Palatal Canals Research Articles

An Unusual Case of Maxillary First Molar: A Case Report

The success of root canal therapy depends on cleaning of all the infected root canals and three- dimensional hermetic seal of the canals. For this, the knowledge of the root canal anatomy plays a vital role. However, the root canal anatomy is not always predictable. It is complex due to various anatomic variations and recognizing it and cleaning it thoroughly is a challenge to clinicians. This case report presents root canal treatment of unusual anatomy of maxillary first molar with six root canals, two mesio-buccal, two disto- buccal and two palatal canals.

PREPARO DO CANAL RADICULAR COM SISTEMA PRODESIGN LOGIC - RELATO DE CASO CLÍNICO

The objective of this study was to describe the preparation of root canals with a rotary system in a maxillary premolar. A 26-year-old patient, classified as ASA I, attended the Faculty of Dentistry of Pernambuco – FOP due to the presence of spontaneous pain in the region of the upper left first premolar. After clinical, radiographic examinations and sensitivity tests with an intense response, it was concluded that the probable diagnosis was symptomatic irreversible pulpitis. The preparation of the root canal was carried out with the ProDesign Logic rotary system and for this purpose, the Glide Path 25.01 file was used in order to explore the buccal and palatal canals. Odontometry was performed with the Root ZX apical locator (J.Morita) and confirmed by the radiographic method. The filling of the root canal system was performed using the single cone technique, 30.05 (HB). The final x-ray of the case was performed. It was concluded that the ProDesign Logic system determined a good shape of the canals, thus facilitating the filling of the root canal system.

Comparison of the Accuracy and Efficiency of Two Dynamic Navigation System Workflow for Fiber-post Removal: Small versus Large Field-of-view Registration Workflows

IntroductionThis study investigates the feasibility of a dynamic navigation system (DNS) small field of view workflow (DNS-SFOVw) for fiber-post removal and compares its accuracy and efficiency to the conventional large field of view workflow (DNS-LFOVw). MethodsFifty-six extracted human maxillary molars were divided into DNS-SFOVw (n = 28) and DNS-LFOVw (n = 28). The palatal canal was restored with an intraradicular RelyX fiber post and luted with RelyX Unicem; a core buildup was used. Teeth were mounted in a 3D-printed surgical jaw. A preoperative cone-beam computed tomography (CBCT) scan was taken with a 40 × 40 mm FOV for the DNS-SFOVw and a single arch CBCT scan for the DNS-LFOVw. The drilling entry point, trajectory, angle, and depth were planned in the X-guide software. The DNS registration method for the DNS-SFOVw was virtual-based registration on teeth, and the marker point-based method was used for the DNS-LFOVw. The fiber posts were drilled out under DNS guidance. A postoperative CBCT scan was taken. Three-dimensional deviations, angular deflection, number of mishaps, registration, and total operation time were calculated. ResultsThe DNS-SFOVw was as accurate as DNS-LFOVw (P > .05). The DNS-LFOVw registration time was less than DNS-SFOVw (P < .05). There was no difference in the number of mishaps (P > .05). Both DNS-SFOVw and DNS-LFOVw were time-efficient, with DNS-LFOVw taking less total operational time (P < .05). ConclusionWithin the limitations of this in-vitro study, the DNS-SFOVw was as accurate as the DNS-LFOVw for fiberpost removal. Both DNS-LFOVw and DNS-SFOVw were time-efficient in removing fiber-posts.

