Biomedical subjects

Cornelis H Pameijer

Publications and source records attributed to Cornelis H Pameijer.

12 recordsLinked to original sources

PubMed2007

An in vitro study of the pH of three calcium hydroxide dressing materials.

Calcium hydroxide is widely used as a root canal dressing material because of its favorable alkalinizing effect. It has been suggested that the action comes from diffusion of hydroxyl ions through the apical foramen. The purpose of this in vitro study was to test the pH changes that occurred over a period of 30 days using a mixture of calcium hydroxide and distilled water and two commercial calcium hydroxide products in a simulated periapical environment. The materials were inserted in glass tubes closed at one end, which were placed in individual vials containing distilled water at a pH 7.4. Unfilled glass tubes were used as controls. Alkalinity changes of the medium were measured at 1 and 24 h and 15 and 30 days. The alkalinizing properties of all materials showed a rapid increase at 1 and 24 h followed by a continuous but more gradual increase from 15 to 30 days. The control tubes did not cause a change in pH of the medium, which remained at pH 7.4. At the end of the observation period, the alkalinizing properties of Calasept and Ultracal XS were significantly higher (P < 0.05) than the calcium hydroxide/distilled water paste.

Analysis of Variance↗

PubMed2006

Flexural properties of endodontic posts and human root dentin.

OBJECTIVES: To evaluate the flexural modulus and flexural strength of different types of endodontic post in comparison with human root dentin. METHODS: Three different types of fiber-reinforced composite (FRC) posts and three metal posts each comprising 10 specimens (n=10) and 20 dentin bars were loaded to failure in a three-point bending test to determine the flexural modulus (GPa) and the flexural strength (MPa). Three randomly selected fiber posts of each group were evaluated using a scanning electron microscope (SEM) to illustrate the differences in mode of fracture. Data were subjected to a one-way ANOVA to determine significant differences between groups and the Bonferroni t-test multiple comparison was applied to investigate which mean values differed from one another with significance levels of P<0.05. RESULTS: The flexural modulus recorded for the dentin bars was 17.5+/-3.8 GPa. The values for posts ranged from 24.4+/-3.8 GPa for silica fiber posts to 108.6+/-10.7 GPa for stainless steel posts. The flexural strength for dentin was 212.9+/-41.9 MPa, while the posts ranged from 879.1+/-66.2 MPa for silica fiber posts to 1545.3+/-135.9 MPa for cast gold posts. The ANOVA test analysis revealed significant differences between groups (P<0.05) for flexural modulus and flexural strength mean values. SIGNIFICANCE: FRC posts have an elastic modulus that more closely approaches that of dentin while that for metal posts was much higher. The flexural strength of fiber and metal posts was respectively four and seven times higher than root dentin.

Carbon↗

PubMed2006

Cross-sectional analysis of root canals prepared with NiTi rotary instruments and stainless steel reciprocating files.

OBJECTIVE: To determine whether the shaping of oval-shaped root canals using 2 different preparation techniques resulted in significant morphologic differences. STUDY DESIGN: Forty lower premolars with oval-shaped root canals were divided into group A, instrumented with the Anatomic Endodontic Technology (AET) system, and group B, treated with ProTaper instruments. A modified Bramante technique was used to analyze changes in root canal diameters (DeltaD), changes in surface area (DeltaA), and the change in buccolingual and mesiodistal ratio (DeltaR). The data were subjected to a Student t test at a significance level of P < 0.05. RESULTS: Statistically significant differences were found between the 2 groups at coronal and middle levels. There was no statistically significant difference at the apical level. CONCLUSIONS: The 2 techniques produced a significant difference in the ultimate shape of the coronal and middle portions of oval-shaped root canals, with the AET system removing more tooth structure at these levels. However, no differences were observed at the apical third.

Dental Pulp Cavity↗

PubMed2006

Three-dimensional imaging using microcomputed tomography for studying tooth macromorphology.

