Type II diabetes mellitus (T2DM) is a metabolic disorder marked by hyperglycemia due to insulin resistance and reduced insulin secretion. According to the International Diabetes Federation (IDF) report (2021), an estimated 537 million adults between 20 and 79 years of age have diabetes, accounting for over 10.5 % of the global population within this age range. This figure is expected to increase to 643 million (11.3 %) by 2030 and 783 million (12.2 %) by 2045 [1]. The situation can be worse from a dentistry perspective because T2DM adversely affects multiple body organs, including dental tissues, which subsequently increases the risk of periodontal diseases (due to impaired immune response, inflammation, and microvascular changes), dental caries, and failure of dental treatment [[2], [3], [4], [5], [6]].

Human teeth comprise of three mineralized tissues (enamel, dentine, cementum) and soft pulp. Hydroxyapatite (HA) is the primary constituent of mineralized tissues: enamel (∼95 wt. % HA, ∼4 wt. % water, ∼1 wt. % organic substances), dentine (∼70 wt. % HA, ∼10 wt. % water, ∼20 wt. % organic substances), and cementum (∼45 wt. % HA, ∼20 wt. % water, ∼35 wt. % organic substances). Dental tissues have similar chemical composition but different proportions of major and trace elements. The proportion of trace elements can also vary due to (i) physiological and quality of life factors (age, gender, diet, habitat, and environmental exposure), and (ii) pathological conditions (diseases, abnormalities, and disorders). However, their concentration must be within the permissible limit set by the World Health Organization (WHO); otherwise, adverse effects on teeth have been widely reported [7,8]. Their absence leads to dental caries, defects, and periodontal diseases, whereas excessive intake harms tooth development. Hence, the characteristics of trace elements in dental health remain an area requiring further exploration. It is significant to comprehend the function of trace elements to explain the reason for their detection [[9], [10], [11]]. Their variations in dental tissues also influence the crystallographic properties (size, shape, and arrangement) of hydroxyapatite crystals, consequently reducing mechanical properties of dental tissues [4].

Several spectroscopic methods have been exploited so far to measure the effect of diabetes on human dental tissues; dissolution techniques such as i) inductively coupled plasma mass spectroscopy (ICP-MS) is employed to evaluate the impact of diabetes on the trace elemental composition of radicular dentine [4], and ii) atomic absorption spectroscopy (AAS) is deployed to measure the effect of diabetic and hypertensive disease on teeth [12]. But these methods are destructive in nature and require complex sample preparation. An alternative in the form of a laser spectroscopy technique, LIBS can be assessed, in which a laser pulse removes a minute portion of material from the sample surface, generating a microplasma. As the plasma cools, it releases characteristic light emissions that uniquely identify the elements present. LIBS has several advantages over contemporary analytical techniques (AAS, ICP-MS, and EDS): rapid, online feedback, less destructive, no complicated sample preparation protocols, multi-elemental detection, portable and handheld availability, and relatively cheap instrumentation [13]. The proven capability of fiber-optic LIBS (FO-LIBS) for real-time, in-situ tissue characterization demonstrates its core potential [14]. However, before its clinical deployment for chairside dental use, empirical validation is necessary to quantify its performance on dental tissues in the oral environment and to assess the influence of tissue curvature on analytical efficiency. For LIBS-dental analysis, familiarity with laser-dental tissue interaction and laser-induced dental tissue plasma characteristics is crucial for understanding the dynamics of laser-assisted dental procedures, as it enables precise control of ablation, collateral damage, and tissue selectivity [15]. Variations in laser-induced plasma parameters of tissues are associated with pathological conditions, which lead us to quantify the abnormalities. Plasma temperature and electron number density are key parameters for understanding the processes of atomization, excitation, and ionization during plasma formation. Accurate plasma parameters are required to evaluate, which subsequently assists in quantifying variation in trace elemental concentration associated with abnormality-induced compositional changes in dental tissues [[16], [17], [18]].

Basic understanding of laser-dental interaction, and evolution of LIBS in the field of dentistry, along with its current status in the medical field, is available in [19]. Clinical Nd: YAG laser operated at different energies depending on applications [20], such as energy i) 150 mJ is used for full mouth scaling and root planning in stage III/IV periodontitis patients [21] and ii) 100 mJ is used for bacterial reduction in class II furcation defects associated with chronic periodontitis [22]. But for LIBS analysis laser pulse energy of 200 mJ, which is a bit higher compared to other dental lasers, can be safely used to ablate and ionize a small portion of tissues for elemental analysis. The principal application of LIBS in dentistry is as a diagnostic and analytical technique for evaluating the composition and safety of dental tissues. An optical fiber-based LIBS system provides real-time feedback during laser treatment, where Er: YAG laser light (2.94 μm) is used to ablate decayed tissue while the LIBS signal monitors elemental changes. When the Zn/Ca ratio decreases, it indicates that decayed tissue has been removed, guiding the dentist to stop ablation at the right depth. This integration provides in vivo feedback during procedures [23]. Femtosecond LIBS (fs-LIBS) enables a precise risk assessment of aging amalgam fillings by detecting the diffusion of mercury and other metals into adjacent dental tissues [24].

In scientific laboratories, LIBS has been widely exploited in dentistry for various reasons, such as studies of plasma dynamics of deciduous dental tissues under varying laser fluences have been investigated, with distinct spectral signatures (Pd, Sr, Zn, Fe) enabling differentiation between carious and healthy regions [17]. Comparative studies of using two laser wavelengths (1064 nm vs. 532 nm) revealed that the fundamental harmonic generates higher plasma temperatures but lower electron number densities in both enamel and dentine [18]. LIBS has been applied for demographic profiling, utilizing elemental ratios to determine age [25]. Elemental imaging of ankylosis teeth was performed to discriminate regions of pathology from surrounding tissues [26]. Determining ablation threshold energy density values for emission of Ca and Mg lines in enamel and dentine [27,28]. The analysis of trace elements (Mg, Sr) in human teeth provides information on subject habits, including nutrition, environment, and habitat [29].

To best of our knowledge, LIBS is an unexplored technique for studying the effects of diabetes on dental tissues. Its advantages over other spectroscopic techniques encourage us to explore its true potential in measuring the effects of diabetes on tooth hard tissues. This work assesses diabetic-induced alterations in the composition of tissues (enamel, coronal dentine, and cementum) by evaluating plasma parameters and elemental composition.