Studies on dental high-speed cutting with carbide burs used on bovine dentin

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 knowledge, attitude and practice of fixed prosthodontics: A survey among Qassim dental practitioners

Aim:

The aim of this study was to evaluate the knowledge, attitude and fixed prosthodontics practice guidelines amongst dental practitioners of Qassim in Saudi Arabia.

Materials and Methods:

A descriptive cross-sectional study was done amongst the Dental Practitioners of Qassim Province, Saudi Arabia in 2018. A total of 290 dentists were selected randomly (from public and private dental clinics and dental schools). A survey was conducted through printed and online questionnaire composed of 19 open and multiple-choice questions. Data from the completed questionnaires were analysed using the SPSS Statistical Software Package (version 25). All statistical analyses were carried out at a significance level of P < 0.05. Results were analysed and compared using the Chi-square test and frequency test.

Results:

This study showed that 227 (78.3%) of the participants assessed abutment tooth radiographically, also most of them fabricated study cast before starting crown and bridge procedures 37.2% (108). The vitality test for restored abutments was always done by 132 (45.5%) respondents, and 111 (38.3%) of them used poly vinyl siloxane for making final impression, which provides the level of quality of final impression. A total of 117 (40.3%) of them always used retraction cord before making final impression. Both written prescriptions and verbal instructions were used by 209 (72.1%) of the practitioners for communication with the lab. The study revealed that there were no significant differences between males and females in answering questions 11, 13 and 17.

Conclusion:

The dental practitioners (DPs) of Qassim displayed an acceptable level of knowledge and a level of awareness of fixed prosthodontics practicing. However, to further enhance the proficiency, efforts should be made to encourage the practitioners to be aware of the advances in fixed prosthodontics practice through state-of-the-art continuous education programmes.

Clinical Significance:

As fixed prosthodontic restorative procedures are widely practiced for dental rehabilitation in Saudi Arabia, it was very important to measure and evaluate the knowledge of DPs about the details of basic steps in the field of fixed prosthodontics and the way of practicing this important branch of dentistry.

The cooling efficiency of different dental high-speed handpiece coolant port designs

The study investigated the cooling efficiency of different numbers of water coolant ports on high-speed handpieces (HSH) under cooling conditions used in clinical practice.

Twenty-four groove cuts with water on and nine cuts without water were made on extracted human premolars using three HSHs with different port configurations. Thermocouples were placed in the pulp chambers and temperature changes were recorded with 1-, 3- and 4-coolant port handpieces. Cooling rate was calculated for each coolant port design system. Temperature changes were statistically analysed with Kruskal-Willis Test.

All three sample groups resulted in a net temperature decrease during the cutting period with water turned on. There was a pattern of increased cooling rate with increasing number of coolant ports (1-port: -4.27 (±0.94) °C, 3-port: -4.66 (±2.90) °C, 4-port: -5.03 (±1.08) °C). The difference was not statistically significant (p = 0.681). Calculations of cooling rate showed a higher cooling rate with an increase in the number of ports (1-port: 46.13 × 10⁻⁴ K⁻¹, 3-port: 51.36 × 10⁻⁴ K⁻¹, 4-port: 56.32 × 10⁻⁴ K⁻¹). In the dry tooth preparation samples, all resulted in a net increase in temperature (1-port: 4.43 (±3.30) °C, 3-port: 5.13 (±3.27) °C, 4-port: 2.87 (±2.97) °C).

All the three water coolant port configurations showed effective cooling of the tooth during cutting and decreased pulpal temperature with no statistical difference. There are HSH designs with varying numbers of coolant ports available in the market for clinicians. The results of the current study could potentially aid clinicians in making a decision while choosing between different dental handpieces.

Comparação da exotermia de resinas durante a restauração provisória direta

Resumo Introdução As resinas de polimetilmetacrilato e as bisacrílicas são materiais amplamente utilizados para a confecção de restaurações provisórias; no entanto, ambas apresentam uma característica de exotermia durante a polimerização que deve ser investigada por causa de possíveis interferências no sucesso clínico. Objetivo Avaliar a variação de temperatura de polimerização da resina bisacrílica e de uma resina acrílica quimicamente ativada, em preparos classe V, pelo método direto. Material e método Para isso, vinte dentes incisivos inferiores bovinos foram divididos em dois grupos: RA (N=10) com dentes restaurados com resina acrílica e RB (N=10) com dentes restaurados com resina bisacrílica. As mensurações das variações térmicas foram realizadas através de termopares tipo J, ligados a um termômetro óptico, e analisadas por um computador equipado com o software específico. Os dados obtidos foram analisados e submetidos à análise de médias comparadas pelo teste de Tukey (significância de 5%). Resultado Foi possível observar que não houve diferença estatística significante entre ambos os grupos experimentais (p=0,0739), mesmo que aumento de temperatura de RA tenha apresentado média maior (0,52 °C) do que RB (0,44 °C). Conclusão Não existe diferença significativa experimental entre o calor emitido pela resina acrílica e pela resina bisacrílica durante seus processos de polimerização, não definindo a característica de escolha de uma destas para as restaurações provisórias diretas.

A Clinical Study on the Effect of Injection Sites on Efficacy of Anesthesia and Pulpal Blood Flow in Carious Teeth

This randomized clinical trial evaluated the efficiency of maxillary infiltration anesthesia in carious teeth at two different injection sites and their impact on the laser Doppler recordings of pulpal blood flow (PBF) during a caries excavation procedure. The null hypothesis tested was that there are no differences in the efficiency of anesthesia and PBF reduction between maxillary infiltrations at the two injection sites. One hundred twenty patients were divided into three groups according to the degree of carious lesion of their maxillary left central incisors (moderate caries, deep caries, or no caries). Forty patients in each group randomly received infiltrations over the root apex of maxillary left central incisors (site X) or over the midpoint of the line connecting the root apexes of both maxillary left central and lateral incisors (site Y) using 0.9 mL 2% lidocaine with 1:100,000 adrenaline. Teeth were pulp tested at five-minute intervals after injection except for the period of cavity cutting, which was done 12 minutes after injection. The PBF changes after injection were monitored by laser Doppler flowmetry. The observation period in this study was 60 minutes. Success of anesthesia was defined as no or mild pain on cavity cutting by visual analog scale recordings. Deep caries group showed significantly higher baseline PBF ( p<0.05). All groups showed 100% success of anesthesia and similar duration time ( p>0.05). Subgroups that had the injection at site Y showed significantly less reduction of PBF ( p<0.05). Cavity-cutting procedures increased the amplitude of the PBF around the lowest value after injection. Independent of the cavity depth, carious anterior teeth anesthetized by infiltration further from the apex had significantly less reduction on the pulpal blood flow compared with teeth anesthetized by infiltration at the apex.

AN APPROACH FOR COMPARATIVE PERFORMANCE TESTING OF SURGICAL BURS

In this paper, a numerical procedure for obtaining a cutting performance "signature" for a bur is proposed. This procedure is applied to a comparative analysis of the cutting performance of a surgical bur under various operating conditions. An experimental method, which uses a constant feed rate and measures feed force, is utilized to perform tests leading to the data needed for the aforementioned procedure. Several proof-of-concept tests are performed and their results are presented. The proposed approach shows capability for tracking the cutting performance of a bur as it gets duller.

Comparison of operative procedure variables on pulpal viability in an ex vivo model

AIM

To measure and compare the responses of pulp tissue to cavity preparation and restoration variables using a novel tooth slice culture model.

METHODOLOGY

Experimental cavities (265) were continuously cut, under carefully controlled conditions, into the dentine of the labial aspect of 28-day-old Wistar rat incisors, and slices of these teeth maintained in organ culture for up to 2 weeks. The experimental variables examined were: the preparation method, remaining dentine thickness, coolant, drill speed, conditioning with EDTA and filling materials. The reactions of the dentine-pulp complex to the experimental variables were measured using pathohistometric analysis and the correlations between variables were determined using analysis of variance statistical tests.

RESULTS

In rank order of surgically induced restorative pulpal injury, from the most to the least injurious were: remaining dentine thickness, absence of coolant during cavity preparation, bur speed, cavity conditioning treatments and the filling material.

CONCLUSIONS

To reduce pulp injury and to promote pulpal repair activity, the correct use of appropriate materials are important. However, of relatively greater importance is the operative technique adopted, the need to avoid the excess removal of dentine and to minimize trauma during preparation.

Increases in intrapulpal temperature during polymerization of composite resin

STATEMENT OF PROBLEM

The polymerization of dental composite resins can generate increases in intrapulpal temperature that may damage the pulp. The development of new polymerization devices such as the argon laser makes the assessment of these temperatures important.

