Pressure-Induced Excitations in the Out-of-Plane Optical Response of the Nodal-Line Semimetal ZrSiS

The anisotropic optical response of the layered, nodal-line semimetal ZrSiS at ambient and high pressure is investigated by frequency-dependent reflectivity measurements for the polarization along and perpendicular to the layers. The highly anisotropic optical conductivity is in very good agreement with results from density-functional theory calculations and confirms the anisotropic character of ZrSiS. Whereas the in-plane optical conductivity shows only modest pressure-induced changes, we found strong effects on the out-of-plane optical conductivity spectrum of ZrSiS, with the appearance of two prominent excitations. These pronounced pressure-induced effects can neither be attributed to a structural phase transition according to our single-crystal x-ray diffraction measurements, nor can they be explained by electronic correlation and electron-hole pairing effects, as revealed by theoretical calculations. Our findings are discussed in the context of the recently proposed excitonic insulator phase in ZrSiS.

Cooperative Cluster Jahn-Teller Effect as a Possible Route to Antiferroelectricity

We report the observation of an antipolar phase in cubic GaNb_{4}S_{8} driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb_{4}S_{4} molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at T_{JT}=31  K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above T_{JT}. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb_{4}S_{8} may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferroelectric.

Complex magnetic order from multiple Ce-sites in Ce3Pd4Sn6

Polycrystalline [Formula: see text] [Formula: see text] [Formula: see text] samples were synthesized by arc-melting and subsequent annealing at 970 K. Specific heat, electrical resistivity and magnetic susceptibility measurements are performed over a wide range in temperature and provide hints for the presence of a complex magnetic ordering below 3 K arising from three crystallographically independent Ce sites. This behaviour is driven by a complex interplay between ferro-, ferri-, and antiferromagnetic correlations among the Ce atoms.

On the nature of superconductivity in the anisotropic dichalcogenide NbSe2{CoCp2}x

We present a detailed study of the superconducting properties of the weakly pinned, quasi-two-dimensional superconductor 2H-NbSe2, and its intercalated variant NbSe2{CoCp2}0.26. The intercalation of 2H-NbSe2 with the organometallic donor molecule cobaltocene (CoCp2) hardly affects the superconducting properties within the layers. However, the properties perpendicular to the layers change significantly due to the large expansion of the layer spacings of the host lattice in the c-direction by a factor of about two. In particular, the superconducting anisotropy factor Γ increases from 3.3 in the parent compound 2H-NbSe2 up to 4.4 in the intercalated species. Therefore, NbSe2{CoCp2}0.26 is an excellent candidate to analyze how the anisotropy effects the superconducting mechanism in layered dichalcogenides, and to evaluate the various models proposed in the literature to account for the anisotropy in 2H-NbSe2. While a two-gap model and an anisotropic single-gap model are competing concepts to describe the almost linear T(2)-dependence of ΔC/T in low-dimensional dichalcogenides, our comparative study suggests that a single-gap model with an anisotropic Fermi-surface is sufficient to capture the ΔC/T(T) behavior in our samples qualitatively.

Experimental and theoretical charge density studies at subatomic resolution

Analysis of accurate experimental and theoretical structure factors of diamond and silicon reveals that the contraction of the core shell due to covalent bond formation causes significant perturbations of the total charge density that cannot be ignored in precise charge density studies. We outline that the nature and origin of core contraction/expansion and core polarization phenomena can be analyzed by experimental studies employing an extended Hansen-Coppens multipolar model. Omission or insufficient treatment of these subatomic charge density phenomena might yield erroneous thermal displacement parameters and high residual densities in multipolar refinements. Our detailed studies therefore suggest that the refinement of contraction/expansion and population parameters of all atomic shells is essential to the precise reconstruction of electron density distributions by a multipolar model. Furthermore, our results imply that also the polarization of the inner shells needs to be adopted, especially in cases where second row or even heavier elements are involved in covalent bonding. These theoretical studies are supported by direct multipolar refinements of X-ray powder diffraction data of diamond obtained from a third-generation synchrotron-radiation source (SPring-8, BL02B2).

