Microcomputed tomographic comparison of posterior composite resin restorative techniques: sonicated bulk fill versus incremental fill.

Sonication technology has recently been touted to decrease composite viscosity during delivery and may allow better cavity preparation adaptation and minimize voids. The purpose of this investigation was to evaluate the difference between conventional, hand-placed, incremental application of a standard hybrid resin-based composite (RBC) and sonicated application of a bulk-fill RBC in box-type and cylindrical cavity preparations. Experimental restorations were fabricated using molds of box-type or cylindrical preparations. For bulk-filled specimens, a single compule of bulk-fill composite was dispensed with a sonic handpiece. The conventional hybrid material was placed in 3 increments (2 mm, 2 mm, and 1 mm). Microfocus x-ray computed tomography was used to analyze voids for percentage and total volume porosity as well as number of actual pores. An analysis of variance indicated that RBC restorations that were applied to cylindrical cavities using a sonicated bulk-filled application method exhibited significantly less porosity (1.42%; P < 0.001) than incrementally placed cylindrical restorations (2.87%); sonicated bulk-filled, cube-shaped restorations (3.12%); and incrementally placed cube-shaped restorations (5.16%). When the groups were subcategorized into the specific characteristics of shape (cube vs cylinder) and application method (bulk vs incremental), the cylindrical group, which included both bulk-filled and incrementally placed specimens, demonstrated significantly less porosity (2.00%; P < 0.001) than other groups. Restorations that were incrementally placed into cube-shaped cavities produced the largest amount of porosity.

The stereochemistry of N-methyl and aryl substituents determine the biological activities of 3-aryl-8-methyl-8-azabicyclo[3.2.1]oct-2,3-enes.

Aryl substituted tropanes and their 2,3-ene analogs are highly selective inhibitors of monoamine uptake. The solution structures of a series of aryl tropanes were determined using NMR spectroscopy and molecular modeling to identify conformational preferences that may determine the overall activity. The majority of these analogs undergo nitrogen inversion, and the rate of interconversion between the axial and equatorial N-methyl conformers is fast on the NMR timescale at room temperature but slow between 217 and 243 K allowing us to determine the thermodynamic parameters of interconversion using dynamic and magnetization transfer NMR. The biological activities correlate strongly with the nature and the orientation of the aryl group. The relative orientation of the N-methyl further modulates the activity by directly influencing the ligand interaction in the protein binding pocket and/or by forcing a favorable orientation for the aryl substituent to fit in the binding pocket.

The impact of retained third molars on the deployed airman.

Dental emergencies can significantly affect the mission of the deployed unit. As many as 22% of all emergency department visits at a deployed Expeditionary Medical Support facility can be attributed to dental problems and many of these problems are caused by impacted third molar teeth. Currently, there is no reliable method of predicting when asymptomatic, partially erupted third molar teeth will become painful. Therefore, it is imperative that Air Force dental providers carefully consider the consequences of giving patients a clean bill of health when asymptomatic, partially erupted third molar teeth are present in the oral cavity. Recommendations for future study are presented.

Efficacy of group cognitive behavior therapy for the treatment of masticatory myofascial pain.

The purpose of this investigation was to evaluate the reduction in perceived pain in patients with myofascial pain (MFP) using a group cognitive behavior therapy (CBT) course. Twenty-six participants diagnosed as having MFP were enrolled. Each CBT session had a small-group format, where participants received instruction in habit reversal, stress management, and progressive relaxation. Participants served as their own control subjects and were surveyed for pain intensity, duration, and frequency at study enrollment, before attending the CBT course, and 2 to 3 weeks after course completion. Wilcoxon signed-rank tests revealed that changes in intensity, frequency, and duration were significant (p < 0.001 to p < 0.045). Thirty-three percent of the participants showed improvement with home care instructions before CBT course start, whereas 65% of the participants showed improvement after the CBT course. Participants attending CBT group training exhibited significant improvements in MFP intensity, frequency, and duration, compared with levels reported at the initial evaluation.

Shear bond strength of an amorphous calcium-phosphate-containing orthodontic resin cement.

INTRODUCTION: Amorphous calcium phosphate (ACP) materials have recently been introduced with the promise of reducing demineralization around orthodontic brackets. The purpose of this in vitro study was to compare the shear bond strength of orthodontic brackets bonded with enamel using a commercially available orthodontic adhesive containing ACP to that of brackets bonded with a conventional resin-based orthodontic adhesive. METHODS: Thirty extracted molars were collected. The first group of 30 brackets was bonded to either the mesiobuccal or distobuccal tooth surface with a conventional resin-based composite adhesive. The second group of 30 brackets was bonded with the ACP adhesive to the buccal cusp that was not used by the first group. Each tooth received 2 brackets; 1 bonded with a conventional resin-based composite adhesive and the other with the ACP-containing orthodontic adhesive. Specimens were stored in water at 37 degrees C for 24 hours and then tested for shear bond strength in an Instron universal testing machine. A paired t-test was used to compare the mean shear bond strength between the 2 adhesives. The ARI scores were analyzed using the chi-squared test. All statistical tests were performed at alpha =.05. RESULTS: The t-test detected a highly significant difference in the mean shear bond strength between the 2 groups (P <.001). There was no evidence to suggest a statistical difference between the groups' ARI scores (P = .37). CONCLUSIONS: Under the conditions of this in vitro study, orthodontic brackets bonded to teeth with an ACP-containing composite material failed at significantly lower forces than brackets bonded to teeth with the conventional resin-based composite orthodontic cement.

Effect of alcohol and unfilled resin in the incremental buildup of resin composite.

OBJECTIVE: The purpose of this in vitro study was to investigate the effect of isopropyl alcohol and unfilled resin on the flexural strength of incrementally layered resin-based composite beams. METHOD AND MATERIALS: Five groups of 30 composite beams were fabricated in a 2 3 2 3 24-mm Teflon split-mold: group 1 (control group), a homogeneous resin composite beam; group 2, 2 increments with an air-inhibited layer between the increments; group 3, 2 increments with a Mylar strip placed against the composite interface during polymerization of the first increment; group 4, 2 increments with the first increment contoured with an isopropyl alcohol (70%) lubricated instrument; and group 5, 2 increments with the first increment contoured with unfilled resin lubricating the application instrument. Each increment was polymerized for 40 seconds on both front and back surfaces. The flexural strength of the composite specimens was determined using 4-point bending in an Instron universal testing machine. RESULTS: The mean flexural strength in MPa and standard deviation were as follows: group 1: 142.5 (17.3); group 2: 98.2 (15.2); group 3: 105.9 (16.3); group 4: 103.4 (19.4); and group 5: 106.1 (21.3). One-way analysis of variance detected a statistically significant difference among the groups (P < .001). Tukey's HSD post hoc tests determined that only group 1 was significantly different from the other 4 groups. CONCLUSION: The use of isopropyl alcohol and unfilled resin as instrument lubricants for incremental composite buildup seems to have little effect on the flexural strength of light-cured composite.

Confocal microscope analysis of depth of etch between self-limiting and traditional etchant systems.

OBJECTIVE: To see whether there is an advantage to using a self-limiting phosphoric acid etchant versus a traditional 34% phosphoric acid etchant for bonding by measuring the depth of etch at multiple time intervals. MATERIALS AND METHODS: A total of 25 bovine teeth were mounted and etched on the facial surface with two different etchants: standard 34% phosphoric acid and a self-limiting 35% phosphoric acid etchant at varied time intervals of 15, 30, 60, 90, and 120 seconds. Teeth were scanned using a three-dimensional laser confocal scanning microscope prior to etching and scanned again after etching to determine the depth of enamel etched compared to the baseline enamel surface prior to etching. RESULTS: The 34% phosphoric acid etchant etched significantly deeper than the self-limiting etch. Etch times exceeding 30 seconds also etched significantly deeper for both types of etchant. CONCLUSION: The etch depth of the self-limiting etchant was consistently less than the standard etchant. Both types of etchant etched deeper after 30 seconds, but the depth of etch at 120 seconds was not different than at 60 seconds, indicating that both etchants are somewhat self-limiting in depth. Therefore, there is no advantage to using the self-limiting etchant.

