Periodontal surgery in plaque-infected dentitions

A clinical trial was performed to study the result of periodontal treatment following different modes of periodontal surgery in patients not recalled for maintenance care. The material consisted of 25 patients distributed into 5 groups. Following an initial examination, all patients underwent presurgical treatment including case presentation and instruction in oral hygiene measures. This instruction was given once. The various patient groups were then subjected to one of the following surgical procedures: 1) the apically repositioned flap operation including elimination of bony defects 2) the apically repositioned flap operation including curettage of bony defects but without removal of bone 3) the "Widman flap" technique including elimination of bony defects 4) the "Widman flap" technique including curettage of bony defects but without removal of bone 5) gingivectomy including curettage of bony defects but without removal of bone. Six, 12 and 24 months after completion of the treatment, the patients were recalled for assessment of their oral hygiene standard and periodontal conditions. The results showed that case presentation and oral hygiene instruction given once, only temporarily improved the patient's oral hygiene habits. Renewed accumulation of plaque in the operated areas resulted in recurrence of periodontal disease including a significant further loss of attachment. All five different techniques for surgical pocket elimination were equally ineffective in preventing recurrence of destructive periodontitis.     

Longitudinal therapeutic effects on the periodontal attachment level and pocketdepth in beagle dogs

Thirteen healthy Beagles, 3 1/2–5 years of age with moderate to advanced periodontal discase received a thorough scaling and prophylasis followed by four weeks of daily tooth cleaning. After one month, each of the fourposterior quadrants of each dog was subjected to one of the following treatments: 1) subgingival curettage, 2) modified Widman flap surgery with root planing, 3) apically repositioned flap and bone surgery for pocket elimination and 4) scaling and root planing as a control. Toothbrushings was carried out daily. In addition, every 14 days the dogs received a rubber cup and pumice prophylaxis throughout the entire length of the study. At the baseline, 1, 6, 12, 24 and 36 months following treatment, oral hygiene and gingival health were scored and the level of periodontal attachment and pocket depth were measured. The results at one Month suggested an increase in attachment levels which was grater after scaling or subgingival curettage than after flap procedures. Up to 36 months, the established attachment levels were maintained for all treatment groups and no significant difference was found between any of the treatments and the scaled controls. However, in advanced periodontal lesion attachment levels were not maintaned with scaling alone.
The present study has shown that the more conservative approaches to the treatment of periodontal disease such as subgingival curettage and Widman flap surgery may be as effective in maintaining clincal attachment levels as elaborate surgical procedures involving osteoectomy.     

Improved periodontal conditions following therapy

The aim of the present clinical trial was to evaluate the effect of different modes of periodontal therapy on patients with moderately advanced periodontal disease and to express the findings in terms of probing pocket depth and attachment level alterations at periodontal sites with different initial probing depths. The material consisted of 16 patients, 35-65 years of age. Following a Baseline examination including assessments of oral hygiene status, gingival conditions, probing pocket depths and probing attachment levels, the patients were subjected to periodontal treatment. A "split-mouth" design approach of therapy was used and the jaw quadrants were randomly selected for the following different treatment procedures: (1) scaling and root planning, (2) scaling and root planing in conjunction with a gingivectomy procedure, (3) scaling and root planing in conjunction with an apically repositioned flap procedure without bone recontouring, (4) scaling and root planing in conjunction with an apically repositioned flap procedure including bone recontouring, (5) scaling and root planing in conjunction with a modified Widman flap procedure without bone recontouring and (6) scaling and root planing in conjunction with a modified Widman flap procedure including bone recontouring. The patients were following active treatment enrolled in a supervised maintenance care program including "professional tooth cleaning" once every 2 weeks during a 6-month period of healing, after which a final examination was performed. The investigation demonstrated that active therapy including meticulous subgingival debridement resulted in a low frequency of gingival sites which bled on probing, a high frequency of sites with shallow pockets (less than 4 mm) and the disappearance of pockets with a probing depth of greater than 6 mm. Between the Baseline examination and the 6-month re-examination, the probing attachment level for initially shallow pockets remained basically unaltered, but with a tendency of a minor apical shift. This occurred in all 6 treatment groups. For sites with initial probing depths of 4-6 mm and greater than 6 mm, there was in all groups some gain of probing attachment. This gain was most pronounced in the initially deeper (greater than 6 mm) pockets. With the use of regression analysis, the "critical probing depth" (CPD) value (i.e. the initial probing depth value below which loss of attachment occurred as a result of treatment and above which gain of probing attachment level resulted) was calculated for each of the 6 methods of treatment used. A comparison of the CPD-values between the 6 treatment groups did not reveal any major differences.     

