Dipeptidase 1 (DPEP1) is a marker for the transition from low-grade to high-grade intraepithelial neoplasia and an adverse prognostic factor in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide. Improvements in the understanding of its molecular mechanism and the characterisation of CRC-specific biomarkers facilitating early detection are considered to increase overall survival. METHODS: A meta-analysis of microarray and Serial Analysis of Gene Expression (SAGE) has been performed to identify differentially regulated genes in CRC. Dipeptidase 1 (DPEP1/MDP/RDP) and Syntenin-2 (SDCBP2/SITAC18) were found to be differentially expressed in tumour tissue compared with normal mucosa. Expression of DPEP1 was assessed in a validation set of 87 normal mucosa samples, 20 hyperplastic polyps, 46 CR adenomas with low- and high-grade intraepithelial neoplasia (IEN) and 217 well-documented CRCs by immunohistochemistry and partially by immunoblotting and real-time PCR. RESULTS: Expression of DPEP1 was specifically increased in human CRC tissue samples compared with normal mucosa (P<0.0001, Mann-Whitney U-test), showing a striking upregulation in high-grade compared with low-grade IEN. Furthermore, high DPEP1 expression was found to strongly correlate with histological stage (P<0.0001, chi-square test) as well as localisation (P<0.0001, chi-square test) and has been recognised as an independent adverse prognostic factor, showing significant prognostic values with an ROC (receiver operating characteristic)-AUC of 0.9230. CONCLUSION: Dipeptidase 1 has been identified as an excellent marker of high-grade IEN and CRC, and may thus be applied for screening of early neoplastic lesions and for prognostic stratification.

COGENT (COlorectal cancer GENeTics): an international consortium to study the role of polymorphic variation on the risk of colorectal cancer.

It is now recognised that a part of the inherited risk of colorectal cancer (CRC) can be explained by the co-inheritance of low-penetrance genetic variants. The accumulated experience to date in identifying these variants has served to highlight difficulties in conducting statistically and methodologically rigorous studies and follow-up analyses. The COGENT (COlorectal cancer GENeTics) consortium includes 20 research groups in Europe, Australia, the Americas, China and Japan. The overarching goal of COGENT is to identify and characterise low-penetrance susceptibility variants for CRC through association-based analyses. In this study, we review the rationale for identifying low-penetrance variants for CRC and our proposed strategy for establishing COGENT.

Increased proteasome subunit protein expression and proteasome activity in colon cancer relate to an enhanced activation of nuclear factor E2-related factor 2 (Nrf2).

An elevated proteasome activity contributes to tumorigenesis, particularly by providing cancer cells with antiapoptotic protection and efficient clearance from irregular proteins. Still, the underlying mechanisms are poorly known. In this study, we report that in colon cancer patients, higher proteasome activity was detected in tumoral tissue compared with surrounding normal tissue, and also that increased levels of proteasomal subunit proteins, such as S5a/PSMD4 and alpha-5/PSMA5, could be detected. Colon tumors showed higher nuclear levels of nuclear factor E2-related factor 2 (Nrf2), a transcription factor supposed to be involved in the control of proteasomal subunit protein expression. The induction or overexpression of Nrf2 led to stronger S5a and alpha-5 expression in the human colon cancer cell lines, Colo320 and Lovo, as well as in NCM460 colonocytes along with higher proteasome activity. The small interfering RNA (siRNA)-mediated Nrf2 knockdown decreased S5a and alpha-5 expression and reduced proteasome activity. Additionally, Nrf2-dependent S5a and alpha-5 expression conferred protection from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, an effect preceded by an increased nuclear factor (NF)-kappaB activation and higher expression of antiapoptotic NF-kappaB target genes. These findings point to an important role of Nrf2 in the gain of proteasome activity, thereby contributing to colorectal carcinogenesis. Nrf2 may therefore serve as a potential target in anticancer therapy.