Comparison of in-vitro bond strengths between resin-modified glass ionomer, polyacid-modified composite resin, and giomer adhesive systems.

INTRODUCTION: The purpose of this in-vitro study was to compare the shear bond strength of orthodontic brackets bonded to tooth enamel with 4 adhesives: a commercially available giomer material, a polyacid-modified composite resin (PMCR), a resin-modified glass ionomer (RMGI), and a standard resin-based composite (RBC) adhesive. MATERIALS: Eighty extracted human molars were collected and divided into 4 groups (n = 20). Two stainless steel premolar brackets were bonded to each tooth with 1 of the 4 adhesives, according to each manufacturers' instructions. One bracket was tested for shear bond strength at 1 hour and the other at 7 days. A shear force was applied to the bracket/tooth interface with a chisel-shaped rod attached to a universal testing machine at a crosshead speed of 0.5-mm per minute until bracket failure. The force in newtons was recorded. Debonded enamel surfaces were examined under a stereomicroscope to assess the amount of residual adhesive. RESULTS: A 2-factor analysis of variance detected significant differences among adhesive types and time of load test. The Tukey HSD test determined that the RBC and the RMGI adhesives had significantly higher shear bond strength than the giomer and the PMCR materials at both 1 hour and 7 days. The chi-square test detected a significant difference in adhesive remnant index scores. The bracket/resin interface was the most common site of failure for all groups except the RMGI group. CONCLUSIONS: RMGI orthodontic cement provides acceptable bond strength in vitro. Further clinical research is needed to validate this laboratory finding.

Effective single-charge end point of cordless light-emitting diode light-curing units.

INTRODUCTION: The purpose of this study was to evaluate the battery lives of cordless light-emitting diodes (LEDs) and their effect on orthodontic bracket bond strength. METHODS: One hundred eighty-six metal orthodontic brackets were bonded to extracted molars. Two LED light-curing units (L. E. Demetron [SDS/Kerr, Orange, Calif] and Ortholux [3M Unitek, Monrovia, Calif]) were evaluated. Each light was used to bond 93 specimens. One bracket was bonded every 5 minutes until the battery ran out. The lights were activated for 20 seconds, then automatically turned off for 40 seconds every minute (33% duty cycle) without recharging. Bonded specimens were stored in water at 37 degrees C for 24 hours and then subjected to shear force with a universal testing machine until bracket failure. RESULTS: Repeated measures ANOVA detected significantly weaker mean shear bond strength and fewer consecutive cures with the Ortholux compared with the L. E. Demetron light-curing unit. However, when the first 5 time points were excluded, there were no differences between the 2 lights, demonstrating that the lights performed similarly after the first 20 minutes of operation Just before battery failure, both lights still provided the same power density as at the beginning. CONCLUSIONS: Both light-curing units provided adequate power density for up to 2 hours without recharging at a 33% duty cycle. There was no significant decrease in power in cordless LED light-curing units as the battery life approached its end point.

Comparison of torsional stability of 2 types of split crimpable surgical hooks with soldered brass surgical hooks.