BACKGROUND: The authors conducted a study to demonstrate potential applications of microcomputed tomography (microCT) in the analysis of tooth morphology. METHODS: The authors selected for microCT analysis five maxillary first molars with a second canal in the mesiobuccal (MB) root, five mandibular first molars with a mesial root possessing a considerable curvature and five single-canal premolars with complicated apical anatomy. The hardware device used in this study was a desktop X-ray microfocus CT scanner (SkyScan 1072, SkyScan bvba, Aartselaar, Belgium). RESULTS: The authors obtained a three-dimensional image from each of the 15 teeth. In three cases, the MB canals coalesced into one canal, while in the other two molars the canals were separate. Four of the five mandibular molars exhibited a single canal in the mesial root, which had a broad, flat appearance in a mesiodistal dimension. In the premolar teeth, the canals were independent; however, the apical delta and ramifications of the root canals were obvious, yet intricate. CONCLUSIONS: MicroCT offers a reproducible technique for 3-D noninvasive assessment of root canal systems. CLINICAL IMPLICATIONS: While this technique is not suitable for clinical use, it can be applied to improve preclinical training and analysis of fundamental procedures in endodontic and restorative treatment.

Humans↗

PubMed2006

Clinical and histological evaluation of white ProRoot MTA in direct pulp capping.

PURPOSE: To evaluate the clinical, radiographical and histological findings in human third molars in which mechanical pulp exposures were capped with white ProRoot mineral trioxide aggregate (WMTA). METHODS: Forty-eight human third molars, caries-free or with incipient caries, scheduled to be extracted, were used and randomly divided into two groups: Group A: (n= 24) received WMTA and control Group B: (n= 24) received chemical set calcium hydroxide (Dycal). The teeth were isolated with rubber dam and Class I cavities prepared. Pulp exposure was performed using a sterile diamond bur and confirmed by frank bleeding. A sterile cotton pellet dipped in saline solution was placed over the exposure for 60 seconds. The preparation was then lightly rinsed with water and gently air-dried. WMTA or CH was placed over the exposure site followed by a small amount of a light-cured compomer. After etching with 35% phosphoric acid gel for 15 seconds, rinsing and blot drying, Prime and Bond NT adhesive was applied and light-cured. The cavity was then restored with a resin composite and light-cured. Evaluations were performed by phone after 7 days and clinically at 30 +/- 5 and 136 +/- 24 days, using standardized tests and radiographs. The teeth were extracted after 136 +/- 24 days; the roots were cut +/- 4-5 mm from the apex to allow for rapid fixation in 10% neutral buffered formalin. They were then processed for routine histological evaluation, embedded in paraffin, sectioned and stained with hematoxylin and eosin and Brown and Brenn for recognition of bacteria. Statistical analyses were performed using a Mann-Whitney U-test, a Chi-square test, a Fisher's exact test and an ANOVA. RESULTS: No significant differences in post-operative sensitivity were reported after 7 days between the two materials (P> 0.05). Clinical examination demonstrated no significant differences at 30 +/- 5 days (P> 0.05) and at 136 +/- 24 days (P> 0.05). Histological findings: 45 of 48 teeth were suitable for microscopic evaluation (22 with WMTA and 23 with CH). Twenty from the WMTA and 18 from the CH group had developed a bridge. No statistically significant differences were found for superficial and deep inflammatory cell response (P> 0.05), presence of a dentin bridge (P> 0.01), and pulp vitality (P> 0.01), between WMTA and calcium hydroxide. A statistically significant difference was found for the diameter of exposure (P< or = 0.05) between WMTA (x= 0.35 +/- 0.19 mm) and CH (x= 0.25 +/- 0.09 mm). Only a minimal association between clinical and histological findings could be established for either material.

Aluminum Compounds↗

PubMed2005

Evaluation of the apical seal in root canals prepared with a new rotary system and obturated with a methacrylate based endodontic sealer: an in vitro study.

