Teaching an engine-driven preparation technique to undergraduates: initial observations.

AIM: This paper describes the initial experiences following the introduction of a rotary engine-driven preparation technique into the undergraduate endodontic programme at the Zurich University Dental Centre. METHODS: Forty third-year students practised the ProFile.04 (PF.04) technique between January and July 2001 in a preclinical course. Between November 2001 and February 2002, 20 of these students (Group A) root-treated 51 teeth in their clinical course using either PF.04, the balanced force technique (BFT) or a combination of both. The second group of 20 students (Group B) similarly treated another 36 randomly selected teeth between April and July 2002. Types of teeth treated by the students and the canal preparation techniques were recorded. The students also completed a short questionnaire, evaluating their opinions of the new course. RESULTS: Of the 87 teeth endodontically treated during the clinical course, 34, 14 and 39 were shaped using PF.04 alone, a combination of PF.04 and BFT and BFT alone, respectively. No rotary instruments were fractured during the 1-year clinical course, although some instruments were fractured during the preclinical laboratory course. Overall, the students rated the rotary technique as positive. CONCLUSION: A rotary technique was successfully introduced into an undergraduate endodontic programme (this will be continued in the foreseeable future). However, the continuity between the preclinical and the clinical courses was poor as a result of the constraints of the general teaching programme.

ProTaper rotary root canal preparation: effects of canal anatomy on final shape analysed by micro CT.

AIM: To evaluate the relative performance of ProTaper nickel-titanium (Ni-Ti) instruments shaping root canals of varying preoperative canal geometry. METHODOLOGY: Extracted human maxillary molars were scanned, before and after shaping with ProTaper, employing micro computed tomography (muCT) at a resolution of 36 mum. Canals were three-dimensionally reconstructed and evaluated for volume, surface area, 'thickness' (diameter), canal transportation and prepared surface. Based on median canal volume, canals were divided into 'wide' and 'constricted' groups. Comparisons were made between mesiobuccal (mb), distobuccal (db) and palatal (p), as well as 'wide' and 'constricted' canals, using repeated-measures anova and Scheffé posthoc tests. RESULTS: Volume and surface area increased significantly and similarly in mb, db and p canals, and gross preparation errors were found infrequently. Root canal diameters, 5-mm coronal to the apex, increased from 0.38 to 0.65 mm, 0.42 to 0.66 mm and 0.57 to 0.79 mm for mb, db and p canals, respectively. Apical canal transportation ranged from 0.02 to 0.40 mm and was independent of canal type; 'wide' canals had a significantly higher (P < 0.05) proportion of unprepared surfaces than 'constricted' canals. CONCLUSIONS: Canals in maxillary molars were prepared in vitro using ProTaper instruments without major procedural errors. These instruments may be more effective in shaping narrow canals than wider, immature ones.

ProTaper rotary root canal preparation: assessment of torque and force in relation to canal anatomy.

AIM: To investigate physical parameters for ProTaper nickel-titanium (NiTi) rotary instruments whilst preparing curved canals in maxillary molars in vitro. METHODOLOGY: A novel torque-testing platform was used to prepare root canals in 15 extracted human maxillary molars with ProTaper rotary instruments. Peak torque and force was registered along with numbers of rotations required to shape the canals. Canals were divided into 'wide' and 'constricted' groups depending on canal volumes assessed by micro computed tomography. Mean scores for each instrument type were calculated and statistically compared using anova and Scheffé posthoc tests. RESULTS: Mean torque varied between 0.8 +/- 0.5 and 2.2 +/- 1.4 N cm whilst mean force ranged from 4.6 +/- 2.6 to 6.2 +/- 2.7 N. Mean numbers of rotations totalled up to 21. All three variables registered were significantly correlated to preoperative canal volumes (P < 0.001) and differed significantly between 'wide' and 'constricted' canals (P < 0.001). CONCLUSIONS: Whilst high forces were used in some cases, no ProTaper instrument fractured when a patent glide path was present. There were significant positive correlations between canal geometry and physical parameters during shaping.

Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography.

