Fracture Forces of Dentin after Surface Treatment with High Speed Drill Compared to Er:YAG and Er,Cr:YSGG Laser Irradiation

Dental tooth restorative procedures may weaken the structural integrity of the tooth, with the possibility of leading to fracture. In this study we present findings of coronal dentin strength after different techniques of surface modification. The fracture strength of dentin beams after superficial material removal with a fine diamond bur high speed drill hand piece, Er:YAG (2.94 μm, 8 J/cm(2)), and Er,Cr:YSGG (2.78 μm, 7.8 J/cm(2)) laser irradiation slightly above the ablation threshold was measured by a four-point bending apparatus. Untreated dentin beams served as a control. A total of 58 dentin beams were manufactured from sterilized human extracted molars using the coronal part of the available dentin. Mean values of fracture strength were calculated as 82.0 ± 27.3 MPa for the control group (n = 10), 104.5 ± 26.3 MPa for high speed drill treatment (n = 10), 96.1 ± 28.1 MPa for Er,Cr:YSGG laser irradiation (n = 20), and 89.1 ± 36.3 MPa for Er:YAG laser irradiation (n = 18). Independent Student's t-tests showed no significant difference between each two groups (p > 0.05). Within the parameter settings and the limits of the experimental setup used in this study, both lasers systems as well as the high speed drill do not significantly weaken coronal dentin after surface treatment.

Temperature Rise in the Pulp Chamber duringDifferent Stripping Procedures

OBJECTIVE

To measure the temperature changes in the pulp chamber when different stripping procedures were used without any type of coolant.

MATERIALS AND METHODS

Ninety intact, freshly extracted human teeth were used in this study. The teeth were separated into nine groups of 10 teeth each. Mesial and distal sides of the teeth were used separately. The stripping procedures were performed on three different tooth groups (incisor, canine, premolar) with a metal handheld stripper, perforated stripping disk, or tungsten carbide bur. A J-type thermocouple wire was positioned in the center of the pulp chamber and was connected to a data logger during application of stripping procedures. The results were analyzed by analysis of variance (ANOVA) and the Duncan test.

RESULTS

Two-factor ANOVA revealed significant interaction between the stripping procedure and the tooth type (P = .000). The results of this study demonstrate that tungsten carbide burs used on mandibular incisors had the highest temperature variation (DeltaT) values, which exceeded the critical level (5.5 degrees C), and this was significantly higher than those of the other stripping procedures (DeltaT: 5.63 +/- 1.73 degrees C). On the other hand, six of the nine groups also produced temperature increases above the critical level (5.5 degrees C) for some of the specimens.

CONCLUSIONS

Frictional heat is a common side effect of stripping procedures, and appropriate measures (ie, cooling application) should be taken particularly for high-speed hand-piece stripping of mandibular incisors.

Bacterial aerosols in dental practice - a potential hospital infection problem?

Aerosols containing microbes from the oral cavity of the patient are created when using modern high-speed rotating instruments in restorative dentistry. How far these aerosols spread and what level of contamination they cause in the dental surgery has become a growing concern as the number of patients with oro-nasal meticillin-resistant Staphylococcus aureus colonization has increased. The present study aimed to determine how far airborne bacteria spread during dental treatment, and the level of contamination. Fall out samples were collected on blood agar plates placed in six different sectors, 0.5-2m from the patient. Restorative dentistry fallout samples (N=72) were collected from rooms (N=6) where high-speed rotating instruments were used, and control samples (N=24) were collected from rooms (N=4) used for periodontal and orthodontic treatment where rotating and ultrasonic instruments were not used. The collection times were 1.5 and 3 h. In addition, samples were taken from facial masks of personnel and from surfaces in the rooms before and after disinfection. After 48 h of incubation at 37 degrees C, colonies were counted and classified by Gram stain. The results showed significant contamination of the room at all distances sampled when high-speed instruments were used (mean 970 colony-forming units/m2/h). The bacterial density was found to be higher in the more remote sampling points. Gram-positive cocci, namely viridans streptococci and staphylococci, were the most common findings. The area that becomes contaminated during dental procedures is far larger than previously thought and practically encompasses the whole room. These results emphasize the need for developing new means for preventing microbial aerosols in dentistry and protection of all items stored temporarily on work surfaces. This is especially important when treating generally ill or immunocompromised patients at dental surgeries in hospital environments.

