Periodontal Disease Monitoring by Raman Spectroscopy of Phosphates: New Insights into Pyrophosphate Activity

Abstract

(1) Background: The intent of this survey was to investigate the quality of the alveolar bone by revealing the different phases for calcified tissues independent of the medical history of the patient in relation to periodontal disease by means of Raman spectroscopy and then to correlate the results by suggesting a possible mechanism for the medical impairment; (2) Methods: The investigation was mainly based on Raman spectroscopy that was performed in vivo during surgery for the selected group of patients. The targeted peaks for the Raman spectra were according to the reference compounds (e.g., calcium phosphates, other phosphates); (3) Results: The variation in the intensity of the spectrum correlated to the specific bone constituents' concentrations highlights the bone quality, while some compounds (such as pyrophosphate, PPi) are strongly related to the patient's medical status, and they provide information regarding a physiological process that occurred in the calcified tissues. Moreover, bone sample fluorescence is related to the collagen (Col) content, enabling a complete evaluation of bone quality, revealing the importance of collagen matrix acting as a load-bearing element for Calcium phosphate (CaP) deposition during the complex bone mineralization process; (4) Conclusions: We highlight that Raman spectroscopy can be considered a viable investigative method for in vivo and rapid bone quality valuation through oral health monitoring.

Keywords: Raman spectroscopy; hydroxyapatite (HAP); octacalcium phosphate (OCP); periodontal disease; pyrophosphate (PPi).

Figure 1

Maxillary sinus floor elevation (patient #3): lateral bony window with the ‘trap-door’ technique (a), sinus filled with inorganic bovine bone mineral (b), lateral window covered by resorbable collagen membrane (c), wound closure (d).

Figure 2

Raman spectra for basic calcium phosphate compounds.

Figure 3

Raman spectra for hydroxyapatite and bone substitutes.

Figure 4

Luminescence corresponding to selected patients according to medical status (healthy, previous periodontitis and periodontitis). (a) Raw data for Raman spectra; (b) Normalized values of Col for Raman shift related to reference value 550 cm⁻¹.

Figure 5

Raman spectra, representative for the patient’s medical status (healthy, previous periodontitis and periodontitis).

Figure 6

The suggested mechanism for OCP transition to HAP and possible explanation for periodontal disease.