Resistance to vertical fracture of roots, previously fractured and bonded with glass ionomer cement, composite resin and cyanoacrylate cement

How does canal taper affect root stresses?

AIM

To examine the effect of specific tapers on root stresses and thus vertical root fracture.

METHODOLOGY

The effect of taper on root stresses was calculated during simulated warm vertical compaction of gutta-percha in a straight rooted premolar for three tapers (0.04, 0.06 and 0.12 mm mm(-1)) using finite element analysis. Stresses in the dentine were observed whilst the root was filled with three subsequent gutta-percha increments. Each increment was compacted at 10 or 15 N and the gutta-percha cooled down to 37 degrees C. After filling, composite was polymerized in the access space. A functional occlusal load of 50 N was then applied on the buccal cusp incline. The stress distribution in the root during the occlusal loading was compared with the stresses during filling.

RESULTS

During filling, the highest stresses were found: (a) at the canal surface; (b) using the smallest taper; (c) in the apical third; and (d) during the first gutta-percha increment. The root stress distribution changed when the functional post-filling load was applied. It generated the highest stresses at the external root surface, with a tensile stress concentration at the lingual surface of the cervical third. Since the stresses during simulated masticatory loading concentrated on the external surface, an increased taper size caused only slightly higher root stress levels.

CONCLUSIONS

With increasing taper, root stresses decreased during root filling but tended to increase for masticatory loading. Root fracture originating at the apical third is likely initiated during filling, whilst fracture originating in the cervical portion is likely caused by occlusal loads.

The use of glass ionomer cements in both conventional and surgical endodontics

The capacity to bond to dental tissues, especially to dentine, their long-term fluoride release and their biocompatibility make glass ionomer cements (GICs) advantageous for use in endodontics, as well as in restorative dentistry. This review provides information on the basic properties of GICs, such as adhesion, antimicrobial effects and biocompatibility, particularly as they relate to use in endodontics. Indications for the use of GICs in endodontics are orthograde root canal sealing, root-end filling, repair of perforations and root resorption defects, treatment of vertical fractures and maintenance of the coronal seal. The paper includes a review on each of these indications. It is concluded that in spite of the critical handling characteristics and the inconclusive findings regarding sealing ability and antimicrobial activity, there is substantial evidence to confirm their satisfactory clinical performance. Both soft tissue and bone compatibility make them suitable for use during endodontic surgery.

Effects of surface treatment and joint shape on microtensile bond strength of reattached root dentin segments

STATEMENT OF PROBLEM

An effective bonding technique for reattaching vertical root fracture segments has not yet been established.

PURPOSE

The purpose of this study was to investigate the effects of surface treatment and joint shape on bond strength of reattached root dentin segments.

MATERIAL AND METHODS

Microtensile dentin specimens (n=120, cross-sectional area=1.5 mm2) were obtained from 12 bovine teeth roots, and fractured under a tensile force. The segments of each group (n=6) were reattached by a 4-META/MMA-TBB adhesive resin after different treatments (etching or polishing, a 50-microm or 500-microm gap space, butt or wedge joint). The group with a 50-microm gap space and butt joint, which was not etched or polished, served as the control. After 24 hours of storage in 0.9% normal saline solution or thermal cycling (3000 cycles, 4 degrees C and 60 degrees C), the specimens were fractured in a universal testing machine at a crosshead speed of 1.0 mm/min. The microtensile bond strengths (MPa) were recorded. The bonded interface and fractured surface were observed by SEM (original magnification x 1000). The results were analyzed by a 2-way analysis of variance and the Fisher protected least significant difference post-hoc test (alpha=.05).

RESULTS

Significantly higher bond strengths (P=.0001) were shown for the nonpolished group (9.78 +/- 4.44 MPa) and the etched group (9.31 +/- 1.23 MPa) than for the polished group (fractured before test). The wedge-shaped joint exhibited the highest bond strength (18.57 +/- 3.40 MPa, P=.0017). SEM observations showed that the penetration of resin tags along the oblique dentinal tubules was within the wedge joint.

CONCLUSION

Etching and oblique tubule orientation contributed to significantly high bond strength of reattached segments to dentin after vertical root fracture.

Treatment of tooth fracture by medium-energy CO2 laser and DP-bioactive glass paste: the interaction of enamel and DP-bioactive glass paste during irradiation by CO2 laser

Acute trauma or trauma associated with occlusal disturbance can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible, it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. We have tried to use a continuous-wave CO2 laser and a newly developed DP-bioactive glass paste (DPGP) to fuse or bridge tooth crack or fracture lines. Both the DP-bioactive glass paste and tooth enamel have strong absorption bands at the wavelength of 10.6 microm. Therefore, under CO2 laser, DPGP and enamel should have an effective absorption and melt together. The interface between DPGP and enamel could be regarded as a mixture of DPGP and enamel (DPG-E). The study focused on the phase transformation, microstructure, functional group and thermal behavior of DPG-E with or without CO2 laser irradiation, by the analytical techniques of XRD, FTIR, DTA/TGA, and SEM. The results of XRD showed that the main crystal phase in the DPG-E was dicalcium phosphate dihydrate (CaHPO4.2H2O). It changed into CaHPO4, gamma-Ca2P2O7, beta-Ca2P2O7 and finally alpha-Ca2P2O7 with increasing temperature. In the FTIR analysis, the 720 cm(-1) absorption band ascribed to the P-O-P linkage in pyrophosphate rose up and the intensities of the OH- bands reduced after laser irradiation. In regard to the results of DTA/TGA after irradiation, the weight loss decreased due to the removal of part of absorption water and crystallization water by the CO2 laser. SEM micrographs revealed that the melted masses and the plate-like crystals formed a tight chemical bond between the enamel and DPGP. We expect that DPGP with the help of CO2 laser can be an alternative to the treatment of tooth crack or fracture.

Diagnosis and management of teeth with vertical root fractures

Vertical fractures in teeth can present difficulties in diagnosis. There are, however, many specific clinical and radiographical signs which, when present, can alert clinicians to the existence of a fracture. In this review, the diagnosis of vertical root fractures is discussed in detail, and examples are presented of clinical and radiographic signs associated with these fractured teeth. Treatment alternatives are discussed for both posterior and anterior teeth.