Fracture resistance and failure pattern of endodontically treated teeth restored with computer-aided design/ computer-aided manufacturing post and cores: A pilot study

Aim: To evaluate the fracture resistance and failure pattern of custom made computer-aided design & computer-aided manufacturing (CAD/CAM) post and cores using a fiber reinforced composite material (FRC) and a high-density-polymer. Materials and methods: Thirty extracted mandibular second premolars were selected, endodontically treated and prepared to receive the posts. The specimens were randomly divided into three groups (n = 10) according to each material: group 1 (RXP): fiber posts (Rely X, 3M-ESPE) with composite core build-up (Filtek Bulk Fill Posterior, 3M-ESPE) as a control group; group 2 (BLC): one-piece milled post and core from fiber reinforced composite blocks (Trilor, Bioloren); and group 3 (AMC): one-piece milled post and core from hybrid ceramic disks (Ambarino, Creamed). All the posts were cemented using a self-adhesive resin cement (Rely X U200, 3M ESPE). Fracture resistance was tested using a universal testing machine, failure patterns were then observed visually and radiographically then evaluated under SEM. Data was analyzed using One-way analysis of variance (ANOVA) followed by Tamhane post-hoc test in order to determine significant differences among groups (α = 0.05). Results: The mean fracture resistance values were: 426.08 ± 128.26 N for group 1 (R X P), 367.06 ± 72.34N for group 2 (BLC), and 620.02 ± 5 4.29N f or g roup 3 ( AMC). S tatistical analysis revealed that group 3 (AMC) had the highest mean load to fracture in comparison to the other groups (p = 0.000). failures were cohesive in group 2 and 3 and mixed in group 1 with no catastrophic failures reported in all groups. Conclusion: All systems evaluated presented sufficient mean load-to-failure values for endodontically treated teeth restorations. CAD/CAM post and cores made from high-densitypolymer showed a better performance than prefabricated fiber posts

Comparison between two methods of working length determination and its effect on radiographic extent of root canal filling: a clinical study [ISRCTN71486641]

BACKGROUND: Obtaining a correct working length is critical to the success of endodontic therapy. Different methods have been used to identify this crucial measurement. The Aim of this clinical study was to compare the effect of working length determination using apex locator alone or in combination with working length radiograph on the apical extent of root canal filling. METHODS: A total number of 66 patients, 151 canals were randomized into two groups, In group (I) working length was determined by apex locator alone, while in group (II) working length was determined by apex locator confirmed by working length radiograph, length of obturation was assessed, and the total number of radiographs was recorded. The data were analyzed using SAS system and T. tests were carried out. Statistical significance was considered to be P ≤ 0.05. RESULTS: Sixty seven canals in group I were treated with a mean distance from the tip of root canal filling to radiographic apex -0.5 mm ± 0.5 and a mean of a total number of radiographs of 2.0, while in group II eighty four canals were treated with a mean distance from the tip of root canal filling to radiographic apex -0.4 mm ± 0.5 and a mean of a total number of radiographs of 3.2. There was no statistically significant difference in the mean distance from the tip of root filling to radiographic apex between group I and group II (P > 0.05). CONCLUSION: The practice of using electronic apex locator in the determination of working length is useful and reliable with no statistical difference of the radiographic extent of root canal filling when using apex locator alone or in combination with working length radiograph. Under the clinical conditions of this study, it is suggested that the correct use of an apex locator alone could prevent the need for further diagnostic radiographs for determination of working length. This method can be useful in patients who need not to be exposed to repeated radiation because of mental, medical or oral conditions

Comparison of two techniques for assessing the shaping efficacy of repeatedly-used NiTi rotary

Aim. The shaping capacity of NiTi rotary instruments is often assessed by photographic or micro-CT measurements, and these instruments are often used more than once clinically. This study was conducted to compare photographic and micro-computed tomography (micro-CT) measurements and to assess if repeated use of NiTi instruments affected the shape of canal preparation. Methods.Ten new sets of ProTaper Universal instruments were used in 60 resin blocks simulating curved root canals. Groups 1 to 6 (n=10) represented 1st to 6th use of the instrument, respectively. Digitized images of the prepared blocks were taken in both mesiodistal (MD) and buccolingual (BL) directions and area measurements (mm2) were calculated using AutoCAD. The volumes of the same prepared canals were measured using micro-CT (mm3). Statistical analysis was performed to detect differences between photographic and volumetric measurements, and differences between uses. Results. Two-way repeated measures ANOVA revealed significant differences between groups (p<0.001). Regarding measurement type, there were no significant differences between BL and MD measurements, but there were significant differences between micro-CT and BL (p<0.001) and micro-CT and MD (p=0.001). Significant differences were also noted between uses. Conclusions. Within the limitations of the present study, micro-CT is more discriminative of the changes in canal space associated with repeated instrument use than photographic measurements. Canal preparations are significantly smaller after the third use of the same instrument

