Clinical indications, advantages and limits of the expansion-condensing osteotomes technique for the creation of implant bed

SUMMARY

The “screw shaped” expansion-condenser are hand instruments that were introduced for the first time at the end of the 70’ in order to improve bone density before the positioning of a dental implant. Thanks to these hand instruments it is possibile to compact the bone apically and along the walls of the implant bed (Fig. 3) improving a lot the bone density and the primary stability of the implant even in situations where the starting bone quality is low (es. D3-D4 as in the classification y Lekholm and Zarb 1985) or in cases of severe bone atrophy. Allowing a manageable raising of the shnaiderian membrane through trans-alveolar way, this technique avoids in many cases the necessity to have recourse to the realisation of bone vestibular “gates” when it comes to the techniques of the big sinus lift. The knoledge of the bone visco-elastic and hystologic properties together with the maximum respect of the surgical protocol allows us to obtein % of success superior than traditional surgical protocol in D3-D4 bone class.

Introduction

The “screw shaped” expansion-condenser are hand instruments (Fig. 1) that belongs to the group of the osteotomes (from the Greek osteon, trad. bone and temno trad. to cut), and for this reason are able to form or shape bone in preparation for the placement of dental implants.

Figure 1.

Osteotomes BTLock.

They were introduced for the first time at the end of the 70’ by Doctor Hilt Tatum (1) in order to improve bone density before the positioning of a dental implant and they have been put as objects of important scientific researches all over the world (2–12, 23).

The goal of this work is to present a precise revision of the international literature with a particular reference to the “indications” and to the “limits” which are linked to the utilisation of the expansion-condensing osteotomes in oral implantology. There are three main indications to the utilisation of the expansion-condensing osteotomes in oral implantology:

• – bone compaction

• – ridge expansion

• – elevation of the schnaiderian membrane in the sinus lift procedure.

Clinical procedures

1. BONE COMPACTION. It’s now reconised that the long term success of a dental implant is linked to a number of factors (13). Among them, one of the main traits for a successful osteointegration is of course the acquisition of a good primary implant stability. This stability depends from different traits like the morphology of the implant, which kind of surgery protocol is used, but above all from the bone quantity and quality. There are some clinical situations for example, in which the bone quality is so low to compromise this important starting condition. It’s for this reason that at the end of the seventies Doctor Hilt Tatum proposed a kit of hand instruments (Fig. 2) in order to improve the bone density before the positioning of a dental implant (1). The biological principle which inspired the idea of it is the trabecular visco-elastic, which is a trait that makes the bone able to be compressed and manipulated. Thanks to these hand instruments it is possibile to compact the bone apically and along the walls of the implant bed (Fig. 3) improving a lot the bone density and the primary stability of the implant even in situations where the starting bone quality is low (es. D3-D4 as in the classification y Lekholm and Zarb 1985). When the bone quality is really bad, a grafting material can be used by putting it in the implant bed, compacting it with the osteotomes long the walls (8). This operation will allow to obtain a better primary stabilisation of the fixture.

Figure 2.

Tatum’s osteotomes.

Figure 3.

Bone condensing plan.

2. RIDGE EXPANSION. The expansion-condensing osteotomes allow to expand the alveolar ridge bucco-lingually in a easier and less invasive way than the traditional surgery techniques that involve to spread the buccal and lingual plates of the bone. (3).

These technique can be used together in cases where the width of the alveolar ridge is less than 3 mm.

Protocol A: width of the alveolar ridge ≥ 3 mm. In these cases the operative sequence expects the utilisation of just one drill, usually a Ø 1.3–2 mm (Fig. 4) which will determine the axis and the depth of the work, and afterwards in a sequence the expansion-condensing osteotomes till reaching a good diameter of the implant bed able to guarantee a good primary implant stability (Fig. 5).

Figure 4.

Pilot drill.

Figure 5.

Surgical steps in cases with bone ≥3mm wide (protocol A).

The dimensions of the working pars of every single instrument are put in a way that the coronal diameter of the first instrument is corresponded with the apical diameter of the next one (Fig. 1). This characteristic, joined to aslow and gradual movements, allows to have a continuous control of the entity of the expansion of the vestibular bone plate, allowing the immediate suspension of the process at the very first sign of complication. Even if sometimes, despite our attentions, some fractures happens at the vestibular portion, especially on its most coronal part (Fig. 6).

