Periodontal Environment Research Articles

Microorganisms in closed periapical lesions

The purpose of this study was to investigate the microorganisms of strictly selected closed periapical lesions associated with both refractory endodontic therapy and pulpal calcification. Definitive criteria were established that assured complete clinical isolation of the periapical lesion from the oral and periodontal environment. A total of 13 criteria-referenced lesions were selected from 70 patients with endodontic surgical indications. A well controlled culturing method was used in all cases and samples were taken by one clinician at three separate sites during each surgery. Samples taken at the surgical window and within the body of the lesion served as controls, whilst a third sample was taken at the apex. In all 13 cases, samples taken from the apex yielded microorganisms comprising 63.6% obligate anaerobes and 36.4% facultative anaerobes. Prevalence of the isolated species was 31.8% for Actinomyces sp., 22.7%, Propionibacterium sp., 18.2%Streptococcus sp., 13.6%Staphlyococcus sp., 4.6%Porphyromonas gingivalis, 4.6%Peptostreptococcus micros and 4.6% Gram-negative enterics. The results of this investigation indicate that closed periapical lesions associated with calcified teeth or those resistant to root canal treatment harbour bacteria. The inability to eradicate all root canal microorganisms during root canal treatment, along with anatomical factors, may allow further bacterial colonization of the root apex and surrounding periapical tissues, and consequently prevent healing.

Microorganisms in closed periapical lesions

The purpose of this study was to investigate the microorganisms of strictly selected closed periapical lesions associated with both refractory endodontic therapy and pulpal calcification. Definitive criteria were established that assured complete clinical isolation of the periapical lesion from the oral and periodontal environment. A total of 13 criteria-referenced lesions were selected from 70 patients with endodontic surgical indications. A well controlled culturing method was used in all cases and samples were taken by one clinician at three separate sites during each surgery. Samples taken at the surgical window and within the body of the lesion served as controls, whilst a third sample was taken at the apex. In all 13 cases, samples taken from the apex yielded microorganisms comprising 63.6% obligate anaerobes and 36.4% facultative anaerobes. Prevalence of the isolated species was 31.8% for Actinomyces sp., 22.7% Propionibacterium sp., 18.2% Streptococcus sp., 13.6% Staphlyococcus sp., 4.6% Porphyromonas gingivalis, 4.6% Peptostreptococcus micros and 4.6% Gram-negative enterics. The results of this investigation indicate that closed periapical lesions associated with calcified teeth or those resistant to root canal treatment harbour bacteria. The inability to eradicate all root canal microorganisms during root canal treatment, along with anatomical factors, may allow further bacterial colonization of the root apex and surrounding periapical tissues, and consequently prevent healing.

The bone morphogenetic protein family: multifunctional cellular regulators in the embryo and adult.

Originally identified as the active components within osteoinductive extracts derived from bone, the BMPs now are known to include a large family of proteins within the TGF-beta superfamily of growth and differentiation factors. Members of the BMP family have been determined to be key signaling molecules in embryogenesis, in species ranging from Drosophila to humans. They are involved in delivering positional information, the development of hard tissues (both bones and teeth), as well as soft tissue types. When implanted into adult animals, several of the BMPs have been shown to initiate the complex cellular process resulting in the induction of bone through both the endochondral and intramembranous bone formation pathways. Preclinical studies have shown the ability of these factors to induce bone and heal large bony defects in a variety of models relevant to clinical problems in orthopedics, as well as the oral and maxillofacial/dental areas. For example, implantation of recombinant human BMP-2 (rhBMP-2) has been shown to augment the alveolar ridge in several animal models, and when placed in a periodontal environment to restore not only new bone, but also the attachment tissues. Results from ongoing clinical studies support the ability of rhBMP-2 implants to induce physiologic bone.

Enhanced chemiluminescent assay for measuring the total antioxidant capacity of serum, saliva and crevicular fluid.

