Temperature rise in cavities prepared by high and low torque handpieces and Er:YAG laser

Heat generated during dental treatments affecting intrapulpal temperature: a review

INTRODUCTION

Heat is generated and transferred to the dentine-pulp complex during various dental procedures, such as from friction during cavity preparations, exothermic reactions during the polymerisation of restorative materials and when polishing restorations. For in vitro studies, detrimental effects are possible when intra-pulpal temperature increases by more than 5.5°C (that is, the intra-pulpal temperature exceeds 42.4°C). This excessive heat transfer results in inflammation and necrosis of the pulp. Despite numerous studies stating the importance of heat transfer and control during dental procedures, there are limited studies that have quantified the significance. Past studies incorporated an experimental setup where a thermocouple is placed inside the pulp of an extracted human tooth and connected to an electronic digital thermometer.

METHODS

This review identified the opportunity for future research and develop both the understanding of various influencing factors on heat generation and the different sensor systems to measure the intrapulpal temperature.

CONCLUSION

Various steps of dental restorative procedures have the potential to generate considerable amounts of heat which can permanently damage the pulp, leading to pulp necrosis, discoloration of the tooth and eventually tooth loss. Thus, measures should be undertaken to limit pulp irritation and injury during procedures. This review highlighted the gap for future research and a need for an experimental setup which can simulate pulp blood flow, temperature, intraoral temperature and intraoral humidity to accurately simulate the intraoral conditions and record temperature changes during various dental procedures.

The impact of Er:YAG laser combined with fluoride treatment on the supragingival plaque microbiome in children with multiple caries: a dynamic study

BACKGROUND

As a minimally invasive tool for caries prevention tool, the pulsed erbium:yttrium-aluminum-garnet (Er:YAG) laser is being used in a large number of studies. Microorganisms are extremely vital in the occurrence and development of dental caries. However, the impact of Er:YAG laser irradiation combined with fluoride on the dynamic microbial changes that occur in dental plaques is still uncertain. In this study, we examined the effect of an Er:YAG laser combined with fluorine on supragingival microbial composition and diversity in children with multiple caries.

METHODS

In this study, dental plaque samples (n = 48) were collected from 12 children with over 8 filled teeth. Supragingival plaques from left mandibular molars before (CB) and after fluoride treatment (CA) and right mandibular molars before (EB) and after fluoride+Er:YAG laser treatment (EA) were collected from each patient. In CB and EB groups, the samples were collected just before the treatments. In CA and EA groups, the samples were collected 1 month after treatments. Then, all specimens were subjected to 16S rRNA high-throughput sequencing to investigate the changes in microbial composition and diversity in mandibular molar supragingival plaques before and after fluoride or fluoride+Er:YAG laser treatment.

RESULTS

The dental plaque microbial diversity was higher in the EA group than in the EB group (baseline levels), and the microbial composition changed in EA group compared with EB group (P < 0.05). The levels of microorganisms associated with caries occurrence, including Proteobacteria, Fusobacteria, and Bacteroidetes, declined, while the levels of Faecacterium, Fastidiosipila, Vibrio, and Shewanella increased in EA group compared with EB group. The declines in Firmicutes, Streptococcus, Fusobacterium, and Veillonella levels were significantly lower in the EA group than in the CA group.

CONCLUSION

The combined application of the Er:YAG laser and fluoride may be more effective than using fluoride alone in reducing the proportion of cariogenic bacteria, increasing the diversity of plaque microorganisms, and further promoting the microecological balance.

Effect of cooling water temperature on the temperature changes in pulp chamber and at handpiece head during high-speed tooth preparation

Objectives

It was the aim of this study to evaluate the effect of cooling water temperature on the temperature changes in the pulp chamber and at the handpiece head during high-speed tooth preparation using an electric handpiece.

Materials and Methods

Twenty-eight intact human molars received a standardized occlusal preparation for 60 seconds using a diamond bur in an electric handpiece, and one of four treatments were applied that varied in the temperature of cooling water applied (control, with no cooling water, 10°C, 23°C, and 35°C). The temperature changes in the pulp chamber and at the handpiece head were recorded using K-type thermocouples connected to a digital thermometer.

Results

The average temperature changes within the pulp chamber and at the handpiece head during preparation increased substantially when no cooling water was applied (6.8°C and 11.0°C, respectively), but decreased significantly when cooling water was added. The most substantial drop in temperature occurred with 10°C water (−16.3°C and −10.2ºC), but reductions were also seen at 23°C (−8.6°C and −4.9°C). With 35°C cooling water, temperatures increased slightly, but still remained lower than the no cooling water group (1.6°C and 6.7ºC).

