Furcation canals in the human mandibular first molar

Middle mesial canal in mandibular first molar: A narrative review

Purpose

This review aimed to assess the incidence, anatomical characteristics, identification, and clinical management using conventional techniques and advanced tools to manage MMCs successfully.

Methods

Medline/PubMed and Scopus databases were searched using "Middle mesial canal," "Middle mesial root canal," OR "Accessory mesial canal" keywords from 1 January 1970 and 1 February 2023. The most pertinent articles were chosen for the review from the retrieved articles. In addition, relevant articles were added by manually searching the list of references.

Results

The incidence of MMC is noticeable in younger people, and the confluent canal is the most common type. The majority of MMCs merged with mesiobuccal (MB) canals rather than mesiolingual (ML) canals. Clinical management could be employed using the standard endodontics protocol, and recent radiography technologies, magnification, rotary, and obturation materials can facilitate the procedures.

Conclusion

The possibility of the incidence of MMC is not unusual. Detection and thorough debridement followed by obturation of the canal could increase the success rate of clinical outcomes.

Clinical identification and endodontic management of furcation canals: a case series

In the case of endodontic infection, the presence of furcation canals can be at the origin of a periodontal lesion located in the furcation. The furcation being very close to the marginal periodontium, this type of lesion can be favorable to the genesis of an endo-periodontal lesion. These furcation canals are lateral canals located on the pulp chamber floor and constitute one of the many physiological communication pathways between endodontic and periodontal tissues. These canals are most often difficult to localize, shape, and to fill because of their small diameter and length. The disinfection of the pulp chamber floor with sodium hypochlorite solution may contribute to the disinfection of furcation canals when they are not identified, shaped, and/or filled. This case series illustrates the endodontic management of visible furcation canals associated with an endo-periodontal lesion. These furcation canals had a large diameter which allowed their identification during the endodontic treatment.

Comparison of ADAMTS Levels in Pulp Tissue Samples of Healthy and Symptomatic Irreversible Pulpitis Teeth

AIM

The aim of this study was to compare the levels of different ADAMTS (-1,-4, and -9) related to the breakdown of the proteoglycans and TIMP-3 levels that inhibit ADAMTS in the extra cellular matrix (ECM) of healthy pulp and symptomatic irreversible pulpitis.

METHODS

Pulp tissue samples diagnosed with healthy and symptomatic irreversible pulpitis were collected from 48 participants. Healthy and inflamed pulps were directly transferred to Eppendorf® tubes and stored at -80 °C (Nüve-DF490, Ankara, Türkiye) until further use. Routine root canal treatment procedures for the teeth were performed, after which the treatment process was completed. The levels of ADAMTS-1, ADAMTS-4, ADAMTS-9, and TIMP-3 were measured in supernatants of human dental pulp tissue extracts using ELISA kits (USCN, Wuhan, China). Independent sample t test and one-way analysis of variance (ANOVA) were used for parametric data, Kruskal-Wallis and Mann-Whitney U tests were used for non-parametric data.

RESULTS

There was a statistically significant difference between ADAMTS-1, ADAMTS-9 and TIMP-3 levels of the healthy pulp and pulpitis groups (p < 0.05), but there was no significant difference for ADAMTS-4 levels (p ˃ 0.05). It was found that the levels of ADAMTS-1 and ADAMTS-9 were higher in the pulpitis group compared to the healthy pulp group, while the TIMP-3 level decreased (p < 0.05).

CONCLUSION

As a result of this study, it was concluded that ADAMTS-1, ADAMTS-9 and TIMP-3 might have a role in pulpal inflammation, while ADAMTS-4 was not related to pulpal inflammation.

Interradicular Canals in 213 Mandibular and 235 Maxillary Molars by Means of Micro-computed Tomographic Analysis: An Ex Vivo Study

INTRODUCTION

Bacteria and/or toxin residuals in the furcation areas of mandibular and maxillary molars can be the cause of persistent periapical tissue inflammation before or after an endodontic treatment.

METHODS

The objective of this ex vivo study was to investigate the frequency of interradicular canals and diverticula in first and second mandibular and first and second maxillary molars by means of micro-computed tomographic imaging. Five hundred thirteen extracted molars, 211 mandibular molars and 302 maxillary molars, were included in this investigation. The area between the pulp chamber floor (PCF) and the furcation area was examined, and the data obtained were evaluated with imaging software that generated the corresponding 3-dimensional images. The results were analyzed by means of descriptive statistics.

