Basal ganglia-spinal cord pathway that commands locomotor gait asymmetries in mice

The basal ganglia are essential for executing motor actions. How the basal ganglia engage spinal motor networks has remained elusive. Medullary Chx10 gigantocellular (Gi) neurons are required for turning gait programs, suggesting that turning gaits organized by the basal ganglia are executed via this descending pathway. Performing deep brainstem recordings of Chx10 Gi Ca2+ activity in adult mice, we show that striatal projection neurons initiate turning gaits via a dominant crossed pathway to Chx10 Gi neurons on the contralateral side. Using intersectional viral tracing and cell-type-specific modulation, we uncover the principal basal ganglia-spinal cord pathway for locomotor asymmetries in mice: basal ganglia → pontine reticular nucleus, oral part (PnO) → Chx10 Gi → spinal cord. Modulating the restricted PnO → Chx10 Gi pathway restores turning competence upon striatal damage, suggesting that dysfunction of this pathway may contribute to debilitating turning deficits observed in Parkinson's disease. Our results reveal the stratified circuit architecture underlying a critical motor program.

The association of parental dental anxiety and knowledge of caries preventive measures with psychological profiles and children's oral health

AIM

As parents and caregivers are responsible for the oral health of children, their own dental anxiety may negatively impact the oral health of their children. This study aimed to assess whether parental dental anxiety and knowledge of caries preventive measures are associated with their psychological profiles and their children's oral health.

METHODS

This case-control study involved parents, who were divided according to whether their children did or did not have active caries. The differences in Short version of the Dental Anxiety Inventory, and Knowledge of Caries Preventive Measures (KCPM) scores between the parents whose children have and do not have active caries was established by the Mann-Whitney U test (P < 0.05).

CONCLUSION

Parental dental anxiety and knowledge of caries preventive measures are associated with the oral health of their children.

In Vitro Evaluation of the Stabilization Time of Chemical Bonds During Setting Reaction and Microhardness of Preheated Glass-Ionomer Cements

OBJECTIVES

To evaluate the effect of preheating glass-ionomer cement (GIC) restorative materials on stabilization time (ST) of their metal carboxylate bonds and on microhardness.

METHODS AND MATERIALS

Two conventional highviscosity GICs, Ketac Universal (3M ESPE) and Equia Forte (GC), were evaluated. The thermographic camera was used to measure the temperature inside the glass-ionomer cement capsules before and after heating. The preheating of capsules was performed at 54°C for 30 seconds in a commercial device. Characterization of ST in the GICs was determined by Fourier Transform Infrared (FTIR) spectroscopy. For this, 10 samples of each material were prepared, five in the non-preheated group (control) and five with preheating. FTIR spectra were obtained 10 minutes after mixing (control group) or after heating and then every 10 minutes for 120 minutes. For the microhardness test, 20 cylindrical specimens (3 mm height × 6 mm diameter) were prepared for each material (10 preheated, 10 control). The microhardness was determined at three time intervals: 10 minutes after mixing, after the ST as detected through the FTIR part of the study, and after one week. Knoop microhardness was assessed using a diamond indenter with a 25 g load and 15 seconds dwell time.

RESULTS

Ketac Universal showed an increase in temperatures of 15.7°C for powder and 3.6°C for liquid, while Equia Forte showed 16.4°C for powder and 8.5°C for liquid. FTIR spectra indicated that preheating reduced the ST for Equia Forte but increased it for Ketac Universal. Preheating increased the initial microhardness (T1) of Equia Forte. With maturation over one week, it was observed that preheating significantly improved the microhardness of both materials compared with the control specimens.

CONCLUSION

Preheating influenced the ST and the microhardness of Ketac Universal and Equia Forte. The ST and microhardness of Ketac Universal increased after seven days, whereas Equia Forte showed a reduced ST and increased microhardness from the outset.

Water-dependent Interfacial Transition Zone in Resin-modified Glass-ionomer Cement/Dentin Interfaces

The function of the interfacial transition zone (absorption layer) in resin-modified glass-ionomer cements bonded to deep dentin remains obscure. This study tested the hypotheses that the absorption layer is formed only in the presence of water derived from hydrated dentin and allows for better bonding of resin-modified glass-ionomer cements to dentin. Ten percent polyacrylic acid-conditioned, hydrated, and dehydrated deep dentin specimens were bonded with 2 resin-modified glass-ionomer cements and sealed with resins to prevent environmental water gain or loss. A non-particulate absorption layer was identified over hydrated dentin only, and was clearly discernible from the hybrid layer when bonded interfaces were examined with transmission electron microscopy. This layer was relatively more resistant to dehydration stresses, and remained intact over the dentin surface after tensile testing. The absorption layer mediates better bonding of resin-modified glass-ionomer cements to deep dentin, and functions as a stress-relieving layer to reduce stresses induced by desiccation and shrinkage.

Role of carbohydrate in central fatigue: a systematic review

Carbohydrate (CHO) depletion is linked to neuromuscular fatigue during exercise. While its role at peripheral level is relatively well understood, less is known about its impact centrally. The aim of this systematic review was to critically analyze the effects of CHO on central fatigue (CF) assessed by various neurophysiological techniques. Four databases were searched using PRISMA guidelines through February 2016. The inclusion criteria were: CHO as intervention against a placebo control, fatigue induced by prolonged exercise and assessed using neurophysiological measures [voluntary activation (VA), superimposed twitch (SIT), M-wave, electromyography], alongside maximal voluntary contraction (MVC). Seven papers were reviewed, where exercise duration lasted between 115 and 180 min. CHO improved exercise performance in three studies, whereby two of them attributed it to CF via attenuation of VA and SIT reductions, while the other indicated peripheral involvement via attenuation of M-wave reduction. Although a few studies suggest that CHO attenuates CF, data on its direct effects on neurophysiological outcome measures are limited and mixed. Generally, measures employed in these studies were inadequate to conclude central contribution to fatigue. Factors including the techniques used and the lack of controls render additional confounding factors to make definitive deductions. Future studies should employ consistent techniques and appropriate neurophysiological controls to distinguish CHO effect at central level. The use of pharmacological intervention should be incorporated to elucidate involvement of central mechanisms.

