Factors Influencing Vertical Radicular Fractures in Teeth Supported by Metallic Dental Core: A Scoping Review

Figures & data

Figure 1 Flow chart of study selection.

Table 1 Characteristics of the Studies Included in the Scoping Review

“Author/Date/Study Type”	“Number of Samples Studied”	“Objectives”	“Study Protocol”	“Results”
1-M Ona and al. (2013)^Citation3 (Finite Element Analysis Studies)	“Finite element models (FEM) are constructed of a second premolar”.	To study the impact of elastic modulus mismatch between dental tissue and root reconstruction materials on radicular fracture mechanisms.	- 3D models of teeth with different restorations (metal and composite). - Tests with and without bonding of the restorations. - Assessment of the risk of dental fracture and restoration debonding.	- Bonded metal restorations have low fracture risk. - Cast post debonding risk is twice as high as fiber posts. - Elastic modulus mismatch contributes to post debonding, possibly increasing radicular fracture risk. - Bonding offers fracture advantages over conventional cementation
2- Torres-Sánchez C. and al.(2013)^Citation4 (“Laboratory Experimental Study”)	Forty-two single-rooted premolars.	Measure the fracture resistance of teeth that have undergone endodontic treatment and have been restored with different types of posts based on the materials and cements used.	- Six groups were formed: three with fiberglass posts and three with cast gold posts. - Each group used one of three dental cement types: resin-modified glass ionomer cement, dual-polymerizing resin cement, or chemically active autopolymerizing resin cement. - Metal crowns were applied to all six groups. - Samples underwent compression testing to measure fracture resistance.	- Fiberglass reinforced posts enhanced fracture resistance in treated teeth. - Among the cement types used, resin-modified glass ionomer cement yielded the highest fracture resistance compared to dual-cure resin and autopolymerizing cement.
3- Dejak B. and al.(2013)^Citation5 (Finite Element Analysis Studies)	Thirteen 3D models of upper first incisors.	Evaluate the influence of the ferrule effect, the length of cast metal posts, and fiberglass posts on the resistance of anterior teeth.	- The research investigated tooth models, including intact teeth, those restored with varying lengths of cast metal posts, and fiberglass posts with or without a ferrule effect. - A standardized load of 100 N was applied to the lingual cingulum of the teeth at a 130degree angle. - Specific criteria were used to assess the strength of dental materials such as tissues, ceramics, composites, fiber posts, and cast metal posts. - Contact stresses at the cement-tooth interface were calculated as part of the analysis.	- The ferrule effect significantly decreases stresses in teeth restored with posts. - Rigid post materials aid in reducing stress in incisors. - Teeth with 10 mm posts exhibit double the fracture resistance of those with 5 mm posts. - Post length does not impact tooth resistance in the presence of a 2 mm ferrule.
4- Barcellos RR. and al.(2013)^Citation6 (Laboratory Experimental Study)	Seventy upper canines	To study the influence of the post system and the amount of remaining radicular tissue on the fracture resistance of endodontically treated teeth.	- The sample was categorized into seven groups, considering the post type (fiber, fiber with resin composite overlay, or nickel-chrome NiCr) and remaining radicular tissue thickness (1 mm or 2 mm). - Restored teeth were subjected to loads in a controlled chewing simulator. - Fracture resistance tests were performed on the samples.	- Fiber posts coated in resin composite showed the highest fracture resistance, followed closely by basic fiber posts and cast posts with comparable resistance levels. - Improved postcanal adaptation significantly enhances frictional retention and boosts fracture resistance.
5- Rippe MP. and al.(2014)^Citation7 (Laboratory Experimental Study)	Eighty single-rooted human teeth.	Assessing the impact of canal preparation type, intraradicular post, and fatigue loading on root fracture resistance.	- The sample was divided into 8 groups based on canal preparation method, post type, and the application of mechanical stress. - Canal preparation was performed for a 10 mm post. - Mechanical stress was applied to specific groups. - Fracture resistance testing was conducted until failure.	- Dental canal preparation did not significantly impact root fracture resistance. - Post type influenced resistance and fracture mode, with fractures occurring at high loads. - Cast posts showed greater fracture resistance than fiber posts under oblique loading. - Cast posts may incur irreparable apical fractures under high stress, while fiber posts typically sustain reparable coronal fractures.