RESULTS

Interradicular canals were observed in 2.8% and 0.3% of the mandibular and maxillary molars, respectively. The diverticula (blind-ended interradicular canals) originated either at the furcation area or at the PCF. The diverticula frequency observed in mandibular molars was 3.3% (PCF) and 4.3% (bifurcation). The maxillary molar diverticula frequency observed was 2.0% (trifurcation), with none of them originating at the PCF. Altogether (n = 513) diverticula originated more frequently from the PCF (59.1%) than from the furcation area (40.9%).

CONCLUSIONS

Although interradicular canals as well as diverticula were observed in a relatively small number of the investigated molars, practitioners should always be aware of their existence because without an adequate chemical debridement/disinfection of the pulp chamber root canal system, successful endodontic treatment could be compromised in up to 10% of the cases.

Comparison of Neurokinin A, Substance P, Interleukin 8, and Matrix Metalloproteinase-8 Changes in Pulp tissue and Gingival Crevicular Fluid Samples of Healthy and Symptomatic Irreversible Pulpitis Teeth

INTRODUTION

The aim of this study was to compare levels of neurokinin A (NKA), substance P (SP), interleukin (IL)-8, and matrix metalloproteinase-8 (MMP-8) in pulp tissue and gingival crevicular fluid (GCF) samples of healthy and symptomatic irreversible pulpitis teeth.

METHODS

Forty patients diagnosed with healthy and symptomatic irreversible pulpitis teeth were included in this study. NKA, SP, IL-8, and MMP-8 levels were measured using the enzyme-linked immunosorbent assay test after pulp and GCF samples were obtained from healthy (n = 20) and symptomatic irreversible pulpitis teeth (n = 20). GCF sampling of 40 teeth was repeated 1 week later. Routine root canal treatment procedures of the teeth were performed, and the treatment process was completed. As a control group, GCF samples were taken from the contralateral teeth in both groups. Statistical analysis was performed using dependent and independent t tests, analysis of variance, Kruskal-Wallis, Mann-Whitney U tests, and Pearson correlation analysis.

RESULTS

Comparing the groups, all mediator levels were significantly higher in the pulp samples in the pulpitis group compared with the healthy group (NKA: P < .001, SP: P = .005, IL-8: P < .001, and MMP-8: P < .001). Likewise, in the pulpitis group, all mediator levels were significantly higher in the first GCF samples compared with the healthy group (NKA: P = .01, SP: P < .001, IL-8: P = .001, and MMP-8: P < .001).

CONCLUSIONS

It was observed that NKA, SP, IL-8, and MMP-8 increased significantly in pulp tissue and GCF specimens of symptomatic irreversible pulpitis teeth compared with pulp tissue and GCF specimens of healthy teeth. Second, it was determined that NKA, SP, IL-8, and MMP-8 levels decreased significantly in GCF samples in teeth diagnosed with symptomatic irreversible pulpitis 1 week after the removal of inflamed pulp. Finally, SP, IL-8, and MMP-8 levels were found to be higher in pulp tissue samples of the patients with symptomatic irreversible pulpitis with higher pain scores than those with low pain scores.

Interradicular Root Canals in Mandibular First Molars: A Literature Review and Ex Vivo Study

INTRODUCTION

Successful endodontic treatment vastly depends to a high degree on an accurate knowledge of root canal system morphology. It is a prerequisite to be aware of all possible reservoirs where bacteria and/or toxins can persist, compromising the surrounding tissues; such knowledge results in endodontic success.

METHODS

The presence of interradicular canals and diverticula between the pulp chamber floor and the bifurcation area surface of 117 mandibular first molars was investigated. Access cavities were prepared, the teeth were embedded in plastic, and the pulp chambers were flooded with methylene blue and then centrifuged. An average of 4.2 (0.145 ± 0.03 mm thickness) slices per tooth were obtained by means of a diamond band saw. The presence of interradicular canals and diverticula was investigated using a light microscope (125×).

RESULTS

Interradicular canals were observed in 9 teeth. Seven teeth had 1 interradicular canal, and 2 teeth had 2 interradicular canals. Diverticula (blind interradicular canals) were observed in 11 teeth originating either on the pulp chamber floor or the bifurcation side. The number of diverticula per tooth varied between 1 and 5 and originated in 3 teeth in the pulp chamber floor and 8 teeth in the bifurcation area. Two teeth had both 1 interradicular canal and 3 diverticula. Of the 117 mandibular molars investigated, 18 had either 1 or 2 interradicular canals, 1 to 5 diverticula, or an interradicular canal and 3 diverticula.

