The development of an altered gingival crevicular microflora in the alloxan-diabetic rat

Dental caries and caries-related periodontitis in type 2 diabetic mice

Diabetic patients are predisposed to periodontal disease as well as dental caries; however, there are contradictory reports about the possible association between dental caries and diabetes. Thus, the authors set out to determine whether diabetes affects onset of dental caries and periodontal disease and to clarify whether dental caries and periodontal disease are associated with each other in diabetic db/db mice. Oral tissue was examined from 68 male mice (diabetic db/db and nondiabetic db/+; aged 20, 30, 40, and 50 weeks) and 20 female mice (db/db and db/+; aged 50 weeks). Macroscopically, caries were seen developing in the diabetic mice by 20 weeks of age. The number of teeth with dental lesions increased with age in the db/db mice at a significantly higher incidence than that of db/+ mice. Histologically, dental caries were detected in 30 of 120 molars in 17 of 20 db/db mice at 50 weeks of age and in 4 of 108 molars in 4 of 18 db/+ mice of the same age. The severity of dental caries in db/db mice was significantly higher than it was in db/+ mice. Dental caries were a primary change that led to bacterial gingivitis and pulpitis. These lesions spread to the dental root and periodontal connective tissue through the apical foramen. Apical periodontitis was more frequent and severe when occurring in close association with dental caries. In conclusion, there is a strong relationship between diabetes and dental caries, but in this model, it is highly probable that the onset of periodontal disease was a secondary change resulting from dental caries.

Relationship Between Periodontitis and Diabetes: Lessons From Rodent Studies

BACKGROUND

A great amount of investigations have provided evidence that both type 1 and type 2 diabetes increase the risk and severity of periodontitis; several alterations in the diabetic periodontium are likely to be involved. Conversely, periodontitis has been shown to have an impact on diabetes, although less evidence is available on the underlying mechanisms. The association between periodontitis and diabetes has been discussed in several reviews over the past years; however, none has focused on the use and contribution of rodent models.

METHODS

This review describes the most commonly used rodent models of diabetes, periodontitis, and the association between the two diseases. Further, we summarize the influence of diabetes in the periodontium as well as the effect of periodontitis on diabetes status with special focus on evidence from experimental studies.

RESULTS

Rodent studies have confirmed human findings and further increased our knowledge on the alterations in the diabetic periodontium. On the other hand, few rodent investigations have explored the consequences of periodontitis for diabetes. Their results clearly indicate that periodontitis can become a health hazard not only for diabetes but also for prediabetes; the exact mechanisms are still to be unraveled.

CONCLUSIONS

Findings from rodent studies have been useful in increasing our understanding of periodontitis, diabetes, and their association and hold great promise for future investigations given the wide variety of possibilities for testing biologic hypotheses.

Update on diabetes mellitus and related oral diseases

Diabetes mellitus (DM) is a group of complex multisystem metabolic disorders characterized by a relative or absolute insufficiency of insulin secretion and/or concomitant resistance to the metabolic action of insulin on target tissues. The chronic hyperglycaemia of diabetes is associated with long-term systemic dysfunction. The present article summarizes current knowledge of DM and details the oral and dental implications of this common endocrine disorder.

Diabetes and periodontal diseases

This position paper on diabetes mellitus was prepared by the Research, Science and Therapy Committee of The American Academy of Periodontology. It is intended to: 1) update members of the dental profession on the diagnosis and medical management of patients with diabetes mellitus; 2) summarize current knowledge on the relation between diabetes mellitus and periodontal diseases; 3) provide an overview of factors in diabetic patients relevant to understanding the pathogenesis of periodontal diseases in these subjects; 4) outline special considerations associated with treatment of periodontal diseases in diabetic patients; and 5) discuss possible approaches to the management of diabetic emergencies in the dental office.