Cervicofacial and mediastinal emphysema complicating a dental procedure

Cervicofacial subcutaneous emphysema is an infrequently reported sequela of dental surgery. It may be caused by the inadvertent introduction of air into the soft tissues during procedures using high-speed, air-driven handpieces or air-water syringes. In this paper, we present a case in which subcutaneous emphysema developed in a middle-aged woman following routine restorative treatment. We review the features of the condition and its treatment and discuss means of prevention.

Effect of Rotary Instrumentation on Composite Bond Strength with Simulated Pulpal Pressure

The bur and its speed may be a factor for improved bonding.

Thermal changes in the pulp chamber during different adhesive clean-up procedures

The aim of this in vitro study was to measure the temperature changes in the pulpal chamber when different adhesive clean-up procedures were used. Ninety intact extracted human maxillary central incisors were used in the study. The teeth were divided into six groups of 15 teeth each. The removal of the remaining composite on the tooth surface was performed with a tungsten carbide bur. The residual adhesive was removed using a high-speed handpiece with and without water cooling and a contra-angle handpiece with and without water cooling at high and low speeds. A J-type thermocouple wire was positioned in the center of the pulp chamber. The results were analyzed with analysis of variance (ANOVA) and the Tukey-honestly significant difference test. Two-factor ANOVA revealed significant interaction between the handpiece type and water cooling. In this study, the high-speed contra-angle handpiece without water cooling group had the highest deltaT values (7.58 degrees C+/-1.84 degrees C) among all the clean-up procedures. The decrease in pulpal temperature with water cooling was -5.34 degrees C for the handpiece, -5.36 degrees C for the low-speed contra-angle handpiece and -4.98 degrees C for the high-speed contra-angle handpiece. Clinicians should be aware of the potential thermal damage to the pulp, which may result from long clean-up procedures without water cooling. Adhesive removal procedures should be performed with adequate water cooling to prevent temperature increases that might be harmful to pulpal tissues.

Subgingival debridement with a teflon-coated sonic scaler insert in comparison to conventional instruments and assessment of substance removal on extracted teeth

OBJECTIVE

Previous studies have shown that endotoxins are located on the periodontally diseased root cementum and not within it. To what extent a Teflon-tubed sonic scaler was capable of removing bacterial deposits in comparison to conventional scaling instruments, and the resulting root surface roughness and root surface topography, were recently assessed. The objective of the present study was to evaluate how much root cementum is removed with these instruments.

METHODS AND MATERIALS

Eighty-two teeth were treated subgingivally on one approximal site either with a Teflon-coated sonic scaler insert (tSS), a Gracey curette, a conventional sonic scaler (SS), a piezoelectric ultrasonic scaler insert (US), or an oscillating Periotor insert (PT) before extraction. The untreated site served as control. The width and length of cementum removal were compared histomorphometrically. Nonparametric analyses were carried out for statistical comparison.

RESULTS

The US, PT, and tSS inserts removed less substance than the curettes or SS inserts. The cementum removed was 40 microm for root surfaces treated with the curette or SS, 30 microm for those treated with US, 20 microm for PT, and 17 microm for tSS.

CONCLUSION

The Teflon-coated sonic scaler inserts can be a reasonable choice for gentle maintenance treatment of compliant patients with good plaque control, and little or no subgingival deposits.

Micro-cracking of tooth structure

PURPOSE

To determine if the cutting procedure utilized in producing a cavity preparation, i.e., a high speed dental handpiece or an Er:YAG laser may be a factor in initiating the formation of micro-cracks during or after preparation of the cavity and before and after placing and curing the dental composite.

METHODS

Class I occlusal and Class II MOD preparations were prepared in extracted third molars using a high speed dental handpiece equipped with a coarse diamond bur or with an Er:YAG laser at 260mJ and 25Hz. Composite was placed into the cavity level with the occlusal surface and bulk cured. The extreme factors of a coarse diamond bur and bulk curing of the composite were utilized to maximize the stresses at the tooth-composite interface. The teeth were vertically sectioned, facio-lingually, and examined, along with resin replicas, under a scanning electron microscope (SEM) to look for the presence of microcracks at the composite/enamel interface and composite/dentin interface.