Evolution of quantum criticality in CeNi(9-x)Cu(x)Ge(4)

Crystal structure, specific heat, thermal expansion, magnetic susceptibility and electrical resistivity studies of the heavy fermion system CeNi(9-x)Cu(x)Ge(4) (0≤x≤1) reveal a continuous tuning of the ground state by Ni/Cu substitution from an effectively fourfold-degenerate non-magnetic Kondo ground state of CeNi(9)Ge(4) (with pronounced non-Fermi-liquid features) towards a magnetically ordered, effectively twofold-degenerate ground state in CeNi(8)CuGe(4) with T(N) = 175 ± 5 mK. Quantum critical behavior, [Formula: see text], is observed for [Formula: see text]. Hitherto, CeNi(9-x)Cu(x)Ge(4) represents the first system where a substitution-driven quantum phase transition is connected not only with changes of the relative strength of the Kondo effect and RKKY interaction, but also with a reduction of the effective crystal field ground state degeneracy.

Pseudoentanglement of spin states in the multilevel 15N@C60 system

We have prepared combined electron and nuclear spin pseudoentangled states Psi+/-27 and Phi+/-18 out of the total number of eight quantum states in the multilevel quantum system of a nitrogen atom with electron spin 3/2 and nuclear spin 1/2 encaged in the endohedral fullerene (15)N@C(60). Density matrix tomography was applied to verify the degree of entanglement.

Entanglement between an electron and a nuclear spin 1/2

We report on the preparation and detection of entangled states between an electron spin 1/2 and a nuclear spin 1/2 in a molecular single crystal. These were created by applying pulses at ESR (9.5 GHz) and NMR (21 MHz, 46 MHz) frequencies. Entanglement was detected by using a special entanglement detector sequence based on a unitary back transformation including phase rotation.

Reproducability and transferability of topological properties; experimental charge density of the hexapeptide cyclo-(D,L-Pro)2-(L-Ala)4 monohydrate

The charge density of a hexapeptide was determined from high-resolution CCD area-detector experiments at 100 K. Two datasets, one from a rotating anode and a second one from synchrotron radiation, were measured and the results are compared. The data are interpreted in terms of the 'rigid pseudoatom' model. The topology of the experimental density is analyzed and compared with the topology of the constituting amino acids, and shows good agreement. All critical points of the electron density at the covalent and hydrogen bonds, as well as those of the Laplacian, were located. With respect to the transferability of electronic and bond topological properties the six peptide bonds were compared with values given in the literature.

The antimicrobial properties of a urea-based handwash lotion with triclosan

The purpose of this study was to determine and compare the antimicrobial action of a urea-based handwash lotion with triclosan with a lipid-depleting detergent-based handwash product with 4% chlorhexidine gluconate. The zones of inhibition produced by the two handwash lotions and the one produced by the positive control were similar against all strains of bacteria tested, indicating that a urea-based handwash lotion with triclosan is as effective as a lipid-depleting handwash lotion in inhibiting bacterial activity.

Agostic deformations based on electron delocalization in the alkyllithium-complex [{2-(Me3Si)2CLiC5H4N }2Electronic supplementary information (ESI) available: experimental and theoretical details of multipole refinements and model systems. See http://www.rsc.org/suppdata/cc/b1/b105452j/

Topological analysis of experimental and theoretical charge densities in the title complex [(2-(Me3Si)2CLiC5H4N)2] 1 reveals the nature of the agostic deformation postulated for this complex: delocalization of the Li-C bonding electrons over the entire agostic alkyl group controls the formation of an acute Li-C-Si angle and thus a sufficient electronic saturation of the electron deficient lithium atom via secondary interactions.

