The potential effect of instrumentation with different nickel titanium rotary systems on dentinal crack formation-An in vitro study

The potential mechanical impact of different rotary systems used for root canal preparation has been a matter of debate for long. The aim of this study was to explore the incidence of dentinal cracks after root canal instrumentation with various rotary systems, in vitro. One hundred and eighty intact lower central incisors were selected and randomly divided into fourteen treatment groups (n = 12/group) and a control group (n = 12). After decoronation, the root canals were instrumented with fourteen different rotary systems (E3, E3 azure, NT2, Hyflex CM, Hyflex EDM, 2Shape, OneCurve, ProTaper Next, ProTaper Gold, WaveOne Gold, Mtwo, Reciproc Blue, TF adaptive, K3XF). All roots were horizontally sectioned at 3, 6, and 9 mm from the apex with a low-speed saw under water-cooling. The slices were then examined under stereomicroscope for dentinal cracks. No cracks were found in the control group. Cracks were found in all treatment groups, predominantly in the 3 mm slices. There was no statistically significant difference in the number of cracks when comparing the different systems to each other at any section level. At 3 mm, however, five of the studied systems, namely K3XF (p = 0.004), Protaper Next (p = 0.001), Reciproc Blue (p<0.001), TF adaptive (p = 0.050), and 2Shape (p = 0.009) presented a significantly higher number of cracks than the control group. Within the limitations of this study, instrumented canals presented dentinal cracks, while uninstrumented ones presented no cracks after sectioning. There seems to be no significant difference among the tested systems regarding crack formation in the instrumented root canal wall. Crack formation occurred irrespective of the motion of the rotary system (rotational or reciprocation). Further studies are needed to clarify the factors that contribute to crack formation in the case of each individual rotary system

Comparison of the Three-Dimensional Accuracy of Guided Apicoectomy Performed with a Drill or a Trephine: An In Vitro Study

Guided apicoectomy performed with 3D-printed polymer-based static surgical guides is an emerging trend in endodontic surgery. Static-guided apicoectomy is carried out with either a drill or a trephine. The aim of this in vitro study was to assess the accuracy of osteotomy and apicoectomy performed through a polymer guide, with both drill and trephine, and to compare the accuracy achievable with the two instruments. Six plaster models of a maxilla master model with extracted human maxillary teeth in polymethyl-methacrylate resin were used. The modeled osteotomies were performed in these. The master model was CBCT-scanned, and digital surgical plans were prepared, based on which the surgical guides were printed. The plans contained both drill and trephine apicoectomies. Digital three-dimensional position analysis was performed with dedicated algorithms. A total of 39 drill and 47 trephine osteotomies were analyzed. A statistically significant difference between the two instruments was found only in the global deviation of the distal endpoint, indicating lower deviation for the trephine procedure (1.53 mm vs. 1.31 mm, p = 0.038). Nevertheless, from a clinical perspective, this distinction is inconsequential. The results suggest that, for all practical purposes, the two approaches to apicoectomy allow the same level of accuracy

Flexibilis és merev üvegszál megerősítésű intraradikuláris csapok törési ellenállásának in vitro összehasonlító vizsgálata - pilot study = Fracture strength of elastic and conventional fibre-reinforced composite intraradicular posts - an in vitro pilot study

Jelen vizsgálat célja a gyökérkezelt üvegszál megerősítésű kompozit csapokkal, különféle technikákkal és anyagokkal helyreállított kisörlő fogak töréssel szembeni ellenállásának és megerősítő hatásának összehasonlítása. Anyag és módszer: 32 darab kihúzott és gyökérkezelt kisörlő fogat 4 csoportba osztottunk (n = 8) a használt csap(ok) száma és anyaga alapján (1–4. csoport). 1: egyetlen hagyományos merev üvegszálas csap, 2: egy merev fő és egy járulékos üvegszálas csap, 3: egyetlen elasztikus csap, 4: egy elasztikus fő és egy járulékos csap. A csapok beragasztását és a csonkfelépítést követően a fogakat statikus terhelési tesztnek tettük ki törésig. A töréssel szembeni ellenállás mellett a törés mintázatát is vizsgáltuk. Eredmények: a 4. csoport nyújtotta a töréssel szembeni legjobb ellenállási eredményeket a tesztelt csoportok között. A több csapot használó restaurátumok (2. és 4. csoport) szignifikánsan jobban teljesítettek, mint az 1. csoport (p = 0,041; p = 0,032). A törési mintázat tekintetében a csoportok többnyire homogének voltak. Megbeszélés: jelen vizsgálat alapján több üvegszálas csap alkalmazása egyazon gyökércsatornában mindig előnyös a végleges restaurátum szempontjából, függetlenül a csap rugalmasságától. A csapok elaszticitása nem befolyásolta a létrejött törés mintázatát