6- Madfa AA. and al. (2014)^Citation8 (Finite Element Analysis Studies)	10 (3D) models of an adult maxillary central incisor.	The objective of this study was to analyze and compare the stability of two dental post forms (parallel-sided and tapered) made from different materials (titanium, zirconia, carbon fiber, and glass fiber) using the finite element method.	- An oblique load of 100 N was applied to each 3D model. - Analyses were conducted along the center of the post, at the crown/cement/inlay core interface, and at the inlay core/cement/dentin interface, and the averages were calculated	- Tapered posts resulted in significantly higher stresses, especially along the post center, compared to parallel-sided posts. - Stainless steel posts showed the highest stress levels, followed by zirconia, titanium, glass fiber, and carbon fiber posts.
7- Kainose K. and al. (2014)^Citation9 (Finite Element Analysis Studies)	Three-dimensional mathematical models of a mandibular premolar tooth.	Examine the distribution of interfacial stresses in teeth restored with different post lengths and crown heights	- Replacement of certain parts of the dental structure with ceramic crowns of three different crown heights (6, 7, and 8 mm) (lack of ferrule). - Either fiberglass posts or NiCr alloy metal posts with four different post lengths (4, 6, 8, and 10 mm) were used. - Linear finite element analysis to calculate equivalent and shear stresses at the interfaces under specific loads.	- The presence of a cervical ferrule eliminates the influence of post length and post core material properties on both fracture resistance and stress distribution in restored teeth. - Without a cervical ferrule, however, post material and length significantly affect stress distribution. - In models with metallic posts, shorter post lengths lead to increased stress levels towards the apex. - Shear stress at the post and canal housing interface was mainly generated in the cast post and increased with decreasing post length. - There is a risk of cast post debonding, especially if it is shorter.
8- Oyar P. (2014)^Citation10 (Finite Element Analysis Studies)	A mandibular second premolar was scanned using computer-assisted tomography to obtain 1 mm-thick slices of dental tissue, and the data was combined with manual data to create three-dimensional finite element models using computer-aided design software.	Determine which combinations of post core cement offer the most favorable stress distribution under load.	- Three-dimensional tooth models were created to simulate different materials for metal-ceramic crowns (nickel-chrome, goldpalladium), cast posts (Ti, NiCr, AuPd), and cements (glass ionomer, composite resin, zinc phosphate, polycarboxylate, Panavia). A chewing force of 400 N was then applied to the occlusal surface.	- Employing a post material with lower elasticity modulus alongside a cement with higher elasticity modulus led to decreased deformation in the residual root, bonding material, and post, as well as a reduction in post stress. - The combination of NiCr ceramic-metal crown / AuPd inlay core / zinc phosphate or Panavia cement may be advantageous for post and core restorations.
9-Sugaya T. and al. (2015)^Citation11 (Retrospective Study)	“304 fractured teeth”.	“Compare dental root fractures in the cervical and apical regions to understand the causes and risks”.	- A retrospective study of patient records with vertical root fractures. - Data collection based on age, gender, tooth type, fracture location, fracture site, and the presence of posts. - Classification of fractures as cervical, middle, or apical. - Evaluation of the fracture condition based on post length.	- Cervical and apical fractures occur with similar frequency, while median fractures are rare. - Apical fractures are only observed in the first maxillary and mandibular premolars, all on the buccal/lingual side. - Post debonding poses a significant risk factor for fractures originating from the cervical region. - Circular root canals distribute occlusal force evenly around the canal wall, while oval root canals concentrate stress on the buccal and lingual sides. - There is no association between post length and fractures originating from the cervical region. - Longer posts are associated with fewer apical fractures.
