Management of atypical occlusal discrepancy after condylar resection: A clinical report

This clinical report describes the prosthetic management of occlusion for a patient who had received condylar resection as part of cancer treatment. Previous reports have identified that patients with unrepaired segmental resection of the mandible experienced a frontal plane rotation of the mandible toward the nonsurgical side. In contrast, because of preservation of temporomandibular muscles and their attachments, the mandible rotated toward the surgical side, and occlusal contacts were limited to a pair of molars on that side. Manual manipulation and instructions for muscular stretching and massages were provided to reduce muscular tension. A mandibular guidance prosthesis was fabricated and gradually adjusted to guide the mandible progressively toward a normal position. These treatments helped improve general comfort, mastication, occlusion, and the gradual rotation of the mandible toward a normal position.

Do onlays and crowns offer similar outcomes to posterior teeth with mesial-occlusal-distal preparations? A systematic review

OBJECTIVE

Teeth prepared for mesial-occlusal-distal (MOD) restorations have a significant risk of cusp fracture. Crowns and onlays can provide cusp coverage to reinforce posterior teeth at risk. Onlays are often more conservative of tooth structure which may be an advantage for teeth with large MOD preparations. It remains uncertain how onlays and crowns compare for posterior teeth with MOD tooth structure loss. The purpose of this systematic review was to compare the resistance to fracture, success rate, survival rate, and failure rate of teeth with MOD preparations restored with onlays or crowns.

MATERIALS AND METHODS

An electronic search queried Medline (PubMed), Embase (Ovid), Scopus, the Cochrane Library, and grey literature (OpenGrey) from database inception through April 29, 2023.

RESULTS

After eliminating duplicates and irrelevant records, 32 manuscripts were assessed. Only three publications met the criteria for inclusion. Most exclusions were due to poor reporting of restorative design and the amount of tooth structure remaining, or due to combining various restorative designs. Due to the limited sample size and high heterogeneity, no meta-analysis was conducted. One study observed a better outcome for onlays and two observed no difference. All three studies reported the mode of failure for crowns as more catastrophic whereas teeth with onlays could be salvaged.

CONCLUSIONS

Onlays may be an advantageous alternative to crowns for teeth with MOD preparations, but the level of evidence is insufficient to draw meaningful conclusions.

CLINICAL SIGNIFICANCE

Current evidence is insufficient to determine whether onlays or crowns are providing a different outcome when used to restore posterior teeth with MOD tooth structure loss. However, the fracture of teeth with MOD tooth structure loss restored with onlays appears to be less catastrophic than when restored with crowns.

A technique to guide implant placement with the long axis parallel to the path of insertion of removable partial dentures

This article describes a novel technique that allows the planning and placing of dental implants with their long axis parallel to a path of insertion chosen for a prospective removable partial denture. The technique is straightforward, uses digital technologies efficiently, and enables prosthetically driven implant placement. It also optimizes the outcome when dental implants are used in association with removable partial dentures.

Effects of remeshing algorithms on trueness of fit when used to compress .stl files for digital dental model: A narrative literature review

OBJECTIVES

In recent years, there has been a transition toward using and storing digitized dental models instead of physical casts. The size of .stl files is directly correlated with a need for higher computer processing power, longer operation time and a need for more storage space. Several studies explored the impact of decreasing the mesh resolution to decrease file size while maintaining trueness of fit between the original and altered files. Multiple authors suggested to compress .stl files by removing a fixed percentage of triangular faces. However, certain variables which are not yet fully investigated may impact the outcome of remeshing and compressing .stl files.

METHODS

This narrative review article explores important concepts and considerations that may have a significant impact on the outcome of remeshing and compressing .stl file.

RESULTS

When restructuring digital meshes to compress .stl files, numerous variables such as initial mesh density, adaptive resolution, scanning technology, rendition and remeshing algorithms, and the clinical situation can affect the outcome.

CONCLUSION

Prior to applying subjective compression to .stl files by a static percentage, multiple variables must be considered to ensure trueness of fit is preserved. The results obtained for specific situations may not extrapolate to others.