Cone Beam Computed Tomography Analysis of Post Space in Bifurcated Premolars Using ParaPost and Peeso Reamer Drills

Introduction Core buildups are usually maintained by the usage of posts. Even so, in curved and narrow canals, such as bifurcated premolars, excessive dentin removal during post-space preparation can result in a vertical root fracture or perforation. In order to preserve root canal dentin during post-space preparation of bifurcated premolars, this study examined and analyzed the effects of two widely used drills: Peeso Reamer (Dentsply Maillefer, Ballaigues, Switzerland) and ParaPost (Coltene/Whaledent, Inc., Altstätten, Switzerland). We also examined the risks associated with using Cone-beam Computed Tomography (CBCT). Methods Three operators with varying levels of experience treated a total of 72 removed bifurcated premolars, dividing them into equal groups. The rotary ProFile system (Dentsply Sirona, Charlotte, NC) was utilized for root canal treatments, and gutta-percha size #30/0.4 was used for obturation. Peeso Reamer #2 and ParaPost #1 were then used to prepare the palatal canals. CBCT was used to assess the total mean intracanal spaces of 3 mm, 5 mm, and 7 mm that were measured both preoperatively and postoperatively. To compare the mean dentin thickness within the canal area across all groups, we used analysis of variance testing. We detected complications, like deviations or perforations, using mesiodistal periapical radiographs. Results When utilizing the Peeso Reamer, the mean dentin thickness (0.749 mm) was slightly more than when using the ParaPost (0.736 mm) with p=0.16. There was no significant difference in the mean dentin thickness of the canal area between the Peeso Reamer and the ParaPost drills. The Pesso Reamer drill had fewer complications since it matched the canal configuration, while the Parapost drill removed somewhat more dentin in the canal area. Only seven teeth with minimum deviation from the center of the canal during preparation were produced by the Peeso Reamer drill (20% of teeth having deviation), whereas twenty-one teeth had deviations (72.2% of teeth) and eight had furcal perforations generated by the ParaPost. Conclusion Within the limitations of our study, the Pesso Reamer drill caused little more dentin removal than the ParaPost drill. However, the Peeso Reamer had fewer risks and was safer to use in bifurcated premolars. The ParaPost drill is not recommended in bifurcated premolars due to the high risks of deviation and perforation because they have narrow canals. The selection of an appropriate drill for post-space use in bifurcated premolars is essential for successful patient outcomes.

The ability of different compositions of calcium silicate and epoxy sealers to withstand gutta percha removal via in vitro pull-out testing

Objectiveexamination of the influence of chemical composition changes on the ability of sealers to withstand a pull-out test.Materials and methodsFifty distal or palatal canals of extracted teeth were prepared by Dc Taper files. The teeth were divided into five groups: AH Plus, BJM RCS, Total Fill BC,AH Plus Bioceramic and a group with Gutta Percha with no sealer added. Ten days after obturation, each cone was subjected to the “pull-out test” with the Shimadzo Universal Testing Machine until it was torn or removed from the canal. A force to Stroke graph was generated and the maximum vertex of this graph was recorded. The number of times the cone was torn or removed was recorded.ResultsThe amount of force needed to remove or rupture the cone was significantly higher in all sealer groups compared to the AH Plus Bioceramic group. The force needed for the AH Plus group was double that needed for the AH Plus Bioceramic group 4 (1.87 ± 0.53 N vs 0.93 ± 0.48 N, respectively, P < 0.001). All of the cones (n = 10) in the AH Plus Bio Ceramic Sealer group were removed in their entirety (P = 0.01 compared to each of the other groups).ConclusionsThe addition of macromolecules to epoxy sealer does not change the material’s ability to withstand the pull-out test. Decreasing the amount of tri- and di-calcium silicate compounds combined with increasing amounts of zirconium oxide in a Bioceramic sealer significantly decreased the material’s ability to withstand the pull-out test.

