Better results can be obtained using the two-step method with secondary implantation (Esser and Dürsch 1996). This study directly compared the one-step and the two-step method: While 35% of the implants were lost with the one-step method, only 5.5% were lost with the two-step method. The total waiting time to exposure (third operation) for the two-step method was 11.4 months. In most cases, patients could be provided with temporary complete dentures 4 weeks after implantation. Since both the augmentation procedure and the exposure procedure necessitate some time in which a denture cannot be worn, the total “toothless” period will be on the order of 6“8 weeks. Esser and Dürsch do not address cases of bone graft loss causing the treatment course to be aborted even before any implants were ever placed.

The bone graft operation in itself could be associated with a complication rate of 15–20% on average. Unloaded bone – and this includes bone transplanted into the maxillary sinus – loses up to 80% of its volume within a year.

Depending on the volume and quality of the bone in the maxilla, both lower and even higher loss rates have been reported for screw implants:

In general, it may be said that the probability of survival for crestal implants in the maxilla increases with the length of the intraossal portion of the implant. The more vertical bone is present prior to augmentation, the better the implant will be retained. Theoretically, larger implant diameters might offer a greater anchoring surface within the bone; in actual practice, however, the advantages of larger implant diameters outweigh the benefits in the maxilla as well as in the mandible.

If the procedures for preparing the implant bed (transplantation, augmentation, distraction) and any other procedures are performed separately, each procedure constitutes a separate medical risk. Patients must be informed of the approximate individual risk figures and possible consequences, as well as of the sum of the risks of all procedures required to obtain treatment success.

Comparative data on BOI success rates can be found as follows:

An interesting study in this context is that of Scortecci (1999) where crestal and basal implants were inserted in the same patients. Here, 72 fixed bridges on 783 implants (142 structured crestal implants and 641 disk implants) were followed over a period of between 10 months and 4 years. None of the implants was lost. Much more important than the consideration of the implant successes is the ratio of 641 BOI implants to 142 screw implants. This ratio impressively shows that a well-versed implantologist who is free from industry interests and who is equally conversant with crestal and basal implant options, has adequate tools for both systems and keeps in store a selection of implants from both systems would use BOI implants with a frequency four to five times higher than for screw implant.

That not a single BOI implant is used at German universities today must therefore be owed to the distorting influence exerted by representatives of industry sponsors who establish screw implant systems in the market by way of these universities and have their prospective customers receive a one-sided, slanted education in the use of these systems – all at the expense of the taxpayer, of course. It is therefore necessary to view the “results” of the university “research” in the light of the fact that the industry donors of so-called “third-party stipends” will influence the direction that university research takes. For this reason, “expert” court opinions by university professors with inadequate practical knowledge and experience may very well have to be viewed most critically when it comes to assessing the value of an innovative treatment method. Only rarely will it be possible to get a court to dismiss an unsuitable “expert” in an actual court case.⁶

Even if the operating dentist – possible because of fear of the unholy alliance between industry and the universities providing the “experts” in the event of a trial – would prefer not to use the BOI technique, he or she could still often avoid the iliac crest operation by using a mixture of industrial bone replacement materials and autologous bone for reducing the size of the maxillary sinus. In these cases, the maxillary sinus is accessed from the mouth and the mixture introduced from there. If the available vertical bone height in the implant region is at least 5 mm, screw implants maybe placed at the same time. Loading can be effected after 6–9 months. The literature, however, reports widely divergent success rates for this “sinus grafting” technique, ranging from 95% to 70%. These differences might be owed to the different indications in the different study and to differences in residual bone volume. In addition, the type of restoration and the residual dentition play an important role, as the following reasoning shows: Khoury (1999) reports on 216 sinus graft patients with 467 crestal implants and only 28 lost implants. This means that an average of 2.16 implants was inserted per patient. This means that most patients must have presented with a unilateral cantilever situation that does not expose the implants to excessive masticatory forces. On the contrary: the masticatory load is usually distributed among the remainder of the dentition in these cases. Implant superstructures are left, wholly or in part, in so-called infra-occlusion. Implants in infra-occlusion or completely non-functional implants have a much higher probability of survival than implants under functional load, because the deleterious lateral forces in the collar region that can result in the formation of bone craters and ultimately even implant loss are absent. This procedure would of course be inconceivable in completely edentulous patients, since their implant-supported dentures are always subject to the full impact of masticatory forces.

Another conclusion that can be drawn from the figures above is that the average age of the patients must have been comparatively low, since most cases involved only unilateral cantilever situations. Younger patients are more favourably situated when it comes to immune responses and vascularization. The study states that the age of the patients was between 22 and 69 years. Perhaps tellingly, their average age was not given.

As the above has shown, the “scientific results” of all studies must be examined in detail and checked for logical plausibility and relevance. Direct comparison between different studies is nearly impossible, since study designs usually diverge greatly, and in most cases, certain details important for any evaluation of the study are missing.

A similarly invasive procedure fraught with similarly great risks to the patient is repositioning the maxilla or mandible. If the spatial relationship of both jaws is incorrect, this will result in considerable unphysiological loading of the teeth and, after eventual tooth loss, in an inability to eat with removable dentures. For this reason, it is attempted to correct occlusal discrepancies in early youth by orthodontic means (growth control). If the discrepancies remain untreated, this will usually have a clearly adverse impact on the static situation of the dentition over the patient’s life.

This is why, in earlier years, it was received procedure that the jaws were brought closer together by surgical means, at the latest when an inability to wear dentures became manifest. The risks of this surgery, over and above the risk of general anaesthesia, include paraesthesia of the mandibular nerve, infections, damage to residual teeth, and – in the maxilla – full or partial necrosis of the relocated bone segment. These risks increase with the age of the patient. In addition, also depending on the age of the patient, systemic risks also exist (diabetes and many others). Sailer reports a long-term result of 6.25% of lost implants after an average 52 months with concurrent Le Fort I osteotomy (maxillary relocation: the maxilla is separated from the rest of the cranium and reattached to it in a more favourable position, where the maxilla becomes reattached to the cranium) and insertion of screw implants into the maxilla. This result indicates that at least the implant success does not suffer on account of the added invasive surgical procedure – provided, of course, that there is enough vertical bone available for inserting crestal implants.

At least the risks posed by accessory surgery can be reduced or avoided today by using the BOI technique: In a single procedure, usually performed on an outpatient basis, at least four implants are inserted per jaw in strategic positions, implants that will subsequently support a prosthetic structure. By optimizing the positions of the abutments, even larger amounts of leverage can be neutralized from the point of view of both the restoration and the implants and transferred to the jawbone without causing damage. Jaw reposition can be avoided, and patients can be provided with adequate and functional fixed dentures.