An anatomical investigation of the mandibular second molar using micro-computed tomography.

PURPOSE: An understanding of root anatomy is an important foundation for providing successful endodontic treatment. The aim of this study was to use micro-computed tomography (micro-CT) to investigate the root anatomy of the mandibular second molar. METHODS: Eighteen mandibular second molars were scanned using micro-CT. Images were reconstructed, and measurements and observations were recorded regarding pulpal floor anatomy, canal configuration, root wall thickness along the root, presence of calcifications in the pulp chamber and in canals, and apical anatomy. RESULTS/CONCLUSIONS: The most frequently found mesial root canal configuration was Vertucci Type 7 (1-2-1-2), which was seen in 33.3% of samples. Distal canals were most frequently Vertucci Type 1 (one canal), with 61.1% of samples showing this configuration. 11.1% of samples had two canals, 44.4% of samples had three canals, 33.3% of samples had four canals, and 11.1% of samples had five canals at some point along the length of the roots. Average root wall thickness between the mesiobuccal canal and the furcation was 1.23 mm. Mesiolingual canal root wall thickness was on average 1.29 mm, and the distal root furcation wall thickness averaged 1.41 mm. 77.8% of samples had calcifications present in both the pulp chamber and within the canals.

Electrical Pulp Testing: Sources of Error.

INTRODUCTION: Accurate identification and assessment of an inflamed or necrotic tooth is essentialfor endodontic treatment. The purpose of this research was to investigate possible sources of error associated with the use of the electric pulp tester (EPT). METHODS: Forty-six intact teeth (23 tooth pairs) in 22 patients were evaluated in vivo. For the tooth pairs, one tooth had to have been previously endodontically treated and restored with a class II amalgam restoration. The restoration was required to have proximal contact with a class II amalgam of another vital posterior tooth. EPT was performed on pulpless and vital teeth for experimental groups (enamel, restoration, contacting, or isolated). RESULTS: The highest rate of false positive responses (82%) was found in the pulpless restored contacting group, suggesting that EPT impulses are able to travel through proximal metallic contacts and stimulate teeth distant from the EPT probe. All vital tooth groups had a high rate of positive responses with no significant diferences. CONCLUSIONS: If a tested tooth contains an interproximal restoration contacting adjacent restorations or the gingival, the teeth must be isolated (rubber dam) and the EPT probe should be placed in a region suspected to have uninterrupted tubule paths to the pulp.

The Incidence of Furcation Region Patency in Molars Before and After Simulated Periodontal Therapy.

PURPOSE: To determine if there is increased bacterial communication through the furcation region in molar teeth after simulated periodontal therapy. METHODS: Sixty-five extracted first and second molars were accessed and the roots were sectioned 4 mm apical to the furcation. The canals and external suface of the root were sealed except the furcation region. In Phase I, the teeth were sterilized and then suspended in Rogosa SL broth. A broth containing Lactobacillus casei was placed in the pulp chamber. The Rogosa SL broth in the bottom chamber was monitored daily for 30 days for turbidity, and once turbidly was noted, the broth was plated to confirm the presence of L. casei. In Phase II, the furcation regions were scaled and cementum removed, the teeth were sterilized, and the microbial leakage was repeated. RESULTS: The Phase I and Phase II median times to turbidity were 9.5 days and 4 days, respectively, and the difference was statistically significant (p = 0.0035). Phase I turbidity rate was 86.5%, and Phase II was 92.3%, which was not statistically significant (p = 0.25). CONCLUSIONS: The root canal system communicated with the furcation region an average of 86.5% and 92.5% after scaling and root planing during the 30 days of the experiment. The time of leakage between the two groups decreased from 9.5 to 4 days (p = 0.0035). CLINICAL SIGNIFICANCE: Periodontal instrumentation of the furcation region in molar teeth can increase the risk of bacterial contamination by 39% while shortening the time for bacterial penetration in teeth with exposed dentin or furcation canals. accessory canals, scaling, and root planing.

Palatal anesthesia: comparison of four techniques for decreasing injection discomfort.

