Vertical root fracture resistance and crack formation of root filled teeth treated with or without minimally invasive endodontics

doi:10.21203/rs.3.rs-2487824/v1

Download PDF

Research Article

Vertical root fracture resistance and crack formation of root filled teeth treated with or without minimally invasive endodontics

https://doi.org/10.21203/rs.3.rs-2487824/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this older preprint version

Read the latest preprint version →

The aim was to investigate the vertical root fracture (VRF) resistance and crack formation of root filled teeth treated with (+) or without (–) minimally invasive endodontic (MIE) preparation. Human maxillary central incisors of similar size were decoronated, randomized into six groups (n = 18, power = 0.9) and embedded in acrylic blocks with artificial periodontal ligament. In the +MIE group, root canals were prepared with nickel-titanium (NiTi) rotary files up to size #40, taper 0.04 and filled with conventional gutta-percha/sealer (C) or adhesive (A) single-cone obturation. Preparations of the –MIE group were enlarged with NiTi rotary and K-files up to ISO size #80 and filled according to C or A. Controls either received no treatment or left unfilled after preparation. After thermocycling and staircase loading in a chewing simulator, the crack formation on the root surface was microscopically examined and classified as no defect, craze line, vertical crack, and horizontal crack. Subsequently, the samples were loaded until root fracture. Data were analyzed by Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction. Post hoc analysis revealed no significant difference in the incidence of defects between the groups (P ≥0.0772). VRF resistance was significantly higher in untreated teeth than in +MIE/C (P = 0.0202), but not significantly different between other groups (P ≥ 0.0680). Both VRF resistance and crack formation of root filled teeth were statistically indistinguishable with or without MIE preparation. Adhesive root filling did not improve the fracture susceptibility. Most dentin defects were vertical root cracks.

Dentin crack

Minimally invasive endodontics

Root canal

Staircase

Vertical root fracture

The primary goal of root canal therapy is to treat or prevent apical periodontitis by removing infected hard and soft tissue, disinfecting the root canal system and preparing the root canal space for a three-dimensional tight root filling [1, 2]. Long-term survival rates of 86% after 20 years have been reported for root filled teeth [3], although success depended on several factors [4]. Reasons for failure included persistent or recurrent infections with and without apical pathology [5], but also root fractures, especially vertical root fracture (VRF) [6]. Multiple factors have been associated with the development of VRF. Literature noted that excessive dentin removal due to access cavity and root canal preparation, altered biomechanical properties of dentin, prolonged exposures to chemical agents (irrigants and intracanal dressings), excessive pressure exerted on the canal wall during root filling, and placement of posts may increase pre-existing cracks within root dentin or cause new crack formation [6]. Subcritical cracks could propagate under mechanical stimuli such as chewing forces or traumatic overload into VRF, often requiring tooth extraction [6]. Although a low prevalence of VRF in root filled teeth has been reported [7], other investigations showed a risk of up to 32% [6, 8].

Several authors suggested that minimally invasive endodontic (MIE) treatment, which consists of a small access cavity and minimal canal preparation, as well as adhesive-based approaches increase the fracture resistance of root filled teeth [9–12]. However, smaller access preparations made cleaning, disinfection and obturation more difficult [13, 14] and did not necessarily improve the fracture susceptibility of root canal-treated teeth [14, 15]. In cases that can be adhesively restored with composite resins, there was no significant difference in fracture resistance between teeth treated with traditional straight-line and minimally invasive access cavity [16]. The important role of adhesive restorative techniques in coronal reinforcement was highlighted [12, 16].

Canal preparations should also be as conservative as practical to preserve the root dentin and the anatomical shape of the root canal [1, 2, 10]. To reduce the risks of crack formation and root fracture or preparation complications such as root perforation, authors suggested MIE preparations with file sizes between #20 to #40 and tapers of 0.04 to 0.06 mm/mm, root canal morphology dependent [9, 10, 17]. On the other hand, arguments were made for better cleaning and disinfection of the root canal with larger file sizes in combination with 0.02 to 0.05 tapers, even if the irrigations were activated with a sonic device [1, 9, 18]. In this regard, larger file tapers could not compensate for smaller file sizes [19]. However, it remains controversial whether the selected file size and taper influence crack formation [17, 21] and fracture resistance [9, 17, 20], respectively, and whether a potential preparation-related root weakening can be tolerated with an adhesive root filling [22–24]. Furthermore, there is no clear evidence regarding the effects of MIE preparation and adhesive obturation technique on the clinical success rate of root filled teeth [2, 10, 11].

