The effect of sealer type and obturation technique on the fracture resistance of endodontically treated roots

OBJECTIVE

This study evaluated the effect of sealer type with various obturation techniques on the fracture resistance of root filled teeth.

MATERIALS AND METHODS

Eighty mandibular premolars were collected, and root canals of 70 of them were prepared by Mtwo system up to 40/04. Thirty teeth were obturated using TotalFill BC sealer, and 30 using AH Plus sealer, with one of the obturation techniques (N = 10), namely cold lateral compaction (CLC), warm vertical compaction (WVC), and single cone (SC). Ten teeth were left without obturation as a positive control, and the other 10 teeth were not prepared serving as a negative control. Teeth were stored for 3 weeks, and the crowns were separated and the roots were subjected to fracture test using a universal testing machine.

RESULTS

Data was analyzed by ANOVA followed by Tukey's test. Fracture resistance of the TotalFill groups was significantly higher than the AH Plus groups in each obturation technique, and SC had the highest fracture resistance regardless of sealer used (P < 0.05). Obturation of the root canal by TotaFill BC sealer increased the calcium/phosphorous ratio in the dentin of the root.

CONCLUSIONS

Obturation with TotalFill BC sealer improved the fracture resistance of the roots more than AH Plus sealer, and obturation with SC resulted in higher fracture resistance than CLC and WVC.

CLINICAL RELEVANCE

Obturation of the root canal with Bioceramic sealer with single cone obturation technique could reduce the incidence of vertical root fracture.

ARTIFICIAL INTELLIGENCE (AI) AS AN AID IN RESTORATIVE DENTISTRY IS PROMISING, BUT STILL A WORK IN PROGRESS

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION

Artificial intelligence applications in restorative dentistry: A systematic review. Revilla-León, M., Gómez-Polo, M., Vyas, S., Barmak, A. B., Özcan, M., Att, W., & Krishnamurthy, V. R. J Prosthet Dent 2021 SOURCE OF FUNDING: Not reported.

TYPE OF STUDY/DESIGN

Systematic review.

Root fracture healing outcome after a revascularization procedure: an 8-year follow-up case report

Pulp revascularization is the traditional protocol for treating immature necrotic teeth; however, it is not the usual management practice for traumatized teeth with horizontal root fracture. This is a case report of an 11-year-old patient subjected to trauma that occurred four years prior to treatment. The trauma led to horizontal root fracture in tooth #11, and the immature tooth #21 became necrotic with periapical radiolucency. Both teeth were treated with revascularization procedures. Each tooth was disinfected with triple antibiotic paste and a coronal seal using mineral trioxide aggregate. During the eight-year follow-up using periapical radiograph and cone beam computed tomography, tooth #21 showed periapical repair with apical closure. The fractured rooted tooth #11 was functional and asymptomatic, with evidence of bone growth inside the fracture line. From this case outcome, revascularization can be a successful treatment modality for traumatized teeth that have either root fracture or necrotic open apex.

Reinforcement effect of intra-orifice barrier materials in teeth treated with regenerative endodontic procedure: Research article

Background. Regenerative endodontic treatment (RET) is a clinically advanced procedure for necrotic immature teeth. However, root canal walls of these teeth are brittle especially in the cervical region and need reinforcement. This in vitro study is conducted to evaluate the effect of intra-orifice barrier materials on the fracture resistance of immature teeth treated with regenerative procedure.

Methods. Forty-eight maxillary central incisors were used. Twelve intact teeth were selected for the control group. Remained teeth were prepared using peeso drills to simulate immature teeth and assigned into three groups according to the intra-orifice barrier material placed over MTA (n = 12); Composite resin (CR), ProRoot MTA and Resin-modified glass ionomer cement (RMGIC). Fracture strength test was applied using a universal testing machine. One-way ANOVA and Tukey post hoc tests were used at P = 0.05.

Results. A significant difference was obtained among groups (P < 0.05). MTA showed the lowest fracture resistance (P < 0.05). However, no significant difference was found among RMGIC, CR, and control groups (P > 0.05).

Conclusion. Intra-orifice restorative materials have reinforcement affect in immature teeth treated with regenerative endodontic procedure. RMGIC or CR can be regarded as a viable choice to reduce the occurrence of cervical root fracture of immature teeth treated with a regenerative therapy.

A new method to test the fracture strength of endodontically-treated root dentin

OBJECTIVE

To develop a new method to test the fracture strength of endodontically-treated root dentin.

