Comparison of micro-CT imaging and histology for approximal caries detection.

Histological sectioning is a generally accepted in vitro validation method for caries detection techniques. However, it requires cumbersome sample preparation and induces irreversible sample destruction. Micro-Computer Tomography (micro-CT) allows non-destructive imaging of tooth structure. The aim of this study was to compare the performance of histological sectioning and micro-CT imaging in detecting approximal carious lesions. Unlike previous studies, evaluation is objectified by comparing visual appearance of exactly corresponding anatomical regions. Sixty extracted human teeth were scanned with a desktop micro CT system. Axial histological slices were prepared and photographed. Sample preparation, combined with dedicated image processing, ensured selection of identical anatomical regions on radiographic and histological images. Evaluation of the presence and extent of carious lesions was performed by four dentists using custom-designed software. Each section was scored independently (histo or micro CT). Scores of approximal surfaces were retained for further analysis. Spearman's correlation coefficients (0.738 to 0.829, p < 0.0001) showed a good agreement between signs of carious lesions in the identical region obtained with both methods. Bland-Altman plots showed that 90.76% of the data points were within the limits of agreement. Micro-CT imaging was shown to provide an interesting alternative to histological sectioning as detection method for carious lesions.

Comparison of occlusal caries detection using the ICDAS criteria on extracted teeth or their photographs.

BACKGROUND: Using photographs of occlusal surfaces instead of extracted teeth for the detection of caries can be useful in multicenter studies or education. Using a panel of observers, ICDAS scores on teeth or photographs were evaluated against the histological gold standard. The hypothesis was that both outcomes were equivalent. METHODS: Four examiners with different experience in ICDAS scored photographs of occlusal surfaces of 100 extracted teeth on a monitor using ICDAS criteria. Two of the examiners had previously scored extracted teeth prior to photography. Digital images of histological sections of the teeth were observed by all examiners and consensus scores were given for each investigation site (gold standard). Kappa statistics and Spearman correlation coefficients as well as repeated measure ANOVA were performed. ROC curves were constructed for each examiner and the areas under the ROC-curves (AUC) of both scoring techniques (extracted teeth, digital images) were compared (α = 0.05). RESULTS: Intra- and inter-rater kappa for ICDAS on teeth were 0.81-0.94 and on photographs 0.54-0.88, respectively. Correlation with histology was 0.58- 0.61 for the teeth and 0.50-0.62 for the photographs. AUC of ICDAS scores of extracted teeth (mean 0.89) were slightly higher than those for photographs (mean 0.84). However, both AUC values were not statistically significant (p = 0.38). CONCLUSION: Using photographs to assess occlusal surfaces with the ICDAS criteria was not statistically different from scoring the extracted teeth.

Pre-clinical endodontics: a survey amongst German dental schools.

AIM: To evaluate the state and level of pre-clinical endodontic education in German dental schools and to evaluate differences with regard to intensity and extent of teaching, time devoted to teaching pre-clinical endodontics, personnel resources in teaching and technical equipment. METHODOLOGY: Twenty-eight questionnaires were e-mailed to those in charge of pre-clinical endodontic education in German dental schools. The extent of education, the student-teacher ratio, the teaching content as well as the application of teaching materials and technologies were asked. If, after 4 weeks, no response had been received, the questionnaire was sent out by e-mail again. In the absence of a reply, a phone call was made to the corresponding university to conduct the survey by phone. RESULTS: With feedback from 27 of 28 dental schools, the response rate was 96%. Pre-clinical endodontic education at German universities varied considerably. Theory classes ranged from 5 to 30 h (13.3 h mean), practical classes from 12.5 to 60 h (45.4 h mean). The student to staff ratio varied between 9 : 1 and 30 : 1 (16 : 1 mean). Forty-eight per cent of the universities had a specialist in endodontics or a teacher with a special interest. A dental microscope was available for pre-clinical teaching purposes in 38% of the universities. The majority (63%) of universities taught root canal preparation with rotary nickel titanium instruments. CONCLUSION: Pre-clinical endodontic education varied considerably between German universities because of differences in programme design, staff and course content.

