The effect of post material on the characteristic strength of fatigued endodontically treated teeth.

STATEMENT OF PROBLEM: The biomechanical properties of post systems may become more important as the amount of remaining tooth structure decreases, thus different materials may influence the characteristic strength of fatigued endodontically treated teeth. PURPOSE: The purpose of this study was to assess the characteristic strength and probability of survival of endodontically treated teeth restored with different intraradicular post systems. MATERIAL AND METHODS: Forty human maxillary canines with similar root lengths were randomly divided into 4 groups (n=10): cast post and core, stainless-steel prefabricated post, carbon-fiber post, and glass-fiber post. Cores and metallic crowns were fabricated for all specimens. Restored teeth were exposed to mechanical fatigue (250,000 cycles) in a controlled chewing simulator. Each intact specimen was mounted in a special device and aligned at a 45-degree angle to the long axis of the tooth. A universal testing machine was used to apply a static load at a crosshead speed of 0.5 mm/min until specimen failure. The maximum value was recorded in newtons (N). Probability Weibull curves (2-sided 90% confidence bounds) were calculated for each group, and a probability of survival as a function of load at failure was plotted for the groups. RESULTS: A significantly higher characteristic strength was observed for groups carbon-fiber post (755.82 N) and cast post and core (750.6 N) (P<.05) compared with glass-fiber post (461.35 N) and stainless-steel prefabricated post (524.78 N) groups. All the roots in the cast post and core group demonstrated catastrophic fracture, whereas the remaining groups had no root fractures. CONCLUSIONS: Prefabricated posts made of glass fiber and stainless steel showed significantly lower characteristic strength and probability of survival than cast post and core, whereas crowns with carbon-fiber posts presented a single load similar to the fracture values of cast posts.

The influence of different cements on the pull-out bond strength of fiber posts.

STATEMENT OF PROBLEM: Glass fiber posts are commonly used to provide adequate support and retention for the restoration of endodontically treated teeth, but their resistance to dislodgement depends on their adhesion to root dentin. PURPOSE: The purpose of this study was to assess the effect of cement type on the pull-out bond strength of fiber posts. MATERIAL AND METHODS: Seventy maxillary canines were endodontically treated and then divided into 7 groups according to the cement used for fiber post cementation as follows (n = 10): RelyX Unicem, BisCem, RelyX Luting 2, RelyX ARC, Panavia F, Enforce, and Allcem. The specimens were subjected to a pull-out bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The results, in newtons, were analyzed with 1-way ANOVA and the Tukey post hoc test (α = .05). RESULTS: RelyX Unicem (472.3 ± 8.9 N), BisCem (506.6 ± 9.2 N), RelyX ARC (498.0 ± 8.2 N), Panavia F (502.3 ± 7.0 N), and Allcem (470.0 ± 11.3 N) presented significantly higher bond strength than RelyX Luting 2 (241.8 ± 9.70 N) and Enforce (309.5 ± 6.3 N) cements (mean ± SD; P < .05). CONCLUSIONS: Except for Enforce, all resin cements produced pull-out bond strength values twice that of resin modified glass ionomer cement. However, all cements promoted adequate retention to fiber posts to withstand functional loads.

Influence of technique and manipulation on self-adhesive resin cements used to cement intraradicular posts.

STATEMENT OF PROBLEM: Resin cements are widely used to cement intraradicular posts, but bond strength is significantly influenced by the technique and material used for cementation. PURPOSE: The purpose of this study was to evaluate the bond strength of 3 self-adhesive cements used to cement intraradicular glass fiber posts. The cements all required different application and handling techniques. MATERIAL AND METHODS: Forty-five human maxillary canines were selected and randomly divided into 3 groups n= 15 by drawing lots: Group BIS - Biscem, Group BRE - Breeze, and Group MAX - Maxcem. Each group was divided into 3 subgroups according to application and handling techniques: Sub-group A - Automix/Point tip applicator, Sub-group L - Handmix/Lentulo, and Sub-group C - Handmix/Centrix. Cementation of the posts was performed according to the manufacturers' instructions. The push-out test was performed with a crosshead speed of 0.5 mm/min, and bond strength was expressed in megapascals. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05). RESULTS: Breeze cement showed the highest average for the subgroups A, L, and C when compared to the Biscem cement and Maxcem Elite (P<.05). Statistically significant differences among the subgroups were only observed for Biscem. CONCLUSIONS: This study shows that application and handling techniques may influence the bond strength of different self-adhesive cements when used for intraradicular post cementation.

Linear dimensional changes in plaster die models using different elastomeric materials.

Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05) and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD=15.0 µm, EF = 14.6 µm, GH=15.2 µm), mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm), polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm) and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm). All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

Evaluation of senior Brazilian dental students about mouth preparation and removable partial denture design.

This study aimed to evaluate the knowledge of senior dental students about mouth preparation and removable partial denture (RPD) design. Two hundred sixty-six senior students from eleven dental schools in the State of São Paulo, Brazil, comprised the sample. The subjects examined two partially edentulous casts mounted on a semiadjustable articulator, answered a questionnaire regarding the treatment plan, and drew the RPD design. The casts consisted of Kennedy Class III, modification 1 maxillary arch and Class II mandibular arch. Ninety percent of the students believed that mouth preparation should be performed although no one was able to name all necessary procedures. For the maxillary arch, 12 percent of the denture designs were completely appropriate, 51 percent were partially appropriate, and 37 percent were inappropriate. For the mandibular arch, the results were 3 percent, 40 percent, and 57 percent, respectively.

Influence of intraradicular post and crown ferrule on the fracture strength of endodontically treated teeth.

The aim of this study was to investigate the fracture strength of endodontically treated teeth restored with different posts and variable ferrule heights. Sixty freshly extracted human canines were treated endodontically and randomly assigned to 6 groups (n=10), being restored with custom-made cast post-and-core (CP0 and CP3 groups), prefabricated post and composite resin core (PF0 and PF3 groups), and composite resin (CR0 and CR3 groups). The CP0, PF0 and CR0 groups presented no ferrule and the CP3, PF3 and CR3 presented 3 mm of coronal structure. All teeth were restored with full metal crowns. The fracture strength was measured in a universal testing machine at 45 degrees to the long axis of the tooth until failure. Data were analyzed statistically by 2-way ANOVA and Tukey's test (alpha=0.05). When the mean fracture strength values were compared (CP0 group - 820.20 N, CP3 group - 1179.12 N; PF0 group - 561.05 N; PF3 group - 906.79 N; CR0 group - 297.84 N; and CR3 group - 1135.15 N) there was statistically significant among the groups (p<0.05), except for the three groups with 3 mm of coronal remaining, which were similar to each other. The results of this study showed that the ferrule in crowns promoted significantly higher fracture strength in the endodontically treated teeth.

Comparison of the fracture resistance of endodontically treated teeth restored with prefabricated posts and composite resin cores with different post lengths.

OBJECTIVE: This study evaluated the fracture strengths of endodontically treated teeth restored with prefabricated posts with different post lengths. MATERIAL AND METHODS: Thirty freshly extracted canines were endodontically treated. They were randomly divided into groups of 10 teeth and prepared according to 3 experimental protocols, as follows; Group 1/3 PP: teeth restored with prefabricated post and composite resin core (Z250) with post length of 5.0mm; Group 1/2 PP and Group 2/3 PP: teeth restored with prefabricated post and composite resin core (Z250) with different combinations of post length of 7.5mm and 10mm, respectively. All teeth were restored with full metal crowns. The fracture resistance (N) was measured in a universal testing machine (crosshead speed 0.5mm/min) at 45 degrees to the tooth long axis until failure. Data were analyzed by one-way analysis of variance (alpha=.05). RESULTS: The one-way analysis of variance demonstrated no significant difference among the different post lengths (P>.05) (Groups 1/3 PP = 405.4 N, 1/2 PP = 395.6 N, 2/3 PP = 393.8 N). Failures occurred mainly due to core fracture. CONCLUSIONS: The results of this study showed that an increased post length in teeth restored with prefabricated posts did not significantly increase the fracture resistance of endodontically treated teeth.

Effect of post length on endodontically treated teeth: analyses of tensile strength

Aim: This study compared the tensile strength of endodontically treated teeth restored withdifferent posts and cores with different post lengths. Methods: Sixty extracted intact canines wererandomly divided into 6 groups. Groups CP1, CP2 and CP3 were restored with custom cast postand-core and groups PF1, PF2 and PF3 were restored with prefabricated post and compositeresin core, with different combinations of post length of 5,0 mm, 7.5 mm and 10 mm, respectively(n = 10). All teeth were restored with a total metal crown. A tensile loading was applied at a 180-degree angle to the long axis until failure. Results: The 2-way analysis of variance (á=0.05)showed statistically significant difference (p<0.001) among the groups. However, when the meanfracture forces for the groups were compared (Groups 1, 2, 3, 4, 5 and 6: 134.5 N (34.2), 178.9N(40.1), 271,5 N (55.9), 161.7 N (22.0), 216.1 N (42.0) and 257.9 N (41.0), respectively), nosignificant differences could be detected among the groups restored with prefabricated post andcast post-and-core. It was found significant differences when it was compared the different lengthsfor each type of post (p<.05). Conclusions: This study showed that increasing post lengthsignificantly increased the tensile strength of prefabricated posts and cast post-and-core used inendodontically treated teeth. On the other hand, significant differences were not found whencomparing endodontically treated teeth restored with custom cast post-and-cores or pre-fabricatedposts and composite resin cores with the same post length.

