Tensile Strength of Glass Fiber Posts Submitted to Different Surface Treatments

The aim of this in vitro study was to evaluate the tensile strength of glass fiber posts submitted to different surface treatments. Forty-eight maxillary canines had their crowns sectioned and root canals endodontically treated. The roots were embedded in acrylic resin and distributed into 3 groups according to the surface treatment: Group I: the posts were treated with silane agent for 30 s and adhesive; Group II: the posts were cleaned with alcohol before treatment with silane agent and adhesive; Group III: the posts were submitted to conditioning with 37% phosphoric acid for 30 s before treatment with silane agent and adhesive. Each group was divided into 2 subgroups for adhesive polymerization or not before insertion into the canal: A - adhesive was not light cured and B - adhesive was light cured. All posts were cemented with Panavia F and the samples were subjected to tensile strength test in a universal testing machine at crosshead speed of 1 mm/min. Data were submitted to one-way ANOVA and Tukey's test at 5% significance level. There was statistically significant difference (p<0.01) only between group GIII-B and groups GI-A and GI-B. No significant difference was found among the other groups (p>0.05). It was concluded that the products used for cleaning the posts influenced the retention regardless of adhesive light curing.

O objetivo deste estudo in vitro foi avaliar a resistência à tração de pinos de fibra de vidro submetidos a diferentes tratamentos de superfície. Quarenta e oito caninos superiores tiveram suas coroas seccionadas e as raízes tratadas endodonticamente. As raízes foram incluídas em resina acrílica e distribuídas em 3 grupos de acordo com o tratamento de superfície aplicado aos pinos: Grupo I: os pinos receberam agente silano por 30 s e adesivo; Grupo II: os pinos foram limpos com álcool e então receberam o agente silano e adesivo; Grupo III: os pinos foram submetidos ao condicionamento com ácido fosfórico a 37% por 30 s, seguido de agente silano e adesivo. Cada grupo foi dividido em 2 subgrupos de acordo com fotoativação do adesivo antes da inserção do pino no interior do canal: A – adesivo não foi fotoativado, B: o adesivo foi fotoativado. Todos os pinos foram cimentados com Panavia F e as amostras foram submetidas a teste de tração utilizando máquina universal de ensaios, com velocidade de 1 mm/min. Os dados obtidos foram submetidos à ANOVA a um critério e ao teste de Tukey com nível de significância de 5%. Houve diferença estatisticamente significante (p<0,01) entre o grupo GIII-B e os grupos GI-A e GI-B. Os demais grupos não apresentaram diferenças significantes entre si (p>0,05). Pode-se concluir que as substâncias utilizadas para a limpeza dos pinos interferiram em sua retenção, independente da fotopolimerização do adesivo.

Tensile strength of glass fiber posts submitted to different surface treatments.

The aim of this in vitro study was to evaluate the tensile strength of glass fiber posts submitted to different surface treatments. Forty-eight maxillary canines had their crowns sectioned and root canals endodontically treated. The roots were embedded in acrylic resin and distributed into 3 groups according to the surface treatment: Group I: the posts were treated with silane agent for 30 s and adhesive; Group II: the posts were cleaned with alcohol before treatment with silane agent and adhesive; Group III: the posts were submitted to conditioning with 37% phosphoric acid for 30 s before treatment with silane agent and adhesive. Each group was divided into 2 subgroups for adhesive polymerization or not before insertion into the canal: A - adhesive was not light cured and B - adhesive was light cured. All posts were cemented with Panavia F and the samples were subjected to tensile strength test in a universal testing machine at crosshead speed of 1 mm/min. Data were submitted to one-way ANOVA and Tukey's test at 5% significance level. There was statistically significant difference (p<0.01) only between group GIII-B and groups GI-A and GI-B. No significant difference was found among the other groups (p>0.05). It was concluded that the products used for cleaning the posts influenced the retention regardless of adhesive light curing.

Effect of different restorative procedures on the fracture resistance of teeth submitted to internal bleaching.

