*4.5. Search Methods*

The search attempted to identify all relevant trials in English. The electronic databases searched were (date of most recent search 19 May 2019) PubMed, MEDLINE via Ovid, EMBASE via Ovid and Web of Science. A sensitive search strategy was developed following the PICO process for the question: Does periodontal treatment improve lipid profiles in individuals with type 2 DM?


The search strategy for PubMed is given as an example: ("periodontal treatment" OR "periodontitis treatment" OR "periodontal therapy" OR "periodontitis therapy" AND "diabet\*"). Incomplete information and ambiguous data were researched further by contacting the author and/or researcher responsible for the study directly. If the corresponding author failed to reply, the studies were excluded. Cross-sectional studies, retrospective studies, literature reviews, systematic reviews, editors'/authors'/reviewers' comments, articles not in English, studies where the intervention was not periodontal treatment, studies which did not have an appropriate control arm, studies where lipids were not analysed both pre and post-trial, and trials involving individuals with diabetes other than type 2 DM were excluded.

### *4.6. Selection of Studies*

Titles and abstracts were managed by downloading to Endnote X8 software. The selection of papers, the decision about eligibility, and data extraction were carried out independently, in duplicate, by three reviewers (S.G., J.E. and M.A.N.). Any disagreement was resolved by discussion. The full text of the included studies was evaluated by two authors (S.G. and M.A.N.). Data entry to a computer and data extraction was carried out by one reviewer (S.G.).