Bypass surgery versus palliative pancreaticoduodenectomy in patients with advanced ductal adenocarcinoma of the pancreatic head, with an emphasis on quality of life analyses.

BACKGROUND: In some centers, palliative resection (PR; partial pancreaticoduodenectomy) is, in selected cases, promoted in preference to double loop bypass (DLB) surgery for advanced pancreatic cancer. This prospective study compares PR with DLB, placing particular focus on patients' quality of life (QoL). METHODS: From 01/1993 to 09/2004, 167 patients were analyzed in a prospective single center study of palliative surgical treatment of advanced ductal adenocarcinoma of the pancreatic head. Thirty-eight underwent PR and 129 underwent palliative DLB. Patients undergoing DLB were divided into: (1) locally advanced disease (LAD-subgroup; n = 61; 47%) and (2) metastasized disease (MD-subgroup; n = 68; 53%). QoL was assessed using the EORTC QLQ-C30 questionnaire supplemented by a pancreatic cancer specific module. QoL data were collected pre-operatively and for up to 12 months after surgery. RESULTS: Median survival was 7.0 months (95% CI 4.09; 9.91) in PR patients and 6.0 months (95% CI 5.39; 6.61) in patients who received DLB. Mortality and morbidity were, respectively, 7.8 and 58% for PR, and 2.6 and 42% for DLB. QoL decreased more after PR than after DLB. The DLB-group recovered quicker, reaching pre-operative QoL levels after 3 months, and were less impaired when discharged. The LAD-subgroup and the MD-subgroup presented with equal levels of QoL. CONCLUSIONS: QoL analysis revealed favorable QoL data after DLB. Additionally, the survival rates of the two groups did not differ significantly, but morbidity and mortality rates in the PR group were elevated. Therefore, the use of PR for advanced pancreatic cancer needs to be carefully evaluated.

Audit of a series of 40 gastrointestinal stromal tumour cases.

AIMS: To analyze prognostic factors influencing survival and tumour recurrence after resection of gastrointestinal stromal tumours. METHODS: Forty patients who underwent surgery for a GIST at our institution were reviewed. Patients were classified on the basis of tumour size, mitotic rate and CD117 positivity. The overall survival and disease free survival were calculated using Kaplan-Meier method considering the extent of surgery comparing local tumour excisions with segmental organ resections. RESULTS: Tumours were localized in the oesophagus, stomach, duodenum, small bowel and large bowel and rectum. Sixty-five percent of the patients had an intermediate or high risk GIST according to tumour size and mitotic count. In 26/40 patients tumour resection was performed using segmental organ resection, in all other patients local tumour excision was carried out. The mean overall survival was 73 months. Disease free survival was significantly better after local tumour excision compared to segmental organ resection (73 months versus 53 months; p=0.05). Large tumour size (p=0.07) and high mitotic count (p=0.14) were negative prognostic factors for disease free survival, although statistical significance was not reached yet. CONCLUSION: Primary surgery remains the cornerstone in the treatment of primary and recurrent GIST. Risk adapted surgery is the most important factor to avoid early tumour recurrence. In case of small tumour size segmental organ resections can be avoided favouring local tumour excisions with a low risk of tumour recurrence.

Open versus laparoscopic appendicectomy: a critical review.

BACKGROUND: The benefit of laparoscopic appendicectomy remains unclear. We have analysed available randomised studies comparing laparoscopic and open appendicectomy regarding their clinical pitfalls and statistical relevance. METHODS: Thirty eight studies were analysed in terms of the following aspects: A. clinical problems (e.g., expertise of the surgeons, pre- and postoperative antibiotic treatment, definition of complications, blinding of outcomes) and B. statistical problems (e.g., definition of primary and secondary outcomes, power and sample size, statistical methods, confidence intervals, comparability of groups and studies). RESULTS: Most of the studies have clinical and statistical pitfalls. The most important pitfalls are the uncertain expertise of the operating surgeons, blinding, and the exploratory nature of the studies. Our analysis aims at giving useful information for the appraisal of existing studies and the conduct of further studies. It also gives some preliminary results. CONCLUSIONS: More than twenty years after Semm performed the first laparoscopic appendicectomy, it is necessary to clarify the superiority of laparoscopic or open appendectomy with well-defined, carefully designed randomised studies.