RESULTS

SEM examination indicated that micro-cracking of the tooth structure was not significant or consistent in any of the specimens examined. This study was unable to confirm that micro-cracks form at the composite/tooth interface.

[Calculus removal efficiency and injury potential of vertically oscillating metallic and carbon ultrasonic tips]

This laboratory study investigated the efficiency and aggressiveness of metallic and carbonic inserts of a vertically oscillating ultrasonic device (Vector-system) at different power settings. The following parameters concerning periodontal treatment were assessed under standardized conditions: calculus and tooth substance removal, mean surface roughness and micro morphological appearance of the treated roots. Concerning the calculus removal potential, no significant differences were found between the types of insert used. The carbon fibre inserts, however, showed significantly more tooth substance loss than the metallic inserts. These findings were confirmed by micromorphological SEM analysis. In view of these results, the repeated use of these carbon fiber inserts during periodonatal sustaining therapy cannot be recommended.

Influence of timing of coronal preparation on retention of cemented cast posts and cores

PURPOSE

This study investigated the effect of coronal preparation by high-speed handpiece on the retention of cemented cast posts and cores.

MATERIALS AND METHODS

Cast posts and cores were fabricated for 90 extracted single-rooted human teeth cemented with zinc-phosphate cement and randomly divided into six groups of 15 specimens each. The six groups were matched randomly two by two, such that one of each of the matched groups was subjected to a 4-minute period of high-speed preparation of the cores. Castings from the first pair (1 and 2) were subjected to an axially directed removal force using a universal testing machine 15 minutes from the start of cement mixing; castings from the second (3 and 4) and third (5 and 6) pairs were tested at 1 hour and 24 hours, respectively, having been stored in water at 37 degrees C for the waiting periods. The forces required for dislodgment of posts from their prepared spaces were recorded. Data were statistically analyzed using two- and one-way ANOVA and the Student's t test.

RESULTS

The results showed increased mean retentive strengths of posts as the time to testing increased for both unprepared and prepared groups. Significantly higher mean retentive strengths of posts were recorded for unprepared compared to prepared groups tested at 15 minutes and 1 hour after cementation.

CONCLUSION

High-speed preparation had a significant negative effect on the retentive strengths of posts tested at 15 minutes and 1 hour after cementation, but not on those tested at 24 hours.

Iatrogenic tooth abrasion comparisons among composite materials and finishing techniques

STATEMENT OF PROBLEM

Many different rotary instruments are available for shaping composite restorations. Whether use of these instruments causes undesirable iatrogenic abrasion of either the tooth surface or the composite restorative material is unknown. Assuming that damage occurs, which technique is least damaging is unknown.

PURPOSE

This in vitro study quantified the loss of surface enamel and dentin surrounding Class V preparations during composite shaping and finishing procedures. The susceptibility of 2 types of composites to tooth abrasion was also examined.

MATERIALS AND METHODS

Standardized Class V cavities were prepared at the amelodentinal junction of 36 human molar teeth. The teeth were randomly assigned to 6 groups of 6 teeth each. They were restored with either a low- or high-viscosity composite (Revolution or Prodigy Condensable, respectively) and finished with aluminum oxide disks, tungsten carbide burs, or ultrafine finishing diamond burs. The preparations were profiled before and after restoration. After each finishing procedure, morphological measurements of surface changes in the dentin and enamel were made and reported as volume (in cubic millimeters); maximum depth, mean maximum depth, and mean depth (in micrometers); and surface area (in square millimeters). The results were subjected to a 2-way analysis of variance for restorative material and finishing technique (P<.05).

RESULTS

Aluminum oxide disks removed significantly less enamel than tungsten carbide burs or ultrafine finishing diamond burs, as measured by volume, maximum depth, mean maximum depth, mean depth, and surface area (P<.05). Conversely, aluminum oxide disks removed significantly greater dentin than either tungsten carbide burs or ultrafine finishing burs as measured by loss of volume, mean depth, and surface area (P<.05). There was no significant difference in the loss of surrounding tooth substance based on resin type (low or high viscosity).