Linear dimensional changes in plaster die models using different elastomeric materials

Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05) and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD=15.0 µm, EF = 14.6 µm, GH=15.2 µm), mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm), polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm) and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm). All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

Influence of intraradicular post and crown ferrule on the fracture strength of endodontically treated teeth

The aim of this study was to investigate the fracture strength of endodontically treated teeth restored with different posts and variable ferrule heights. Sixty freshly extracted human canines were treated endodontically and randomly assigned to 6 groups (n=10), being restored with custom-made cast post-and-core (CP0 and CP3 groups), prefabricated post and composite resin core (PF0 and PF3 groups), and composite resin (CR0 and CR3 groups). The CP0, PF0 and CR0 groups presented no ferrule and the CP3, PF3 and CR3 presented 3 mm of coronal structure. All teeth were restored with full metal crowns. The fracture strength was measured in a universal testing machine at 45o to the long axis of the tooth until failure. Data were analyzed statistically by 2-way ANOVA and Tukey's test (?=0.05). When the mean fracture strength values were compared (CP0 group - 820.20 N, CP3 group - 1179.12 N; PF0 group - 561.05 N; PF3 group - 906.79 N; CR0 group - 297.84 N; and CR3 group - 1135.15 N) there was statistically significant among the groups (p<0.05), except for the three groups with 3 mm of coronal remaining, which were similar to each other. The results of this study showed that the ferrule in crowns promoted significantly higher fracture strength in the endodontically treated teeth.

O objetivo neste estudo foi avaliar a resistência à fratura de dentes tratados endodonticamente restaurados com diferentes pinos e diferentes alturas de remanescente dentinário da coroa. Sessenta caninos recém-extraídos foram tratados endodonticamente, separados em 6 grupos (n=10) e restaurados com núcleo metálico fundido (CP0 e CP3), pino pré-fabricado e núcleo em resina composta (PF0 e PF3) ou resina composta (CR0 e CR3). Os grupos CP0, PF0 e CR0 não possuíam férula e os grupos CP3, PF3 e CR3 apresentaram 3 mm de remanescente coronário. Todos os dentes foram restaurados com coroas totais metálicas. A resistência à fratura foi medida em máquina universal de ensaios com o longo eixo do dente posicionado a 45 graus em relação ao carregamento axial, até que ocorresse fratura. A análise de variância 2 critérios (?=0,05) mostrou diferença estatisticamente significativa entre os grupos. Quando as médias das forças para fratura foram comparadas (CP0 = 820,0 N; CP3= 1179,12 N; PF0 = 561,05 N; PF3 = 906,79 N; CR0 = 297,84 N; e CR3 = 1135,15 N) não foram observadas diferenças significativas entre os 3 grupos com 3 mm de remanescente coronal. Os resultados mostraram que a presença de férula em coroas aumenta significantemente a resistência à fratura de dentes tratados endodonticamente.

Comparison of the fracture resistance of endodontically treated teeth restored with prefabricated posts and composite resin cores with different post lenghts

OBJECTIVE: This study evaluated the fracture strengths of endodontically treated teeth restored with prefabricated posts with different post lengths. MATERIAL AND METHODS: Thirty freshly extracted canines were endodontically treated. They were randomly divided into groups of 10 teeth and prepared according to 3 experimental protocols, as follows; Group 1/3 PP: teeth restored with prefabricated post and composite resin core (Z250) with post length of 5.0mm; Group 1/2 PP and Group 2/3 PP: teeth restored with prefabricated post and composite resin core (Z250) with different combinations of post length of 7.5mm and 10mm, respectively. All teeth were restored with full metal crowns. The fracture resistance (N) was measured in a universal testing machine (crosshead speed 0.5mm/min) at 45 degrees to the tooth long axis until failure. Data were analyzed by one-way analysis of variance (alpha=.05). RESULTS: The one-way analysis of variance demonstrated no significant difference among the different post lengths (P>.05) (Groups 1/3 PP = 405.4 N, 1/2 PP = 395.6 N, 2/3 PP = 393.8 N). Failures occurred mainly due to core fracture. CONCLUSIONS: The results of this study showed that an increased post length in teeth restored with prefabricated posts did not significantly increase the fracture resistance of endodontically treated teeth.

