an innovative design in a mandibular overdenture with too-lingualy-inserted implants: a case report

Prosthetic rehabilitation of patients with unfavorable-implant-position or problematic implant angulation is complicated. a completely-edentulous-patient with lower lip squamous-cell-carcinoma had undergone resective surgery twice. after radiotherapy of a total dose of 60cgy of 30 sessions for about 3 months, moderate trismus was developed. mouth commisurotomy was accomplished in order to insert three implants in the mandibular-anterior-region. two distal implants were excessively tilted to achieve better biomechanical advantages and to obtain greater anterior-posterior-distance which made prosthetic rehabilitation of the patient challenging. in the mandibular- custom-tray a lingual “window” was designed to accommodate the open-impression-copings. trial-denture-bases were tried-in. a putty index was recorded from arranged-mandibular-teeth. according to this index, a zigzag bar similar to letter “m” was designed using custom abutments. so that three ball anchors were placed on this “m-designed-bar” (mdb) more labial than the inserted implants to support the mandibular-implant-supported-overdenture. using mdb permits teeth-set-up with minimal interfere with tongue function. the major disadvantage of this design is its inevitable-buccal-cantilever. distolingual areas of mandibular tray were border-molded excessively in order to overcome this problem and to increase stability and also to reduce detrimental-lateral forces to implants.