Root surface caries subsequent to gingivectomy in rats inoculated with Streptococcus sobrinus (mutans) and Actinomyces viscosus

Evaluation of Clinical, Biochemical and Microbiological Markers Related to Dental Caries

Our aim was to evaluate clinical, biochemical and microbiological markers related to dental caries in adults. A sample that consisted of 75 volunteers was utilized. The presence of caries and the presence of plaque and gingival indices were determined. Unstimulated salivary flow, pH, lactate, Streptococcus mutans and Streptococcus dentisani were measured in the participants’ plaque and saliva samples before and after rinsing with a sugar solution. Lactate in plaque was found to be significantly related to age, gender, tooth-brushing frequency, the presence of cavitated caries lesions and plaque and gingival indices (p < 0.05). The levels of S. dentisani in plaque increased significantly with tooth-brushing frequency (p = 0.03). Normalized plaque S. dentisani values and the percentage of S. dentisani were slightly higher in patients with basal lactic acid levels ≤ 50 mg/L. After rinsing with a sugary solution, the percentage of S. mutans levels in plaque were higher in patients with lactic acid levels > 350 mg/L (p = 0.03). Tooth-brushing frequency was the factor which was most associated with oral health. Women reflected better clinical and biochemical parameters than men. Low pH and high lactic acid levels tended to be associated with high caries rates. No association was found between bacteria levels and caries indices.

Scardovia wiggsiae and its potential role as a caries pathogen

BACKGROUND

Streptococcus mutans has been strongly associated with dental caries but caries also occurs in its absence. Association of a new species, Scardovia wiggsiae with childhood caries suggests this could be a new caries pathogen.

HIGHLIGHT

S. mutans is considered a caries pathogen based on its association with caries, and on its ability to produce acid, to survive low pH environments, and to induce caries in experimental animals. S. wiggsiae was significantly associated with severe-early childhood caries in the presence and absence of S. mutans. Further S. wiggsiae was elevated in initial carious lesions in adolescents with fixed orthodontic appliances. S. wiggsiae detection was enriched on a low pH agar suggesting acid-tolerance. S. wiggsiae isolates were acid tolerant and produced acid from several sugars at low initial pH values, and were not arginine deiminase positive, characteristics consistent with potential cariogenicity. Cariogenicity of S. wiggsiae was tested in a rat animal model in parallel with S. mutans. While S. wiggsiae by itself showed minimal caries induction, when co-inoculated with S. mutans, there was significant cavity production.

CONCLUSION

S. wiggsiae was associated with advanced and initial caries, is acid tolerant and produces acid to low pH at initial neutral and low pH conditions. In combination with S. mutans, S. wiggsiae was detected in caries in an animal model. Together, these data suggest that S. wiggsiae has many of the characteristics consistent with its being a caries-associated species.

Animal caries models for evaluating fluoride dentifrices

To determine the ability of animal caries models to evaluate the cariostatic potential of fluoride dentifrices, we examined four different coronal caries models. These currently used rat caries models were: Francis' hypomineralized area model, Gaffar's CARA rat model, the Connecticut model, and the Indiana model. Available data indicated that all of these models were capable of detecting significant cariostatic benefits from clinically proven fluoride dentifrices. For the most part, these animal models were also able to demonstrate a response to increasing concentrations of fluoride, particularly if the fluoride was provided in an ionic rather than a complexed form. Data were also presented which indicated the potential for animal caries models to be used to predict the clinical benefits of non-fluoride systems as well as the utility of fluoride systems for the prevention of root-surface caries. It is concluded that animal caries models play a significant role in the development and evaluation of fluoride and other systems for the clinical prevention of dental caries.

Operative dentistry considerations for the elderly

As the mean age of an older dentate population increases, so does the incidence of dental caries in its primary and secondary forms. Primary and secondary root decay gingival to existing restorations are significant operative problems prevalent in the elderly. Treated root decay is prone to recurrence if the etiology is ignored. Effective, customized prevention must parallel operative intervention. The dentist today has a wider selection of techniques and materials than ever before to treat the elderly patients. Use of preventive restorative materials such as conventional and hybrid glass ionomer materials for the treatment of root decay are discussed.

The effect of phenytoin on parathyroid hormone stimulated cAMP activity in cultured murine osteoblasts

Cells were isolated by sequential collagenase digestion from the parietal segments of one day old mice (Swiss albino BNL strain) and characterized for osteoblast parameters by alkaline phosphatase histochemistry and bovine parathyroid hormone (bPTH-(1-34] induced cAMP activity (protein binding assay). Phenytoin (DPH) reduced PTH stimulated cAMP activity nearly 3-fold in the presence and nearly 1.5-fold in the absence of added calcium. In the absence of PTH, DPH exerted no significant effect. Bay-K-8644, a calcium channel activator, appeared to approximate the PTH stimulation of cAMP activity, even in the presence of DPH. This study demonstrates that DPH has a direct effect on PTH stimulated cAMP activity in cultured murine osteoblasts.