Reproducibility and accuracy of the ICDAS-II for detection of occlusal caries in vitro.

AIM: The aim of this study was to assess inter- and intra-examiner reproducibility and accuracy in the detection and assessment of occlusal caries in extracted human teeth using a newly developed visual method for caries diagnosis (International Caries Detection and Assessment System, ICDAS-II). Serial sectioning and microscopy were used as the 'gold standard'. METHODS: The occlusal surfaces of 100 teeth were examined by 4 dentists using the ICDAS-II graded scores 0-6. Thereafter the teeth were serially sectioned and assessed for depth of the lesion with two histological classification systems. RESULTS: The weighted kappa values for inter- and intra-examiner reproducibility for the ICDAS-II examination were 0.62-0.83. There was a moderate relationship between the visual and both histological examinations (r(s) = 0.43-0.72). At the D1 diagnostic threshold (enamel and dentine lesions) specificity was 0.74-0.91 and sensitivity was 0.59-0.73. At the D3 diagnostic threshold (dentine lesions) specificity was 0.82-0.94 and sensitivity was 0.48-0.83 for the 4 examiners. CONCLUSION: The ICDAS-II system has demonstrated reproducibility and diagnostic accuracy for the detection of occlusal caries at varying stages of the disease process which are comparable to previously reported data using similar visual classification systems.

Approximal caries diagnosis after data import from different digital radiography systems: interobserver agreement and comparison to histological hard-tissue sections.

AIMS: To evaluate the agreement of approximal caries diagnosis obtained with different types of digital radiography systems after image import into a reference system. METHODS: Digital radiographs were taken from 30 extracted human premolars with 60 diagnostic surfaces using a reference and two test systems from which images were imported as TIFF files. Four observers evaluated the radiographs using the reference software. Teeth were sectioned for histology. Agreement between histology and each technique was calculated using receiver operating characteristic (ROC) statistics. RESULTS: The areas under the ROC curves were not significantly different between reference and test systems. CONCLUSIONS: Importing files from different programs did not affect diagnostic accuracy.

Survival of inlays and partial crowns made of IPS empress after a 10-year observation period and in relation to various treatment parameters.

UNLABELLED: This study evaluated the long-term survival of inlays and partial crowns made of IPS Empress. For this purpose, the patient data of a prospective study were examined in retrospect and statistically evaluated. MATERIALS AND METHODS: All of the inlays and partial crowns fabricated of IPS-Empress within the Department of Operative Dentistry at the School of Dental Medicine of Philipps University, Marburg, Germany were systematically recorded in a database between 1991 and 2001. The corresponding patient files were revised at the end of 2001. The information gathered in this way was used to evaluate the survival of the restorations using the method described by Kaplan and Meyer. RESULTS: A total of n = 1624 restorations were fabricated of IPS-Empress within the observation period. During this time, n = 53 failures were recorded. The remaining restorations were observed for a mean period of 18.77 months. The failures were mainly attributed to fractures, endodontic problems and cementation errors. The last failure was established after 82 months. At this stage, a cumulative survival probability of p = 0.81 was registered with a standard error of 0.04. At this time, n = 30 restorations were still being observed. Restorations on vital teeth (n = 1588) showed 46 failures, with a cumulative survival probability of p = 0.82. Restorations performed on non-vital teeth (n = 36) showed seven failures, with a cumulative survival probability of p = 0.53. Highly significant differences were found between the two groups (p < 0.0001) in a log-rank test. No significant difference (p = 0.41) was found between the patients treated by students (n = 909) and those treated by qualified dentists (n = 715). Likewise, no difference (p = 0.13) was established between the restorations seated with a high viscosity cement (n = 295) and those placed with a low viscosity cement (n = 1329).

Determination of root canal curvatures before and after canal preparation (part II): A method based on numeric calculus.