Regeneration of alveolar bone following surgical and non-surgical periodontal treatment

The purpose of this investigation was to examine the regeneration of alveolar bone following surgical and non-surgical periodontal treatment. A total of 16 patients who had advanced periodontitis and demonstrated angular bony defects on radiographs participated in the study. After the initial examination, they received instruction in oral hygiene and had their teeth thoroughly scaled. When the individual patient at 2 succeeding appointments had plaque on less than 20% of the tooth surfaces, one maxillary and one mandibular quadrant was treated with the modified Widman flap procedure while one of the remaining quadrants was treated with the reverse bevel flap procedure. The last quadrant was treated with root planing under local anesthesia. None of these procedures included bone contouring. Following treatment, the patients were recalled every 2 weeks for professional tooth cleaning. Radiographs taken 12 months following treatment revealed that only minor changes in the bone level had occurred in areas with horizontal bone loss following the various treatment modalities. Following the modified Widman flap procedure, however, a statistically significant coronal regrowth of bone (0.5 mm) had occurred in angular bony defects. The majority of the angular bony defects persisted following all 3 treatment modalities.     

A comparative clinical study of three periodontal surgical techniques

Abstract A comparative 4-month trial was performed after initial preparation. The procedures used were curettage, replaced flap and apically repositioned flap procedures with osseous recontouring respectively in a split-mouth technique in 17 male and 23 female patients, 22 to 65 years old. Changes were assessed with plaque and gingival indices, and measurements of pocket depths, attachment levels and tissue contours. All procedures reduced pocket depths. Apically repositioned flaps were the most successful, reducing overall mean pockets from 3.5 to 1.9 mm. Changes in attachment levels post-operatively showed only a small degree of variation among the three surgical procedures, and would not affect the choice of the apically repositioned flap as the most effective method for pocket reduction. A marked improvement in tissue contour was obtained in those areas treated by apically repositioned flap procedures and osseous recontouring. Despite failure to improve tissue contour, replaced flap procedures showed an equal degree of success in maintaining plaque control when compared to apically repositioned flaps, as evidenced by static plaque indices. Replaced flap procedures were also the only group to show improved gingival health over the 4-month post-operative period with lower gingival indexes. It would seem that good healing, followed by a high standard of oral hygiene, may overcome the presence of gingival and marginal osseous deformities.     

Short term results of three modalities of periodontal treatment.

Short term data were obtained from 74 patients who recieved comprehensive periodontal treatment using a split mouth approach to test three variables; subgingival curettage, pocket elimination surgery, and modified Widman flap procedure. The patients initially had an average interproximal loss of attachment of 3.2 mm and an average interproximal pocket depth of 3.9 mm. Evaluation of the data indicate that after 4 to 6 weeks: 1. All three surgical procedures reduce pocket depths. In order of effectiveness they are: pocket elimination surgery, modified Widman flap, and subgingival curettage. 2. Pocket elimination surgery reduces pockets more than subgingival curettage on the buccal, lingual and interproximal, and more than the modified Widman flap on the lingual. The modified Widman flap procedure reduces pockets more interproximally than subgingival curettage. 3. Subgingival curettage results in a gain of attachment interproximally, and on the lingual side, while the modified Widman flap resulted in a gain of attachment interproximally only. 4 Pocket elimination surgery resulted in a loss of attachment buccally. 5 Subgingival curettage results in a more favorable postoperative attachment level on all surfaces than did pocket elimination surgery.     

Treatment of localized juvenile periodontitis

Abstract The present investigation was performed to study the effect on localized juvenile periodontitis (LJP) of a treatment program which included tetracycline administration, surgical elimination of inflamed tissues, scaling and root planing, and careful plaque control during healing. Treatment of LJP lesions was carried out on 16 individuals aged 14 to 18 years (JP group). Lesions in first molars and incisors in a group of patients with adult periodontal disease (AP) were treated in an identical manner and served as controls. The presence of angular bony defects adjacent to first molars and incisors was first documented in all patients. Thereafter, a clinical examination was carried out, including assessments of oral hygiene status, gingival conditions, probing depths and attachment levels. The patients were subjected to a treatment program involving administration of tetracycline (250 mg 4 times per day for 2 weeks), removal of granulation tissue after flap elevation, and root curettage. After surgery, the patients were instructed to rinse the mouth with 0.2% chlorhexidine for 2min twice a day during the first 2 postsurgical weeks. Professional tooth cleaning was carried out once every 3 months during a 5-year period. At 6, 12, 24 and 60 months after surgical treatment, the patients were re-examined regarding oral hygiene, gingival conditions, probing depths and attachment levels. Treatment of LJP lesions resulted in resolution of gingival inflammation, gain of clinical attachment, and refill of bone in angular bony defects. The healing of the lesions of this patient sample was similar to healing observed in patients with AP.     