The aim of this study was to evaluate the influence of different restorative procedures on the fracture resistance of endodontically treated teeth submitted to intracoronal bleaching. Fifty upper central incisors were distributed into 5 groups: GI - healthy teeth; GII - endodontically treated teeth sealed with Coltosol; GIII - endodontically treated teeth bleached and sealed with Coltosol; GIV - endodontically treated teeth bleached and restored with composite resin; and GV - endodontically treated teeth bleached and restored with a fiberglass post and composite resin. In the bleached specimens, a cervical seal was made prior to bleaching with 38% hydrogen peroxide. The gel was applied on the buccal surface and in the pulp chamber, and was then light-activated for 45 s. This procedure was repeated three times per session for four sessions, and each group was submitted to the restorative procedures described above. The specimens were submitted to fracture resistance testing in a universal testing machine. There were statistically significant differences among the groups (p < 0.05). The mean value found for GIII was the lowest (0.32 kN) and was significantly different from the values found for GI (0.75 kN), GII (0.67 kN), GIV (0.70 kN), and GV (0.72 kN), which were not significantly different from each other (p > 0.05). The restorative procedures using composite resin were found to successfully restore the fracture resistance of endodontically treated and bleached teeth.

Effect of different restorative procedures on the fracture resistance of teeth submitted to internal bleaching

The aim of this study was to evaluate the influence of different restorative procedures on the fracture resistance of endodontically treated teeth submitted to intracoronal bleaching. Fifty upper central incisors were distributed into 5 groups: GI - healthy teeth; GII - endodontically treated teeth sealed with Coltosol; GIII - endodontically treated teeth bleached and sealed with Coltosol; GIV - endodontically treated teeth bleached and restored with composite resin; and GV - endodontically treated teeth bleached and restored with a fiberglass post and composite resin. In the bleached specimens, a cervical seal was made prior to bleaching with 38% hydrogen peroxide. The gel was applied on the buccal surface and in the pulp chamber, and was then light-activated for 45 s. This procedure was repeated three times per session for four sessions, and each group was submitted to the restorative procedures described above. The specimens were submitted to fracture resistance testing in a universal testing machine. There were statistically significant differences among the groups (p < 0.05). The mean value found for GIII was the lowest (0.32 kN) and was significantly different from the values found for GI (0.75 kN), GII (0.67 kN), GIV (0.70 kN), and GV (0.72 kN), which were not significantly different from each other (p > 0.05). The restorative procedures using composite resin were found to successfully restore the fracture resistance of endodontically treated and bleached teeth.

In vitro fracture resistance of glass-fiber and cast metal posts with different designs / Resistência à fratura de pinos de fibra de vidro e metálicos fundidos com diferentes configurações

PURPOSE: To evaluate the in vitro fracture resistance of roots with glass-fiber and metal dowels with different designs. METHODS: Fifty-endodontically treated maxillary central incisors were embedded in acrylic resin. Ten of them received only the coronary preparation, and the remaining forty were embedded (except for 4mm of the cervical area) after removing the clinical crowns. Specimens were divided into five groups (n=10): control (teeth with only coronary preparation), cylindrical cast dowel, conical cast dowel, cylindrical glass-fiber dowel and conical glass-fiber dowel. Specimens were subjected to an increasing compressive load (N) until fracture. RESULTS: ANOVA indicated significant difference (P<.05) among the groups, and the Tukey-Kramer´s test identified these differences. The control group (867±243 N) presented the highest values and was statistically similar to cylindrical glass-fiber dowel group (711±180 N). There is no significant difference among the metal dowel cylindrical (435±245 N) or conical (585±164 N) group and conical glass-fiber dowel (453±112 N). Cylindrical glass-fiber dowel (711±180 N) and conical cast dowel and core (585±164 N) groups had intermediate values and did not differ from each other. CONCLUSIONS: Cylindrical glass fiber dowels represent a viable alternative to the cast-metal dowel cylindrical or conical. Cylindrical glass fiber dowels also increase endodontically treated incisors' resistance to fracture.

