Restoring Dental Implants While Mitigating Peri-Implant Disease Risk

Greg Gillespie, DDS

September 2016 Course - Expires September 30th, 2019

United Concordia

Abstract

Pre-planning multiple aspects of implant treatment, as well as the different components of the restoration, can help to ensure precise placement and angulation along with proper fit and connection of the implant abutment and restoration, while also helping mitigate peri-implant disease risks. Among the considerations when pre-planning implant cases is the selection of cement- or screw-retained restorations. Understanding how to best integrate cement-retained and screw-retained implant restorations is beneficial to the treatment planning process and helps prevent known risk factors for peri-implant diseases that are associated with the implant restorations themselves.

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The long-term health and stability of dental implant treatment is predicated on preventing and/or managing known risk factors for peri-implant diseases, as well as planning overall treatment with the end in mind. These two requisites are not mutually exclusive. In fact, risk factors for peri-implant diseases that have been shown to be associated with the implant restorations themselves can be controlled and/or mitigated by thoroughly pre-planning dental implant cases.1-3

Among the known risk factors for peri-implant diseases is an inability to maintain proper oral hygiene and/or access the implant area for cleaning.4 Cleaning implants is significant to plaque control, which helps to prevent the development of inflammatory cell responses. Studies indicate that peri-implantitis has developed in 48% of implants when no accessibility for cleaning was present.5

Poor prosthetic fit and implant location/angulation are also risk factors for peri-implant diseases that not only impact oral hygiene, but also directly affect peri-implant bone and soft-tissue integrity. Each of these factors has been associated with promoting accumulation of plaque on open margins, as well as exposing cement that contributes to pathogenic bacteria, which subsequently leads to inflammation and bone loss.6,7 In particular, research has demonstrated that the implant-abutment interface—and any microgaps that may be present—dictates the intensity and location of peri-implant inflammatory cell accumulation.8 Additionally, inflammatory cell accumulation below the original bone crest is significantly correlated with bone loss.8 Conversely, the absence of an implant-abutment interface (ie, associated microgap) at the bone crest has been found to be linked with reduced peri-implant inflammatory cell accumulation and minimal bone loss.9

Therefore, location and angle of implant placement requires astute assessment of existing bone to ensure the implant will be centrally secured10 and to set the foundation for long-term peri-implant bone and soft-tissue health. Interestingly, the biggest problems found with restoring implants—and which have forced clinicians to use cement-retained restorations—have been implants placed in the wrong location and implants placed at the wrong angulation.11 Improperly positioned implants (eg, too far buccally) could lead to buccal bone resorption, recession, and exposure of implant surfaces, further promoting pathogenic bacteria and the onset of peri-implant diseases.1,12

Not surprisingly, an additionally significant risk factor for peri-implant diseases that has been increasingly discussed in the literature is retained cement.13,14 Studies of implants with peri-implant disease have shown that 81% of cases were associated with cement that required removal and treatment, after which 74% of cases were absent of disease.13

Contributing to the presence of retained cement is the fact that the deeper the restorations are placed into the sulcus, the greater the possibility that retained cement will be found.14,15  Unfortunately, despite meticulous care and post-placement evaluation, not all cements are visible radiographically (eg, deep and on the buccal aspect),16,17 which underscores the need for extraoral cementation of implant-supported crowns to allow extrusion of the cement.18 In particular, researchers have found that some types of cements that are commonly used for the cementation of implant-supported prostheses have poor radiodensity and may not be detectable following radiographic examination.16,17

Therefore, pre-planning multiple aspects of the implant treatment, as well as the different components of the restoration, can help to ensure precise placement and angulation, as well as proper fit and connection of the implant abutment and restoration.19,20 Implant position, angulation, and restoration margin placement can be ideally planned based on preoperative analysis (eg, CBCT, planning software), and the anticipated outcomes achieved using surgical templates, guided surgery, and virtual/traditional restoration models (Figure 1 through Figure 7).21

Among the considerations when pre-planning implant cases are the patient’s oral health status and hygiene habits/abilities, anticipated occlusion, level of esthetic desires (ie, which could impact selection of cement- or screw-retained restorations), and other factors. Communication with the patient—as well as with other members of the treatment team (eg, surgeon, laboratory, restorative dentist, treatment coordinator)—is essential. It is often helpful to use a start-to-finish checklist so everyone knows exactly what is needed to begin and complete the case (eg, implant placement, implant body, implant abutment, healing cap, restoration, provisional, etc), in what timeframe, and at what cost (Figure 8).