The aim of this paper is to present a new method based on numeric calculus to provide data on any type of root canal curvature at any point of the long axis of the canal. Twenty severely curved, simulated root canals were prepared with rotary FlexMaster and Profile instruments in the crown-down technique and manually in the step-back technique. The inner and outer curvatures were registered in a system of coordinates before and after preparation in increments of 0.5 mm. Using an equalising function, the curvatures were first represented in graphic and algebraic form. The maximum and the mean curvature as well as the length of the arc from the apical foramen to the point of maximum curvature were determined mathematically. An increase in maximum curvature was registered for all four shaping systems investigated. The radius of the inner curvature decreased by 0.5-1.2 mm in the manual systems as a result of the preparation. The Profile system displayed the smallest changes in radius (-0.9 mm) even with the outer curvature, and manual preparation with stainless steel files the most pronounced change (-1.8 mm). The point of maximum curvature at the inner curvature was displaced by 1.6 mm to the apical foramen through manual preparation with Ni-Ti files. At the outer curvature, the maximum displacement (1.8 mm) recorded was also the result of preparation with Ni-Ti hand files, while a displacement of only 0.3 mm to the apical foramen was recorded with the other systems. The method offers a means of determining curvatures precisely without random specification of reference points. The method is also capable of registering only minor changes in curvature in the two-dimensional long axis of the canal.

Determination of root canal curvatures before and after canal preparation (part 1): a literature review.

The continuing development of methods and materials for root canal preparation is resulting in enhanced preparation techniques with only minor alterations to the canal morphology. Improved evaluation methods are required for differentiated assessment of these innovations. One criterion for assessment of the preparation quality of curved root canals is preparation-induced straightening of the canal. The first canal curvature measurements served to divide teeth into different curvature classes. However, their actual execution represented mere angular measurement rather than root curvature assessment. This purely graphic method lacked precision, nor could it be readily applied to all tooth groups. Further developments of that method resulted in it being applicable to molars and to canals with multiple curvatures. Some years ago, the graphically determined curvature radius was added as a further parameter to measurement of the canal deviation angle, thus permitting a curvature to be correctly described for the first time in geometric and analytic terms. The first mathematically accurate description was presented by Dobó-Nagy et al., who correctly described the mean canal curvature in a two-dimensional image in concrete terms by means of fourth-degree polynomial functions. Recent developments in the application of microcomputed tomography of extracted teeth permit non-destructive three-dimensional assessment of root canal configurations. It remains to be seen whether this resource-intensive form of in vitro examination can assert itself.

Root-canal shaping with manual and rotary Ni-Ti files performed by students.

AIM: To investigate root-canal shaping with manual and rotary Ni-Ti files performed by students. METHODOLOGY: Thirty undergraduate dental students prepared 150 simulated curved root canals in resin blocks with manual Ni-Ti files with a stepback technique and 450 simulated curved canals with rotary Ni-Ti files with a crowndown technique. Incidence of fracture, preparation length, canal shape and preparation time were investigated. Questionnaires were then issued to the students for them to note their experience of the two preparation methods. RESULTS: Zips and elbows occurred significantly (P < 0.001) less frequently with rotary than with manual preparation. The correct preparation length was achieved significantly (P < 0.05) more often with rotary files than with manual files. Instrument fractures were recorded in only 1.3% of cases with both rotary and manual preparation. The mean time required for manual preparation was significantly (P < 0.001) longer than that required for rotary preparation. Prior experience with a hand preparation technique was not reflected in an improved quality of the subsequent rotary preparation. Approximately 83% of the students claimed to have a greater sense of security in rotary than in manual preparation. Overall 50% felt that manual and engine-driven preparation should be given equal status in undergraduate dental education. CONCLUSIONS: Inexperienced operators achieved better canal preparations with rotary instruments than with manual files. No difference in fracture rate was recorded between the two systems.

Root canal shaping with manual stainless steel files and rotary Ni-Ti files performed by students.