OBJETIVO: Avaliou-se in vitro a resistência à fratura de raízes com pinos metálicos fundidos e de fibra de vidro, variando sua configuração geométrica. METODOLOGIA: Cinquenta incisivos centrais superiores tratados endodonticamente foram incluídos em resina acrílica. Dez receberam apenas preparo coronário (controle) e quarenta tiveram coroas seccionadas e raízes incluídas em resina (deixando 4 mm cervicais). Distribuiu-se os espécimes em 5 grupos: controle, pino metálico cilíndrico, metálico cônico, pino de fibra de vidro cilíndrico e cônico. Submeteram-se os corpos-de-prova a ensaio de compressão, até ocorrer a fratura. RESULTADOS: A ANOVA indicou diferença significante entre os grupos (P<.05) e no teste de Tukey-Kramer´s o controle (867±243 N) apresentou os maiores valores de resistência à fratura, sendo similar ao grupo do pino de fibra cilíndrico (711±180 N). Não houve diferença significante entre os pinos metálicos cilíndricos (435±245 N) ou cônicos (585±164 N) e os de fibra cônicos (453±112 N). Os grupos dos pinos de fibra cilíndricos (711±180 N) e pinos metálicos cônicos (585±164 N) apresentaram valores intermediários e não foram diferentes entre si. CONCLUSÃO: Pinos de fibra de vidro são uma alternativa viável ao pino metálico fundido cilíndrico e cônico. Os pinos de fibra cilíndricos aumentaram a resistência à fratura dos incisivos tratados endodonticamente.

Effect of eugenol-based endodontic sealer on the adhesion of intraradicular posts cemented after different periods.

OBJECTIVE: This study evaluated in vitro the influence of an eugenol-based sealer (EndoFill) on the retention of stainless steel prefabricated posts cemented with zinc phosphate and resin-based (Panavia F) cements after different periods of root canal obturation, using the pull-out test. MATERIAL AND METHODS: Sixty upper canines were decoronated and the roots were embedded in resin blocks. The specimens were distributed into 3 groups, according to the period elapsed between canal obturation and post cementation: Group I - immediately; Group II - 72 h and Group III - 4 months. The groups were subdivided according to the type of cement used for post cementation: A - zinc phosphate and B - Panavia F. Following the experimental periods, specimens were subjected to pullout test in an Instron machine with application of tensile force at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal were recorded (kN) and means were subjected to statistical analysis by 2-way ANOVA and Tukey-Kramer test (alpha=0.001) RESULTS: There were statistically significant differences (p<0.01) between the posts cemented with zinc phosphate cement (0.2112 kN) and Panavia F (0.0501 kN). However, no statistically significant differences (p>0.05) were found between the three post cementation periods, regardless of the cement. CONCLUSIONS: It was concluded that the eugenol-based sealer influenced the tensile strength of the posts cemented with the resin cement, but had no influence on the time waited between root canal obturation and post space preparation/post cementation.

Effect of eugenol-based endodontic sealer on the adhesion of intraradicular posts cemented after different periods

OBJECTIVE: This study evaluated in vitro the influence of an eugenol-based sealer (EndoFill) on the retention of stainless steel prefabricated posts cemented with zinc phosphate and resin-based (Panavia F) cements after different periods of root canal obturation, using the pull-out test. MATERIAL AND METHODS: Sixty upper canines were decoronated and the roots were embedded in resin blocks. The specimens were distributed into 3 groups, according to the period elapsed between canal obturation and post cementation: Group I - immediately; Group II - 72 h and Group III - 4 months. The groups were subdivided according to the type of cement used for post cementation: A - zinc phosphate and B - Panavia F. Following the experimental periods, specimens were subjected to pullout test in an Instron machine with application of tensile force at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal were recorded (kN) and means were subjected to statistical analysis by 2-way ANOVA and Tukey-Kramer test (á=0.001) RESULTS: There were statistically significant differences (p<0.01) between the posts cemented with zinc phosphate cement (0.2112 kN) and Panavia F (0.0501 kN). However, no statistically significant differences (p>0.05) were found between the three post cementation periods, regardless of the cement. CONCLUSIONS: It was concluded that the eugenol-based sealer influenced the tensile strength of the posts cemented with the resin cement, but had no influence on the time waited between root canal obturation and post space preparation/post cementation.

