Root-end filling materials alter fibroblast differentiation.

UNLABELLED: Root-end filling materials are commonly used following endodontic surgical procedures; however, their effect on adjacent soft tissues is poorly understood. We predict that, due to the differences in their chemical composition, these materials will have profoundly different effects on the survival and differentiation of fibroblasts. Many of the root-end filling materials examined were initially cytotoxic to both PDL and gingival fibroblasts in co-culture experiments; however, this was reduced after the materials were washed in either mineral trioxide aggregate (MTA) or hybrid ionomere composite resin (HICR) for 2 wks. Additionally, PDL fibroblasts displayed enhanced proliferation on MTA and survival on amalgam when compared with gingival fibroblasts. MTA preferentially induced alkaline phosphatase expression and activity in both PDL and gingival fibroblasts. In contrast, HICR inhibited alkaline phosphatase expression and activity. In addition, MTA and HICR repressed pleiotrophin in PDL fibroblasts, while HICR repressed periostin in both fibroblasts. Thus, root-end filling materials differentially affect periodontal fibroblast differentiation. ABBREVIATIONS: mineral trioxide aggregate (MTA), zinc-oxide eugenol cement (ZOEC), hybrid ionomer composite resin (HICR), reverse-transcriptase polymerase chain-reaction (RT-PCR).

Cell-to-cell communication of osteoblasts.

Osteoblasts were investigated by two methods, electrical conductance and dye injection. Current injection into one cell caused a change in the recorded transmembrane potential of a second cell, indicating high conductance pathways between the two cells. Dyes injected into a single osteoblast were transmitted to numerous surrounding cells.

Transmembrane potentials of osteoblasts.

Transmembrane potentials were recorded in situ from osteoblasts on the parietal bones of albino rat pups, 3 to 24 days of age. Osteoblasts exhibit a uniquely low polarization of their cell membranes (3.93 mV, inside negative). Osteoblasts respond rapidly, but transiently, to parathyroid hormone by depolarization, and to thyrocalcitonin by hyperpolarization.

Effects of ultrasonic root-end preparation on microcrack formation and leakage.

Root-end preparations made with conventional ultrasonic (CUS) tips, diamond-coated ultrasonic (DUS) tips, and high-speed stainless-steel burs (HSB) were compared for the incidence of microcracks and dye leakage. One hundred twenty incisors were instrumented, obturated, and had 3 mm resected from their apices. Sixty teeth were used for microcrack evaluation before and after root-end preparation with CUS, DUS, or HSB. Three types of microcracks were observed: intracanal, extracanal, and communicating. Four of the five cracks observed after root resection (before root-end preparation) were of the extracanal or intracanal type. After root-end preparation, 19 of the 41 new microcracks that developed were the communicating type. There was no significant difference among CUS, DUS, or HSB for the number or type of cracks. Of the remaining 60 resected teeth, 25 were prepared with DUS, 25 with CUS, and 10 served as controls. All of the DUS and CUS teeth were filled with Super-EBA. Dye penetration was measured after immersion in Pelikan ink for 5 days. The dye penetration difference between DUS and CUS was not significant.

In vitro evaluation of a carbon fiber post.

The purpose of this study was to evaluate the influence of endodontic and restorative procedures on fracture resistance of teeth, and to compare the incidence of root fracture in teeth with clinical crowns removed that were restored with three different types of post and a composite core build-up. Seven groups of 10 extracted maxillary canines were used. A control group had only a crown preparation, but no endodontic treatment. Three groups had endodontic treatment, crown preparation, and the access restored. Three groups had endodontic treatment, the crown totally removed, a tapered, parallel, or carbon post placed, and a composite build-up. All specimens were subjected to a 45-degree load at 0.5 mm/min until failure occurred. The force at failure and the location of fracture were recorded. The groups with post and composite build-ups failed at significantly lower force than the teeth in which the crowns had not been removed. There were no significant differences in the amount of force required to produce failure among the three groups with different posts and a composite build-up. The group restored with the carbon post had no root fractures, whereas there were five fractures in each of the parallel and tapered post groups.

Effect of an acid environment on leakage of root-end filling materials.