METHOD

Bovine tooth roots were transversely cut into 2-mm thick sections and the root canals were enlarged with a taper of 0.06. An outer layer of resin composite was bonded to each section to make the root canal-to-outer radius ratio smaller than 1/3. The resulting discs were treated with irrigants at the inner surface and then fractured by inserting through the center a steel rod of the same taper attached to a universal test system. Fracture strength was calculated by using Lame's equations for thick-walled cylinders. Micro-indentation was performed to evaluate the depth of dentin affected by irrigation. Finite element analysis (FEA) was performed to verify the reasonableness of using resin composite to surround the dentin section as well as the analytical solution.

RESULTS

The fracture strength of endodontically-treated root dentin based on the analytical solution for a homogeneous section was 139.69 ± 32.59 MPa. However, FEA that took into account root canal softening caused by the irrigants showed that this was overestimated by about 33.5%. The corrected fracture strength of treated dentin was 114.58 ± 26.74 MPa. By incorporating the layer of affected dentin into the analytical solution, the difference in the fracture-causing stress between the analytical and numerical solutions dropped to around 9.5%.

SIGNIFICANCE

A relatively simple but clinically relevant method has been developed for measuring the fracture strength of endodontically-treated root dentin. The method could be applied to root dentin that is treated by conventional canal opening and irrigation.

Dental Trauma

Dental trauma and injuries to the dentition are difficult to treat because the treatment goals serve to restore esthetics and function. The oral and maxillofacial surgeon is often called on to coordinate the efforts of rehabilitation after a dentoalveolar injury. A comprehensive understanding of the ideal treatments and use of endodontic, orthodontic, periodontal, and pediatric dental colleagues leads to the best possible results with regards to a restoration of form and function. This article provides a succinct review of the oral and maxillofacial surgeon's treatment in dentoalveolar trauma. Epidemiology, treatment, and preventative measures are discussed in this article.

Diagnosis of root fractures using cone-beam computed tomography: difference of vertical and horizontal root fracture

OBJECTIVES

The aim of this study was to investigate the occurrence of vertical and horizontal root fractures using cone-beam computed tomography (CBCT).

METHODS

We reviewed the CBCT images of 51 patients who were examined by CBCT for the diagnosis of root fracture. The occurrences of vertical and horizontal root fractures were investigated concerning the pulpal vitality and the kind of tooth, and analyzed by cross-tabulation. The fracture direction of vertical root fracture and the fracture angle were also investigated, and analyzed by cross-tabulation and Kruskal-Wallis test, respectively.

RESULTS

The occurrence of vertical and horizontal root fractures was statistically significantly different between vital tooth and non-vital tooth (p = 0.044). The occurrence of vertical and horizontal root fractures was also different among anterior, premolar, and molar teeth (p = 0.004). The kind of tooth on traumatized tooth was only anterior teeth and the number was larger on horizontal root fracture. The occurrence of vertical and horizontal root fractures on non-traumatized tooth was different among the kind of tooth (p = 0.007), and the number of vertical root fracture was larger than that of horizontal root fracture on premolar teeth. Fracture direction was not different, but the fracture angle was different among the kind of tooth on vertical root fracture (p = 0.027).

CONCLUSIONS

The results suggested that the number of vertical root fracture was larger on non-vital tooth and that of horizontal root fracture was larger on vital tooth. The number of vertical root fracture was larger on premolar teeth.

Effect of digital enhancement on the radiographic assessment of vertical root fractures in the presence of different intracanal materials: an in vitro study

OBJECTIVES

To evaluate the effect of enhancement tools of intraoral digital radiographs on the assessment of vertical root fracture (VRF) and to quantify the resultant image noise.

MATERIALS AND METHODS

Thirty single-rooted human teeth (15 control and 15 fractured) were each radiographed in four intracanal conditions: no filling, gutta-percha, metal post, and fiberglass post, totaling 120 original images. Two filters were applied to the original images-Sharpen filter (SF) and Edge Enhancement filter (EE), and brightness and contrast were adjusted in four combinations (B&C1 to 4), resulting in 840 images. Five oral radiologists analyzed the images for VRF detection. Pixel intensity was obtained in two regions from the radiographs. Diagnostic values were calculated and compared by two-way ANOVA, and the SD values of pixel intensity values were compared by one-way ANOVA (α = 0.05).

