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Biomedical subjects

A Volchansky

Publications and source records attributed to A Volchansky.

At least 19 recordsLinked to original sources
PubMed2004

Scientific surface roughness values for resin based materials.

INTRODUCTION: Surface roughness of dental restorative materials is most often established with the Ra value obtained using profilometry or by assessing surface topography with the scanning electron microscope (SEM). Both methods should validate each other in confirming surface roughness. AIMS AND OBJECTIVES: The purpose of this study was to compare surface roughness values obtained with a profilometer to the SEM appearance of 6 resin-based restorative materials and assess whether Ra was appropriate as a sole surface roughness measure. Methods Six 5mm diameter specimen discs of Prodigy (Pr); Z100 (Z); Compoglass F (C); Hytac Aplitip (H); Photac-Fil (Pf) and Vitremer (V) were prepared against Mylar strips and stored in distilled water for 14 days. One side of each disc was sequentially polished with Soflex discs to super fine state, the other side remained unpolished. Three surface roughness measurements were made on each surface (n=18) recording Ra, Rv, Rp and Rt values, this data was subjected to a four way ANOVA and Tukey's Studentised Range Test (p=0.05). Two unpolished and two polished discs per material were prepared for SEM, evaluated and visually grouped for surface roughness. RESULTS: Approximate ascending order of roughness was Z, Pr, H, C, V, Pf for Ra, Rv, Rp and Rt and un/polished treatment. Polishing increases surimens into a "bland" (Pr, H, Z, C) and "textured" group (Pf and V). The polished specimens gave four groups: (Pr), (Z and C), (H) and (V and Pf) of increasing surface complexity. Polishing caused surface scratching, removed the matrix, reduced or removed filler particles and exposed voids within the material. CONCLUSIONS: This study emphasises the importance of using more than one technique to assess surface roughness. Rv and Rp values should be utilised to better understand polish induced surface feature changes. Rv maximum is a better measure to identify surface defects which could affect restoration longevity.

Analysis of Variance↗
PubMed2001

Clinical crown height (length)--a review of published measurements.

BACKGROUND, AIMS: Clinical crown height is an objective measure of the position of the gingival margin which could be used in determining the 'normal' position of the gingival margin. The aim of this study was to do a systematic review of published clinical crown heights in the human permanent dentition to compare the measurements and to see if a clear trend with age exists. MATERIAL AND METHODS: An on-line literature search was done using the key words clinical crown height (or) clinical crown length. From January 1975 to August 2000, 11 published papers have listed measurements; three of these report on all tooth types, the remainder on anterior teeth. RESULTS: All studies used the same measuring technique but age group reporting differed as did the tooth types measured. Measurements from the 10 acceptable studies of the clinical crown height of the same teeth are comparable at similar ages, so published values are reasonable estimates of 'normality' for diagnosis. There is a statistically significant increase in clinical crown height of central and lateral incisors with age that slows as age increases.

Age Factors↗
PubMed2001

Surface roughness of aesthetic restorative materials: an in vitro comparison.

The purpose of this study was to compare the surface roughness of three types of aesthetic restorative material. Six standard samples of two brands of each type of material were prepared namely: hybrid composites (Prodigy, Z100), compomers (Compoglass F, Hytac Aplitip) and glass ionomer cements (Photac-Fil, Vitremer) in a perspex mould (N = 36). Upper and lower surfaces were covered with Mylar strips which, in turn, were covered with glass slides and compressed to express excess material. After light curing, specimens were stored in distilled water for 14 days. Thereafter, one side of each specimen was polished sequentially with medium, fine and super fine Soflex discs (treatment). Untreated surfaces served as controls. All surfaces were examined with Talysurf and the surface roughness (Ra) of each specimen was recorded. Three measurements were made of each specimen. A 4-way ANOVA and Tukey's Studentised range test were used to analyse the data. Statistically significant effects were found for both type of material (P = 0.0001) and for treatment process (P = 0.0065). Among unpolished specimens: Compoglass F is significantly rougher than Vitremer, Z100, Prodigy and Hytac Aplitip, and compomers are significantly rougher than hybrids. Among polished specimens: Photac-Fil is significantly rougher than Z100 but does not differ from Compoglass F, Vitremer, Prodigy and Hytac Aplitip, and glass ionomers are also significantly rougher than hybrids. The smoothest surface is obtained when curing materials against a Mylar strip.

