Genetic influences in caries and periodontal diseases

Deciphering the relative roles of heredity and environmental factors ("nature vs. nurture") in the pathogenesis of dental caries and diseases of the periodontium has occupied clinical and basic researchers for decades. Success in the endeavor has come more easily in the case of caries; the complex interactions that occur between host-response mechanisms and putative microbiologic pathogens in periodontal disease have made elucidation of genetic factors in disease susceptibility more difficult. In addition, during the 30-year period between 1958 and 1987, only meager resources were targeted toward the "nature" side of the nature/nurture dipole in periodontology. In this article, we present a brief history of the development of genetic epistemology, then describe the three main research mechanisms by which questions about the hereditary component of diseases in humans can be addressed. A critical discussion of the evidence for a hereditary component in caries susceptibility is next presented, also from a historical perspective. The evolution of knowledge concerning possible genetic ("endogenous", "idiotypic") factors in the pathogenesis of inflammatory periodontal disease is initiated with an analysis of some foreign-language (primarily German) literature that is likely to be unfamiliar to the reader. We identify a turning point at about 1960, when the periodontal research community turned away from genetics in favor of microbiology research. During the past five years, investigators have re-initiated the search for the hereditary component in susceptibility to common adult periodontal disease; this small but growing body of literature is reviewed. Recent applications of in vitro methods for genetic analyses in periodontal research are presented, with an eye toward a future in which persons who are at risk--genetically predisposed--to periodontal disease may be identified and targeted for interventive strategies. Critical is the realization that genes and environment do not act independently of each other; the appearance or magnitude of heritability may differ with various environments.

Molecular characterization of a 40-kDa outer membrane protein, FomA, of Fusobacterium periodonticum and comparison with Fusobacterium nucleatum

The 40 kDa-outer membrane protein FomA of Fusobacterium periodonticum ATCC 33693 was found to exhibit heat modifiable properties, typical for a porin, and N-terminal sequencing indicated a close relationship to the porin FomA of Fusobacterium nucleatum. A polymerase chain reaction approach was therefore applied for sequencing the fomA gene of F. periodonticum, and nucleotide and deduced amino acid sequences were aligned and compared with the corresponding sequences of different strains of F. nucleatum. In all strains we found a common protein upstream of the fomA gene. The noncoding area upstream of the putative -35 region of the F. periodonticum fomA gene exhibited little sequence similarity with the F. nucleatum gene. The transcriptional unit of FomA, on the other hand, was very similar, with the similarities concentrated in domains that were interspersed with hypervariable regions. A topology model was made and compared with those made for F. nucleatum. This indicated that the great similarities reside in the membrane-spanning segments of the protein, while most cell surface exposed loops were hypervariable. The results strongly support the proposed model for FomA and also indicate that these taxa are related but on a lower level than the subspecies level. The codon usage of F. periodonticum is comparable to that of F. nucleatum, and the triplet AGA is the only codon used for arginine.

Longitudinal dynamics of infection and serum antibody in A. actinomycetemcomitans periodontitis

OBJECTS

This report describes one of the first prospective studies delineating the relationship between infection, host antibody responses and disease exacerbations and remissions in a distinct subset of periodontitis patients infected with A. actinomycetemcomitans.

DESIGN

The design of this longitudinal study included visits for each patient approximately every 2 months for up to 3 years.

SUBJECTS AND METHODS

Subjects (n=51) included 16 adult periodontitis (AP) and 11 early-onset periodontitis (EOP) patients with elevated serum IgG antibody to A. actinomycetemcomitans and infection with this microorganism, 12 AP patients with normal levels of anti-Aa antibody, and 12 normal subjects. MEASUREMENT OUTCOMES: Clinical parameters included a gingival index, plaque index, bleeding on probing, pocket depth, and attachment level. Disease activity was defined as loss of attachment during the monitoring intervals. Serum IgG, IgM and IgA antibody to A. actinomycetemcomitans Y4 (serotype b) was quantitated using an ELISA. Subgingival plaque samples were examined for A. actinomycetemcomitans using colony immunoblotting. Human serum IgG antibody specificities to outer membrane antigens (OMA) of A. actinomycetemcomitans Y4 were determined using Western immunoblotting.

RESULTS

A. actinomycetemcomitans-infected AP patients had a higher frequency of teeth infected when compared to the EOP patients. However, the EOP patients exhibited a trend for higher levels of A. actinomycetemcomitans in those teeth that were infected. Active disease patients demonstrated a significantly greater frequency of infected sites, as well as significant elevations in the proportions of A. actinomycetemcomitans. Both EOP and AP groups showed significantly elevated IgG, IgM and IgA antibody to A. actinomycetemcomitans when compared to a periodontally normal group. The level of IgG antibody was significantly elevated in A. actinomycetemcomitans-positive patients with active disease, while IgA antibody was decreased in a number of the active group patients. Plaque samples derived from active sites showed a clear and significant increase in A. actinomycetemcomitans that occurred from 2-6 months prior to the identification of disease activity. Approximately 70% of the active disease patients showed an increase in IgG antibody level by 2-4 months prior to disease activity. Studies of the antigen reactivity patterns of serum IgG indicated that antibody to antigens of 65, 58, 48, 29 and 24 kDa were more frequent in patients who showed active disease, while those patients with the greatest frequency of active disease appeared to show a general decrease in the recognition of the A. actinomycetemcomitans OMA.

CONCLUSIONS

It appears that A. actinomycetemcomitans infection relates to a particular type of disease with accompanying antibody responses that reflect periods of active disease. The dynamics of A. actinomycetemcomitans infection and the level and specificity of systemic antibody responses to this pathogen support an important contribution of the immune response to managing this infection.

