Effect of photon induced photoacoustic streaming (PIPS) on bond strength to dentine of two root canal filling materials.

OBJECTIVES: The aim of this study was to evaluate the effect of photon induced photoacoustic streaming (PIPS) technique in combination with EDTA on bond strength of gutta-percha/AH Plus and Resilon/RealSeal SE root canal fillings to root dentine. MATERIALS AND METHODS: Forty freshly extracted human maxillary anterior teeth with intact straight roots, were instrumented endodontically with rotating ProTaper instruments and randomly divided into two experimental groups. In group 1 (n = 20), root canals were rinsed for 1 minute with 2 ml of 17% EDTA. In group 2 (n = 20), Er:YAG laser, with a 14 mm long 400 µ diameter tapered PIPS tip, was used for 1 minute with 2 ml of 17% EDTA. The laser parameters used were: 20 mJ per pulse, 15 Hz, 50 microsecond. In each experimental group, half of the root canals (n = 10) were obturated with gutta-percha/AH Plus and other half (n = 10) with Resilon/RealSeal SE. A micropush-out test was performed on sectiond specimens of the filled roots using a universal testing machine and resistance to failure plus failure modes were determined. RESULTS: Both gutta-percha/AH Plus groups had higher bond strength to root dentin than the Resilon/RealSeal SE groups (P < 0.05). The smear layer removal protocol, with EDTA only or combining PIPS technique with EDTA, had no influence on bond strength of either gutta-percha/AH Plus, or Resilon/RealSeal SE (P > 0.05). CONCLUSION: Within the limitations of this study, it was found that the application of the PIPS technique did not have an affect on the push-out bond strength of Resilon/RealSeal SE root canal filling to dentin nor on the gutta-percha/AH Plus. A significant difference in bond strength was noted between the two root canal filling materials. Lasers Surg. Med. 48:951-954, 2016. © 2016 Wiley Periodicals, Inc.

Push-out bond strength of an experimental self-adhesive resin cement.

The adhesion of fiber posts luted with simplified adhesive systems has been a matter of great interest over the past years. The aim of this study was to assess the post retentive potential of experimental self-adhesive resin cement (EXP) when used alone and in combination with a self-etch adhesive. Fiber posts were placed in endodontically treated teeth and divided into four groups (n = 6) according the luting material, as follows: group 1 (EXP alone); group 2 (EXP used with self-etch adhesive); group 3 (marketed dual-cured cement used with self-etch adhesive); and group 4 (marketed self-adhesive cement). The push-out test was used to assess the retentive strength of fiber posts (expressed in MPa), and specimens were analyzed under a stereomicroscope to determine failure mode. The adhesive interface between the cement and root canal dentin for each group was evaluated using scanning electron microscopy. The post retentive potential of group 1 (EXP) (7.48 ± 4.35 MPa) was comparable with that of marketed cements from group 4 (6.79 ± 3.68 MPa) and group 3 (8.77 ± 4.58 MPa). When EXP was used in combination with self-etch adhesive (group 2), significantly higher push-out bond-strength values were measured (15.87 ± 4.68 MPa) compared with the other groups.

Shear bond strength to enamel and flexural strength of different fiber-reinforced composites.

