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A Microsurgical Approach for the Regeneration of Osseous Defects

October 1, 2011
by Peter C. Fritz, BSc, DDS, FRCD(C), PhD (Perio), Certified Specialist in Periodontics


INTRODUCTION
A major issue for the near future is the growing incidence of peri-implant osteitis (Fig. 1). Depending on the study, between 25-53% of patients with implants in Europe have peri-implant osteitis.1 It is not surprising that patients that did not take care of their natural teeth do not take better care of their implants. The strategies for the treatment of peri-implant osteitis are presently unclear. For these and other reasons, novel strategies of saving the periodontally compromised tooth must be developed. To do so, numerous patient, tooth and defect parameters need to be considered. Furthermore, the correct approach to treat the defect is critical for a successful outcome. Resective therapy has proved effective in some instances, however, the results are often disfiguring and esthetically unacceptable. A microsurgical approach is a predictable and effective strategy to regenerate significant bone defects around teeth and implants.

OBJECTIVE
To regenerate osseous defects, several essential interrelated components of a microsurgical approach are required. These include strict and appropriate patient, tooth and defect selection criteria (Tables 1-3), clinical ability/learned surgical skill set, biomaterials (Emdogain® and allografts), specialized instrumentation, flap design, wound closure techniques and carefully presented post-operative instructions the patient faithfully follows during the healing period.

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APPROACH
Clinical outcomes using regenerative approaches can be quite variable among clinicians, largely due to inadequate training in this emerging field. Although it is well documented that Emdogain® can be used effectively to regenerate periodontal defects, neutral outcomes have also been reported.2 It is clear that attempting regeneration using the flap design and suturing techniques used in traditional periodontal surgery often results in a disappointing clinical outcome for the patient and the clinician. It is likely that the surgical trauma that leads to retraction of tissues during healing accounts to the unfavourable cosmetic results. The technique as well as the regenerative materials used to attempt regeneration of a periodontal defect govern the degree of success and hence the benefit of the procedure to the patient (Fig. 2).

Regenerative surgery using minimally invasive microsurgical techniques is an attractive alternative to traditional techniques and is associated with fewer complications and has a higher predictability of a successful outcome for the patient.3 From consultations among periodontists, and vascular, plastic and oral surgeons, novel approaches and techniques are being used to predictably regenerate bone where previously this was highly challenging. Minimally invasive microsurgery is not new, but when used with innovative flap designs, specialized instruments, the correct use of enamel matrix proteins, primary flap closure and strict pre- and post-operative protocol, a predictable positive outcome is achieved for the patient. Moreover, patients have an easier recovery.4

Conventional non-surgical and surgical techniques are still important in the management of periodontal disease. These tested approaches can certainly help achieve predictable pocket reduction and stop further disease progression. However, the outcomes are usually associated with an increase in soft tissue recession and bone loss with the formation of a long-junctional epithelium. The treatment aim of regeneration (versus repair) is the formation of new cementum, periodontal ligament and alveolar bone. The complete restoration of the structure and function of the periodontal tissues is only possible with guided tissue regeneration techniques using a membrane and/or with enamel matrix proteins, such as Emdogain®. Histology continues to be the only reliable method of evaluating the efficacy of treatment aimed at achieving periodontal regeneration.

PERIODONTAL WOUND HEALING 
Periodontal wound healing is quite different than healing in any other system in the human body. It is much more complex than a simple skin injury and has been described as the “most complex healing process” in the human body. One challenge is that a mucogingival flap sandwiches an instrumented root surface that has had its periodontal attachment removed. The wound margins are broken by a rigid, mineralized, non-vascular root surface creating an open system of wound healing. In this high humidity (100%) and permanently infected area, a complex structural and functional interrelationship must occur between cementum, periodontal ligament, alveolar bone and gingiva to achieve wound healing. Finally, the wounded area is constantly under function and exposed to food debris and plaque. It is a wonder it heals at all.