Functional properties of nonhuman primate antibody to Porphyromonas gingivalis

The nonhuman primate (NHP) serves as a useful model for examining the host-parasite interactions in Porphyromonas gingivalis-associated periodontal disease. This study determined the influence of NHP sera on (i) the direct killing of P. gingivalis, (ii) P. gingivalis-induced superoxide anion (O2-) release from human polymorphonuclear leukocytes (PMNs), and (iii) the ability of PMNs to bind and phagocytize P. gingivalis. Three types of NHP sera were utilized: (i) normal or baseline sera; (ii) sera obtained after ligature-induced periodontitis; and (iii) sera obtained following active immunization with formalinized P. gingivalis. All assays were performed with or without the addition of human complement. Significantly more (P < 0.01) direct killing of P. gingivalis occurred with immunized sera and complement than with any of the other treatments. The sera from ligature-induced periodontitis NHPs had significantly less (P < 0.03) killing capacity than the baseline sera, which contained natural antibody produced to P. gingivalis colonization. Sera from immunized NHPs were used to opsonize P. gingivalis and caused significantly greater (P < 0.01) levels of O2- release from PMNs. Finally, the sera from immunized NHPs significantly enhanced (P < 0.009) the uptake of P. gingivalis by PMNs, although binding of the bacteria to PMNs was similar among all three serum types. Active immunization of NHPs with P. gingivalis elicited a functional antibody that enhanced direct killing, positively influenced the activation of PMNs, and enhanced the ability of PMNs to phagocytize P. gingivalis. Moreover, antibody produced as a sequela of progressing periodontitis appeared to lack these functions. A wide variability in functional capacity of the sera from individual NHPs, which may contribute to an individual's susceptibility to P. gingivalis-induced disease, was noted. This variability suggested that results from functional tests of serum antibody may aid in predicting host susceptibility to disease and response to therapy.

Comparative virulence of periodontopathogens in a mouse abscess model

OBJECTIVE(S)

This report compares the virulence of selected strains of P. gingivalis, A. actinomycetemcomitans, C. rectus, F. nucleatum and T. denticola in a murine model as a measure of pathogenic potential of these oral microorganisms. The characteristics of the tissue destruction associated with these monoinfections were then related to a potential model for bacterial synergism in progressing periodontitis.

DESIGN AND METHODS

All bacterial strains were grown to mid-logarithmic to early stationary growth phase, harvested and used at various doses to challenge BALB/c normal and BALB/c dexamethasone (DEX) treated mice to mimic a neutrophil dysfunction. The characteristics of tissue destruction, and overt tissue destructive capacity of these species were examined as a function of challenge dose and time.

OUTCOME MEASURES

The mice were examined for an interval of approximately 15 days post-challenge and the presence/absence of lesions, localized or generalized nature of the lesion (including size in mm2), and lethality of the infection were assessed.

RESULTS

Comparison of the virulence of the various P. gingivalis strains related to lethality and lesion size associated with destruction of the connective tissue, indicated a virulence capacity of P. gingivalis strains 53977>W50 = T22>3079>33277>381. C. rectus elicited localized necrotic lesions which were limited to the epithelial layers of the skin. The size of the lesions also indicated a graded difference in virulence, such that C. rectus strains 234>576>>33238. A. actinomycetemcomitans caused the formation of classic localized abscesses with a PMN infiltrate and inflammatory exudates. Although each of the A. actinomycetemcomitans strains exhibited a similar virulence pattern in this murine model, A. actinomycetemcomitans serotype b representative strains were potentially more pathogenic with a virulence capacity of 3113D-N = 3975A>JP2 > or = Y4>29523>33384. Both C. rectus and A. actinomycetemcomitans strains showed clear evidence that recent clinical isolates were more virulent than laboratory strains. Challenge with F. nucleatum resulted in tissue destructive responses which were different from those observed with the other strains used in this study. A rapid onset of dose-dependent lesion development, related to the formation of either closed abscesses or open lesions, was observed with F. nucleatum. Tissue involvement was also greater at lower F. nucleatum doses when compared to the other bacteria. F. nucleatum challenge of DEX-treated mice resulted in a shift to open lesions. T. denticola appeared to be more tissue invasive than the other species examined in this study. Challenge of mice with T. denticola resulted in involvement of multiple tissues, including epithelial and connective tissues, as well as appearing to invade muscle layers and deeper tissues. In addition to invading deeper tissues, the resulting lesions took considerably longer to resolve. In the DEX-treated mice (neutrophil depleted), P. gingivalis, C. rectus, and A. actinomycetemcomitans were significantly more virulent. In contrast, while DEX treatment altered the characteristics of lesions caused by F. nucleatum, the extent of lesions produced by F. nucleatum and T. denticola was not substantially enhanced.

CONCLUSIONS

The results obtained from this study suggest that different microorganisms have the ability to provide individual pathologies which may act in an additive/synergistic fashion contributing to the tissue destruction noted in periodontitis.

Smoking and its effects on early-onset periodontitis

The findings of a recent study show that smoking was more prevalent in a group of patients with generalized early-onset periodontitis and adult periodontitis than in patients with localized juvenile periodontitis or healthy periodontium. In patients with generalized early-onset periodontitis, smoking had a significant effect on periodontal attachment loss; these patients had significantly more teeth with affected sites and a greater mean loss of attachment than patients who did not smoke. Thus, the risk of smoking could greatly accelerate tooth loss in this relatively young group of individuals who are already at high risk for progressive periodontal attachment loss.

Clinical and microbiological changes associated with the use of 4 adjunctive systemically administered agents in the treatment of periodontal infections

The purpose of the present investigation was to assess the effects of periodontal surgery and 4 systemically administered agents, Augmentin, tetracycline, ibuprofen or a placebo on clinical and microbiological parameters of periodontal disease. 98 subjects were monitored at 2-month intervals at 6 sites per tooth for clinical parameters. Subgingival plaque samples were taken from the mesial surface of each tooth at each visit and evaluated for their content of 14 subgingival species using DNA probes and a colony lift method. 40 subjects who exhibited loss of attachment > 2.5 mm at 1 or more sites during longitudinal monitoring were treated using modified Widman flap surgery at sites with probing pocket depth > 4 mm, subgingival scaling at all other sites and were randomly assigned 1 of the 4 agents. Treatment was completed within 30 days during which time the subject took the assigned agent. Overall, subjects exhibited a mean attachment level "gain" of 0.34 +/- 0.10 mm (SEM) and a mean pocket depth reduction of 0.62 +/- 0.09 mm 10 +/- 4 months post-therapy. However, certain subjects in each treatment group showed a poor response. Subjects receiving antibiotics exhibited significantly more attachment level "gain" (0.57 +/- 0.15 mm, SEM) than subjects receiving either ibuprofen or a placebo (0.02 +/- 0.10). The differences between Augmentin and tetracycline groups were not significant, nor were the differences between ibuprofen and placebo. 10 months post-therapy, there was a reduction in the number of sites colonized in any subject group by detectable levels (10(3)) of P. gingivalis. Species showing similar reductions were B. forsythus, P. intermedia and P. micros. Subjects receiving systemically administered antibiotics had a significant increase in the proportion of sites colonized by C. ochracea coupled with a greater decrease in the number of sites colonized by P. gingivalis, B. forsythus, P. intermedia and P. micros post-therapy than subjects not receiving antibiotics. The results of this investigation indicate that adjunctive systemic antibiotics increase periodontal attachment "gain" and decrease the levels of some suspected periodontal pathogens in subjects with evidence of current disease progression.

