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PubMed2006

A simple mounting model for consistent determination of the accuracy and repeatability of apex locators.

AIM: To develop a precise and simple mounting model (MM) for evaluating apex locators and to compare the repeatability of the MM with a conventional visual method (VM). METHODOLOGY: Electronic working length determination was performed in 32 maxillary central incisors using two methods: (i) the MM method and (ii) a conventional VM. The MM utilizes a micrometer to determine the distance travelled by the measuring file during working length determination. In the VM, the length of the measuring file (representing the working length) is determined visually using a caliper and a microscope at 6x magnification. Each measurement was repeated once. The repeatability of each method was evaluated by calculating the coefficient of repeatability. RESULTS: The coefficient of repeatability, which includes 95% of the differences between repeated measurements, was 0.04 mm for MM compared with 0.9 mm for VM. The measurement error of MM was significantly lower than VM (0.02 and 0.4 mm respectively). There was a statistically significant difference between the means of absolute difference in repeated measurements: MM 0.01 mm (95% confidence interval (CI): 0.01; 0.02 mm) compared with VM 0.4 mm (95% CI: 0.3; 0.5 mm). CONCLUSION: The new MM had superior repeatability in comparison with the conventional method where visual interpretation is a source of inaccurate measurement.

Electronics, Medical↗
PubMed2005

In-vitro microleakage of repaired fissure sealants: a randomized, controlled trial.

UNLABELLED: The aim of this study was to investigate whether differences in surface treatment prior to repair influenced the seal of a resin fissure sealant placed on the occlusal surfaces of permanent molar teeth. SETTING: In-vitro study. SAMPLE AND METHODS: One hundred and twenty-eight extracted human first and second molars were randomly allocated to one of four groups of 32 teeth each. A light cured, unfilled, opaque resin fissure sealant (Delton) was placed on their occlusal surface following cleaning by prophylaxis and acid etching. Following storage in artificial saliva (Saliva Orthana) for a week, duplication of sealant failure was carried out. The teeth were then subjected to one of four different surface treatments: Group 1: with a slow-speed prophylaxis brush followed by acid etching (control method); Group 2: a slow-speed bur and acid etching; Group 3: air abrasion and acid etching; and Group 4: acid etching and application of a bonding agent. Following a further week of storage in artificial saliva two layers of impermeable varnish were applied to the nonocclusal surfaces of the teeth; their apices were then sealed with wax and the teeth were immersed in 1% methylene blue for 48 h. The teeth were then sectioned (ISOMET 1000) to achieve three cuts resulting in a maximum of four blocks, i.e. six surfaces per tooth. A total of 715 sections from 126 teeth were scored for microleakage on the intact and repaired side of the fissure sealant. RESULTS: Statistical analysis did not demonstrate any one single method of repair to be superior to the control method for reapplication of the sealant. CONCLUSION: All four techniques compared in this study seem to be acceptable for replacing or repairing lost or fractured fissure sealants. As prophylaxis with a brush rotating at slow speed followed by acid etching, which probably represents current practice, is also the simplest technique that can be practised on children, it is therefore recommended.

Acid Etching, Dental↗
PubMed2005

Evaluation of apical sealing ability and adaptation to dentine of two resin-based sealers.

The purpose of this study was to evaluate the apical sealing ability and adaptation to dentine of two resin-based root canal sealers. The root canals of 55 human maxillary anterior teeth were prepared using a step-back technique and the smear layer removed with 17% ethylenediaminetetraacetic acid. The teeth were divided into two groups of 25 teeth and the remaining five teeth served as control. Then the teeth were prepared and obturated with gutta-percha by a lateral condensation and either AH plus and EndoRez used as a sealer. Twenty teeth from each group were used for the apical leakage test and the remaining five teeth from each group were used for examination under the scanning electron microscope (SEM). For apical leakage test, teeth were covered with nail varnish and sticky wax to within 1 mm of the apical foramen and placed in 2% methylene blue for 7 days. After this period, the teeth were sectioned longitudinally and apical leakage measurements made. The mean value of dye penetration for AH plus was 2.87 +/- 0.43 mm, while that of EndoRez was 4.54 +/- 0.36 mm. The difference between mean of dye penetration was statistically significant (P < 0.01). The SEM examination showed both sealers had better adaptation and penetration in coronal and middle thirds than apical third of root canal. In apical third, AH plus was adapted better adpated to dentine than EndoRez. In conclusion, AH plus sealer has better apical sealing ability and adaptation to dentine than EndoRez sealer.

Composite Resins↗
PubMed2005

An experimental analysis of stresses in simulated flared root canals subjected to various post-core applications.

Cervical root fracture is a major clinical problem in flared root canals treated with different post and core applications. This in vitro study evaluated the stress transfer of different post and core systems to the cervical part of the artificially created flared root canals, by using strain gauges. The post-core systems investigated were: (a) cast post-core system without resin reinforcement, (b) cast post-core system with resin reinforcement, (c) pre-fabricated post and resin core with resin reinforcement. The post-core systems which were cemented on simulated roots were subjected to a load applied at an angle of 45 degrees to the long axis of the simulated roots. The strain gauges which were cemented to the cervical part of simulated roots were connected to the data acquisition module to measure and record the changes in strain data. Specimens restored with resin reinforcement either with cast post-core or pre-fabricated post and resin core transferred the stress to the cervical part of the artificial roots at a rate lower than conventional cast post-core system (P = 0.001; anova and Tukey's post hoc test). It was concluded that the resin reinforcement of root canals before post-core applications reduces the stresses at the cervical part of the root surfaces.

Dental Restoration Failure↗
PubMed2005

Retrospective survival analysis of 3-unit fixed-fixed and 2-unit cantilevered fixed partial dentures.

To evaluate the cumulative survival (CS) rates of fixed partial dentures (FPDs) retained by full-veneer retainers, and those of resin-bonded FPDs provided by graduating dental students for the replacement of a single missing tooth. In 168 patients, 61 3-unit fixed-fixed FPDs and 25 2-unit cantilevered FPDs retained by full-veneer retainers, and 77 3-unit fixed-fixed resin-bonded FPDs and 47 2-unit cantilevered resin-bonded FPDs, were examined for their retention and integrity. The periodontal health, endodontic status and coronal tissues of all abutment teeth were also evaluated. The survival rates of these various designs were analysed with the Kaplan-Meier method. The mean age of all FPDs was 31 months. At 48 months after their insertion, 3-unit FPDs retained by full-veneer retainers had a CS rate of 82%, followed by 2-unit resin-bonded FPDs at 81%, 2-unit FPDs retained by full-veneer retainers at 77%, and 3-unit resin-bonded FPDs at 63%. No significant difference was found between the four designs (P>0.05). Up to both 48 and 60 months, the most common causes of failure were endodontic for FPDs retained by full-veneer retainers, and dislodgement for resin-bonded FPDs. The 3-unit fixed-fixed FPDs retained by full-veneer retainers had the most favourable prognosis after 48 months for replacing a single missing tooth, but the difference between designs was not statistically significant.

Bicuspid↗
PubMed2005

The aesthetics of all-ceramic veneered and monolithic CAD/CAM crowns.

The aim of this study was to examine whether crowns fabricated from machinable blocks would achieve acceptable aesthetics and whether these could compete with the aesthetics of restorations obtained by individual layering technique. Fourteen patients, who were to receive single anterior crown restorations, participated in this study. For each person two kinds of crowns were provided: one crown was made with the Cergogold system. The second one was produced in a Cerec machine and was additionally stained. Three independent examiners assessed the aesthetic appearance of crowns fabricated to match each subject's anterior shade. A scale of 1-6 was used to assess the aesthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 marking the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analysed with the Wilcoxon signed rank test (P<or=0.05). Regardless of the fabrication method the crowns were aesthetically acceptable in all 14 patients. The mean values for the layering technique and for the machined restorations did not differ significantly. Within the limits of this study it was documented, that machinable blocks could attain aesthetically satisfying results.

Ceramics↗
PubMed2005

Clinical marginal and internal gaps of In-Ceram crowns fabricated using the GN-I system.