This paper reports the development of an enhanced chemiluminescent (ECL) assay for measuring the total antioxidant (AO) capacity of serum, saliva and a fluid collectable from the gum margin called gingival crevicular fluid (GCF). The theory behind the assay is explained, and the optimum conditions for the assay, and for storage of reagents and clinical samples is described. Calibration lines were linear (R > or = 0.99; P < 0.0001) and the within batch coefficient of variations for a water soluble vitamin E analogue (Trolox), serum and saliva samples were < 5%. In saliva and GCF, a characteristic AO response not seen in serum of the same patients, was identified. Total peripheral (serum) and local (saliva) AO capacities (mumol/L Trolox) were investigated in patients with (n = 18) and without (n = 16) adult periodontitis. Serum AO status did not differ between groups. Salivary total AO concentrations were lower in the peridontitis (P) group [175 (53) mumol/L] than in the non-periodontitis (NP) group [254 (110) mumol/L1: P < 0.01], as were saliva:serum AO ratio's [0.37 (0.11) versus 0.5 (0.18): P < 0.01]. Periodontitis patients may have a reduced salivary AO concentration, which could result from, or predispose to, the damaging effects of reactive oxygen species (ROS). The potential for ROS production in the oral and periodontal environment may explain the presence of a specific antioxidant in oral fluids that is not detectable in serum. The ECL assay described provides a rapid, simple and reproducible method of measuring total antioxidant defence in small volumes of biological fluids.

PH Changes Observed in the Inflamed Gingival Crevice Modulate Human Polymorphonuclear Leukocyte Activation In Vitro

Previous studies have noted a positive correlation between gingival inflammation and crevicular pH, which reportedly varies from 6.5 to 8.5. In the present study, we characterized the manner in which deviation from the "physiological" pH of blood (7.2) influences activation of chemotaxis, phagocytosis, superoxide generation, and degranulation by human polymorphonuclear leukocytes (PMNs). Purified PMNs were suspended in HEPES-buffered balanced salts solutions adjusted to pH 6.7, 7.2, 7.7, or 8.2. In a modified Boyden chamber, the chemotactic response to fMet-Leu-Phe was maximal at pH 7.2. In comparison, chemotaxis was significantly depressed at pH 7.7 and pH 8.2 (P < 0.05), but was not significantly different at pH 6.7. Activation of the respiratory burst by fMet-Leu-Phe was optimal at pH 7.2, but was significantly depressed at pH 6.7 and 8.2 (P < 0.05). pH had little effect on N-acetyl-beta-glucosaminidase release from primary granules. However, lactoferrin release from the secondary granules of fMet-Leu-Phe-activated PMNs was significantly lower at pH 7.2 than at pH 6.7 or 8.2 (P < 0.05). Moreover, phagocytosis of opsonized bacteria was significantly lower at pH 7.2 than at pH 7.7. In addition to these effects on functional activation, extracellular pH influenced the magnitude of intracellular Ca2+ mobilization. Peak fMet-Leu-Phe-induced Ca2+ levels were significantly higher at pH 8.2 than at pH 7.2 (P < 0.01). These findings suggest that the pH of the periodontal environment can selectively influence PMN activation, thereby altering the balance between bacteria and the host response.

Interaction of Porphyromonas gingivalis with transferrin

In this study, we characterized the binding of transferrin to Porphyromonas gingivalis using a classical receptor-binding assay, and examined the relationship between the binding and availability of transferrin for the growth of P. gingivalis. The binding of 125I-labeled human transferrin to P. gingivalis occurred rapidly, reversibly and specifically. Scatchard analysis yielded a K d of 1.37 ± 0.16 μM and an apparent number of 1.13 ± 0.26 × 10 5 receptors per cell. The binding of transferrin was much increased when organisms were grown in iron-limited conditions. Among the species of black-pigmented anaerobic rods, those strains of P. gingivalis which had high transferrin-binding activity exhibited unrestricted growth following the addition of transferrin to the hemin-free culture medium. On the other hand, the presence of transferrin in the culture medium did not support unrestricted growth of organisms that had low transferrin-binding activity. These results suggest that the binding of transferrin to P. gingivalis cells may be a preliminary step in iron acquisition, which allows them to survive in the healthy periodontal environment.

Role of Porphyromonas gingivalis-derived fibroblast-activating factor in bone resorption.

A 24-kDa protein was isolated from the outer membrane vesicles of Porphyromaonas gingivalis W50. This protein, referred to as fibroblast-activating factor (FAF), was examined for its bone-resorptive ability by the rat long-bone assay and the mouse bone marrow cell culture system. FAF resulted in a significant release of 45Ca from cultured bones, as well as the formation of tartrate-resistant acid phosphatase-positive monocytes. These cultures were compared with control cells. FAF therefore might be considered a significant bacterially expressed protein which could affect and modulate the resorption or destruction of tissue and alveolar bone in the local periodontal environment.