One hundred fifty-six single-rooted human extracted teeth received root canal treatment, apicoectomy, and ultrasonic root-end preparations. The roots were divided into six groups of 24 teeth. The groups were filled with Amalgam, Geristore, Super-EBA, Mineral Trioxide Aggregate (MTA), Calcium Phosphate Cement (CPC), or MTA with CPC matrix, respectively. Immediately after root-end filling, 12 teeth from each group were exposed to a pH of 5.0 for 24 h, and 12 teeth were exposed to a pH of 7.4 for 24 h. Twelve teeth served as controls. All teeth were exposed to Pelikan Ink for 5 days and cleared. Linear dye leakage was recorded. Data were statistically analyzed. An acid pH significantly reduced dye leakage of Geristore (0.67 vs. 3.93 mm) and MTA with CPC matrix (0.54 vs. 2.41 mm), whereas leakage of all other materials was not affected by pH. In conclusion an acid environment did not hinder the sealing ability of any of the materials tested, and enhanced the sealing ability of Geristore and MTA with CPC matrix.

Coronal leakage: effects of smear layer, obturation technique, and sealer.

Coronal microleakage may be a major factor in the etiology of treatment failure. This study examined the effect of obturation technique, sealer, and the presence of smear layer on coronal microleakage. Two hundred extracted human teeth were assigned to 20 treatment groups. Groups were examined with the smear layer present or smear layer removed (17% REDTA). Access cavities were exposed to artificial saliva then Pelikan Ink. Teeth were cleared and linear dye penetration measured. When all groups with the smear layer removed were compared with all groups with the smear layer present, significantly less leakage was seen when the smear layer was removed. Ultrafil displayed significantly more leakage than all other groups. Vertical compaction of lateral condensation and Thermafil obturations significantly reduced leakage. AH-26 displayed significantly less leakage than Roth's 811 sealer. These results indicate that removal of the smear layer, the use of AH-26, and vertical compactin have cumulative effects in reducing coronal leakage.

Ferric sulfate hemostasis: effect on osseous wound healing. Left in situ for maximum exposure.

Ferric sulfate solution is an accepted soft tissue hemostatic agent for use in dermatology and dentistry. This study was designed to test its effect on osseous healing when used during surgery to control osseous hemorrhage. Standardized osseous defects were created bilaterally in the naturally edentulous zone in rabbit mandibles. The control site was sutured immediately after clot formation in the defect. The contralateral experimental site received ferric sulfate application until complete hemostasis was achieved. The defect was filled with ferric sulfate solution to maximize any effect on healing and then closed with sutures. The experimental and control specimens were examined histologically after 18 and 46 days and scored for healing. Statistical analysis by Wilcoxon signed rank test showed significant adverse effects on osseous healing when ferric sulfate solution was left in situ.

Ferric sulfate hemostasis: effect on osseous wound healing. II. With curettage and irrigation.

Hemorrhage control is often a problem for the clinician during osseous surgery. Ferric sulfate is an effective hemostatic agent, but with prolonged application to an osseous defect can cause persistent inflammation and delayed healing. The purpose of this investigation was to evaluate the effectiveness of ferric sulfate as a hemostatic agent and to determine its effect on healing after thorough curettage and irrigation from osseous surgical wounds. Standard size osseous defects were created bilaterally in the mandibles of rabbits. Ferric sulfate was placed in one defect until hemostasis was obtained; the contralateral defect was allowed to fill with blood and clot. After 5 min both defects were curetted and irrigated. The repair of the defects was evaluated histologically at 18 and 46 days. There were no significant differences between the ferric sulfate-treated defects and the untreated controls. When adequately curetted and irrigated from the surgical site prior to closure, ferric sulfate did not cause persistent inflammation or delay osseous repair in comparison to controls.

The effect of guided tissue regeneration on the healing of osseous defects in rat calvaria.

The effect of guided tissue regeneration procedures on the healing of osseous defects was studied in Sprague-Dawley rats. A full thickness flap was reflected and two 5 mm defects were made in the calvaria of 17 rats. A resorbable membrane was placed over one defect in each animal, while the remaining defect served as a control. After 3, 5, or 7 wk, healing of the osseous defects was evaluated histologically. There was no statistical difference in bone regeneration between experimental and control sites at any time period.

Current trends in endodontic treatment: report of a national survey.

The authors surveyed 360 general dentists and 291 endodontists to obtain information on routine, nonemergency endodontic treatments adapted to clinical practice. Frequent practices and recent advances in treatment modalities-including instrumentation, obturation, intracanal preparations, medications and restorations-are highlighted.

Coronal microleakage in conservatively restored endodontic access preparations.