[Emergent treatment of a malignant peripheral epineurial tumour]. / Notfallversorgung eines seltenen malignen Nervenscheidentumors: Anforderungen an eine Klinik der Maximalversorgung.

BACKGROUND: Malignant peripheral epineurial tumours are a group of tumours that derive histomorphologically from peripheral nerve sheaths. They occur sporadically, with an incidence of approximately 0.001%, and very rarely require emergency operation. PATIENT AND PROCEDURE: An athletic 19-year-old man presented to an orthopaedic outpatient clinic with lumboischialgia and weakness of the third and fourth left toes. A 12 x 10 x 8-cm paravertebral/retroperitoneal tumour was diagnosed by CT, and the patient was referred to our clinic. For classification, CT-assisted puncture of the tumour was carried out. A haemorrhage into the tumour resulted from the puncture, with consequently lower Hb level and progressive peripheral sensomotoric deficits demanding emergency surgery on a weekend. On this occasion, the tumour was resected together with the L5 and S1 nerve roots through cooperation between the general surgical and neurosurgical departments and was classified as a malignant peripheral epineurial tumour in the rapid stage. Due to the spinal R2 resection, after-loading probes were inserted and the tumour bed was clip-marked. Percutaneous radiotherapy and brachytherapy followed postoperatively. Shortly afterwards, relaparotomy had to be performed due to an adhesive ileus, from which the patient recovered quickly. Chemotherapy was carried out due to a G2 tumour classification. The patient is currently undergoing rehabilitation, during which the peripheral neurological deficits are improving gradually. CONCLUSION: This rare case of a malignant peripheral epineurial tumour with acute symptoms demonstrates the ability of hospitals with maximum care facilities to maintain services even in times of financial cuts in health care services.

Significant growth inhibition of orthotopic pancreatic ductal adenocarcinoma by CpG oligonucleotides in immunodeficient mice.

BACKGROUND/AIMS: The high rate of local recurrence after radical resection of pancreatic ductal adenocarcinoma fosters intensive efforts to develop new approaches for adjuvant treatment. Antisense and modified oligodeoxynucleotides (ODNs) have demonstrated significant tumour growth inhibitory effects in preclinical systems. Our aim was to evaluate the possible therapeutic potential of ODNs containing unmethylated deoxycytidyl-deoxyguanosine dinucleotides (CpG motifs). METHODOLOGY: For in vitro analysis, [(3)H]thymidine incorporation for DNA synthesis, colorimetric cell vitality assay (EZ4U assay), and DNA fragmentation assay (JAM-[(3)H]thymidine incorporation assay) to test for apoptosis were performed. In vivo testing was done on an orthotopic pancreatic xenotransplantation model using severe combined immunodeficient (SCID) beige and nude mice. RESULTS: No significant differential effect of either control ODN or CpG-1826 ODN with regard to tumour cell proliferation or induction of apoptosis was observed in vitro. In vivo, ODN-1826 proved to have a significant inhibitory effect (up to 40% reduction of tumour weight) when compared with tumour-bearing animals treated with saline or control ODN. This was accompanied by sevenfold increase in splenomegaly and moderate hepatomegaly. The reduction of tumour weight by ODN-1826 was only slightly more pronounced in nude compared with SCID beige mice. CONCLUSION: CpG-1826 induces significant growth-inhibitory effects on orthotopic xenotransplanted pancreatic tumours in highly immunodeficient mice, which might be explained by innate immunity mechanisms and possibly a complex interaction of tumour and stroma cells.

Comparative investigation of alloplastic materials for hernia repair with improved methodology.

