Cross sectional: use of coolant for high-speed tooth preparation: a survey of pediatric dentist members of the American Academy of Pediatric Dentistry

PURPOSE

To report the findings of a survey to determine the educational experiences, opinions and clinical practices relative to the use of coolant during cavity preparation of pediatric dentist members of the American Academy of Pediatric Dentistry (AAPD) and to determine whether teaching policies influenced the type of coolant used in private practice.

METHODS

Four thousand fifty surveys were emailed to AAPD members and included questions regarding demographics and predoctoral, graduate, and current practice policies for the use of dry cutting.

RESULTS

Returned survey numbered 1730 for a response rate of 43%. Fifteen percent were taught the concept of dry cutting in their predoctoral programs and 34% in their specialty, programs. Sixty percent never or rarely prepare teeth without water coolant. Slightly more than 40% prepared teeth with air coolant alone. Patient behavior (25%) and sedation (21%) were reported as determining factors for cutting dry. Thirty-one percent of private practice clinicians and 34% of part time academics use dry cutting, while only 15% of full time academicians use the technique (P<0.0001).

CONCLUSIONS

Respondents tend to use the technique they were taught during their residency. Use of dry cutting was more likely to be utilized during sedations or general anesthesia to avoid airway compromise.

Learn-a-prep II as a predictor of psychomotor performance in a restorative dentistry course

This investigation assessed whether early student performance with a dental handpiece on a didactic training aid known as the Learn-A-Prep II (LAP II) was predictive of performance on subsequent practical examinations in a preclinical restorative dentistry course. Eighty-one first-year students were given initial handpiece training and formative feedback using the LAP II and were then instructed to independently prepare four LAP II patterns within the pattern lines and at a specified depth. Performance on the LAP II was compared with the summative assessment on two subsequent amalgam preparation practical examinations given at the middle (Class II) and end (Complex) of the course. Pattern preparation within the lines did not significantly improve the likelihood of receiving an A or B on the Class II practical (p=0.53) or on the Complex practical (p=0.37). Students who had an acceptable depth on the LAP II were 3.73 times more likely to receive an A or B on the Class II practical than those students who did not have acceptable depth (p=0.03). Performance at an acceptable depth did not significantly improve the likelihood of receiving an A or B on the Complex practical (p=0.15). The LAP II may aid in identification of students who would benefit from early intervention with additional focused instruction.

[SEM comparative analysis of the composite diacrylic resin-enamel interface in laser and bur prepared cavities]

The aim of this study was to demonstrate that the size of the hybrid layer (HL) in the prepared enamel mechanic (M) and kinetic (K) with laser (WaterlaseMDBiolase), evaluated by scanning electron microscopy (SEM) restored with two types of resin composite is different.

MATERIAL AND METHOD

The study was realized in vitro on a sample of 40 extracted human premolar and molars teeth for orthodontic or periodontal reasons. The teeth were divided at random into equal four groups (Gr). There has been Class I cavities with a depth of 2 mm (M) at high and low speed with cylindrical diamond No.1 and globular carbide and (K) peaks MZ6-5, 5W+20 Hz 30% water 60% air. The teeth were restored using 3M Schotchbond Etch, 3M Single Bond Dental Adhesive System: Gr. 1: (K)(n = 10)-3M Filtekflow; Gr.2 : (K)(n = 10)3M FiltekZ250; Gr.3: (M)(n = 10)3M Filtekflow; Gr.4: (M)(n = 10)3M FiltekZ250. The materials were placed in a single layer and photoactivate source LED SmartLite (Dentsply), termocycling 500 cycles (5 degrees-55 degrees), stored (48h), cut lengthwise (diamond), polished, conditioned (H3PO4-37% -5s) analyzed by SEM (JEOLJSM 6390), SPSS 13.00 statistically analyzed (ANOVA, p = 0.05).

RESULTS

Analysis of the (HL) has highlighted differences between groups p = 0.05 average size (HL) being Gr.1;20.80 (+/- 0.72)microm, Gr.2;4.034 (+/- 0.0076)microm, Gr.3, 14.13 (+/- 0.63)microm, Gr.4, 1,43 (+/- 0.16)microm. Value size (HL) was influenced by the cavity preparation method for samples prepared by laser p = 0,005 in terms of size and in advantage of mechanical preparations in terms of quality (HL). Also the value of (HL) size was influenced by the type of material used in advance Gr.2 p = 0.0017.

CONCLUSIONS

The sealing of cavity depends more on the creep of materials and less on the type of preparation. Permission was obtained from a institutional ethical committee of "Gr.T. Popa" University of Medicine and Pharmacy Iaşi and that subjects gave written, informed consent).

Marginal microleakage of alternative restorative treatment and conventional glass ionomer restorations in extracted primary molars

PURPOSE

The objective of this study was to compare the marginal leakage of cervical glass ionomer restorations made using alternative restorative treatment (ART) and conventional restoration techniques.

METHODS

Twenty primary molars with Class V carious dentin on the buccal surfaces were prepared using ART, and a second set of 20 noncarious molars had Class V preparations made with a high-speed handpiece. The occlusal margin was located in enamel and the gingival margin in dentin/cementum. All teeth were restored with high-density glass ionomer cement (GIC; Fuji IXgp) according to manufacturers' instructions, thermally stressed for 300 cycles, and stained with methylene blue. Samples were sectioned and evaluated for microleakage.

RESULTS

One-way analysis of variance revealed no statistically significant difference between leakage at margins of ART and conventional restorations. (P=.92) There was no significant difference between leakage at the enamel and dentin margins.

CONCLUSIONS

Alternative restorative treatment with high-density glass ionomer cement provides enamel and dentin margins that show marginal leakage comparable to conventionally restored primary teeth. These results show the potential of ART in conjunction with high-density GIC in providing treatment for children and adolescents in situations where traditional cavity preparation and restoration is not possible.

In vitro microleakage of composite restorations prepared by Er:YAG/Er,Cr:YSGG lasers and conventional drills associated with two adhesive systems

PURPOSE

The objective of this in vitro study was to compare the degree of microleakage of composite restorations performed by lasers and conventional drills associated with two adhesive systems.

MATERIALS AND METHODS

Sixty bovine teeth were divided into 6 groups (n = 10). The preparations were performed in groups 1 and 2 with a high-speed drill (HD), in groups 3 and 5 with Er:YAG laser, and in groups 4 and 6 with Er,Cr:YSGG laser. The specimens were restored with resin composite associated with an etch-and-rinse two-step adhesive system (Single Bond 2 [SB]) (groups 1, 3, 4) and a self-etching adhesive (One-Up Bond F [OB]) (groups 2, 5, 6). After storage, the specimens were polished, thermocycled, immersed in 50% silver nitrate tracer solution, and then sectioned longitudinally. The specimens were placed under a stereomicroscope (25X) and digital images were obtained. These were evaluated by three blinded evaluators who assigned a microleakage score (0 to 3). The original data were submitted to Kruskal-Wallis and Mann-Whitney statistical tests.

RESULTS

The occlusal/enamel margins demonstrated no differences in microleakage for all treatments (p > 0.05). The gingival/dentin margins presented similar microleakage in cavities prepared with Er:YAG, Er,Cr:YSGG, and HD using the etch-and-rinse two-step adhesive system (SB) (p > 0.05); otherwise, both Er:YAG and Er,Cr:YSGG lasers demonstrated lower microleakage scores with OB than SB adhesive (p < 0.05).

CONCLUSION

The microleakage score at gingival margins is dependent on the interaction of the hard tissue removal tool and the adhesive system used. The self-etching adhesive system had a lower microleakage score at dentin margins for cavities prepared with Er:YAG and Er,Cr:YSGG than the etch-and-rinse two-step adhesive system.