This study evaluated the coronal microleakage of endodontic access preparations restored with glass ionomer cement (GIC), composite resin (CR), or the "sandwich" (GIC/CR) techniques. The size of access preparation for 32 freshly extracted maxillary premolars was standardized by using a stainless steel template. The teeth were randomly divided into three experimental groups of 10 teeth and one group of two control teeth. Group One: light cured glass ionomer cement, Vitra Bond (3M Dental Products Division, St. Paul, MN). Group Two: composite resin, Silux Plus (3M Dental Products Division, St. Paul, MN). Group Three: "sandwich" technique, consisting of a 3 mm glass ionomer cement base and composite resin restoring the remaining access. The restorative materials were placed incrementally and cured from the facial, lingual and occlusal planes for 20-second intervals. The teeth were thermocycled for 24 hours, immersed in methylene blue dye for 48 hours, and then sectioned to measure dye penetration. This study differed substantially from similar leakage studies. The "sandwich" (GIC/CR) and the composite resin restorations allowed significantly less coronal leakage than the glass ionomer cement restorations. Although not statistically significant, less leakage was measured with the "sandwich" restoration than the composite resin restoration.

Fluoride action on acid resistance of unaltered human surface enamel.

Unaltered surface enamel of extracted human teeth was subjected to tests of resistance to dissolution in 10 mM acetic acid at pH 4.0 and 10 mM EDTA at pH 7.4 in a miniature continuous flow system. Fluoride in EDTA had no effect on enamel dissolution. Inclusion of 0.25, 0.50 and 5.0 mM NaF in the acid at pH 4.0 greatly increased the resistance of the enamel to dissolution. The 0.5 mM NaF in the acid almost instantly reduced enamel dissolution and the effect persisted through the 1 h experiments. These results suggested that the acid labile fluoride in plaque and tooth minerals may provide the primary beneficial effect of all types of enamel fluoridation.

Timing of calcium hydroxide therapy in the treatment of root resorption in replanted teeth in dogs.

The effect of time of the onset of calcium hydroxide (CH) pulpectomy on root resorption of 31 permanent dog incisors was investigated. CH pulpectomy was delayed 4, 9, 14 and 18 days after the teeth were extracted and replanted. Control teeth were replanted 1) without pulpectomy, 2) with a pulpectomy only or 3) with a pulpectomy and CH filling. All teeth were prepared for histologic evaluation 8 weeks after the teeth were replanted. Cross section were examined using a computer microscope and linear (micron) and/or square areas (micron 2) of surface (SRR), inflammatory (IRR), and replacement (RRR) root resorption were calculated. From this data the percentage of linear and area resorption was averaged for each group. Duncan multiple range t-test (P < or = 0.05) revealed that teeth in which a pulpectomy with CH filling was done extraorally had significantly greater SRR than the rest of the groups; teeth in which a pulpectomy without CH filling was done extraorally had significantly greater RRR than teeth in which CH pulpectomy was delayed for 18 days; there was no significant difference in SRR, IRR or RRR when CH placement was delayed 4, 9, 14 or 18 days after replantation. Although it was not significant the overall resorption was least when CH pulpectomy was delayed 18 days.

beta-Hemolytic streptococci and other beta-hemolytic organisms in apical periodontitis and severe marginal periodontitis.

Thirteen teeth with necrotic pulps and apical periodontitis and nine severe periodontal pockets were cultured for presence of beta-hemolytic streptococci and other beta-hemolytic organisms. Samples were dispersed and plated on two non-selective and one selective growth media and incubated anaerobically and in 10% CO2 in air. A total of 59 beta-hemolytic colonies were purified and identified. Eight beta-hemolytic streptococcal isolates were obtained from three of the severe marginal periodontitis sites. All were identified as belonging to the Streptococcus sanguis group. No beta-hemolytic streptococci were detected in apical periodontitis samples. Twenty obligately anaerobic isolates were detected, all of which were known periodontal and endodontic pathogens. Isolates from apical periodontitis sites were identified as Propionibacterium acnes, Actinomyces naeslundii, Actionomyces odontolyticus and Peptostreptococcus micros, while severe marginal periodontal sites contained the same species with the addition of Actinomyces viscosus and Actinomyces meyeri. Of 19 staphylococci and micrococci, Staphylococcus epidermidis was the predominant isolate in both apical periodontitis and severe marginal periodontitis sites. However, less commonly known organisms such as Staphylococcus cohnii and Micrococcus sp. were identified in severe marginal periodontitis sites. The isolation of Bacillus sp. (12 isolates) in one severe marginal periodontitis and two apical periodontitis subjects was especially interesting, warranting consideration of this organism as a legitimate isolate and potential pathogen in oral disease.