BACKGROUND: A variety of alloplastic materials are used for hernia repair. We discuss the long-term stability and possible shrinkage of these materials. In the past, measurement of pore sizes was used to study the physical properties of alloplastic meshes. The aim of this study was to evaluate the measurement of pore sizes with regard to its correlation to possible mesh alteration. METHODS: The water absorption of different polypropylene (PP) and polyester (PE) mesh materials under defined conditions was studied. For shrinkage studies, meshes were stored in formaldehyde, distilled water, saline solution, trypsin solution, urea solution, and hydrogen peroxide. The measurement of the relation between material and pore was evaluated to investigate the potential shrinking and enlargement processes. This material-pore index (MPI) before as well as 1, 7, and 14 days after incubation was measured. RESULTS: In comparison to measuring single pore sizes, MPI determination is the more efficient method to evaluate the possible shrinking or enlargement processes of alloplastic materials. With this technique, incorrect determination of pore sizes due to the dynamic textile structure of meshes and to shrinkage or enlargement, is excluded. All tested alloplastic materials showed an insignificant increase in water absorption under the condition of rehydration up to 0.4%. We did not observe variances in the material in shrinking or enlargement. CONCLUSIONS: MPI was found to be more reliable than measuring single pores to investigate possible external influences on polymer materials. Biomaterials such as PP and PE proved to be absolutely inert under various in vitro conditions.

Precoating of alloplastic materials with living human fibroblasts--a feasibility study.

BACKGROUND: The use of alloplastic materials such as polypropylene and polyester has reduced the recurrence of abdominal wall hernias. Concomitantly, new problems have arisen such as inflammatory response against the implanted material and the development of enteric fistulas in case of direct contact of the bowel to polypropylene and polyester. A precoating of the PP with collagen and other absorbable materials seems to reduce the incidence of adhesions and fistulas. The aim of this study was to show the technical feasibility of a precoating of polypropylene with living human fibroblasts and to investigate the growth properties of the cells under these conditions in vitro. METHODS: The textile structure of three different alloplastic materials is described (SurgiPro), TycoHealthcare; Parietene3 PP1510, Dallhausen; VIPRO II, Ethicon Endosurgery). Enhanced Green Fluorescence Protein (EGFP) transduced human foreskin fibroblasts (KiF5) were seeded onto these different alloplastic materials. Proliferation was analyzed by FACS analysis of Ki67 expression. The coating process of the whole mesh area was observed over time with UV-light microscopy, immunostaining, and scanning electron microscopy (SEM). The expression of collagen type I and III was investigated by immunostaining. RESULTS: The three alloplastic materials used were knitted fabrics with different textile structures. KiF5 colonized the entire alloplastic material within 4-6 weeks. Cells were proliferating, as detected by Ki67 expression. SEM showed surface ruffles and long cellular extensions, indicating an active cell metabolism. Light microscopy and SEM suggested that the cells modify the apolar surface by deposition of extracellular matrix components before colonization. CONCLUSION: Our study shows the feasibility of precoating of polypropylene meshes with living human fibroblasts and opens the possibility for clinical use in the future.

[Open versus laparoscopic operation for perforated appendicitis--a comparative study]. / Konventionelle oder laparoskopische Operation der perforierten Appendizitis - Eine vergleichende Studie.

