The sixth and last article in this series advises dentists and technicians on this challenging protocol with a continuation of clinical guidance on the stages of treatment necessary for conversion to the definitive bridge. The article begins by discussing the steps to be undertaken in the laboratory



When we started the definitive restorations, we used a basic milled bar with complete acrylic wraparound and a titanium frame with composite when the clinical need dictated greater strength. These procedures are detailed, as they are simple cornerstones for technicians new to the All-on-4™ procedure (Nobel Biocare®), and we have used them for the majority of the 100+ cases we have treated to date. More recently, we have improved the procedure, using the latest scanning techniques and equipment so that frames can now be designed and manufactured from the approved try-in as well as utilizing new designs for copy milling. These techniques will be the subject of a future article.

Titanium frame and acrylic wrap-around
As most definitive All-on-4™ bridge specifications require little change from those of the temporary bridge, we can proceed to the fabrication of the titanium frame. The frame is first modeled using 4-mm plastic sticks (Metrodent), Pi-Ku-Plast (bredent), and Nobel Biocare® titanium temporary multiunit cylinders (Figure 1). These temporary cylinders are cut to size, 2 mm below the occlusal surface posteriorly and 2 mm below the palatal contour anteriorly and secured with long 20 mm guide pins, (Figure 2). The use of the long guide pins prevents Pi-Ku-Plast from entering the cylinder. Using the labial and lingual indices (Figure 3) as a guide to place the replica frame, the 4-mm plastic rods can be cut to size and secured with Pi-Ku-Plast (Figures 4 and 5). The frame is finally checked (Figure 6) before dispatching for scanning and milling in titanium.

If modifications are necessary to the tooth arrangement on the temporary bridge, then a wax and tooth try-in will be required. (titanium temporary multiunit copings joined together with plastic sticks are needed to prevent rotation during the try-in stage). When the wax and tooth try-in has been approved, new putty indices will need to be made so that the framework for the copy milling of the titanium structure can be prepared in the correct position.

When the titanium frame is returned from copy milling, it is placed on the master model (Figure 7) to check the fit and then fixed with long 20-mm guide pins. The labial index is then positioned and molten wax flooded into the index and around the titanium frame (Figure 8). After the wax has set, the labial index is removed (Figure 9), and the long guide pins are exchanged for short laboratory screws. The master model is returned to the articulator and the wax modified to ensure that vertical dimension is maintained.

Acrylic teeth can now be individually set in the exact positions of the teeth formed in the wax index (Figure 10) until all the wax teeth have been replaced (Figure 11). The try-in is then returned to the operatory for checking and patient approval.

Appointment 4: Try-in (60 minutes)
Although the technical steps for titanium/acrylic and titanium/composite are different, the aims of this appointment are the same—to confirm the occlusion, esthetics, and phonetics of the bridge at try-in as detailed below.

At try-in, the clinician will:

•    Record the closed vertical dimension
•    Remove the temporary bridgework
•    Fit try, and check the fit
•    Check the occlusion
•    Verify esthetics
•    Check the vertical dimension
•    Assess the phonetics.

The clinician and patient must both be satisfied with the occlusion, esthetics, and functional aspects of the bridge prior to its finishing in acrylic.The temporary bridgework is removed and then replaced at the end of the appointment as in previous appointments. The titanium/acrylic try-in will be delivered in the form of the final frame with the eventual acrylic teeth set up in wax (Figure 12).



The titanium/composite try-in will be presented in the form of a plastic strengthening frame on temporary multiunit copings with the eventual acrylic teeth again set up in wax. Again, the aim is to establish that the clinician and patient are happy with the bridge’s occlusion, esthetics, and functionality. In this case, it is essential to establish the final configuration of the bridge before the titanium frame is constructed because this involves a veneering technique to a depth of only 2 mm.

The assistant will lay out equipment as for a denture try-in, with Willis gauge, Fox’s occlusal plane guide, wax knife, Bunsen, and waxes available. It is a simple and familiar procedure to make alterations to acrylic teeth set up in wax. A speech assessment is a necessary part of the try-in because some patients find they lisp while wearing an upper temporary bridge. It is vital to give the patient confidence at this stage, especially if adjustments have been made to incisor tooth position(s) and the palatal contours of the definitive bridgework to overcome such problems. The usual verbal distortions associated with maxillary bridgework relate to pronouncing consonants, the plosive alveolar sounds (D and T) and bilabial sounds (M and N). Even after changes in tooth position, the patient’s speech may still be affected. Without exception, in all of our own cases, we have found that patience and practice bring a speedy resolution to these difficulties.

It is helpful after the surgeon and patient have approved alterations if a close friend or relative is allowed to see the try-in. This is reassuring for the patient, and also allows a spouse, partner, or friend to express an opinion at a stage when changes are still possible.