Studies were usually concerned with fracture resistance and crack formation under static loading [25]. Few authors focused on fatigue loading of root filled teeth [21, 26, 27], which provides better clinical insight compared to static loading [25]. Since the number of cycles to root fracture is high under functional chewing force [6], staircase loading with gradually increasing force for a certain number of cycles has also been proposed [26, 28]. The aim of this study was to evaluate the influence of MIE preparation on resistance against VRF and dentin defects of conventionally or adhesively root filled teeth after chewing simulation. The null hypothesis to be tested was that the results would not differ significantly between the groups.

Sample size calculation

The sample size was calculated using unpublished pilot data (n = 5) and the two-sided Welch's t-test for unequal variance at a significance level of alpha = 0.05 and a power of 0.9 (nQuery Advisor version 7, Statistical Solutions, Cork, Ireland). The sample size was evaluated as n = 15 for each group. Considering possible dropouts and a deviation of normality assumptions a sample size of n = 18 was used in the study.

Sample Preparation

Extracted human maxillary central incisors with similar dimensions, straight root canal, and mature apical foramen were collected and disinfected in accordance with the university’s policy. The teeth were cleaned with scalers and stored in 1% chloramine trihydrate solution. Crowns were removed using a diamond saw at slow speed (WOCO 50/Med, Conrad, Clausthal-Zellerfeld, Germany) to obtain a standardized 13 mm root length. A stereomicroscope (Stemi SV8, Zeiss, Oberkochen, Germany) at 12 x magnification was used to exclude teeth with carious lesions or pre-existing dentin defects. After numbering the teeth, the cross sections of the roots were measured at the level of the cutting surface in the mesio-distal and bucco-palatal direction with a digital caliper (Garant, Hoffmann, Munich, Germany). The area of the ellipsed root cross section (A) was calculated according to: A = π/4 x a x b (where a and b were the mesio-distal and bucco-palatal dimension in mm). Roots of extreme size were excluded. The remaining samples were randomized into six groups (two control and four experimental groups) of 18 roots each using the randomization software at the university’s institute of epidemiology and medical biometry. No significant differences were found between the groups regarding cross-sectional area (35.7 ± 3.6 mm²). To simulate the periodontal ligament with relatively uniform stress distribution, the roots were wrapped in one layer of latex rubber milk (Suter Kunststoffe, Jegenstorf, Switzerland) with a thickness of approximately 250 µm and embedded in acrylic resin (Technovit 4071, Heraeus Kulzer, Hanau, Germany) with the cervical root third being exposed.

Root Canal Treatment

In the negative control, the root canals were left untreated. Root canal treatments were performed by a single operator with (+) or without (–) MIE preparation. Canal patency was controlled with hand files ISO size #10 (K-file, Kerr, Orange, California, USA). The working length was set to 12 mm and K-files up to ISO size #20 were used to create a glide path. Canals in the + MIE group were prepared with nickel-titanium (NiTi) rotary files (Twisted File, Kerr) using the single-length technique in the file sequence of size #25, size #30, and size #35 in combination with 0.06 tapers up to size #40 and 0.04 taper. The files were rotated with a 4:1 reduction handpiece (WD-77 M, W & H, Buermoos, Austria) powered by a torque-control motor (Endo IT professional, VDW, Munich, Germany). During instrumentation, the canals were irrigated with 5 ml of 3% sodium hypochlorite (NaOCl) and 15% ethylenediaminetetraacetic acid (EDTA) solutions (Glyde File Prep, Dentsply Sirona, Ballaigues, Switzerland). After a flush with 5 ml distilled water, the canals were dried with paper points and filled according to the single-cone technique and respective manufacturer’s instructions. For conventional gutta-percha/sealer obturation (C), a calcium hydroxide sealer (Sealapex, Kerr) was mixed in equal amounts of base and catalyst paste for 15–20 s and applied to the canal walls using a lentulo spiral (VDW). The matched Twisted File gutta-percha cone (Kerr) was inserted in the canal to working length and condensed with a plugger 1 mm below the canal opening. For adhesive obturation (A), a self-adhesive methacrylate resin sealer (RealSeal SE, Kerr) was mixed using the automix syringe provided by the manufacturer and applied to the canal walls with the lentulo spiral. A matched polymer-based cone (Resilon, Kerr) was seated in the canal to working length and condensed 1 mm below the canal opening. The adhesive obturation was light cured for 40 s with an LED curing light (Bluephase, Ivoclar Vivadent, Schaan, Liechtenstein) at 1200 mW/cm² light intensity. Canals of the –MIE group were prepared as those of the + MIE group, but then enlarged with Twisted File size #50 and 0.04 taper, followed by manual widening with K-files from ISO size #60 and ISO size #70 up to ISO size #80. During instrumentation, the canals were irrigated with 5 ml of 3% NaOCL and 15% EDTA. After a flush with 5 ml distilled water and drying with paper points, the canals were either left unfilled (positive control) or filled according to C and A, respectively. The canal orifices were filled with a temporary filling material (Cavit, 3M Espe, Seefeld, Germany).

