Thermal analysis of the intact mandibular premolar: a finite element analysis

Thermal Load and Heat Transfer in Dental Titanium Implants: An Ex Vivo-Based Exact Analytical/Numerical Solution to the ‘Heat Equation’

Introduction: Heat is a kinetic process whereby energy flows from between two systems, hot-to-cold objects. In oro-dental implantology, conductive heat transfer/(or thermal stress) is a complex physical phenomenon to analyze and consider in treatment planning. Hence, ample research has attempted to measure heat-production to avoid over-heating during bone-cutting and drilling for titanium (Ti) implant-site preparation and insertion, thereby preventing/minimizing early (as well as delayed) implant-related complications and failure. Objective: Given the low bone–thermal conductivity whereby heat generated by osteotomies is not effectively dissipated and tends to remain within the surrounding tissue (peri-implant), increasing the possibility of thermal-injury, this work attempts to obtain an exact analytical solution of the heat equation under exponential thermal-stress, modeling transient heat transfer and temperature changes in Ti implants (fixtures) upon hot-liquid oral intake. Materials and Methods: We, via an ex vivo-based model, investigated the impact of the (a) material, (b) location point along implant length, and (c) exposure time of the thermal load on localized temperature changes. Results: Despite its simplicity, the presented solution contains all the physics and reproduces the key features obtained in previous numerical analyses studies. To the best of our knowledge, this is the first introduction of the intrinsic time, a “proper” time that characterizes the geometry of the dental implant fixture, where we show, mathematically and graphically, how the interplay between “proper” time and exposure time influences temperature changes in Ti implants, under the suitable initial and boundary conditions. This fills the current gap in the literature by obtaining a simplified yet exact analytical solution, assuming an exponential thermal load model relevant to cold/hot beverage or food intake. Conclusions: This work aspires to accurately complement the overall clinical diagnostic and treatment plan for enhanced bone–implant interface, implant stability, and success rates, whether for immediate or delayed loading strategies.

Mechanical and thermal stress evaluation of PEEK prefabricated post with different head design in endodontically treated tooth: 3D-finite element analysis

An endodontic post is required to retain and support the core restoration in case of insufficient remaining coronal dentin after root canal therapy. This study analyzed the biomechanical and thermal behavior of PEEK prefabricated post after choosing the head design that produces the least amount of stress on the core and remaining tooth structure. These results were compared with the most common commercially available prefabricated post, which is titanium and glass fiber post. Thus a CBCT scanning of a maxillary central incisor with its supporting structure was used to construct a 3D solid model of an endodontically treated teeth for finite element analysis (FEA). The restored tooth with the spherical head design of PEEK prefabricated post yielded a more benign stress distribution and repairable failure mode on the crown, luting cement, core, and dentin under both mechanical and thermal loads, followed by glass fiber post and titanium post respectively.

DOES PEEK DENTAL IMPLANT HAVE THERMAL ADVANTAGE OVER ZIRCONIA OR TITANIUM IMPLANTS?

Purpose: To evaluate the thermal performance of PEEK dental implant and compare it with its conventional counterparts, i.e., titanium (Ti) and zirconia ([Formula: see text]). Materials and Methods: A three-dimensional finite element model of the dental implant and the surrounding bone was developed to simulate thermal analysis of the implant with three different materials, i.e., Ti, ZrO2 and PEEK for two types of heat load. Zirconia artificial crown was utilized in all three different implant materials. Results: In loading type I, the maximum temperature of the mandible bone at the cervical implant/bone interface was almost the same (37.7∘C) in all models, but the time to reach this temperature was 18[Formula: see text]s for Ti, 30[Formula: see text]s for ZrO2 and 65.7[Formula: see text]s for PEEK implant. The maximum temperature in loading type II was 41.8∘C, 41.6∘C and 41.3∘C, respectively, in ZrO2, Ti and PEEK models. Ti implant showed the fastest rising and recovery time. Conclusions: Under the considered heat loads, the maximum temperatures in the bone were below the bone necrosis temperature in all three cases. In addition the temperature change along the implant body in [Formula: see text] and PEEK implants are smaller than that in Ti. Moreover, PEEK was found to be a thermally viable option for dental implants.

