2.1 Introduction

For decades, clinicians and researchers have aimed to develop therapies to predictably regenerate periodontal structures and regain attachment lost due to periodontal disease. The advent of new surgical procedures, growth factors, and other biomimetic agents to complement existing bone replacement grafts has fundamentally changed the field of regenerative dentistry by increasing the long-term survival rate of teeth often categorized as having a poor prognosis. In the last decade, several new techniques have been demonstrated both preclinically and clinically, to further improve the success rate of periodontal regeneration.

2.2 Clinical Decision Considerations

Guided tissue regeneration (GTR) was formally introduced by Isidor et al. [1] where an occlusive membrane was utilized to allow only cells from the periodontal ligament to repopulate the root surface. The concept of cell occlusion and space provision prevented the gingival epithelium and connective tissue from entering the defect. Since then, the need for an occlusive membrane for defect isolation has been questioned by several authors, and the focus has shifted to the role of the undisturbed fibrin clot and wound stabilization between the tooth and gingival flap to prevent the downgrowth of epithelium [2, 3].

Based on current evidence, the predictability of GTR procedures has been shown to be influenced by several factors related to the defect site such as intrabony defect depth, angle, and configuration. According to Reynolds et al. [4]_, narrow defects less than 3 mm in width show a higher gain in attachment level, and bone fill suggesting defects which were shallow and wide would benefit more from osseous resective surgery. Indeed, several authors have consistently shown deep intrabony defects greater than 3 mm to have improved clinical outcomes using GTR compared to shallow defects [5, 6].

As our understanding of wound healing and periodontal regeneration has improved, a shift in treatment strategy from primarily one of cell occlusion to blood clot stability has occurred. Several minimally invasive surgical procedures have been introduced with the primary objectives of minimal flap reflection, wound stabilization, and establishing primary closure of the surgical flap(s). These approaches have demonstrated similar clinical outcomes irrespective of the defect configuration. The use of microsurgical instruments and microscopes has allowed for smaller surgical flaps with more predictable flap positioning, thereby stabilizing the blood clot and maintaining the integrity of the blood supply. With the help of these techniques and tools, a prognostic change has been reported whereby periodontally involved teeth with a hopeless prognosis show significant improvement and increased survivability after treatment.

Although there are many advantages to minimally invasive techniques such as improved patient comfort, reduced surgical trauma, improved wound stability, and primary closure of the flap, the main disadvantages lie in the added cost of the equipment and additional training required by the surgeon. Further, strict patent compliance and proper case selection are necessary with the application of these techniques primarily limited to localized and smaller interproximal defects with an intrabony component. The rationale of treatment utilizing these techniques is thus focused on regenerative approaches and less on resection of osseous tissues.

2.3 Systemic and Behavioral Factors

Patient-centered factors can have a significant impact on the success of regenerative therapy. Therefore, it is imperative that systemic and behavioral factors are carefully reviewed prior to initiating regenerative therapy as these factors can often relate to poor outcomes. It is well established that hyperglycemia, as occurs in poorly controlled diabetics, is associated with increased occurrence of infection and inflammation owing to impaired cellular immune responses and microcirculation during the wound healing process [7]. The combination of compromised wound healing and reduced bone turnover in the presence of hyperglycemia needs to be taken into consideration during treatment planning. Environmental factors such as smoking have also shown to have a negative impact on regeneration of new bone. Stavropoulos et al. [8] reported that smokers had a reduced gain in clinical attachment level following GTR as compared to non-smokers after 1 year. This finding is supported in a study by Tonetti et al. [9], who also showed the deleterious effects of smoking on the outcome of GTR. Matuliene [10] et al. in their study showed that teeth with probing depths of over 5 mm were at risk for loss and progression of periodontal disease. Therefore, supportive periodontal therapy such as routine maintenance care and good oral hygiene practices and behavior management are crucial to the long-term success of regenerative therapy.