INTRODUCTION: The purpose of this in-vitro study was to compare the torsional stability of split crimpable surgical hooks and soldered brass surgical hooks on a rectangular stabilizing archwire. METHODS: Coated split crimpable hooks (Never-Slip Grip, TP Orthodontics, LaPorte, Ind), ribbed crimpable hooks (TP Orthodontics), and .032-in brass soldered hooks/notched electrodes (Ormco/Sybron Dental Specialties, Orange, Calif) were attached to a 0.019 x 0.025-in stainless steel archwire. The archwire/hook attachment assembly was secured into a dual contact jig and statically mounted to the base of a universal testing machine. The hooks were engaged by a wire loop attached to the upper load cell of the machine, which pulled the wire until the hook was torsionally displaced from the archwire. RESULTS: The mean forces, measured in newtons (N), required to dislodge the hooks were as follows: soldered brass surgical hooks (51.3 +/- 5.2 N), coated split crimpable hooks (49.9 +/- 6.6 N), and ribbed split crimpable hooks (31.3 +/- 5.4 N). Data were analyzed with 1-way ANOVA and Tukey HSD post-hoc tests at alpha = .05. Ribbed split crimpable hooks provided significantly less resistance to torsional displacement than the other types of hooks (P <001). There was no difference between coated split crimpable hooks and soldered brass surgical hooks (P >05). CONCLUSIONS: Under the conditions of this study, the results suggest that soldered brass surgical hooks and coated split crimpable hook attachments provide more stability to torsional dislodgement from a rectangular stabilizing archwire than ribbed split crimpable hooks.

Pain control in orthodontics using a micropulse vibration device: A randomized clinical trial.

OBJECTIVE: To investigate the relationship between a micropulse vibration device and pain perception during orthodontic treatment. MATERIALS AND METHODS: This study was a parallel group, randomized clinical trial. A total of 58 patients meeting eligibility criteria were assigned using block allocation to one of two groups: an experimental group using the vibration device or a control group (n  =  29 for each group). Patients used the device for 20 minutes daily. Patients rated pain intensity on a visual analog scale at appropriate intervals during the weeks after the separator or archwire appointment. Data were analyzed using repeated measures analysis of variance at α  =  .05. RESULTS: During the 4-month test period, significant differences between the micropulse vibration device group and the control group for overall pain (P  =  .002) and biting pain (P  =  .003) were identified. The authors observed that perceived pain was highest at the beginning of the month, following archwire adjustment. CONCLUSION: The micropulse vibration device significantly lowered the pain scores for overall pain and biting pain during the 4-month study period.

Shear bond strength and SEM evaluation of composite bonded to Er:YAG laser-prepared dentin and enamel.

OBJECTIVES: The purpose of this study was to evaluate dentin and enamel bond strength to resin composite following high-speed rotary or Er:YAG laser preparation using a total etch adhesive system. The microstructure of resin-tooth interfaces was also investigated. METHODS: Human dentin and enamel specimens were prepared with a high-speed handpiece (KaVo) or Er:YAG laser (DELight) at manufacturer's recommended settings and etched with either 37% H(3)PO(4), laser etched, or not etched. Composite rods (Z-250, 3M/ESPE) were bonded to specimens with an adhesive (Adper Scotchbond Multi-Purpose, 3M/ESPE). After thermocycling, specimens were tested in shear to failure. RESULTS: Two-factor ANOVA detected significant differences in the main effects of preparation and etch type, and interaction (p<0.001). Post hoc analyses showed that in both dentin and enamel, only the acid-etched specimens had significantly higher mean bond strengths, with rotary-prepared specimens having significantly higher mean bond strengths versus laser prepared specimens. Within each preparation type, in both dentin and enamel, acid etch was better than laser etch, and laser etch was better than no etch. Scanning electron microscopy of laser-ablated specimens demonstrated significant surface scaling and subsurface fissuring beyond normal resin penetration depth. SIGNIFICANCE: Adhesion to laser-ablated or laser-etched dentin and enamel was inferior to that of conventional rotary preparation and acid etching.

Immediate esthetic management of a catastrophically fractured anterior.

A quick, failsafe method for the esthetic replacement of a catastrophically fractured anterior tooth was presented. This method required minimal armamentarium and no anesthesia. In addition, it employed a technique that is not technique sensitive. The patient and the dental team both benefit by resolving the esthetic crisis using simple methods and excellent time resource management.

Structure-activity relationships for substrate recognition by the human dopamine transporter.

