Surface Morphology Of Dentin Research Articles

Effect of chitosan and CMCS on dentin after Er:YAG laser irradiation: shear bond strength and surface morphology analysis.

The aim of the present study was to evaluate the effect of chitosan and carboxymethyl chitosan (CMCS) on dentin surface morphology and bonding strength after irradiation of Er:YAG laser. Eighty-four laser-irradiated dentin samples were randomly distributed into three groups (n = 28/group) according to different surface conditioning process: deionized water for 60s; 1wt% chitosan for 60s; or 1wt% CMCS for 60s. Two specimens from each group were subjected to TEM analysis to confirm the presence of extrafibrillar demineralization on dentin fibrils. Two specimens from each group were subjected to morphological analysis by SEM. Seventy-two specimens (n = 24/group) were prepared, with a composite resin cone adhered to the dentin surface, and were then randomly assigned to one of two aging processes: storage in deionized water for 24h or a thermocycling stimulation. The shear bond strength of laser-irradiated dentin to the resin composite was determined by a universal testing machine. Data acquired in the shear bond strength test was analyzed by one-way ANOVA with the Tukey honestly significant difference post hoc test and Independent Samples t-test (α = 0.05). CMCS group presented demineralized zone and a relatively smooth dentin surface morphology. CMCS group had significantly higher SBS value (6.08 ± 2.12) without aging (p < 0.05). After thermal cycling, both chitosan (5.26 ± 2.30) and CMCS group (5.82 ± 1.90) presented higher bonding strength compared to control group (3.19 ± 1.32) (p < 0.05). Chitosan and CMCS group preserved the bonding strength after aging process (p > 0.05). CMCS has the potential to be applied in conjunction with Er:YAG laser in cavity preparation and resin restoration.

The effect of silver nanoparticles in addition to sodium fluoride on remineralization of artificial root dentin caries.

Silver nanoparticle was developed to overcome the drawback of silver diamine fluoride. However, evidence is limited, especially in root caries. The aim of this study was to evaluate the remineralization effect of silver nanoparticles on root caries. Fifty-five root human dentin slices size 5 × 5 mm2 from patients aged over 60 years old were immersed in demineralized solution to create artificial caries. Specimens were allocated into five groups according to the remineralizing agents: silver diamine fluoride (SDF), silver nanoparticles solution (AgNPs), silver nanoparticle solution followed by sodium fluoride varnish (AgNPs+NaF), sodium fluoride varnish (NaF), and tap water. After 8 days of pH-cycling challenge, the microhardness test, lesion depth evaluation, dentin surface morphology, and elemental analysis were performed. Data was analysed using F-test One-way ANOVA followed by Tukey's post hoc test and paired T-test. All test groups demonstrated a significantly higher microhardness value and lower lesion depth compared with the control group. AgNPs+NaF and NaF-treated groups showed lower efficacy than SDF. Crystal precipitation was presented in all groups composed of silver. Addition of fluoride varnish did not benefit for silver nanoparticles in preventing further demineralization. SDF provides the highest effectiveness in elderly root carious dentin.

Ultrasound device as a minimally invasive approach for caries dentin removal.

The aim of this study was to evaluate the efficacy of an ultrasound device and the dentin surface morphology after removal of the caries dentin lesions by removal rate and scanning electron microscopy (SEM). The Knoop hardness test on the bovine dentin blocks (n = 20, 4x4x2mm) was performed to standardize the samples and only those with 38 ± 2 KHN were included. The dentin blocks were submitted to induction of artificial caries lesions, using the bacterial model. Strains of Streptococcus mutans and Lactobacillus acidophilus were used for 7 days. The caries dentin lesion was removed for 1 min, according to two methods: G1 - carbide bur under low-speed rotation (control group) and G2 - ultrasound device under refrigeration. For the removal rate, the samples were weighed 3 times: T0 (before induction), T1 (after induction) and T2 (after removal). Morphology evaluation of the residual dentin surface was performed by SEM. Data normality was verified by Shapiro-Wilk test (p ≥ 0.240). T-test for independent samples was applied to evaluate the removal rate. A significance level of 5% was adopted. G2 provided lower removal rate than G1 (G1: 3.68 mg and G2 = 2.26 mg). SEM images showed different morphological characteristics between the groups. G2 showed absent of smear layer, while G1 showed a visible smear layer over the surface. We concluded that ultrasound device provides minimally invasive removal with residual dentin exhibiting open dentin tubules and no smear layer formation and no bacteria, which infer the removal of the infected tissue.

