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S D Heintze

Publications and source records attributed to S D Heintze.

9 recordsLinked to original sources
PubMed2006

How to qualify and validate wear simulation devices and methods.

The clinical significance of increased wear can mainly be attributed to impaired aesthetic appearance and/or functional restrictions. Little is known about the systemic effects of swallowed or inhaled worn particles that derive from restorations. As wear measurements in vivo are complicated and time-consuming, wear simulation devices and methods had been developed without, however, systematically looking at the factors that influence important wear parameters. Wear simulation devices shall simulate processes that occur in the oral cavity during mastication, namely force, force profile, contact time, sliding movement, clearance of worn material, etc. Different devices that use different force actuator principles are available. Those with the highest citation frequency in the literature are - in descending order - the Alabama, ACTA, OHSU, Zurich and MTS wear simulators. When following the FDA guidelines on good laboratory practice (GLP) only the expensive MTS wear simulator is a qualified machine to test wear in vitro; the force exerted by the hydraulic actuator is controlled and regulated during all movements of the stylus. All the other simulators lack control and regulation of force development during dynamic loading of the flat specimens. This may be an explanation for the high coefficient of variation of the results in some wear simulators (28-40%) and the poor reproducibility of wear results if dental databases are searched for wear results of specific dental materials (difference of 22-72% for the same material). As most of the machines are not qualifiable, wear methods applying the machine may have a sound concept but cannot be validated. Only with the MTS method have wear parameters and influencing factors been documented and verified. A good compromise with regard to costs, practicability and robustness is the Willytec chewing simulator, which uses weights as force actuator and step motors for vertical and lateral movements. The Ivoclar wear method run on the Willytec machine shows a mean coefficient of variation in vertical wear of 12%. Force measurements have revealed that in the beginning of the stylus/specimen contact phase the force impulse is 3-4 times higher during dynamic loading than during static loading. When correlating material properties to the wear results of 23 composite resins subjected to the Ivoclar method, some parameters could be identified and incorporated into a wear formula to predict wear with the Ivoclar method. A round robin test evaluating the wear of ten dental materials with five wear simulation methods showed that the results were not comparable, as all methods follow different wear testing concepts. All wear methods lack the evidence of their clinical relevance because prospective studies correlating in vitro with long-term in vivo results with identical materials are not available. For direct restorative materials, amalgam seems to be a realistic reference material. For indirect, namely crown and bridge materials, low strength ceramic is appropriate.

Biomechanical Phenomena↗
PubMed2005

A comparison of three different methods for the quantification of the in vitro wear of dental materials.

OBJECTIVE: Different approaches are utilized to quantify the wear generated on flat specimens with a wear simulator. However, there are no systematic studies comparing different wear quantification methods with a series of materials that exhibit different wear rates. METHODS: Sixteen restorative materials, including 14 composites (BelleGlass, Chromasit, Estenia, Esthet-X, Four Seasons, Heliomolar RO, Heliomolar HB, Herculite XRV, InTen-S, Point 4, SureFil, Targis cured at 95 and 130 degrees C, Tetric Ceram) as well as an amalgam (Amalcap) and a ceramic (Empress) material, were subjected to attrition wear against standardized Empress antagonists in the Willytec wear simulator (120,000 cycles, 5 kg, 1.6 Hz). The volume and maximal vertical loss were quantified directly on the specimens with a profilometry device (Perthometer) and the FRT MicroProf optical sensor. After the fabrication of plaster replicas, the loss was also determined with a 3D laser scanning device. For the statistical analysis, the data were subjected to a logarithmic transformation. Intraclass correlation was calculated to measure the agreement among all three methods, while limits of agreement were used to compare one method against another. RESULTS: There was a very good agreement between all three quantification methods for both volume and vertical loss. The mechanical sensor measured consistently higher values compared to the optical sensors for the volume loss (correction factor 0.95), whereas for the vertical loss, consistently lower values were obtained (correction factor 1.17). However, the ranking of the materials was only marginally influenced by the quantification method. SIGNIFICANCE: All three sensors are suitable for the quantification of wear facets. Due to speed and simplicity, the laser sensor has greater advantages over the two other sensors.

Acrylic Resins↗
PubMed2005

Surface roughness and gloss of dental materials as a function of force and polishing time in vitro.