INTRODUCTION: The aim of this study was to evaluate the patient's perceived pain response to injection and anesthetic deposition for the greater palatine nerve block. METHODS: Heft-Parker Visual Analog Scale (VAS) pain scale measurements were used to compare the following techniques for the injection: (1) control (no concurrent stimulation), (2) pressure, (3) pressure and topical anesthetic (20% benzocaine), and (4) pressure and cold (TFE). Forty-two volunteers, 21 male and 21 female, participated in the study. A bilateral model was used on each patient to give an injection on each side of the palate with two different techniques followed by the next appointment (> or = two weeks later), when the two other injection techniques were used. Following injection given in the supine position, the patients were returned to an upright position and asked to rate their pain on a VAS. RESULTS: Pain upon needle insertion appears less than that of anesthetic deposition. There was no statistically significant difference in perceived pain response among the four techniques, the visit, the order, the side, or patient gender at either time point. Following the application of Endo Ice, 81% of participants reported a sore on their palate occurring two to 48 hours after cold application and persisting for one to 10 days. The pain score for this injection had a mean value of 30% (51.4/170). CONCLUSIONS: This prospective, single-blind study evaluating three injection techniques to reduce posterior palatal injection pain to a control injection method showed no significant reduction in pain with any of the three techniques. Furthermore, 1,1,1,2-tetrafluoroethane placed with pressure for 10 seconds appeared injurious to the oral mucosa.

The effect of powder:liquid ratio and pre-mixing on sealing properties of Roth 801 sealer.

OBJECTIVES: To investigate the sealing ability of Roth 801 sealer mixed using two different powder/liquid ratios and prepared up to seven days prior to canal obturation. STUDY DESIGN: Of the 152 maxillary anterior teeth endodontically instrumented for this study, 144 were randomly assigned to the treatment group, and eight were assigned to the control group. Of the 144 teeth in the treatment group, 72 were obturated using gutta-percha and Roth 801 sealer mixed with a 10:1 ratio, while the remaining 72 were obturated with a sealer ratio of 7.5:1. Within both treatment groups, the teeth were further subdivided into six groups of 12 teeth based upon the amount of time between sealer mixing and canal obturation, which varied from 0 days to seven days. Teeth were analyzed with fluid filtration either immediately after obturation or 14 weeks after obturation. The data were analyzed using a three-way analysis of variance. RESULTS: For teeth tested at the time of obturation, leakage decreased for older sealer, p < 0.0001. After the 14-week storage period, there was no significant difference in leakage. No significant differences were noted between either powder/liquid ratios. CONCLUSIONS: Pre-mixed Roth 801 sealer maintained an apical seal when prepared up to seven days prior to canal obturation. Varying the powder/liquid ratio of Roth 801 sealer did not significantly affect the apical seal.

The effect of rotary instrumentation on dentin thickness in the danger zone of the MB2 canal of maxillary first molars.

The aim of this study was to measure the initial and remaining dentin thickness in the danger zone of the second mesiobuccal (MB2) canal of maxillary first molars after rotary instrumentation using cone beam computed tomography (CBCT) imaging. After determining initial dentin thickness, each sample was subjected to a standardized protocol of rotary instrumentation files: ProTaper Gold Sx Orifice Opener (maximum depth of 7 mm); Vortex Blue 15.04, 20.04, 25.04, ProTaper Gold S1, S2, F1, F2, and finally Vortex Blue 30.06. Subsequent CBCT measurements were made to compare changes in remaining dentin thickness in comparison to initial presentation. Preoperative dentin thickness in the danger zone had a mean of 0.82 ± 0.17mm. Significant levels of dentin removal in the danger zone were noted after all instrumentation groups when compared to the pre-instrumentation mean (Sx P < 0.001, 25.04 P < 0.0006, F2 P < 0.0001, 30.06 P < 0.0001). It was concluded that a thin area of dentin exists along the distal wall of the MB2 (danger zone) from the furcation to 4 mm apically.

Preoperative Factors Associated with Anesthesia Failure for Patients Undergoing Nonsurgical Root Canal Therapy: A National Dental Practice-Based Research Network Study.