Intensity-dependent alterations in the excitability of cortical and spinal projections to the knee extensors during isometric and locomotor exercise

We investigated the role of exercise intensity and associated central motor drive in determining corticomotoneuronal excitability. Ten participants performed a series of nonfatiguing (3 s) isometric single-leg knee extensions (ISO; 10-100% of maximal voluntary contractions, MVC) and cycling bouts (30-160% peak aerobic capacity, W peak). At various exercise intensities, electrical potentials were evoked in the vastus lateralis (VL) and rectus femoris (RF) via transcranial magnetic stimulation (motor-evoked potentials, MEP), and electrical stimulation of both the cervicomedullary junction (cervicomedullary evoked potentials, CMEP) and the femoral nerve (maximal M-waves, M max). Whereas M max remained unchanged in both muscles (P > 0.40), voluntary electromyographic activity (EMG) increased in an exercise intensity-dependent manner for ISO and cycling exercise in VL and RF (both P < 0.001). During ISO exercise, MEPs and CMEPs progressively increased in VL and RF until a plateau was reached at ∼ 75% MVC; further increases in contraction intensity did not cause additional changes (P > 0.35). During cycling exercise, VL-MEPs and CMEPs progressively increased by ∼ 65% until a plateau was reached at W peak. In contrast, RF MEPs and CMEPs progressively increased by ∼ 110% throughout the tested cycling intensities without the occurrence of a plateau. Furthermore, alterations in EMG below the plateau influenced corticomotoneuronal excitability similarly between exercise modalities. In both exercise modalities, the MEP-to-CMEP ratio did not change with exercise intensity (P > 0.22). In conclusion, increases in exercise intensity and EMG facilitates the corticomotoneuronal pathway similarly in isometric knee extension and locomotor exercise until a plateau occurs at a submaximal exercise intensity. This facilitation appears to be primarily mediated by increases in excitability of the motoneuron pool.

Glass-ionomer cement restorative materials: a sticky subject?

Glass-ionomer cement (GIC) materials have been in clinical use since their inception 40 years ago. They have undergone several permutations to yield different categories of these materials. Although all GICs share the same generic properties, subtle differences between commercial products may occur. They have a wide range of uses such as lining, bonding, sealing, luting or restoring a tooth. In general, GICs are useful for reasons of adhesion to tooth structure, fluoride release and being tooth-coloured although their sensitivity to moisture, inherent opacity, long-term wear and strength are not as adequate as desired. They are useful in situations where they are not disadvantaged by their comparatively lower physical properties, such as where there is adequate remaining tooth structure to support the material and where they are not subject to heavy occlusal loading. The last decade has seen the use of these materials being extended. However, they are likely to retain their specific niches of clinical application.

Expansion of nanotechnology for dentistry: effect of colloidal platinum nanoparticles on dentin adhesion mediated by 4-META/MMA-TBB

PURPOSE

To investigate the effect of Colloidal Platinum Nanoparticles (CPN) on the bond strength between dentin and 4-META/MMA-TBB resin using different concentrations of CPN.

MATERIALS AND METHODS

Twenty-five extracted human third molars were stored in 0.5% chloramine T. The occlusal dentin slices were prepared by grinding occlusal surfaces of each tooth and polishing with 600-grit silicon carbide paper under running water. One control and four experimental groups (2 specimens per group) were used as follows: a) dentin surfaces treated with 10-3 solution, followed by rinsing with water and subsequently an acrylic rod bonded with hand-mixed 4META/MMA-TBB resin (Super-Bond C&B, Sun Medical) (control); b) dentin surfaces treated with 10-3 etching solution, followed by rinsing with water and application of CPN (100% or 10%) as a primer solution for 60 s and rinsed with water for 20 s, then an acrylic rod bonded with Super-Bond C&B(Etch-CPN [100% or 10%]); c) dentin surfaces treated with CPN (100% or 10%) for 60 s, rinsed with water for 20 s, followed by application of 10-3 solution, then an acrylic rod bonded with Super-Bond C&B (CPN-Etch [100% or 10%]). After storage in 37°C water, specimens were sectioned into beams (cross-sectional area: 1 mm2) for microtensile bond strength testing at a crosshead speed of 1mm/min. The data were analyzed using the Games-Howell method (p < 0.05; n = 15).

RESULTS

Etch-CPN (100), CPN-Etch(100) and CPN-Etch (10) showed significantly higher bond strengths compared to the control. When using 10% CPN, the highest bond strength was demonstrated. The bond strength of 4META/MMA-TBB resin was approximately doubled by CPN application.

CONCLUSION

The results of this study showed that higher bond strengths are obtained when treating dentin with a lower concentration of CPN. Further evaluation to optimize conditions such as the application time and rinsing time are required.

Effects of Temperature on the Fluoride Release and Recharging Ability of Glass Ionomers

The use of a higher temperature during topical fluoride applications may increase the fluoride recharging and re-release ability of glass ionomers, and a low oral environment temperature should be avoided during topical fluoride application.

