Implant Micro-Gap Modification

Dental implants are a well-established treatment for edentulism, are now widely available, and are used with ever more frequency. Implant success is largely measured by the aesthetic quality, restored function, and longevity. Risk of failure, most often involving implant loss due to peri-implant infection, is associated with periapical lesions, periodontitis, bone disease, smoking, and alcohol consumption.1-9 Most retrospective (5-year) studies of failed implants show progressive bone loss.10 Longer-term (14-year) studies reveal that peri-implant infection (6.6%), bone loss (7.7%), and bleeding with probing (6.6%) are not rare.11-14


Controlled, prospective studies of multiple implant types will be required to fully characterize the causes and prevention of peri-implant infection. However, many characteristics of implants and surgical technique have been modified and studied. Studied factors include implant length and coating, and timing and location of placement and loading, with mixed results. Regardless of what factors cause the infection, failed osseointegration is caused by an inflammatory response to bacteria thriving in the peri-implant region, similar to that which occurs with periodontitis.15,16 Because the periodontal pathogens found in periodontal disease have been linked to systemic health problems, it is logical to question whether peri-implant infection contributes to similar health complications for dental implant patients.

More than 30 known species of bacteria are associated with periodontal disease. They exist within heterogeneous biofilms and are difficult to eradicate with current antimicrobial agents. Millions of oral bacteria are in contact with an ulcerated epithelium tissue that surrounds the coronal portion of the tooth, thus providing access to the circulatory system and causing bacteremia. Inflammatory mediators (cytokines, PMN, B-cells, and T-cells) and enzymes (collagenase, gelastinase, elastase, and proteases) are also produced, which cause a local response by damaging the periodontium and bone. The ensuing immune system response causes the liver to produce C-reactive protein (CRP), which may elevate the risk of heart attacks and strokes. In a recent study, subjects with periodontal disease had significantly higher levels of CRP than healthy controls.17 Via bacteremia, periodontal pathogens are associated with increased risk of systemic illness and complications, including cardiovascular and pulmonary disease, and diabetes.18-24 Oral infections have been statistically associated with mortality.25

Periodontal pathogens surrounding dental implants also cause peri-implant infections, the main cause of implant loss.26-29 Dental implants have been shown to harbor bacteria within the micro-gap at the implant-abutment junction (IAJ).28,30-33 The microbiota of peri-implantitis are the same as those that occur with periodontitis.28-37 These are the same pathogens shown to contribute to systemic problems. Many patients may have local peri-implant infections with no symptoms. Professional and patient hygiene care is important, but because the IAJ is usually subgingival, infection within and around implant components is difficult to prevent, even with scrupulous professional and patient home care. The IAJ of most dental implants is a noncleansable area that harbors periodontal pathogens, which lead to infection and bone loss38-41 and may pose a risk to systemic health, similar to periodontitis.

Periodontitis and peri-implantitis have many similarities. They both involve the same bacteria and cause the same inflammatory processes that result in bone loss.28-43 Treatment of each condition also involves antimicrobial agents as well as nonsurgical and surgical strategies. Because periodontal bacteria exist within a biofilm, treatment with traditional antimicrobial agents is not as successful with peri-implantitis, just as is seen in periodontitis with root fractures, abnormal root topography, and deepened periodontal pockets.44 Even without symptoms, bone loss can occur.45 In the case of peri-implantitis, implant removal, treatment, and restoration is especially time-consuming, costly, and inconvenient, and treatments may threaten the bone surrounding the implant. Recent reviews suggest that despite continued research, the emphasis has shifted from treatment of peri-implantitis to prevention.46-54

Most dental implants have a 2-stage design in which (1) the implant is placed and the surrounding tissues are allowed to heal, and then (2) the abutment is placed and the restoration is completed. To prevent the unsightly metal ring that occurs with supragingival placement of the IAJ, most implants involve subgingival placement. This subgingival placement makes the IAJ inaccessible for routine hygiene care and raises legitimate concerns about bacterial colonization within the IAJ micro-gap. One study of 350 implants (203 patients) confirms an association between local bone loss and the position of the IAJ.40 At an average of 4.2 years after placement, only 14.9% of implants with supragingival IAJ placement had accompanying bone loss, but 100% of those with subgingival placement had varying degrees of bone loss.

Bone loss does not appear to be the primary concern of many dental implant manufacturers and clinicians. However, as seen with periodontal disease, it is the inflammatory response elicited by periodontal pathogens that may pose the systemic health risks. Considering concerns of systemic problems caused by periodontal pathogens, the placement of this noncleansable area has been re-evaluated. Some implant manufacturers propose a one-piece design to resolve this problem, but premature loading of the implant and interference with osseointegration is often a problem with this approach.55 Sealing of the micro-gap would prevent possible entry of periodontal microbes56 and bacterial growth within this site. To date, no material has yet been developed that can maintain a seal at the IAJ.57 To address the problems of bacterial growth within the micro-gap, an evaluation of a novel implant design is underway.