INTRODUCTION: The aim of this study was to identify preoperative factors associated with local anesthesia failure. METHODS: The National Dental Practice-Based Research Network (www.NationalDentalPBRN.org) data from 534 patients who received a nonsurgical root canal treatment completed in a single appointment were included in this analysis. Three methods for defining anesthesia failure were used: definition 1, patient-reported level of numbness; definition 2, provider-reported quality of anesthesia; and definition 3, provider-reported use of supplemental anesthesia. Fifty-one preoperative factors were investigated and analyzed individually against the overall failure rate for each method, and multivariate generalized estimating equation logistic models were fit with predictors chosen using stepwise model selection to evaluate factors that may interact with each other. RESULTS: The overall anesthesia failure rates were 5%, 15%, and 30% for definitions 1, 2, and 3, respectively. Provider experience, diabetes, absence of sharp or aching pain, absence of smoking, and a fair expected outcome were associated with anesthesia failure (definition 1). Provider level of training, absence of a sinus tract, bite sensitivity, and stress making the pain worse were associated with anesthesia failure (definition 2). Provider level of training, pain provoked by stimulus, mandibular teeth, teeth with vital pulps, and pain interfering with daily activities were associated with the use of supplemental anesthesia (definition 3). CONCLUSIONS: With the range of 5%-30% of anesthesia failures, a few common factors across the models assessed were elucidated. Providers with higher levels of training had significantly fewer anesthesia failures. Patient self-reported history of diabetes and preoperative pain-related interference with daily activities were associated with more anesthesia failures. Greater severity of various tooth-related pain characteristics, as a group but not individually, accounted for more anesthesia failures.

Postoperative Pain after Treatment Using the GentleWave System: A Randomized Controlled Trial.

INTRODUCTION: Cleaning and shaping are necessary to allow for the delivery of irrigants and medicaments to the apical third of the canal. Standard treatment irrigation generally uses a conventional needle and some frequency of sonic activation. The GentleWave System (GWS; Sonendo, Inc, Laguna Hills, CA) combines irrigant delivery with multisonic activation. This randomized clinical trial aimed to determine if the GWS significantly decreases the incidence and intensity of postoperative pain. METHODS: Patients used a numeric rating scale to record their pain level at the 6-hour time point before treatment. All participants were randomly divided into 2 groups and were blind to the treatment they received. The standard (control) group received endodontic treatment with conventional side-vented needle irrigation and ultrasonic activation. The second group received treatment with the GWS. Following treatment, patients used a numeric rating scale to record their pain level at 6, 24, 72, and 168 hours. RESULTS: In the standard treatment group, 72.2% of patients experienced at least 1 occurrence of postoperative pain, whereas in the GWS group, 83.3% of patients experienced at least 1 occurrence of postoperative pain. The highest pain intensity level for both treatments occurred at the 6-hour posttreatment time point. All pain decreased with time after the 6-hour posttreatment time point (P < 1.237e-7). CONCLUSIONS: There was no significant difference in the incidence or intensity of postoperative pain after either treatment group. However, both groups reported a statistically significant decrease in pain with time.

Anatomic Analysis of Palatal Roots of Maxillary Molars Using Micro-computed Tomography.

INTRODUCTION: The morphology of the palatal root of maxillary first and second molars was analyzed and compared using micro-computed tomographic scanning. METHODS: Forty-seven extracted maxillary molars were scanned with a micro-computed tomographic device to analyze the palatal radicular dentin dimensions, canal working width, root length, canal curvature, lateral canals, and apical constriction anatomy. Quantitative data were analyzed with mean and standard deviation for first and second molars, respectively. Comparison was made between first and second molars using an unpaired t test. RESULTS: The palatal root of maxillary first molars was found to have statistically significantly thinner dentin than second molars on the palatal aspect of the root 8-11 mm from the apex, correlating to the coronal and middle thirds of the root. First molar palatal roots also had a statistically significantly wider canal mesiodistally than second molars at 13-15 mm from the apex, correlating approximately to the level of the cementoenamel junction and pulpal floor. Significant canal curvature was present. These findings suggest the need for conservative coronal flaring and instrumentation. CONCLUSIONS: The absence of an apical constriction in 76.6% of the specimens highlights the importance of creating an apical seat through instrumentation to maintain obturation materials. A minimum master apical file size of 40 is recommended based on preoperative working widths in the apical 0.5-1.0 mm. A root-end resection of 3.5 mm would remove a greater majority of lateral canals.

