Table 1.

Comparison of the different hypotheses.

Hypothesis	References	Bacteria involved in disease	Relates to
			Ecological changes	Host specific factors*
Traditional NSPH	Miller, 1890	All	−	−
SPH	Loesche, 1976	Specific bacteria	−	−
Updated NSPH	Theilade, 1986	All, difference in virulence	+	−
EPH	Marsh, 1994	All, enrichment of specific pathogenic bacteria	+++	−
KPH	Hajishengallis et al., 2012	Specific bacteria, dependent on (some of) remaining microbiota	++	+

^*Factors that could differ amongst hosts, e.g., innate immune system (levels of cytokine and TLR expression), response to certain bacteria, GCF properties (iron concentration), saliva properties (buffer capacity) and enamel repair. − not or only briefly mentioned, + mentioned, ++ mentioned and described, +++ described in detail.