The purpose of this study was to evaluate in vitro the apical seal of root canals prepared with a new rotary system, Anatomic Endodontic Technology (AET) and filled with a methacrylate based endodontic sealer and a single gutta-percha cone and a lateral condensation technique, using the methacrylate based endodontic sealer/filler or Grossman's cement. The root canals of 45 freshly extracted human maxillary anterior teeth were prepared and then randomly assigned to three groups of 15 teeth each. After cleaning and shaping the teeth were obturated as follows: in group 1 the canals were filled with a methacrylate based sealer and a single gutta-percha cone; in group 2 the canals were filled using a lateral condensation technique with gutta-percha and the methacrylate based sealer; and in group 3, the canals were filled by means of lateral condensation of gutta-percha and Grossman's cement (control group). The specimens were stored in 100% relative humidity at 37 degrees C for 72 h, after which the coronal portion and the root surface of each tooth was covered with three layers of nail varnish and a final layer of sticky wax. After immersion in 2% methylene blue dye for 7 days, the specimens were imbedded in clear orthodontic resin and sectioned. Dye penetration was evaluated by an independent investigator using a stereo microscope. The results demonstrated that more pronounced leakage occurred in root canals obturated with the lateral condensation technique and Grossman's cement (p < 0.05). The least amount of dye leakage was observed for group 1 and 2 in which the methacrylate based sealer was used, either with a single gutta-percha cone or with lateral condensation of gutta-percha.

Dental Leakage↗

PubMed2005

Bone tissue response to a methacrylate-based endodontic sealer: a histological and histometric study.

Biocompatibility of endodontic sealers is a prime requisite for successful endodontic therapy. The purpose of this study was to evaluate the reaction of bone to a methacrylate-based endodontic sealer. Silicone tubes, filled with a methacrylate-based sealer and silicone rods used as controls, were implanted in the tibias of white male Wistar rats. Ten and 60 days after implantation the reaction of the bone was analyzed by means of histological and histometric methods. After 10 days the amount of reactionary bone in contact with the methacrylate-based sealer was significantly lower than that observed for the controls (p < 0.05). Cell counts demonstrated that the number of inflammatory cells that were in contact with the sealer were significantly higher (p < 0.05). After 60 days, no significant differences were observed in the amount of reactionary bone that was in contact with either material. The initial inflammatory reaction observed for the methacrylate-based sealer was resolved. Furthermore the cell counts demonstrated no statistically significant differences (p > 0.05) between the methacrylate based sealer and control.

Analysis of Variance↗

PubMed2004

Coronal microleakage of three temporary restorative materials: an in vitro study.

The sealing properties of three temporary restorative materials, Cavit, IRM, and a polycarboxylate-based cement, Ultratemp Firm, were investigated in vitro. Standardized access cavities were prepared in 45, intact, extracted, human molars. The teeth were randomly assigned to three groups and the access openings filled with one of three temporary filling materials. In five teeth (negative control), no restorative material was placed but the preparations were coated entirely with sticky wax. The five teeth of the positive control group had no restorative material and no sticky wax applied. After thermocycling for 500 cycles (5-55 degrees C), the experimental teeth were dipped in molten sticky wax to the CEJ. The coronal enamel was subsequently coated with two layers of nail varnish, leaving an area of 1 mm around the filling material uncovered. The samples were then immersed in 2% methylene blue dye solution for leakage assessment. The teeth were sectioned and the greatest depth of dye penetration was recorded. Positive control sections exhibited complete dye penetration, whereas negative controls had none. There was no statistically significant difference in marginal leakage between Cavit, IRM, and Ultratemp Firm (p > 0.05). All materials leaked at the interface material-dentin, whereas some IRM specimens absorbed the dye into the bulk of the material.

Acid Etching, Dental↗

PubMed2004

Clinical and radiographic evaluation of a resin-based root canal sealer.

PURPOSE: To conduct a preliminary clinical and radiographic evaluation of a resin-based root canal sealer used in conjunction with gutta percha. METHODS: In a retrospective study on 180 patients who were seen for root canal therapy, a total of 295 root canals were treated with laterally condensed gutta-percha cones in conjunction with a methacrylate-based endodontic sealer (EndoRez). Root canal therapy had been carried out in one visit using standardized techniques. The results were assessed clinically and radiographically 14-24 months postoperatively and a comparison to baseline radiographs was made. 145 patient records were available for a follow-up examination. Success of root canal treatment was based on absence of clinical symptoms, a normal or slightly widened periodontal ligament and reduction of periapical radiolucencies with an absence of pain in patients that had pre-existing lesions associated with pain. RESULTS: The overall success rate was 913%. Root canals had been adequately filled to the working length in 110 teeth (75.7%), short from the working length in six cases (4.1%) and flush in 19 teeth (13.1%). Extruded sealer occurred in 10 (6.9%) instances. 49 teeth out of 55 (89.1%) that had preoperative apical radiolucencies revealed partial or total healing at the 14-24 months recall evaluation. 83 teeth out of 90 (92.2%), without preoperative radiolucencies, showed no radiographic changes. At the 14-24 months recall all patients reported being comfortable. 13 (9.0%) cases were judged failures.

