A comparative analysis of metal allergens associated with dental alloy prostheses and the expression of HLA-DR in gingival tissue

Abstract

The present study aimed to provide guidance for the selection of prosthodontic materials and the management of patients with a suspected metal allergy. This included a comparison of the sensitivity of patients to alloys used in prescribed metal‑containing prostheses, and correlation analysis between metal allergy and accompanying clinical symptoms of sensitized patients using a patch test. The results from the patch test and metal component analyses were processed to reach a final diagnosis. In the present study, four dental alloys were assessed. Subsequent to polishing the surface of a metal restoration, the components were analyzed using an X‑ray fluorescence microscopy and spectrometry. Immunohistochemical analysis, reverse transcription‑polymerase chain reaction and western blotting were used to detect the expression levels of human leukocyte antigen (HLA)‑DR in gingival tissues affected by alloy restoration, and in normal gingival tissue samples. Positive allergens identified in the patch test were consistent with the components of the metal prostheses. The prevalence of nickel (Ni) allergy was highest (22.8%), and women were significantly more allergic to palladium and Ni than men (P<0.05). The protein and gene expression levels of HLA‑DR in the Ni‑chromium (Cr) prosthesis group were significantly higher, compared with those in the other groups (P<0.01); followed by cobalt‑Cr alloy, gold alloy and titanium alloy. In conclusion, dentists require an understanding of the corrosion and allergy rates of prescribed alloys, in order to reduce the risk of allergic reactions. Patch testing for hypersensitive patients is recommended and caution is required when planning to use different alloys in the mouth.

Figure 1

(A) A patch test was performed on 92 subjects with dental alloys, in order to compare the sensitivity to dental metal materials. The positive ratio of the various allergens are presented. (B) Patch test exhibited a delayed reaction. Results are usually observed at 72 h; however, in the present study, results were observed at either 96 h, 7 days or longer if necessary, in order to exclude false-negative results. This is an example of a delayed reaction to palladium.

Figure 2

Case 1: Removal or replacement of a prosthesis in a patient diagnosed with metal allergy improved the majority of clinical symptoms at follow-up. Clinical features of case 1: Following restoration with a 25–27 fixed bridge, cheilitis and recurrent perioral dermatitis and eczema were observed. (A) Patch test results. Patch test results showed NiSO₄ (++), PdCl₂ (+), CoCl₂ (+), and MnO₂ (+). +, ++, and +++ were determined as positive reactions, subject to the allergic reaction of the patient. (B) Detection of alloy restoration composition using X-ray fluorescence microscope spectrometry (XFMS). The composition of Ni (87.52%), Cr (9.65%) and Mo (2.65%) components detected by XFMS was in accordance with the metal component of prosthesis obtained by patch test method. (C) Before treatment: Cheilitis, recurrent skin eczema and perioral dermatitis lasted for 1 year following placement of bridge implants. After treatment: 1 month following-removal of the dental implants and replacement with a whole porcelain-fixed bridge.

Figure 3

Clinical features of case 2. Following repair to 36 porcelain crowns, dermatitis of the face and ear were observed. (A) Patch test results. Patch test results showed ZnCl₂ (+), and CoCl2 (+). +, ++, and +++ were determined as positive reactions, subject to the allergic reaction of the patient. (B) Detection of alloy restoration composition using X-ray fluorescence microscope spectrometry (XFMS). The composition of Co (73.96%), Cr (17.82%) and Fe (8.22%) components detected by XFMS was in accordance with the metal component of prosthesis obtained by patch test method. (C) Before treatment: Dermatitis of the face and ear lasted for 1 year after the patient received 36 porcelain crowns implants. After treatment: following removal of the dental implants and replacement with porcelain crowns.

Figure 4

(A) Expression levels of human leukocyte antigen-DR in the oral mucosa epithelium of the normal gingival tissue and gingival tissue of patients with alloy restorations was determined using immunohistochemistry (horseradish peroxidase staining technique). Scale bar=0.5 μm. (B) Compared with normal gingival tissue, HLA-DR positivity was increased in the alloy restoration groups. ^*P<0.05 and ^**P<0.01, vs. control group. Ni, nickel; Cr, chromium; Co, cobalt; Au, gold; Ti, titanium.

Figure 5

(A) Total RNA was extracted from gingival tissues and relative expression levels of HLA-DR were detected by polymerase chain reaction. ^*P<0.05 and ^**P<0.01, vs. control. (B) Following treatment with alloy restorations for ~1 year, the protein expression levels of HLA-DR were detected by western blotting. ^*P<0.05 and ^**P<0.01, vs. control. HLA, human leukocyte antigen; Ni, nickel; Cr, chromium; Co, cobalt; Au, gold; Ti, titanium; GAPDH, glyceraldehyde 3-phosphate dehydrogenase.