Tooth Failure Research Articles

Tooth-level predictors of tooth loss and exposed bone after radiation therapy for head and neck cancer

BackgroundThe objective of this study was to identify tooth-level risk factors for use during preradiation dental care management to predict risk of tooth failure (tooth lost or declared hopeless) and exposed bone after radiation therapy (RT) for head and neck cancer (HNC). MethodsThe authors conducted a prospective observational multicenter cohort study of 572 patients receiving RT for HNC. Participants were examined by calibrated examiners before RT and then every 6 months until 2 years after RT. Analyses considered time to tooth failure and chance of exposed bone at a tooth location. ResultsThe following pre-RT characteristics predicted tooth failure within 2 years after RT: hopeless teeth not extracted pre-RT (hazard ratio [HR], 17.1; P < .0001), untreated caries (HR, 5.0; P < .0001), periodontal pocket 6 mm or greater (HR, 3.4; P = .001) or equaling 5 mm (HR, 2.2; P = .006), recession over 2 mm (HR, 2.8; P = .002), furcation score of 2 (HR, 3.3; P = .003), and any mobility (HR, 2.2; P = .008). The following pre-RT characteristics predicted occurrence of exposed bone at a tooth location: hopeless teeth not extracted before RT (risk ratio [RR], 18.7; P = .0002) and pocket depth 6 mm or greater (RR, 5.4; P = .003) or equaling 5 mm (RR, 4.7; P = .016). Participants with exposed bone at the site of a pre-RT dental extraction averaged 19.6 days between extraction and start of RT compared with 26.2 days for participants without exposed bone (P = .21). ConclusionsIndividual teeth with the risk factors identified in this study should be considered for extraction before RT for HNC, with adequate healing time before start of RT. Practical ImplicationsThe findings of this trial will facilitate evidence-based dental management of the care of patients receiving RT for HNC. This clinical trial was registered at Clinicaltrials.gov. The registration number is NCT02057510.

Initial impact force analysis and simulation of planetary helical gear transmission

The planetary gear transmission is widely used because of its advantages such as large transmission ratio and high transmission efficiency. But at the moment of starting, there is a speed difference between driving gear and driven wheel due to the backlash between the teeth, this will easily cause the initial collision and impact force, which seriously affect the life of gear transmission, even lead to tooth surface pitting and root fracture failure, therefore, it is necessary to conduct a quantitative analysis of the initial collision. Based on the gear meshing principle and the system dynamics theory, the analytical calculation formula of initial impact force for the internal and external meshing gear pair was derived. The impact simulation analysis model of planetary helical gear transmission was established based on the finite element LS-DYNA, and the simulation analysis results were compared with the analytical calculation results, which verified the correctness of the analytical calculation model. This paper reveals the impact collision mechanism and studies the influence law of the speed and temperature on the impact force, thus laying a good theoretical foundation for the dynamic modification design of the planetary gear transmission and preventing the failure of the gear teeth from impact collision.

Impacted Deciduous Second Mandibular Molar Tooth

A 9-years-old boy presented to the Department of Oral and Maxillofacial Surgery with pain in the posterior region of the left mandible. The child was healthy with an unremarkable medical history. There was no family history of the same condition. Intra-oral clinical examination showed the absence of lower left deciduous molar and multiple carious deciduous teeth at both dental arches. Orthopantogram (OPG) confirmed the complete impaction of the lower-left deciduous 2nd molar with inferior retention of the lower 2nd permanent premolar close to the lower border of the mandible [Panel A]. Under local anesthesia, a two-sided flap was raised, surgical removal of the impacted deciduous 2nd molar and extraction of adjacent 1st deciduous molar, the flap was sutured with 3/0 silk suture [Panel B and C]. Failure of eruption or impaction of deciduous molar was linked to the disturbance of the development of the successor's permanent teeth. Deciduous tooth failure of eruption or impaction is rare in comparison with permanent teeth. Among deciduous dentitions, the 2nd molar was the most commonly affected tooth, followed by central incisors. Impaction can cause many serious problems to underlying tooth buds of the permanent dentition including their delayed eruption or even ectopic eruption. Therefore, proper history and clinical examination, and precise treatment are mandatory. After one month, OPG showed complete healing [Panel D] and the patient was satisfied with the aesthetic and functional outcomes.

