Endodontics: part 4. Morphology of the root canal system

Micro-CT and histological examination of accessory canals in 34 equine cheek teeth

Accessory canals and apical deltas have been extensively studied in human dentistry. Their clinical role as a difficult to clean reservoir for bacteria during endodontic treatments has been well described. Many papers describe in detail the pulp anatomy of equine dentition but little attention has been given to their apical ramifications. The goal of this paper is to describe the presence and anatomy of these accessory canals and apical deltas in healthy equine cheek teeth and discuss their possible relevance in the light of equine endodontics. To accomplish this, 15 maxillary and 19 mandibular healthy cheek teeth were collected ranging from Triadan 06 s to 11 s with eruption ages from 4 to 9 years. Their root anatomy was documented in detail based on micro computed tomography images. A subset of 3 teeth also underwent histological examination. Accessory canals were found in all but two teeth examined. Up to 44 accessory canals per tooth have been found with locations ranging from the root furcation down to the apex of the root and with highly variable diameters. Apical deltas in different stages of development were found in 84% of the roots. The presence of accessory canals identified on microCT images could be confirmed using histological examination although some of them were obliterated by reparative dentin. Accessory canals can be found in most equine cheek teeth and add complexity to their endodontic anatomy. This could have important implications for their treatment in case of pulp pathology. In humans, failure to remove bacterial biofilm from such canals has been associated with failure of endodontic treatment. Research on diseased equine teeth is required to gain a better understanding of their clinical relevance in horses.

Improvement and analysis of mechanistic modeling of root canal preparation by a computer-based method

BACKGROUND AND OBJECTIVE

Root canal preparation is a cutting process between nickel-titanium (Ni-Ti) file and root canal, which aims to remove the bacteria and to keep teeth from infection. A mechanistic model in root canal preparation is proposed to investigate the mechanical mechanism of Ni-Ti file, which is essential to prevent physical and thermal damage on root canal.

METHODS

First, the mathematic modeling is introduced based on oblique cutting theory, which the loading condition of Ni-Ti file is derived from each cutting element by expressing a function of geometric parameters. For the modeling improvement, a cutting simulation algorithm (CSA) based on Boolean operation is proposed to achieve the complicated cutting situation between root canal and Ni-Ti file instantaneously. After establishment of model, the predictive precision is verified by conducting in vitro experiments. Eighteen artificial root canals were prepared in 6 mm straight and 2 mm C-shaped curved specification with 0.3 mm diameter, which was a single canal for each position, all the canals do not have connections with each other. During experiments, root canals were prepared using Wave One Gold (GWO) instruments with reciprocating rotational motion. Different influential factors (curvatures of root canal and movements of Ni-Ti file) and cutting parameters (feed rate and spindle speed) were analyzed by conducting a series of simulations under the mechanistic model.

RESULTS

Experiment results show that the predictive error of thrust force based on the proposal model is around 15%. The thrust force will increase dramatically after Ni-Ti file gets into craved canal. It can be indicated that the curvatures of root canal, movements of Ni-Ti file have a strong influence on root canal preparation. 20° increasement of curved degrees can lead to the 0.73 N increase of thrust force, while pecking movement can decrease 19.88% of thrust force compared with continues one. Furthermore, investigation on pecking distance represent that 2-1 mm movement can effectively reduce the thrust force of 15.82% compared to 4-2 mm movement.

CONCLUSION

Based on simulation results, 2-1 mm pecking movement is recommended for dentists compared with 4-2 mm pecking movement or continues movement. In addition, this paper provides a novel insight of interactive mechanism between Ni-Ti file and root canal, so as to contribute to both the theoretical and practical research by elucidating mechanisms and providing quantitative predictions that can be validated. Compared with conventional analytical model, both calculated precision and efficiency are improved in the proposed model.

Shaping ability of three nickel-titanium rotary instruments in simulated L-shaped canals: OneShape, Hero Shaper, and Revo-S

Background

Shaping ability of a file plays an important role during instrumentation in an endodontic treatment. This study aimed to compare the shaping ability of OneShape (OS), Hero Shaper (HS), and Revo-S (RS) instruments in simulated L-shaped canals.

Methods

Forty-eight simulated L-shaped canals were prepared to an apical size of 25 using OS, HS, and RS (all from Micro-Mega SA, Besançon, France), (n = 16 canals/group) systems. The amount of resin removed after each canal's preparation was measured and compared after producing a composite image made from the superimposition of pre and post-instrumented canals. Canal aberrations and the preparation time were also recorded. The data were statistically analysed by using ANOVA, Tukey, and Chi-square tests.