Periodontal attachment loss among adults aged 60+ in South Australia

This study aimed to provide oral epidemiological data describing periodontal destruction among older adults in South Australia. A cross-sectional survey design was employed and periodontal assessments were made among 801 persons aged 6+ drawn at random from the non-institutionalized population. Measurements of pocket depth (PD) and gingival recession (GR) were made at three sites on all teeth and used to compute loss of attachment (LOA). An average of 17 teeth per person were measured. LOA of 4+ mm at one or more sites was observed among 89.1% of persons. A mean of 78.1% of sites per person had LOA of 2+ mm (extent) and the mean LOA at sites with LOA of 2+ mm was 3.09 mm (severity). Extent and severity were greater for males and for persons aged 80+ years. Extent was virtually identical for mesio-buccal and disto-lingual sites, while severity was virtually identical for mid-buccal and disto-lingual sites. Patterns of GR and PD varied according to the jaw and type of tooth. Maxillary first and second molars had the greatest mean LOA, and the majority of LOA in the maxilla was due to PD. In the mandible there was less variation in LOA among anterior and posterior teeth, and LOA tended to be more equally divided between GR and PD. Levels of periodontal destruction of South Australia were broadly similar to results from North American studies of older adults which have used full-mouth periodontal assessments.

Factors associated with different responses to periodontal therapy

In a study of the efficacy of modified Widman flap surgery and scaling and root planning accompanied by 1 of 4 systemic adjunctive agents, Augmentin, tetracycline, ibuprofen or placebo, it was observed that subjects differed in their response to therapy. The difference was only partially accounted for by the adjunctive agent employed. The purpose of the present investigation was to examine clinical and microbiological features in subjects who showed different levels of attachment change post-therapy. 40 subjects were subset into 3 groups based on mean attachment level change post-therapy. 10 poor response subjects showed mean attachment loss; 19 moderate response subjects showed mean attachment gain between 0.02-0.5 mm and 11 good response subjects showed a mean gain of attachment > 0.5 mm. Clinical parameters were measured at 6 sites per tooth both pre- and post-therapy. Microbiological samples were taken from the mesial aspect of each tooth and evaluated individually for their content of 14 subgingival taxa using a colony lift method and DNA probes. % of sites colonized by each species was computed for each subject both pre- and post-therapy. Significant differences were observed among treatment response groups for mean probing pocket depth, attachment level and % of sites with plaque pre-therapy. The poor response subjects had the lowest mean probing pocket depth and attachment level, but the highest plaque levels. Post-therapy, the poor response group exhibited the greatest degree of gingival inflammation as assessed by gingival redness and bleeding on probing.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term follow-up of cross-arch fixed partial dentures in patients with advanced periodontal destruction. Evaluation of the supporting tissues

The aim of the study was to evaluate the periodontal conditions in patients treated more than 10 years ago for advanced periodontal disease and rehabilitated with cross-arch fixed partial dentures (FPDs). Of 50 randomly selected patients, 34 subjects carrying 43 FPDs agreed to participate in a clinical and radiographic follow-up examination. The FPDs were divided into three groups on the basis of prosthesis design (end abutments, unilateral cantilever, and bilateral cantilevers) and amount of supporting tissues at the time of bridge installation. Seventy per cent of the FPDs were found to be unchanged, whereas the rest had been modified due to various complications leading to extraction of one or more of the abutment teeth. Six FPDs (14%) had been partially replaced by FPDs anchored to osseointegrated dental implants. A total of 21 (8%) of the original 274 abutment teeth had been extracted. Longitudinal changes in the amount of periodontal support were minimal over the average of 15 years of follow-up. FPD design or initial amount of supporting tissues was found not to have significant influence on longitudinal changes in periodontal conditions. It was concluded that combined periodontal and prosthodontic treatment of patients with advanced loss of periodontal support may provide a high rate of long-term successful outcome, provided proper adequate periodontal and prosthetic treatment and maintenance care are given.

The influence of the design of two different bioresorbable barriers on the results of guided tissue regeneration therapy. An intra-individual comparative study in the monkey

The aim of the present study was to compare two bioresorbable barriers to evaluate whether differences in design influence the result of guided tissue regeneration (GTR) therapy. Twenty-four (24) plaque exposed, recession type defects in 4 monkeys were treated. Contralateral defects were randomized for test or control treatment. During a healing period of 6 weeks, gingival recession resulting in device exposure occurred at 3 test and 10 control sites. One control barrier was exfoliated. Histologically, 9 of the 12 test barriers were completely integrated with the surrounding tissues. At 3 test sites, epithelium had migrated apically outside the barrier to a level not exceeding one-third of the height of the device. Seven of the 11 control barriers were enclosed by dentogingival epithelium. The adjacent connective tissue exhibited local inflammatory cell infiltrates (ICT). At the remaining 4 control sites, the epithelial downgrowth as well as the adjacent ICT areas were limited to the coronal 1/3 of the device. New attachment; i.e., new cementum with inserting collagen fibers, averaged 2.2 mm and 0.8 mm at the test and control sites respectively (P < 0.01). Based on the results of the present study, it was concluded that a bioresorbable GTR device, designed to prevent epithelial downgrowth along the barrier surface, has a higher potential to promote new attachment formation than a device which does not have this property.

Long-time etching at low pH jeopardizes periodontal healing

The purpose of the present investigation was to examine whether the immediate necrotizing effects of low pH etching agents also impair periodontal healing in the long-term perspective. It was concluded that long-time etching (3 min) at low pH of root surfaces surrounded by vital periodontal issues resulted in impaired periodontal healing. In contrast, short-time etching appeared to promote connective tissue formation by preventing epithelialization of the periodontal wound despite its low pH. However, clinical inferences should be drawn with caution from the present results, since healing results recorded at 8 weeks may not prove to be stable, especially for those cases sensitive to the immediate influence of marginal infection such as connective tissue attachments and epithelial junctions, unless optimal oral hygiene is maintained. Furthermore, the choice of acid may be of importance.