Dental hypodontia in dogs

Hypodontia is a type of dental anomaly that can affect dogs, characterized by the congenital absence of up to six deciduous or permanent teeth. According to reports in the literature, the absence of a dental element is an incidental finding and the absence of the first premolar teeth is observed more frequently. It is believed that there is a genetic component and viral factors that predispose to the non-development of dental elements. However, an interruption in the development of these same dental elements can cause tooth failure. It is not possible to discern whether there is a dental element or not just through the macroscopic examination of the oral cavity. In this sense, it is necessary to carry out an intraoral radiographic examination for diagnostic elucidation, which will lead to an appropriate treatment. According to the literature, non-eruption of teeth can generate a dentigerous cyst, whose treatment is based on the extraction of any remaining tooth tissue.&#x0D;

Reliability Evaluation of Transmission Planetary Gears “bottom-up” approach

The reliability study is the most important part of the engineering design process, as it is the basis of analysis and assessment of future product performance in exploitation. Since performance cannot be predicted with absolute certainty, the application of reliability theory includes probability theory and unreliability modeling. The proposed approach has been applied to assess the reliability of gear planetary power transmissions. The assessment of system reliability was determined on the basis of the block diagram method, as a function of the reliability of individual components, calculated by statistical analysis. Using the Weibull model, the reliability of the planetary gear was defined on the basis of the probability of failure of the gear teeth and the results were interpreted to assess the reliability of the component and the entire planetary train. For a more precise assessment of reliability and to avoid modeling every failure and mode of occurrence, a competitive risk model was developed. The reliability assessment study was conducted with a “bottom-up” approach. Reliability has been assessed, for instantaneous, estimated and assigned failures rate of planetary train and component.

Influence of alveolar bone height on the biomechanical behavior of roots restored with custom-made posts-and-cores.

This study evaluated the influence of alveolar bone height and post type on compressive force resistance, fracture pattern, and stress distribution in endodontically treated teeth. Bovine roots were endodontically treated and divided into eight groups (n=10) according to alveolar bone height (normal alveolar bone and alveolar bone loss - 2 and 5 mm from the margin of the crown, respectively) and post type (prefabricated glass fiber post, anatomic glass fiber post, customized milled glass fiber post-and-core and customized milled polyetheretherketone (PEEK) post-and-core). Mechanical fatigue was simulated (300.000 cycles/50 N/1.2Hz). Compression force resistance (N) was analyzed by two-way ANOVA and Tukey test (α=0.05). Fracture patterns were described as percentages. Stress distribution was analyzed by finite element analysis. Significant diferences were found for alveolar bone height (P < 0.0001): normal alveolar bone groups showed higher mean values of compression force resistance compared to alveolar bone loss groups, while no significant differences were found for post type (P=0.4551), and there was no double interaction between them (P=0.5837). Reparable fractures were more predominant in normal alveolar bone groups, especially in the milled glass fiber and PEEK post-and-core groups. Stress distribution was similar in groups with prefabricated glass fiber posts and milled PEEK posts-and-cores, and the alveolar bone loss condition significantly increased stress concentration and strain values, mainly on apical dentin. Alveolar bone loss due to physiological aging and/or periodontal disease may lead to increased risk of restored tooth failure, although milled glass fiber and PEEK posts-and-cores provide more reparable fractures. Custom-made glass fiber and PEEK post-and-cores are interesting options, since they enable clinicians to work with a single-body post-and-core system that avoid several materials interfaces and fits well in the root canal provided promising results to improve the failure behavior of restored roots, as they offer more reparable fractures even in situations of alveolar bone loss.

An Erupted Compound Odontoma: A Rare Clinical Entity

ABSTRACT Odontomas are the most common developmental hamartomatous anomalies that are caused due to the growth and development of completely differentiated epithelial and mesenchymal cells, which give rise to functional odontoblasts and ameloblasts. These cells lay down enamel and dentin, respectively, in an abnormal pattern mainly due to the failure of the cells to reach a normal state of morphodifferentiation. The exact etiology of odontomas is currently unknown; however, they have been related to localized trauma and various other hereditary conditions. They are typically asymptomatic and are usually detected as a chance radiographic finding. This condition is frequently associated with one or more unerupted teeth and is often detected through a failure of teeth to erupt during an expected timeframe.

Dynamic Analysis and Fault Diagnosis for Gear Transmission of a Vibration Exciter of a Mine-Used Vibrating Screen under Different Conditions

The helical gear pair of a box-type vibration exciter of a mine-used linear vibrating screen is subjected to complex excitation and prone to broken tooth failures. At present, investigation regarding the difference and particularity between gear transmission in vibrating screens (i.e., vibration machinery) and that in rotating machinery is still a challenge, which is the key to revealing the performance and failure mechanism of gear transmission in the premise of application to vibrating screens. In order to intuitively display the peculiarity of gear transmission on the exciter, an innovative virtual prototype model of a gear pair of a vibrating screen exciter is proposed. This model considers the effects of internal and external excitation, such as the friction and lubrication of the gear, strong alternating load produced by a large eccentric block, the reciprocating motion of the screen body, the large clearance of bearing and so on, and its correctness is verified. Based on the comparison, the inducement for the high fatigue rate of exciter gears is revealed. Models of a vibrating screen’s excitation system with different degrees of broken teeth are also established, and tooth fault features are proposed for fault detection. Sensitive indicators for the degradation degree of tooth damage are put forward, and the monitoring strategy is presented that with the increase of damage degree, the waveform index and pulse index of axial vibration acceleration increase. The analysis results provide powerful support for the optimal design of the vibrating screen’s exciter gears and fault diagnosis.

Modal analysis of spur gears for varied teeth root cracks characteristics: finite element analysis (FEA) simulations

Gear failure is considered the main alarming and undesirable event in gearboxes. Usually, cracks happen by fatigue caused due to cyclic loading. Fatigue stress is focused on the teeth root because of the small tooth fillet radius. This causes progressive damage to gear teeth which causes teeth failure, and hence, a damaged gear. This work shows a numerical framework to identify and quantify cracks' existence at the teeth root of spur gears. The problem is numerically analysed through finite element-based simulation with ANSYS by conducting a modal analysis. There are nine cases of gears with different cracks on their tooth; these cracks are varied by their number (single or multiple), Crack Length Percentage (CLP %), and location. The FEA is used to simulate all nine cases to predict the bending natural frequency of teeth and to investigate the effects of the variation of the crack by looking at the natural frequency of the teeth bending as well as the deformation level. Results revealed that the teeth bending natural frequency decreases as the CLP% increases. In addition, the gear stiffness is calculated based on the natural frequency and gear’s mass and it is indicated that the stiffness decreases as the CLP% increases, while the deformation level increase with CLP%.

An improved Smoothed Particle Hydrodynamics (SPH) method for modelling the cracking processes of teeth and its applications

The present work aims to propose a meshless method to establish the tooth meso-structures and model the tooth fracturing processes as well as investigate the influencing factors that affect the dental mechanical properties. To this end, the traditional kernel function in the SPH method has been improved by introducing a fracture mark ξ to realize the progressive failure processes of teeth; The “Particle Searching Method” has been proposed, which can realize the establishments of microstructures of teeth such as enamel, dentine, pulp, PDL and alvedar bones. The Weibull function is introduced to represent the heterogeneity of teeth, which can realize the random distribution characteristics of dental mechanical parameters. The simulation results of homogeneous and heterogeneous teeth show that the failure mode changes from tensile splitting (homogeneous) to shear failure (heterogeneous). Meanwhile, the fracture networks become more complex, and the failure stress decreases sharply. The cuspal angles also have a great impact on the teeth fracture characteristics. The failure modes changes from tensile splitting of the enamel tip to the cracking from the contact points between the enamel and the rigid ball; Different fssural morphologies have little influences on the teeth failure characteristics. The research results can provide some references for the applications of SPH method into biomechanical simulations such as teeth failure. Meanwhile, it can also provide some guidance for the understandings of the internal mechanisms of teeth fracture processes, the diagnosis and treatments of clinical diseased teeth as well as the design of bionic teeth materials.

Gear fault detection using noise analysis and machine learning algorithm with YAMNet pretrained network

Gears are an essential machine element in every machinery. Faults in gears must be detected promptly to reduce downtime and avoid the sudden failure of the machine. Intelligent fault diagnosis techniques are gaining impetus due to Industry 4.0. This work proposes to use the YAMNet network for fault detection of gear pairs using transfer learning. YAMNet is a pre-trained network trained on audio data for sound event detection. The knowledge of the pretrained network is transferred to the fault diagnosis model. Research in this area suggests that noise and vibration data in the time-frequency domain is used to train pre-trained networks for fault detection. However, the research on applying pre-trained audio networks is minimal. An experimental setup is fabricated with two identical gear pair sub-assemblies, one in healthy condition and another with one gear tooth failure condition. Noise data is collected and preprocessed to extract Mel Spectrogram and is given at the input size requirement of the YAMNet pretrained network. The final connected layer is replaced, and hyperparameters are fine-tuned to improve accuracy. The final prediction accuracy is 95% for the random test dataset.

Mechanical Analysis and Structural Optimization of Air Hammer Drill Teeth Based on ANSYS /LS_DYNA

Air drilling is a prevailing technology of oil and gas energy industry in today’s world, it can solve problems when drilling in complex layer that can not be done by conventional drilling way. At the same time, some failures of dill bit teeth in air hammer drilling like teeth falling, breaking and severe abrasion seriously affect the drilling efficiency. Thus this paper intended to investigate rock breaking criteria and damage constitutive model, establish a finite element simulation model of single tooth rock breaking and use the impact of dynamic finite element software ANSYS/LS-DYNA to analysis characteristics of rock crushing under confining pressure, which includes fragmentation process, drilling tooth impact and the crush volume of rock broken. The study found that the tapered tooth has the highest efficiency in rock breaking under the same conditions and with edge teeth at 25°angle that increases the rock crushing volume significantly. In addition, the configuration of tooth surface was examined, which showed that the pattern of “spherical teeth in the middle and tapered teeth in the peripheral” has highest rock breaking efficiency.

Mechanical Analysis and Structural Optimization of Air Hammer Drill Teeth Based on ANSYS /LS_DYNA

Air drilling is a prevailing technology of oil and gas energy industry in today’s world, it can solve problems when drilling in complex layer that can not be done by conventional drilling way. At the same time, some failures of dill bit teeth in air hammer drilling like teeth falling, breaking and severe abrasion seriously affect the drilling efficiency. Thus this paper intended to investigate rock breaking criteria and damage constitutive model, establish a finite element simulation model of single tooth rock breaking and use the impact of dynamic finite element software ANSYS/LS-DYNA to analysis characteristics of rock crushing under confining pressure, which includes fragmentation process, drilling tooth impact and the crush volume of rock broken. The study found that the tapered tooth has the highest efficiency in rock breaking under the same conditions and with edge teeth at 25°angle that increases the rock crushing volume significantly. In addition, the configuration of tooth surface was examined, which showed that the pattern of “spherical teeth in the middle and tapered teeth in the peripheral” has highest rock breaking efficiency.

Risk Factor Assessment for Survival of Removable Partial Dentures and Their Abutment Teeth: A Retrospective Analysis.

To investigate the risk factors related to failure of removable partial dentures (RPDs) and to compare the survival of RPDs when abutment teeth have good vs reduced bone support. In this longitudinal patient record-based cohort study with a mean follow-up of 44.9 months, Cox regression models were used to evaluate the associations between clinical covariates and abutment tooth failure, as well as prosthesis failure. A total of 142 patients and 172 RPDs were included. Of the 172 prostheses, 64 (nearly 40%) failed after a mean time of about 4 years. Loss of abutment teeth was the main reason leading to RPD failure, followed closely by poor fit and adaptation. No factor was shown to be statistically significant at the prosthesis level. Women (Hazard Ratio [HR] = 0.542), endodontic treatment (HR = 3.460), presence of post and core (HR = 0.302), presence of a prosthetic crown (HR = 3.403), and abutment tooth type (in relation to incisor: canine HR = 0.196, premolar HR = 0.449) were the risk factors statistically significantly associated with the loss of abutment teeth. The pre-prosthesis amount of bone support of the teeth did not affect their prognosis as abutments for RPDs. RPD treatment modality presented a high failure rate after a mean follow-up of 4 years. Vital abutment teeth had a better survival rate than the ones treated endodontically (whether restored with or without a post and core); nevertheless, the amount of bone support did not affect their survival.

CAUSAL ANALYSIS AND SOLUTION OF THE FAILURE OF SPROCKET DRIVERS IN A CLINKER SCRAPER CONVEYOR

This study discusses the causal analysis and solution of the teeth failure in sprocket drivers in a clinker scraper conveyor of a cement plant. The failure consisted of the progressive surfacing shape loss of the teeth, progressively deteriorated to the operating conditions of the system, causing dynamic loads, which affected the mechanical transmission and the conveyor general performance. The assessment includes an analysis of the sprocket material and calculations of the stress fields in the teeth surface. The results show the failure is the result of using a sprocket material with high-abrasive resistance, but with yield strength lower than required for operating conditions. This failure can be addressed by replacing the entire sprocket that results in significant downtime and economic losses. The main contribution of this study is developing a solution based on the local quality principle to repair and prevent the failure without removing the sprocket. Furthermore, the analysis considers the surface forces resulting from the high friction coefficient caused by the lack of lubrication, resulting in stress values higher than the fluence limit of the teeth material. Therefore, the solution proposed is manufacturing the teeth with a different material with higher strength and abrasion resistance to prevent failures by deformation. The proposed solution takes advantage of the damaged sprocket wheels available in the plant. The teeth manufactured are welded in a plate that is later bolted to the sprocket wheel, which was previously machined to remove the damaged teeth and prepare the surface to assemble the new teeth.

Reduction of tooth wear on asymmetric spur gear through profile correction factors

ABSTRACT Surface tooth wear is one of the major causes of tooth failures in gear drives. Boosting tooth wear resistance is a significant research objective for designing high-quality asymmetric spur gears with longer life against wear. The main goal of the present work is to boost the wear resistance of the asymmetric spur gear by changing the tooth shape through profile modification. The proper distribution of correction factor to the pinion and gear is necessary to enhance the gear performance. The asymmetric spur gear with different values of sum of profile correction factors (−0.2, 0 and 0.2) is chosen to evaluate the wear depth. This sum of correction factors is accurately distributed between the asymmetric pinion and gear for attaining balanced sliding velocity at the tip and root, balanced slide to roll ratio at the tip and root, equal bending strength in the asymmetric drive and maximum balanced wear in the face and flank regions of the pinion. The optimum values of the correction factor of the asymmetric pinion and the maximum tooth wear are evaluated for the above four different balanced cases. The calculated tooth wear is lower in the balanced wear method than that in other balanced methods.

In vitro attrition wear resistance of four types of paste-like bulk-fill composite resins

BackgroundRecently, the application of bulk-fill composite resins has increased significantly. Attrition wear and the consequently increased surface roughness of composite resins are among the causes of restoration failure in the posterior teeth. This study aimed to compare the attrition wear and surface roughness of four types of bulk-fill composite resins compared to a conventional composite resin.MethodsEverX-Posterior, X-tra fil, SonicFill 2, and Filtek Bulk-Fill composites (bulk-fill) and Z250 composite (conventional resin composite) were evaluated. Thirty cylindrical specimens (n = 6) were weighed and monitored for 24 h until their weight was stabilized. The primary surface roughness of the specimens was measured by a profilometer. The specimens were then subjected to attrition wear in a chewing simulator. Next, the specimens were weighed, and the surface roughness was measured again. Data were analyzed by one-way ANOVA and Tukey’s post-hoc test at P < 0.05 significance level.ResultsAccording to one-way ANOVA, the difference in weight loss was significant among the groups (P = 0.004) but the difference in surface roughness of the groups was not significant after the attrition wear (P > 0.05). Tukey’s post-hoc test showed that the weight loss of bulk-fill composites was not significantly different from that of Z250 conventional composite after the attrition wear (P > 0.05).ConclusionWithin the limitations of this study, it appears that the tested bulk-fill composite resins are comparable to the conventional composite regarding their attrition wear, increased surface roughness, and weight loss.

Ontogeny of the elemental composition and the biomechanics of radular teeth in the chiton Lepidochitona cinerea

BackgroundThe radula, a chitinous membrane with embedded teeth, is one important molluscan autapomorphy. In some taxa (Polyplacophora and Patellogastropoda) one tooth type (the dominant lateral tooth) was studied intensively in the last decades with regard to its mechanical properties, chemical and structural composition, and the relationship between these parameters. As the dominant lateral tooth is probably one of the best studied biological materials, it is surprising, that data on elements and mechanical properties of the other tooth types, present on a chiton radula, is lacking.ResultsWe provide data on the elemental distribution and mechanical properties (hardness and elasticity, i.e. Young’s modulus) of all teeth from the Polyplacophora Lepidochitona cinerea (Linnaeus, 1767) [Chitonidae: Ischnochitonidae]. The ontogeny of elements, studied by energy-dispersive X-ray spectroscopy, and of the mechanical properties, determined by nanoindentation, was analysed in every individual tooth type. Additionally, we performed breaking stress experiments with teeth under dry and wet condition, highlighting the high influence of the water content on the mechanical behaviour of the radula. We thereby could determine the forces and stresses, teeth can resist, which were previously not studied in representatives of Polyplacophora. Overall, we were able to relate the mineral (iron, calcium) content with the mechanical parameters (hardness and Young’s modulus) and the breaking force and stress in every tooth type. This led to a better understanding of the relationship between structure, material, and function in radular teeth. Further, we aimed at determining the role of calcium for the mechanical behaviour of the teeth: we decalcified radulae by ethylene diamine tetra acetic acid and performed afterwards elemental analyses, breaking stress experiments, and nanoindentation. Among other things, we detected that wet and decalcified radular teeth could resist highest forces, since teeth have a higher range of bending motion leading to a higher capability of teeth to gain mechanical support from the adjacent tooth row. This indicates, that the tooth material is the result of a compromise between failure reduction and the ability to transfer forces onto the ingesta.ConclusionWe present novel data on the elemental composition, mechanical properties, and the mechanical behaviour of chiton teeth, which allows conclusions about tooth function. We could also relate the parameters mentioned, which contributes to our understanding on the origins of mechanical property gradients and the processes reducing structural failure in radular teeth. Additionally, we add more evidence, that the elemental composition of radular is probably species-specific and could be used as taxonomic character.