PURPOSE: To assess the shear bond strength to unground human enamel (ESBS) and flexural strength (FS) of different reinforcing fibers used in combination with a flowable composite resin. MATERIALS AND METHODS: For ESBS testing, 90 human molars were selected and randomly divided into 9 groups (n = 10) according to the reinforcing fiber to be tested: 1. RTD Quartz Splint additionally impregnated at chairside with Quartz Splint Resin (RTD); 2. RTD Quartz Splint without additional impregnation; 3. Ribbond-THM (Ribbond) impregnated with OptiBond FL Adhesive; 4: Ribbond Triaxial (Ribbond) impregnated with OptiBond FL Adhesive; 5. Connect (Kerr) impregnated with OptiBond FL Adhesive; 6. Construct (Kerr) impregnated with Opti- Bond FL Adhesive; 7. everStick PERIO (Stick Tech); 8. everStick C&B (Stick Tech); 9. nonreinforced composite Premise flowable (Kerr). Cylinders of flowable composite reinforced with the fibers were bonded to the intact buccal surface of the teeth. After 24 h of storage, shear loading was performed until failure occurred. FS was assessed performing three-point bending test according to ISO Standard 4049/2000. ESBS and FS data were analyzed using one-way ANOVA, followed by Tukey's HSD test for post-hoc comparisons (p < 0.05). RESULTS: For each group, the ESBS and FS, respectively, in MPa were: 1. 17.07 ± 4.52 and 472.69 ± 30.49; 2. 14.98 ± 3.92 and 441.77 ± 61.43; 3. 18.59 ± 5.67 and 186.89 ± 43.89; 4. 16.74 ± 6.27 and 314.41 ± 148.52; 5. 14.38 ± 4.14 and 223.80 ± 77.35; 6. 16.00 ± 5.55 and 287.62 ± 85.91; 7. 16.42 ± 3.67 and 285.35 ± 39.68; 8. 23.24 ± 5.81 and 370.46 ± 29.26; 9. 12.58 ± 4.76 and 87.75 ± 22.87. For most fibers, no significant difference in ESBS was found compared to the control group, except for everStick C&B, which yielded higher ESBS. Nonreinforced composite exhibited the lowest FS, while all fibers positively affected the FS. CONCLUSIONS: Fiber reinforcement of flowable composite does not affect its ESBS. The flexural strength of FRCs is significantly influenced by fiber composition and pattern.

Post-retentive ability of new flowable resin composites.

PURPOSE: To investigate the applicability of flowable composites as post luting agents by assessing the push-out strength of posts. METHODS: 36 intact single rooted human premolars were selected. The endodontic treatment was performed and half of the specimens were restored with light transmitting posts (DT Light Post Illusion) and the other half with opaque posts (Tech 21 X-OP). In both groups the following combinations of adhesive/cement were tested: OptiBond Solo Plus/Nexus Third Generation (NX3), XP Bond/SureFil SDR Flow (SDR), and Vertise Flow (VF). Push-out test was used to assess the retentive strength of fiber posts, which was expressed in megapascals (MPa). Specimens were analyzed under a stereomicroscope to determine failure mode (adhesive between luting agent and post, adhesive between luting agent and dentin or mixed failure). Push-out data and failure mode distribution were analyzed by two-way ANOVA and Chi-square test, respectively (P< 0.05). RESULTS: The statistical analysis revealed that only the type of luting material significantly influenced push-out bond strength of the post (P< 0.001). SDR (9.00 +/- 2.17 MPa) performed similarly to the control group NX3 (7.15 +/- 1.74 MPa), while VF (4.81 +/- 1.51 MPa) should significantly lower bond strength. Failure modes differed significantly among groups.

Microtensile bond strength evaluation of self-adhesive resin cement to zirconia ceramic after different pre-treatments.

PURPOSE: To evaluate the influence of different surface treatments and metal primer application on bond strength of zirconia ceramic to a self-adhesive resin cement. METHODS: 40 cylinder-shaped (Ø 12 x 5.25 mm high) of zirconia ceramic (Aadva Zirconia) were randomly divided into four groups (n= 10), based on the surface treatment to be performed: (1) Sandblasting with 125 microm Al2O3 particles (S) (positive control); (2) Selective infiltration etching (SIE); (3) Experimental heated etching solution applied for 30 minutes (ST); (4) No treatment (C). Half of the zirconia specimens of each group received the application of Metal Primer II. Eight disks for each group were luted using a self-adhesive resin cement (G-Cem Automix) to composite overlays (Paradigm MZ100). After 24-hour storage (37 degrees C, 100% RH) bonded specimens were cut into microtensile sticks and loaded in tension until failure. Data were analyzed with two-way ANOVA and Games-Howell (P < 0.05). Failure mode distribution was recorded and scanning electron microscopy (SEM) was used to examine the fractured microbars. The remaining cylinders of each group (n = 2) were used for SEM surface analysis. RESULTS: Both surface treatments and Metal Primer II application improved bond strength values (P < 0.05). When Metal Primer II was not applied ST treatment achieved highest bond strength values (22.17 +/- 10.37 MPa). Sandblasting in combination with Metal Primer II enhanced bond strength values compared to the other groups (23.46 +/- 11.19 MPa).