Chewing Simulation And Vrf Testing

After storage in water for 24 h at 37°C, the samples were subjected to 1500 thermocycles in distilled water at 5–55°C with a dwelling time of 20 s in each bath and a transfer time of 5 s (Haake W15, Willytec, Gräfelfing, Germany). Mechanical loading was performed according to the staircase method starting at a load of 25 N at an angle of 10° to the axial direction of the roots in a chewing simulator (Standard 2002, Willytec). Every 20,000 cycles at a frequency of 2 Hz, the load was increased in increments of 25 N until 120,000 cycles were reached. The 1 mm unfilled canal space ensured that the force applied by the coneshaped metal antagonist with an angle of 120° was transmitted to the root dentin rather than the root canal filling. The diameter of the truncated cone was dimensioned in such a way that the metal tip fitted exactly into the canal space.

VRF resistance and crack formation was determined from the samples that survived chewing simulation. Pre-testing failures (PTFs) were recorded. The external root surfaces were examined under the microscope using a cold light source (Stemi SV8, Zeiss). Because of the latex milk, the roots could easily be removed from the acrylic blocks. Pictures were taken with a digital camera at 12–100 x magnification (3CCD Color Video Camera, Sony, Tokyo, Japan). Crack formation was analyzed per root third (cervical, middle, apical) as follows: (a) no defect, (b) craze line, (c) vertical crack, and (d) horizontal crack. Representative images of the defect patterns are shown in Fig. 1. Different defect patterns in the same root third were recorded, resulting in a maximum of nine defects per root. After microscopic analysis, the roots were returned to the acrylic blocks and subjected to VRF testing. The same antagonist as used for the chewing simulator was attached to the load cell of a universal testing machine (Zwicki 1120, Zwick, Ulm, Germany). The samples were loaded until fracture with a crosshead speed of 1 mm/min. The fracture load (N) was recorded when the force in the load-strain curve decreased by 30%.

Statistics

Statistical analysis was performed with IBM SPSS version 19 for Windows (Chicago, IL, USA). The significance level was set in advance at α = 0.05. As the Shapiro-Wilk test indicated that the data of the VRF resistance (P = 0.002) and crack formation (P = 0.0001) were not normally distributed, differences between the groups were compared with the non-parametric Kruskal-Wallis test. Post hoc multiple comparisons were performed using the Mann-Whitney-U-test with Bonferroni correction for 15 two-group comparisons.

A total of seven PTFs were recorded. Two samples each from the negative control (untreated teeth) and the groups + MIE/A and -MIE/A as well as one sample from the group + MIE/C showed visible fractures after chewing simulation. VRF resistance and crack formation of the survived samples are presented as median with interquartile range in Table 1. Regarding the incidence of dentin defects, the results of the Kruskal-Wallis test indicated significant intergroup differences (P = 0.006). However, post hoc multiple comparisons did not show statistical evidence for significant difference between the groups (P ≥ 0.077). Minimally invasive preparation followed by adhesive obturation (+ MIE/A) resulted in the lowest number of dentin defects (1 [0–2]), while the unfilled preparation (positive control) caused the highest incidence of defects (3 [2–4]). Among the groups, 31.7% of the samples showed dentin defects in the apical root third, while 63.4% and 73.3% of the samples had defects in the cervical and middle root section, respectively. Majority of the dentin defects were vertical root cracks (56.3%) followed by horizontal root cracks (23.6%) and craze lines (20.1%).