AIM: To investigate root canal shaping with manual stainless steel files and rotary Ni-Ti files by students. METHODOLOGY: Two hundred and ten simulated root canals with the same geometrical shape and size in acrylic resin blocks were prepared by 21 undergraduate dental students with manual stainless steel files using a stepback technique or with rotary Ni-Ti files in crown-down technique. Preparation length, canal shape, incidence of fracture and preparation time were investigated. RESULTS: Zips and elbows occurred significantly (P < 0.001) less frequently with rotary than with manual preparation. The correct preparation length was achieved significantly (P < 0.05) more often with rotary Ni-Ti files than with manual stainless steel files. Fractures occurred significantly (P < 0.05) less frequently with hand instrumentation. The mean time required for manual preparation was significantly (P < 0.001) longer than that required for rotary preparation. Prior experience with a hand preparation technique was not reflected in an improved quality of the subsequent engine-driven preparation. CONCLUSIONS: Inexperienced operators achieved better canal preparations with rotary Ni-Ti instruments than with manual stainless steel files. However, rotary preparation was associated with significantly more fractures.

Marginal adaptation of partial crowns cast in pure titanium and in a gold alloy - an in vivo study.

The aim of the present study was to assess in vivo the marginal integrity of partial crowns cast in pure titanium and in a gold alloy. For this purpose, two groups of 25 molars were prepared for partial crowns and then restored with partial crowns cast in Degulor M gold alloy and in pure titanium. At a subsequent session, replicas were produced using a special impression-taking technique. The scanning electron microscope (SEM) technique was used to perform quantitative margin analysis (Tiffmess 1.8 program). The gold alloy partial crowns displayed significantly (P < 0.05) more continuous margin (marginal quality A, <50 microm), and the titanium partial crowns significantly more marginal quality B (50-100 microm) and C (>100 microm). The results show that better marginal integrity can be achieved with gold alloy than with titanium partial crowns. However, in practical terms the difference in marginal quality is only slight, so that the use of pure titanium for single-tooth restorations is justified.

Marginal adaptation of cast partial crowns made of pure titanium and a gold alloy under influence of a manual burnishing technique.

The aim of this study was to determine the marginal adaptation of partial crowns from pure titanium and a gold alloy after two different cementation techniques. Forty freshly extracted human molars were prepared and randomly divided in four groups. Two groups were restored with partial crowns using the gold alloy Degulor M*. In one group, the crowns were fixed on the tooth by using a zinc phosphate cement. In the other group the margins were additionally burnished by using a hand burnisher No. 660. In the other two groups, partial crowns from pure titanium were cemented in the same way. The marginal quality was determined by quantitative margin analysis in the SEM using a replica technique. Partial crowns from a gold alloy showed significantly (P < 0.05) more margin quality A (vertical marginal discrepancy < 50 microm) while partial crowns from pure titanium had significantly (P < 0.05) more margin quality B (vertical marginal discrepancy 50-100 microm) and over-extended margins (quality D). No significant (P < 0.05) difference was found between the conventional cementation technique and the technique with manual burnishing in both material groups.

Longevity of oroincisal ceramic veneers on canines--a retrospective study.

PURPOSE: The longevity of oroincisal veneers on canines of IPS-Empress ceramic for the restoration of lost canine guidance was determined in a retrospective study. MATERIALS AND METHODS: Since 1992, all ceramic restorations made in the Department of Operative Dentistry have been entered in a data base. In that time period, 17 patients with 36 oroincisal veneers on canines to restore lost canine guidance have been documented. The survival rate of the restorations was calculated with the Kaplan-Meier method. RESULTS: The mean follow-up period was 6.74 years. The 6.5-year survival rate was 76%. The 6.5-year survival rate of canine oroincisal ceramic veneers in the maxilla was 74%, and in the mandible 78%. The difference in the survival rate of maxillary and mandibular restorations was not statistically significant. In the follow-up period, 8 of the 36 IPS-Empress canine veneers failed. Reasons for failure were ceramic fracture, fracture of the adhesive bond, and loss of function. CONCLUSION: In view of the longevity, the excellent properties of the IPS-Empress ceramic material, i.e., minimum abrasion of the opposing teeth, and good esthetics, we consider the restoration of lost canine guidance using this technique a viable alternative to the classical precious-metal pinledge or composite buildup.