PURPOSE

This study compared increases in temperature generated by argon laser and halogen light when polymerizing a bonding system and a composite resin, and also sought to determine whether both types of polymerization lights generate temperature increases below the safe limit of 5.5 degrees C.

MATERIAL AND METHODS

Thermocouples linked to a temperature reading system were positioned in the pulp chamber of 10 extracted bovine incisors. Class V cavities were prepared, etched, and filled with a 1-bottle bonding system (Single Bond) and composite resin (Z-100). The test groups were as follows (n = 5 for all groups): halogen light for bonding system (HB); halogen light for composite resin (HC); argon laser for bonding system (LB), and argon laser for composite resin (LC). The polymerization parameters were halogen light operated at 600 mW/cm2 for 40 seconds, which served as control, and argon laser operated at 200 mW for 10 seconds. Data were analyzed by a 2-way (light versus material) analysis of variance (ANOVA) (alpha = .05).

RESULTS

The average temperature increases were 2.35 degrees C (HB), 2.69 degrees C (HC), 1.25 degrees C (LB), and 1.5 degrees C (LC). Significant differences between halogen light and argon laser (P = .002), but not between composite and bonding system, were demonstrated.

CONCLUSIONS

The argon laser produced significantly lower increases in pulpal temperature than the halogen light, independent of the thickness of the polymerized material.

Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies

Every year, despite the effectiveness of preventive dentistry and dental health care, 290 million fillings are placed each year in the United States; two-thirds of these involve the replacement of failed restorations. Improvements in the success of restorative treatments may be possible if caries management strategies, selection of restorative materials, and their proper use to avoid post-operative complications were investigated from a biological perspective. Consequently, this review will examine pulp injury and healing reactions to different restorative variables. The application of tissue engineering approaches to restorative dentistry will require the transplantation, replacement, or regeneration of cells, and/or stimulation of mineralized tissue formation. This might solve major dental problems, by remineralizing caries lesions, vaccinating against caries and oral diseases, and restoring injured or replacing lost teeth. However, until these therapies can be introduced clinically, the avoidance of post-operative complications with conventional therapies requires attention to numerous aspects of treatment highlighted in this review.

The magnitude of cutting forces at high speed

STATEMENT OF THE PROBLEM

Previous research has used a range of cutting forces for preparing teeth, but there are no data available on the forces actually imposed while cutting teeth with high-speed handpieces.

PURPOSE

The purpose of this study was to measure the forces imposed while cutting teeth with tungsten carbide burs used in high-speed handpieces.

MATERIAL AND METHODS

Thirty-one dentists each cut 8 conventional class II MO and DO preparations in intact extracted third molars, by use of 2 different air turbine handpieces with different torque-speed characteristics. Two different flat fissure, plain and cross-cut tungsten carbide burs, cutting wet and dry in each handpiece/bur combination. The teeth were mounted in a custom-made transducer unit that displayed the forces imposed by the bur. Data were analysed with a 1-way ANOVA (alpha =.05) and Spearman correlation test.

RESULTS

The results showed that there was no significant difference in the applied force between plain and cross-cut burs, cutting wet or cutting dry, but there was a significant difference between the high and the lower torque handpieces. The higher torque handpiece was used at a mean cutting force of 1.44 N and the lower torque handpiece at 1.20 N (P<.002). The overall general mean force observed was 1.30 N.

CONCLUSION

It was concluded that the forces used in cutting teeth with the tungsten carbide burs tested related both to the type of the handpiece and to the forces chosen by clinical operators. There was no difference between the plain and cross-cut burs, there was no difference between the cutting wet or dry, and the higher torque handpiece required a higher mean cutting force.

High-speed cavity preparation techniques with different water flows

STATEMENT OF PROBLEM

Cavity and tooth preparations generate heat because the use of rotary cutting instruments on dental tissues creates friction. Dental pulps cannot survive temperature increases greater than 5.5 degrees C.

PURPOSE

This study evaluated the efficiency of 3 different water flows for 2 different tooth preparation techniques to determine which are safe for use.

MATERIAL AND METHODS

Thermocouples were placed in the pulpal chambers of 30 bovine teeth, and 1 of 2 tooth preparation techniques was used: a low-load intermittent tooth preparation technique or a high-load tooth preparation technique without intervals. Water flows of 0, 30, and 45 mL/min were associated with each technique, for a total of 6 different groups. The results were analyzed with a 2-factor analysis of variance (P<.05).