Dentin surface and hybrid layer morphological analysis after use of a copaiba oil- based dentin biomodifier

This study evaluated dentin surface and hybrid layer’s morphology, using copaíba (CO) emulsion as dentin biomodifier before traditional and self-etching adhesive, by environmental scanning electron microscopy (ESEM). Ninety-six third sound molars were divided into 16 groups, according to the dentin substrate, tested substances, and the adhesive system used. The conditioned dentin surface treated with clorexidina (CHX) 2% showed phosphate salts on two dentin substrates as well as the sound conditioned or not surface treated with calcium hydroxide solution (CHS), where the mineral precipitate deposition obstructs the tubules lumen. A significant difference (p &lt;0.0001) in dentin surface morphology was observed at the CHS group on conditioned and not conditioned sound dentin. The CO emulsion produced a regular and homogenous hybrid layer with many resin tags on both dentin surfaces, irrespective of the adhesive system used, with better performance than CHS and CHX 2% (p =0.0007) on caries-affected dentin at the self-etching group. CO emulsion showed no morphological changes on sound and caries-affected dentin and presented a regular hybrid layer, regardless of the adhesive system used.&#x0D; Keywords: Copaiba oleoresin; Emulsions; Dentin-bonding agents; Phytotherapy.

COMPARATIVE MORPHOLOGICAL ANALYSIS OF ENAMEL AND DENTIN SURFACES’ RECONSTRUCTIONS BY MEANS OF AUTOMATED DIGITAL ODONTOMETRY

Abstract. Studies of teeth represent a significant part of palaeoanthropological research. Over the past two decades these studies have significantly developed with implementation of high resolution imaging based on x-ray scanning techniques. Highly informative reconstructions based on image processing have provided an opportunity to study morphological layers and structures of teeth which are usually hidden under the outer layer of dental enamel. Thus micro-computed tomography of the studied teeth has been performed in order to obtain reconstructions of enamel and dentin surfaces. The material is represented by well-preserved teeth of an adolescent from Upper Palaeolithic archaeological site of Sunghir world-renowned archaeological site in Vladimir Oblast in the Russian Federation. The characteristic feature of the studied teeth is in their unusual, presumably archaic, morphology, which has been previously studied and described through measurements by application of automated digital odontometry method; however the mentioned study referred to the enamel surface. And in the current study these algorithms are applied to measure the surface of dentin. As this is the first successful attempt of measuring dentin surface morphology, the process has to be improved for complete automation. Nevertheless even currently applied approaches allow to compare enamel and dentin morphology through measurements.

Physiochemical characteristics: A robust tool to overcome teeth heterogeneity on predicting laser ablation profile.

To avoid excessive tissue removal and collateral damage, the high-power density laser is apt for dental surgery also need to have high precision. For high-precision dental surgery with minimal tissue damage, the present work frames a method to predict laser ablation profile based on surface morphology and chemical composition of dentin. The surface morphology and chemical composition were studied on different dentin samples using scanning electron microscope (SEM) and Energy Dispersive X-ray Analysis (EDAX), respectively. The key laser ablation parameters (ω0 , Deff , and Fth ) were determined by laser irradiation study using 800 nm, Ti:Sapphire femtosecond laser at processing condition of 100 fs, 10 kHz and 10 mm/s. The dentin samples show a strong linear correlation between physiochemical characteristics and laser ablation parameters. The surface morphology exhibits a negative linear correlation with threshold fluence, whereas the converse is true for chemical composition. The laser ablation parameters of a random dentin sample are derived from the knowledge of linearity data. From the obtained laser ablation parameters, the complete theoretical ablation profile is constructed and validated with experimental ablation profile. Even though the surface morphology of dentin shows high linearity, the concentration of Ca and P can be used as the most feasible probe in clinical settings. Furthermore, the laser ablation rate and ablation efficiency are predicted by the method to optimize the laser processing condition for any specific teeth. The versatility of the method overcomes the problem of heterogeneity on various teeth and simplifies the method of finding optimal laser processing condition for immaculate laser surgery.

