Neville J. McDonald

The effect of post type and length on the fracture resistance of endodontically treated teeth

STATEMENT OF PROBLEM Few studies have been conducted to determine a correlation between the flexural modulus of metal and fiber-reinforced posts and the fracture resistance and failure mode of teeth restored with posts. Questions remain as to whether a longer post length or a post with a higher flexural modulus will significantly improve the fracture resistance of a tooth restored with a prefabricated post and core. PURPOSE The purpose of this study was to compare the fracture resistance and mode of failure of endodontically treated teeth restored with 3 different post systems, including 2 fiber-reinforced posts (Light-Post and Snowlight) and a stainless steel post (ParaPost XP). MATERIAL AND METHODS Seventy single-rooted premolars were sectioned at the cemento-enamel junction and then endodontically treated. Teeth were distributed into 7 groups. Three different prefabricated posts were cemented into a post space either 5 or 10 mm in depth, and composite resin (ParaPost ParaCore automix) cores were fabricated. A composite resin core group without a post served as a negative control. Specimens were loaded at 90 degrees to the longitudinal axis until ultimate failure occurred. An initial failure load and mode of failure were also recorded. Statistical analysis was performed for initial and ultimate failure loads of groups by using 2-way ANOVA (P=.05). RESULTS The groups with ParaPost XP posts demonstrated significantly higher initial and ultimate mean failure loads when compared with the fiber-reinforced post groups. The highest mean (SD) initial failure load was with the ParaPost XP group with a 10-mm post length (170.05 (60.08) N), and the lowest was with the Snowlight group with the 5-mm post length (62.85 (18.47) N). CONCLUSIONS The stiffness and the load to initial fracture of the teeth restored with ParaPost XP posts were higher compared with the fiber-reinforced post groups.

A comparative retrofill leakage study utilizing a dentin bonding material

A study was undertaken to evaluate the in vitrosealing ability of composite with a dentin bonding agent, composite alone, Cavit, amalgam without cavity varnish, hot-burnished gutta-percha, and cold-burnished gutta-percha when used as retrofilling materials. Single-rooted teeth were instrumented, filled with gutta-percha using a lateral condensation technique, and subjected to a standardized apicoectomy procedure. A retrofilling material was placed and the teeth were coated with sticky wax, then immersed in a 37°C water bath for 30 days. At the end of this period they were placed in silver nitrate dye, washed, sectioned, and leakage values determined. The amalgam without cavity varnish, Cavit, hot-and cold-burnished gutta-percha groups all showed significant leakage patterns. The composite with dentin bonding agent group demonstrated the least amount of leakage followed by the composite-only group.

Canal-Centering Ability of Two Rotary File Systems

The ability of two nickel-titanium rotary file systems to maintain the original path of the canal were compared by using a new split-mold design (the Endodontic Cube). The mesial roots of 10 mandibular first- and second-molar teeth with separate canals from orifice to foramen were divided into two groups based on canal curvature and morphology. Working lengths for each canal were determined 1.0 mm short of where the file tip was visible on the external surface of the root. The teeth were embedded in composite resin by using the Endodontic Cube as a mold and sectioned into five pieces. ProFile Ni-Ti.06 taper Series 29 and ProFile GT rotary instrumentation techniques were randomly assigned to one of the canals and used in a crown-down fashion to a 0.217 ProFile and a 0.06 GT master apical file, respectively. Digital photographs were made of the middle three sections and software features of Adobe Photoshop were used to measure the movement of the canal centers by superimposing the images of the instrumented and uninstrumented canals. Data were analyzed using ANOVA. Both systems remained centered within the canal with minimal deviation from the original canal path. The largest mean movement was less than 0.15 mm. The Endodontic Cube was an effective tool for studying and comparing instrumentation techniques.

Apical extrusion of thermoplasticized obturating material in canals instrumented with profile 0.06 or profile GT

The purpose of this in vitro study was to compare the extrusion of thermoplacticized gutta-percha in teeth instrumented with Profile 0.06 or Profile GT, and obturated with Thermafil Plus and Thermafil GT, respectively. A total of 120, extracted, human maxillary central incisors were divided into four equal groups. Group 1 was instrumented with Profile 0.06 and obturated with Thermafil Plus. Group 2 was instrumented with Profile 0.06 and obturated using warm vertical condensation (negative control). Group 3 was instrumented with Profile GT and obturated with Thermafil GT. Group 4 was instrumented with Profile GT and obturated like Group 2 (negative control). Extrusion was graded as present or absent. Results found 9 of 30 extruded for group 1, 1 of 30 for group 2, 15 of 30 for group 3, and 2 of 30 for group 4. The results suggest that, in vitro, Thermafil GT may be more prone to extruding gutta-percha past the apical foramen than Thermafil Plus.

The expression of periostin in dental pulp cells.