Effect of different combinations of surface treatment on adhesion of resin composite to zirconia

Jihad Saade,1 Hasan Skienhe,2 Hani Ounsi,3 Jukka P Matinlinna,4 Ziad Salameh51Faculty of Dental Medicine, Lebanese University, Beirut, Lebanon; 2Department of Prosthodontics, Faculty of Dental Medicine, Lebanese University, Beirut, Lebanon; 3Department of Restorative Dentistry and Endodontics, Faculty of Dental Medicine, Lebanese University, Beirut, Lebanon; 4Dental Materials Science, Faculty of Dentistry, University of Hong Kong, Sai Ying Pun, Hong Kong; 5Research Center, Faculty of Dental Medicine, Lebanese University, Beirut, LebanonPurpose: The purpose of this laboratory study was to evaluate the effect of different surface treatment combinations on resin zirconia bonding.Materials and methods: One hundred and five pre-sintered zirconia quadrangles were prepared out of zirconia blocks, polished, then sintered and divided into five groups (n=21). Group I (control): samples were untreated, group II: grit-blasting with 50 &mu;m alumina particles, group III: grit-blasting with 100 &mu;m alumina particles, group IV: Er,Cr:YSGG laser, and group V: selective infiltration etching technique. Microstructural analysis was performed using scanning electron microscopy, atomic force microscopy, a diffractometer, and a profilometer. Cylinders of composite resin were luted with Panavia resin composite cementand Clearfil ceramic primer. Shear bond strength (SBS) was determined using a universal testing machine.Results: SBS results were analyzed using one-way ANOVA followed by Tukey post hoc tests for multiple comparisons. The level of significance was set to 0.05. SBS values of the studied groups II, III, IV, and V were 16.2&plusmn;1.8 MPa, 15.7&plusmn;3.7 MPa, 14.8&plusmn;3.4 MPa, and 16.8&plusmn;3.0 MPa, respectively. All values were significantly higher than the control group (10.48&plusmn;1.80 MPa), but without a significant difference between them. Group III exhibited the roughest surface, and Group I had a more significantly reduced surface roughness value than any other group. Group III presented the highest significant increase of tetragonal to monoclinic phase transformation (13%).Conclusion: The use of grit-blasting with greater particles size enhanced SBS with resin composite cement, but induced a higher amount of monoclinic phase transformation. The use of primer based on adhesive monomer with the resin cement is required to enhance the bonding efficiency. The use of laser enhanced the surface roughness and the bonding ability to zirconia.Keywords: air abrasion, laser, MDP primer, resin cemen

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Shaping effectiveness and surface topography of reciprocating files after multiple simulated uses

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer’s instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals

The effect of different full-coverage crown systems on fracture resistance and failure pattern of endodontically treated maxillary incisors restored with and without glass fiber posts.

6The aim of this study was to compare the fracture resistance and failure pattern of endodontically treated maxillary incisors restored using composite resin with or without fiber-reinforced composite (FRC) posts under different types of full-coverage crowns. The null hypothesis tested was that fracture resistance and the failure pattern of these teeth were not affected by the use of FRC posts or by the type of full-coverage crown. One hundred twenty maxillary incisors were endodontically treated and divided into 4 groups of 30 each. Each group was divided into two subgroups: restoration with or without fiber post. PFM crowns were placed in group 1, Empress II crowns in group 2, SR Adoro crowns in group 3, and Cercon crowns in group 4. Fracture tests were performed by loading specimens to fracture. Data were analyzed with two-way analysis of variance (alpha = 0.05). The type of crown was not a significant factor affecting fracture resistance (p = 0.4), whereas the presence of a post was (p = 0.001). Both the presence of post and the type of crown had a significant influence on the proportion of restorable versus unrestorable fractures. Although prosthodontics textbooks do not generally advocate the placement of fiber posts in endodontically treated incisors, the results of this study indicate that the use of fiber posts in such teeth increases their resistance to fracture and improves the prognosis in case of fracture.nonenoneSALAMEH Z; SORRENTINO R; OUNSI HF; SADIG W; ATIYEH F; M. FERRARISalameh, Z; Sorrentino, Roberto; Ounsi, Hf; Sadig, W; Atiyeh, F; Ferrari, Marc