Restorative dentistry productivity of senior students engaged in comprehensive care.

In dental education, various clinical delivery models are used to educate dental students. The quantitative and qualitative measures used to assess the outcomes of these models are varied. Georgia Health Sciences University College of Dental Medicine has adopted a version of a general dentistry comprehensive care dental education hybrid model. Outcome assessments were developed to evaluate the effectiveness of this delivery model. The aim of this study was to compare the number of restorative procedures performed by senior dental students under a discipline-based model versus senior student productivity engaged in comprehensive care as part of a hybrid model. The rate of senior students' productivity in performing various restorative procedures was tracked over four years, and a comparison was made. In the first two years, the seniors operated in a discipline-based model, while in the last two years the seniors operated in a comprehensive care hybrid model. The results showed that there was a significant increase in productivity by the students in terms of direct and indirect restorations. This increase in productivity may indicate that the comprehensive care model may be a more productive model, thereby enhancing clinical experiences for the students, improving operating efficiency for the schools, and ultimately increasing clinical income.

Practical fluoride and remineralization protocols for adult patients.

There is a wealth of information on preventive measures and procedures that can be used to care for paediatric and adolescent patients. However, few studies have been conducted in adult or geriatric populations, and an understanding of preventive and non-surgical treatment regimens for these patients is lacking. Traditionally, caries incidence is high among risk groups of low income, low dental IQ and certain ethnic subgroups, but we are now witnessing a high incidence of caries among middle-income and healthy adult patients with an imbalance of protective factors and cariogenic factors. We will direct our attention to the adult population and attempt to address some of the most common questions.

Shedding new light on composite polymerization.

Life usually gets simpler, but in the case of photocuring dental restorative materials, just the opposite is true. Confusing and contradictory barrages of clinical claims have been made with the ever-growing variety of light-curing sources available today. Often, laboratory research or clinical studies related to these systems are lacking prior to their being introduced to the market, leaving the clinician to become the "testing ground." Manufacturers prefer to market the newest technology available, yet, depending on the type of practice and composite system in use, such "state-of-the-art" devices may offer no advantage. For some clinicians, changing to a "fast cure" composite in combination with a traditional QTH light, instead of purchasing a $4,000 PAC light, may be the only improvement in efficiency needed. However, others may want to spend as little time as possible per procedure and do not mind investing in the newest, yet "unproven" technology. Either way, today's clinician needs to be wary of the many claims made by manufacturers of all light-curing units. It is prudent that the clinician, prior to selecting a device, aggressively ask questions and dig for the truth before "buying into" a particular unit or system philosophy. At stake are the durability of restorations, the satisfaction of patient and the well-earned reputation of the operator.

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. Purpose. This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). RESULTS: For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. PURPOSE: This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: . Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). Results. For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Tray delivery of potassium nitrate-fluoride to reduce bleaching sensitivity.

OBJECTIVE: Tooth sensitivity is a common side effect associated with tooth whitening. The purpose of this study was to determine if bleaching tray delivery of potassium nitrate-fluoride reduces bleaching sensitivity enough to allow continuation of whitening treatment. METHOD AND MATERIALS: Thirty patients were enrolled in a university-approved clinical study and had their teeth bleached at night with 10% carbamide peroxide in a custom-fitted tray. The bleaching tray was a rigid experimental design for which sensitivity was expected. If tooth sensitivity was experienced, the patient applied a gel containing 5% potassium nitrate and 1,000 ppm sodium fluoride in the bleaching tray for various time periods. Log forms were collected upon completion of bleaching, and patient interviews were used to compare effects of the gel before and after sensitivity treatment. RESULTS: Sixteen out of 30 patients experienced tooth sensitivity. Of those 16 patients, 12 used the gel, and 11 of the 12 reported a reduction in sensitivity. Treatment times ranged from 10 minutes before bleaching to 30 minutes before and after. The number of applications ranged from one to continuous use. Some patients were able to continue bleaching after one gel application with no subsequent sensitivity. Other patients were unable to continue bleaching unless they continued using the gel. The incidence of tooth sensitivity (53%) reported in this study is consistent with sensitivity reported in studies using semi-rigid custom-fitted trays made from stone casts with a nonscalloped, nonreservoir design. CONCLUSION: The use of a 5% potassium nitrate-fluoride gel applied in the tray as needed for tooth sensitivity associated with nightguard vital bleaching can reduce sensitivity in a majority of patients and allow most patients to continue bleaching to completion.

