Biomedical subjects

R Parak

Publications and source records attributed to R Parak.

4 recordsLinked to original sources

PubMed2005

Does mechanical pressure force bacteria into the dentinal tubules of carious and non-carious teeth--an exploratory study.

BACKGROUND: Although many researchers have confirmed bacterial migration within dentine, no evidence was found to show whether bacteria can be easily forced into dentine during caries treatment. OBJECTIVES: This exploratory study was to see if bacteria could be easily forced into dentinal tubules of carious and non-carious teeth using hand excavation and air pressure. METHODS: Two (2) carious and ten (10) non-carious teeth were used. Class I (Black's Classification) cavities were created using rotary instruments in the non-carious teeth, while the carious teeth were excavated using hand instruments to remove the caries. The cavity of one carious tooth was etched and in the other tooth was not. Five (5) of the non-carious tooth cavities were etched, of which, one tooth was also disinfected. The remaining five non-carious teeth were not etched and included one tooth that was disinfected. Bacterial cultures of S. mutans, E. coli and Veilonella were placed in the prepared cavities and hand excavators and air pressure were used in an attempt to force bacteria down into the dentinal tubules. Thereafter, the teeth were fixed, decalcified and prepared for electron or light microscopy. RESULTS: One etched, and one etched and disinfected non-carious tooth showed bacteria in the dentinal tubules. One carious tooth (etched) showed bacterial presence in the dentinal tubules. CONCLUSION: This study shows that it is difficult to force bacteria into dentinal tubules using hand excavation (as in the Atraumatic Restorative Treatment technique) so a definitive study is not indicated.

Acid Etching, Dental↗

PubMed2004

Pulpitis induction in baboon primary teeth using carious dentine or Streptococcus mutans.

The objective of this equivalency study was to see if a colony of Streptococcus mutans placed into cavities in primary molar teeth produced pulpitis similar to an established pulpitis induction method using carious dentine. In two juvenile baboons (Papio ursinus), occlusal cavities were cut in all 16 primary molar teeth, followed by making a small pulpal exposure after which the cavity was swabbed with 37 per cent phosphoric acid. In one half of the teeth, fresh soft human carious dentine was placed over the pulpal exposure; in the remaining teeth the exposure was covered with a colony of Streptococcus mutans in agar. All the cavities were restored with unlined light-cured composite resin. After 14 days specimens were harvested and examined under the light microscope with the examiner blind to the induction method. In both groups of teeth there was recognisable pulp, hyperaemia, micro-abscesses in the pulp and peri-apical abscesses. Reactions to soft caries were more severe than to Streptococcus mutans. The results show that Streptococcus mutans placed in a cavity with an exposure produces comparable pulpitis to fresh soft human carious dentine in the same type of cavity and that both methods produce pulpitis suitable for testing pulpotomy or pulpectomy treatments.

Abscess↗

PubMed2004

Zinc oxide-eugenol and calcium hydroxide pulpectomies in baboon primary molars: histological responses.

AIM: To compare histological responses to zinc oxide-eugenol (ZOE) and calcium hydroxide (CH) pulpectomies in primary molar teeth with inflamed pulps. STUDY DESIGN: This was an experimental study in 17 juvenile baboons (Papio ursinus). METHODS: Pulpitis was induced with fresh human carious dentine or Streptococcus mutans placed into occlusal cavities in 78 primary molars; after 14 days a pulpectomy was performed on the same primary molars with the two root fillings randomly allocated. The root canal openings were then covered with IRM and the cavity filled with amalgam. After 90 days specimens were harvested and examined under the light microscope with the examiner blind to the treatment. RESULTS: Reaction frequencies in the ZOE-treated versus CH-treated teeth were: no recognisable pulp 89% and 82%, internal root resorption 0% and 1%, external root resorption 11% and 24%, presence of bacteria 5% and 18%, periapical abscesses 24% and 52%. STATISTICS: Fisher's exact probability test showed a statistically significant higher prevalence of periapical abscesses in the CH-treated group (P=0.03, relative risk 2.2). CONCLUSIONS: ZOE pulpectomy is preferred to CH for the treatment of infected pulps in primary molars.

Animals↗

PubMed2003

Clinical, histological and microbiological study of hand-excavated carious dentine in extracted permanent teeth.

Changes in cultivable flora in dentine samples collected before and after hand excavation were examined in association with clinical status of the cavity surface, light microscopy and scanning electron microscopy (SEM). Thirty-five extracted permanent molar teeth with an occlusal caries lesion were excavated with hand instruments according to the atraumatic restorative treatment (ART) approach. Excavation pressure, dentine colour and consistency were recorded at the dentine-enamel junction (DEJ) prior to carious dentine removal and at the cavity floor after the final excavation; a microbiological sample of dentine was taken at both stages. Twelve restored teeth; six with positive and six with negative bacterial growth on the second sample, were selected for light microscopy and SEM. The hand-excavation removed tooth structure was soft, irreversibly damaged, dark and highly infected. Hand excavation reached dentine of increased hardness with a more normal colour to provide a sound structural base for restoration. Light and SEM examination of the cavity floor showed infected dentinal tubules in all 12 teeth examined. Linear logistic analysis showed a statistical association between light-yellow dentine on the cavity floor and an absence of bacterial growth (P = 0.006). This short-term in vitro study showed that caries-producing bacteria remained in dentine close to the cavity floor in 26/35 teeth despite clinical observations that indicated a suitably prepared cavity floor.

Bacteria↗