Influence of heat treatment on torsional resistance and surface roughness of nickel-titanium instruments.

AIM: To evaluate the influence of controlled memory (CM) thermal treatment on the torsional resistance and surface roughness of nickel-titanium instruments with identical geometric and dimensional characteristics. The influence of environmental temperature on torsional resistance was also evaluated. METHODOLOGY: A sample of 25 conventional NiTi alloy and 25 CM thermal-treated NiTi instruments, with an identical geometric design and a nominal size of 0.25 mm at D0 and a nominal taper of .06 mm mm-1 were selected. The torsional strength and the angle of rotation of the instruments were tested following ISO 3630-1 at two temperatures: 21 and 35 °C. The fracture surfaces of all tested instruments were verified with a scanning electron microscope. The surface roughness of the blades of conventional NiTi alloy and CM wire files was evaluated by using a New View 7100 Profilometer. Statistical analysis was performed using Student's t-test and paired t-test to analyse the torsional resistance and surface roughness at a significance level of P < 0.05. RESULTS: The torsional strength of thermally-treated instruments was significantly lower than nontreated instruments (P < 0.05). However, thermally-treated instruments had significantly greater angular rotation to fracture than nontreated instruments (P < 0.05). Temperature did not influence the torsional strength (P > 0.05) and the angular rotation (P > 0.05) of the instruments. Regarding the roughness measurements, groove depth was lower at the surface of thermally-treated instruments when compared to nontreated instruments (P < 0.05). CONCLUSION: Thermal treatment influenced the torsional resistance and surface roughness of NiTi instruments with identical geometric and dimensional characteristics. Temperature did not affect torsional behaviour.

Mechanical characteristics of counterfeit Reciproc instruments: a call for attention.

AIM: To report the main differences seen by direct visual inspection between original and counterfeit Reciproc instruments, together with an evaluation of instrument bending resistance, cyclic fatigue, surface finish, Vickers microhardness and chemical composition. METHODOLOGY: The visual aspects of original Reciproc R25 (VDW, Munich, Germany) and counterfeit Reciproc R25 instruments (claimed to be original, supposedly with dimensions similar to those of Reciproc R25 files, bought at www.mercadolivre.com.br) were evaluated under direct observation, stereomicroscopy and scanning electron microscope. The flexibility of original and counterfeit Reciproc R25 was determined via 45° bending tests according to the ISO 3630-1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and 5-mm radius of curvature. The fracture surfaces of all fragments were examined under a scanning electron microscope. Roughness of the instruments was quantified using a profilometer, and the microhardness test was carried out using a Vickers hardness tester. Energy-dispersive X-ray microanalysis (EDX) was also carried out. Results were analysed statistically using the Student's t-test at a significance level of P < 0.05. RESULTS: Although the packaging of the original and counterfeit instruments was similar, a number of differences were observed such as ISO colour coding, measurement marks, stopper and morphologic characteristics. Original Reciproc instruments had significantly longer cyclic fatigue life and significantly lower bending resistance than counterfeit Reciproc instruments (P < 0.05), as well as significantly lower microhardness and roughness (P < 0.05). EDX results revealed differences in the chemical composition of the instruments (P < 0.05), indicating that the instruments were manufactured with different raw material. CONCLUSION: Original Reciproc files outperformed counterfeit instruments in all tests. It is thus important that identification strategies for these counterfeit instruments be developed, thereby preventing their inadvertent use.

Extended cyclic fatigue life of F2 ProTaper instruments used in reciprocating movement.

AIM: To evaluate the cyclic fatigue fracture resistance of engine-driven F2 ProTaper instruments under reciprocating movement. METHODOLOGY: A sample of 30 NiTi ProTaper F2 instruments was used. An artificial canal was made from a stainless steel tube, allowing the instruments to rotate freely. During mechanical testing, different movement kinematics and speeds were used, which resulted in three experimental groups (n = 10). The instruments from the first group (G1) were rotated at a nominal speed of 250 rpm until fracture, whilst the instruments from the second group (G2) were rotated at 400 rpm. In the third instrument group (G3), the files were driven under reciprocating movement. The time of fracture for each instrument was measured, and statistical analysis was performed using parametric methods. RESULTS: Reciprocating movement resulted in a significantly longer cyclic fatigue life (P < 0.05). Moreover, operating rpm was a significant factor affecting cyclic fatigue life (P < 0.05); instruments used at a rotational speed of 400 rpm (approximately 95 s) failed more rapidly than those used at 250 rpm (approximately 25 s). CONCLUSIONS: Movement kinematics is amongst the factors determining the resistance of rotary NiTi instruments to cyclic fracture. Moreover, the reciprocating movement promoted an extended cyclic fatigue life of the F2 ProTaper instrument in comparison with conventional rotation.

In vitro degradation of poly-L-D-lactic acid (PLDLA) pellets and powder used as synthetic alloplasts for bone grafting.