BACKGROUND AND OBJECTIVE Dental pulp repair is a common process triggered by microbial and mechanical challenges. Matricellular modulators, such as periostin, are key for extracellular matrix stability and tissue healing. In the scope of the dental pulp, periostin expression has been reported during development and active dentinogenesis. However, the specific dental pulp cell population capable of expressing periostin in response to known regulators has not been clearly defined. Among the different relevant cell populations (i.e., stem cells, fibroblasts and pre-odontoblasts) potentially responsible for periostin expression in the dental pulp, this study aimed to determine which is the primary responder to periostin regulators. METHODS Human dental pulp stem cells (DPSCs), human dental pulp fibroblasts (DPFs), and rat odontoblast-like cells (MDPC-23) were treated with different concentrations of TGF-β1 or different regimens of biomechanical stimulation to evaluate periostin expression by qRT-PCR, Western blot and ELISA. Statistical analyses were performed by Students t-test and ANOVA with Fishers LSD post hoc tests (p ≤ 0.05). RESULTS DPSC and MDPC-23 showed a statistically significant increase in periostin mRNA expression after exposure to TGF-β1 for 48 h. TGF-β1 also up-regulated periostin protein levels in DPSC. However, periostin significantly down-regulated protein expression in DPF. Different regimens of biomechanical stimulation showed different patterns in protein and mRNA periostin expression. CONCLUSIONS Expression of periostin was identified in each of the analysed dental pulp cell lines, which can be regulated by TGF-β1 and biomechanical stimulation. Overall, DPSCs are the most responsive cells to stimulation.

The Prevalence of Hypertension in Endodontic Clinics: A Pilot Study

Background: Hypertension is one of the leading causes of death worldwide, and a major risk factor for heart diseases and strokes. A lot of undiagnosed or uncontrolled hypertensive patients seek dental treatment in regular basis. However, neither doctors nor patients are doing enough to fight and diagnose this silent killer disease. This study investigated the prevalence of undiagnosed or uncontrolled hypertensive patients who visited our endodontic clinic for dental treatment. Methods: 102 patients were included in this study. Patients were non-smokers and only presented a history of hypertension alone or a clear medical history. We measured blood pressure using a digital sphygmomanometer after patients had been seated in a dental chair for at least 10 minutes. We present the data as descriptive and percentage values. Results: A large fraction of patients (63.7%) were found to be hypertensive irrespective of their awareness of having hypertension. Nearly half (52.9%) of participants were unaware they had hypertension, and only 10.8% of patients knew they had hypertension. Only approximately half of the latter group of patients (4.9%) was already receiving medication for their hypertension. Conclusion: Our data reveals that dentists play a critical role in detecting undiagnosed patients with hypertension; this role should be emphasized in our specialty as a standard of care.

Efficacy of Articaine versus Lidocaine in Supplemental Infiltration for Mandibular First versus Second Molars with Irreversible Pulpitis: A Prospective, Randomized, Double-blind Clinical Trial

Introduction: Profound pulpal anesthesia is difficult to achieve in mandibular molars with irreversible pulpitis (IP). However, there are no published randomized controlled clinical trials comparing the success of supplemental buccal infiltration (BI) in mandibular first versus second molars with IP. The purpose of this prospective, randomized, double‐blind study was to compare the efficacy of 4% articaine with 2% lidocaine for supplemental BIs in mandibular first versus second molars with IP after a failed inferior alveolar nerve block (IANB). This studys sample was combined with data from a previous trial. Methods: One hundred ninety‐nine emergency subjects diagnosed with IP of a mandibular molar were selected and received an IANB with 4% articaine. Subjects who failed to achieve profound pulpal anesthesia, determined by a positive response to cold or pain upon access, randomly received 4% articaine or 2% lidocaine as a supplemental BI. Endodontic access was begun 5 minutes after infiltration. Success was defined as less than mild pain during endodontic access and instrumentation on the Heft‐Parker visual analog scale. Results: There was a 25% IANB success rate with 4% articaine. The success rate for articaine supplemental BI in first molars was 61% versus 63% for second molars (P > .05). The success of lidocaine in first molars was 66%, but for second molars it was 32% (P = .004). Conclusions: The success rate for IANB with 4% articaine was 25%. Articaine and lidocaine had similar success rates for supplemental infiltration in first molars, whereas articaine was significantly more successful for second molars. However, because BI often did not provide profound pulpal anesthesia, additional techniques including intraosseous anesthesia may still be required.