Caries on root surfaces exposed following gingivectomy in conventional rats infected with Streptococcus sobrinus and Actinomyces viscosus

To study the ability of bacteria associated with coronal caries to initiate root surface caries, a rat model was used. Root surfaces were exposed by gingivectomy in rats fed a caries-promoting diet and orally inoculated with either Actinomyces viscosus M-100, Streptococcus sobrinus (mutans) 6715, or both. A fourth group received a diet containing antibiotics. The animals were sacrificed 64 days following the gingivectomy performed on the right molar quadrants. Gingivectomy significantly increased exposed lingual root length and root caries incidence. There were no caries on non-gingivectomy root surfaces. Root surface caries incidence in the groups inoculated with A. viscosus and A. viscosus plus S. sobrinus did not differ. For both these groups, root caries incidence was significantly greater than that for the group inoculated with S. sobrinus alone. Root caries incidence in this latter group did not differ from that in the control group.

The effects of different levels of dietary sucrose on root caries subsequent to gingivectomy in conventional rats infected with Actinomyces viscosus M-100

Three groups of weanling, Sprague-Dawley-derived rats were inoculated with Actinomyces viscosus M-100 and fed powdered diet containing either 67%, 5%, or 0% confectioner's sugar. Two further groups were fed diet containing 5% confectioner's sugar and inoculated with Streptococcus sobrinus 6715 or S. sobrinus 6715 plus A. viscosus M-100. The most coronal 1 mm of gingiva was removed from maxillary and mandibular right molar quadrants (gingivectomy), and the animals re-inoculated following gingivectomy. The animals were killed 64 days following gingivectomy, and the lingual surface of mandibular first molar roots was measured for exposed root-surface area and root caries. In the groups of rats infected with A. viscosus M-100, root caries area was significantly greater in the group fed diet containing 67% confectioner's sugar. Sucrose level did not significantly affect the amount of exposed lingual first molar root area regardless of whether the tooth had been subjected to a gingivectomy. In the groups of rats receiving diet containing 5% confectioner's sugar, there were no significant differences in root caries area or exposed root-surface area, regardless of the infection status of the animals. In the rat model presented here, a high level of dietary sucrose was a necessary condition for the initiation of root caries in the absence of other readily fermentable carbohydrates.

Comparison of two scoring methods for root surface caries in hamsters

The aim of this investigation was to compare two methods of scoring root surface caries in hamster teeth. The experimental material was mandibles from hamsters which had been infected with Actinomyces viscosus, fed a caries-promoting diet, and received either 0, 1, 10, or 25 ppm fluoride in the drinking water during an 18-week experimental period (Stookey, 1986). Root surface caries on the lingual surfaces of mandibular first molars was scored according to the grid method of Doff et al. (1977) and by the quantitative planimetric method of Firestone et al. (1986). Data from both methods confirmed that 25 and 10 ppm fluoride were significantly more caries-inhibitory than 1 ppm fluoride, which, in turn, significantly reduced root surface caries compared with the 0 ppm control group. Correlation coefficients for caries scores (0.92) and ranking of the scores (0.88) for each animal between the two methods were highly significant (p < 0.0001). The planimetric measurement of root surface caries in hamsters was as sensitive as the grid-scoring method.

Root surface caries subsequent to gingivectomy in rats inoculated with Streptococcus sobrinus (mutans) and Actinomyces viscosus

We studied the effect of oral infection with cariogenic micro-organisms on alveolar bone loss and root surface caries subsequent to gingivectomy in rats. Thirty-six rats were fed diet MIT 200 (67% sucrose); one-half, the controls, had antibiotics added to the diet. At ages 18, 19, and 21 days, the experimental group was orally infected with streptomycin-resistant Streptococcus sobrinus (mutans) 6715 and Actinomyces viscosus M-100. At age 30 days, all animals were subjected to a gingivectomy on maxillary and mandibular left quadrants. The experimental group was re-inoculated at age 36 days. Animals were killed seven weeks after surgery. Jaws were stained, and planimetric measurements of exposed root surface area and caries on lingual/palatal surfaces of 1st and 2nd molars were made from video images with a computer/digitizer. Compared with the non-operated contralateral quadrants, gingivectomy significantly increased exposed root surface area in the maxilla and in the mandible in both the control and experimental groups. Oral inoculation significantly increased exposed root surface in mandibular (but not maxillary) quadrants which had received a gingivectomy, but had no effect on non-gingivectomized quadrants. There was no caries in the control group, whereas ten rats in the experimental group had root surface caries lesions, all in quadrants which had received a gingivectomy. This rat model should prove useful in further studies of root surface caries.