Microcirculation changes in gingival tissue after ultrasonic tooth preparation in beagle dogs

Abstract Ultrasonic wave technology is widely used during dental treatments. We previously demonstrated that this method protects the gingival tissue. However, the physiological change on the gingival microvasculature caused by this method remains unclear. Objective The aim of this study was to investigate the relationship between the morphological and physiological effects on gingival microcirculation when preparing teeth, using the conventional dental turbine or ultrasonic method. Methodology The lower premolar teeth of beagle dogs were prepared along the gingival margin by using a dental turbine or ultrasonic wave instrument. Gingival vasculature changes were investigated using scanning electron microscopy for corrosion resin casts. Gingival blood flow at the preparation site was determined simultaneously by laser Doppler flowmetry. These assessments were performed immediately (Day 0), at 7 days and 30 days after tooth preparation. Results At day 0, in the turbine group, blood vessels were destroyed and some resin leaked. Furthermore, gingival blood flow at the site was significantly increased. In contrast, the ultrasonic group demonstrated nearly normal vasculature and gingival blood flow similar to the non-prepared group for 30 days after preparation. No significant alterations occurred in gingival circulation 30 days after either preparation; however, the turbine group revealed obvious morphological changes. Conclusions Based on multiple approach analyses, this study demonstrated that ultrasonic waves are useful for microvascular protection in tooth preparation. Compared with a dental turbine, ultrasonic wave instruments caused minimal damage to gingival microcirculation. Tooth preparation using ultrasonic wave instruments could be valuable for protecting periodontal tissue.

An automatic robotic system for three-dimensional tooth crown preparation using a picosecond laser.

BACKGROUND: Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for tooth crown preparation have several drawbacks which affect the long-term success of the dental treatment. OBJECTIVE: To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) tooth ablation, and thus to realize automatic tooth crown preparation in clinical operations. METHOD: We present an automatic laser ablation system for tooth crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy crown preparation. The system consists of an end-effector, a real-time monitor and a tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth. RESULTS: The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin. CONCLUSIONS: The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for tooth crown preparation. Also, the errors of tooth shape and preparation angle are able to satisfy the requirements of clinical crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D tooth crown preparation, many research issues still need to be studied before the system can be applied to clinical operations.

Assessment of anxiety related to dental treatments among patients attending dental clinics and hospitals in Ranga Reddy District, Andhra Pradesh, India.

PURPOSE: To assess the levels of dental anxiety among patients anticipating dental treatments in dental clinics/hospitals of Ranga Reddy district. MATERIALS AND METHODS: A cross-sectional study was conducted among a representative sample of 1200 subjects (at least 18 years old) in dental clinics/hospitals which were selected from a list obtained through systematic random sampling. The data were collected using a pre-tested and calibrated questionnaire consisting of the Modified Corah Dental Anxiety Scale (MDAS) to assess anxiety levels. RESULTS: The majority (52.4%) of subjects showed a low level of anxiety. Females (11.44 ± 4.41) were found to have higher mean MDAS scores than males, and the highest mean MDAS scores were found among 18- to 34-year-olds (11.28 ± 4.67) (P < 0.05). Significant differences were found among subjects anticipating different treatments, with higher MDAS scores for extraction (11.25 ± 5.4), followed by examination, root canal treatment, gum surgery, scaling, restoration and others, e.g. orthodontic treatment, restoration with crowns, bridges and dentures (7.79 ± 3.80). The highest mean MDAS scores were found among subjects who were apprehensive due to 'past difficult experience in dental treatments', followed by 'drill' and 'injection', with the lowest scores among subjects indicating 'other reasons' (7.82 ± 3.84). CONCLUSION: The present data show that anxiety levels are higher in patients who have to undergo extractions than those who must be fitted with dentures. Thus, dental health care providers should pay more attention to patients' anxiety levels associated with different types of treatment.

Pulp hyperthermia during tooth preparation: the effect of rotary--instruments, lasers, ultrasonic devices, and airborne particle abrasion.

The rise in pulp temperature during restorative therapy can compromise vitality of the dental pulp. Of the various reasons for the increase in intrapulpal temperature, tooth preparation is considered to be the primary cause. This article describes the reasons for the rise in pulp temperature during various modalities of tooth preparation. The article also comments on the measures that need to be taken to avoid the risk of pulp hyperthermia during tooth preparation.

Aerial dispersal of blood-contaminated aerosols during dental procedures.