Such a checklist enables treatment components like abutments and final restorations to be pre-planned prior to actual implant placement. Their consideration, selection, and design (ie, cement-retained, screw-retained, or screwmentable) based on the overall treatment plan will help to avoid the negative sequelae that lead to peri-implant diseases, as well as disappointment and frustration when expectations aren’t met.2,3,21 Understanding a few nuances for integrating cement-retained and screw-retained implant restorations is beneficial to the treatment planning process.

Cement-Retained Implant Restoration Considerations

Cement-retained restorations present the greatest difficulties—restoratively speaking—when attempting to avoid failures. Yet, in the presence of angulation problems (Figure 9), nonparallel implants, and fixed partial dentures, cement-retained implant restorations are sometimes required. Therefore, due to the difficulties associated with screw-retained implant restorations in such scenarios, retaining implant restorations to underlying abutments using cementation protocol has gained in popularity.22 However, despite the frequency with which implants are restored with cement-retained restorations, residual cement at or below the implant margins continues to be a problem that has been positively associated with peri-implant diseases that, ultimately, have led to implant failure.13

Utilizing custom abutments can help to minimize the likelihood of residual cement contaminating peri-implant tissues and the amount of cement required for retaining the restoration. Creating a custom abutment enables dentists to establish the abutment/restoration margins at the ideal location—tissue level, rather than deep within the sulcus, to avoid remnants of undetectable retained cement.19

To create a custom abutment, polyvinyl siloxane (PVS) impression material is placed into the restoration (Figure 10) and allowed to set (Figure 11). Prior to removal, any spurs of impression material are removed and the margin area refined (Figure 12), with attention paid to placing the margins exactly where they should end for optimal peri-implant health and stability. Ultimately, the resulting abutment form is a replica of the internal aspect of the restoration (Figure 13).

Then, when placing the abutment/crown in the mouth, complications can be avoided by aligning the abutment to ensure the restoration does not dislodge. The restoration can be lightly primed by coating the internal aspect. When applying cement, note that due to the manner in which restorations are fabricated against implant abutments today, minimal cement is required to achieve retention (Figure 14 and Figure 15).18

Another caveat when incorporating cement-retained implant restorations—particularly in the anterior—is establishing ideal tissue contours (eg, sulcus) and concavity during healing by placing a provisional restoration.19,20 The literature has confirmed that peri-implant soft-tissue esthetics can be sculpted and managed by placing provisional restorations.20

Screw-Retained Implant Restoration Considerations

Screw-retained implant restorations require management of the screw-access hole closure to ensure proper occlusal anatomy, prevent microleakage and bacterial infiltration, and establish ideal function and esthetics.22 Although beneficial in terms of avoiding the negative sequelae associated with intraorally cemented restorations, screw-retained implant restorations are typically challenging and demanding. However, screw-retained restorations are often favored based on retrievability.20

Over the past few years, hybrid implant abutment/restorations that combine an abutment with a crown have increasingly been used (Figure 16). The abutment aspect of a “screwmentable” component can be a stock abutment, prefabricated abutment, or custom abutment. This unit can then be cemented extraorally onto a base using an adhesive (Figure 17), after which the “screwmentable” abutment/crown complex can be screwed onto the implant (Figure 18). This eliminates the need for removing excess cement intraorally, reducing the likelihood of cement contamination to the peri-implant tissues that has been shown to cause peri-implant diseases.7,13

A benefit of “screwmentable” abutment/restorations is preparation margin placement at the gingival level. This geometry integrates well with the restoration and makes removal of excess cement easy.7 With “screwmentable” abutment/restorations, margin placement is less of a concern, because the two components are cemented extraorally, then screwed into place.

The design of this “screwmentable” abutment/restoration, however, necessitates specific location/angulation requirements, including opening of the screw-access hole away from contact points and/or occlusal function. The screw-access hole can then be filled with a composite material.

In its most simplistic form, the protocol for creating a “screwmentable” implant abutment/restoration involves the following sequence of steps: First, the correctly sized, predictable healing abutment (Figure 19 and Figure 20) is selected, and then an implant impression taken. The appropriate abutment (eg, prefabricated or custom) is then obtained (Figure 21). Gold-hue titanium and zirconia abutments produce less peri-implant soft-tissue color differences compared to the soft tissue around natural teeth than titanium or metal abutments.23 The clinician then works with the laboratory for the fabrication of the restoration, with the access holes occluded (Figure 22). Then, outside of the mouth, self-adhesive resin cement is used to connect the restoration to the abutment. Any excess cement must be thoroughly cleaned from the margin area with the unit outside of the mouth (Figure 23 and Figure 24). The abutment/restoration is screwed into place using either a screw wrench or torque wrench at the proper torque setting (Figure 25 and Figure 26), and, finally, the access hole is filled with composite (Figure 27 and Figure 28).