Effect of Dentin Pretreatment with Arginine on Microshear Bond Strength of Etch-and-Rinse or Self-Etch Adhesive Systems.

Objective The main purpose of this study was to evaluate the effect of dentin pretreatment with 8% arginine on the immediate and 6-month bond strength (BS) of adhesive systems and surface morphology of dentin. Materials and Methods Dentin bovine specimens (5 × 5 mm) were allocated into following pretreatments: without pretreatment (conventional technique, C) or exposure to arginine solution (A) for 5 minutes prior to tooth restoration. The adhesive procedure was performed using ( n = 12): 3-step etch-and-rinse adhesive (Scotchbond Multipurpose—SBMP [C+SBMP and A+SBMP]); 2-step etch-and-rinse adhesive (Single Bond 2 - SB [C+SB and A+SB]); or 2-step self-etch adhesive (Clearfil SE Bond - CSEB [C+CSEB and A+CSEB]). After 24 hours, the composite resin restorations were evaluated immediately and after 6 months of water storage using a microshear test and fracture pattern. The dentin surface exposed to A was assessed by scanning electron microscopy (SEM). The immediate BS data were submitted to a two-way analysis of variance and Tukey's test, and the long-term BS results were analyzed using Kruskal–Wallis and Dunn tests (α = 0.05). Results There was a significant decrease in immediate and 6-month BS for the A+SB and A+CSEB groups, which differed statistically from the C group. The fracture pattern was predominantly adhesive for SB and CSEB adhesive for C and A. The SEM images presented a different conditioning pattern of the dentin exposed to A. Conclusion The dentin pretreatment with arginine interfered negatively in the immediate and long-term BS of the simplified adhesive system. However, the SBMP adhesive was not affected by arginine pretreatment presenting the most satisfactory results.

Dynamic Irrigation Promotes Apical Papilla Cell Attachment in an Ex Vivo Immature Root Canal Model

IntroductionThe use of dentin preconditioning techniques in regenerative endodontic procedures is currently promising. Several growth factors have been detected on dentin after ultrasonic irrigation with EDTA. This study aimed to evaluate the effects of dynamic irrigation with different solution regimens on apical papilla cell (APC) attachment in an ex vivo immature tooth model. MethodsVarious dynamic irrigation techniques, needle irrigation (NI), NI with EndoActivator, and NI with passive ultrasonic irrigation, were used with different solution regimens, normal saline solution (NSS), EDTA, and chlorhexidine digluconate followed by EDTA, in enlarged root canal models where calcium hydroxide–medicated dentin slices were inserted. The initial number of attached fibronectin-positive APCs was counted. Dentin surface morphology was also inspected by using scanning electron microscopy. ResultsThe number of APCs was significantly greater in the dynamic irrigation groups than in the control group (P < .001). Greater APC numbers were observed in the groups in which NSS was used than in those in which EDTA or chlorhexidine digluconate/EDTA was used, when using the same techniques (P < .001). Cell numbers were similar at all levels of the root canals; however, in the ultrasonically supplemented group irrigated with NSS, the number of attached cells was significantly increased at the middle and apical levels (P < .05). ConclusionsThe use of dynamic irrigation techniques in an immature tooth model definitely promoted APC attachment to calcium hydroxide–medicated dentin. Furthermore, when NSS was used as a final irrigant, the number of attached cells was significantly increased.

