Role of Streptococcus mutans in human dental decay.

Microbial etiological agents of destructive periodontal diseases

Although specific bacteria, dental plaque, and age are associated with periodontal disease, there are currently no reliable predictors of periodontitis severity. Studies in twins have suggested a genetic contribution to the pathogenesis of periodontitis, but previous attempts to identify genetic markers have been unsuccessful. The pro-inflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) are key regulators of the host responses to microbial infection. IL-1 is also a major modulator of extracellular matrix catabolism and bone resorption. We report a specific genotype of the polymorphic IL-1 gene cluster that was associated with severity of periodontitis in non-smokers, and distinguished individuals with severe periodontitis from those with mild disease (odds ratio 18.9 for ages 40-60 years). Functionally, the specific periodontitis-associated IL-1 genotype comprises a variant in the IL-1B gene that is associated with high levels of IL-1 production. In smokers severe disease was not correlated with genotype. In this study, 86.0% of the severe periodontitis patients were accounted for by either smoking or the IL-1 genotype. This study demonstrates that specific genetic markers, that have been associated with increased IL-1 production, are a strong indicator of susceptibility to severe periodontitis in adults.

The interleukin-1 genotype as a severity factor in adult periodontal disease

This article describes the subgingival microflora of the healthy periodontium, gingivitis, advanced adult periodontitis, and juvenile periodontitis. A total of seven to nine subjects were examined in each of the four periodontal clinical entities listed. The individual bacteriological samples included material from the base of a single periodontal pocket. The sampling, the treatment of the samples, and the bacteriological cultivations were carried out using continuous anaerobic techniques.

Briefly, the healthy gingival sulcus harbored a scant microflora dominated by Gram-positive organisms (85%), usually Streptococcus and facultative Actinomyces species. The development of gingivitis was accompanied by a marked increase in the total number of Gram-negative organisms. Fusobacterium nucleatum, Bacteroides melaninogenicus ss. intermedius, Haemophilus species, and other Gram-negative organisms comprised about 45% of the total gingivitis isolates. Streptococcus and facultative and anaerobic Actinomyces species constituted the majority of the Gram-positive gingivitis isolates. The micro-flora of advanced adult periodontitis was comprised mainly of Gram-negative anaerobic rods (about 75%), B. melaninogenicus ss. asaccharolyticus and F. nucleatum being the most predominant isolates. The deep pocket microflora in juvenile periodontitis was also made up mainly of Gram-negative organisms (about 65%), but was of a nature different from that of adult periodontitis, being predominated by isolates of Bacteroides species and other organisms of unknown species.

The present article also concerns factors of importance for the colonization of Gram-negative anaerobic rods in the oral cavity and periodontal pockets. In vitro experiments showed that cells of B. melaninogenicus ss. asaccharolyticus and other Gram-negative organisms attached in high numbers to epithelial cells, hydrosyapatite (HA) surface, and Gram-positive bacteria when suspended in phosphate-buffered saline; however, the bacterial attachment to epithelial cells and HA was strongly inhibited in the presence of human saliva and serum. In contrast, saliva and serum had little effect upon the attachment of Gram-negative bacteria to Gram-positive bacterial cells. These findings agreed well with data from an in vivo study, in which streptomycin-labeled cells of B. melaninogenicus ss. asaccharolyticus were introduced into the mouth of two volunteers. A significantly higher number of B. melaninogenicus cells was recovered from dental plaque than from the other oral surfaces studied.

The present series of studies has pointed to certain Gram-negative organisms as potential pathogens in rapidly progressing periodontal lesions. The available data on oral microbial ecology suggest that the presence of dental plaque containing Gram-positive organisms may be essential for the attachment and colonization of several Gram-negative species after their initial introduction into the mouth and the periodontal pocket area. The clinical relevance of these findings is discussed.

Subgingival microflora and periodontal disease

The most common forms of destructive periodontal disease have been thought to slowly and continuously progress until treatment or tooth loss. Recently, data have become available which are inconsistent with this "continuous disease" hypothesis. Data from longitudinal monitoring of periodontal attachment levels and alveolar bone in humans and in animals suggest that periodontal disease progresses by recurrent acute episodes. In addition, rates of attachment loss have been measured in individual sites which are faster than those consistent with the continuous disease hypothesis or slower than those expected from estimates of prior loss rates. To account for these observations, a model of destructive periodontal disease is described in which bursts of activity occur for short periods of time in individual sites. These bursts appear to occur randomly at periodontal sites throughout the mouth. Some sites demonstrate a brief active burst of destructive periodontal disease (which could take a few days to a few months) before going into a period of remission. Other sites appear to be free of destructive periodontal disease throughout the individual's life. The sites which demonstrate destructive periodontal activity may show no further activity or could be subject to one or more bursts of activity at later time periods. Comparison of monitored loss rates for a year with mean loss rates prior to monitoring suggested that there may be relatively short periods in an individual's life in which many sites undergo periodontal destruction followed by periods of extended remission. An extension of the random disease model is also suggested in which bursts of destructive periodontal disease activity occur with higher frequency during certain periods of an individual's life.

New concepts of destructive periodontal disease.

This paper describes: (1) a system for classification and treatment of furcation involvements, and (2) a 5-year post-operative evaluation of 100 patients treated for periodontal breakdown in the bi/tri-function areas. The results of this study demonstrate that it is possible to arrest further destruction within the root furcation area. The successful treatment of the multirooted teeth was probably the consequence of: (1) the quasi total elimination of plaque retention areas from the bi/tri-furcation area, and (2) meticulous oral hygiene by the patients.

