Background Dentofacial injuries are a risk while playing field hockey. Wearing mouthguards is recommended.
Objective To synthesise findings on the prevalence and characteristics of dentofacial injuries sustained by field hockey players. We also investigated the prevalence of regular mouthguard use and players’ attitude towards use of mouthguard.
Material and methods A literature search was performed using PubMed, EMBASE, OvidSP, Web of Science, Cochrane and Cinahl databases. Eligible studies were identified based on the title, abstract and full text of articles. If applicable, a random effects model was used to calculate the overall effect size; otherwise, pooled prevalence was reported.
Results 11 studies were eligible for the analysis. The average proportion of field hockey players who had sustained at least one dentofacial injury varied from 12.7% (95% CI 8.5% to 17.0%) among junior and senior players to 45.2% (95% CI 39.3% to 51.0%) among elite players. We did not observe any significant differences with respect to gender. In the 2000s, a significantly higher proportion of players regularly wore a mouthguard, 84.5% (95% CI 69.3% to 99.7%) as compared with players 20 years ago, 31.4% (95% CI 22.7% to 40.1%). The most common complaints about the mouthguard were that it was unnecessary and uncomfortable.
Conclusion Dentofacial injuries pose a serious problem in field hockey and a substantial number of players do not regularly wear a mouthguard. Greater use of mouthguards would be expected to reduce dentofacial injuries in field hockey.
- Field hockey
- Systematic review
Statistics from Altmetric.com
Field hockey is a growing team sport officially played in 128 countries around the world.1 The number of athletes participating in professional, college and recreational field hockey is increasing, especially in Europe and North America.2 ,3 In the Netherlands, it is one of the most popular sports, with more than 241 000 hockey players and 323 sports clubs registered in 2013.4
Though all team sports carry a particular risk of injury, players who participate in stick sports, such as ice hockey, field hockey and lacrosse, face an increased risk of trauma because of the high-speed stick movement required to hit a puck or a ball.5 ,6 The most common sites of injury in field hockey are lower limbs (47–51%), followed by head and face (27–34%), upper limbs (14–20%) and torso injuries (1–9%).7–9 In most cases, injuries are not so severe and may prevent a player from playing hockey for 7 or fewer days; however, in 20% of injury cases, players sustain serious injuries, such as concussion and fractures,7 ,10 ,11 that require a longer recovery time.12 ,13 Also, previous studies have reported that injuries are more common during games than in practice7 and that these occur more in males than in females.5 ,14
One of the growing concerns of the organisations involved in the safety of field hockey is aimed at the injuries that can be prevented or lessened with the use of a mouthguard.15 ,16 Field hockey players had a higher proportion of facial injuries (25% for males and 20% for females) compared with ice hockey (10% males and 18% females), and lacrosse (10% boys and 20% girls).5 One of the explanations for the lower proportion of facial injuries in ice hockey is the mandatory use of helmets and full face masks.17 Furthermore, mouthguards are mandatory only for male and not for female lacrosse players, which might explain the similar proportion of female players’ face injuries in field hockey and lacrosse. According to the international field hockey rules, protective equipment, such as shin, ankle and mouth protectors are not mandatory, except for goalkeepers.1 However, the international field hockey rulebook states that players are advised to wear a mouthguard at all times while participating in the sport.18
Considering currently imposed rules and recommendations on the use of mouthguard in field hockey, the objective of the current study was to systematise available evidence about: (1) the prevalence and (2) characteristics of dentofacial injuries sustained by field hockey players. Additionally, we investigated (3) the prevalence of mouthguard use and (4) the players’ attitude towards mouthguard use in field hockey.
This study was conducted using PRISMA guidelines for reporting systematic reviews of studies.19 The aim and search criteria for this systematic review and meta-analysis were defined prior to the study, and documented in a protocol registered under number CRD42014012842 at the International Prospective Register of Systematic Reviews, PROSPERO, on 17 September 2014. The full description of this protocol is accessible via the web page: http://www.crd.york.ac.uk/PROSPERO/.