Laboratory details on finishing
After a successful try-in, the returned structure is ready for the wax to be changed to high-impact acrylic resin. As we require the fitting surface of the bridge to be convex to contact the convex surface of the ridge, any slight undulations or concave areas in the wax pattern need to be filled to prevent food debris becoming trapped (Figure 13). New model analogs are then attached to the frame using the short laboratory screws (Figure 14). A model now needs to be cast recording the shape of the fit of the bridge and to secure the model analogs. The case is then flasked in the normal way (Figure 15), remembering to wax out the access holes before topping. Following the boiling out process, the titanium bar (Figure 16) is removed from its model, sand blasted with 50 μm alumina oxide at 4-bar pressure, metal primed, masked with pink opaque, and refixed to the model with the short laboratory screws before the access holes are filled with Impregum™ (3M™ ESPE™) impression material (Figures 17 and 18). The flask can now be packed and processed. Care must be taken when de-flasking to avoid damaging the model analogs and screws. After trimming, the case can be returned to the master model to check occlusion before final polishing (Figure 19).

Titanium frame and composite
The procedure for this type of restoration differs in the need to provide a wax and tooth try-in using temporary multiunit copings, linked together to prevent rotation during the try-in. Using long 20-mm guide pins to secure the linked temporary copings, and with the labial matrix in position, hot wax is flooded around the bar, the copings, and into the labial matrix.
Acrylic teeth are now set one at a time into the same positions as the temporary bridge as indicated by the labial matrix, and the case is returned for try-in (Figures 20 and 21).



When the wax and tooth try-in has been approved, a new labial putty index is prepared incorporating new cut-down temporary copings and long 20-mm guide pins. Pi-Ku-Plast self-curing resin is then flowed into the matrix and around the temporary copings (Figures 22-24).

The case is returned to the articulator to confirm occlusion and lingual contour. We are now ready to cut back the Pi-Ku-Plast frame by 2 mm to create adequate space for the veneer of composite. The cut back (Figure 25) can be verified with labial/lingual matrices to ensure even reduction where composite is to be placed (Figure 26). There may be areas where it will be intended to expose polished metal for reasons of strength or for the reduction of bulk, and in these areas, no reduction will be necessary. The copy frame is now ready to be despatched for scanning and milling.

While the frame is being milled, the wax/tooth try-in is used to make the clear mold that will be required to press the composite onto the titanium frame. To do this, we must again secure new model analogs to the try-in. The try-in now needs to be invested in a clear plastic flask using putty with a shore hardness of at least 90 to hold the model analogs firm during pressing (Figure 27). A thin smear of Vaseline® is applied to the set surface of the putty to ensure separation between the two mixes of silicone.
Memosil® (Heraeus Kulzer), a clear silicone, is used to form the secondary part of the mold. This is injected into the flask and around the try-in before the flask is closed. After setting, the flask is opened, and the try-in is removed.

The returned milled titanium frame is checked on the master model using the putty indices prior to veneering. To prepare the surface for metal priming and opaquing, the titanium frame’s polished surface is waxed out using sticky wax to prevent damage during the subsequent sandblasting with 50-μm alumina oxide at 4-bar pressure (Figure 28).

The sticky wax is chipped off under cold running water. Metal primer is then applied to the sandblasted area followed by a layer of opaque. When set/cured, the light-cured opaqued frame is fixed into the flask using short lab screws with the holes filled with Impregum™ impression material to prevent composite from entering the screw heads. Escape channels are cut into the hard investing putty to allow excess composite to flow out (Figure 29).

The mold, together with the chosen shade of dentin, is heated with a hair dryer to improve the flow of the composite and then filled with dentin, closed, and placed in a dark drawer to allow the composite to flow without curing (Figure 30). (We currently use Heraeus Kulzer composite because of its optimal handling characteristics.)



After curing, the flask is opened (Figure 31), the incisal edges and posterior cusps are cut back (Figure 32), surface connector is applied, and enamel is placed into the appropriate areas of the mold (Figure 33). The flask is closed once more and light cured. When completed, the bridge is removed from the flask after first removing the Impregum™ sealer, which prevented the composite from entering the screw heads. The case is then replaced on the articulated model, and the occlusion is refined, if necessary. A small amount of dentin will now need to be removed where it has flowed onto the pink tissue area (Figure 34).

A variety of pink composites and subtle stains are used freehand to create the contour and character of the pink tissue area (Figure 35). The bridge receives its final polish with the clinician’s preferred method before insertion (Figures 36 and 37).
(The latest CAD/CAM systems produce metal frameworks that are cut back by 2 mm as part of the milling process. Currently, this process is system specific and is not universally available.)

Appointment 5: Fit (45 minutes)
The temporary bridgework is removed, as in all prior appointments, and the new bridgework is fitted with the screws torqued to 15 Ncm. As stated previously, even slight over-tightening is likely to cause a screw to fracture.