Table 1

Median values with interquartile range of VRF resistance (N) and incidence of dentin defects (absolute number) of the different groups
Group	n	PTF	VRF resistance (N)			Dentin defect (absolute number)
Group			Median	Lower quartile	Upper quartile	Median	Lower quartile	Upper quartile
Positive control	18	0	1266.0	999.5	1501.7	3	2	4
Negative control	18	2	1433.0	1180.7	1539.3	2.5	2	4.75
+MIE/C	18	1	971.7	868.4	1184.5	2	0.5	3
+MIE/A	18	2	1185.0	1076.9	1377.3	1	0	2
–MIE/C	18	0	1287.1	1096.1	1457.0	2.5	2	3.25
–MIE/A	18	2	1396.9	1056.9	1540.1	1.5	0.25	3
Total	108	7	1239.5	1038.1	1460.0	2	1	3
A = adhesive Resilon/sealer obturation; C = conventional gutta-percha/sealer obturation; MIE = minimally invasive endodontics; PTF = pre-testing failure; VRF = vertical root fracture. Groups connected by vertical lines are significantly different (P < 0.05).

VRF resistance was significantly different between the groups (P = 0.008). Post hoc analysis revealed that the VRF resistance was significantly higher in untreated teeth than in root filled teeth involving minimally invasive preparation and conventional gutta-percha/sealer (+ MIE/C) (P = 0.020). No significant difference was shown between the other groups (P ≥ 0.068). Among the experimental groups, +MIE/C showed the lowest resistance to cause VRF (972 N [868–1185]), while adhesively root filled teeth without MIE preparation (–MIE/A) had the highest resistance to cause VRF (1397 N [1057–1540]).

The present study showed that vertical root fracture (VRF) resistance is significantly higher in untreated teeth than in root filled teeth treated with minimally invasive endodontic (MIE) preparation and conventional gutta-percha/sealer obturation. Regardless of the obturation material (conventional or adhesive), MIE prepared teeth did not differ significantly from their more invasively prepared counterparts. Therefore, the null hypothesis was partially accepted.

The teeth were loaded without considering the coronal access cavity to avoid confounding effects such as cuspal flexure and coronal reinforcement by adhesive restorative materials [24, 28, 29]. The data could not support the intuitively obvious theory that MIE treated teeth are less susceptible to fracture [9–12]. Finite element method (FEM) analysis of a maxillary central incisor revealed higher radicular stresses during loading when the root canal was prepared to larger diameters [30]. Fracture load data of maxillary central incisors confirmed a significant correlation between canal enlargement and fracture susceptibility [31, 32], whereas no such correlation was found in another FEM study using root dentin sections [33]. More recently, combined experimental and FEM analyses showed that the fracture load of root dentin sections increases with larger diameter of prepared canals [34]. This could be due to the fact that the circumferential area for stress distribution increases with canal enlargement [34]. However, the stress distribution was less uniform when the canal shape was oval, resulting in stress concentration areas [35]. Other factors such as the root morphology, the taper of the canal and its curvature also had an influence on fracture susceptibility [34, 35]. In the present study, the same group of teeth (maxillary central incisors) was used, with similar morphology (root length and cross-sectional shape) and relatively straight canals (Vertucci Type I). The diameter at the orifice level was ~ 1 mm in all canal preparations, while the apical canal diameter of the more invasive preparation was almost twice that of the MIE preparation. A wide range of apical canal diameters has been reported [9], and files up to size #80 were used for maxillary central incisors [31, 32]. Apical enlargement has been recommended in these teeth to remove bacteria and infected dentin in the oval canals [1]. For sufficient debridement in the buccolingual direction, a hybrid technique combining rotary NiTi files with conventional hand files has been proposed [1], which was also used in this study. FEM analysis suggested that eliminating stress-increasing areas such as in buccal and lingual recesses of oval canals reduces tensile stress in root dentin [35]. On the other hand, the use of larger and stiffer K-files may have resulted in more instrumentation stress on the root canal wall, especially at the narrow mesiodistal diameter of the canal [21]. This could explain the higher incidence of dentin defects compared to the MIE preparation with no significant difference between the two preparations.