4 modalities of periodontal treatment compared over 5 years

The purpose of the present study was to assess in a clinical trial over 5 years the results following 4 different modalities of periodontal therapy (pocket elimination or reduction surgery, modified Widman flap surgery, subgingival curettage, and scaling and rool planing). 90 patients were treated. The treatment methods were applied on a random basis to each of the 4 quadrants of the dentition. The patients were given professional tooth cleaning and oral hygiene instructions every 3 months. Pocket depth and attachment levels were scored once a year. 72 patients completed the 5 years of observation. Both patient means for pocket depth and attachment level as well as % distribution of sites with loss of attachment greater than or equal to 2 mm and greater than or equal to 3 mm were compared. For 1-3 mm probing depth, scaling and root planing, as well as subgingival curettage led to significantly less attachment loss than pocket elimination and modified Widman flap surgery. For 4-6 mm pockets, scaling and root planing and curettage had better attachment results than pocket elimination surgery. For the 7-12 mm pockets, there was no statistically significant difference among the results following the various procedures.     

The long-term effectiveness of periodontal therapy in a clinical practice

A retrospective study was conducted of 620 patients in a periodontal practice over the years 1960 to 1982. Various periodontal therapies were assessed by using careful office protocols, meticulous record-keeping and well-defined outcome criteria. Four treatment outcome categories were used: two representing satisfactory outcomes (referred to as "STABLE"), and two unsatisfactory outcomes ("UNSTABLE"). The percentages of patients in the STABLE categories following different therapies were: (1) nonsurgical treatment, 63.6%; (2) closed curettage, 73.1%; (3) open curettage, 95.0%; (4) modified Widman flap, 91.6%; (5) full flap and osseous surgery, 71.1%. The major conclusions were that the modified Widman flap and open curettage were more effective than flap and osseous surgery, and much more effective than closed curettage when it was employed as an alternative treatment (54.8% STABLE) to the osseous surgery (71.1% STABLE). Thus, moderate surgical therapies appear to be at least as effective as ostectomy procedures in the treatment of periodontal disease, while nonsurgical and closed curettage therapies appear to be less effective.     

Alterations of the position of the marginal soft tissue following periodontal surgery

The present study was performed to examine the alterations of the position of the marginal soft tissue ("gingival margin") on the buccal surface of teeth in patients who following periodontal surgery were enrolled in a supervised maintenance care program for 10--11 years. The material consisted of 43 patients with severe destruction of the periodontal tissues. Following initial treatment comprising scaling, root planing and instructions in plaque control measures, deepened periodontal pockets were eliminated by the use of an apically repositioned flap procedure including osseous surgery to eliminate bony defects. After treatment, the patients were recalled once every 3--6 months for maintenance care. In all patients, the distance between the cemento-enamel junction and the gingival margin on the buccal surfaces of all treated teeth was assessed (1) prior to surgery, (2) after initial healing, and (3) at a reexamination 10--11 years after treatment. In addition, the presence or absence of keratinized gingiva was determined. The results showed that (1) during active periodontal treatment the position of the gingival margin was shifted in an apical direction, (2) this displacement was to some extent compensated for by a coronal regrowth during the postoperative maintenance care period, (3) the alterations of the position of the gingival margin followed a similar pattern in areas with and without a zone of keratinized gingiva, (4) the number of gingival units devoid of keratinized gingiva decreased during the maintenance care period.     

Histometric evaluation of periodontal surgery I. The modified Widman flap procedure

Abstract The present investigation was performed in the Rhesus monkey to determine the effect of the modified Widman flap procedure on the level of the connective tissue attachment and supporting alveolar bone. Two adult male Rhesus monkeys were used. Eighteen contralateral pairs of periodontal pockets were produced in a standardized manner. Surgical treatment of the pockets was performed around experimental teeth and the contra-lateral teeth were used as the unoperated controls. Twelve months following treatment the animals were sacrificed and histological sections obtained. Using the cemento-enamel junction (CEJ) as a fixed reference point, linear measurements along the. root surface were made to the most apical cells of the junctional epithelium (JE), to the crest of the inter-proximal alveolar bone (CR), and to the apical extent of angular bony defects (AAD). These measurements from operated and unoperated pockets were then compared. The data revealed that treatment of periodontal pockets using the modified Widman flap procedure produced no gain in connective tissue attachment and no increase in crestal bone height. In angular bony defects a certain degree “bone fill” was noted. This bone repair was never accompanied by new connective tissue attachment.     