FREQUENCY OF SECOND MESIOBUCCAL CANAL IN PERMANENT MAXILLARY SECOND MOLARS AT A TERTIARY CARE CENTRE OF NEPAL

Background: The success of endodontic treatment relies on the precise identification of root canals followed by cleaning, shaping, and obturating the canals. Mesiobuccal root of maxillary second molar teeth present wide variations with regard to the number and type of root canals. The complexity of the root canal varies widely in different ethnic groups. The study aimed to determine the prevalence of second mesiobuccal canal (MB2 canal) in maxillary second molar. Methods: A descriptive cross-sectional study was conducted at Department of Conservative Dentistry and Endodontics, Universal College of Medical Sciences, Bhairahawa. A total of 100 permanent maxillary second molar undergoing endodontic treatments were studied. After access cavity preparation ultrasonic tips and magnification loupes were used to open the subpulpal groove in a direction from first mesiobuccal (MB1) canal towards the palatal canal to locate the second mesiobuccal (MB2) canal. Radiovisiography (RVG) was taken to confirm the presence of MB2 canals. Results: MB2 canals were detected in 52 teeth out of 100 teeth that were studied. It was found that the younger adult (18-35 years) tends to have a higher proportion of MB2 canals (65.6%) as compared to the middle-aged elderly (36-55years) in whom it could be identified only 33.4% of the time. Conclusions: Based on this study, it can be concluded that the prevalence of MB2 canal in mesiobuccal root of the permanent maxillary second molar is high.

Augmented Reality Head-Mounted Device and Dynamic Navigation System for Postremoval in Maxillary Molars

IntroductionThis study evaluates the feasibility of an augmented reality (AR) head-mounted device (HMD) displaying a dynamic navigation system (DNS) in the surgical site for fiber postremoval in maxillary molars and compares it to the DNS technique. MethodsFifty maxillary first molars were divided into 2 groups: AR HMD + DNS (n = 25) and DNS (n = 25). The palatal canal was restored with RelyX fiber post (3M ESPE) luted with RelyX Unicem (3M ESPE). A core buildup was performed using Paracore (Coltene/Whaledent). Cone beam computed tomography (CBCT) scans were taken before and after postremoval. The drilling trajectory and depth were planned under X-guide software (X-Nav Technologies, Lansdale, PA). For the AR HMD + DNS group, the AR HMD (Microsoft HoloLens 2) displayed the DNS in the surgical site. The three dimensional (3D) deviations (Global coronal deviation [GCD] and global apical deviation [GAD]) and angular deflection (AD) were calculated. The number of mishaps and operating time were recorded. ResultsFiber post was removed from all samples (50/50). The AR HMD + DNS was more accurate than DNS, showing significantly lower GCD and GAD deviations and AD (P < .05). No mishap was detected. The AR HMD + DNS was as efficient in time as DNS (P > .05). ConclusionsWithin the limitations of this in vitro study, the AR HMD can safely display DNS in the surgical site for fiber post-removal in maxillary molars. AR HMD improved the DNS accuracy. Both AR HMD + DNS and DNS were time-efficient for fiber postremoval in maxillary molars.

Comparison between apex locater and conventional radiography in working length determination of maxillary first molars: a clinical study

Aim of the study: The purpose of this study is to compare the working length (WL) measurement results of conventional periapical radiographies and electronic apex locater (EAL).&#x0D; Materials and method: This study was conducted during sessions of root canal treatment of 10 patients diagnosed with acute pulpitis. A total 30 root canals measurement (ten 1st upper molars, each with 1 palatal canal and 2 buccal canals) were included in the data analysis. A linear correlation and linear regression tests were utilized to check for a linear association between apex locator and X-ray measurements. Measurements of all roots were first included in the linear correlation test, and then measurements of each type of roots (palatal, mesio- buccal and disto- buccal) were tested separately. Significant linear correlations were then tested with linear regression test to formulate an equation which can predict X-ray measurements from corresponding apex locator measurements.&#x0D; Results: Generally, apex locator shows a linear correlation with X-ray in terms of measuring working length of the root (P &lt;0.001). The accuracy of apex locator varies according to the site of the tooth root under investigation, with being most accurate at disto-buccal (Pearson’s r= 0.98, P&lt; 0.001) and least accurate at palatal roots (Pearson’s r=0.57, P=0.084).&#x0D; Conclusion: Working length measurement of mesio-buccal and disto-buccal roots using electronic apex locater was precise when compared to radiographic method. While in palatal roots, WL measurements using apex locator were inaccurate when compared to radiographic method.