Results

One file fractured during instrumentation in the RS group. A significant difference was found at the apical end of the prepared simulated canal between the groups, with RS showing the least amount of resin removal from the inner side of the canals and HS showing the highest amount of resin removal from the outer side (P < 0.05). Regarding the total width of the canals after preparation, a significant difference was found between the groups at the apical end and the straight portion of the canals, and RS removed the least amount of resin at the straight portion of the canals (P < 0.05). No statistically significant differences were found between the different instruments regarding canal aberrations' incidence (P > 0.05).

Conclusions

All of the files showed a tendency to straighten the canals, whereas OS files maintained the original canal curvatures well.

Nanotherapeutics for regeneration of degenerated tissue infected by bacteria through the multiple delivery of bioactive ions and growth factor with antibacterial/angiogenic and osteogenic/odontogenic capacity

Therapeutic options are quite limited in clinics for the successful repair of infected/degenerated tissues. Although the prevalent treatment is the complete removal of the whole infected tissue, this leads to a loss of tissue function and serious complications. Herein the dental pulp infection, as one of the most common dental problems, was selected as a clinically relevant case to regenerate using a multifunctional nanotherapeutic approach. For this, a mesoporous bioactive glass nano-delivery system incorporating silicate, calcium, and copper as well as loading epidermal growth factor (EGF) was designed to provide antibacterial/pro-angiogenic and osteo/odontogenic multiple therapeutic effects. Amine-functionalized Cu-doped bioactive glass nanospheres (Cu-BGn) were prepared to be 50-60 nm in size, mesoporous, positive-charged and bone-bioactive. The Cu-BGn could release bioactive ions (copper, calcium and silicate ions) with therapeutically-effective doses. The Cu-BGn treatment to human umbilical vein endothelial cells (HUVEC) led to significant enhancement of the migration, tubule formation and expression of angiogenic gene (e.g. vascular endothelial growth factor, VEGF). Furthermore, the EGF-loaded Cu-BGn (EGF@Cu-BGn) showed pro-angiogenic effects with antibacterial activity against E. faecalis, a pathogen commonly involved in the pulp infection. Of note, under the co-culture condition of HUVEC with E. faecalis, the secretion of VEGF was up-regulated. In addition, the osteo/odontogenic stimulation of the EGF@Cu-BGn was evidenced with human dental pulp stem cells. The local administration of the EGF@Cu-BGn in a rat molar tooth defect infected with E. faecalis revealed significant in vivo regenerative capacity, highlighting the nanotherapeutic uses of the multifunctional nanoparticles for regenerating infected/damaged hard tissues.

Characteristics of the Irrigant Flow in a Simulated Lateral Canal Under Two Typical Laser-Activated Irrigation Regimens

BACKGROUND AND OBJECTIVES

Photon-induced photoacoustic streaming (PIPS) and shockwave-enhanced emission photoacoustic streaming (SWEEPS) are two promising laser-activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (μPIV) measurement and will be compared with that of ultrasonic-activated irrigation (UAI).

STUDY DESIGN/MATERIALS AND METHODS

A μPIV system with 7 μm fluorescent tracer particles was adopted to measure two-dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non-cutting insert) operating at 40% unit power, was also measured for a direct comparison.

RESULTS

It was found that both SWEEPS and PIPS can activate a so-called "breath mode" during the irrigation. Namely, the induced irrigant flush presented a back-and-forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 μm and lower than LAI (P < 0.05).

CONCLUSION

Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back-and-forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

A Rare Case of Nonsyndromic Generalized Radiculomegaly with a Literature Review

Radiculomegaly is a rare condition involving elongated tooth roots. This condition has significant clinical implications and has been associated with syndromes such as oculofaciocardiodental syndrome. However, only a few nonsyndromic cases of radiculomegaly have been reported. Here, we report a case of nonsyndromic radiculomegaly in a Saudi individual. A subsequent review of the literature suggests endodontic management modalities for individuals with the dental findings demonstrated in the present case.

Root and root canal diversity in human permanent maxillary first premolars and upper/lower first molars from a 14th-17th and 18th-19th century Radom population

OBJECTIVE

The aim of this study was to assess whether analyzed groups from two historical periods: Late Medieval (LMP), and Modern (MP) from Radom varied in the number of tooth roots and root canal system morphology.

METHODS

Root morphology of 229 permanent human teeth were analyzed using Cone Beam Computed Tomography. Additionally, the mitochondrial DNA (mtDNA) of 29 individuals from the LMP and 31 from the MP was analyzed.

RESULTS

In LMP, the maxillary first premolars were dominated by one root, while in MP second and third roots also appeared. Maxillary first molars in LMP presented three roots, while two-rooted forms occurred in MP. All mandibular first molars from the LMP and almost all (98%) from MP presented two roots. The greatest diversity in terms of root canal number occurred in one-rooted maxillary first premolars, the mesiobuccal root of the maxillary first molars, and the mesial and distal roots of the mandibular first molars in both groups. A few haplogroups from outside Europe (C, N, and R) were recorded in the MP Radom population. Moreover, this population had substantially higher haplogroup diversity compared with the LMP population.

