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Biomedical subjects

F Barbakow

Publications and source records attributed to F Barbakow.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of Nd:YAG lasers on root canal walls: a light and scanning electron microscopic study.

OBJECTIVE: This study evaluated amounts of debris, smear layer, and recrystallized dentin on root canal walls treated with an Nd:YAG laser. The presence of carbonized material was also assessed. METHOD AND MATERIALS: The root canals of 36 extracted incisors were prepared by stepdown and stepback techniques and divided into 4 groups. One group was not treated further, while 3 others were exposed to the laser beam at an energy density of 159, 239, or 318 J/cm2. The roots were split longitudinally, photographed, and examined using a scanning electron microscope. The amounts of debris, smear layer, and recrystallized dentin were recorded from horizontal bands around the root, 2, 6, and 10 mm from the apices. RESULTS: Mean smear layer scores were similar for all groups at the 3 levels examined, ranging from 2.157 to 2.851 on a scale of 0.0 to 3.0. Mean debris scores were similar for all groups at the 3 levels examined, ranging from 0.774 to 1.408 on a scale of 0.0 to 3.0. Recrystallized dentin was recorded in all 3 irradiated groups at the 2-mm level, but only in the group irradiated with 318 J/cm2 at the 6- and 10-mm levels. Severe carbonization was recorded at the 2-mm level. CONCLUSION: Use of the Nd:YAG laser did not reduce the mean amounts of debris and smear layer compared to a nonirradiated group. Carbonization was recorded in the apical part of the canal, but this is not obvious when only scanning electron photomicrographs are examined.

Dental Pulp Cavity↗
PubMed1998

Preparation of the apical part of the root canal by the Lightspeed and step-back techniques.

This study measured in vitro the displacement of natural canal centres in 18 human teeth before and after shaping by the step-back or Lightspeed techniques. Experimental roots (n = 9 per group), embedded in clear plastic, were cross-sectioned using a 0.1-mm-thick band saw at distances 1.25 mm, 3.25 mm and 5.25 mm from the apices. A stereo microscope was used to take 35 mm slides of the cut surfaces of the sectioned roots and canals. The slides of the uninstrumented canals were scanned into a computer and saved. Each sectioned root was then reassembled and the canals shaped by the step-back or Lightspeed technique. File size 40 and instrument size 50 were selected as the master apical file and master apical rotary for the step-back and Lightspeed groups, respectively. The 18 prepared canals were photographed, and the 35 mm slides scanned and computer stored as previously. This allowed the positions of the pre- and postinstrumented roots to be electronically superimposed for subsequent analyses. Displacements of the root canal centres before and after preparation were assessed in relation to the cross-sectional diameter of the files or instruments used. In addition, increases in cross-sectional area of the root canals after preparation were evaluated in relation to the cross-sectional area of the files or instruments used. Engine-driven nickel-titanium Lightspeed instruments caused significantly less (P < 0.001) displacement of the canal centres, so roots in the Lightspeed group remained better centred than those in the step-back group. The mean cross-sectional area after preparation in the Lightspeed group was significantly less (P < 0.001) than that recorded in the step-back group. Clinically, this implies less apical transportation and less dentine destruction with the Lightspeed technique than with the step-back technique.

Dental Instruments↗
PubMed1998

Effects of sodium hypochlorite on nickel-titanium Lightspeed instruments.

Sodium hypochlorite is a major irrigant in endodontics, and nickel-titanium instruments are gaining in popularity. This paper investigated the corrosion of nickel-titanium Lightspeed instruments in 1% and 5% NaOCl solutions. The instruments were immersed in ultrasonicated NaOCl solutions for varying times up to 1 h. Corrosion was determined by electrothermal absorption spectrometry in 100 microL aliquots of NaOCl. Background contamination of nickel in the 1% and 5% NaOCl solutions used was low, but high enough to interfere in detecting any increases in nickel after immersing the instruments. The amounts of titanium recorded in the 1% NaOCl solutions were insignificant. However, a statistically significant amount of titanium was detected from the Lightspeed instruments after immersion times of 30 and 60 min in 5% NaOCl. Clinically such instruments do not have an 'in situ' time of 30 min, and this corrosion may be considered irrelevant clinically.