Atraumatic tooth preparation

One of the tenets of operative dentistry is to maintain the health and vitality of teeth whenever possible. Methods of tooth preparation can adversely affect the tooth structure and the pulp. This paper will review the research on methods and devices used to prepare teeth, the possible sequelae of tooth preparation, and the best methods that can be recommended from the research to maintain tooth vitality and marginal integrity.

An in vitro comparison of marginal microleakage of alternative restorative treatment and conventional glass ionomer restorations in extracted permanent molars

PURPOSE

The objective of this study was to compare the marginal leakage of cervical restorations made using alternative restorative treatment (ART) and conventional glass ionomer restorations.

METHODS

Sixteen permanent maxillary and mandibular first and second molars extracted for periodontal reasons with Class V carious dentin on the buccal surfaces were prepared using ART while a second set of 29 noncarious molars had Class V preparations made with a high-speed handpiece. The occlusal margin was located in the enamel, and the gingival margin was located in the dentin/cementum. All teeth were restored with glass ionomer cement (GIC). The teeth were thermally stressed for 300 cycles and stained with methylene blue. Samples were sectioned and evaluated for microleakage.

RESULTS

One-way analysis of variance on ranks revealed no significant difference in leakage at both the dentin and enamel margins between the conventional and ART groups. The microleakage at the dentin margin, however, was significantly greater (P < .001) than at the enamel margins in the conventional group.

CONCLUSION

Alternative restorative treatment with GIC provides enamel and dentin margins that show comparable marginal leakage to conventionally restored permanent teeth. For the conventional restorations, leakage at the dentin margins occurs to a significantly higher extent than at the enamel margins.

In vitro effectiveness of a chemo-mechanical method for caries removal

AIM

The aim of the study was to assess the efficacy of chemo-mechanical method for caries removal based on histological analysis and scanning electron microscopy of dentine samples.

METHODS

Forty-five freshly extracted human deciduous and permanent teeth with dentinal caries were used in this in vitro study. The teeth were allocated to two different technique groups. Chemo- mechanical caries removal using Carisolv was performed in 30 teeth and in 15 teeth caries was removed using conventional rotary instruments. The caries status of dentine was judged according to clinical criteria (probing and visual inspection). After caries removal had been completed, teeth were sectioned through the prepared cavities and the two halves of each tooth were processed for light microscopy and scanning electron microscopy. Light microscope was used to examine the specimens for the presence of bacteria in dentine tubules. Scanning electron microscope was used to determine surface characteristics of the cavity floor after caries removal.

RESULTS

All examined dentine surfaces were clinically caries free. Regarding the presence of bacteria, 53% of chemo- mechanically prepared teeth and 87% of conventionally prepared teeth were bacteria-free (p>0.05). Efficacy of both methods was confirmed using scanning electron microscope, but different dentine topography was recorded after chemo-mechanical and conventional caries removal.

CONCLUSION

Based on histological and scanning electron microscope analyses it could be concluded that this chemo-mechanical method is efficient in the removal of carious dentine.

Computerized navigation surgery for the safe placement of palatal implants

Palatal endosseous implants are increasingly recognized as an important alternative for achieving maximal intraoral orthodontic anchorage; however, their safe surgical placement is a matter of concern. Available palatal bone is frequently limited, and erroneous drilling can damage adjacent structures. Computerized navigation surgery is an advanced surgical modality in which the surgical drill is accurately tracked and animated in real time on the radiological image of the surgical site. In implant dentistry, this surgical modality allows accurate navigation of the implant drilling procedure and increases safety and accuracy, compared with conventional dental implant surgery. This article outlines the principles of computerized navigation surgery and describes its application for the placement of palatal orthodontic implants. The merits of this approach are particularly important for patients with limited palatal bone when implant placement requires high surgical precision.

Chemomechanical caries removal in children: efficacy and efficiency

BACKGROUND

The authors investigated the effectiveness of chemomechanical caries removal (CMCR) compared with the traditional method (TM) of caries removal using a round bur when treating dentinal-depth occlusal lesions with minimal enamel access in primary molars. The authors also compare CMCR with TM to determine if it had a higher efficacy and could be used more frequently without the subject's having to undergo local anesthesia.

METHODS

The authors collected data from 50 children during operative appointments at which caries was removed using one of the two methods.

RESULTS

Complete caries removal within 15 minutes was achieved in only 57.7 percent of the CMCR-treated teeth. In 42.3 percent of these teeth, residual caries was removed using TM. CMCR was almost eight times more time-consuming than was TM when used to excavate dentinal-depth occlusal lesions with minimal cavitation. There was no significant difference between CMCR and TM in the number of subjects who needed to undergo local anesthesia.

CONCLUSIONS

The authors found no direct clinical advantage in using CMCR over using TM for treating occlusal dentinal lesions with minimal cavitation in pediatric patients.

Temperature changes in the deciduous pulp chamber during cavity preparation with the Er:YAG laser

PURPOSE

The purpose of this in vitro study was to evaluate the temperature changes in the pulp chambers of deciduous molars during cavity preparation with an Er:YAG (erbium substituted: yttrium aluminium garnet) laser.

METHODS

Two cavities were prepared in 14 maxillary deciduous molars: one with the Er:YAG laser and other with a diamond bur using a high-speed handpiece (control), providing 4 groups with 7 cavities each. The laser treatment was applied for 30 seconds (group 1) and 60 seconds (group 3). The internal pulp temperature was recorded during preparation procedures with a thermocouple, and temperature changes were calculated by the difference between the maximum and initial temperature.

RESULTS

There were significant differences (P<.01) between Er:YAG laser irradiation for 60 seconds and 30 seconds and the 2 high-speed drilling groups, which were similar. The Er:YAG laser used for 60 seconds provided the highest temperature alteration (4.01 degrees C).

CONCLUSION

Er:YAG laser irradiation increased the temperature of the deciduous teeth compared to the high-speed drilling treatment. The temperature increments, however, remained below the critical value (5.5 degrees C).

Microleakage study of different adhesive systems in Class V cavities prepared by Er,Cr:YSGG laser and bur preparation

This study sought to compare the microleakage of composite resin restorations using two different dentin adhesive systems and two different modes of cavity preparation: a high-speed handpiece and an Er,Cr:YSGG laser. Twenty-five caries-free permanent human premolars were assigned randomly into five groups of five. A high-speed handpiece was used to prepare Class V cavities on the buccal and lingual surfaces of 10 randomly selected teeth. Class V cavities were cut on the buccal and lingual surfaces of the remaining 15 teeth using the Er,Cr:YSGG laser system. Fifty cavities were prepared with enamel and dentin margins 1.0 mm below the cemento-enamel junction and assigned into five groups: I, II, and III by the Er,Cr:YSGG laser and IV and V by the high-speed handpiece. In all groups, the differences between gingival and occlusal leakage scores were statistically significant (p < 0.05). The occlusal and gingival scores of groups I and IV demonstrated statistically significant differences (p < 0.05). The lased group with additional acid etching revealed less microleakage than groups III and IV (p < 0.05). Both self-etch and total-etch adhesive systems demonstrated acceptable microleakage scores when used on Er,Cr:YSGG laser-prepared cavities; however, additional acid etching after Er,Cr:YSGG laser preparation is recommended.

