One hundred and fifty patients with oral lichen planus (LP) seen over a period of about 12 years were retrospectively studied and evaluated. Age, gender, site of lesion, presence of dental restorations and/or appliances were recorded and analyzed. Findings showed a slight preponderance of females (53%) to males (47%). The highest prevalence was found to be between 41-50 years of age. Among the different ciinical forms of oral LP, the reticular type was the most common (56%) followed by erosive (26%), plaque (f 1%) atrophic (6%) and bullous (0.4%) types. The buccal mucosa was the most commonly affected site (83%) while the least affected was the ventrum of the tongue (5%). Beside pathogenesis and premaiignant potential of lichen planus, local and systemic findings are discussed.
 

Lichen planus (LP) is one of the important mucocutaneous lesions that should be of concern to dental clinicians. Its prevalence among the general population was reported to vary between 0.02% and 2%.'"³ A study of 981 patients with oral lesions referred to an oral medicine private practice clinic showed that 20% of patients had oral LP.⁴ The different clinical and histological features of oral LP had been extensively discussed in several review reports.⁵"⁹ The literature show that only two studies were reported on oral LP among the Saudi populations with a prevalence of 0.6% and 1.7%, respectively.¹⁰"¹¹

The purpose of this study was to present our clinical experience with 150 Saudi patients who had oral LP and were seen over a period of about 12 years.
 

One hundred and fifty patients with oral LP were examined in the Oral Medicine Clinic at the College of Dentistry, King Saud University during the period 1981-1993. Some of these patients were referred by general practitioners in the city of Riyadh, where the College is considered to be one of the main referral centers for oral diseases. Other patients were referred from different parts of the Kingdom of Saudi Arabia. Another group of patients was referred from oral diagnosis clinic in the same College where their lesions were discovered during a routine dental examination.

Age, gender, site of lesion, presence of dental restorations and/or appliances were recorded and analyzed. Classification of cases was based on the scheme of Scully and El-Kom.⁶ The diagnosis, especially for the reticular or plaque type of LP, was based on the history and clinical examination. Cases presenting atrophic, erosive or bullous type were biopsied whenever the diagnosis was questionable [Figs. 1-2].
 

Age-range of patients was 16 to 80 years, with the highest prevalence among the 41-50 years old. There was a slight preponderance of females (53%) in comparison to the males (47%). Females were affected almost equally between the ages of 31-40 (16%) and 41-50 (17%) years. Males showed a significantly higher prevalence at the age of 41-50 years (19%) compared to other age ranges. Distribution of age and gender is presented in Table 1.

Two-hundred and forty clinical lesions were seen in 150 patients (Table 2). In both males and females, the reticular form predominated followed by the erosives, the plaque and the atrophic forms, respectively. Bullous type was rare and seen in only one female patient.

The distribution of lesions in the oral cavity is shown in Table 3. The right and left buccal mucosa were affected almost equally with 123 and 124 lesions, respectively.

Similarly, the upper and lower gingiva were almost equal with 31 and 29 patients affected, respectively. The least commonly affected site was the dorsum of the tongue (5%).

The presence of dental restorations and/or appliances is summarized in Table 4. One hundred and two patients (68%) had amalgam restorations, 21(14%) had fixed metal prostheses, while those wearing partial or complete dentures were 27(18%) and 19 (13%), respectively.
Table 5 presents the relationship of local factors to the site of lesions. Amalgam restorations were found to be associated with a significantly high percentage of oral LP lesions on the right buccal mucosa (55%), left buccal mucosa (56%), lateral border and dorsum of tongue (63%), ventrum of tongue (41%) and palate (65%). On the other hand, lesions of the upper and lower gingivae were associated with fixed metal prostheses, 78% and 73%, respectively.

Systemic findings showed that diabetes mellitus was the most common condition among the studied cases (19%) followed by skin lesions (16%), allergy (13%), hypertension (9%), and history of stress (9%). In fifty one patients (34%) no medical condition were detected or reported (Table 6).
 

The current study of 150 cases of oral LP is the largest report to date from a single center in Saudi Arabia. In 1985, Mani¹⁰ reported four cases among 674 dental patients. Salem" reported 72 cases in 1989 among a Saudi population of 4,277 individuals.

Findings of the present study in regard to age and gender of patients and the site distribution of oral LP lesions are in agreement with previously reported studies from different parts of the world.¹²"¹⁵ Among the clinical forms of oral LP in this study, the reticular type was the most common, followed by the erosive, plaque and atrophic types, respectively. One study, however, reported that the erosive type was the most common.¹⁶ This could be explained by the fact that the erosive type presents with associated clinical symptoms, thus, patients are more likely to report for treatment. In our institution the initial examination of all patients seeking any type of dental treatment is usually carried out by a trained oral diagnosis specialist, thus, the reticular type of oral LP is recognized and referred to the oral medicine clinic.

Several reports linked LP with some systemic conditions, like diabetes, hypertension, stress, liver diseases and others.¹⁷"²⁰ In this study, the general percentage of patients with diabetes mellitus (19%) was found to be higher than the reported incidence of 6.5% and 4.3.% among normal individuals.'¹" The association of LP in this regard could not be determined due to shortage of information on the prevalence of other systemic conditions among the general population of Saudi Arabia.

The pathogenesis of LP is not fully understood, but recent investigations at both cellular and molecular levels indicate that cell mediated immunity plays a major role in the histopathological changes of LP lesions. Jontell and co-workers reported an increase in mast cells in the subepithelial infiltrate similar to that seen in classic reactions of delayed hypersensitivity. Walsh et al²⁴ noted changes in the number of Langerhans and mast cells and suggested that oral LP may be initiated by degranulation of mast cells, which induces adhesion of molecules on the endothelium and, subsequently, facilitates lymphocytic infiltrate to the involved tissues. Hypersensitivity reactions to dental materials, such as mercury, ammonium chloride, and nickel sulfate, were noted in a significant number of patients with lichenoid oral mucosal lesions.²⁵"²⁹

In this study, the distribution of local factors in relation to the site of LP lesions (Table 5) showed that 78% of the gingival lesions were associated with fixed bridges whereas no cases of palatal lesions were seen in patients with complete dentures. This might give some indication about the importance of local factors in the development of LP lesions, an observation for further investigation.

The malignant potential of lichen planus is still controversial. In an extensive study involving 722 Indian patients, Murti et al³⁰ observed malignant change in only 0.4% after, a follow-up period ranging between three and ten years. This observation was not significantly different from the estimated number in the general Indian population. Holmstrup³¹ and co-workers reported a 50-fold increase in malignant development in oral lichen planus cases compared to the general Danish population. Krutchkoff and Eisenberg³² coined the term lichenoid dysplasia to describe conditions diagnosed clinically as lichen planus but which, histologically, showed some features of epithelial dysplasia. The lichenoid dysplasia concept was supported by Lovas et al who suggested that the apparent malignant transformation of oral lichen planus might likely represent erythroplakia or leukoplakia, which were dysplastic ab initio. In the present study, there was no malignant transformation in oral lichen planus in contrast to the study conducted in Gizan region of Saudi Arabia by Salem¹' who reported such malignant transformation in 4 cases of 72 patients after a follow-up period of 3.2 years. Moreover, Gizan region is noted for a relatively high prevalence of oral cancer due to 'Shama' usage. This explains the significant difference between our observation and those reported by Salem.