Torsion Resistance of the Ball Head System Screw and Screwdriver for Angled Screw Channels on Implant Prosthetics.

The primary objective of this study was to determine the torsion resistance of the Ball Head System (BHS) screw and screwdriver set at 0°, 20°, and 30° angulations. The secondary objective was to compare the BHS set with the 1.3-mm hexagonal screwdriver system (HexS) at 20° and analyze the condition of the BHS after 10 and 30 iterations with 30 N·cm torque at 30° angulation. A workbench made from type 4 plaster with 6 steel implant replicas (external hexagon, 4.1 mm) inserted at 0°, 20°, and 30° angulation was designed. An analogical torque meter was used. The deformations produced on the whole set were examined by field emission scanning electron microscopy. A descriptive analysis was performed. The maximum torque performance for BHS at 30° angulation was 54 ± 12 N·cm. Most screws could be removed despite the deformations produced. At 20° angulation, the BHS set achieved an average torque resistance of 67 ± 12 N·cm, whereas the HexS failed at 45 ± 2 N·cm. Although the iterations performed at 30 N·cm torque and 20° angulation produced some deformations on BHS sets; these could be tightened and unscrewed. The BHS allows tightening at a torque of up to 54 N·cm. Under the same conditions, BHS showed more torque resistance than HexS. Deformation of BHS sets was directly related to the number of iterations.

Novel Ball Head Screw and Screwdriver Design for Implant-Supported Prostheses With Angled Channels: A Finite Element Analysis.

The primary objective of this study was to design the optimal geometry of a novel screwdriver, create the grooves on a ball head screw, and demonstrate its resistance to a torque of up to 40 Ncm at angulations of 0°, 15°, and 30° by using nonlinear finite element analysis. A secondary objective was to create a foolproof, easily recognizable system. The grooved ball head screw and geometry of the screwdriver, functioning from an angulation of 0° to 30°, was generated using Pro-ENGINEER Wildfire 5.0 software. Static structural analyses among bodies in contact were performed at different angles of 0°, 15°, and 30° at a torque of 20 Ncm and 40 Ncm using nonlinear finite element simulation by means of ANSYS 12.0. The maximum stress supported by the ball head screw and screwdriver was similar at 20 Ncm and 40 Ncm. Although greater deformations were found at 40 Ncm, these were small and might not affect the performance of the system. Further, the rupture torque value for the M2 connection was 55 Ncm for 0° and 30°, and 47.5 Ncm for 15°. Numerical simulation showed that the ball head system design can achieve the mechanical strength requirements expected for screws used in implant-supported restorations at an angulation of up to 30°. Finite element analysis showed this novel ball head screw and screwdriver system to be a good solution for angled screw channels in implant-supported prostheses.

Study of two MTA cements.

INTRODUCTION: To determine and compare the pH, conductivity and calcium release of an experimental Portland cement (PE) consisting of trioxid mineral aggregate and a comercially available modified Portland cement (C.P.M.) after 1, 2, 3, 4, 8, 10, 15 and 30 days. MATERIAL AND METHODS: Cements were mixed following the manufacturer's instructions, with a powder: liquid ratio of 3:1. Each cement was placed in 12 PVC tubes 1 mm in diameter and 10 mm in length and allowed to set. Four empty tubes were used as negative controls. Tubes were submerged in plastic flasks containing 10 ml deionized water and stored at 37 C and 100% humidity. After 1, 2, 3, 4, 8, 10, 15 and 30 days tubes were removed from the flasks and these were refilled with deionized water. We measured pH, conductivity and calcium content of the recovered solution. Data were analyzed using repeated measures ANOVA. RESULTS: pH was 0.3 units more alkaline with PE cement (p=0.023). pH experienced a slight decrease with time (p<0.001), independently of the cement type (p>0.05). Conductivity of PE and CPM cements diminished at 4 days and almost recovered at 30 days (p<0.001). PE cement had a higher conductivity (p<0.001). Calcium release diminished from the first day and recovered at 30 days (p<0.001) similarly for both cements (p>0.05). CONCLUSIONS: PE cement raised pH slightly more and had higher conductivity than CPM. Calcium release diminished after the first day and recovered at 30 days, similarly for both cements.

Root canal retreatment of root canals filled with "Neo MTA 2" and epoxy resin, using continuous and asymmetric reciprocal rotation systems: In vitro study.

Background: The study aimed to compare the amount of extrusion, the time taken to achieve apical patency and duration for removing filling material during the retreatment of teeth filled with NeoMTA 2® (Avalon Biomed, Houston, TX, USA), a calcium silicate hydraulic cement and AHPlus™ (Denstsply, Konstanz, Germany), a resin-based cement, using continuous rotation and asymmetric reciprocating rotation instruments. Material and Methods: 60 monoradicular human teeth were selected and instrumented with Race #35.06 (FKG Dentaire, La Chaux-de-Fonds, Switzerland). The teeth were randomly assigned to two groups based on the cement used for filling (n = 30 each) AHPlus™ and NeoMTA 2®. Both groups were obturated with gutta-percha, using the lateral condensation technique. During non-surgical retreatments, each group was further divided into two subgroups: D-Race (FKG) and Reciproc (VDW, Munich, Germany) (n = 15 each). The total time to achieve apical patency and complete the retreatment were recorded. Extruded debris were collected and weighted. Student t-tests were employed for mean comparisons to assess significant differences between variables. Results: No statistically significant differences were found in terms of type of cement and apical extrusion. Regarding the rotation system, using the Reciproc system resulted in longer time to achieve patency and retreatment times compared to D-Race system, with statistically significant differences (P< 0.05). Conclusions: All systems used in retreatment led to apical extrusion. Apical patency was achieved in all cases. Key words:D-Race, Reciproc, calcium silicate-based cement, root canal retreatment.