UNLABELLED: The objective of this study was to evaluate the in vitro degradation of pellet and powder forms of a poly-L-D-lactic acid material used to produce plates and screws for orthopedic, oral, and maxillofacial applications. MATERIALS AND METHODS: In order to produce the powder form the as-received pellets were milled in a cryogenic chamber. Particles size distribution (PSD) histograms were developed for both forms. The materials were then characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA) before and after immersion in simulated body fluid for 30, 60, and 90 days. RESULTS: SEM showed that for both forms material degradation started after 30 days of immersion in SBF and evolved until 90 days. Degradation started at the amorphous zones of the polymer and exposed of deeper crystalline layers. The pellet and powder samples PSD showed polydispersed patterns with mean diameters of 673.98 microm and 259.55 microm. Thermal onset degradation temperatures were 365.64 degrees C and 360.30 degrees C, and of 363.49 degrees C and 359.83 degrees C before immersion and after 90 days in SBF for the pellet and powder forms, respectively. The Tg's of the pellets and the powder were approximately 61.5 degrees C and 66 degrees C, and their respective endothermic peaks were observed at approximately 125 degrees C and 120 degrees C. The specific heat (c) was approximately 8.5 J/g and 6.2 J/g for the pellet and powder material, respectively. CONCLUSION: According to the results obtained, cryogenic milling resulted in particle plastic deformation, and alterations in glass transition temperature, melting temperature, and specific heat of the material.

Caracterização do óxido de titânio formado nas superfícies Vulcano Actives e TiUnite / Characterization of titanium oxide on dental implants Vulcano Actives and TiUnite surfaces

A osseointegração dos implantes de titânio sem tratamento de superfície está associada à presença de uma fina camada de óxido de titânio do tipo rutilo presente em sua superfície. Para acelerar os mecanismos envolvidos na osseointegração e permitir a colocação da prótese em menor tempo que o inicialmente recomendado pelo Prof. Branemark, foram desenvolvidos os tratamentos das superfícies dos implantes por jateamento, ataque com ácido, deposição de nanopartículas de hidroxiapatita, flúor, magnésio e anodização em soluções eletroquímicas contendo fósforo e cálcio. Após os tratamentos da superfície dos implantes há formação de uma camada mista de óxidos de titânio composta de rutilo e anatase. O índice de êxito destes implantes mostra que a presença dos dois tipos de óxido de titânio não compromete a osseointegração. O presente trabalho tem o objetivo de caracterizar a camada de óxido de titânio existente em implantes anodizados com designações comerciais Vulcano Actives® e TiUnite® produzidos pelas empresas Conexão Sistemas de Prótese e Nobel Biocare, respectivamente. Os resultados das análises com XPS, difração de raios-X e Raman mostraram que nas superfícies dos implantes tratados por anodização há predomínio do óxido de titânio do tipo anatase. Considerando que os implantes sem tratamento de superfície possuem óxido de titânio na superfície diferente dos implantes com tratamento de superfície e todos apresentam osseointegração, conclui-se que existem os modos de interação entre a superfície do implante e as células são diferentes

The osseointegration of machined titanium dental implants is associated to the presence of a thin layer of rutile titanium oxide present on its surface. To accelerate the mechanisms involved in the osseointegration and to allow the placement of the prosthesis in less time as originally recommended by Professor Branemark, implants surface treatments were developed. Nowadays the implant surface is sandblasted, acid etched, receive a deposition of hydroxiapatite nanoparticles, fluorine, magnesium and anodized in solutions containing phosphorus and calcium. After the surface treatment was formed a layer of mixed oxides of titanium composed of rutile and anatase. The rate of success of anodized implants shows that the presence of two types of titanium oxide does not compromise the implant osseointegration. The aim of this work is to characterize the oxide layer of commercially titanium implants anodized branded as Vulcano Actives® and TiUnite® manufactured by Conexão Sistemas e Prótese (Brazil) and Nobel Biocare (Swede), respectively. The results of analyses with XPS, X-ray diffraction and Raman showed that the anodized dental implants surface has anatase titanium oxide. The machined dental implants without surface treatment and implant treated surface have different surface titanium oxide. As these implants show osseointegration it is suggested that they may be found to interact differently with cells

Scanning electron microscopic investigation of the surface of gutta-percha cones after cutting.

The surface of auxiliary gutta-percha cones after cutting with different methods was evaluated. The tips of gutta-percha cones size fine were cut off using scissors, a razor blade against a glass slab, a razor blade combined with a calibrator, or a razor blade/calibrator followed by a further cutting with a razor blade against a glass slab. Samples were examined under scanning electron microscopy. Cutting with scissors and razor blade/calibrator produced significant irregularities in the cone surface. Cutting with razor blades against a glass slab, with or without previous use of a calibrator, allowed the development of a smooth gutta-percha cone surface.

Assessment of the apical transportation of root canals using the method of the curvature radius.

The purpose of this investigation was to evaluate the occurrence of apical transportation after root canal instrumentation using only K-Flexofiles or K-Flexofiles intercalated with K-Flexofile Golden Mediums. For this purpose, the degree (Schneider's method) and the radius of the curvature was recorded before and after instrumentation. The results showed that there was no statistically significant difference between the techniques. The correlation between the degree and the radius of curvature of the root canal was not consistent, nor was there a relationship between the original radius of curvature and the apical transportation. However, determination of curvature by use of its radius has proved to be an effective method.

Influence of diameter variation of Gates-Glidden drills on torsion resistance.

The aim of this study was to determine the variation of the shaft diameter close to the active cutting region and close to the radius of concordance of 28- and 32-mm Gates-Glidden drills and to analyze the diameter influence on the torsion fracture resistance. Seventy-two stainless steel Maillefer drills were studied. The drill diameter varied along the shaft, the smallest diameter occurring close to the radius of concordance. This variation causes stress concentration which leads to complete fracture of the instrument.