The Effect of Marginal Ridge Thickness on the Fracture Resistance of Endodontically-treated, Composite Restored Maxillary Premolars

Abstract

This study evaluated the effect of varying thicknesses of marginal ridge on the fracture resistance of endodontically-treated maxillary premolars restored with composite.Ninety non-carious maxillary premolars, extracted for orthodontic reasons, were selected for this experimental in vitro study. The teeth were randomly assigned to six groups (n=15). Group 1 received no preparation. In groups 2 through 6, the premolars were root filled and DO preparations were created, while MOD preparations were also created for group 2. The condition of the boxes was: the gingival seat was 1.5 mm above the CEJ and the buccolingual dimensions were 3.5 mm in gingival and 3 mm in occlusal. In groups 3 through 6, the dimensions of the mesial marginal ridge were measured using a digital caliper as follows: 2 mm, 1.5 mm, 1 mm and 0.5 mm, respectively. All samples in groups 2 through 6 were restored with a dentin bonding system (DBS: Single Bond, 3M) and resin composite (Z 250, 3M). Subsequently, premolars from all six groups were subjected to a thermocycling regimen of 500 cycles between 5°C and 55°C water baths. Dwell time was 30 seconds, with a 10-second transfer time between baths.The premolars were submitted to axial compression up to failure at a 45° angle to the palatal Preserving the marginal ridge of endodontically-treated composite restored maxillary premolars can act as a strengthening factor and improve fracture resistance. The mean load necessary to fracture the samples was recorded in newtons (N), and data were subjected to analysis of variance (ANOVA) and LSD post-hoc test.According to these results, the mean loads necessary to fracture the samples in each group were (in N): group 1: 732 ± 239, group 2: 489 ± 149, group 3: 723 ± 147, group 4: 696 ± 118, group 5: 654 ± 183 and group 6: 506 ± 192).Differences between group 1 and groups 2 and 6, and also differences between groups 3, 4 and 5 compared with group 2 and 6 were statistically significant (p<0.05).

Influence of Immediate Dentin Sealing Techniques on Cuspal Deflection and Fracture Resistance of Teeth Restored with Composite Resin Inlays

“…Group 2 recovered 58% of the resistance of a sound tooth, group 3 35%, and group 4 41%. These findings are in agreement with those of other studies 36,37,40 that verified that the different restorative techniques did not restore the resistance of a sound tooth. Nevertheless, the use of adhesive restorations has been recommended for reinforcing remaining dental structures, 38,41 even if full strength is not recovered.…”

Dentists' decisions regarding the need for cuspal coverage for endodontically treated and vital posterior teeth

“…Scotti et al () found the remaining wall thickness to be a very important clinical parameter in the resistance of fracture in endodontically treated premolars and suggested that an axial wall thickness of less than 2 mm is an indication for cuspal coverage to improve the fracture resistance in maxillary premolars. Other in vitro studies have reported a reduction in tooth resistance to fracture with a wider isthmus preparation in MO/DO and MOD cavities (Mondelli et al, ; Reagan et al, ) and with a marginal ridge thicknesses of less than 1 mm in ETT (Shahrbaf, Mirzakouchaki, Oskoui, & Kahnamoui, ).…”

Mandibular Molar Rehabilitation Using Orthodontic Extrusion Associated with Odontoplasty

“…Commonly, the tooth has been structurally compromised by removal of tooth substance during endodontic treatment and restorative procedures. Moreover, endodontically treated teeth can be easily fractured because of pulp chamber roof removal, 8 mainly when the marginal ridge is thin or totally removed 22 . During mastication, occlusal contacts occur on almost every chewing cycle.…”