Multiple Cervical Root Resorption in a Young Adult Female Previously Treated with Chemotherapy: A Case Report.

Multiple idiopathic cervical root resorption is an aggressive form of external root resorption that occurs at the cementoenamel junction and can affect multiple teeth (a minimum of 3) throughout the entire dentition. Most of the individuals affected are healthy with noncontributory medical histories. The resorption is usually detected as an incidental finding on radiographs or during dental examination. This case report describes an adult female with multiple cervical root resorptions who had been treated with chemotherapy for ovarian cancer at 16 years old. Nine years later, a total of 12 teeth were diagnosed with cervical root resorption. All of the known causative factors for external cervical resorption were discarded. To our knowledge, this is the first case reported of multiple cervical root resorption related to chemotherapy.

Porosity analysis of MTA and Biodentine cements for use in endodontics by using micro-computed tomography.

BACKGROUND: The purpose of this study is to compare the porosity of two repair cements, White ProRoot® MTA and Biodentine®. These samples were analyzed by using micro-computed microtomography. MATERIAL AND METHODS: Sixteen samples were used in the study that were divided according to the composition of the materials used. White ProRoot® MTA (n = 8) and Biodentine® (n = 8) were the samples prepared according to the manufacturer's instructions. They were placed in silicone molds of 5 ± 0.1mm in height and an internal diameter of 5 ± 0.1mm, 24 hours after its preparation, the samples were scanned through a micro-CT, the porosity results were analyzed statistically by independent "t" tests. RESULTS: It is evident that Biodentine® has better porosity properties than ProRoot® MTA. The results of the study quantify a smaller number of pores per surface, a smaller volume in each pore per mm3 and a lower total porosity present in samples of Biodentine® unlike ProRoot® MTA samples which is larger in both. CONCLUSIONS: The results obtained in computerized microtomography endodontic biomaterial samples concluded that Biodentine® has a lower porosity than ProRoot® MTA. Key words:Porosity, microleakage, micro-CT, endodontic cements.

Porosity analysis of mineral trioxide aggregate Fillapex and BioRoot cements for use in endodontics using microcomputed tomography.

AIM: The purpose of this study is to compare the porosity of two sealant cements, mineral trioxide aggregate (MTA) Fillapex® and BioRoot® root canal sealer (RCS). These samples were analyzed using microcomputed tomography. MATERIALS AND METHODS: Sixteen samples were used in the study that were divided according to the composition of the materials used. MTA Fillapex® (n = 8) and BioRoot® RCS (n = 8) were the samples prepared according to the manufacturer's instructions. They were placed in silicone molds of 5 ± 0.1 mm in height and an internal diameter of 5 ± 0.1 mm; 24 h after its preparation, the samples were scanned through a microcomputed tomography, and the porosity results were analyzed statistically by independent t-tests. RESULTS: It is evident that MTA Fillapex® has better porosity properties than BioRoot® RCS. The results of the study quantify a smaller number of pores per surface, a smaller volume in each pore per mm3, and a lower total porosity present in samples of MTA Fillapex® unlike BioRoot® RCS samples which is larger in both. CONCLUSIONS: The results obtained in computerized microtomography endodontic biomaterial samples concluded that MTA Fillapex® has a lower porosity than BioRoot® RCS.

Micro-computed tomography assessment of different obturation techniques for filling lateral canals.

BACKGROUND: The aim of this study was to evaluate obturation depth and volume by means of micro-CT when filling lateral canals. MATERIAL AND METHODS: Thirty single-rooted teeth were used. After instrumentation, three artificial lateral canals were created on each mesial and distal surface (one on each third). The samples were then separated randomly into three groups according to the obturation technique used (n=10): lateral condensation (Group 1), Tagger's hybrid technique (Group 2) and GuttaCore™ (Group 3). Samples were scanned and data was processed with Avizo software. Depth and volume of the infilling were measured in each lateral canal. Values were expressed as percentages and were analyzed using the Kruskal-Wallis test. RESULTS: Mean depth showed statistically significant differences between Group 3 and Groups 1 (p=0.001) and 2 (p=0.003), whereas no significant difference was found between Groups 1 and 2 (p≈1). As for mean volume, significant differences were found between Group 3 and Groups 1 (p=0.01) and 2 (p=0.003) but no differences were found between Groups 1 and 2 (p=1.00). CONCLUSIONS: GuttaCore provided the best lateral canal sealing among the three techniques compared. Key words:Lateral canals, Micro-CT, obturation.

Effect of abutment angulation in the retention and durability of three overdenture attachment systems: An in vitro study.

PURPOSE: This in vitro study investigated and compared the durability and retention of three types of attachments. MATERIALS AND METHODS: Three commercially available attachments were investigated: Clix®, Dalbo-Plus® and Locator®. In total, 72 samples of these attachments were placed in the acrylic resin forms and subjected to mechanical testing (5400 cycles of insertion and removal) over the respective ball or Locator abutments immersed in artificial saliva at pH 7 and 37℃. The abutments were placed at angulations of 0°, 10° and 20°. The retention force was recorded at the beginning and after 540, 1080, 2160, 3240, 4320 and 5400 insertion-removal cycles. RESULTS: The results revealed that there were significant differences in the average values of the insertion/removal force due to angulation (F (2.48) = 343619, P<.05) and the type of attachment (F (7.48) = 23.220, P<.05). CONCLUSION: Greater angulation of the abutments was found to influence the retention capacity of the attachments, and the fatigue test simulating 5 years of denture insertion and removal did not produce wear in the metal abutments.