The Prognosis of Root Canal Therapy: a 20-year Follow-up Ambispective Cohort Study on 411 Patients With 1169 Endodontically Treated Teeth

PURPOSE To evaluate the 20-year prognosis of endodontically treated/re-treated teeth in a population with multiple patient/tooth/site risk factors, and to investigate the prognostic factors that could predict the long-term outcome of endodontic therapy. MATERIALS AND METHODS This ambispective cohort study included patients who received primary/secondary root canal therapy from 1986 to 1998 performed by a single operator in a private practice. Outcomes measures were: tooth survival; clinical and radiographic success, as assessed by the treating clinician and an independent outcome assessor; and complications, as evaluated 20 years after treatment. Descriptive statisti-cs, life table and Cox regression analyses for survival were fitted. RESULTS Four hundred and eleven patients (59% affected by advanced periodontitis) with 1169 endodontically treated teeth were identified (703 treatment, 466 retreatment). Drop-outs at 20-year follow-up were 128 patients (31.1%) with 388 (33.2%) teeth. Forty teeth (3.4%) in 30 patients experienced endodontic complications, subsequently successfully treated. Clinical and radiographic evaluation revealed: complete clinical success in 542 teeth (69.7%), partial success in 10 (1.3%), partial failure in 75 (9.6%), and failure in 151 (19.4%) (10 extracted for endodontic reasons, 58 due to periodontitis, and 58 vertical fracture). Life table analysis revealed 86% tooth survival at 20-year follow-up. The chance of survival decreased with increasing patient age (P = 0.006). Re-treated teeth had better survival than treated teeth (P = 0.024) Canines and premolars had better chances of survival than incisors (P = 0.002 and P = 0.015, respectively). Teeth treated at two sittings (with intermediate medication) had reduced chances of survival as compared to teeth treated at one sitting (P = 0.027). Teeth treated for the first time for endodontic reasons exhibited a better chance of survival than teeth treated for periodontal and prosthetic reasons (P = 0.012). CONCLUSIONS The 20-year prognosis of endodontically treated/re-treated teeth as part of multidisciplinary rehabilitation of patients affected by advanced periodontitis is good. Aging, two-stage endodontic treatment, and endodontic treatment for non-endodontic reasons are important predictors of failure

Robotic Wrist Mechanism with Redundancy: Thesis,"Computer

Haptic Interface, ” submitted to the 4th Internationa

Simultaneous remote haptic collaboration for assembling tasks

Stand-alone virtual environments (VEs) using haptic devices have proved useful for assembly/disassembly simulation of mechanical components. Nowadays, collaborative haptic virtual environments (CHVEs) are also emerging. A new peer-to-peer collaborative haptic assembly simulator (CHAS) has been developed whereby two users can simultaneously carry out assembly tasks using haptic devices. Two major challenges have been addressed: virtual scene synchronization (consistency) and the provision of a reliable and effective haptic feedback. A consistency-maintenance scheme has been designed to solve the challenge of achieving consistency. Results show that consistency is guaranteed. Furthermore, a force-smoothing algorithm has been developed which is shown to improve the quality of force feedback under adverse network conditions. A range of laboratory experiments and several real trials between Labein (Spain) and Queen's University Belfast (Northern Ireland) have verified that CHAS can provide an adequate haptic interaction when both users perform remote assemblies (assembly of one user's object with an object grasped by the other user). Moreover, when collisions between grasped objects occur (dependent collisions), the haptic feedback usually provides satisfactory haptic perception. Based on a qualitative study, it is shown that the haptic feedback obtained during remote assemblies with dependent collisions can continue to improve the sense of co-presence between users with regard to only visual feedback.Peer reviewe

Performance measures for haptic interfaces

A haptic interface is distinct from other display devices because it is bi-directional � it is capable of both reading and writing input to and from a human user. Due to both the direct human interaction and bi-directionality there has been much ambiguity in describing and evaluating these devices, making evaluation and comparison di-cult. The goal of this paper is to set out requirements and guidelines for the performance measures of haptic devices and to hopefully lead towards resolving the current equivocal situation. In particular, performance measures are introduced whichhaveso far not been pertinent in traditional robotics � these include, peak force, peak acceleration and frequency dependent measurements. Performance measures often quoted in traditional robotics are also discussed, however, the focus and relevance of these measures are different in haptic devices. Each of the suggested performance measures in this paper is discussed with respect to its importance, its measurabilty and the condition under which it should be measured.