RESULTS

There were no significant differences in accuracy for VRF detection between the experimental groups (p > 0.05). Teeth with metal post presented the lowest sensitivity (p < 0.05) for all experimental conditions, except for SF and EE (p > 0.05). B&C2, B&C3, and B&C4 had higher specificity than SF (p ≤ 0.05) for all intracanal conditions. Analysis of pixel intensity showed that all enhanced images presented statistically significant higher noise compared to those of the original images (p ≤ 0.05).

CONCLUSION

Digital enhancement tools in digital radiography increase image noise; however, they can be used without compromising VRF detection.

CLINICAL RELEVANCE

The use of digital enhancement does not impair the detection of VRF and, therefore, can be applied for this purpose according to the observer preference.

Effect of occlusal slope related to uneven attrition on root stress distribution and potential fracture

Background/purpose

Severely uneven occlusal attrition is thought to play an important role in the occurrence of spontaneous vertical root fracture (VRF), a frequent problem among Chinese people. This study evaluated the influence of occlusal slope related to uneven attrition on the root stress condition.

Materials and methods

A finite element model of the mandibular first molar was established. Two different occlusal slope patterns were simulated in 5 models: (A) sound tooth, (B) 0.5–1.5 mm and (C) 2–3 mm attrition increased buccally, and (D) 0.5–1.5 mm and (E) 2–3 mm attrition increased distally. A static load of 200 N was applied vertically or angled at 45° to the longitudinal axis. The von Mises stress was evaluated.

Results

Under vertical loading, more stress was transferred from the cervical to the middle root with attrition, especially the mesial root, while stress declined with attrition under oblique loading. Stress was mainly distributed in the buccal surface and mesial root with vertical loading, or in the lingual surface and distal root with oblique loading. The maximum von Mises with oblique loading was significantly higher than with vertical loading.

Conclusion

Uneven occlusal attrition made the middle of the mesial root bear more stress, increasing fracture risk under vertical load. This finding suggests that timely restoration of the sloped occlusal morphology in teeth with severe attrition should be recommended to prevent VRFs. Lateral loading was not a risk factor of typical vertical root fractures, but the high stress could cause distal root cervical fracture.

Influence of elastic modulus mismatch between dentin and post-and-core on sequential bonding failure

PURPOSE

Clinical failures of teeth restored with post-and-core are critical issues for the survival of teeth and maintenance of oral functions. A tooth with post-and-core restoration is a complex structure. Cement adhesion is believed to be the weakest component, and breakage in this component leads to changes in stress distribution in the complex structure. The tested hypothesis was that cement breaking processes of prosthetic treated teeth were affected by elastic properties of post-and-cores.

METHODS

Finite element analysis focused on sequential adhesion failure between the dentin and cement; the penalty function method was used to analyze stress during each stage of bonding conditions. Failure patterns of adhesion and stress distribution within dentin under load of different materials of post-and-core was observed.

RESULTS

Although, an initial failure of cement was observed at the palatal crown margin regardless of the material. Different patterns of adhesion failure between dentin and post-and-cores were observed by different elastic properties of post-and-cores. Stress concentration was observed at the corresponding areas of interface between adhesion failure and continued elements using both post-and-cores.

CONCLUSIONS

Using failure criteria for cement adhesion, sequential changes of adhesion failure between dentin and post-and-cores were observed. Local stress concentrations leading to severe destruction of dentin were caused by not only materials of post-and-cores but their adhesive conditions to dentin. Nonlinear finite element analysis (FEA) using complex structure model which deals with alterations of interfacial condition between components could provide the simulation for the clinical failure of teeth restored with post-and-cores.

Diagnosis, Clinical Management and Three-Year Follow-Up

Objective:

The aim of this retrospective analysis is to describe and to evaluate the middle third horizontal root fractures, long term clinical management results and to estimate the effect of treatments factors upon healing and survival rate.

Methods:

Our clinical study included 42 patients presenting a middle third horizontal root fracture in permanent dentition. For each patient at t₀ the parameters recorded were: diastasis, mobility, sensibility, periodontal inflammation, pulpal pathology, associated fracture and dislocation of the coronal fragment. The follow-up was performed after 6 (t1), 12 (t2) and 36 (t3) months after the trauma, both clinically and radiologically. Clinical examination, vitality tests and a radiological evaluation (periapical x-ray) were performed.

Results:

At t₀ it was observed: diastasis (14, 3%), mobility (28, 6%), thermal sensibility (61, 9%), periodontal inflammation (4, 8%), pulpal pathology (38, 1%) and dislocation of the coronal fragment (47, 6%) of the patients. The treatment plan started with the coronal fragment repositioning and the blockage (splint) with the adjacent teeth in 47, 6% of cases.