OBJECTIVES: Dental procedures with high-speed instruments produce large amounts of aerosols. The present study aimed to clarify whether blood-contaminated aerosols were existent and floating in air during dental procedures and to evaluate the effect of an extraoral evacuator system. METHOD AND MATERIALS: An extraoral evacuator system with a test filter was used for sample collection at distances from 50 cm (n = 102) and 100 cm (n =124) behind the patient. A leucomalachite green presumptive test was performed on the test filter. One or more positive reactions on the test filter was considered a positive result, and the positive ratio in each procedure was compared. To assess the effect of the extraoral evacuator, an additional extraoral evacuator was introduced, and the positive ratio during third molar extractions at 100 cm behind the patient was compared (n = 55). RESULTS: At 50 cm from the mouth of the patient during third molar surgery, full-crown preparation, inlay cavity (Black Class II) preparation, and scaling with an ultrasonic scaler, positive results were obtained in 92% (12/13), 70% (21/30), 35% (9/26), and 33% (11/33) of cases, respectively. At a distance of 100 cm, positive ratios sustained 90% (35/39), 48% (15/31), 29% (6/21), and 12% (4/33), respectively. When the second extraoral evacuator was utilized, the positive ratio, at a distance of 100 cm, decreased significantly from 90% (35/39) to 60% (33/55) (P = .0015, chi-square test). CONCLUSION: This study showed that blood-contaminated aerosols can be suspended in air, even in general dental settings, and that extraoral evacuators are useful for reducing contaminated aerosols.

Retentive strength of luting cements for stainless steel crowns: an in vitro study.

The present study evaluated and compared the retentive strength of three luting cements. A total of forty five freshly extracted human primary molars were used in this study. The teeth were prepared to receive stainless steel crowns. They were then randomly divided into three groups, of fifteen teeth each, so as to receive the three different luting cements: conventional glass ionomer resin modified glass ionomer and adhesive resin. The teeth were then stored in artificial saliva for twenty four hours. The retentive strength of the crowns was determined by using a specially designed Instron Universal Testing Machine (Model 1011). The data was statistically analyzed using ANOVA to evaluate retentive strength for each cement and Tukey test for pair wise comparison. It was concluded that retentive strength of adhesive resin cement and resin modified glass ionomer cement was significantly higher than that of the conventional glass ionomer cement.

Energy output reduction and surface alteration of quartz and sapphire tips following Er:YAG laser contact irradiation for tooth enamel ablation.

BACKGROUND: Despite the recent increase in application of Er:YAG laser for various dental treatments, limited information is available regarding the contact tips. This study examined the changes in energy output and surface condition of quartz and sapphire contact tips after Er:YAG laser contact irradiation for tooth enamel ablation. MATERIALS AND METHODS: Ten sets of unused quartz or sapphire contact tips were employed for contact irradiation to sound enamel of extracted teeth. The teeth were irradiated with Er:YAG laser at approximately 75 J/cm(2)/pulse and 20 Hz under water spray for 60 minutes. The energy output was measured before and every 5 minutes after irradiation, and the changes in morphology and chemical composition of the contact surface were analyzed. RESULTS: The energy output significantly decreased with time in both tips. The energy output from the sapphire tips was generally higher on average than that of the quartz. The contact surfaces of all the used quartz tips were concave and irregular. Most of the sapphire tips also appeared rough with crater formation and fractures, except for a few tips in which a high energy output and the original smooth surface were maintained. Spots of melted tooth substances were seen attached to the surface of both tips. CONCLUSION: In contact enamel ablation, the sapphire tip appeared to be more resistant than the quartz tip. The quartz tips showed similar patterns of energy reduction and surface alteration, whereas the sapphire tips revealed a wider and more characteristic variation among tips. Lasers Surg. Med. 41:595-604, 2009. (c) 2009 Wiley-Liss, Inc.

Thermal safety of Er:YAG and Er,Cr:YSGG lasers in hard tissue removal.

OBJECTIVE: The aim of this study was to compare the thermal safety of Er:YAG and Er,Cr:YSGG lasers with conventional multi-use and single-use diamond burs. BACKGROUND DATA: Thermal effect of tooth preparation is mostly evaluated through the pulp chamber because it is difficult to measure the temperature of the preparation surface. A new in vitro method was introduced to simultaneously evaluate the heat increase of the preparation surface together with the pulp chamber. METHODS: Six laser and bur instrument groups were used to make standardized preparations on buccal surfaces of 60 intact third molars. The preparations removed an equal volume of hard tissue from each tooth (4 mm occluso-gingival x 8 mm mesial-distal x 1.6 mm bucco-lingual). The teeth also included tunnel preparations from the opposite (lingual) surface, exposing the pulpal axial wall (axial dentin wall in contact with the pulp chamber from the preparation surface site). An infrared thermal camera was positioned to capture the preparation surface in direct vision, while the pulpal axial wall was indirectly reflected to the thermal camera via a minimal-energy-loss mirror. Data from both surfaces were analyzed statistically using Nested Least Squares Analysis. RESULTS: The laser groups generated significantly lower heat compared to bur groups on the preparation surfaces. In contrast, both lasers generated greater pulpal heat increase, and the Er:YAG laser group showed significance (p < 0.0001). CONCLUSIONS: Lasers produced less heat on the preparation surface but more on the pulpal axial wall. However the temperature rise was less than the 5.5 degrees C threshold margin of safety.