CONCLUSION

Odontological research indicates an increase in the diversity in the number of roots and the shape of root canals in MP. This information corresponds to genetic research, which also indicates an increase in the diversity of haplogroups during the MP.

Three-dimensional evaluation of labial alveolar bone overlying the maxillary and mandibular incisors in different skeletal classifications of malocclusion

OBJECTIVES

The purpose of this study was to investigate differences in the thickness of the labial bone overlying the maxillary and mandibular incisors in class I, II, and III skeletal classifications using three-dimensional cone-beam computed tomographs (CBCT) technology.

METHODS

Pretreatment CBCTs of 54 Caucasian subjects (44 males, 10 females) were collected from the archives of a graduate orthodontic clinic. The subjects were divided into three groups based on their skeletal classification. CBCT scans were oriented to the long axis of each maxillary and mandibular incisor from the root apex to incisal tip and the axial inclination of each incisor was measured and recorded. Labial bone thickness was measured at the apex (A) and at the midpoint (MP) on each maxillary and mandibular incisor. A linear measurement, perpendicular to the long axis, was recorded from the labial bone surface to the most anterior root surface at two points. The effects of skeletal classification, jaw, incisor position, and side on A, MP, and Inclination were evaluated using mixed-model ANOVA. A 5% significance level was used for all tests.

RESULTS

Significantly greater bone thickness at the apex and midpoint was reported in class III individuals than class I or II. Central incisors had significantly greater bone thickness at both the root apex and midpoint. Significantly greater bone thickness was noted in the mandible at the level of the apex. At the level of the midpoint, significantly greater thickness was reported in the maxilla. There was a positive correlation between thickness and angle within each jaw-incisor combination for class I patients and for central incisors in class III patients.

CONCLUSION

The thickness of labial alveolar bone over the incisors varies based on the underlying skeletal discrepancy in each patient. Skeletal discrepancy influences the inclination of the maxillary and mandibular incisors.

Root canal morphology of native Tanzanian permanent mandibular molar teeth

Introduction

Research has shown variations in morphology of root canals to differ amongst ethnic groups. We aimed to investigate the root morphology and canal configuration of permanent mandibular molars in a native Tanzanian population.

Methods

146 first and 85 second mandibular molars were collected from Tanzanian patients. After removal of the pulp tissues and staining using Methylene blue ink from the canal system, the teeth were decalcified and rendered clear using 98% methyl salicylate. The teeth were then examined under magnification of 10X for: number of roots, tooth length, number of canals, location of apical foramen, presence of an apical delta and canal configuration using Vertucci's classification.

Results

All mandibular molars had two separate roots. The mean tooth length for mandibular 1^st and 2^ndmolars were 21.7 mm and 20.5mm, respectively, with no statistically significant difference in mean tooth length between males and females. All the mesial roots 1st and 2^nd mandibular molars possessed two root canals, while 40.4% and 54.1% of the distal roots of 1^st and 2^nd molars, respectively, had two canals. The majority of the examined teeth had their apical foramen located centrally, with an apical delta present in the distal root of one-second molar. Root canal configuration types commonly reported were Type II in the mesial and Type I in the distal roots of the mandibular 1^st molar; while the 2^nd molar had, respectively, root types II / IV and type I.

Conclusion

There were observed variations in the morphology of root canals in a Tanzanian population. Caution is advised to clinicians when performing root canal treatment.

Root Canal Morphology of Maxillary First Premolars Using the Clearing Technique in a South Indian Population: An In vitro Study

Background:

The success of root canal therapy requires a good knowledge of root canal morphology. Literature review shows variations in a number of roots and canal morphology in studies done across the globe.

Aim:

The purpose of this study was to evaluate the root canal morphology in maxillary first premolars using the clearing technique in a South Indian population.

Methodology:

Two hundred and twenty-five extracted noncarious, nonfractured, sound maxillary first premolars were collected, cleaned, and were injected with India ink to stain the root canals. Teeth were then decalcified and cleared using methyl salicylate. Teeth were then viewed under a stereomicroscope to evaluate the number of roots, root canal morphology based on the Vertucci's classification, variations, and additional features such as accessory root canals, lateral canals, furcation canals, isthmus, and apical delta.

Results:

Nearly 52.88% of maxillary first premolars were single rooted, 44.88% had two roots, and 2.22% had three roots. Vertucci's Type IV root canal configuration was the most common type in maxillary first premolars and was seen in 66.51% of cases followed by Type II in 13.4%. Type I was seen in 9.76%, Type VI in 6.51%, Type VIII in 2.32%, Type III in 0.46%, Type V in 0.46%, and Type VII in 0% of teeth.