Bonding characteristics of newly developed all-in-one adhesives

This study evaluated the microtensile bond strength and the interfacial morphology of newer adhesives. The occlusal surfaces of extracted teeth were ground flat for random allocation to four equal groups. Resin composite was bonded to each surface using either Clearfil SE Bond [SEB], Clearfil Protect Bond [PB], G-Bond [GB], or an experimental adhesive, SSB-200 [SSB]. After storage for 24 h in water at 37 degrees C, they were sectioned into beams (cross-sectional area 1 mm(2)) for microtensile bond strength testing (muTBS) at a crosshead speed of 1 mm/min. The load at failure of each was recorded; the data were analyzed by one-way ANOVA and Games Howell tests. The surfaces of the fractured specimens were observed using SEM. For the ultra-morphology of the interface, the occlusal surfaces of four more teeth were prepared as before and a thin layer of flowable resin composite was bonded to each surface using one of the four adhesives. The mean muTBS ranged from 39.68 MPa (GB) to 64.97 MPa (SEB). There were no statistical differences between SEB and SSB, or between PB and GB (p > 0.05). The muTBS of SEB and SSB were significantly greater than that of PB and GB (p < 0.05). SEMs of the fractured surfaces revealed a mixed (cohesive/interfacial) failure. TEM examination highlighted differences in the hybrid layer; SEB had a thicker layer than the others. In conclusion, the newer all-in-one adhesives produced a thin hybrid layer but varied in their bond strengths. The 2-step self-etching adhesives do not necessarily produce higher bond strengths than that of the all-in-one systems.

Salivary contamination and bond strength of glass-ionomers to dentin

This study evaluated the effect of salivary contamination on the shear bond strength of two highly viscous glass ionomer cements (Fuji IX GP Fast and Ketac-Molar Maxicap) to conditioned dentin and assessed the effect of cleaning the contaminated field prior to bonding. The buccal surfaces of 90 human molars and premolars were ground to expose dentin and the teeth were then set in resin. The specimens were divided into two groups for each material, then further subdivided into three groups of 15 teeth each: Group 1--uncontaminated (control), Group 2--dentin contaminated with saliva, Group 3--dentin contaminated, washed and air dried. The specimens were made by bonding the test material to dentin using a 4 mm diameter gelatin capsule. All specimens were protected with varnish and placed in distilled water at 37 degrees C for seven days prior to measuring bond strength in shear. Fractured surfaces were examined visually and by using SEM to assess mode of failure. There were no significant differences in mean shear bond strength among the three test groups for either material (ANOVA). However, shear bond strength of Fuji IX to dentin was significantly greater than Ketac-Molar (p=0.019) for all groups. Weibull analysis showed that contaminated (Group 2) specimens had a greater probability of failure at low stresses. Modes of failure were mostly cohesive for Fuji IX and adhesive/cohesive for Ketac-Molar. In conclusion, salivary contamination did not affect the mean shear bond strength of Fuji IX GP Fast and Ketac-Molar Maxicap to conditioned dentin; however, it increased the probability of failure at low stresses.

Interaction of glass-ionomer cements with moist dentin

Glass-ionomer cements (GICs) are regarded as aqueous gels made up of polyalkenoic acid salts containing ion-leachable glass fillers. The consequence of water permeation across the GIC-dentin interface is unknown. This study used SEM, field-emission/environmental SEM (FE-ESEM), and TEM to examine the ultrastructure of GIC-bonded moist dentin. Dentin surfaces bonded with 6 auto-cured GICs were examined along the fractured GIC-dentin interfaces. Additional specimens fractured 3 mm away from the interfaces were used as controls. SEM revealed spherical bodies along GIC-dentin interfaces that resembled hollow eggshells. FE-SEM depicted similar bodies with additional solid cores. Energy-dispersive x-ray analysis and TEM showed that the spherical bodies consisted of a silicon-rich GIC phase that was absent from the air-voids in the controls. The GIC inclusions near dentin surfaces result from a continuation of the GI reaction, within air-voids of the original polyalkenoate matrix, that occurred upon water diffusion from moist dentin.

The biocompatibility of glass-ionomer cement materials. A status report for the American Journal of Dentistry

Since their introduction in the market, some 30 yrs ago, the biocompatibility aspects of glass-ionomer cements (GICs) have been intensively studied. In general, cytotoxicity of fully set conventional preparations in previous studies was shown to be minimal. However, a resin-modified preparation proved to be cytotoxic under these conditions. This product was also observed to be mutagenic, but data in this area are sparse and difficult to interpret. There is also evidence that certain GICs exert some antibacterial properties which is claimed to be related to the fluoride release; however, the mechanisms for this fluoride release are still unclear. Pulp response studies have shown conflicting results. However, unfavorable initial reactions, if present, resolved with time if a bacterial layer under the restoration and pulp exposures were prevented. Pain reactions after cementation of cast restorations with GICs have been reported in the past but there are no such reports in the more recent literature.

Confocal and multi-photon microscopy of dental hard tissues and biomaterials

Confocal microscopy is a technique that can be used both in the clinic and the high-resolution microscopy suite. This form of optical microscopy enables high-resolution images to be made of samples with minimum requirements for specimen preparation. Images may be made of either reflections from the sample surface or, if an immersion medium is used to optically couple the objective lens, then sub-surface images can be produced of reflective or fluorescent structures within semi transparent materials such as cells and dental hard tissues. These images are like optical sections, giving thin (> 0.35 microm) slices up to 200 microm below the surface of a mineralized tissue. The technique generates significant improvements in resolution, lying somewhere between that of conventional light microscopy and TEM/SEM. Instruments that work at video-rate allow high-speed events to be examined, such as in vivo clinical studies, cutting of dental tissues and fracture of adhesive interfaces. New dyes offer many exciting prospects for labeling changes in chemical composition in materials or biological tissues, while new imaging techniques such as multi-photon laser excitation of dyes give the potential of greater depth penetration and improved resolution. As with all new techniques the inexperienced should be aware of some of the artifacts inherent to the system. However, the widespread availability of conventional confocal microscopes should give ample opportunity for dental researchers to capitalize on this new technology.