The types of studies eligible for this systematic review were observational: case–control, cohorts and cross-sectional studies. We included these studies if they contained information related either to: the number of hockey players who sustained at least one dentofacial injury in the past, the number of sustained injuries compared with other types of injuries, and studies which provided quantitative data on characteristics of dentofacial injuries, such as type, site, cause of injury, information on gender, position in the field and if an injury occurred during a match or practice. Dentofacial injury was defined as an injury to structures that are either covered or supported by a mouthguard and, therefore, only injuries of teeth, alveolar bone, jaws, lips and cheeks were included. Other injuries that might include a nose, eye (cheek bone), ear, head and neck injury were excluded. Furthermore, studies were included if these reported on the number of players who possess and regularly wear a mouthguard, taking into account factors that may have influenced the use of mouthguard (eg, gender differences, previous injury, etc), or if the studies analysed data on player's attitude towards mouthguards. Data collection procedures of studies eligible for this systematic review were self-reported questionnaires, injury surveillance reports during matches and practices, and injury records documented in hospitals or emergency departments. No restriction criteria regarding age, sex and competition level (elite or recreational) related factors were applied. Exclusion criteria were: abstracts only, systematic reviews, letters and conference proceedings. Other exclusion criteria were studies that investigated: floorball, indoor field hockey, roller hockey, lacrosse, ice hockey, bandy and other similar sports. There were no time or language restrictions, and studies that were written in languages other than English were translated with the help of associates fluent in that language.
A literature search was performed between 1 September 2014 and 1 February 2015. The last update of the literature search was carried out on 19 January 2015, and the literature search was conducted using the following electronic databases: PubMed (from 1950 to present), EMBASE (from 1970 to present), OvidSP (from 1950 to present), Web of Science (from 1970 to present), Cochrane (from 1970 to present) and Cinahl (from 1970 to present). Subsequently, a more detailed search was performed by going through the reference list of relevant studies or via direct email contact with authors.
First, electronic databases were explored by combining similar search terms within six word groups using inclusive (OR) Boolean operator (asterisk denotes a truncated term):
facial OR face OR dent* OR jaw OR mandib* OR maxill* OR lip OR lips OR tooth OR teeth OR head
injur* OR trauma OR fracture* OR wound* OR lesion
mouth guard OR mouth guards OR mouth protector OR mouth protectors OR protective mouth piece OR protective mouth pieces OR mouthguard* OR mouth protective piece OR mouth protective pieces OR occlusal splint OR occlusal splints
dental OR mouth
protect* OR guard*
Second, word groups were joined using inclusive (OR) or exclusive (AND) Boolean operators and brackets:
((1 AND 2) OR (3 OR (4 AND 5))) AND 6
MeSH terms were omitted since the total number of retrieved records was a subsample of the retrieved records without the MeSH terms being used.
Using the criteria aforementioned, two investigators (SV and RWD) performed the literature search independently, following steps presented in the flow diagram according to the PRISMA guidelines (see online supplementary file 1).20 At the end of each stage, investigators compared the list of retrieved records with each other. In case of disagreement, they reached an agreement by involving a third investigator. Cohen’s κ inter-rater agreement was calculated after: (1) duplicate records were removed, (2) titles and abstracts were screened, and (3) full texts were assessed. Lastly, the final number of studies were classified as being related to dentofacial injury, mouthguard use or both.
On retrieving the final number of studies, two independent investigators (SV and RWD) assessed the quality of eligible studies using Newcastle-Ottawa Quality Assessment Scale.21 This tool was developed for cohort and case–control studies. It contains eight items, divided into three categories: selection of participants (selection), comparability of study groups (comparability) and exposure assessment (outcome). A study was graded with a star for each item where it shows a high quality.
For this tool to be applicable for cross-sectional studies, Newcastle-Ottawa Quality Assessment Scale for cohort studies was modified by removing items 2, 3, 4 and 8 (see online supplementary file 2). Furthermore, following items were reformulated; item 1: a study sample was considered representative if authors clearly described study participants taking into account gender and competition level in the outcome measure; item 5: studies were awarded a star if these reported that goalkeepers were excluded or analysed separately, and an additional star was given to a study that controlled for any other factor besides gender and competition level; item 6: assessment of exposure and outcome; item 7: studies received a star if these collected information on participants for more than three seasons.
