Vertical reconstruction of horizontal periodontal defects using a bioactive glass

Introduction

The goal of regenerative periodontal therapy is to predictably reconstruct the tooth's supporting apparatus. This treatment should lead histologically to the formation of a new connective tissue attachment (i.e. new cementum with inserting collagen fibers) and new alveolar bone, whereas clinically, a gain of attachment level and alveolar bone are expected (^{Caton and Greenstein, 1993} ; ^{Karring et al., 1997}). Several therapeutical approaches, such as the treatment with autogenous bone grafts, guided tissue regeneration (GTR), growth factors or root conditioning with enamel matrix proteins have provided histological documentation for periodontal regeneration, especially in intrabony and degree II furcation defects (^{Dragoo and Sullivan, 1973} ; ^{Gottlow et al., 1986} ; ^{Bowers et al., 1989} ; ^{Hammarström et al., 1997} ; ^{Karring et al., 1997} ; ^{Camelo et al., 1998} ; ^{Sculean et al., 1999a} and ^b).

Data from epidemiological studies have, however, shown that the great majority of periodontal lesions displays a predominantly horizontal pattern (for review see ^{Papapanou and Lindhe, 1997}). Results from histological studies have also indicated that in horizontal type of defects the healing resulted in the formation of a long junctional epithelium along the instrumented root surfaces and no, or only very limited, periodontal regeneration (^{Warrer and Karring, 1992} ; ^{Vuddhakanok et al., 1993}). Thus, none of the available treatment approaches may yield periodontal regeneration with reasonable predictability in horizontal defects. Up to now, only a few case reports have clinically documented positive soft and hard tissue improvements following regenerative treatment in such defects (K^{assolis and Bowers, 1999}). These data in turn indicate that the clinical applicability of regenerative periodontal treatment is, for the vast majority of patients, still limited. In cases with advanced horizontal attachment and bone loss, the main treatment goal is to arrest the disease process by mostly a resective surgical approach and to maintain the results through a thorough recall programme. Major drawbacks of this approach are the increase in tooth mobility and in dentin hypersensitivity as well as unsatisfactory esthetic results. Moreover, a loss of the supporting bone over 80 %, especially in the anterior frontal area, is considered by many clinicians as hopeless and, in many cases, tooth extraction and further prosthetic rehabilitation are considered as treatment of choice.

Among the alloplastic synthetic bone grafts, bioactive glass has the property to promote adsorption and concentration of proteins utilized by osteoblasts to form a mineralized extracellular matrix and thus to promote osteogenesis by allowing rapid formation of bone (^{Hench and West, 1996}). Histological studies have furthermore indicated that the material has a good clinical manageability, hemostatic properties and is not only osteoconductive, but can also act as a barrier retarding epithelial downgrowth (^{Fetner et al., 1994} ; ^{Karatzas et al., 1999}). Recent histological results from a monkey experiment have demonstrated that treatment of intrabony defects with bioglass, may lead to significantly greater amounts of new connective tissue attachment and of alveolar bone than conventional flap surgery alone (^{Karatzas et al., 1999}). Data from human clinical studies have also indicated that treatment with bioglass may result in higher gains of clinical attachment and alveolar bone than conventional flap surgery (^{Zamet et al., 1997} ; ^{Froum et al., 1998}).

Until now, at least to our knowledge, no published data are available, evaluating the treatment of advanced horizontal-type periodontal defects with bioactive glass. Therefore, the aim of the present case report is to present the surgical technique and the 36 months clinical results in one patient displaying advanced horizontal periodontal attachment and bone loss.

Material and methods

A 55-years old, caucasian, female patient presenting severe horizontal destruction of supporting attachment apparatus localized at the anterior frontal area came to the dental office presenting as main complains an increase in tooth mobility and frequently occurring abscesses. The patient suffered neither of any general disease which may influence the periodontal health nor was she a smoker. The X-ray status revealed at the lower frontal incisors a loss of the supporting bone of about 80 % and a loss of clinical attachment level varying from 8.0 mm to 11.0 mm (^{fig. 1} and ² , ^{table I}). The patient wished to preserve all her teeth and to avoid any prosthetic solution.

Treatment planning

The treatment included two sessions of oral hygiene instructions and professional tooth cleaning. Additionally, the mandibular front teeth were splinted with composit resin in order to decrease tooth mobility, and to increase the chewing comfort of the patient. Four weeks prior to surgery, subgingival scaling and root planing under local anesthesia were performed. As option for regenerative surgery, a fill of the defects with bioglass (PerioGlas^®, US Biomaterials) was chosen. The reason for choosing a bioactive glass were the chemical characteristics and the clinical handling properties of the material (^{Hench and West, 1996}). The baseline clinical measurements (^{table I}) are those measured 4 weeks after completion of subgingival scaling and root planing.

Surgical technique

Following local anesthesia, intracrevicular incisions were placed and full thickness mucoperiosteal flaps were raised vestibulary and orally. Special effort was made in order to preserve the interdental papillae (^{fig. 3}). One vertical releasing incision was performed mesially from tooth 43 in order to mobilize the flap and to allow for a better access. All granulation tissue was removed from the defects and the roots were thoroughly scaled and planed using hand and ultrasonic instruments. As revealed during surgery, the bone loss was predominantly of a horizontal type (^{fig. 3}). Following debridement, the defects were completely filled with bioglass (PerioGlas^®). Special effort was made to reform as correctly as possible the anatomy of the alveolar ridge (^{fig. 4}). Once the material was adapted, the flaps were coronally repositioned and sutured, using the modified vertical mattress technique. As suture material a 5 : 0 monofilament suture was used (Ethicon^®, Norderstedt, Germany) (^{fig. 5}). No periodontal dressing was placed over the wound area.

The post-operative care consisted of an analgetic regimen (3 × 400 mg ibuprofen) for the first 3 post-operative days, 0.2 % chlorhexidine rinses twice a day for 4 weeks, and administration of antibiotics (amoxicillin 3 × 500 mg daily for 10 days). Sutures were removed 14 days after surgery. Recall appointments were scheduled once per week during the first 3 weeks after surgery and once every 6 months for the rest of the observation period of 36 months. Neither probing nor subgingival instrumentation were performed during the first year after surgery.

Results

The post-operative healing was uneventful. No complications such as allergic reactions, abscesses or infection were observed throughout the entire observation period of 36 months. The soft tissue healing was excellent, already after a few days following surgery (^{fig. 6}).

The clinical measurements revealed a substantial PPD reduction and CAL gain although a slight bleeding on probing occurred (^{fig. 7} and ^{table I}). The radiographic examination also revealed a good integration of the graft material into the surrounding bone. At 36 months the X-ray still showed a stable height of the alveolar crest. This was especially evident when comparing the immediately post-operative X-ray to those taken at 30 and 36 months (^{fig. 8}, ⁹ and ¹⁰). At 36 months the case was considered clinically and radiographically successful and stable.

Discussion

The present case report has demonstrated that satisfactory clinical results in terms of probing depth reduction, gain of clinical attachment and radiographical hard tissue formation may be obtained following treatment of advanced horizontal periodontal defects with bioglass. The obtained clinical and radiographical results were maintained stable for 36 months.