Tetracyclines inhibit connective tissue breakdown by multiple non-antimicrobial mechanisms

A seminal experiment involving a germ-free rat model of connective tissue breakdown (followed soon thereafter by a series of in vitro studies) identified an unexpected non-antimicrobial property of tetracyclines (TCs). This ability of TCs to inhibit matrix metalloproteinases (MMPs) such as collagenase was found to reflect multiple direct and indirect mechanisms of action, and to be therapeutically useful in a variety of dental (e.g., adult periodontitis) and medical (e.g., arthritis, osteoporosis, cancer) diseases. The site on the TC molecule responsible for its MMP-inhibitory activity was identified which led to the development of a series of chemically modified non-antimicrobial analogs, called CMTs, which also have therapeutic potential but do not appear to induce antibiotic side-effects. Longitudinal double-blind studies on humans with adult periodontitis have demonstrated that a sub-antimicrobial dose of doxycycline (previously reported to suppress collagenase activity in the periodontal pocket) is safe and effective and has recently been approved by the FDA as an adjunct to scaling and root planing.

Enhanced interaction of advanced glycation end products with their cellular receptor RAGE: implications for the pathogenesis of accelerated periodontal disease in diabetes

The prevalence and severity of periodontal disease is increased in patients with both insulin-deficient and insulin-resistant forms of diabetes. While a number of underlying factors likely contribute to enhanced periodontal inflammation and alveolar bone loss in diabetes, a common characteristic of these disorders, regardless of etiology, is the presence of hyperglycemia. A critical consequence of hyperglycemia is non-enzymatic glycation and oxidation of proteins and lipids. After a series of reversible reactions which lead to the generation of Schiff bases/Amadori products, a further series of complex molecular rearrangements ensues which results in the formation of the irreversible advanced glycation end products, or AGEs. AGEs accumulate during the process of normal aging in the plasma and tissues, but to an accelerated degree in patients with diabetes. A central means by which AGEs are believed to impart their pathogenic effects is via interaction with specific cellular receptors; the best-characterized of these is receptor for AGE, or RAGE. RAGE, a member of the immunoglobulin superfamily of cell surface molecules, is present in increased levels on target cells in diabetes, such as endothelial cells and monocytes. One consequence of AGE-RAGE interaction is the generation of enhanced cellular oxidant stress, a means by which cell signaling pathways may be activated, thereby resulting in altered cellular phenotype and cellular dysfunction. In this report, we will review our studies to date on AGEs and RAGE and consider the implications of their enhanced interaction in the pathogenesis of accelerated periodontal disease in diabetes.

Physiological approaches to the control of oral biofilms

Evidence that physiological strategies may be potential routes for oral biofilm control has come from (i) observations of the variations in the intra-oral distribution of members of the resident oral microflora, (ii) changes in plaque composition in health and disease, and (iii) data from laboratory model systems. Key physiological factors that were identified as significant in modulating the microflora included the local pH, redox potential (Eh), and nutrient availability. Increases in mutans streptococci and lactobacilli occur at sites with caries; growth of these species is selectively enhanced at low pH. In contrast, periodontal diseases are associated with plaque accumulation, followed by an inflammatory host response. The increases in Gram-negative, proteolytic, and obligately anaerobic bacteria reflect a low redox potential and a change in nutrient status due to the increased flow of gingival crevicular fluid (GCF). Consequently, physiological strategies for oral biofilm control should focus on reducing the frequency of low pH in plaque by (i) inhibiting acid production, (ii) using sugar substitutes, and (iii) promoting alkali generation from arginine or urea supplements. Similarly, strategies to make the pocket environment less favorable to periodonto-pathogens include (i) anti-inflammatory agents to reduce the flow of (and hence nutrient supply by) GCF, (ii) bacterial protease inhibitors, and (iii) redox agents to raise the Eh locally. Most laboratory and clinical findings support the concept of physiological control. However, some data suggest that the ordered structure and metabolically interactive organization of mature dental plaque could generate a community with a high level of homeostasis that is relatively resistant to deliberate external manipulation.