Using the modified Newcastle-Ottawa Quality Assessment Scale, a study could be graded with a maximum of five stars.
Data collection process and summary measures
Country, data source, sample size, gender, competition level and exposure interval were reported for each study. Furthermore, quantitative variables were extracted from the reviewed studies: (1) the number of hockey players who sustained at least one dentofacial injury in the past; (2) the number of dentofacial injuries sustained by the hockey players in comparison to the total number of sustained injuries; (3) gender differences in a sustained injury; (4) information about the cause of the injury; (5) information on whether the injury occurred during the match or practice; (6) the proportion of players who regularly wore a mouthguard; (7) information about players’ attitude towards mouthguard use; (8) gender differences in the regular use of a mouthguard. If applicable, we considered following potential confounders for the stratified analysis: the exposure time, gender, competition level and the year of article publication.
If appropriate, data were pooled using a random effects Mantel-Haenszel model and presented in a forest plot.22 All variables entered in the model were binary variables and the results were expressed as Mantel-Haenszel pooled prevalence ORs with 95% CIs and a p value of the overall effect.23 The I2 was used to show the percentage of variation attributable to the heterogeneity across the studies. Other quantitative data were expressed as the pooled prevalence with 95% CI. Studies from which a pooled prevalence was calculated were weighted using a random effects Mantel-Haenszel model, which takes into account between-studies and within-studies variance. A χ2 test was used to compare the between-studies differences. All statistical analyses were performed using the Cochrane Review Manager V.5.3 (The Nordic Cochrane Centre, Copenhagen, Denmark, 2014).
The selection process of studies for this systematic review and meta-analysis is presented in the online supplemental file 1. Using the search criteria as mentioned earlier, a total of 1828 records were retrieved from six electronic databases. After exclusion of duplicate records, 671 records remained (very good agreement, κ=0.91; 95% CI 0.88 to 0.93). Further, by screening titles and abstracts, 625 records were excluded, leaving a total number of 46 records (very good agreement, κ=0.82; 95% CI 0.71 to 0.92). Finally, by going through full-text articles and evaluating quantitative variables presented in those articles, 35 studies were excluded, leaving a final number of 11 studies for the systematic review and meta-analysis (good agreement, κ=0.83; 95% CI 0.67 to 0.99). Out of these 11 studies, 6 provided data related to dentofacial injury, 1 provided data related to mouthguard use and 4 studies had information on both outcomes.
Characteristics of the 11 studies included in this systematic review are provided in table 1. Studies counted a total of 4868 hockey players and 3275 hockey injuries. The time span of the included studies ranged from 1981 to 2008. Four studies investigated North American field hockey players (USA and Canada),3 ,5 ,24 ,25 four investigated European field hockey players (Germany, the Netherlands and England),18 ,26–28 and one study investigated international hockey players at a tournament.29 Most of the studies collected their data using questionnaires (N=7)18 ,24 ,26 ,27 ,29–31 ; two of these studies collected their data using injury surveillance systems,3 ,25 and the rest of the studies used emergency department records.5 ,28 Three studies investigated elite and semielite hockey players,18 ,29 ,30 and seven studies investigated junior and senior players, including school and college players.3 ,5 ,24–28 ,31 Most of the studies included players of both genders (N=5),5 ,26–29 while four studies were done on females3 ,18 ,24 ,25 and two on males.30 ,31
Risk of bias
All studies included were cross-sectional besides one which accounted for the follow-up time in their analysis.3 The quality of studies ranged from 1 to 4 out of 5 stars with an average score of 2.8±1.3 stars. With regard to selection bias, only one study grouped both males and females together.28 Eight studies did not explicitly report whether they have excluded goalkeepers,3 ,5 ,24 ,25 ,28–31 and four studies did not control for an additional factor besides gender and competition level of the players.24 ,25 ,28 ,31 Seven studies collected their data through self-reported questionnaires,18 ,24 ,26 ,27 ,29–31 and four studies had a shorter exposure time than three hockey seasons.5 ,25 ,28 ,31
The prevalence of dentofacial injury in field hockey
The prevalence of dentofacial injury stratified by the exposure time is presented in figure 1. Four studies reported the proportion of hockey players who sustained at least one dentofacial injury during their gaming career. On average, 21.5% (95% CI 5.7% to 37.4%) of the hockey players experienced at least one dentofacial injury; however, due to considerable heterogeneity (I2=95%, p≤0.01), we stratified the analysis based on competition level and gender. A significantly higher proportion, 45.2% (95% CI 39.3% to 51.0%), of international elite hockey players have experienced at least one dentofacial injury,29 compared with non-elite players,18 ,26 ,30 12.7% (95% CI 8.5% to 17.0%; I2=59%, p=0.09). We did not observe any significant differences with respect to gender (elite level: p=0.24 and non-elite: p=0.74). Studies on dental injury during two seasons or a shorter period reported a proportion of 1–3%.24 ,25 ,31
Studies on mouth and dental injuries when compared with other field hockey injuries reported a relatively small proportion of these injuries: 1.5% (95% CI 0.9% to 2.1%; I2=25%, p=0.27) and 0.6% (95% CI −0.3% to 1.55%; I2=82%, p≤0.01), respectively (figure 2).