Failure of resin-modified glass-ionomers subjected to shear loading

The mechanism of bond failure of resin-modified glass-ionomers is unknown. This study examined the failure on shear loading at the dentine interface of these materials. Twenty-five teeth (embedded in acrylic blocks) were sectioned longitudinally to expose a flat dentine surface. Cylinders of materials were made by injecting into a tube placed on the dentine of each section surface. The materials used were Fuji Cap II and Fuji II LC (GC Corp., Japan), Vitremer (3M Dental Products, USA), Photac-Fil (original) and Photac-Fil* (new) (ESPE Dental-AG, Germany). After a week, a fluorescent dye was placed in the pulp chamber of each tooth and left for 3 h. The specimens were sectioned through the cylinders before both halves were tested in shear. The failure was observed using a confocal microscope, with video rate images (stored) digitally. The shear load at failure and locus of failure were recorded. All specimens had intact interfaces before testing, except the original Photac-Fil specimens which dislodged from their tooth surfaces even before testing, while being mounted on the device. An amorphous zone or absorption layer was noted at the dentine interface of 60% of Fuji II LC, 22% of Vitremer and all of the Photac-Fil* (new) specimens, but not in Fuji Cap II. Failure was cohesive in Fuji II LC, adhesive in Vitremer, cohesive/adhesive in Photac-Fil* (new) and cohesive in Fuji Cap II. In specimens with the absorption layer present, the failure was at the material/absorption layer interface, leaving it behind on the dentine surface. The mean stresses at failure (MPa) and standard deviations were 5.60, 2.46 (Fuji II LC); 4.82, 0.99 (Vitremer); 4.97, 2.10 MPa (Photac-Fil*); and 3.48, 1.06 (Fuji Cap II). All data were normally distributed as tested by the Shapiro-Francia test. One-way analysis of variance using exact inferential statistics indicated no significant difference between the mean failure stress for all the systems, p = 0.08. The mechanism of failure of resin-modified glass-ionomer materials to shear loading at the dentine interface varies between products. In materials in which the absorption layer is present, it appears to play an important role in mediating the bond of the glass-ionomer to dentine.

A 10-year retrospective study on benzocaine allergy in the United Kingdom

BACKGROUND

Benzocaine has been labeled a notorious sensitizer. It is thought to be a common and potent sensitizer. It is suggested that such patients should routinely avoid tetracaine and procaine, as cross-reactions between benzocaine and such caines occurred commonly. Benzocaine also currently remains the screening chemical on the European Standard Battery (ESB) for topical caine allergy.

OBJECTIVE

To identify the rate of incidence of benzocaine allergy in the United Kingdom, and the level of cross reactivity between other caines in the ESB.

METHODS

The results from a 10-year retrospective study of 5,464 patients, subjected to patch testing with a modified ESB, which included caine mix III (Chemotechnique Diagnostics, Tygelsjo, Sweden), and the results of caine mix IV (Chemotechnique) reactions in 265 of these patients who complained of anogenital symptoms, are discussed.

RESULTS

Majority of allergic reactions occurred with the constituents of caine mix III, with benzocaine reactions being the least common allergen in this group. Cross reactivity between benzocaine and other caines, occurred infrequently.

CONCLUSION

Our data indicate that benzocaine allergy is not common in the United Kingdom. As cross-reactivity between benzocaine and other caines did not occur commonly, a significant number of relevant allergic reactions to other caines may go undetected, as benzocaine remains the screening chemical for topical anaesthetic allergy on the ESB. We suggest benzocaine be removed from the ESB, and be replaced by caine mix III.

Allergic contact dermatitis to acrylates in disposable blue diathermy pads

We report 2 cases of elicitation of allergic contact dermatitis to acrylates from disposable blue diathermy pads used on patients who underwent routine surgery. Their reactions were severe, and took approximately 5 weeks to resolve. Both patients gave a prior history of finger tip dermatitis following the use of artificial sculptured acrylic nails, which is a common, but poorly reported, cause of acrylate allergy. Patch testing subsequently confirmed allergies to multiple acrylates present in both the conducting gel of disposable blue diathermy pads, and artificial sculptured acrylic nails. We advocate careful history taking prior to surgery to avoid unnecessary exposure to acrylates in patients already sensitized.

Multiple familial trichoepitheliomas

We present the case of a 28-year-old woman with multiple familial trichoepitheliomas, characterized by the presence of many small tumors occurring predominantly on the face. This condition constitutes a genodermatosis that follows an autosomal dominant mode of inheritance. These lesions can lead to marked facial disfigurement, and treatment is generally disappointing.

Interfacial characteristics of resin-modified glass-ionomer materials: a study on fluid permeability using confocal fluorescence microscopy

The tooth interface with resin-modified glass-ionomer cements (RM GICs) is poorly understood. This study examined the interface, especially with dentin. Cervical cavities in extracted teeth were restored with Fuji II LC, Vitremer, Photac-Fil, or a conventional GIC, Fuji Cap II. Fluorescent dye was placed in the pulp chambers for 3 hrs before the specimens were sectioned. Examination of the tooth/material interface with a confocal microscope showed that dye uptake by the restoration varied among materials. A "structureless", non-particulate, highly-stained layer of GIC was observed next to dentin in Fuji II LC. This layer varied in width, was prominent where the dentin tubules were cut "end-on" and in areas closer to the pulp, and was not seen adjacent to enamel. Vitremer showed minimal dye uptake, and the "structureless" layer was barely discernible. Photac-Fil showed more uniform uptake and absence of this layer. Cracking of enamel was also noted with these materials. The conventional GIC did not show any dye uptake, presence of a "structureless" layer, or enamel cracking. We elucidated the potential mechanisms involved in the formation of a "structureless" interfacial layer in Fuji II LC by studying the variables of cavity design, surface pre-treatment, water content of the tooth, time for it to develop, early finishing, and coating of the restoration. This layer, the "absorption layer", is probably related to water flux within the maturing cement, depending on environmental moisture changes and communication with the pulp in a wet tooth. The "micropermeability model" was useful in this study of the interfacial characteristics of RM GICs.

