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.