The characteristics of dentofacial injuries in field hockey
The most common causes of dentofacial injuries are presented in figure 3. A study performed by Dick et al3 revealed that the highest percentage of injuries in the dentofacial region was caused by a hockey ball, 56.5% (95% CI 45.9% to 67.0%), while hockey stick injuries were 37.7% (95% CI 27.4% to 48.0%). Other reasons accounted for the remaining 5.9% (95% CI 0.9% to 10.9%) of injuries.
Two out of three studies26 ,29 reported a higher occurrence of dentofacial injuries in male hockey players, pooled OR 1.3 (95% CI 0.7 to 2.4; I2=82%, p≤0.01; figure 4); however, the overall effect was not statistically significant (p=0.27). The only significant effect was demonstrated in the largest study (N=3577) performed in the junior and senior, non-elite Dutch hockey players (OR 2.0, 95% CI 1.5 to 2.7).29 Only one study conducted in the USA5 showed that dentofacial injuries occurred more in females, OR 0.7 (95% CI 0.5 to 1.1); however, the effect was not statistically significant (p=0.57).
The prevalence of hockey players who regularly wore a mouthguard
The overall proportion of hockey players who regularly wore a mouthguard was 57.9% (95% CI 24.8% to 91.0%); however, due to substantial heterogeneity (I2=100%, p≤0.01), prevalences were pooled separately for older and newer studies (figure 5). Recent studies conducted in 2002 and 200818 ,30 reported a significantly higher proportion of players who regularly wore a mouthguard, 84.5% (95% CI 69.3% to 99.7%; I2=90%, p≤0.01), as compared with studies conducted earlier in 1986 and 1987, 31.4% (95% CI 22.7% to 40.1%; I2=89%, p≤0.01).26 ,29 Still, even after the stratification, heterogeneity was significantly high.
With regard to gender, our results showed that females had greater odds for regular wear of a mouthguard during a field hockey match than males (figure 6). However, due to considerable heterogeneity between the two studies, we did not present the pooled OR. Female hockey players were significantly wearing a mouthguard more regularly than their male counterparts at the international elite competitive level, OR 5.5 (95% CI 3.3 to 9.3),24 as compared with those in the non-elite Dutch national junior and senior league, OR 1.7 (95% CI 1.1 to 2.5).27
Furthermore, a hockey player who had experienced a dentofacial injury in the past had significantly higher odds to regularly wear a mouthguard than a player without any dentofacial injury, OR 2.0 (95% CI 1.4 to 2.9, I2=0%, p=0.83; figure 7).