Analysis of Variance↗
PubMed1998

Evaluating the sizes of Lightspeed instruments.

The diameters of six different sized Lightspeed cutting heads were measured using a modified optical micrometer. Six specimens of instrument sizes 20, 22.5, 27.7, 30, 32.5 and 45 were examined. Except for one cutting head of size 30, all the recorded diameters were oversized compared to the expected diameter and the permitted tolerance (+/- 0.005 mm). Perfectly machined instruments would increase by 12.5%, 9.09% and 8.3% from instrument sizes 20-22.5, 27.5-30 and 30-32.5, respectively. Under the conditions of this study, the corresponding increases were 7.1%, 6.75% and 8.54%. Instrument size 20 had the widest range and is the smallest instrument in the Lightspeed set. The largest differences between the recorded and expected means were registered for the size 45 group. An earlier study using a different measuring method reported that Lightspeed instruments were mostly undersized.

Dental Instruments↗
PubMed1998

Scanning electron microscope appearances of Lightspeed instruments used clinically: a pilot study.

The cutting heads of the first 18 instruments in six sets of clinically used Lightspeed instruments (sizes 20-65) were examined in a scanning electron microscope (SEM). Three sets had been used by full-time faculty and discarded as follows: instrument sizes 20-32.5 after 18 treated root canals; instrument sizes 35-47.5 after 36 treated root canals; and instrument sizes 50-65 after 54 treated root canals. Three other sets had been used by a private clinician who discarded all Lightspeed instruments after preparing 20 root canals. The cutting heads of the 108 instruments were examined for the presence of surface debris, metal strips, metal flash, disrupted cutting edges, microfractures, tears, pitting and fretting and fatigue cracks. Fewer instruments ultrasonically cleaned before examination in the SEM had debris than those not cleaned before examination. The prevalence of metal strips and metal flash was similar for both groups. In contrast, microfractures and tears were more prevalent in instruments used by the full-time faculty group, who used their instruments more frequently before discarding them. Pitting and fretting occurred equally frequently in both groups whilst no fatigue cracks were noted in any of the 108 instruments. Overusage of Lightspeed instruments may predispose the flutes of the cutting heads to microfractures and clinicians should be aware of this possibility.

Alloys↗
PubMed1997

The 'Lightspeed' preparation technique evaluated by Swiss clinicians after attending continuing education courses.

This survey evaluated acceptance of the Lightspeed canal preparation (LS) technique by Swiss practitioners. The technique was introduced to Switzerland in June 1994 and 10 other continuing education (CE) courses were held at the Zurich Dental School by July 1995. Acceptance was assessed by posting questionnaires to the CE course attendees. Of the 305 questionnaires posted, 177 (58%) were returned. Of the CE participants 80% had used the technique with 60% finding the method easier and 43% finding it quicker than their usual preparation techniques. Of the respondents 58% used the technique on all tooth types and 76% of the LS users had fractured an instrument at least once. Amongst others, fractures were caused by too much pressure (25%), incorrect insertion angles (17%) and by a complicated root morphology (15%). Fractures occurred high up on the instrument shaft (74%) and near the tip (7%). Working lengths were claimed by 62% to be easier to maintain by LS than their usual preparation techniques. Among the respondents 52% obturated LS prepared canals more easily and quickly compared with their usual preparation techniques. Only 10% of LS users would not recommend the technique, but those who would suggested that proper tuition was necessary to minimize the risk of instrument fracture. The LS technique was positively assessed by clinicians who attended the CE courses in Switzerland where endodontics is not accepted as a specialty.

Education, Dental, Continuing↗
PubMed1996

An in vivo comparison of gradient and absolute impedance electronic apex locators.