OBJECTIVES: The purpose of this study was (1) to analyze the influence of polishing time and press-on force on the surface gloss and roughness of dental materials by using a three-component rubber-based polishing system and to compare the results with those obtained in conjunction with an optimal polishing procedure and application of the specimens to a metal matrix, (2) to estimate the correlation between surface gloss and surface roughness. METHODS: Eight flat specimens were made of each dental material (Tetric Ceram [TC], Tetric EvoCeram [TE], Heliomolar [HM], Compoglass [CO] and Amalcap [AM]) and polished with 4000-grit SiC and a polishing liquid. Subsequently, the mean surface roughness (Ra) was measured with an optical sensor (FRT MicroProf) and the gloss (Gl) with a glossmeter (Novocurve). Prior to polishing the specimens with the polishing system, the surface was pre-roughened with 320-grit SiC paper and polishing was performed under water cooling at 10,000rpm, applying a controlled force of 2N. Each component of the Astropol system (F/P/HP) was used for 30s and Ra and Gl were measured at 5-second intervals. Other specimens of the same materials were polished with a controlled force of 4N or they were applied to a metal matrix and, subsequently, Ra and Gl were measured. To measure the influence of the polishing time on the surface gloss and roughness, repeated ANOVA with post-hoc paired t-tests was carried out in log-transformed Ra and gloss values. To estimate the correlation between Ra and Gl, the Spearman and Pearson correlation was calculated. RESULTS: (1) Surface gloss and surface roughness were time-dependent, showing the greatest improvement already after 5s of polishing with each of the polishing components, with the exception of AM, for which HP was not effective. The patterns of improvement varied considerably from material to material, but they were more consistent with regard to Gl than to Ra. (2) Ra was statistically significantly higher only in TC, TE and CO when 4N of force was applied instead of 2N. (3) Polishing the surface with a polishing machine resulted in a significantly better surface gloss in all materials. (4) After applying the specimens to a metal matrix, the surface roughness of all dental materials was significantly higher when compared to polished specimens except for TC. (5) Correlations between gloss and roughness were in general negative but they were higher for individual measurements compared to the differences between two consecutive measurements. SIGNIFICANCE: Both surface gloss and surface roughness were material-dependent and influenced by the polishing time and applied force. As gloss and roughness proved to be closely associated with each other, gloss assessment may be a sufficient method to screen materials with regard to their polishability.

Acrylic Resins↗
PubMed2005

Influence of the antagonist material on the wear of different composites using two different wear simulation methods.

OBJECTIVES: The aim of the study was to evaluate two ceramic materials as possible substitutes for enamel using two wear simulation methods, and to compare both methods with regard to the wear results for different materials. METHODS: Flat specimens (OHSU n=6, Ivoclar n=8) of one compomer and three composite materials (Dyract AP, Tetric Ceram, Z250, experimental composite) were fabricated and subjected to wear using two different wear testing methods and two pressable ceramic materials as stylus (Empress, experimental ceramic). For the OHSU method, enamel styli of the same dimensions as the ceramic stylus were fabricated additionally. Both wear testing methods differ with regard to loading force, lateral movement of stylus, stylus dimension, number of cycles, thermocycling and abrasive medium. In the OHSU method, the wear facets (mean vertical loss) were measured using a contact profilometer, while in the Ivoclar method (maximal vertical loss) a laser scanner was used for this purpose. Additionally, the vertical loss of the ceramic stylus was quantified for the Ivoclar method. The results obtained from each method were compared by ANOVA and Tukey's test (p<0.05). To compare both wear methods, the log-transformed data were used to establish relative ranks between material/stylus combinations and assessed by applying the Pearson correlation coefficient. RESULTS: The experimental ceramic material generated significantly less wear in Tetric Ceram and Z250 specimens compared to the Empress stylus in the Ivoclar method, whereas with the OHSU method, no difference between the two ceramic antagonists was found with regard to abrasion or attrition. The wear generated by the enamel stylus was not statistically different from that generated by the other two ceramic materials in the OHSU method. With the Ivoclar method, wear of the ceramic stylus was only statistically different when in contact with Tetric Ceram. There was a close correlation between the attrition wear of the OHSU and the wear of the Ivoclar method (Pearson coefficient 0.83, p=0.01). SIGNIFICANCE: Pressable ceramic materials can be used as a substitute for enamel in wear testing machines. However, material ranking may be affected by the type of ceramic material chosen. The attrition wear of the OHSU method was comparable with the wear generated with the Ivoclar method.

Aluminum Silicates↗
PubMed2005

Wear of ten dental restorative materials in five wear simulators--results of a round robin test.