Effect of dentin desensitizers and cementing agents on retention of full crowns using standardized crown preparations.

STATEMENT OF PROBLEM: Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. PURPOSE: This research controlled crown preparation surface area and evaluated the effect of various dentin desensitizers and conventional cementing agents on the in vitro retentive strength of cast crowns. METHODS AND MATERIAL: Freshly extracted human molars were prepared for a standardized crown preparation (26 degrees total convergence, 4 mm axial height) with a custom-made pantograph. Dentin desensitizers included none (control), a polymerizable material (All-Bond 2), and a nonpolymerizable desensitizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck's), glass ionomer (Ketac-Cem), resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test condition (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative humidity using a universal testing machine at a crosshead speed of 1.27 mm/min. The proportion of cement retained on the tooth and casting after debonding was quantified according to treatment. Statistical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05.Results. Resin cement exhibited the highest retentive strength and all dentin treatments resulted in significantly different retentive values (All-Bond 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma (4.12 +/- 0.37 MPa)). Retention of resin-modified glass ionomer was between the resin cement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.81 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer values were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0. 20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 MPa). Zinc phosphate had the lowest retention values: control (1.68 +/- 0. 08 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The majority of cement was retained on the debonded tooth surface versus the casting, with the exception of zinc phosphate when used with dentin pretreatments. CONCLUSION: Controlled crown surface areas reduced the variation in strength values permitting high discrimination among retention values of desensitizer/cement combinations. In all but 1 combination, Gluma desensitizer significantly decreased crown retention. With resin cement and resin-modified glass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.

Carbamide peroxide whitening of nonvital single discolored teeth: case reports.

Patients who present with a single discolored tooth represent a significant restorative challenge. These case reports describe an economic and conservative treatment option for these patients. The situations presented demonstrate techniques for bleaching with carbamide peroxide in a traditional nightguard or with an inside-outside technique to achieve acceptable esthetic results on isolated nonvital discolored teeth. Although these techniques may not be effective in all cases, they do not compromise or eliminate any future treatment options.

Novel approach to measure composite conversion kinetics during exposure with stepped or continuous light-curing.

PURPOSE: The objective of this research was to evaluate a novel approach to monitor the polymerization reaction during a light-curing exposure by using infrared (IR) spectroscopy. MATERIALS AND METHODS: An IR spectrometer was equipped to use an attenuated total reflectance (ATR) element as an IR-active substrate. The uncured composite (Herculite XRV, Shade A2, Kerr, Orange, California) was placed against the crystal, and the IR spectrum was continuously obtained during various exposure scenarios. The degree of conversion and the maximum rate of reaction were monitored at 0 mm (top surface), 1 mm, 2 mm, and 3 mm beneath the surface. The exposure conditions included continuous 40-second or 60-second exposures at 100% intensity (800 mW/cm2) or a stepped output of 10 seconds at 17% maximal output (133 mW/cm2) followed by full output for the remainder of the 40-second or 60-second exposure (Elipar Highlight, ESPE, Norristown Pennsylvania). The results were analyzed using MANOVA with appropriate post hoc tests (p < or = .05). RESULTS: For 40-second exposures, the peak conversion rates were significantly reduced (p < .05) when using the stepped exposure mode compared to the continuous exposure: 40-second top surface: stepped = 5.5%/s +/- 0.4, continuous = 10.5%/s +/- 1.0; 1 mm step = 3.6%/s +/- 0.4, continuous mode = 4.8%/s +/- 0.2. The same trend was noted when using the 60-second exposure. Equivalent conversion values (p > .05) beneath the surface between stepped and continuous exposure modes at similar depths 60 seconds after light initiation were only attained at 3 mm 4 for the 40-second exposure. However, using the 60-second exposure, equivalent conversion values between step and continuous exposure modes at similar depths were obtained. Even with a reduced conversion rate at the surface using the stepped cure mode, polymerization shrinkage forces were sufficient to debond the specimens from the test crystal after only 20 seconds into the exposure. This result indicated that stress development in the curing composite was non-uniform, and stress values developed at the surface of the restoration were the greatest. CLINICAL SIGNIFICANCE: Stepped intensity curing for the ESPE Highlight unit was shown to produce significantly lower conversion rates at the surface and at 1-mm depths, but longer exposure times were still required to provide conversion values equivalent to continuous exposure.