An in vivo comparison of the antimicrobial activities of three mouthrinses

The purpose of this in vivo study was to determine and compare the antimicrobial effectiveness of three commercial mouthrinses and a water control. The antimicrobial efficacy of the products was determined against aerobic, micro-aerophilic, and anaerobic bacteria. Twenty human subjects participated in this study. At each experimental session for a given subject, a pre-test saliva sample was taken. This sample was divided and used to grow three bacteria cultures under the different incubation environments. After giving the pre-test sample, the subject rinsed with one of the mouthrinses or the water control for 30 seconds, then waited one hour, at which time a post-test saliva sample was collected. Again, the sample was divided and used to culture the different types of bacteria. Following a 48-hour incubation period, the numbers of microbial colonies on each plate were counted and compared. The results indicated that all of the mouthrinses tested performed significantly better than the water control. Herbal Mouth and Gum Therapy and Peridex did not demonstrate a statistically significant difference in inhibiting aerobic, microaerophilic, and anaerobic bacteria. Both Herbal Mouth and Gum Therapy and Peridex were significantly more effective than Listerine in inhibiting the three different types of bacteria.

Yttrium calix[4]arene complexes. Silylation and silylamine elimination reactions on model oxo surfaces

The synthesis and the spectroscopic and structural characterization of lower-rim-silylated and rare-earth-metalated calix[4]arenes are presented. Hexamethyldisilazane, HN(SiMe3)2, reacted in a selective manner with [p-tert-buttylcalix[4]arene]H4 (1) in refluxing mesitylene to give the 1,3-silylated product [p-tert-butylcalix[4]arene(SiMe3)2]H2 (2) in high yield. The molecular structure of compound 2, as revealed by X-ray crystallography, shows the pinched cone conformation of the calixarene bowl, featuring hydrogen bonding between the phenylsilyl ether and phenolic oxygen atoms (O...O, 2.838 A). From the reaction of the sterically more crowded tetraphenyldimethyldisilazane, HN(SiMePh2)2, only starting material could be recovered. In contrast, tetramethyldisilazane, HN(SiHMe2)2, afforded the tetrakis-silylated product [p-tert-butylcalix[4]arene(SiHMe2)4] (3) in hexane solution at ambient temperature. A single-crystal X-ray diffraction study of compound 3 established the 1,2-alternate conformation, which is also present in solution, as indicated by 1H NMR spectroscopy. The yttrium complex Y[N(SiHMe2)2]3(THF)2 (4) exchanged all of its silylamide ligands when treated with an equimolar amount of 1 in toluene at ambient temperature to yield compound 5, as indicated by IR and NMR spectroscopy. The molecular structure of 5 revealed a centrosymmetric dimer of composition [Y(p-tert-butylcalix[4]arene(SiHMe2)(THF)]2. Three of the deprotonated phenolic oxygen atoms of the calixarene bowl bind to the metal center, two as terminal ligands and one in a bridging mode, while the fourth undergoes in situ silylation (nu(SiH) 2127 cm-1). The distorted-trigonal-bipyramidal coordination geometry is completed by a THF molecule. Bis-silylated 2 reacted with 4 to form the heteroleptic complex (Y[p-tert-butylcalix[4]arene(SiMe3)2][N(SiHMe2)2]) (6). Crystal data: C50H72O4Si2 (2), triclinic, P1, a = 12.8914(3) A, b = 14.9270(5) A, c = 15.1652(4) A, alpha = 77.293(2) degrees, beta = 65.019(2) degrees, gamma = 72.234(2) degrees, Z = 2; C52H80O4Si4 (3), triclinic, P1, a = 10.1774(2) A, b = 14.1680(2) A, c = 18.7206(2) A, alpha = 95.8195(8) degrees, beta = 95.5294(8) degrees, gamma = 98.1098(7) degrees, Z = 2; C100H132O10Si2Y2, 2(C6H6) (5), triclinic, P1, a = 13.2625(4) A, b = 14.5894(3) A, c = 17.0458(5) A, alpha = 65.0986(14) degrees, beta = 77.8786(8) degrees, gamma = 85.5125(13) degrees, Z = 1.

