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PubMed2005

An in vitro comparison of cast metal dowel retention using various luting agents and tensile loading.

STATEMENT OF PROBLEM: No clear consensus exists regarding the choice of luting agents for the retention of cast metal dowels used as a treatment alternative for endodontically treated teeth with excessive loss of coronal tooth structure. PURPOSE: The purpose of this in vitro study was to investigate the retention of the dowel/luting agent/tooth complex while applying different luting agents to cast metal dowels under vertical tensile loading. MATERIAL AND METHODS: Sixty extracted, noncarious mandibular premolars with roots of approximately 15-mm length were selected. For each tooth, a tapered root canal preparation was completed to a maximum diameter of 1.60 mm and a length of 11 mm, a common clinical configuration to accommodate cast metal dowels. Sixty cast metal dowels were fabricated for the tooth specimens and cemented with 1 of 3 luting agents (n = 20): zinc-phosphate cement (ZPC) as a control, phosphate-methacrylate resin luting agent (PMRL, Panavia F), and phosphate-methacrylate resin luting agent with metal dowel surfaces modified with a silane coating technique (PMRLS, Panavia F + Siloc). Tensile bond strength (TBS) of the specimens was measured with a universal testing machine at a crosshead speed of 0.5 mm/min. Data (kg) were statistically analyzed using a 1-way analysis of variance and a Scheffe multiple range test (alpha=.05). The homogeneity of variances was analyzed using the Levene test. RESULTS: The TBS values of ZPC (34.2 +/- 10.54 kg) were significantly higher than PMRL (22 +/- 9.57 kg) and PMRLS (21.7 +/- 7.64 kg). There was no significant difference between the PMRL and PMRLS groups. CONCLUSION: Within the limitations of this study, the use of zinc-phosphate cement provided greater TBS for cast metal dowels than the resin luting agent with and without the silane coating technique. The TBS values with and without the silane coating technique were not statistically different.

Dental Cements↗
PubMed2001

Effects of implant design and surface on bone regeneration and implant stability: an experimental study in the dog mandible.

BACKGROUND: Previous experimental studies have shown a higher degree of bone-implant contact for surface-enlarged implants compared with machined implants. Yet, there is insufficient evidence that such implants show higher stability and an increased survival rate. PURPOSE: The purpose of this investigation was to study the integration and stability of grit-blasted implants with retention elements on the implant neck, with and without marginal bone defects, compared with machined implants without retention elements. MATERIALS AND METHODS: After tooth extraction of the mandibular premolars in six dogs, two grit-blasted, partly microthreaded Astra Tech implants and one standard Brånemark implant were bilaterally placed in each dog. On one side, 3 x 3 mm large buccal defects were created, to expose three to four implant threads. The contralateral side served as control, and no defects were made. The animals were sacrificed after 4 months of healing. Implant stability was measured using resonance frequency analysis at implant installation and after 4 months of healing. Histologic and histomorphometric evaluation was made after 4 months of healing. RESULTS: Resonance frequency analysis indicated that all implants in the test and control groups were osseointegrated after 4 months, with a tendency toward higher implant stability for the Astra Tech implants. There was a statistically significant higher increase in resonance frequency for the Astra test implants compared with their corresponding controls. Histology and histomorphometry showed well-integrated implants with varying degrees of bone repair at the defect sites. The greater bone-implant contact for the Astra implants was statistically significant. No significant difference between the implants in amount of bone filling the threads was recorded. CONCLUSIONS: The Astra Tech implants tested showed a higher degree of bone-implant contact and higher level of bone regenerated at defect sites compared with the Brånemark implants. Resonance frequency analysis demonstrated a significantly higher increase in the Astra test implants compared with their control groups than did the Brånemark test implants versus their controls.

Alveolar Bone Loss↗
PubMed2005

The effect of luting agents on the retention of dental implant-supported crowns.

