Relationship between Restorative Treatment and Periodontal Health
Surgical Clinical Crown Lengthening
Osseous surgery aims to reshape the alveolar bone to remove any anatomic discrepancy between the soft tissues and the underlying bone so that it can heal with a normal physiologic gingival architecture (Figure 13-1). The different types of bone lesions can be treated with three approaches.
Clinical crown lengthening is a resective procedure that can be performed with two different techniques: ostectomy (remodeling technique combined with removal of bone support structures) and osteoplasty (bone remodeling without removal of supporting bone).
The clinical crown is the portion of the tooth protruding through the gum. A clinical crown lengthening can be achieved through a surgical procedure or can be the unwelcome result of a periodontal treatment.
For many years the surgical approach that took only the disease into account, ignoring esthetic aspects, yielded optimal clinical outcomes for the disease but was inevitably detrimental to the patient’s appearance.
The pictures of the outcomes of clinical crown-lengthening procedures performed about 20 years ago (Figures 13-2 and 13-3) clearly show the cosmetic damage that at the time was considered inevitable for proper treatment of the disease.
The first study that examined the healing process with insufficient biologic width was conducted on canine dentition by Parma Benfenati, Fugazzotto, and Ruben (1985). The protocol entailed creating cavities at different locations as follows:
Figure 13-4 The mouth was divided into two parts. The right maxillary and mandibular quadrants represented the experimental side, whereas the left quadrants served as controls. (From Parma Benfenati S, Fugazzotto PA, Ruben MP: The effect of restorative margins on the postsurgical development and nature of the periodontium. Part I, Int J Periodontics Restorative Dent 5:31, 1985.)
The partial-thickness flaps of the experimental side were sutured on the ridge. Healing took place with the formation of reddened, retractable tissue prone to bleeding on periodontal probing. Almost all restorations were hidden by the edematous tissue caused by the inflammatory process.
On the control side, however, the tissues healed without complications and exhibited a pink and healthy appearance. In all cases the gingival tissue had completely covered the notch that served as landmark.
The histologic sections of the contralateral side—where the amalgam filling invaded the biologic width—clearly showed the bone resorption process and destruction of the epithelial attachment, which was inevitably positioned more apically.
One can easily infer that the junctional attachment apparatus should be factored in before any direct or indirect restorative approach can be performed. Therefore before the dental disease is addressed, it is imperative to solve the issue of the space required for regeneration of the physiologic junctional attachment apparatus.
Esthetic needs greatly affect the choice of treatment. It should be remembered that osseous resective surgery with apical positioning of the flap changes the emergence profile of the tooth, which will be more apical and palatal with respect to its original position. This may greatly affect subsequent restoration treatment (Figure 13-5).
In the presence of a free gingival margin, pseudopockets, or suprabony pockets, a gingivectomy will always be the treatment of choice and consists of removing gingival tissue in order to expose a greater portion of the root, leaving an adequate band of attached gingiva.
Removal of the fractured tooth fragment makes it possible to establish the site of the fracture. Heavy bleeding usually indicates a lesion of the connective attachment, but whether the fracture ends above or below the ridge can be assessed only after detachment of the flap.
Here ostectomy is mandatory, and the root will be prepared at the bony ridge level by reducing the thickness of the dentin. The international literature reports undisputed data from human histologic sections showing that the insertion of Sharpey’s fibers on the root requires a new cementogenesis process, regardless of dentin thickness.
There are two main reasons for this approach: Survival of the tissue above a surface devoid of a blood supply is ensured by the formation of vascular bridges in the area adjacent to the defect. Therefore it is obvious that the shorter the bridge, the higher the probability of obtaining a sufficient blood supply to ensure survival of the tissue above the root.
It goes without saying that a curved line is much longer than a straight one, and this is one reason for flattening the roots. The other reason is that the gingival attachment regenerates regardless of the thickness of dentin.
Figures 13-8 and 13-9 show a case of clinical crown lengthening I performed many years ago. Placement of the rubber dam is mandatory for this procedure in order to remove the decayed tissue (even if it is below the gingival margin) and to choose the most appropriate restoration for the specific case.
Bleeding after removal of the tooth fragment confirms the diagnosis of fracture below the gingival attachment. In the clinical case treated over 20 years ago (Figures 13-10 and 13-11), the palatal cusp of the premolar was reduced to prevent further fracture.