Information is available on the structure-activity relationships for dopamine as a substrate for uptake by the dopamine transporter. However, dopamine transport is a complex process involving substrate binding, translocation, release as well as transporter reorientation. The present study examines only the substrate recognition step by assessment of the potency of various dopamine-related compounds in inhibiting the binding of the cocaine analog [3H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane ([3H]WIN 35,428) to human dopamine transporters expressed in HEK-293 cells. alpha-Methylation of the side chain, the presence of the amine, and the 2-carbon-length of the side chain were found to be important for binding affinity, whereas beta-hydroxylation of the side chain and methoxylation at the phenyl ring generated weaker compounds. In addition, the presence of both m- and p-OH at the phenyl ring bestowed an increase in potency but the presence of p-OH alone a decrease. N-alkylation (propylation or methylation) had little or an even slightly beneficial effect on affinity, whereas alpha-carbonylation and alpha-methanoylation reduced affinity. Amino naphthalene compounds with a fused benzenoid ring system retained some potency consonant with the extended (i.e. beta-rotameric) trans (=anti) form of the side chain in dopamine when interacting with the transporter. In a second series of experiments, the interaction between dopamine and structural variants was assessed by monitoring the capability of a compound to shift the dopamine inhibition curve to the right as expected for a competitive inhibitor acting at the same site. Appreciable deviation from competitive interaction was observed by removal of the amine from the side chain, by alpha-carbonylation, and by alpha-methanoylation. Two blocker-type compounds, semi-rigid variants of cocaine, also displayed significant deviation. A substrate-based compound, inhibiting cocaine analog binding without interfering with dopamine recognition, could be a cocaine antagonist allowing conformational changes to occur during dopamine uptake.

A comparison of polymerization by light-emitting diode and halogen-based light-curing units.

BACKGROUND: Light-emitting diode, or LED, technology provides certain advantages over halogen-based light polymerization of resin-based composites. The authors investigated the adequacy of cure of LED light-curing units, or LCUs. METHODS: The authors used two halogen-based light-curing units (Optilux 400 and 501, Demetron Research Corp., Danbury, Conn.) and two commercially available LED LCUs (LumaCure, LumaLite, Spring Valley, Calif., and VersaLux, Centrix, Shelton, Conn.) to polymerize top surfaces of hybrid (Filtek Z-250, 3M, St. Paul, Minn.) and microfilled (Renamel, Cosmedent, Chicago) resin-based composite specimens. Specimens were indented on their top and bottom surfaces with a Knoop hardness tester and measured for hardness. Bottom:top hardness ratios determined the percentage of cure. The authors separated the data into eight groups (two composites cured with four different lights) with 15 observations per group, for a total sample size of 120. RESULTS: The authors compared composites and curing lights by a two-way analysis of variance, and results indicated significant main effects. The main effect of composite was statistically significant (P < .0001) when microfilled composite was compared with hybrid composite, regardless of curing light, for all top and bottom hardness measurements, with the hybrid producing much higher hardness measurements overall. The main effect of light was significant as well (P < .0001), regardless of composite type, with the two halogen-based lights producing harder top and bottom composite surfaces than the two LED LCUs. CONCLUSIONS: The light output of commercially available diodes for resin-based composite polymerization still requires improvement to rival the adequacy of cure of halogen-based LCUs. Additional studies are necessary. CLINICAL IMPLICATIONS: Commercially available LED LCUs were introduced just in the past year. However, they may not adequately polymerize resin-based composites, which can lead to restoration failures and adverse pulpal responses to unpolymerized monomers.

The effect of saliva contamination on enamel and dentin using a self-etching adhesive.