Figure 6.

Fractures can appear during final preparation with osteotomes.

When happens these fractures, as long as they don’t compromise the primary stability implant stability, are of no importance, since they reconsolidate in the following osteointegration phases (20–29). Possibly, the gaps among the fractures can be filled with autologos bone chips which are taken from the close sites or with grafting material (Fig. 7).

Figure 7.

Provided they don’t compromise primary implant stability, these fractures consolidate during the osteointegration phase.

A fundamental condition for the success of both this and all the other protocols which expect the utilisation of the expansion-condensing osteotomes, is that every instrument must remain in the implant bed, at the fixed work depth, at least one minute before proceeding with the next one. At the same way in the moment of their removal, in case there is an excessive resistance, it should be waited another minute before proceeding ahead. All this is very important in order to give the exact time for the bone to adapt itself at the new spatial conformation and to avoid the ialinization of peri-implant bone.

Protocol B: width of the remaining bone ridge < di 3 mm or in D1-D2 bone class.

In these cases, the described technique must be associated always to a split crest technique (Figs 8–12). In this way after the initial osteotomies the expansion-condensing osteotomes can take the place of the traditional cuneal osteotomes allowing a major control of the entity of the movement of the vestibular cortical bone joined to a major comfort for the patient instead of the traditional technique with surgical mallet (3, 5, 14). In some rare cases, moreover, in presence of very bad atrophies of the bone it’s possible to proceed with a splitting in two times. So, at the end of the first surgery phase and before the closure some wedges made with spongiosa riassorbibile or collagen are put in order to maintain dinstant the two corticals (30). Afterwards, after 45 days approx, that is when all the mechanisms for the bone reparation are activated, but the mineralization is still not finished, there is the second phase of splitting making the best of the natural elasticity of the bony corn, until the positioning of the implant. In this way there’s much less risk of determine some sharp fractures of the vestibular cortical and following necrosis (15).

Figure 8.

Denta-scan shows a serious mandibolar atrophy.

Figure 12.

In this way we can put implants of correct dimensions also in cases of serious atrophy.

3. SINUS FLOOR ELEVATION. The third major indication for using osteotomes is when alveolar bone in the posterior maxilla has resorbed so much that less than 10 mm remains between the crest of the ridge and the sinus floor (Fig. 13) (16, 17). The bone condensing osteotomes can be used in these cases in order to elevate the Shnaiderian membrane in both the minus and the big sinus lift technique (Figs 14, 15) (7–18). We want to remember that instruments never have to entry inside the sinus, and that the elevation of the membrane is dued to the hydraulic pressure of bloody and the grafting materials, according to Pascal principle. An interesting application is the PEMSL technique (post-extractive-minor-sinus-lift) (18). According to this technique in presence of a good inter-radicolar post-estractive bone settus (width ≥ 3 mm and height ≥ 7 mm), is possible, by using bone condensing osteotomes, put an implant of correct size and simultaneously have a minus sinus lift (Figs 16, 17). In these cases, by using the screw shaped osteotomes insetad of the traditional osteotomes with surgical mallet, we increase the confort for the patient during the surgery, and we annul totally the risk of paroxysmal positional vertigo as a complication of osteotome sinus floor elevation (19).

Figure 13.

The post-extraction atrophy and the sinus pneumatization prevent in much cases implant placement.

Figure 14.

The osteotomes guarantee a greater control during bone preparation with big control of the sinus membrane.

Figure 15.

The osteotomes technique in the big sinus lift.

Figure 16.

Post-extracive bone crest. The protocol foresees the implant preparation in the inter-dental and inter-radicolar bone set.

Figure 17.

Thanks to the osteotome technique all the implants have been correctly positioned also in this critical situation.

Clinical advantages

From Our clinical esperience and from the analysis of the international literature emerge several clinical advantages. First of all, the preparation of an implant bed through the protocol of the expansion-condensing osteotomes guarantees the maximum preservation of the remaining bone. The surgery protocol includes as a matter of fact the utilisation of just one drill able in cutting the bone followed in sequence by manual instruments of progressively growing diameter. In this way it is very reduced the missing of the bone respective to the traditional protocol exclusively through drillings (Fig. 18). And all this together with the increasing of bone properties will contribute to guarantee an improvement of the primary implant stability. After that, the bone condensig osteotomes that are used manually and put each of them over an esagonal screwdriver (Fig. 19), in their progressive action inside the bone cancel completely the risk of over-heating thanks to a big control of heat generation. Moreover and thanks to the manual action they guarantee a major tactile sensibility and a major visibility and control of the axis and of the depth of the job (Fig. 20). For this reason, for the preparation of the implant bed in the pterigoidea area, these instruments should be preferred to the traditional drilling protocol, in order to avoid the damage of the close nervose and vascular structures (31).

