SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
This article discusses the fracture resistance of 4 post and core systems including a combined obturator/post system before and after fatigue loading. The obturator/post demonstrated the highest fracture resistance values. The use of a combined obturator/post with a single resin endodontic sealer/luting cement seems promising.
OBJECTIVE: To evaluate marginal adaptation, fracture modes, and loads to failure of composite crowns with different substructures on root-canal-treated premolars. METHODS: Forty-eight mandibular teeth with single root canals were selected and assigned to six equal groups: group I, untreated; group II, root-canal-treated (RCT), access cavity restored with composite resin; group III, RCT, ferrule (2 mm), no post, standardized composite resin crown (SRCC); group IV, RCT, ferrule, glass fiber post, SRCC; group V, RCT, ferrule, zirconium post, SRCC; group VI, RCT, ferrule, cast gold post, SRCC. All teeth were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49N, 1.7Hz, 3000 temperature cycles of 5-50-5 degrees C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at x200 at the tooth-to-luting-composite (IF1) and the luting-composite-to-crown (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5mm/min. RESULTS: A significant decrease in marginal adaptation was found in groups III and IV after TCML at IF1. A significant decrease was observed at IF2 in group V. Mean loads to failure did not differ significantly between the groups with SRCCs. Those of groups II, III, and IV did not differ from that of unrestored teeth. Half the specimens exhibited partial root fractures, independent of the substructures used. No deep or vertical root fractures were observed in any group. CONCLUSION: All studied posts had a positive effect on marginal adaptation at IF1, but not on failure modes or loads to failure of composite resin crowns.
Results of previous studies have indicated that the use of different ceramic materials and differing bonding/luting systems may affect resistance to fracture of teeth restored with dentine-bonded crowns. It is the purpose of this investigation to examine in vitro fracture resistance of dentine-bonded ceramic crowns, using materials in combination which have demonstrated increased fracture resistance when they are used individually. Ten sound maxillary premolar teeth were selected. These teeth were prepared for full crowns in a similar manner to previous, related studies. Standardised crowns were constructed in a leucite reinforced ceramic (Empress: Ivoclar-Vivadent, Liechten-stein) and placed using a dentine-bonding system and resin-composite luting system (3M; St. Paul, MN, USA). Compressive force was applied through a 4 mm diameter steel bar applied to the occlusal surface of the restored specimens. A mean fracturing force of 1.67 kN was recorded, statistical analysis indicating that this was significantly greater than any previously used combination of ceramic material and bonding/luting system, and greater than a group of sound, unrestored teeth. The fracture resistance of teeth restored in vitro by dentine bonded crowns may be enhanced by the combination of the materials described.
Core build-ups should provide satisfactory strength and resistance to fracture both before and after crown preparation. This paper examines the resistance to fracture of core build-ups in different materials and the fracture resistance of core build-ups when these have been reduced for full crown preparation. Standardized core build-ups were made on groups of extracted molar teeth of similar size, with 10 teeth per group. Three resin-composite (prisma APH: Dentsply, Weybridge, UK; Ti-Core, Essential Dental Systems, NJ, US and Coradent, Vivadent, Liechtenstein), one cermet (Ketac-Silver, ESPE GmbH, Seefeld, Germany) and one amalgam material (Duralloy, Degussa Ltd, Cheshire, UK). These specimens were subjected to compressive force on a universal testing machine and the force at fracture noted. Standardized full crown preparations were made on a further five groups of core build-up specimens using the same materials as above. These prepared specimens were subjected to compressive force on a universal testing machine and the force to fracture noted. The results indicated that amalgam core build-ups demonstrated higher fracture resistance than the other materials examined. There was a general decrease in the fracture strength of the specimens following crown preparation, with the teeth restored with the amalgam core build-ups showing a greater percentage reduction in fracture strength than the other materials tested. Prepared core build-ups in a hybrid composite material provided the highest fracture resistance. The cermet material used provided the lowest resistance to fracture in both the core build-up and crown preparation specimens. In terms of fracture resistance, no advantage was apparent in using the two composite materials designated as being specifically appropriate for core build-ups.