Analysis of Variance↗
PubMed2000

Temperatures in and around mandibular fractures.

This study measured the temperature in and around mandibular fractures in 20 anaesthetized patients. A fine calibrated thermocouple attached to a digital thermometer was used to measure temperature at the bone surface margin of a mandibular fracture and 5 and 10 mm from the fracture; within the fracture against the bone at 5, 7 and 10 mm depths and at the base of 7 mm deep biopsy cavities 5 and 10 mm distant from the fracture line immediately after biopsy, then 1 and 2 min later. On the surface the temperature was approximately 1 degrees C warmer than at the 5 and 10 mm sites distant from the fracture. Temperature reduced at the 1 and 2 min readings after the biopsy cavity cutting. This study confirmed that the surface temperature is lower than internal bone temperatures.

Adult↗
PubMed1996

Epidemiological profile of graduates of the Wits Dental Faculty 1927-1995.

The Wits dental school was first proposed in 1921 but had no premises until a private dental clinic was taken over in 1924 by the University, the same year that the Bachelor of Dental Surgery regulations were agreed to. In 1925 the first dental students registered and a year later, in 1926, the first seven lecturers in dental surgery were appointed. Since the first two graduates in 1927, 1916 dentists have graduated from the school as have 63 oral hygienists. Of the dentists 116 are female and 127 are black, Chinese, coloured or Indian. Regarding postgraduate qualifications, 346 have been awarded by the University on behalf of the dental school. This paper describes patterns in numbers of graduates, proportions registered in South Africa and contrasts registered South African dental school graduates with registered graduates from outside the country. It is clear that the Wits dental school has made a major contribution to South African society.

Dentists↗
PubMed1996

Maxillary premolar extraction--a possible link to later periodontal breakdown?

The palatal embrasure angles between the maxillary first molar and adjacent premolar were measured in 60 children who had had orthodontic treatment (29 with premolar extractions and 31 without), and in 20 adults with periodontal breakdown in the palatal embrasure angle area, who had had premolar extractions. Mean angles were orthodontic groups non-extraction 31 degrees, extraction 42 degrees and the adult group, 57 degrees. Statistical analysis showed significant differences between the groups. A wide palatal angle between maxillary first molar and adjacent premolar appears to predispose to periodontal breakdown in the area. Rotation of teeth which open the palatal embrasure angle should be minimized.

Adult↗
PubMed1994

Variations in oral temperature.

This study investigated the temperature of healthy oral mucosa and underlying bone. Using a fine thermocouple and digital thermometer, four groups of temperatures were measured: (i) adjacent to unerupted third molars before and after surgical removal (n = 51); (ii) at the same site in patients not undergoing surgery (n = 30); and (iii) at the buccal incisor mucosa (n = 30). In each group sublingual temperatures were measured in order to calculate the temperature differential between measurement site and sublingual temperature to compensate for variations between sites and individuals. In the final group (iv) (n = 10) sublingual temperature was recorded in a closed mouth. Mean alveolar bone temperature was 5 degrees C cooler than overlying mucosa, and mean post-operative mucosal temperature was some 2.5 degrees C cooler than before operation (t = 2.32, P < 0.001). Sublingual temperature, in a closed mouth, remained relatively constant. In an open mouth, in both anterior and posterior regions, there were statistically significant decreases in sublingual temperature and in mucosal temperature differentials. Significant differences were also found between temperature differentials calculated using sublingual temperature measured at baseline and after 10 min. This indicates that sublingual temperature should be measured just prior to measuring a mucosal site.

Adolescent↗
PubMed1991

Temperature gradients in periodontal pockets.

This study was undertaken to determine whether there is any correlation of temperature within periodontal pockets with their depths. Pocket temperatures were measured with a thermocouple at 1 mm intervals of depth in 247 pockets, in 20 patients with periodontitis, mesiobucally and mesiopalatally/mesiolingually in relation to 6 standard teeth. Pocket temperatures increased consistently with pocket depth. Maxillary pockets were cooler than mandibular pockets, but in both jaws the differences between buccal and palatal/lingual pockets were not statistically significant. The findings are in keeping with knowledge about the increased temperature of inflamed tissues and the study appears to have relevance to the diagnosis of disease activity in pockets, but further studies are necessary to establish reference levels of pocket temperature.

Adult↗