Three-Dimensional Finite Element Analysis of Stress Distribution on Different Bony Ridges With Different Lengths of Morse Taper Implants and Prosthesis Dimensions

This finite element analysis (FEA) compared stress distribution on different bony ridges rehabilitated with different lengths of morse taper implants, varying dimensions of metal-ceramic crowns to maintain the occlusal alignment. Three-dimensional FE models were designed representing a posterior left side segment of the mandible: group control, 3 implants of 11 mm length; group 1, implants of 13 mm, 11 mm and 5 mm length; group 2, 1 implant of 11 mm and 2 implants of 5 mm length; and group 3, 3 implants of 5 mm length. The abutments heights were 3.5 mm for 13- and 11-mm implants (regular), and 0.8 mm for 5-mm implants (short). Evaluation was performed on Ansys software, oblique loads of 365N for molars and 200N for premolars. There was 50% higher stress on cortical bone for the short implants than regular implants. There was 80% higher stress on trabecular bone for the short implants than regular implants. There was higher stress concentration on the bone region of the short implants neck. However, these implants were capable of dissipating the stress to the bones, given the applied loads, but achieving near the threshold between elastic and plastic deformation to the trabecular bone. Distal implants and/or with biggest occlusal table generated greatest stress regions on the surrounding bone. It was concluded that patients requiring short implants associated with increased proportions implant prostheses need careful evaluation and occlusal adjustment, as a possible overload in these short implants, and even in regular ones, can generate stress beyond the physiological threshold of the surrounding bone, compromising the whole system.

Morse taper implants at different bone levels: a finite element analysis of stress distribution

AIM: To explore the biomechanical effects of the different implantation bone levels of Morse taper implants, employing a finite element analysis (FEA). METHODS: Dental implants (TitamaxCM) with 4x13 mm and 4x11 mm, and their respective abutments with 3.5 mm height, simulating a screwed premolar metal-ceramic crown, had their design performed using the software AnsysWorkbench 10.0. They were positioned in bone blocks, covered by 2.5 mm thickness of mucosa. The cortical bone was designed with 1.5 mm thickness and the trabecular bone completed the bone block. Four groups were formed: group 11CBL (11 mm implant length on cortical bone level), group 11TBL (11 mm implant length on trabecular bone level), group 13CBL (13mm implant length on cortical bone level) and group 13TBL (13 mm implant length on trabecular bone level). Oblique 200 N loads were applied. Von Mises equivalent stresses in cortical and trabecular bones were evaluated with the same design program. RESULTS: The results were shown qualitatively and quantitatively by standard scales for each type of bone. By the results obtained, it can be suggested that positioning the implant completely in trabecular bone brings harm with respect to the generated stresses. Its implantation in the cortical bone has advantages with respect to better anchoring and locking, reflecting a better dissipation of the stresses along the implant/bone interfaces. In addition, the search for anchoring the implant in its apical region in cortical bone is of great value to improve stabilization and consequently better stress distribution. CONCLUSIONS: The implant position slightly below the bone in relation to the bone crest brings advantages as the best long-term predictability with respect to the expected neck bone loss.

Effect of pre-flaring and file size on the accuracy of two electronic apex locators

Objective: This ex vivo study evaluated the effect of pre-flaring and file size on the accuracy of the Root ZX and Novapex electronic apex locators (EALs). Material and methods: The actual working length (WL) was set 1 mm short of the apical foramen in the palatal root canals of 24 extracted maxillary molars. The teeth were embedded in an alginate mold, and two examiners performed the electronic measurements using #10, #15, and #20 K-files. The files were inserted into the root canals until the "0.0" or "APEX" signals were observed on the LED or display screens for the Novapex and Root ZX, respectively, retracting to the 1.0 mark. The measurements were repeated after the pre-flaring using the S1 and SX Pro-Taper instruments. Two measurements were performed for each condition and the means were used. Intra-class correlation coefficients (ICCs) were calculated to verify the intra-and inter-examiner agreement. The mean differences between the WL and electronic length values were analyzed by the three-way ANOVA test (p<0.05). Results: ICCs were high (>0.8) and the results demonstrated a similar accuracy for both EALs (p>0.05). Statistically significant accurate measurements were verified in the pre-flared canals, except for the Novapex using a #20 K-file. Conclusions: The tested EALs showed acceptable accuracy, whereas the pre-flaring procedure revealed a more significant effect than the used file size.