Avaliação da influência da técnica de aplicação e manipulação na força de retenção de cimentos resinosos autoadesivos empregados na cimentação intrarradicular de pinos de fibra / Evaluation of the influence of application and handling technique in the retention strength of self-adhesive resin cements used in intra-radicular fiberglass posts

Atualmente, existem cimentos resinosos que dispensam o uso prévio de sistemas adesivos (autoadesivos) e aliam as vantagens dos cimentos resinosos às dos cimentos não resinosos, sendo recomendados para todas as restaurações indiretas, inclusive a cimentação de pinos intrarradiculares. Devido à falta de conhecimento do comportamento desses cimentos perante as diferentes técnicas de manipulação e aplicação, o objetivo deste trabalho foi avaliar a força de retenção de 3 cimentos autoadesivos, quando empregados na cimentação de pinos intrarradiculares de fibra de vidro. Para isso, foram selecionados 45 caninos humanos, divididos aleatoriamente em três grupos (N=15) diferenciados pelos cimentos: Grupo I - BisCem (Bisco), Grupo II - Breeze (Pentron Clinical Technologies, LLC) e Grupo III Maxcem (Kerr). Esses grupos foram divididos em três subgrupos, variando a técnica de aplicação e de manipulação: Subgrupo A - Ponta automisturadora/Ponta aplicadora, Subgrupo B - Espatulação/Lentulo, Subgrupo C - Espatulação/Centrix. O teste de push-out foi realizado com uma velocidade de 1 mm/min, e a força de retenção foi expressa em Mega Pascal (MPa). O cimento Breeze apresentou os maiores resultados médios para os subgrupos A, B e C (12,27 ± 3,19 Mpa; 13,65 ± 2,51 MPa; 13,64 ± 3,65 MPa), quando comparados aos cimentos Biscem (7,25 ± 2,37 MPa; 13,37 ± 1,80 MPa; 9,48 ± 2,38 MPa), e Maxcem Elite (7,87 ± 1,12 MPa; 7,21 ± 1,43 MPa; 9,89 ± 1,43 MPa. Somente para o cimento Biscem houve diferença estatística significante entre seus subgrupos. Assim, pôde-se concluir que, de acordo com os resultados deste estudo, a técnica de aplicação e manipulação pode influenciar na resistência retentiva, dependendo do cimento autoadesivo utilizado.

Currently, there are resin cements that do not require prior use of adhesive systems (self-adhesive), and combine the advantages of resin cements with that of non-resin cements, and are recommended for all indirect restorations, including intraradicular cementation. Due to the lack of understanding about the behavior of these cements in the presence of the different handling and application techniques, the objective was to evaluate the retention strength of 3 self-adhesive cements, when used in cementing intra-radicular fiberglass posts. For this, 45 human canines were selected and divided randomly into three groups (N = 15) for different cements: roup I - Bisco (Bisco), Group II - Breeze (Pentron Clinical Technologies, LLC) and Group III - Maxcem (Kerr). These groups were divided into three sub-groups by varying the application and handling technique: Sub-group A - Automix/Point tip applicator, Sub-group B - Handmix/ Lentulo, Sub-group C Handmix/ Centrix. The test of push-out was performed with a speed of 1 mm / min, and the retention strength was expressed in Mega Pascal (MPa). The Breeze cement, showed the highest average for sub-groups A, B and C (12.27 ± 3.19 MPa, 13.65 ± 2.5 MPa, 13.64 ± 3.65 MPa)when compared to the Biscem cement (7.25 ± 2.37 MPa, 13.37 ± 1.80 MPa, 9.48 ± 2.38 MPa), and Maxcem Elite (7.87 ± 1.12 MPa, 7.21 ± 1 , 43 MPa, 9.89 ± 1.43 MPa. Only for the Biscem cement was there statistically significant difference between the sub-groups. Thus, one can conclude that according to the results of this study, the application and handling technique may influence the retentive strength depending on the self-adhesive cement used.

Nobel Direct - Um novo conceito de implantes para ativação imediata - Relato de caso clínico / Nobel Direct – A new implant design for immediate loading - Clinical case report

Implantes unitários permitem altos índices de sucesso e, quando submetidos à ativação imediata, podem preservar o osso alveolar e permitir ótimas condições de tecido mole. Implantes de corpo único eliminam a necessidadede intermediários e podem evitar a manipulação de tecidosmoles. Este trabalho discute as indicações, vantagens e a técnica cirúrgica para instalação e ativação imediata de implantes Nobel Direct em áreas estéticas.