The prepared canals were filled using the single-cone obturation technique to reduce the potential risk of dentin defects during root filling [29]. It was assumed that the filling forces are lower compared to other obturation techniques that exert compaction forces on the canal wall [29]. Nevertheless, no 'reinforcing' capabilities of the root filling were observed in this study, in contrast to other authors who confirm that the use of obturation materials can increase the fracture resistance of root filled teeth [23, 24]. Neither did obturation materials per se increase the VRF resistance of prepared teeth (positive control), nor were adhesively filled teeth more VRF resistant than their conventionally non-adhesively filled counterparts. Root filling also showed no significant effect on crack formation. Previous studies highlighted that the flexural properties such as tensile strength and elastic modulus of both gutta-percha and Resilon core materials and root canal sealers are too low compared to dentin to reinforce the root against fracture [22, 32]. The adhesive-based Resilon system was claimed to create a 'monoblock' in which the self-adhesive resin-based sealer is bonded to both the canal wall and the core material [22, 23]. However due to the high configuration factor and the associated shrinkage stress during polymerization of adhesive root fillings, the formation of a monoblock within the root canal was considered critical [22].

Regardless of the control or experimental group, the incidence of dentin defects decreased towards the apical third of the root. Most of these dentin defects were vertical root cracks. One of the possible reasons could be that direct loading of the root filling was avoided, which may have contributed to a stress reduction in the apical third. Instead, the load was transmitted to the root canal walls, which was more likely to cause vertical cracks and VRF due to the wedge effect, as previously described using a similar loading model [28]. Another explanation could be that the tubular density in the root canal decreases from cervical to apical. At high tubule density, cracks propagated more frequently through peritubular dentin, whereas at low tubule density, crack propagation was determined by intertubular dentin [36]. Fatigue analyses showed that peritubular dentin is more mineralized than intertubular dentin, more brittle and easier to crack [37]. Indeed, in microtensile tests using maxillary anterior roots, a significantly lower tensile strength was measured in cervical dentin than in middle-apical dentin [38]. In the clinical setting, however, coronal reinforcement by adhesive restorative materials or cusp coverage could lead to a more favorable stress distribution in the cervical region of the root.

Seven of the original 108 teeth tested did not survive the chewing simulation and were rated as pre-test failures (PTFs). It has been reported that in mechanical engineering, ~ 10% of fatigued samples are early technical failures due to inadequate design, manufacturing faults or accidental loads [25]. Failure fatigue of human tooth samples is also influenced by other factors such as differences in age, microstructure, dentin toughness, and functional or dysfunctional occlusal loading. The present sample selection did not show any external defects on the root surface when analyzed at 12 x magnification under a stereomicroscope. Nevertheless, defects in the root dentin could not be ruled out. Pre-existing cracks were observed in extracted teeth that may be due to storage, dehydration and procedural errors during extraction, rather than merely being due to the root canal therapy [21, 26, 27]. After chewing simulation, crack formation and two PTFs were also observed in untreated teeth. For further analysis in studies, PTFs were either assigned the fracture strength value of zero [39] or discarded after chewing simulation [40] as in this study. The rationale for exclusion was that PTFs also occurred in untreated teeth, for which high fracture load values were consistently reported in the literature and therefore used as negative controls [23, 27–29]. Furthermore, cyclic mechanical loading was found to cause dentin defects but not VRF in untreated teeth [26, 28]. The prospective power analysis indicated that significant results can be obtained with a sample size of n = 15 per group.

Within the limitations of this study, it can be concluded that root filled teeth with and without MIE preparation behaved similarly in terms of VRF resistance and crack formation after chewing simulation. Adhesive root filling of these teeth did not improve the fracture susceptibility compared with their gutta-percha filled counterparts. Most dentin defects were vertical root cracks.

Acknowledgements The authorsthankDr. MT. Bechtold for conducting the experiments in partial fulfillment of requirements for doctoral degree. The authors also thank Prof. B. Haller, Center of Dentistry, University Hospital Ulm for co-supervising the dissertation and Kerr, Sybron Endo for providing the file-obturation systems.

Author contributions AR conceived, designed and supervised the study, contributed to data analysis and interpretation, wrote, and revised the manuscript; HF supervised the experiments, contributed to study design, data analysis and interpretation, and revised the manuscript; RM contributed to data interpretation and performed the statistical analysis. All authors gave approval of the work.

Conflict of interest HF declares that he has no conflict of interest. RM declares that he has no conflict of interest. AR is an employee of Dentsply Sirona in Konstanz.

Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors.