RESULTS

Temperature increases with the high-load technique were 16.40 degrees C without cooling (group I), 11.68 degrees C with 30 mL/min air-water spray cooling (group III), and 9.96 degrees C with 45 mL/min cooling (group V). With the low-load tooth preparation technique, a 9.54 degrees C increase resulted with no cooling (group II), a 1.56 degrees C increase with 30 mL/min air-water spray cooling (group IV), and a 0.04 degrees C decrease with 45 mL/min cooling (group VI). The low-load technique was associated with more ideal temperature changes.

CONCLUSION

The results of this study confirm the necessity of using a low-load technique and water coolants during cavity and tooth preparation procedures.

Saving pulps--a biological basis. An overview

AIM

Cavity preparation and restoration variables have an uncertain relationship to pulp injury and repair responses. The purpose of this paper is to determine the importance of cavity preparation and restoration variables, by ranking them according to their effect on pulp injury (odontoblast survival) and pulp repair (reactionary dentine secretion).

METHOD

The seven studies reviewed are all based on the protocols described by Murray, Smith and colleagues in 2000 and 2001.

RESULTS

The studies reviewed provide new perspectives on the importance of cavity preparation and restoration variables in mediating pulp activity.

CONCLUSIONS

The onset of post-operative complications may be most productively minimised by focusing practitioner attention to aspects of treatment highlighted in this review.

The effect of cavity restoration variables on odontoblast cell numbers and dental repair

OBJECTIVES

Dentinal repair following cavity restoration is dependent on several parameters including the numbers of surviving odontoblasts. The purpose of this study was to examine the effects of cavity cutting and restoration treatments on post-operative odontoblast numbers.

METHODS

353 Standardised non-exposed rectangular Class V cavities, were cut into the buccal dentin of intact 1st or 2nd premolar teeth of 165 patients, aged between nine and 25 years of age. Composite cavity restorations with various etching treatments were compared with resin-modified glass ionomer cements, enamel bonding resins, as well as polycarboxylate, calcium hydroxide, and zinc oxide eugenol materials. Following tooth extraction (20-381 days) for orthodontic reasons, the area of the reactionary dentine and the area of the odontoblasts was measured histomorphometrically.

RESULTS

Odontoblast numbers and dentine repair activity were found to be influenced more by cavity restoration variables, than the choice of cavity filling materials or patient factors. The most important cavity preparation variable was the cavity remaining dentine thickness (RDT); below 0.25mm the numbers of odontoblasts decreased by 23%, and minimal reactionary dentine repair was observed.

CONCLUSIONS

Odontoblast injury increased as the cavity RDT decreased. In rank order of maintaining odontoblast numbers beneath restored cavities with a RDT below 0.5mm, and using calcium hydroxide for comparison; calcium hydroxide (100%), polycarboxylate (82.4%), zinc oxide eugenol (81.3%), composite (75.5%), enamel bonding resin (49.5%) and RMGIC (42.8%). The vitality and dentine repair capacity of the pulp is dependent on odontoblast survival. Variations in the extent of odontoblast injury caused during operative procedures, may be the major underlying reason for the success or failure of restorative treatments.

Human odontoblast cell numbers after dental injury

OBJECTIVES

The purpose of this study was to measure the changes in odontoblast cell numbers in response to cavity restoration variables and patient factors, and the effect these factors have on dental repair by tertiary dentinogenesis. The number of vital odontoblasts is a critical factor for pulpal repair following restorative surgery, and yet little information is available on these cell numbers.

METHODS

Class V non-exposed cavities were prepared in the buccal surface of intact first or second premolar teeth of 27 patients, between 9 and 17 years of age. Following tooth extraction (28-163 days) the area of reactionary dentine and the area of the odontoblasts were measured histomorphometrically.

RESULTS

Patient factors, as well as cavity preparation and restoration variables, had little effect on the numbers of odontoblasts per pulpal unit area. However, the age of the patient did appear to have an effect on the reactionary dentine secretory capacity of odontoblasts per unit area, and on the relative number of odontoblasts beneath cut dentinal tubules.

CONCLUSIONS

Odontoblast cell numbers were maintained following the preparation of cavities cut into dentine with a 0.5mm residual dentine thickness. The repair capacity of the pulp-dentine complex would appear to be age dependent, this may explain differences in the success of various restorative treatments between patients.