INTRODUCTION: Laparoscopic therapy of complicated appendicitis is still discussed controversially. This retrospective study compared the clinical results of open and laparoscopic appendectomy in a single centre. PATIENTS AND METHODS: Within a period of three years (1999 to 2001) 493 patients with suspected acute appendicitis were operated prospectively at a German district hospital (250 open appendectomies, 243 laparoscopic appendectomies). Twenty percent of the patients in every group had a complicated appendicitis (48 open, 44 laparoscopic appendectomies) and were analysed retrospectively considering demographic data, operative time, body mass index, preoperative inflammatory parameters (white blood cell count, C-reactive protein and body temperature) and postoperative complication rate. RESULTS: Both groups were comparable with regard to demographic data. One patient of the laparoscopic group needed an open operation (conversion rate 2.3 %). The body mass index of the laparoscopic group was significantly higher (26.3 vs. 24.1 kg/m(2)). Preoperative white blood cell count, C-reactive protein, body temperature as well as postoperative antibiotic therapy and analgesics requirement were comparable in both groups. There was no significant difference between the length of operative time (open 48 min, laparoscopic 53.5 min). The postoperative hospital stay was significantly shorter in the laparoscopic group (8 vs. 9 days, p = 0.032). Complication rate was significantly lower in the laparoscopic group (11.5 vs. 35 %, p = 0.014). CONCLUSION: Laparoscopic appendectomy is a safe procedure for the treatment of complicated appendicitis with a significantly decreased complication rate and shorter postoperative stay.

Intraoperative radiofrequency ablation (RFA) for irresectable liver malignancies.

AIMS: To evaluate the outcome of patients who received radiofrequency ablation (RFA) at open laparotomy in patients with irresectable liver malignancies. METHODS: Twenty-six consecutive patients who underwent explorative laparotomy and were found to be irresectable or who had been assessed not suitable for either resection or percutaneous RFA received intraoperative RFA. An expandable electrode (RITA Medical systems) was used. Follow-up comprised CT-scans in 6-12 week intervals. RESULTS: Patients' age ranged from 35 to 72 years (median 61). A variety of pathologies were treated. In 26 patients, 88 hepatic lesions were treated: 32 with resection and 56 with RFA. The mean diameter was 4.0+/-2.6 cm with a maximum of 10 cm. In 22 patients with hepatic metastases (18 colorectal, one leiomyosarcoma, one endometrium carcinoma, one renal cell carcinoma, one malignant phaeochromocytoma) 74 lesions (median 3.4 per patient) were treated (25 by resection, 49 by RFA). Eleven patients received simultaneous resection and RFA: resection of anatomical segments in six and atypical resection in seven patients. Procedure related complication rate was 19.2%. The mean follow-up was 14.6+/-9.2 months (2-36 months). Three patients developed recurrence at the site of previous RFA indicating incomplete ablation. The overall local control rate after one year was 92 and 90.9% for patients with colorectal liver metastases, respectively. Seventeen patients (65.4%) suffered from tumour progress. In 14 patients (53.9%) tumour occurred at new hepatic localisations and in five patients extrahepatic tumour relapse was diagnosed. Twelve patients have died so far (median survival 18 months, range 4-27). Nineteen patients had either completed a follow-up of at least 12 months or died within this period, resulting in an one year survival rate of 79% (80% for liver metastases). CONCLUSION: Intraoperative RFA is a valuable tool in liver surgery which extends the surgical spectrum in cases of irresectable malignancies.

[Modification of the liver resection technique with radiofrequency coagulation]. / Modifikation der Leberresektionstechnik durch Radiofrequenzkoagulation.

INTRODUCTION: Since the introduction of liver resection, intraoperative blood loss is considered to be a major risk factor for perioperative morbidity and mortality. Radiofrequency energy-an established technique for in situ ablation-was used to facilitate liver resection by creating a nearly bloodless tissue plane. METHODS: After thorough manual and sonographic exploration of the liver, the planned and marked resection plane was coagulated by radiofrequency and then transected. Seven patients with liver metastases of colorectal carcinoma were operated on employing this technique. RESULTS: A nearly bloodless transection of the parenchyma could be achieved in all cases. Only two patients received blood transfusions: one due to a low preoperative hemoglobin and one due to extended additional abdominal surgery. Procedure-related complications included one case of a second-degree burn to the thigh and one case of postoperative bile leakage requiring hemihepatectomy. CONCLUSIONS: Radiofrequency-assisted resection offers a valuable additional option in liver surgery, especially in patients with an increased risk of intraoperative bleeding (cirrhosis, coagulopathy).