PURPOSE: This article presents a review of the literature on factors that affect the resistance to fracture of post-core reconstructed teeth. MATERIALS AND METHODS: Articles cited in a MEDLINE search were obtained from the journals and reviewed with respect to factors affecting fracture resistance of post-core reconstructed teeth. RESULTS: A large part of the literature reviewed emphasizes the stress distribution during insertion of posts and during function. Other factors, like post length, post diameter, amount of remaining dentin, post material, post adaptability, post design, cement, core material, core and crown design, biocompatibility of post material, use of treated tooth, and load experienced by restored tooth, are also found to influence the fracture resistance of a reconstructed tooth. Of all the factors enumerated, crown design, occlusal forces, and use of the treated tooth are found to have direct impact on the longevity of the restored tooth. CONCLUSION: Literature indicates that (1) preservation of tooth structure is a must; (2) posts should not be used with the intention of reinforcing the tooth; (3) review of functional and parafunctional forces must be undertaken before restoring the tooth, as these will influence the prognosis; and (4) controlled prospective clinical studies evaluating each factor should be undertaken.
STATEMENT OF PROBLEM: The increase in wall thickness of weakened roots using composite resins may increase the root resistance to fracture. However, little is known about the recently developed methods for intraradicular reinforcement of weakened roots. PURPOSE: The purpose of this study was to determine the fracture resistance of experimentally weakened roots reinforced with composite resins, compared with conventional systems that use cast and prefabricated posts. MATERIAL AND METHODS: Forty-eight maxillary incisors were divided into 6 groups (n = 8). The control group (C) used a conventionally prepared root canal filled with cast CuAl posts. Experimental groups had the root canals overprepared to weaken them and were restored as follows: CP, cast CuAl posts; LT, light-transmitting polymerization post (Luminex) + Tetric Ceram resin + prefabricated titanium post (PTP); LF, Luminex posts + Filtek Supreme resin + PTP; LZ, Luminex posts + Z100 resin + PTP; and LR, Luminex posts + Renew resin + PTP. All posts were cemented with a resin luting agent (C & B Cement). Specimens were subjected to compressive load (N) until fracture. Data were submitted to 1-way analysis of variance and the Dunnett test (alpha = .05). RESULTS: There was significant difference (P < .01) between the conventionally prepared specimens and those filled with a cast post (C, 447.8 +/- 167.9) and the overprepared specimens and those filled with a cast post (CP, 212.8 +/- 62.4). No significant differences were found among the control specimens (447.8 +/- 167.9) and the weakened-roots filled with Luminex and composite resins LT (520.9 +/- 173.1), LF (479.9 +/- 214.9), LZ (391.6 +/- 173.6), and LR (333.0 +/- 112.2). CONCLUSION: The use of composite resins in root canals reinforced the weakened roots during fracture resistance testing.
STATEMENT OF PROBLEM: Controversy exists concerning the preferred cavity design for posterior ceramic restorations to improve their resistance to fracture under occlusal load. PURPOSE: The aim of this study was to assess the resistance to fracture of leucite-reinforced ceramic restorations placed on molars with different cavity preparation designs. MATERIAL AND METHODS: Ninety noncarious molars were selected, stored in 0.2% thymol solution, and divided into 9 groups (n = 10): IT, intact teeth; CsI, conservative inlay; ExI, extensive inlay; CsO/mb, conservative onlay with mesio-buccal cusp coverage; ExO/mb, entensive onlay with mesio-buccal cusp coverage; CsO/b, conservative onlay with buccal cusp coverage; ExO/b, entensive onlay with buccal cusp coverage; CsO/t, conservative onlay with total cusp coverage; ExO/t, extensive onlay with total cusp coverage. Teeth were restored with a Leucite-reinforced ceramic (Cergogold). The fracture resistance (N) was assessed under compressive load in a universal testing machine. The data were analyzed with 1-way and 2-way analyses of variance, followed by the Tukey HSD test (alpha = .05). Fracture modes were recorded, based on the degree of tooth structure and restoration damage. RESULTS: One-way analysis showed that intact teeth had the highest fracture resistance values. Two-way analyses showed no significant differences for the isthmus extention factor, but showed a significant difference for the preparation design type of fracture (P = .03), and also for the interaction between both factors (P = .013). The fracture mode observed in all groups tended to involve only restorations. CONCLUSION: Within the limitations of this study, it was observed that cuspal coverage does not increase fracture resistance of the posterior tooth-restoration complex restored with leucite-reinforced ceramics.