Comparative study of the effect of ultrasound on the removal of intracanal posts.

This study sought to evaluate how ultrasound affected the removal of stainless steel and titanium posts that had been attached with two different resin cements. The crowns of 32 maxillary canines were removed, the roots were embedded in acrylic resin blocks, and the canals were treated endodontically. The specimens were randomly distributed into two groups (n = 16) according to the brand of cement and subdivided (n = 8) according to the type of post. The specimens were submitted to ultrasonic vibration applied perpendicularly to the long axis of the tooth for 60 seconds. Data were submitted to ANOVA and showed no significant statistical difference among the groups (p > 0.05). It may be concluded that the effects of ultrasonic vibration used to remove intraradicular posts were not significantly different when applied to stainless steel or titanium posts cemented with chemically or dual-activated resin cements.

In vitro fracture resistance of glass-fiber and cast metal posts with different lengths.

STATEMENT OF PROBLEM: Dental fractures can occur in endodontically treated teeth restored with posts. PURPOSE: The purpose of this study was to evaluate the in vitro fracture resistance of roots with glass-fiber and metal posts of different lengths. MATERIAL AND METHODS: Sixty endodontically treated maxillary canines were embedded in acrylic resin, except for 4 mm of the cervical area, after removing the clinical crowns. The post spaces were opened with a cylindrical bur at low speed attached to a surveyor, resulting in preparations with lengths of 6 mm (group 6 mm), 8 mm (group 8 mm), or 10 mm (group 10 mm). Each group was divided into 2 subgroups according to the post material: cast post and core or glass-fiber post (n=30). The posts were luted with dual-polymerizing resin cement (Panavia F). Cast posts and cores of Co-Cr (Resilient Plus) crowns were made and cemented with zinc phosphate. Specimens were subjected to increasing compressive load (N) until fracture. Data were analyzed with 2-way ANOVA and the Tukey-Kramer test (alpha =.05). RESULTS: The ANOVA analysis indicated significant differences (P<.05) among the groups, and the Tukey test revealed no significant difference among the metal posts of 6-mm length (26.5 N +/-13.4), 8-mm length (25.2 N +/-13.9), and 10-mm length (17.1 N +/-5.2). Also, in the glass-fiber post group, there was no significant difference when posts of 8-mm length (13.4 N +/-11.0) were compared with the 6-mm (6.9 N +/-4.6) and 10-mm (31.7 N +/-13.1) groups. The 10-mm-long post displayed superior fracture resistance, and the 6-mm-long post showed significantly lower mean values (P<.001). CONCLUSIONS: Within the limitations of this study, it was concluded that the glass-fiber post represents a viable alternative to the cast metal post, increasing the resistance to fracture of endodontically treated canines.

The castability of pure titanium compared with Ni-Cr and Ni-Cr-Be alloys.

