Written by Tom Bereznicki, BDS Wednesday, 04 April 2012 10:46
In high lip-line aesthetic cases, not only is the success of treatment dependent on the skills of the technician but also on the management of the soft tissues by the prosthodontists who should be highly involved in the design of the definitive fixed partial denture (FPD). It is generally accepted that the use of an ovate pontic in short span FPDs, whether conventionally or implant supported, is the most predictable approach to achieving an excellent and natural appearance.
Figure 1. A 3-unit fixed partial denture (FPD) with a poor ridge-lap pontic and uneven gingival heights.
Figure 2. A 3-unit FPD with a poorly designed ridge-lap pontic and open embrasures.
The aesthetic deficiencies shown in the 2 cases (Figures 1 and 2) are clear. Although the standard of the porcelain work is not ideal, in both cases, little or no attention has been paid to the soft-tissues profiles and so success has been further compromised. The ridgelap pontic design gives an unnatural appearance, with the pontic appearing to “sit” on the gingivae rather than emerging from the gingival tissues as natural teeth do in nature. The lack of tissue support from the pontics has further contributed to the appearance of open embrasures and unsightly “black triangles.” Little effort has been made to ensure that the gingival heights of the central incisors are even.
Figure 3. An ovate pontic with poor aesthetics.
Figure 4. Palatal view of the ovate pontic showing poor tissue support for aesthetics.
Figure 5. The 20-year-old ovate pontic still providing a degree of tissue support for the papillae.
The issue of aesthetics is further demonstrated in the contrasting results achieved with the 2 markedly different designed FPDs shown in Figures 3 to 5. Both prostheses were placed around 20 years ago.
In the first case, the lack of support to the gingivae from the design of the pontic is obvious. The ongoing recession of the underlying bone and soft tissues has further exacerbated the clinical appearance with a space above the pontic and a complete absence of papillae.
The second case demonstrates how the ovate pontic form has helped in supporting the tissues and maintaining the emergence profile and papillae despite the on-going recession. The aesthetics are compromised by the dark exposed root of the abutment tooth rather than the minimal failings around the ovate pontic.
Figure 6. The emergence profile refined during the temporization phase of treatment following extraction of the lateral incisor.
Figure 7. View of the definitive FPD on fitting.
If the emergence profile is correctly created and the gingival tissues adequately supported by the pontics, papillae can be formed interproximally and the pontic teeth shaped to appear to be emerging from the gingival tissues, mimicking the appearance of natural teeth (Figures 6 and 7).
Figure 8. Healing abutment after 3-plus months of integration overgrown by gingival tissues.
Figure 9. Emergence profile refined with a provisional screw-retained restoration.
Figure 10. The definitive cemented abutment supported FPD with pink porcelain merging with the natural tissues.
Figure 11. The final aesthetic result.
This also applies to short span implant supported FPDs. In the case shown in Figures 8 to 11, where the accidental loss of a diminutive lateral incisor and deciduous canine not only complicated treatment by the lack of space but also the tissue loss which was such that the use of pink porcelain was required to optimise aesthetics. The harmonious blend of the pink porcelain with the natural tissues was disguised by the creation of an emergence profile with a provisional screw retained composite FPD prior to impressions being taken. It is unlikely that the final aesthetic result could have been achieved without prior planning of the soft tissues.
Three possible techniques for the creation of the emergence profile for ovate pontics are:
• prior to impression taking, during temporization
• at the time of impression taking
• at the time that the definitive FPD is fitted.
It is the author’s opinion that the most predictable and aesthetic outcome is achieved if the emergence profile is defined during the phase of temporization and prior to impression taking. The versatility of modern composites is such that it is far easier and quicker to work with these materials rather than to try to achieve the same outcome working in porcelain during the definitive phase of FPD fabrication.
One commonly advocated technique is to trim the working models to the desired ovate shape and form in the pontic areas. This technique is, however, reliant on the clinical experience of the operator as the same amount of tissue requires to be removed clinically at the trial fit appointment. Even if this can be accurately and successfully carried out, without modification of the fit surface of the provisional FPD, the soft tissues invariably rebound during the healing phase prior to the final fit. Consequently, the same degree of tissue removal would be required at that visit, along with the administration of further local anesthesia.