Two electronic apex locators based on the gradient (Apit) and absolute (Odontometer) impedance principles were evaluated. Distances of file tips to apical foramina were determined in vivo with the electronic apex locators and subsequently verified after extraction. Mean differences between file tips and apical foramina were +0.14 +/- 0.27 mm and -0.36 +/- 0.71 mm for the Apit and Odontometer, respectively. These differences were statistically significant (p < 0.001). the Apit's and Odontometer's results ranged from +0.85 to -0.65 mm and from +0.35 to 2.45 mm from the apical foramen, respectively. Ninety-three and 73% of the findings for the Apit and the Odontometer, respectively, were within the +/- 0.5 mm range, whereas 100% and 86%, respectively, were within the +/- 1.0 mm range. Thirty-three and 43% of the results for the Apit and the Odontometer, respectively, were 1.0 mm or less coronal to the apical foramen. The Apit tended to yield the more reliable results because of the narrower range.

Adult↗
PubMed1996

The status of root canal therapy in Switzerland in 1993.

No data are available on materials or techniques used by Swiss clinicians for root treatments. Two questionnaires were posted to almost all dentists in Switzerland. The first concerned the materials and techniques used while the second detailed the endodontic procedures carried out during 10 consecutive working days. Reply rates for both questionnaires were 62 per cent and 30 per cent, respectively. Major results showed that 50 per cent of the responding clinicians used AH26 to obturate canals, 45 per cent Endomethasone and 36 per cent N2. Canals were disinfected using Ledermix (81 per cent), Asphaline (67 per cent), Ca(OH)2 (60 per cent), and CMCP (22 per cent). Clinicians used H2O2 and NaOCl equally frequently (75 per cent). Hedström files, reamers and flexo-files were used by 52 per cent, 29 per cent and 26 per cent of the clinicians, respectively. Canals were obturated by the single-cone technique (68 per cent), lateral condensation (34 per cent), or by using only a paste or sealer (23 per cent). Too many Swiss clinicians still use formaldehyde-containing products in root canal therapy coupled with a "single cone" or a "no cone" obturation technique. During the 10 day period Swiss dentists began 4 root treatments or retreatments, changed 2 root canal dressings and root filled 5 teeth. They also completed 8 retreatments and 1 definitive pulpotomy every 100 days.

Humans↗
PubMed1995

[Materials and technics in root canal treatments in Switzerland--a determination of their status].

No data is available on either the materials nor techniques used by Swiss clinicians when doing root canal therapy (RCT). Consequently, in January 1993 questionnaires were posted to all dentists registered with the Swiss Dental Association, excluding those known not to practice RCT. Sixteen questions were answered detailing the disinfecting and obturating materials used, which types of files, preparation and obturation techniques were used and which radiographs were taken during RCT. Demographic details were also answered. Of the 3353 questionnaires posted, 2091 (62.4%) were completed and returned. Major results showed that 50.6% of the responding clinicians used AH26 to obturate canals, 45% Endomethasone and 36.6% N2. Canals were disinfected using Ledermix (81.2%), Asphaline (67.6%), Ca(OH)2 (60.2%). Clinicians used H2O2 and NaOCl equally frequently (75%). Hedstroem files, reamers and flexofiles were used by 52%, 29% and 26% of the clinicians, respectively. Canals were obturated by single-cone technique (68%), lateral condensation (34%), or by using only a paste or sealer (23%). 86.4% take a diagnostic radiograph, 69.2% determine working length from radiographs, and 91.5% take a final radiograph as well. Too many Swiss clinicians still use formaldehyde-containing products in root canal therapy coupled with a "single cone" or a "no cone" obturation technique.

Humans↗
PubMed1995

[Root canal treatment in Switzerland. The quantitative aspects--a determination of its status].