Use of a compomer in Class V restoration: a microleakage study

OBJECTIVE

The purpose of this investigation was to evaluate the microleakage of Class V lesions restored with a compomer material (Dyractflow) using 2 single-bottle bonding systems.

METHOD AND MATERIALS

Sixty-four Class V cavity preparations were made on 32 sound, extracted human premolars, 1 preparation on the facial surface and 1 on the lingual surface. Teeth were then randomly divided into 2 groups. Group 1, which served as the control group, was restored as follows: group 1a, facial surface with PQ1 single-bottle bonding system plus TPH resin composite; group 1b, lingual surface with Prime & Bond NT single-bottle bonding system plus TPH. Group 2 was restored as follows: group 2a, facial surface with PQ1 plus Dyractflow compomer material; group 2b, lingual surface with Prime & Bond NT plus Dyractflow. After 24 hours of storage in water and subsequent thermocycling, each specimen was immersed in 0.2% basic fuchsin dye for 24 hours. The teeth were sectioned longitudinally and horizontally, and dye penetration at enamel and cementum margins was viewed at x30 magnification by 2 independently calibrated evaluators. Specimens were evaluated as either having leaked or not having leaked.

RESULTS

No statistically significant differences in microleakage were noted between group 1 and group 2 specimens.

CONCLUSION

Both single-bottle bonding systems, PQ1 and Prime & Bond NT, demonstrated equal effectiveness in reducing microleakage beneath compomer and composite restorations.

Microleakage of a condensable resin composite: an in vitro investigation

OBJECTIVE

The purpose of this investigation was to evaluate microleakage in Class II cavities restored with the condensable resin composite SureFil, placed with or without a liner and 1 of 2 different dentin bonding agents.

METHOD AND MATERIALS

Extracted noncarious human teeth were randomly divided into 4 groups of 15 each and restored according to manufacturer's instructions: group 1, SureFil and Prime & Bond NT; group 2, SureFil and PQ1; group 3, SureFil, PermaFlow, and PQ1; group 4, Heliomolar and Syntac Single-Component (control). Specimens were stored in 37 degrees C water for 24 hours. All specimens were thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Each specimen was immersed in 0.2% basic fuchsin dye for 24 hours and then sectioned longitudinally and horizontally. Dye penetration at enamel and cementum margins were viewed at x30 magnification by 2 independent, calibrated evaluators. Specimens exhibiting dye penetration > or = 0.1 mm beyond the cavosurface margin were considered to have leakage.

RESULTS

Chi-square tests revealed no statistically significant differences in the presence of microleakage when all groups were analyzed together. However, 2 by 2 comparisons revealed that group 3 had significantly fewer specimens with microleakage than did group 1, 2, or 4.

CONCLUSION

To limit microleakage, a flowable composite should be used as a liner when a condensable composite material is used.

Evaluations of the interface between amalgam and dentin with a single component dentin bonding system

The purpose of this scanning electron microscope study was to observe the dentin-amalgam interface after utilizing a standard restorative liner and a single-component dentin adhesive. Continuous interface gaps of over 15 mu were observed in specimens containing no lining and Copal varnish. Discontinuous 5 microns gaps were observed in specimens treated with PQ1. Additionally, specimens treated with PQ1 exhibited resin interpenetration into the dentin surfaces.

An in vitro investigation of the antimicrobial activity of an herbal mouthrinse

The purpose of this study was to determine the antimicrobial activity of one prescription and two commercially available over-the-counter mouthrinses and positive and negative controls against bacteria commonly found in the oral cavity. The bacteria used in this study were Streptococcus mutans, Streptococcus sanguis and Actinomyces viscosus. Sterile discs which were treated with the mouthrinses were placed on agar plates along with the controls. Zones of microbial inhibition were measured in millimeters after 48 hours. The results indicated that all of the mouthrinses demonstrated antimicrobial activity against the bacteria tested. Herbal Mouth and Gum Therapy mouthrinse, containing natural ingredients, produced the largest zones of microbial inhibition when compared to Listerine against all three of the bacteria tested. Herbal Mouth and Gum Therapy mouthrinse produced larger zones of microbial inhibition when compared to Peridex against two of the three bacteria tested, and produced similar zones of inhibition against the third bacteria.