Commercially-prepared allograft material has biological activity in vitro

The well-established finding that implantation of demineralized bone matrix at non-skeletal sites results in formation of cartilage and bone has been attributed to bone morphogenetic proteins/factors. Commercially-available demineralized bone allograft materials are being used currently to reconstruct/regenerate bone. The studies described here focused on establishing biological activity of protein extracts prepared from commercially obtained bone graft material in vitro. Furthermore, the biological activity of these protein extracts in vitro was compared with similar extracts prepared from freshly obtained human bone. Biological activities of bone matrix proteins examined included their ability to promote proliferation, attachment, and migration of gingival fibroblasts using an in vitro system. Guanidine followed by guanidine/EDTA was used to separate bone matrix proteins into proteins associated with soft tissues of bone and proteins retained within the mineral compartment, respectively. Two preparations of each starting material were tested and the biological activity of each preparation was evaluated in triplicate at least three times. Slot blot analysis revealed that commercially-prepared material contained type I collagen; fibronectin; BSP; and BMP-2, 4, and 7. However, the freshly prepared bone extracts appeared to have higher BMP concentrations. The ability of commercial extracts to promote cell proliferation, while significant, was limited and significantly less when compared with similar extracts prepared from freshly obtained bone. All extracts promoted cell attachment significantly, while none of the extracts promoted cell migration. Thus, commercially-prepared material retained proteins having the capacity to influence cell behavior in vivo. However, some biological activity as measured in vitro was lost as a result of tissue processing.

Patterns of antibody response in subjects with periodontitis

Periodontal diseases comprise a heterogeneous group of infections that are difficult to distinguish on a clinical basis alone. The purpose of the present investigation was to group periodontitis subjects according to their elevated serum antibody levels to specific subgingival species. A total of 119 subjects (19-70 years) with evidence of prior periodontal destruction were monitored at 2-month intervals (maximum 8 visits), prior to therapy, using clinical parameters measured at 6 sites per tooth. The probing attachment level was measured twice at each visit, and an increase of > 2.5mm at a site was used to define subjects with progressing disease. Serum samples were obtained from each subject at each visit and the level of antibody determined by enzyme-linked immunosorbent assay to 12 subgingival species. Subgingival plaque samples were taken from the mesial aspect of all teeth in each subject at each visit, and the levels of 14 different subgingival species were determined using a colony-lift method and DNA probes. Subjects were grouped by cluster analysis of their elevated antibody levels using a simple matching coefficient. Ninety-two subjects fell into 9 clusters with 100% similarity; 29 subjects in one cluster group exhibited elevated antibody to none of the test species. Seven subjects in a second cluster group showed elevated antibody to Bacteroides forsythus. Subjects in the other 7 clusters showed elevated antibody to Actinobacillus actinomycetemcomitans serotype a only or in combination with B. forsythus, A. actinomycetemcomitans serotype b, Prevotella intermedia or Porphyromonas gingivalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal pathogens on polytetrafluoroethylene membrane for guided tissue regeneration inhibit healing

This study determined the microbial composition of the apical parts of the expanded polytetrafluoroethylene membrane surfaces facing the gingiva and the tooth in guided tissue regeneration. Microbial and clinical features of 2-to-3 wall periodontal bony defects treated with membranes with and without concomitant use of systemic Augmentin therapy were also determined. 18 patients with 18 study sites participated. 9 patients received systemic 500 mg Augmentin 1 h prior to surgery, and 500 mg TID for 8 days thereafter. 9 patients received no systemic antimicrobial therapy. Microbiological examination was performed 1 h prior to surgery, at the time of membrane removal at week 6, and at 6 months post-surgery. Microbial morphotypes, total viable counts, and the occurrence of selected microbial species were determined by phase-contrast microscopy, selective and non-selective culture, and DNA probes. Study sites were examined for probing pocket depths and attachment levels. At baseline, no microbial or clinical parameter showed statistical differences between groups. At 6 months, the Augmentin group demonstrated a significantly higher (P = 0.032; Student t-test) mean probing attachment gain (36.5% of potential gain to the cemento-enamel junction) than the 9 control patients (22.4% of potential gain). At the time of removal, membranes in the Augmentin group showed significantly fewer organisms than membranes in the control group (52.2 x 10(6) versus 488.6 x 10(6)). Sites free of pathogens on the membrane surface toward the tooth gained the most clinical attachment, even in the presence of various pathogens on the gingiva-facing membrane surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns and rates of growth of microcosm dental plaque biofilms

Rates of growth in wet weight and changes in them over time were established for microcosm dental plaques cultured from the mixed salivary bacteria in an artificial mouth. Standardized conditions included a continuous supply of medium containing 0.25% mucin and 1.5 ml of 5% w/v sucrose in 6 min every 8 h. Plaques were weighed daily. Plaque wet weight and total protein were highly correlated. Plaque doubling times were 3-7 h over day 1 and 9-21 h over day 2, which is similar to in vivo plaques. Subsequently, growth curves were either linear or between a linear and exponential increase. Evidence was obtained for plaque blooms. Methyl paraben (0.2%) applied for 15 min (3.75 ml) 6 times daily inhibited growth but only for 3 days, after which the rate was similar to control plaques, indicating that selection for resistance had occurred. It was concluded that the regulation of plaque growth rates is complex and does not conform to simple growth pattern models. Detailed studies of plaque growth and the effects of antiplaque agents can be carried out using this experimental system.

Simultaneous isolation of Actinobacillus actinomycetemcomitans from subgingival and extracrevicular locations of the mouth

In the present study, a total of 619 subgingival and extracrevicular samples from 66 early-onset periodontitis, 42 adult periodontitis/gingivitis and 36 treated Actinobacillus actinomycetemcomitans-associated periodontitis patients were selectively cultivated for presence of A. actinomycetemcomitans. The organism was recovered from 68% cases with early-onset periodontitis, 24% cases with adult periodontitis/gingivitis and 50% of treated patients. Associations between recovery from pooled subgingival plaque and samples from extracrevicular locations as well as between different extracrevicular samples, were not heterogeneous with regard to different groups with the exception for cheek/saliva comparisons (odds ratios: early-onset periodontitis 825; adult periodontitis 8.1; treated patients 117; 0.05 < p < 0.1). For associations between recovery of A. actinomycetemcomitans from pooled subgingival plaque/extracrevicular samples, Mantel-Haenszel's odds ratios of between 12.2 and 21.6 were calculated (p < 0.0001). The organism was isolated from 17 cheek mucosa samples of 18 patients identified as still harboring the organism after therapy. Present results point to the considerable value of cheek mucosa samples especially in treated patients to diagnose persistent A. actinomycetemcomitans colonization of the oral cavity.