THE POTENTIAL OF SEVERAL FLUORIDE-BASED VARNISHES AS REMINERALIZATION AGENTS: MORPHOLOGICAL STUDIES, DENTIN SURFACE HARDNESS, AND CRYSTALLINITY TESTS

Objectives: This study was conducted to analyze the effects of several fluoride-based varnishes: Sodium diamine fluoride (SDF), nanosilver fluoride (NSF), and propolis fluoride (PPF). Fluoride-based varnish is proven to remineralize and arrest caries progression with minimal side effects. SDF, the gold standard for this study, compared to NSF and PPF to observe the dentin morphology, hardness, and crystallinity test.Methods: Dentin blocks were allocated and divided into control groups and treatment groups with SDF (38%), NSF (3.16%, 3.66%, and 4.16%), and PPF (3%, 6%, and 10%). The dentin discs were demineralized using a demineralization solution (pH 4.4) for 96 h. Each dentin disc in the treatment group received a topical application of various fluoride-based varnishes and was then subjected to pH cycling for 8 days. The surface morphology of dentin was observed by a scanning electron micrograph (SEM), dentin hardness was analyzed by a Vickers microhardness tester, and the crystal characteristics of dentin blocks were investigated by X-ray diffraction (XRD).Results: This study showed crystal fluorapatite on the dentin surface of SDF and NSF. There was an amorphous layer on the dentin surface of PPF (10%) detected when using SEM. The Vickers hardness number of dentin increased after the application of SDF, NSF, and PPF. XRD revealed precipitates of apatite compounds, calcium compounds, and metal compounds in the treatment groups in higher concentrations than in the control (demineralized) group.Conclusion: It was concluded that SDF, NSF, and PPF were effective for dentin remineralization. Hence, NSF and PPF fluoride-based varnishes are promising as anticariogenic agents.

Effect of laser activated bleaching on the chemical stability and morphology of intracoronal dentin

ObjectivesTo evaluate the effect of the bleaching with 35% hydrogen peroxide either activated or not by a 970nm diode laser on the chemical stability and dentin surface morphology of intracoronary dentin. MethodsTwenty-seven slabs of intracoronary dentin specimens (3×3mm) were distributed into three groups (n=9), according to surface treatment: HP – 35% hydrogen peroxide (1×4’), DL – 970nm diode laser (1×30”/0,8W/10Hz), HP+DL – 35% HP activated with 970nm diode laser (1×30”/0,8W/10Hz leaving the gel in contact to the surface for 4′ after activation). Three Raman spectra from each fragment were obtained to calculate the mean intensity of peaks of inorganic component (a.u.), organic collagen content (a.u.), and the ratio of inorganic/organic content, before and after treatment. Analyses of the samples by confocal laser microscopy were performed to evaluate the surface roughness, percentage of tubules, perimeter and area percentage of tubules, before and after treatment. Data were analyzed by Kruskal-Wallis, Dunn’s, and Wilcoxon test (P<0.05). ResultsData analysis showed that HP+DL did not change the inorganic content peaks 8.31 [29.78] or the inorganic/organic ratio 3.37 [14.67] (P>0.05). Similarly, DL did not affect the chemical stability of the dentin surface (P>0.05). However, HP significantly increased inorganic content peaks 10.87 [22.62], as well as the inorganic/organic ratio 6.25 [27.78] (P<0.05). Regarding the morphological alterations, all surface treatments increase tubules exposure; HP treatment significantly increases perimeter and area percentage; and HP+DL increases surface roughness. ConclusionsBleaching HP combined with DL offers an improvement in terms of intracoronal dentin surface protection, yielding better maintenance of dentin chemical stability and morphology.