Water sorption in resin-modified glass-ionomer cements: an in vitro comparison with other materials

The pattern of water uptake into a polyacid-modified composite resin (compomer), Dyract (D), was assessed using gravimetric analysis and tritiated water absorption. The results were compared with a resin composite, Herculite (H), a resin-modified glass-ionomer, Fuji II LC (FL), and a conventional glass-ionomer, Fuji II (F). Samples were stored in tritiated water for periods varying between 6 h and 6 months. The resulting change in gravimetric weight and dimensions was recorded. The tritiated water content was then assessed using liquid scintillation counting and this was compared to the gravimetric changes. The inherent water content of each material was also established. D and H showed a slow steady net uptake to 3% and 1.3% weight by volume (WV) respectively at 6 months. FL showed a rapid uptake reaching 8.9% WV at 7 days and 9.3% WV at 6 months. F showed a steady, less dramatic water uptake reaching 5.3% WV by 6 months. For the glass-ionomer materials, values for gravimetric water uptake and tritium release differed due to the ongoing acid base reaction and an increase in firmly bound water. This phenomenon was noted in D suggesting evidence of a similar reaction in this material.

Confocal microscopic observation of structural changes in glass-ionomer cements and tooth interfaces

This study aimed to develop techniques to allow dynamic imaging of a cavity before, during and after placement of glass-ionomer restorative materials. Cavities were cut in recently extracted third molars and the teeth longitudinally sectioned. Each hemisected tooth surface was placed in green modelling compound at 90 to the optical axis of the microscope. The cavity surface was imaged using a video rate confocal microscope in conjunction with an internally focusable microscope objective. The sample on the stage was pushed up to the objective lens which 'clamped' the cover glass onto it. Water, glycerine or oil was placed below the coverglass, with oil above. Internal tooth structures were imaged by changing the internal focus of the objective. The restorative material was then placed into the cavity. Video images were stored either onto video tape or digitally, using a frame grabber, computer and mass memory storage. Software controls produced time-lapse recordings of the interface over time. Preliminary experiments have examined the placement and early maturation of conventional glass-ionomer cements and a syringeable resin-modified glass-ionomer cement. Initial contact of the cement matrix and glass particles was visible as the plastic material rolled past the enamel and dentine, before making a bond. Evidence for water movement from the dentine into the cement has also been seen. After curing, the early dimensional changes in the cements due to water flux were apparent using the time-lapse facility. This new technique enables examination of developing tooth/restoration interfaces and the tracking of movement in materials.

A study on the radiopacity of different shades of resin-modified glass-ionomer restorative materials

There are several resin-modified glass-ionomer restorative materials available to the dental profession today. The commercially available brands are presented in a range of shades. There is little information on their radiopacity and whether this varies with differences in shade. While the general radiopacity of various products may have been studied, only assumptions are available regarding their consistency between shades. The purpose of this study was to investigate if there were any significant differences in the radiopacity of the shades available within each commercial product. The products evaluated were Fuji II LC, Vitremer, and Photac-Fil. The optical densities of standardized radiographs of samples of these materials were determined and radiopacity values of materials expressed in millimeter equivalents of aluminum. Of the three resin-modified glass-ionomer restorative materials tested, Fuji II LC was the most radiopaque and Photac-Fil the least. Fuji II LC and Vitremer showed radiopacity values equivalent to > 2.5 mm and > 1.5 mm aluminum respectively; Photac-Fil demonstrated very low radiopacity values (equivalent to < 0.6 mm aluminum). Statistical analysis revealed that there was no significant difference in radiopacity among the shades within each of these brands.

The effects of maturity and dehydration shrinkage on resin-modified glass-ionomer restorations

The dimensional change, including hygroscopic change, of adhesive dental materials is a clinically important topic, since excessive changes could cause debonding from tooth structure. The water balance of glass-ionomer cements arises mainly from their sensitivity to the environment; depending on the surroundings, they can gain or lose water, either of which can be potentially damaging. These effects become less noticeable as the cement ages. The effects of maturity of the newer resin-modified glass-ionomer materials and their responses to changes in moisture are unknown. Using confocal microscopy, we examined the effects of dehydration stress on the glass-ionomer/tooth interface in specimens of various degrees of maturity. Wedge-shaped cervical cavities in extracted teeth were restored with one of three resin-modified glass-ionomer restorative materials. The control specimens were restored with a conventional glass ionomer. The samples were left to mature, then sectioned and examined at 1 day, 1 wk, 1 mo, 3 mos, 6 mos, and 1 yr. After being sectioned, each specimen was examined immediately with a confocal microscope with water-immersion objectives so that the subsurface interfacial characteristics could be studied. The specimen was then allowed to dehydrate under the microscope, with further examinations at 15, 30, and 60 min. Generally, gap formation at the interface occurred within 15 min of dehydration. All materials showed a different pattern of gap change with maturity, probably due to the different setting mechanisms involved. All of them were susceptible to dehydration shrinkage up to 3 mos of maturity. At 6 mos and 1 yr, Fuji II and Fuji II LC showed insensitivity to dehydration. Vitremer and Photac-Fil showed less sensitivity to dehydration at 1 yr than at 6 mos. The results of this study of the maturing polymerized resin-modified cements have potential clinical implications in the handling of these materials; the addition of resin has not significantly reduced the glass ionomer's susceptibility to dehydration problems.

In vivo changes in roughness of resin-modified glass ionomer materials

OBJECTIVES

The clinical changes in roughness of resin-modified glass ionomer materials is relatively unknown. This study examined the in vivo wear of these materials using surface roughness as an indicator of wear patterns.