BACKGROUND: This study was designed to evaluate the retentive strength of 7 different luting agents on cement-retained implant abutment/analog assemblies. METHODS: Fifty-six Steri-Oss implant abutment/analog assemblies and cast superstructures were randomly divided into 7 groups: definitive cements included zinc phosphate cement, Advance, All-Bond 2, Panavia F, and Durelon, while provisional cements included Temp Bond and ImProv. After the superstructures were cemented onto the implant abutments, the specimens were subjected to 100,000 cycles on a chewing machine (75 N) and 1000 cycles on a thermocycling machine (0-55 degrees C). A universal testing machine was used to test the cement failure load values for each specimen. One-way ANOVA and Duncan's multiple-range analysis were used to determine the effects of luting agents on cement failure load values. RESULTS: The following values for the mean and standard deviation of cement failure loads for each group were obtained: zinc phosphate, 1.225 +/- 0.229 MPa; Advance, 1.205 +/- 0.197 MPa; All Bond 2, 1.752 +/- 0.211 MPa; Panavia F, 1.679 +/- 0.176 MPa; Durelon, 0.535 +/- 0.161 MPa; Temp Bond, 0.274 +/- 0.079 MPa; and ImProv, 0.319 +/- 0.107 MPa. CONCLUSIONS: There were significant differences in cement failure loads among the various cements tested. Values significantly differed among 4 groups consisting of All-Bond 2 and Panavia F resin cements, zinc phosphate cement and Advance hybrid ionomer cement, Durelon carboxylate cement, and ImProv and Temp Bond provisional cements (p < 0.0001). All-Bond 2 and Panavia F resin cements had statistically significantly higher values for cement failure loads compared to the other 5 types of cement.

Crowns↗
PubMed1998

Capsulated versus hand-mixed glass-ionomer luting cements for post retention.

OBJECTIVES: Glass-ionomer luting cements are supplied in two forms, as loose powder and liquid to be hand-mixed (HM) or pre-proportioned in a capsule to be mechanically mixed (MM). This study was to determine if post retention in pull-out tests was affected by the method of mixing the cement. METHODS: Two hundred stainless steel posts of diameter 1.75 mm were cemented within post-channels prepared in stainless steel cylinders using two hand-mixed cements FJL and KCL (Fuji I Luting Cement and Ketac-Cem Luting Cement) and two capsulated cements FJC and KCM (Fuji Cap I and Ketac-Cem Maxicap). Three groups of test specimens were prepared. In Group I each cement was mixed as recommended by the manufacturer, Group II cements were placed within a capsule and mechanically mixed and in Group III cements were removed from the capsule and mixed by hand. Specimens were stored for 1 h at 37 degrees C and 100% humidity prior to post pull-out tests at a crosshead speed of 10 mm min-1. The maximum loads at failure were subjected to Weibull analysis and Mann-Whitney tests to determine probabilities of survival and significant differences between the groups. RESULTS: Significant differences (P < 0.05) were found between all pairs of cements tested except KCM(MM) vs FJL(HM), FJL(MM) vs KCL(HM), KCL(MM), vs KCL(HM), FJC(HM) vs FJC(MM), KCL(MM) vs FJL(MM). CONCLUSIONS: The capsulated cements as supplied by the manufacturers are preferable to the equivalent hand-mixed formulations, as they give higher probabilities of survival when subjected to a given load. Both capsulated and hand-mixed formulations of Fuji had higher probabilities of survival compared to the corresponding Ketac cements. The probability of post survival can be altered by the method of mixing the cement.

Capsules↗
PubMed2006

The effect of preparation taper on the retention of cemented cast crowns under lateral fatigue loading.

