Adhesive cementation of zirconia posts to root dentin: Evaluation of the mechanical cycling effect

This study evaluated the effect of mechanical cycling on the bond strength of zirconia posts to root dentin. Thirty single-rooted human teeth were transversally sectioned to a length of 16 mm. The canal preparation was performed with zirconia post system drills (CosmoPost, Ivoclar) to a depth of 12 mm. For post cementation, the canals were treated with total-etch, 3-steps All-Bond 2 (Bisco), and the posts were cemented with Duolink dual resin cement (Bisco). Three groups were formed (n = 10): G1 - control, no mechanical cycling; G2 - 20,000 mechanical cycles; G3 - 2,000,000 mechanical cycles. A 1.6-mm-thick punch induced loads of 50 N, at a 45° angle to the long axis of the specimens and at a frequency of 8 Hz directly on the posts. To evaluate the bond strengths, the specimens were sectioned perpendicular to the long axis of the teeth, generating 2-mm-thick slices, approximately (5 sections per teeth), which were subjected to the push-out test in a universal testing machine at a 1 mm/min crosshead speed. The push-out bond strength was affected by the mechanical cycling (1-way ANOVA, p = .0001). The results of the control group (7.7 ± 1.3 MPa) were statistically higher than those of G2 (3.9 ± 2.2 MPa) and G3 (3.3 ± 2.3 MPa). It was concluded that the mechanical cycling damaged the bond strength of zirconia posts to root dentin.

Conservative management of severe intrusion in a primary tooth: A 4-year follow-up

The purpose of this report was to describe the case of an 18-month-old boy who was referred to the pediatric clinic of the School of Dentistry of Araçatuba, São Paulo State University, Araçatuba, São Paulo, Brazil, 3 days after sustaining severe trauma that led to the complete intrusion of the primary maxillary right lateral incisor, a crown fracture of the primary maxillary right central incisor without pulp involvement, and disruption of the superior labial frenum. Four months later, spontaneous re-eruption was observed in the intruded tooth and no endodontic intervention was necessary in either traumatized teeth. Four years after the trauma, a morphological change in the germ of the permanent successor was noted. Clinical follow-up and periodic radiographies are necessary after traumatic intrusion of primary teeth to monitor possible sequelae in the permanent successors.

Severe fracture of the maxillary alveolar process associated with extrusive luxation and tooth avulsion: A case report

Aim: The aim of this report is to present a case of severe fracture of the maxillary anterior alveolar process with substantial bone dislodgement associated with extrusive tooth luxation and avulsion. Background: Dentoalveolar trauma is a challenge to dentistry, especially in young patients, for it can lead to early tooth loss which compromises oral function, esthetics, self-esteem, and alter the long-term plan of care for the victim. Case Report: A 12-year-old girl with severe dentoalveolar trauma to the maxillary anterior region presented for emergency care for her injury. Treatment consisted of fracture reduction of the alveolar process, repositioning of the teeth that had suffered extrusive luxation, placement of a semi-rigid splint, and suturing of soft tissue lacerations. The traumatized teeth presented with pulpal necrosis and were treated endodontically. After 24 months of follow up, the fracture of the alveolar process was completely healed and the displaced teeth presented no signs of ankylosis or root resorption. Summary: First-aid care contributed remarkably to this case allowing the re-establishment of esthetics, function, and patient's self-esteem. In spite of trauma extension the treatment outcomes were favorable. Clinical Significance: Cases of dentoalveolar trauma should be evaluated on an individual basis. However, early emergency management and adequate follow-up can prevent further complications and contribute to treatment success.