METHODS

Ten patients with four cervical abrasion lesions each were selected. The four cavities in each patient were restored with Fuji II LC (GC Corp., Japan), Vitremer (3M Dental, USA), Photac-Fil (ESPE, Germany) and Fuji Cap II (GC Corp., Japan). After light-curing, the restorations were polished and left uncoated. Silicone impressions were made of the surface of each restoration after polishing, and then at 3 monthly intervals up to 24 mon after restoration placement. Gold-coated resin replicas were made from the impressions for surface wear evaluation. Quantitative assessment of wear was performed by measuring surface roughness with a confocal microscope for topographical reconstruction of the specimen surface. The effect of material at each time period was analyzed using the Kruskal-Wallis test with exact non-parametric inference. Rugosity, as determined by the center line average, was determined by image analysis. SEM images of the same surfaces provided the qualitative analysis.

RESULTS

All restorations showed a cyclic distribution of rugosity with time as demonstrated by lowess plots. There were significant differences between materials at 6, 9 and 18 mon. The rugosity curves appeared to converge at 24 mon.

SIGNIFICANCE

It was concluded that the in vivo surface changes in roughness of resin-modified glass ionomer materials is cyclic in nature over the first 2 y.

Radiopacity of resin-modified glass ionomer liners and bases

STATEMENT OF PROBLEM

Lining and base materials for restorations have traditionally been autopolymerized and include conventional glass ionomer cements. Light-cured resin-modified glass ionomer cements have recently become available, but a lack of information exists regarding their radiopacity.

PURPOSE OF STUDY

In this study the radiopacity of glass ionomer cements was assessed with a standard method that related densitometric measurements to an equivalent thickness of aluminum.

MATERIAL AND METHODS

Radiographs were made of specimens with seven materials commonly used as liners and bases: two reinforced zinc oxide-eugenol cements (Kalzinol and Intermediate Restorative Material, De Trey Dentsply), a zinc phosphate cement (SS White, S.S. White Manufacturing), three resin-modified glass ionomer liners (Vitrebond [3M Dental Products], Fuji Lining LC [GC Dental], and Photac-Bond [ESPE Dental Medizin GmbH]), and a conventional glass ionomer liner/base (Ketac-Bond, ESPE Dental-Medizin GmbH), with dentin as a control. The radiopacity of all materials was compared with dentin.

RESULTS

Kalzinol had the greatest radiopacity of the materials tested. The glass ionomer cements were substantially less radiopaque than other materials. The conventional glass ionomer cement, Ketac-Bond, was more radiopaque than the three resin-modified glass ionomer cements. Of the three resin-modified glass ionomer materials, Vitrebond was the most radiopaque and Fuji Lining LC was the least radiopaque.

CONCLUSION

Future resin-modified glass ionomer materials are recommended to be formulated to increase radiopacity for improved clinical detection.

Radiopacity of resin-modified glass-ionomer restorative cements

This in vitro study compared the relative radiopacities of three commercially available resin-modified glass-ionomer cements (Vitremer, Fuji II LC, and Photac-Fil), an experimental resin-modified glass-ionomer (V-66), two conventional glass-ionomers (ChemFil and Fuji Cap II), and amalgam (as the control). Radiopacity was assessed densitometrically and expressed as equivalent thicknesses of aluminum. All the glass-ionomer cements were more radiopaque than enamel and dentin, with the exception of ChemFil and Photac-Fil. Apart from the control material, the experimental resin-modified glass-ionomer material, V-66, had the highest radiopacity of all the materials tested. Of the three resin-modified glass-ionomer materials tested, Fuji II LC was the most radiopaque and Photac-Fil the least. For the radiopacity of restorative glass-ionomer materials to exceed that of enamel, it should be greater than 1.5 mm of equivalent thickness of aluminum.

Radiopacity of potential root-end filling materials

OBJECTIVES

In recent years various root-end filling materials have been suggested for clinical use. The purpose of this study was to assess the radiopacity of some potential materials according to ISO specification 6876.

STUDY DESIGN

Radiographs were taken of 1-mm thick specimens of eight materials (amalgam, Kalzinol, IRM, Super EBA, Vitrebond, Fuji II LC, Chemfil, gutta-percha); light transmission was assessed densitometrically and related to equivalent thickness of aluminum.

RESULTS

Commercial glass ionomer cements (Vitrebond, Fuji II LC, Chemfil) had radiopacities below the international standard for root canal sealers (< 3-mm aluminum); three zinc oxide-eugenol cements (Kalzinol, Super EBA, IRM) had radiopacities equivalent to 5 to 8 mm aluminum; and gutta-percha had a radiopacity equivalent to 6.1-mm aluminum.

CONCLUSIONS

We recommend that root-end filling materials should have a radiopacity greater than that for root canal sealers.

Resin-modified glass-ionomer materials. Part 2: clinical aspects

The resin-modified (light-cured) glass-ionomer cements are a relatively recent introduction to restorative dentistry, especially in their restorative form. In Part 1 of this review, the physical and biological properties of these materials were discussed. In this second paper their clinical applications and handling will be addressed.

Resin-modified glass-ionomer materials. Part 1: Properties

The resin-modified (light-cured) glassionomer cements were developed as hybrids of the conventional glass-ionomer materials to overcome some of their disadvantages. These new materials will be reviewed in two parts. This first article deals with their physical and biological properties. Part 2 will cover their clinical applications and handling.

Cracked teeth--treatment rationale and case management: case reports

The treatment rationale for, and successful management of, six teeth with cracks in the form of incomplete vertical fractures are reported. Further crack propagation was prevented by placement of either stainless steel orthodontic bands or aluminum or acrylic resin provisional crowns, and endodontic treatment was subsequently carried out. The teeth were restored with intraradicular amalgam cores and complete veneer crowns. The teeth were reexamined periodically for up to 3.5 years after treatment. During the period of review, all teeth remained asymptomatic.

