Introduction
Periodontal disease is the main chronic infectious disease of the oral cavity and a principal cause of tooth loss in humans. It involves inflammatory reactions which cause tissue destruction in tooth supporting structures, i.e. gingiva, cementum, periodontal ligament, and alveolar bone. (Lang and Brägger, 1991) There are different types of destructive periodontal diseases detailed in different classification systems, but chronic periodontitis is the most common form. (Flemmig, 1999) In general, chronic periodontitis progresses slowly, and is characterized by bursts of disease activity, separated by quiescent periods. (Socransky et al., 1984) On the contrary, aggressive periodontitis progresses rapidly and relentlessly to periodontal destruction (Tonetti and Mombelli, 1999), and often commences during adolescence and early adulthood.

If periodontal disease is left untreated, it inevitably leads to more attachment loss and increased mobility or even loss of teeth. Various studies (Phipps and Stevens, 1995; Murray et al., 1996; Ong, 1998) have already shown that the majority of tooth loss nowadays is due to periodontal disease. The consequence of tooth mobility and tooth loss somehow affects mastication and speech, whilst aesthetics may also be compromised by loss of anterior teeth. In addition, tooth loss without replacement and increased mobility of teeth has an adverse impact on the quality of life (Adell et al., 1990; Spiekermann et al., 1995; Lekholm et al., 1999; Steele et al., 2004; Wong and McMillan, 2005; Mack et al., 2005). The success of osseointegrated dental implants has revolutionized dentistry. The ability to permanently replace missing teeth with a function and appearance close to that of the natural dentition has never been greater. With more than 3 decades of evidence to support the clinical use of osseointegrated dental implants, it is possible to confidently resolve that implants are predictable and provide patients with long-term functional tooth replacement (Albrektsson et al., 1986; Adell et al., 1990; Zarb and Schmitt, 1990; Spiekermann et al., 1995; Lazzara et al., 1996; Lekholm et al., 1999). This is a remarkable accomplishment, considering the many challenges and stresses that the oral environment and forces of mastication present for dental implants. The success of dental implants has transitioned dentistry into an entirely different approach to treatment compared to just 20 years ago.

Changed Philosophy and Practice of Periodontics
Perhaps more than any other dental specialty, the current success of dental implants has dramatically changed the philosophy and practice of periodontics. Many of the “rules” of periodontal therapy have been changed forever, with a paradigm shift from the practice of saving teeth at all costs toward one that will consider the extraction of “maintainable” teeth to improve aesthetics, function, and long-term success of dental implant restorations. Prior to the current era of predictability of dental implants, periodontal patients, along with their dentists and/or periodontists, would strive to maintain periodontally compromised teeth. Many times, the goal was to preserve their “natural” teeth to avoid a removable prosthesis.

Surgical periodontal therapy, although beneficial for improving periodontal health and maintaining compromised teeth, is often destructive to the tooth (root removal, tooth hemisection) and supporting structures (pocket reduction surgery, osseous resective surgery). Each of these treatment modalities has the potential to compromise form, function, and aesthetics. Because of periodontal therapy, patients who are struggling to keep their teeth often suffer from root sensitivity, increased interdental spaces, poor aesthetics, and limited function. When teeth have compromised periodontal support, they often have increased mobility and may become (subjectively) uncomfortable or painful in function.

Splinting is another treatment used to help maintain periodontally compromised teeth and overcome the discomfort of mobility. Compromised teeth are splinted to adjacent teeth to gain support, functional stability, and comfort, and to potentially protect against additional bone loss. The ultimate form of tooth splinting therapy is the periodontal prosthesis, which typically involves full-crown restoration and splinting of many if not all of the remaining teeth.

With these forms of periodontal treatment and good plaque control, it is possible to maintain severely perio-dontally compromised teeth for long periods of time without additional loss of tissue attachment or bone support, but the periodontal condition of the tooth rarely if ever improves over time, regardless of treatment. At best, the tooth is kept in place and may or may not provide a significant functional purpose for the individual. The predictability of dental implants has changed the perspective on periodontal therapy and the ability to provide reconstructive treatment for patients who suffer from the destruction of periodontal disease. The “maintainance” of periodontally compromised teeth to avoid tooth loss is no longer necessary. In fact, removal of severely periodontally compromised teeth and replacement with implants will usually enhance the overall function, esthetics, and comfort of the definitive implant-supported or implant-assisted dental prosthesis. Whereas compromised teeth with severe attachment loss, moderate to severe bone loss, and mobility have a very limited capacity to regain natural periodontal form, function, and aesthetics, implants placed in conjunction with tissue-regenerative procedures can restore not only the missing teeth but in some cases the surrounding tissues as well.