Longitudinal bond strength evaluation using the deproteinized dentin technique

This study evaluated bond strength to dentin as a result of storage time for conventional adhesive systems (with or without collagen) that had been deproteinized with 10% sodium hypochlorite (NaOCl). For this study, 72 human molars were sectioned in a mesiodistal axial plane and embedded in acrylic resin; at that point, the vestibular and lingual surfaces were worn down with abrasive paper. Acid etching was performed for 15 seconds (using 37% phosphoric acid) and the specimens were divided into 12 groups (n = 6), depending on the adhesive system used, the dentin treatment performed, and the length of evaluation (24 hours or six months). A resin composite was inserted over the prepared area with the aid of a metal matrix. Following a mechanical shear test, fractured surfaces were analyzed by stereomicroscope and the data were submitted to ANOVA and Tukey's test. It was concluded that the dentin deproteinization treatment with 10% NaOCI improved the bond strength in five of the six groups. The bond strength after 24 hours was significantly higher than the bond strength measured after six months. Of the three adhesive systems tested in this study, DenTASTIC UNO demonstrated the lowest bond strength.

Overdenture as a restorative option for hypocalcified-hypoplastic amelogenesis imperfecta: a case report.

AIM: The aim of this report is to describe the restorative treatment of an 18-year-old patient diagnosed with autosomal recessive hypocalcified-hypoplastic amelogenesis imperfecta (AI). BACKGROUND: Esthetic and functional rehabilitations in AI cases are challenging and should consider individual aspects, such as age, socioeconomic status, AI type, and intraoral condition. REPORT: AI was diagnosed in an 18-year-old patient. SUMMARY: Considering the short length of crowns and roots, patient life expectancy, minimal invasiveness, amount of treatment time required, and lower costs, oral rehabilitation with overdentures provided an adequate functional and esthetic rehabilitation of the patient. CLINICAL SIGNIFICANCE: This report demonstrated overdentures to be a viable, relatively inexpensive, and non-invasive treatment choice of a patient with AI with concerns about treatment longevity, invasiveness, cost, esthetics, and long-term maintenance.

Knowledge on dental trauma and orthodontic tooth movement held by a group of orthodontists

The objective of this work was to assess the knowledge about orthodontic tooth movement and dental trauma held by a group of orthodontists in specific areas of Brazil. For this purpose, 166 questionnaires with 15 objective questions about this subject were distributed. One hundred and five questionnaires were properly filled and collected after 30 days. It was concluded that, except for avulsion, the knowledge on dental injuries held by the professionals interviewed was considered unsatisfactory, and about 40% of them were not acquainted with the recommendations for the orthodontic movement of traumatized teeth.

Theoretical and experimental evaluation of the influence of the length of drill rods in the SPT-T test

The influence of soil drill rod length on the N value in the SPT-T test has been studied extensively by Mello (1971), Schmertmann & Palacios (1979), Odebrecht et al. (2002) and Cavalcante (2002). This paper presents an analysis of the Standard Penetration Test supplemented with torque measurement (SPT-T). A theoretical study of the resistance of the rod material to torsion and bending indicated that the shear stress caused by the rod self-weight represents less than 1% of that caused by the torsional moment. An experimental study with electric torquemeters attached to a horizontal rod system, as well as two field tests in the vertical direction, were also carried out to compare and substantiate the results. The purpose of these tests was to analyze changes along the length of the rod in response to successive increments at 1-meter intervals. Torque measurements were taken at each increment of the length to ascertain the accuracy of the theoretical data. The difference between the applied torque and the measured torque at the end of rod system was lower than the minimum scale of mechanical torquemeters used in practice.

Temporal localization of osteocalcin protein during healing of tooth extraction sockets in rats.

The aim of this study was to evaluate the expression of osteocalcin protein during the alveolar bone healing process in rats. Twenty four rats were used in this study and, after anesthetic induction, they had their right upper incisors extracted. At 7, 14, 21 and 28 days after the tooth extraction, the animals were injected 4% formaldehyde. The histological tissue pieces were colored in hematoxilin and eosin and the immunohistochemistry reaction for osteocalcin was performed. At seven days lesser neoformed trabeculae bone and a small quantity of osteocalcin labeling were observed. At 14 and 21 days a larger quantity of neoformed trabeculae bone and higher osteocalcin values were detected. At 28 days the largest quantity of neoformed trabeculae bone and a decrease on the amount of osteocalcin immunolabelling were noticed. According to our results and considering the limits of the present study it is possible to conclude that a greater osteocalcin expression is observed at 14 and 21 days postoperatively, characterizing the periods when intense mineralization of the bone tissue occurs during the alveolar bone healing process.