In general, clinical advances in periodontics can be grouped into three main categories: tools, techniques, and materials. In this section we will describe advances in these categories.

2.4 Tools

2.4.1 Imaging

Dental radiography has been widely accepted and utilized in the field of periodontology. Recent advancements have made this diagnostic technology increasingly relevant, especially with regard to cone beam computed tomography (CBCT). Currently, two-dimensional imaging is performed regularly but with well-documented limitations [11–13]. CBCT has given clinicians the ability to better visualize and ascertain more information about the dentition and adjacent or surrounding bone with three-dimensional imaging resulting in better prognosis evaluation, treatment planning, and surgical management of a variety of periodontal diseases and conditions [14, 15]. Currently, the majority of literature supports the usage of CBCT for the management of surgical implant patients as well as conditions related to implant site preparations such as sinus grafting and location of anatomic structures [16]. The use of CBCTs to assess dentoalveolar bone change for dehiscences or fenestrations as a result of orthodontics has been recommended [17]. For patients with periodontitis, CBCT has significant improved visualization of furcations, root fractures, periodontal-endodontic lesions, and location of alveolar bone changes [18]. Although CBCT is currently not recommended as a replacement of the traditional 2D imaging for diagnosis, it is important to recognize advancements in CBCT technology that offer distinct advantages. Prakash and colleagues demonstrated the ability of CBCT to provide images of lamina dura and the periodontal space with higher quality and greater accuracy than 2D imaging [19]. With regard to bone levels, CBCT offers the advantage of analyzing buccal and lingual/palatal surfaces [20]. In a clinical study by Raichur et al. it was reported that CBCT imaging can significantly and more accurately detect infrabony periodontal defects (Fig. 2.1) [21]. Root morphologies and furcations of maxillary molars were visualized with higher accuracy using CBCT [22]. In addition, CBCT images were shown to more accurately detect furcation involvement compared to clinical measurement [23–25]. As CBCT technology advances, companies are manufacturing CBCTs that utilize less radiation and produce higher resolution images with a variety of field of views (FOV) [26]. With these advances, there may soon come a time where CBCT may replace the traditional 2D radiograph images currently used in periodontology.

2.4.2 Magnification

Microscopes have been widely used in the field of endodontics and restorative dentistry. In recent years, these microscopes have been utilized in periodontal therapy with more literature supporting this technology to aid with positive outcomes from periodontal therapy, both nonsurgical and surgical. Belcher highlighted three key principles that support the usage of microscopes in periodontics: refined surgical skills, magnification, and illumination [27]. Outside of adequate surgical training to successfully perform periodontal surgical procedures, magnification and illumination have aided surgical outcomes with respect to postoperative scarring and pain and reduced healing time [28]. Fiber-optic technology in illumination has been utilized to help focus light to provide a clear visual of specific areas [29]. Operatively, it has been suggested that there is a distinct advantage of the utilization of the microscope in extending the longevity of practice and health of the clinician. Indeed, studies have documented the ergonomic benefit of posture while using microscopes which results in a reduction of soreness and pain in areas of the body including the back, shoulder, and neck [30], while the elevated position of the head reduces eye fatigue and improved vision [31]. Recent advances in microscope usage in the field include HDTV integration in a single camera three-dimensional system to project a surgery onto a high-definition display [32]. This technology aids visual acuity for microsurgery and provides specific advantages for clinicians who become proficient in microsurgical knowledge and procedures (Fig. 2.2).

2.4.3 Instruments

As minimally invasive periodontal surgery procedures gain more popularity, the tools clinicians use have adapted accordingly. In addition to magnification using microscopes and loupes, microsurgical instruments are becoming increasingly more important to manage tissue trauma and minimize bleeding during surgery. Microsurgical instruments are shorter than standard surgical instruments to allow for adequate tactile grip between the thumb and index fingers. Instruments are circular in cross section than the traditional rectangular or oval shape, allowing a more flexible rotational movement. Additionally, the use of titanium metal for tissue forceps and needle holders is increasing compared to the heavier alternative of surgical stainless-steel instruments. A thorough knowledge of microsurgical principles in addition to the appropriate usage of these instruments will help the clinician achieve the benefit of using these microsurgical instruments (Fig. 2.3).

