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Biomedical subjects

M J Noack

Publications and source records attributed to M J Noack.

18 recordsLinked to original sources
PubMed2003

Efficacy of differently concentrated chlorhexidine varnishes in decreasing Mutans streptococci and lactobacilli counts.

The objective of the present prospective trial was to compare the efficacy of differently concentrated chlorhexidine varnishes (EC40) = 40% chlorhexidine and Cervitec = 1% chlorhexidine + 0.1% thymol) on levels of Mutans streptococci (ms), lactobacilli (lb) and plaque formation in interproximal plaque and saliva. Twenty-four volunteers with a high level of ms in saliva were randomized into two groups and treated with the experimental varnishes. Varnish applications were performed in accordance with literature. Over a period of 2 weeks Cervitec was applied three times and EC40 once or twice, depending on ms counts after first application. Four and 12 weeks after final varnish application ms in plaque and saliva were evaluated. Furthermore, lactobacilli (lb) counts in saliva and the effect on plaque formation were recorded. Both varnishes revealed a reduction of ms in interproximal plaque and saliva after 4 and 12 weeks. The highly concentrated varnish revealed a significantly stronger reduction of ms in plaque and saliva compared with the lowly-concentrated varnish. No effect could be demonstrated on lb counts and plaque formation. The results indicate that the chlorhexidine varnishes tested may reduce ms in both interproximal plaque and saliva. However, the application of the highly concentrated varnish EC40 results in a higher decrease of ms in plaque sites and saliva.

Adult↗
PubMed2002

Influence of room lighting on grey-scale perception with a CRT-and a TFT monitor display.

OBJECTIVES: To determine the influence of ambient lighting on grey-scale perception using a cathode-ray tube (CRT) and a thin film transistor (TFT) computer display. METHODS: A cathode ray tube (Nokia XS 446) and a liquid crystal display (Panasonic LC 50S) were used at reduced room lighting (70 lux) and under conditions recommended for a dental operatory (1000 lux). Twenty-seven observers examined twice a modified SMPTE test pattern [0 to 255; 255 to 0] grey-scale values. The corresponding contrast differences were allocated to four ranges of grey levels (I: 0-63; II: 64-127; III: 128-191; IV: 192-255). The influences of monitor type, grey-scale range and illumination were evaluated by means of repeated measures analysis of variance. RESULTS: Detection of differences in monochromatic intensity was significantly earlier with reduced lighting (P<0.0001). When full ambient lighting was used, the TFT display was superior compared to the CRT monitor in ranges II and III (P<0.0001), whereas no differences could be detected for grey intensities between 0 and 63 (P=0.71) and between 192 and 255 (P=0.36). CONCLUSIONS: Background lighting hampers grey-scale perception on computer displays. In this study of one TFT and one CRT monitor, the TFT in full ambient lighting was associated with earlier detection of grey scale differences than CRT.

Adult↗
PubMed2000

Does chemomechanical caries removal affect dentine adhesion?

The purpose of this study was to determine whether shear bond strengths (SBS) to chemomechanically excavated dentine (Carisolv) differed from the SBS after conventional caries removal (bur). The following adhesive systems were used: Dyract AP/NRC/Prime & Bond NT; Dyract AP/Prime & Bond NT; Tetric Ceram/ Syntac SC; Tetric Ceram/Syntac SC (no etch) (TC 2); Definite/Etch & Prime 3.0; Definite/experimental. One-hundred and twenty human molars with occlusal caries were assigned to 12 groups. Sequential caries removal was controlled with laser fluorescence. After water storage, the samples were tested in a single-plane shear test assembly. The results demonstrated differences between the bonding systems, whereas the mode of caries removal had no consistent effect. If total etch technique was neglected, the results of the composite resin (TC 2) indicated a tendency to higher SBS in the Carisolv group (18.6 +/- 4.6 MPa) compared with conventional treatment (14.1 +/- 3.9 MPa). The present data demonstrate that chemomechanical caries removal has no adverse effect on bonding of modern adhesive systems to dentine. Smear layer-dissolving or -modifying bonding systems could potentially benefit from chemomechanical pretreatment.

Analysis of Variance↗
PubMed1999

Glycaemic disorders in denture stomatitis.

The prevalence of glycaemic disorders was investigated in native Upper-Austrians with Candida-associated denture stomatitis. All patients with previously unknown diabetes mellitus were subjected to an oral glucose tolerance test (OGTT) and as a result diabetes was diagnosed in 13% of the patients over 50 years of age. Thirty-five percent of all inspected patients over 50 years of age with denture stomatitis had type 2 diabetes mellitus and 36% had impaired glucose tolerance (IGT). The correlation between Candida-associated denture stomatitis and diabetes mellitus indicates a means for the early diagnosis of diabetes. Hyperglycaemia could not be a predisposition to denture stomatitis, since all patients with denture stomatitis in the age-bracket 26-50 years were without diabetes and only very few of the older patients with diabetes were obese. The correlation between Candica-associated denture stomatitis and type 2 diabetes mellitus could be traced back to a reduced resistance to Candida that preceded the diabetes.

