Abstract:
This article aims to determine the indication criteria for a maxillary and mandibular implant-supported overdenture utilizing a milled titanium bar. A case report delineating the treatment plan sequence is presented.
Implant supported over-dentures are one of the traditional treatment modalities for completely edentulous patients.
There are several ways to fabricate an implant supported over-denture. In cases where three or more implants are placed, often a cast, gold dolder bar is used to connect the implants (Fig. 1).
Until recently, one of the challenging areas in implant dentistry was to achieve passive insertion and fit of a cast screw-retained metal framework for a bar-retained over-denture or a fixed partial denture. Occasionally after receiving the cast framework from the lab, it had to be sectioned, the segments needed to be reunited and the united framework had to be picked up in an impression, sent back to the lab for soldering or welding. Due to limitations of the casting process, complications such as misfit, cracks and fractures of the bar occurred (Fig. 2).1-3
The introduction of CAD/CAM technology eliminated this predicament. The cast gold dolder bar framework is replaced by a milled bar from a solid block of Medical Grade 4 titanium alloy. Once an accurate impression is taken, the model is scanned and an over-denture bar is designed using specialized software and equipment. (Implant/Cad software).
The bar is then milled using a Pantogram milling device. This milled framework is a mono-block that has a truly passive fit (the bars are milled with an accuracy of 8 microns between interfaces). As a result, no welding or soldering is necessary, which in turn means a stronger infrastructure for the over-denture.
The lab can create a wide variety of bar designs and attachment configurations as well as many platforms for different implant systems. They can be screwed directly to the implant restorative platform or to the abutments restorative platform. These bars are extremely lightweight, have no porosities and are polished with a mirror polish result (Fig. 3).
The result is an over-denture that is easy to maintain and does not cause harm to the surrounded soft tissue.
Case Presentation
A 54-year-old Caucasian male presented to our clinic with a main concern: “My teeth are loose, I can not eat.” His medical history had no significant findings other than controlled diabetes type II.
An intra-oral clinical examination combined with a radiographic exam revealed a diagnosis of partial edentulism, severe generalized periodontitis, bilateral sinus pneumatisation, mesial drift of the molars, maxillary interdental spacing and poor oral hygiene (Figs. 4-8).
The patient was presented with fixed and removable treatment options. The plan that was subsequently agreed upon was to extract all the remaining teeth and provide the patient with four mandibular implants and six maxillary implants joined by a CAD/CAM milled titanium bar, maxillary and mandibular implant supported over-dentures.
The treatments sequence was as follows:
• Full mouth extractions, delivery of immediate complete upper and lower dentures. (Follow-up appointments took place to ensure post-operative healing).
• Four months post extractions: Re-evaluation and assessment of bone volume and quality for implants placement (Figs. 9-11).
• Ten Endosseous implants (“A.B. Dental Devices”) were placed in a single stage protocol. (Six A.B. implants in the Maxilla and four A.B. implants in the anterior mandible) (Fig. 12).
• Trans-mucosal healing abutments (A.B.) were placed on all implants (Fig. 13).
• Pick-up, open tray impressions were taken using heavy and light body Poly-vinyl-siloxane (Affinis Pecious – Coltene/Whaledent) (Figs. 14,16).
• Upper and lower titanium alloy milled bars (Bio-Cad, Nobel Bio-care*) were designed, fabricated and tried intra-orally (Figs. 17-19).
• Implant supported over-dentures were constructed and delivered. The stability, retention and support that the six implants provided allowed the fabrication of a maxillary prosthesis with no palatal coverage (Figs. 20-21).
• One year follow-up revealed an extremely happy patient, no deterioration of the bars or prostheses (Fig. 22).4,5
Summary
Restorative dentistry is all about predictability and long-term prognosis. CAD/CAM technology can provide us with a one piece custom milled titanium alloy bar with a truly passive fit. This eliminates the weakness that may be caused by porosity in casting, soldering or laser welded joints. The result is a structure that is more durable, superior in strength and weight less than the conventional cast gold bar.
This mode of treatment increases the denture retention, stability and predictability of the treatment, which in turn improves the patient’s quality of life.6-8
Conclusions
Implant supported milled bar overdentures is an optimal treatment option for completely edentulous patients with limited bone volume or limited finances. They offer the advantages of removable prostheses with the retention, stability and support of fixed prostheses.OH
Roy Raviv, DMD, Lecturer, Faculty of Dentistry, Department of prosthodontics, McGill University, Montreal, Canada.
Mili Harel-Raviv, DMD, Private practice, Montreal, Canada.
Eli Raviv, DMD, Associate Prof. Faculty of Dentistry, McGill University; Director of Prosthodontics, Dep. of Dentistry J.G.H, Montreal, Qc. Canada.
Oral Health welcomes this original article.
REFERENCE
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