Change detection on longitudinal data in periodontal research.

Longitudinal data of attachment level (AL) or the alveolar bone level are often used to assess the progression of periodontal disease. This paper tries to identify the most efficient method to detect the changes of AL in a general periodontal research environment; that is, a sequential decision based on multiple sites. Several existing methods suggested in the periodontal research literature such as the tolerance, running median, cusum, and regression methods as well as change-point detection methods in the statistical literature are examined. It is found that the regression method is most convenient among the several methods that are equally effective in change detection. Formulae, tables and their usage are discussed in detail.

ORTHODONTIC ADJUNCTIVE TREATMENT IN FIXED PROSTHODONTICS

The purpose of this article has been to increase the restorative dentist's appreciation for the rationale justifying preprosthodontic orthodontic treatment. It has not been intended to identify all the specific indications for the use of orthodontic treatment to enhance prosthodontic treatment nor has it been intended as a reference to assist the restorative dentist in placing and using orthodontic appliances. Figure 12 illustrates a typical case in which the combination of orthodontic and prosthodontic treatment resulted in a more favorable outcome than prosthodontic treatment alone. When planning prosthodontic treatment, the dentist should embrace a dynamic view of tooth position and determine whether restorative treatment can be enhanced by tooth movement. Improved tooth position can eliminate potentially pathologic occlusion and create a healthier periodontal environment that is easier to maintain. In addition, it permits the dentist to place restorations that often require less natural tooth reduction during preparation, and that are more esthetic, functional, stable, and durable. Orthodontic treatment that accomplishes these benefits may be limited to a partial fixed appliance localized to one segment of an arch or require a more extensive fixed appliance. Much of this treatment can be accomplished by the interested restorative dentist. Addressing more comprehensive orthodontic problems in patients requiring prosthodontic care is best managed through a restorative dentist and orthodontist team approach to treatment.

Periodontics and prosthodontics: Goals, objectives, and clinical reality

Prosthodontics and periodontics are collaborative disciplines. A successful prosthesis depends on a healthy periodontal environment, and periodontal health depends on the continued integrity of the prosthodontic restoration. To facilitate this collaboration, prosthodontists should not only appreciate the periodontic implications of gingival displacement procedures and tooth preparation, but should be knowledgeable about the types of gingival tissues, osseous topography, occlusal effects, and their implications for abutment choice. Working as a team, the periodontist can identify for the prosthodontist a patient's periodontal strengths and limitations. In that way, the prosthodontist can then assume responsibility for a given treatment plan based on a mutual understanding of the critical factors involved.

Characterization of coaggregation between Bacteroides gingivalis T22 and Fusobacterium nucleatum T18

Bacterial adherence is a key factor in the colonization of the oral ecosystem, yet little is known about the mechanisms by which the pathogen Bacteroides gingivalis adheres in the periodontal environment. We examined the ability of strains of B. gingivalis to coaggregate with selected microorganisms isolated from the subgingival microbiota of the cynomolgus monkey. A strong interaction was demonstrated between strains of B. gingivalis and Fusobacterium nucleatum, whereas less pronounced or no interaction was observed with other oral isolates. Electron microscopic examination of coaggregates revealed large masses of bacteria, in which the fusiform F. nucleatum T18 and coccobacillary B. gingivalis T22 cells formed a woven pattern. To investigate this interaction and the nature of the bacterial cell surface molecules involved, we used a microcoaggregation assay. Galactose and galactose-related sugars blocked coaggregation, in contrast with the lack of effect of glucose or glucose-related sugars. The ability of F. nucleatum T18 cells to coaggregate was diminished by pretreatment with pronase. Pretreatment of B. gingivalis T22 cells with pronase resulted in an inhibition of coaggregation, whereas pretreatment with sodium metaperiodate completely abolished coaggregation. These data suggest that the coaggregation between B. gingivalis T22 and F. nucleatum T18 represents a carbohydrate-lectin interaction, mediated by a galactose-containing carbohydrate on B. gingivalis T22 and a protein on F. nucleatum T18.

Phospholipase A activity of extracellular products from Bacteroides melaninogenicus on epithelium tissue cultures.