This study measured the resistance to fracture of Class IV resin composite restorations prepared with either butt joints, bevels, or chamfer margins. Seventy extracted intact, non-carious maxillary central incisors, of approximately the same size, were collected and randomly divided into the following seven groups: 90 degrees butt joint (control)), 1 and 2 mm 45 degrees bevels, 1 and 2 mm 60 degrees bevels, and 1 and 2 mm chamfer margins. The teeth were restored with a hybrid resin composite and tested in an Instron Universal testing machine in a compressive mode at 45 degrees to the long axis. Statistical analysis indicated that there were no significant differences between the control group and any of the 1 mm bevel or chamfer margins and that the 2 mm bevel and chamfer margins yielded the highest fracture resistance.
STATEMENT OF PROBLEM: Inlay-retained resin-bonded fixed partial dentures (RBFPDs) are conservative prosthetic restorations; however, their resistance to fracture is not clear. PURPOSE: The purpose of this study was to compare fracture loads of posterior complete coverage metal-ceramic restorations with all-ceramic inlay-retained RBFPDs. MATERIAL AND METHODS: Thirty-two posterior ceramic RBFPD restorations were divided into 4 groups (n=8): (1) Complete metal-ceramic fixed partial dentures (MC-FPDs) fabricated of Ni-Cr-based alloy (Wirolloy) and veneered with a ceramic (IPS d.SIGN) as the control group; (2) inlay-retained metal-ceramic (MC RBFPDs) with the same materials as the control; (3) inlay-retained lithium disilicate (LD) glass-ceramic (IPS Empress 2) RBFPDs; and (4) inlay-retained zirconia-based (Z) ceramic (Cercon) RBFPDs. Control specimens were prepared to receive conventional complete MC-FPDs designed to include a 1.3-mm-circumferential, 90-degree flat shoulder with rounded angles. Inlay-retained RBFPD specimens were prepared with 2-mm occlusal reduction but without bevels at the occlusal or gingival margins. Specimens were loaded and fracture loads (N) measured at fracture with a universal testing machine at a crosshead speed of 1.0 mm/min and 250 kgf load cell. Data were analyzed with 1-way ANOVA and Duncan test (alpha=.001). RESULTS: Fracture loads (mean +/- SD) were greatest for control specimens (1318.43 +/- 211.00 N) and Z-RBFPD (1247.70 +/- 262.51 N) specimens as compared to MC-RBFPD or LD-RBFPD (P < .001). MC-RBFPD exhibited the next highest fracture loads (958.01 +/- 194.29 N), and LD-RBFPD exhibited the significantly lowest values (303.23 +/- 92.54 N) of the materials tested (P < .001). CONCLUSION: Inlay-retained zirconia-based ceramic RBFPDs demonstrated the greatest fracture resistance among all inlay-retained restorations tested.
