Lars E. Linder

Clinical management of nonhealing periradicular pathosis : Surgery versus endodontic retreatment

OBJECTIVES This prospective randomized study compared the outcome of retreatment and surgical intervention in root canal treated teeth with nonhealing periradicular pathosis. STUDY DESIGN One such tooth from each of 38 patients was randomly allotted to retreatment or root-end resection and root-end filling. Treatment outcome after 1 year was evaluated and compared clinically and radiographically. RESULTS The success rate for surgery was higher than for conventional retreatment, but the difference was not statistically significant. CONCLUSIONS For management of nonhealing periradicular pathosis associated with root canal treated teeth, surgical intervention should be considered as an alternative to retreatment. In cases with a similar prognosis for both modes of treatment, the choice should be governed by consideration of intrinsic and extrinsic factors.

The influence of Streptococcus mutans on adhesion of Candida albicans to acrylic surfaces in vitro

Adhesion of Candida albicans and Streptococcus mutans was studied by incubation of radiolabelled cells with acrylic test specimens in a chemically defined growth medium. Strep. mutans adhered firmly in the presence of sucrose, while C. albicans was only loosely attached to the acrylic in both glucose and sucrose media. Firm adhesion of C. albicans occurred when the yeast was incubated simultaneously with Strep. mutans, in the presence of sucrose. The adhesion of C. albicans was also stimulated by incubation with Strep. mutans culture supernatants. Adhesion was not affected by the presence of partially purified glucosyltransferase from Strep. mutans IB. Coaggregation between C. albicans and Strep. mutans upon growth in sucrose medium was observed by light and scanning electron microscopy. No coaggregation was observed in the presence of glucose.

Outcomes of periradicular surgery in cases with apical pathosis and untreated canals

OBJECTIVE Surgical management is intended to eliminate or block infection originating in the root canals. The root end is customarily sealed to prevent pathogenic products remaining in the root canal from reaching the periradicular tissues. The purpose of this study was to evaluate the microbiologic and radiographic outcomes of surgical treatment of periradicular pathosis associated with teeth with necrotic pulps. STUDY DESIGN One tooth from each of 10 patients was root-end resected and root-end filled without prior root canal treatment. One year postoperatively, the outcomes were assessed radiographically and the root canals were sampled for bacteria. RESULTS Radiographic examination showed complete or incomplete (scar tissue) healing in 5 teeth and uncertain healing in the other 5 teeth. Bacteriologic samples from the root canals were positive in 9 of the 10 cases. CONCLUSIONS In teeth with necrotic pulps, treatment of periradicular pathosis by surgery and root-end filling may show radiographic evidence of satisfactory healing 1 year postoperatively. However, viable bacteria may persist in the canals, constituting a potential risk factor for recurrence of periradicular pathosis.

Effect of four dental varnishes on the colonization of cariogenic bacteria on exposed sound root surfaces.

The aim of this study was to evaluate the effect of four different dental varnishes on the colonization of mutans streptococci, total streptococci and lactobacilli on exposed sound root surfaces. Sixty–five individuals were randomly allotted to one of four groups for treatment with Cervitec® varnish containing 1% chlorhexidine and 1% thymol, a thymol varnish or one of two different fluoride varnishes, Fluor Protector and Duraphat. The varnish was applied to three buccal root surfaces in each patient at baseline and after 1 week. Dental plaque from the root surfaces was collected and analysed on four different occasions: at baseline, after 1 week, 1 month and 6 months. The Cervitec varnish caused a statistically significant reduction in the number of mutans streptococci over time. The reduction was significant at 1 week and 1 month relative to baseline. The numbers of total streptococci and lactobacilli were not significantly affected by treatment with Cervitec. No statistically significant difference over time was found for mutans streptococci, lactobacilli or total streptococci after treatment with the fluoride varnishes or the thymol varnish.

Cytokines in periradicular lesions: the effect of linezolid treatment.

OBJECTIVE The purpose of this study was to quantify the cytokines interleukin (IL)-1 receptor antagonist (RA), IL-6, and transforming growth factor beta(1) found in extracts of inflammatory periapical tissues and to study the effect of a new antibiotic (linezolid) on the levels of these cytokines. STUDY DESIGN Twenty-two patients with root-filled teeth with persisting periapical pathoses were randomly divided into a control group or an antibiotic group. One tooth from each of the patients was resected at the root-end, and the periapical tissue was collected. IL-1RA, IL-6, and TGF-beta(1) were quantified in tissue extracts through the use of enzyme-linked immunosorbent assays. RESULTS Measurable amounts of all 3 cytokines were found in all extracts. A statistically significant reduction in IL-1RA per milliliter was observed in the linezolid group in comparison with the control group (P <.05). The difference in variation of IL-1RA in the treatment and control groups was also highly statistically significant (P <.001). CONCLUSIONS Although drawn from a limited sample size, the results indicate that IL-1RA is a sensitive indicator of the effect of antibacterial treatment on the immune response in periapical inflammatory tissues.