SEM and profilometric evaluation of enamel surface after air rotor stripping--an in vitro study

The aim of the study was to evaluate roughness of the enamel surface after Air Rotor Stripping (ARS). Thirty interproximal surfaces of human premolars were used as the biological material. Research was conducted using a contact profilometer and a scanning electron microscope (SEM). Sets of 3D parameters and topographical maps of enamel surface before and after ARS treatment were used to define roughness of the surfaces. SEM images of stripped surfaces were taken with microscopic magnification of 100x and 1000x. The data revealed a general roughness of enamel arising after ARS procedure. Summarized values of chosen parameters increased after ARS procedure compared to the values of untreated enamel. Topographical maps showed areas of both well polished and badly polished enamel. In conclusion, comparison of the mean values of the measured parameters of ARS treated enamel surfaces indicated that roughness of the enamel arises after ARS, but it must be emphasized that on every evaluated surface well polished areas were also present. Moreover, the well polished areas were smoother than those on the untreated enamel surfaces. Contact fluoridation and improved oral hygiene after ARS appear to be necessary because of the presence of areas of increased roughness on evaluated surfaces.

Heat generated by residual adhesive removal after debonding of brackets

AIM

To measure the rise in temperature during mechanical removal of residual adhesive after debonding of brackets in vitro.

METHODS

Different carbide burs on a high-speed handpiece were tested. Acrylic on the buccal surfaces of recently extracted human maxillary incisors was removed using 3 types of carbide burs (6-, 12-, 40-fluted) with a varying number of windings relative to the long axis of the shaft. The temperature was measured using a thermocouple probe in the pulp chamber of the extracted teeth.

RESULTS

The highest mean rise in temperature was measured using a 6-fluted bur (+9.4 degrees C, P < .001), followed by the 12-fluted bur (+6.5 degrees C, P <.001). The lowest rise in temperature (+1.2 degrees C, not significant) was seen with a 40-fluted bur. After 3 to 8 seconds of continuous grinding, the rise in temperature seems to slow down.

CONCLUSION

The removal of residual adhesive after debonding is best performed with fine burs. If 6-fluted burs are used, a pause after 5 to 10 seconds of continuous grinding is recommended, especially in the mandibular anterior area.

The effect of wear on ultrasonic scaler tip displacement amplitude

AIM

During clinical usage, scaler tips may become worn and reduced in length. It is unknown what effect wear has on the magnitude of scaler tip vibrations when they are utilized under typical clinical loads. The aim of this investigation was to assess the effect of simulated wear on ultrasonic scaler tip displacement amplitude, using a scanning laser vibrometer.

MATERIALS AND METHODS

A Cavitron SPS (Dentsply) ultrasonic generator and three scaler insert designs (FSI-100, FSI-1000 and FSI-SLI-10S) were selected for the investigation. Tip vibration displacement amplitude was assessed unloaded and then contacting against tooth surfaces with loads of 0.5 and 1.0 N. Tips were then ground down by 1 mm and then 2 mm and scans were repeated.

RESULTS

For all tips, load and length were found to be significant variables (p<0.0001). The scaler tips showed a fall in displacement amplitude with a reduction in tip length. However, all scaler tips showed variability in the amount oscillation that occurred. This was most pronounced with FSI-SLI-10S.

CONCLUSIONS

This investigation demonstrated that tip wear could affect the performance of dental ultrasonic scaler inserts by reducing their vibration displacement amplitude. Clinicians should be aware of this variability, which may be significant enough to affect clinical procedures.

Cutting on triangle mesh: local model-based haptic display for dental preparation surgery simulation

A new method to realize stable and realistic cutting simulation using an impedance display haptic device and microcomputer is presented in this paper. Material removal or cutting simulation is a critical task in dental preparation surgery simulation. In this paper, a piecewise contact force model is proposed to approximately describe the cutting process. Challenging issues of minimizing the difference between the cutting simulation and haptic contact simulation are analyzed. The proposed contact-based simulation method is developed for a one-dimensional cutting task and can be expanded to three-dimensional cases. Local model-based multirate simulation cutting architecture is proposed and force control of the haptic device is decoupled from the cutting simulation loop, which can both ensure high fidelity of dynamical simulation as well as maintain stability of the haptic device. The cutting operation is realized using spherical and cylindrical shaped tools. An experiment based on the Phantom desktop proves that fidelity in one-dimensional cutting can be realized and stability in three-dimensional cutting can be ensured using the force-filtering method.

An evaluation of the effects of handpiece speed, abrasive characteristics, and polishing load on the flexural strength of polished ceramics

STATEMENT OF PROBLEM

Many studies on the strengthening effects of grinding and polishing, as well as heat treatment on ceramics, are not well standardized or use commercially available industrial polishing systems. The reported effectiveness of these strengthening mechanisms on ceramics may not be applicable to clinical dentistry.

PURPOSE

The purpose of this study was to evaluate the effects of controlled polishing on the flexural strength of dental ceramics by using a custom-made machine that applied standardized loads and speeds that coincided with the mean loads and speeds used by experienced prosthodontists.

MATERIAL AND METHODS

A total of 140 aluminous dental ceramic bar-shaped specimens (Vitadur Alpha Enamel) measuring 1.5 x 2.0 x 25 mm were fabricated and divided into 12 groups (for most groups, n=10). Specimens were untreated, polished with different polishing systems, polished at different speeds, ground and autoglazed, polished and autoglazed, autoglazed and polished, polished with loose (paste) and bonded abrasives, or overglazed. Simulated clinical polishing was performed on the ceramic specimens by using a customized polishing apparatus that allowed independent control over the relevant polishing parameters (abrasive hardness, applied load, linear speed, rotational velocity, and wheel stiffness). Flexural strength (MPa) was measured with a 4-point bending test, and subjective surface roughness was assessed with scanning electron microscopy. Autoglazing was performed at various stages of the polishing sequence to determine the effects of polishing on surface stresses. Mean values, standard deviations, independent-sample t tests, 1-way and 2-way analyses of variance, Dunnett t tests and Kruskal-Wallis tests were applied to the data (alpha=.05).

RESULTS

Under a clinical load of 0.6 N for a coarse polishing wheel, 1.0 N for a medium polishing wheel, and 1.3 N for a fine polishing wheel, a linear speed of 499 mm/min, and a rotational velocity of 10,000 rpm, the use of clinical polishing instruments did not affect the flexural strength of the aluminous ceramics studied (P=.274). At higher rotational velocity (20,000 rpm), specimens polished with the diamond polishing system produced statistically weaker specimens compared with those that had been polished at 10,000 rpm (P=.019). Autoglazing treatment of the diamond-polished specimens did not reverse the strength degradation (P=.125). Conversely, diamond polishing of the autoglazed specimens resulted in significant flexural strength reduction (P=.029). Fine-diamond-bonded abrasive significantly reduced flexural strength (P=.025).

CONCLUSIONS

Simulated clinical polishing at 10,000 rpm did not appear to substantially strengthen or weaken the ceramic specimens. Polishing at 20,000 rpm reduced flexural strength of the ceramic bars.

Oral surgical handpiece use time parameters

PURPOSE

To evaluate the clinical usage time parameters of handpieces used in oral surgical procedures.

METHOD AND MATERIALS

One hundred randomly selected clinical oral surgery exodontia procedures were timed to record lengths of continuous segments of both handpiece use and non-usage. Providers with experience ranging from general dentists to board certified oral surgeons were timed during surgical exodontia treatment involving 1 to 4 teeth of various complexities. Usage times were compared with manufacturers' recommendations that on times should not exceed 20 seconds in any 50-second interval (20/50 rule).

RESULTS

Handpiece run time increased with the number of teeth and surgical case complexity (both P < .001) but was unrelated to operator experience (P = .763), in a 3-predictor model (R2 = 0.20; P < .001). Ninety-four of the 100 cases experienced at least 1 second in violation of the 20/50 rule and 42% of all run seconds were in violation.