A root canal treatment was performed at t₀ in 52,4% of the fractured teeth. Statistical analysis showed the highest level of significance between pulpal lesions (t₀) and associated fractures. The mobility, sensibility and pulpar lesions parameters, showed a reduction in relation to the follow up timing, with a main variation remarkably evident between t₀ and t1. The ratio between observation time and the presence of diastasis was statistically significant.

Conclusion:

The analysis of the clinical results exhibits the high success rate of a conservative approach in the treatment of teeth fractured in the middle third of the root.

Intentional Replantation of an Immature Incisor with a Transverse Root Fracture and Endo-Perio Condition: 4 Year Follow-Up

This case report describes the importance of continual examination for dental trauma and the efficacy of intentional replantation with retrograde root canal filling for a transverse root fracture in an immature incisor accompanied by subsequent periodontal-endodontic disease. In the treatment of traumatically fractured roots in immature incisors, continual examination is indispensable for the final diagnosis because roots in immature teeth are less calcified, resulting in less detailed radiological examinations. Thus, common dental trauma complications such as pulp necrosis may appear months after the initial examination. Endodontic treatment for transverse root fracture is mainly determined according to radiographic examination findings; for fractured immature roots, apexification with calcium hydroxide of the coronal fragment is generally applied. However, this method requires removal of considerable amounts of enamel and dentin to allow access to the cavity for preparation, which may increase the risk of future fractures. In contrast, intentional replantation with retrograde root canal filling does not require the removal or long-term application of calcium hydroxide. However, it requires careful extraction of the tooth, maintenance of root wetness during the extraoral procedure, rigid splinting, and oral hygiene control. Management of tooth mobility is also important in the post-replantation course.

The use of a fiber sleeve to improve fracture strength of pulpless teeth with flared root canals

OBJECTIVES

This study aimed to investigate how use of a fiber sleeve may reduce interfacial debonding and improve fracture strength of pulpless teeth with flared root canals.

METHODS

Pulpless premolars with flared root canals were restored either with a fiber-reinforced post (FRP) alone or with an FRP wrapped in a hollow tubular fiber sleeve. A normal root restored with an FRP alone served as a control. The integrity of resin-dentin and resin-fiber interfaces in the restored roots was evaluated by a stereoscopic system after penetrating a dye. Four roots were tested for each experimental group. Fracture resistance in pulpless premolars with flared root canals restored with an FRP alone or with an FRP/sleeve combination were investigated under bonded and non-bonded conditions with static fracture testing (n=8), and stress distribution in these restored premolars were tested by finite element analysis (FEA).

RESULTS

Flared root canals restored with an FRP/sleeve combination demonstrated superior integrity at the cervical resin-dentin interface to root canals with an FRP alone. Premolars with a flared root canal restored with an FRP/sleeve combination showed significantly greater fracture resistance compared with premolars restored with an FRP alone. FEA showed that once interfacial de-bonding extended to the cervical region of the root, stress concentration in the root dentin dramatically increased.

SIGNIFICANCE

The FRP/sleeve combination was effective in reducing debonding and, hence, improving the fracture strength of pulpless premolars with flared root canals.

Restoration of fractured endodontically treated mandibular first molar using custom made cast post and core

The successful treatment of posterior tooth with substantial damage to the tooth structure not only depends on root canal treatment but also by prompt restoration of lost coronal tooth structure. Endodontically treated teeth undergo loss of tooth substance due to dental caries, endodontic therapy or previous restoration and changes in physical characteristics, such as a reduced modulus of elasticity, which often leads to increased fracture susceptibility when compared to unrestored vital teeth.(1) Restoration of endodontically treated posterior teeth is more challenging because of their additional functional requirements. The restorative treatment of such teeth includes the decision of whether or not a post should be used. Post is a dental material placed in the root of structurally insufficient tooth when additional retention is needed to retain the core and coronal restoration.(2,3) However, preparation of a post space adds a certain degree of risk to restorative procedure like perforations and root fracture, especially if an over sized post channel is prepared.

Effects of different root canal preparation methods on root fracture resistance: A systematic review of the literature

AIM: To study the root fracture resistance after root canal preparation with Ni-Ti rotary instruments and stainless hand instruments by means of meta-analysis.