GUIDED TISSUE REGENERATION
Guided tissue regeneration (GTR) using expanded polytetrafluroethylene (ePTFE) barriers results in effective regeneration where the bone fills into the periodontal defect. However, if the barrier collapses into the defect, no regeneration occurs. Moreover sites experiencing suture line dehiscences and membrane exposures all exhibit large inflammatory infiltrates with no regeneration, despite systemic and local antibiotics. Bacterial contamination of the wound is devastating for periodontal regeneration. Wound failure and membrane exposure can occur in more than 50% of surgeries. The variable outcomes are primarily due to poor patient or defect selection, or surgical errors. As such, the limitations with ePTFE GTR include danger of infection of the membrane and the wound, uncertain predictability, a technically demanding surgery, a high financial burden for the patient and a removal of the membrane involving extra time, cost, and patient discomfort.
The role of enamel matrix proteins in the development of cementum and periodontal tissues has been studied extensively since 1986. The most important protein to promote regeneration was identified as amelogenin. This is hydrophobic proteins practically insoluble at physiological pH and body temperature. Emdogain® is a purified, lyophilized product extracted from porcine enamel matrix from the crowns of developing premolars and molars from 6-month old pigs. The differences between amelogenins from various species are very small, which is likely why porcine amelogenin in Emdogain® can be used predictably for the treatment in periodontal defects in humans without any adverse immune reactions.

MICROSURGICAL CONCEPT 
The microsurgical approach begins with an ideal patient, tooth and defect selection as outlined in Tables 1-3. It then requires an accurate and gentle soft and hard tissue management (Figs. 3&4). Meticulous debridement and tension-free suturing is also paramount. These determinants are essential for primary wound closure. This is achieved when intact wound margins show intimate contact without any signs of tension or pressure. Fast bridging of the incision wound by fibrin, in-growth of blood vessels and epithelial wound closure in five days. The area to be replaced by granulation tissue is kept to an absolute minimum. Any inflammatory reaction to eliminate necrotic and bacterial contaminated tissue fragments must be minimized. A closed environment without contamination facilitates healing and promotes regeneration.

MAGNIFICATION DEVICES 
Several systems for magnification loupes and operating microscopes have been introduced into dentistry. For periodontal surgery, loupes with a magnification factor up to 5.2 is adequate (Fig. 5). Higher magnification factors are often difficult because the field size is too small, the depth of focus too shallow and the working distance too short. An additional light source will brilliantly illuminate the site and is highly recommended. Operating microscopes offer higher magnification but difficulty in handling the device to accommodate the dynamic surgical fi
eld prevents its routine use.

MICROSURGICAL INSTRUMENTS
Traditional tweezers and elevators may traumatize the marginal and interdental tissues and jeopardize the post-operative healing process. The motion that can be performed with the highest amount of precision is rotation between the fingers. Round handled instruments with reduced working ends should be used. The plastic surgery literature suggests that the overall length of the instruments should not exceed 18cm and the center of gravity should be in the first third of the instrument (Figs. 6-11).

MICROSURGICAL BLADES
Post-operative wound healing depends on the precision of the incision. A Keydent blade, modified from the SM69 microsurgical blade is appropriate for intrasulcular incisions, mainly in delicate and narrow interdental areas (Figs. 11 &12). The circular edge of the blade enables accurate preparation through a rotating motion through the fingertips.

WOUND CLOSURE 
The most fundamental phase of surgery is the effective closure of the wound. Suturing the access route can never be neglected, put in place quickly or performed less than adequately. In oral and facial surgery it is of fundamental importance. In facial surgery, the consequences of a badly executed wound closure can readily be understood by disfigurement. However, in daily practice, many bone grafts have become infected because the sutures did not provide a proper seal. The complication of an exposed membrane or gingival recession can be linked to a technical defect in suturing. Suturing materials and techniques have a direct and determinate influence on the phases of healing (Figs. 13 &14). The physical, chemical and technological properties of the suture material are also critical. The primary function of sutures is to help stabilize the flap during the healing process without imposing unnecessary tension on the soft tissue. They must also ensure haemostasis, create a seal on the different planes to guarantee hermetic closure and optimize the functional and esthetic outcome. Taken together and performed properly, this will reduce the scar and promote regeneration.