The ability of an herbal mouthrinse to reduce gingival bleeding

Forty healthy adult volunteers from the Junior Comprehensive Care Clinics at New York University College of Dentistry were accepted as subjects for this three-month, examiner-blinded, parallel-group clinical trial. To be eligible for a baseline clinical examination, subjects had to first indicate that during the previous six months they habitually brushed their teeth two or more times per day and had noticed "bleeding gums" or "blood in the toothpaste" after brushing or after flossing their teeth. At the baseline examination, subjects were enrolled in the study if they were found to have at least five Löe-Silness gingival bleeding sites and 20 natural teeth, including four molars. Subjects were assigned to one of the two following treatment groups: 1) Herbal Mouth and Gum Therapy; or 2) Control (distilled water and dye). Subjects were instructed to clean their teeth in their usual manner, not to use any other mouthrinses or oral irrigation products for the duration of the study. Subjects were to return for clinical examinations after three months of product use. At these examinations, gingivitis and gingival bleeding scores were recorded. An independent t-test before treatment indicated that there were no significant differences between the baseline evaluations of the two groups in the study. A one-way analysis of variance (ANOVA), comparing gingivitis and bleeding scores from baseline and three months with the baseline scores as a covariate, indicated that Herbal Mouth and Gum Therapy produced a statistically significant effect (p < 0.01) on both parameters relative to the control mouthrinse. The results of this study support the clinical efficacy of Herbal Mouth and Gum Therapy in reducing gingivitis and gingival bleeding.

Clinical efficacy of an herbal toothpaste

The purpose of this three-month, double-blind, parallel-design clinical study was to compare the efficacy of two commercially available dentifrices, Herbal Toothpaste and Gum Therapy and Colgate Total, in controlling gingivitis, gingival bleeding, plaque and stain. Forty healthy adult volunteers from the Junior Comprehensive Care Clinics at New York University College of Dentistry were accepted as subjects for this clinical trial. To be eligible for a baseline clinical examination, subjects had to first indicate that during the previous six months they habitually brushed their teeth two or more times per day, and had noticed "bleeding gums" or "blood in the toothpaste" after brushing or flossing their teeth. At the baseline examination, subjects were enrolled in the study if they had at least five Löe-Silness gingival bleeding sites and 20 natural teeth, including all anterior teeth and four molars. An independent t-test before treatment indicated that there were no significant differences between the two groups at baseline. A one-way Analysis of Variance indicated that both dentifrices had a significant effect on gingivitis, gingival bleeding, plaque, and dental stain (p < 0.05). No significant statistical differences were observed between Herbal Toothpaste and Gum Therapy and Colgate Total for gingivitis or gingival bleeding. Herbal Toothpaste and Gum Therapy produced statistically significant differences in reducing plaque and stain relative to Colgate Total (p < 0.05). The results obtained in this study support the clinical efficacy of both products in reducing gingivitis and plaque, and demonstrate the efficacy of Herbal Toothpaste and Gum Therapy in maintaining reductions of plaque and stain.