Human allografts of iliac bone and marrow in periodontal osseous defects

The purpose of this study was to statistically compare the bone regeneration and/or remodeling that occurred in human periodontal osseous defects treated with frozen allogenic, cancellous, iliac bone and marrow grafts, to defects treated by nongrafted flap curettage using a split-mouth protocol. Six patients were selected to participate in the study. These patients exhibited bilateral intrabony periodontal defects that had been refractory to nonsurgical periodontal therapy. Twenty-three intrabony defects were treated by osseous grafting using allogenic iliac bone and marrow and 32 intrabony defects were treated by open debridement procedures. The bony regeneration in each defect treated was evaluated by probing measurements taken from a fixed reference made at the initial surgery and at reentry 1 year after transplantation. The overall results of this study demonstrated that the percentage of osseous regeneration that occurred in intrabony defects treated by allogenic bone and marrow grafting was statistically greater than that which occurred in defects treated by nongrafted flap curettage procedures.     

The significance of alveolar bone in periodontal disease

The present experiment was designed to study if a gingival unit with a long supraalveolar connective tissue attachment provides less resistance against progression of periodontal disease than a unit with a supraalveolar connective tissue attachment of normal length. A long supraalveolar connective tissue attachment was established at the buccal aspect of mandibular premolars and molars in dogs by surgical removal of the marginal portion of the buccal alveolar bone after elevation of a muco-periosteal flap. Attempts were made to minimize mechanical injury to the root cementum and the supraalveolar fibrous attachment during the surgical procedure. Contralateral, non-operated teeth with a supraalveolar connective tissue attachment of normal length were used as controls. Following surgery, plaque control was initiated and maintained for 3 months by topical application of 0.2% chlorhexidine digluconate solution twice daily. During the following 6 months, the oral hygiene measures were abandoned and plaque was allowed to accumulate on both groups of teeth. In order to enhance plaque formation and to promote the development of subgingival plaque, cotton floss ligatures were placed at the entrance of the gingival sulci. The dogs were sacrificed 6 months after the initiation of the plaque accumulation period. The jaws were removed and histological sections prepared of test and control teeth including their surrounding periodontal tissues. The histological analysis revealed that the plaque induced inflammatory lesion in the gingival connective tissue did not extend more apically in sites with a long supraalveolar connective tissue attachment than in sites with a supraalveolar fibrous attachment of normal length. A small but statistically significant loss of connective tissue attachment had occurred in both groups of teeth. This attachment loss, however, was similar in sites with a long supraalveolar connective tissue attachment and in sites with a supraalveolar fibrous attachment of normal length. These findings suggest that the loss of attachment in periodontal disease is unrelated to the presence or absence of the bony component of the periodontium.     

The effect of systematic plaque control on bone regeneration in infrabony pockets

Abstract A clinical trial was undertaken to test the hypothesis that periodontitis can be cured and that bone regeneration occurs in infrabony pockets in patients maintained on an optimal standard of oral hygiene. The material comprised 24 patients with advanced periodontal disease. After an initial examination, the patients were randomly distributed into one test group and one control group. All the patients were given instruction and practice in a proper oral hygiene technique, and then subjected to periodontal surgery using the modified Widman flap procedure. Following treatment, during a 2-year period the patients of the test group were recalled once every second week for professional tooth cleaning. The control patients were recalled once every 12 months for prophylaxis. The results showed that all osseous defects of the patients of the test group were refilled with bone. The control patients, on the other hand, could not maintain a high standard of oral hygiene, and exhibited a progressive deterioration of the periodontal tissues during the postsurgical observation time.     