10- Uzun İ. and al.(2015)^Citation12 (Laboratory Experimental Study)	Seventy mandibular premolars with oval root canals were dissected. Fourteen teeth were used as the control group.	The objective of this study was to evaluate the effects of root canal preparations with circular and oval burs and the placement of oval and circular posts on the fracture resistance of roots with oval canals.	- The root canals were filled, and the samples were randomly divided into 4 experimental groups. - A fracture resistance test was conducted on each specimen, and the data were statistically analyzed.	- Oval posts did not provide higher fracture resistance to endodontically treated roots with oval canals compared to circular posts
11- Samran A. and al.(2015)^Citation13 (In Vitro Experimental Study)	Seventy-two extracted human mandibular premolars.	The objective is to compare the effect of ferrule placement on the fracture resistance of mandibular premolars that have undergone endodontic treatment.	6 groups were formed: - Control Group: Endodontically treated teeth without endodontic posts or crowns - Teeth with a 2mm circumferential ferrule - Teeth with a 2mm buccal ferrule - Teeth with a 2mm lingual ferrule - Teeth with both 2mm buccal and lingual ferrules - Posts were cemented with a self-adhesive resin cement - NiCr crowns were cemented on each prepared tooth. - All samples were subjected to a quasistatic load at a 30° angle in a universal testing machine until fracture.	- No statistically significant differences were observed between the groups, except for the differences between the control group and the groups of teeth with a 2mm lingual ferrule and those with both 2mm buccal and lingual ferrules. - The ferrule placement had no significant effect on the fracture resistance of mandibular premolars that had undergone endodontic treatment.
12- Abdulmunem A. Dabbagh and al. (2016)^Citation14 (Finite Element Analysis Studies)	Sixty extracted maxillary incisors collected from the dental and orthodontic clinics of the University of Malaya.	- To investigate the impact of post type (titanium, fiber, and stainless steel) and cement type (zinc phosphate and composite resin) on the fracture resistance and failure mode of endodontically treated teeth.	- The teeth were randomly restored using three types of dental posts: titanium, fiber, or stainless steel. - Two types of luting cements were used: zinc oxyphosphate or composite resin. - Restored teeth were subjected to thermocycling cycles. - Samples were loaded at a 135degree angle until failures were observed.	- Zinc oxyphosphate cement showed higher fracture resistance. - The choice of post material and luting cement significantly impacted fracture resistance and failure mode in restored teeth after endodontic treatment.
13- Liao WC. and al. (2017)^Citation1 (Retrospective cohort study)	A total of 65 teeth with 68 vertically fractured roots in 58 Chinese patients were studied.	The clinical and radiographic features of vertical root fractures.	- Clinical examination records and radiographic images were thoroughly reviewed. - Clinical features such as patients’ gender, age, the number of teeth with vertical root fractures, periodontal probing depth, the presence of prostheses, and the overall condition of the dentition were assessed.	- Vertical root fractures were more common in the mesial roots of mandibular molars. - Teeth with vertical root fractures generally exhibited a periodontal probing depth of >5 mm, and they were often associated with dental prostheses and relatively intact dentition. - Radiographic characteristics of teeth with vertical root fractures were related to previous endodontic treatments, periodontal bone loss, apical bone loss, and widening of the periodontal ligament.
14- Teshigawara D. and al.(2019)^Citation15 (Finite Element Analysis Studies)	A dental model was created and then divided into 4517 sections using eight-noded hexahedral elements.	Analyzing the failure processes of the cement in teeth restored with posts and determining how the elastic properties of the posts affect these failure processes.	- The finite element analysis focused on the sequential failure of adhesion between dentin and cement. - The penalty function method was used to analyze the stresses at each step of the adhesion conditions. - Failure models of adhesion and the stress distribution in dentin under the load of different post materials were observed.	- With the use of a metal post, bonding material failure initially occurred at the palatal edge, extending along the crownpost interface towards the vestibular side. - Stress concentration was noted at the interface areas, correlating with adhesive failure. - This stress concentration may lead to cracks in these areas, resulting in vertical root fractures with metal posts and horizontal fractures with resin posts. - Local stress concentrations are influenced not only by the post material but also by the quality and bonding conditions to dentin.
