Table 1. Search strategies for five databases.

Electronic databases and search strategies
PubMed Central	#1 (”Anesthesia”[Mesh]) #2 ((((”Injections”[Mesh]) OR (Injectable)) OR (Injectables)) OR (Injection)) #3 #1 OR #2 #4 ((”Periodontal Ligament”[Mesh]) OR (intraligamentary)) OR (intraligamental) #5 (((subperiosteal) OR (intraseptal)) OR (supraperiosteal)) OR (infiltration) #6 #3 AND #4 AND #5
Embase	#1 ’anesthesia’/exp OR ’anaesthesia’ OR ’anesthetization’ #2 ’injection’/exp OR ’injections’ #3 #1 OR #2 #4 ’periodontal ligament’/exp OR ’intraligamentary’ OR ’intraligamental’ #5 ’subperiosteal’ OR ’intraseptal’ OR ’supraperiosteal’ OR ’infiltration’ #6 #3 AND #4 AND #5
MEDLINE	1 exp Injections/ 2 exp Anesthesia/ 3 1 or 2 4 exp Periodontal Ligament/ 5 intraligamental.mp. 6 intraligamentary.mp. 7 4 or 5 or 6 8 subperiosteal.mp. 9 intraseptal.mp. 10 supraperiosteal.mp. 11 infiltration.mp. 12 8 or 9 or 10 or 11 13 3 and 7 and 12
Cochrane Library	#1 MeSH descriptor: [Anesthesia] explode all trees #2 MeSH descriptor: [Injections] explode all trees #3 (Injection) OR (Injectables) OR (Injectable) #4 #1 OR #2 OR #3 #5 MeSH descriptor: [Periodontal Ligament] explode all trees #6 (intraligamental) OR (intraligamentary) #7 #5 OR #6 #8 (subperiosteal) OR (intraseptal) OR (supraperiosteal) OR (infiltration) #9 #4 AND #7 AND #8
Scopus	( ALL ( ( subperiosteal OR intraseptal OR supraperiosteal OR infiltration ) ) AND ALL ( ( injection OR anesthesia ) ) AND ALL ( ( intraligamental OR intraligamentary OR {periodontal ligament} ) ) )