OBJECTIVE: The purpose of the present study was to prove the hypothesis that different wear measurement methods generate different material rankings. METHODS: Ten restorative materials, eight composites (BelleGlass, Chromasit, Estenia, Heliomolar RO, SureFil, Targis cured at 95 and 130 degrees C, Tetric Ceram) an amalgam (Amalcap) and a ceramic (Empress) have been evaluated with regard to the wear with five different wear methods (IVOCLAR, ZURICH, MUNICH, OHSU, ACTA). Every center received specimens, which Ivoclar Vivadent had made using the same batch. The test centers did not know which brand they were testing. After completion of the wear test, the raw data were sent to IVOCLAR for further analysis. The statistical analysis of the data included logarithmic transformation of the data, the calculation of relative ranks of each material within each test center, measures of agreement between methods, the discrimination power and coefficient of variation of each method as well as measures of the consistency and global performance for each material. RESULTS: Relative ranks of the materials varied tremendously between the test centers. When all materials were taken into account and the test methods compared with each other, only ACTA agreed reasonably well with two other methods, i.e. OHSU and ZURICH. On the other hand, MUNICH did not agree with the other methods at all. The ZURICH method showed the lowest discrimination power, ACTA and IVOCLAR the highest. Materialwise, the best global performance was achieved by Empress, which was clearly ahead of BelleGlass, SureFil and Estenia. In contrast, Heliomolar RO, Tetric Ceram and especially Chromasit demonstrated a poor global performance. The best consistency was achieved by BelleGlass and SureFil, whereas the consistency of Amalcap and Heliomolar RO was poor. SIGNIFICANCE: As the different wear simulator settings measure different wear mechanisms, it seems reasonable to combine at least two different wear settings to assess the wear resistance of a new material.

Acrylic Resins↗
PubMed1998

Urinary fluoride levels and prevalence of dental fluorosis in three Brazilian cities with different fluoride concentrations in the drinking water.

Urine samples from three daytime periods were collected from 545 5-50-year-old residents of three different Brazilian cities: Garça had fluoridated drinking water since 1973, Bauru since 1975 and Itápolis was not fluoridated. Dental fluorosis was examined in 985 5-24-year-olds using the Thylstrup-Fejerskov index (TF). The subjects were asked to estimate their daily intake of liquids and frequency of beverage consumption. The analysis of 94 water samples showed high variations in the fluoride content of the drinking water. The mean fluoride concentration of the water samples in Garça was 0.9 mg/L (range 0.75-1.2), in Bauru 0.64 mg/L (range 0.01-1.3), and in Itápolis 0.02 mg/L. Mean urinary fluoride concentration was 1.31 mg/L (s 0.61) in Garça, 0.88 mg/L (s 0.49) in Bauru, and 0.39 mg/L (s 0.21) in Itápolis. Self-reported daily liquid intake was not related to urinary fluoride concentration. The mean prevalence of fluorosis was 13.3% in Garça, 6.8% in Bauru, and 1.7% in Itápolis, with mainly categories TF 1 and TF 2 being recorded. Subjects with dental fluorosis tended to show a higher mean urinary fluoride concentration but the difference was not statistically significant. The study showed that fluoride exposure measured by urinary fluoride excretion was within the range expected for the level of fluoride concentration in the drinking water. However, enamel fluorosis tended to be markedly lower than expected. This study revealed that fluoride levels in the two cities with fluoridated drinking water were variable. To optimise anticaries benefits and minimise the risk of fluorosis greater control of the fluoride dosing of the drinking water is required.

Adolescent↗
PubMed1996

Effectiveness of three different types of electric toothbrushes compared with a manual technique in orthodontic patients.

Patients undergoing orthodontic treatment with fixed appliances are at risk of developing carious white spot lesions and gingival inflammation because of the challenge of oral hygiene. The purpose of this study was to evaluate under home conditions the effectiveness of three different types of electric toothbrushes during active appliance therapy: Interplak (Bausch & Lomb, Berlin, Germany), Rota-dent (Rota-dent, Kusnacht, Switzerland), and Braun Oral-B Plaque Remover (Braun/Oral-B, Kronberg, Germany). A manual technique, which included normal toothbrush, interdental brush, and dental floss, served as reference. The study was structured as a single-blind "Latin square design" study. Thirty-eight orthodontic patients were randomly allocated to groups who, within the test period, alternately used the toothbrushes. Before getting a new toothbrush that was to be used for a period of 4 weeks, each patient received video and written instructions. For another 4 weeks, the patient returned to the usual oral hygiene procedures before receiving the next new toothbrush. Oral hygiene was evaluated at the start of a new test period and after 2 and 4 weeks. Clinical scores included a modified O'Leary Plaque Index and Ainamo Gingival Bleeding Index. Wilcoxon rank testing for aggregated surfaces revealed statistically significantly lower plaque scores for Rota-dent than for the manual technique (p < 0.01). For all other toothbrushes, no differences were found in comparison to the manual technique. For Plaque Indices of specific sites, statistical analysis revealed all electric toothbrushes to be equal to the manual technique. No differences in Gingival Bleeding Indices were found after 4 weeks with either toothbrush. Patients with poor oral hygiene who used Rota-dent and Braun Oral-B Plaque Remover OD5 had statistically significantly lower plaque scores compared with the manual technique (p < 0.01; p < 0.05); for patients with good oral hygiene, these differences were neutralized. It may be concluded that electric toothbrushes of the new generation are a real alternative to the often laborious manual tooth cleaning procedures used during active appliance therapy. Patients with poor oral hygiene may benefit from them especially because plaque removal can be achieved easier and faster.

Adolescent↗