Table 1.

Characteristics of the studies included in the systematic review

Authors and year of publication	Aim	Type of study	Sample size, comparison group, and control group	Periodontal parameters assessed	Conclusion
Azizi A, Rezaee M 2012[7]	To examine the periodontal status of subjects with gingival oral lichen planus (OLP) compared to control	Case-control study	Total of 64 subjects (32 with oral lichen planus, 32 without oral lichen planus controls)	Plaque index (PI), Bleeding on probing (BOP), Clinical attachment level (CAL), Gingival Index (GI), Probing depth (PD)	PI, GI, PD, BOP, and CAL were significantly higher in the case group compared with the control group.
Ramon-Fluixa C, Bagan-Sebastian JV, Milian-Masanet MA, Scully C 1999[4]	To investigate the possible influence of dental plaque and derived periodontal alterations upon OLP lesions.	Case-control study	90 individuals with Oral Lichen Planus and 52 individuals without lichen planus (controls)	PI, Simplified calculus Index (CIS), Periodontal Disease Index (PDI)	Increased plaque and calculus deposits are associated with a significantly higher incidence of atrophic-erosive gingival lesions in individuals with OLP.
Rai NP, Kumar P, Mustafa SM, Divakar DD, Kheraif AA, Ramakrishnaiah R, et al. 2016[5]	To evaluate the periodontal status of OLP patients and compare it with that of healthy controls.	Pilot study	30 (erosive and reticular) OLP and 30 controls	GI, Russell’s periodontal index (RPI), and BOP	Periodontal status was poor in the study group as compared to the control group.
Wang H, Luo Z, Lei L, Sun Z, Zhou M, Dan H, et al. 2014[8]	To compare serum expression levels of IL-23 and IL-17 in chronic oral lichen planus patients with periodontitis (OLP-CP), patients only with chronic periodontitis (CP) or OLP, and healthy controls (HC).	Case-control study	35 Oral Lichen Planus-chronic periodontitis patients (OLP-CP), 35 Oral Lichen Planus patients (OLP), 30 Chronic Periodontitis patients (CP), and 30 healthy controls (HC)	Serum IL-17 and IL-23 PD, attachment loss (AL), PI, GI	There was a significantly positive correlation between serum IL-17 level, probing depth, and plaque index in OLP-CP group patients
Ertugrul AS, Dursun R, Dundar N, Avunduk MC, Hakki SS 2013[9]	To investigate matrix metalloproteinase (MMP)-1, MMP-9, and MMP inhibitor-1 (TIMP-1) levels in gingival crevicular fluid (GCF) by enzyme-linked immunosorbent assay and by immunohistochemical staining of samples from patients with and without OLP.	Case-control study	27 patients with OLP and 30 healthy non-OLP patients	MMP-1, MMP-9, and TIMP-1 levels in GCF PI, GI, PD, CAL	Increased levels of MMP-1 and MMP-9 with decreased levels of TIMP-1 in GCF and in the gingival tissue of OLP patients, in combination with poor oral hygiene, may cause increased tissue breakdown.
Liu H, Chen H, Liao Y, Li H, Shi L, Deng Y, et al. 2021[10]	To compare the microbiota composition and bacterial diversity of subgingival plaque in chronic periodontitis patients with and without gingival erosive oral lichen planus.	Case-control study	20 chronic periodontitis patients with gingival erosive oral lichen planus (CP-OLP group) and 19 chronic periodontitis patients without gingival erosive oral lichen planus (CP group)	Subgingival microbiota, Full mouth probing depth (FMPD), CAL	Microbiome in erosive OLP with CP was significantly different from that found in only CP, and microbiome changes might be related to the presence or absence of OLP disease.
Wang H, Han Q, Luo Z, Xu C, Liu J, Dan H, et al. 2014[11]	To compare the expression levels of interleukin (IL)-17 and IL-23 in local periodontal tissues from patients with both chronic periodontitis and oral lichen planus (CP-OLP), patients with chronic periodontitis (CP) only, patients with oral lichen planus (OLP) only, and healthy controls (HC).	Case-control study	15 CP-OLP patients, 15 CP patients, 15 OLP patients, and ten healthy controls.	CAL, PD, Silness–Loe plaque index (PI), and Loe–Silness gingival index (GI) scores.	There was an increased expression level of IL-17 and IL-23 in periodontal tissues from periodontitis patients with oral lichen planus, which might aggravate the inflammatory response in local lesions.
Ertugrul AS, Arslan U, Dursun R, Hakki SS 2013[12]	To identify the prevalence of the detection of periodontopathogenic microorganisms (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia and Treponema denticola in OLP patients and to compare with this prevalence of periodontopathogenic microorganisms in healthy non-OLP patients.	Case-control study	27 (18 chronic periodontitis (OLPP) and nine gingivitis (OLPG) patients diagnosed with OLP, along with 26 (13 chronic periodontitis (HP) and 13 gingivitis (HG) healthy non-OLP patients.	Periodontopathogenic microorganisms present in subgingival plaque samples Actinomycetemcomitans, P. Gingivalis, P.Intermedia, T. Forsythia and T. Denticola) PI, GI, PD, CAL	OLP patients have higher levels of infection with A. Actinomycetemcomitans, P. Gingivalis, P. Intermedia, T. Forsythia and T. Denticola as compared to non-OLP patients.