No recent data is available on the number of patients treated for root canal therapy in Switzerland. The aim of this study was to determine, by means of questionnaires, how many and which teeth were root canal treated in Switzerland by private practitioners. One questionnaire concerned the frequency of certain endodontic treatments performed during 10 consecutive working days. 30.1% of the posted questionnaires were correctly completed, returned and evaluated. Per dental practitioner, a total of 4.4 root canal treatments were begun during the 10 consecutive working days. A further 2.2 antiseptic dressings per practitioner were changed during the 10 days. Each dentist completed a root canal therapy on 5.3 teeth, 0.7 re-treatments and 0.1 pulpotomies during the 10 consecutive working days. 40% of all root canal treated teeth were molars which is rather high when compared to data available from other countries. Extrapolating the results to the entire Swiss population, 12.1 patients have a root canal therapy or a re-treatment per year. A similar result (12.9 patients) was recorded for the USA in 1979.

Humans↗
PubMed1994

[Amalgam as the measure in filling therapy. A determination of its place].

As the value of amalgam restorations is increasingly being questioned in modern dentistry, the clinical potential of amalgam restorations in general has been evaluated in this literature review. The major factors limiting the longevity of amalgam restorations are operator- and patient-related. Both factors will likewise influence the longevity of any new restorative concepts. Nevertheless, amalgam restorations remain the standard against which alternative materials are evaluated. Amalgam restorations are slowly loosing ground to the use of tooth-colored materials, which are gaining in popularity. However, amalgam can not currently be withdrawn from the list of possible restorative materials used for patients in Switzerland.

Costs and Cost Analysis↗
PubMed1993

Self-adjusting abrasiveness: a new technology for prophylaxis pastes.

An ideal prophylaxis paste should have both cleaning and polishing properties. Key elements would be abrasive particles that become less aggressive under load. The abrasive perlite, a volcanic glass with a sheetlike geometry, is claimed to have these unique properties. This study evaluated the average particle size, size distribution, and morphology of perlite in raw form, in an unused prophylaxis paste, and a used prophylaxis paste. The surface roughness induced on enamel and dentinal specimens was quantitated after paste application in either a rubber cup or a nylon brush. Flour of pumice, a standard prophylaxis paste, a polishing paste, and water were tested similarly. The luster induced by the tested pastes and controls was assessed. Perlite blunted and disintegrated under load. The perlite-containing prophylaxis paste acted as a fine or superfine prophylaxis paste, although it was ranked as medium, based on the mean particle size of its abrasive in the fresh, unused form. Perlite might provide the properties required for the abrasive material of an ideal prophylaxis paste.

Aluminum Oxide↗
PubMed1993

Comparison of the efficacy of prophylaxis pastes with conventional abrasives or a new self-adjusting abrasive.

A newly developed prophylaxis paste that contains perlite as an abrasive medium (Cleanic) was compared to conventional prophylaxis pastes with regard to relative dentin and enamel abrasion, cleaning ability, and polishing power. Rubber cups and nylon brushes were used as paste carriers. Water, flour of pumice, and the dentin-polishing paste CCS 40 served as controls. The tested prophylaxis pastes, selected according to their popularity among clinicians, were CCS 250, Détartrine Z, Nupro Coarse, and Zircate. The Prophylaxis Paste Index was created to assess the clinical potential of the various prophylaxis pastes more accurately. The Index was computed for dentin as cleaning ability dended by relative dentin abrasion x surface roughness (in Ra) x 10, and for enamel as cleaning ability dended by relative enamel abrasion x surface abrasion (in Ra). On dentin and enamel, Cleanic consistently yielded low relative dentin and enamel abrasion values, a good cleaning ability, and low surface roughness scores with both rubber cups and nylon brushes. Of all tested prophylaxis pastes, Cleanic excelled in the Prophylaxis Paste Index on dentin and enamel and with both rubber cup and nylon brush applications. Therefore, a perlite-containing prophylaxis paste has broad professional therapeutic indications and may be used universally as a single paste to clean and polish both dentin and enamel.

Aluminum Oxide↗
PubMed1992

A critical comparison of dentifrice abrasion scores on dentine recorded by gravimetric and radiotracer methods.

