# Photodynamic Therapy Effects on Oral Dysplastic Keratinocyte Cell Cultures: A Systematic Review
## 2 Materials and Methods  
A systematic literature search was performed using a different database (PubMed, the Cochrane Library, and ISI Web of Science) following the PRISMA checklist. The search operations ended on 28 October 2022. The search terms used (MeSH terms) were \"(\"photodynamic therapy\") AND (\"in vitro\" OR \"cell culture\") AND (\"oscc\" OR \"oral squamous cell carcinoma\" OR \"opmd\" OR \"oral potentially malignant disorders\" OR \"oral pre-cancerous\")\". The flowchart in Figure 1 shows all the results. A structured approach was used to formulate the research question using five components (\"PICOS\"):the study population (P) consists of dysplastic cell culture treated by topical photodynamic therapy; the intervention (I) was in vitro photodynamic therapy; the comparison (C) was no treatment; the outcome (O) was to assess the results of topical photodynamic therapy in the treatment of pre-malignant and malignant lesions; and the study designs (S) included cross-sectional studies, retrospective cohort studies, prospective comparative studies, case-control studies, case series, and case report. The selection took different steps: after collecting all the initial results, three reviewers ([PERSON], [PERSON], and [PERSON]) read the titles and abstracts, excluded duplicates, and ruled out all those articles that did not meet the inclusion criteria during this initial analysis. Then, two reviewers ([PERSON] and [PERSON]) read the full texts of the remaining articles in depth to better evaluate the content.  
The inclusion criteria were as follows:  
* In vitro studies regarding PDT and potentially or frankly malignant conditions;
* Abstract and main text in English;
* Studies published since 1990.  
The exclusion criteria were as follows:  
* In vivo or ex vivo studies;
* Full text not available;
* Reviews, Acts of Congress, and Letters to the Editor.  
The quality of the included studies was assessed with the QUIN tool (risk-of-bias tool for assessing in vitro studies conducted in oral medicine [23]. Twelve bias domains were assessed, and final assessment was performed by categorizing each of the studies as having \"low\", \"medium\", or \"high\" risk of bias. [PERSON] and [PERSON] performed the bias analysis independently; a third author ([PERSON]) refereed the conflicts. Data were extracted from the  
Figure 1: PRISMA flowchart of the search phase.  
included studies using a standardized data extraction form. Extracted data included the following:  
* Study characteristics: author, publication year, study design, and sample size;
* Photodynamic therapy parameters: light source, photosensitizer used, concentration, exposure time, and irradiance;
* Outcome measures: cell viability, apoptosis, necrosis, reactive oxygen species generation, and other relevant endpoints.  
Any discrepancies in data extraction were resolved through discussion and consensus between the three reviewers. Data were synthesized due to the anticipated heterogeneity of the included studies. Results from individual studies were summarized and presented descriptively. Key findings, trends, and limitations of the included studies were discussed. As this systematic review focused on in vitro studies, no ethical approval was required.  
This review was registered on PROSPERO (registration number: CRD42022362349). Table 1 presents a summary of the results retrieved.  
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