In this study, the effect of flowable composite reinforced with a leno wave ultra high modulus (LWUHM) polyethylene fiber (Ribbond) on fracture resistance of endodontically treated molars with MOD cavity and lingual cuspal fracture was evaluated. Sixty sound extracted human mandibular molars were randomly assigned to six groups (n = 10). Group 1 served as control. Teeth in groups 2-6 received root canal treatment and a MOD cavity preparation. Teeth in group 2 were kept unrestored. Lingual walls of specimens in groups 3-6 were fractured at the CEJ and reattached (C&B Super-Bond). Group 3 was kept unrestored, and group 4 was restored with a composite resin (CR) (AP-X). In group 5, a flowable resin (FR, Protect Liner F) and in group 6, a Ribbond in combination with FR were inserted inside the cavity before CR restoration. After finishing and polishing, the specimens were subjected to compressive loading perpendicular to the occlusal surface at a crosshead speed of 1 mm/min. The mean load necessary to fracture were recorded in Newton and the results were statistically analyzed. MOD cavity preparation reduced fracture resistance of endodontically treated teeth (p < 0.05). Fracture resistance of rebonded fractured specimens was found to be similar to that of the nonfractured samples (p > 0.05). Use of LWUHM polyethylene fiber Ribbond increased fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture (p < 0.05). As a result, it was concluded that the insertion of Ribbond inside the cavity has a positive effect on fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture.
Sixty bovine teeth with simulated mesio-incisal angle fracture were randomly and equally divided in one untreated (control) group and three experimental groups (Bevel, Chamfer and newly introduced Stair-step Chamfer preparation group) to evaluate the effect of enamel preparations on the fracture resistance of composite resin. Post restoration, fracture mechanics approach was used to quantify the failure of composite resins in testing the samples in Instron testing machine. Mean peak failure load (Newton) of composite amongst experimental groups was observed in the order; Chamfer (326.09 +/- 72.73), Stair-step chamfer (315.21 +/- 81.77) and Bevel (253.83 +/- 67.38). Results of the One-Way ANOVA revealed significant difference in the mean peak failure load values of the four different groups. (P<0.001) Scheffe's Post-Hoc comparison test (Subset for alpha = 0.05) revealed that there was no significant difference in the mean peak failure load values of the bevel, stair-step chamfer and chamfer preparation when considered together, but the mean peak values of control group (605.22 +/- 48.96) were observed significantly higher. Failure mode evaluation revealed, majority of failures occurred as cohesive and mixed type for all the experimental groups. Adhesive type failure was observed maximum (33%) in the bevel group. Stair-step chamfer preparation showed greatest potential for application and use as it no only demonstrated comparable values to Chamfer preparation ['t' value (0.39) (P > 0.05)] but also involved sacrificing less amount of tooth structure adjacent to fractured edge.
305 extracted human front teeth and premolars were investigated for their dynamic resistance to fracture. Morphological factors, such as the anatomical class of tooth and root lengths, and patho-anatomical factors, such as infractions, occlusal and cervical abrasions, composite and amalgam restorations and damage resulting from previous traumatic impacts, were taken into consideration. A comparison of stability after a defined impact stress showed that maxillary canines and premolars had the highest resistance to fracture; this differs significantly from the resistance of maxillary and mandibular incisors. The root length correlates directly with fracture energy and therefore to stability. Composite restorations with an adhesive joint were found to increase the resistance of a tooth to fracture, but amalgam restorations had a weakening effect. Cervical wedge-shaped defects of the tooth cause considerable destabilization, but occlusal abrasion and infractions have only a moderate weakening influence. Previous traumatic stress reduces the resistance to fracture of a tooth by up to 85%. The fracture patterns generated were very similar to clinically observed tooth fractures, indicating the results to be clinically relevant.