STATEMENT OF PROBLEM: Titanium is the most biocompatible metal available for dental casting; however, there is great concern about its castability since this aspect of a casting metal/alloy has direct influence on the marginal fit of dental crowns. PURPOSE: The purpose of this study was to compare the castability of commercially pure titanium with 2 Ni-Cr base metal alloys. MATERIAL AND METHODS: Castability was evaluated indirectly by determining the sharpness of cast crown margins using the lost-wax technique. Castability was expressed in terms of the deficiency (mum) between an actual casting margin and a potentially perfect margin. Crown margins were recorded in a silicone impression material. The degree of marginal rounding was measured and margin length deficiencies (mum) were calculated. Sixty acrylic resin crown patterns with wax margins were prepared on a stainless steel stylized crown die having a 30-degree beveled finish line. The degree of wax margin rounding was determined in the control group (group W, n=15). The remaining 45 crown patterns were divided into 3 groups (n=15) and cast in commercially pure titanium (Tritan, group Ti), Ni-Cr-Be alloy (Verabond; group VB), and Ni-Cr alloy (Verabond II; group VBII). Margin configurations for both wax patterns and cast specimens were measured and recorded with the same method, using silicone impressions of the margins. After polymerization, the silicone material was sectioned in 8 locations through the margin area so that cross sections of the margins could be observed. Marginal deficiency was determined using microscopic measurements from the silicone sections and calculations. Data were subjected to 1-way ANOVA and Tukey HSD test (alpha=.05). RESULTS: Statistical analysis showed significant differences among the groups W, Ti, VB, and VBII (P<.001). The Tukey test revealed that Ti (108 +/-26 microm) was not significantly different from VBII (95 +/-35 microm), but was significantly different than Groups VB (22 +/-5 microm) and W (19 +/-6 microm), which were similar. CONCLUSIONS: Within the limitations of this study, the castability of titanium was poor compared to Ni-Cr-Be alloy, but similar to Ni-Cr alloy.

Effect of the use of die spacer on the marginal fit of copings cast in NiCr, NiCrBe and commercially pure titanium.

The goal of this study was to evaluate the effect of using die spacers on the marginal fit of NiCr (M1) and NiCrBe (M2) alloys and commercially pure titanium (cpTi) (M3) copings cast by the lost wax technique. Using a metal matrix, 45 resin added extra hard type IV stone models were obtained for the fabrication of wax patterns under the following conditions: no die spacer (A), with one die spacer layer (B) and with two die spacer layers (C), with five repetitions for each condition (alloy x die). Each die was waxed and the wax patterns were invested as per manufacturer's instructions. Three wax patterns were embedded in each casting ring, each corresponding to one of the conditions. Each coping, seated to the metal matrix by a seating pressure standardizing device (SPSD), was taken to an optical microscope for measurement of marginal discrepancy. The obtained data (microm) were analyzed statistically by ANOVA and Tukey' test (a=5%). There was statistically significant difference (p<0.05) among the materials (M1=110.67; M2=130.33 and M3=148.33). Regarding the use of the die spacer, there was a statistically significant difference (p<0.05) among the three conditions (A=162.00; B=131.06 and C=96.67). It was concluded that there is less marginal discrepancy with two die spacer layers.

Effect of the use of die spacer on the marginal fit of copings cast in NiCr, NiCrBe and commercially pure titanium

The goal of this study was to evaluate the effect of using die spacers on the marginal fit of NiCr (M1) and NiCrBe (M2) alloys and commercially pure titanium (cpTi) (M3) copings cast by the lost wax technique. Using a metal matrix, 45 resin added extra hard type IV stone models were obtained for the fabrication of wax patterns under the following conditions: no die spacer (A), with one die spacer layer (B) and with two die spacer layers (C), with five repetitions for each condition (alloy x die). Each die was waxed and the wax patterns were invested as per manufacturer's instructions. Three wax patterns were embedded in each casting ring, each corresponding to one of the conditions. Each coping, seated to the metal matrix by a seating pressure standardizing device (SPSD), was taken to an optical microscope for measurement of marginal discrepancy. The obtained data (µm) were analyzed statistically by ANOVA and Tukey' test (a=5 percent). There was statistically significant difference (p<0.05) among the materials (M1=110.67; M2=130.33 and M3=148.33). Regarding the use of the die spacer, there was a statistically significant difference (p<0.05) among the three conditions (A=162.00; B=131.06 and C=96.67). It was concluded that there is less marginal discrepancy with two die spacer layers.

