since the introduction of extra - oral implants in reconstruction of craniofacial defects , achieving proper prosthesis retention has become more promising .
these problems include ulceration of hard and/or soft tissues used for retention , lack of retention due to prosthesis movement , and tissue irritation caused by adhesives .
the ideal position and number of implants for restoring orbital defects would be three non - linear implants in lateral , supraorbital , and infra - orbital rims . however , such implant arrangement is not always conceivable considering the extension of the defect , and bone quality and quantity of defect s walls .
two of the most common retention systems used in reconstruction of orbital defects include freestanding abutments with magnetic retention and bar - clip retention .
magnetic abutments are more common because they resolve the potential problems associated with bar - clip attachment including difficulty in insertion and removal of prosthesis by the patient , difficulty in regular hygiene measurements , and rigidity of the attachment resulting in implant overloading .
however , magnetic attachment might not provide sufficient retention if implants have been placed adjacently .
the presence of implant in the defective area might complicate the usual impression - taking procedures used in fabrication of conventional craniofacial prostheses .
accuracy of the impression is affected by defect shape , retention system , number , and divergence of the implants .
moreover , anatomical undercuts in the defect , and proximity or remoteness of the implants could complicate the impression - taking procedure .
use of multiple trays , elastomeric impression materials , and dual impression technique have been suggested to overcome such problems [ 2,1214 ] .
the purpose of this article was to present a case treated with an implant - supported prosthesis to reconstruct a relatively large orbital defect using three adjacent implants in the lateral orbital rim .
a 60-year - old woman with a left orbital defect due to removal of periocular basal cell tumor was referred to the implant department of tehran university of medical sciences , school of dentistry , for prosthetic reconstruction of the eye .
three implants ( superline , dentium , seoul , south korea ) , 8 mm in length and 3.6 mm in diameter were placed in the lateral rim of the orbit . although the most suitable sites for orbital implants are the superior and lateral rims , in the present case the implants have been placed adjacently , due to insufficient bone thickness in superior and inferior orbital rims .
the defect was relatively deep with undercuts in the medial wall which could complicate impression making .
the preferred prosthesis design was an implant - supported prosthesis with a custom bar containing properly distributed magnetic components .
the healing abutments were unscrewed and three hexed direct - casting abutments ( implantium , dentium , seoul , south korea ) with 4.5 mm diameter were directly secured to the implants .
the medial undercuts were blocked out , using a gauze pack to avoid the penetration of acrylic resin . an auto - polymerizing acrylic resin ( pattern resin , gc , tokyo , japan ) pattern
was formed directly on the abutments in a manner that cobalt samarium ( co5sm ) magnets ( implantium , dentium , seoul , south korea ) , with 5.5 mm diameter and retention force of 700 gram could be placed at proper distances in the superior , inferior and lateral segments of the acrylic bar ( fig .
the acrylic resin bar was casted using base metal alloy ( aalba dent inc . ;
cordelia , c.a , usa ) and the magnet keepers were cemented in corresponding sites with panavia f 2.0 resin cement ( kurary medical inc , japan ) . acrylic resin pattern of bar containing indentations for magnets ( a ) , try - in of metal bar on the implants with magnet keepers in place ( b ) .
the space beneath the superstructure and also the undercuts in defect walls were blocked out with gauze packs .
the final impression was made in order to pick up the magnets and simultaneously record the rest of the orbital defect .
light viscosity addition silicone ( panasil , kettenbach , germany ) was used as the first layer to cover the entire defect as well as the intact side of the midface . afterwards , regular viscosity addition silicone ( panasil , kettenbach , germany ) was used over the light viscosity material to create mechanical retention projections for the gypsum layer ( herostone vigodent inc .
the wax pattern of the orbit was formed containing an ocular prosthesis which simulated the properties of a healthy eye .
the pattern was tried on the patient and some modifications were made to improve its esthetic and adaptation .
the prosthesis was made of a combination of heat - cured acrylic resin for holding the magnets , and high - temperature vulcanizing silicone with internal / external staining and other characterizations of the skin , such as wrinkles , eye brow and eye lashes .
the final prosthesis was delivered to the patient and necessary home care instructions were provided such as removing the prosthesis during night , cleaning the eye defect with damp gauze , and the need for regular biannual follow - ups [ 69 ] .
tissue side of the prosthesis with three magnets ( a ) , delivery of the prosthesis ( b )
the patient presented here has been treated with an implant - supported orbital prosthesis with bar - magnetic attachment .
this retention mechanism might minimize the risk of mechanical overload on the implants compared to a conventional bar - clip attachment with cantilever arms . despite the proximity of implants ,
the mentioned distribution of magnetic attachments has increased the retention through creating a tripod . furthermore , since the acrylic resin pattern of the bar was made directly in the defective area , no implant or abutment analogues were used in final impression procedure .
prolonged chair - side time is a disadvantage of the stated method which could be justified considering the mentioned advantages .
 implant - supported craniofacial prostheses are made to restore defective areas in the face and cranium . 
 this clinical report describes a technique for fabrication of an orbital prosthesis with three adjacent implants in the left lateral orbital rim of a 60-year - old woman . 
 selection of appropriate attachment system ( individual magnetic abutments versus bar - clip attachment ) for implant - supported orbital prostheses depends upon the position of implants . 
 bar - magnetic attachment has been selected as the retention mechanism in the present case . 
INTRODUCTION
CLINICAL REPORT
SUMMARY