Peters OA, Peters CI, Basrani B. Cleaning and shaping the root canal system. In: Berman LH, Hargreaves KM, editors. Cohen’s pathways of the pulp. St. Louis, MO: Elsevier; 2020. pp. 209–79.
Neelakantan P, Vishwanath V, Taschieri S, Corbella S. Present status and future directions: minimally invasive root canal preparation and periradicular surgery.Int Endod J. 2022;55 Suppl 4:845 – 71.
Mareschi P, Taschieri S, Corbella S. Long-term follow-up of nonsurgical endodontic treatments performed by one specialist: a retrospective cohort study about tooth survival and treatment success. Int J Dent. 2020;2020:8855612.
Ng YL, Mann V, Gulabivala K. Tooth survival following non-surgical root canal treatment: a systematic review of the literature. Int Endod J. 2010;43:171–89.
Siqueira JF Jr. Aetiology of root canal treatment failure: why well-treated teeth can fail. Int Endod J. 2001;34:1–10.
Patel S, Bhuva B, Bose R. Present status and future directions: vertical root fractures in root treated teeth.Int Endod J. 2022;55 Suppl 3:804 – 26.
Haueisen H, Gärtner K, Kaiser L, Trohorsch D, Heidemann D. Vertical root fracture: prevalence, etiology, and diagnosis. Quintenssence Int. 2013;44:467–74.
Yoshino K, Ito K, Kuroda M, Sugihara N. Prevalence of vertical root fracture as the reason for tooth extraction in dental clinics. Clin Oral Investig. 2015;19:1405–9.
Gluskin AH, Peters CI, Peters OA. Minimally invasive endodontics: challenging prevailing paradigms. Br Dent J. 2014;216:347–53.
Bürklein S, Schäfer E. Minimally invasive endodontics. Quintessence Int. 2015;46:119–24.
Mannocci F, Bitter K, Sauro S, Ferrari P, Austin R, Bhuva B. Present status and future directions: the restoration of root filled teeth. Int Endod J. 2022;55:1059–84.
Schestatsky R, Dartora G, Felberg R, Spazzin AO, Sarkis-Onofre R, Bacchi A, Pereira GKR. Do endodontic retreatment techniques influence the fracture strength of endodontically treated teeth? A systematic review and meta-analysis. J Mech Behav Biomed Mater. 2019;90:306–12.
Shabbir J, Zehra T, Najmi N, Hasan A, Naz M, Piasecki L, Azim AA. Access cavity preparations: classification and literature review of traditional and minimally invasive endodontic access cavity designs. J Endod. 2021;47:1229–44.
Silva EJNL, De-Deus G, Souza EM, Belladonna FG, Cavalcante DM, Simões-Carvalho M, Versiani MA. Present status and future directions – minimal endodontic access cavities. Int Endod J. 2022;55(Suppl 3):531–87.
Nawar NN, Kataia M, Omar N, Kataia EM, Kim HC. Biomechanical behavior and life span of maxillary molar according to the access preparation and pericervical dentin preservation: finite element analysis. J Endod. 2022;48:902–8.
Özyürek T, Ülker Ö, Demiryürek E, Yılmaz F. The effects of endodontic access cavity preparation design on the fracture strength of endodontically treated teeth: traditional versus conservative preparation. J Endod. 2018;44:800–5.
Puleio F, Lo Giudice G, Militi A, Bellezza U, Lo Giudice R. Does low-taper root canal shaping decrease the risk of root fracture? A systematic review. Dent J. 2022;10:94.
Aminoshariae A, Kulild JC. Master apical file size – smaller or larger: a systematic review of healing outcomes. Int Endod J. 2015;48:639–47.
McGurkin-Smith R, Trope M, Caplan D, Sigurdsson A. Reduction of intracanal bacteria using GT rotary instrumentation, 5.25% NaOCl, EDTA, and Ca(OH)₂. J Endod. 2005;31:359–63.
Yildiz ED, Fidan ME, Sakarya RE, Dinçer B. The effect of taper and apical preparation size on fracture resistance of roots. Aust Endod J. 2021;47:67–72.
Heberer MT, Roggendorf HC, Faber FJ, Lawrenz NA, Frankenberger R, Roggendorf MJ. Longitudinal craze line propagation in human root dentin after instrumentation with NiTi rotary files of different instrument tapers after long-term chewing simulation. Clin Oral Investig. 2022;26:2671–79.