CONCLUSION

Clinicians should be aware of recommended handpiece duty use cycles. Manufacturers' recommendations about handpiece use time cycles do not reflect actual clinical usage. Under the conditions of this study, actual surgical handpiece use time was not correlated with user experience. Less experienced providers did require longer to complete treatment, but increased treatment times were due to time spent that did not require surgical handpiece use.

[In vitro comparison of root canal preparation with step-back technique and GT rotary file--a nickel-titanium engine driven rotary instrument system]

The aim of the authors' study was to compare the remaining root canal wall thickness and the preparation time of root canals, prepared either with step-back technique, or with GT Rotary File, an engine driven nickel-titanium rotary instrument system. Twenty extracted molars were decoronated. Teeth were divided in two groups. In Group 1 root canals were prepared with step-back technique. In Group 2 GT Rotary File System was utilized. Preoperative vestibulo-oral X-ray pictures were taken from all teeth with radiovisiograph (RVG). The final preparations at the mesiobuccal canals (MB) were performed with size #30 and palatinal/distal canals with size #40 instruments. Postoperative RVG pictures were taken ensuring the preoperative positioning. The working time was measured in seconds during each preparation. The authors also assessed the remaining root canal wall thickness at 3, 6 and 9 mm from the radiological apex, comparing the width of the canal walls of the vestibulo-oral projections on pre- and postoperative RVG pictures both mesially and buccally. The ratios of the residual and preoperative root canal wall thickness were calculated and compared. The largest difference was found at the MB canals of the coronal and middle third level of the root, measured on the distal canal wall. The ratio of the remaining dentin wall thickness at the coronal and the middle level in the case of step-back preparation was 0.605 and 0.754, and 0.824 and 0.895 in the cases of GT files respectively. The preparation time needed for GT Rotary File System was altogether 68.7% (MB) and 52.5% (D/P canals) of corresponding step-back preparation times. The use of GT Rotary File with comparison of standard step-back method resulted in a shortened preparation time and excessive damage of the coronal part of the root canal could be avoided.

[Cavity micro-morphology following caries removal]

The objective of this research was to observe the effect of different caries removal techniques on human dentin topography. Thirty-six dentin samples of bisected carious human molars were treated with six different caries removal techniques, replicated and then examined by using a scanning electron microscope. The surfaces were observed before and after the smear layer removal at a magnification of 200- and 1000-fold. At a magnification of 200 the sono-abraded samples showed a significantly more undulated dentin topography than samples treated with other techniques. Using Carisolv hand instruments for caries removal resulted both at a magnification of 200 and 1000 in a significantly rougher, flakier and more fissured dentin surface texture compared to other techniques. Microcracks were observed in samples from all excavation methods but most frequently when treated with Carisolv hand instruments. The excavation process results in a dentin topography marked by smooth, flaky and fissured surface textures as well as by microcracks. The relative incidence in which these textures occur may indicate whether the removed dentin was rather cut or fractured.

Chemical analysis and surface morphology of enamel and dentin following 9.6mu CO2 laser irradiation versus high speed drilling

OBJECTIVES

The purpose of the present in vitro study was to determine whether there is a change in the chemical composition and surface morphology of enamel and dentin following 9.6mu CO2 laser irradiation and high-speed drilling.

MATERIALS AND METHODS

Ten permanent, non-carious, young premolars, extracted for orthodontic reasons, were selected. The crowns were separated longitudinally into two equal parts at their mesiodistal axis. Two areas on the inner enamel surface of each specimen and two on the dentinal surface were selected. A high-speed drill and 9.6mu CO2 laser irradiation were applied to the selected enamel and dentinal areas. A random area on the unlased enamel and on the unlased dentin of each specimen served as controls. The morphology of the specimens was evaluated using scanning electron microscopy. Calcium, phosphorus and oxygen levels were measured using an energy dispersive spectrometer.

RESULTS

Mineral analysis revealed no significant difference in the mineral content of the enamel and dentin after laser irradiation or high speed drilling versus the control. Use of the high-speed drill on enamel and dentin resulted in very clear cavity margins, with characteristic grooves, whereas laser irradiation of enamel and dentin did not produce clear margins and the floor of the cavity displayed an irregular surface.

CONCLUSIONS

The 9.6mu CO2 laser appears to be a promising tool in the clinical setting. However, further investigation is indicated to ensure maximum effectiveness.

Resin bond strength and micromorphology of human teeth prepared with an Erbium:YAG laser

PURPOSE

To evaluate the in vitro effect of the Er:YAG laser and high-speed rotary instrumentation on the bond strength of resin composite to human enamel and dentin, and determine which conditioner, either phosphoric acid or a self-etching primer, resulted in higher bond strengths with either of the surface treatments.

METHODS

48 third molars were used. Dentin and enamel specimens were sectioned and polished with 600-grit SiC paper and treated either with carbide bur or an Erbium:YAG laser and treated with one of three different conditions, acid-etch/bonding agent (Scotchbond Multi-Purpose Plus), no etching and same bonding agent, and an experimental self-etching primer (EXL 547). After storage for 48 hours at 37 degrees C and 100% humidity, specimens were prepared in an hourglass shape for microtensile bond test (ca. 1 mm2) and debonded in tension. Areas were measured and bond strengths were calculated for each specimen. Failure modes, micromorphology of surface treatments and bonding interfaces of representative specimens from acid-etched and self-etched groups were analyzed with scanning electron microscopy. Means were compared using three-way analysis of variance, and Scheffé post-hoc test (P < 0.05) was used to determine differences among surface treatments, tooth substrate and conditioners.

RESULTS

Dentin prepared with the carbide bur and treated with phosphoric acid followed by the application of Scotchbond Multi-Purpose had the highest bond strengths (35.7 MPa). Enamel and dentin prepared with the Er:YAG laser had the highest bond strengths when the surfaces were acid-etched followed by Scotchbond Multi-Purpose (25.8-21.1 MPa). Carbide bur exhibited higher bond strengths than laser with the use of the experimental self-etching primer but laser showed higher bond strengths than the bur with the use of Scotchbond Multi-Purpose and no etching. The predominant failure mode of most of the treatment conditions was partially adhesive between the bonding resin and enamel or dentin, and partially cohesive within the bonding resin. SEM analysis revealed the absence of a smear layer on laser-treated teeth when compared to untreated control and bur-cut teeth.

Influence of the use of Er:YAG laser for cavity preparation and surface treatment in microleakage of resin-modified glass ionomer restorations

This study quantitatively assessed the amount of microleakage on Class V cavities prepared by Er:YAG laser and high-speed handpiece, varying the surface treatment and restoring with a resin-modified glass ionomer cement. Fifty cavities were prepared using either an Er:YAG laser device or a carbide bur at high speed. The surface treatment was performed as follows: Er:YAG laser irradiation (G1); 40% polyacrylic acid (G2); laser + acid (G3); finishing with low speed + laser + acid (G4); conventional bur preparation + acid (G5-control). The samples were restored with Fuji II LC, thermocycled, isolated and immersed in a 50% AgNO3 solution. The restorations were serially sectioned and the extent of dye penetration was measured in milimeters using specific computer software. Data were analyzed by two-way ANOVA and Tukey test. The lowest degree of microleakage was observed for G5, which was statistically similar (p>0.05) to G4 but different (p<0.05) from all the other experiental groups. Lesser microleakage was observed at the occlusal margins than at the cervical margins (p<0.05). It may be concluded that the use of Er:YAG laser for cavity preparation and surface treatment negatively affected the marginal sealing of resin-modified glass ionomer restorations.