Factors affecting light transmission of single-use, plastic light-curing tips.

Recently, manufacturers introduced presterilized, single-use, plastic light-curing tips to be used either routinely or on patients with known or questionable communicable health concerns. The purpose of this study was to examine the effect of these single-use tips on light transmission compared to conventional fiber-optic bundles in a variety of commercial light-curing units. Also, the effects of surface contact with the plastic tips (human tissues, reflective or opaque media, and barrier films) were evaluated. Where applicable, single-use tips from two sources (Caulk/Dentsply and Demetron) were placed in commercial curing units (Optilux 150 and 500, MAX 100, Spectrum Curing Light, and 3M XL-3000), and the intensity was compared to that of the conventional glass curing tip used with that specific curing unit. Intensity readings were also made for 6 continuous minutes using plastic tips in a high-intensity curing unit to simulate veneer bonding. If the sides of the plastic tip came in contact with the operator's fingers or the patient's tongue and/or cheek during a clinical procedure, a lowering of transmitted light intensity resulted. The glow emitted from the sides of the tip when in use may be annoying to the operator. To prevent this glare, the operator may be tempted to treat the sides of the tip by painting, applying a thin polymer barrier, abrasion, or wrapping in an opaque reflective material (aluminum foil). A significant decrease in light intensity can result if plastic curing tips contact oral tissues or bare hands. Application of thin polymer barriers was found to significantly reduce light transmission value. Also, surface modification (coating with paint or surface scratches) was found to greatly reduce light intensity levels, while wrapping the tip in aluminum foil produced a very small increase. Results indicated that transmitted light intensity with use of plastic tips was dependent upon both the brand of plastic tip tested and the different photocuring units. Either a slight increase or a slight decrease in intensity was noted. Plastic tips did not degrade in transmitted intensity when exposed to the heat produced during a simulated veneering scenario. In summary, use of plastic, single-use light-curing tips can provide adequate intensity for photoactivated restorative techniques; however, the clinician must be aware of specific, clinically relevant limitations with their use. Clinicians must also note that these tips are not designed for re-use.

Assessing the effect of extraneous light on photoactivated resin composites.

The authors investigated the effect of an operatory light and ambient fluorescent illumination on the curve values of three photoactivated resin composite materials. Infrared spectroscopy was used to evaluate the specimens after they were exposed to an operatory light at a distance of 30 inches for two, five or 10 minutes as well as after a blue-blocker shield was placed between the light source and the composite. The authors also measured cure values after exposing some specimens to 10 minutes of ambient ceiling fluorescent light only. Maximal cure values were determined by conventionally photocuring specimens. After 10 minutes' exposure to the operatory light, specimens were cured at a level from 70 to 80 percent of the maximal cure resulting from conventional light curing. The blue-blocker shield reduced curing to a level equivalent to that of a 10-minute exposure to ambient fluorescent lighting, which was nearly 0 percent.

Effect of heating delay on conversion and strength of a post-cured resin composite.

