Potential of Operative Torque in Evaluating NiTi Instruments.

The role of nickel-titanium (NiTi) in the production of endodontic instruments increased in the last few decades; therefore, the way of evaluation of its performance increased as well. Nowadays, there are several ways to evaluate NiTi instruments, divided into static and dynamic tests. The static ones are cyclic fatigue tests, torsional resistance tests, flexibility, and cutting efficiency tests. These methodologies have been deeply used to evaluate some of the metallurgical properties of the instruments on the market. Up-to-date, we know very well the behavior of NiTi under static conditions, but these knowledges are too fragmented to be relevant for understanding and evaluating the complexities of intracanal instrumentation. Starting from the purpose to introduce the variable of movement in the testing procedure, some dynamic tests have been proposed, such as dynamic cyclic fatigue test.1,2 Although these kinds of studies were capable of evaluating more precisely the behavior of rotary instruments inside the root canal, they could not take into account, at this moment, the complexities of stresses that instruments undergo during the shaping procedure.3-5 Therefore, some of these tests are not accepted anymore by the scientific community and on the contrary they do not help the general practitioner to orientate in the large amount of rotary instruments present on the market.6 This tends to withdraw the general dentistry from the scientific literature, wearing a groove between the practice and the science.7 Starting from these ideas, in the last couple of years some authors started to think the proper way to real-time evaluation of the performance of NiTi rotary instruments inside the root canal. To do so, a countable and repeatable measurement of instrument's developed stresses was needed. Setzer and Böhme8 first used the torque generated by Revo-S, Vortex, and ProFile to evaluate their performance during instrumentation. The so-called "operative torque" is the summation of torque generated in each point of the instrument during its simultaneous movement around its own axis and up and down inside the canal. The recorded values are influenced by both torsional and flexural stresses, becoming this way a reliable method to analyze, evaluate, and compare the performance of NiTi instruments inside the root canal.9 This methodology is applicable for not only in vitro but also in vivo measurement, as demonstrated by Gambarini et al.10 The main drawback of this kind of evaluation is the not well-determined correlation between the torsional and the flexural stresses; therefore, it is still unpredictable how each influence the other. In conclusion, the potential of real-time torque measurement is wide and still unexplored, but further studies are needed to better understand how torque is developed inside the root canal.

Precision of Dynamic Navigation to Perform Endodontic Ultraconservative Access Cavities: A Preliminary In Vitro Analysis.

INTRODUCTION: Ultraconservative access cavities (UCACs) have been proposed to reduce crown weakening, but there is no consensus about their design and size and about their advantages and disadvantages, which are also related to how differently they are performed. The purpose of the present study was to evaluate the possible use of a novel Dynamic Navigation System (DNS) in planning and executing UCACs and its precision in vitro, compared with a manual approach (MA) without any guide. METHODS: Twenty radiopaque, artificial teeth replicas were randomly divided into 2 identical groups and scanned using cone-beam computed tomography. In the first group (MA) MB1 canal orifice was reached, starting from the central part of the molar occlusal surface, using a micro endodontic bur. In the second group, DNS allowed to plan and execute a more direct, straight-line truss access. After cavity preparation, teeth were scanned again, and cone-beam computed tomography images were compared. Data were statistically analyzed with analysis of variance test. RESULTS: Significant differences (P < .05) were found in the tested parameters between the 2 groups. The DNS group was significantly more precise, showing smaller mean values in the angulation (4.8°) and in the maximum distance from the ideal position (0.34 mm), when compared with MA group (mean values, 21.2° and 0.88 mm, respectively). CONCLUSIONS: Hence, we may conclude that the use of DNS increased the benefits of UCACs by minimizing the potential risk of iatrogenic weakening of critical portions of the crown and reducing negative influences to shaping procedures.

Surgical and orthodontic rapid palatal expansion in adults using a modified palatal partial osteotomy technique (ppot): Technique description and clinical experience.

Transversal hypoplasia of the upper maxilla is a frequent condition between malocclusions. The rapid maxillary expansion (RME) is an already consolidated technique for these types of defects. This case report analyzes the outcome of a novel surgical technique that we named TOPP (Partial Palatal osteotomy technique) aiming to provide scientifically proven data over the percentage of relapse and the long-term stability of this type of surgical assisted palatal expansion. A 24 year old male patient with a hyperdivergent class III, presenting the absence of 1.1 due to a teenage trauma and a transversal contraction of the upper arch was selected for the surgery. The mucoperiosteal flap was performed at a palatal level with a paramarginal arch shape (from region 1.4 to 2.4) due to preserve the nasal-incisal vascular bundle and the mucoperiosteum was detached from the floor of the nose. A horizontal osteotomy was performed at 4-5 mm above the roots apexes; a sagittal osteotomy in a posterior direction was done at the level of the midline to divide the mesiopalatine suture and separate the maxilla in two halves. The only bony attachment that remained was represented by the perpendicular lamina of the palatal bone. The TOPP technique showed that it is possible to have a better control of both the intercanine and intermolar expansion, that is more difficult in the case of a conventional SARME. Other goals were a greater view and access to the site and the reduction of the risk of damaging the palatine fibromucosa. The incision of the archform paramarginal flap improves certainly the conditions of the palatal fibromucosa in the post operative and allows the reduction of the soft tissues' elastic return. Key words:Rapid maxillary expansion, orthognatic surgery, maxillary osteotomy.