O objetivo deste trabalho foi avaliar o efeito do uso de espaçadores na adaptação marginal de "copings" de ligas de NiCr (M1) e NiCrBe (M2) e titânio (M3) fundidos pela técnica de cera perdida. A partir de uma matriz metálica, foram obtidos 45 troquéis de gesso resinado tipo IV para confecção dos padrões de cera nas seguintes condições: sem a presença de espaçador (A), com uma camada de espaçador (B) e com duas camadas de espaçador (C), com cinco repetições para cada condição (liga x espaçador). Foi realizado o enceramento de cada troquel e os padrões de cera foram incluídos no revestimento indicado pelo fabricante. Em cada anel de fundição foram incluídos 3 padrões de cera, sendo cada um correspondente a cada condição. Cada "coping", adaptado à matriz metálica por meio de um dispositivo padronizador da pressão de assentamento, foi levado ao microscópio óptico para aferição das medidas da desadaptação marginal. Os dados obtidos (µm) foram submetidos à análise estatística por ANOVA e teste de Tukey (a=5 por cento). Entre os materiais houve diferença estatisticamente significante (M1=110,67, M2=130,33 e M3=148,33). Em relação ao fator espaçador, houve diferença estatisticamente significante entre as três condições (A=162,00; B=131,06 e C=96,67). Conclui-se que a presença de duas camadas de espaçador propicia menor desadaptação marginal.

Fracture resistance of weakened roots restored with a transilluminating post and adhesive restorative materials.

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.

Effect of eugenol-based endodontic cement on the adhesion of intraradicular posts.

The present study evaluated, in vitro, the influence of an eugenol-based endodontic sealer (EndoFill) on the adhesion of intra-radicular posts cemented with a resin-based cement (Enforce) ou a zinc phosphate cement. Twenty-four single-rooted maxillary canines were divided into 2 groups (n=12) and obturated with either gutta-percha points plus EndoFill or gutta-percha points alone (no cement). In each group, half of intracanal posts (n=6) were cemented with Enforce resin-based cement and half with zinc phosphate cement. Specimens were submitted to pull-out test in an Instron machine and tensile force was applied at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal was recorded (N) and means were submitted to statistical analysis by Kruskal-Wallis test (p<0.01). Posts cemented with zinc phosphate cement were significantly more retentive (353.4 N) than those cemented with Enforce (134.9 N) (p<0.01). Regarding the influence of the eugenol-based cement (EndoFill) on post retention, there was statistically significant difference (p<0.01) only between the groups cemented with Enforce, i.e., in the canals filled with EndoFill + guta-percha there was lower bond strength than in the canals filled with gutta-percha points alone (101.5 and 168.2 N, respectively). In conclusion, the zinc-phosphate-based cement showed greater post retention than the resin-based cement. The findings of this study suggest that the eugenol-containing sealer interfered with the adhesive properties of the resin-based cement.

Removal resistance of glass-fiber and metallic cast posts with different lengths.

This study evaluated the strength required to remove glass-fiber and metallic cast posts with different lengths. Sixty endodontically treated canines were included and their roots were embedded in acrylic resin after discarding the crowns. Samples were randomly assigned to 3 groups according to the post length (n = 20): I- 6 mm, II - 8 mm and III- 10 mm. Each group was divided into 2 subgroups based on the post material (n = 10): A- glass fiber or B- metallic cast. Post-space was prepared with Fibrekor Post Kit attached to a parallelometer. In subgroup A, prefabricated glass fiber posts from Fibrekor Post Kit were utilized. In metallic post group (subgroup B), an impression of post space was obtained, followed by casting. All posts were luted with Panavia F cement. A universal testing machine determined the force required to dislodge each post. ANOVA analysis indicated significant differences (P < 0.01) among post length. Tukey test showed that posts with 10 mm-length showed higher resistance on removal than posts with 6 mm-length. Posts with 8 mm-length did not exhibit difference when compared to 6 and 10 mm posts. No significant differences (P > 0.05) were observed between the tested post materials. It was concluded that the type of post did not influence the removal resistance and that posts with 10 mm-length required greater force to be dislodged.

Influence of investment type and sprue number on the casting accuracy of titanium crown margins.

