In order to clarify the aetiological factors related to OLP, the present study purposed to investigate the relationship between dental restorative materials and OLP. Differences between patients with and without metal or amalgam were studied. As a clinical consequence, advice on dental sanitation should be given. Furthermore, the hypothesis that individual and intra-oral factors correlate with OHIP-values, needs to be considered. The influence of individual and intra-oral factors on the presentation form of the disease must be analyzed.
Patients had an average age of 60 years and 81.25% were women. In general, more middle-aged women than men are affected. They also achieved significantly higher OHIP values, although the severe generalized cases of lichens of this study occurred more often in men. A Swedish group analyzed the gender-specific incidence of autoimmune diseases from national registers and revealed that the classical view of the female predominance of autoimmune diseases may be far from striking than previously believed .
Adverse reactions in the oral cavity due to contact to dental material have been described in numerous studies. The most commonly problems of local exposure to restorative materials are local inflammatory reactions due to toxic irritant or allergic effects . Especially the safety of amalgam has been discussed. The continuous low-level release of mercury of amalgam fillings is concerning. The main concerns relate to the potential toxic effects of mercury and the possibility that mercury may induce adverse immunological reactions .
Several studies suggest that dental amalgam fillings and metal restorations may induce oral lichen planus or oral lichenoid reactions in the oral mucosa in susceptible patients. Skin patch test studies investigated the contact sensitivity response to dental materials of OLP patients. Several studies produced conflicting results with a span of 8 to 92% of OLP patients being positive [9, 21]. A review of Issa et al. concluded that the evidence from observational studies suggests that patch testing seems to be of limited value as an indicator for replacing amalgam restorations and predicting outcome . Regardless of the results of the patch tests a regression of oral mucosal lesions after removal of amalgam has been found .
This raises the question of whether amalgam fillings of patients with OLP need to be removed? In a review the proportion of individuals achieving complete healing varied from 37 to 100% although, in total 15% of patients showed no improvement after replacement of their amalgam restorations [10, 21]. The disease course after replacement of amalgam is not uniform across the reported studies.
How can we identify lesions that would respond to amalgam replacement? A close topographical relationship between lesions and amalgam fillings appears to be the best predictor [8–11].
According to the grading of Thornhill, the strength of association between the mucosal lesions and the amalgam restoration is the key criterion. Only amalgam fillings in direct contact with the mucosa need to be removed to achieve lesion resolution . Our results show that the grading did not differ between the presentation forms or the clinical form of OLP.
This leads to the question; which material can be recommended to the affected patients? According to Thornhill et al., the different replacement filling or crown materials used were equally effective. Inert materials are preferable .
Martin et al. defined risk factors for OLP: number of teeth with amalgam, total surfaces of amalgam, number of teeth with gold, corrosion, and bimetallism . This is difficult to apply to our results, as the patients studied had fewer fillings, especially fewer amalgam fillings. The most common filling material in our study was composite.
Ahlgren et al. found a high incidence of contact allergy to gold in patients with OLP. The frequency of contact allergy to gold was 28.9% in patients with oral lichen lesions and 22.9% in the clinically examined control patients. They suggest dental gold to be part of the etiology or a maintenance factor for patients with oral lichen lesions . Our investigation showed a correlation between gold and the generalized lichen form, which represents a more severe manifestation of OLP. We found no correlation with amalgam or metal.
The OHIP score of the 112 patients examined by us was more than 3 times higher than the average value of the German general population . Numerous studies have examined the quality of life of patients with OLP. The OHIP scores were between 9.42 and 21.6 [26–31].
Patients with a reticular form of OLP had less pain and lower OHIP scores. We revealed in another study that patients with a reticular OLP had lower OHIP scores which implies a higher OHRQoL .
Our results show a high positive correlation between OHIP and pain. That means, the higher the pain, the higher the OHIP-value. Oral mucosal disease not only causes a local reaction but affects the whole patient. That means, pain severity is the most important contributor to the increase of OHIP-values, and severe pain is the most influential to increase OHIP-values.
A recent Cochrane review quoted that the impact of pain on physical, emotional, and social functions required multi-dimensional qualitative tools and health-related quality of life instruments that are uncommonly used in OLP trials .
One third of patients with OLP have psychological comorbidities like anxiety, depressive or distress symptoms [33–35]. It is believed that autoimmune diseases influence the psyche of affected patients. Interesting research by Pippi et al. investigated the influence of the clinical form of OLP on these psychological aspects. Patients with severe forms of OLP were not associated with certain psychological traits . In our study patients with non-reticular OLP forms suffered more and had higher OHIP values.
Several external factors have been proposed to trigger OPL, including dental materials and psychological stress . Stress is an important etiological factor that can trigger an attack of pain. So we have to not only treat the local reaction of the oral mucosa we have to treat the patient as a whole. Especially psychological factors need to be considered.
Early diagnosis and treatment of oral mucosal diseases can reduce the impact on the quality of life of affected patients in the future [38, 39].
Our sample included only patients from one dental clinic which limits generalization. The main limits are the reduced number of study subjects and not having a control group with patients after removal/replacement of dental restoration materials. So far, dental status, periodontal health, and oral hygiene have not been taken into account in our investigations. These factors additionally influence the OHRQoL and have to be regarded in the future.