The marginal and internal gaps of ceramic crowns with alumina copings fabricated using a computer-aided design, computer-aided manufacturing system, were evaluated in vivo using silicone materials. Black and white silicone materials were used to record the marginal and internal gaps of 82 In-Ceram crowns before final cementation. The silicone materials were sectioned bucco-lingually and mesio-distally and viewed under a microscope to measure the thickness of the white silicone layer. Sixteen reference points were measured on each specimen. The mean marginal gaps were compared among the anterior, premolar and molar teeth, and the mean gaps at the reference points within the groups were compared by analysis of variance and the Dunnett T3 test. The mean marginal gap was 66.8 mum. There were no differences in marginal gaps among the three groups. In all the groups, the marginal gaps were the smallest, whereas the occlusal gaps were the largest. The mean marginal gaps of the In-Ceram crowns with the alumina copings fabricated using the GN-I system were within the range of clinically acceptable values.

Aluminum Oxide↗
PubMed1996

A retrospective clinical study of resin-bonded cingulum rest seats.

PURPOSE: The purpose of this study was to evaluate the success of the resin-bonded cingulum rest seats (RBCRS) supporting removable partial dentures. MATERIALS AND METHODS: Twenty-six patients who had been treated with RBCRSs were recalled and examined. RESULTS: None of the patients who had RBCRSs placed on their teeth experienced debonding, and none of the teeth showed clinically significant signs of wear to the rest seats. CONCLUSIONS: The use of RBCRSs to support removable partial dentures is a highly successful method of treatment.

Adult↗
PubMed1997

Short-term results of IPS-Empress full-porcelain crowns.

PURPOSE: A leucite-reinforced, glass-ceramic material was recently introduced for clinical use. In this clinical trial, IPS-Empress material was tested in the form of full-porcelain crowns. MATERIALS AND METHODS: Thirty-four patients were restored with 78 full-porcelain crowns. After etching the crowns with hydrofluoric acid, they were silanized and luted using dentin bonding agents and resin composite cement, which was primarily a dual-cured type. The 41 anterior and 37 posterior crowns were evaluated clinically with a mirror and probe, radiographically, and using clinical photographs, according to the modified United States Public Health Service criteria. Restorations having neither charlie nor delta criteria were defined as successful, and their survival rate was calculated according to Kaplan-Meier analysis. RESULTS: The mean observation period for the 78 restorations was 19.7 +/- 8.5 months. Seventy-four crowns were defined as successful. Four restorations failed because of fractures. Three of the four failures occurred in the first 2 months after cementation. The survival rate was estimated to be 95% successful after 2 years in service. Eighty percent of the crowns demonstrated an excellent esthetic result. CONCLUSIONS: The initial clinical results of this esthetic full-porcelain crown system are encouraging. However, because of fatigue phenomena for all ceramic materials, a longer observation period is needed to provide a definitive prognosis about the long-term clinical behavior.

Aluminum Silicates↗
PubMed1999

Dental cutting with diamond burs: heavy-handed or light-touch?

PURPOSE: The cutting efficiency of diamond dental burs using different handpiece loads was evaluated against simulated enamel, a machinable glass ceramic (Macor). MATERIALS AND METHODS: An ultra-high-speed dental handpiece was mounted in a frictionless bearing so that the pressure applied at the contact interface between the dental bur and the cutting substrate was controlled. One type of coarse- and two types of medium-grit diamond burs were studied. Handpiece loads of 44, 91.5, and 183 g were applied at the bur/Macor interface, and cutting efficiency was determined as the amount of Macor removed in ten 30-second-duration cuts that were 4 mm in length. The data were analyzed by one-way ANOVA and a post-hoc Scheffé test at an a priori alpha = 0.05. RESULTS: Cutting efficiency depended on both the diamond grit of the bur and the load applied to the handpiece. CONCLUSIONS: The pressure used by most dentists, about 100 g at the bur tip, appears to be optimal for medium-grit burs. If the pressure applied to the handpiece is markedly increased, there was no increase in cutting efficiency for medium-grit burs. In contrast, an increased handpiece pressure raises the cutting efficiency of coarse-grit burs but the effect of this enhanced rate of cutting on the pulpal tissues is uncertain. Cutting efficiency also appeared to be dependent on debris accumulation between the diamond chips.

