Metal allergy and implant failures: a growing diagnostic challenge

Although dental implants offer a highly effective functional solution for replacing missing teeth, metal hypersensitivity is emerging as a significant cause of clinical failure. The integration of exogenous materials into the oral cavity or paranasal sinuses can not only alter the balance of the oral microbiota but also generate deleterious galvanic currents. Given the rise in implant and orthodontic treatments, the prevalence of these allergic complications is increasing, requiring heightened vigilance from the practitioner.

This study, conducted by Besh et al., aims to evaluate current diagnostic approaches to allergic reactions triggered by dental metallic constructions. Based on a literature review of the past five years and the analysis of three complex clinical cases, the authors examine the relevance of available protocols for identifying these sensitisations in daily practice.

The central hypothesis is based on the need for a rigorous and multidisciplinary diagnostic approach. The authors suggest that a thorough medical history, combined with skin tests (patch tests) and the measurement of galvanic potentials, allows a formal link to be established between systemic or local symptoms — sometimes atypical, such as facial oedema or headaches — and the presence of metallic components such as titanium, nickel or chromium.

Study design and setting

This study is based on a dual approach combining a scientific literature review and the analysis of prospective clinical cases. The literature search was conducted via the Pubmed database, targeting publications issued over the last five years (2021-2026). The objective was to evaluate current diagnostic approaches to allergic reactions to metallic structures in dentistry.

Clinical sampling

The clinical illustration is based on a cohort of three patients (n=3) presenting with chronic local or systemic symptoms following the placement of metallic devices:

• Case 1: A 45-year-old female patient with metal bridges (placed 8 and 2 years ago).
• Case 2: A 37-year-old patient who underwent immediate implantation of tooth 36 (Osstem system, South Korea) two years previously.
• Case 3: A 54-year-old female patient with metal bridges placed 9 months and 10 years ago.

Experimental protocol and analysis

The applied diagnostic protocol includes the following steps:

• Comprehensive anamnesis: Evaluation of a history of metal intolerance (jewellery) and prosthetic/implant history.
• Imaging: Use of computed tomography (CT) for the examination of oral and dental structures and paranasal sinuses.
• Patch-testing: Specific skin tests to identify sensitisation to titanium, nickel and chromium.
• Assessment of galvanism: For the third case, a measurement of the electrical potential difference was performed intraorally to detect any potential galvanic currents between the various metallic restorations.

Clinical results and diagnostic observations

The authors of this study structured their results around a recent literature review (last 5 years) and three documented clinical cases. The data confirm that hypersensitivity reactions to metallic components, although sometimes delayed, present varied systemic and local manifestations.

Summary of reported clinical cases

The following table summarises the clinical observations and allergy test results for the three patients monitored as part of this study:

Qualitative and diagnostic observations

The case analysis highlights several critical points for the practitioner:

• Symptom latency: In case no. 1, although an initial metallic structure was tolerated for 8 years, the addition of a new construction two years previously triggered severe systemic deterioration.
• Polysensitisation: The patch test of the first case revealed cross or multiple sensitivity (Titanium, Nickel, Chromium), highlighting that the implant is not always the sole vector involved.
• Extra-oral manifestations: The results show that allergy to dental metals is not limited to the oral mucosa. Symptoms such as nasal obstruction, sleep disturbances and skin reactions on the limbs (Case No. 2) have been directly linked to the presence of intra-oral devices.
• The role of galvanism: For case no. 3, the presence of prostheses of different ages and compositions (10 years vs 9 months) suggests that galvanic currents may exacerbate or simulate an allergic response.

The study emphasises that cone beam computed tomography (CBCT) and meticulous allergy history taking (particularly intolerance to metal jewellery) are major predictive indicators prior to any complex implant or prosthetic procedure.

Clinical analysis and implications of metal hypersensitivities

The study by Besh et al. highlights a major clinical finding: the failure of prosthetic or implant integration is not exclusively due to mechanical or infectious factors. The three clinical cases presented demonstrate that metal sensitisation, particularly to titanium (identified in the 45-year-old female patient), can induce severe systemic symptoms ranging from airway obstruction to anxiety disorders. Notably, the study emphasises that allergic manifestations can be delayed by several years (up to 8 years in case 1) or masked by concomitant allergies, such as dust mites in the case of the 37-year-old patient with an Osstem implant.

The analysis suggests that the accumulation of different metals in the oral cavity promotes oral galvanism, particularly evident in case 3 where the 54-year-old female patient presented an overlap of old and recent restorations. Although this study is limited to a case series and a 5-year literature review, it proves that the patch test remains an essential diagnostic tool when the patient's complaints (oedemas, stomatitis, glossodynia) find no obvious periodontal or occlusal explanation.

Summary of results

This study highlights the clinical reality of type IV hypersensitivity reactions related to implant and prosthetic materials. Through three clinical cases (37 to 54 years), the authors demonstrate that the presence of titanium, nickel or chromium can induce severe extra-oral symptoms, such as chronic facial oedema or respiratory disorders, confirmed by a positive patch test.

In practical terms, for the practitioner:

• Anamnestic screening: Systematically include a question about intolerance to costume jewellery (earrings, watches) in the pre-implant medical questionnaire to identify a predisposition to metal allergies.
• Differential diagnosis: In the presence of persistent atypical symptoms (glossodynia, morning oedema, metallic taste), measure the electrical potential difference between the different restorations to rule out oral galvanism before any removal.
• Test protocol: In case of suspected biological implant failure, refer the patient for a specific patch test including titanium, nickel and chromium to validate the need for replacement with alternative materials (such as zirconia).

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