Kim YK, Grandini S, Ames JM, Gu L, Kim SK, Pashley DH, Gutmann JL. Tay Fr. Critical review on methacrylate resin-based root canal sealers. J Endod. 2010;36:383–99.
Tan M, Chai Z, Sun C, Hu B, Gao X, Chen Y, Song J. Comparative evaluation of the vertical fracture resistance of endodontically treated roots filled with Gutta-percha and Resilon: a meta-analysis of in vitro studies. BMC Oral Health. 2018;18:107.
Uzunoglu-Özyürek E, Küçükkaya Eren S, Karahan S. Effect of root canal sealers on the fracture resistance of endodontically treated teeth: a systematic review of in vitro studies. Clin Oral Investig. 2018;22:2475–85.
Ordinola-Zapata R, Fok ASL. Research that matters: debunking the myth of the “fracture resistance” of root filled teeth. Int Endod J. 2021;54:297–300.
Barreto MS, Moraes Rdo A, Rosa RA, Moreira CH, Só MV, Bier CA. Vertical root fractures and dentin defects: effects of root canal preparation, filling, and mechanical cycling. J Endod. 2012;38:1135–9.
Missau T, De Carlo Bello M, Michelon C, Mastella Lang P, Kalil Pereira G, Baldissara P, Valandro LF, Souza Bier CA, Pivetta Rippe M. Influence of endodontic treatment and retreatment on the fatigue failure load, numbers of cycles for failure, and survival rates of human canine teeth. J Endod. 2017;43:2081–7.
Rathke A, Frehse H, Hrusa B. Vertical root fracture resistance and crack formation of root-canal-treated teeth restored with different post-luting systems. Odontology. 2022;110:719–25.
Lin GSS, Singbal KP, Noorani TY, Penukonda R. Vertical root fracture resistance and dentinal crack formation of roor canal-treated teeth instrumented with different nickel-titanium rotary systems: an in-viro study. Odontology. 2022;110:106–12.
Ricks-Williamson LJ, Fotos PG, Goel VK, Spivey JD, Rivera EM, Khera SC. A three-dimensional finite-element stress analysis of an endodontically prepared maxillary central incisor. J Endod. 1995;21:362–7.
Okitsu M, Takahashi H, Yoshioka T, Iwasaki N, Suda H. Effective factors including periodontal ligament on vertical root fractures. Dent Mater J. 2005;24:66–9.
Hanada T, Quevedo CG, Okitsu M, Yoshioka T, Iwasaki N, Takahashi H, Suda H. Effects of new adhesive resin root canal filling materials on vertical root fractures. Aust Endod J. 2010;36:19–23.
Chai H, Tamse A. Fracture mechanics analysis of vertical root fracture from condensation of gutta-percha. J Biomech. 2012;45:1673–8.
Munari LS, Bowles WR, Fok ASL. Relationship between canal enlargement and fracture load of root dentin sections. Dent Mater. 2019;35:818–24.
Versluis A, Messer HH, Pintado MR. Changes in compaction stress distributions in roots resulting from canal preparation. Int Endod J. 2006;39:931–9.
Jainaen A, Palamara JEA, Messer HH. Effect of dentinal tubules and resin-based endodontic sealers on fracture properties of root dentin. Dent Mater. 2009;25:e73–81.
Arola D, Reprogel RK. Effects of aging on the mechanical behavior of human dentin. Biomaterials. 2005;26:4051–61.
Mannocci F, Pilecki P, Bertelli E, Watson TF. Density of dentinal tubules affects the tensile strength of root dentin. Dent Mater. 2004;20:293–6.
Naumann M, Preuss A, Frankenberger R. Reinforcement effect of adhesively luted fiber reinforced composite versus titanium posts.Dent Mater. 2007;138 – 44.
Büttel L, Krastl G, Lorch H, Naumann M, Zitzmann NU, Weiger R. Influence of post fit and post length on fracture resistance. Int Endod J. 2009;42:47–53.

Download PDF

Version 1

posted

You are reading this older preprint version

Read the latest preprint version →

Vertical root fracture resistance and crack formation of root filled teeth treated with or without minimally invasive endodontics

Status:

Version 1

Abstract

Figures

Introduction

Materials And Methods

Sample size calculation

Sample Preparation

Root Canal Treatment

Chewing Simulation And Vrf Testing

Statistics

Results

Discussion

Conclusions

Declarations

References

Status:

Version 1