Fracture resistance and fracture modes of endodontically treated maxillary central incisors restored with different post-and-core systems covered with all-ceramic copings were evaluated. Ten samples were prepared for each group. Groups 1, 2 and 3 consisted of tooth-coloured post-and-core, zirconia post (Cosmopost) with a composite core (Tetric Ceram), zirconia post (Cosmopost) with a custom made ceramic core (Cosmo Ingot), glass fibre-reinforced post (FRC Postec) with a composite core (Tetric Ceram), respectively. Group 4 consisted of a titanium post (ERpost) with a composite core (Tetric Ceram). The control group (group 5) consisted of root-filled incisors without posts. Tooth-coloured posts were cemented in the roots using Variolink-2, while titanium posts were cemented in the roots using Harvard cement. The all-ceramic copings were cemented using Variolink-2. Static load was applied to 2 mm below the incisal edge on the palatinal surface of each sample until they were fractured. Fracture data were obtained and statistically analysed with One-way anova and a Tukey's test. The results of the means and standard deviations of the fracture resistance during static loading were: 497.5 +/- 61.94 (1), 474.61 +/- 96.84 (2), 494.61 +/- 104.67 (3), 581.34 +/- 105.36 (4), 420.42 +/- 127.48 (5). There were statistically significant differences between groups 4 and 5. Glass fibre-reinforced posts and composite cores (group 3) showed the most catastrophic failure. Consequently, zirconia ceramic posts can be used in clinical practice.
The fracture resistance of provisional restorations is an important concern for the restorative dentist. The fracture resistance of a material is directly related to its transverse strength. Six specimens of similar dimensions were prepared from three resins (PMMA, PEMA and BIS acryl-composite). The resins were reinforced with glass and aramid fibers. The samples were tested immediately after the material set, following seven days of wet storage using three-point compression loading. The results were analyzed with an analysis of variance (ANOVA). Fracture resistance of the specimens was statistically different (p < 0.001) among the materials. Specimens reinforced with glass fibers showed higher transverse strength (149.82 MPa). The fiber reinforcement of resin materials increased the strength values (20-50%). Within the limitations of this study, the transverse strengths of PMMA, PEMA and BIS acryl-resin composites were improved after reinforcement with glass and aramid fibers.
The purpose of this study was to evaluate whether intracoronal delivery of an apical barrier of mineral trioxide aggregate (MTA) placed ultrasonically, non-ultrasonically, or ultrasonically with the addition of an intracanal composite resin provided a better seal against bacterial leakage. A second purpose was to determine whether intracanal composite resin or gutta-percha and sealer placed against an apical barrier of MTA provided greater resistance to root fracture. In a standardized in vitro open apex model, MTA was placed as an apical barrier at a thickness of 4 mm, with and without ultrasonic vibration. The barriers were challenged with bacteria exposure within a leakage model, and fracture resistance was assessed with increasing forces applied via an Instron machine. After 45 days, the addition of ultrasonics significantly improved the MTA seal, compared with the non-ultrasonics treatment (Kruskal Wallis nonparametric ANOVA with Dunn multiple comparison test p < 0.05). Bacterial leakage occurred in 6 (33%) of 18 in the non-ultrasonic MTA group, 2 (11%) of 18 in the ultrasonic MTA group, and 1 (6%) of 18 in the ultrasonic MTA-composite group. There were no significant differences at 90 days. A 4-mm thickness of MTA followed with an intracanal composite resin demonstrated a significantly greater resistance to root fracture than MTA followed with gutta-percha and sealer (one-way ANOVA with Newman-Keuls multiple comparison test, p < 0.01). The MTA-gutta-percha group was not significantly different than the MTA unrestored positive control.