Relationship between design features of endodontic instruments and their properties. Part 3. Resistance to bending and fracture.

Stainless-steel prototypes characterized by five different cross-sectional shapes (square, triangular, rhomboidal, "S"-shaped, and the cross-sectional design of H-type files) and three different number of flutes (16, 24, and 32) were used for investigation of the relationship between design features and the resistance to bending and fracture of root canal instruments. Both resistance to bending (bending moment) and resistance to fracture (angular deflection and torque) were determined in accordance to ISO 3630-1. Numbers 15, 25, and 35 prototypes were tested with a sample size of 10 instruments each. Whereas prototypes with the rhombus-shaped cross-sectional design displayed the lowest resistance to bending, those of the square cross-section showed the greatest. In general, S-shaped prototypes and those with the H-type cross-section achieved lower angular deflection than all other prototypes, whereas those with the triangular cross-sectional shape and 32 flutes reached the greatest angular deflection. Overall, rhombus-shaped prototypes showed lower torque values than all other prototypes. Results indicate that bending and torsional properties of endodontic instruments are mainly influenced by their cross-sectional design. Moreover, these properties are also affected by the number of flutes and the manufacturing process (twisted or milled) of endodontic instruments.

Properties of endodontic hand instruments used in rotary motion. Part 3. Resistance to bending and fracture.

Bending and torsional properties of 24 different types of nickel-titanium K-files, titanium-aluminium K-files and reamers, conventional stainless steel K-files and reamers, and flexible stainless steel instruments were investigated corresponding to ISO 3630-1 by determination of the bending moment on the one hand and the torque and angular deflection on the other. Numbers 15, 25, and 35 instruments were tested with a sample size of 10 instruments for each type and size. In ascending order of bending moment the instruments ranked: nickel-titanium K-files, titanium-aluminium K-files and reamers, flexible stainless steel instruments, conventional stainless steel K-files, and reamers. Nickel-titanium, titanium aluminium, and flexible stainless steel instruments displayed lower torque values than conventional stainless steel K-files and reamers. The average angular deflection ranged from 380 degrees (#15 reamer) to 2370 degrees (#35 K-file). Overall, the fracture risk of the instruments tested in this study was comparably low.

Endodontic hand instruments: cutting efficiency, instrumentation of curved canals, bending and torsional properties.

In an assessment of the usefulness of different root canal instruments, two aspects are of particular interest for the endodontist: the cutting efficiency of the instruments and their ability to enlarge curved canals without undesirable changes of the canal shape such as the formation of zips and elbows. This review paper is based on own investigations on the cutting efficiency and instrumentation of curved canals. Additionally, two parameters which are described in ISO 3630-1, resistance to bending and resistance to fracture, are discussed. With regard to cutting efficiency in rotary motion, flexible stainless steel reamers and K-files clearly display the best results and are superior to conventional stainless steel as well as titanium-based reamers and K-files. Regarding cutting efficiency in linear motion, stainless steel Hedström files made by certain manufacturers are significantly superior to stainless steel and titanium-based Hedström files of other brands. Flexible stainless steel instruments with modified noncutting tips clearly produce the best canal shape in curved canals. With only rare exceptions, all the instruments tested fulfilled the requirements of the ISO standard concerning resistance to fracture and resistance to bending.

Long-term results of patients with clinical stage C prostate cancer treated by phototherapy and early orchiectomy. A retrospective analysis of 169 cases.

