|Mouthguards in sport activities: history, physical properties and injury prevention effectiveness
|Knapik J J, Marshall S W, Lee R B, Darakjy S S, Jones S B, Mitchener T A, delaCruz G G, Jones B H
This review assessed the effectiveness of mouthguards to prevent injury during sport and exercise activities. The authors concluded that mouthguards offer protection against orofacial injuries, but there was insufficient evidence to determine protection against concussion. The extent to which these conclusions are reliable is unclear given the limited reporting of review methods and questions about the appropriateness of pooling results from variable studies.
To assess the effectiveness of mouthguards to prevent injury during sport and exercise activities. This review was conducted in parallel to others (not included in this abstract) examining the history of mouthguard use, and mouthguard material and construction.
MEDLINE, CINAHL, Academic Search Premier, Biomedical Reference Collection, the Cochrane Database of Systematic Reviews and DARE were searched for relevant studies written in English; the search terms were reported. In addition, reference lists of selected studies were screened and authors were contacted for additional studies.
Study designs of evaluations included in the review
There were no inclusion criteria for study design.
Specific interventions included in the review
Studies that compared mouthguard users with non-users while undertaking sporting activities or exercise were eligible for inclusion. Most of the included studies assessed mouthguards while participants played American football, hockey, rugby or basketball. Custom mouthguards were the most frequent type of mouthguard investigated, however, stock and boil-and-bite mouthguards were also assessed. Several studies included mouthguard wearing participants within a non-user control group.
Participants included in the review
Participants undertaking sporting activities or exercise were eligible for inclusion. The participants in over half of the included studies were U.S. high-school students.
Outcomes assessed in the review
Studies were considered for inclusion if they presented quantitative information on orofacial injury or concussion. Information relating to the numbers of participants injured and not injured while wearing and not wearing a mouthguard had to be available to be included in the review. This information was supplied by the author in one study. Only half of the studies explicitly stated the definition of injury they used. The injuries reported by the studies varied widely and included mouth and dental injury, head, face, neck and jaw injury, concussion, dental referrals and dental claims. A variety of outcome measures were used.
How were decisions on the relevance of primary studies made?
The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.
Assessment of study quality
Six authors independently rated the included studies using twenty-two quality assessment criteria, which were presented in the review and were based around four broad areas: problem definition and sample; study design and methodology; statistical analysis; and presentation of data. The maximum score available was 100 and the average score for each study was generated by averaging the six reviewers' scores. Any differences were resolved by discussion.
The authors did not state how the data was extracted for the review, or how many reviewers performed the data extraction.
Data on the percentage of injuries for mouthguard users and non- users were presented separately. Risk ratios (RRs) comparing mouthguard non-users and mouthguard users were calculated, along with 95% confidence intervals (CIs), for each study after 0.5 was added to zero cells. Authors were contacted for additional data, where necessary.
Methods of synthesis
How were the studies combined?
Pooled RRs comparing orofacial injuries and concussions sustained by mouthguard non-users and mouthguard users were calculated alongside 95% CIs using a general variance-based model.
How were differences between studies investigated?
Sensitivity and subgroup analysis were undertaken for pre- and post-1980 studies, and for studies not relying on retrospective recall.
Results of the review
Fourteen studies were included in the review. Thirteen studies reported 296,967 participants. The other study reported only the number of sporting exposures, of which there were 70,936, rather than the number of participants. There was one randomised controlled trial (n=301), two non-randomised interventions (n=1000), four prospective cohorts (n=1,043 plus 70,936 exposures), three ecological interventions (n=246,319), three cross-sectional surveys (n=47,914) and one unclear study design (n=390).
The quality of the included studies ranged from 16 to 75 out of a possible 100, with older studies generally receiving lower scores than more recent studies. Few studies reported on the compliance of participants to wear mouthguards.
Overall, mouthguard non-users received significantly more orofacial injuries (RR 1.86, 95% CI: 1.76, 1.96) than mouthguard users (all studies). This result remained significant for all subgroup analyses.
Overall, mouthguard non-users received significantly more concussions than mouthguard users (RR 3.94, 95% CI: 2.69, 5.80; 4 studies). The evidence was less conclusive for the reduced risk of concussion in mouthguard users when the study based on retrospective recall was removed from the analysis (RR 0.82, 95% CI: 0.43, 1.58; 3 studies).
Mouthguards offer significant protection against orofacial injuries. However, there was insufficient evidence to determine whether mouthguards offer protection against concussion.
The review question was clear and the inclusion criteria for the participants, intervention and outcomes were broad but generally well defined. The search strategy used to identify published studies was reasonable but only English language papers were included, which raises the possibility of language bias within the review. Although some attempt was made to identify unpublished studies, publication bias was not assessed. The assessment of study quality appeared thorough and the results were summarised adequately. The authors did not state how the papers were selected or the data extracted, which makes it difficult to assess the potential for errors and bias within the review process. Statistical heterogeneity was not assessed. However, as the studies differed widely in terms of their design, outcomes measured, method of assessment and results presented, the appropriateness of pooling the results may be questionable. Given the variable quality of the included studies and some methodological limitations in the review process, the extent to which the authors' conclusions are reliable is unclear.
Implications of the review for practice and research
Practice: Mouthguard use should be promoted where there is significant risk of orofacial injury.
Research: More studies of good methodological quality are needed to assess the effectiveness of mouthguards to protect against concussion.
Knapik J J, Marshall S W, Lee R B, Darakjy S S, Jones S B, Mitchener T A, delaCruz G G, Jones B H. Mouthguards in sport activities: history, physical properties and injury prevention effectiveness. Sports Medicine 2007; 37(2): 117-144
Subject indexing assigned by NLM
Athletic Injuries /prevention & control; Boxing /injuries; Equipment Design; Football /injuries; Hockey /injuries; Humans; Mouth Protectors; Risk Factors; Safety; Tooth Injuries /prevention & control; United States
Database entry date
This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.