Handpiece speed and postoperative outcomes in third molar surgery

OBJECTIVE

This study was performed to assess surgical outcomes when externally irrigated slow-speed surgical handpieces (30,000 rpm) were compared to externally irrigated high-speed handpieces (90,000 rpm) in the removal of impacted lower third molar teeth.

STUDY DESIGN

One hundred patients with bilater ally impacted third molar s were enrolled in the study; 53 remained to completion. Each patient served as his/her own control. The experimental side was treated using a 30,000 rpm electric rotary drill incorporating irrigation, while the control side was treated using the same drill system, but with a 90,000 rpm handpiece. Drill speeds used were alternated between the right and left sides of patients to avoid bias introduced by the dominant hand of the surgeon. Patients were blinded to drill speed, and were asked to complete a standardized pain/swelling questionnaire for seven days immediately following surgery. Data was analyzed to determine differences in pain, swelling, and complications in relation to the drill type used.

RESULTS

No statistically significant differences were found in degree of pain, swelling, or complications when the slower drill was compared to the high-speed instrument.

CONCLUSIONS

The study suggests that there is no difference in postoperative outcome when impacted third molar teeth are removed with either slow- or high-speed instrumentation, and that the choice of the drill type should be determined solely by the preference of the operator.

Comparative Study of Carious Dentin Removal by Er,Cr:YSGG Laser and Carisolv

OBJECTIVE

The present study aimed to compare carious dentin removal by air turbine, Carisolv and erbium,chromium:yttrium,scandium,gallium,garnet (Er,Cr:YSGG) laser, and examine morphological changes before and after these caries removal techniques under light microscopy and scanning electron microscopy (SEM).

BACKGROUND DATA

Although there have been numerous studies on removing caries by Er,Cr:YSGG laser, none has compared Er,Cr:YSGG laser and Carisolv, or reported on the usage of DIAGNOdent as a diagnostic tool particularly for advanced caries in in vitro experiments.

MATERIALS AND METHODS

Sixty extracted human teeth diagnosed as advanced caries were divided into three groups based on the treatment received, namely air turbine, Carisolv, and Er,Cr:YSGG laser groups. Each group was sub-divided into two in order to examine the results with or without finishing using nylon brush, 15% ethylene diamine tetraacetic acid (EDTA) or low-power laser, respectively. After evaluation by DIAGNOdent, specimens were observed under light microscopy or SEM.

RESULTS

Light microscopic observations varied considerably in the three treatment groups. SEM revealed that the surfaces treated by air turbine were very smooth, but with substantial debris. The Carisolv group exhibited a very rough surface with a thick smear layer, while the Er,Cr:YSGG group demonstrated smooth undulations with little smear layer and debris. Among the finishing techniques, the laser group demonstrated the best efficiency. DIAGNOdent scores supported the results of light microscopy.

CONCLUSION

These results suggest that caries removal by Er,Cr:YSGG laser is very effective even without finishing and DIAGNOdent is useful for diagnosing advanced caries in in vitro experiments.

Displacement amplitude of ultrasonic scaler inserts

OBJECTIVES

Scanning laser vibrometry is a noninvasive method of measuring the velocity, displacement amplitude and oscillation frequency of vibrating objects. The purpose of this study was to assess, using a scanning laser vibrometer (SLV), the performance of different designs of commercially available ultrasonic scaler generators by measuring the oscillatory characteristics of various scaler tips.

METHODS

Four ultrasonic generators were tested (Cavitron SPS and Cavitron Select (Dentsply, York, PA, USA) and Piezon Master 400 and Mini Piezon (Electro-Medical Systems, Switzerland)) with various designs of scaler tip. The tips were positioned with their anterior surface perpendicular to the direction of the laser. A graduated scale, placed over the manufacturer's power dial, enabled incremental power setting selection. For each power setting, the laser beam from the SLV was scanned over the surface of the oscillating tip.

RESULTS

The ranges of longitudinal displacement amplitudes (in micrometres) were as follows: Mini Piezon (P-tip): 12.90+/-1.44 to 44.03+/-7.80; Piezon Master 400 (P-tip): 16.02+/-2.66 to 35.85+/-5.29; Cavitron SPS (TFI-10 tip): 7.81+/-0.51 to 29.70+/-1.12; Cavitron Select (TFI-10 tip): 13.13+/-1.44 to 33.77+/-4.27; Cavitron SPS (TFI-3 tip): 5.50+/-0.46 to 31.35+/-3.62.

CONCLUSIONS

This study shows that there are differences between commercially available generators and that tip movement varies between tips of the same style as well as between the generator and tip design. Users of ultrasonic scalers should be made aware of this inherent variability that may influence clinical procedures.

Safety and efficiency of novel sonic scaler tips in vitro

BACKGROUND

The aim of the study was to evaluate a novel sonic scaler tip for subgingival root surface instrumentation combining high efficiency in calculus removal with minimized risk of root damage through subgingival debridement.

METHODS

A metal sonic scaler tip with a paddle-like working end covered with spheroid convexities of 0.8 mm diameter and 0.3 mm height was designed from the aspect of optimized adaptation to the root anatomy (tip-end dimension: 3.0 x 1.5 x 0.6 mm). Using a customary sonic scaler tip as control, instrument efficiency was quantified by measuring the time needed to completely remove calculus on extracted teeth (n=52) under standardized conditions. To quantify the amount of calculus removed, the mean calculus area per tooth was measured on photographs taken before instrumentation. The tips safety was evaluated instrumenting calculus-free root surfaces in vitro (n=18, lateral forces 0.5, 1, 2 N, 20 s instrumentation time, tip angulation 0 degrees ) with subsequent laser-optical determination of resulting root substance loss.

RESULTS

Debridement efficiency was significantly higher for the novel tip (0.78+/-0.81 mm2/s completely debrided) than for the conventional tip (0.42+/-0.33 mm2) (Mann-Whitney test, p<0.05). Concerning instrument safety, the novel tip caused significantly less root substance loss than the conventional tip.

CONCLUSION

The novel scaler tip appears to be significantly more efficient in calculus removal and less damaging to the root surface than the assessed conventional tip.

A pilot investigation of enamel reduction procedures

OBJECTIVE

To test and describe the use of various combinations of mechanical and chemical techniques for enamel reduction to obtain a smooth surface.

METHODS

Bovine teeth (2 surfaces on each of 32 teeth) were used. The teeth were mounted in blocks of dental plaster, which were then mounted in a vise. The mesiodistal enamel contact areas were reduced by various combinations of mechanical and chemical aids. The mesiodistal width of each tooth was measured with a digital caliper after initial reduction of the enamel surface and again after polishing. The teeth were subsequently prepared and mounted for scanning electron microscopy.

RESULTS

All combinations yielded statistically significant enamel reduction (p < 0.05). The use of acid stripping in conjunction with mechanical procedures produced especially smooth enamel surfaces.

CONCLUSIONS

Steps must be taken to ensure that a smooth enamel surface remains after enamel reduction and polishing. It is recommended that conventional enamel etchants be added to the polishing procedure. Enamel reduction can increase available space, but the quantity of enamel that can be removed without adverse consequences should be carefully evaluated.

Methicillin-resistant Staphylococcus aureus and infection control for restorative dental treatment in nursing homes

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in nursing home residents now averages 20-35%. This includes both numerous asymptomatic mostly unidentified carriers, and the occasional patient with an active infection. Among the most common sites for positive MRSA colonization are the nares and mouth (saliva). Ohio State University (OSU) dental students perform routine restorative dental care onsite in local nursing homes using portable equipment including handpieces that can generate aerosols. Using a series of cultured test swabs and plates, this pilot study suggests that protection for both dental health care personnel and patients are provided by the following: 1. universal barrier precautions (for example, gloves, gowns, masks, hats, facial shields, glasses), 2. surface disinfectants, 3. pre-op 0.12% chlorhexidene mouth rinses, 4. high volume evacuation, 5. perioral skin scrubs. Additional infection control methods, techniques and equipment were evaluated and compared including rubber dam isolation, hand excavation and bond technique, high-speed air turbine and electric "high" speed handpiece. There was no indication of a special tendency or heightened ability of MRSA to aerosolize.