STATEMENT OF PROBLEM: Clinicians have used resistance form as a basis for determining guidelines for preparation design to ensure clinical success of cemented cast restorations. Disagreement on whether clinical success follows the on-off or linear nature of resistance form continues. PURPOSE: The purpose of this study was to evaluate the number of cycles required to dislodge a cemented complete crown casting under a cyclic lateral load as a function of taper and to compare this relationship for the resistive and nonresistive ranges of taper. MATERIAL AND METHODS: Three dies were milled from stainless steel at each of the following tapers: 4, 8, 12, 16, 20, 24, 28, and 32 degrees. A gold-palladium metal-ceramic alloy crown was fabricated for each die, cemented, and subjected to lateral cyclic loading until failure or 1,000,000 cycles. The limiting taper for the dies with their given height and base was 26.6 degrees. Dies with taper less than 26.6 degrees had resistance form, whereas dies with taper larger than 26.6 degrees did not. A linear regression (alpha=.05) was used to evaluate the relation of cycles at dislodgement to taper. RESULTS: The average number of cycles to crown dislodgement or completion for each taper (SD), in units of 10,000, was as follows: 4 degrees, 100 (0); 8 degrees, 100 (0); 12 degrees, 93.54 (16.56); 16 degrees, 61.33 (38.47); 20 degrees, 25.73 (34.67); 24 degrees, 4.33 (7.36); 28 degrees, 0.06 (0.08); and 32 degrees, 0.05 (0.09). The crowns in the resistive area less than 26.6 degrees that demonstrated failure showed a linear regression with a correlation coefficient of -0.995 between the average number of cycles to dislodge the crown and the taper. The slope was significantly different from zero (P=.0048), with a value of -7.58 and a standard error of 0.53. CONCLUSION: The number of cycles required to cause crown dislodgement was linear after 12 degrees in the resistive area and nearly zero for preparations in the nonresistive area. The limiting taper concept closely predicted the transition point where the slope of the graph of cycles to dislodgement as a function of taper abruptly changed.

Cementation↗
PubMed2003

Effect of endodontic instrument taper on post retention.

The purpose of this study was to evaluate the effect of various tapers of canal preparations on the retention of posts. Ninety human central or lateral mandibular incisors were prepared by removing the clinical crown at the CEJ and instrumenting the canals with instruments of varying tapers. The groups comprising 10 teeth each were divided as follows: Taper 0.02 Ni-Ti hand files (control), Taper 0.04 ProFile Series 29, Taper 0.06 ProFile Series 29, Taper 0.08 ProFile GT Rotary, Taper 0.10 ProFile GT Rotary, Taper 0.12 ProFile GT Rotary, Taper 0.08* ProFile GT Rotary 0.08 taper with #50/.12 taper in coronal third, Taper 0.10* ProFile GT Rotary 0.10 taper with #50/.12 taper in coronal third, Taper 0.12* ProFile GT Rotary 0.12 taper with #50/.12 taper in coronal third. Canals were filled with gutta-percha and AH 26 sealer using lateral condensation. Gutta-percha was removed with a heated 5/7 plugger until a level of 5 mm of gutta-percha was left in the apical segment of the root. Post channel preparation was made to the appropriate size with minimal change in canal shape with the Premier IntegraPost drill, and the corresponding IntegraPost was cemented with 3M Vitremer cement. The roots were fixed in copper rings with mounting plaster and mounted on an Instron TT machine. The posts were subjected to gradually increasing vertical tensile force until dislodgment of the post occurred. Force (lb) required to dislodge the post was obtained for each tooth, and the average force of the groups was compared using a one-way ANOVA with Tukey's multiple comparisons. The highest resistance to dislodgment was obtained with Taper 0.04 (79.10 +/- 10.73), whereas the lowest was obtained by the Taper 0.02 (18.70 +/- 13.44). No statistical difference was found between six of the groups: Taper 0.08*, Taper 0.10, Taper 0.12*, Taper 0.10*, Taper 0.12, and Taper 0.06. Taper 0.08 was statistically inferior to Taper 0.04 but not Taper 0.02. The 0.04 taper seems to be the best taper for maximal resistance to post dislodgment.

Analysis of Variance↗
PubMed1996

Retention of metal ceramic crowns cemented with resin cements: effects of preparation taper and height.

