The association between Nd:YAG laser and desensitizing dentifrices for the treatment of dentin hypersensitivity.

This study aims to evaluate the association between Nd:YAG laser (with and without a photoabsorber) and two desensitizing dentifrices containing 15% NovaMin or 8% arginine, as potential treatments for dentin hypersensitivity (DH). DH was simulated by EDTA application for 2 min. Specimens were then analyzed with an environmental scanning electron microscope (ESEM) to ensure open dentin tubules (ODT), counted by using ImageJ software. Specimens were randomized into eight groups (n = 10): Laser (L), Laser+Photoabsorber (LP), Arginine (A), Arginine+Laser (AL), Arginine+Laser+Photoabsorber (ALP), NovaMin (N), NovaMin+Laser (NL), and NovaMin+Laser+Photoabsorber (NLP). Laser irradiation was performed with 1 W, 100 mJ, 10 Hz, ≅85 J/cm2; 4 irradiations of 10 s each, with 10 s intervals between them. After treatment, specimens were again analyzed by ESEM and submitted to erosive/abrasive cycling for 5 days. A final ESEM analysis was performed. Data were analyzed with two-way repeated measure ANOVA and Tukey tests (α = 0.05). After treatment, groups N, NL, and NLP presented the lower number of ODT, but they did not different from LP, ALP, and AL. Group A presented the highest number of ODT and it did not differ from group L. Groups L, AL, ALP, and LP presented intermediate results, without differing from each other. After cycling, group A presented the highest number of ODT and did not differ significantly from the other groups, except NLP. None of the associations tested presented better tubule occlusion than NovaMin by itself. Arginine was the only treatment that presented improved tubule occlusion when associated with Nd:YAG laser.

Calcium sodium phosphosilicate had some benefit on dentine hypersensitivity.

DATA SOURCES: Medline (via Pubmed), Embase, Web of Science, CENTRAL (The Cochrane Library), and the Chinese Biomedical Literature Database. Search strategy was limited to articles published in English and Chinese. No restriction applied to date of publication and a supplemental manual search was conducted by reviewing the reference lists for related paper and articles. Grey literature was also searched in ClinicalTrials.gov, the National Research Register, OpenGrey and the WHO's international clinical Trial Registry Platform. STUDY SELECTION: Randomised controlled trials in humans with DH that compared topical CSPS in any modality and any concentration to a negative (placebo) control. The primary outcome was the DH pain response to routine activities or to thermal, tactile, evaporative or electrical stimuli, and the secondary outcome was the side effect of CSPS use including discomfort, oral hygiene deterioration or dental staining.Data extraction and synthesisStudy selection, data extraction and risk bias assessment were carried out in duplicate by two calibrated reviewers. Any disagreement was resolved via discussion after consulting a third reviewer. Mean differences (MDs) and standard deviations (SDs) were used to summarise data in studies with continuous outcomes. Heterogeneity was assessed using the I(2) test. Meta-analysis was performed when similarities were found among the included studies. The Grading of Recommendations Assessment Development and Evaluation (GRADE) System's Profiler was used to assess the quality of the body of the evidence. RESULTS: Eleven trials were included comparing CSPS with a negative control. Four articles that focused on post-periodontal therapy were extracted as an independent analysis group. CSPS was used in topical administration with concentrations ranging from 2.5%-15%. Follow-up times ranged from 15 days to eight weeks. DH pain was elicited by tactile, evaporative or thermal stimuli. A 10 cm visual analogue scale (VAS) was the most commonly used for measurements. Five studies revealed a low risk of bias, one study had a high risk of bias and five studies had an unclear risk of bias. Seven of the studies were regarded as having a potential conflict of interest.For the primary outcome (DH) Subjects in the DH group (four studies) showed that toothpaste containing 5% CSPS was favoured compared with a negative control at almost every time point, however one study did not report a significant difference between these treatments at two weeks.The results from the from the grey literature (two studies) did not show significant differences between the CSPS and control groups and the results were not in agreement with the other studies. Another study observed effects of both 2.5% and 7.5% CSPS-containing toothpaste: 7.5% CSPS was more effective at relieving DH than a negative control, whereas no significant difference was found between 2.5% and the negative controls.For the secondary outcome (adverse events): six studies did not observe adverse reactions. The remaining studies reported minor adverse events, although most were not orally related.Toothpaste containing 5% CSPS versus negative control: the 5% CSPS-containing toothpaste showed a better desensitising effect at both two and six weeks regardless of the applied stimuli (evaporative, two weeks: MD = -0.68; 95% CIs = -1.15, -0. 20; I2 = 59%; evaporative, six weeks: MD = -1.69; 95% CIs = -1.86, -1.52; I2 = 42%; thermal, two weeks: MD = -0.59; 95% CIs = -1.33, 0.14; I2 = 84%; and thermal, six weeks: MD = -1.70; 95% CIs = -2.17, -1.23;I2 = 72%). The quality of evidence was categorised as 'moderate'.Prophylaxis paste containing 15% CSPS versus negative control: prophylaxis paste containing 15% CSPS showed a better desensitising effect on post-periodontal therapy DH pain than a negative control, immediately after prophylaxis and at four weeks, as determined using evaporative or tactile stimuli, and the results showed relatively low heterogeneity (evaporative, immediate: MD = -0.87; 95% CIs = -1.23, -0.51; I2 = 0%; evaporative, four weeks: MD = -0.93; 95% CIs = -1.11, -0.75; I2 = 41%; tactile, immediate: MD = -9.59; 95%CIs = -12.17, -7.01; I2 = 55%; and tactile, four weeks: MD = -8.34; 95% CIs = -10.87, -5.80; I2 =0%). The quality of evidence was classified as 'low'.The two studies that assessed patients' self-assessments of dentine sensitivity were not pooled because of clinical heterogeneity. CONCLUSIONS: The majority of the studies included in the review found that sodium phosphosilicate was more effective than negative control at alleviating dentine hypersensitivity, used either as toothpaste to alleviate DH or as a prophylaxis paste to treat post-periodontal therapy DH. The review found moderate quality of evidence that 5% CSPS-containing toothpaste is effective for use as an at-home treatment to relieve DH. There is low quality evidence that prophylaxis paste containing 15% CSPS is favoured over a negative control at reducing post-periodontal therapy hypersensitivity. It remains unclear whether concentrations of more than 5% CSPS have increased risk of side effects. The results are based on a small number of clinical trials. Seven of the studies were industry or partially industry-sponsored.