Guided tissue regeneration in human furcation defects after using a biodegradable barrier: a multi-center feasibility study

This multi-center study evaluated guided tissue regeneration (GTR) in Class II furcation defects using a polylactic acid biodegradable barrier in 29 patients with mandibular and maxillary molar defects. Following an initial hygienic phase, surgical flaps were elevated, and the sites scaled and root planed. Furcation defect perimeter was measured and a customized barrier (thickness 600 to 750 mu) was applied to cover the defect. Barriers adhered directly to tooth and bone. At baseline, sites were measured for probing depth (PD) (6.0 +/- 0.2 [SE] mm), gingival margin location (GML) (-0.2 +/- 0.2 mm), and attachment level in both vertical (AL-V) (6.2 +/- 0.2 mm) and horizontal (AL-H) (5.4 +/- 0.2 mm) directions. After the surgical procedure, there was good compatibility between the gingival tissues and barrier material. Clinically, barriers fragmented and became displaced in 3 to 6 weeks. Substantial granulation tissue was sometimes present between barrier and root surfaces. Comprehensive periodontal examination parameters were measured 3, 4, 6, 9, and 12 months after baseline. A repeated measures ANOVA was used to evaluate changes from baseline. At 6 and 12 months postsurgery, GML was close to the presurgical level (-0.5 +/- 0.2 mm). There was clinically and statistically significant improvement in all other parameters: mean PD reduction (2.2 mm), AL-V gain (1.7 mm), and AL-H gain (2.5 mm). These results indicated favorable clinical regenerative outcomes after using this barrier material in Class II furcation defects in humans.

Risk factors for periodontal diseases in Ilala, Tanzania

The purpose of this study was to evaluate associations between periodontal diseases and the common risk factors in Ilala, Tanzania. To determine behavioural and socioeconomic background, a total of 1764 subjects (827 males and 937 females) aged 3-84 years were randomly selected and interviewed. The subjects were examined clinically for the presence of plaque, calculus, gingival inflammation, periodontal probing depths and gingival recessions. Logistic regression analyses showed that the risk factors for gingivitis were male sex, presence of plaque or calculus and use of local "mswaki", the risk factors for periodontal pockets were age of 35 years or more, presence of plaque, and rural residence. The risk factors for gingival recession were identified as age of 35 years or more, male sex, lower educational status, presence of plaque and gingival inflammation. The most significant risk factors to have periodontal diseases in this study population were age, sex, education, rural residence, plaque and calculus.

Localization and expression of osteopontin in mineralized and nonmineralized tissues of the periodontium

To summarize results from various studies focusing on determining the expression/localization of BSP and OPN during tooth root development, there is general agreement that OPN is expressed/localized to the root surface during cementogenesis and is also seen throughout the PDL region. The expression/localization of OPN to odontoblasts and its role in dentinogenesis is less apparent. Recent studies directed at establishing odontoblast cell lines should help to resolve this conflict. Studies on BSP expression during tooth root formation indicate a very precise expression and localization of this molecule during cementogenesis indicating that this molecule may play an important role in the formation of this mineralized tissue. However, as with OPN, the expression of BSP and its role in dentin formation is not clearly defined.

Characterization of nodules induced by bioactive glass on cultured periodontal-ligament fibroblasts

We previously reported that materials leached from bioactive glass (BG) and vitamin D3 induced the formation of nodules on cultured periodontal-ligament fibroblasts (PLF). In this study, we have investigated the relationship between the conditions of the materials and nodule formation, analyzed morphologically, and also studied whether the production of nodules was specific to cultured PLF. PLF and skin fibroblasts were cultured in the presence or absence of BG. The amounts of calcium, phosphate, sodium and silicon in the culture medium and the number of nodules were measured at the 55th day. The nodules were observed microscopically and analyzed using an X-ray microanalyzer. In PLF, nodules were formed regardless of the presence or absence of BG; however, they were more numerous in the presence of BG. In skin fibroblasts, nodules were not observed. The amounts of calcium and silicon were higher in the presence of BG, while the amount of phosphate was lower. The nodules appeared crystalline with a spongy structure and contained calcium and phosphorus. Our results show that the nodules were associated with PLF and precipitated by the materials (higher concentrations of calcium and silicon), and they were spongy crystal composed of calcium and phosphorus.

Critical issues in periodontal research

The purpose of this paper is to highlight briefly the major achievements and the remaining critical issues in the areas of epidemiology, microbiology, pathogenesis, diagnosis, and therapy. Periodontitis affects a relatively small proportion of study populations in the United States and other countries. Prevalence may be decreasing, but that remains to be seen. The identity and characteristics of susceptible individuals and groups are not known, and risk indicators for severe disease are only beginning to be identified. A very large number of different microbial species has been implicated in the etiology. It seems unlikely that all of these are essential participants. Essential participants need to be identified and better characterized. Whether putative pathogens are members of the commensal flora or exogenous species that must be transmitted is unclear. The relationship between the presence of a pathogenic flora and disease status is obscure. Pathogenic bacterial species are essential, but insufficient to cause disease. A susceptible host and local environmental factors--for example, elevated iron concentration--may be necessary for disease to occur. Many clonal types may not be virulent, and numbers greater than certain threshold levels appear to be necessary. The pathways by which bone and connective tissues of the periodontium are destroyed are sufficiently understood to permit development of therapies aimed at their modification. Examples are the use of vaccines, topical application of anti-inflammatory drugs, and use of chemically modified tetracyclines.

Successful bone fill in late peri-implant defects using guided tissue regeneration. A short communication

Severe loss of peri-implant supporting bone traditionally leads to the removal of the affected implant, but this may not be necessary in all cases. This paper presents a novel treatment approach aimed at the successful regeneration of bone lost to peri-implantitis using guided tissue regeneration (GTR). Four years after implant placement two patients presented with severe peri-implant tissue breakdown. Clinical signs of disease included bleeding on probing, suppuration, increased probeable pocket depth (4 to 9 mm) and a decreased level of clinical attachment (2 to 10 mm). Radiographic analysis revealed 2.6 to 7.1 mm loss of supporting bone. Treatment of these lesions included raising flaps, wound debridement, and rinsing with sterile saline and 0.2% chlorhexidine digluconate. Subsequently, ePTFE membranes were adapted around the necks of the implants and the flaps sutured around the necks of the implants, allowing for transmucosal healing. Both patients were placed on a 10-day antibiotic regimen and instructed to rinse twice daily with a 0.12% chlorhexidine solution. They were reevaluated every 3 weeks at which time professional plaque control was performed. After 4 1/2 and 6 1/2 months, respectively, the membranes required removal due to infection. The radiographic analysis 1 year after membrane removal revealed 1.5 to 3.6 mm of bone gain. As a result of regenerative therapy the implants in both these patients were successfully maintained. It can be concluded that implants with severe loss of bone resulting from peri-implantitis need not always be extracted. A potential approach for the treatment of peri-implant bone destruction is GTR therapy using strict attention to good antimicrobial therapy.