Bone apposition in surgical bony defects following orthodontic movement: a comparative histomorphometric study between root- and periodontal ligament-damaged and periodontally intact rat molars

BACKGROUND: The influence of orthodontic tooth movement with diminished periodontal support is unclear. The aim of the present study was to evaluate bone healing in surgical defects following orthodontic tooth movement with and without periodontal ligament (PDL) and root surface damage. METHODS: The study comprised 33 adult male Wistar rats, divided into two groups: group 1 (n = 14) with bony defect and no root damage and group 2 (n = 19) with periodontal bony defect including root/PDL damage on the mesial root of the maxillary first molar. One week after a surgical defect was created, orthodontic protraction of the right maxillary first molar was initiated in both groups. After 2 weeks of protraction, retention of 1 week was established; at the end of this period block sections were made. Histomorphometric analysis through light microscopy of decalcified tissue was performed. Results were statistically analyzed using independent samples t test and analysis of variance (ANOVA) with repeated measures. RESULTS: Differences between groups in total area of bone defect and bone apposition were not statistically significant. Bone apposition calculated as percentage of the bone defect was significantly (t-test) greater (P = 0.002) in group 2 (46.21%) than in group 1 (24.95%). Within each group, area of bone apposition was significantly (ANOVA) greater in the distal than in the mesial quadrants of the bony defect (P = 0.006) and in the apical than the occlusal ones (P = 0.021). CONCLUSION: Following orthodontic tooth movement, periodontal bony defects showed enhanced bony healing compared with alveolar bone defects with no direct association with the periodontal attachment apparatus.     

Microbiological and clinical effects of surgical treatment of localized juvenile periodontitis

Since Actinobacillus actinomycetemcomitans appears to be a key etiologic agent in localized juvenile periodontitis, this study determined the effectiveness of different treatment modalities in suppressing A. actinomycetemcomitans in localized juvenile periodontitis lesions. A total of 25 deep periodontal lesions from 7 patients with localized juvenile periodontitis were included in the study. The test periodontal lesions either received scaling and root planing alone, scaling and root planing together with soft tissue curettage, or modified Widman flap surgery. Subgingival A. actinomycetemcomitans were enumerated using selective culturing. Clinical measurements included changes in probing periodontal attachment level, probing periodontal pocket depth, gingival index, plaque index, and digital subtraction of standardized serial radiographs. The microbiological and clinical effects of treatment were monitored over a period of 16 weeks. All periodontal lesions studied demonstrated high numbers of A. actinomycetemcomitans prior to treatment. Scaling and root planing alone did not markedly change the subgingival A. actinomycetemcomitans counts, nor any of the clinical parameters studied. In contrast, soft tissue curettage as well as modified Widman flap surgery suppressed A. actinomycetemcomitans to undetectable levels immediately after therapy in more than 80% of the lesions studied. A total of 5 periodontal lesions exhibited gain of probing periodontal attachment after subgingival curettage or Widman flap treatment; 3 of these sites revealed no detectable A. actinomycetemcomitans, and the remaining 2 sites harbored only low levels of A. actinomycetemcomitans. 5 periodontal lesions which lost probing attachment after treatment all demonstrated high numbers of subgingival A. actinomycetemcomitans. Changes in alveolar bone, assessed by digital subtraction of serial radiographs, correlated with changes in probing periodontal attachment level, confirming the clinical results. The present study revealed a close relationship between post-treatment A. actinomycetemcomitans levels and the clinical response to treatment, which supports the concept that A. actinomycetemcomitans is an important organism in the etiology of localized juvenile periodontitis. This study also showed that a substantial suppression of subgingival A. actinomycetemcomitans cannot be achieved by periodontal scaling and root planing alone, but can be accomplished by surgical removal of periodontal tissues.(ABSTRACT TRUNCATED AT 400 WORDS)     

Evaluation of clinical and radiographic scoring methods before and after initial periodontal therapy

The purpose of the present study was to compare the determination of the attachment level by probing and by measuring bone heights prior to and after the completion of a hygienic phase of periodontal therapy. 68 patients with moderate to severely advanced periodontitis underwent initial (hygiene phase) therapy including scaling and root planing, oral hygiene instructions and the elimination of plaque retention factors. Measurements of pocket probing depths, probing attachment levels and the location of gingival margins in relation to the cemento-enamel junction were performed at 4 aspects of each tooth with a thin calibrated probe at a baseline examination and 3 to 5 months following treatment. During these 3 to 5 months, the patients were kept in a maintenance care program. On the full-mouth radiographs obtained at baseline, the distance from the cement-to-enamel junction to the marginal alveolar crest was measured in millimeters and as a % of the root length. Furthermore, a subgroup of 11 patients, who were scheduled for modified Widman flap procedures, received another full-mouth radiographic examination before the surgical treatment. In addition, the level of the alveolar crest was assessed with a periodontal probe during the surgical procedure. The comparison of the different clinical and radiographic parameters showed the best correlations between the various radiographic measurements of bone heights (r = 0.87; r = 0.86). Clinical measurements of probing attachment level and probing level of the alveolar crest revealed slightly weaker correlations (r = 0.72). When comparing radiographic bone heights with clinical measurements of probing attachment levels, the lowest correlations were found (r = 0.65; r = 0.61; r = 0.61).     