Dentin tubule occluding ability of dentin desensitizers.

PURPOSE: To compare the dentin tubule-occluding ability of fluoroaluminocalciumsilicate-based (Nanoseal), calcium phosphate-based (Teethmate Desensitizer), resin-containing oxalate (MS Coat ONE) and diamine silver fluoride (Saforide) dentin desensitizers using artificially demineralized bovine dentin. METHODS: Simulated hypersensitive dentin was created using cervical dentin sections derived from bovine incisors using phosphoric acid etching followed by polishing with a paste containing hydroxyapatite. The test desensitizers were applied in one, two, or three cycles, where each cycle involved desensitizer application, brushing, and immersion in artificial saliva (n= 5 each). The dentin surfaces were examined with scanning electron microscopy, and the dentin tubule occlusion rate was calculated. The elemental composition of the deposits was analyzed with electron probe microanalysis. Data were analyzed by one-way ANOVA and the Tukey honestly significant different test. RESULTS: Marked deposit formation was observed on the specimens treated with Nanoseal or Teethmate Desensitizer, and tags were detected in the specimens' dentin tubules. These findings became more prominent as the number of application cycles increased. The major elemental components of the tags were Ca, F, and Al (Nanoseal) and Ca and P (Teethmate Desensitizer). The tubule occlusion rates of MS Coat ONE and Saforide were significantly lower than those of Nanoseal and Teethmate Desensitizer (P< 0.05).

Interactions of dentine desensitisers with human dentine: morphology and composition.

OBJECTIVE: To evaluate the effect of desensitising agents on human dentine morphology and composition. METHODS: Randomly assigned human coronal-dentine specimens were subjected to: (a) no treatment (smear-layer control, n=4); (b) acid etching with 6% citric acid (demineralised control, n=4); (c) treatment with desensitising agents (12 cycles of 60 s treatment with 60 s between-treatment rinsing, n=6 per agent); and (d) exposure to acidic challenge (pH 5.0 for 90 s, n=6 per agent). The tested products were: Listerine® Advanced Defence Sensitive (LADS; 1.4% potassium oxalate) mouthrinse, Colgate® Sensitive Pro-Relief™ mouthrinse, and toothpaste slurries (paste/water 1:2 wt/wt ratio) of Colgate® Sensitive Pro-Relief™ paste, Crest® Sensitive paste and Sensodyne® Repair and Protect paste. All dentine surfaces were studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Raman microscopy and high vacuum scanning electron microscopy with energy-dispersive X-ray microanalysis (HV-SEM/EDX). RESULTS: Desensitising slurry treatments occluded tubule orifices of acid-etched dentine, creating a randomly distributed surface pattern of particle aggregates. The greatest intratubular penetration of occluding particles was found in dentine treated with LADS. The atomic ratios of Ca/N and Ca/P, and the mineral/matrix ratios increased after toothpaste-slurry treatments compared with the acid-etched dentine. However, the acidic challenge removed most surface precipitates and further demineralised these substrates. Before the acidic challenge, the surface features were least affected in specimens treated with Sensodyne® Repair and Protect. After the acidic challenge, the sub-surface occlusion features were least affected in specimens treated with LADS. CLINICAL SIGNIFICANCE: Although most tested products achieved occlusion of dentinal tubules and provided evidence of mineral deposits, the deposit formed by LADS demonstrated the greatest resistance to acidic challenge, which simulates intra-oral demineralisation phases.