15- Sarkis-Onofre R. and al.(2020)^Citation16 (Randomized controlled study)	A total of 119 patients and 183 posts (72 cast metal posts and 111 fiber posts) were analyzed.	Evaluate the survival and success of fiber posts compared to cast metal posts in teeth without ferrules	- The teeth were randomly divided into the two groups. - All teeth were restored with individual ceramic-metal crowns. - Statistical analysis was conducted to evaluate post success and survival. - Annual failure rates were calculated for both post types after five years. - Results were analyzed taking into account the type of failure and its location.	- Cast metal posts had an annual failure rate of 1.2%, while fiber posts had an annual failure rate of 1.7%. - The majority of failures occurred in posterior teeth (primarily premolars) with 16 out of 23, including 10 root fractures and 5 post dislodgements. - No significant difference between fiber posts and metal posts regarding the risk of root fracture was observed. - Both types of posts demonstrated similar clinical performance when used with single crowns.
16- Veeraganta SK. and al. (2020)^Citation17 (In Vitro Experimental Study)	Sixty-four first mandibular premolars, which had undergone endodontic treatment, were divided into 8 test groups.	The aim of this in vitro study was to assess the influence of post material and diameter on the fracture resistance of endodontically treated mandibular premolars.	Grouping: Samples were divided into 8 groups based on wall count, post material, and post diameter. Sample prep: Posts were cemented, and resin cores with a 2mm ferrule were created. Crowns: CoCr crowns were cemented with glass ionomer. Cycles: Specimens underwent 1,200,000 chewing cycles and thermocycling. Testing: Specimens were loaded until fracture at a 30° angle.	- Post material and post diameter had a significant influence on fracture resistance. - When smaller diameter posts are used, a titanium system may be more suitable than a fiber post because it demonstrated higher fracture resistance. - Beyond a 2 mm ferrule, the amount of tooth substance loss had no influence on the fracture resistance of endodontically treated teeth restored with posts.
17- Iemsaengchairat R. and al. (2021)^Citation18 (In Vitro Experimental Study)	Forty-eight single-rooted mandibular premolars with single root canals were endodontically treated.	To assess the fracture resistance and failure characteristics of simulated thin-walled endodontically treated teeth restored with various techniques.	- The roots were randomly divided into four groups of 12 roots, based on the post reconstruction techniques used: composite post (CP), multiple fibers (FP), anatomical CAD/CAM post (AP), and cast metal post (MP). - All specimens underwent thermocycling and were subjected to axial compression until failure at a 45degree angle.	- The group with a cast post provided the highest fracture load. - Cast posts provided the highest fracture resistance for the reconstruction of thin-walled endodontically treated teeth without ferrules.
18- Mosharaf R. and al. (2023)^Citation19 (Finite Element Analysis Studies)	A 3D scan of a central incisor	To study the effect of the ferrule height-to-crown ratio on the strength of maxillary anterior central teeth using finite element analysis.	- 3D scan of a maxillary central incisor. - Application of 300 N load at 135degree angle to tooth model, horizontally and vertically. - Ferrule height variation on palatal surface from 5% to 25%, with buccal surface at 50%. - Inlay core length variation in model to 11, 13 and 15 mm.	- Increasing the ferrule/crown ratio resulted in elevated stress and strain distribution within the dental model, while decreasing within the post itself. - Augmenting the cervical ferrule ratio enhances dental fracture resistance against applied forces. - Elevating the ferrule height to 2 mm significantly boosts dental fracture resistance. - The synergistic impact of ferrule height and post length suggests that in the presence of a high residual coronal cervical height, a shorter post length may lead to successful treatments.

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