Case histories

14 March, 2013 / Infocus
 

In the last article, we looked at the principles and history behind the All–on–4 dental implant concept. In this article, I will outline a typical case and how the practical aspects of the treatment progresses.

As a practice, we have, over the last 15 to 20 years, carried out full arch implant rehabilitation in, quite literally, hundreds of cases.

As explained in the last article, we have seen, over the last five years,a gradual move from delayed (three to six months) loading of the implants to immediate (same day) loading.

This is quite different from the ’teeth in a day/hour’ procedure which found favour a few years ago and had significant limitations.

Critical differences between All-on-4 and “teeth in a day/hour”

‘Teeth in a day/hour’ advocates fitting of the final bridgework on the same day that the implants are placed. Cone Beam Computerised Tomographic (CBCT) information gained at the planning stage is used to fabricate a surgical guide which, sufficiently accurately for the procedure, allows placement of the implants (usually without the need for raising a flap).

The guide is used, prior to surgery, by the laboratory to fabricate the final bridgework such that everything comes together on the day. Without going into detail, the reader will appreciate that there are many potential pitfalls with such an approach.

All–on–4 by contrast involves fitting of a provisional bridge on the day of surgery. Due to the frequent need for teeth to be extracted and the residual ridge to be resected, on the day the use of a surgical guide is rarely possible. CBCT is usually not necessary. The final bridge is fabricated after confirmation of successful integration of the implants and complete tissue healing.

Please note that some dental practitioners have been advocating the use of the provisional bridge as a long-term solution. This should be avoided if at all possible, as the unsuspecting patient will likely incur significant additional costs at a later date when the ’provisional’ restoration fails.

All-on-4 case history

A 74 year old female in good health presented with an inability to eat comfortably due to mobility of remaining upper teeth. Her dental history revealed that she had developed periodontitis in her 20s and for over 50 years has been’managing’ her periodontal condition. She has had specialist periodontal treatment in both North America and the UK.

Treatment has comprised deep scaling, root planing, subgingival curettage and flap surgery, with regular hygienist appointments throughout. The patient is well motivated in carrying out required oral hygiene measures and has been determined to keep her teeth as long as possible.

There has been continued slow progression of the disease process and tooth loss. The patient has delayed inevitable loss of remaining upper teeth as she does not wish for a complete denture.

Patient’s additional concerns:

  • Does not wish for a complete removable denture
  • Significant anxiety over loss of remaining teeth
  • Has ‘hidden’ her smile for many years and would like to improve the appearance (fig 1)Examination found eight teeth remaining in the upper arch, 70-90 per cent bone loss, all G2/3 mobility. There were 14 teeth remaining in the lower arch, with 30-40 per cent bone loss and minimal mobility, heavily restored dentition, with no active caries, and good oral hygiene but plaque deposits evident (fig 2).

TMJs were healthy, with full range of movement and no pain on loading in centric relation.

Occlusion was unstable, with only two posterior contacts on mobile teeth. Centric relation and centric occlusion were not coincident. No evidence of parafunction.

Class II div II occlusion with deep overbite. Upper anterior teeth have drifted labially and imbricated, lower anteriors have over-erupted with compensatory alveolar overgrowth (fig 3).

In terms of aesthetics, the patient had a medium smile line, although she reported never showing her teeth through years of hiding unfavourable dental aesthetics.

Additional investigations for treatment planning:

  • full dental and periodontal charting
  • mounted models in centric relation
  • OPG radiograph (fig 4).

Treatment options:

  • conventional – complete upper denture
  • implant – implant retained overdenture or fixed implant bridgework.

Treatment discussion

Over a number of appointments, the patient elected for a fixed implant bridge using the minimum number of implants (four). Conventional delayed placement was something that the patient wished very strongly to avoid. As she met the criteria of:

  • sufficient bone height in front of the sinuses and below the floor of the nose
  • not showing any evidence of parafunction
  • manageable aesthetic transition zone
  • accepting of the limitations.
  • The All–on–4 procedure was then suggested and agreed upon.

Challenges

Every case has unique concerns. In this particular situation, the challenges faced were primarily restorative:

  • anticipation of the patient’s final smile line and vertical dimension
  • how to manage the complete overbite.

Treatment progression

Surgical consultation &ndash this is an essential stage where, separate from discussion on the overall plan, the surgeon discusses in detail the planned procedure, fully covering the processes involved and gaining informed consent. The surgical staff also have the opportunity to meet with the patient and reassure her about any concerns and anxieties that she may have outlining how they will care for her on the day.