Periodontal treatment of multirooted teeth. Results after 5 years.

The present investigation was carried out in order to study some aspects of the clinical, roentgenographical and histopathological alterations of periodontal tissues in dogs which during a 4-year period were allowed freely to accumulate plaque.

Twenty inbred Beagle dogs, at the start of the study 10 months of age, were used. During a preparatory period of eight weeks the animals were once weekly subjected to a careful prophylaxis and had their teeth brushed twice daily. At the end of this period the dogs were divided into two groups of ten (test and control). From day zero of experimentation and onwards the teeth of the control dogs were twice daily subjected to meticulous toothbrushing, whereas the teeth of the test dogs were not cleaned. Examinations of the periodontal tissues were performed at days 0, 7, 14, 21, 28 and after 2, 4, 6, 8, 12, 18, 24, 36 and 48 months. Biopsies of different tooth regions were made on day zero and after 6, 12, 18, 24, 36 and 48 months of experiment. In the sections were measured (i) the distance from the cemento-enamel junction (CEJ) to the most apical cells of the dento-gingival epithelium, and (ii) the distance from CEJ to the level of the marginal alveolar bone.

The study demonstrated that it is possible in dogs to establish and maintain a normal gingiva simply by eliminating calculus and then subjecting the animals to daily repeated and carefully performed tooth cleanings. Dogs allowed freely to accumulate plaque rapidly developed signs of gingivitis and eventually also clinical, radiographical and histopathological signs of periodontal tissue breakdown. The observations show that at least one type of periodontal disease is induced by factors within the dental plaque.

Plaque induced periodontal disease in beagle dogs. A 4-year clinical, roentgenographical and histometrical study.

The present investigation was undertaken (1) to analyze the prevalence of root surface caries prior to and after periodontal treatment and (2) to determine the feasibility of using simple clinical criteria for predicting a patient's risk of developing root surface canes following periodontal therapy.

Thirty-one patients were given advanced periodontal treatment including periodontal surgery. At baseline they were examined for oral hygiene status, periodontal status, root surface canes experience and number of lactobacilli per ml saliva as evaluated by the Dentocult® dip-slide method. Follow-up examinations 1, 2 and 4 years after baseline showed that a majority of the patients were treated successfully and maintained in periodontal health. Root surface caries developed in approximately two-thirds of the patients during the 4–year observation period. However, the total increment of root lesions during these years was mostly extremely low. i.e. less than 5% of exposed root surfaces.

In higher risk patients developing new root surface caries, significant correlations were demonstrated with initial pretreatment scorings for (1) their previous root surface caries experience, (2) high lactobacillus counts and (3) advancing age. In addition, root surface caries incidence and low saliva secretion rates were found to correlate significantly during the course of the study.

Prediction of root surface caries in patients treated for advanced periodontal disease

Caries development on exposed root surfaces was evaluated in 31 patients who had been subjected to surgical and/or nonsurgical periodontal treatment 8 years earlier due to advanced chronic periodontitis. Besides assessments for evaluation of the periodontal treatment, a number of examinations and tests were carried out in order to assess variables presumed to influence the root surface caries development. Both statistical and graphical analyses were carried out to test differences between groups of subjects and to evaluate the variables studied as possible risk factors for root surface caries. The variables studied were: salivary lactobacillus count, salivary Streptococcus mutans count, plaque score, salivary secretion rate, salivary buffer effect, oral sugar clearance time, dietary habits and the age of the subject. The final results support previous findings from an initial 4-year period that root surface caries occurs, though to a minor extent, in this patient category demonstrating good or excellent periodontal conditions after periodontal treatment. A positive correlation was found between the baseline and final root surface caries scores. After the second 4-year period, the salivary counts of S. mutans and lactobacilli, the plaque score and the dietary habits differed significantly between groups of subjects who had developed 0 or greater than 5 new DFS %. Root surface caries was far more prevalent when risk values of the variables studied were present than when they were absent. The important variables in this respect differed considerably between the subjects. No single variable was found to be discriminative in all subjects.

Long-term evaluation of root surface caries in periodontally treated patients.

The periodontal condition in 53 adolescents undergoing long–term orthodontic treatment with fixed appliances was examined longitudinally for 4 years. In each case measures aimed at establishing a proper oral hygiene standard were carried out prior to and during active orthodontic treatment. Sixteen adolescents matched with regard to age and free from orthodontic treatment served as controls.

The results showed that multiband orthodontic treatment led to a slight but significant loss of periodontal support despite good or excellent individual oral hygiene. At the end of 24±3.5 months of active orthodontic treatment the average loss of buccal and lingual attachment for banded teeth amounted to 0.28 mm and 0.22 mm, respectively. A mean reduction of 0.29 mm of interproximal marginal bone height was found. These alterations were irreversible but no further deterioration was observed during a subsequent retention and follow-up period of 20 ±3.0 months.

A detailed analysis of the periodontal condition of the second premolars indicated that the changes occurring adjacent to the different tooth surfaces could not be explained solely by the presence of dental plaque. Extraction of neighbouring first premolars and tooth movements during active orthodontic treatment may also have played a role.

Sven-Erik Hamp

Papers

Periodontal treatment of multirooted teeth. Results after 5 years.

Plaque induced periodontal disease in beagle dogs. A 4-year clinical, roentgenographical and histometrical study.

Prediction of root surface caries in patients treated for advanced periodontal disease

Long-term evaluation of root surface caries in periodontally treated patients.

Periodontal conditions in adolescents subjected to multiband orthodontic treatment with controlled oral hygiene.