Marginal characteristics of different filling materials and filling methods with standardized cavity preparation.

PURPOSE: The aim of the present study was to investigate the influence of different filling materials and methods on marginal integrity in Black Class I fillings. MATERIALS AND METHODS: Standardized occlusal cavities were prepared in 80 extracted human molars. The preparations were filled with composite resin (1), with composite resin using the incremental technique (2), an experimental glass-fiber-reinforced (3) and polyester-reinforced (4) composite resin, a direct composite inlay (5), a ceramic insert (6), a Cerafil inlay (7), and with an experimental direct filling using Dyract AP compomer (8). Allocation of the teeth to the test groups was randomized; further processing was done on a blind basis. After the preparation of replicas, the teeth were subjected to a thermomechanical cycling process of 2,000 temperature cycles (5 degrees C/55 degrees C) and 50,000 stress cycles (50 N). This was followed by production of a second set of replicas and quantitative margin analysis by SEM (200X). A dye penetration test was then performed on the mesiodistal section. RESULTS: Groups 1, 2, 5, 6 and 7 displayed a good primary marginal quality, with the proportion of continuous margins reaching more than 85%. Significantly poorer results were recorded for the experimental glass-fiber-reinforced composite resins and Dyract compomer, where the proportion of perfect margins was only between 36% and 73%. In groups 1, 2, 5, 6 and 7, marginal integrity remained stable after the thermomechanical stress cycles, with the Cerafil inlays recording the best values: 89% perfect margins and 3% marginal gaps. In contrast, the experimental composite resins and the compomer underwent a significant (p < 0.05) increase in the proportion of marginal gaps and a significant (p < 0.05) reduction in the proportion of continuous margin. CONCLUSION: The results of this study show that neither Dyract compomer nor the glass-fiber-reinforced composite resins tested can be recommended for use in the occlusally stressed posterior region, whereas the other filling materials and methods were sufficiently stress resistant.

Influence of a high-speed polymerization method on the marginal integrity of composite fillings in Class-II cavities.

The aim of this study was to evaluate the effect of a rapid photopolymerization method on the marginal integrity of composite fillings. Ninety two-surface cavities were prepared in extracted human molars using the SonicSys preparation system. All cavities were bonded with one bonding agent (Syntac) and filled with a microfilled composite (Herculite XRV), a heavy filled composite (Z100 MP), and an Ormocer (Definite) in two increments. Each increment had a thickness of approximately 1.5 mm and was polymerized using either halogen light or the plasma light of Apollo 95 E. In this process, six trial groups each containing 15 fillings were created. After replicas were made, the test teeth were subjected to a thermocycling process of 2000 temperature cycles (5 degrees C/55 degrees C) followed by a wear simulation of 50,000 stress cycles each with 50 N. This was followed by the creation of a second set of replicas, quantitative margin analysis, and dye penetration. A significant (P < 0.05) influence of the thermomechanical stress and a significant (P < 0.05) influence of the factor "material" were shown for the margin criterion "continuous margin" using MANOVA. The factor "light source" produced no significant influence (P = 0.57) on the amount of continuous margin. During the dye penetration, no significant differences between the polymerization methods could be established with the materials Herculite XRV and Z100 MP (H-test according to Kruskall and Wallis). Only with the material Definite was a significantly higher dye penetration observed at the occlusal measuring point in the plasma light group. A rapid polymerization with high light intensity had no adverse effects on the margin quality within the limitations of this in vitro study. However the marginal integrity might have been influenced by the chosen adhesive system/composite resin combination, which does not represent the respective product line. Additionally, further studies ought to show which exposure time is necessary for a sufficient degree of conversion.