Autolysis in Strains of Viridans Streptococci

Seven strains of viridans streptococci of the species Streptococcus sanguis, S. mutans and S. mitis were investigated for autolysis. The effect of pH, salt concentration and temperature on the autolytic process was studied in Na2HPO4/NaH2PO4 buffer. Whole cells and walls of all strains autolysed most rapidly at pH values above 7. Autolysis of whole cells of S. sanguis and one strain of S. mitis (ATCC15909) was maximal in 0-05 TO 0-2 M buffer, while the two S. mutans strains and S. mitis ATCC15912 showed maximal autolysis in 0-5 and 1-0 M buffers. Cultures harvested in the stationary phase of growth possessed only slightly decreased autolytic activity compared with those from the exponential phase. Whole cells autolysed more rapidly at 37 degrees C Than at 45 degrees C and 10 degrees C. Autolysis of isolated walls of three strains of S. mitis (ATCC903, ATCC15909 and ATCC15912) was maximal at pH 7-0 AND 7-5 and in 1-0 M buffers. Streptococcus mitis ATCC15909 also showed maximal lysis in 0-01 M and 0-5 M buffers. An endopeptidase action of the autolytic system of S. mitis ATCC15912 was indicated by the progressive release of soluble amino groups during autolysis of the walls. No release of reducing groups was observed. Several free amino acids were released during autolysis of these walls, alanine, lysine and glutamic acid being in greatest quanitity.

Arginine catabolism by strains of oral streptococci

Arginine catabolism via the arginine deiminase pathway was found in Streptococcus sanguis 903. Citrulline and ornithine were released from resting cells incubated with arginine, arginine‐containing peptides, or saliva. Maximum arginine catabolism by resting cells of S. sanguis 903 was found in the pH range 7–8 and at 45–48°C. Arginine deiminase activity was found in the cytoplasm and in the cell‐wall extract of this strain, while ornithine carbamoyltransferase activity was found in the cytoplasm and in extracts of cell walls and cytoplasmic membranes. Streptococcus mutans GS‐5 and Streptococcus sobrinus strains OMZ 176 and 6715 could release arginine from salivary peptides but were incapable of significant arginine catabolism.

Isoelectric focusing studies on the beta-fructofuranosidases and alpha-glucosidases of Streptococcus mitis.

Extracts of Streptococcus mitis ATCC 903 were analysed for beta-fructofuranosidase and alpha-glucosidase activities by isoelectric focusing in thin-layer polyacrylamide gels combined with zymogram procedures. Three bands of activity were visualized in the gels after incubation with sucrose (pI 4.05, 4.25 and 4.85) and three other bands after incubation with p-nitrophenyl alpha-D-glucopyranoside (pI 3.90, 4.45 and 4.65). The enzymes responsible for the reaction with sucrose were identified as beta-fructofuranosidases (EC 3.2.1.26) for the following reasons: identical enzyme bands were visualized in the gels after incubation with raffinose; no enzyme bands appeared in the gel after incubation with the alpha-glucosides maltose, turanose, trehalose and melezitose; and the soluble fraction hydrolysed sucrose to equimolar amounts of glucose and fructose.

Characterization of dextran glucosidase (1,6-a-D-glucan glucohydrolase) of Streptococcus mitis.

Dextran glucosidase (EC 3.2.1.70) isolated from cell extracts of Streptococcus mitis ATCC 903 was purified 925-fold by DEAE-Sephadex, Sephadex G-100 and hydroxylapatite chromatography. The enzyme showed normal Michaelis-Menten kinetics when tested with p-nitrophenyl-α-D-glucopyranoside (pNPG), dextran (MW 9,400) or isomaltose as substrates. The apparent Km values were 1.60, 4.95 and 15.7 mM, respectively. The molecular weight of the enzyme was estimated to 54,000 and the pi was 4.45. Among the metal ions tested (1 mM solutions), Hg2+ and Zn2+ inhibited the enzyme activity completely. In spite of an inhibiting effect of EDTA, no cationic metallic cofactor was found. Glucose exerted competitive inhibition of enzyme activity (KI = 2.5 mM). Optimal enzyme activity was found at pH 7.2 in the temperature range of 37–40 °C and at a low salt concentration (I = 0.06).

Purification and characterization of an aminopeptidase from Streptococcus mitis ATCC 903

An aminopeptidase isolated from the cytoplasmic fraction of a cell extract ofStreptococcus mitis ATCC 903 was purified 330-fold by ion-exchange chromatography, gel filtration, and hydroxyapatite chromatography. The partially purified enzyme had a broad substrate specificity. Twelve aminoacyl-ß-naphthylamide substrates were hydrolyzed and also several di-, tri-, tetra-, and pentapeptides and bradykinin. The enzyme hydrolyzed arginine-ß-naphthylamide at the highest rate. Optimal conditions for activity were at pH 7.0–7.2 and at 37–40°C. The molecular weight of the enzyme was estimated to be 93,000. The enzyme was activated by Co2+ ions. Hg2+ inhibited the activity completely. SDS, EDTA, urea, and pCMB also inhibited activity. Inhibition by EDTA could be completely reversed by dialysis and addition of Co2+ ions. Reducing agents, sodium fluoride, and PMSF had no effect on the activity of the enzyme. The isoelectric point of the enzyme was at pH 4.3. High substrate concentrations inhibited activity. Substrate inhibition increased in the presence of high concentrations of Co2+ ions.