CONCLUSIONS

Based on the results obtained with this ex vivo study and because of the difficulties involved in the clinical performance of mechanical cleaning of possibly existing interradicular canals, it is highly recommended to perform thorough chemical cleaning and disinfection of the pulp chamber floor area in order to enhance the sealing possibility of such structures and minimize treatment failure.

Wavelength dependence of photon-induced photoacoustic streaming technique for root canal irrigation

Laser-enhanced irrigation of complex root canals appears to be a very promising technique to improve the outcome of root canal treatment. This applies, in particular, if the technique can be effective at very low laser energies in irrigating not only the main canal but also the small lateral canals. This is important in order to avoid potential undesirable effects at higher laser energies such as temperature increase, dentin ablation, or extrusion of irrigating solution beyond the apical foramen. An improved understanding of the role of laser parameters, such as laser wavelength and pulse duration, in irrigation of lateral canals is therefore desired in order to optimize treatment efficacy. The influence of laser wavelength and pulse duration on cavitation phenomena was studied using shadow photography and a method of measuring fluid flow in lateral canals based on tracking of movements of small air bubbles naturally forming in liquid as a result of laser agitation. A simulated model of a root canal including a narrow lateral canal designed to represent typical root canal morphology was used for the water flow measurements. The following three laser wavelengths with relatively high absorption in water were studied: Er:YAG (2.94  μm), Er,Cr:YSGG (2.73  μm), and Nd:YAP (1.34  μm). Among the three wavelengths studied, the Er:YAG laser wavelength was found to be the most effective in formation of cavitation bubbles and in generating fluid motions within narrow lateral canals. A comparison between the shadow photography and fluid motion data indicates that it is the bubble’s radius and not the bubble’s volume that predominantly influences the fluid motion within lateral canals. Based on the results of our study, it appears that effective minimally invasive laser-assisted irrigation can be performed with low Er:YAG laser pulse energies below 10 mJ.

Furcation Canals of the Maxillary Fourth Premolar and the Mandibular First Molar Teeth in Cats

The furcation region morphology was evaluated in 103 mature feline carnassial teeth (54 maxillary fourth premolar and 49 mandibular first molar teeth). Patent furcation canals were present in 27.2% of teeth. No significant difference (p = 0.88) in distribution of this anatomical variation was found between maxillary fourth premolar and mandibular first molar teeth. The mean width of these furcation canals was 104.0 μm with two-thirds of the canals having a buccal orientation. The presence of furcation canals could be a factor in the etiopathogenesis of feline dental resorptive lesions, as well as a characteristic to be considered in the diagnosis, prognosis, and treatment of endodontic or periodontic-endodontic lesions in cat teeth.

An endodontic conundrum: the association between pulpal infection and periodontal disease

This paper reviews the classification of periodontal-endodontic lesions and considers the pathways through which inflammatory lesions or bacteria may communicate between the pulp and the periodontium. Such communications have previously underpinned the classification of periodontal-endodontic lesions but a more up-to-date approach is to focus specifically on those lesions that originate concurrently as pulpal infection (and necrosis) and periodontal disease on the affected teeth. In doing so, both conventional periodontal and endodontic treatments are indicated for the affected teeth, although more complex management strategies may occasionally be indicated.

Influence of endodontic treatment in the post-surgical healing of human Class II furcation defects

BACKGROUND

Treatment of molar furcation defects remains a considerable challenge in clinical practice. The degree of success in the management of furcation involvement is highly variable and related to the baseline clinical status of these defects. The identification of clinical parameters influential to the treatment outcomes is critical to optimize the results of surgical periodontal therapy. The impact of the endodontic treatment (ET) of the tooth on the healing potential of the periodontium is controversial. Therefore, the objective of this study is to evaluate the clinical response of buccal Class II furcation defects to open-flap debridement (OFD) and to determine the influence of ET in the clinical outcomes of therapy.

METHODS

Sixty patients were divided into two treatment groups (n = 30): 1) OFD; and 2) OFD in endodontically treated teeth (OFD + ET). The clinical variables evaluated were plaque (full-mouth plaque score), bleeding on probing, gingival recession, probing depth (PD), and vertical (VAL) and horizontal (HAL) attachment levels. Reevaluation was performed 12 months after the surgical procedures.

RESULTS

Both treatments resulted in improvements in all the clinical variables evaluated. Postoperative measurements from OFD-treated and OFD + ET-treated sites showed, respectively, 1.2 ± 1.2 and 1.3 ± 1.3 mm reduction in PD, 0.6 ± 0.8 and 0.7 ± 0.6 mm VAL gains, and 0.7 ± 1.1 and 0.8 ± 1.6 mm HAL gains. No significant differences were found between the groups.