CONCLUSION

Within the limitations of this study, the 3 finishing systems tested resulted in varying degrees of iatrogenic abrasion of enamel and dentin. The composite material used had no significant effect on abrasion of the surrounding enamel or dentin.

Thermal changes observed at implant sites during internal and external irrigation

In the preparation of osseointegrated dental implant sites, the use of bone drilling with conventional external irrigation has been shown to be thermally non-injurious to bovine bone, when employed as a model for dental implantology. The use of internal irrigation drilling systems is promoted on the basis of improved delivery of coolant to the bone/drill interface, which should subsequently improve local debridement and cooling, and therefore reduce thermal insults to the bone. The aim of this bovine model study was to compare the temperatures that were generated with external and internal irrigation systems during bone preparation for dental implants. A constant drill load of 1.7 kg was applied throughout the drilling procedures via a drilling rig. The burs that were used for both irrigation methods were a 2 mm twist drill for cutting the channel and a 3.25 mm drill for trephining this channel. The principal recorded parameter was the change in temperature generated via the drilling procedure. The 2 mm twist drills produced a maximum change in temperature of only 3.0 degrees C and 3.1 degrees C for the internal and external irrigation systems, respectively. Maximum changes for the 3.25 mm drills were 1.34 degrees C and 1.62 degrees C, respectively. Using the t-test, no statistical benefit was observed for one irrigant delivery system over the other. The clinical benefit of using the more expensive internal irrigation systems is therefore deemed unjustifiable, on the grounds that these systems do not appear to reduce the thermal challenge to the bone over and above that of simple flood irrigation.

Subcutaneous emphysema after restorative dental treatment

Subcutaneous emphysema is an uncommon phenomenon in dentistry, usually occurring with the use of air-driven, high-speed handpieces during dental and oral surgery, operative, endodontic, or periodontal treatment. Air is forced into a surgical wound or subepithelial laceration in the oral cavity, dissecting through the different layers of tissue fasciae, and usually creating a unilateral enlargement of the facial and/or submandibular regions. This occurs with or without crepitus, pain, and airway obstruction. Treatment usually consists of antibiotic and mild analgesic therapy, close observation, and reassurance by the attending dentist. Symptoms generally subside in 3 to 10 days; however, consultation with a physician is necessary to rule out further complications.

Subcutaneous, orbital, and mediastinal emphysema secondary to the use of an air-abrasive device

Subcutaneous emphysema can occur whenever compressed air is employed intraorally. A case is presented of subcutaneous, orbital, and mediastinal emphysema subsequent to the use of an air-abrasive device. The case is believed to be the first reported case of an air-abrasive-related emphysema and is presented as a cautionary report.

Temperature changes in bovine mandibular bone during implant site preparation: an assessment using infra-red thermography

OBJECTIVES

Changes in bone temperature during the sequence of drilling for implant site preparation using the Branemark technique were monitored using infra-red thermography.

METHODS

Bovine mandibles were used to provide cortical bone of a similar quality to human mandibular bone. To ensure the consistency in the drilling procedure, one operator used a conventional dental handpiece with a motor provided by Nobelpharma. The manufacturer's specifications were followed during the implant site preparation, except that no irrigation was employed since infra-red radiation does not transmit through water. Thermal images were recorded using the Thermovision 900 system. A sequence of images was recorded during implant site preparation. Three drills were examined in terms of temperature changes during drilling over the entire area involved. The three drills used were a round bur, which determines the site of the fixture, a spiral drill (2 mm twist drill) which establishes the direction of the implant and finally a pilot drill (3 mm) which progressively increases the diameter of the site.

RESULTS

Average values (n = 10 drill sequences) for maximum recorded temperature (Max T degrees C), change in temperature (delta T degrees C) from baseline and the area of involvement (mm2) for each drill in the 10 drill sequences were as follows: round, spiral (2 mm) and pilot (3 mm) drills gave maximum temperatures of 82.7 degrees C, 130.1 degrees C and 126.3 degrees C, respectively. The changes in temperature, delta T degrees C, were 45.7 degrees C, 79.0 degrees C and 78.9 degrees C for the round, 2 mm twist and 3 mm pilot drill, respectively. The average areas recorded for the round, spiral and pilot drills were 49 mm2, 140.1 mm2 and 273.0 mm2, respectively.