Membrane-guided bone regeneration. Segmental radius defects studied in the rabbit

We tested the principle of guided tissue regeneration (GTR) for healing segmental long-bone defects. 7 mm (3 animals) or 10 mm (5 animals) long segmental defects were created in the diaphyses of both radii in 8 rabbits. The defect on one side was covered with a barrier membrane of expanded polytetrafluoroethylene membrane shaped as a tube, while the contralateral side with no membrane served as the control. Healing was followed with radiographs obtained repeatedly during a 13- (n 3) or 27- (n 5) week period. Thereafter, the animals were killed and ground sections of the defect sites were prepared for histologic examination. Radiographically, the control sites showed some early subperiosteal callus formation and nonunion of the defects after 6 weeks. The bone ends were rounded off and sealed with cortical bone. No major changes were noted after 6 weeks. At the test sites, subperiosteal bone formation at the bone ends was first observed radiographically at 2 weeks. At 9 weeks, a thin cortical bone bridged the defect along the inner surface of the membrane. Histologically, an interrupted line of thin, cortical bone was observed along the inner surface of the barrier membrane. Fatty bone marrow occupied the central and largest volume of the defect. We conclude that it seems possible to use the principle of GTR to accomplish bone union of segmental long-bone defects.

The effect of flap management and bioresorbable occlusive devices in GTR treatment of degree III furcation defects. An experimental study in dogs

The present experiment on guided tissue regeneration had 2 objectives namely: (i) to study if an improved anchorage of the soft tissue flaps during the initial healing period after membrane placement would reduce the tendency for soft tissue recession and allow for healing of also large furcation defects; (ii) to determine if the use of biodegradable membranes in GTR procedures may promote new attachment formation in degree III furcation defects. 2 experiments were performed which included 5 and 8 dogs each. In each animal, the 3rd premolar of the left or right side of the mandible was selected as test site using the contralateral tooth as control. 2 months prior to the start of the experiment, the 2nd and 4th premolars in each side of the mandible were extracted. The extractions were performed to create a large edentulous space mesial and distal to the 3rd premolar. During GTR therapy the incisions prepared in this edentulous region were used to allow proper suture retention and flap stability during the initial phase of healing. In study 1, furcation defects (degree III) were prepared and subsequently treated according to GTR using e-PTFE membranes in the test and no membrane in the control site. In study 2, a bioresorbable membrane (Resolut) was installed in the test and an e-PTFE membrane in the control sites. The non-resorbable membranes were removed after 30 days. The animals were sacrificed 5 months after reconstructive surgery, biopsies were harvested, sectioned and analyzed histologically for new connective tissue attachment and bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Removal of interproximal subgingival plaque by hand and automatic toothbrushes

Subgingival plaque removal at interproximal sites by automatic and hand toothbrushes was compared with control sites at which cleansing was not performed. There were 58 patients, 35 to 63 years of age, each with one hopeless tooth requiring extraction. Each patient was randomly assigned to one of four test groups: hand brush; automatic toothbrush 1; automatic toothbrush 2; and no brushing. The brushing instructions as stated by the manufacturers were demonstrated and the patient brushed the sextant containing the test tooth for 20 seconds. The level of the gingival margin was marked at each interproximal test site. The teeth were extracted and processed for SEM, and subgingival plaque was viewed at X100 and X2000 magnifications. A montage of photomicrographs of the gingival groove to the occlusal margin of the bacterial plaque at X100 magnification was made and the distance from the groove to the margin was measured. An ANOVA was performed using P = 0.05 level for significance. Due to processing difficulties, only 33 specimens were available for analysis. The average distances from the groove to the subgingival plaque front for the four test groups were 0.514, 0.132, 0.163, and 0.111 mm respectively. The maximum distance (1.5 mm) of plaque removal was greatest for the hand toothbrush. Due to the large standard deviation (0.636 compared to 0.146, 0.250, and 0.124 respectively), the hand brushing group was excluded from ANOVA. There were no statistically significant differences among the automatic toothbrushes and the no brushing control (P = 0.8393). It was concluded that a single session of oral hygiene instruction with an automatic toothbrush did not result in subgingival interproximal plaque cleansing.

The microbiota of osseointegrated implants in patients with a history of periodontal disease

The purpose of this study was to determine the presence of suspected periodontal pathogens in the peri-implant microflora of osseointegrated implants exposed 3 and 6 months to the oral environment of patients previously treated for periodontal disease. Subgingival microbial samples were taken in the deepest residual pocket of each quadrant in 10 patients before placement of ITI implants and in 10 patients before abutment connection of Brånemark implants. The samples were cultured using continuous anaerobic techniques. 4 patients were positive for P. gingivalis, 13 for P. intermedia, 2 for A. actinomycetemcomitans, 16 for Fusobacterium, 7 for C. rectus and 12 showed microscopic evidence of spirochetes. After 3 and 6 months exposure of the implants to the oral environment, one sample was obtained from the peri-implant sulcus in each patient. P. gingivalis was found in 2 patients in the peri-implant samples after 3 and 6 months. 6 peri-implant samples were positive for P. intermedia after 3 months, 7 after 6 months. Fusobacterium was present in 13 peri-implant samples after 3, and in 12 samples after 6 months. 4 patients showed evidence of for C. rectus after 3 months, 2 after 6 months. Spirochetes were seen in 3 peri-implant samples after 3 and in 5 after 6 months. None of the implants were found to be colonized by A. actinomycetemcomitans, although the organism was detected on teeth in 1 individual. Similar distribution patterns were noted for ITI and Brånemark type implants.(ABSTRACT TRUNCATED AT 250 WORDS)

Root surface texture and early cell and tissue colonization after different etching modalities

The purpose of the present study was to compare the texture of dentin surfaces after etching with citric and phosphoric acids as well as EDTA with respect to mode of application and exposure time, and to assess possible effects on early cell and tissue colonization. It was concluded that EDTA operating at neutral pH was able to selectively remove mineral from a dentin surface, exposing a collagenous matrix. This was in contrast to etching with citric and phosphoric acids, both of which operate at a low pH. They both appeared to remove not only the mineral component but also the collagenous matrix. EDTA-treated dentin surfaces, compared to surfaces etched at low pH, appeared to be more inviting for cellular colonization and subsequent connective tissue formation. The reason for this may have been twofold: Dentin surfaces etched with an etching agent operating at neutral pH, as indicated above, retain more exposed collagen fibers than dentin surfaces etched at low pH. Furthermore, it can not be excluded that a low pH etching agent necrotized an area of the periodontal ligament in the immediate vicinity of the denuded dentin surfaces.