Effect of irrigants and cementum injury on diffusion of hydroxyl ions through the dentinal tubules.

This study measured hydroxyl ion diffusion through dentinal tubules into a bathing solution. Eighty single-canal, instrumented teeth were divided into 8 groups. Control groups 1 and 3 were irrigated with 10 mL 0.9% saline and 10 mL 6% sodium hypochlorite (NaOCl), respectively. Control groups 5 and 7 were irrigated with 3 mL and 1 mL 17% ethylenediaminetetraacetic acid (EDTA) and then 10 mL 6% NaOCl, respectively. Experimental groups 2, 4, 6, and 8 were irrigated as groups 1, 3, 5, and 7, followed by placement of calcium hydroxide (Ca(OH)2) into canals. Bathing solution pH was recorded for 30 days, a cementum defect was made, and then pH was recorded for another 30 days. With a paired difference test, average pH during steady state was statistically different and higher after the defect (P < .001). With Tukey multiple comparisons, post-defect pH for group 6 was found to be significantly greater (P < .01) than in other groups. This study indicated final canal irrigation with 3 mL 17% EDTA and 10 mL 6% NaOCl before Ca(OH)2 placement allowed the greatest hydroxyl ion diffusion to the root surface.

Shaping abilities of two different engine-driven rotary nickel titanium systems or stainless steel balanced-force technique in mandibular molars.

The purpose of this study was to compare apical transportation, working-length changes, and instrumentation time by using nickel-titanium (Ni-Ti) rotary file systems (crown-down method) or stainless steel hand files (balanced-force technique) in mesiobuccal canals of extracted mandibular molars. The curvature of each canal was determined and teeth placed into three equivalent groups. Group 1 was instrumented with Sequence (Brasseler USA, Savannah, GA) rotary files, group 2 with Liberator (Miltex Inc, York, PA) rotary files, and group 3 with Flex-R (Union Broach, New York, NY) files. Pre- and postoperative radiographs were superimposed to measure loss of working length and apical transportation as shown by changes in radius of curvature and the long-axis canal angle. Sequence rotary files, Liberator rotary files, and Flex-R hand files had similar effects on apical canal transportation and changes in working length, with no significant differences detected among the 3 groups. Hand instrumentation times were longer than with either Ni-Ti rotary group, whereas the rotary NiTi groups had a higher incidence of fracture.

Leakage and sealer penetration in smear-free dentin after a final rinse with 95% ethanol.

Forty extracted maxillary incisors were decoronated, prepared in a crown-down fashion and randomly divided into two groups of 16 roots each. Remaining roots served as controls. Smear layer was removed with 17% EDTA followed by 5.25% NaOCl, the canals in group N were again rinsed with NaOCl before obturation with laterally compacted gutta-percha and Roth's 801 sealer. The roots in group E were rinsed with 95% ethyl alcohol instead of NaOCl for the final rinse. Leakage was determined using a fluid-flow model. Roots were cleared, split, and sealer penetration into the dentinal tubules was measured under light-microscopy. Group E demonstrated significantly greater sealer penetration (p = 0.002) and significantly less leakage (p = 0.040), than group N. Leakage could not be significantly correlated with sealer penetration (p = 0.725). Under the conditions of this study, we found that a final rinse with 95% ethyl alcohol increased sealer penetration and decreased leakage.

Cemental tear: a case report of a rare root fracture.

A 79-yr-old female presented to the clinic for endodontic evaluation of an unresolved periodontal defect. The patient's dental history included extraction of tooth #30 with subsequent placement of two dental implants. The patient presented with a localized periodontal defect on the distal of tooth #29. Radiographic evaluation revealed a thin radiopacity and associated radiolucency along the entire lateral aspect of tooth #29. Periodontal surgery and biopsy resulted in a diagnosis of cemental tear. Cemental tears have been rarely reported in the endodontic literature. Case reports of cemental tears have been associated with age, trauma, and traumatic occlusion. With the increasing age of the dental population and longer retention of teeth, clinicians should be aware of this rare entity.