Figure 18.

Simulated implant preparation on the left it’s easy to verify the very good bone preservation with the osteotomes protocol.

Figure 19.

Every osteotome is mounted during bone preparation on an esagonal screwdriver.

Figure 20.

The osteotomes allow also in difficolt cases a greater control of the axes and the depth of the implant preparation.

Limits

Starting from the matter of fact that these instruments for reasons of obstacle find difficult to be used in posterior sectors above all in patients with a limitate open of the mouth, the main limits linked to the utilisation of the expansion-condensing osteotomes happen because of two factors: clinical and histological. Clinically, as described above, it’s necessary at least a 3mm width of the remaining bone crest; if this doesn’t happen other alternative surgery techniques will be used (eg. Split Crest).

What is important, though, is the densimetric analysis of the bone that is very important in this technique because bone condensing osteotomes are not indicated in D1-D2 bone class for the risk to determinate an important damage to the vessels microcirculation for compression and trabecolar fractures (12), causes a 2–3 months average extention of the times for healing and complete osteointegration respect to the normal protocol (20), and in some cases the loosing of the implant aftre loading.

The condensed bone in this way will have to put in act a double repairing mechanism, from one side represented by the normal processes of osteointegration an on the other side from the processes of the reparation post fracture like (22). There are real BMU (bone modelling unit) which at first have to create new spaces for the new vessels and afterwards filling all the gaps bone-implant. This would explain why the major part of the istomorphometrics studies followed on groups of implant put with this protocol in D1-D2 bone class were reporting % di BIC (bone implant contact) on average always lower than the implant which were put in a traditional way, even after 28 days (12, 21). In front of these conclusions there is the consideration of the fact that a series of studies (24–26) were showing, on the other side, % di BIC always superior in the groups of implants put in D3-D4 bone class, joined to a more intense signal of bone formation, with % success of very high implants instead of the almost total failures reported in similar studies (12, 20, 21).

Discussion

The our experience in the application of this tecnhique in all bone classes allows us to elaborate a surgical protocol depending on the respect of some golden rules. First of all the “passive fit” principle suggested by Stavropoulos e Lang (20) should be ri-examinated according to the new considerations about the primary implant stability and the new implant design. That is achieving of good primary stability and torque insertion values can not be obteined damaging micro-vessels without dangerous bone peri-implant remodelling. Moreover the “passive fit” principle is not in line with current international trend that foresees an immediate patients riabilitation. An intelligent preparation of the implant bed by using expanding-condensing osteotomes, in D3-D4 bone class and also in D1-D2 bone class in association with split-crest technique, allows to keep microdeformatios value under 3000 μstrains that Frost (27) thinks would be the maximum limit after which the bone would be incapable to heal and would go in necrosis. To increase the value of research of this “no stress implant fitting” there is the confirm of the fact that actually some experimental studies (28) demonstrated that the osteointegration happens 1–2 weeks before in those pars of the fixture that initially are not touching the mineralised bone instead of those one that touch the bone and that are responsible of the primary stability.

Conclusions

The technique of the expansion-condensing osteotomes allows the implant positioning even in cases of important bone atrophy, without using surgery techniques that are more difficult and invasive, improving at the same time and clearly the stability of the implant through trabecular compactation Allowing a manageable raising of the shnaiderian membrane through trans-alveolar way, this technique avoids in many cases the necessity to have recourse to the realisation of bone vestibular “gates” when it comes to the techniques of the big sinus lift. Nevertheless the technique in these cases needs more learning time but at the end the confort for the patients and the results are excellent. The knoledge of the bone visco-elastic and hystologic properties together with the maximum respect of the surgical protocol allows us to obtein % of success superior than traditional surgical protocol in D3-D4 bone class.

Figure 9.

The initial osteotomies.

Figure 10.

After osteotomies the pilot drill giudes the depth preparation.

Figure 11.

The osteotomes guarantee a greater control of the bone expansion.