Conclusion

Risk factors for peri-implant diseases that have been shown to be associated with implant restorations and abutments themselves can be controlled and/or mitigated. Thoroughly pre-planning dental implant cases in terms of abutment margin placement, choosing between cement-retained or screw-retained restorations, and establishing proper implant location and angulation is essential. In particular, pre-planning can help to prevent the circumstances that contribute to an inability to clean implants, accumulation of plaque on open margins, and peri-implant soft-tissue inflammation and bone loss.

DISCLOSURE

Dr. Gillespie received an honorarium for the webinar program that was the basis of this article.

ABOUT THE AUTHOR

Greg Gillespie, DDS
Private Practice, Vancouver, Washington

REFERENCES

1. Salama H, Salama MA, Li TF, et al. Treatment planning 2000: an esthetically oriented revision of the original implant protocol. J Esthet Dent. 1997;9(2):55-67.

2. Rossi R, Morales RS, Frascaria M, et al. Planning implants in the esthetic zone using a new implant 3D navigation system. Eur J Esthet Dent. 2010;5(2):172-188.

3. Tischler M. Treatment planning implant dentistry: an overview for the general dentist. Gen Dent. 2010;58(5):368-374.

4. Lindhe J, Meyle J, Group D of European Workshop on Periodontology. Peri-implant diseases: Consensus Report of the Sixth European Workshop on Periodontology. J Clin Periodontol. 2008;35(8 suppl):282-285.

5. Serino G, Ström C. Peri-implantitis in partially edentulous patients: association with inadequate plaque control. Clin Oral Implants Res. 2009;20(2):169-174.

6. Roos-Jansåker AM, Renvert H, Lindahl C, Renvert S. Nine- to fourteen-year follow-up of implant treatment. Part III: factors associated with peri-implant lesions. J Clin Periodontol. 2006;33(4):296-301.

7. Wadhwani C, Piñeyro A, Hess T, et al. Effect of implant abutment modification on the extrusion of excess cement at the crown-abutment margin for cement-retained implant restorations. Int J Oral Maxillofac Implants. 2011;26(6):1241-1246.

8. Broggini N, McManus LM, Hermann JS, et al. Peri-implant inflammation defined by the implant-abutment interface. J Dent Res. 2006;85(5):473-478.

9. Broggini N, McManus LM, Hermann JS, et al. Persistent acute inflammation at the implant-abutment interface. J Dent Res. 2003;82(3):232-237.

10. Lin MH, Mau LP, Cochran DL, et al. Risk assessment of inferior alveolar nerve injury for immediate implant placement in the posterior mandible: a virtual implant placement study. J Dent. 2014;42(3):263-270.

11. Chee W, Jivraj S. Failures in implant dentistry. Br Dent J. 2007;202:123-129.

12. Froum SJ, Rosen PS. A proposed classification for peri-implantitis. Int J Periodontics Restorative Dent. 2012;32(5):533-540.

13. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: a prospective clinical endoscopic study. J Periodontol. 2009;80(9):1388-1392.

14. Linkevicius T, Puisys A, Vindasiute E, et al. Does residual cement around implant-supported restorations cause peri-implant disease? A retrospective case analysis. Clin Oral Implants Res. 2013;24(11):1179-1184.

15. Linkevicius T, Vindasiute E, Puisys A, et al. The influence of the cementation margin position on the amount of undetected cement. A prospective clinical study. Clin Oral Implants Res. 2013;24(1):71-76.

16. Wadhwani C, Hess T, Faber T, et al. A descriptive study of the radiographic density of implant restorative cements. J Prosthet Dent. 2010;103(5):295-302.

17. Wadhwani C, Rapoport D, La Rosa S, et al. Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: a clinical report. J Prosthet Dent. 2012;107(3):151-157.

18. Present S, Levine RA. Techniques to control or avoid cement around implant-retained restorations. Compend Contin Educ Dent. 2013;34(6):432-437.

19. Wadhwani CP, Piñeyro AF. Implant cementation: clinical problems and solutions. Dent Today. 2012;31(1):56-62.

20. Lewis MB, Klineberg I. Prosthodontic considerations designed to optimize outcomes for single-tooth implants. A review of the literature. Aust Dent J. 2011;56(2):181-192.

21. Angelopoulos C, Aghaloo T. Imaging technology in implant diagnosis. Dent Clin North Am. 2011;55(1):141-158.

22. Wadhwani C, Piñeyro A, Avots J. An esthetic solution to the screw-retained implant restoration: introduction to the implant crown adhesive plug: clinical report. J Esthet Restor Dent. 2011;23(3):138-143.