Analysis of Variance↗
PubMed1999

A technique to create appropriate abutment tooth contours for removable partial dentures.

A technique is presented for using light-cured composite resin to create desirable contours on abutment teeth for the retention and support of removable partial dentures. The desired tooth shape is created on a diagnostic cast, captured in a clear temporary splint material, and formed in resin on the abutment teeth with the splint acting as a matrix.

Composite Resins↗
PubMed2001

In vitro comparison of the fracture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration.

PURPOSE: This in vitro study evaluated 6 post systems over 4 simulated clinical stages of tooth restoration to (1) determine quantitatively the fracture resistance strength at each stage when a static loading force is applied to cause failure; (2) determine the failure mode for each post system at each simulated clinical stage; and (3) determine the feasibility of removing failed post systems. MATERIALS AND METHODS: Ten post systems made with various materials and designs were tested at the following 4 stages of simulated clinical treatment: stage #1: posts only, loaded using a 3-point loading model to failure, to determine transverse strengths and failure modes for each post system; stage #2: posts alone, bonded into teeth; stage #3: posts bonded into teeth with core build up; stage #4: post and core build up and full veneer restoration. For stages #2 through #4, the coronal portion of 60 mandibular premolars was amputated at the cemento-enamel junction, the canals were treated endodontically, and the specimens were mounted in acrylic blocks. A testing force was applied to the posts at 90 degrees to the long axis of the tooth, 4 mm from the cemento-enamel junction. The O'Brien test for constant variance was performed over the treatment groups. For nonconstant variance, the Welsh analysis of variance was used to test for equalities of treatment means. The Tukey Kramer procedure determined which treatment procedures differed. RESULTS: The failure thresholds for each post system were significantly different at each stage of testing, but the order of test results by post type remained generally consistent from one stage to the next. ParaPosts (Coltene, Whaledent Int, New York, NY) and core build up resulted in significantly higher failure thresholds through all 4 stages of testing. This post system also consistently displayed a high number of nonfavorable tooth fractures. FibreKor post and cores (Jeneric Pentron Inc, Wallingford, CT) resulted in significantly lower failure threshold values in stages #2 through #4. This post system displayed no tooth fractures in stages #2 and #3 and a similar number of nonfavorable tooth fractures in stage #4 when compared with the other systems. C-Post (Bisco Dental Products, Schaumburg, IL), CosmoPost (Ivoclar Vivadent North America Inc, Amherst, NY), and AesthetiPost (Bisco Dental Products) grouped in descending order through stages #2 to #4. These systems displayed intermediate fracture resistance strengths, as well as a moderate number of nonfavorable tooth fractures. CosmoPost exhibited a significant number of brittle post fractures with fragments left in the root canal at all stages. The fracture resistance of the cast metal post varied from stage to stage. No teeth fractured at stage #2. At stage #3, 9 of 10 teeth fractured nonfavorably, and all teeth fractured nonfavorably in stage #4. CONCLUSIONS: The fiber posts evaluated provided an advantage over a conventional post that showed a higher number of irretrievable post and unrestorable root fractures. At the stage of final restoration insertion, there was no difference in force to failure for all but the FibreKor material, which continued to be weaker than all other tested materials. The fiber posts were readily retrievable after failure, whereas the remaining post systems tested were nonretrievable. J Prosthodont 2001;10:26-36.

Analysis of Variance↗
PubMedDate not supplied

Effect of core diameter and surface treatment on the retention of resin composite cores to prefabricated endodontic posts.

PURPOSE: With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. MATERIALS AND METHODS: One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. RESULTS: The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. CONCLUSIONS: Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.

Analysis of Variance↗
PubMed1996

Endodontic measurements in digital radiographs acquired by a photostimulable, storage phosphor system.

