Biomedical subjects

H G Schaller

Publications and source records attributed to H G Schaller.

At least 19 recordsLinked to original sources

PubMed2001

Tensile bond strengths of four different dentin adhesives on irradiated and non-irradiated human dentin in vitro.

This study evaluated the influence of irradiation on dentin bond strength. Sixty irradiated and 60 non-irradiated human third molars were used. The irradiation dose of 60 Gy was fractionally applied over 6 weeks (2 Gy day(-1), 5 days week(-1). All teeth were prepared in a special manner allowing the simulation of intra-pulpal pressure and dentin perfusion. Dentin specimens with a thickness of 2.0 mm were obtained under standardized conditions. The specimens were randomly assigned to four experimental groups. Tensile bond strength of four different dentin bonding agents (Scotchbond 1, Solobond Plus, Prime&Bond 2.1 and Syntac) was evaluated using an Instron Universal testing machine. Pairwise comparison did not show any significant differences between the irradiated and non-irradiated groups. The influence of the different dentin adhesives was significant (P=0.0001; ANOVA). Compared with Solobond Plus and Prime&Bond 2.1, the use of Scotchbond 1 resulted in a significantly higher tensile bond strength in non-irradiated specimen (P< 0.05; closed test procedure based on Kruskal-Wallis test). Within the limitations of an in vitro study, it can be concluded that adhesive restoration procedures can be successfully used in patients irradiated for cancer of the head and neck.

Adhesives↗

PubMed1999

Root lesions in a group of 50-60 year-old Germans related to clinical and social factors.

From a preventive point of view collection of data concerning carious and non-carious cervical tooth defects is definitely important. Consequently, the prevalence and distribution of different root lesions were studied and correlated with behavioral and biological factors in 50- to 60-year-old German individuals (n = 298). Additionally, the data were correlated with characteristics concerning oral health and known risk factors such as gender, educational level, and presence of plaque. An interview included questions on sociodemographic and socioeconomic characteristics, dental and general health status, and various behavioral parameters. During clinical examination data concerning coronal and root lesions, restorations, probing depth, gingival bleeding, and dental plaque were obtained. The participants represented a social middle class population with a high awareness of dental health. Obviously, for the participants, known risk factors for root decay such as gender, educational level and plaque index were of minor importance. Factors correlating with root caries were: (a) number of missing teeth, (b) probing depth, (c) smoking habit, (d) regular dental attendance and (e) the reason for the last dental treatment. Additionally, the prevalence of non cariogenic lesions, primarily resulting from increased but wrongly performed oral self care, seems gradually to relieve carious root destruction.

DMF Index↗

PubMed1998

Marginal leakage in class II-restorations after use of ceramic-inserts luted with different materials.

The efficiency of using prefabricated ceramic inlays to prevent microleakage has been discussed in different investigations. The purpose of this study was to evaluate the marginal microleakage of a new glass ceramic inlay system in combination with two different composite luting materials and one polyacid-modified composite, respectively. Standardized class II cavities (n = 60) were filled with (1) Empress inlays fixed with a highly viscous luting composite as a control group, and with glass ceramic inlays (Cerana) in combination with (2) a highly viscous luting composite, (3) a low-viscous luting composite and (4) a polyacid-modified composite, respectively. After thermocycling the marginal quality was analysed with scanning electron microscopy, and the dye penetration along the cavity walls was measured. The use of the Cerana inlays with a polyacid-modified composite resin did not reveal a good marginal adaptation. However, the combination of the Cerana and the Empress inlays with the highly viscous composite exhibited a comparable marginal fit. Within the limitations of an in vitro study it is concluded that the combination of the new glass ceramic inlays with a polyacid-modified composite cannot be recommended for clinical use.

Aluminum Silicates↗

PubMed1997

Fluoride uptake in dentin with and without simulating dentinal fluid flow.

The aim of the present study was to compare fluoride uptake of dentin with and without simulating dentinal fluid flow. Eighty-five dentinal discs were prepared from retained human molars. Seventeen discs were used to assess baseline fluoride content (controls). Sixty-eight discs were evenly distributed among two experimental groups and were fixed for 24 h in a two-chamber device allowing for simulating dentinal fluid flow. Thirty-four samples were treated with dentifrice slurry containing a low fluoride concentration (Elmex, dilution 1:5); the remaining discs were treated with a solution of a high fluoride concentration (Elmex Fluid). For the perfused group, each of the 17 discs of the high and low concentration fluoride groups were constantly perfused during the experiment. The remaining fluoridated specimens were not perfused. All specimens were assayed for KOH-soluble fluoride and structurally bound fluoride. Structurally bound fluoride was determined in three successive layers of 20 microns each. Uptake of KOH-soluble fluoride was significantly higher in the specimens fluoridated with Elmex Fluid compared to the samples treated with the dentifrice slurry. The uptake of KOH-soluble fluoride was not influenced by perfusion of the dentinal discs. However, perfusion resulted in lower acquisition of structurally bound fluoride in the samples treated with the dentifrice slurry. After application of Elmex Fluid, no significant difference was found in the amount of structurally bound fluoride between the perfused specimens and non-perfused samples. It is suggested that further studies on fluoride uptake in dentin should use a model simulating outward dentinal fluid flow.

Analysis of Variance↗

PubMed1997

Correlation of microhardness and wear in differently eroded bovine dental enamel.