Evaluation of the adhesion of fiber posts cemented using different adhesive approaches.

The aim of this study was to investigate the adhesion of fiber posts cemented with luting agents that utilize three currently available adhesive approaches: etch-and-rinse, self-etch, and self-adhesive. Forty-two intact single-rooted human premolars were used in the study. Teeth were divided into six groups. In each group, a different resin cement with its adhesive system (if needed) and a fiber post were used. The groups were classified, according to the adhesive approach, into the following three categories. (i) Etch-and-rinse groups: Calibra resin cement/XPBond adhesive + self-curing activator (SCA)/RadiX Fiber Post (Dentsply Caulk), FluoroCore 2 core build-up material/XPBond + SCA/RadiX Fiber Post (Dentsply Caulk), and MultiCore Flow luting and core build-up material/Excite DSC adhesive/FRC Postec Plus fiber post (Ivoclar Vivadent). (ii) Self-etch group: Panavia F 2.0/ED primer (Kuraray)/RadiX Fiber Post (Dentsply Caulk). (iii) Self-adhesive groups: experimental self-adhesive cement/RadiX Fiber Post (Dentsply Caulk), and RelyX Unicem/RelyX Fiber Post (3M ESPE). The adhesion between the post and the root canal walls was assessed using the 'thin-slice' push-out test. In the test arrangement used, the self-etching approach may offer less favourable adhesion to root canal dentin in comparison with etch-and-rinse and self-adhesive approaches.

Flowable composites as intermediate agents without adhesive application in resin composite repair.

PURPOSE: To evaluate the effect of different intermediate resin agents on composite-to-composite microtensile bond strength (microTBS). METHODS: Composite disks (8 x 4 mm) of Gradia Direct Anterior (N = 15) and Filtek Supreme XT (N = 15), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (Microetcher, 50 microm-Al2O3), cleaned (35% H3PO4), and randomly divided into five groups (N = 3) according to the intermediate agent applied. Two flowable composites (Gradia LoFlo; Filtek Supreme XT Flow) and two adhesives (Adper Scotchbond 1XT, Scotchbond Multi-Purpose) were used. As a control, no intermediate agent was applied. Each disk was incrementally repaired (8x8 mm) with the same resin as the respective substrate. By serially cutting each repaired specimen, multiple sticks of about 0.8 mm2 in cross-section were obtained and loaded in tension until failure at a cross-head speed of 0.5 mm/minute. Data were statistically analyzed. Failure mode was examined by stereo- and scanning electron-microscopy (SEM). Additional specimens were prepared to morphologically evaluate the composite-to-composite interfacial quality by SEM analysis. RESULTS: Composite substrate and intermediate agent were significant factors (Two-way ANOVA, P < 0.001). Bond strengths achieved with Gradia Direct Anterior were higher than Filtek Supreme XT. The application of flowable composites resulted in statistically superior microTBS than adhesives and control (Tukey test, P < 0.001). Failure mode was predominantly cohesive (flowable composites), cohesive/adhesive (adhesives) and adhesive (no treatment). Flowable composites and adhesives showed a good interfacial quality.

Fatigue resistance and structural integrity of different types of fiber posts.

The study aimed at assessing and estimating the fatigue resistance of different fiber posts and to observe their ultrastructures through SEM. Six types of fiber posts were used: GC Fiber Post (Group 1), ParaPost Fiber White (Group 2), FibreKor (Group 3), DT Light-Post radiopaque (Group 4), FRC Postec (Group 5), and Luscent Anchors (Group 6). Ten out of 15 posts within each group were used for the fatigue test, and the other five were processed for SEM evaluation. The fatigue test revealed that Groups 1, 4, and 5 performed better than all the other groups, and that their performance differed significantly from the other tested groups from a statistical standpoint. For SEM analysis, Groups 1, 4, and 5 also obtained better results. Through correlation analysis, an absence of correlation between fatigue resistance and structural characteristics suggested that the latter reflected more of the divergence inherent in the manufacturing process of fiber posts.