Endodontic management of type I maxillary first molar with two palatal roots using cone-beam computed tomography

Background: Understanding the anatomical variations in the root canal system is vital for the successful outcome of endodontic treatment. Anatomical variation with respect to palatal roots is rare compared with other roots of maxillary molars. Purpose: This case report describes a rare case of cone-beam computed tomography (CBCT)-guided endodontic treatment of a maxillary first molar with two palatal roots. Case: A 35-year-old Saudi woman complained of continuous pain in the right maxillary first molar. Past dental history revealed root canal treatment of the same tooth four weeks prior. Master cone radiographs recovered from her general dentist revealed a missing second palatal canal. Case Management: A CBCT image was taken to confirm if there were any aberrations in root canal morphology. Clinical exploration presented four distinct orifices: two palatal and two buccal. All the root canals were prepared and irrigated with 2.5% NaOCl and normal saline during instrumentation. All the canals were obturated with gutta-percha and AH 26 sealer using the continuous wave obturation technique. Conclusion: Clinical exploration of the pulpal floor, along with multiple angled radiographs, is needed to confirm any anatomic aberration.

Endodontic management of maxillary first molar with two palatal canals - A case report

An awareness and understanding of unusual root canal morphology is essential as it deter-mines the successful outcome of endodontic treatment. Aberrations in root canal anatomy are commonly occurring phenomena. I report a clinical case of a maxillary left first molar with two palatal root canals. The morphology is atypical because it has two palatal canals with separated orifices, running parallelly but joined at the apex. Modifications to the usual access opening and examination of the pulpal floor for additional canals are essential in such atypical cases for the success of endodontic treatment

Impact of Access Cavity Design on Fracture Resistance of Endodontically Treated Maxillary First Premolar: In Vitro.

This study was designed to investigate the impact of access cavity designs on fracture resistance of endodontically treated maxillary first premolars. The study sample consisted of 72 intact maxillary first premolars, randomly divided into six groups (n = 12). A standardized proximal cavity preparation was prepared for all samples using standard bur. Groups I: control group with only standard proximal cavity and no endodontic access, group II: Truss access cavity, group III: Separated access to buccal and palatal canals without removal of dentine in between, group IV: Access to buccal and palatal canals with removal of dentine in between, group V: Traditional access cavity, group VI: Mesio-occlusal-distal cavity (MOD). For groups I and VI, only composite restoration was used to restore the proximal cavity, while for groups II- V, the access was prepared and endodontic treatment was performed on all teeth, then composite restoration was placed. The root canals were instrumented using nickel-titanium files, irrigated with sodium hypochlorite, and filled with AH plus sealer and gutta-percha using warm vertical condensation. All samples were then placed in an acrylic mold and underwent thermal aging for 10,000 cycles between 5 and 55°C. The samples were fixed in a universal testing machine with the long axis of the roots positioned at 20° to a load applied at a crosshead speed of 1 mm/min using a stainless steel semi-spherical indenter (Ø = 3 mm) until fracture occurred to determine the fracture resistance force in Newton. The normality test (Shapiro-Wilk) showed that data are normally distributed. Group II exhibited the highest mean fracture resistance, and group VI was the least likely to resist the fracture. No statistically significant differences between tested groups (p-value = 0.237). The MOD group showed a more unfavorable mode of fracture compared to other groups. No significant difference in fracture resistance between conservative and traditional access cavities. The missing marginal ridges, such as in MOD cavities played an important role in decreasing the fracture resistance of endodontically treated teeth.

Micro-computed tomography (micro-CT) evaluation of root canal morphology in immature maxillary third molars.

The endodontic treatment of immature permanent teeth with necrotic pulp is a significant clinical challenge. The success of regenerative endodontic procedure is highly dependent on disinfection of the root canal and an accurate anatomical knowledge of the root canal. The aim of this study was to use micro-computed tomography (micro-CT) analysis to investigate the configuration of root canals in the upper permanent third maxillary molars with incomplete root development in their coronal, apical and middle third portions. Thirty immature third permanent maxillary molars were scanned using a micro-CT system. Then, we measured the diameters and areas of the root canal in the coronal, middle and apical third of the roots. The ratio between the long and short diameter of each root canal was then calculated and the canals were divided into several groups: round, oval, long oval, flat and irregular. The round configuration was not observed in the distobuccal and mesiobuccal roots in any of their anatomical regions. Oval and long oval canals predominated in the distobuccal root. The greatest variations were observed in the mesiobuccal root, with the ribbon-shaped canal predominating in the middle region and an irregular shape in the apical region. In the coronal region of the palatal canal, the round configuration predominated; in the middle third, we observed an almost equivalent distribution between round and oval configurations; apically, the oval shape predominated. In conclusion, we observed significant complexity and variation in the morphology and configuration of root canals in immature permanent molars, thus generating additional obstacles for the success of regenerative endodontics.

2D and 3D Erosion Landscape Analysis of Endodontic-Treated Teeth Using EDTA and HEDP as Chelating Agents: A High-Resolution Micro-Computed Tomographic Study.

This study aimed to assess the amount of erosion during activated endodontic irrigation with either HEDP or EDTA via high-resolution micro-computed tomography. Two root canals of twenty premolars were prepared with ProTaper Next and irrigated with sodium hypochlorite. Palatal canals, which served as control groups, were sealed, while buccal canals were further irrigated with either EDTA (n = 10) or HEDP (n = 10), which served as test groups. Micro-CT was performed to measure erosion depth. For 2D and 3D measurements, non-parametric repeated ANOVA measurements and post hoc tests were performed. 2D analysis showed highly significant differences between the case groups at each position of the root (p ≤ 0.01). The cervical and apical positions showed significant differences in the EDTA group (p = 0.03). The 3D analysis also showed significant differences between both chelating agents (p < 0.01) and the case and control groups (p = 0.01). The mean erosion depths in the cervical, middle, and apical thirds of the EDTA group were 45.75, 41.79, and 32.25 µm, and for the HEDP group were 20.25, 16.40, and 15.96 µm, respectively. HEDP seems to have a significantly less erosive effect. Different irrigation protocols with harsher conditions, as might be the case during endodontic retreatment, could be assessed with micro-CT.

Cone-beam computed tomography assessment of the root canal morphology of primary molars

BackgroundThis study aimed to assess the root canal morphology of primary molars using cone-beam computed tomography (CBCT).MethodsThis cross-sectional study evaluated 60 maxillary and mandibular primary first and second molars on CBCT scans of patients retrieved from the archives of Hamadan School of Dentistry between 2018–2020. The teeth were evaluated regarding the number of roots and canals, canal type according to the Vertucci’s classification, and root surface concavities. Data were analyzed descriptively and by independent t-test.ResultsThe most frequent number of canals and roots in the maxillary right and left first molars was 3 canals (60%) and 3 roots (80%). These values were 4 canals (80%) and 5 canals (50%) with 3 roots in the maxillary right and left second molars, respectively, 4 canals (100%) and 2 roots (50%), and 3 canals (60%) and 2 roots (50%) in mandibular right and left first molars, respectively, and 4 canals (92.3%) and 3 roots (61.5%) in mandibular right and left second molars. Vertucci’s type IV was the most common canal type in mesial and distal canals, type I was the most common in mesiobuccal, mesiolingual, distobuccal, and distolingual, and types I and II were the most common in the palatal canal. The maximum and minimum concavities were noted in the buccal (26.7%) and mesial (8.3%) surfaces, respectively.ConclusionsA wide variation exists in the number of roots and canals of maxillary and mandibular primary molars, which calls for further attention in treatment of such teeth.