Conclusion:

The majority of the maxillary first premolars included in our study were single rooted and Vertucci's Type IV was the most common type of root canal configuration.

Comparison of the implementation of extra root canal treatment before and after fee schedule change in the Taiwan National Health Insurance System

BACKGROUND/PURPOSE

Endodontic treatment success depends on treatment of all root canals, but the implementation status is affected by various factors. We examined whether the fee payment change affected the extra root canal endodontic treatment (EXRCT) in adult teeth in the National Health Insurance (NHI) system of Taiwan since 2008. The effect of hospital level, sex, and age on EXRCT was also examined.

MATERIALS AND METHODS

Two longitudinal health insurance databases for 2005 and 2010 were used. Excluding third molars and endodontic retreatment, the EXRCT rate in permanent dentition were compared for different tooth positions, hospital levels, sex and age between 2005 and 2010.

RESULTS

In total, 80,995 teeth in 2005 and 76,018 in 2010 underwent root canal filling. The rate of EXRCT increased markedly from 2005 to 2010, particularly for the upper first molar (1.84% to 3.18%), lower first premolar (3.45% to 4.58%), lower first molar (12.4% to 18%), and lower second molar (0.95% to 1.87%). The difference between 2005 and 2010 remained statistically significant after adjustment for hospital level, sex, and age. The lower second molar had the highest adjusted odds ratio for the difference between 2005 and 2010 (1.99; CI: 1.49-2.66), followed by the upper first molar (1.91; CI: 1.55-2.35), lower first molar (1.60; CI: 1.47-1.75), and lower first premolar (1.38; CI: 1.11-1.72).

CONCLUSION

The payment change of Taiwan NHI seems to encourage the use of EXRCT in molars. Hospital level, sex, and age also affected the rate of EXRCT.

Differentiation of root canal morphology – a review of the literature

The morphological diversity of the inner anatomy of root canals in human permanent teeth is an issue mainly described in endodontics research. In recent years, it is a relatively new point in anthropological studies because it varies by sex, geographic and ethnic circumstances. An unusual number of root canals or their specific systems can differentiate populations around the world. The multiplicity of available methods for detecting root canal systems helps to better understand their complexity; however, most cannot be applied to anthropology due to limitations that occur in the bioarcheological material. Thorough knowledge of the heterogeneity and internal anatomy of the root canals supplies numerous classification systems proposed and improved over the years by many authors. A limited number of studies in the anthropological literature and future research will shed light onto the internal tooth morphology in historical populations. The aim of this paper is to describe various classification systems of root canals applied in endodontics. However, due to the often poor state of preservation and damage of archaeological derived remains, it seems that the best method is the approach that is the simplest and least complicated.

A computational simulation study on the acoustic pressure generated by a dental endosonic file: effects of intensity, file shape and volume

One of the uses of ultrasound in dentistry is in the field of endodontics (i.e. root canal treatment) in order to enhance cleaning efficiency during the treatment. The acoustic pressures generated by the oscillation of files in narrow channels has been calculated using the COMSOL simulation package. Acoustic pressures in excess of the cavitation threshold can be generated and higher values were found in narrower channels. This parallels experimental observations of sonochemiluminescence. The effect of varying the channel width and length and the dimensions and shape of the file are reported. As well as explaining experimental observations, the work provides a basis for the further development and optimisation of the design of endosonic files.

Anomalous morphology of an ectopic tooth in the maxillary sinus on three-dimensional computed tomography images

We describe a case of an incidentally-diagnosed ectopic tooth showing anomalous morphology in the maxillary antrum, using three-dimensional reconstruction of computed tomography images of the tooth obtained by multi-detector computed tomography.

Comparison of the flow characteristics of irrigants with standard and Max-i-Probe needles

The objectives of this study were to determine the direction and pattern of flow of irrigating solutions inside simulated root canals with different irrigation needles; and to determine whether different needle designs increase the likelihood of irrigating solution passing through the apical foramen. Two types of needles were compared: a standard needle with a bevel and an open end, and a needle with a side opening and closed rounded tip. Observations of irrigant flow within the canals indicated that the side-venting needle can be dangerous if the needle gauge is small and it reaches the full length of the canal, since this allowed irrigants to flow into the periapical area. With the standard needle, the fluid did not go beyond the tip of the needle when minimal irrigating pressure was employed. As the size of canal increased, the fluid did not extrude beyond the tip of both needles. However, if the needles bound in the canals, then the fluid was forced away from the needle tip, and the pressure applied to the syringe was directly proportional to the distance the fluid flowed away from the needle tip. Both side-venting and standard needles can be used for irrigation safely and effectively if a dynamic irrigation technique (moving the needle up and down inside the canals while irrigating) is employed.