The application of hydrogen peroxide in composite repair.

This study examined the influence of different surface conditioning methods on composite-to-composite microtensile bond strength. Thirty two-year old composite resin discs were randomly divided into three groups according to the different mechanical/chemical surface pretreatment tested: (1) 38% hydrogen peroxide (H(2)O(2))-treatment; (2) 50-microm aluminum oxide sandblasting; (3) no treatment. Depending on the intermediate agent applied, two subgroups were created: (A) three-step adhesive system; (B) prehydrolyzed silane coupling agent + three-step adhesive system. Microtensile bond strength measurements were performed and the data were statistically analyzed with Kruskall-Wallis Analysis of Variance and Dunn's multiple range test for post hoc comparisons (p < 0.05). Failure mode was evaluated with a scanning electron microscope. Changes in composite surface topography after H(2)O(2) treatment were also investigated. Composite repair strength did not benefit from H(2)O(2) treatment and adhesive application. Preliminary sandblasting significantly improved interfacial bond strength regardless of the intermediate agent applied. No changes in surface texture were produced after H(2)O(2) treatment. An atypical fracture pattern was detected at the interfacial level between H(2)O(2)-treated composite surfaces and the overlying adhesive and composite. H(2)O(2) treatment affected the composite-to-composite repair strength: a compromised resin polymerization may occur, resulting in a poor interfacial quality and a weak bond. Sandblasting still remains a reliable technique for composite repair.

The effect of application sustained seating pressure on adhesive luting procedure.

OBJECTIVES: To evaluate the effect of short versus long application seating pressure on the bond strength of resin blocks, luted with a dual-cured resin cement (Panavia F) to pre-coated or non pre-coated dentin with an hydrophobic light-cured adhesive (Clearfil Protect Bond). METHODS: Sixteen non-carious human third molars were randomly divided into six Groups (four teeth each). Cylindrical composite blocks were luted with Panavia F (Group Ia) and with Clearfil Protect Bond with Panavia F (Group IIa) and seating pressure was applied for 5s. In Groups Ib and IIb, the two bonding procedures were respectively repeated, but the resin cylinder was maintained under constant pressure during the entire 3min polymerization period for the resin cement. After storing in distilled water for 24h, 0.9mmx0.9mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. RESULTS: The use of Clearfil Protect Bond with Panavia F produced higher bond strengths than the use of Panavia F (p<0.05). Extending the time of pressure application up to 3min increased the bond strength (p<0.001) and improved the integrity of the interfacial quality. SIGNIFICANCE: The application of sustained seating pressure during luting procedures and the additional use of a hydrophobic light-cured adhesive both improve the final bond strength of the resin cement.

Composite-to-composite microtensile bond strength in the repair of a microfilled hybrid resin: effect of surface treatment and oxygen inhibition.

PURPOSE: To compare the 24-h microtensile bond strength of a microfilled hybrid composite to the same material after mechanical and/or chemical treatment and assess the effect of oxygen inhibition on the composite-composite bond. MATERIALS AND METHODS: Forty composite cylinders of Gradia Direct Anterior (GC) were prepared and stored 24 h prior to the following surface treatments: 50-microm aluminum oxide air abrasion and 37% phosphoric acid etching (group 1); hydrochloric acid and 6.9% hydrofluoric acid etching (group 2); diamond bur roughening and 37% phosphoric acid etching (group 3); diamond bur roughening (group 4). In all groups, Prime & Bond NT (Dentsply De Trey) was applied and light cured in air or under a nitrogen atmosphere, prior to layering a buildup of the repairing resin composite. Microtensile bond strength measurements were performed. Data were statistically analyzed with two-way ANOVA and Tukey's test (alpha = 0.05). RESULTS: The curing atmosphere did not significantly influence the interfacial strength (p < 0.05). Surface treatment significantly affected the composite-composite bond (p > 0.05). Air abrasion, regardless of curing atmosphere, resulted in the strongest bond (p < 0.05). The other treatments were comparable. CONCLUSION: Air abrasion and the application of a bonding agent offer satisfactory bond strengths for composite repair. The oxygen inhibition layer on a light-cured adhesive is not crucial to the success of the 24-h composite-composite bond.

