Table 1 Full texts obtained and excluded with reason for exclusion (n = 23 studies)

Areias et al., 2011 [34]

No quantifiable measure of DMFT/dmft - descriptive only.

Altun et al. 2010 [35]

Included children with physical disabilities as well as learning disabilities and data could not be separated.

Areias et al., 2012 [36]

This seems to be the same group or a repeat study dataset of Areias et al., 2013. This was not clear as it’s not detailed in the paper, but it included the same population of exactly the same age. DMFT and dmft were different but because of duplicate sampling, even if not the same dataset, we excluded.

Chadha et al., 2012 [37]

No comparison group

Bakarcic et al., 2009 [38]

Not all children in the study population have a learning disability

Fahlvik-Planefeldt et al., 2001 [39]

Index for caries recording/detection system not specified, no DMFT/dmft data

Fuertes-Gonzales et al., 2014 [40]

This study included adults (age range 2–37 years) and did not allow for extraction of age groups.

Fung et al., 2008 [41]

Data collection through questionnaire (no clinical examination carried out)

Lowe et al., 1985 [42]

This study included adults (age range 3–30 years) and did not allow for extraction of age groups.

Macho et al., 2013 [43]

This study included adults (age range 2–26 years) and did not allow for extraction of age groups.

Mattila et al., 2001 [44]

No learning disabled children in the study population.

Oredugba et al., 2007 [45]

This study included adults and did not allow for extraction of age groups for DMFT/dmft indices

Pollard et al., 1992 [46]

No learning disabled children in the study population.

Purohit et al., 2010 [47]

Not all children in the study population have a learning disability

Radha et al., 2016 [48]

Errors in study authors’ conclusions from dataset: Table 10 shows CLD to have a lower caries experience than CNLD group, however the discussion and conclusion sections state the opposite to be true.

Rai et al., 2012 [50]

Index for caries recording/detection system not specified, no DMFT/dmft data

Rekha et al. 2012 [51]

No DMFT/dmft data given, only caries prevalence

Ruiz et al., 2018 [52]

This study included adults (age range 4–20 years) and did not allow for extraction of age groups.

Sarnat et al., 2016 [53]

Index for caries recording/detection system not specified, no DMFT/dmft data

Shaw et al., 1985 [54]

Dataset includes disabled children from a very wide group also no consistency between children’s ages in the study group and control group.

Suhaib et al., 2017 [55]

No quantifiable measure of DMFT/dmft - descriptive only.

Subramanium et al., 2011 [56]

No comparison group

Weckwerth et al., 2016 [57]

Errors in study authors’ conclusions from dataset calculations; Table 1 demonstrates incorrect results for the CI calculations in the permanent dentition for both groups 1 and 2.