Dentifrice abrasivity on dentine is conventionally ranked by various in vitro methods. The abrasivity of selected dentifrices in Switzerland was ranked in 1985 by the gravimetric and in 1989 by the radiotracer method. Because same-named brands of dentifrices were differently ranked by these methods, Swiss clinicians were unsure which ranking to follow. This paper lists the errors known to occur in both techniques, but unfortunately it is difficult to quantitate the magnitudes of these errors. Consequently, it is impossible to determine which method yields the more reliable results. Thus, researchers should look into the problem of dentifrice abrasion scores and try to formulate tests which could simplify the selection of brand-named dentifrices by clinicians and the consumers.

Densitometry↗
PubMed1992

Chewing pressure vs. wear of composites and opposing enamel cusps.

The effects of various chewing pressures on the wear of composites and enamel were assessed in vitro. Standardized composite discs (8 mm in diameter, 2 mm in height) were made of a fine-particle hybrid (FPH), a coarse-particle hybrid (CPH), and a homogeneous microfilled composite (HMC). The composite specimens were chemically degraded by immersion in 75% ethanol for 24 h, brushed for 30 min, and then thermocycled 300 times (5-55-5 degrees C) while being occlusally loaded 120,000 times at 1.7 Hz, with chewing forces of 25, 50, 75, and 100 N. Standardized human enamel cusps with a uniform contact area of 0.384 mm2 served as antagonists in the chewing machine. Wear of the composites and enamel cusps, their combined wear, and the increase of the enamel contact surfaces were quantified. An increase in chewing pressure significantly enhanced the wear of both composite and enamel in all groups except for the antagonists opposing a HMC. The FPH was most wear-resistant to in vitro chewing pressures in the range of 6.58 to 19.74 MN/m2, the CPH at 26.32 MN/m2, while the HMC was the most enamel-friendly of the three composites tested. The FPH composite had the least disintegration in the occlusal contact area. The ranking of the composites generally varied at the different chewing pressures with respect to the three types of quantified wear--that is, composite wear, enamel wear, and total wear.

Acrylic Resins↗
PubMed1992

The importance of proximal curing in posterior composite resin restorations.

This in vitro study compared the marginal adaptation of enamel-bonded mesio-occlusodistal composite resin restorations placed using two different insertion techniques (one-step and two-step) and three different curing techniques (occlusal using opaque matrix and wedge systems and interproximal using transparent matrix systems and either transparent, non reflecting, or transparent, laterally reflecting wedges). The micromorphology of the enamel-restoration interface and the marginal seal were evaluated after the restorations were exposed to mechanical and thermal stresses. Although the difference was not statistically significant, the marginal quality of the restorations placed with the two-step technique was better than that of the restorations placed with the one-step technique. The restorations cured from the interproximal direction had significantly better marginal adaptation than did restorations cured only from the occlusal direction. The quality among the groups of interproximally cured restorations was not significantly different, because all the restorative techniques that were evaluated resulted in generally poor marginal quality.

Analysis of Variance↗
PubMed1992

Restoration quality in relation to wedge-mediated light channeling.

Thirty large mesio-occlusodistal cavities with their margins totally in enamel were restored using the three-sited light-curing technique in five different ways: group 1 = Mark I version of a light-reflecting wedge; groups 2 and 3 = interproximal curing with transparent, nonreflecting wedges; groups 4 and 5, Mark II version of the light-reflecting wedge with increased resiliency. In groups 3 and 5, the light that was not conducted by the transparent wedges was shielded by a piece of aluminum foil. It was found that, when used directly and unshielded, both Mark I and Mark II versions of the light-reflecting wedge induced significantly better marginal adaptation than the transparent, nonreflecting wedge, especially gingiovproximally. With both the nonreflecting and reflecting wedges, the shielding had no effect on the overall percentage of excellent margin. However, gingivoproximally, the shielding significantly improved the marginal quality in the nonreflecting wedge groups, leading to the conclusion that the first increment should be cured as thoroughly as possible from a gingivoproximal direction, preferably indirectly via light-conducting wedges. Direct irradiation from a lingual or buccal direction is less favorable.

Composite Resins↗