The effect of immediate versus delayed cementation on the retention of different types of fiber post in canals obturated using a eugenol sealer.

Post can be placed immediately after the completion of the endodontic procedure or at a later stage after setting of the sealer. In this in vitro study, post space preparation and post cementation were performed immediately (group 1), 24 h (group 2), and 7 days (group 3) after root filling. A control group with no root canal obturation was included (group 4). Each group was further divided into three subgroups, according to the post type and to the materials used for luting the post. A push-out test was performed to evaluate post-root canal dentin interfacial strength. Differences among experimental groups were analyzed with two-way ANOVA and the Tukey test. Significant differences (p < 0.05) in interfacial strengths were observed for the factors post cementation interval and post type. Clinicians should be careful in performing immediate cementation of fiber posts, as delayed cementation shows higher post-dentin interfacial strengths irrespective of the post type.

Is an oxygen inhibited layer required for bonding of resin-coated gutta-percha to a methacrylate-based root canal sealer?

Removal of the oxygen inhibition layer from the surface of resin-coated gutta-percha cones during packaging has been hypothesized for their weak adhesion to a methacrylate-based root canal sealer, resulting in their frequent delamination from the sealer after root canal obturation. This study examined the feasibility of creating oxygen inhibition layers on resin-coated gutta-percha cones via the adjunctive application of a dual-cured dentin adhesive just before bonding. Composite cylinders were bonded with EndoREZ to flat, resin-coated gutta-percha disks and similar disks that were post-treated with Prime&Bond NT Dual Cure adhesive and stressed to failure using a modified microshear testing design. Although shear strengths for both groups were relatively low, a 5-fold increase in shear strength was observed after adhesive application, with complex interfacial failures instead of complete sealer delamination from the resin-coating. In-situ dentin adhesive application appears to have merits in enhancing the coupling of resin-coated gutta-percha to methacrylate sealers.

Noninvasive pit and fissure sealing: microtensile bond strength to intact bovine enamel of different pit and fissure sealants in a simplified fissure model.

PURPOSE: To measure the microtensile bond strength of different pit and fissure sealants in a simplified fissure model. MATERIALS AND METHODS: Twenty extracted bovine mandibular permanent incisors were randomly divided into 4 groups for treatment: G1: 35% phosphoric acid/Clinpro Sealant; G2: 35% phosphoric acid/Delton; G3: Non-Rinse Conditioner/Dyract Seal; G4: 20% polyacrylic acid/Fuji IILC. Each tooth was sectioned into 6 pieces (4 x 6 mm) of buccal enamel. SEM examination was used to confirm the presence of aprismatic enamel on each tooth. Using a spacer, two pieces of etched enamel were secured to a glass slide at a mean distance of 0.6+/-0.1 mm. The space between enamel substrates was then etched/conditioned and sealed with different materials according to the tested groups. By serially cutting each double-bonded sample, multiple beam-shaped specimens about 0.8mm(2) in cross section were obtained and tested in tension (0.5 mm/min) until failure occurred at either one of the two stressed interfaces. Failure modes were classified by stereomicroscopy. RESULTS: G1 and G2 showed statistically higher bond strengths than G3 and G4. G4 demonstrated the significantly lowest bond strength. Failures were mostly adhesive in G1, G2, G3, and mainly cohesive/mixed in G4. CONCLUSION: According to this model, resin-based materials (Clinpro Sealant, Delton) showed better microtensile bond strength than compomer (Dyract Seal) or resin-modified glass ionomer (Fuji IILC).

The influence of operator variability on adhesive cementation of fiber posts.