Advanced glycation endproducts (AGEs) induce oxidant stress in the gingiva: a potential mechanism underlying accelerated periodontal disease associated with diabetes

We hypothesized that one mechanism underlying advanced periodontal disease in diabetes may involve oxidant stress in the gingiva, induced by the effects of Advanced Glycation Endproducts (AGEs), the irreversible products of non-enzymatic glycation and oxidation of proteins and lipids which accumulate in diabetic plasma and tissue. Infusion of AGE albumin, a prototypic ligand, into mice resulted in increased generation of thiobarbituric acid reactive substances (TBARS) compared with infusion of non-glycated albumin in the gingiva, as well as in the lung, kidney and brain. Pretreatment of the animals with the antioxidants probucol or N-acetylcysteine (NAC) prevented the generation of TBARS in the gingiva. Affinity-purified antibody to AGEs demonstrated increased immunoreactivity for AGEs in the vasculature and connective tissues of the gingiva in streptozotocin-induced diabetic mice compared to non-diabetic controls. Increased immunoreactivity for AGEs was also demonstrated in the gingiva of diabetic humans compared with non-diabetic individuals via immunohistochemistry and ELISA. Consistent with these data, immunohistochemistry for heme oxygenase-1, a marker of enhanced oxidant stress, was increased in the gingival vasculature of diabetic mice and humans compared with non-diabetic controls. These data suggest that AGEs present in diabetic gingiva may be associated with a state of enhanced oxidant stress, a potential mechanism for accelerated tissue injury.

Diabetes--a risk factor for periodontitis in adults?

With the increasing number of diabetics in an aging population and controversial research reports on the relationship of diabetes to periodontitis, clarification of diabetes as a risk factor for periodontitis would be helpful. This review notes variations in type, metabolic control, and duration of diabetes and highlights the results of studies that have considered these variations. Diabetics who maintained reasonably good metabolic control had not lost more teeth or experienced more periodontal attachment loss than non-diabetics, although they had more periodontal pockets. Poorly-controlled diabetics with extensive calculus on their teeth had more periodontitis and tooth loss than well-controlled diabetics or non-diabetics. Long-duration diabetics were also at greater risk for periodontitis. Mechanisms by which diabetes may contribute to periodontitis include vascular changes, neutrophil dysfunction, altered collagen synthesis, and genetic predisposition. Minimizing plaque and calculus in the oral cavity through careful self-care and regular professional care is important to reduce the risk of periodontitis in diabetics.

New views on periodontal microbiota in special patient categories

The microorganisms in periodontitis of special patient categories have been only partially elucidated. The periodontitis microbiota of HIV-infected individuals, cancer patients on myelosuppressive therapy, and persons with other medical disorders includes common suspected periodontal pathogens as well as enteric rods, pseudomonads, staphylococci and yeasts. Failing implants also may be associated with classical periodontal pathogens as well as primarily nonoral potential pathogens. Refractory periodontitis in systemically healthy adults can show a great variety of oral and nonoral organisms. The frequent occurrence of unusual periodontal organisms in special patient categories may be due to a weakened host response and/or usage of various chemotherapeutic regimens. The unusual organisms may contribute to progressive periodontitis and in leukemia patients may even give rise to life-threatening systemic manifestations. The primary therapeutic goal in special periodontitis patients is control of pathogens and amid the wide range of pathogenic microfloras, an effective treatment strategy should include a comprehensive microbiological analysis, especially if systemic antimicrobial therapy is contemplated.

Tetracyclines inhibit connective tissue breakdown: new therapeutic implications for an old family of drugs

Tetracyclines have long been considered useful adjuncts in peridontal therapy based on their antimicrobial efficacy against putative periodontopathogens. However, recently these drugs were found to inhibit mammalian collagenases and several other matrix metalloproteinases (MMPs) by a mechanism independent of their antimicrobial activity. Evidence is presented that this property may be therapeutically useful in retarding pathologic connective tissue breakdown, including bone resorption. The experiments leading to this discovery are described and possible mechanisms are addressed, including the specificity of tetracyclines' anti-collagenase activity, the role of the drugs' metal ion (Zn2+, Ca2+)-binding capacity, and the site on the tetracycline molecule responsible for this nonantimicrobial property. Of extreme interest, the tetracycline molecule has been chemically modified in multiple ways, generating a new family of compounds called CMTs (chemically modified tetracyclines) that lack antimicrobial but still retain anti-collagenase activity. The first of these CMTs, 4-de-di-methylaminotetracycline, was found not to produce a major side-effect of antimicrobial tetracycline therapy--its administration to experimental animals did not result in the emergence of tetracycline-resistant microorganisms in the oral flora and gut. Numerous examples of the clinical potential of this non-antimicrobial property of tetracyclines in the treatment of periodontal and several medical diseases (e.g., sterile corneal ulcers, rheumatoid arthritis, skin bullous lesions, tumor-induced angiogenesis and metastasis) are discussed.

