Table 1.

Characteristics of the included studies.

Author and Year of Publication.	Main Characteristics of Models	Cell Lines Origin	Post-OVX Period (months)	Outcomes	Method for the Measurement of Bone Density and/or Oestrogen Deficiency
OU Q. et al., 2018 [22]	12 caries-free premolars extracted for orthodontic reasons from donors aged between 18 and 20	hPDLSCs	NR	Effects of E2 on hPDLSCs	Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR); Western blotting; Immunofluorescence staining analysis
LING-LING E. et al., 2016 [23]	48 healthy Sprague-Dawley female rats were randomly divided into three groups: OVX group; OVX + 17β oestradiol (E2) group, and Sham group	PDLSCs cells of animal origin	3	Effect of oestrogen on osteogenic differentiation in the PLDSCs; The role of oestrogen in regulating the mRNA expression levels of ALP, OCN, ERα and ERβ in the PLDSCs	Immunochemistry assay; Scanning electron microscopy (SEM) analysis; Real-Time reverse transcription polymerase Chain Reaction; Histological and morphometric study
CAI C. et al., 2013 [24]	Periodontal ligament (PDL) tissues were harvested from healthy premolars extracted for orthodontic reasons. Seven donors (12-16 years of age; four females and three males)	hPDLSCs	NR	ALP activity and OCN level of PDLSCs in the presence of oestrogens	Real-time reverse transcription polymerase chain reaction; Immunohistochemical analysis
WANG Y. et al., 2013 [25]	12 caries-free human premolars extracted from six patients due to the orthodontic reasons	human DPSCs	NR	Effects of 17b-oestradiol on odonto/osteogenic differentiation of DPSCs	Real-time reverse transcription polymerase chain reaction
ZHANG B. et al., 2011 [26]	20 Sprague Dawley (SD) rats were randomly divided into two groups: to the OVX group and Sham group.	PDLSCs cells of animal origin	3	The effect of oestrogen depletion on osteogenic differentiation of PDLSCs	Real-Time polymerase Chain Reaction
PAN F. et al., 2011 [27]	Partially impacted third molars (n = 6) were collected from three female individuals aged 18, 19 and 22	human PDLSCs	NR	Effect of oestrogens on the osteogenic differentiation of PDLSCs in vitro	Real-Time polymerase Chain Reaction; Western Blot analysis Immunocytochemical analysis
LIANG L. et al., 2008 [28]	Premolars extracted from 4 premolars Donor’s age: 12 to 14 years old	PDL cells of human origin (hPDL) obtained from the middle of tooth root	NR	The effect of oestrogen depletion on osteogenic differentiation of hPDL cells The effect of oestrogen receptor beta (ERβ) inhibition on osteoblastic differentiation function of human periodontal ligament cells (hPDL)	Real-Time polymerase Chain Reaction; Western Blot analysis
LIANG L. et al., 2008 [29]	Premolars extracted from 4 premolars. Donor’s age: 10 to 12 years old	PDL cells of human origin (hPDL) obtained from the middle of tooth root	NR	The effect of oestrogen on the expression of OPG and RANKL in human PDL (hPDL)	Short interfering RNA technique