Adolescent↗

PubMed2003

The effect of different power densities and method of exposure on the marginal adaptation of four light-cured dental restorative materials.

PURPOSE: To determine whether marginal adhesion is sensitive to different irradiation parameters, we investigated the in vitro adhesion values of four dental resins on metal surfaces. METHODS: Four groups of eight specimens each of Z250, Filtek flow, Dyract AP and Dyract flow were placed in pre-treated stainless steel cavities and irradiated using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 and 450 mW/cm(2) and an Optilux 501 ramping light. The maximum amount of push-out force required to displace the resin from the metal cavity was equated with adhesive value (shear bond strength). Comparisons (ANOVA, p<0.0001) were made within the same material and between the different materials when using different curing protocols. RESULTS: Significant lower bond strengths were recorded when curing was done by gradually increasing the intensity (ramping method) compared to curing with the fixed intensities (p>0.0001) Comparing the fixed intensities, significant lower bond strength values were obtained at 800 mW/cm(2) compared to 450 mW/cm(2) (p<0.0001). For all exposures, the two flowable materials demonstrated weaker values when compared to the higher filled materials. CLINICAL SIGNIFICANCE: The advantage of initial slow polymerization (more elasticity and less tension) obtained by the so-called "soft start" method, was offset by a rise in total polymerization shrinkage, when final curing was completed at 1130 mW/cm(2). These tests demonstrated that using halogen units, exposure for 40s with an intensity of 450 mW/cm(2) appeared to be the most promising for light-curing dental resin composites.

Dental Marginal Adaptation↗

PubMed2003

The effects of light intensity and method of exposure on the hardness of four light-cured dental restorative materials.

AIM: To determine the microhardness of several light-curing dental restorative materials at the top surface as well as at a depth of 2mm. METHODS: Comparisons were made using different light sources. Four groups of five specimens each (3mm diameter, 2mm thick) of Z250 (composite), Filtek Flow (flowable composite), Dyract AP (compomer) and Dyract Flow (flowable compomer) were cured using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 mW/cm2 and 400 mW/cm2 and an Optilux 501 ramping light. Vickers microhardness tests were performed at the top surface and at the bottom surface. RESULTS: Significant differences in microhardness between the top and bottom surfaces were demonstrated for all materials and with all light sources (p<0.05). The different exposures also produced significant differences (p<0.05). The light source used had less of an effect on the hardness of the compomers than the composites. CONCLUSIONS: Effective hardness ratios between the top and bottom surfaces were achieved with all three curing protocols. The effect of total energy application must be taken into account before assumptions can be made as to the effect on hardness using different exposure methods.

Compomers↗

PubMedDate not supplied

Effect of power density on shrinkage of dental resin materials.

This study compares volumetric changes and rates of shrinkage during different stages of polymerization of dental resin composites and compomers exposed to the same total energy by using two different combinations of power density and exposure duration. A hybrid composite and its equivalent flowable and a compomer and its equivalent flowable were exposed using a halogen curing unit set at 400 mW/cm2 for 40 seconds and 800 mW/cm2 for 20 seconds: delivering 16 J/cm2 in both cases. Volumetric changes were recorded every 0.5 seconds using a mercury dilatometer. Ten replications per test condition were performed and the data were subjected to ANOVA. Statistically significant differences in shrinkage values and rates among different power densities were determined by means of paired t-tests at a 95% confidence level. Significantly more shrinkage (p<0.05) was found for the higher filled materials, Z250 and Dyract AP, when higher power density was used. However, no significant differences were found between their flowable counterparts when exposed to various power densities. Of the four materials, only Dyract AP exhibited no significant difference in shrinkage rate when various power densities were used. All the other materials exhibited significantly higher rates (p<0.05) at the higher power density.

Compomers↗