Conclusions

The temperature changes in the pulp chamber and at the handpiece head were above harmful thresholds when tooth preparation was performed without cooling water. However, cooling water of all temperatures prevented harmful critical temperature changes even though water at 35°C raised temperatures slightly above baseline.

Effect of different dry-polishing regimens on the intrapulpal temperature assessed with pulpal blood microcirculation model

OBJECTIVE

The aim of the study was to evaluate the effect of different dry-polishing regimens on the intrapulpal temperature assessed using a pulpal blood microcirculation model.

MATERIALS AND METHODS

Eighty extracted human mandibular premolar teeth were used. Standardized class V cavity preparations were performed and were then restored. Teeth were divided into four main groups (n = 20): Fine polishing disc (SSF; 3M Sof-Lex, 3M ESPE, Minnesota); Super-fine polishing disc (SSS; 3M Sof-Lex); Spiral finishing wheel (SSW; 3M Sof-Lex); Enhance PoGo-One step diamond micro-polisher cup (EPO; Dentsply Sirona, Inc, Delaware). The main groups were divided: the low-load pressure (0.4N) and the high-load pressure (0.8N). The average change in intrachamber temperatures (Δt), from initial to highest, were measured.

RESULTS

The highest temperature increase was recorded in SSF08 (9.55°C). The lowest value was recorded in EPO04 (1.9°C). SSS08, SSW08, and EPO08 demonstrated significantly higher Δt values than the low-load mode in SSS04, SSW04, and EPO04, respectively (P < .0001).

CONCLUSIONS

Temperature was the least affected by the diamond cup in both pressure modes, and it was also less affected by the spiral finishing wheel in the low-load mode than in the high-load mode. Fine and super-fine discs had the greatest effect on intrachamber temperatures.

CLINICAL SIGNIFICANCE

The present study suggests intrachamber temperature can rise among different dry-polishing regimes. Dental practitioners should pay attention to dry-polishing regimens and pressures for reducing heat-related dental problems.

Influence of the material for preformed moulds on the polymerization temperature of resin materials for temporary FPDs

PURPOSE

Temperature increase of 5.5 ℃ can cause damage or necrosis of the pulp. Increasing temperature can be caused not only by mechanical factors, e.g. grinding, but also by exothermic polymerization reactions of resin materials. The aim of this study was to evaluate influences of the form material on the intrapulpal temperature during the polymerization of different self-curing resin materials for temporary restorations.

MATERIALS AND METHODS

30 provisonal bridges were made of 5 resin materials: Prevision Temp (Pre), Protemp 4 (Pro), Luxatemp Star (Lux), Structure 3 (Str) and an experimental material (Exp). Moulds made of alginate (A) and of silicone (S) and vacuum formed moulds (V) were used to build 10 bridges each on a special experimental setup. The intrapulpal temperatures of three abutment teeth (a canine, a premolar, and a molar,) were measured during the polymerization every second under isothermal conditions. Comparisons of the maximum temperature (T_Max) and the time until the maximum temperature (t_TMax) were performed using ANOVA and Tukey Test.

RESULTS

Using alginate as the mould material resulted in a cooling effect for every resin material. Using the vacuum formed mould, T_Max increased significantly compared to alginate (P<.001) and silicone (P<.001). In groups Lux, Pro, and Pre, t_TMax increased when the vacuum formed moulds were used. In groups Exp and Str, there was no influence of the mould material on t_TMax.

CONCLUSION

All of the mould materials are suitable for clinical use if the intraoral application time does not exceed the manufacturer's instructions for the resin materials.

Thermal effects and morphological aspects of varying Er:YAG laser energy on demineralized dentin removal: an in vitro study

The aim of this study was to evaluate thermal changes, dentin ablation removal capacity, and morphological aspects of sound and demineralized human dentin surface irradiated with different output energies of an erbium: yttrium-aluminium-garnet (Er:YAG) laser. Eighty sound human tooth specimens were assigned into two groups: demineralized dentin and sound dentin (control group). The dentin groups were subdivided into four subgroups (n = 10) according to the irradiation energy used (120, 160, 200, or 250 mJ) at a constant frequency level of 6 Hz, in focused mode, and under refrigeration. Quantitative analysis of the sound and carious dentin ablation was performed using light microscopy (LM) by measuring (mm) the remaining demineralized tissue with the Axion Vision™ software. Qualitative analysis was performed using the images obtained with a scanning electron microscope (SEM), and the temperature increase was recorded with an infrared digital thermometer. The Er:YAG laser promoted a gradual increase in temperature for all groups, and no difference was observed between the sound and demineralized dentin. The groups of 200 and 250 mJ showed the highest values, yet a variation in temperature did not exceed 5 °C. The energy output of 120 mJ selectively removed demineralized tissue when compared to 250 mJ, while also providing more regular surfaces in the cavity preparation. It was concluded that the temperature increase during sound and demineralized dentin removal had a strong positive correlation with the Er:YAG laser energy level output. However, the higher energies used did not present selectivity to the demineralized tissue, and the parameters used did not cause an increase in temperature over 5 °C.