Figure 13-11 A, Suturing of the flap. B, Healing at 6 months.
Buccally the flap was positioned apically, waiting for healing by second intention without taking esthetic aspects into consideration. Today this approach would not be acceptable. In fact, the modern surgical approach strives to avoid vertical releasing incisions as much as possible in favor of a mesio-distal extension, in order to permit apical positioning of the flap without leveling the mucogingival line.
Any releasing incision should be performed in less visible areas. For instance, in the case of a central incisor it is preferable to extend the incision mesio-distally up to the canines or premolars in order to reposition the flap apically. The palatal approach is always a good alternative for cosmetic purposes.
Today, infrabony pockets can no longer be treated with open flap curettage, because this would cause significant cosmetic damage and prevent the clinician from treating the defect with regenerative techniques. In general, partial-thickness flaps are preferred because leaving the periosteum in place means preserving the vascular supply of the underlying bone and having a substrate available on which to anchor the sutures.
Consequently, even the dental hygienist’s approach must be completely different. The hygienist cannot perform a root planing procedure inside a pocket that is 8 to 10 mm deep because this would do more harm than good. In fact, the proprioceptors that detect the inflammatory process activate the osteoclasts. The latter, in turn, promote bone resorption, which occurs much earlier with respect to destruction of the attachment. Therefore with a closed treatment there is the risk of tearing fibers that are still inserted without any certainty of having completed the mechanical treatment necessitated by the underlying cause.
In the case of clinical crown lengthening, the flap will be repositioned apically by means of periosteal sutures that will push the flap over the periosteum, thus facilitating healing by primary intention.
The prosthetic restoration of a lower molar—where cosmetic aspects are not an issue—is quite easy because tooth preparation can be performed outside the biologic width. This facilitates all subsequent impressions (taken without retraction cords) and fabrication of the prosthetic artifact, which can easily be luted with the rubber dam in place.
In a visible cosmetic area of the mouth, it is indispensable to wait until complete maturation of the tissues in order to have absolute control of the preparation margin with respect to the gingival margin.
1. After administration of local anesthesia, an intrasulcular incision is performed in order to preserve the existing keratinized tissue, extending the incision into the grooves of two adjacent teeth and reducing the thickness of their mesial and distal papillae. A partial-thickness flap is then raised a few millimeters beyond the mucogingival junction, which makes the flap extremely mobile and permits the proper and desired apical positioning.
2. After probing, a palatal flap is created on the palatal side and is reduced in thickness by outlining the shape of the bony ridge. The shape of this flap is created with a scalpel blade no. 15C oriented perpendicular to the long axis of the tooth. The surgery begins with a paramarginal incision, which is more pronounced in the area of the tooth to be restored prosthetically. The incision then becomes intrasulcular, next to the mesial and distal ends of the adjacent teeth. This is followed by a series of incisions, placing the scalpel blade parallel to the long axis of the tooth in order to thin it out (primary palatal flap). After the desired apical extension has been achieved, a full-thickness incision is then performed apically, reaching the palatal bone structure only at this point.
4. At this point the surgery requires removal of the bone support (ostectomy) from the interproximal areas with a CTG-O bone chisel, in order to reduce the bone by approximately 3 to 4 mm starting from the healthy tooth structure. The ostectomy is also performed on the palatal and vestibular aspect of the ridge with a Rhodes chisel and round-shaped diamond burs. This procedure produces the desired bone architecture: scalloped, with parabolic contours and physiologic in appearance. A universal curette can be used to remove small spicules of interproximal bone and residue of support bone that may affect the desired result. At the end of this surgical phase, the desired clinical crown lengthening—performed respecting the bone architecture—is assessed with a periodontal probe.
The periosteal anchoring on the buccal aspect offers the clinician the option to place the partial-thickness flap in the desired position, according to clinical needs. If there is enough keratinized tissue, the buccal flap is sutured right at the bony ridge level to cover the underlying bone. On the palatal aspect—where the interdental spaces and papillae are usually larger—the horizontal mattress technique can be used.
The case can be completed after the appropriate time required for the healing process (usually 6 to 9 months), fully satisfying the functional esthetic requirements of the clinician and patient alike (Case Report 1, Figures 13-12 to 13-17, and Case Report 2, Figures 13-18 to 13-27).