CONCLUSIONS

It is concluded that the methodology employed accurately recorded temperature changes at and around the dental implant site, and provided preliminary baseline data against which the cooling efficacy of different irrigant systems may be compared.

Heat propagation in dentin during instrumentation with different sonic scaler tips

It is important to know how much heat is generated when a root surface is debrided with sonic scalers and if that heat can be released satisfactorily into the environment. The temperature changes that occurred in dentinal specimens treated with two different sonic scaler tips, used with and without coolant, were studied. Temperature increases of up to 4 degrees C were observed for both tips when a coolant was used. Heat propagation during instrumentation was dependent to a considerable degree on the temperature of the coolant. Sonic scalers should not be used without coolant, because the dentinal temperature may increase up to 35 degrees C, depending on the force of application. A high positive linear correlation was found between increase in temperature and force of application.

Heat generated during preparation of titanium implants of the ITI Dental Implant System: an in vitro study

The aim of the present study was to assess in vitro the heat generated within the implant body when preparing titanium implants of the ITI Dental Implant System to estimate the potential risk of tissue damage of individual abutment preparation. The speed and the pressure were applied according to routine clinical procedures used in the patient's mouth. Much attention was paid to ensure optimal cooling at the point where the implant and secondary part were being cut. For each of 3 preparations the change from the original temperature was measured over a period of 40 s. Each type of preparation was repeated on 5 implants fitted with temperature probes. Three different preparatory procedures performed with rotating diamond burs and stainless steel finishing burs under cooling with spray from the dental unit may result in a maximal increase in temperature of 10 degrees, 7 degrees and 3 degrees measured coronally, both at the implant shoulder and at the coronal extent of the plasma-sprayed surface after 10 s. The use of additional spray and pressured air significantly reduced this maximal increase to 5 degrees C, 5 degrees C and 4 degrees C, respectively at 10 s. At the 30-s and 40-s time points, all the measured temperatures were significantly lower. Preparation of implants or abutments does not lead to detrimental effects on peri-implant tissues provided that adequate cooling with spray is used. However, without cooling, extreme overheating could be provoked, reaching the critical temperature that would lead to irreversible bone damage within only a few seconds.

Measurements of shaft speed while drilling through bone

PURPOSE

This study investigated the effect of force on drill speed and measured the energy consumed during the drilling process.

MATERIAL AND METHODS

Applied force, drill speed, and energy consumed were measured during drilling in bovine cortical bone specimens. A commercial surgical drill was fitted with a custom-designed speedometer for measuring the rotational speed. The handpiece was attached to a laboratory drill press and positioned above a bone specimen mounted on a load cell. To apply steady loads, weights were placed on the drill platform, and tests were conducted for forces between 1.5 and 9.0 N and for free-running speeds from 20,000 to 100,000 rpm.

RESULTS

The simultaneous measurements of speed and load for the electrically powered instrument showed that the average operating speed changed with the force applied: at low starting speeds, the speed increased slightly with force; at high starting speeds, the speed decreased with force by as much as 50%. The measurements of electric power showed that the total energy consumed generally decreased with speed and force, primarily because of decreased drilling time.

CONCLUSION

The decrease in energy suggests that drilling at high speed and with a large force may be desirable because bone temperature is reduced.

Fixed prosthodontics: avoiding pulp death

Fixed prostheses & crowns have become a major part of dental services due to aging population & increase in retention of natural teeth. In some practices, alarming numbers of endodontic procedures are necessary because of pulp damage after prosthesis cementation. Third party payment companies show many teeth receiving crowns require endodontic therapy within 5 years. Following report describes: (1) 14 potential causes of endodontic need related to fixed prosthodontics; & (2) state-of-art concepts to prevent pulp damage.