METHODS: Literature was researched in CNKI and CBMDisc, PubMed, CALIS, Proquest, Web of Science and 11 kinds of Chinese or English dentistry journals. Retrieval time on Internet was in all years and hand retrieval time was from January 2013 to October 2013. The literatures were selected through reading abstracts and full texts by two reviewers independently and Revman 5 software was used to analysize the literature.

RESULTS: Six articles met the inclusion criteria. According to Meta-analysis of tooth root bending properties, total standardized mean difference (SMD) was 0.63 (95%CI: -0.24-1.50, P > 0.05). That indicated there was no statistically significant between the two groups. Subgroup analysis was carried out. SMD were 2.22 (95%CI: 0.23-4.20, P < 0.05) and -0.61 (95%CI: -1.05- -0.17, P < 0.05) when the premolar teeth with a single canal or the mesiobuccal roots of molars were used as the materials for tests to compare the effects of different root canal preparation methods on root fracture resistance. That only indicated that there were statistically significant in two subgroups.

CONCLUSION: In vitro experiments, the effects on the fracture resistance of root had no statistical difference with Ni-Ti rotary instruments and stainless steel hand instruments in root canal preparation.

Effects of root canal preparation, various filling techniques and retreatment after filling on vertical root fracture and crack formation

AIM

To investigate the incidence of cracks in root dentin after rotary instrumentation and filling with cold lateral condensation (CL), single-cone obturation (SC), and warm vertical compaction (WV) and retreatment of each filling system.

METHODOLOGY

One-hundred sixty mandibular incisors were selected. Twenty teeth were left unprepared and served as a control, and the remaining 140 teeth were instrumented. Twenty teeth were assigned to an only prepared group. The remaining 120 teeth were assigned to three root canal filling groups and three retreatment groups (n = 20), as follows: CL, WV, SC, and retreatment of each filling system. All the roots were sectioned perpendicular to the long axis at 2, 4, 6, and 8 mm from the apex, and the sections were then observed under a stereomicroscope. The absence/presence of cracks and vertical root fractures were recorded, and the data were analyzed with a Pearson's chi-square test (P = 0.05).

RESULTS

No complete vertical root fractures were observed in the unprepared and only prepared groups. However, vertical fractures were observed in the filling and retreatment groups. There were significantly more cracks in the retreatment after WV group than the other groups, with the exception of the retreatment after SC, WV, and CL resulted in significantly more cracks than the only prepared and SC.

CONCLUSIONS

The filling techniques (except SC) caused more cracks than preparation only. The SC caused fewer cracks compared to the other filling techniques. The retreatment following the different filling techniques (except CL) caused more cracks than the original fillings.

Interdisciplinary rehabilitation of a root-fractured maxillary central incisor: A 12-year follow-up case report

Single-tooth implantation has become a common treatment solution for replacement of a root-fractured maxillary incisor in adults, but the long-term esthetic results can be unfavorable due to progressive marginal bone loss, resulting in gingival recession. In this case report, a maxillary central incisor with a root fracture in its apical one-third was orthodontically extruded and extracted in a 21-year-old female. Implant surgery was performed after a 3-month healing period, and the final crown was placed about 12 months after extraction. After 12 years, favorable osseous and gingival architectures were visible with adequate bone height and thickness at the buccal cortical plate, and no gingival recession was seen around the implant-supported crown. Although modern dentistry has been shifting toward simplified, clinical procedures and shorter treatment times, both general dentists and orthodontists should be aware of the possible long-term esthetic advantages of orthodontic extrusion of hopelessly fractured teeth for highly esthetically demanding areas and should educate and motivate patients regarding the choice of this treatment solution, if necessary.

Management of horizontal root fractures by fabrication of canine protected occlusion using composite resin

Traumatic injuries of the face often involve root fractures especially in anterior teeth. The prognosis and the treatment of the root fracture depend on the extent of the fracture line, general health and patient compliance. This case report outlines a new conservative trial treatment modality to stabilize the maxillary central incisors with horizontal root fracture on the cervical to middle third by fabricating canine guidance to remove loading on the traumatized maxillary central incisors during eccentric movements and thus inducing spontaneous healing of the fractured line between the fragments. Radiographs after thirty months showed adequate healing with no signs of pathological changes including root resorption, ankylosis or displacement. Long term follow-up revealed that vitality, stability and aesthetics were maintained and the patient was satisfied with the outcome.

Fracture resistance of retreated roots using different retreatment systems

OBJECTIVES

This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems.

METHODS

Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests.

RESULTS

There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups.

CONCLUSIONS

Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.