Physical property enhancement in light-cured resin composites from post-cure heating is attributed to free radicals created during initial photocuring, the number of which decreases following initial light-curing. Clinically, it is important to know when the number of remaining free radicals is too low to provide for additional conversion of monomer in post-cure-heated specimens. The hypothesis tested is that the potential for additional conversion in post-cure-heated resin composite restorations is dependent upon the time after initial light-curing at which the specimen is exposed to heat treatment. This research examined the effect of delay in post-cure heating after initial photo-activation on strength and monomer conversion of a commercial resin composite material. Discs (10 x 1 mm) of Herculite XRV (Kerr/Sybron, Orange, CA) were photocured at standardized conditions. One group was left unheated, and another was subjected to post-cure heating (Brilliant DI-500, Coltène AG, Altstätten, Switzerland) at the following times after being light-cured: 5 and 30 min, and 6, 24, 48, 72, 96, and 120 hrs. After the appropriate delay time, unheated and heated specimens (n = 10) were tested for biaxial flexural strength at a constant stressing rate. Recovered, fractured strength specimens (n = 10) were analyzed for cure by means of IR spectroscopy. Post-cure heating increased strength over that of the unheated specimens only for the shortest delay times: 5 or 30 min. Thereafter, strength values were statistically equivalent (p < 0.05). Delay in heating did not significantly enhance strength of post-cure-heated specimens, but delay in time did improve strength of the unheated groups. The greatest monomer conversion was obtained when post-cure heating was applied within 6 hrs following light-curing. The difference in cure between unheated and heated specimens remained significant up to 96 hrs of delay. Flexural strength of post-cure-heated specimens remained unchanged with time delay for heating specimens. Maximal monomer conversion of post-cured specimens is obtained only within 6 hrs of light-curing. The potential for additional conversion arising from post-cure heat treatment is dependent upon the time following initial curing at which heat is applied following initial light-curing. However, delay in heat application has no influence on flexural strength.

Effect of glutaraldehyde cold sterilants on light transmission of curing tips.

This research examined the effect of immersion in glutaraldehyde-based cold sterilizing solutions on the ability of light-curing tips to transmit a standardized light intensity. Five commercial cold sterilizing solutions were selected, based on their classification: neutral (Cetylcide-G, 3.2%), acidic (Banicide, 2.0%), or alkaline (Cidex Plus, 2.5%; Cidex 7, 3.4%; and Sporicidin, 0.5%). Distilled water was used as the control. The light intensity transmitted through 24, 8-mm-diameter curing tips of similar type was determined by applying a standardized intensity (500 m W/cm2). Three tips were placed into each type of solution. The percentage of preimmersion intensity was determined at periodic intervals until all tips had received a total of 1,000 hours of immersion. After 1,000 hours' immersion, light transmission decreased significantly more in tips subjected to Cidex 7 than in tips subjected to all other treatments, which were all equivalent to the water control (an average increase of 1.5% over preimmersion values). The decrease in intensity seen with Cidex 7 averaged 49% and could not be totally recovered after use of conventional tip-polishing methods. Reduction in light levels could not be correlated with the pH of the sterilizing solutions.

The effect of autoclaving on energy transmission through light-curing tips.

The authors subjected three groups of curing lights to 25 sterilization cycles to test the effects of autoclaving on the curing tip's ability to transmit light. They also investigated whether polishing the tip at various intervals would reduce the effects of autoclaving on light transmission. They found that autoclaving does diminish the ability of the tips to transmit light, but that these effects can be minimized if the tip is polished at frequent intervals between autoclaving cycles.

Clinical guidelines for photocuring restorative resins.

Success in using light-cured resin composites relies heavily on proper curing time and intensity. Because these factors are so critical, the authors reviewed the literature to arrive at guidelines for optimal curing conditions. The guidelines emphasize maintenance of the curing lights, consideration of the type of restorative material used and duration of exposure.

Effect of restoration composition, shade, and thickness on the cure of a photoactivated resin cement.