Adult↗
PubMed1992

Marginal adaptation of four tooth-coloured inlay systems in vivo.

This study investigates the margin quality of four different tooth-coloured inlay systems using computer-aided quantitative margin analysis under scanning electron microscopy. Three types of restorations involved chairside procedures using a commercial CAD-CAM apparatus: one type of inlay restoration was milled from preformed glass ceramic blocks, the other two inlay types were milled from preformed porcelain blocks. The fourth system was based on an experimental indirect composite inlay system. Each inlay type was luted with its respective dual-curing luting composite, which was supplied with the system. After 6 months of clinical service, all four systems revealed a significant percentage of submargination indicating occlusal wear of the luting composite. The porcelain inlays and the composite inlays luted with their respective experimental luting composite showed the best marginal adaptation. Luted glass ceramic inlays, in particular, suffered from a significantly higher percentage of inlay margin fractures (9 per cent) and marginal openings (4 per cent) than the other systems. A possible explanation is that the glass ceramic subsurface structure at the inlay-lute interface was weakened by etching with ammonium bifluoride.

Acid Etching, Dental↗
PubMed1991

Margin quality of Class III and IV composites in vitro.

Polymerization shrinkage and thermal expansion/contraction of composites counteract marginal bonding. The purpose of this study was to determine the margin quality of Class III and IV microfilled and hybrid composite restorations placed with adhesive techniques. Two experiments were conducted. In experiment 1, small, beveled Class III cavities were prepared in 24 incisors. Twelve cavities were filled with an experimental microfilled composite (COMPAFILL) and 12 with a control microfilled material (DURAFILL). In experiment 2, standardized large, beveled Class IV cavities were prepared in 24 incisors. Twelve of these incisors were filled with DURAFILL and 12 with the hybrid composite HERCULITE XR. The teeth were stored in water for 21 days. Before and after the restorations were thermocycled (5 degrees C-55 degrees C), replicas were obtained for quantitative analysis in the SEM. Statistical analysis (non-parametric tests, p less than 0.05) revealed that the two microfilled materials behaved very well (greater than 95% excellent margins) in Class III restorations before being thermocycled. After the restorations were thermocycled, the margin quality of DURAFILL decreased to 90% excellence, due to the increase in restoration fractures. Thermocycling did not affect the margin quality in the Class IV cavities, and the hybrid composite showed superior margin qualities (89% excellent). Better margin qualities were obtained in Class III cavities. Class IV restorations showed more overhangs (12%) and submargination (6%) which were technique-related. In no cases were greater than 1% marginal openings found.

Acid Etching, Dental↗
PubMed1991

Radiopacity of composites compared with human enamel and dentine.

A 99.5 per cent pure aluminium step-wedge served as reference for evaluating the radiopacity of 55 anterior and posterior composites. The radiopacity of all materials evaluated was compared with the radiopacity of human enamel and human dentine of equivalent sample thickness. Seventeen composites exhibited a radiopacity significantly greater than that of enamel. Some composites intended for posterior use lack the radiopacity required for posterior composite restorations.

Analysis of Variance↗
PubMed1991

Tooth-colored inlays.

There is an increasing need for conservative treatment with tooth-colored inlay restorations due to esthetic concerns and the decreasing acceptance of amalgam. The use of ceramic materials has become possible by using adhesive luting techniques, in which enamel and ceramic inlays are etched and luted with composite resins. The weakest point is still the poor tensile strength of brittle inlay materials, so most efforts are concentrated on strengthening porcelains by ion exchange, tempering, or improving the composition. Despite the fact that adhesively luted inlays show good marginal adaptation, the luting composite layer is worn out because of the low filler fraction of the resins. For composite inlays, the same resins are used as for direct placement. Despite more effective curing techniques, the wear behavior of composite inlays may have been improved, but it is still less than ideal. In clinically orientated studies, it is clearly demonstrated that the luting procedure is technically sensitive with all systems. The clinical experience is limited to only a few years, so to assess the longevity of adhesively luted inlays, more clinical studies must be done. However, tooth-colored inlays are the most esthetic, conservative restorations dentistry has ever offered its patients.

Composite Resins↗
PubMed1991

[Effects of dentin bonding agents on the proximal margins of ceramic inlays].