The other issues encountered with this technique are related to the degree of empirical removal of tissue on the working model—too much and the bridge may not fully seat if sufficient gingival tissue to maintain the biologic width is retained and, if too little, the aesthetic result may not be ideal, necessitating further modifications to the working model and additions of porcelain to the fit surface of the pontics.
It is the author’s experience that the technique of creating the emergence profile prior to impression taking is the most consistently reliable in achieving the desired aesthetic result. The clinical problem encountered with this technique has been related to the impression stage of treatment. The time taken between removal of the provisional restoration and conventional impression taking consistently resulted in a master working model which did not accurately reproduce the created tissue contours seen on removal of the provisional restoration. Consequently, at the try-in stage of the definitive FPD, the pontic shape and form were poor and unsupportive to the desired tissue profile.
Figure 12. The emergence profile created with a provisional screw-retained composite restoration.
Figure 13. The collapsed emergence profile 30 minutes after removal of the provisional restoration.
Figure 14. The developed ovate pontic form on removal of the provisional restoration.
Figure 15. The degree of distortion of the gingival tissues following placement of retraction cord and removal of the final impression.
The cause of these discrepancies seemed to be due to the rapid collapse of the sculpted tissue upon removal of the provisional FPD. The degree of loss of contour as developed in an implant case is shown in Figure 12 as the provisional is removed, and 30 minutes later in Figure 13.
In conventional tooth supported FPDs further tissue distortion is created by the introduction of retraction cord prior to impression taking. The excellent initial created emergence profile is shown almost immediately following removal of the provisional FPD in Figure 14. Some 30 minutes later, the distorted and collapsed nature of the tissues after removal of the retraction cord prior to impression taking are clearly seen in Figure 15. Further alteration takes place in the laboratory following die trimming. A second pour solid model has rarely proved to be of any predictable help.
In general, with patients becoming better informed about advances in cosmetic dentistry, their expectations are getting ever more demanding. As a result, cases such as the one shown, are presenting more frequently. The patient was dissatisfied with the appearance of his metal skeleton removable partial denture and its associated instability. He wished to explore his options of fixed prostheses and ultimately decided on a conventional FPD rather than one supported by implants. His high lip-line and broad smile dictated the need for the creation of an emergence profile and ovate pontic design within the treatment plan.
Figure 16. View of the edentulous ridge prior to the development of an emergence profile.
Figure 17. The provisional restoration used to develop the emergence profile.
Figure 18. The developed emergence profile.
After administration of the local anaesthetic, the abutment teeth were prepared for a fixed-fixed design for the FPD. Prior to temporisation, the edentulous ridge was modified with electrosurgery to create papillae and an emergence profile. A temporary bridge constructed in a bisacryl provisional material (Protemp 4 [3M ESPE]) was fabricated with ovate pontic design to help maintain this profile during the healing phase of the gingival tissues (Figures 16 to 18).
After allowing 12 weeks for initial healing and tissue maturation, the provisional FPD was removed, retraction cord placed in the conventional manner and an impression taken with a polyether impression material (Impregum Penta Soft Quick [3M ESPE]). The resultant silver-plated working model is shown following sectioning and some modifications to the emergence profile (Figures 19 and 20).
Figure 19. A view of the silver plated working model after sectioning.
Figure 20. The occlusal view of the same model.
Figure 21. The emergence profile prior to impression taking.
Figure 22. A view of the working model following sectioning.
In Figures 21 and 22 it is clearly seen that there is no physical resemblance between the patient’s soft tissues and those on the working model especially after die trimming.
A second hard-tissue model poured from the same impression was of little help. The collapse of the created emergence profile and its reproduction such that, despite some arbitrary model trimming in the soft-tissue area, the temporary restoration, which fits accurately and fully supports the tissues in the mouth, will simply not seat onto the working model (Figures 23 and 24). It follows that any definitive restoration made on these models would be deficient and lacking in the necessary shape to support the gingival tissues in their desired profile.
It was the frustration experienced in this case that lead to the development of the following technique to replicate the created emergence profile in the working models. Figure 25 shows the accuracy of fit of the same temporary restoration as in Figure 24 fitted onto a hard-tissue model made using the technique.
