Donald P. Callan, DDS Private Practice Little Rock, Arkansas Phone: 501.224.1122 Email: drdoncallan@aol.com

In the rapidly changing world of dentistry, a heightened desire for optimal esthetic results is clearly evident among the dental consumer population. Dental implants can be an excellent option for replacing teeth and restoring function. As much as restoring function, achieving the most appealing appearance possible is a key driving force in choosing dental implants.

Throughout the evolution of implant dentistry, a central problem has been making implants appear as much as possible like natural teeth. Early implant designs often yielded a "tell-tale ring" (metal margin) around the base of the clinical tooth on the implant. Although most implant manufacturers have tried to eliminate that unattractive result, concerns remain regarding failure of the implant to integrate and peri-implant infections, which can lead to bone loss. These concerns are not only important for immediate esthetic and functional outcomes, but for the long-term health of the patient. This article discusses the importance of balancing esthetics, function, and patient health in the successful placement of dental implants.

Risks Associated with Dental Implant Designs
Traditionally, dental implants are placed in 2 stages; the implant surgical site is allowed to heal before attaching the abutment and prosthesis. Although the 2 stages are intended to prevent implant-bone interface movement and exposure during healing, the early implant designs yielded less than optimal esthetic results. This was because the implant abutment junction (IAJ) was above the gum line, leaving the metal implant/abutment interface visible just apical to the dental crown (Figures 1 and 2).

Some manufacturers attempted to solve this problem by elongating the restoration at the facial surface, covering the metal IAJ, but that yielded an unnaturally long tooth appearance (Figure 3). Subsequent designs had a pink-colored material added to the prosthesis in an attempt to visually "blend" the elongated crown with the gingival tissue. This, too, did not produce a natural-looking restoration (Figure 4). This esthetic problem was resolved by most manufacturers by moving the abutment location to below the gingival margin so that the crown sits much closer to the gingival surface (Figure 5). However, growing evidence supports concerns about the subgingival location of the IAJ because of the possibility of periodontal pathogens within the IAJ causing infection of gingival and bone tissues.^1-6 With the IAJ in an area inaccessible to patients and clinicians, efforts for preventing and treating infection are ineffective (Figures 6 through 9). These figures show representative cases of the classic "coneype" of bone loss that occurs when the IAJ is subgingival.

It has been suggested that periodontal disease proximal to dental implants contributes to peri-implant infections and can be the main cause of implant loss, such as is seen with the loss of natural teeth by periodontal disease.^7-10 This is because with most 2-stage implant designs, the "micro-gaps" at the IAJ are large enough to harbor periodontal bacteria.^1,4,5 Oral fluids can easily penetrate the micro-gaps, enabling growth of the same bacteria that cause periodontal disease.¹¹ Moreover, these bacteria reside in the form of biofilms, which are particularly resistant to dental hygiene, immune mechanisms, and antibiotics. Biofilms can persist as subclinical infections for a long time without the dentist's or patient's knowledge. The resulting inflammatory process damages the soft tissues surrounding the implant and, as with periodontal disease, ultimately leads to devastating bone loss (Figures 8 and 9).^1-6,9,12-15

The relationship between bone loss and the positioning of the IAJ was demonstrated in a study of 350 implants in 203 patients.^9,10 This study showed an overwhelmingly significant difference between subgingival and supragingival placement of the IAJ, with regard to bone loss.⁹ At an average postrestoration follow- up of 4.2 years, only 14.9% of implants with supragingival placement had bone loss, as compared with 100% of those with subgingival IAJ placement. Some implant designers proposed to eliminate the IAJ micro-gap by using a 1-piece design. This design however, may cause premature loading of the implant, preventing integration.

In addition to implant failure and bone loss, the risks associated with peri-implant infection may affect more than the patient's oral health. Many studies^8,16 link periodontal pathogens, the same ones that are sequestered in the IAJ micro-gap,^10,16-18 with increased risk of systemic illness and complications in existing disease. By entering the bloodstream,^19-24 periodontal pathogens increase the risk of cardiovascular^25-32 and pulmonary^33-35 diseases, and hinder glycemic control in diabetes.^27,28,36,37 Although long-term studies have not established a direct link between these conditions and dental implants, one is prudent to consider that placement of any device that permits periodontal pathogens to flourish may be risky. Why implant a noncleansable device into patients and risk their systemic health?