The last 20 years have been significant in periodontics, not only because of the success of osseointegrated dental implants, but also because of an improved understanding of periodontal disease, the host response to periodontal disease, and the requirements for guided tissue regeneration. A great deal has been learned from experience with implants. Initial implant success and surgical protocols were established primarily in a completely edentulous patient population. The implants and the armamentarium were initially designed for the edentulous patient.

Review of Literature
Longitudinal Studies Conducted Over A 10-Year Follow-Up Of Implants Inserted Into Patients With Perio¬dontal Disease Who Did Not Receive Regular Treatment Resulted In The Following Conclusion: (Christoph et al., 2002, and Ioannis et al., 2003) Over the years, a positive correlation was found between peri-implant bone loss and periodontal bone loss. A higher percentage of biological complications (peri-implantitis) over 10 years were found in periodontal patients than in healthy subjects. A posi¬tive correlation was found between the attachment level, periodontal pockets and marginal bone level around the implant and the periodontal pockets and attachment level of the entire mouth. Longitudinal Studies Conducted Over A 10 Year Follow Up Of Implants Inserted Into Patients With Periodontal Disease Who Received Regular Treatment Resulted In The Following Conclusion: (Marc et al., 2001; Åsa et al., 2002; Marc et al., 2001) No relation was found between ongoing periodontal disease and peri-implant bone loss. The presence of periodontal pathogens around implants did not cause loss of attachment or implant failure as predicted. Similar rates of success and amount of peri-implant bone loss were found in periodontal patients who received regular treatment and care, and in healthy subjects.

Considerations when Placing Dental Im-plants in Periodontally Susceptible Patients
Before implant placement
Correctly screen/diagnose patients with susceptibility to periodontitis.

Consider referral to a periodontal specialist.

Effectively treat and stabilize the periodontal condition.

Allowing up to 6 months to elapse for re-evaluation and to ensure the periodontal condition is stable and maintainable.

The prognosis of periodontally involved, including already-treated teeth needs to be carefully assessed after active periodontal therapy.

The risk profile must be established and the patient informed (e.g. smoking habit, history of periodontitis, diabetes mellitus).

After implant installation
Early detection of peri-implant complications by systematic and continuous monitoring of peri-implant tissues, including plaque assessment, presence or absence of bleeding on probing, suppuration on pressure or after probing, peri-implant probing depth changes relative to baseline and radiographic bone loss. Advice from or referral to a periodontist should be initiated for any patient with peri-implant complications not responding to Cumulative Interceptive Supportive Therapy CIST (Table 1).

Table 1 

Recommended Treatment Sequence in Periodontal Patients who are Candidates for Implant Insertion
Enhancement of patient awareness of periodontal disease its relation to implants.

Instruction in oral hygiene

Scaling and root planning

In cases of aggressive periodontal disease adjuvant antibiotic therapy indicated.

Conservative treatment, root canal therapy and posts with temporary crowns.

Re-evaluation
Periodontal surgery as necessary (pocket reduction, regneration, flap elevation for debridement).

Phase II evaluation Insertion of implants, sinus eleva-tion and augmentaion as necessary and final rehabilitation Regular preventive maintenance every 3 months

Conclusion
In conclusion, implant reconstruction in periodontal patients has been shown to be a successful and predictable treatment option for the replacement of missing teeth due to tooth loss resulting from destructive periodontal disease. Some long-term studies have demonstrated a higher risk of peri-implantitis in this group of patients. Therefore, stabilizing the periodonal condition before implant installation is mandatory, and providing long-term supportive periodontal therapy is of the utmost importance. This should include monitoring and managing both periodontal and peri-implant health, with a view to ensuring the best possible conditions for the long-term survival of the remaining dentition and dental implants.

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