 

CASE STUDY

Figure 1. Exposure of implant with the prosthetic abutment placed.

Figure 2. The final prosthetic crown cemented to place, demonstrating an excellent aesthetic result for the patient.

Figure 3. An occlusal view of the prosthetic crown on the implant, demonstrating proper form and anatomy to obtain a functional result.

Figure 4. The prosthetic margin is apical to the IAJ.

Figure 5. Micro-gap of the IAJ is captured and sealed within the cemented dental crown.

A 62-year-old female presented with a missing maxillary right first bicuspid. The tooth was removed due to endodontic complications. The patient did not want the 2 adjacent teeth prepared for a 3-unit bridge. Therefore, the patient made the decision to proceed with a dental implant. A review of the medical history revealed no contra-indications to perform a regeneration procedure and the placement of a dental implant in the edentulous area. A treatment plan was coordinated with the restorative dentist and approved by the patient. A bone regenerative procedure was completed to support a dental implant. There were no complications, and the regenerative procedure healed as anticipated.


Allowing 4 months for complete healing of the regenerated site, the patient returned to the restorative dentist for a wax-up and approval of the anticipated result. A surgical guide was fabricated from the wax-up by the restorative dentist and forwarded to the surgical dentist. The patient was appointed for implant placement. After obtaining complete anesthesia at the implant site, and isolation of the site, the implant was placed as indicated by the surgical guide and according to the manufacturer’s instructions. There were no complications during the implant surgical procedure. The areas were closed with 4.0 plain gut sutures followed by 4.0 glycolidecoca-prolactone suture. The patient was recalled in 10 days for suture removal. All areas healed as anticipated and there were no postoperative problems.

After 4 months of healing time, the dental implant was exposed and a healing abutment was placed. Fourteen days later, the patient was referred back to the restorative dentist for the completion of the restorative procedures. The healing abutment was removed and the prosthetic abutment was placed (Figure 1). The aesthetic and functional result was obtained as planned (Figures 2 and 3).

The PerioSeal Dental Implant System (PerioSeal) was chosen for this case at the patient’s request. It is the only system that can eliminate the exposure of the micro-gap that harbors periodontal pathogens to both the subgingival and supragingival oral environment, while providing an excellent aesthetic result. The neck of the implant diverges apically, which allows for a ferrule interface as seen with a standard dental crown on a natural tooth. The prosthetic margin is apical to the IAJ (Figure 4), therefore the micro-gap is captured and sealed within the cemented dental crown58 (Figure 5). The implant system also has a hex collet locking mechanism for attaching the abutment to the implant to prevent abutment rotation after the restorative phase. The restorative dentist for this case also requested the PerioSeal Implant for its simplicity, lower cost, selection of implant sizes, multiple restorative approaches, stronger abutment attachment, and safety for the patient.

 

CONCLUSION

Because a dense and diverse population of oral microbes exists in all patients, transient bacteremia may be caused by many dental procedures or even normal daily hygiene routines. The link between periodontal disease and systemic health risks is now well-accepted, therefore a prudent dental professional must consider dental implants as a source of bacteremia caused by peri-implant infection from the IAJ. The micro-gap is not a cleansable location amenable to even the most scrupulous patient or professional care. It may provide a safe harbor for bacteria to thrive, allowing for possible entry into the oral mucosa and bloodstream. As with periodontitis, peri-implant infection may exist without any symptoms, and the inflammatory response may progress unnoticed by patients, even in the presence of an otherwise optimal implantation result. The ferrule design approach seals off this location, which reduces the risks associated with oral infection and optimizes the chances for long-term success with a dental implant. Although the periodontal pathogens are the same for teeth and dental implants, long-term clinical studies will be required to determine whether peri-implantitis constitutes significant risks to systemic health—studies similar to those that have linked periodontal disease and serious systemic health complications. The author’s concern is this: Should the dental profession wait for the systemic problems to occur with implants? Why not take steps to prevent the problem using a dental implant that will prevent the potential risk?


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Dr. Callan received his DDS and certificate in periodontics from the University of Missouri at Kansas City. Since 1983 he has maintained a private practice emphasizing dental implants in Little Rock, Ark. He has published more than 50 peer-reviewed papers, is active in the American Academy of Periodontology, International Congress of Oral Implantologists (ICOI), and American Academy of Implant Dentistry, and was awarded the 2001 Ralph V. McKinney Jr. award from ICOI. Dr. Callan can be reached at (501) 224-1122, or This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Disclosure: Dr. Callan is a consultant for PerioSeal and helped design the PerioSeal implant system. He previously served as a consultant to several major dental implant companies.

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