Ceramic inlays have shown good marginal seal as long as the margins of the cavities are located in enamel. The purpose of this study was to investigate the marginal seal of ceramic inlays with the cervical margins situated in dentin and to determine the effectiveness of dentin bonding agents. Sintered ceramic inlays were adhesively luted either without dentin bonding agents or with the use of Gluma or Miragebond. After thermocycling and incubation in a colored dye the penetration depth of the dye was measured on sequential sections. The used dentin bonding agents did not improve marginal seal. The glass ionomer cement base was able to prevent further penetration in most of the cases when deep leakage occurred. Unless a tight marginal seal in dentin can be achieved, the indication for adhesively luted inlays must be limited to cavities with margins located in enamel.

Ceramics↗
PubMed1991

Criteria for substituting amalgam with composite resins.

In recent years patients' aesthetic requirements have increased as knowledge of new materials and techniques has spread. Enamel etching and composite filling materials have enabled dentists to meet high functional and aesthetic standards in the placing of anterior and, latterly, posterior restorations. There has been a dramatic growth in the use of posterior composites and the aim of this paper is to provide the practising dentist with guidelines for the use of these materials.

Composite Resins↗
PubMed1991

Marginal adaptation with glass-ceramic inlays adhesively luted with glycerine gel.

The purpose of this study was to examine the effectiveness of glycerine gels in preventing the formation of an oxygen-inhibition layer during the polymerization of composite resin materials. Sixteen glass-ceramic inlays were adhesively luted with and without the application of glycerine gels on the inlay margins before the polymerization of the luting composite resin material. To remove the oxygen-inhibition layer, the inlays were brushed with acetone. Replicas were obtained before and after acetone brushing, and a computerized quantitative marginal analysis was carried out under the scanning electron microscope. Statistical analysis revealed significant differences between the polymerization with and the polymerization without the use of a glycerine gel. The inlay margins polymerized after the application of a glycerine gel showed better marginal adaptation than did the inlay margins polymerized without it, suggesting that oxygen inhibition during polymerization can be prevented by the application of glycerine gels to the surface of composite resin materials.

Ceramics↗
PubMed1990

[Effect of cavity design on the marginal fit of Class I composite fillings].

16 butt joint (Group A) and 16 beveled (Group B) class I cavities were prepared in extracted molars and filled with two hybrid composite resin materials using the enamel etching technique. Replicas were obtained before and after thermocycling (TC) and a computerized quantitative margin analysis was carried out in the SEM. Statistical analysis revealed significant differences (p less than 0.01) between the two groups only after TC. Group B showed significantly less marginal openings than Group A (A: 50.7%, B: 8.4%) after TC. Class I cavities for hybrid composite resin materials should be beveled.

Acid Etching, Dental↗
PubMed1989

[Erosions of hard tooth substance].

Lemon juice was applied to intact and eroded tooth surfaces in vivo to demonstrate the development of erosions based on morphological changes. Under the influence of the fruit acid the protecting pellicles are removed and the enamel demonstrates the typical etch lesion with a honeycomb surface structure. In the dentin the acid works mainly on the peritubular area. Abrasive brushing techniques wear down the already damaged tooth surfaces.

Acid Etching, Dental↗
PubMed1989

[Opacity of composites and hard tooth substance on X-ray].

The opacity of eleven composites, enamel, and dentin was determined quantitatively using densitometric measurements of X-rays. The reference material was aluminium 99.5% which was exposed with each film. Opacity values were 215% for enamel and 118% for dentin. Three of the composite materials demonstrated an opacity similar to enamel, one similar to dentin. The other materials showed higher values than enamel. Consequently, the majority of composites reaches opacity values necessary for the diagnosis of secondary caries.

Composite Resins↗
PubMedDate not supplied

Conventional, digital and contrast-enhanced bitewing radiographs in the decision to restore approximal carious lesions.

The purpose of the present investigation was to compare the accuracy of treatment decisions in proximal sites using three intra-oral radiographic systems. Additionally, the impact of an automated non-linear grey-level display was evaluated. Ten observers assessed 84 surfaces on bitewing radiographs for their requirement of restorative treatment using a 6-rank confidence scale. Radiographs were taken with conventional film images (Ultraspeed), a storage phosphor plate (Digora) and a CCD system (Dexis). Additionally, the Dexis software was expanded by a contrast enhancement routine (Dexis+). The restorative treatment threshold was defined as presence of macroscopic cavitation. Regarding the areas below mean ROC curves no significant differences were detected between the groups (p>0.05). Likelihood ratios for positive test results were: 5.29 (Ultraspeed), 8.14 (Digora), 9.67 (Dexis) and 11.37 (Dexis+). The accuracy of restorative treatment decisions based on digital and conventional radiographs is comparable. If a dichotomous treatment decision was requested, the digital systems demonstrated a notable tendency towards higher likelihood of true-positive decisions.

Confidence Intervals↗