Robust multi-objective optimization of gear microgeometry design

Gear microgeometry is important as it can change the tooth flank contact pattern effectively. In gear design, it is important to minimize the peak-peak transmission error (PPTE) for lower Noise, Vibration and Harshness (NVH), and to minimize the generated stresses for higher durability that can help to avoid tooth failure. In the current article, a structured approach is developed that combines the advantages of applying meta-models and robust optimization. For the Design of Experiments (DOE), the LDP software tool was used to obtain the objective functions of PPTE, contact stress, and root stresses at all design points. Probability distribution and worst-case scenario measures were applied to weigh the objective functions and make them robust against torque. The generated data were used in MATLAB to build meta-models for each objective function using squared exponential Gaussian regression. The generated meta-models were then used in a multi-objective optimization algorithm to obtain a Pareto set of solutions. These solutions were examined and ranked from the highest to the lowest, based on the weights of the PPTE and stress safety factors. Using Rank 1 design, the gains of -25, -7, +3 and -5% for the PPTE, contact stress, gear 1 root stress and gear 2 root stress respectively were obtained. However, these gains can be different in other design cases because these gains were calculated using Rank 1 design as compared to the manually selected benchmarked design which mainly depends on the engineer's experience. The developed approach can save time and help to obtain a unique optimal design solution in a structured format.

Editorial: Save the Tooth or Place an Implant: A Routine Dental Decision

Richard Herman, DDS: Single-tooth replacement is frequently considered in most dental practices. Thoughtful diagnostic treatment planning is required when evaluating endodontic vs implant treatment in order to ensure comfort, esthetics, and longevity for the patient. The American Association of Endodontists position statement on implants states that, apart from survival rates, components such as the restorability of the tooth, quality of bone, esthetic demands, cost-benefit ratio, and systemic factors should be taken into account when deciding whether to treat the tooth endodontically or to place a single implant.¹ One study evaluated the 10-year success rate of 1,175 endodontically treated teeth, and the life table analysis reported that 93% of the teeth survived 10 years after endodontic treatment.² Further, it was shown that the ability to locate second mesiobuccal canals increased from 53% to 93% when evaluated under a surgical operating microscope.^3–7 Technologic and technical advances in endodontics continue to enhance a dental treatment regime that has been universally accepted. These advances include the surgical operating microscope, mechanical titanium instrumentation, hydrodynamic irrigation, mineral trioxide aggregate, bioceramics, CBCT, and microsurgical instrumentation. It must be stated that dental implants are an extraordinary service and have made possible some treatment options that were never before imagined. The science of osseointegrated implants has advanced considerably with the development of new implant designs, surface characteristics, materials, and methods. High success rates have helped make single-tooth implants a viable and accepted option for tooth replacement. However, a healthy, natural dentition is still the best alternative requested by patients. Assessing whether to rehabilitate a tooth requiring endodontic treatment or to replace it with an implant involves a challenging and complex decision-making process,⁷ and all treatment decisions must be evidence-based. When comparable criteria are applied to the outcome, survival rates of endodontically treated teeth and single-tooth implants are similar. A compromised tooth should be managed with a multidisciplinary approach (endodontics, periodontics, and prosthetics), and implants should be reserved for the patient with true end-stage tooth failure. Endodontics, periodontics, and implantology should complement each other, not compete. The overall goal is the long-term health of the patient, using the least invasive treatment method possible, and incorporating function, comfort, and esthetics. Richard Herman, DDS Boca Raton, Florida, USA