Two in-office bleaching systems: a scanning electron microscope study

The purpose of this investigation was to analyze by scanning electron microscopy the effects of heated and light-absorbing bleaching agents on enamel surface morphology. Twelve freshly extracted human anterior teeth were selected for this study. The teeth were randomly divided into four equal groups: Group I (control), Group II (teeth treated with Opalescence Quick, a heated bleaching agent), Group III (teeth treated with Opalescence Xtra, a light-absorbing bleaching agent), Group IV (teeth treated with Ultra-Etch 35% phosphoric acid etchant). After receiving a prophylaxis with a slurry of pumice, the bleaching materials were applied to the facial enamel surfaces following the manufacturer's specifications. The teeth in Group IV were etched for 15 to 20 seconds, washed, and air-dried. All specimens were prepared for scanning electron microscope evaluations. Scanning electron microscope micrographs indicated that only those specimens etched with phosphoric acid (Group IV) exhibited an etching pattern on the enamel surface. No differences in enamel surface morphology were observed between the untreated control specimens and the specimens treated with the bleaching materials.

Antimicrobial activity of cavity disinfectants

The purpose of this study was to determine the antimicrobial activity of four commercially available cavity disinfectants and one prescription mouthwash as they came into contact with bacteria commonly found in the oral cavity. Streptococcus mutans, salivarius, and Actinomyces viscosus were used in the study. Zones of microbial inhibition were measured in millimeters after 48 hours. The results of this study indicate that all of the antimicrobial agents demonstrated activity against the bacteria tested. Consepsis Solution produced the largest zones of inhibition against all three of the bacteria used.

Treating enamel surfaces with a prepared pumice prophy paste prior to bonding

The use of pumice to remove the salivary pellicle, plaque, and/or surface debris is a well-known procedure. However, pumice can act as a contaminant. Therefore, a slurry of pumice without additives is recommended for use prior to bonding procedures. This article presents a review of the shear bond strengths obtained by bonding composite resin to enamel after the enamel had been cleansed with a slurry of pumice and a premixed caplet of pumice.

The use of resin-ionomer in restorative procedures

As the average age of the population increases, we are seeing a significant rise in root caries and in the need for restorative procedures associated more often with an older population. This paper describes the subgingival placement of a resin-ionomer for several restorative procedures, including root caries, resorption, endodontic perforation and root fracture. After endodontic therapy, full thickness flaps may be used to gain access to the lesion or root defect. The defects may be prepared with ultrasonic instruments and the preparations treated with a dentin conditioner. The preparations are then washed and lightly air-dried and treated with a dentin bonding agent. A resin-ionomer may then be syringed into the preparations and either light-activated or allowed to undergo a chemical set. No untoward effect has been observed during the time frame of this project. The cases presented indicate that a resin-ionomer may be used as a subgingival restorative and may be placed in lesions originally thought to be unrestorable. Thus, teeth may be saved that were previously designated for extraction.

Antimicrobial activity produced by six dentifrices

The antimicrobial activity of six commercially available dentifrices and positive and negative controls as they come into contact with Streptococcus mutans, S. sanguis, and Actinomyces viscosus commonly found in the oral cavity. Sterile discs treated with the dentifrices were placed on agar plates with the controls. Zones of microbial inhibition were measured in millimeters after 48 hours. All of the test dentifrices demonstrated antimicrobial activity against the bacteria.

A single-component bonding system microleakage study

The microleakage of a one-component bonding system is compared to a two-component system and a control. Class V cavity preparations were prepared in extracted teeth under high speed and water coolant so that incisal/occlusal margins were in enamel, and gingival margins were in dentin. Group I was restored with composite and no bonding agent; Group II was restored with Prime and Bond and composite, and Group III was restored with ProBond and composite. All specimens were thermocycled in fuchsin dye to evaluate the degree of microleakage. Significant differences were observed between the no bonding agent group and the Prime and Bond and ProBond groups. The results indicate that the one-step dentin bonding system has the ability to prevent microleakage effectively at both composite-enamel and composite-dentin tooth surface interfaces.

Effective tooth bleaching in 5 days: using a combined in-office and at-home bleaching system

This article compares the bleaching efficacy of a combined at-home and in-office system with that of an in-office system alone. Twenty people participated in the study. Ten of these participants were treated with an in-office 35% carbamide peroxide bleaching product in 2 visits of 15 minutes each. The remaining participants were treated with a combination at-home and in-office system that included a 15% carbamide peroxide at-home bleaching agent. After 5 days of treatment, the participants using the combination system demonstrated increased tooth whitening compared to those using the in-office system alone. Based on the sample size (20 patients), statistical significance was achieved.