In vitro antifungal efficacy of four irrigants as a final rinse.

The purpose of this study was to compare the antifungal efficacy of 6% sodium hypochlorite (NaOCl), 2% chlorhexidine gluconate (CHX), 17% ethylene-diaminetetraacetic acid (EDTA), and BioPure MTAD as a final rinse on Candida albicans in vitro. Forty-eight, single rooted teeth were randomly divided into four groups each with a positive and a negative control. After root canal preparation, experimental teeth were inoculated with Candida albicans (ATCC 60193) and incubated for 72 hours. The groups were rinsed as follows: 1 ml of 6% NaOCl, 0.2 ml of 2% CHX, 1 ml of 17% EDTA, and 5 ml of BioPure MTAD. Aliquots from the experimental teeth were plated on Sabouraud 4% dextrose agar plates and colony-forming units were counted as a measure of antifungal activity. The results showed that 6% NaOCl and 2% CHX were equally effective and statistically significantly superior to BioPure MTAD and 17% EDTA (p < 0.05) in antifungal activity.

Furcation perforation repair comparing gray and white MTA: a dye extraction study.

The purpose of this study was to evaluate the ability of gray and white ProRoot MTA to seal furcation perforations in mandibular molars using a dye extraction leakage model. Sixty-four mandibular molars were randomly divided into four experimental groups. Six teeth with perforations were used as positive controls and six teeth without perforations were used as negative controls. Perforations in groups 1 and 2 were repaired with white MTA. Groups 3 and 4 were repaired with gray MTA. Dye leakage was tested from an orthograde direction (groups 1 and 3) and a retrograde direction (groups 2 and 4). After dye extraction, absorbance was measured on a spectrophotometer at 550 nm. No statistically significant difference in leakage was found between gray and white MTA when used as a furcation perforation repair material. However, there was significantly more leakage when the perforations were challenged from the orthograde than the retrograde direction (p < 0.001).

In vitro radiographic determination of distances from working length files to root ends comparing Kodak RVG 6000, Schick CDR, and Kodak insight film.

Previous studies suggest that digital and film-based radiography are similar for endodontic measurements. This study compared the accuracy and acceptability of measured distances from the tips of size #10 and #15 files to molar root apices in cadaver jaw sections using the newly developed Kodak RVG 6000, and the Schick CDR digital systems to digitized Kodak film. Standardized images were taken of files placed 0.5 to 1.5 mm short of true radiographic lengths. Images were imported into Adobe PhotoShop 7.0, thereby blinding observers who measured distances from files to root apices and assessed images for clarity (acceptability). Repeated measures ANOVA and Tukey-Kramer post hoc tests demonstrated that Kodak RVG 6000 images with enhanced contrast produced significantly less measurement error than unenhanced contrast Schick CDR images (p < 0.05) and significantly higher acceptability ratings than all other systems (all p < 0.002). Among these conditions, the newly developed Kodak RVG 6000 system provided the best overall images.

The effect of ultrasonic post instrumentation on root surface temperature.

This study measured root surface temperature changes when ultrasonic vibration, with and without irrigation, was applied to cemented endodontic posts. Twenty-six, extracted, single-rooted premolars were randomly divided into two groups. Root lengths were standardized, canals instrumented, obturated, and posts cemented into prepared spaces. Thermocouples were positioned at two locations on the proximal root surfaces. Samples were embedded in plaster and brought to 37 degrees C in a water bath. Posts were ultrasonically vibrated for 4 minutes while continuously measuring temperature. Two-way ANOVA compared effects of water coolant and thermocouple location on temperature change. Root surface temperatures were significantly higher (p < 0.001) when posts were instrumented dry. A trend for higher temperatures was observed at coronal thermocouples of nonirrigated teeth and at apical thermocouples of irrigated teeth (p = 0.057). Irrigation during post removal with ultrasonics had a significant impact on the temperature measured at the external root surface.

Effects of an intracanal glass ionomer barrier on coronal microleakage in teeth with post space.