Histopathologic effects of kinetic cavity preparation for the removal of enamel and dentin. An in vivo animal study

Recent developments in technology, direct placement restorative materials, and cavity preparation design have renewed interest in kinetic cavity preparation, a term to describe the use of air-abrasion for removal of tooth structure. This study compared the pulpal response of 120 teeth in mixed-breed dogs treated with four kinetic cavity preparation combinations of pressure (80 psi and 160 psi) and aluminum oxide particle sizes (27 microns and 50 microns) to those treated with high-speed rotary burs. Class V buccal preparations were made and restored with an interim material. Teeth were collected 72 hours after surgery, decalcified, sectioned, stained with hematoxylin and eosin, and blindly evaluated by two examiners at the minimal dentin thickness. Samples were graded for extent of displacement, disruption, inflammation, and necrosis of pulpal structures. Differences between groups were analyzed with the use of Bonferroni-adjusted multiple Mann-Whitney-Wilcoxon tests with p < 0.05 being significant. Higher pressures and smaller particles yielded significantly fewer pulpal effects than the high-speed treated teeth whereas lower pressures and larger particles were not significantly different for most effects evaluated. No adverse soft tissue effects were noted when kinetic cavity preparation was directed at attached gingiva.

Preventing root tip loss in the maxillary sinus during endodontic surgery

Exclusion of infected root tips, dentinal debris, and inflammatory tissue from the maxillary sinus during endodontic surgery is imperative. A simple technique for preventing accidental root tip intrusion into the maxillary sinus using a 6-0 suture and needle and a hole prepared in the root tip with a #2 round bur prior to apicoectomy is presented.

Emphysematous complications in dentistry, 1960-1993: an illustrative case and review of the literature

Seventy-four reports of emphysematous complications in ambulatory dental patients, published in the English literature between the years 1960 and 1993, are reviewed, and an additional case of subcutaneous, retropharyngeal, and mediastinal emphysema following an impression-taking procedure for a crown preparation is presented. This rare complication occurred mainly in patients in the third and fifth decades of life, after dental procedures on the third molar, in particular during mandibular extractions and treatment on the right side. The use of an air syringe, high-speed handpieces, or their combination was reported in 71% of cases. Centripetal air dissection, with retropharyngeal and mediastinal emphysema, occurred in 35% of the patients, especially following extractions.

The effect of tooth preparation on retention and microleakage of cemented cast posts

PURPOSE

Vibration from the high-speed handpiece may adversely affect the cement layer between a casting and a tooth, causing loss of retention or increased microleakage. This study assessed the effect of crown preparation on retention and microleakage of cemented cast post and cores.

MATERIALS AND METHODS

Post and cores were fabricated for extracted teeth and cemented. Specimens were prepared for crown restorations, varying the preparation time and the rotary diamond instrument used. After thermocycling and immersion in a dye bath, tensile unseating force and linear dye penetration were measured.

RESULTS

In general, retention decreased with increased severity of crown preparation; however, differences were not statistically significant (alpha = .05). Although the differing preparation conditions resulted in significant differences in microleakage, no consistent trends were evident.

CONCLUSIONS

Crown preparation using high-speed rotary diamond abrasives of cast post and cores luted with zinc phosphate cement had no significant effect on their retention, but had varying effects on subsequent microleakage at the cement-tooth interface.

Air-rotor stripping and enamel demineralization in vitro

This investigation sought to evaluate the effects of air-rotor stripping on the susceptibility of human enamel to demineralization using an in vitro caries model. Crowns of extracted premolar teeth were abraded (0.5 mm) on one proximal surface by air-rotor stripping. The teeth were placed in a demineralizing gel and removed at various intervals up to 336 hours. Lesion depth and mineral content on the abraded and intact surfaces was measured with contact microradiography and computerized image analysis (double window technique). For each time interval measured, lesion depth was greater (p < 0.05) on the abraded surfaces and mineral density was significantly less (p < 0.05). In a second experiment, the effect of fluoride supplements (dentifrice or topical gel) were examined on abraded and intact enamel surfaces that were exposed to the acid gel for 192 hours. The data showed that fluoride treatments significantly reduced lesion penetration on intact and abraded surfaces compared with a no fluoride group. Lesion depth on the abraded, fluoride treated surfaces was significantly greater (p < 0.05) than on the intact untreated surfaces. No significant differences (p < 0.05) were apparent between the fluoride treatment groups with respect to lesion depth and mineral density within the lesion. These results suggest that air-rotor stripping significantly increases the susceptibility of proximal enamel surfaces to demineralization. As a result, the clinician should use caution in the application of this technique until the long-term effects on caries susceptibility have been determined.