CLINICAL SIGNIFICANCE

Remeshing algorithms used to reduce .stl file size, or to optimize the files prior to manufacturing, may cause the loss of important data. Further research is needed to guide clinicians safely altering digital meshes.

Virtual Oral Health across Canada: A Critical Comparative Analysis of Clinical Practice Guidances during the COVID-19 Pandemic

During the COVID-19 pandemic, teledentistry was suggested as a cost-effective and promising approach to improve access to oral health care. In response, Canadian provincial and territorial dental regulatory authorities (DRAs) published teledentistry-related clinical practice guidances (TCPGs). However, an in-depth comparison between them is needed to understand their gaps and commonalities so as to inform research, practice, and policy. This review aimed to provide a comprehensive analysis of TCPGs published by Canadian DRAs during the pandemic. A critical comparative analysis of these TCPGs published between March 2020 and September 2022 was conducted. Two members of the review team screened the official websites of dental regulatory authorities (DRAs) to identify TCPGs and performed data extraction. Among Canada's 13 provinces and territories, only four TCPGs were published during the relevant time period. There were some similarities and differences in these TCPGs, and we identified gaps pertaining to communication tools and platforms, and measures to safeguard patients' privacy and confidentiality. The insights from this critical comparative analysis and the unified workflow on teledentistry can aid DRAs in their development of new or an improvement to existing TCPGs or the development of nationwide TCP guidelines on teledentistry.

Comparison of the torque transferred to the implant-bone interface when tightening abutment screws and when torque testing implants: An in vitro study

STATEMENT OF PROBLEM

Before dental implants are restored, osseointegration is often verified by torque testing the implant. For this test, it might be appropriate to select the torque subsequently used to tighten the abutment screw during prosthetic delivery. However, whether the full torque applied to the abutment screw is transferred to the implant-bone interface remains unknown.

PURPOSE

The purpose of this in vitro study was to assess whether the same torque is transferred to the implant-bone interface when tightening abutment screws and when torque testing implants and to investigate whether the implant system used affects the torque transfer.

MATERIAL AND METHODS

A digital torque gauge was used to register the torque directed to a simulated implant-bone interface. Twenty implants from 4 different manufacturers were successively secured to the digital torque gauge. An implant driver was used to torque test the implant. An implant abutment screw was then tightened to attach a universal base (TiBase) abutment to the implant. During both tests, a mechanical torque limiting device was used to apply the same manufacturer-specific torque. For both experiments, the peak torque transferred to the simulated implant-bone interface was recorded. To allow pooling data from different torque targets, the data were converted into absolute difference. A t test was used to evaluate whether the same magnitude of torque was transferred to the implant-bone interface when tightening abutment screws and when torque testing implants. An ANOVA was used to test whether the percentage of torque transferred to the implant-bone interface was impacted by the implant system used (α=.05).

RESULTS

No significant difference was found between the torque transmitted when tightening an abutment screw and that transmitted when torque testing the implant (P=.600). Also, no difference was found in the percentage of torque transferred to the simulated implant-bone interface of different implant systems (P=.996).

CONCLUSIONS

Regardless of the implant system used, when tightening abutment screws and when torque testing implants, the same amount of torque is transferred to the implant-bone interface.

A Prolonged Time to Diagnosis Due to Misdiagnoses: A Case Report of an Atypical Presentation of Eagle Syndrome

BACKGROUND Eagle syndrome is an unusual condition in which the styloid process (SP) becomes elongated and causes different clinical symptoms due to pressure on adjacent anatomical structures. The symptoms are non-specific and include severe throat, facial, and ear pain, or headaches. They are usually exacerbated by head rotation, swallowing, yawning, or chewing, but atypical presentations exist. It is a difficult pathology to diagnose and it can take several years before a proper diagnosis is made. CASE REPORT This report describes the case of a dental student presenting with an atypical presentation of Eagle syndrome. His styloid processes were 75 mm long and he was affected with severe pain to his throat, the anterior part of his ears, his submandibular area, and his molar teeth. The pain was exacerbated during maximal mouth opening, yawning, mandibular protrusion, and during downward head tilt, but not during the classically described movements of head rotation, swallowing, yawning, or chewing. Due to the absence of the classic symptoms, even with knowledge of the condition and unusual direct access to several oral and maxillofacial specialists, it took 4 years and multiple misdiagnoses to reach the final diagnosis. Following bilateral styloidectomy, all pain subsided. CONCLUSIONS The clinical presentation of Eagle syndrome varies, and the symptoms are non-specific. This greatly increases the complexity of diagnosing the condition and raises the time to diagnosis and the chances of misdiagnoses. It is, therefore, crucial to recognize the diagnostic tools, applicable imaging, and definitive treatment alternatives to successfully identify and treat patients affected.