Bacterial microleakage of the remaining gutta-percha in teeth prepared for post space with and without the use of an intracanal glass ionomer barrier was evaluated. Forty distal roots of mandibular molars were instrumented, obturated with gutta-percha and AH Plus sealer, and post spaces created. Teeth were divided as follows: Group I, 3 mm of gutta-percha; group II, 4 mm of gutta-percha; group III, 2 mm of gutta-percha plus 1 mm of Vitrebond; and group IV, 3 mm gutta-percha plus 1 mm Vitrebond. The roots were suspended in Rogosa SL broth and Lactobacilli casei was used as a microbial marker. At the end of 92 days, the mean number of days for the broth to turn turbid was group I, 23.8; group II, 43.0; group III, 57.4, and group IV, 70.5. A two-way ANOVA showed differences between the groups and a post hoc Tukey HSD analysis revealed the following significant differences (p < 0.05): Group I leaked faster than groups III and IV and group II leaked faster than group IV. In clinical situations of teeth with compromised crown-root ratio that require a post and core, 1 mm of Vitrebond over 2 or 3 mm remaining gutta-percha could reduce the risk of recontamination of the apical gutta-percha.

Mandibular Canal Location: Cone-beam Computed Tomography Examination.

INTRODUCTION: The increased use of implants and potential endodontic misadventures can lead to nerve damage. The purpose of this study was to use cone-beam computed tomography (CBCT) measurements to investigate mandibular canal (MC) location in relation to mandibular posterior teeth, the dimension of the buccal and lingual bone over the MC, the diameter of the MC, and the anterior loop location near the mental foramen. METHODS: CBCT scans from 106 patients (age, 18-69 years) were used to evaluate measurements from 636 teeth and respective MC areas. RESULTS: Respective locations of MC to teeth (buccal, inferior, or lingual) were as follows: second molar (57% buccal, 40% inferior, and 3% lingual), first molar (18% buccal, 55% inferior, and 27% lingual), and second premolar (33% buccal, 55% inferior, and 11% lingual). Buccal bone thickness over the MC was thickest at mesial root of second molars and thinnest over the second premolar (5.4 versus 2.6 mm). The lingual bone next to the MC was thickest over the second premolar and thinnest at distal root of first molars (3.8 versus 1.7 mm). The average diameter of the MC along the length of the canal from second molar to second premolar was 3.03 mm on left and 2.91 mm on right. The anterior loop was present in 10.4% of patients, with the average depth below bone of 13.43 mm. The anterior loop was more often seen on the left side than right and occurred bilaterally 50% of the time. CONCLUSIONS: Mandibular bone thickness, nerve location, and dimension data all contribute to a useful knowledge base for practitioners. The application of CBCT imaging techniques aids in the surgical treatment, while offering advantages over conventional periapical and panoramic films.

Cone-beam Computed Tomography: Anatomic Analysis of Maxillary Posterior Teeth-Impact on Endodontic Microsurgery.

INTRODUCTION: It is imperative that the endodontic surgeon be knowledgeable of the anatomic dimensions of the surgical site. If cone-beam computed tomography is not available because of location/cost, it is prudent for the clinician to consult a knowledge base for the surgical site. An understanding of the root thickness of maxillary premolars and molars at the preferred level for root resection (3.0-3.6 mm), bone thickness over these roots, and the proximity of each root apex to the maxillary sinus will help the surgeon before and during the surgical procedure. METHODS: Cone-beam computed tomography scans from 155 patients were used to evaluate measurements from 505 teeth and respective areas. RESULTS: (1) Buccal bone was thinnest over the buccal root of the 2-rooted first premolar (0.66 mm) and the mesiobuccal (MB) root of the first molar (0.84 mm) and thickest over the MB root of the second molar (1.91 mm). (2) The palatal bone was thinnest over the palatal root of the maxillary first molar (1.24 mm) and thickest over the single-rooted second premolar (3.26 mm). (3) The longest distances to complete resection were found for the 2-rooted first and second premolars (8.81 mm and 9.14 mm, respectively) and the MB root of the second molar (7.40 mm). (4) The MB root of the second molar had the closest proximity to the sinus floor, with an average distance of 0.66 mm. CONCLUSIONS: An understanding of the maxillary posterior tooth anatomy for apical resection is beneficial to the endodontist.