Evaluation of microtensile bond strength of glass ionomer cements to dentin after conditioning with the Er,Cr:YSGG laser.

OBJECTIVE: The purpose of this study was to evaluate the hypothesis that conditioning with Er,Cr:YSGG laser energy would affect bond strength of glass ionomers to dentin. METHODS: Forty extracted caries-free human premolars were selected and ground to expose occlusal dentin. Then the teeth were randomly divided into eight groups of five each and were conditioned in two ways: with and without laser conditioning, and were then restored using Fuji II, Vitremer, and Fuji II LC (with and without polyacrylic acid conditioning) glass ionomers. After immersion in water for 24 h, the teeth were vertically sectioned into 1 x 1-mm beams for microtensile bond strength (microTBS) evaluation. The beams were then subjected to tensile forces in a microtensile tester at a cross-head speed of 0.5 mm/min. Failure patterns were analyzed using a stereomicroscope and unbonded dentin surfaces were evaluated using scanning electron microscopy (SEM) as well. Data were analyzed using one-way ANOVA, Dunnet C, and t-test at the 95% level of confidence. RESULTS: In unlased dentin, bond strength of Fuji II LC after conditioning with polyacrylic acid (PAA) was significantly higher than that of Vitremer and Fuji II. In the laser-irradiated group, bond strength of Fuji II LC after PAA conditioning and Fuji II were significantly less than those of Vitremer and Fuji II LC without PAA conditioning. With laser irradiation, bond strength of Fuji II and Fuji II LC after PAA conditioning were significantly reduced, while bond strength of Vitremer and Fuji II LC without PAA conditioning were not affected. CONCLUSION: Laser irradiation with Er,Cr:YSGG energy at 1 W for conditioning does not improve bond strength of Fuji II LC and Vitremer to dentin, and even reduced bond strength of Fuji II and Fuji II LC after PAA conditioning.

Effect of enamel preparation method on in vitro marginal microleakage of a flowable composite used as pit and fissure sealant.

OBJECTIVES: The aim of this in vitro study was to evaluate the microleakage in occlusal surfaces, after preparation with Er:YAG laser and compared to the diamond-bur conventional technique. METHODS: Thirty premolars were divided into three groups: I - high-speed handpiece + 37% phosphoric acid; II - Er:YAG laser (350 mJ, 4 Hz and 112 J/cm(2)) + 37% phosphoric acid; and III - Er:YAG laser (350 mJ, 4 Hz and 112 J/cm(2)) + Er:YAG laser (80 mJ, 4 Hz, and 25 mJ/cm(2)). All cavities received the same adhesive system and were restored with flowable composite according to manufacturer's instructions. Teeth were submitted to thermal cycling and immersed in 50% silver nitrate solutions for 8 h in total darkness. Specimens were sectioned longitudinally in the bucco-lingual direction, in slices of 1 mm thick. Each slice was immersed into photo developing solution and was photographed, and microleakage was scored from 0 to 7, by three calibrated examiners. RESULTS: A statistically significant difference (P < 0.0001) was observed between Er:YAG laser prepared and etched specimens and those in the other groups. CONCLUSIONS: It can be concluded that no significant difference was noted between the two types of enamel preparation when etching was performed. Preparing and treating the enamel surface exclusively by Er:YAG laser resulted in the highest degree of leakage.

[Advancements in dental preparation technique (literature review)]. / Fejlódés a fogorvosi preparációs technikában (irodalmi áttekintés).

This paper has reviewed the literature on the methods of cavity preparation. The different methods are summarised in Table 1. Nowadays rotary instruments are accepted as standard for cavity preparation. The limitation of using a rotary instrument is the iatrogenic damage to adjacent teeth. Therefore some of the hand instruments remained an essential part of quality restorative dentistry. In order to reduce iatrogenic injury oscillating instruments had been developed. The oscillating instruments change the rotary movement into an oscillating movement and copy the shape of the working tip through an abrasive medium to the tooth surface. The abrasive medium is generally diamond. A new possibility in tooth preparation is the Er:YAG laser. It can be used for both cavity preparation and caries removal. The chemo-mechanical caries removal means the selective chemical softening is followed by the mechanical removing of carious dentin.