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Limited possibilities to predict bone loss of relevance in periodontitis pacients

BJörn Klinge – LDS, Odont dr, Professor,
Anders Gustafsson – LDS, PhD,
Margareta Hultin – LDS,
Carlos Marcelo S Figueredo – LDS.

Karolinska Institutet, Institute of Odontology, Department of Periodontology, Stockholm, Sweden

Running title: Predictability of bone loss for implant placement in periodontitis patients.
Key words: attachment, bone, implant, periodontitis.

Treatment of patients with severe periodontal disease often involves complicated decisions concerning disease activity and prognosis of teeth with extensive attachment loss. Many factors, in addition to the periodontal status, contributes to the definitive treatment plan. The decision to extract or retain severely periodontally involved teeth is based on a combination of evaluating disease activity, prognosis and restorative possibilities of these teeth. The treatment with osseointegrated dental implants is a well documented and predictable treatment of edentulous or partially edentulous patients [1-8]. The possibility of an implant-anchored fixed bridge or an overdenture prosthesis has greatly improved the restorative alternatives in edentulous or partially edentulous patients. Even in patients treated for periodontal disease, restorative treatment with osseointegrated implants has shown to be successful and predictable [9].

In some periodontal patients, not responding to conventional periodontal therapy or suffering recurrent periodontitis, the treatment scenario may also include a strategy of preserving alveolar bone of sufficient quality and volume for future implant placement.

Bone loss in untreated and treated periodontitis

Untreated periodontal disease results in progressive loss of the alveolar bone. Ellegaard et al. [9] showed a mean annual bone loss of 0.2 mm on buccal surfaces and 0.3 mm on interproximal surfaces in periodontitis patients 40 years of age or younger. Becker et al [11] studied the bone loss in 27 diagnosed but untreated patients (mean age 44.6) who were re-examined between 18 and 115 months after the initial examination. The study showed an overall average bone loss of 6.3% of the total tooth length. The bone loss was most pronounced at molars, with a relative decrease in bone height between baseline and final examination of 19.8%, followed by bicuspids (10.6%) and anterior teeth (7.9%). Several longitudinal studies of untreated periodontitis indicate a random disease progression with bursts of destructive activity occurring with various frequency at various sites in certain individuals [10 - 11]. At individual sites it is therefore complicated to foresee the tissue response.

Long term studies on the outcome of periodontal treatment show limited bone loss following periodontal therapy. Lindhe and Nyman [12] followed 61 patients with periodontitis who had been maintained for 14 years in a well-supervised maintenance care programme. The individual mean values of probing pocket depth, attachment level and marginal bone height did not vary significantly over the 14 years of observation. However, some sites showed continuous bone loss albeit maintenance and repeated therapy. The authors concluded that this site-specific bone loss is unpredictable and that individual means of probing depth and attachment level fail to disclose sites with recurrent disease. Goldman et al. [13] followed 211 patients treated for periodontal disease from 15 to 34 years and found that molar teeth were most prone to bone loss and that mandibular cuspids were most resistant to destructive bone loss.

Periodontally “hopeless” teeth

The influence of retained “hopeless” teeth on the proximal periodontium of adjacent teeth was evaluated by DeVore et al. [14]. Seventeen teeth, each being mesially adjacent to one “hopeless” tooth, was evaluated for probing pocket depth and radiographic alveolar bone level. All teeth, both the “hopeless” and the adjacent teeth, received conventional periodontal treatment including surgical therapy. The follow-up period of this study was 2-5 years. It was concluded that retained and treated “hopeless” teeth had no effect other than reduced probing pocket depth on the proximal adjacent periodontium, provided periodontal therapy was performed. Radiographic alveolar bone levels showed no significant differences between initial examination and final examination.

Proximal bone loss adjacent to periodontally “hopeless” teeth, with and without extraction, was studied by Machtei et al. [15]. In their retrospective study 145 “hopeless” teeth in 129 patients were included, with patients pooled into two groups: A and B. Group A included 82 “hopeless” teeth and their proximal neighbour teeth which were retained throughout the study period. Group B included 63 “hopeless” and adjacent teeth which were extracted at the commencement of the study. Teeth were considered “hopeless” if they had lost 50% or more of alveolar bone height at either of the proximal sites, or were present with radiographic evidence of total bone loss in the furcation area. The average follow-up period was 4 years. During the study period no periodontal treatment was performed. Alveolar bone changes were measured as a percentage of the anatomic root ( radiographic apex-CEJ). The retained “hopeless” teeth showed progressive bone loss at a mean annual rate of 3.4%, as compared to the proximal surface of the adjacent teeth with a bone loss of 3.1%. In the extraction group B, bone loss adjacent to extraction site was 0.2%. Bone loss was greatest adjacent to retained multi-rooted teeth. It was concluded that, in the absence of periodontal treatment, the retention of hopeless teeth has a destructive effect on the alveolar bone of the adjacent teeth.

