Table 3.

Analysis of the results of the included studies relying on saliva samples in pSS compared to HC and sicca.

Authors	Aim	Alpha diversity	Beta diversity	Phylum	Genus	Species in pSS
Almstahl et al. (13)	Analyse and compare the oral microflora in 4 groups of individuals with the same age, similar numbers of teeth and hyposalivation of different origins	Similar total microbial counts for pSS and HC				High number of mutans Streptococcus, Candida albicans and Lactobacillus spp in pSS
Leung et al. (14)	Microbiota of noncaries associated supra-gingival plaque microbiology in Sjögren’s syndrome in China compared to HC.					Higher Lactobacillus species in SWS and SGP culture. Lower proportion of gram-negative species in SGP
Siddiqui et al. (15)	Bacterial profile in whole saliva of pSS patients with a normal salivary flow rate by HTS compared to HC.	Lower species richness, alpha diversity in pSS compared to HC		Higher Firmicutes in pSS compared to HC Synergistetes and Spirochaetes were lower	Streptococcus was higher in pSS than in HC. 8 other taxa were lower in pSS than HC	Increase of Veillonella sp._Oral_Taxon_917 Decreases of P. gingivalis, Tannerella forsythia, and Treponema sp._Oral _Taxon_237
van der Meulen et al. (16)	Oral microbiome pSS patients compared with sicca and HC.	No differences among the 3 groups	Large variation in bacterial composition in pSS and non-SS compared with HC		Lower Streptococcus and higher Selenomonas in pSS compared to HCs
Zhou et al. (17)	Composition of the oral microbial flora in pSS patients and HC using HTS in China to provide guidance for treatment.	No difference between pSS patients and HC		16 phyla in total. Bacteroidetes and Firmicutes were more abundant in pSS. Proteobacteria was less abundant. No differences for Actinobacillus and Fusobacterium.	10 genera, including Prevotella, Bacteroides and Actinomyces, were more abundant in pSS patients. 17 genera, including Neisseria, were less abundant in pSS patients.
Zhou et al. (18)	Oral microflora profile of pSS patients in the oral cavities by using HTS.	Lower oral bacterial community evenness and diversity in pSS patients compared to HC	No difference between pSS and HC		No difference between Streptococcus and Lactobacillus. Veillonella was higher in pSS than HC.
Rusthen et al. (19)	Compare the salivary bacterial composition in pSS patients with sicca and HC to investigate a possible dysbiosis in pSS.	No differences among the 3 groups		No differences between groups.	No differences between groups for the most predominant genera. Only Haemophilus and Neisseria were decreased in pSS and sicca patients compared to HC.	Porphyromonas pasteri was decreased in pSS and sicca patients compared to HC.
Sembler-Moller et al. (20)	Characterize and compare the salivary microbiota in pSS and sicca and to relate the findings to their oral health status and saliva flow rates.	No differences between pSS and sicca
Sharma et al. (21)	Evaluate the salivary microbiome in pSS patients using 16S rRNA sequencing approach.	No differences between pSS patients and HC. Low alpha diversity in patient with steroids			Bifidobacterium, Dialister and Lactobacillus were enriched, while Leptotrichia was depleted in pSS patients compared to HC
Alam et al. (22)	Characterize the oral microbiota in SS patients and to investigate its potential role in the pathogenesis of SS.	Higher diversity in pSS patients compared to the control group with Shannon index, particularly in a non-dry condition		Increased Firmicutes and decreased Proteobacteria, Fusobacteria, TM7, and Spirochaetes in pSS patients	Streptococcus, Prevotella, Lactobacillus, Atopobium, and Staphylococcus were increased but 34 genera were underrepresented in SS patients compared to HC	Lower Porphyromonas gingivalis in pSS patients

pSS, primary Sjögren’s syndrome; HC, healthy controls; sicca, patients with dryness symptoms; SGP, supra-gingival plaques; SWS, stimulated whole saliva; HTS, high-throughput sequencing; rRNA, ribosomal ribonucleic acid.