure 4 shows 61.5% of the subjects reported very good or excellent retention; while 92% of the subjects found that the mouthguards had good to excellent retention. Retention was also subjectively assessed by the clinician by instructing the patient to repeatedly open to maximum opening and close their mouth. Poor retention resulted in displacement of the mouthguard. Figure 5 illustrates the scores based on mandibular opening and mouthguard movement. The jaw movement test indicated that 29 subjects (55.7%) exhibited excellent or very good retention while 18 (34%) were classified as having good retention. A total of 47 subjects showed good or excellent mouthguard retention. The majority (88.5%) of the subjects were assessed by the clinician to have good to excellent retention (grade 3 and 4 levels combined) (Figure 6). No difference in retention was noted between ceramic and metal bracket appliance systems.
Figure 4.
Patient assessment of retention.
Figure 5.
Retention open close max.
Figure 6.
Operator assessment of retention.
A subjective assessment of the bulk and smoothness, considered a measure of the acceptance of the mouthguards, revealed that 47 of the 52 patients (90.3%) found the mouthguards acceptable and is illustrated in Figure 7.
Figure 7.
Patient assessment bulk.
There were four patients who were viewed as antagonistic to mouthguard use which was invariably contrary to the parent’s wishes. This attitude was usually expressed in the lower scores of 1 and 2 of assessments.
Following the construction of the first twenty mouthguards and the feedback provided by the patients, the mouthguard polyolefin was modified to a slightly softer form by changing the polypropylene and polyethylene proportions. The results are presented for all assessments combined.
The Oxford English Dictionary5 defines protection as “keep safe, defend, guard”. The Cambridge University Press6 suggests that protection is “the condition or state of being kept safe from injury, damage or loss”. Wikipedia7 suggests that protection is “any measure taken to guard against damage caused by outside forces”.
In absolute terms, to imply that a mouthguard provides protection for oral tissues could be misleading. Wearing a mouthguard does not mean that no injury can occur to a person during contact sport.8 An impact force of sufficient magnitude and direction can fracture jaws and teeth and possibly cause concussion whether or not a sportsperson is wearing a mouthguard. McCrory9 in 2001 reported that there was no convincing evidence to support a protective effect of mouthguards against any type of sporting injury because studies to date lacked sufficient power. In a later investigation incorporating a user interview technique, McCrory10 suggested custom-made mouthguards provided protection when compared with usual mouthguard wear during sport. The authors, however, identified problems with the methodology used in the study.
Mouthguards reduce the severity of injuries to oral tissues.11 They are often described in relation to the protection afforded to a user. Some mouthguards claim more protection than others; however, the problem with using protection to describe mouthguard effectiveness is compounded by uncertainty related to how, and to what level, protection is measured.
Following a literature review, Patrick et al.12 developed a classification of protection delivered by different mouthguards. The study suggested a theoretical material design, based on hard laminations, offered a high score in the 10 grades of protection which was considered appropriate. However, the introduction of hard layers of 5 mm thickness or less into a laminated mouthguard produced changes in the elasticity or compliance of the material. If hard layers replace elastic material, less energy is absorbed and a transmitted impaction force is increased.13 It was significant, however, that Patrick et al.12 mentioned tooth displacement as a consideration of impact. Greater rigidity of the mouthguard material will lead to less displacement of the teeth due to impact forces.
Tribst et al.14 suggested that the use of any mouthguard is beneficial and assists in dampening generated stress. Unstated or uncalculated in their paper is how much more protection is delivered by a well-fitted custom-made mouthguard when compared with a tested stock mouthguard.
The New Zealand Dental Association15 describes a satisfactory mouthguard as one having the following characteristics: sufficient thickness in correct areas, resilience, well retained, comfortable and should not interfere with speaking nor breathing. The NZ Dental Association website also suggests that a properly fitted custom-made mouthguard offers the best protection against trauma.
The Australian Dental Association16 provides the following mouthguard advice on its website: self-fitted mouthguards do not protect the teeth, are loosely adapted, impede breathing and speaking and can even lodge in the back of the throat which could be life threatening following impact. No evidence of a mouthguard lodged in the back of the throat was found in a recent Medline search. The ADA further asserts that custom-fitted mouthguards allow normal speech, do not restrict breathing, stay firmly in place and allow full concentration on playing sport.
The Oxford English Dictionary defines custom as pertaining to one particular person and therefore, a satisfactory custom mouthguard will fit only one person. Fortunately, stock mouthguards with their one-size-fits-all promise, are now rarely a part of the mouthguard market. Custom mouthguards may be fabricated in a many ways but usually involve dental professionals who take impressions to produce plaster casts upon which the appliance is made.
The intraoral fabrication of custom mouthguards is also now possible. However, the fabrication process suffers when traditional EVA material is used. EVA exhibits a relatively short working time which limits the time available for moulding (plastic phase) in the mouth. The cooling of EVA changes the material to its elastic phase after which no further adaption is possible. Improved technology has resulted in a mouthguard material, a polyolefin, which is ideally suited to intraoral appliance fabrication. The adherence to simple instructions makes the fabrication of a satisfactory mouthguard possible by intraoral moulding. No impressions and models are required but the mouthguards enjoy the qualities recommended by both the Australian and New Zealand Dental Associations.
The polyolefin, as a polymer of polypropylene and polyethylene, is a thermo plastic material (heat to a plastic phase, cool to an elastic phase) which enables a cold “heat moulding”. The mouthguard blank, after heating in a microwave oven, is cooled to room temperature before adaption to the teeth. The moulding time available before the material changes from its plastic to the elastic phase is approximately 3 min. Using the polyolefin material and if instructions are followed, heat damage to the oral tissues is impossible but remains a common complaint with EVA self-fabricated mouthguards. Hot blanks in a ‘boil and bite’ process of self-fabricated mouthguards is a cause for concern. A high temperature is a factor in the poor adaption of these mouthguards which contributes to their lesser performance.
The present paper examines the fabrication of intraorally-formed mouthguards in a clinical setting, under the supervision of a dental professional and using a new polyolefin material.
The provision of a polyolefin mouthguard to fifty-two subjects undergoing orthodontic treatment suggests that the material is suitable for direct fabrication over fixed orthodontic appliances. The results of the study indicate that the polyolefin mouthguards provide acceptable retention aided by the presence of the fixed appliances. A major benefit of the polyolefin mouthguards is that they can be clinically fabricated in less than six minutes. All subjects were provided additional mouthguards during their regular orthodontic adjustment appointments.
The ease of use and minimal time of fabrication for the clinician and the patient proved to be a key advantage of the polyolefin over other materials. This trial indicates that polyolefin is a suitable material for the fabrication of mouthguards over fixed orthodontic appliances. (Figures 8–10).
Figure 8.
Fixed orthodontic appliances.
Figure 9.
Polyolefin mouthguard fitted over fixed orthodontic appliances.
Figure 10.
Polyolefin mouthguard blank.