Seven‐day‐old cultures of epithelial outgrowths from hamster cheek pouch were incubated with 3H‐arachidonic acid for 24 hours and then subjected for 60 and 90 minutes to partially purified preparations of phospholipase A obtained from a strain of Bacteroides melaninogenicus subspecies melaninogenicus and from a strain of the subspecies intermedius, both isolated from periodontal pockets. In the cultures incubated with enzyme there was a significant release of radiolabel into the medium. A lipid analysis of the tissue cultures indicated that incubation with the enzymes produced a loss of the cells' phosphatidyl choline and phosphatidyl ethanolamine and a concomitant release of free fatty acids. These results describe for the first time a possible mechanism for epithelial cell injury mediated by an extracellular product of bacteria from the periodontal environment with phospholipase A activity.

Chronic mucogingival defects in miniature swine.

Controversy surrounds the importance of keratinized gingiva in maintaining periodontal health. A well-defined animal model system is necessary to evaluate longitudinally the role of keratinized gingiva when plaque control is inadequate or where dental procedures (restorative, prosthetic or orthodontic) alter the periodontal environment. Facial gingiva was excised from eight primary incisors in miniature swine. Contralateral teeth were used as controls. The experimental teeth exhibited mucogingival defects at 3 and 6 month observation periods. The secondary teeth erupting into the experimental regions also exhibited recession and chronic mucogingival defects. The marginal tissue in regions devoid of keratinized gingiva demonstrated clinical signs of inflammation. No progressive gingival recession was present. Excision of keratinized gingiva to produce mucogingival defects in swine provides a convenient model system for evaluating the effect of dental procedures on periodontal health where little or no keratinized gingiva is present.

A segmental approach to mandibular molar uprighting

Diagnosis and treatment in molar uprighting are discussed. The over-all objective in molar uprighting is ideal positioning of the molar which will eventually become an abutment tooth for a fixed prosthesis. The ideal position will provide an optimal periodontal environment for the molar(s). The specific objectives concerning protection against inflammatory periodontal diseases and occlusal traumatism, which together determine the optimal periodontal environment, are explained. Emphasis is placed on the biomechanics of molar uprighting which will achieve the desired periodontal treatment result. The specific technique recommended for the instances in which the molar is considerably angulated involves a segmental approach which utilizes a modification of the Burstone root spring. Proper application results in the dissociation of the correction of angulation and the extrusion of the molar tooth. It is explained that molar extrusion is, for the most part, an undesirable side effect of molar uprighting. When extrusion of the periodontally involved molar is required, then it should follow the correction of molar angulation. Other advantages of this approach involve the precision and ease of symmetrical preactivation, favorable load/deflection considerations, the low level of patient discomfort, and the reduced tendency of normal function distorting or dislodging the spring. This technique is compared by these parameters to other popular molar-uprighting techniques. It is recognized that a multidisciplinary approach to this type of dental therapy is ideal and that since treatment planning in individual cases varies greatly, each malocclusion and associated periodontal involvement should be evaluated on an individual case basis.

Direct bonding in the management of an ankylosed second deciduous molar

A simple and efficient bonding procedure has been described for the management of an ankylosed deciduous second molar. This has, in our experience, provided a satisfactory occlusal and periodontal environment in selected patients. Based on a limited number of cases, restorations have been maintained for about two years to date.

Periodontal considerations in implant dentistry

In spite of the tremendous progress that has been made and the information that has been accumulated, the oral implantologist operates with relatively meager knowledge. He works on an empirical platform, only because so little research has been done and so many questions are unanswered. It will probably be years before his science begins to catch up with his art. In the meantime, by borrowing from the wealth of knowledge in the field of periodontology and by applying it directly, he can operate with direction and confidence. The more the oral implantologist appreciates the similarity, almost the congruency, between the periodontal environment of the teeth and that surrounding an endosteal implant, the more frequently he will be able to achieve success in this demanding area. But to do this, he must at present work on an assumption. It is a most logical assumption. Time will give the final answer, but in the meantime, the occlusion must be designed to protect implants from occlusal trauma. Plaque retention must be avoided by (1) using open embrasures, (2) using supragingival margins wherever esthetics will allow them, (3) elimination of furcations, (4) meticulous removal of plaque by the patient, (5) placement of implant posts in attached gingiva rather than movable mucosa wherever feasible, and (6) avoiding muscle pull on the posts.