STATEMENT OF PROBLEM: Titanium offers biocompatibility and adequate mechanical properties for fabricating dental prostheses; however, casting difficulties can compromise the accuracy of titanium crown margins. PURPOSE: The aim of this study was to evaluate the influence of investment type and number of sprues on accuracy of crown castings made with commercially pure titanium. MATERIAL AND METHODS: The casting accuracy was evaluated indirectly by determining the deficiency of titanium crown margins cast using the lost-wax technique. Crown margins were recorded in a silicone impression material. The degree of marginal rounding was measured and margin deficiencies were calculated. Seventy-five acrylic resin crown patterns with wax margins were prepared on a stainless steel stylized crown die having a 30-degree beveled finish line. Fifteen patterns were selected for the control group, and the degree of wax margin rounding was determined (group W, control). The remaining 60 were divided into 4 groups of 15 each, and cast using 2 different titanium investments: a monoammonium dihydrogenphosphate-bonded investment (Rematitan Plus; groups PI and PII), and a magnesium oxide-bonded investment (Rematitan Ultra; groups UI and UII). Each pattern was cast with either 1 (groups PI and UI) or 2 (groups PII and UII) sprues. Margin configurations for both wax pattern and cast specimens were measured and recorded with the same method, using silicone impressions of the margins. After polymerization, the silicone material was sectioned precisely in 8 locations through the margin area so that cross-sections of the margins could be observed. Marginal deficiency was determined using microscopic measurements from the silicone patterns and calculations. Data were subjected to 2-way analysis of variance (alpha=.05). RESULTS: Specimens from group W presented a mean marginal deficiency of 19 +/- 6 microm. The analysis of variance indicated a significant difference for the main factors, investment (P<.01) (P=91 +/- 28 microm and U=78 +/- 17 microm) and sprue number (P<.001) (I=97 +/- 23 microm and II=72 +/- 16 microm), as well as for interaction (P<.05) (PI=109 +/- 25 microm; PII=73 +/- 17 microm; UI=85 +/- 15 microm; and UII=71 +/- 16 microm). CONCLUSION: Within the limitations of this study, investment U provided better casting accuracy than investment P. Two sprues provided more accurate results than 1 sprue; however, this effect was more notable for investment P, as it produced similar results between groups PII and UII.

Effect of eugenol-based endodontic cement on the adhesion of intraradicular posts

No presente estudo avaliou-se, in vitro, a influência do cimento endodôntico à base de óxido de zinco e eugenol (EndoFill) na adesão de pinos intra-radiculares cimentados com cimento resinoso (Enforce) ou cimento fosfato de zinco. Vinte e quatro caninos superiores uniradiculares foram distribuídos em dois grupos e obturados com cimento a base de oxido de zinco e eugenol + cones de guta-percha ou somente cones de guta-percha (sem cimento). Em metade dos espécimes em cada grupo (n=6), os pinos intra-radiculares foram cimentados com cimento resinoso Enforce e na outra metade com cimento de fosfato de zinco. Os espécimes foram submetidos a ensaios de resistência à tração numa máquina Instron 4444, sendo os valores de força máxima necessária ao desprendimento dos retentores registrados e submetidos à análise estatística pelo teste de Kruskal-Wallis (p<0,01). Os pinos cimentos com cimento fosfato de zinco apresentaram valor médio de resistência à tração superior (353,4 N) ao dos pinos cimentados com Enforce (134,9 N). Em relação à influência do cimento à base de eugenol na retenção dos pinos intra-radiculares, houve diferença significante (p<0,01) somente entre os grupos cimentados com Enforce, sendo que nos canais obturados com EndoFill + guta-percha houve menor resistência à tração que nos canais obturados apenas com guta-percha (respectivamente 101,5 e 168,2 N). Conclui-se que o cimento à base de fosfato de zinco apresentou maior retenção que o cimento resinoso Enforce e que o cimento obturador contendo eugenol (EndoFill) somente afetou as propriedades adesivas do cimento resinoso.

Effect of the diameter on Cu-Al post retention.