Cervicofacial and thoracic barotrauma following a minor dental procedure

A case of cervicofacial subcutaneous emphysema and pneumomediastinum following a seemingly minor dental procedure is described. This dramatic but usually benign complication of dental work is rare and has not been reported in the pediatric emergency medicine literature. A brief review of this entity and an overview of diagnostic considerations and management are presented.

Measuring harmful levels of bacteria in dental aerosols

The potential spread of the bacteria in aerosols emphasizes the familiar triad--gloves, masks and eyewear--for all operative procedures.

[Bacterial contamination of the atmosphere of the dental surgery during preparation with turbin equipment. 2. Microbiological examination of water of stomatological sets]

Water forms a substantial part of aerosol particles formed during preparation with turbin equipment. The authors assessed therefore before aerobiological examination of the atmosphere of the dental surgery which will be the subject of part III whether the water used for cooling of dental sets is contanined by pathogenic bacteria. Microbiological examination of water specimens of the cooling system of four dental sets of two types revealed only the presence of Baccilus subtilis and Gram-negative rods. The results of aerobic cultivation of all 48 water specimens were identical. The authors did not find a difference between water samples at the beginning and at the end of working hours nor between specimens collected on different days. The measurements were made as part of a student contest and the results were presented at a student conference at the Faculty of General Medicine, Charles University Prague and in a nation-wide contest in Kosice.

[Bacterial contamination of the atmosphere in the dental surgery during preparation with turbine tools]

The aerosol formed during work with turbine tools has an undesirable impact on the environment of dental surgeries. It may cause atmospheric transmission of infection. Recent qualitative and quantitative evaluation of aerosols assumes theoretical knowledge of physical and chemical properties and transformation of the aerosol system. These findings which influenced the selection of methods of the author's more recent measurements are the subject of the submitted paper.

Effects of the temperature of cooling water during high-speed and ultrahigh-speed tooth preparation

In vitro measurements of heat production in the pulp chamber during tooth preparation were performed on intact third molars. The experiments were designed to simulate physiologic temperature conditions in the tooth and oral cavity and to standardize parameters of tooth preparation. Two drive systems, the turbine and the high-speed angle, were compared by using two ranges of cooling water temperature. The critical temperature of 41 degrees C to 42 degrees C that is irreversibly harmful to pulpal tissue was not reached with a cooling water temperature of 30 degrees C to 34 degrees C. Because the temperature elevation during turbine preparation was dependent on the diminishing thickness of remaining dentin, in preparing teeth close to the pulp, a high-speed angle was advantageous.

[Heat distribution within the bone tissue by rotary cutting instrument for IMZ implant. Heat analysis by a real-time thermography]

A highly skilled surgical technic is an important factor for the success of implant. But the heat generation during bone preparation will greatly affect the healing process of bone and prognosis of implant. In this study, the heat occurrence and distribution during bone preparation which performed on an in vitro mandible model (ribs of pig) were considered with the aid of a real-time thermography. IMZ implant drills and bur, designed for cylindrical type implant were used for the bone preparation. The conclusion are as follows: 1. Any drill or bur generates higher heat without water irrigation. 2. Heat distribution produced different shape of range according to different type of drills. 3. On a relationship of preparating time to heat generation, spiral drill takes the longest time to complete drilling but heat rising ratio is slow. Round bur and Canon drill take short time to complete drilling but it is accompanied with rapid heat rising.

Dentine/pulp reactions to full crown preparation procedures

Scanning electron microscopy was used to study the formation of a dentine smear in ten premolars ground with a water-cooled diamond in an air turbine. In another ten teeth the pulp reaction in full crown preparation with the same armamentarium was investigated by histological techniques. The findings revealed the formation of a dentine smear which was easily removed by light polishing with wet pumice, leaving plugs of debris in the tubule apertures. The clinical significance of these findings needs further investigation. No bacteria were demonstrated on the prepared surfaces either in the scanning electron micrographs or histologically when stained with Brown & Brenn stain. Severe, acute pulp reactions were observed subjacent to the dentinal tubules cut in full crown preparation. This technique should therefore be limited to superficial use only.