CONCLUSION

The present findings demonstrate that adequate endodontic therapy performed ≥6 months before surgical treatment does not significantly influence the clinical parameters of healing of human mandibular buccal Class II furcation defects.

Resolution of Furcation Bone Loss Associated with Vital Pulp Tissue After Nonsurgical Root Canal Treatment of Three-Rooted Mandibular Molars: A Case Report of Identical Twins

This case report demonstrates the simultaneous development of furcation bone loss in three-rooted tooth #30 with vital pulp tissue in identical twins. In the first report, resolution of furcal bone loss was seen after nonsurgical root canal treatment. In the second report, furcal bone loss resolved after non-surgical root canal treatment, and periodontal therapy reduced probing depths to maintainable levels.

Incidence of patent furcal accessory canals in permanent molars of a Turkish population

AIM

To determine the incidence of patent furcal accessory canals in permanent molars of a Turkish population.

METHODOLOGY

Two-hundred extracted teeth consisting of 50 maxillary first molars, 50 maxillary second molars, 50 mandibular first molars and 50 mandibular second molars from Turkish patients attending the Oral Surgery Department of the Faculty of Dentistry, Istanbul University, Istanbul, Turkey, were included in the study. After preparation of access cavities and removal of pulp tissue, the teeth were stored in 5.25% sodium hypochlorite for 1 h. Following double-sealing of the access cavities, all tooth surfaces except the furcation regions were covered with nail varnish. The teeth were stored in 0.5% basic fuchsin for 1 week. The teeth were sectioned at the cemento-enamel junction and the presence of patent furcal canals was established by examining the pulp chamber floor with a stereomicroscope (10x) to determine staining.

RESULTS

Patent furcal accessory canals were detected in 24% of maxillary first molars, 16% of maxillary second molars, 24% of mandibular first molars, and 20% of mandibular second molars. No statistically significant differences were found between the tooth types.

CONCLUSIONS

In a Turkish population, the incidence of patent furcal accessory canals on the pulp chamber floor of maxillary and mandibular first and second molars ranged between 16 and 24%.

Pathologic interactions in pulpal and periodontal tissues

Both endodontic and periodontal disease are caused by a mixed anaerobic infection. The pathways for the spread of bacteria between pulpal and periodontal tissues have been discussed with controversy. This article is an attempt to provide a rational approach to the perio-endo/endo-perio question based on a review of the relevant literature. In the light of evidence, clinical concepts for the diagnosis and treatment of lesions involving both periodontal and pulpal tissues are discussed.

Endoperiodontal lesion. A case report

The purpose of this case report is to present an unusual endoperiodontal lesion on tooth 46 in an 8-year-old child. The absence of any carious process and the presence of the typical radiographic aspect of an infrabony defect, led us to consider the periodontal aetiopathogenesis. In spite of all this, an accurate periodontal probing of all the teeth and the use of the pulp tester for teeth 46 and 36 led us to diagnose properly a truly endodontic lesion. The endodontic treatment of the involved tooth achieved the complete healing of the lesion.

Molar root anatomy and management of furcation defects

BACKGROUND, AIMS

Furcally-involved teeth present unique challenges to the success of periodontal therapy. Anatomical and morphological complicating factors dictate modifications in treatment approaches used for managing these areas.

METHOD

Various treatment approaches are available for furcally-involved teeth, the choice of which depends on selected interdependent factors.

RESULTS

These factors, along with various approaches used in the treatment of furcally compromised teeth are discussed in this review, with particular emphasis on morphology, etiology, classification and diagnosis.

Tooth-related issues

Several conditions exist around teeth that may predispose the periodontium to disease. These situations may occur as a result of the condition or position of teeth or as a result of tooth treatment. In certain cases these tooth-related factors may contribute to the initiation of periodontal disease. While the etiology of periodontal disease is bacterial, factors that enhance bacterial accumulation or allow the ingress of bacteria into the periodontium should be considered in the classification and diagnosis of periodontal diseases. This is because many times these tooth-related issues can cause site-specific problems that require treatment in an otherwise intact periodontium. Several factors related to tooth/root anatomy, restorative, and endodontic considerations have been associated with gingival inflammation, attachment loss, and bone loss. These factors will be reviewed as they relate to their potential to promote damage to the periodontium.

