Penetration of Streptococcus sobrinus and Streptococcus sanguinis into dental enamel.

The aim of this pilot study was to assess the difference in virulence of acidogenic and aciduric oral streptococci in an in vitro caries model using their penetration depths into dental enamel. 30 caries-free extracted molars from 11- to 16-year-olds were cleaned ultrasonically for 1 min with de-ionized water and, after air-drying, embedded in epoxy resin. After 8-h of setting at room temperature, the specimens were ground on the buccal side with SiC-paper 1200 (particle size 13-16 µm). Enamel was removed in circular areas sized 3 mm in diameter; the mean depth of removed enamel was 230 ± 60 µm. 15 specimens each were incubated anaerobically under standardized conditions with 24 h-cultures of Streptococcus sanguinis 9S or Streptococcus sobrinus OMZ 176 in Balmelli broth at 37 ± 2 °C; the pH-values of the broths were measured at the beginning and end of each incubation cycle. After 2, 4, 6, 8, and 10 weeks 3 teeth each were fixed in 2.5% glutaraldehyde in cacodylate buffer for 24 h, washed 3× and dehydrated 30-60min by sequential washes through a series of 30-100% graded ethanol. The teeth were cut in half longitudinally; afterward, two slits were made to obtain fracture surfaces in the infected area. After critical-point-drying the fragments were gold-sputtered and viewed in a scanning electron microscope at magnifications of ×20-20,000. After 10 weeks of incubation, penetration of S. sanguinis of 11.13 ± 24.04 µm below the break edges into the enamel was observed. The invasion of S. sobrinus reached depths of 87.53 ± 76.34 µm. The difference was statistically significant (paired t test: p = 0.033). The experimental penetration depths emphasize the importance of S. sanguinis versus S. sobrinus in the context of the extended ecological plaque hypothesis.

Identification of Lactobacilli from deep carious lesions by means of species-specific PCR and MALDI-TOF mass spectrometry.

BACKGROUND: The aim of the present study was to compare MALDI-TOF results for the identification of 87 lactobacilli, isolated from soft or hard carious dentin from 70 first molars of 7- to 8-year-old children with those obtained by species-specific PCR. METHODS: The 87 isolates were analyzed by MALDI-TOF MS (Microflex LT, MALDI Biotyper 3.0, Bruker Daltonik, Bremen, Germany), using a reference data base of 4110 strains including > 90 lactobacillus species. For the identification with species-specific PCR, oligonucleotide primers (16S rRNA) specific for L. casei, L. paracasei, L. rhamnosus, L. gasseri, L. plantarum, and L. acidophilus were used; type strains served as controls. The PCR-products were separated electrophoretically on a 1.5% agarose gel and identified by their position on the gel. RESULTS: For 93% of the strains both methods produced concordant results: 40 strains were identified as L. rhamnosus, 16 as L. paracasei subsp. paracasei, 15 as L. paracasei subsp. tolerans, 4 as L. paracasei, 3 as L. gasseri, 2 as L. plantarum, and 1 as L. casei. In 4.5% of the cases the results were discordant. Of the 3 strains, not identified by species-specific PCR, 1 strain was identified by MALDI-TOF MS as L. spec. and 1 as L. parabuchneri. One strain could not be identified by either method. CONCLUSIONS: Both methods are highly sensitive. Limitations can be the precision of the primers (PCR) or the scarcity of strains from a certain habitat in the data base. Additional information is necessary for the strains without or with discordant identification.

Modeling of S mutans and A naeslundii acid production in vitro with caries incidence of low- and high-risk children.

OBJECTIVES: Nowadays, the extended ecological plaque hypothesis equates dental health with the occurrence of acidogenic generalists in the plaque flora and explains disease?the irreversible demineralization of the dental hard tissue?by an ecologic shift in plaque composition, favoring acidogenic and aciduric specialists, following repeated conditions of high sugar. In the present study, aspects of the extended ecological plaque hypothesis were examined in retrospect. METHOD AND MATERIALS: Serving as a basis were data on (1) the caries incidence of children, classified according to their DMFT as having low or high caries risk; (2) the qualitative plaque composition of the children with the prevalence of mutans streptococci and actinomyces; (3) the amounts of acid and acid tolerance, determined by pH state titration (glucose), of representatively isolated strains of mutans streptococci and actinomyces; (4) the extrapolation of the acid amount to the occurrence of mutans streptococci and actinomyces in the plaque of children; and (5) the relationship between the extrapolated acid amount in plaque and caries incidence and the respective classification of the children into low and high caries risk. RESULTS: The synoptic consideration of the numbers of A naeslundii and S mutans in plaque of children, with their capacity for acid production in vitro, reflected the caries risk classification. CONCLUSION: The analysis of the clinical, microbiologic, and in vitro findings concerning the virulence of the plaque isolates supports the extended ecological plaque hypothesis. Children with low caries risk had developed one new decayed surface within 4 years; children with high caries risk developed four within the same time period.

Simultaneous dental implant placement and endoscope-guided internal sinus floor elevation: 2-year post-loading outcomes.

AIMS: To determine whether endoscope-guided sinus elevation procedures can be consistently used to create sufficient bone support for stable implant placement and long-term implant success. MATERIAL AND METHODS: Sixty-two implants were surgically placed into 30 patients (14 men and 16 women) following internal sinus elevation without the use of graft material. Panoramic radiographs were made pre-, post-operative and after 24 months in order to evaluate the peri-implant bone and maxillary sinuses. Resonance frequency analysis (RFA) was used to evaluate implant stability immediately upon placement and just before prosthesis delivery. RESULTS: The average pre-operative height of the maxillary alveolar bone was 8.4+/-2.2 mm at the premolar and 7.3+/-3.1 mm at the molar regions. The average bone gain was 3.5+/-1.8 and 4.5+/-1.9 mm in the premolar and molar sites, respectively. Clinical parameters and the RFA (4 and 12 weeks post-operative) outcomes show sufficient stability (ISQ=60) of the inserted implants. Three implants failed during the healing period of 12 weeks. The overall implant success rate was 94%. After loading, no further implant failure was observed. The overall success rate after beginning of implant loading was 100%. CONCLUSIONS: Sinus floor elevation is a well-established procedure for augmentation of the atrophic maxillary posterior region. The minimally invasive internal sinus floor elevation procedure visually guided by an endoscope helped to prevent, diagnose and manage complications such as sinus membrane perforation. The clinical outcomes of this study show that endoscope-controlled internal sinus floor elevation combined with implant placement results in low intra operative trauma, good implant stability upon placement, low incidence of post-operative symptoms and high success rates after 24 months of loading.