The purpose of the study was to compare the microhardness data of differently eroded enamel surfaces with the wear caused by toothbrushing. Sixty bovine enamel specimens were polished and prepared for microhardness determination. The polished surfaces were covered with tape except for a 1.3 x 10.0 mm window. Fifteen specimens each were stored in an erosive beverage (Sprite Light) for either 1, 5 or 15 min. Each specimen was immersed in 10 ml of the beverage. The remaining 15 specimens were not eroded. Interferometrical analysis revealed that substance loss after 15 min of erosion was negligibly low (about 75 mm). In all specimens Vickers microhardness determinations were conducted on eroded (= final hardness) and non-eroded (= initial hardness) enamel surfaces. The specimens were subsequently submitted to toothbrushing abrasion using a slurry consisting of 1 g non-fluoridated dentifrice in 5 ml artificial saliva. The total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed a significant decrease in hardness and a significant increase in wear with increasing time of storage in the erosive beverage. Overall regression analysis yielded a statistically significant correlation between both initial and final hardness and the amount of tooth wear. The correlation of abrasion and final hardness could be described by a quadratic mathematical function. It is concluded that the susceptibility of eroded enamel to toothbrushing abrasion can be correlated with Vickers microhardness values, thereby suggesting an overproportionate increase of abrasion with decreasing hardness values.

Animals↗

PubMed1997

Permeability of dentine after Nd:YAG laser treatment: an in vitro study.

The purpose of this investigation was to determine the effects of Nd:YAG laser treatment on the permeability of dentine. Forty dentine discs were prepared by horizontal sectioning through the middle coronal third of freshly extracted non-carious third molars. After the removal of the pulp the discs were finished with 600 grit and divided into three test groups and one control group (n = 10). For the test group three different laser power settings were chosen: test group A: 3 x 60 sec, 60 mJ; test group B: 3 x 60 sec, 90 mJ; test group C: 3 x 60 sec, 120 mJ. No laser treatment was performed on the control group. In a two-chamber system the filtration rate of dentine tubules from an exactly defined area of the specimens was measured using a radioactive Ringer solution under a pressure of 30 cm H2O. Permeability measurements were carried out three times prior to lasing, three times immediately following laser treatment and six times after the application of phosphoric acid. Analysis of variance showed a significant influence of the Nd:YAG laser treatment on the permeability of dentine (P < 0.001). The mean quotient of non-treated control vs. lased dentine was 2.19 +/- 0.86 for the 60 mJ beam, 1.49 +/- 0.88 for the 90 mJ beam, and 2.04 +/- 2.17 for the 120 mJ beam. Etching the lased surfaces had a statistically significant influence on the permeability of the dentine only in the 60 mJ group (P < 0.001). The data show that the Nd:YAG laser treatment often increases the permeability of smear layer covered dentine but moderates the increase of permeability after etching the surface with phosphoric acid.

Acid Etching, Dental↗

PubMed1996

Clinical comparison of postoperative sensitivity for a glass ionomer and a zinc phosphate luting cement.

In 60 patients, 120 partial and full-coverage restorations were cemented on vital abutment teeth with either a glass ionomer or a zinc phosphate luting cement. A split-mouth design and a patient blind data acquisition protocol were used. During an average observation period of 17.3 months there were no differences between the two types of luting cements in regard to subjective and clinical parameters. A high incidence of postoperative hypersensitivity, which is often said to accompany the use of glass ionomer luting cements, was not observed. With the cementation method used in this study, the glass ionomer cement Ketac-Cem Maxicap was an acceptable alternative to conventional zinc phosphate cement. Capsule systems make the clinical handling of glass ionomer luting cements safe and easy and should be used routinely in dental practice.

Adult↗

PubMed1995

Endodontic therapy in a postirradiated child: review of the literature and report of a case.

Exodontia of extremely carious teeth leads to a significant risk of osteoradionecrosis in patients who have undergone radiotherapy. In these patients, endodontic treatment could be an alternative. Successful root canal therapy in a girl who had been irradiated for head and neck neoplasms is reported. The results indicated that use of calcium hydroxide to obturate the root canals is a viable method of postirradiation endodontics in primary teeth.

Animals↗

PubMed1991

[The influence of dentin conditioning on permeability of dentin].

In this study the influence of four different pretreatments showed significant differences on the permeability of cut dentin. On the average the application of 25% polyacrylic acid increased the permeability by approximately 10 percent, the application of 34% polyacrylic acid by 30 percent. The treatment with 0.1% chlorhexidin-digluconate produced no change of permeability. Calciumhydroxide suspension reduced the permeability by 15 percent and diminished the increase caused by phosphoric acid significantly.

Acid Etching, Dental↗

PubMed1991

[Examination of shear strength of repaired composite specimen].

The test of the shearstrength of two composite-inlay-materials and two posterior composites exhibited a statistically significant less bond-strength of repaired specimen compaired with unrepaired control-groups, whereas each material showed different results. The indirect-inlay-system proved to have the lowest bondstrength after repairing. The combination of the two posterior composites as well as the two inlay-systems with each other showed that none of these materials was convincing as a repairing material.

Acrylic Resins↗

PubMed1989

[The correlation among pulp chamber, tooth length and tooth width in different age groups].

Computing the quotients of pulp chamber length/tooth length and pulp chamber width/tooth width for canines and lower premolars on orthopantomograms of subjects aged between 19 and 65 years led to the following result: significant reduction in length quotient and highly significant reduction in width quotient with increasing age. The reduction in width was considerably greater than in length.

Adult↗

PubMed1989

[Flexural strength tests of repaired amalgam specimen].

Test results of four types of alloys: Flexural strength declined significantly with increasing age of the specimen, however, differently for the tested alloys. The increase in mercury content of the repair amalgam did not influence flexural strength. The combination of materials with each other demonstrated that none of the amalgams was particularly suitable as a repair amalgam.

Dental Alloys↗

PubMed1989