An assessment of the ability of various materials to seal furcation canals in molar teeth

Ninety-seven maxillary and mandibular molar teeth were evaluated for the presence of naturally occurring furcation canals using the fluid filtration method. Only one specimen demonstrated a naturally occurring patent furcation canal. An artificial furcation canal was created with a 0.33-mm drill bit in the 96 teeth lacking naturally occurring furcation canals. Fluid filtration measurements were made before and after the artificial canal was made, and these served as the negative and positive controls for each tooth. The 96 teeth were randomly divided into eight equal groups, and the floor of the pulp chambers was sealed using 3 mm of either Tytin or Dispersalloy amalgams, Vitremer, FluoroCore, gutta-percha with sealer, Tytin with Ali-Bond 2 or Amalgambond, or Dispersalloy with Ali-Bond 2. Analysis of measured microleakage at 3 months indicated that Tytin amalgam used alone had significantly more microleakage than all other materials; however, this difference did not exist when bonding agents were used with Tytin. All materials leaked significantly less than the positive controls.

An in vitro comparison of microleakage of restorative materials in the pulp chambers of human molar teeth

Ninety-six human molars were accessed. After flattening of the occlusal surface and removal of the apical two-thirds of the roots, the remaining canal space was instrumented by conventional methods. The teeth were divided into six groups of 15 teeth with three positive and three negative controls. The six experimental groups were based on the material used to restore the pulp chamber and remaining canal space: 1, gutta-percha with sealer; 2, amalgam; 3, IRM; 4, light-cured posterior composite; 5, chemical-cured core paste; and 6, light-cured glass ionomer. After placement of the restorative material, the teeth were thermocycled and evaluated for microleakage using 2% methylene blue dye and incremental sectioning. The amalgam and glass ionomer groups showed significantly less leakage than the other materials. The composite, core paste, and IRM did not differ significantly from one another. The gutta-percha with sealer group showed significantly greater leakage than all other groups.

Dye ingress in molars: furcation to chamber floor

An in vitro dye leakage study was performed to determine the incidence of patent furcal accessory canals following exposure of the pulp chamber to 5.25% sodium hypochlorite. One hundred extracted molars were labeled, endodontically opened, and irrigated for 1 h at 5-min intervals. The external furcations were exposed to 0.5% basic fuchsin for 24 h. Patency was determined by dye presence on the chamber floor. Statistical analysis revealed that first and second molars, regardless of arch position or location, demonstrated a patent accessory canal at a rate of 57% +/- 19.6% in the furcal area. It was concluded that accessory canal exposure to 5.25% sodium hypochlorite in the furcal area of molars produced patency which was demonstrable via passive methods--no vacuum or injection pressures were utilized.

In vitro permeability of furcation dentin in permanent teeth

Extracted unerupted permanent third molars with the occlusal half of the crown and apical half of the roots removed were cemented to Plexiglas blocks. Using a positive pressure system in which the movement of fluid across the dental tubules could be measured, the permeability of furcation dentin was measured before and after alteration of the furcation thickness. Subsequently, measurements of reduction in thickness of cementum and dentin were performed. Furcation dentin permeability was found to increase as the cementum and dentin thickness was reduced and the smear layer removed. The permeability values obtained for the furcation dentin were similar to those found in radicular dentin in general, indicating that root dentin has a low permeability and that it has good barrier properties. The data would suggest that any bone resorption seen under the furcation region of permanent molars is more likely to be due to the presence of accessory canals than due to permeation directly through furcation hard tissues.

A scanning electron microscopic investigation of accessory foramina in the furcation and pulp chamber floor of molar teeth

Observations of the pulp chamber floor and furcation surface of human maxillary and mandibular first and second molars were made with the scanning electron microscopic to determine the incidence, size, and location of patent accessory foramina. Accessory foramina on both the pulp chamber floor and the furcation surface were found in 36% of maxillary first molars, 12% of maxillary second molars, 32% of mandibular first molars, and 24% of mandibular second molars. Mandibular teeth had a higher incidence (56%) of foramina involving both the pulp chamber floor and furcation surface than did the maxillary teeth (48%).

Endodontic morphology. II. A radiographic analysis

Radiographs of 164 extracted human teeth were examined under magnification subsequent to the infusion of a radiopaque contrast medium under vacuum into their empty canal systems. An analysis of the results was made from the recorded statistics, and some conclusions have been drawn from these. The form and number of canals generally conformed to those of the roots which housed them, with some exceptions. The presence of two canals in the mesiobuccal roots of maxillary first molars and the incidence of lateral, accessory, and furcation canals have been noted. The role of the endodontist in the treatment of teeth with such anatomic features was discussed.