## 1 Introduction
In fact, while FTIR shows some limitations due to the diffraction limit, which restricts the achievable spatial resolution to 10-20 \(\upmu\)m, the shorter wavelengths exploited by RMS yield a diffraction-limited spatial resolution of 1 \(\upmu\)m or less, depending on the objective [3; 15]. Vibrational techniques have also been employed in dentistry for the analysis and chemical characterization of both dental materials and teeth components [17; 20; 21; 22; 23]. Indeed, FTIR was used to track the polymerization kinetics of dental resin composites [24; 25; 26; 27] and adhesives [28; 29]. Furthermore, the IR technique was exploited to determine the effects of materials containing nanohydroxapatite on the enamel surface [30; 31], to analyze new generation biomimetic materials mimicking the mineral organic dentin and enamel complex [32], and to characterize implant materials, biopolymers, ceramics, and resin nanocomposites [33; 34; 35]. Regarding RMS, its applicative potential in the dental field has not yet been fully exploited, even if recent results suggest a promising use of this technique for the characterization of hard dental tissues, also for diagnostic purposes [13; 36]. RMS has been demonstrated to be a successful tool for the diagnosis of oral cancer [37] and for the study of tooth mineral tissues, due to its sensitivity in the analysis of both mineral and organic components, as well as for the detection of early caries by using innovative fiber optical probes [9; 38; 39; 40] and the evaluation of caries progression [19; 41]. Other techniques have already been exploited for the study of dental tissues, such as scanning electron microscopy [42; 43; 44], X-Ray diffraction [42; 45], microcomputed tomography [46; 47], and energy dispersive X-ray spectroscopy [36; 48]: all these imaging techniques can obtain high-resolution information on the morphological features and/or the elemental composition of the samples of interest. Conversely, RMS can acquire maps, both on the surface of the tooth or at depth, that provide a morpho-chemical correlation between the microscopic information derived from the visual analysis of the sample and its chemical and macromolecular composition, at the same time and on the same sample. In this light, RMS represents an innovative and non-invasive technique to study both inorganic and organic teeth components in vitro [49]. Therefore, this narrative review aims to summarize the application of Raman Microspectroscopy in the dental field. In particular, specific Raman markers representative of sound and pathological hard dental tissues will be discussed. The possibility of simultaneously obtained detailed and objective information on biochemical structure and chemical composition is crucial to relate the morphological alterations characterizing the different dental pathologies with variations in terms of the chemical features of hard dental tissues. Moreover, the benefits and the limitations of this technique will be outlined. Finally, this narrative review may be a useful starting point for new research on this topic and for possible future diagnostic application in clinical practice: from bench-top to chair-side.