Eliminating the Micro-Gap While Enhancing Esthetics
In support of preventing infection, providing a desirable appearance, and providing proper function, a new dental implant design approach offers a superb alternative. The PerioSeal implant system (PerioSeal, Inc) uses a standard ferrule dental crown and cement for restoration, and has a unique collet locking mechanism for attaching the abutment to the implant. Instead of having an implant neck with parallel walls, the neck diverges in an apical direction, permitting a ferrule to interface with the crown. The prosthetic margin of the crown is placed apical to the IAJ; thus, the IAJ is captured and sealed within the cemented crown, eliminating a potential haven for periodontal pathogens that contribute to alveolar bone loss and possible systemic complications.³⁸

Presentation of Cases
In the cases presented, general health, dental history, medical history, oral hygiene, and oral health factors were reviewed for all patients before implant placement. A treatment plan was formulated with the surgical and restorative dentist and approved by the patients. Standard implant placement protocol, as recommended by the manufacturer, was followed. There were no surgical contraindications in performing grafting or implant placement.

Case 1
A 66-year-old woman presented with a nonrestorable maxillary left bicuspid (tooth No, 12). The patient explained that the visit was for a second opinion for the removal of the bicuspid, bone grafting, and placement of a dental implant. The first restorative dentist had recommended a dental implant from a very large implant company because it was probably the best on the market. However, the patient was concerned about esthetics, function, and the ability to maintain the implant with routine hygiene procedures.

After explaining the differences between implant systems, the patient became very concerned about the possibility of bacterial infection within the micro-gap around the implant leading to possible systemic problems. She elected to proceed with the PerioSeal implant and another dentist.

The implant was placed as indicated by the surgical stent and 3 month's healing time was allowed for integration. The patient was restored by the restorative dentist, as recommended by the manufacturer. There were no complications in placement or restorative procedures. After 4 years, the clinical evaluation demonstrated excellent health and esthetics (Figure 10), and the x-rays showed no bone loss (Figure 11) relative to the condition of the bone at the time of implantation.

Case 2
A 63-year-old man presented with multiple missing teeth. The maxillary first bicuspid shown in Figure 12 is typical of the condition of all sites of missing teeth. Tissue regeneration procedures and implants were recommended. The patient's daughter was the treating dentist and was concerned with esthetics, function, and hygiene maintenance. After reviewing the benefits, the dentist and the patient elected to proceed with the PerioSeal implants for all missing teeth.

Surgical protocols were followed as indicated. After proper healing time, the patient was referred back to the dentist for restoration. There were no surgical or restorative complications. The implant shown in Figure 13 is representative of the other PerioSeal implants in this patient. After 10 years, the clinical evaluation reveals excellent health and esthetic results (Figure 13) and the radiograph shows no bone loss (Figure 14).

Discussion
PerioSeal is currently the only dental implant system to eliminate concerns about bacterial contamination of the micro-gap between the implant and the prosthetic abutment. In dental literature, over 137 published articles raise concerns about bacterial colonization within the IAJ. Bacteria within the micro-gap have been shown to be periodontal pathogens. These bacteria are the main cause of periodontal bone loss, which would also cause loss of the implant. The design of the PerioSeal system has eliminated exposure of the micro-gap to the oral environment. In addition, many dentists have found additional advantages (Table).³⁸

Conclusion
The goal of placing dental implants is to provide function, longevity, and quality esthetics that can be maintained with routine oral hygiene procedures. Ultimately, longevity of the implant, prevention of bone loss, and overall health must be considered equally with esthetics when evaluating one's choices of dental implants. It is critical for patients and clinicians to be aware that achieving a good-looking exterior result is not the only criteria for successful implant results. Infection residing beneath the gum surface can be detrimental beyond the loss of the implant. Based on clinical experience, the PerioSeal implant system seals the IAJ within the restoration, providing excellent esthetic results, while also protecting against bacterial growth within the micro-gap.

Disclosure: Dr. Callan has a financial interest in PerioSeal Inc. and has served as a consultant to other major dental implant companies.

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