Rapid periodontal destruction in adult humans with poorly controlled diabetes. A report of 2 cases

Out of a pool of 12 middle-aged or elderly diabetic patients demonstrating rapid periodontal break-down, the 2 oldest cases with follow-up periods of 19 and 16 years are described. The common feature of all 12 patients was that they were either unaware of or unable to control their diabetic condition at the time of the active stage of their periodontal disease. The bone loss progressed in spite of specialist periodontal care and the patients again responded to treatment only after their elevated blood glucose levels had been brought back to normal. Thus, the rapid periodontal breakdown was not found to be associated with the diabetic condition per se, but rather with the hyperglycemia. This clinical follow-up study does not answer the question of whether rapid periodontal destruction occurs in all patients with poorly controlled diabetes. Neither do the observations imply that rapid bone loss would be pathognomic of high blood glucose levels. However, the observations seem to suggest that there may be an inter-relationship between rapid periodontal breakdown and elevated blood glucose levels. Therefore, any sudden change towards an increased progression rate of periodontal breakdown at adult age, as observed from periodic radiographs with intervals of only a few years, should be followed up with a medical examination in order to outrule or verify the possibility of a high blood glucose level.

Microbiological and immunological studies of adult periodontitis in patients with noninsulin-dependent diabetes mellitus

The subgingival microflora and serum antibody response was examined in periodontitis patients with noninsulin-dependent diabetes mellitus (NIDDM), impaired glucose tolerance (IGT), and normal glucose tolerance (NGT). The predominant cultivable microflora was determined for subgingival plaque sampled from two deep periodontal pockets in each of eight adult periodontitis patients with NIDDM. Indirect immunofluorescence for Bacteroides intermedius, Bacteroides gingivalis, and Haemophilus actinomycetemcomitans was used to examine these same samples as well as 186 additional subgingival plaque samples from 47 patients with moderate to severe generalized periodontitis including 25 subjects with NIDDM, six subjects with IGT, and 16 subjects with NGT. Serum antibody levels to 13 microorganisms including seven oral bacterial species and one nonoral control species were measured by enzyme-linked immunosorbent assays (ELISA) in 377 subjects including 84 normal subjects without periodontal disease, 112 normal subjects with periodontitis, 19 periodontally normal subjects with IGT, 65 periodontitis patients with IGT, 15 periodontally normal subjects with NIDDM, and 82 periodontitis patients with NIDDM. Three hundred eighty-two bacterial isolates were recovered from the eight patients. B. intermedius was the most frequently isolated microorganism constituting 16% of the total isolates followed by Wolinella recta and B. gingivalis, which each accounted for 13% of the total. Streptococcus sanguis was the most prevalent microorganism, which was found in 75% of the sites. Subgingival plaque samples examined by immunofluorescence demonstrate a high prevalence of black-pigmented Bacteroides and suggest that the proportion of B. gingivalis but not B. intermedius is higher in NIDDM with periodontitis than in other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Root surface caries and periodontal disease in long-term alloxan diabetic rats

