the success of an apicoectomy with aretrofilling is dependent upon obtaining an acceptable apical seal . the placement of the variously approved retrograde materials requires adequate access , visibility , lighting , and a sterile dry environment . ideally , it would be wonderful if a rubber dam could be applied to the apex of a tooth and the reverse fill placed under the dry , clean conditions the dam offers . the purpose of this article is to present the use of the rubber dam as an isolation tool for the placement of a suitable root end filling on teeth with large periapical lesions . an18-year - oldpatient came to the department of endodontics with a complaint of pain in the right upper front region since 1 month . history revealed trauma to the maxillary anterior teeth due to accidental fall 10 years back . intraoral periapical radiograph ( iopa ) of the concerned region showed periapical radiolucency in relation to tooth 11 and 12(>2 cm ) , which was diagnosed as periapical cyst after clinical and radiographical analysis [ figure 1a and g ] . rubber dam isolation of root end tip root canal treatment was decided in relation to tooth 11 and12 with cyst enucleation and apicoectomy along with retrograde filling with mineral trioxide aggregate . rubber dam sheet was modified to the size of 4  4 inches and hole was punched in the center of this modified sheet to the size of mandibular central incisor [ figure 1b ] . plastic spatula was modified by drilling a hole at its tip to correspond to the apex of root of the tooth concerned . punched rubber dam sheet was loosely placed over the apex of the tooth concerned , which was then stretched over the lingual aspect of the apex with the apex isolating instrument . the rubber dam was held in place by the isolating instrument and the remaining uncut portion of the root tip protruded through the hole . the apex isolating instrument also served later to retract the soft tissues [ figure 1e ] . all excess filling material from the retrograde filling was removed with the rubber dam sheet in place [ figure 1f and h ] . rubber dam sheet was modified to the size of 4  4 inches and hole was punched in the center of this modified sheet to the size of mandibular central incisor [ figure 1b ] . plastic spatula was modified by drilling a hole at its tip to correspond to the apex of root of the tooth concerned . punched rubber dam sheet was loosely placed over the apex of the tooth concerned , which was then stretched over the lingual aspect of the apex with the apex isolating instrument . the rubber dam was held in place by the isolating instrument and the remaining uncut portion of the root tip protruded through the hole . the apex isolating instrument also served later to retract the soft tissues [ figure 1e ] . all excess filling material from the retrograde filling was removed with the rubber dam sheet in place [ figure 1f and h ] . the need to work under dry conditions and the idea of using a sheet of rubber to isolate the tooth dates almost 150 years . the introduction to surgical endodontics of innovative and versatile endodontic devices , techniques , and materials such as sonic instruments , thermoplastic gutta - percha , and reinforced zinc oxide - eugenol - based cements are available for improving the success and management of complicated surgery cases . the rubber dam isolation of the tooth apex is essential for the success for such procedures as it provides adequate access , visibility , lighting , and a sterile dry environment . with a proper case selection , ideally , the use of this technique during a retrograde surgery involves a maxillary or a mandibular anterior tooth with a large enough periapical lesion so that the apex isolating instrument can be easily positioned . additionally , there must be enough of the lingual apical surface of the root tip remaining for the rubber dam to be stretched and retained apically . the rubber dam when properly placed prevents the scattering of the apical canal contents into the periradicular area during canal preparation . there is improved visualization and less trauma to the soft tissues during the preparation and filling of the apex . moreover , the apex - isolating instrument blade and the remaining rubber dam itself aid in tissue retraction . the constraint of this technique is its inability to be used on molar apices due to the forces of the perioral structures . also there is difficulty in positioning the apex - isolating instrument around such small apices of posterior teeth . further research is still needed regarding the manufacturing of clamps for apex isolation and the use of rubber dam as an isolation tool in surgical cases in endodontics .
the success of an apicoectomy with a retrofilling is dependent upon obtaining an acceptable apical seal . 
 the placement of the variously approved retrograde materials requires adequate access , visibility , lighting , and a sterile dry environment . 
 there are instances , however , in which it is difficult to use the rubber dam . 
 one such instance is during retrograde filling . 
 this case report highlights an innovative technique for rubber dam isolation of root end retrograde filling .