2.5 Techniques

Significant advances in the treatment of periodontal disease, specifically in periodontal regenerative, have come in the way of development and refinement of microsurgical techniques. These techniques capitalize on progress in our understanding of wound healing, and the role of space maintenance, clot stabilization, and primary closure on tissue regeneration.

2.5.1 Minimally Invasive Techniques

Harrel and Rees were the first to propose the minimally invasive surgical (MIS) technique [33]. In this technique, thorough granulation tissue removal and root debridement were accomplished using minimal flap reflection and gentle manipulation of soft tissues. This technique was subsequently modified by the incorporation of microscopes and microsurgical instruments to improve surgical precision. In 2007, Cortellini and Tonetti [34] introduced the MIST (minimally invasive surgical technique) in combination with enamel matrix derivative (EMD) to treat isolated intrabony defects. In this approach, the intrabony defect was accessed using either a simplified papilla preservation flap in narrow interdental spaces or the modified papilla preservation flap in wide interdental spaces. The authors owed the success of this technique to clot stability and primary wound closure. In 2009, the same group proposed M-MIST, consisting of reflection of only the buccal papilla using buccal sulcular incisions connected by a horizontal incision close to the papilla tip to gain access to the interproximal defect in what they described as the “buccal window.” The authors described the same principles used for the previous technique, emphasizing the importance of space provision on success rates [35]. However, a major drawback to this technique is the lack of application to interproximal defects that extend buccally and/or lingually.

A recent retrospective study by Nibali et al. [4] showed significant improvements in intrabony defects by means of clinical attachment gains and radiographic bone fill using minimally invasive nonsurgical therapy (MINST). Following, supra- and subgingival debridement using thin piezoelectric devices and Gracey mini curettes under a magnification lens, an attempt was made to stimulate and stabilize a blood clot within the defect. One-year results from baseline showed a probing depth reduction of 3.5 mm and 2.8 mm for the buccal and lingual interproximal sites, respectively, with average attachment gains of 3.1 mm and 2.4 mm on the buccal and lingual interproximal aspects. In addition, a significant improvement in radiographic vertical defect depth from 6.74 mm to 3.8 mm and defect angle from 28.4 to 44.3° was noted. According to the author, the significant widening of the defect angle could be attributed to bone remodeling which occurs in addition to the formation of a long junctional epithelium following MINST. This minimally invasive, nonsurgical technique using microsurgical instruments reduced the risk of soft tissue trauma and may have a significant positive impact in the treatment of medically compromised patients or patients that are not good surgical candidates.

The major limitations to the microsurgical techniques mentioned above are the lack of visualization and accessibility to intrabony defects. To address these limitations, Harrel [36] recently introduced the V-MIS technique which permits either buccal or lingual access. After flap reflection, the site is visually debrided with the aid of a videoscope; the root surface is treated with EDTA, followed by grafting with a mix of demineralized freeze-dried bone allograft (DFDBA) and EMD. A single suture at the base of the papilla followed by finger pressure with a soaked gauze is used to stabilize the clot and achieve primary closure of the wound. The results showed a significant improvement in clinical parameters as compared to traditional periodontal regenerative techniques at 36 months. However, the most significant finding was a similar gain in attachment irrespective of the defect configuration (one-, two-, three-walled defects). The author attributes the success of this technique to the removal of “micro-islands” of calculus on the root surface and has been shown to be associated with an increase in subgingival inflammation which was not previously visible with high magnification surgical telescopes but easily visualized using the videoscope. This technique is described in the chapter by Harrel in this volume (Figs. 2.4 and 2.5).