Resin-modified glass ionomer materials. A status report for the American Journal of Dentistry

The resin-modified glass ionomer materials are hybrid materials of traditional glass ionomer cement with a small addition of light-curing resin, and hence exhibit properties intermediate to the two, with some characteristics superior to conventional glass ionomer materials. Generally, they have the advantages of both such as adhesion to tooth structure, esthetics, fluoride release and rapid hardening by visible light. Issues surrounding other physical properties, such as the mechanism of adhesion, sensitivity to water, long-term wear and strength, need to be addressed and substantiated. There are other considerations, which are not features of the conventional materials, but are of importance with the resin-modified glass ionomer cements i.e. light-curing, which require further research to provide evidence of their behavior. The future for this group of materials is unknown, but the currently available materials appear to be promising.

The effect of acid-etched dentin on marginal seal

Treatment of dentin with acids results in a surface change that is potentially useful for mechanical retention of resins in tooth structure. This study examined the effect of etching of dentin on the seal of cavities restored with composite resin. Eighty cavities, each measuring 2.0 mm in diameter and 1.5 mm in depth, were prepared in dentin of extracted human teeth and randomly assigned to two equal groups. The experimental group was etched with 37% phosphoric acid for 15 seconds before restoration. The control specimens were similarly restored but without any etching of dentin. After the specimens were thermocycled, the seal of each cavity was assessed by measurement of the gap between the restorative material and the tooth structure. The experimental group registered significantly better adaptation to the cavities than did the control group.

The effect of smear layer removal on marginal contraction gaps

The presence of the smear layer prevents direct contact between dentine and a dentine adhesive. The use of agents to remove the smear layer theoretically should improve the bonding of composite resins to dentine. This study examined the effect of smear layer removal on the effectiveness of a dentine bonding agent in reducing marginal contraction gaps. The agent used for smear layer removal in this study was ethylenediamine tetra-acetic acid (EDTA). Eighty cavities measuring 2 mm in diameter and 1.5 mm in depth were prepared in dentine and randomly assigned to two equal groups. The control group was restored with Prisma Universal Bond 2 Adhesive and Prisma Fil Resin. The experimental group was similarly restored after pretreatment of dentine with 0.5% EDTA for 60 s. All specimens were thermocycled and the marginal contraction gaps were assessed using a Nikon Measurescope. The mean contraction gap was expressed as a percentage of the cavity diameter. Results showed that the experimental group registered smaller contraction gaps (mean: 0.021%) than the control group (mean: 0.027%). No penetration of material into dentine was observed. Pretreatment with EDTA did not significantly improve the effectiveness of the dentine bonding agent used in terms of reduction of marginal contraction gaps.

The effect of dentinal conditioning on light-activated glass-ionomer cement

This article reports the effect of conditioning of dentinal surfaces on the sealing capability of a light-curing glass-ionomer restorative material, Fuji II LC. The in vitro evaluation measured gap formation at the tooth-restoration interface. The control specimens were restored with Fuji II LC after dentinal surface treatment with a polyacrylic acid solution, while the experimental specimens were restored without pretreatment. The sealing ability of the material to dentin was assessed by measuring the gap between the restorative material and tooth structure. The control group registered a mean marginal gap of 7.75 microns, and the experimental group registered a mean gap of 10.75 microns, but statistical analysis indicated that there was no significant difference between the two groups. Dentinal surface treatment prior to restoration with the light-curing glass-ionomer cement used in this study resulted in a smaller gap at the dentin-restoration interface, but this difference was not significant.

Marginal contraction gap formation of light-cured glass ionomers

The capability of dental restorative materials to effectively seal the margins of tooth preparations is critical. The adhesive properties of the conventional chemically-cured glass ionomer cements have provided a potential for sealing cavity margins, but recently light-cured versions of the glass ionomer cements have been introduced. This study examined the adhesion to dentin of two new light-cured glass ionomer cement restorative materials, Fuji II LC and VariGlass VLC. Gap formation at the tooth/restoration interface in dentin cavities was recorded as a measure of the sealing ability of the materials. Cylindrical cavities were prepared in dentin of extracted teeth and randomly assigned to three equal groups. The control group of specimens was restored with a chemically-cured glass ionomer, Fuji Cap II, while the experimental groups were restored with one of the two light-cured materials. All specimens were subjected to thermocycling. The sealing of each material to dentin was evaluated by measuring the gap between the restoration and tooth structure. The control group registered mean gaps of 26 microns while the experimental groups registered mean gaps of 8 microns (Fuji II LC) and 10 microns (VariGlass VLC). The light-cured materials displayed substantially better adaptation to the cavity preparations than the conventional materials (P < 0.005), with no significant difference between the two experimental groups.

A comparative analysis of techniques of restoring cervical lesions

There are several methods of restoring cervical abrasion or erosion lesions, including the use of composite resin, glass-ionomer cement, or a combination of these materials. This paper reports the effectiveness of three different materials and techniques in restoring cervical lesions, using marginal leakage as the means of comparison. Wedge-shaped cervical cavities were prepared so that the gingival cavosurface margin of each cavity involved dentin. Half of the specimens in each group were thermocycled. Differences in marginal leakage were more pronounced at the gingival margin. There was no significant difference between the leakage of thermocycled and nonthermocycled specimens. Microleakage can be expected to be minimal in cavities restored with the "sandwich" technique, in which a glass-ionomer cement liner and composite resin restorative material are placed.

The surface finish of light-cured composite resin materials

A necessity for any dental restorative material is its ability to take and maintain a smooth surface finish. Composite resin restorative materials with fillers and matrix of differing hardness are difficult to finish and polish. The use of aluminum trioxide discs is a popular and acceptable method of finishing composite restorative materials where the material is accessible. Burs and stones are used for finishing and polishing inaccessible areas. This study was undertaken to compare the surface finish of composite resin restorative material when finished with white stones, superfine diamond burs and aluminum trioxide discs. The finished surface was measured with a profilometer and the roughness average value used to compare the surfaces. The aluminum trioxide discs gave the best and most consistent results. It was possible to attain similar results with the superfine diamond bur. However, the results were highly variable. None of the methods used achieved the smoothness of composite resin cured against a transparent matrix.