Deciphering Endodontic Microbial Communities by Next-generation Sequencing

Introduction: Biofilms are present in more than 70% of endodontically diseased teeth. Through the advancements in the next‐generation sequencing (NGS) technologies, microbiome research has granted a deeper analysis of the microbial communities living in human hosts. Here, we reviewed previous studies that used NGS to profile the microbial communities of root canals. Methods: A total of 12 peer‐reviewed articles from PubMed were identified and critically reviewed. The study criteria were as follows: NGS platforms, sequenced bacterial hypervariable regions, teeth diagnosis with available patient information, sample characteristics, collection method, and microbial signatures. Results: The most common NGS platforms used were 454 pyrosequencing (Roche Diagnostic Corporation, Risch‐Rotkreuz, Switzerland) and Illumina‐based technology (Illumina Inc, San Diego, CA). The hypervariable regions sequenced were between the V1 and V6 regions. The patient and sample population ranged from ages 12–76 years and asymptomatic and symptomatic teeth diagnosed with pulp necrosis with or without apical periodontitis. Microbial sampling was conducted directly from the infected pulp or the extracted teeth. The most abundant phyla were Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria, and Fusobacteria. The most frequently detected genera were Prevotella, Fusobacterium, Porphyromonas, Parvimonas, and Streptococcus. Other notable microbial signatures at different taxa levels were identified but were widely variable between studies. Conclusions: Technologies based on high‐throughput 16S ribosomal RNA NGS can aid in deciphering the complex bacterial communities of root canal biofilms. Thus far, only a few studies have been published with relatively small sample sizes, variable sample collection protocols, and community analyses methods. Future larger clinical studies are essential with validated standardized protocols for improved understanding of the pathogenic nature of bacterial biofilm communities in root canals. Highlights:Polymicrobial communities are associated with endodontic diseases.Next‐generation sequencing (NGS) offers deep coverage of microbial communities.Newer NGS provides improved accuracy and deeper coverage at reduced costs.NGS is useful for studying the microbiome of differing endodontic conditions.

Maxillary and Mandibular Non-Hodgkin Lymphoma with Concurrent Periapical Endodontic Disease: Diagnosis and Management

Extranodal non-Hodgkin lymphoma (NHL) in the oral region can present similarly to diseases of odontogenic origin. The objective of this report was to describe a rare case of maxillary and mandibular NHL that presented similarly to and concurrently with lesions of odontogenic origin.A unique case of extranodal NHL, which presented at the apices of maxillary and mandibular teeth in conjunction with lesions of odontogenic origin in a 68-year-old white man, is described. The patient sought care because of a lesion in the right maxillary paranasal region that caused him paresthesia. Radiographically, periapical radiolucencies were present along teeth #5-8, #23 and 24, and #30 and 31. Biopsies of the right maxillary and anterior mandibular lesions were completed and led to a diagnosis of NHL at the apices of teeth #5-8 extending to the hard palate and granulation tissue at the apices of teeth #23 and 24. Two years later, the patient returned because of pressure and sensitivity associated with teeth #30 and 31. Vestibular swelling was noted clinically, and a multilocular periapical radiolucency was present radiographically. Via endodontic therapy and a positron emission tomographic scan, the lesion associated with teeth #30 and 31 was determined to be of both odontogenic and nonodontogenic origin because it possessed both a sinus tract associated with tooth #30 and NHL. Lesions of odontogenic and nonodontogenic origin possess diagnostic and treatment challenges because they may present similarly and/or concurrently. Thoughtful and conservative management of odontogenic lesions with associated NHL is imperative. Interprofessional collaboration and communication among providers must be thorough and clear to properly coordinate care and prevent delays in diagnosis and treatment when these entities occur together.

Endodontists' Intravenous Sedation–related Attitudes and Professional Behavior: A National Survey

Introduction Research shows that a high percentage of endodontic patients are interested in receiving intravenous (IV) sedation. The objectives of this study were to assess endodontists’ IV sedation–related education, attitudes, and professional behavior and to explore whether providing versus not offering IV sedation procedures was associated with IV‐related education and attitudes and whether background characteristics and education were related with IV sedation attitudes and behavior. Methods Data were collected with an anonymous Web‐based survey from 616 members of the American Association of Endodontists (response rate = 29%). Results Only 10% of respondents agreed/strongly agreed that they had adequate training in IV sedation. However, 48% agreed/strongly agreed that there was a need for IV sedation in their practice. Although 69% did not offer IV sedation, 26% had another professional provide it, and 4% provided it themselves. These 3 groups of providers differed in the mean quality of their IV sedation–related education (scale from 1–5 with 5 = best education: 1.50 vs 1.62/2.37, P < .001) and the positivity of their attitudes toward IV sedation (2.90 vs 3.50/4.21, P < .001). Although the quality of IV sedation education was not correlated with the graduation year, the more recently respondents had graduated, the more positive they were toward providing education about IV sedation (r = .16, P < .001). Conclusions Most endodontists did not evaluate their IV sedation–related graduate education positively. However, nearly half acknowledged the need for IV sedation in endodontics. The more recently they graduated, the more they agreed that IV sedation–related graduate education was needed but also that staff training and maintenance of equipment would be a problem.