This study investigated the effect of varying crown preparation taper and height on the retention of metal ceramic crowns cemented with resin cements. In part 1, 32 extracted molars were divided into four groups. All groups received complete-veneer crown preparations, two with a 12-degree wall angle and two with a 35-degree wall angle. Crowns were cemented with zinc phosphate and dentin-bonded resin cements. After 24 hour water storage at 37 degrees C, the crowns were separated in tension. Crowns cemented with zinc phosphate were cleaned and recemented with another dentin-bonded resin cement and after similar storage, the crowns were separated. Mean separation forces of resin-cemented crowns were higher than those of crowns cemented with zinc phosphate cement. Mean separation force of 35-degree crowns cemented with one dentin-bonded resin cement was found to be significantly higher than for the 12-degree crowns cemented with zinc phosphate cement. In part II, 32 extracted molars were divided into two groups of complete-veneer crown preparations (group I preparations were 3 mm high and group II were 5 mm high). Crowns for all teeth were cast and cemented with zinc phosphate. After 48 hours' water storage at 37 degrees C, the crowns were separated in tension. Crowns and teeth were then cleaned and each group was subdivided into 2 equal subgroups. In one subgroup of teeth with 3 mm and in one with 5 mm high preparations, the crowns were recemented with one of the two resin cement systems and the other two subgroups were recemented with the other resin cement. After 48-hour water storage, the crowns were separated. Mean separation forces of the resin-cemented crowns were greater than those of crowns cemented with zinc phosphate. Also, mean separation force of 3 mm crowns cemented with one resin cement was significantly greater than the 5 mm crowns cemented with zinc phosphate. Cohesive dentin fracture on separation was observed with some resin-cemented crowns but never with crowns cemented with zinc phosphate.

Analysis of Variance↗
PubMed2006

Effect of silica coating and silanization on flexural and composite-resin bond strengths of zirconia posts: An in vitro study.

STATEMENT OF PROBLEM: The bond strength of composite resin cores to the smooth surface of prefabricated zirconia-based ceramic posts is problematic because it might not be sufficient to ensure stability of the post-and-core system. It is also not clear whether any alteration of the post surface to provide additional mechanical or chemical retention would compromise flexural strength of the posts. PURPOSE: This study tested the effect of a tribochemical treatment on the bond strength (BS) between zirconia-based ceramic posts and composite resin and on the flexural strength (FS) of the posts. MATERIAL AND METHODS: For the BS test, 2 groups of specimens (n = 10) were prepared as follows: In the experimental (E) group, zirconia-based ceramic posts (Cosmopost), 21 mm long and 1.7 mm in diameter, were treated with a tribochemical silica coating and silanization system (Rocatec). For the control (C) group, zirconia-based ceramic posts were used as supplied by the manufacturer. For the 2 groups, posts were centered and vertically positioned in a metal mold, and composite resin (Tetric Ceram) was polymerized around the posts to form rings (6 mm diameter x 4 mm height). All specimens were positioned in a universal testing machine, and a load was applied axially on the protruding heads of posts in a shear push-out mode test until bond failure (MPa). Fracture mode was assessed as cohesive, cohesive/adhesive, or adhesive. Following this, the FS of the posts was measured in MPa using a 3-point bending test. Data were recorded and statistically analyzed using the Student t test for both tests (alpha = .01). RESULTS: Mean fracture load values +/- SDs for the BS test were 28.1 +/- 2.3 MPa and 8.9 +/- 3.97 MPa for the E and C groups, respectively. The mean FS values were 1544.9 +/- 214.1 MPa and 844.8 +/- 50.8 MPa for the E and C groups, respectively. The tribochemically treated posts exhibited significantly higher values for both bond strength to composite resin and resistance to fracture when compared to posts in the control group (P < .001). Fracture analysis showed 100% cohesive/adhesive fractures for group E specimens and 100% adhesive fractures for group C specimens. CONCLUSIONS: The use of a tribochemical silica coating process and silanization on zirconia-based ceramic posts increased both the bond strength to composite resin as well as the fracture strength of posts.

Adhesiveness↗
PubMed1992

[Repair of residual cleft palates in older adult patients].

Residual cleft palates in adult patients are hard to repair. A prosthesis may cause patients to complain of loss of fluid through the nose when they drink. Furthermore, there may be problems with the retention of the prosthesis. In sixteen adult patients the residual cleft palate was successfully closed. In three patients a second surgical procedure was required.

Adult↗
PubMed2005

Effect of surface treatment of titanium posts on the tensile bond strength.