A comparison of antimicrobial activity of etchants used for a total etch technique

The purpose of this study was to determine the antimicrobial activity of eight commercially available etchant materials and positive and negative controls as they came into contact with bacteria commonly found within the oral cavity. The following bacteria were used in this study: Streptococcus mutans, Streptococcus salivarius, and Actinobacillis actinomycetocomitants. The study was conducted in two parts: Part I--Etchants and controls placed within wells in agar plates; Part II--Enamel-dentin disks saturated with the etchants for 20 seconds and placed on the agar plates with the controls. Zones of microbial inhibition were measured in millimeters after 48 hours. The results of the study indicate that all of the etchants demonstrated antimicrobial activity against the bacteria tested.

The use of a resin ionomer in the regenerative treatment of an interproximal lesion: a case report

This article documents the clinical observations made in the course of a surgical procedure in which a resin ionomer was used as a barrier for guided tissue regeneration. The results indicate that this material appears to demonstrate potential in such procedures.

Root surface biomodification using a dentin bonding conditioner

OBJECTIVE

The purpose of this investigation was to compare by scanning electron microscopy (SEM) the surfaces of roots treated with a dentin conditioning agent and other materials that have been used routinely in periodontal therapy for root surface demineralization, namely, citric acid and tetracycline hydrochloride.

MATERIALS AND METHODS

Sixteen freshly extracted human teeth were randomly divided into four equal groups; each tooth was hand scaled and planed prior to root surface conditioning with citric acid, tetracycline hydrochloride, and a dentin bonding conditioner; Tenure Dentin Conditioner (DenMat Corporation, Santa Maria, CA). The last has been used previously in conjunction with a resin-ionomer barrier in cases involving guided tissue regeneration. Root specimens were prepared for scanning electron microscopy and representative micrographs were taken at 1000x and 2000x.

RESULTS

The results of this study indicate that there are morphological similarities between surfaces obtained with the dentin conditioning agent and the other acidic materials that are used routinely in periodontal regenerative therapy.

CONCLUSIONS

Root surface demineralization has been shown to remove the smear layer, and provides a surface which is conductive to mechanical adhesion and cellular mechanisms for growth and attachment.

The use of a resin-ionomer in varying restorative procedures: case reports

The purpose of this paper is to describe the subgingival placement of a resin-ionomer for several restorative procedures, namely, root resorption, endodontic perforation, and root fracture. After endodontic therapy, a combination scallop flap (in attached gingiva)-full thickness flap (at affected tooth only) was raised to gain access to the lesion and root defect. The root defects were prepared with ultra-sonic instruments under an operating microscope and the preparations treated with Tenure Dentin Conditioner (DenMat Corporation, Santa Maria, CA). The preparations were washed and lightly air-dried, and the Tenure All-Purpose Bonding System (Den Mat Corporation, Santa Maria, CA) was placed in the prepared areas. Geristore resin-ionomer (DenMat Corporation, Santa Maria, CA) was then syringed into the preparations and either light-activated or allowed to undergo a chemical set. Once set, the material was finished with fine diamonds under water spray. The flap was then sutured to place with Gore-Tex sutures when a non-resorbable Gore-Tex membrane (Gore Corporation, Flagstaff, AZ) was used or 4-0 nylon sutures when resorbable Guidor membranes (Butler Company, Bensenville, IL) were used. The sutures were removed after two days. The patients were observed weekly for the first month and then monthly until released. No untoward effects have been observed during the time frame of this project. All of the cases have been responding satisfactorily.

CLINICAL SIGNIFICANCE

The cases presented indicate that a resin ionomer, Geristore, may be used as a subgingival restorative, and may be placed in lesions thought to be unrestorable. Thus, teeth may be saved that were previously designated to be extracted.