Figure 23. The poor fit of the patient’s provisional restoration on the working model.
Figure 24. The poor fit of the patient’s provisional restoration on the working model.
Figure 25. The excellent fit of the provisional restoration on a hard-tissue model fabricated from the proposed impression technique.
Figure 26. The patient with his removable partial denture (RPD) prior to commencement of treatment.
Figure 27. The appearance of the fitted definitive FPD.
Figure 28. Lateral view of the patient with his RPD.
Figure 29. Lateral view of the completed case.
Figure 30. View of the created emergence profile on removal of the provisional screw-retained restoration.
Figure 31. View of the soft-tissue working model showing accurate and undistorted reproduction of the gingival tissues.
The before and after photos of the case are shown in Figures 26 to 29. The shape of the ovate pontics of the provisional FPD were so accurately reproduced in porcelain that the only adjustments required following the try-in stage were related to occlusal refinement and issues with colour matching.
The developed technique was then further refined and adapted to short span implant-retained FPDs and the degree of accuracy achieved shown in Figures 30 and 31. The technique will be demonstrated in a series of future articles.
The technique uses a stent that accurately replicates the fit surface of the provisional FPD (Figure 32) that was used to create, maintain and support the emergence profile of the soft tissues. The untrimmed stent is shown in Figure 33.
In this case, the edentulous ridge prior to, and following the creation of, the emergence profile is shown (Figures 34 to 36). It is not within the scope of this article to describe the technique behind the creation of the emergence profile itself, merely its reproduction.
The provisional FPD, which is used to maintain the tissue contours during their maturation, is also used to create the impression stent. Once cleaned, of all temporary cement, the bridge is submerged to around one third of its fit surface in Provil Novo Soft Fast Set impression putty (Heraeus Kulzer). Once the putty has set, the provisional FPD is removed (Figure 37 and 38).
Flowable light-cured composite Venus Flow (Heraeus Kulzer) is then injected into the mould in layers and cured until flush with the level of the putty. Ordinary light-cured composite Venus (Heraeus Kulzer) can then be used to bulk up the stent and create a retention tag to facilitate removal in the definitive impression (Figure 39).
As polymerization shrinkage will have occurred during the curing process, the composite stent will not fit accurately onto the abutment teeth in the mouth without further adaptation. The inside surfaces of the stent abutting the tooth preparations are therefore cored out (Figures 40 and 41) and all excess “flash” trimmed.
The stent is then trial fitted to ensure a passive fit on the abutments and correct tissue displacement in the pontic areas (Figure 42). There is invariably some tissue blanching for one or 2 minutes, indicating that the gingivae are being pushed back into the same position that was supported by the provisional FPD prior to removal.
The impression stent is now ready for final adaptation. A water soluble separating medium (Wink [Pulpdent]) is applied to the abutment teeth. Composite Activator (BISCO Dental Products) followed by Bonding Fluid (BISCO) are applied to the internal surface of the stent as per the manufacturer’s instructions. Composite bonding agent (OneStep Plus [BISCO]) is then applied to the fit surface of the stent and light-cured for 10 seconds. Finally, flowable composite is applied as shown to the abutment teeth (Figure 43), the stent fitted and maintained in place with finger pressure (Figure 44) while the composite is light-cured (Figure 45).
Figure 32. The fit surface of the provisional restoration used to create the emergence profile.
Figure 33. The fit surface of the duplicated provisional restoration prior to conversion to an impression stent.
Figure 34. The edentulous ridge prior to creation of the emergence profile.
Figure 35. The developed emergence profile.
Figure 36. View of the provisional composite restoration used to develop the emergence profile.
Figure 37. The provisional restoration submerged in impression putty.
Figure 38. View of the impression putty on removal of the provisional restoration.
Figure 39. The finalised stent in impression putty prior to removal and trimming—the retention tag is clearly visible.
Figure 40. The fit surface of the duplicated provisional restoration prior to conversion to an impression stent.
Figure 41. The stent with the surface abutting the tooth preparations cored out
Figure 42. Trial fit of the stent to ensure a passive fit.
