Table 1. Active vibration modes in the spectrum of intact enamel and enamel area with the emerging caries process and their assignment to specific molecular groups.

Point 1. Enamel.	Point 2. Caries.	Assignment	Ref.
	380	DCPD	[17]
	410	DCPD	[17]
437	448	${\nu }_2{\text{PO}}_{\text{4}}^{\text{3-}}$ (HAp)	[9–11], [21]
581	572	${\nu }_4{\text{PO}}_{\text{4}}^{\text{3-}}$ (HAp)	[9–11], [21]
	607	${\nu }_4{\text{PO}}_{\text{4}}^{\text{3-}}$ (HAp)	[9–11], [21]
649	647	OH libration (HAp)	[9–11], [21]
	710	CaCO3 hydrated	[9–11], [21]
754	766	B-type ${\nu }_4{\text{CO}}_{\text{3}}^{\text{2-}}$ (HAp)	[9–11], [21]
835	841	ν(O—P—O)	[9–11], [21]
	877	DCPD	[17]
	927	P-OH stretch (HAp)	[9–11], [21]
960	960	${\nu }_1{\text{PO}}_{\text{4}}^{\text{3-}}$(HAp)	[9–11], [21]
	986	DCPD (max.int.)	[17]
	1015	${\nu }_3{\text{PO}}_{\text{4}}^{\text{3-}}$(HAp)	[9–11], [21]
1043	1049	1. ${\nu }_3{\text{PO}}_{\text{4}}^{\text{3-}}$(HAp) 2. DCPD 3. ν(C—O)	[17] [9–11], [21]
1072	1072	1. B-type ${\text{CO}}_{\text{3}}^{\text{2-}}$ (HAp)—PO4 substitution 2. DCPD 3. CaCO3 hydrated	[17] [9–11], [21]
	1117	A-type ${\text{CO}}_{\text{3}}^{\text{2-}}$ (HAp)—OH substitution	[17]