Fracture Resistance of Immature Teeth Submitted to Different Endodontic Procedures and Restorative Protocols

INTRODUCTION

The purpose of this in vitro study was to determine whether the methods used to treat endodontically and restore anterior immature teeth with a necrotic pulp influence their resistance to fracture.

METHODS

After access opening and cleaning and shaping, 80 specimen teeth were assigned into 5 groups according to the endodontic obturation method and coronal restoration as follows: A1, apexification with a composite restoration in the crown area; A2, apexification with a composite restoration in the crown and 3 mm into the root; IR, immediate revascularization with a composite restoration in the crown area; SR, successful revascularization with a composite in the crown area; and the control group, a mature tooth treated with gutta-percha and sealer with a composite restoration in the crown area. The teeth were mounted in acrylic blocks and brought to fracture under compressive forces in a universal testing machine. Both the fracture strength and the location where the fracture occurred were recorded.

RESULTS

There were no statistically significant differences in the fracture resistance among the 5 groups (1-way analysis of variance, F₄ = .545, P = .703). No statistically significant differences were found in the location where the fracture occurred either (χ²₄ = 4.1, P = .391).

CONCLUSIONS

Within the limitations of this in vitro study, it can be concluded that the treatment options used to treat nonvital immature teeth provided the same resistance to fracture.

Resistance to fracture of extracted teeth used for pre-clinical endodontic procedures: Influence of storage conditions

OBJECTIVES

The purpose of this in vitro study was to determine whether different storage conditions used during endodontic procedures affect the fracture resistance of extracted teeth used for pre-clinical dental education.

METHODS

Freshly extracted mandibular incisors and canines were sterilised in an autoclave for 40 minutes at 24°F under a pressure of 20 psi and then stored in distilled water at 4°C until use. Specimens were randomly assigned to two groups based on the storage method used whilst undergoing endodontic procedures. Between endodontic sessions, teeth in the Wet Group (n = 16 incisors; n = 4 canines) were stored in distilled water and teeth in the Dry Group (n = 16 incisors; n = 4 canines) were stored in a dry container. All specimens were kept at room temperature and away from sunlight. Endodontic treatments were performed in 3 sessions over a 3-week period. The specimens were then brought to fracture under compressive forces along the long axis of the tooth in an Instron universal testing machine. The data were analysed using t tests (α = 0.05).

RESULTS

None of the teeth fractured during endodontic procedures. However, the compressive load required to fracture teeth stored under wet conditions was significantly higher than the load needed for teeth stored dry (P < .05).

CONCLUSIONS

Fracture resistance is affected by storage conditions; teeth stored in water have a higher resistance to fracture than teeth that are stored dry. Fracture resistance was, however, not reduced enough to lead to tooth fracture during pre-clinical endodontic procedures.

Reversing the Effects of 0.5% Bupivacaine Using Phentolamine Mesylate: A Preliminary Randomized Controlled Clinical Trial