Figure 43. Flowable composite being applied to the abutment teeth.
Figure 44. Finger pressure being applied to the stent to ensure it is fully seated and the soft tissues correctly displaced.
|Figure 45. The stent being firmly held in place while light curing is carried out.|
The stent could be left located in place, but any excess composite that may overlap the margins of the preparation could, at a later stage, interfere with the accurate location of the master dies resulting in an inaccurate soft-tissue working model. It is recommended that the stent be removed and trimmed as necessary. A trial relocation of the stent on the abutment teeth should then be carried out to ensure a positive fit. If there is any hint of instability, it is likely that the stent could be dislodged during impression taking and a resultant distorted working model. If movement is detected then it is advisable to use provisional cement such as Temposil (Coltène/Whaledent) to aid retention as it can be easily peeled out of the stent on removal out of the mouth without leaving any residue, which would be the case if a more conventional cement was used. Alternatively, some further OneStep Plus could be added to the fit surface of the stent and light-cured. To allow future accurate location of the working dies in the stent it is essential that the fit surface is clean and undistorted by temporary cements which usually require removal in an ultrasonic bath—these types of cements should be avoided.
The located stent is now ready for the final impression. It is important to realize that the soft-tissue impression technique shown in this article should be taken prior to the final impression. The degree of distortion created by the retraction cord and on-going tissue collapse cannot be compensated for by the formed impression stent.
Although the retention tag should ensure accurate removal of the impression from the mouth without distortion, it could additionally be painted with tray adhesive recommended by the manufacturer of the chosen impression material. As tissue reproduction is provided by the stent itself a quick-setting material (such as Template [CLINICIAN'S CHOICE]) can be used. The impression is shown after removal and location of the working dies, which were taken from the definitive working master model (Figures 46 and 47).
Figure 46. A view of the stent located in the impression.
Figure 47. The stent with the working dies accurately located ready for pouring.
Gingival retraction cord was then placed around the abutment teeth and after being left in place for the appropriate period of time, removed, and the definitive impression taken in a polyether impression material (Impregum Penta Soft Quick [3M ESPE]). The huge difference between the soft-tissue details in the stent impression compared with the normal working impression is clearly visible (Figures 48 and 49).
It is the author’s preference to silver plate the final impression in cases where the dies will require to be moved from one working model to another. After the dies from the definitive working model are trimmed, they are carefully and accurately transferred to the stent impression and a soft-tissue model poured. The stent impression can also be used to pour a hard model in stone as shown (Figures 50 to 52). The impressive reproduction of the gingival tissues in both the soft and hard tissues is clearly visible.
This definitive FPD was constructed in porcelain fused to precious metal. The metalwork and most of the porcelain work was carried out on the working silver plated model. Refinement of the fit surface of the porcelain pontics was achieved by transfer to both the soft- and hard-tissue models. The degree of accuracy achieved by the duplication technique is shown in Figures 53 and 54.
Only one trial fit of the definitive FPD was needed. At this appointment the fit of the pontics was passive yet supportive to the created emergence profile and further modifications were not required.
Figure 48. View of the distorted tissues in the “working” impression.
Figure 49. View of the accurate reproduction of the soft tissues with the stent.
Figure 50. The created emergence profile.
Figure 51. The accurate reproduction of the soft tissues achieved with the technique.
Figure 52. The hard-tissue working model.
Figure 53. The definitive FPD on the hard-tissue working model.
Figure 54. The FPD one week after final fit.
The author has consistently found it easier to work with composite during the temporisation phase rather than in porcelain at try-in of the definitive FPD. Any extra time spent at this stage is more than made up for later on.
The putty impression of the provisional FPD can be taken at the last check appointment of the emergence profile and the stent made at a convenient time prior to the definitive impression appointment. Needless frustration, both clinically and in the laboratory, is also avoided. This technique produces excellent and consistently reliable.
The author would like to thank his technician Mick Kedge for all his support and help in the development of the technique. The author would also like to thank his patients, John McGarrell and Andrew Fraser, for the endless hours in the chair while he worked on refining the technique itself at the chair side.
Disclosure: Dr. Bereznicki reports no disclosures.
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