OBJECTIVES: Retention of composite resins to metal can be improved when metal surfaces are conditioned. The purpose of this investigation was to investigate the effect of two conditioning treatments on the tensile bond strength of four resin-based luting cements and zinc phosphate cement to titanium posts. METHODS: The effect on tensile bond strength of (1) air-particle abrasion (50 microm Al2O3) and (2) silica coating (30 microm SiO(x)) and silanization of tapered titanium posts prior to luting with any of the four resin composite luting cements (Compolute) Aplicap, Flexi-Flow cemTM, Panavia 21 EX, Twinlook) were evaluated. The posts luted with zinc phosphate cement (Tenet) were considered as the control group. Following endodontic preparation of 100 intact anterior human teeth with hand instruments, the post spaces were prepared using the opening drills of the corresponding size of the posts. All posts were cemented into the roots according to the manufacturer's instructions of each cement. The specimens were first stored in water at 37 degrees C for 24 h and then subjected to thermocycling (5000 cycles, 5-55 degrees C, 30 s). The tensile strength values were measured on a universal testing machine at a cross-head speed of 0.5 mm/min. Data were analyzed statistically using ANOVA and corrected with Scheffé-test due to the significance levels (P<0.05). RESULTS AND SIGNIFICANCE: The composite resin luting cements did not show significant differences (P<0.05) showing values between (352+/-76N-475+/-104N) when the posts were air-abraded. After silica coating and silanization, significantly higher (P<0.05) tensile strengths were obtained for Compolute Aplicap (600+/-123N) than those of the other luting cements (Flexi-Flow cemTM: 191+/-62N; Panavia 21 EX: 375+/-77; Twinlook: 430+/-78N). No significant differences (P>0.05) were found between the tensile strength of the posts luted with zinc phosphate (414+/-102N) and the resin composite cements. Silica coating and silanization revealed the highest tensile bond strength in posts luted with Compolute Aplicap but it was not effective for the other experimental groups. Zinc phosphate cement exhibited tensile bond strength as good as resin composite cements.

Air Abrasion, Dental↗
PubMed2004

Natural frequency assessment of stability of root keeper magnetic devices.

The aim of the study was to evaluate the potential for using natural frequency (NF) as an indicator for assessing the stability of a magnetic keeper device used in prosthodontic treatment. A three-dimensional finite element (FE) model of a root keeper-cement-dentine system was established for NF analysis. The model was first validated against a series of in vitro experiments. Then, NF values of the first vibrational mode of the FE model with various boundary conditions were calculated. The in vitro results showed that the measured NF values of the root keeper-incisor units decreased significantly (p<0.01) from 9.07 +/- 0.37 to 5.73 +/- 0.10 kHz when the units were embedded in simulated bony tissue. Results obtained from FE simulations demonstrated that the root keeper would fully loosen when the constant values of the spring elements were lower than 10(4) N-m(-1). Furthermore, a linear increase in the NF values of the model was observed from 6.16 to 15.52 kHz, when the constant was increased from 10(4) to 10(7) N-m(-1), and the values then reached a plateau. The results indicate that the NF value of a root keeper has the potential to be used for monitoring the stability of such a device.

Biomechanical Phenomena↗
PubMed2006

Biomechanical consequences of progressive marginal bone loss around oral implants: a finite element stress analysis.

The purpose of this study was to explore the biomechanical effects of progressive marginal bone loss in the peri-implant bone. Finite element model of a Ø 4.1 x 10 mm Straumann dental implant and a solid abutment was constructed as predefined eight-layers around the implant neck. The implant-abutment complex was embedded in a cylindrical bone model to analyze bone biomechanics regardless of anatomical influences. Angular and circular progressive marginal bone loss was simulated by sequential removal of each layer, resulting crater-like defects and a total of ten finite element models for analysis. Each model was subjected to a vertical and oblique static load of 100 N in separate load cases. Principal stress minimum and maximum, displacement, and equivalent of elastic strain outcomes were compared. Under vertical loading, principal stresses minimum and maximum decreased remarkably as with the increase in bone resorption. Under oblique load simulations, decrease in principal stress maximum and minimum was evident. With progressive bone loss and under oblique load simulations, displacement and equivalent of elastic strain increased considerably in trabecular bone contacting the implant neck. The presence of cortical bone contacting a load-carrying implant, even in a bone defect, improves the biomechanical performance of implants in comparison with only trabecular bone support as a sequel of progressive marginal bone loss.