Scanning electron microscopic evaluation of the root apex of mandibular premolars.

This aim of this study was to evaluate the root apex of mandibular premolars regarding the presence of main and accessory foramina. The root apexes from fifty extracted mandibular single-rooted premolars were examined by scanning electron microscopy (SEM). The apical openings had their diameter measured and were identified as main or accessory foramina. Double blinded and calibrated examiners analyzed the SEM photographs and classified the premolar roots into three types, based on the presence and size of the apical openings. Type I: roots with a single main apical foramen and no accessory foramina; type II: roots with a main foramen and one or more accessory foramina; type III: roots with accessory foramina only. For the first premolar, 16 roots were classified as type I (48.48%), 4 as type II (12.12%) and 13 as type III (39.40%). For the second premolars, 10 roots were classified as type I (58.83%), 3 as type II (17.65%) and 4 as type III (23.52%). The high incidence of roots with accessory foramina only (type III), mainly in the first premolar, warns of the need for caution during working length determination and apical debridement.

Avaliação de Diferentes Compósitos na Resistência à Fratura de Núcleos de Preenchimento

Objective: To evaluate and compare the fracture strength of different composite resins used for core buildup. Method: Thirty-six bovine teeth were decoronated at the cervical third to standardize the length of specimens at 20 mm. Under constant irrigation, the canals were prepared with #5 Largo drills corresponding to the size and diameter of #3 Reforpost fiberglass post. The posts were cemented with Enforce resin sealer, being 16 mm inside the root canal and 4 mm outside the root canal, and the material was light-activated for 30 seconds at each side. The specimens were divided into 3 groups (n=12), in which cores (4 mm diameter and 5 mm high) were prepared from a prefabricated standard with three types of composite resins: Group 1: Z100 (3M), Group 2: Z250 (3M) and Group 3: P60 (3M). The specimens were fixed in a cylindrical device with an adaptor at 45o inclination. This device was adapted to a universal testing machine (EMIC) to simulate the force until fracture of the specimen. Data were subjected to ANOVA (p<0.05). Results: The Z250 resin cores presented the highest mean fracture strength (45.453 kgf), while the mean fracture strengths in Group 1 and Group 3 were 38.014 and 39.506 kgf, respectively. P60 caused the largest number of root fractures. Conclusion: Considering the characteristics and properties of the tested resins, Z250 appears as the most indicated for core buildup.

Cementation of fiber post: influence of the cement insertion techniques on the bond strength of the fiber post-root dentin and the quality of the cement layer.

The aim of this study was to assess the influence of resin cement insertion methods on the bond strength of a fiber post to root dentin and quality of the cement layer. Forty bovine single-roots (length =16 mm) were randomly allocated into four groups, according to the cement insertion methods (N.=10): Gr1- Lentulo drill #40, Gr2- Centrix syringe, Gr3- Explorer #5, Gr4- fiber post. The root canals were prepared at 12 mm, using preparation bur # 3 of a cylinder quartz-FRC post (Aesthet post-plus, Bisco). The fiber posts were cemented using a multi-step etch-and-rinse adhesive system (All Bond 2®, Bisco) and a dual-cured resin cement (Duolink, Bisco). Each root was cut into seven samples: four samples of 1.8 mm thickness for push-out testing, and three with 0.5 mm for cement layer quality analyzing. One-way ANOVA was used for the push-out test values and the One-Way Kruskal-Wallis (P<0.05) and Dunn (10%) tests for the cement layer analyzes. ANOVA showed that the cement layer quality was affected by the cement insertion methods (P=0.0044): Gr1 (3.8 ± 1.3a), Gr2 (3.2 ± 1.3a), Gr3 (5.2 ± 1.5a,b) and Gr4 (5.2 ± 1.5b) (Dunn test), whereas the bond strength (MPa) was not affected by cement insertion methods: G1 (4.2 ± 1.3), G2 (3.2 ± 1.8), G3 (4.5 ± 0.9), G4 (3.1 ± 1.3). The fiber posts should be cemented with the assistance of the lentulo drill or centrix syringe to promote the best cement layer results.