The purpose of this study was to investigate the fracture resistance of re-attached coronal fragments of teeth using different materials and tooth preparations. Seventy-two recently extracted bovine incisors were selected. Eight incisors were maintained without any preparation as a control group. The incisal third of the other teeth was sectioned using a diamond saw. In one group (n = 32), a 2-mm bevel was prepared, whereas in the second group no preparation was made (n = 32). The specimens (beveled and non-beveled) were divided in four groups (n = 8) and re-attached with the following materials: a dual-cured resin cement RelyX ARC (RX); a chemically cured composite Bisfil 2B (B2); a light-cured composite Z250 (Z2); and a one-bottle adhesive Single Bond (SB). The bevel region was restored with adhesive and composite. All materials were used according to manufacturer's directions. A light-curing unit was used to polymerize the materials. Specimens were stored in saline solution for 72 h. De-bonding procedures were performed in a testing machine with cross-head speed of 0.6 mm min(-1). The load was applied in the incisal third. The resistance to fracture for control group was 70 (7) kg. The fracture resistance for non-beveled and beveled specimens were: SB, 3.3 (2.4) and 17.0 (4.1); RX, 11.5 (3.0) and 16.3 (3.1); Z2, 14.4 (4.2) and 20.5 (1.7); and B2, 19.5 (3.5) and 32.5 (7.4) kg. Analysis of variance (anova) and Fisher's protected least significant difference (PLSD) test disclosed significant influence for materials and cavity designs (P = 0.001). The highest failure loads were obtained with the B2 group and then with the Z2 with either bevel or non-bevel. RX produced lower failure loads than the restorative composites. The lowest failure load was obtained with SB in the non-beveled group. No technique studied was able to attain the fracture resistance of the control group and both materials and tooth preparation influenced the fracture resistance.
Laboratory studies have demonstrated satisfactory fracture resistance of all-ceramic crowns placed using a conventional resin-composite luting material and a dentine bonding system. This study investigated the fracture resistance of teeth restored with dentine-bonded ceramic crowns luted with a self-etching luting material. Standardized preparations were carried out on two groups of ten sound, unrestored, maxillary premolar teeth. Ceramic crowns were constructed, their internal surfaces etched and placed using two luting system combinations. Compressive fracture resistance was determined for each group using a Universal Testing Machine. Mean compressive fracture resistance of 890 (222) N and 760 (271) N were recorded for the RelyX Unicem Aplicap and Mirage groups, respectively. There was no significant difference in the mean compressive fracture resistance of the restored teeth in both groups (P<0.05). The failure modes were different for each cements with more severe (Mode V)failures associated with the Mirage group compared with the consistent Mode II failures associated with RelyX Unicem Aplicap. We conclude that the fracture resistance of dentine-bonded crowns luted with a self-adhesive resin-based luting material was no different from that of a conventional resin-based luting system. The fracture resistance of dentine-bonded ceramic crowns may be clinically satisfactory when a self-adhesive resin-based luting material is utilised.
PURPOSE: The aim of the present study was to compare the fracture resistance of endodontically treated maxillary premolars with mesio-occlusodistal (MOD) cavities restored using various restorative materials and luting agents. MATERIALS AND METHODS: Eighty extracted human maxillary premolars satisfying certain predetermined criteria were subjected to seven different restoration methods (10 premolars per method). After endodontic treatment, an MOD cavity was prepared in each specimen, and restoration was carried out by one of the following methods: group 1 = control (intact premolars); groups 2 and 3 = restoration using a photo-cure resin composite with and without bonding, respectively; groups 4 and 5 = restoration using a cast-metal inlay with zinc phosphate and adhesive resin cements, respectively; groups 6 and 7 = restoration using a cast-metal onlay with zinc phosphate and adhesive resin cements, respectively; and group 8 = restoration using a hybrid resin onlay. A fracture test was conducted to determine the fracture resistance and fracture mode of each specimen. RESULTS: Fracture resistance was greatest for teeth restored using a cast-metal onlay cemented with adhesive resin cement, but those fractures that did occur were generally unrestorable. Fracture resistance of teeth restored using a cast-metal inlay was also high. Fracture resistance for teeth restored using a resin composite was significantly lower, but the majority of these fractures were restorable. CONCLUSION: Endodontically treated maxillary premolars with MOD cavities could be successfully restored by cast onlay and inlay restorations luted with adhesive resin cement, but their failure mode was often unfavorable.