Assessment of pH Value and Release of Calcium Ions in Calcium Silicate Cements: An In Vitro Comparative Study.

Four materials were tested (ProClinic MTA; Angelus MTA; ProRoot MTA; Biodentine). The palatal canal root of acrylic upper molars was filled with each cement. Afterwards, they were set in phosphate-buffered saline. Measurements were taken by atomic adsorption spectroscopy (AAS) at 3, 24, 72, 168, 336, 672, and 1008 h. The pH was measured at the same timepoints. Kruskal-Wallis tests were carried out in each period, as the Kolmogorov-Smirnov and Shapiro-Wilk tests showed no parametric results. Significant differences (p < 0.05) in calcium release were found at the 3-, 24-, and 72-hour evaluations. All of the analyzed groups presented a release of calcium ions up to 168 h, and the general tendency was to increase up to 672 h, with a maximum release of 25.45 mg/g in the ProRoot group. We could only observe significant differences (p < 0.05) in pH value over 168 h between the Biodentine (7.93) and Angelus MTA (7.31) groups. There were significant differences (p < 0.05) in calcium release. Nevertheless, no significant differences (p > 0.05) in the pH values were found at the studied timepoints, except for the values at 168 h.

Endodontic treatment in a maxillary second molar with four root canals: A case report

Endodontic treatment is based on an understanding of the internal anatomy, which facilitates the precise exploration of the canals. The present study aimed to report a clinical case referring to the endodontic treatment of the upper left second molar, presenting the mesiopalatal canal and communication with the periodontal tissues in the distal region of the pulp chamber, in the furcation region, due to dental caries. The 41-year-old patient did not present any systemic health problems. The treatment was divided into three sessions. In the first consultation, the diagnosis of pulpal necrosis was obtained with a periapical area without changes in normality, no pain on vertical and horizontal percussion, in addition to no pain on palpation at the bottom of the sulcus and around the tooth. The radiographic examination revealed a vast region suggestive of caries in the distal region of the tooth crown, so the carious tissue was removed and the pulp chamber was accessed. In the second session, disinfectant penetration, working length determination, and instrumentation of the root canals were performed with the Reciproc R25 system for the mesiopalatal, mesiobuccal, and distobuccal canals, and R50 for the palatal canal. Bio-C Temp was used as an intracanal medication. After 18 days, the root canals were filled with apical gutta-percha cones and Bio-C Sealer, a silicate-based cement. Then, the communication in the furcation region was sealed with the repair cement, Biodentine. The pulp chamber floor was sealed with light-curing glass ionomer, and the pulp chamber was filled with composite resin.

Finite element analysis of maxillary first molar with mesial-occlusal-distal-palatal defect restored with different post-and-core strategies

PurposeTo explore which restoration strategy generates the most favorable stress distribution in an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect. MethodsModels with one post in palatal canal (PP), each post in palatal and distobuccal canals (PDP), each post in palatal and mesiobuccal canals (PMP), and each post in all canals (PDMP) were established for an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect either with fiber-reinforced composite (FRC) post or gold alloy cast (GAC) post. A 400-N vertical force and a 225-N lateral force were respectively applied. The Mohr-Coulomb stress ratio (σMC ratio) in the residual tooth structure (RTS), the resin cement, and the crowns, the tensile stress (σt) and compressive stress (σc) in the FRC posts, the von-Mises stress ratio (σvM ratio) in the GAC post-and-cores, and the σt and shear stress (σs) at the adhesive interfaces were calculated using finite element analysis. ResultsFRC posts generated lower σMC ratio than GAC posts in the RTS (0.3274–0.3643 vs. 0.3399–0.4118). Among the FRC post groups, the PDMP group got the lowest σs at the dentin-post interface (14.92 MPa) and the abutment-crown interface (8.242 MPa) under vertical loading, as well as the lowest σMC ratio in the RTS (0.3381) and the lowest σs at the dentin-post interface (38.00 MPa) under lateral loading. ConclusionsFrom the point of stress distribution, placing FRC posts in the palatal, distobuccal, and mesiobuccal canals is the optimal strategy in restoring a severely damaged maxillary first molar, provided that lateral occlusal force is reduced.