BACKGROUND: To evaluate the value of radiotherapy and immediate hormonal therapy in the treatment of stage C prostate cancer. PATIENTS AND METHOD: From 1977 to 1986, 169 patients with clinically stage C prostate cancer underwent irradiation with curative intent following early orchiectomy. Sixty-four patients had a transurethral resection, 22 patients a prostatectomy and 83 patients had only a biopsy. In 38 patients a grade Ia/b tumor was found, in 78 patients a grade IIa/b tumor and in 43 patients a grade IIIa/b tumor using the German grade of malignancy. Treatment fields included the prostate, the seminal vesicles and the locoregional lymphatics. Until 1979 the dose was 60 Gy for the tumor encompassing isodose and from then on 65 Gy with a single dose of 2 Gy. RESULTS: With a median follow-up of 98 months, the overall survival rate for 8 and 10 years was 51% and 37% and the cause specific survival rate was 84% and 77%, respectively. Thirty-two patients (19%) developed distant metastases. Patients with local tumor control (n = 148) had a significantly better overall survival rate of 45% for 10 years compared to patients with clinical local progression of disease (n = 21) of 22% (p < 0.05). Multivariate analysis showed the grade of malignancy and local control as independent factors for overall survival and cause-specific survival (p < 0.05). Twenty-three patients (14%) had at least one late side effect for the rectum or the bladder, in almost all cases grade I or II. Five patients (3%) showed severe late side effects RTOG grade III (n = 2) or IV (n = 3). One patient had a colostomy, in 2 patients a severe haemorrhagic cystitis was seen. CONCLUSIONS: Radiotherapy with photons and early orchiectomy for patients with stage C prostate cancer achieves high local control rates and a 30% to 40% 10-year survival rate with a low incidence of late side effects. The value of the radiotherapy of the locoregional lymphatics remains controversial.

Cutting efficiency of Hedstrom, S and U files made of various alloys in filing motion.

The cutting efficiency for sizes 25 and 35 stainless steel Hedstrom S and U files from 10 manufacturers, and titanium-alloy Hedstrom S and U files from five manufacturers, tested for linear (filing) motion under standardized conditions were determined. Special plastic samples having well-defined abrasive properties were used as the substrate and constant pressure was applied until the instruments were blunt. The depth of the groove achieved by filing was used to measure cutting efficiency. For both sizes there were significant differences in the cutting efficiency of files made by the various manufacturers (P < 0.001). Hedstrom files made of stainless steel, made by VDW, gave the best cutting efficiency for sizes 25 and 35. Overall, under the conditions of this study. Hedstrom files had better cutting efficiency than S or U files. Likewise, stainless steel files provided better cutting efficiency than instruments made of titanium alloys.

Properties of endodontic hand instruments used in rotary motion. Part 2. Instrumentation of curved canals.

The shaping abilities of nickel-titanium K-files, stainless steel reamers, K-files, and flexible stainless steel instruments with conventional cutting tips and with modified noncutting tips were investigated under standardized conditions using a computer-driven testing device simulating the clinical use of the instruments. Simulated root canals with a 42-degree curvature were sequentially enlarged from #15 to #35. Undesirable changes in the canal shape as a result of instrumentation occurred in all cases. None of the instruments were able to remove material on the whole length of the inner side of the curvature, whereas all instruments removed material on the whole length of the outer side of the curvature, resulting in slight to severe bulging. The extent of undesirable changes in the canal shape depended typically of the type of instrument used. Best instrumentation results were obtained with flexible instruments with noncutting tips.

Properties of endodontic hand instruments used in rotary motion. Part 1. Cutting efficiency.

Cutting efficiency of 24 different types of endodontic hand instruments, which are primarily designed for a rotary (reaming) working action, was investigated under standardized conditions. With a computer-driven testing device, resin specimens with simulated cylindrical canals were instrumented using a defined working motion simulating the clinical use of the instruments. Maximum penetration depth was the criterion for cutting efficiency. Sample size was 12 instruments for each type and size (#25 and #35). Nitinol K-files showed the least cutting efficiency. Stainless steel reamers and especially K-files showed better cutting efficiency than Nitinol K-files. Flexible stainless steel instruments displayed the best results. With regard to cutting efficiency, flexible stainless steel instruments were clearly superior to stainless steel reamers and K-files, and especially to Nitinol K-files.