Abstract. Direct laser metal forming (DLMF) is a new technique which allows solids with complex geometry to be produced by annealing metal powder microparticles in a focused laser beam, according to a computer-generated three-dimensional (3D) model. For dental implants, the fabrication process involves the laser-induced fusion of titanium microparticles, in order to build, layer by layer, the desired object. Modern computed tomography (CT) acquisition and 3D image conversion, combined with the DLMF process, allows the fabrication of custom-made, root- analogue implants (RAI), perfect copies of the radicular units that need replacing. This report demonstrates the successful clinical use of a custom-made, root- analogue DLMF implant. CT images of the residual non-restorable root of a right maxillary premolar were acquired and modified with specific software into a 3D model. From this model, a custom-made, root-analogue, DLMF implant was fabricated. Immediately after tooth extraction, the root-analogue implant was placed in the extraction socket and restored with a single crown. At the 1-year follow-up examination, the custom-made implant showed almost perfect functional and aesthetic integration. The possibility of fabricating custom-made, root- analogue DLMF implants opens new interesting perspectives for immediate placement of dental implants.
Keywords: immediate implants; primary stabi- lity; direct laser metal forming; custom-made root-analogue implants.
Accepted for publication 18 January 2012 Available online 28 February 2012 Immediate implants are implants inserted immediately after surgical extraction of the teeth to be replaced 2 . The idea under- pinning immediate implant placement is to preserve the alveolar height and width, reducing the marginal bone resorption that typically follows extraction socket heal- ing 2 . The advantages of immediate implantation include shortening of the rehabilitation treatment time and the avoidance of a second surgical interven- tion 1 . There are some disadvantages related to immediate implant placement in fresh alveolar sockets 2 . Primary stability represents a funda- mental pre-requisite for osseointegration and in a fresh extraction socket it can be difficult to achieve 2 . As adequate bone quantity and quality are essential prere- quisites for achieving primary implant stability, the surgical requirements for immediate implantation include extraction with the least trauma possible and the careful preservation of the alveolar socket walls. Primary implant stability seems to be related to the implant macroscopic features (shape, length and diameter). Until now, primary implant stability in fresh post-extraction sockets has been achieved by placing implants exceeding the alveolar apex by 3–5 mm, or by insert- ing implants of greater diameter than the remnant alveolus 2,6 . One possible alternative to the tradi- tional threaded, straight or tapered implant systems intended to replace a missing tooth is the fabrication of a customized, dental root-analogue implant (RAI) 6,10 . Few studies describing the techniques of creating and placing custom-made RAI have been noted in the literature 3,4,6–10 . In the last few years, considerable pro- gress has been made in the development of rapid prototyping (RP) methods, including direct laser metal forming (DLMF) 6,5 . DLMF is a timesaving procedure in which a high power laser beam is directed on a metal powder bed and programmed to fuse particles according to a computer assisted design (CAD) file, generating a thin metal layer. Apposition of subsequent layers gives shape to a desired 3D form with minimal post-processing requirements 5 . With DLMF it is possible to fabricate dental implants of different size and shape, directly from CAD models 5 . Modern computed tomography (CT) acquisition and 3D image conversion, combined with the DLMF process, allows the fabrication of custom-made RAI, which are perfect copies of the radicular units to be replaced 6 . Perfect implant fit could lead to excellent primary stability, however, it might be responsible for the intermediate term failure, because of the subsequent uniform pressure-induced resorption concerning the entire alveolar surface 4,8,9 simultaneously affecting the thin buccal layer, which is prone to frac- ture and pressure-induced resorption 4,8,9 . The aim of the present study was to demonstrate how new DLMF technologies permit the fabrication of a custom-made, titanium RAI, which can be predictably inserted in a fresh extraction socket, with immediate restoration.
Case study A 50-year-old healthy female patient with a fractured non-restorable second maxillary right premolar was selected for this study. The patient gave consent for implant ther- apy. This study was performed according to the principles outlined in the World Med- ical Association’s Declaration of Helsinki on experimentation involving human sub- jects, as revised in 2008.
Results One year after placement, the custom- made implant was still in function ( Fig. 3 ). The implant was stable, with no signs of infection, such as pain or suppuration. The good conditions of the peri-implant tissues were confirmed by the radiographic examination, with unchanged peri-implant marginal bone level and no peri-implant radiolucency ( Fig. 4 ). The radiographic profile of the implant–crown complex was very similar to that of natural tooth. No prosthetic complications occurred. The prosthetic restoration showed optimal functional and aesthetic integration.
Discussion Implant dentistry has evolved toward sim- plification of clinical procedures and shortened treatment times, with such developments as immediate implant pla- cement 2 . Primary stability is of paramount importance with immediate implantation, and a good fit between the implant and the host bed is an important factor for implant success 2 . For this reason, it could be an advantage to design a dental implant according and congruent to the individual extraction socket. Hodosh et al. 1 were the first to use a custom-made RAI placed into the extraction socket, reducing bone and soft tissue trauma. The polymethacrylate tooth-analogue was encapsulated by soft tissue rather than osseointegrated 1 . Ani- mal studies with root-identical titanium implants yielded extremely favourable results with clear evidence of osseointe- gration 4 . In several instances implant insertion led to fractures of the thin buccal wall of the alveolar bone 3,4 . A subsequent clinical study revealed excellent primarystability, but with a high disappointing fail- ure rate of 48% at 9 months’ follow-up 3 . Owing to this high failure rate, the use of these titanium RAI was not recommended for clinical use 3 . In a recent clinical study, however, the immediate placement of a non-submerged zirconia RAI with macro- retention in the interdental space and a diameter reduction of 0.1–0.3 mm next to the buccal cortical bone yielded excellent functional and aesthetic results 7 . No clini- cally noticeable bone resorption or soft tissue recession was reported at the 2-year follow-up 7 . These results were confirmed in more recent clinical studies 8,9 .