Influence of endodontic motors on the behaviour of root canal shaping instruments: an in vitro comparative study.

AIMS: The endodontic literature reports a lot of comparative study on endodontic instruments, concerning as well their geometry, instrumental dynamics, material, mechanical behavior or heat treatment. However, to our knowledge, no study has focused on the influence of endodontic motors on the shaping abilities of endodontic instruments. Thus, the aim of this study was to analyze the influence of the endodontic motors on root canal shaping instruments. METHOD: Dual Move (MICRO-MEGA, Besançon, France), Canal Pro CL2i (COLTENE, Alstätten, Suisse), Canal Pro Jeni Motor (COLTENE, Alstätten, Suisse), Ai Motor (WOODPECKER, Guilin, China), Wave One motor (VDW, Postfach, Munich) and Smart A (WOODPECKER, Guilin, China) were pre-clinically compared in continuous rotation and reciprocating motion on a traction/compression bench using resin blocks. Canal shaping in continuous rotation and reciprocating motion were performed with One Curve and One RECI instruments (MICRO-MEGA, Besançon, France), respectively. The penetration/removal forces, making it possible to objectify the cutting effect and screwing effect of the instruments during root canal shaping, were analyzed. RESULTS: The results showed (i) that endodontic motors influence the mechanical behavior of endodontic instruments, (ii) that the influence of the motors is essentially felt during reciprocating motion and (iii) that the reciprocating angles influence the mechanical behavior of endodontic instruments. CONCLUSION: Only endodontic instruments are widely studied in literature while endodontic motors have a direct influence on root canal treatment. This study analyzes the influence of the endodontic motors on root canal shaping instruments. This study tends to demonstrate that Jeni Motor could optimize the mechanical behavior of endodontic instruments.

Study of the use in autonomy of intraoral scanning systems to optimise dental students' performances in fixed prosthodontics practical learning in second year.

AIM: The purpose of this study was to evaluate if the use of intraoral scanner analysis could help students to optimise their performance and their self-assessment abilities in prosthetic preparation without the teacher's assistance in the preclinical course. MATERIALS AND METHODS: Ninety-five second-year dental students were randomly divided into three groups: Control group (C), CeRec group (CR) and PrepCheck group (PC). Group C only use silicon keys to control the preparation thickness. The students in Group CR analysed their work with Cerec™ software. The Group PC use a pedagogic software (PrepCheck™) which allowed comparison with the "master" preparation. They used control tools preparations for three consecutive training sessions. Then a final assessment session without control tool to evaluate their performance was organised. All preparations were objectively evaluated thanks to stl. analysis software (Geomagic® Control X). Each preparation was compared with the master preparation by defining tolerance ranges. An objective overall score out of 20 was assigned to each preparation according to their degree of correspondence. In addition, a questionnaire was performed to analyse the students' perceptions regarding the use of intraoral camera. RESULTS: During the assessment session, no significant difference was revealed between the different groups with respect to the students' performance. The comparative analysis between the self-assessment scores and the objective scores using Geomagic® software showed that digital control tools did not help the student to improve their self-assessment abilities without the teacher's assistance. CONCLUSIONS: The intraoral cameras and specific pedagogic software in autonomy could not improve students' performance for teeth preparation and self-assessment abilities in second year. These digital tools facilitate objective feedback on preparation defects, but constructive criticism needs human reflection. The teacher's opinions and advice remain essential to develop their students' performance and self-assessment skills. The use of digital tools must be integrated in dentistry course to develop the interpret of the results and optimise feedback.

Virtual aids and students' performance with haptic simulation in implantology.

OBJETIVES: This study aims to validate that haptic simulator assistance could improve drilling ability in implantology and that the repetition of training session could highlight a learning curve. METHODS: This work was carried out with 88 first-year dental students. After randomization, students were divided into two groups. Group 1 was assigned to prepare an implant site for a left first mandibular molar (36) on haptic simulator with assistance provided by simulator. Group 2 had to perform the same exercise without assistance. Whatever the group, the maximum time for each reparation was restricted to 5 min. An interval of 1 week was done between each session. For each test, different objective parameters provided by the simulator were recorded and analyzed. RESULTS: This study showed that the presence of virtual aids led to quickly obtain better results, and the training led to gradually acquire sufficient competence to do without virtual aids. CONCLUSION: By associating virtual assistance and repetition, the student will acquire more quickly the skills allowing to carry out his clinical gestures in real conditions.