BACKGROUND: The authors conducted a study to evaluate the effect of saliva contamination on enamel and dentin before or after application of a self-etching adhesive. METHODS: The authors divided 120 extracted molars into enamel and dentin groups of 60 specimens each, and then further divided each group into three groups of 20 specimens each. Resin-based composite cylinders were bonded to tooth specimens that were uncontaminated (control) or were contaminated with saliva either before or after application of the adhesive and then loaded to the failure point. The authors calculated the mean shear bond strength for each group and subjected data to a one-way analysis of variance, or ANOVA, to test for differences among groups. RESULTS: Mean shear bond strength was 16.7 megapascals (+/- 3.0 standard deviation, or SD) for the dentin control group, 14.8 MPa (+/- 2.3 SD) for dentin contaminated with saliva before adhesive application, 15.9 MPa (+/- 3.8 SD) for dentin contaminated with saliva after adhesive application, 19.1 MPa (+/- 4.8 SD) for the enamel control group, 12.3 MPa (+/- 4.4 SD) for enamel contaminated with saliva before adhesive application, and 13.1 MPa (+/- 5.5 SD) for enamel contaminated with saliva after adhesive application. One-way ANOVA detected no difference in the dentin groups, but the authors found a significant difference among enamel groups. Uncontaminated enamel had higher bond strengths than either of the contaminated enamel groups. CONCLUSIONS: Saliva contamination did not affect the dentin shear bond strength of the self-etching adhesive. Saliva did have a detrimental effect on enamel bond strength. CLINICAL IMPLICATIONS: Newer generations of adhesives appear to be more tolerant of saliva contamination, but proper isolation still should be accomplished until further research proves otherwise.

Establishing proximal contacts with pre-polymerized composite inserts.

A technique of restoring Class II posterior restorations with resin-based composite and a pre-polymerized composite insert was presented. This technique is intended to aid the practitioner in obtaining tight, broad, proximal contacts without having to purchase special instruments or materials. This method is not time-consuming, nor technically difficult. Another benefit of this technique is that it reduces the total amount of volumetric shrinkage of restorative material inside the cavity preparation, as the composite insert is pre-polymerized before placement.

Surface roughness of various packable composites.

Packable composite restorations have become a popular alternative to dental amalgam restorations in posterior teeth. A drawback inherent to composites is their difficulty in polishing, which often results in a dull or rough surface. This study compared the surface roughness of a resin-based hybrid composite material and five packable resin-based composites polished with either aluminum oxide disks or a rubber polishing system. Sixteen specimens of each of the six composite materials were polished with either Sof-Lex XT disks or Enhance rubber polishers followed by fine and superfine polishing pastes. The specimens were evaluated for surface roughness using surface profilometry. Mean values were calculated for each material type and method of polishing. Data were subjected to a two-way ANOVA. Post hoc comparison was accomplished using Tukey's HSD. No significant difference in surface roughness was detected among polishing techniques (p=0.067); however, a strong trend-that aluminum oxide disks provided a smoother surface than rubber polishers in five out of six materials-was noted.

Polytetrafluoroethylene (PTFE) tape as a matrix in operative dentistry.

A method for using PTFE tape as a matrix to prevent the etching and/or bonding of adjacent tooth structure was presented. This technique is simple, quick and inexpensive. PFTE tape in the form of plumber's tape is readily available at any hardware store. Despite manufacturers' varying thicknesses of PTFE tape, it can be stretched, yielding a matrix thinner than other matrix systems. The tape will also adhere and conform to adjacent tooth structure, offering the operator an unhindered access to perform sculpting of the restorative material.

Fracture strength of amalgam crowns with repaired endodontic access.

Endodontic therapy is accessed occlusally in posterior teeth, many of which have large, pre-existing amalgam restorations. These teeth are also commonly restored with an occlusal amalgam to repair the access opening. This study determined the fracture resistance of complex amalgam restorations that have repaired endodontic access compared with original, unrepaired, complex amalgams on endodontically-treated teeth. Two groups of 30 molars were used in the study. The first group was decoronated and received an endodontic access preparation. These teeth were restored using chamber retention and four TMS pins. The second group was decoronated and restored using pin retention. Later, they received an endodontic access through the restoration. The access was then repaired with amalgam. The samples were loaded in an Instron Universal Testing Machine until failure. The Group 1 samples failed at a mean force of 2297.5 N. The mean failure load for the samples in Group 2 was 1586.1 N. Student's t-test found this difference to be statistically significant. Endodontic access through an amalgam crown significantly compromises the fracture strength of the original restoration.