Effect of hydroxyapatite film formed by powder jet deposition on dentin permeability.

A powder jet deposition (PJD) process can be used to create a thick hydroxyapatite (HA) film on the surface of a human tooth. This study aimed to investigate in vitro the ability of an HA film, applied using PJD, to diminish dentin permeability. Discs of human coronal dentin were cut perpendicular to the tooth axis and the smear layer was removed by EDTA treatment. The HA film was created by accelerating HA particles, calcinated at 1200°C, onto the dentin discs at room temperature and atmospheric pressure. The surfaces and cross-sections of the HA PJD-treated samples were observed using scanning electron microscopy. Their permeability was indirectly recorded with a split-chamber device utilizing a chemiluminescence technique. MS-coat, a commercial dentin-desensitizing agent, was also evaluated for its effect on reducing liquid flow through the dentin. The scanning electron microscopy images showed that the HA particles were successfully deposited onto the dentin and solidly into the dentin tubules. The permeability of dentin after application of the HA films was significantly lower than that following application of MS-coat. This study showed the potential clinical application of PJD techniques in desensitizing dentin hypersensitivity.

Occluding effect of Nd:YAG laser and different dentin desensitizing agents on human dentinal tubules in vitro: a scanning electron microscopy investigation.

OBJECTIVES: This in vitro study aimed to microscopically evaluate and compare the occluding effect of the Nd:YAG laser and different dentin desensitizing agents on human dentinal tubules. MATERIALS AND METHODS: The Nd:YAG laser (SunLase™ 800) and four commercially available and professionally applied dentin desensitizers (Gluma® desensitizer, Tenure Quick®, Quell™ desensitizer, and VivaSens®) were investigated in this study. Sixty-four extracted intact human molars were used. Each dentin surface was divided by shallow indentation into two halves, one of which was used for treatment and the other of which served as a control. The dentin surfaces were etched to remove any smear plugs and to mimic the open dentinal tubules of sensitive dentin using 0.5 M ethylenediaminetetraacetic acid (pH 7.4) for two minutes (applied with a microbrush) and then rinsed with an air-water syringe for 30 seconds. The laser samples (n=16) were randomly divided into four groups of four samples each. These groups were the step-up technique group, the 14-day group, the one-minute group, and the two-minute group. Forty-eight samples were treated with the four tested desensitizing agents and were randomly divided into four groups (n=12/group). Each group was further subdivided into three subgroups (n=4). Samples of the first subgroup were treated for 14 days, while those of the second subgroup were treated once. Samples of the last subgroup were fractured longitudinally after a single treatment. All of the samples were then examined under a scanning electron microscope. RESULTS: The Nd:YAG laser-irradiated dentin showed reduction or complete obliteration of the dentinal tubule lumen; thus, the treatment modified the original dentinal structure. The lased dentin surface in the two-minute group showed bubble-like changes in the area of the dentinal tubules' orifices. Statistically, the two-minute group was found to have a significantly higher percentage of partially or fully occluded tubules than did the one-minute group. All of the studied desensitizing agents produced occlusion of the dentinal tubules; however, the appearance of the precipitates, the level of coverage, and the degree of dentinal occlusion varied among the tested products. CONCLUSION: Throughout the specified period of this study, occlusion and/or narrowing of the open dentinal tubules have been successfully achieved with both treatment approaches.

Effects of dentifrice containing hydroxyapatite on dentinal tubule occlusion and aqueous hexavalent chromium cations sorption: a preliminary study.