Digora is a newly developed digital system for intraoral radiography utilizing photostimulable storage phosphor image plates. The aim was to test the quality of the system in respect to the visibility of endodontic files and root apices at different exposures. In teeth from five dry mandibular jaw sections, Hedstrom files no. 15 were placed with the file tip at varying distances from the apex. The specimens were covered with soft tissue equivalent material and placed behind a 2-cm thick polymethyl methacrylate cylinder filled with water. Distance from focus to image plate was 30 cm. Exposures were made at 60 kV and 7 mA at 7 timer settings from 16 ms to 1000 ms in 50% increments. All images were viewed from the monitor by each of 8 observers allowed to use available contrast enhancement facilities to obtain subjectively good image quality. Utilizing built-in measurement functions, distances from file tip and root apex, respectively, to a reference line were measured in 0.1 mm. For measurements between file tip and reference line, and root apex and reference line, there was no statistically significant difference between measurements made at the lowest exposure, compared to the second lowest exposure but there was a statistically significant difference compared to the 5 highest. Measurements at the second lowest exposure were not significantly different from those obtained at the 5 highest exposures. Interobserver variability expressed as standard deviation between observers showed the largest value for measurements obtained at the lowest exposure. The mean observed distances between the tip of the file and the root apex were calculated and showed no statistically significant differences between different exposures. We concluded that the Digora intraoral image plate system provided reliable endodontic measurements even at very low exposures.

Analysis of Variance↗
PubMed1997

Three independent canals in the mesial root of a mandibular first molar.

Endodontic therapy was performed in a mandibular first molar with three canals in the mesial root. The mesiobuccal and the mesiolingual canals were found in their normal locations. The third was located in the middle of the distance between the other two. Radiographically, it ended in its own distinct foramen. Many reports deal with three orifices in the mesial root, but very few describe three independent canals, indicating a rare anatomical configuration. To locate the third possible intermediate canal it was suggested to reduce the mesial dentinal wall of the pulp chamber after instrumenting the main two canals.

Adult↗
PubMed1997

A comparison of dentine removal using safety or conventional Hedstrom files.

Mandibular molars (n = 20) were divided and the mesial roots mounted in an acrylic mould which allowed them to be removed, sectioned horizontally and then reassembled. The furcal root canal wall thickness 7 mm from the apex was measured prior to instrumentation. The roots were allocated to two groups (n = 10). One group was instrumented using the step back technique with safety Hedstroms in one canal and conventional Hedstrom files in the other canal. The second group was instrumented using a crown down approach (using files and Gates Glidden drills to provide early radicular access). The furcal root canal wall thickness was then remeasured and the amount of dentine removed calculated. The results showed that the safety Hedstrom file removed less dentine from the furcal region of the canal compared to the conventional Hedstrom file. This however was not statistically significant (Paired t test, n = 10, p > 0.05). The amount of dentine removed using the crown down technique was significantly greater than that using the step back technique (Two sample t, n = 20, p < 0.01). In conclusion, less dentine was removed from the furcal region with safety Hedstrom files compared to conventional Hedstrom files; however, Gates Glidden drills removed more dentine than either type of hard file.

Dental Instruments↗
PubMed1997

Effect of laser treatment on the root canal of human teeth.

The purpose of this study was to examine the morphological and temperature changes of the apical portion of human extracted teeth treated by Nd: YAG, CO2 and Argon-lasers. Seventy-two single-rooted human teeth were studied. The root canals were prepared conventionally. Laser treatment of the apical portion of the canal was carried out by means of an optic fiber or metal tip. Temperatures were recorded thermographically. Two-thirds of the specimens were stained with black India ink and 36% silver ammonium fluoride solution. All specimens were irradiated by the three types of lasers at several intensities and the temperatures were recorded. Half of the specimens were prepared for the telescopic light microscope and for scanning electron microscopic observation, and the rest for histopathological examination by light microscope. The scanning electron microscopic evaluation showed that the laser energy vaporized the deposited debris, producing a glaze-like surface. The histopathological investigation revealed a tapered, enlarged apical lased area. All three laser devices were capable of vaporizing the debris in this way but the degree of morphological change was highly dependent on energy level and duration. The Argon-laser produced the highest temperatures.

Argon↗