Mechanical analysis of conventional and small diameter conical implant abutments

PURPOSE. The aim of the present study was to evaluate if a smaller morse taper abutment has a negative effect on the fracture resistance of implant-abutment connections under oblique compressive loads compared to a conventional abutment MATERIALS AND METHODS. Twenty morse taper conventional abutments (4.8 mm diameter) and smaller abutments (3.8 mm diameter) were tightened (20 Ncm) to their respective implants (3.5 x 11 mm) and after a 10 minute interval, implant/abutment assemblies were subjected to static compressive test, performed in a universal test machine with 1 mm/min displacement, at 45 degrees inclination. The maximum deformation force was determined. Data were statistically analyzed by student t test. RESULTS. Maximum deformation force of 4.8 mm and 3.8 mm abutments was approximately 95.33 kgf and 95.25 kgf, respectively, but no fractures were noted after mechanical test. Statistical analysis demonstrated that the evaluated abutments were statistically similar (P=.230). CONCLUSION. Abutment measuring 3.8 mm in diameter (reduced) presented mechanical properties similar to 4.8 mm (conventional) abutments, enabling its clinical use as indicated. [J Adv Prosthodont 2012;4:158-61]

Efficacy of NiTi rotary instruments in removing calcium hydroxide dressing residues from root canal walls

The aim of this study was to evaluate the efficacy of three rotary instrument systems (K3, Pro Taper and Twisted File) in removing calcium hydroxide residues from root canal walls. Thirty-four human mandibular incisors were instrumented with the Pro Taper System up to the F2 instrument, irrigated with 2.5% NaOCl followed by 17% EDTA, and filled with a calcium hydroxide intracanal dressing. After 7 days, the calcium hydroxide dressing was removed using the following rotary instruments: G1. - NiTi size 25, 0.06 taper, of the K3 System; G2 - NiTi F2, of the Pro Taper System; or G3 - NiTi size 25, 0.06 taper, of the Twisted File System. The teeth were longitudinally grooved on the buccal and lingual root surfaces, split along their long axis, and their apical and cervical canal thirds were evaluated by SEM (x1000). The images were scored and the data were statistically analyzed using the Kruskall Wallis test. None of the instruments removed the calcium hydroxide dressing completely, either in the apical or cervical thirds, and no significant differences were observed among the rotary instruments tested (p > 0.05).

Fracture susceptibility of endodontically treated teeth

Aim: To assess the influence of cervical preparation on fracture susceptibility of roots. Material and methods: During root canal instrumentation, the cervical portions were prepared with different taper instruments: I: no cervical preparation; II: #30/.08; III: #30/.10; IV: #70/.12. The specimens were sealed with the following filling materials (n = 8), A: unfilled; B: Endofill/gutta-percha; C: AH Plus/gutta-percha; D: Epiphany SE/Resilon. For the fracture resistance test, a universal testing machine was used at 1 mm per minute. Results: anova demonstrated difference (P < 0.05) between taper instruments with a higher value for group I (205.3 +/- 77.5 N) followed by II (185.2 +/- 70.8 N), III (164.8 +/- 48.9 N), and IV (156.7 +/- 41.4 N). There was no difference (P > 0.05) between filling materials A (189.1 +/- 66.3 N), B (186.3 +/- 61.0 N), C (159.7 +/- 69.9 N), and D (176.9 +/- 55.2 N). Conclusions: Greater cervical wear using a #70/.12 file increased the root fracture susceptibility, and the tested filling materials were not able to restore resistance.

Effect of Nitrogen Ion Implantation on the Flexibility of Rotary Nickel-Titanium Instruments

Introduction: The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30 degrees angle. Methods: Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), voltage 200 KeV, current density 1 mu A/cm(2), temperature 130 degrees C, and vacuum conditions of 10 x 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30 degrees. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. Results: The mean load required to bend instruments at a 30 degrees angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. Conclusions: Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments. (J Endod 2012;38:673-675)

Alternativa protética para correção da angulação com componentes não indexados sobre implantes Cone Morse indexados: sistema tubo parafuso

From a recent perspective the morse-taper dental implants connections are increasingly being used as an alternative for replacement of a missing teeth. Nevertheless, there are a large variety of prosthetic components available on the market with some limitations regarding the final prothesis. This article demonstrated the difficulties and limitations of prosthesis implant-retained connections when using morse-taper implants (with a prosthetic index) case in which the surgical placement of the implant wasn’t successfully performed. The alternative to overcome this scenario was the technique using the tube screw over the top of a mini abutment component. It was possible to manufacture and to have satisfactory adaptation, achieving the satisfaction of the patient, restoring function and esthetics.