This systematic review aimed to examine the incidence of hard (teeth) and soft tissue complications relating to oral piercings, with a particular focus on complications caused by metal ion release. To the author’s knowledge, this is the first systematic review that examines metal ion release from oral piercings and the subsequent complications. The results of this review showed that metal ion release can occur from oral piercings when subject to the oral environment. They may corrode and release metal ions into surrounding oral tissues, causing local soft tissue reactions. Oral piercings are made from a variety of metals, such as surgical stainless steel, titanium, platinum, or gold, as mentioned above (Masood et al. 2023). Two included studies examining metal ion release investigated piercings made from surgical stainless steel only (Domingo et al. 2019; Lupi et al. 2010). Stainless steel piercings were found to cause a high incidence of tooth chipping (Hickey et al. 2010). One study that examined different oral piercing materials showed that titanium piercings cause greater gingival recession (Hickey et al. 2010). Teflon or acrylic piercings showed lower levels of dental complications, and the change in composition avoided the problem of metal allergy (Hickey et al. 2010; Dougherty et al. 2005).

Complications caused by metal ion release were reported by two studies (Domingo et al. 2019; Lupi et al. 2010); Domingo et al. (2019) examined both lip and tongue piercings, and reported the presence of metal particles, such as aluminium, tungsten and molybdenum, in keratinocytes at sites where the oral mucosa was pierced. Lupi et al. (2010) investigated only tongue piercings, and noted concentrations of iron, nickel, and chromium in tongue mucosal keratinocytes. These metal ions may exert local cytotoxic effects on keratinocytes (Lupi et al. 2010), which may result in local mucosal changes, such as atrophic, “hyperplastic, leukoedematous, erythematous, and/or erosive lesions” (Domingo et al. 2019). Interestingly, the rate of metal ion release is also influenced the surface quality of the piercings, where surface defects can be a site of metal corrosion (Masood et al. 2023; Domingo et al. 2019); Domingo et al. (2019) noted surface defects on both used and unused piercings.

Of the 25 articles included for analysis, there were no articles published prior to 2002 that examined lip or tongue piercings and related dental complications. The majority of the included studies had more female participants than males, indicated a higher prevalence of oral piercings in females (Walsh et al. 2008; Dougherty et al. 2005; Kapferer et al. 2007; Samoilenko et al. 2019; Simoes et al. 2014; Tomaževič et al. 2017). There may also be a higher willingness of females to participate in studies, and they may seek oral health input more readily than males (Dougherty et al. 2005; Kapferer et al. 2007).

The included studies generally reported that tongue piercings cause significantly more dental complications than lip piercings (Ebrahim et al. 2008). Pain, difficulty speaking and eating problems were reported more often with tongue piercings (Kapferer et al. 2010; Firoozmand et al. 2009; Vieira et al. 2011). These were similar findings to the 2022 systematic review by Passos et al. Immediately after piercing placement, common complications included pain, swelling, bleeding and irritation (Kapferer et al. 2007; Samoilenko et al. 2019; Ebrahim et al. 2008). One study showed that 86% of subjects with oral piercings experienced these complications (Kapferer et al. 2007). Pain was reported to occur in between 58.3 and 69% of cases and swelling in between 47.2 and 52% of cases (Kapferer et al. 2007; Samoilenko et al. 2019). Furthermore, mucosal changes were reported in 6 of the 25 studies included for analysis. Atrophy or de-papillation around the oral piercing was the most common mucosal change with tongue piercings (Oberholzer et al. 2010). Hyperplasia or tissue overgrowth at the pierced site was seen mainly in tongue piercings, at a prevalence of 16.2% to 33.3% (Vieira et al. 2011; Samoilenko et al. 2019). Complete resolution was achieved when the piercings were removed (Vieira et al. 2011).

Most studies showed that tongue piercings are associated with tooth injuries such as chipping or fractures (Firoozmand et al. 2009; Ziebolz et al. 2012; Oberholzer et al. 2010). The study by Tomaževič et al. (2017) showed that dental damage of any type, such as enamel fractures, enamel–dentin fractures, and complicated crown–root fracture, occurred twice as frequently in people with tongue piercings (76.5%) compared to community controls (32.1%). About 59% of people with tongue piercings had enamel fractures (Tomaževič et al. 2017). The majority of teeth with enamel damage (92%) were molars and premolars (Campbell et al. 2002). This may be explained by the habit of patients playing with, biting, or knocking the piercing against their teeth (Campbell et al. 2002). Of subjects with fractured teeth, this habit of playing with the piercing was noted in some 51.6% of cases (Hickey et al. 2010).

Lip or labial piercings cause more gingival recession (Kapferer et al. 2010; Firoozmand et al. 2009; Kapferer et al. 2012; Vilchez-Perez et al. 2009; Plessas et al. 2012). As such, labial piercings have been shown to be more damaging to periodontal tissues (Kieser et al. 2005; Lopez-Jornet and Camacho-Alonso 2006; Slutzkey et al. 2008). In contrast, Pires et al. (2010) noted that subjects with tongue piercings are at 11 times increased risk of developing lingual anterior gingival recession. This is supported by Dougherty et al. (2005) who reported that tongue piercings were commonly associated with the presence of calculus, which may lead to higher levels of periodontal disease. The systematic review and meta-analysis by Passos et al. showed that 33% of individuals with oral piercings had gingival recession. The problem of gingival recession is primarily related to the position of the piercing. Studies examining this issue showed that piercings placed at the CEJ caused a greater rate of buccal gingival recessions, (Kapferer et al. 2007) whilst lip piercings placed coronally to the CEJ had a lower incidence of lower lip buccal recession (Kapferer et al. 2012). This important finding regarding piercing placement is something which body piercing professionals should consider when advising patients about possible long-term complications.

The rate of oral complications may be related to piercing length and the wear period. The barbell rod or stem length on tongue piercings appears to be directly proportional to the risks of gingival recession and tooth chipping (Campbell et al. 2002). Longer stems cause more recession due to the greater ease of the barbell piercing coming into direct contact with the gingival tissues (Campbell et al. 2002; Hickey et al. 2010). Similarly, several studies also reported a higher prevalence of gingival recession and tooth chipping with longer wear periods (Campbell et al. 2002; Plessas et al. 2012; Ebrahim et al. 2008). Interestingly, one study found that the greatest incidence of complications occurred within 2 years and involved 57.6% of cases (Lopez-Jornet and Camacho-Alonso 2006).

Multiple studies reported limitations to their study design. The main limitation reported was convenience sampling, where the participants were recruited specifically for participation in the study (Stead et al. 2006; Dougherty et al. 2005; Kieser et al. 2005; Ebrahim et al. 2008). Some studies did not have a control group (Domingo et al. 2019; Plessas et al. 2012), which prevents comparisons with the experimental group. Lastly, the majority of studies included a questionnaire in the study design, with four studies relying solely on the information collected from the survey to draw conclusions (Kapferer et al. 2010; Stead et al. 2006; Hickey et al. 2010; Ebrahim et al. 2008). Memory bias is a key limitation that may influence the results from questionnaire-based studies (Stead et al. 2006; Kapferer et al. 2007; Pires et al. 2010). Despite these limitations, the included studies have a consistent and recurring message that oral piercings frequently cause hard and soft tissue complications. Thus, education of patients and increasing their awareness of these risks is imperative, and a key responsibility of healthcare professionals.