Overview of effects of electrical stimulation on osteogenesis and alveolar bone

One endpoint of periodontal therapy is to regenerate structure lost to periodontal disease. Periodontal regeneration requires both formation of a new connective tissue attachment to the tooth and formation of alveolar bone. Several procedural advances may support regeneration of the attachment, however, regeneration of alveolar bone does not occur consistently. Therefore, factors which stimulate bone repair are areas for research in periodontal reconstructive therapy. Effects of cytokines or growth factors on bone repair are examples of such areas. Another one is electrical stimulation which naturally occurs in bone, and as such bone may be particularly susceptible to electrical therapy. This overview describes the potential of electrical stimulation for bone regeneration and applications in alveolar and periodontal research.

Clinical and experimental bone changes after intraosseous implantation

Long-term prosthodontic rehabilitation has been extensively documented with the use of osseointegrated biocompatible materials in the mandible and maxilla with resultant improvements in quality of life for patients. In addition, clinical evidence is accumulating to show that mandibular atrophy may slow and even be reversed after implantation. Increased bone height and density have been reported: a finding not unexpected in the light of Wolff's law, which is a universal response of bone to increased functional loads.

Increased intracellular levels of lysosomal beta-glucuronidase in peripheral blood PMNs from humans with rapidly progressive periodontitis

Release of potent lysosomal enzymes by degranulation of polymorphonuclear leukocytes (PMNs) in host gingiva may contribute significantly to tissue destruction and the pathogenesis of periodontal disease. A pilot study established that peripheral blood PMNs from humans with rapidly progressive periodontitis (RPP) contained significantly increased amounts of intracellular lysosomal beta-glucuronidase as compared to healthy controls. This investigation gained insight into the question: are the increased levels of beta-glucuronidase in persons with RPP an a priori genetically determined PMN characteristic, or a reactive phenomenon induced by the periodontal disease process during granulopoiesis? Twelve healthy controls and twelve otherwise healthy individuals with RPP participated in a repeated measures design to T0 (initial, baseline), T1 (four weeks after disease control therapy), and T2 (two months later). At each visit clinical indices (GI, pocket depths, GCF flow, plaque index) were performed and peripheral blood obtained. PMNs were isolated and suspended as 5 x 10(6) cells in 2.0 ml of HBSS. PMN suspensions were tested for total intracellular beta-glucuronidase, degranulation induced by 1 x 10(-6)M and 5 x 10(-7) M FMLP challenges, and unchallenged for non-specific enzyme release. PMNs from individuals with RPP contained significantly higher absolute amounts of beta-glucuronidase and released greater absolute amounts at FMLP challenge at T0, T1, and T2 compared to controls. No relationship was found between any of the clinical indices and beta-glucuronidase levels and no pattern was discovered relating to the repeated measures over time. We conclude that RPP peripheral blood PMNs contain elevated levels of beta-glucuronidase that are not induced by the periodontal disease process.

Controlled clinical evaluation of the subpedicle connective tissue graft for the coverage of gingival recession

The purpose of this study was to clinically evaluate the 1-year coverage of gingival recessions by a subpedicle connective tissue graft according to the original technique compared to untreated recessions by measuring probing sulcus depth (PSD), height of keratinized tissue (HKT), and mucogingival junction location changes. Paired gingival recessions were selected in 15 patients. In each patient, one recession was randomly assigned for treatment (test group) and the other recession was left untreated (control group) for 1 year. Surgery consisted of a connective tissue graft covered by a double papilla full thickness flap. Height of recession (HR), PSD, HKT, and cemento-enamel junction to mucogingival junction distance (CEJ-MGJ) were recorded with a calibrated probe before surgery and 1 year postoperatively. The control group showed no statistically significant differences in any of the parameters. In the test group, HR mean decreased significantly (P < 0.0006) from 3.66 mm to 1.09 mm, representing a mean root coverage of 70.5%. HKT mean increased significantly (P < 0.0006) from 1.60 mm to 4.30 mm, and PSD mean showed no statistical difference. CEJ-MGJ remained statistically unchanged. The subpedicle connective tissue graft may provide a good amount of root coverage and a substantial increase of keratinized tissue. Connective tissue grafted beneath the alveolar mucosa does not induce its transformation into keratinized gingival tissue.

Osteoporosis: a risk factor in periodontal disease

Osteoporosis is suspected as a risk factor in periodontal disease, but previous studies have failed to establish a relationship. Possible explanations for this could be lack of precise methods for assessment of osteoporosis in the jaws and confounding of the result by other factors such as age, gender, or smoking. In the present study 12 female patients with osteoporotic fractures (Group O) and 14 normal women (Group N) were examined clinically for plaque (VPI), gingival bleeding (GBI), and loss of attachment on the 6 Ramfjord index teeth. Bone mineral content (BMC) of the mandible and forearm was determined by dual photon scanning. Results were presented as arithmetic means +/- standard error, and differences between groups were tested by 2-sample t-test. The two groups were comparable with respect to age (O: 68.3 +/- 1.8 years, N: 68.1 +/- 1.5 years), menopausal age (O: 47.5 +/- 1.8 years, N: 47.2 +/- 1.3 years), and smoking habits (O: 4 smokers, N: 3 smokers). The osteoporotic women had significantly lower BMC values than controls in the mandible (O: 0.63 +/- 0.04 in U/cm2; N: 0.78 +/- 0.02 in U/cm2, P < 0.01) and forearm (O: 1.05 +/- 0.05 in U/cm; N: 1.28 +/- 0.05 in U/cm, P < 0.01). No significant differences were found with respect to plaque (O: 46.67 +/- 10.00%, N: 36.67 +/- 6.67%) and gingival bleeding (O: 46.67 +/- 11.67%, N: 43.33 +/- 10.00%), whereas significantly greater loss of attachment was seen in osteoporotic women (O: 3.65 +/- 0.18 mm, N: 2.86 +/- 0.19 mm, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of an absorbable collagen membrane in treating Class II furcation defects