Using chemomechanically assisted diamond bur cutting for improved efficiency

BACKGROUND

Surface active agents added to handpiece coolants enhance bur cutting rates, or CRs, through chemomechanical effects, or CMEs. The authors evaluate the effect of CMEs on long-term cutting by diamond burs.

METHODS

The authors tested medium-grit diamonds in a high-speed handpiece under a 147.5-gram load at 350,000 revolutions per minute, with 22 milliliters per minute coolant flow consisting of distilled water or a 1:10 mouthwash/water mixture. Repeated 6-millimeter-long edge cuts were made through machinable glass ceramic bars until the CR (determined as the time to transect the bars) had decreased by more than 75 percent. The authors used six burs for each coolant and analyzed the data via one-way analysis of variance with post hoc Scheffé tests.

RESULTS

CRs with water irrigation continuously decreased with the number of cuts and declined by 87 percent over eight cuts. The authors found faster CRs with CMEs; after 12 cuts, the CR was still close to 40 percent of the initial CR, compared with only 13 percent of the initial CR for water irrigation after eight cuts. These differences between CME-enhanced CRs and those found with water irrigation were statistically significant.

CONCLUSIONS

Diluted alcohol- and glycerol-based mouthwash/water mixtures significantly enhanced the CRs of diamond burs and prolonged their service life by more than 50 percent compared with water irrigation alone.

CLINICAL IMPLICATIONS

Dentists can increase bur CRs and extend bur cutting life by as much as 200 percent through the addition of diluted alcohol and glycerol mouthwash to the handpiece coolant.

Heat generation during implant drilling: the significance of motor speed

PURPOSE

The purpose of this study was to measure the heat generated from 3 drilling speeds (1,225, 1,667, and 2,500 rpm) using the armamentarium of 4 implant systems.

MATERIALS AND METHODS

The mean rise in temperature, the time of drilling, and the time needed for pig jaw bone to return to the baseline temperature were monitored using 4 thermocouple technology.

RESULTS

The mean rise in temperature, the time of drilling, and the time needed for the specimens to return to the baseline temperature were lower at 2,500 rpm than at 1,667 or 1,225 rpm (P < or =.05), regardless of the system used. The rpm also directly correlated to the amount of time the bone remained at an elevated temperature.

CONCLUSION

From a heat generation standpoint, we conclude that preparing an implant site at 2500 rpm could decrease the risk of osseous damage, which may affect the initial healing of dental implants. This may decrease the devital zone adjacent to an implant after surgery and be most advantageous in immediate load application to dental implants.

Changes in dentin after insertion of self-threading titanium pins with 3 methods: a scanning electron microscope pilot study

STATEMENT OF PROBLEM

Inserting a self-threading pin can cause dentinal cracks, but it is not known whether dentin bonding agents can penetrate these cracks.

PURPOSE

Part I of this in vitro pilot study was conducted to document the presence of dentinal cracks after the placement of self-threading pins with 3 methods. Part II was conducted to observe changes in dentin when a dentin bonding agent was applied before insertion of the self-threading pins.

MATERIAL AND METHODS

The crowns of 14 noncarious third molars were sectioned horizontally 2 mm above the cemento-enamel junction, and the occlusal portions were discarded. The teeth were put into a nontransparent bag and divided randomly into 2 groups. Group 1 consisted of 12 teeth. In each tooth, 4 pinholes were prepared with a handpiece at normal rotation speed (30,000 rpm). Self-threading pins were placed into 3 of the pinholes in each tooth: 1 manually, 1 by handpiece at 7000 rpm, and 1 by handpiece at 30,000 rpm. The fourth pinhole was left empty and served as the control. All group 1 teeth were sectioned vertically through the pins, dental hard tissue, and control pin holes. The examination surface of each specimen in group 1 was polished, and the smear layer was removed with Calcinase and NaOCl solutions. After dehydration in ascending grades of alcohol, specimens were coated with a 10- to 15-nm-thick layer of gold and examined with a scanning electron microscope. In the remaining 2 teeth (group 2), a dentin bonding agent was introduced into the pinholes prior to pin placement. Two pins were placed manually and 2 by handpiece at 30,000 rpm. After pin placement, sectioning, cleaning, and dehydration, the specimens were examined with a scanning electron microscope, and x-ray mapping was performed to determine the presence of titanium, silicon, and calcium.

RESULTS

Craze lines in dentin were associated with 54.5% of pins placed manually and 54.5% of pins placed with a handpiece at reduced speed (7000 rpm). Dentinal cracks were associated with 50% of pins placed with a handpiece at standard speed and with 16.7% of the control pinholes. X-ray mapping analysis revealed the presence of the dentin bonding agent between the pin and dentin wall. The dentin bonding agent was not found in the dentinal cracks except at the crack orifice.

SUMMARY

Within the limitations of this pilot study, the method of pin insertion had no direct bearing on the presence of dentinal cracks. The dentin bonding agent tested did not fill the entire space of dentinal cracks but did occlude their orifices and fill the spaces between pin surface and dentin walls in the pin preparation.

Comparison of distortion and separation utilizing profile and Pow-R nickel-titanium rotary files

The purpose of this study was to determine whether there was a difference in the frequency of file distortion and separation between nickel-titanium (Ni-Ti) ProFile 0.04 ISO taper rotary files and Ni-Ti Pow-R 0.04 ISO taper rotary files. For this study, 60 mesial root canals in 30 human mandibular first molars were chosen with the curvature angle of the mesiobuccal and mesiolingual canals of the same tooth within five degrees. ProFile and Pow-R files were randomly assigned to either the mesiobuccal or mesiolingual canal of the same tooth. Instrumentation proceeded per the manufacturer's recommendations, in a crown-down technique, using Gates Glidden burs and rotary files in sizes #50 to #20. Positive and negative controls were used. The instruments were evaluated for signs of distortion or separation by three independent evaluators using magnification under microscope. A total of 420 files were evaluated, 210 files for Pow-R and 210 files for ProFile. There was no statistically significant difference in the incidence of instrument distortion or separation between the two file systems that were studied.

Cyclic fatigue of nickel-titanium rotary instruments after clinical use with low- and high-torque endodontic motors

This study investigated the cyclic fatigue resistance of used nickel-titanium rotary instruments, clinically operated by a traditional high-torque motor and a new low-torque electric motor. Fifty instruments (ProFile, Maillefer, Baillagues, Switzerland) for each of the following sizes were used: .06-25, .06-20, and .04-25. They were divided into three groups: A = 10 new instruments (control), B = 20 used instruments operated by a high-torque motor, and C = 20 used instruments operated by a low-torque motor. Each instrument was used in 10 clinical cases (at least six molars). Cyclic fatigue testing of new and used instruments was performed with a device that allowed the instruments to rotate freely inside a stainless-steel artificial canal at 350 rpm. Data were recorded and statistically analyzed. Mean (and SD) numbers of rotation-to-breakage cycles for .06-25, .06-20, and .04-25 instruments were, respectively: group A 463 (85), 535 (101), and 613 (105); group B 229 (64), 343 (92), and 233 (84); and group C 352 (77), 454 (89), and 466 (86). Results showed that group A instruments exhibited significantly higher values of rotation-to-breakage cycles (two-sample t test, p < 0.01), when compared with groups B and C, respectively. Statistically higher resistance to cyclic fatigue was noted for group C in all sizes compared with group B (two-sample t test, p < 0.01), showing that the use of endodontic motor with lower torque values reduced cyclic fatigue of nickel-titanium rotary instruments.

Defects in GT rotary instruments after use: an SEM study

Used rotary nickel-titanium instruments require frequent replacement. This laboratory study evaluated defects of GT Rotary instruments before and after usage. The instruments were fixed into custom-made holders and photographed in an SEM at x 260 to x 12,000 magnification at preset points. Instrument sizes 20 with 1.0, 0.8, and 0.6 taper and instrument sizes 35 with 1.2 taper were used in 12 canals. The used instruments were cleaned and then reexamined in an SEM as before. The presence of 11 types of conditions was scored from the pre- and postusage photographs. No instruments fracturing or plastic deformation was observed during the test. The presence of debris, pitting, and scraping changed significantly. Imperfections were found on used GT Rotary instruments and the presence of defects (pitting, scraping, and blunt-cutting edges) increased in all of the instruments. The behavior of GT Rotary instruments with usage seems to be different, compared with that found in other instruments.

Effects of mechanical and thermal fatigue on dental drill performance

Osseous integration of dental implants depends on the use of proper surgical technique during site preparation, including the prevention of thermal injury to the surrounding bone. Heat generation during drilling has been reported to positively correlate with the production of forces at the surgical site. In this study, peak torque and axial load levels were measured during a drilling procedure into a polymeric material simulating the human mandible. Axial rotary milling was performed using 5 different twist drill designs (3i Irrigated Tri-Spade, 3i Disposable, Nobel-Biocare, Straumann, and Lifecore) of 15 to 20 mm in length and 2 to 2.3 mm in diameter, at a free-running rotational speed of 1,500 rpm and continuous feed rate of 3.5 mm/second, to a total depth of 10.5 mm. Ten drills representing each of the 5 types (n = 50) were subjected to 30 individual drill "pecks" and heat-sterilized every 3 "pecks" to determine the effects of cyclic mechanical and thermal loading on drill performance. Normal stress (sigma) and shear stress (tau) were calculated from the kinetic data and drill geometries. A drill efficiency coefficient (mu) was also calculated as the ratio of torsional resistance to translational resistance. Overall, the hypotheses of drill performance dependency on drill type as well as mechanical and thermal accumulated loading were tested and confirmed (P < .05). The 5 drill types produced a range of normal stresses (2.54 to 5.00 MPa), shear stresses (9.69 to 29.71 MPa), and efficiency (1.16 to 3.16) during repeated testing. Scanning electron microscopic images revealed minor deformations in the cutting edges of the tri-spade drills following testing.

Microleakage of class V resin composite restorations after bur, air-abrasion or Er:YAG laser preparation

This in vitro study compared the microleakage of Class V resin composite restorations placed in cavities prepared with a high-speed dental bur, air-abrasion or Er:YAG laser. Twenty sound extracted human third molars were selected and randomly assigned to four equal Groups (n=10): Group I, cavities were cut by dental drill at high-speed; Group II, aluminum oxide air-abrasion was used for cavity preparation, and in Groups III and IV, cavities were prepared by Er:YAG laser. Following cavity preparation, Groups I and II were acid-etched, Group III was treated only by Er:YAG laser and Group IV was conditioned by Er:YAG laser followed by acid-etching. Cavities were restored (Single Bond + Z-100) and the teeth stored for seven days in distilled water. Then, the restorations were polished and the specimens thermocycled, immersed in a 0.2% Rhodamine solution, sectioned and analyzed for leakage at the occlusal (enamel) and cervical (dentin/cementum) interfaces using an optical microscope connected to a video camera. The images were digitized and software was utilized for microleakage assessment. Upon analyzing the results, statistically significant differences (p<0.01) between the occlusal and cervical regions for all groups was observed, and, as a rule, there was better marginal sealing at the enamel margins. The highest degree of infiltration was observed for cavities prepared and treated exclusively by Er:YAG (Group III). The other experimental groups showed statistical similarities in the amount of marginal leakage at the enamel margins. However, at the cervical margins, there was a significant difference (p<0.05) between Group I and the remaining groups. None of the techniques completely eliminated marginal microleakage at the dentin/ cementum margins.

A reconstructed computerized tomographic comparison of Ni-Ti rotary GT files versus traditional instruments in canals shaped by novice operators

AIM

The aim of this study was to compare the effects of preparation with conventional stainless steel Flexofiles and Gates Glidden burs versus nickel-titanium GT rotary files in the shaping of mesial root canals of extracted mandibular molars.

METHODOLOGY

A total of 54 canals from 27 mesial roots of mandibular molar teeth were prepared using one of two methods by novice dental students. One canal in each root was prepared by a crown-down approach. utilizing stainless steel Flexofiles and Gates Glidden burs. The other canal was prepared using nickel-titanium GT rotary files in a crown-down fashion as recommended by the manufacturer. Preoperative CT scans of each root were recorded and 50 canal specimens were available for postoperative comparisons. Following canal shaping, postoperative scans were superimposed on the original images. Changes in canal area, canal transportation and thickness of remaining root structure at strategic levels of the root were analyzed. The time taken for each method was also noted.

RESULTS

At the coronal and mid-root coronal one-third sections, the rotary GT files produced a significantly smaller postoperative canal area (P < 0.05). In the mid-root sections there was significantly less transportation of the root canal toward the furcation, and less thinning of the root structure with GT files compared to the stainless steel files (P < 0.05). Overall, there was greater conservation of structure coronally and more adequate shape in the mid-root level. The GT rotary technique was significantly faster than the stainless steel hand-held file technique (P < 0.0001). Two GT instruments fractured during the study.

CONCLUSIONS

Under the conditions of this study, novice dental students were able to prepare curved root canals with Ni-Ti GT rotary files with less transportation and greater conservation of tooth structure, compared to canals prepared with hand instruments. The rotary technique was significantly faster.

Influence of structure on nickel-titanium endodontic instruments failure

The purpose of this work was to investigate the process history on fracture life of nickel-titanium endodontics files. The results are based on microstructural investigations of nickel-titanium engine-driven rotary instruments based on X-ray diffraction, scanning electron microscopy, and microhardness tests. Endodontic files are very work-hardened, and there is a high density of defects in the alloy that can disturb the phase transformation. The microhardness Vickers confirmed these observations (dislocations and precipitates). The X-rays show that experimental spectrum lines are extended, typical of a distorted lattice. The surface state of the endodontic files (scanning electron microscopy) is an important factor in failure and fracture initiation.

Apical extrusion of debris and irrigants using two hand and three engine-driven instrumentation techniques

AIM

To evaluate the weight of debris and irrigant volume extruded apically from extracted teeth in vitro after endodontic instrumentation using the balanced force technique, a hybrid hand instrumentation technique, and three engine-driven techniques utilizing nickel-titanium instruments (ProFile .04, Quantec 2000 and Pow-R).

METHODOLOGY

Five groups of 20 extracted human teeth with single canals were instrumented using one or other of five techniques: balanced force, hybrid, Quantec 2000, ProFile .04, or Pow-R. Debris extruded from the apical foramen during instrumentation were collected into preweighed 1.5 mL tubes. Following instrumentation, the volume of extruded irrigant fluid was determined by visual comparison to control centrifuge tubes filled with 0.25 mL increments of distilled water. The weight of dry extruded dentine debris was also established.

RESULTS

Overall, the engine-driven techniques extruded less debris than the manual ones. However, there was no statistical difference between the balanced force technique and the engine-driven methods. The volume of irrigant extruded through the apex was directly associated with the weight of extruded debris, except within the ProFile group. The hybrid technique was associated with the greatest extrusion of both debris and irrigant.

CONCLUSIONS

Overall, the engine-driven nickel-titanium systems were associated with less apical extrusion.

Cyclic fatigue of ProFile rotary instruments after prolonged clinical use

AIM

The purpose of the present study was to evaluate resistance to cyclic fatigue of new and used ProFile Ni-Ti rotary instruments.

METHODOLOGY

Used instruments were operated in 10 clinical cases using passive instrumentation and a crown-down preparation technique. Cyclic fatigue testing of new and used engine-driven instruments was then performed with a specific device which allowed the instruments to rotate freely inside a stainless steel artificial canal, whilst maintaining conditions close to the clinical situation. Instruments were rotated until fracture occurred and time to fracture was visually recorded with a chronometer.

RESULTS

A significant reduction of rotation time to breakage (life span) was noted between new and used instruments. In all sizes new instruments were significantly more resistant than used ones (two-sample t-test, P < 0.01). No instrument underwent intracanal failure during clinical use.

CONCLUSIONS

Prolonged clinical use of Ni-Ti engine-driven instruments significantly reduced their cyclic fatigue resistance. Nevertheless, each rotary instrument was successfully operated in up to 10 clinical cases without any intracanal failure.

Clinical evaluation of a new technique for interdental enamel reduction

In orthodontics, reduction of tooth-size by grinding interproximal surfaces (stripping) of teeth is a common procedure. In order to achieve perfectly smooth surfaces, clinicians have carefully tested various methods and progressively improved this therapeutic procedure. In this in-vivo study we used scanning electron microscopy (SEM) to evaluate the morphologic effect of a 3-step technique using an oscillating perforated diamond-coated disc for enamel reduction and 2 Sof-Lex XT discs for polishing. This technique was applied in 32 patients with an average age of 15.5 years. A total of 296 interproximal surfaces was treated and replicas were produced for scanning electron microscopy evaluation. The scanning electron microscopy investigations demonstrated that more than 90% of the reproximated surfaces were very well or well polished, resulting in polished enamel surfaces smoother than untreated enamel. This technique proved to be clinically expedient as it finished each interproximal surface within about 2.2 minutes. At the same time, it was demonstrated to be safe and comfortable for the patient, eliminating the need for lip or cheek protectors and making injuries unlikely.

Clinical evaluation of chemomechanical caries removal in primary molars and its acceptance by patients

The purpose of this study was to evaluate the clinical efficiency and patient acceptance of the chemomechanical caries removal agent Carisolvtrade mark in deciduous teeth. Contralateral primary molars of sixteen 7- to 9-year-old patients (32 teeth) were treated with the air-motor and with Carisolv, respectively. Patients replied to a pre- and a postoperative questionnaire. Complete caries removal (CCR) was accomplished in all air-motor sessions. It was not achieved within the time limit of 15 min in 6 (37.5%) Carisolv sessions. Air-motor CCR time ranged between 6 and 18 s (mean: 11.81 s ). Carisolv CCR time, where accomplished within 15 min, ranged between 6 min 46 s and 13 min 57 s (mean: 6 min 51 s). Preoperatively, the majority of the children reported disliking the drilling, and that they would visit the dentist more often and prefer sitting in the chair longer if they could avoid it. Postoperatively, the majority of the children reported disliking the taste of Carisolv, estimated Carisolv to have taken longer, would not recommend it to their friends, and preferred the air-motor. In conclusion, Carisolv, although a step forward in terms of solution volume required, is not in a position to replace rotary instruments for caries removal: it did not remove decay completely in one third of our sample; it was much slower than the air-motor; it had a chlorine taste/odor our patients disliked.

Effects of rotary instrumentation and different etchants on removal of smear layer on human dentin

STATEMENT OF PROBLEM

Various methods of rotary preparation and conditioning of teeth affect surface topography and may affect the retention of dental restorations.

PURPOSE

This study microscopically evaluated dentin surfaces prepared by different rotary instruments and etched using several types of acid etchants that have been deemed suitable dentin conditioners.

MATERIAL AND METHODS

Occlusal surfaces of 35 extracted human molars were ground wet with 320-grit silicon carbide paper to the depth of the central groove and then prepared with diamond (n = 5) and finishing burs (n = 30). Five specimens from each group were used for SEM evaluation of mechanical preparation effects. Dentin specimens (n = 5) prepared with finishing burs were then etched with 1 of 5 etchants (25% polyacrylic acid, 10% phosphoric acid, 10% citric acid, 20% lactic acid, or 32% phosphoric acid) for 10 seconds. Specimens were critical-point dried and freeze fractured for SEM analysis.

RESULTS

Diamond rotary instruments created more undulating surfaces than finishing burs. Fine grooves were observed running perpendicular to undulations and parallel to the direction of instrument rotation. Specimens prepared with finishing burs exhibited a smooth surface interrupted by only a slight granularity. The amorphous smear layer was partially removed after the application of 25% polyacrylic acid (pH 1.53), but all dentinal tubules contained plugs. The number of dentin tubules containing plug material and the amount of material in the tubules decreased noticeably with 10% phosphoric acid (pH 0.86), and the dentin surface had an appearance similar to the specimen etched with 10% citric acid (pH 1.70). The surfaces treated with 20% lactic acid (pH 1.40) produced a clearly etched surface with minimal demineralization. Etching of dentin with 32% phosphoric acid (pH 0.16) revealed significant changes in dentin with the evidence of increased tubule diameter.

CONCLUSION

Differences related to the method of instrumentation were found in the surface characteristics of dentin. The degree of smear layer removal was related to the pH of the acid etchant.

Cutting efficiency of three diamond bur grit sizes

BACKGROUND

Tooth preparation requires safe, efficient and rapid cutting, and diamond burs routinely are used for extracoronal preparation and gross tooth reduction. Coarser-grit diamond burs often are used for gross tooth reduction, with tooth surface finishes being sacrificed for the presumed greater cutting rates, or CRs, of the coarser diamond burs. The authors compared the CRs of medium-, coarse- and super-coarse-grit diamond burs.

METHODS

The authors used a self-contained dental treatment system with digitally controlled handpiece speed, torque and water flow rate to cut a machinable glass ceramic cutting substrate with medium-, coarse- and super-coarse-grit diamond burs from the same manufacturer under a load of 147.5 grams (0.9 kilonewton at the bur tip) and a coolant flow rate of 22 milliliters per minute. They made three cuts through 13-millimeter bars of the cutting substrate with six diamond burs of each grit size. They determined CRs as the transection time per millimeter and analyzed CR data by one-way analysis of variance and post hoc Scheffé tests.

RESULTS

The authors found no statistically significant difference in CR (P > .05) between the three diamond bur grit sizes for the first (13 mm) cuts. When they compared the three cuts (39 mm total cut length), they found no difference (P > .05) between CRs for coarse- and super-coarse-grit diamond burs, but they did find that the super-coarse-grit diamond burs cut faster than the medium-grit diamond burs (P < .01).

CONCLUSION

Differences in CR for the three diamond bur grit sizes are due to the greater decrease in CR for the medium-grit diamond burs (50 percent) compared with the CRs of the coarse- and super-coarse-grit diamond burs (35 percent and 25 percent, respectively) over the total cutting period.

CLINICAL IMPLICATIONS

Coarser-grit diamond burs may be useful for extensive gross tooth preparations, but dental professionals should be aware of the associated effects of the coarser grit on surface finish, heat generation and enamel damage.