PURPOSE: The aim of this study was to evaluate the influence of the operator's experience on the outcome of fiber post cementation using an etch-and-rinse acetone-based adhesive. MATERIALS AND METHODS: Fifteen human anterior teeth were used in the study. One trained operator performed the endodontic procedures and prepared the roots for the insertion and cementation of the posts. At this point, teeth were divided into 3 groups and distributed to 3 operators to lute the posts: an expert operator (EO), a moderately experienced operator (ME), and an operator with a low level of experience (LE). Quartz fiber posts (DT Light Post #1 or #2, RTD) were used. Posts were cemented using Prime&Bond NT Dual Cure adhesive system (Dentsply Caulk) in combination with the dual-curing resin cement Calibra (Dentsply Caulk). The post retention was assessed with the "thin-slice" push-out test. One-way ANOVA was performed to examine the effect of the operator on push-out strength, followed by post-hoc multiple comparisons using Tukey's test, with the significance level set at alpha = 95%. RESULTS: The results of push-out strength testing were as follows: EO (12.44+/-3.63 MPa), ME (11.68+/-2.64 MPa), LE (11.18+/-3.12 MPa). No statistically significant differences were determined among the three groups. CONCLUSION: There was no statistically significant difference in the retention measured for fiber posts luted by operators with different levels of clinical experience. Given the parameters of this investigation, the level of operator experience in luting fiber posts does not affect post retention under laboratory conditions.

Effect of dentin adhesives used as sealers and provisional cementation on bond strength of a resin cement to dentin.

PURPOSE: To evaluate the effects of dentin adhesives employed as resin sealers and provisional cementation on the bond strengths of a resin cement to dentin. METHODS: A two-step etch-and-rinse adhesive (Excite DSC--Group 1) and two-step self-etch adhesive (AdheSE--Group 2) were applied to exposed dentin surfaces prepared from human molars (N=4). Water was used instead of a resin sealer in control Groups 3 and 4. A eugenol-free provisional cement (except for Group 4) was applied to the treated surfaces. After storing in distilled water for 1 week, the provisional cement was removed and cylindrical composite blocks were luted with a resin cement (Variolink II). 0.9 x 0.9 mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. RESULTS: One-way ANOVA revealed that neither the resin sealer nor the temporary eugenol-free cement had a negative effect on the final bond strength (P> 0.05). Mixed failures were predominantly identified from SEM.

Effect of the seating pressure on the adhesive bonding of indirect restorations.

PURPOSE: To evaluate the effect of two different techniques of seating pressure application on the adhesive-dentin bond of indirect restorations. METHODS: Eight non-carious human third molars were randomly divided in two treatment groups (four teeth each). Cylindrical composite blocks were luted with a resin cement (Panavia F). In Group 1, the seating pressure was applied for 5 seconds. In Group 2, the resin cylinder was maintained under constant pressure during the entire 3-minute polymerization period of the resin cement. After storing in distilled water for 24 hours, 0.9 x 0.9 mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. RESULTS: The Student t-test showed a significant difference (P < 0.05) in bond strength between Groups 1 and 2. SEM revealed the presence of structural defects and resin globules on the seating surface of the composites. These features were exclusively identified from Group 1 specimens and were probably caused by fluid transudation from the underlying dentin through the simplified self-etch adhesive (ED primer).

Influence of different pulse durations of Er:YAG laser based on variable square pulse technology on microtensile bond strength of a self-etch adhesive to dentin.

OBJECTIVE: The aim of the study was to evaluate the microtensile bond strength of a composite resin to dentin modified with three different pulse durations of the Er:YAG laser based on variable square pulse technology and with one self-etch adhesive. MATERIALS AND METHODS: The entire occlusal enamel was removed to obtain flat dentin surface for 48 human molar teeth. The teeth were randomly divided into four experimental groups (n=12 per group), according to the pretreatment of dentin: (1) control group; (2) super short pulse (SSP) (50 µsec); (3) medium short pulse (MSP) (100 µsec); and (4) short pulse (SP) (300 µsec) with Er:YAG laser. The energy of the laser used was 80 mJ with average power of 0.8 W. The microtensile bond strength was tested with a universal testing machine. Two specimens from each experimental group were subjected to scanning electron microscopic (SEM) examination, to observe the irradiated surface. RESULTS: Dentin surface treated with SSP showed significantly lower microtensile bond strength values (24±9.8 MPa) in comparison with the control group and SP group (35.3±12.8 and 32.9±10.7 MPa, respectively), (p<0.05). The MSP and SP groups did not show any statistically significant difference in microtensile bond strength in comparsion with the control group (p>0.05). CONCLUSIONS: The use of SP and MSP of the Er:YAG laser with one step self-etch adhesive does not impair or improve the microtensile bond strength in dentin, whereas SSP may not be suitable for dentin surface treatment prior to bonding procedures.