In order to endow environmental protection features to dentifrice, hydroxyapatite (HA) was added to ordinary dentifrice. The effects on dentinal tubule occlusion and surface mineralization were compared after brushing dentine discs with dentifrice with or without HA. The two types of dentifrice were then added to 100 µg/ml of hexavalent chromium cation (Cr(6+)) solution in order to evaluate their capacities of adsorbing Cr(6+) from water. Our results showed that the dentifrice containing HA was significantly better than the ordinary dentifrice in occluding the dentinal tubules with a plugging rate greater than 90%. Moreover, the effect of the HA dentifrice was persistent and energy-dispersive spectrometer (EDS) revealed that the atomic percentages of calcium and phosphorus on the surface of dentine discs increased significantly. Adding HA to ordinary dentifrice significantly enhanced the ability of dentifrice to adsorb Cr(6+) from water with the removal rate up to 52.36%. In addition, the sorption was stable. Our study suggests that HA can be added to ordinary dentifrice to obtain dentifrice that has both relieving dentin hypersensitivity benefits and also helps to control environmental pollution.

Physical and chemical characterization of the surface layers formed on dentin following treatment with a fluoridated toothpaste containing NovaMin.

OBJECTIVE: To characterize in vitro the formation and robustness of a layer formed on dentin following treatment with a fluoridated toothpaste containing calcium sodium phosphosilicate (NovaMin) using modem imaging and analysis techniques. METHODS: Calcium sodium phosphosilicate (CSPS)-containing toothpaste was brushed on to etched dentin specimens twice daily for up to five days. In between applications the samples were stored in artificial saliva. Additionally, certain samples underwent a chemical challenge in the form of a dietary acid, whereby samples were exposed to a cola or grapefruit juice beverage for five minutes on day 4 of the five-day study. The ability of the CSPS-containing formulation to occlude tubules was assessed visually by scanning electron microscope (SEM) imaging and compared to a water control. In a second experiment, the mechanical resistance of the layer was assessed using profilometry after controlled brushing for 200 brush strokes with a wet medium-bristled toothbrush. To visualize the layer and characterize the tubule occlusion, longitudinal cross-sections were prepared using a focused ion beam scanning electron microscope (FIB SEM), and analysis performed by energy dispersive x-ray spectroscopy (EDS) and electron diffraction. Owing to the complexity of the mixed material deposited after application of the toothpaste, material from inside a dentin tubule was selectively removed after five days of treatment, and the morphologically different materials imaged and analyzed by electron diffraction in the transmission electron microscope (TEM). RESULTS: SEM inspection showed significant coverage of the dentin samples after application of CSPS toothpaste for all five days, in contrast to the water control where the majority of tubules remained open after all five days. Exposure of the NovaMin-treated samples to common dietary acids did not lead to re-exposure of the tubules. Profilometry measurements demonstrated an intact layer covering the dentin surface after one and five days. EDS analysis and electron diffraction indicated the layer and the material plugging the tubule to be a calcium phosphate material with a crystallographic structure similar to hydroxyapatite. CONCLUSION: CSPS contained in toothpaste formulations adhered to exposed dentin surfaces. The layer formed was resistant to acid and mechanical challenges. Characterization of this layer indicated it was hydroxyapatite-like in nature.

[Occluding effects of three new calcium desensitizers on dentinal tubules in vitro].

OBJECTIVE: To evaluate the occluding effects of three new calcium desensitizers on dentinal tubules in vitro. METHODS: Twenty-five dentin specimens of 1.00 mm thick from freshly extracted third molars were divided into five groups randomly. After treatment with 6% citric acid, group A was treated with distilled water, and group B-E were treated with NovaMin, Pro-Argin, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and 75% NaF glycerin for 2 min respectively. Then the teeth were vertically cleaved into two sections. The surfaces and cross sections were observed by the scanning electron microscope (SEM) and energy dispersive X-ray (EDX), which were analyzed by the Image-Pro Plus software. RESULTS: The percentage of dentin tubules sealed were (81.6 ± 6.1)%, (71.5 ± 6.3)%, (43.2 ± 2.6)%, (39.9 ± 4.1)% for groups B, C, D and E respectively, and the occluding depth were (30.33 ± 2.26), (24.55 ± 2.58), (16.10 ± 4.65) and (8.90 ± 1.51) µm respectively. The differences between these groups were statistically significant (P < 0.01) except for group B and C (P > 0.05). However, there was no significant difference between all the groups for the Ca/P ratios (P = 0.342). CONCLUSIONS: NovaMin may have better immediate occluding effects than other desensitizers and could deposit a dentin-like mineral.

