Effect of Ferrule Location with Varying Heights on Fracture Resistance and Failure Mode of Restored Endodontically Treated Maxillary Incisors

Abstract

Purpose To investigate the effect of the location of a partial ferrule on 2 walls and the influence of ferrule height variations on remaining walls, fracture resistance, and failure mode of maxillary incisors endodontically treated and restored with fiber posts. Materials and Methods Sixty intact human maxillary central incisors were divided into 6 groups (n = 10): no ferrule (NF), 2‐mm ferrule (CF2), absence of lingual wall and 1 proximal wall with remaining walls’ height, 1 mm (IF1), 2 mm (IF2), 3 mm (IF3), and 4 mm (IF4). They were restored with a fiberglass post and composite resin core. Complete metal crowns were then cemented on all specimens. Completed specimens were subjected to thermal cycling (6000 cycles, 5°C/55°C) followed by the immediate testing of fracture resistance. After failure, the specimens were sectioned buccolingually and evaluated to identify the mode of failure. The data were analyzed with an ANOVA and the Student‐Newman‐Keuls multiple comparison tests (α = 0.05). Results An incomplete ferrule (IF2) with the lingual wall missing and 1 proximal wall had a fracture resistance of 494 ± 137 N, which was significantly less that of a complete ferrule (CF2) (707 ± 162 N, p = 0.002). An increase of 3 to 4 mm in height of the remaining walls had negligible influence on the fracture resistance: 514 ± 117 N (IF3), 557 ± 177 N (IF4). Partial decementation was observed in all specimens of IF3 and IF4, in 9 of IF1 and IF2, in 6 in NF, and in 3 in CF2. Root fractures occurred in 7 specimens, 4 in CF2, 1 in IF1, 1 in IF2, and 1 in IF4. Cracks under the cemento‐enamel junction occurred in 4 specimens (NF and IF1), in 5 (IF2 and IF3), and in 6 (CF2 and IF4) and were considered catastrophic failures. Conclusions Specimens with a complete ferrule of 2 mm height were more resistant to fracture than specimens with 2 mm height and absence of the lingual wall and 1 proximal wall. A 3 or 4 mm wall height increase was associated with an insignificant increase in fracture resistance and cannot compensate for the absence of the lingual wall and 1 proximal wall.

Influence of one-wall remaining coronal tooth with resin abutment and fiber post on static and dynamic fracture resistance

“…After abutment build-up, it is necessary to place a crown and adequately maintain the final prosthesis. Retention of the restoration is dependent on the bond strength of post and root canal dentin [3][4][5][6] , abutment form, and the presence or absence of a ferrule on the remaining tooth [7][8][9][10][11] . In particular, a ferrule on the remaining coronal dentin of the tooth contributes to the increase of fracture resistance of the resin abutment improving the 3-year survival rate 8) .…”

“…In the premolar region, resin abutment with FRC post effectively retains restorations even if there is no ferrule on the tooth 9) . Studies have reported that the heights of the lingual or one of the proximal walls affect fracture resistance 10,11,13) . However, the load-bearing capacity and durability of abutments reinforced with resin composite and FRC post when there is very little coronal tooth remaining, has not been clarified.…”

Influence of New Sleeve Composite on Fracture Behavior of Anterior Teeth with Flared Root Canals

“…One of the factors underlying the increased risk of vertical root fracture is the absence of ferrules in teeth: the presence of the ferrule is thought to extend the tooth life, a supposition supported by the frequency with which non-ferrule teeth are seen in clinical practice [ 18 , 19 , 20 ].…”

Influence of remaining axial walls on of root filled teeth restored with a single crown and adhesively bonded fibre post: A systematic review and meta-analysis

“…Failure of fibre post restorations in root filled teeth with varying amounts of remaining coronal tooth structure have been reported in laboratory [25][26][27] and clinical studies [8,[28][29][30][31][32][33][34][35][36][37]. Laboratory studies have used a variety of tests to determine load capacity and failure modes of samples with various post designs and coronal restorations.…”