Players’ attitude towards wearing a mouthguard
In total, 55.4% (95% CI 47.1% to 63.7%) of the elite players reported that wearing a mouthguard is unnecessary, which was significantly a greater percentage than that for players in the national Dutch non-elite league, 33.9% (95% CI 32.1% to 35.7%; figure 8). The percentage of players who thought that a mouthguard is uncomfortable was significantly lower in a recent study, 25.8% (95% CI 17.1% to 34.5%),18 as compared with the older studies, 42.3% (95% CI 30.4% to 54.1%).26 ,27 ,29
Our findings show that a relatively high proportion (22%) of field hockey players sustained at least one dentofacial injury in their sports career; however, these percentages varied across studies.18 ,26 ,29 ,30 A larger proportion of injuries was identified at the international elite level (45%)29 as compared with the proportion of injuries in the national junior and senior leagues (13%);18 ,26 ,30 this is presumably due to greater competitiveness, frequent practices and low use of mouthguards at the elite level.32
Current evidence about the patterns of dentofacial injuries by gender is inconclusive. Out of three studies, only one showed two times greater odds for dentofacial injuries in males than in female players.26 Still, two other studies, as well as the overall effect estimate, showed that there were no significant differences between genders. Furthermore, comparing prevalences of dentofacial injury between males and females did not reveal any significant differences. Minor differences in the number and pattern of injuries among males and females were also observed in other sports.33 However, our results did show that female hockey players had higher odds to regularly wear a mouthguard than males. This discrepancy was especially pronounced at the elite level, where females had 5.5 times greater odds than males. Also, the results of our study showed that an injured player had two times higher odds of regularly wearing a mouthguard than a non-injured player. Psychological aspects that may explain this behaviour pattern in athletes is that a previous injury acts as a strong motivator for players to use a protective equipment.34
Rules of field hockey sanction dangerous play that involve lifting a stick over the head or raising the ball off the ground near the opponent.1 Findings of a previous study showed that the most common causes of dentofacial injuries were a hockey ball and a hockey stick.3 Apart from the conduct of play, the use of protective equipment has been also regulated by the official International Hockey Federation rulebook.1 Previous studies have demonstrated the effectiveness of mouthguards in the protection against dental and other types of facial injuries in field hockey.35–37 Moreover, studies have pointed out other advantages of mouthguard, such as a positive effect on the spine posture in athletes.38 Though mouthguards are often promoted as effective in the prevention of cerebral injuries,39 several studies were unable to confirm these findings.40 ,41 Still one of the leading properties of a mouthguard is the protection against dental injuries.40 ,42 Taking into account the high number of field hockey dentofacial injuries and low usage of mouthguards especially by male players, organisations should further promote the use of mouthguards. In rugby and ice hockey, the mandatory use of mouthguards proved to be an efficient solution to decrease the number of dentofacial injuries.43–45 Similarly, a rule change has been already introduced by the Dutch Hockey Association (Koninklijke Nederlandse Hockey Bond). From season 2015/2016, all hockey players are obligated to wear a mouthguard during national field hockey matches. Further studies are planned to estimate the effectiveness of mandatory mouthguard use in Dutch field hockey league.
A large proportion of hockey players reported that a mouthguard is either unnecessary or uncomfortable. In the studies from the 1980s, a higher proportion of elite players thought that a mouthguard is unnecessary (55%), compared with non-elite players (34%). Regarding the comfort of the mouthguard, by comparing a recent study with older studies, we were able to identify that a smaller percentage of players reported that a mouthguard was uncomfortable in recent years and this was most likely due to improvement in materials and construction.36 Not all mouthguards offer the same protection and comfort. Stock mouthguards provide inadequate protection and can cause breathing and talking problems. Some studies presented evidence that the use of these mouthguards should be discouraged.16 On the other hand, although mouth-moulded mouthguards provide better protection than stock mouthguards, these can be too thin when put over prominent teeth and thus expose the teeth to injury.46 Furthermore, they can negatively affect the physical performance of athletes, opposed to custom-made mouthguards that are made by dental technicians based on the dentist's instruction.47 ,48 Custom-made mouthguards seem to offer the most protection and do not obstruct breathing, speaking, do not cause nausea and last longer.49–51
Strengths and limitations of the review
To our knowledge, this is the first systematic review and meta-analysis that investigated dentofacial injury and players’ attitude towards mouthguard use in field hockey. One previous review summarised results from different studies about field hockey injuries, including head and face injuries, stratified by sex and competition level.8
The inclusion of observational studies in the meta-analysis may produce misleading overall estimates due to bias and heterogeneity.52 We tried to minimise the heterogeneity by applying a strict set of inclusion criteria and by controlling for potential confounders in the analysis such as gender, competition level, years of study and exposure time. We opted for stratified analysis rather than meta-regression because of the limited number studies. To account for the heterogeneity between studies due to residual confounding, we applied the random effects model for the meta-analysis.