A comparative study of mechanical resistance of two reciprocating files.

BACKGROUND: To evaluate the cyclic fatigue resistance of two different Nickel-Titanium instruments, Reziflow (Komet, Brasseler GmbH & Co., Lemgo, Germany) and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland). MATERIAL AND METHODS: Two groups of 20 different NiTi endodontic instruments of identical tip size of 0.25 mm were tested; Reziflow and Wave-One Gold primary. Cyclic fatigue testing was performed in a stainless steel simulated root canal manufactured by reproducing the instrument's size and taper. A simulated root canal with a 90 degrees angle of curvature and 5 mm radius of curvature was constructed for the instruments tested. The centre of the curvature was 5 mm from the tip of the instrument and the curved segment of the canal was approximately 5 mm in length. Both the instruments were used in the same preset program specific for the WaveOne instruments. Each instrument was rotated until fracture occurred and the time to fracture (TtF) and the length of the fractured fragment were recorded. Means and standard deviations of TtF and fragment length were calculated and data were subjected to statical analysis (P<0.05). RESULTS: Statistically significant differences (P<0.05) were noted between Reziflow and WaveOne Gold instruments. There were no significant differences (P>0.05) in the mean length of the fractured fragments between the instruments. CONCLUSIONS: Rezifllow instruments were associated with a significantly higher cyclic fatigue resistance than WaveOne Gold instruments. Key words:Endodontic instruments, NiTi alloy, Reciprocating motion, Cyclic Fatigue, Heat treatment.

Endodontic Microsurgery Using Dynamic Navigation System: A Case Report.

Dynamic navigation systems were introduced to facilitate dental implantology by improving the accuracy of dental implant positioning. Dynamic navigation integrates surgical instrumentation and radiologic images by using an optical positioning device controlled by a dedicated computerized interface. These features could help in reducing the risk of unintentional iatrogenic damage to nearby anatomic structures and perform minimally invasive or flapless surgery, leading to reduced patient postoperative discomfort and improved healing. The present case report showed the use of the Navident dynamic navigation system (ClaroNav, Toronto, Ontario, Canada) by an undergraduate student for bone cavity preparation and root-end resection in the surgical endodontic treatment of a lesion in an upper lateral incisor. The system allowed precise localization of the root and precise apicoectomy with a minimal invasive cavity. The dynamic navigation system allowed the student to precisely direct the bur in 3 dimensions. The osteotomy and root-end resection were easily and quickly performed by the undergraduate student with a minimally invasive approach without iatrogenic errors. The navigation system allowed the operator to precisely perform a minimally invasive osteoctomy and root-end resection during endodontic surgery. The development of dedicated surgical navigation systems for endodontic surgery could facilitate the operator's maneuvers and reduce the risk of iatrogenic errors.

In vitro resistance to fracture of two nickel-titanium rotary instruments made with different thermal treatments.

AIM: Aim of the study was to evaluate effectiveness of different heat treatments in improving Ni-Ti endodontic rotary instruments' resistance to fracture. METHODS: 24 new NiTi instruments similar in length and shape: 12 M3 instruments, tip size 25 and .06 taper (United Dental, Shanghai, China), and 12 M3 Pro Gold instruments tip size 25 and .06 taper (United Dental, Shanghai, China), were tested in a 60° curved artificial root canal. Each group received a different heat treatment. Cycles to fracture were calculated for each instrument. Differences among groups were evaluated with an analysis of variance test (significance level was set at P<0.05.). RESULTS: Statistical analysis found significant differences (p<0.0213) between groups. The M3 Pro Gold instruments were significantly more resistant to fatigue (mean values = 1012, SD +/- 77) than M3 instruments (mean values = 748, SD +/- 62). No statistically significant differences were found between fragments' lengths (p>0,05). CONCLUSIONS: An increased flexibility and the reduction of internal defects produced by heat treatments during or after manufacturing processes, may be responsible for improving resistance to cyclic fatigue and flexural stresses.