Cytotoxicity evaluation of dentin contacting materials with dentin barrier test device using erbium-doped yttrium, aluminum, and garnet laser-treated dentin

Objectives:

The effect of dentin contacting materials on three-dimensional cultures of pulp-derived cells was evaluated in a dentin barrier test device using erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser-treated dentin.

Methods:

The test materials (iBond®, G-Bond™, and Vitrebond™) were applied on laser-treated or untreated dentin discs. After 24 h of exposure with perfusion of the test chamber, cell survival was evaluated by enzyme activity and related to a nontoxic control material. The mean values of control tissues were set to represent 100% viability. Data were analyzed using Kruskal–Wallis and Mann–Whitney U test.

Results:

Vitrebond was the most toxic material for both laser-treated and untreated dentin. On untreated dentin, G-bond was cytotoxic to the pulp-derived cells ( p < 0.05), and iBond was similar to the negative control group ( p > 0.05). However, G-Bond and iBond were not cytotoxic when they were applied to Er:YAG laser-treated dentin ( p > 0.05).

Conclusion:

Er:YAG laser treatment of dentin may protect the pulp cells from toxic substances of dentin contacting restorative materials; however, this effect is material related. Taking into consideration the limitations of this in vitro study, the Er:YAG laser treatment of dentin before restoration might be an option for decreasing the cytotoxic effects of the dental materials. Further research is required for clinical applications.

Thermal irritation of teeth during dental treatment procedures

While it is reasonably well known that certain dental procedures increase the temperature of the tooth's surface, of greater interest is their potential damaging effect on the pulp and tooth-supporting tissues. Previous studies have investigated the responses of the pulp, periodontal ligament, and alveolar bone to thermal irritation and the temperature at which thermal damage is initiated. There are also many in vitro studies that have measured the temperature increase of the pulp and tooth-supporting tissues during restorative and endodontic procedures. This review article provides an overview of studies measuring temperature increases in tooth structures during several restorative and endodontic procedures, and proposes clinical guidelines for reducing potential thermal hazards to the pulp and supporting tissues.

Thermal effects and morphological aspects of human dentin surface irradiated with different frequencies of Er:YAG laser

This study reports the effects on micromorphology and temperature rise in human dentin using different frequencies of Er:YAG laser. Sixty human dentin fragments were randomly assigned into two groups (n = 30): carious or sound dentin. Both groups were divided into three subgroups (n = 10), according to the Er:YAG laser frequency used: 4, 6, or 10 Hz (energy: 200 mJ; irradiation distance: 12 mm; and irradiation time: 20 s). A thermocouple adapted to the tooth fragment recorded the initial temperature value (°C); then, the temperature was measured after the end of the irradiation (20 s). Morphological analysis was performed using images obtained with scanning electron microscope. There was no difference between the temperatures obtained with 4 and 6 Hz; the highest temperatures were achieved with 10 Hz. No difference was observed between carious and sound dentin. Morphological analyses revealed that all frequencies promoted irregular surface in sound dentin, being observed more selectively ablation especially in intertubular dentin with tubule protrusion. The caries dentin presented flat surface for all frequencies used. Both substrates revealed absence of any signs of thermal damage. It may be concluded that the parameters used in this study are capable to remove caries lesion, having acceptable limits of temperature rise and no significant morphological alterations on dentin surface.

Influence of various polishing methods on pulp temperature : an in vitro study

OBJECTIVE

After orthodontic debonding, adhesive removal can lead to rises in pulp temperature, causing histological changes or pulp necrosis. The objective of this study was to measure increases in pulp temperature during adhesive removal using different instruments and various cooling procedures.

MATERIALS AND METHODS

A thermoelement was introduced into the pulp chamber of 10 human incisors. The teeth were immersed in a 36°C water bath up to the cementoenamel junction. Two carbide burs, one polishing disk and two rubber points were used for polishing. All measurements were taken over a 10 s period by a single investigator, under slight pressure and with constant motion. Three cooling procedures were examined: no cooling, air cooling and water cooling. Pulp temperatures were measured before polishing and after 10 s of polishing.

RESULTS

Without cooling, the two rubber points revealed clinically relevant temperature increases of 6.1°C and 12.4°C. Cooling with air and with water reduced pulp temperature in conjunction with all polishing methods. Air cooling was most efficient, except in combination with the polishing disk.

CONCLUSION

Under these study conditions, carbide burs and polishing disks can be used safely and without risk to the pulp, even without cooling. On the other hand, rubber points cause a marked increase in pulp temperature when used without cooling.