Effects of heat conduction of implant surface at thermal stimulation on implant placement

The purpose of this study is to investigate, in vitro, how two different implant placement methods (one and two-stage implant placement) affect implant surface temperature after thermal stimulation. Two titanium screw implants were used and three thermocouples were attached to the implant surface at 0.5 mm (ch1), 5.5 mm (ch2) and 9.0 mm (ch3) under each platform. Experimental devices were fabricated pouring polymerization resin under a condition that imitated the two embedded technique with the one-stage implant placement model (1-stage) and the two-stage implant placement model (2-stage). A hot water storage device was installed in each model and hot water at three temperatures (60 °C, 70 °C and 100 °C) was flowed. The temperature change over time at the implant surface by the thermocouple was recorded. From the measurement data, the maximum temperature (Max-temp) at the implant surface, the time to reach 47 °C (47 °C r-time), and the duration of 47 °C or more (47 °C c-time) were calculated, and the test was repeated 26 times using the same method. The mean of repeated measurements was determined and statistical analysis was performed. Max-temp showed significant differences between each implant placement method, each channel and each thermal stimulation (p < 0.01). In this study suggested that the implant surface could reach 47 °C with 60 °C thermal stimulation in a 1-stage. In addition, it rose over 47 °C at 70 °C. The 2-stage implant surface did not rise to 47 °C.

Thermal analysis of the dentine tubule under hot and cold stimuli using fluid-structure interaction simulation

The objective of this study is to compare the thermal stress changes in the tooth microstructures and the hydrodynamic changes of the dental fluid under hot and cold stimuli. The dimension of the microstructures of eleven cats' teeth was measured by scanning electron microscopy, and the changes in thermal stress during cold and hot stimulation were calculated by 3D fluid-structure interaction modeling. Evaluation of results, following data validation, indicated that the maximum velocities in cold and hot stimuli were - 410.2 ± 17.6 and + 205.1 ± 8.7 µm/s, respectively. The corresponding data for maximum thermal stress were - 20.27 ± 0.79 and + 10.13 ± 0.24 cmHg, respectively. The thermal stress caused by cold stimulus could influence almost 2.9 times faster than that caused by hot stimulus, and the durability of the thermal stress caused by hot stimulus was 71% greater than that by cold stimulus under similar conditions. The maximum stress was on the tip of the odontoblast, while the stress in lateral walls of the odontoblast and terminal fibril was very weak. There is hence a higher possibility of pain transmission with activation of stress-sensitive ion channels at the tip of the odontoblast. The maximum thermal stress resulted from the cold stimulus is double that produced by the hot stimulus. There is a higher possibility of pain transmission in the lateral walls of the odontoblast and terminal fibril by releasing mediators during the cold stimulation than the hot stimulation. These two reasons can be associated with a greater pain sensation due to intake of cold liquids.

Finite element investigation of human maxillary incisor under traumatic loading: Static vs dynamic analysis

BACKGROUND AND OBJECTIVE

Traumatic loading is the main form of injury sustained in dental injuries. In spite of the prevalence of dental trauma, little information is available on traumatic dental damage and the evaluation of tooth behavior under traumatic loading. Due to the short period of traumatic loading, at first sight, a dynamic analysis needs to be performed to investigate the dental trauma. However, it was hypothesized that dental traumatic loading could be regarded as quasi-static loading. Thus, the aim of the present study was to examine this hypothesis.

METHODS

Static and dynamic analyses of the human maxillary incisor were carried out under traumatic loading using a 3D finite element method. Also, modal analysis of the tooth model was performed in order to evaluate the assumption of the dental traumatic loading as a quasi-static one.

RESULTS

It was revealed that the static analysis of dental trauma is preferred to the dynamic analysis when investigating dental trauma, mainly due to its lower computational cost. In fact, it was shown that including the inertia of the tooth structure does not influence the results of the dental trauma simulation. Furthermore, according to the modal analysis of the tooth structure, it was found that the mechanical properties and geometry of the periodontal ligament play significant roles in the classification of dental traumatic loading as a quasi-static one, in addition to the time duration of the applied load.

CONCLUSIONS

This paper provides important biomechanical insights into the classification of dental loading as quasi-static, transient or impact loading in future dental studies.

Thermal-stress analysis of ceramic laminate veneer restorations with different incisal preparations using micro-computed tomography-based 3D finite element models

Main objective of this study is to investigate the thermal behavior of ceramic laminate veneer restorations of the maxillary central incisor with different incisal preparations such as butt joint and palatinal chamfer using finite element method. In addition, it is also aimed to understand the effect of different thermal loads which simulates hot and cold liquid imbibing in the mouth. Three-dimensional solid models of the sound tooth and prepared veneer restorations were obtained using micro-computed tomography images. Each ceramic veneer restoration was made up of ceramic, luting resin cement and adhesive layer which were generated based on the scanned images using computer-aided design software. Our solid model also included the remaining dental tissues such as periodontal ligament and surrounding cortical and spongy bones. Time-dependent linear thermal analyses were carried out to compare temperature changes and stress distributions of the sound and restored tooth models. The liquid is firstly in contact with the crown area where the maximum stresses were obtained. For the restorations, stresses on palatinal surfaces were found larger than buccal surfaces. Through interior tissues, the effect of thermal load diminished and smaller stress distributions were obtained near pulp and root-dentin regions. We found that the palatinal chamfer restoration presents comparatively larger stresses than the butt joint preparation. In addition, cold thermal loading showed larger temperature changes and stress distributions than those of hot thermal loading independent from the restoration technique.