The fact that neither allergic reactions nor abscesses occurred and that an excellent soft tissue healing was observed already after a few days after surgery indicates that the material is well tolerated. Similar clinical observations concerning the early healing events following implantation of bioglass were made by others (^{Fetner et al., 1994} ; ^{Low et al., 1997} ; ^{Zamet et al., 1997} ; ^{Froum et al., 1998} ; ^{Lovelace et al., 1998} ; ^{Karatzas et al., 1999}). Histological observations from monkeys have also shown that no foreign body reactions occur after the application of PerioGlas^® (^{Fetner et al., 1994} ; ^{Karatzas et al., 1999}). Furthermore, results of a histologic study in monkeys investigating the healing of artificially created periodontal defects have indicated that significantly more new cementum and less epithelial down-growth is present in the sites treated with bioglass than in those treated with conventional access flap (control) (^{Karatzas et al., 1999}). Thus, these data indicate that bioglass may have some potential to enhance a regenerative type of healing (^{Fetner et al., 1994} ; ^{Karatzas et al., 1999}). However, up to now, there are no published histological data investigating the effect of bioglass on the healing of human intrabony defects.

The results obtained in the present case report corroborate, to a certain extent, the results of a recently published case report study evaluating the effect of the same bioactive glass in the treatment of intrabony defects (^{Low et al., 1997}). The authors have treated 17 intrabony defects in 12 patients and obtained a mean CAL gain of 1.56 mm at 6 months after surgery. At 24 months the mean CAL gain measured 1.92 mm and was neither statistically nor clinically different when compared to the 6 months data. Furthermore, results from a controlled clinical trial have shown that treatment of intrabony defects with bioglass results in comparable results to those obtained with DFDBA (^{Lovelace et al., 1998}). However, results from another controlled clinical trial comparing treatment with bioglass to that with access flap surgery failed to demonstrate a statistically significant difference between the treatments, although a greater tendency for CAL gain was observed in the bioglass group (^{Zamet et al., 1997}). On the other hand, in a recently published clinical trial, comparing the same treatments, bioglass yielded significantly more attachment gain and bone fill than flap surgery alone (^{Froum et al., 1998}).

It is also important to emphasize that the technique for applying bioglass into the defects was simple. From a clinical point of view, the material was easy to handle, and once in place, remained stable. Moreover, due to its hemostatic property no post-operative bleeding occurred. These clinical properties of the material may be advantageous to the clinician when compared to other more technique sensitive procedures as for example GTR or the combination of bone grafts and GTR. A common complication with GTR is the post-operative exposure of the membrane followed by a bacterial colonization and even infection which in turn may seriously jeopardize the healing process (^{Selvig et al., 1992} ; ^{Nowzary et al., 1995} ; ^{Sander and Karring, 1995}).

However, it is important to emphasize that although the presented results are positive, they represent observations made in one single case and thus, they should be interpreted as such. Furthermore, it is still unknown to what extent the radiographic hard tissue fill represents a real bone and connective tissue attachment formation or only a connective tissue encapsulation of the graft material (^{Caton and Greenstein, 1993} ; ^{Karring et al., 1997}). In this context, it should be pointed out that neither the clinical nor the radiological or reentry measurements are adequate means for evaluating the effects of any type of regenerative periodontal therapy. A reentry procedure may give some information concerning the bone fill of the defect but it is unable to determine whether the bone regrowth is accompanied by a new connective tissue attachment. There is extensive evidence from the literature demonstrating that the formation of a new attachment and of new bone are not necessarily related phenomena. A new cementum with perpendicularly inserting collagen fibers may develop without the formation of new alveolar bone (^{Nyman et al., 1982} ; ^{Karring et al., 1997} ; ^{Sculean et al., 1999b}). On the other hand, a bone regrowth can occur with an epithelial lining interposed between the bone and the root surface (^{Caton and Greenstein, 1993} ; ^{Karring et al., 1997}). Consequently, the only way for assessing periodontal regeneration is the histologic analysis. This is especially true for horizontal type defects, where until now no histological studies have been able to show periodontal regeneration (^{Warrer and Karring, 1992} ; ^{Vuddhakanok et al., 1993}). For obvious ethical reasons, a histologic analysis was not performed in the present case and, so far, no statements can be made concerning the type of healing. However, the results from the present case report may indicate that there are reasons to support further investigations on the potential of this material for treating advanced periodontal defects.

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