Day of surgery

  • Implant placement &ndash on the day of surgery, under zoned aseptic and sterile conditions, the remaining teeth are removed and the remaining ridge carefully debrided and recontoured (fig 5). The anterior borders of the sinuses are mapped and the 30&ndashdegree angled posterior implants placed first, attempting to engage cortical bone in the floor of the sinus and floor of the nose.
  • Generally, placement starts in the region of the second premolar, with the implant angled to the canine region. The anterior implants are placed in the positions of the lateral incisors, but this is adapted depending on available bone. The anterior implants are placed vertically using the incisal edges of the lower teeth as a reference point (fig 6). Two 15mm implants were placed posteriorly and two 13mm implants anteriorly. All implants were regular platform NobelActive implants. All implants must tighten to >35cm if an immediate loading protocol is to be followed. In this case, torques of 50cm were recorded for all implants.
  • Abutment attachment – the goal of implant positioning is a screw&ndashretained final restoration where the access holes are to the palatal. This is facilitated through the use of 30-degree angled abutments on the posterior implants. While it is possible to work at fixture head level on the anterior implants, abutments are also used in order to raise the restorative level to tissue level. This makes for a far easier and more comfortable restorative procedure for the patient (fig 7).
  • Bone grafting and tissue resection &ndashsockets are filled with bone grafting materials in order to anticipate a rounded ridge for good bridge adaptation. In most cases, there is significant soft tissue remaining that needs to be resected in order to allow close adaptation to the implant abutments and residual ridge. Failure to do so results in excessive ridge height and likely compromise with the transition zone and oral hygiene measures (fig 8).
  • Working impressions and recording of vertical dimension &ndash in this particular case, there was little usable aesthetic information from the remaining upper dentition. An ’open tray’ working impression using polyether impression material and a special tray was carried out. Vertical dimension was recorded in centric relation &ndash this is essential as it allows control of the anterior guidance in the provisional restoration.The OVD was estimated based on extraoral aesthetics and lip competence. Healing caps were placed on the abutments and the patient escorted to the recovery room where they are waited on by the support staff.
  • Laboratory steps – a working model is cast and mounted on an articulator. The technologist sets up the teeth according to the previously decided aesthetic parameters. In this case, these were based on required overjet and overbite, using the lower anteriors and photographs as reference points. There are no functional cantilevers at this stage.
  • Due to lack of technical support, the original protocol called for adapting a prefabricated denture by luting it to metal cylinders intraorally and cutting back the flange area. While an understandable procedure of necessity, this has a number of limitations, not the least of which is the discomfort for the patient as the local anaesthetic wears off during the lengthy procedure.
  • Using a denture also results in significant weakness in the provisional bridge where the cylinders are luted, as well as where the individual denture teeth are bonded. We have developed a process whereby the bridge is a homogenous acrylic structure ’poured’in tooth–coloured acrylic and backed with high-impact denture base material.We have had no fractures with more than 100 cases fabricated in this way, compared with significant fractures when the compromise approach is used (fig 9).
  • Securing the provisional bridge – this is a short procedure of approx 5 minutes with minimal patient discomfort. The retaining screws are torqued to the manufacturer’s final setting and access holes sealed. Occlusion is adjusted to even contacts spread across the implants with ’flat’ guidance. In this case, due to the deep overbite, it was decided to only create contacts on lower 3–3 and reduce the posterior ’step’with the Dahl principle (figs 10 and 11)
  • Post–operative instruction and guidance-home care advice is given and a review appointment made before patient discharge. Essentially the patient is advised on a soft diet for the first four to six weeks, which is the critical implant integration period. Oral hygiene consists of chlorhexidine soaks three times a day, for one to two weeks until initial soft tissue healing and the patient can brush and –flush’under the bridge. All patients are provided with a waterjet to aid home care.
  • Review and follow up
    • A surgical review is arranged for one week.
    • Dental hygienist and oral health consultant appointments arranged.
    • Critically, the provisional bridge is not removed until definitive restoration is required or other problems arise.

    Definitive restoration after three months

    Various options for finishing the restoration are available and will depend on the patients wishes. The standard is a CAD/CAM milled titanium bar veneered with denture teeth and high-impact acrylic (figs 12, 13 and 14). If sufficient space is available, and the patient elects for it, individual porcelain crowns can be fabricated and luted to a zirconium or titanium framework (fig 15).

    As the implants have now been confirmed to have integrated successfully, the final bridge is extended with bilateral cantilevers to the first molar position, the usual occlusal criteria for posterior cantilevers being followed.

    The complete overbite was managed through use of the Dahl concept, whereby initial occlusal contacts were on lower 3–3 only. Review appointments confirmed contact of the posterior units (figs 16 and 17).

    About the author

    This article was submitted by Kevin Lochhead, specialist prosthodontist and clinical director at Edinburgh Dental Specialists. Implant surgical expertise provided by Martin Paley, Prof Glenn Lello, Prof Lars Sennerby and Gillian Ainsworth.

    All technical work by the technologists at Edinburgh Dental Implant Laboratory.
    The next article will cover maintenance procedures as well as problems and complications.

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