Recent research has focused upon the utilization of an absorbable collagen membrane in guided tissue regeneration (GTR). Concern exists as to whether this type of membrane is beneficial in the treatment of periodontal defects. The purpose of this study was to evaluate the effect of a type I bovine collagen membrane on treatment of Class II furcation defects. Twelve systemically healthy patients (six male and six female, ages 32 to 68) were treated. Each had bilateral mandibular furcation defects with attachment loss > or = 6 mm. Prior to surgery all patients completed initial therapy including scaling and root planing. At the time of the surgery, teeth were randomly assigned to either a control (flap debridement alone) or test (flap debridement plus collagen membrane) group. Data were collected on the day of surgery, and 2, 4, and 6 months post-surgery and at the 12 month re-entry surgery. Clinical measurements included probing depth (PD), clinical attachment level (CAL), gingival recession (GR), stent to base of defect (SB), crestal bone to base of defect (CB), width of defect, and mobility. Statistical analysis was performed utilizing the paired t test. Both control and test groups demonstrated significant (P < 0.05) improvement at 12 months re-entry in PD, CAL, SB, and CB when compared to the presurgery status. While there is no significant difference in PD, CAL, GR, width of defect, and mobility between control and test groups, sites treated with the collagen membrane had significantly higher bone fill (SB and CB) at re-entry.(ABSTRACT TRUNCATED AT 250 WORDS)

Subepithelial connective tissue grafts in the treatment of gingival recessions. A comparative study of 2 procedures

Thirty (30) class I and class II recessions in 30 subjects were treated with a subepithelial connective tissue graft procedure. In one group (15 sites), the surgery was carried out in a traditional fashion: the epithelial collar of the graft was preserved and left exposed (CTG group). In the second group (15 sites), the epithelial collar of the graft was removed and the recession areas were conditioned with citric acid. The graft was then sutured and completely immersed under the facial flap which was coronally repositioned (CR group). Clinical assessments included probing depth, probing attachment level, surface area of the recession, and gingival width. These measurements were taken at baseline and at 6 months. In addition, an esthetic evaluation was done. The differences between treatments were not statistically significant except for the augmentation of gingiva (P < or = 0.05). Based on the midfacial measurements taken in the central area of the recession, the mean percentage of root coverage was 69.2%. In the CR group, 3 of the 15 recessions exhibited complete root coverage; the gingival augmentation was 65.5%. In the CTG group, 5 of the 15 recessions exhibited complete root coverage; the gingival augmentation was 94.4%. The mean surface area of root exposure was reduced from 13.82 mm2 and 13.67 mm2 to 2.15 mm2 and 2.34 mm2 for the CR group and the CTG group, respectively. One-hundred percent (100%) of good-to-moderate esthetic results were found by a panel of independent examiners; there was tendency toward better results in the CR group.(ABSTRACT TRUNCATED AT 250 WORDS)

Saliva-bacterium interactions in oral microbial ecology

Saliva is thought to have a significant impact on the colonization of microorganisms in the oral cavity. Salivary components may participate in this process by one of four general mechanisms: binding to microorganisms to facilitate their clearance from the oral cavity, serving as receptors in oral pellicles for microbial adhesion to host surfaces, inhibiting microbial growth or mediating microbial killing, and serving as microbial nutritional substrates. This article reviews information pertinent to the molecular interaction of salivary components with bacteria (primarily the oral streptococci and Actinomyces) and explores the implications of these interactions for oral bacterial colonization and dental plaque formation. Knowledge of the molecular mechanisms controlling bacterial colonization of the oral cavity may suggest methods to prevent not only dental plaque formation but also serious medical infections that may follow microbial colonization of the oral cavity.

Attachment loss trends over 3 years in community-dwelling older adults

Most of our knowledge regarding the natural history of periodontitis in adults has come from clinical studies of dental patients. However, it is known that dental patients usually are not representative of what actually happens in the population. For this type of information, epidemiologic studies are required. The purpose of this paper is to present the trends in attachment loss over a 3-year period in a population of community-dwelling elderly blacks and whites. Specifically, this paper presents attachment loss trends both at the person and site level to address the following issues: 1) whether attachment loss during one period in time makes a person at higher risk for attachment loss at a subsequent period; 2) whether sites with deeper periodontal pockets at baseline are more likely to experience future attachment loss; and 3) whether teeth that experience attachment loss during one time period are more likely to be lost at the next time period. In 1988, the University of North Carolina School of Dentistry initiated the Piedmont 65+ Dental Study, which is a subsample of the parent study, the Piedmont 65+ Study of the Elderly under the direction of investigators from Duke University. The dental study subsample was designed to elicit 800 dentate respondents in the 5-county area who were examined again at 18 and 36 months. Our findings indicated that, for the two 18-month periods investigated, attachment loss during the first period was related positively to the incidence of attachment loss at a subsequent period at the person level, but not at the site level.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal guided tissue regeneration with a new resorbable polylactic acid membrane

The aim of the present study was to evaluate the use of 3 types of biodegradable, high molecular weight DL-lactic acid (PLA) membranes containing respectively 0%, 10%, and 30% low molecular weight oligomers for obtaining guided tissue regeneration following treatment of experimental buccal periodontal defects created surgically in 6 young adult beagle dogs. On the buccal aspects of test and control teeth, a mucoperiostal flap was raised and the buccal alveolar bone removed. The exposed root surfaces were scaled and a notch was prepared in the root surface at the level of the reduced crest. PLA membranes containing respectively 0%, 10% and 30% oligomers, drawn at random, were placed over the experimental defects, while no membrane was placed over the control roots. The animals were sacrificed 2, 4, and 6 months after surgery. For comparison between control sites (without membrane) and experimental sites (with 3 types of membrane), serial bucco-lingual sections were made of the experimental and control sites and studied histologically and histometrically. It appeared that a satisfactory regeneration of the periodontal tissues could be obtained with all 3 types of experimental PLA membranes and statistically significant differences could be observed for epithelial attachment, alveolar bone regrowth, connective tissue attachment, and new cementum formation in the experimental group when compared with the controls. All 3 types of membranes were well tolerated. The resorption of the membranes started in the coronal portions and extended progressively in an apical direction and the resorption time seemed to be related to the content of oligomers. PLA membranes could be used as interesting alternatives for GTR in advanced human periodontal lesions.