AIM: The aim of this study was to compare the effects of four preparation techniques on canal volume and surface area using three-dimensionally reconstructed root canals in extracted human maxillary molars. In addition, micro CT data was used to describe morphometric parameters related to the four preparation techniques. METHODOLOGY: A micro computed tomography scanner was used to analyse root canals in extracted maxillary molars. Specimens were scanned before and after canals were prepared using Ni-Ti - K-Files, Lightspeed instruments, ProFile.04 and GT rotary instruments. Differences in dentine volume removed, canal straightening, the proportion of unchanged area and canal transportation were calculated using specially developed software. RESULTS: Instrumentation of canals increased volume and surface area. Prepared canals were significantly more rounded, had greater diameters and were straighter than unprepared canals. However, all instrumentation techniques left 35% or more of the canals' surface area unchanged. Whilst there were significant differences between the three canal types investigated, very few differences were found with respect to instrument types. CONCLUSIONS: Within the limitations of the micro CT system, there were few differences between the four canal instrumentation techniques used. By contrast, a strong impact of variations of canal anatomy was demonstrated. Further studies with 3D-techniques are required to fully understand the biomechanical aspects of root canal preparation.

Temperature-related reversible birefringence changes in rat tail tendon.

By use of a highly sensitive method for measuring slight variations in birefringence it is shown here that a strong reversible correlation exists between rat tail tendon birefringence and temperature. This phenomenon is totally different from the loss of birefringence that results from a denaturation process. Below the threshold temperature leading to denaturation, an increase in temperature is systematically accompanied by a reversible increase in birefringence (0.25% degrees C(-1)). This phenomenon is observed at very fast heating rates (250,000 degrees C s(-1)), such as those induced by pulsed infrared lasers, and confirmed by experiments conducted with slow homogeneous heating of the sample medium (0.1 degrees C s(-1)). The good correlation between birefringence and temperature observed during the fast heating suggests that there are only small modifications of the tissue structure at the fibril level.

Polarization discrimination of coherently propagating light in turbid media.

We describe the use of degree of polarization to discriminate unscattered and weakly scattered light from multiply scattered light in an optically turbid material. We use spatially resolved measurements of the degree of polarization to compare how well linearly and circularly polarized light survives in a sample. Experiments were performed on common tissue phantoms consisting of polystyrene and Intralipid microsphere suspensions and on adipose and arterial tissue. The results indicate that polarization is maintained even after unpolarized irradiance through each sample has been extinguished by several orders of magnitude. The results also show that polarized light propagation in common tissue phantoms is distinctly different from polarized light propagation in the two tissues investigated. Further, these experiments illustrate when polarization is an effective discrimination criterion and when it is not. The potential of a polarization-based discrimination scheme to image through the biological and nonbiological samples investigated here is also discussed.

[High-caloric nutrition in chronic obstructive lung disease]. / Hochkalorische Ernährung bei chronischer obstruktiver Lungenkrankheit.

A body weight lower than 90% of the optional value has an unfavorable influence on the prognosis of chronic obstructive pulmonary disease (COPD). Short term studies of up to three months duration have shown improved function of respiratory muscle exercise tolerance and immunologic parameters by an increased caloric intake of 45 kcal/kg body weight. In a randomized trial of twelve months 14 of 30 patients with an average FEV1 of 0.8 l were instructed to take a high calorie diet. For simplicity a part of the calories were administered as Fresubin, a fluid nutrient formula. Although a weight gain of 7 kg (p = 0.003) was obtained the difference to the control group was statistically not significant (p = 0.08). The same was true for skin fold thickness (12.4 vs 5.7 mm), change of ventilatory parameters and the 6 minute walking distance (-33 vs -86 m). Subjective improvement was, however, impressive in all patients with dietary intervention, explainable probably by increased attention. Dietary counselling for increased intake of calories, vitamins and also calcium is thus very important in the treatment of patients with COPD.

Double ligand ELISA technique for the estimation of antibodies to brain tissue antigens in patients with neurological disorders.

A double ligand enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibodies against brain tissue antigens in the sera of patients with neurological diseases. The sera were tested on human white matter homogenate. The technique consists of successive incubations with the human serum to be tested, rabbit immunoglobulin G (IgG) to human immunoglobulins (Ig), alkaline phosphate-labeled protein A and alkaline phosphatase substrate. This procedure has the advantage of increased sensitivity compared to the classical ELISA. Application of this procedure to the sera of patients with neurological diseases showed that the unspecific binding is very low and the results are reliable. Moreover the test allows the detection of antibodies to chemically different antigenic structures that can occur in a variety of neurological diseases.