We check periapicals at this stage to ensure the superstructure is fitting correctly, to compare with the previous radiographs at 2 months post-placement, and to act as a baseline for future assessment (Figure 38). The occlusion is finessed to allow even contacts in retruded contact position (RCP) and lateral and protrusive excursions. A final assessment is made of the esthetics and phonetics, and any required alterations are carried out chairside.



Any residual difficulties in speech are evaluated by asking the patient to recite the days of the week and the numbers between 60 and 69, and the results duly recorded. The patient can be reassured that any abnormalities will normally resolve after the re-establishment of neural pathways, which can be expedited by speaking more slowly and practicing reading aloud. The patient should be made aware that he or she might temporarily sound slightly different before leaving the dental office to minimize any potential embarrassment following unhelpful comments by family or friends.

Monitoring and maintenance
We recommend the use of the Philips Sonicare® powered toothbrush for cleaning the bridgework and surrounding mucosa. The action is gentle, the unit is easy to manipulate, and it is able to access surfaces that some patients find difficult to reach.
The patient’s commitment to oral hygiene can be assessed by the condition of the temporary bridge, and encouragement given where necessary. We recommend the less abrasive denture toothpastes to protect the luster of the acrylic surfaces. If any natural teeth are present, they should be brushed with a standard dentifrice after the bridgework to minimize its exposure to the more abrasive paste. Many patients are able to master the use of Oral-B® Super Floss® or interdental brushes, and these are invaluable in keeping the sub-structure of the bridgework clear of debris and plaque. Some patients prefer to use the Waterpik®.
Oral hygiene regimens should be reviewed periodically. It is our experience that patients are now highly motivated and happy with their smile, and their oral hygiene improves as a result. However, many of these patients present with problems exacerbated by a lifetime of poor oral hygiene, and they should be carefully monitored and encouraged positively to maintain their newly achieved high standards.

We follow our normal protocol for all implant restorations with review after 1 month, 6 months, and annually thereafter. Radiographs using positioning devices should be taken annually up to 5 years and, in the absence of pathology, every 2 years afterwards to monitor bone levels. The periodic removal of calculus and staining is often required, particularly in the mandibular arch. Removal of the bridge at the annual check up greatly facilitates this, and the abutments can be washed and irrigated with chlorhexidine spray.

(Readers should note that the illustrations used in this article have been taken from a number of different cases to more clearly demonstrate the points made in the text.)

Bios
John Moorhouse
BDS, DDH, MFGDP, DPDS, Dip Implant Dent RCS Eng was awarded the degree of bachelor of dental surgery, BDS, at Manchester University in 1978, winning the prize for periodontology.

He has worked extensively abroad establishing dental clinics in Zaire, Thailand and Malawi. He was the lecturer in oral health for the School of Medicine in the University of Malawi and has published several research papers on oral health and health education. He was awarded a Diploma in Dental Health for Educators, DDH, in Dublin in 1989 winning the Presidents prize. He was awarded the diploma of membership in the Faculty of General Dental Practitioners MFGDP(UK) and the Bristol diploma in postgraduate dental studies, DPDS, in 2001. John was one of the first groups of dentists to be awarded the FGDP  diploma in implant dentistry and has been a tutor on the course ever since. He has taught on the Manchester MSc course and is an ITI speaker. He has held an annual 3-day implant restorative course since 2005. John is lead implant surgeon at Oasis Eaglebrow implant referral centre, Lymm, Cheshire.

Frances Trainer BDS, FDS RCS (Eng), qualified in Dundee and after postgraduate posts in London and Edinburgh gained her fellowship from the Royal College of Surgeons, England. She has spent the last 20 years in general dental practice, the last 10 years in Lymm with John Moorhouse, where restoration of dental implants has become a major part of her clinical work. She has been involved with undergraduate teaching at The Manchester Dental School and is currently a postgraduate tutor for the Manchester and Stockport areas. Frances is also a clinical support advisor for Oasis Healthcare, and a regional clinical services advisor at Oasis.

Colin J Dean, FBIDST, Dip RCS (Eng), qualified as a dental technician in 1966 and has spent many years completing both NHS and private prosthetic and crown and bridgework. He worked for a time at Birmingham Dental Hospital before taking up a post as Senior Lecturer in Dental Technology at Manchester Polytechnic.

He became co-owner of Bolton Dental Laboratory in 1979 and was awarded Fellowship of the British Institute of Dental and Surgical Technologists in the same year. Colin further qualified as a Clinical Dental Technician in 2003 while working as a Senior Dental Technician at Manchester Dental Hospital. In 2005, together with his son Jonathan, Colin opened C&J Dental Technologists Ltd. where they specialize in implant-retained prostheses. The business also incorporates a surgery where they see patients directly for the provision of dentures. Colin is an occasional Lecturer in Dental Technology at Manchester Metropolitan University.