Clinical and microbiologic study of periodontal surgery by means of apically positioned flaps with and without osseous recontouring

In periodontitis lesions with interproximal craters, periodontal flap surgery with osseous recontouring allows more apical positioning of the soft periodontal tissue than flap surgery without osseous recontouring. The present study determined the clinical and microbiologic responses to periodontal surgery with and without osseous recontouring in adult periodontitis lesions with interproximal craters. In 7 osseous surgery patients, osteoplasty and ostectomy were performed from the lingual/palatal aspect to eliminate interproximal osseous defects and to partly mimic the original alveolar bony transition to neighboring teeth. In 7 nonosseous surgery patients, the surgical flap was adapted to the preexisting osseous level. Clinical monitoring included periodontal probing depth, Plaque Index, gingival bleeding index, and radiographic examination. Samples of the subgingival microbiota were examined. In sites treated with osseous surgery, mean pocket depth was 5.5 mm at baseline, 1.9 mm at 1 month, 2.0 mm at 3 months, and 2.1 mm at 6 months. In sites not receiving osseous recontouring surgery, the corresponding pocket depths were 5.9 mm, 3.1 mm, 3.8 mm, and 4.1 mm. At baseline in the osseous surgery group, Actinobacillus actinomycetemcomitans was recovered from one patient and Porphyromonas gingivalis from 5 patients; posttreatment, these microbiota were not detected in any patient. In the nonosseous surgery group, the presence of A actinomycetemcomitans increased posttreatment, and levels of P gingivalis remained essentially unchanged after therapy. This study suggests that in patients not receiving adjunctive antibiotic therapy, apically positioned flap surgery with osseous recontouring is more effective than apically positioned flap surgery without osseous recontouring in reducing periodontal pocket depth and levels of major periodontal pathogens.     

Fate of pocket epithelium in an apically positioned flap

The fate of periodontal pocket epithelium when sulcular incisions are used in apically positioned flap surgery was investigated by serial histology. Human subjects received apically positioned flap segments on the facial aspect of anterior teeth timed to give 1, 3, 5, 7, 21 and 35 days of healing on the day of extraction. Companion surgeries for comparison consisted of similar flaps, but utilized an inverse bevel primary incision. Assessment of the sulcular incision specimens revealed that epithelial degeneration and dissolution occurred within 7 days and resulted in a collagen-to-collagen attachment of the periodontal flap to the alveolar bone. The inverse bevel incision was consistently effective in removing the pocket epithelium and resulted in healing by a connective tissue union of the flap to the alveolar bone. By 21 days of healing, the 2 surgical methods were indistinguishable histologically. On the basis of this investigation, it is suggested that the inverse bevel primary incision traditionally advocated for apically positioned flap surgeries may be replaced by the more rapid and simple sulcular incision as the preferred technique.     

Clinical and histological characteristics of lyophilized allogenic dura mater in periodontal bony defects in humans

Abstract This clinical and histological study investigated the use of lyophilized, allogenic dura mater (Lyodura ®) as a periodontal implant material in interdental bony defects (2-wall lesions) in humans. For 23 defects in 8 subjects a modified Widman flap was raised, curettage performed and the defects bridged with the implant. The same procedure, without Lyodura implantation, was performed on 23 contralateral teeth. By a standardized method, involving the use of a removable stent, the following clinical measurements were recorded after 24 and 48 weeks: the probing attachment level, the probing bone level, the probing pocket depth and the labial and interdental gingival recession. For the histological study 5 additional, interdental craters arid 5 control defects were treated as in the clinical study. They were block-sectioned after 1,2,6,12 and 24 weeks and processed in the usual manner for routine examination by light and polarization microscopy. From the clinical study it could be concluded that, in absolute values, only the experimental side showed a significant gain in probing attachment level and a greater reduction of the probing pocket depth. In percentage values the labial gingival recession was significantly lower and the bone formation significantly more pronounced on the experimental side. The histological examination showed that the implant remodelled completely without rejection phenomena. It was replaced gradually, after enzymatic breakdown, by the host's own collagen through the action of invading fibroblasts. Bone formation occurred along but never in the implant. The implant material seems to act as a barrier against epithelial downgrowth and infiltration of inflammatory cells.