Phentolamine mesylate is the only commercially available dental local anesthetic reversal agent. It has been proven safe and effective for reversing most local anesthetics used in dentistry but was never tested with bupivacaine. The aim of this project was to evaluate the effectiveness of 0.4-mg phentolamine mesylate in reversing an inferior alveolar nerve block (IANB) with 0.5% bupivacaine, 1:200,000 epinephrine. Sixty-six participants were recruited and were administered an IANB with bupivacaine. After confirmation of anesthesia, they were randomized into 1 of 2 groups (phentolamine mesylate or control). Participants in the phentolamine mesylate group received a second injection with 1.7-mL OraVerse (0.4-mg phentolamine mesylate), while participants in the control group received a second injection with 1.7-mL sterile saline water. Participants were trained to self-assess sensation (lower lip and tongue) and function (drinking, speaking, and smiling), which they did every 20 minutes, and they recorded the time when sensation/function returned to normal. Comparative analysis was completed using independent sample t-tests, univariate linear regressions, and Pearson chi-square. Forty-three participants were randomized, and 34 completed the study (phentolamine mesylate, n = 15; control, n = 19). There was a statistically significant difference between the 2 treatment groups for return of normal sensation to the lower lip (mean difference of 2 hours and 17 minutes; P = .027) and the tongue (mean difference of 1 hour and 35 minutes; P = .046) in favor of the phentolamine mesylate group. The results indicate that phentolamine mesylate hastens the return to normal sensation of an IANB with bupivacaine.

Reversing the effects of 2% Lidocaine: A randomized controlled clinical trial

OBJECTIVES

Prolonged soft tissue anesthesia following a dental appointment is a complaint that is frequently reported by patients. Soft tissue anesthesia generally exceeds the duration of pulpal anesthesia by a few hours. This can lead to difficulties with smiling, drinking, speaking and lip/cheek biting following dental appointments. Phentolamine Mesylate (PM) is a pharmacological agent capable of reducing the duration of soft tissue anesthesia following dental treatments. Many clinical trials supporting its efficacy have used sham injections compared to injections with PM. The present study aims to evaluate the effect of PM on the duration of soft tissue anesthesia compared to a control injection of saline water.

METHODS

This randomized controlled trial recruited 40 participants above 18 years of age. Following an inferior alveolar nerve block using 1.8 ml of Lidocaine 2%, 1:100 000 epinephrine, participants were randomized into one of 2 groups. The test group received an injection of 0.4 mg PM (OraVerse). Participants in the control group received an injection of sterile saline water. Participants were trained in self-assessing their anesthesia, which they did until return to normal sensation.

RESULTS

Thirty-six participants completed the study. PM significantly reduced the duration of soft tissue anesthesia in the lower lip (104 vs 170 min, p = .001), and tongue (83 vs 134 min, p = .004) compared to the control injection. No serious adverse events were encountered. The only adverse events observed were post-operative pain and discomfort.

CONCLUSIONS

Phentolamine Mesylate hastens the return to normal soft tissue sensation and function by approximately one hour compared to a control injection of water.

CLINICAL SIGNIFICANCE

Phentolamine Mesylate can be considered a safe and effective way of reducing the duration of soft tissue anesthesia following a dental appointment. This controlled clinical trial is registered at the National Institutes of Health (ClinicalTrials.gov) #NCT02861378.

Hereditary gingival fibromatosis with extreme ridge thickness and insufficient interarch distance: A clinical report of surgical and prosthetic management

Hereditary gingival fibromatosis is a rare genetic disorder resulting in gingival overgrowth that can be found in both dental arches. As a result of the gingival overgrowth and associated dental displacement, affected patients occasionally present with increased occlusal vertical dimension and/or inadequate lip closure. Depending on the disorder's severity, these patients can be challenging to treat. This clinical report describes a comprehensive surgical and prosthetic approach to the rehabilitation of a middle-aged patient with severe manifestations of hereditary gingival fibromatosis and severe generalized chronic periodontitis.

Effect of High Irradiance on Depth of Cure of a Conventional and a Bulk Fill Resin-based Composite

OBJECTIVES

This study evaluated the effect of using three commercial light curing units (LCUs) delivering a range of irradiance values, but delivering similar radiant exposures on the depth of cure of two different resin-based composites (RBCs).

METHODS

A conventional hybrid RBC (Z100 shade A2, 3M ESPE) or a bulk fill RBC (Tetric EvoCeram Bulk Fill shade IVA, Ivoclar Vivadent) was packed into a 10-mm deep semicircular metal mold with a 2-mm internal radius. The RBC was exposed to light from a plasma-arc-curing (PAC) light (Sapphire Plus, DenMat) for five seconds, a quartz-tungsten-halogen (QTH) light (Optilux 501, Kerr) for 40 seconds, or a light-emitting-diode (LED) light (S10, 3M ESPE) for 20 seconds and 40 seconds (control). The Knoop microhardness was then measured as soon as possible at the top surface and at three points every 0.5 mm down from the surface. For each RBC, a repeated measures analysis of variance (ANOVA) model was used to predict the Knoop hardness in a manner analogous to a standard regression model. This predicted value was used to determine at what depth the RBC reached 80% of the mean hardness achieved at the top surface with any light.