Longevity of cast gold inlays and partial crowns--a retrospective study at a dental school clinic.

From 1963 to 1993, 890 patients were treated with 3518 cast gold restorations by students and postgraduate dentists. The longevity of these restorations was studied retrospectively using the patient files. Longevity was calculated using the method described by Kaplan and Meier. After the observation period, 111 (3.2%) of the examined restorations were not in place anymore. The most frequent reasons for failure were caries (33.7%), lack of retention (32.7%), endodontic treatment (29.6%), insufficient marginal adaptation (3.1%) and extraction (1%). The cumulative survival rate and a 95% interval of confidence was calculated for all restorations and for each of the locations and surfaces included in the trial. The 10-year survival rate for occlusal inlays was, 76.1% (12.1) for MO inlays 88.3% (4.2), for DO inlays 83.4% (4.6), for MOD inlays 87.5% (2.4), for partial crowns 86.1% (3.3) and 85.7% (1.7) for all restorations. Based on the statistical method used, the cast gold restorations demonstrated satisfactory longevity results.

Prevalence and quality of root canal fillings in a German adult population. A survey of orthopantomograms taken in 1983 and 1992.

The few studies in which prevalence, technical quality, and success rates of root canal fillings performed in daily practice have been assessed demonstrated a high proportion of inappropriate root fillings and a great variety of periapical radiolucencies (25-60%). The aim of the present retrospective radiographic study was to determine if changes in prevalence, technical quality, and success of root canal fillings had occurred within a decade. To achieve this goal, orthopantomograms taken in patients who attended a University Dental Clinic for the first time in 1983 (group A) and in 1992 (group B) were evaluated by a calibrated examiner. The following criteria were applied to assess the root-filled teeth: length and homogeneity of the root fillings and the periapical state. The prevalence of root-filled teeth increased significantly from an average 0.5 per person in 1983 to 0.8 per person in 1992. The increase was proportionally greater in older patients. In group A, 55.2% of the root fillings ended 0-2 mm before the radiographic apex and in group B this percentage was 56.8. Insufficient homogeneity was found in 25.0% (group A) and 21.9% (group B) of the root fillings. The prevalence of root-filled teeth without periapical destructions was 76.1% (group A) and 74.1% (group B). It is concluded that, in the future, endodontic treatment need will increase because of the steadily growing number of older people. Further efforts in research and dental education should focus on the treatment of curved root canals.

[Mercury concentrations in the urine of children with and without amalgam fillings]. / Quecksilberkonzentration im Urin von Kindern mit und ohne Amalgamfüllungen.

Studies on adults documented that most of the urinary concentration in occupationally non-exposed persons is determined by the number and extent of their amalgam fillings. Very few data concerning the mercury exposure of children are available. In this study the mercury concentration in the urine of 3-15-year-old children with and without amalgam fillings was determined. The mean urinary mercury concentration for the children without amalgam (n = 93) was 0.17 microgram/l, and for the children with amalgam fillings (n = 86) it was 0.70 microgram/l. The creatinine adjusted values were 0.19 microgram/g and 0.64 microgram/g, respectively. This difference was significant (p < 0.001). Also, a significant correlation was found between the number of amalgam points (each amalgam surface had been given 1 to 3 points depending on its extent) and the urinary mercury concentration (r = 0.69).

[The dimensional stability of hydrophilic impression materials after application of a disinfectant]. / Zur Formhaltigkeit hydrophiler Abformmaterialien nach Behandlung mit einem Desinfektionsmittel.

The influence of a disinfectant solution containing glutaraldehyde on the dimensional stability of 2 alginate and 4 elastomeric impression materials has been investigated. Die models were measured using a computer-controlled method and compared to the master die to assess the three-dimensional change in the impression material. After an immersion time of 10 min, a dimensional change did not occur. When using immersion times longer than 10 min, the accuracy of the alginate materials was generally more affected by the disinfecting solution than that of the elastomeric impression materials.