Effect of silane contamination on dentin bond strength

Statement of problemIntraoral repair of porcelain or other silica-based ceramics typically requires the use of silane in the repair protocol. Some porcelain intraoral repairs also involve bonding to exposed or involved tooth tissues including dentin. A study is needed to evaluate whether the cross-contamination of dentin with silane affects bond strength to this tissue. PurposeThe purpose of this in vitro study was to investigate the effect of silane cross-contamination on dentin bond strength. Material and methodsFlat surfaces of human dentin specimens were created, followed by wet polishing with 320-grit silicon carbide paper. The dentin specimens were divided into 4 groups: group SE (All-Bond Universal Adhesive used in self-etching mode); group SiSE (silane applied to dentin followed by All-Bond Universal Adhesive used in self-etching mode); group ER (All-Bond Universal Adhesive used in total-etch (etch-and-rinse) mode); and group ERSi (Etch and rinse and silane applied to dentin followed by All-Bond Universal Adhesive). The dentin specimens were treated with a universal adhesive (All-Bond Universal) and bonded with a composite resin, using an Ultradent jig mold. Shear bond strength (n=10) was measured after 24 hours of water storage at 37°C. After the shear bond strength test, the dentin sides of fractured specimens in each group were examined with a stereomicroscope at ×15 magnification to determine failure modes. Data were statistically analyzed by 2-way and a 1-way ANOVA followed by post hoc Tukey honest significant difference test (α=.05). Scanning electron microscopy examination was used to evaluate the dentin surface morphology before and after bonding. ResultsThe shear bond strength of composite resin to dentin was not affected adversely when the dentin was contaminated with silane prior to using All-Bond Universal in the self-etch or total- etch (phosphoric acid) mode. SE, 30.3 ±3.8 MPa; SiSE, 32.9 ±3.9 MPa; ER, 34.9 ±3.1 MPa; ERSi: 35.2 ±4.9 MPa (P>.05) ConclusionsUnder the conditions of this study, cross-contamination of dentin with silane before the use of All-Bond Universal in the self-etch or total-etch with phosphoric acid mode did not adversely affect composite resin bond strength to dentin.

Evaluation of the Morphological Characteristics of Laser-Irradiated Dentin.

The aim of this study was to investigate the effect of different energy settings of Er:YAG laser irradiation on dentin surface morphology with respect to the number of opened dentinal tubules. An ideally prepared dentin surface with opened dentinal tubules is a prerequisite for adhesive fixation. No study, however, has yet compared the numbers of opened dentinal tubules with regard to statistical differences. Conventional preparations using a bur with or without additional acid etching acted as control groups. Dentin specimens were prepared from human third molars and randomly divided into eight groups according to the energy settings of the laser (1, 1.5, 4, 6, 7.5, and 8 W) and two controls (bur and bur plus acid etching). After surface preparation, dentin surfaces were analyzed with a scanning electron microscope, and the number of opened dentinal tubules in a defined area was counted. The control groups showed smooth surfaces with (bur plus acid etching) and without opened dentinal tubules (bur), whereas all laser-irradiated surfaces showed rough surfaces. Using the energy setting of 4 W resulted in significantly more opened dentinal tubules than the conventional preparation technique using the bur with additional acid etching. In contrast, the energy setting of 8 W showed significantly fewer opened dentinal tubules, and also exhibited signs of thermal damage. The Er:YAG laser with an energy setting of 4 W generates a dentin surface with opened dentinal tubules, a prerequisite for adhesive fixation.

The influence of hemostatic agents on dentin and enamel surfaces and dental bonding: A systematic review

Hemostatic agents have been used clinically in dentistry for many years to control bleeding. The authors reviewed scientific publications in which researchers investigated the effects of hemostatic agents on dentin and enamel surfaces and on bonding of adhesive systems and resin cements. The authors screened PubMed and Scopus databases for studies in English published from 1980 to 2013. They read the titles and abstracts to identify literature that fulfilled the inclusion criteria. The authors included studies in which researchers evaluated the hemostatic action on the dentin and enamel surfaces or its influence on the bond strength of adhesive systems or resin cements. They used cross-referencing to identify more articles. Twenty in vitro studies met the inclusion criteria. Investigators in 12 of these studies evaluated the bond strength to contaminated dentin. Investigators in 10 of these studies reported a significant decrease in bond strength. Those in two studies evaluated the influence of a hemostatic agent on the dental enamel and reported decreases in bond strength. Researchers also reported significant increases in microleakage of self-etching adhesives on contaminated dentin. Scanning electron microscopy revealed partial removal of the smear layer or an etching effect of dentin as a result of the application of hemostatic agents on dentin. Adhesive procedures may be affected adversely when performed on dentin and enamel contaminated by hemostatic agents. Hemostatic agents may induce changes in the dentin surface morphology. The results of this review indicate that the bond strength of self-etching adhesive systems is affected more negatively than is that of etch-and-rinse systems. The authors found that a 60-second application of ethylenediaminetetraacetic acid followed by a water spray restored the bond strength of a self-etching adhesive to dentin; use of phosphoric acid for 15 seconds followed by a water spray also was an effective cleaning method. Direct comparison of selected studies was not possible, however, mainly because of methodological differences hampering definitive conclusions.