Caries, periodontal disease, and occlusal wear were studied in rats with short-term (one month) and long-term (12 months) untreated alloxan diabetes and in age-matched control rats. Standard laboratory diet and water were given ad libitum. Streptococcus mutans and lactobacilli were naturally occurring inhabitants of the oral bacterial flora. In short-term diabetic rats, there was less dental plaque in the gingival region of the first mandibular molar than in control rats, but the density of leukocytes in the junctional epithelium was increased. Interdentally, the gingival papillae were intact, and the prevalence of foreign material was as low as for the controls. No caries lesions were seen. The proportion of the oral flora which was lactobacilli was positively correlated with the blood glucose level. In long-term diabetic rats, there was more periodontal breakdown than in the age-matched control rats. The periodontal breakdown was always associated with large interdental impactions of foreign material. Caries was seen only in the diabetic rats and in sites with interdental impactions. The decay was shown to start in the cementum at the cemento-enamel junction. The amount of alveolar bone loss, but not the amount of dental caries, was related to the degree of hyperglycemia. Occlusal wear of the molars in long-term diabetic rats was significantly increased as compared with that in the controls.

Diabetes mellitus and associated oral manifestations: a review

Oral research concerning diabetes mellitus has revealed a number of clinical implications. These include, among others, the need for more intense management of the diabetic patient with periodontal disease because tissue destruction may be accelerated, the need for rapid control of oral infection in these patients in order to prevent exacerbation of the existing metabolic imbalance, and the desirability of performing a screening for diabetes mellitus on all patients exhibiting asymptomatic parotid enlargement. Despite the explosion of knowledge concerning diabetes mellitus that has occurred since the discovery of insulin, its definitive etiology continues to elude the scientific community and its treatment remains in the realm of clinical management rather than in that of prevention and cure. In the past, research on diabetes has focused on the role of insulin in seeking the fundamental etiology of diabetes and its complications. With the progression of research, it has become apparent that the initiation and progression of the disease probably involve the interplay of a multiplicity of factors. Hereditary and immunologic factors, as suggested earlier, appear to be operated on by environmental factors, subsequently altering the body's metabolic milieu with widespread primary and secondary effects. Fertile areas for future oral research in diabetes mellitus will include, therefore, genetics, immunology, enzymology, and basement membrane pathology. On the cellular and molecular levels, particularly, the oral cavity and associated structures comprise a somewhat under-investigated area in diabetes mellitus research and, thus, hold great promise for increasing our knowledge of this complex disease.

In vivo crevicular leukocyte response to a chemotactic challenge: inhibition by experimental diabetes

Diabetes in rats inhibits the migration of neutrophils into the healing gingival crevice, an effect associated with impaired in vitro neutrophil chemotactic activity. We recently described the in vivo response of human and rat crevicular neutrophils to a chemotactic challenge and used this assay in the present study on streptozotocin-induced diabetic rats. Optimal concentrations of two chemotactic agents, casein (0.2 mul, 2 mg/ml) or N-formylmethionylleucylphenylalanine (0.2 mul, 10(-4) M), were placed into the gingival crevices of control and diabetic rats (time zero) after the resting neutrophil count was measured. After a 15-min delay, the neutrophil counts and gingival crevicular fluid flow were assessed every 5 min for another 0.5 h. The control rats (n = 14) showed an increase in neutrophil counts which reached maximum levels 30 min after the N-formylmethionylleucylphenylalanine challenge ("peak" neutrophil response) and decreased dramatically 5 min later. Diabetes of 4 days (n = 4), 14 days (n = 8), and 20 days (n = 5) duration reduced the peak neutrophil response 45, 66, and 71%, respectively. Casein produced the same response as N-formylmethionylleucylphenylalanine in control rats. Uncontrolled diabetes of 20 days duration reduced the peak neutrophil response to casein by 83%; diabetics administered insulin on a daily basis showed a reduction of only 34%. The pattern of change in gingival crevicular fluid flow in response to chemoattractants paralleled the neutrophil response. The chemotactic activity of peritoneal neutrophils was assessed in vitro with the agarose gel technique and was found to be correlated (r = 0.84; P < 0.01) with the in vivo chemotactic response in the same rats. If the same in vivo defect is observed in humans with diabetes (or with other systemic diseases associated with leukocyte dysfunction), this test could be useful diagnostically to rapidly assess neutrophil chemotaxis in lieu of in vitro assays and to identify patients who are unusually susceptible to aggressive periodontal disease.