POST-OPERATIVE PROTOCOL 
A lack of supportive periodontal therapy and smoking are the strongest risk factors for regenerative failure. Also important is the patient’s compliance to well explained and detailed post-operative instructions. Key post-operative instructions following regenerative surgery are as follows:
• Gently rinse with chlorhexidine, pooling the rinse around the surgery site for oneminute twice daily;
• Begin gentle brushing with a post-surgical (delicate) toothbrush dipped in chlorhexidine after 72 hours;
• Do not chew or bite hard on the surgical site.

The sutures are removed at two or three weeks post-operatively. At this point one must instruct and motivate the patient to achieve a high level of self-performed plaque control. This control should be maintained throughout the tissue maturation phase to optimize the reconstructive outcome and reinforced during supportive therapy to maintain the achieved attachment gain. We need to teach patients how to maintain areas that have recently undergone regenerative surgery.

• Regular brushing can resume once sutures are removed and it does not cause discomfort.
• Gentle interdental brushing may begin after three weeks if the space is sufficient. Avoid flossing for six weeks post-surgery.
• Have supportive periodontal therapy provided by a periodontal specialist every two to three months for at least one year.
• Do not probe the area for at least six months. When the area is being assessed, probing pressure must not exceed 25 grams (Figs. 16 & 17)
• Radiographs should be taken at six and 12 months using a reasonably standardized technique so that the follow-up radiograph can be compared with the baseline radiograph.

LIMITATIONS
The regeneration of osseous defects through microsurgery has limitations. For example, it is unpredictable for supra-alveolar defects (horizontal bone loss) and class III furcations. Often it is possible to achieve significant probing depth reductions and gain of clinical attachment, however, residual defects remain (Fig 17 &18). There is limited knowledge on the extent to which such remaining deep sites (residual pockets) are prone to bacterial recolonization and subsequent destruction. Regenerative therapy can only restore a fraction of the original tissue extent. Complete periodontal restoration is still a desirable goal. Long-term maintenance is required involving hygienists who have been appropriately trained in providing specialized care as it pertains to regenerative procedures.

CONCLUSION
Regeneration using Emdogain® is a low risk and highly predictable procedure if you select appropriate patients and utilize microsurgical techniques. OH

Peter Fritz is a certified specialist in Periodontics and is in full-time private practice in Fonthill, Ontario. The focus of his periodontal practice is dental implant therapy, microsurgical bone and soft tissue reconstruction, and oral medicine. Dr. Fritz is an Adjunct Professor in the Faculty of Applied Health Sciences at Brock University. For more information on microsurgical regeneration visit www.drpeterfritz.com.

Oral Health welcomes this original article.

REFERENCES
1. Lang NP, Berglundh T; Working Group 4 of Seventh European Workshop on Periodontology. J Clin Periodontol. Periimplant diseases: where are we now? – Consensus of the Seventh European Workshop on Periodontology. 2011 Mar;38 Suppl 11:178-81.
2. Esposito M, Grusovin MG, Papanikolaou N, Coulthard P, Worthington HV. Enamel matrix derivative (Emdogain®) for periodontal tissue regeneration in intrabony defects. Cochrane Database Syst Rev. 2009 Oct 7;(4):
3. Wachtel H, Schenk G, Böhm S, Weng D, Zuhr O, Hürzeler MB. Microsurgical access flap and enamel matrix derivative for the treatment of periodontal intrabony defects: a controlled clinical study. J Clin Periodontol. 2003 Jun;30(6):496-504.
4. Sculean, A. Periodontal Regenerative Therapy, 2011, Quintessence.