Effects of NaOCl or combination of NaOCl and various acids on dentin surface morphology: A SEM study

The aim of this study was to evaluate by SEM morphological changes of dentin surfaces under the use of 5% NaOCl before applying different acids for etching. In the study, dentin surfaces were prepared from the middle third of 20 non-carious human third molars. Samples were divided into 2 groups with 3 subgroups each. In the first group, no application was performed on dentin surfaces. In the second group, 5% NaOCl was applied for 60 seconds on the dentin surfaces then rinsed with distilled water for 5 seconds. In all of the subgroups, dentin surfaces were etched by different conditioning agents for 15 seconds then rinsed for 30 seconds. After surface applications, all of the specimens were placed in distilled water. Morphological changes of dentin surfaces were determined by SEM. The results were evaluated by the scoring system based on Brannström et al. In the NaOCl treated groups, scores were as follows: The score of dentin without NaOCl treatment was 0, while it was 4 after phosphoric acid application, 3 after only citric acid-ferric chloride, and 1 after only maleic acid application. In the group where only NaOCl was applied, the score was not exactly 1 but slightly less. The score for NaOCl with phosphoric acid was 4, NaOCl with citric acid-ferric chloride was 3, and NaOCl with maleic acid was 2. Weak acid was found more effective on NaOCl treated dentin surfaces when compared with non-treated dentin surfaces.

Microtensile bond strength analysis of adhesive systems to Er:YAG and Er,Cr:YSGG laser-treated dentin

The aim of this in vitro study was to evaluate the effect of different surface treatments (control, diamond bur, erbium-doped yttrium aluminum garnet (Er:YAG) laser, and erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser) on sound dentin surface morphology and on microtensile bond strength (μTBS). Sixteen dentin fragments were randomly divided into four groups (n = 4), and different surface treatments were analyzed by scanning electron microscopy. Ninety-six third molars were randomly divided into eight groups (n = 12) according to type of surface treatment and adhesive system: G1 = Control + Clearfil SE Bond (SE); G2 = Control + Single Bond (SB); G3 = diamond bur (DB) + SE; G4 = DB + SB, G5 = Er:YAG laser (2.94μm, 60mJ, 2Hz, 0.12W, 19.3J/cm(2)) + SE; G6 = Er:YAG + SB, G7 = Er,Cr:YSGG laser (2.78μm, 50mJ, 30Hz, 1.5W, 4.5J/cm(2)) + SE; and G8 = Er,Cr:YSGG + SB. Composite blocks were bonded to the samples, and after 24-h storage in distilled/deionized water (37°C), stick-shaped samples were obtained and submitted to μTBS test. Bond strength values (in megapascal) were analyzed by two-way ANOVA and Tukey tests (α = 0.05). G1 (54.69 ± 7.8MPa) showed the highest mean, which was statistically significantly higher than all the other groups (p < 0.05). For all treatments, SE showed higher bond strength than SB, except only for Er,Cr:YSGG treatment, in which the systems did not differ statistically from each other. Based on the irradiation parameters considered in this study, it can be concluded that Er:YAG and Er,Cr:YSGG irradiation presented lower values than the control group; however, their association with self-etching adhesive does not have a significantly negative effect on sound dentin (μTBS values of >20MPa).

Morphology of resin–dentin interfaces after Er,Cr:YSGG laser and acid etching preparation and application of different bonding systems