23. Bressan E, Paniz G, Lops D, et al. Influence of abutment material on the gingival color of implant-supported all-ceramic restorations: a prospective multicenter study. Clin Oral Implants Res. 2011;22(6):631-637.

Figure 1. Preoperative occlusal view of a 35-year-old man missing his second premolar, which would be replaced with an implant and screw-retained abutment/restoration.

Figure 1

Figure 2. Preoperative radiograph suggests a straightforward implant placement case, with ample space and sufficient bone for positioning the implant.

Figure 2

Figure 3. However, simply delegating implant placement to the surgeon—without having the end in mind—may result in implant placement at the improper angulation.

Figure 3

Figure 4. View of the correctly planned and properly proposed implant placement, taking into consideration angulation and position for the anticipated screw-retained abutment/restoration.

Figure 4

Figure 5. Note that even slightly changing the angulation would result in the implant screw-access hole coming out of the buccal cusp.

Figure 5

Figure 6. View of the digitized treatment plan, illustrating implant angulation, restoration placement, and access hole alignment if original plan is altered.

Figure 6

Figure 7. View of the corrected treatment plan, illustrating proper implant angulation, ideal restoration placement, and correct access hole alignment/location.

Figure 7

Figure 8. Example of a checklist that can be used from start to finish to ensure that all members of the treatment team—including the patient—are aware of and understand the components of the implant treatment that must be planned.

Figure 8

Figure 9. In the presence of angulation problems or implants placed in the wrong location, cement-retained restorations are often required.

Figure 9

Figure 10. To create a custom abutment, PVS impression material is placed into the restoration.

Figure 10

Figure 11. The impression material is allowed to set inside the restoration to create an exact duplicate of the internal aspect.

Figure 11

Figure 12. Prior to removal, the margin area is refined, with care taken to place the margins exactly where they should be (ie, tissue level, rather than deep within the sulcus) for optimal peri-implant health and stability.

Figure 12

Figure 13. The resulting abutment form is a replica of the internal aspect of the restoration.

Figure 13

Figure 14. Close-up postoperative view following cementation of the restoration onto the custom-made abutment from Figure 10 through Figure 13.

Figure 14

Figure 15. Post-cementation radiographic view of the implant/abutment/restoration complex from Figure 14.

Figure 15

Figure 16. A hybrid “screwmentable” abutment/crown features a stock, prefabricated, or custom abutment and a crown that are cemented together extraorally.

Figure 16

Figure 17. This singular abutment/crown complex is then screw-retained inside the mouth.

Figure 17

Figure 18. A screw-access hole is created in the crown component, through which the abutment/crown restoration is screw-retained into place.

Figure 18

Figure 19. Close-up view of healing abutments in place for a patient who presented for implant restorations. Note this case was treated 4 years prior.

Figure 19

Figure 20. Upon removal of the healing caps, each site exhibited a deep sulcus, making “screwmentable” abutment/crown restorations ideal in order to avoid retentive cement subgingivally.

Figure 20

Figure 21. In this case, prefabricated abutments were selected, and the laboratory was instructed to fabricate the crown restorations with an access hole in the middle. Note a paper dowel was placed into the abutment to indicate the placement/location of the access hole.

Figure 21

Figure 22. Petroleum jelly was placed onto the dowel, and the crown was loaded with cement, after which it was placed onto the abutment and fully seated. Given the depth of the patient’s sulcus, had the restoration been cemented intraorally, in all likelihood a tremendous amount of cement would have been retained in the peri-implant tissues, leading to peri-implant disease.

Figure 22

Figure 23. Excess cement was cleaned from the abutment/restoration margins using a gold knife, and they were tried on the model to confirm fit.

Figure 23

Figure 24. View of a completed “screwmentable” abutment/restoration unit.

Figure 24

Figure 25. A screw wrench or torque wrench can be used to force the implant abutment/restorations into place.

Figure 25

Figure 26. View of the “screwmentable” abutment/restorations in place in the mouth, prior to closing the access holes with composite.

Figure 26

Figure 27. The access holes were sealed with composite, masking any evidence of the underlying metal abutment and/or implant screw.

Figure 27

Figure 28. Radiograph taken 4 years after placement demonstrating stable and healthy peri-implant bone and no indication of peri-implant disease.

Figure 28

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Learning Objectives:

  • Identify risk factors for peri-implant diseases that can be prevented by thoroughly treatment planning implant cases.
  • Discuss how poorly planned aspects of implant treatment contribute to specific risk factors for peri-implant diseases.
  • Describe characteristics of cement-retained and screw-retained restorations that should be considered when treatment planning implant cases.