Periodontal surgery involves modification of hard and/or soft tissues to achieve a therapeutic goal. These goals include treatment of periodontal defects, including furcation involvement of molars, and crown lengthening procedures to facilitate restoration of a tooth or teeth. Traditionally, resective and regenerative techniques focus on osseous structures with little attention given to modification of tooth surface. Unfortunately, this could lead to excessive removal of the bone and/or creation of an environment that is not cleansable and biologically incompatible. Further, regenerative techniques can yield unpredictable results in furcation lesions thus predisposing molars to further attachment loss. Biologic shaping is intended to create a cleansable, biologically compatible root surface that is manageable by both patients and dentists/hygienists. Here modification of tooth surface is the primary focus with removal of the bone performed only when absolutely necessary to create a biocompatible environment. This chapter will focus on biologic shaping during the course of periodontal therapy.
4.2 Indications and Rationale for Biologic Shaping
Biologic shaping was first reported by Melker and Richardson in 2001 and described for esthetic dentistry in 2003 [1, 2]. It combines periodontic and restorative phases of dentistry and aims to facilitate home care by patients using simple hygiene aids such as floss and a toothbrush, as well as facilitate professional maintenance by hygienists to remove plaque and calculus. It also creates biologically compatible dimensions necessary for the restoration of a tooth without infringement on biologic width. Further, biologic shaping removes tooth-derived risk factors such as developmental grooves, enamel projections, and concavities. This is particularly important if a developmental groove, concavity, or enamel projection is in close proximity to an existing crown margin resulting in a void or retainment of cement in the groove (Fig. 4.1). This can create an unmanageable situation and increases risk of further attachment loss. Therefore, the ideal therapy will involve modification of tooth structure to eliminate these anatomical discrepancies and create a new restorative margin that is supragingival to the previous margin. The point being that biologic shaping limits the unnecessary removal of bone and creates a biocompatible environment.
Biologic shaping is an alternative to conventional crown lengthening surgery [3–5]. Crown lengthening utilizes the margins of an existing restoration or the cementoenamel junction (CEJ) of a non-restored tooth to gauge the amount of ostectomy necessary to reestablish the biologic width (see Chap. 12 by Karateew et al. in this volume). Creating proper space ensures that a new margin will not impinge upon the attachment apparatus. This creates challenges in the furcation as removal of the bone in this region further compromises the tooth by creating an environment that is not cleansable for both the patient and the hygienist (Fig. 4.2). Thus, it is critical to preserve as much bone in the furcation area as possible. Therefore, rather than removing the bone away from the planned restorative margin, biologic shaping moves the restorative margin away from the bone, minimizing the amount by which the crown must be lengthened to establish biologic width. Table 4.1 lists the rationale for biologic shaping.
Reducing or eliminating furcation anatomy, thus facilitating margin placement
Allowing supragingival or intrasulcular impression techniques
Removing all CEJs
When treating combined periodontal and restorative cases, the periodontist must facilitate creation of a final margin (supragingival or just into the sulcus), improve tissue health to facilitate an accurate impression, and provide an abundance of dense connective tissue for augmentation of keratinized gingiva to protect the underlying periodontal support (Fig. 4.3). The dense connective tissue is essential for taking accurate impressions and cementing final restorations as there is greater probability of chronic inflammation if the restorative margin approximates mucosa . This is discussed in greater detail in the Chaps. 9 and 10 and by Zadeh et al. and Chambrone et al., in this volume. For esthetic surgical procedures, the periodontist must provide ideal clinical anterior crown length to aid the restorative dentist in providing the highest level of esthetic treatment. The periodontist also must make every attempt to avoid black triangles as a result of periodontal surgery and support the restorative dentist by motivating patients to accept the comprehensive treatment plan.