Heat Transfer Behavior across the Dentino-Enamel Junction in the Human Tooth

During eating, the teeth usually endure the sharply temperature changes because of different foods. It is of importance to investigate the heat transfer and heat dissipation behavior of the dentino-enamel junction (DEJ) of human tooth since dentine and enamel have different thermophysical properties. The spatial and temporal temperature distributions on the enamel, dentine, and pulpal chamber of both the human tooth and its discontinuous boundaries, were measured using infrared thermography using a stepped temperature increase on the outer boundary of enamel crowns. The thermal diffusivities for enamel and dentine were deduced from the time dependent temperature change at the enamel and dentine layers. The thermal conductivities for enamel and dentine were calculated to be 0.81 Wm-1K-1 and 0.48 Wm-1K-1 respectively. The observed temperature discontinuities across the interfaces between enamel, dentine and pulp-chamber layers were due to the difference of thermal conductivities at interfaces rather than to the phase transformation. The temperature gradient distributes continuously across the enamel and dentine layers and their junction below a temperature of 42°C, whilst a negative thermal resistance is observed at interfaces above 42°C. These results suggest that the microstructure of the dentin-enamel junction (DEJ) junction play an important role in tooth heat transfer and protects the pulp from heat damage.

Thermal Analysis of Dental Implants in Mandibular Premolar Region: 3D FEM Study

PURPOSE

The distribution of temperature in a dental implant following hot food and beverage consumption is essential for evaluating the hazard this process may have on bone health. The purpose of this study was to predict the temperature distribution in the dental implant with/without a crown and the bone crest in contact with it using the finite element method.

MATERIALS AND METHODS

A 3D model of the implant and the mandible was prepared by using computer-aided design software. Implants were investigated in three cases: without crown (BHI), with ceramic crown (MHIc), and with zirconia crown (MHIz). Subsequently, temperature distribution was numerically determined along the implant system for two heat loadings.

RESULTS

In loading type I, the maximum temperature of the surrounding bone at the cervical implant/bone interface was obtained in the BHI model (39.1°C), and the lowest was obtained in the MHIc model (37.6°C). The maximum temperature rise in loading type II also took place in the BHI model (41.7°C). Moreover, the BHI model showed a rapid rise to the maximum temperature followed by a fast recovery compared to its two counterparts (MHIc, MHIz). In both loading types, the maximum temperature at the first point of contact between the implant and bone, and apical implant/bone interface was slightly higher in the MHIz than that in the MHIc. The maximum temperature in all the models was higher when subjected to cyclic loading. The maximum temperatures reached in all the models were lower than threshold temperatures, so thermal loading alone does not harm the jawbone. Moreover, the BHI was more vulnerable than the MHIc and the MHIz.

CONCLUSIONS

The results of this study suggest that dental implants should be covered with crowns as soon as possible, and patients with dental implants should avoid consumption of hot food and beverages without allowing time for the heat to dissipate.

In vitro investigation of heat transfer phenomenon in human immature teeth

Background and aims. Heat generated within tooth during clinical dentistry can cause thermally induced damage to hard and soft components of the tooth (enamel, dentin and pulp). Geometrical characteristics of immature teeth are different from those of mature teeth. The purpose of this experimental and theoretical study was to investigate thermal changes in immature permanent teeth during the use of LED light-curing units (LCU). Materials and methods. This study was performed on the second mandibular premolars. This experimental investiga-tion was carried out for recording temperature variations of different sites of tooth and two dimensional finite element models were used for heat transfer phenomenon in immature teeth. Sensitivity analysis and local tests were included in the model validation phase. Results. Overall, thermal stimulation for 30 seconds with a low-intensity LED LCU increased the temperature from 28°C to 38°C in IIT (intact immature tooth) and PIT (cavity-prepared immature tooth). When a high-intensity LED LCU was used, tooth temperature increased from 28°C to 48°C. The results of the experimental tests and mathematical modeling illustrated that using LED LCU on immature teeth did not have any detrimental effect on the pulp temperature. Conclusion. Using LED LCU in immature teeth had no effect on pulp temperature in this study. Sensitivity analysis showed that variations of heat conductivity might affect heat transfer in immature teeth; therefore, further studies are required to determine thermal conductivity of immature teeth.

Effect of thermal stresses on the mechanism of tooth pain

INTRODUCTION

Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism.

METHODS

Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation.

RESULTS

Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings.

CONCLUSIONS

The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory.