Factors involved in microbial colonization of oral prostheses.

The presence of biofilm or denture plaque on the tissue contacting the (intaglio) surface of a denture is a major etiologic factor in the pathogenesis of both denture stomatitis and inflammatory papillary hyperplasia. This article reviews the literature concerning the various factors that contribute to the development of denture plaque and its colonization by Candida albicans and other microorganisms.

The effect of mucine, IgA, urea, and lysozyme on the corrosion behavior of various non-precious dental alloys and pure titanium in artificial saliva.

The corrosion of dental alloys has biological, functional, and aesthetic consequences. Various studies have shown that protein solutions can inhibit the corrosion of alloys. This study is planned to determine the relationship of organic constituents of saliva and the corrosion of dental alloys. The organic constituents are IgA, mucine, urea, and lysozyme which are encountered in the highest amounts in saliva and the dental materials are titanium (Ti), Co-Cr-Mo and Ni-Cr-Mo alloys, and dental amalgam, the most often used metallic components in dentistry. In particular, the interactions between the commonest salivary proteins, IgA, mucine, urea and lysozyme, and Ti, Co-Cr-Mo, Ni-Cr-Mo and dental amalgam were investigated. Each alloy was evaluated by cyclic polarization in each medium. The general anodic and cathodic behavior during forward and reverse cycles, the corrosion and passivation current densities (muA/cm2 ), and the corrosion and the pitting potentials (mV) were determined. The results have shown that Ni-Cr-Mo and dental amalgam alloys are highly susceptible to corrosion in all the investigated media. The Co-Cr-Mo alloy has shown high passive current densities in the solution of mucine and lysozyme in artificial saliva. Titanium instead, has shown a high resistance to corrosion and a stable passive behavior in all media, especially in a solution of mucine and IgA in synthetic saliva. Mucine and IgA, as well as urea and lysozyme, appeared to enhance the formation of a passive film layer on the Ti metal surface, thus inhibiting the corrosion. Based on the study findings, and especially considering the problem of nickel allergy and toxicity of mercury released from dental amalgam, the use of Co-Cr-Mo alloys and Ti to Ni-Cr-Mo alloys is recommended and alternatives to dental amalgam should be sought for patients with impaired salivary flow.

The effect of a mouthrinse containing essential oils on dental restorative materials.

Mouthrinses that contain essential oils are effective for controlling plaque and periodontal disease. Recent studies have shown that such mouthrinses are effective at preventing the formation of biofilm in dental unit waterlines. However, there is no information in the literature regarding the effect of such mouthrinses on restorative materials used within the oral cavity. Specimens of three common restorative materials (a glass ionomer, a composite resin, and amalgam) were subjected to continuous exposure to Listerine and distilled water for 10 days; at that time, the strength, fluid sorption, and surface appearance of the specimens were compared. Specimens of the test materials also were placed in intraoral devices; volunteer patients wore these devices for 12 hours per day for a period of 10 days. During that time, the patients were instructed to rinse twice daily for 30 seconds with Listerine Cool Mint or a non-active mouthrinse. After 10 days, the specimens were salvaged from the devices and inspected by visible and SEM examination. This study indicates that routine use of mouthrinses containing essential oils (or even prolonged exposure to such mouthrinses) has no adverse effects on restorative materials that might be expected to react to such mixtures because of their chemical compositions. It was concluded that active mouthrinses do not appear to have any adverse effects on a variety of restorative biomaterials.

Resin-based sealing of root canals in endodontic therapy.

This study evaluated the effect of the obturation technique on leakage, which may be the primary cause of failure in endodontic treatment. The apical seal and leakage behavior of teeth obturated with a resin-based sealer and gutta-percha alternative were compared to conventionally obturated teeth. Sound premolars (N = 10) were instrumented and treated by conventional root canal obturation. A second group (N = 10) was treated with the Resilon-Epiphany system and the remaining 10 roots were divided into two groups (N = 5) and obturated without sealer. A detector electrode was placed coronally in each root in contact with the obturation system and sealed in place and the apices were left patent. The teeth were immersed in 0.9% sodium chloride with a stainless steel counter electrode. A 20V potential was connected between the stainless steel and each tooth in turn with current flow determined by voltage drop across a standard resistor. Leakage was followed for 30 days and statistically analyzed for differences between groups. All teeth in Groups 1, 3A, and 38 (p > 0.05) leaked at 30 days. In Group 2, four roots showed no leakage, five roots showed minimal leakage, and one root exhibited a leakage current at a greater magnitude than the others in the group. A significant difference (p < 0.005) was found between Groups 1 and 2 but not between Group 1 and Groups 3A and 3B (p > 0.05) or between Group 2 and Groups 3A and 3B.

The effect of base/liner use on restoration leakage.

Central to the success of a restoration is the quality of the restoration-dentin interfacial seal; any compromise of the seal can lead to secondary or recurrent decay. Class V restorations have a high leakage propensity and this study evaluates the effect of base/liner placement on leakage behavior. Class V intracoronal half enamel/half dentin preparations (3.0 x 2.0 x 2.0 mm) were cut in four groups (n = 10) of extracted human teeth with a new bur used for each cavity preparation. All teeth were single-rooted, single-canal anterior teeth. Base/liner usage differed between each group. The first group of teeth had no liner or base, while a liner was placed in the second group of teeth prior to conditioning and restoration. A base was placed in the third group of cavity preparations and both the base and liner were placed in the fourth group. After preparation, a small diameter bare-end PVC-insulated copper wire was inserted within the root canal of each tooth from the apex to firm contact with the pulp chamber roof. The tooth-wire interface and root surface was sealed and leakage was followed electrochemically for 35 days in 0.9% NaCl solution. All of the teeth leaked to some degree; however, teeth that were restored without liner or base demonstrated the smallest amount of leakage. The greatest leakage was noted in teeth restored with both a base and a liner; teeth restored with only a base showed greater leakage than those restored with only a liner. The findings indicate that the presence of a base and/or a liner results in greater leakage compared with intracoronal Class V preparations that were conditioned and restored only. The data suggest that placing both a base and a liner increases restoration leakage significantly.

Effect of a dental unit waterline treatment solution on composite-dentin shear bond strengths.

OBJECTIVE: The control of biofilm and effluent contamination of dental unit water lines (DUWL) includes additions of antimicrobial solutions, as well as automatic dosing units. There are, however, varying reports on the effects of such agents on the bond strength of restorative dental materials and, particularly, between these agents and dental hard tissues. METHODOLOGY: The possible effects of an antimicrobial DUWL treatment solution on the adhesion of composite resin to dentin was evaluated by shear bond strength (SBS) testing. A total of 20 caries-free human molar and premolar teeth were used as the test substrates. The teeth were divided into two sets of 10 teeth which, after appropriate cleaning with water and pumice, were embedded horizontally in dental die stone. The buccal surface of each tooth was ground flat to a 17 microns finish using water-lubricated SiC paper. The teeth were then etched for 15 seconds with 37% H3PO4 and rinsed with either water (control) or a proprietary DUWL treatment (ICX) solution. Thereafter, the teeth were lightly blown dry with clean dry air, and the dentin conditioned with Prime & Bond NT for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. A second group of 20 caries-free human molar and premolar teeth were used as test substrates to evaluate the effect of the ICX DUWL treatment solution on a different dentin priming system (OptiBond Solo Plus). The teeth in the second group were divided into two sets and after a 15 second etch with 37% H3PO4, were rinsed with water (control) or the proprietary ICX DUWL treatment solution. Thereafter, the teeth were lightly blown dry with clean, dry air and the dentin conditioned with OptiBond Solo for 20 seconds. The excess solvent was then removed by gentle air drying for 5 seconds, and the conditioner cured with visible light for 10 seconds. A cylinder of composite was placed on the conditioned surface and cured. Shear bond strength testing was performed with a universal test machine at the default cross-head speed of 0.1 mm/min. A set of teeth, sectioned, mounted and etched as above but rinsed with a 0.01% mineral oil/water mix prior to conditioning and bonding, was used as the negative control. A separate corrosion testing was performed by immersing brass coupons in water and ICX for 31 days and measuring the weight loss. The brass coupons were bright-dipped, electroless nickel-plated and bright nickel electroplated. RESULTS: The bonding studies indicated that the DUWL treatment solution applied to a cut and etched dentin surface prior to conditioning and bonding with an adhesive system has no effect (p > 0.05) on bond strength for either group of specimens, compared to water. Negative control specimens were found to have minimal bond strengths. The corrosion study indicated no difference in the behavior of the test specimens in ICX compared to those in water, although differences were noted between the different surface finishes applied to the brass substrate. CONCLUSION: The findings of this study demonstrate that exposure of an etched dentin surface to a water-based DUWL treatment mixture has no adverse effects on subsequent adhesion strength. Minimal corrosive attack was noted in the ICX solution and water for brass coupons provided with three different surface finishes.

The role of cavity preparation and conditioning in the leakage of restorations.

PURPOSE: Restoration microleakage is thought to be determined by the method and location of cavity preparation, enamel etching, and dentin conditioning, as well as the restorative material. This study compared the microleakage of composite restorations placed in preparations cut with carbide and diamond burs and those treated with different bonding/conditioning agents. MATERIALS AND METHODS: Class V preparations (3 x 2 x 2 mm) were cut wholly in enamel or in enamel and cementum in 100 human premolars. Twenty teeth were prepared with carbide burs and the preparations etched and conditioned with Prime&Bond NT but not restored. A second set of 20 teeth had enamel-only preparations cut with carbides (n = 10) or diamonds (n = 10), and the preparations etched, conditioned (Prime&Bond NT) and restored with Prisma TPH. The other 60 teeth were divided into 3 groups of 20 teeth each with enamel-only (n = 10) or enamel/cementum preparations (n = 10). The 3 groups of teeth were conditioned with Optibond Solo, Clearfil SE Bond or Prompt-L-Pop prior to restoration with Prisma TPH. Two mm of root was resected from all teeth, pulpal tissue removed, and insulated copper wires inserted via the root canals to contact with the pulp chamber roof before the tooth-wire interfaces and root surfaces were sealed. The teeth were immersed in 0.9% NaCl and leakage assessed over 30 d by iR drop across a resistor in series with a DC source and stainless-steel counter electrode. RESULTS: Differences (p < 0.05) in leakage were found for enamel preparations cut with carbides and diamonds, and the relationship of leakage vs time was linear. Enamel/cementum preparations showed greater leakage, and the relationship of leakage vs time was sigmoidal. Conditioned-only preparations showed the same leakage as those conditioned and restored, while preparation leakage varied with the conditioning agent. CONCLUSION: Cavity preparation location, method of cutting, and the conditioning agent markedly affect leakage behavior.

Effect of a dental unit waterline additive on resin bond strengths.

The literature indicates that the addition of an antimicrobial mouthrinse to self-contained water systems in dental units will control biofilm and effluent contamination; however, reports have varied concerning the possible effects of such agents on adhesive dentistry bond strengths. This study evaluated shear bond strengths and the potential effects of a mouthrinse containing essential oils on cut tooth surfaces by grinding flat the buccal surface of extracted human teeth. Seven groups consisting of five teeth each were etched with 37% H3PO4 solution and rinsed with water or different dilutions of the mouthrinse. Each tooth was blotted dry before a film of adhesive resin was applied to the surface and photocured. A cylinder of composite was placed on the surface and photocured. Shear bond strength testing was performed using a universal test machine. The cut tooth surfaces were ground (using water or the test mouthrinse mixtures as coolant) and evaluated by scanning electron microscopy.

Effect of light source and time on the polymerization of resin cement through ceramic veneers.

PURPOSE: The purpose of this study was to evaluate the efficiency of 3 different light sources to polymerize a light curing resin cement beneath 3 types of porcelain veneer materials. MATERIALS AND METHODS: A conventional halogen light, a plasma arc light, and a high intensity halogen light were used to polymerize resin cement (Variolink II; Ivoclar North America Inc, Amherst, NY) through disks of veneer materials. Equal diameter and thickness disks of feldspathic porcelain (Ceramco II; Ceramco Inc, Burlington, NJ), pressable ceramic (IPS Empress; Ivoclar North America Inc), and aluminous porcelain (Vitadur Alpha; Vident Inc, Brea, CA) were used as an interface between the curing light tips and the light polymerized resin cement. The resin cement/veneer combinations were exposed to 4 different photopolymerization time protocols of 5 seconds, 10 seconds, 15 seconds, and 20 seconds for high intensity light units (Apollo 95E [Dental Medical Diagnostic Systems Inc, Westlake Village, CA] and Kreativ 2000 [Kreativ Inc, San Diego, CA]), and 20 seconds, 40 seconds, 60 seconds, and 80 seconds for conventional halogen light (Optilux; Demetron Research Inc, Danbury, CT). A surface hardness test (Knoop indenter) was used to determine the level of photopolymerization of the resin through the ceramic materials with each of the light sources. The data were analyzed by one-way analysis of variance and a post-hoc Scheffe test (p < .05). RESULTS: The data indicates that the Variolink II Knoop Hardness Number values vary with the light source, the veneer material, and the polymerization time. For a given light and veneer material, Knoop Hardness Number increases with longer polymerization times. The Kreativ light showed statistically significant differences (p < .05) between all test polymerization times. Use of this light required a polymerization time of greater than 20 seconds to reach maximum resin cement hardness. For samples polymerized with the Apollo light, there were statistically significant (p < .05) differences in surface hardness between samples polymerized at all times, except for the 15-second and 20-second times. Samples polymerized with the halogen light showed no statistically significant (p < .05) differences in hardness between polymerization times of 60 seconds and 80 seconds. CONCLUSIONS: High intensity curing lights achieve adequate polymerization of resin cements through veneers in a markedly shorter time period than the conventional halogen light. However, the data in this report indicate that a minimum exposure time of 15 seconds with the Kreativ light and 10 seconds with the Apollo 95E light should be used to polymerize the Variolink II resin, regardless of the composition of the veneer. Conventional halogen lights required a correspondingly greater polymerization time of 60 seconds.

Irrigation rates and handpieces used in prosthodontic and operative dentistry: results of a survey of North American dental school teaching.

PURPOSE: A data baseline on dental cutting methodologies was established by means of a survey of North American dental school teaching. MATERIALS AND METHODS: Sixty-four North American dental schools were surveyed regarding their recommendations on handpiece usage and coolant flow rates in fixed prosthodontics and operative dentistry. RESULTS: High-speed handpieces were the instruments of choice for tooth preparation in fixed prosthodontics. In operative procedures, recommendations for sole use of the high-speed, the low-speed, or both handpiece types were more uniform. CONCLUSIONS: North American dental schools advocate greater use of high-speed than low-speed handpieces. Although the use of high-speed handpieces predominate in schools in Canada and Puerto Rico, there is a proportionately higher use of low-speed handpieces than in US dental schools. Few (approximately 1 in 5) schools made recommendations on coolant flow rates during cutting procedures.

Enhanced dental cutting through chemomechanical effects.

BACKGROUND: Previous studies have shown that certain surface-active agents--compounds that reduce interfacial tension--in a dental handpiece's irrigation water can enhance cutting rates, or CRs. This study evaluated these effects under test conditions simulating dental practice. METHODS: The authors used a self-contained cutting system with a digitally controlled handpiece speed, torque and water flow rate to cut machinable glass ceramic (Macor, Corning Inc.) with medium-grit diamond burs and cross-cut fissure carbide burs under a load of 147.5 grams and 22 milliliters per minute coolant flow rate using water with mouthwash (Scope, Procter & Gamble) additions. They used six burs for each irrigant mixture to make three 5-millimeter edge cuts through 13 mm of Macor; CRs were quantified as the time necessary to transect the Macor cutting substrate. RESULTS: Additions of small amounts of mouthwash to the coolant water accelerated the CR for both carbide and diamond burs. The CRs for carbide burs in millimeters per second were distilled water, 0.21; 1:2.5 mouthwash:distilled water mixture, 0.12; 1:5 mixture, 0.64; and 1:10 mixture, 0.66. The CR differences for the 1:5 and 1:10 mixtures were significant (P < .001). The CRs for diamond burs in millimeters per second were distilled water, 0.09; 1:1 mouthwash:distilled water mixture, 0.13; 1:2.5 mixture, 0.16; 1:5 mixture, 0.21; and 1:10 mixture, 0.18. When it came to the diamond burs, the CR differences between water and the mouthwash:distilled water mixtures were significant (P < .001). The authors found that the mouthwash additions ensured higher CRs compared with those for water alone over the entire cutting regimen; that is, while the CRs for both carbide and diamond burs dropped with prolonged cutting with water irrigation, the addition of mouthwash resulted in the burs' cutting faster and for longer than with water alone. CONCLUSION: Adding small amounts of mouthwash to the coolant water significantly enhanced cutting by diamond and carbide burs and maintained higher CRs with prolonged cutting. CLINICAL IMPLICATIONS: Making low additions of mouthwash (1:5 and 1:10 mouthwash:distilled water mixtures) to the handpiece irrigant system can lead to two- to threefold increase in the dental diamond and carbide bur cutting rate compared with that for water alone.

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.

The effect of tooth preparation on microleakage behavior.

Many factors contribute to the microleakage of a restoration. One of the more important is the method of cavity preparation. This study compared the microleakage behavior of composite restorations placed in cavities prepared by different techniques. It also compared and correlated the microleakage data produced by an electrochemical vs a staining technique. Class V cavities were prepared in 48 premolars by four techniques: (1) tungsten carbide bur in a high-speed handpiece followed by acid etching; (2) air abrasion (27 microns Al2O3) followed by acid etching; (3) air abrasion (50 microns Al2O3) and (4) air abrasion (27 microns Al2O3), with n = 12 in each group. All teeth were restored with Prime and Bond 2.1 and Tetric Flow, then thermocycled between 5 degrees and 55 degrees C for 5000 cycles with a one minute dwell at each temperature. After thermocycling, a PVC-covered Cu wire was inserted apically into the pulp chamber of each tooth and sealed into position. Leakage was continuously followed by a conductimetric method for 75 days. The teeth then were immersed in 50% AgNO3 for two hours, rinsed in distilled water for 60 seconds, then placed in a rapid photographic developer solution for two hours, followed by rinsing and sectioning for microscopic examination. Electrochemical data were examined by ANOVA and Newman-Keuls multiple comparison tests, while Kruskal-Wallis and Rank Sum Difference tests were used on the staining evaluations. Spearman's rho test was used to correlate the two test techniques. Electrochemical data for cavities prepared with a bur or air abrasion followed by acid etching prior to restoration showed significantly less (p < or = 0.05) microleakage (mean leakage currents of 1.89 & 1.57 microA, respectively) than teeth prepared with air abrasion alone (mean leakage currents of 3.60 & 3.40 microA, respectively). Rank sum AgNO3 staining data (196 & 242 vs 371 & 368) supported these findings. The correlation between the electrochemical and staining data was significant (p < or = 0.05) for all four groups of test specimens.

Handpiece coolant flow rates and dental cutting.

High-speed handpieces incorporate water coolant sprays to remove cutting debris and minimize thermal insult to the pulp. Little data exists on optimal coolant flow rates during clinical procedures. This study compared the effect of different coolant flow rates on diamond stone cutting efficiency. Cutting studies were performed on Macor machinable ceramic using a previously developed test regimen--a KaVo high-speed handpiece at a cutting force of 91.5 g (0.9 N). Cutting was performed with round end tapered medium grit diamond stones under cooling water flow rates of 15, 20, 25, 30 and 44 ml/min, with cutting rates determined as the time to transect the 13 mm square cross-section of the Macor bar. Each bur was used for five cuts, with six burs used for each flow rate, for a total of 150 measurements. The data were analyzed by one-way ANOVA with a post hoc Scheffé test. The cutting studies indicated that diamond stone cutting rates increased with higher coolant flow rates over the range of 15-44 ml/min. The data suggest that higher coolant flow rates promote cutting efficiency.

Evaluation of the slope of the articular eminence and the transverse angle of the glenoid fossa in an Anatolian population.

The purpose of this study was to compare a computer-aided method specially programmed for the measurement of the posterior angle of the articular eminence with formerly used methods, to investigate the angulation differences at different depths of slices, and to evaluate correlation with the transverse angulation. Three slices (central, medial, and lateral) at various depths of the glenoid fossa belonging to 64 dry skulls and two measurement methods were used in this study. The angulation of the articular eminence were measured and the transverse angle of each fossa calculated. No statistical difference was found between the articular eminence results of the two methods. According to the results, the one factor ANOVA central slice was found to be statistically steeper than the other two slices (p < 0.05) (central = 60.33 +/- 10.19, medial = 58.26 +/- 8.6, lateral 58.28 +/- 10.1). No correlation was found between the transverse angle of the inclination of the posterior slope angulation. It was concluded that the computer-aided method is more reliable and accurate and is much easier to use when compared to the manual method. An additional important finding of this study is that the inclination of the articular eminence should be evaluated at various depths of the temporomandibular joint.

The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study.

AIM: The purpose of this study was to evaluate the effects of smear layer and canal instrumentation on leakage in root-filled teeth. METHODOLOGY: Six groups (n = 12) of freshly extracted human canines and premolars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand files. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove the smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl, then obturated with AH-26 sealer and either the lateral condensation (Groups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth and, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connected between each tooth and a stainless steel electrode. The current flow in the circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Range Test were used to compare Groups A-F at time intervals of 10, 20, 30 and 45 days and identify statistically significant differences. RESULTS: Significantly less microleakage occurred when the smear layer was removed and when the canals were obturated with thermoplasticized gutta-percha. Canals instrumented with engine-driven NiTi files exhibited less leakage than hand-instrumented canals irrespective of obturation method. CONCLUSIONS: Smear layer removal is beneficial to root canal sealing. Obturation with thermoplasticized gutta-percha provides a superior seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals.

Flow characteristics and sealing ability of fissure sealants.

This study evaluated the relationship between fissure sealant viscosity, leakage prevention and the incidence of void formation of five commercially available pit-and-fissure sealants. Seventy-two intact, caries free human pre-molars and molars were divided into six test groups of 12 teeth each. All teeth were cleaned with a flour of pumice prophylaxis followed by etching for 60 seconds with 37% H3PO4, rinsing for 30 seconds and drying with oil-free air. Five commercial, light-cured fissure sealants and an unfilled version of one sealant were applied following manufacturers' instructions. Teeth were thermal cycled for 5000 cycles from 5-50 degrees C with a one-minute dwell time at each temperature. Silver nitrate staining followed by mesiodistal sectioning was performed. Leakage and void formation were evaluated at X50 optical magnification. Viscosity was assessed by syringing the fissure sealants into short pipettes, allowing free flow for 30 seconds and then light curing for one minute. The length of unfilled capillary was measured with a Vernier gauge. All experimental data was subjected to a one-way ANOVA, and where differences were detected, they were identified by a post hoc Tukey hsd test at a priori alpha = 0.05. Based on the conditions of the study, viscosity and flow characteristics had no effect on sealing ability or void formation.

Dental cutting with diamond burs: heavy-handed or light-touch?

PURPOSE: The cutting efficiency of diamond dental burs using different handpiece loads was evaluated against simulated enamel, a machinable glass ceramic (Macor). MATERIALS AND METHODS: An ultra-high-speed dental handpiece was mounted in a frictionless bearing so that the pressure applied at the contact interface between the dental bur and the cutting substrate was controlled. One type of coarse- and two types of medium-grit diamond burs were studied. Handpiece loads of 44, 91.5, and 183 g were applied at the bur/Macor interface, and cutting efficiency was determined as the amount of Macor removed in ten 30-second-duration cuts that were 4 mm in length. The data were analyzed by one-way ANOVA and a post-hoc Scheffé test at an a priori alpha = 0.05. RESULTS: Cutting efficiency depended on both the diamond grit of the bur and the load applied to the handpiece. CONCLUSIONS: The pressure used by most dentists, about 100 g at the bur tip, appears to be optimal for medium-grit burs. If the pressure applied to the handpiece is markedly increased, there was no increase in cutting efficiency for medium-grit burs. In contrast, an increased handpiece pressure raises the cutting efficiency of coarse-grit burs but the effect of this enhanced rate of cutting on the pulpal tissues is uncertain. Cutting efficiency also appeared to be dependent on debris accumulation between the diamond chips.

Irrigating solution and pressure effects on tooth sectioning with surgical burs.

OBJECTIVE: The purpose of this study was to determine the influence of the applied load on the handpiece, type of cooling agent, and type of tooth on surgical tooth dissection with a tapered crosscut fissure bur. STUDY DESIGN: Cutting studies were performed at handpiece loadings of 295 and 590 g through use of an oral surgery straight handpiece, tapered crosscut fissure burs, and an established cutting regimen. Extracted molars were dissected under irrigation with water, 0.9% saline solution, and lactated Ringer's solution at constant flow rates of 15 and 25 mL/min. Cutting efficiencies were analyzed by 1-way analysis of variance and Scheffé tests. RESULTS: No difference in cutting efficiency was found at low loads under irrigation with water or saline solution, but under irrigation with lactated Ringer's solution, a higher cutting efficiency was found (P < .05). There was no difference in cutting efficiency for lactated Ringer's solution and saline solution at high loads, but both cut more efficiently than water (P < .01). CONCLUSIONS: Saline solution is a useful coolant/irrigant for the dissection of teeth under most conditions, but lactated Ringer's solution might be beneficial with respect to cutting efficiency when lower handpiece loads are required.

Comparison of sectioning rates among carbide and diamond burs using three casting alloys.

PURPOSE: This study compared the sectioning rates of commercially available high noble, noble, and base metal casting alloys using two new cross-cut tungsten carbides specifically manufactured for alloy sectioning and two medium grit diamond burs. MATERIALS AND METHODS: Rectangular bars cast from a base metal alloy (Ni-Cr-Mo-Be), a noble alloy (Pd-Cu-Au), and a high noble alloy (Au-Ag-Cu-Pd) were sectioned under controlled conditions. Two types of cross-cut tungsten carbide and two types of medium grit diamond burs were tested using a high-speed handpiece under a coolant flow rate of 20 mL/min and an applied load at the bur tip of 0.9 N (91.5 g). Three 4-mm cuts were made through the alloy specimens using six burs of each type. The time required for Cuts 1, 2, and 3 was recorded, and sectioning rates in millimeters per minute were calculated as a relative measure of cutting efficiency. For each alloy, the total time required for the three cuts was analyzed using one-way analysis of variance (one-way ANOVA) and Scheffé tests (alpha = 0.05) to determine differences in sectioning rate among bur types. RESULTS: In general, mean sectioning rate for Cut 1 through Cut 3 decreased with longer use of the bur. Regarding total sectioning times, the carbide burs sectioned the base metal alloy significantly faster (P < .001) than the diamond burs. However, diamond burs sectioned the high noble alloy significantly faster (P < .001) than the carbide burs. Diamond burs also sectioned the noble alloy more quickly than the carbide burs, but the difference was not statistically significant. CONCLUSIONS: The cross-cut tungsten carbide burs should be used to section the base metal alloy but the medium grit diamond burs should be used to section the high noble alloy.