This study compared the resistance to removal by traction of abraded cylindrical metal cast posts of Cu-Al (Goldent-LA). The posts had constant length (9 mm) and three different diameters (0.9, 1.3 and 1.7 mm), and were cemented with zinc phosphate cement. The crowns of 36 sound maxillary canines were sectioned, the roots were immersed in resin blocks and the root canals were endodontically treated. The teeth were divided into three groups to be prepared and standardized with the use of a parallelometer with the following burs: Group 1 Largo n. 2; Group 2--Largo n. 4; Group 3--Largo n. 6. The posts were molded with chemically activated resin and after casting they were abraded and their dimensions were confirmed with a digital caliper. After cementation of the posts in the prepared root canals, the samples were kept at 37 degrees C in distilled water for 7 days and subsequently submitted to the traction test in a universal testing machine (Instron 4444). The results showed no statistical difference between the groups. Diameter variation (0.9 mm, 1.3 mm and 1.7 mm) in abraded cylindrical posts cemented with zinc phosphate did not affect resistance to removal.

Análise da eficiência do ultra-som, com e sem refrigeração ar/água, na remoção de pinos fundidos com variação do comprimento e do diâmetro / Analysis of the efficacy of ultrasound with and without air/water cooling in removing cast posts varying in length and diameter

O objetivo deste estudo foi avaliar a eficiência do ultra-som, com e sem refrigeração, na remoção de pinos fundidos com diferentes comprimentos e diâmetros, por meio do teste de tração. 108 caninos foram seccionados a 13mm do ápice radicular e, após tratamento endodôntico, as raízes foram incluídas em resina. Os corpos-de-prova foram divididos em dois grupos: GrupoI- condutos preparados com broca de largo n. 06 e subdivididos segundo o comprimento dos pinos: Ia- 9mm, Ib- 7mm e Ic- 5mm; GrupoII- condutos preparados com broca de Largo de 9mm de comprimento e subdivididos segundo o diâmetro da broca: IIa- 0,9mm, IIc- 1,7mm. Os condutos foram moldados e, após fundição, os pinos foram cimentados com cimento resinoso Panavia F. Cada subgrupo foi subdividido em dois, onde um recebeu aplicação de vibração ultra-sônica sem refrigeração e o outro com refrigeração. Os corpos-de-prova foram submetidos ao teste de tração na máquina de ensaios Instron 4444 e a análise estatística evidenciou diferença significante entre os comprimentos testados (p<0,01) e na utilização do ultra-som com e sem refrigeração (p<0,05). Em relação ao diâmetro, não houve diferença significante (p>0,05) e, quanto à refrigeração, houve diferença significante (p<0,01). Concluiu-se que os pinos de maior comprimento necessitaram de maior força para sua remoção, enquanto que o diâmetro não influenciou na força necessária para a sua remoção. A utilização do ultra-som sem refrigeração foi mais eficiente na remoção de pinos

Effect of the diameter on Cu-Al post retention

Este estudo in vitro comparou a resistência à remoção por tração de núcleos metálicos fundidos em liga de Cu-Al (Goldent-LA) cilíndricos, jateados, de comprimento constante igual a 9 mm, cimentados com cimento de fosfato de zinco e com três diferentes diâmetros: 0,9 mm, 1,3 mm e 1,7 mm. Trinta e seis caninos superiores hígidos tiveram suas coroas seccionadas, sendo as raízes incluídas em blocos de resina acrílica, e os canais, tratados endodonticamente. Os dentes foram divididos em três grupos para serem preparados e padronizados com o auxílio de um paralelômetro com as seguintes brocas: Grupo 1 - Largo nº 2; Grupo 2 - Largo nº 4; Grupo 3 - Largo nº 6. Os núcleos foram moldados com resina acrílica ativada quimicamente e, após a fundição, foram jateados e tiveram as suas dimensões conferidas com um paquímetro digital. Após a cimentação, os corpos-de-prova foram armazenados em água destilada durante 7 dias, em estufa a 37ºC e, posteriormente, submetidos a teste de tração em uma máquina universal de ensaios Instron 4444. Com a análise estatística dos resultados, pôde-se concluir que não houve diferença estatisticamente significante entre os grupos testados. A variação do diâmetro em núcleos cilíndricos jateados cimentados com fosfato de zinco não afetou a resistência à remoção.