Clinical
Fig 7
Removal of failed immediately loaded implant
Continued »
implant treatment for more than ı5 years. As a result, we have had the opportunity to manage most problems which may arise. Dental implant treatment
has more research and litera- ture than almost any other aspect of dental care and, in most instances, problems can be resolved. In addition to the general problems which can occur with implant planning, placement and restoration, there are some specific to the All-on-4 technique. These problems can be
loosely addressed as implant or restoration based:
ı. Implant problems: Short term • Failure to achieve primary stability – if only four implants are being used, in order to move to immediate loading, a minimum of 35ncm torque is required for all implants or a complete denture becomes the interim restoration. • Failure to integrate – again if the minimum of four implants has been used and one fails to integrate, treatment cannot be completed until an
Fig 8
Original provisional with luted temporary cylinders, high incidence of fracture
additional implant is placed. • Incorrect positioning – this protocol usually calls for alveolar and soft tissue resec- tion. As such, fabricating a useful surgical guide is not usually possible. Fortunately, accurate implant positioning is not as important as with single or partial cases, but implants placed too far out of the arch can create oral hygiene and bridge fabrica- tion challenges (Figure 4). • Lack of osseous reduction – without correct reduc- tion, the transition zone can end up in the wrong place, creating the need for an unhygienic ridge lap or anterior cantilever (Figure 5).
Long term • Continued bone loss – this can be due to any one of more than 40 reasons (of which peri-implantitis is only one)6 (Figure 6). Treatment may be indicated, although ulti- mately may procede to: • Loss of integration – with only the minimum number of four implants, not only replacement, but also fabrica- tion of a new bridge will be required (Figure 7). • Fracture of implants and
Fig 9 Homogenous casting provisional
components – as yet, long- term survival data (more than ı5 years) on four implants does not exist and mechanical failure must be anticipated as a possibility.
2. Restorative problems: Planning • Aesthetic compromises in the transition zone – the high lip line must be accurately recorded and communicated to the surgeon or an unaes- thetic restoration will result. • Too few implants – this can result in a lack of poste- rior support; despite the financial attraction of using only four implants, tried and tested biomechanical implant protocols should be main- tained and when sufficient bone is available additional implant support should be sought. • Bruxism – this is cited as the single biggest risk factor in immediate loading. Micro motion results in implant failure. Bruxists should not be offered this treatment option7.
Provisional restoration • Unacceptable aesthetics – the goal is to fit the
provisional on the day of surgery and not remove it until after boney healing. It is, therefore, essential that the required aesthetic informa- tion OVD etc. is gathered and transferred to technologists. • Fracture – original protocols using temporary cylinders luted to a complete denture which is cut back, resulted in many fractures during the critical integration period (Figure 8). As a result, a number of novel ideas have been postulated: e.g. fibre/ metal reinforcement, custom casting and delayed delivery and our own homogenous one-piece acrylic casting (Figure 9).
Definitive restoration • Fracture of veneering mate- rial – using the standard protocol of a CNC titanium and resin bridge, an esti- mated 20 per cent of final bridges will suffer fracture of veneering material within five years8 (Figure ı0). While there are porcelain-based solutions, these are consid- erably more expensive and there is a need for a more
Continued » Fig 10 Fractured veneering resin Fig 11
Clinical dilemma: is a 35-year-old patient with a history of periodontitis suitable for implant bridgework?
44 Scottish Dental magazine
“While there are porcelain-based solutions, these are considerably more expensive”
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