Methodological Approach to the Endodontic Treatment of First Premolars with Three Root Canals: Two Case Reports.

AIM: The aim of this article was to promote a methodology in the endodontic management of complex premolars with multiple root canals Background: The success of endodontic treatment depends on a meticulous clinical and radiographic analysis, the creation of a suitable access cavity and chemical and mechanical preparation, followed by three-dimensional filling of the entire root canal system. Consequently, it is essential to look for the presence of additional root canals to prevent endodontic treatment failure Case description: Two cases are presented. The first case concerned a 50-year-old male patient of North African origin who consulted in the context of a global prosthetic restoration including endodontic treatment of the maxillary left first premolar (tooth no. 24). The second case concerned a 29-year-old male patient of North African origin who was referred to us by his primary care practitioner in an urgent context of pain and infection present for two weeks (tooth no. 44). In both cases, it was the in-depth radiographic analysis, combined with manual exploration under the surgical micro- scope, that led to the relatively rare identification of a third root canal. Shaping, disinfection and three-dimensional filling of the entire root canal system were then performed in accordance with widely validated protocols. CONCLUSION: The maxillary and mandibular premolars, due to their highly variable root canal system configuration and a number of root canals and roots, appear to be teeth for which treatment is potentially complex. The acuteness of digital-tactile sense and the advent of 3D imaging and optical aids optimize the treatment of all the root canals of a tooth Clinical significance: These case reports demonstrate the importance of clinical and radiographic inspections to guide practitioners in the search for additional root canals in premolars and promote a methodological approach.

Porosity of flowable resin composites is not influenced by applicator tip diameter.

PURPOSE: To assess the influence of applicator tip diameter on the inclusion of porosities in three different flowable resin composites. METHODS: The initial porosity of three syringes [Filtek Supreme XTE Flowable (XTE), Grandio Flow (GRF), Gradia Direct Flo (GDF)] was determined by 3D tomography. 25 samples per syringe, i.e. 75 samples in total, were prepared using five applicator tips of different diameters (n= 5). The porosity of the 75 samples was assessed by 3D tomography. RESULTS: For each of the materials, the applicator tips, irrespective of type, all generated an increase in the average porosity percentage compared to the initial porosity of the syringes. For XTE and GRF, the applicator tips, irrespective of type, all generated a decrease in the average porosity volume compared to the initial average porosity volume in their respective syringes. Conversely, for GDF the average porosity volume of the samples was increased. Furthermore, for each of the materials, varying the diameter of the applicator tips had no significant influence on the porosity percentage and volume. Using the present study conditions, the applicator tip generated a variation in the initial porosity of the materials; however, the diameter of the tip had no influence on said variation. CLINICAL SIGNIFICANCE: It appears that practitioners can choose an applicator tip with a diameter that best suits the size and shape of the cavity to be filled using a syringe of flowable resin composite without this having any impact on the percentage and volume of porosities in the final filling of the cavity.

Dynamic thermo-mechanical properties of various flowable resin composites.

BACKGROUND: This study compared the storage modulus (E'), the loss modulus (E'') and the loss tangent (tan δ) of various flowable resin composites. MATERIAL AND METHODS: Grandio Flow (GRF), GrandioSo Heavy Flow (GHF), Filtek Supreme XTE (XTE) and Filtek Bulk Fill (BUL) flowable resins and Clinpro Sealant (CLI) ultra-flowable pit and fissure sealant resin were used. 25 samples were tested using a dynamical mechanical thermal analysis system in bending mode. Measurements were taken within a temperature range of 10 to 55°C. The results were statistically analyzed using mixed-effect and repeated-measure analysis of variance followed by paired multiple comparisons. RESULTS: For all the materials, the E' values decrease with temperature, whereas the tan δ values increase. Irrespective of the temperature, GHF and GRF present E' and E'' values significantly higher than all the other materials and CLI presents values significantly lower than all the other materials. Observation of the values for all the materials reveals a linear progression of the tan δ values with temperature. CONCLUSIONS: A variation in temperature within a physiological range generates modifications in mechanical properties without damaging the material, however. Filler content in volume terms appears to be the crucial parameter in the mechanical behavior of tested materials. Key words:Dynamic mechanical thermal analysis, elastic modulus, filler content, flowable resin composites, loss modulus, loss tangent.