CHAPTER 19 Crête Mince, Mini-Implant, Transitional, Temporary Anchorage Devices, and other Implant Surgical and Prosthodontic Procedures
The optimum prognosis is supported by slow drilling to keep intraosseous temperatures low, use of chilled saline irrigants, carefully planned implant placement, accurately directed drills, maintenance of the integrity of cortical plates, and use of a gentle, pressure-free, well-irrigated sharp instrument.
Small, cruciform incisions should be used, to prevent forced implantation of epithelial cells into the bone. Implanted epithelial cells may later proliferate, causing epithelial invagination and implant failure.
Crête Mince translates from the French as “thin ridge” (Fig. 19-1). Crête Mince implants were designed and introduced by Michel Chérchève and have been referred to as mini-implants or M-C implants. Because they are very thin, they lack strength and cannot be depended on to serve as free-end saddle abutments. However, their versatility and resilience when used in multiples, particularly in pier or interabutment regions, make them an extremely valuable adjunct to the armamentarium of the eclectic implantologist.
FIGURE 19-1. The Michel Chérchève Crête Mince (M-C or mini) thin-ridge implant is now produced in titanium by Bauer-Chérchève of Germany and by Michel Garard of Megève, France. Although these implants are self-tapping, a No. 4 starter bur should be used through the cortex, followed by a series of special twist drills supplied by the manufacturers. Implants of varying lengths are available.
When Crête Mince implants are used, they are placed in medullary bone between cortical plates. The ridge thickness can be as slight as 2.5 mm. The implants are available in lengths as long as 20 mm, but they can be cut shorter. The surgeon should attempt to create bicortical osteotomies to gain maximum strength and longevity from these devices.
Mini-implants are most successfully used in the anterior maxilla or mandible, where a long edentulous span can be found, such as from premolar to premolar. Fixed bridge prostheses are constructed on posterior implants or molars and, when available, premolars. When superior esthetics are required, a unit-built bridge design is used. This involves construction of individual cast gold pontics, which are stabilized by internal mini-implants after they are connected. Each is completed with an individually made, telescoped, porcelain jacket crown. With this technique, the multiple threaded pins are used to pin and abut the anterior and formerly unsupported portion of a long bridge to the underlying bone. The pins serve as reliable anterior pier abutments when used in this fashion. Observation, care, and troubleshooting are the same as the rules governing other root form implants (Fig. 19-2). In the anterior region, the laboratory should construct an appropriate number of pontics of the classic unit-built design, each well centered over the bony ridge. Each should be hollow from incisal edge to ridge lap and have a 2.5-mm diameter accommodation. This is sufficient to accept a mini-implant head. The laboratory should restore each pontic in the complex with a separate porcelain jacket made to telescope over it.
FIGURE 19-2. A, A significant traumatic incident caused this long edentulous span. The ridge width was affected materially, but more than 15 mm of height remained. B, The length of the edentulous spans discouraged any approach involving traditional fixed prostheses. C, A fixed maxillary prosthesis was fabricated with six separate anterior porcelain crowns. In this view, four of the six have been removed, revealing the hollow pontic design. D, On the day of surgery, a local anesthetic is administered and the fixed prosthesis is placed being used as a surgical guide,. E, Each pontic is used as a surgical template, and the twist drills, in graduated sizes and under saline coolant, are used to make the osteotomies. They must be made directly in the center of each pontic so that when the self-tapping mini-implants are introduced, their abutments are accommodated without trauma within the pontic walls. F, All implants have been placed concentrically. G, Each implant is shortened so that it will fall within the confines of its assigned pontic and allow complete seating of the individual porcelain crowns. H, After abutment scoring, the bridge is cemented with composite resin to lock the pontics to the implants. The jackets are cemented separately to complete the reconstruction. I, A panoramic radiograph demonstrates the prosthe/>