**1. Introduction**

According to the World Health Organization (WHO), cancer would take the lives of 10.3 million people globally by 2020, and patients with oral cancer would have a five-year survival rate of just 50% globally. Oral cancer is a challenging disease that affects about 600,000 individuals worldwide each year and is linked to a high rate of morbidity and mortality [1–4]. Mouth cancer is a group of tumors that may affect any area of the mouth, including the pharynx and salivary glands, as well as the surrounding tissues [5]. This term, on the other hand, is often interchanged with oral squamous cell carcinoma (OSCC), the most common malignant epithelial tumor of the oral cavity. OSCC is thought to be responsible for more than 90% of all oral neoplasms [6]. According to the current study results, year survival rates for OSCC range from 50 to 60%, depending on a number of factors such as the patient's lifestyle, the timing of diagnosis, and the location of the primary tumor [7, 8]. As a consequence, OSCC is linked with a poor prognosis in the medical community. Patients with OSCC who get conventional therapy have a significant recurrence rate of the illness, regardless of when treatment started (18–76%). The use of biopsy or histology testing to diagnose OSCC is time intensive, resulting in a

delay in treatment initiation, and as a result, a shorter overall survival time period is obtained [9]. Early-stage cancer detection is critical in determining the most suitable treatment for the patient, which has an impact on their total survival, as stated in the previous paragraph. According to recent research studies, the development of cancer is related to the molecular level of particular indicators in tumor tissue and bodily fluids. Molecular biomarkers, which are categorized as genomic, proteomic, and metabolomic profiles of body specimens, are used to identify the existence or absence of a certain malignancy, as well as its spread and recurrence, among other things. Science and technology focused on extremely small objects, and nanoscience and nanotechnology are providing innovative methods to cancer treatment and detection. Site-specific chemoprevention/therapy using nanoparticles for local drug delivery has recently gained popularity. It is a novel method for treating cancer that aims to overcome and minimize the limits of current cancer treatment and diagnostics. It can detect a single cancer cell *in vivo* and administer drugs straight to it. Nanotechnology has also improved the detection of cancer biomarkers [10–12]. Oral cancer is often treated with a multidisciplinary approach that involves surgery, chemotherapy, and radiation. However, conventional chemotherapy medicines may be ineffective and have side effects. Many nanoparticles have been employed as technological drivers of innovation to overcome these constraints. The present book chapter seeks to highlight developments in the use of new methods in the detection and treatment of oral cancer due to the significance of OSCC as a widespread public health issue. The purpose of this book chapter is to describe the current preclinical state of nano-based methods for oral cancer detection and therapy. This review also discussed (a) oral squamous cell carcinoma, (b) OSCC diagnosis using serum and saliva biomarkers, (c) nano-based OSCC biomarker detection, (d) OSCC therapy methods, and (e) nanotechnology techniques for OSCC treatment or diagnostic.

#### **2. Squamous cell carcinoma of the oral cavity**

Oral cancers are a group of cancers that develop in different parts of the mouth, each with its own set of risk factors, incidence, and treatment options [13]. Understanding the mechanisms of cancer initiation and progression may aid us in selecting the most appropriate therapeutic strategy at the appropriate time. Despite advances in therapeutic methods, the morbidity and mortality ratios for squamous cell carcinoma of the oral cavity have remained unchanged for the past 30 years. After a carcinogenic insult to the oral cavity, it occurs in several steps, resulting in various molecular changes that disrupt cellular growth, proliferation, and differentiation. The latter is marked by cellular transformation and carcinogenesis. Oral carcinogenesis follows the same pattern as other cancers, starting with a precursor lesion and progressing to localized and metastatic disease [14]. The histological grade of dysplasia indicates how far the disease has progressed from normal to hyperplasia. The most common cellular events discovered in these examinations are changes in nuclear size and shape, enlarged cells and nuclei, enhanced mitotic picture, and increased nucleus/cytoplasm ratio. Elevated cellular density, dyskeratosis, hyperplasia of basal cells, bulbous drop-form of rete pegs, and secondary nodules on rete tips are pathological features of tissues in the later stages of squamous cell carcinoma.