Ablative potential of four different pulses of Er:YAG lasers and low-speed hand piece.

OBJECTIVE: The aim of the study was to evaluate the ablation rate of caries in dentin with fluorescence-feedback controlled Er:YAG, Variable Square Pulse technology (VSPt) based Er:YAG working in different pulse durations, and steel bur. MATERIALS AND METHODS: Sixty human molar teeth with caries in dentin, extracted for periodontal reasons, were selected for this study. All selected teeth were randomly divided into five groups, each containing twelve specimens: (1) group FFC, fluorescence feedback-controlled Er:YAG laser; (2) group SSP (super short pulse: 50 µs); (3) group MSP (medium short pulse; 100 µs); (4) group SP (short pulse; 300 µs); and (5) group SB, steel bur in a slow-speed hand piece. A profilometer was used to determine the volume of the ablated caries in dentin. The clinical and real ablation rates of caries in dentin were calculated. Two specimens from each experimental group were selected randomly and subjected to SEM examination. RESULTS: The volumes of the ablated caries in dentin in the SSP and SB groups were statistically significantly different in comparison with other experimental groups (p<0.05). The clinical and real ablation rate of caries in dentin was the highest for the SSP group (0.15±0.05 and 0.17±0.05 mm(3)/sec, respectively) and statistically significantly different in comparison with the MSP and SB groups (p<0.05). The SB and FFC groups revealed a dentin surface with a smear layer and closed dentinal tubules on SEM micrographs. In the SSP, MSP, and SP groups, an irregular surface without a smear layer was found. CONCLUSIONS: Taking into consideration the experimental conditions of the present study, SSP was the most efficient in ablation of caries in dentin, providing a smear layer-free surface with open dentinal tubules.

Post retentive ability of a new resin composite with low stress behaviour.

OBJECTIVES: To assess by means of push-out test the post retentive potential of a new flowable resin composite with low polymerization stress. METHODS: SureFil(®) SDR™ (Dentsply, S) was compared with the resin cement Calibra (Dentsply, C). S and C were used in combination with the adhesive XP Bond (Dentsply, XPB). In C group the Self-Cure Activator was mixed with XPB. The following types of fibre posts were luted into 30 extracted premolars: Radix Fiber Post (Dentsply, R), DT Light Post (RTD, LP), ER Dentin Post (Komet, ER), DT Light SL (VDW, SL), FibreKleer (Jeneric Pentron, F). Six posted roots per group were tested. Each root provided three to five 1mm-thick slices. Measured push-out strengths were differentiated by post space level and statistically analysed (p<0.05). The failure mode of each debonded specimen was assessed. RESULTS: Cement type did not have a significant effect on post retention (p=0.54). Post type was a significant factor for push-out strength (p<0.001). LP exhibited significantly higher retentive strength than SL and F; push-out strengths of ER and R were significantly higher than those of F. Post retention was significantly influenced by post space level (p<0.001). Significantly higher push-out strengths were recorded at the coronal third than at the middle and apical levels. The post-cement interaction was significant (p=0.002). Posts luted with S most often failed at the cement-post interface. CONCLUSIONS: When the new flowable low-stress composite was used to lute fibre posts, similar retentive strengths to those of a marketed cement from the same manufacturer were achieved. CLINICAL SIGNIFICANCE: SureFil(®) SDR™, a flowable composite originally proposed for bulk filling of posterior restorations, exhibited post retentive strengths similar to those of a cement by the same manufacturer. With a relatively high filler load, yet a low curing stress, SureFil(®) SDR™ may be adequate for both post cementation and core build-up.