The use of cone beam computed tomography in endodontic re-treatment

Radiography plays an integral role in endodontics. However, conventional radiographic techniques have limitations, such as background noise, providing only a two-dimensional representation of the image, superimposition and distortion. Cone beam computed tomography (CBCT) provides the clinician with a three-dimensional image of the structures involved in the clinical situation. When considering options for endodontic re-treatments, it is vital to identify the cause of the initial failure and here, the use of CBCT images can be beneficial. This is illustrated through an endodontic re-treatment case owing to a palatal canal missed with conventional radiographic techniques. CPD/Clinical Relevance: Cone beam computed tomography can be beneficial in cases of endodontic re-treatment.

A New Criteria to Assess Quality of Obturation in Primary Teeth: KEDOO Classification.

The success of the pulpectomy depends on adequate access, cleaning, shaping, and good-quality obturation. Evaluating the quality of obturation is the major tool that determines the success of the procedure. The present study aimed to assess the quality of obturation in all the canals of primary teeth and suggest a new classification. A total of 1,000 radiographs of the pulpectomy procedure performed in primary molars were evaluated. The quality of obturation was assessed for each canal using the criteria given by Coll and Sandrian. The prevalence of each obturation criterion in every canal was represented in the form of a percentage. It was observed that among the mandibular primary molars, most of the mesial canals were underfilled, and in the distal canal, most of the canals were overfilled. Among the maxillary primary molars, most of the mesial canals were overfilled, more distal canals were underfilled, and with respect to palatal canals, optimal obturation was seen. The pitfalls of the previous classification were revised, and a new classification for assessing the quality of obturation was proposed, which is arch, segment, and canal specific. The new classification will give a more precise assessment for the evaluation of various techniques and materials used for pulpectomy in primary teeth. Jeevanandan G, Govindaraju L, Kotian N, et al. A New Criteria to Assess Quality of Obturation in Primary Teeth: KEDOO Classification. Int J Clin Pediatr Dent 2023;16(2):376-379.

Evidence for a novel cranial thermoregulatory pathway in thalattosuchian crocodylomorphs.

Thalattosuchian crocodylomorphs were a diverse clade that lived from the Early Jurassic to the Early Cretaceous. The subclade Metriorhynchoidea underwent a remarkable transition, evolving from semi-aquatic ambush predators into fully aquatic forms living in the open oceans. Thalattosuchians share a peculiar palatal morphology with semi-aquatic and aquatic fossil cetaceans: paired anteroposteriorly aligned grooves along the palatal surface of the bony secondary palate. In extant cetaceans, these grooves are continuous with the greater palatine artery foramina, arteries that supply their oral thermoregulatory structures. Herein, we investigate the origins of thalattosuchian palatal grooves by examining CT scans of six thalattosuchian species (one teleosauroid, two early-diverging metriorhynchoids and three metriorhynchids), and CT scans of eleven extant crocodylian species. All thalattosuchians had paired osseous canals, enclosed by the palatines, that connect the nasal cavity to the oral cavity. These osseous canals open into the oral cavity via foramina at the posterior terminus of the palatal grooves. Extant crocodylians lack both the external grooves and the internal canals. We posit that in thalattosuchians these novel palatal canals transmitted hypertrophied medial nasal vessels (artery and vein), creating a novel heat exchange pathway connecting the palatal vascular plexus to the endocranial region. Given the general hypertrophy of thalattosuchian cephalic vasculature, and their increased blood flow and volume, thalattosuchians would have required a more extensive suite of thermoregulatory pathways to maintain stable temperatures for their neurosensory tissues.