RESULTS

The PAC light delivered an irradiance and radiant exposure of 7328 mW/cm(2) and 36.6 J/cm(2), respectively, to the RBCs; the QTH light delivered 936 mW/cm(2) and 37.4 J/cm(2) and in 20 seconds the LED light delivered 1825 mW/cm(2) and 36.5 J/cm(2). In 40 seconds, the control LED light delivered a radiant exposure of 73.0 J/cm(2). For Z100, using 80% of the maximum hardness at the top surface as the criteria for adequate curing, all light exposure conditions achieved the 2.0-mm depth of cure claimed by the manufacturer. The LED light used for 40 seconds achieved the greatest depth of cure (5.0 mm), and the PAC light used for five seconds, the least (2.5 mm). Tetric EvoCeram Bulk Fill achieved a 3.5-mm depth of cure when the broad-spectrum QTH light was used for 40 seconds delivering 37.4 J/cm(2). It required a 40-second exposure time with the narrow-spectrum LED, delivering approximately 73 J/cm(2) to reach a depth of cure of 4 mm.

CONCLUSIONS

When delivering a similar radiant exposure of 37 J/cm(2), the QTH (40 seconds) and LED (20 seconds) units achieved a greater depth of cure than the PAC (five seconds) light. For both resins, the greatest depth of cure was achieved when the LED light was used for 40 seconds delivering 73 J/cm(2) (p<0.05).

BMP-2 functions independently of SHH signaling and triggers cell condensation and apoptosis in regenerating axolotl limbs

Background

Axolotls have the unique ability, among vertebrates, to perfectly regenerate complex body parts, such as limbs, after amputation. In addition, axolotls pattern developing and regenerating autopods from the anterior to posterior axis instead of posterior to anterior like all tetrapods studied to date. Sonic hedgehog is important in establishing this anterior-posterior axis of limbs in all tetrapods including axolotls. Interestingly, its expression is conserved (to the posterior side of limb buds and blastemas) in axolotl limbs as in other tetrapods. It has been suggested that BMP-2 may be the secondary mediator of sonic hedgehog, although there is mounting evidence to the contrary in mice. Since BMP-2 expression is on the anterior portion of developing and regenerating limbs prior to digit patterning, opposite to the expression of sonic hedgehog, we examined whether BMP-2 expression was dependent on sonic hedgehog signaling and whether it affects patterning of the autopod during regeneration.

Results

The expression of BMP-2 and SOX-9 in developing and regenerating axolotl limbs corresponded to the first digits forming in the anterior portion of the autopods. The inhibition of sonic hedgehog signaling with cyclopamine caused hypomorphic limbs (during development and regeneration) but did not affect the expression of BMP-2 and SOX-9. Overexpression of BMP-2 in regenerating limbs caused a loss of digits. Overexpression of Noggin (BMP inhibitor) in regenerating limbs also resulted in a loss of digits. Histological analysis indicated that the loss due to BMP-2 overexpression was the result of increased cell condensation and apoptosis while the loss caused by Noggin was due to a decrease in cell division.

Conclusion

The expression of BMP-2 and its target SOX-9 was independent of sonic hedgehog signaling in developing and regenerating limbs. Their expression correlated with chondrogenesis and the appearance of skeletal elements has described in other tetrapods. Overexpression of BMP-2 did not cause the formation of extra digits, which is consistent with the hypothesis that it is not the secondary signal of sonic hedgehog. However, it did cause the formation of hypomorphic limbs as a result of increased cellular condensation and apoptosis. Taken together, these results suggest that BMP-2 does not have a direct role in patterning regenerating limbs but may be important to trigger condensation prior to ossification and to mediate apoptosis.