The goal of this study was to show the modifications in the ultrastructure of the dentin surface morphology following different surface treatments. The stability of the adhesive compound with dentin after laser preparation compared with conventional preparation using different bonding agents was evaluated. An Er,Cr:YSGG laser and 36% phosphoric acid in combination with various bonding systems were used. A total of 100 caries-free human third molars were used in this study. Immediately after surgical removal teeth were cut using a band saw and 1-mm thick dentin slices were created starting at a distance of 4 mm from the cusp plane to ensure complete removal of the enamel. The discs were polished with silicon carbide paper into rectangular shapes to a size of 6 × 4 mm (±0,2 mm).The discs as well as the remaining teeth stumps were stored in 0.9% NaCl at room temperature. The specimens were divided into three main groups (group I laser group, group II etch group, group III laser and etch group) and each group was subdivided into three subgroups which were allocated to the different bonding systems (subgroup A Excite, subgroup B Scotchbond, subgroup C Syntac). Each disc and the corresponding tooth stump were treated in the same way. After preparation the bonding composite material was applied according to the manufacturers' guidelines in a hollow tube of 2 mm diameter to the disc as well as to the corresponding tooth stump. Shear bond strength testing and environmental scanning electron microscopy were used to assess the morphology and stability of the resin-dentin interface. The self-etching bonding system showed the highest and the most constant shear values in all three main groups, thus enabling etching with phosphoric acid after laser preparation to be avoided. Thus we conclude that laser preparation creates a surface texture that allows prediction of the quality of the restoration without the risk of negative influences during the following treatment steps. This can easily and repeatedly be achieved.

Effect of pulse duration of Er:YAG laser on the dentin surface morphology

The purpose of this study was to investigate the effects of different pulse durations of Er:YAG laser on the morphology of human dentin. Dentin discs obtained from extracted human third molars were exposed to a single pulse irradiation with an Er:YAG laser at 150 mJ/pulse and 80, 100, 150, 200, 250, 300, 400 and 500 μs of pulse duration. The irradiated surfaces and the cross sections were evaluated using an scanning electron microscope (SEM). There was no difference among the diameters of each irradiated area. The morphology pattern was similar in the 80 to 200 μs, without melted surfaces. The 250 to 500 μs groups presented more melted surfaces. It was concluded that the difference of pulse duration partially affected the pattern of the irradiated dentin surface.

Effect of XeCl-308nm excimer laser on the mineral content of human dentin.

The effect of the XeCl-308nm excimer laser on the mineral content and surface morphology of cut dentin was examined in ten extracted human teeth. Each dentin specimen was lased for 4 s at a fluence of 1 J/cm2 and a frequency of 25 Hz. Non-lased area of the same specimen served as control. Scanning electron microscopy and energy dispersive spectrometry revealed a significant decrease in the phosphorus levels following laser treatment. A decrease in calcium levels also occurred but was not statistically significant. Nonsignificant changes in sulphur and potassium levels were also noted. Morphologically, the lased dentin showed an apparently melted surface with partial obstruction of the dentin tubules as well as cracks along the lased surface. Therefore, it appeared that laser treatment may alter the chemical structure as well as the surface morphology of the dentin.

Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhesive systems.

Cross-sections of resin-dentin interfaces were etched with an argon-ion beam to make their substructure detectable by scanning electron microscopy. The dentin adhesive systems were categorized morphologically into three groups, and an attempt was made to clarify their adhesive mechanism. The first group of products removed the smear layer. The argon-ion bombardment clearly disclosed a hybrid or resin-impregnated dentin layer. It is hypothesized that conditioning with acidic or chelating agents demineralized the dentin surface-layer to a certain depth, leaving behind a collagen-rich mesh-work. Hydrophilic monomers are then believed to alter this collagen-fiber arrangement in a way that facilitates penetration of the adhesive resin, resulting in a mechanical, intermingled link between collagen and the adhesive resin. The second group preserved the smear layer. In this case, the dentinal tubules were obliterated with globular particles at their orifices and remained patent underneath these smear plugs. This type of adhesive system aims at the incorporation of the smear layer into the hydrophilic monomers, which have an affinity for the organic and/or inorganic components of the underlying dentin. Finally, a third, small group only partly dissolved the smear layer, creating a thin resin-impregnated dentin layer and a resin-impregnated smear plug. This study clearly showed that the application of recent adhesive systems induced structural changes in the dentin surface morphology, creating a retentive interface, called the inter-diffusion zone, between the deep, untouched dentin layers and the composite filling material. This resin-dentin interdiffusion zone offers bonding sites for copolymerization with the resin composite and, concurrently, might have protective potential for the pulp tissues.