Sealing effectiveness of light-cured glass ionomer cement liners

Glass ionomer materials have been used as liners or bases beneath restorations, but light-cured varieties have recently been introduced. Microleakage at the restoration/tooth interface in cervical cavities was used to test the adhesion to dentin of two new light-cured glass ionomer cement lining materials, XR-Ionomer and Fuji Lining LC. Wedge-shaped cervical cavities were prepared on extracted teeth with a gingival cavosurface margin involving dentin, and the specimens were assigned randomly to three groups. The experimental groups were restored with two light-cured glass ionomer cements, the controls were restored with a chemically cured glass ionomer cement; and marginal leakage was assessed by dye penetration. The two light-cured glass ionomer cements displayed some adhesion to dentin in class V test cavities, but there was no significant difference between the two materials.

Dentin adhesives and microleakage in cervical resin composites

This paper reports the effect of dentin bonding agents on marginal leakage in cervical cavities without the classical cavity preparation design. Wedge-shaped cervical cavities were cut on extracted teeth with the gingival cavosurface margin of each cavity involving dentin. The specimens were randomly assigned to three groups of 40 each: Group 1 (control), restored with Fuji glass ionomer; Group 2, restored with Scotchbond 2 adhesive and Silux Plus resin and Group 3, restored with Tenure adhesive and Perfection resin. Half of the specimens in each group were thermocycled. All specimens were then stored in basic fuchsin dye after which microleakage of the restorations was assessed by dye penetration. A grading scale of 0 to 3 was used as the scoring criteria. The results showed that differences were more pronounced at the gingival margin. The control group specimens exhibited the least microleakage. There was no significant difference between thermocycled and non-thermocycled specimens for each category of materials used. There was, however, a significant difference between the experimental groups and the control groups. The dentin adhesives tested did not completely eliminate microleakage at the gingival margin of cervical cavities.

In vitro marginal leakage of cervical composite restorations lined with a light-cured glass ionomer

The purpose of this research effort was to investigate the microleakage of cervical restorations lined with a light-cured glass-ionomer liner. Wedge-shaped cervical cavities were cut on extracted teeth with the gingival cavosurface margin involving dentin. The cavities were randomly assigned to each of each of three groups: (1) restored with a microfilled composite resin, (2) restored with a light-cured glass-ionomer liner and microfilled resin as in the "sandwich" technique, and (3) restored entirely with the light-cured glass-ionomer liner. Half of the specimens in each group were thermocycled. Microleakage of these restorations was assessed by dye penetration. The results showed that differences were more pronounced at the gingival margin. Composite restorations inserted over the glass-ionomer liner demonstrated significantly less leakage than when the liner was not used.

Effect of dentin age on effectiveness of dentin bonding agents

The purpose of this research effort was to investigate the effect of age changes in dentin on the effectiveness of two dentin adhesives in minimizing microleakage at the tooth-restoration interface. Cavities were prepared in permanent teeth extracted from patients below 20 years or over 55 years of age. Wedge-shaped cervical preparations were made with the gingival cavosurface margin on dentin. Treatment groups were randomly restored with one of two composite restorative materials, together with the appropriate dentin adhesives. The control group specimens were restored with the respective composite restorative materials without the adhesives. All specimens were thermocycled, then placed in 0.5% basic fuchsin dye solution for 24 hours and subsequently sectioned longitudinally. Microleakage at the tooth-restoration interface was assessed by dye penetration. The results showed that the use of adhesives significantly reduced microleakage along the tooth-restoration interface. The adhesive formulated with glycidyl methacrylate was significantly more effective in reducing microleakage in dentin of the over-55 age group.

A comparative study of porcelain repair materials

Intra-oral fracture of metal-ceramic restorations sometimes occurs when clinical and laboratory techniques have been inadequate. Removal and refabrication of the prosthesis is the ideal solution, but may not always be practical. Recently, several products have been marketed for expediting the repair of fractured restorations in the mouth. This study compared the effectiveness of three of these repair systems (Super-C, Command Ultrafine and 3M Porcelain Repair Kits) with a control group of porcelain-fused-to-metal specimens. Measurement of failure load of each material being tested was carried out in compression using a universal testing apparatus and a specially designed jig. Each experimental and control group contained ten specimens. Each material was tested individually for repairs against metal and against porcelain. A comparison of the failure load values indicated that the control samples gave the highest mean value of 881.6 +/- 192.9 N, while that of Super-C against metal was the lowest at 385.4 +/- 102.4 N. The Command Ultrafine Repair Kit was the strongest of the repair systems studied.

Effect of Oral Contraceptives on Faecal Porphyrins

A quantitative assay -of faecal prophyrins was undertaken by spectrophotometric method of Rimington in forty women, of child-bearing age Thirty women- On Oral contraceptives constituted the study group and ten on other methods of contrace on served as controls. In the study group the mean and standard deviation of faecal CoProporphyrins were 6.747 and 7.215 respectively and of faecal protoporphyrin levels 13.549 and 9.509 respectively.It was observed that 10 per cent of the women on oral contraceptives had raised faecal copro and protoporphyrins, which however, was statistically not significant.

Effect of Oral Contraceptives on Urinary Porphyrins

Urinary porphyrins were measured in thirty women on oral contraceptives who constituted the study group and in ten women using conventional methods of contraception who constituted the control group. The difference of theme an so furinary copro and uroporphyrin in the two groups.was found to be statistically insignificant. Further, the effect of duration of treatment of females using oral contraceptives was also studied. The difference of means was not significant a the cases oral contraceptives for a period Of less than six months and cases using the same for more than six months.