Abstract: Endodontic treatment is a common dental procedure used for treating teeth which the pulp tissue has become irreversibly inflamed or necrotic as a result of the carious process or dental trauma. This procedure which involves mechanical and chemical preparation of root canal may affect several mechanical and physical properties of the tooth structure. The endodontic treatment can also influence the longevity of the rehabilitation of endodontically treated teeth and biomechanics during the oral function. For restoring endodontically treated teeth several factor and clinical decisions should be observed. The decision of the fiberglass post usage and the restorative materials are related to several factors such as the quantity and quality of remaining dental structure, presence of ferrule, post cementation length and final coronal restoration. In this review, the authors will address the effect of the endodontic treatment procedures on canal shape and mechanical properties of a tooth, and also discuss the parameters and the biomechanical principles of root canal treated teeth.

The aim of this study was to evaluate the effect of parallel and tapered threaded post placement on the strain and stress distribution of endodontically treated teeth. Fifteen bovine incisors were sectioned 15 mm from their apices, endodontically treated, and divided into three groups (n = 5) according to three different threaded posts: parallel threaded post (Radix-Anker, RA); tapered threaded post (Euro-Post, EP) and tapered threaded post (Reforpost II, RII). A strain-gauge was fixed on the proximal surface perpendicular to the long root axis, 2 mm from the cervical limit. Strain generated during post placement was recorded and compared using one-way ANOVA and Tukey's test (α= .05). A scanning electron microscope was used to examine the longitudinal root sections. Stress was evaluated for each group in a two-dimensional finite element analysis. The models were meshed with tetrahedron elements and loaded with 2 N at an angle of 135° to the lingual face. The equivalent Von Mises stress was calculated. The one-way ANOVA showed significant difference among the groups. The RA group (150.0 ± 12.2 A) produced higher external strain than the RII (80.0 ± 12.2 B) and the EP (70.0 ± 6.1 B) groups. The inner strain was approximately five times greater than the external dentin strain. High stress concentrations in each thread of the posts were observed. Scanning electron micrographs showed cracks that started in the threads of the posts. The threaded post placement induced root strain mainly on the parallel side post. Root strain and stress concentration on the post threads tended to create cracks in the inner root canal dentin.

O tempo de presa de cimentos endodônticos pode afetar a resistência de união de pinos de fibra de vidro à dentina radicular. Quarenta dentes foram selecionados e tratados endodonticamente com cimento à base de hidróxido de cálcio. Em seguida, os mesmos foram divididos em dois grupos de acordo com o tempo decorrido entre o tratamento endodôntico e a cimentação definitiva (n=20): Imediato - pinos de fibra de vidro cimentados após o tratamento endodôntico; e Mediato - cimentação do pino realizada 7 dias após o tratamento endodôntico. As raízes foram subdivididas de acordo com o cimento resinoso (RelyX ARC e RelyX Unicem). As amostras foram armazenadas a 37 °C durante 24 h e seccionadas em seis fatias de 1 mm de espessura relacionadas com terços cervical, médio e apical. Os espécimes foram submetidos a teste de push-out a uma velocidade de 0,5 mm/min e os valores de resistência de união obtidos (MPa) foram submetidos à análise de variância em esquema de parcelas subdivididas e teste de Tukey (α=0,05). Para os cimentos RelyX ARC e Unicem, a resistência de união foi maior quando os pinos foram cimentados 7 dias após o tratamento endodôntico. RelyX Unicem apresentou valores de resistência de união superiores ao RelyX ARC para os períodos de cimentação. Concluiu-se que a cimentação do pino de fibra de vidro deve ser feita após o completo tempo de presa do cimento endodôntico. Cimentos resinosos auto-adesivos devem ser preferidos para cimentação de pinos de fibra.

The cure time of endodontic sealers may influence the bond strength of fiber posts to root dentin. Forty teeth were selected and endodontically filled using calcium hydroxide cement and then divided into 2 groups according to the time elapsed between endodontic filling and post luting (n = 20): Immediately - glass fiber post luting immediately after endodontic filling; and Delayed - post luting performed 7 days after endodontic filling. The roots were also subdivided according to resin cement used for post luting (RelyX ARC and RelyX Unicem). The specimens were stored at 37°C for 24 h and sectioned in six 1-mm-thick slices from cervical, middle and apical thirds. The slice specimens were submitted to a push-out test at a crosshead speed of 0.5 mm/min, and the bond strength values obtained (MPa) were submitted to two-way ANOVA in a split-plot arrangement and Tukey's test (α=0.05). For both RelyX ARC and Unicem, the bond strength was significantly higher when the posts were cemented 7 days after the endodontic treatment. RelyX Unicem showed significantly higher bond strength values than RelyX ARC for both cementation periods. It was concluded that post luting should be made after the complete setting of the root canal sealer. Self-adhesive resin cement should be preferred for fiber post luting.