Biomechanical Phenomena↗
PubMed1990

Dental implant abutment resembling the two-phase tooth mobility.

Natural teeth and dental implants have differing degrees of mobility thus causing a potential biomechanical problem when connected by fixed bridgework. The clinical follow-up often discloses marginal bone loss around an implant neck probably due to high stress factors. An implant with a built-in compliance resembling the tooth mobility could be advantageous for stress distribution. With axial loading the proposed 'elastic'-test model accomplishes this demand. By means of theoretical and experimental studies this 'elastic'-test model is optimized and compared with a stiff implant-model. The results show a 20 times reduction of stress accumulation in bone with the 'elastic'-test model.

Biocompatible Materials↗
PubMed1985

Acrylic resin stents for marsupialization.

Marsupialization is a surgical technique that may be preferred to enucleation in treatment of benign cysts. The acrylic resin obturator maintains the surgical opening during healing and assures success of the surgery. Two basic techniques to construct a stable and retentive obturator prosthesis were described.

Acrylic Resins↗
PubMed1993

Assessment of oral implant mobility.

Most of the implant literature suggests that successful dental implants are immobile and any detected mobility indicates implant failure. This study evaluated the ability of the Periotest instrument to measure implant mobility in a controlled in vitro model with a sample of 56 in vivo implants. In the in vitro portion of the study, implant model mobility was determined by an axial testing machine (0 to 5 N at 0.2 mm/minute) and the Periotest instrument. The comparison showed a high level of correlation (Pearson's r 0.984). The load that the Periotest placed on the implants during mobility measurements was approximately 5 N, depending on the compliance of the test object. The in vivo portion evaluated the range of mobility of 56 clinically successful endosseous implants. The range of mobility as determined by the Periotest instrument was -6 to +2. This range corresponds to an in vitro model displacement (5 N load) of 0.038 mm to 0.113 mm with a mean of 0.066 mm +/- 0.018 mm (SD). These data demonstrate that clinically successful implants are not immobile, but have a range of mobility.

Analysis of Variance↗
PubMed1994

Comparison of tensile and peel bond strengths of resilient liners.

Previous studies have shown little agreement between the test methods used to assess the bond strength and the mode of failure of resilient liners. This study evaluated the bond strength characteristics of resilient liners by means of 180-degree peeling and butt tensile strength testing. Seventy-two specimens were divided into peel bond and tensile bond specimen groups and were then subdivided into four test groups to evaluate each resilient liner. Tests were conducted with an Instron universal testing machine at a cross-head speed of 2 mm/minute for the tensile specimens and 5 mm/min for the peel specimens. Tensile bond strength and peel bond strength varied significantly among resilient liners except between Novus and Palasiv-62 liners in tensile testing. The mode of failure of Molloplast-B and Novus liners was significantly different between the tensile bond and peel bond test methods. It was concluded that bond strength characteristics can vary according to the test method used.

Acrylic Resins↗
PubMed1994

Investigation of stiffness and microstructure of joints soldered with gas-oxygen torch and infrared methods.

The stiffness of soldered connectors fabricated with the gas-oxygen torch technique was compared with those fabricated with the infrared technique. Untreated solder materials were used as controls. Untreated solder materials of gold-palladium, palladium-silver, and chromium-cobalt alloys exhibited significantly higher stiffness than the soldered specimens fabricated with either method. There was no significant difference between the gas-oxygen torch and the infrared groups of the gold-palladium and palladium-silver alloys. Photomicrographs revealed that the soldered specimens displayed porosities. For the chromium-cobalt alloy, the infrared group demonstrated significantly higher stiffness than the gas-oxygen torch group. Photomicrographs also disclosed that the chromium-cobalt alloy soldered with the gas-oxygen torch technique had a significant heat-affected zone.

Analysis of Variance↗