PURPOSE: This study investigates the effect of selected properties of a restorative material (type, shade, and thickness) on the cure of a photoactivated resin cement. MATERIALS AND METHODS: Disks of ceramic and resin-based restorative materials of two extreme shades were made to provide thicknesses of 0.5 to 3.0 mm in 0.5-mm intervals. Light transmission was measured through various thicknesses and shades of each restorative material type. The effect of light transmission, as influenced by restorative material type, shade, and thickness on resin cement cure was also determined. RESULTS: Thickness and shade of restorative material had the greatest influence on light transmission. For simulated restoration thicknesses 1.5 mm and greater, Dicor (Dentsply International Inc, York, PA) had greater transmission of light than the other materials, regardless of shade. At equal restorative material thickness, light transmission was similar for identical shades of the other three materials. Restoration shade and thickness also had the greatest influence on resin cement cure. Material type, although significant, had only a minor influence. At thicknesses of 1 to 2 mm, Dicor consistently yielded greater resin cement cure values than any other material tested. CONCLUSIONS: When considering the ability of restorative materials to transmit light for curing of photo-activated resin cements, the thickness of the restoration and its shade are much more influential than the choice of restorative material. Dicor provides greater light transmission that results in the ability to photobond restorations of greater thicknesses than the other materials. For restorations greater than 1 mm in thickness, a dual cure or chemical cure resin cement should be used to provide maximal cement properties.

Provisional treatment for resin-bonded fixed partial dentures.

The resin-bonded fixed partial denture is a conservative option for the replacement of a missing tooth. It has a good prognosis and offers several advantages over a conventional fixed partial denture. However, it does not allow for placement of a provisional fixed partial denture. In some situations, it is important to provide some type of interim treatment. This can be accomplished by several techniques, that include placement of either a removable or bonded replacement tooth. The provisional treatment can provide an esthetic solution and maintain tooth position while the fixed partial denture is being made by the dental laboratory.

A predictive model for the polymerization of photo-activated resin composites.

This study investigated the relative significance of irradiation duration (20, 40, 60, or 80 seconds) and intensity; filler type (Silux Plus, a microfill or P-50, a hybrid); and shade (Universal or Gray) on the polymerization of resin composite within the depth of a simulated photopolymerized restoration. From the data, a mathematical model that predicts the extent of resin polymerization based upon the above stated variables was generated. The monomer conversion of specimens was determined by infrared spectroscopy. The results are of great clinical use and indicate that the most significant factor influencing resin composite polymerization is thickness of overlying resin composite. Both duration of exposure and light intensity demonstrate high and equal impact. Color and filler type have only minimal influence. The predictive model for resin composite polymerization provided a very good fit (r2 = .949).

Effect of light intensity and exposure duration on cure of resin composite.

Of the many factors under their control, clinicians can manipulate light-exposure duration but must deal with a set intensity of light emitted from the dental curing unit. This research investigates the interdependence of exposure duration and source intensity on resin cure at various depths within a simulated light-cured resin composite restoration. This wafers of composite were obtained from a simulated cylindrical restoration such that the wafer could be removed from the top or from a distance of 1, 2, and 3 mm beneath the surface. The composites used in this study were a microfill and hybrid of Universal and Gray shades. All the data concerning filler type and shade were pooled so that generalized statements could be made regarding curing of light-activated composite in general. Specimens were cured using various source intensities and for different durations at each level within the cured cylinder. The cure of the specimens resulting from the different treatments was determined using infrared spectroscopy. The results indicate a dramatic effect of depth on the cure of composite. At depths greater than 2 mm, poor cure results, and polymerization is very susceptible to changes in light intensity and exposure duration. From these results, routine exposure times of 60 seconds are recommended using light-source intensities of at least 400 mW/cm2 as measured with a commercial dental light intensity meter. Incremental layer thickness should not exceed 2 mm, with 1 mm being ideal. Sources with intensity values less than 233 mW/cm2 should not be used because of their poor cure characteristics.

Effect of powder/liquid ratio on physical and chemical properties of C&B Metabond.

The purpose of this study was to examine the effect of varying the powder/liquid ratio on the physical properties and the degree and rate of curing of C&B Metabond cement. The powder/liquid ratios evaluated had no effect on the tensile bond strength of Rexillium III to etched enamel or on the retention of cemented full cast crowns. The higher P/L ratio resulted in an increased vertical displacement of the cemented crowns. The rate of monomer conversion and the total conversion were not affected significantly by the different P/L ratios.