To address the bias of the included studies we used a modified version of the Newcastle-Ottawa Quality Assessment Scale. We identified several issues regarding the quality of the included studies. First, most of the studies collected data using self-reported questionnaires.18 ,24 ,26 ,27 ,29–31 Second, some studies did not explicitly report that they have excluded goalkeepers.3 ,5 ,24 ,25 ,28–31 The inclusion of goalkeepers might under-represent the percentage of dentofacial injuries as it is mandatory to wear a protective helmet. Third, the non-elite competition level stratum was a group that included a broad spectrum of players, from different leagues and ages. Next, a variable was used to indicate whether a hockey player had ever experienced a dentofacial injury in his gaming career, which is directly related to the years involved in the sport, and can vary between juniors and senior players. The time of the study has substantial importance since the field hockey rules and the applied preventive measures have also been changing over time, that is, in 1997 a non-offside and a corner kick rule was introduced which reduced the number of breaks during matches and imposed a more fast-paced game. Also, field hockey organisations and dental associations made an effort in the recent years to increase field hockey players’ awareness of the importance of wearing a mouthguard.3 Finally, some of the articles that were included in this systematic review dated from almost 30 years ago and may not reflect the current situation.
The calculated overall effect estimate requires a cautious interpretation. We presented a pooled prevalence or OR across studies with considerable heterogeneity in the crude analysis, and our results should be mainly interpreted in terms of stratified analysis and individual studies where a greater precision of the effect estimate has been obtained. Furthermore, since most of the included studies are cross-sectional, ORs presented in this meta-analysis represent prevalence OR which is used to compare two groups with different characteristics (for instance males and females), rather than risk OR which estimates the risk of developing or obtaining a certain outcome given a particular exposure.23 ,53
Although one of the aims of this study was to include quantitative variables for the characteristics of dental injuries, and players’ attitude towards mouthguard use, we encountered very limited information. Owing to lack of data, we could not investigate the proportion of dentofacial injuries in comparison to other hockey injuries, and the differences in dentofacial injuries during matches and training sessions. Also, only two studies could be included in the meta-analysis when the following associations were investigated: gender differences in regular mouthguard use and impact of previously sustained injury on regular mouthguard use. Further investigations, which control for age, gender, competition level, country, position, cause of injury, trainings per week and type of mouthguard used, are necessary to explore patterns of dentofacial injury and mouthguard use in field hockey.
Findings of this study indicate that dentofacial injuries pose a serious problem in field hockey and that still a substantial number of field hockey players do not regularly wear a mouthguard. Organisations involved in field hockey have the responsibility to ensure the safety of their members and should further improve preventive strategies that will result in a greater use of mouthguards and reduction of dentofacial injuries. Also, further studies are necessary to monitor the effectiveness of newly introduced preventive measures.
What are the findings?
Our results show that a relatively high proportion (22%) of field hockey players have sustained at least one dentofacial injury in their gaming career.
We did not observe any significant gender differences with regard to the proportion of dentofacial injuries; however, female hockey players had two times higher odds for regular wear of a mouthguard than males.
The most common causes of dentofacial injuries were a hockey ball (56.5%) and a hockey stick (37.7%).
An injured player had two times higher odds of regularly wearing a mouthguard than non-injured players.
We observed a significant increase in regular mouthguard use from the 1980s (31.4%) to 2000s (84.5%).
The most common complaints about the mouthguard were that it was unnecessary and uncomfortable.
How might it impact on clinical practice in the future?
Issuing guidelines regarding the use of mouthguards or the adding of a rule making mouthguard use mandatory in field hockey may reduce admissions to the hospital or dental practice due to dentofacial injury.
Contributors SV and EBW were involved in study concept and design. SV and RWD contributed to the acquisition of the data and quality assessment. EBW and EMO supervised the study. SV, EBW and EMO contributed to the writing of the paper. SV provided statistical support.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.