Bone resorption following tooth extraction

Following tooth extraction, the bony socket heals with normal trabecular bone. As part of the healing sequence a subsequent resorption of the alveolar ridge can be observed. This residual ridge resorption (RRR) is most pronounced during the first year following extraction. The average RRR during the first year has been reported to be 4 mm in the mandible and 2 mm in the maxilla, while the additional annual long-term (10-25 years) resorption was 0.2 mm in the mandible and 0.07 mm in the maxilla [16]. Denissen et al. [17] proposed 4 stages of mandibular resorption (Fig.1). Even in cases of severe periodontitis with extensive loss of bone height the remaining teeth seem to prevent resorption of the width of the mandible (stage III in Figs. 1 and 2). The loss of bone height is most extensive in the anterior region of both jaws. Tallgren [16] found an average loss of anterior mandibular bone height after 25 years amounting to 13 mm, the corresponding value in the maxilla was 5 mm.

A number of studies suggests a correlation between alveolar atrophy and metabolic factors such as osteoporosis [18-20]. It has been suggested also that the gonion index, i.e. the cortical thickness at the gonion reference point could be used as an indicator of bone resorption. A gonion index of less than 1 mm indicates an on- going metabolic bone loss [20]. However, not all RRR can be explained by systemic factors. Some of the resorptive activity, especially the resorption taking place just after a tooth extraction, seems to be influenced by a local biochemical inheritance from the dentate period. Other factors affecting the speed and extent of RRR are original bone volume, muscle function and extraction history. The duration of edentulousness also seems to be an important factor for RRR [20].

One aspect in the treatment of patients with severe periodontitis, may relate to the question whether the extensive initial RRR following tooth extraction will be the same whether the tooth is extracted with most of the bone height remaining or if this response is different if the tooth is extracted after extensive bone loss. We have not been able to find any conclusive answer to this question in the literature. Until conclusive studies exist, it is reasonable to assume that the local biochemical inheritance from the dentate period is the same independently of the attachment level of the extracted tooth.

Periodontitis as a prognostic factor for implant treatment

There are only a few studies evaluating the long-term survival and prognosis of oral implants inserted in periodontally compromised partially edentulous patients [8], [21].

Nevins and Langer [21] report on the successful use of 309 implants placed in 59 patients treated for advanced periodontitis. A success rate of 98% was demonstrated. Of the 309 implants placed only 4 mandibular and 3 maxillary implants failed for survive.

Ellegaard et al. [9] evaluates the outcome of implant therapy in periodontally compromised patients. A total of 124 implants in 75 partially edentulous patients were observed during 3-84 months. 3 implants failed, yielding a 3-year survival rate of 95%. After 3 years 76-86% of all implants remained free from radiographic bone loss >1.5 mm. These results indicate that periodontally compromised patients, who have experienced a considerable loss of alveolar bony support, can be successfully treated with implants.

Conclusions

Studies of the retention of periodontally severely damaged teeth show that untreated periodontal lesions give rise to continuous bone loss also at neighbouring teeth. In contrast, the retention of treated “hopeless” teeth do not cause any increased bone loss at adjacent teeth. This means that “hopeless”, but strategically important, teeth can be retained without risk of losing bone height for future implants, provided that they are carefully treated and maintained. Long-term studies show that periodontal therapy with careful maintenance is successful and predictable on an individual level and that the average bone loss is not worse in patients treated for periodontitis than in edentulous patients. Some sites will show a continuous deterioration in spite of an active treatment and a careful maintenance program. These sites are very difficult to predict by clinical parameters such as probing pocket depth and bleeding on probing. This indicates that it is dubious to extract still functioning teeth in order to save bone height for future implants. It is reasonable to believe that single-rooted teeth have the best periodontal prognosis making it even more dubious with strategic extractions in these areas suitable for later implant placement. Additional studies are needed to guide us in clinical decision making of saving or extracting teeth to preserve bone for future implant placement.

References

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16. Tallgren A. The continuing reduction of residual alveolar ridges in complete dentures wearers: A mixed longitudinal study covering 25 years. J Prosthet Dent 1972; 27: 120-32.

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Legends

Fig. 1. Cross sections of edentulous mandibles at the sites of the central incisors

Stage I Anatomic situation directly after extraction

Stage II After the initial resorption of the edentulous ridge – the ridge still has width and height.

Stage III Ridge has atrophied to a knife-edge shape

Stage IV Only basal bone is present in a vertical direction.

Address:

Björn Klinge

Department of Periodontology, Institute of Odontology, Karolinska Institutet P.O. Box 4064 S-141 04 Huddinge, Sweden Email: Bjorn.Klinge@ofa.ki.se