Análise quantitativa e qualitativa da condutividade hidráulica da dentina após tratamento com diferentes agentes dessensibilizantes: estudo in vitro / Quantitative and qualitative analysis of the dentin hydraulic conductance after treatment with different desensitizing agents: in vitro study

O tratamento das lesões cervicais não cariosas hipersensíveis com agentes dessensibilizantes pode ser uma opção prática e eficaz devido, principalmente, à capacidade desses produtos de obliterarem os túbulos dentinários expostos. Portanto, o objetivo deste estudo foi analisar, in vitro, o efeito quantitativo e qualitativo de cinco agentes dessensibilizantes em relação ao seu potencial de obstrução dos túbulos dentinários. Para a análise quantitativa, foram utilizados testes de condutividade hidráulica da dentina em diferentes condições experimentais. Os ensaios foram realizados na seguinte sequência experimental: na presença de smear layer (PMin); após condicionamento com ácido fosfórico a 37%, por 15 segundos (PMax); após a aplicação dos agentes dessensibilizantes e após o desafio com ácido cítrico a 6%, por um minuto. Para isso, foram selecionados 50 terceiros molares humanos hígidos não irrompidos, a partir dos quais foram confeccionados discos de dentina com espessura de 0,80 ± 1,00 mm e divididos em 5 grupos (n=10) de acordo com os diferentes agentes dessensibilizantes: Grupo 1 (Sensiactive); Grupo 2 (Sensitive Pro-Alívio); Grupo 3 (Flúor gel);Grupo 4 (Desensibilize Nano-P); e Grupo 5 (Enamel Pro@ Varnish). As medidas de condutividade hidráulica dentinária (Lp) foram analisadas através do teste ANOVA a dois critérios (p<0,05) para se determinar as diferenças intra e intergrupos. As diferenças individuais foram determinadas pelo teste Tukey, também a um nível de significância de 5%. Já a análise qualitativa foi realizada através da observação de imagens feitas através do microscópio confocal a laser (MCL). Nesse caso, foram selecionados 18 terceiros molares humanos hígidos não irrompidos, sendo que a preparação e armazenamento dos discos para as condições experimentais seguiram os mesmos passos descritos para os experimentos de condutividade hidráulica. Os espécimes foram divididos em 6 grupos, n=3, conforme os materiais experimentais estudados, e os...

The treatment of hypersensitive non carious cervical lesions with desensitizing agents may be a practical and effective alternative, mainly due to the ability of these products to obliterate the exposed dentinal tubules. Therefore, the aim of this study was to investigate, in vitro, the quantitative and qualitative effect of five desensitizing agents in relation to their ability to obstruct dentinal tubules. The quantitative analysis was based on dentin hydraulic conductance tests achieved under different experimental conditions. The tests were performed in the following experimental sequence: in the presence of smear layer (PMin); after a 15-second acid etching (37% phosphoric acid- PMax); after the application of the desensitizing agents; and after a 1-minute acid challenge (6% citric acid). Fifty sound not erupted extracted human third molars were randomly selected and, from them, 0.08±1.00 mm-thickness dentine discs were obtained for distribution into 5 groups (n=10), according to the different desensitizing agents: Group 1 (Sensiactive); Group 2 (Sensitive Pro-Relief); Group 3 (Fluoride gel); Group 4 (Desensibilize Nano-P) and Group 5 (Enamel Pro@ Varnish). Dentin hydraulic conductance measures (Lp) were analyzed by two-way ANOVA (p<0.05) to determine intra and intergroup differences. Individual differences were determined by Tukey test, also at a significance level of 5%. The qualitative analysis was performed by observing images obtained from specimens via laser scanning confocal microscopy (LSCM). Here, 18 sound not erupted extracted human third molars were randomly selected and specimens preparation and storage for each experimental condition followed the same steps described for the experiments regarding dentin hydraulic conductance tests. Specimens were divided into 6 groups (n=3), according to studied materials, and each dentin disc was dimidiate to allow performing of the two phases of the experiment on the same disk. A group of...

Properties of a new mouthrinse for patients receiving radiation therapy.

INTRODUCTION: Patients receiving radiation therapy due to oral cancer develop complications such as hyposalivation, mucositis, oral infections, dental hypersensitivity and caries. Mouthrinses can alleviate some of these problems. AIMS AND OBJECTIVES: To investigate the in vitro antimicrobial properties and cytotoxicity of an experimental mouthrinse. METHODS: The mouthrinse contained 30% hexylene glycol (glycerine), 7% potassium nitrate and 0.025% sodium fluoride. The minimal inhibitory concentration (MIC) of these ingredients and the mixture was determined for C. albicans, S. aureus and S. mutans over 24 hours at different concentrations. The MICs of two commercial mouthrinses, Corsodyl and Plax, were also determined using the same organisms. All mouthrinses were then tested to determine the percentage kill over 1, 2, and 3 minutes. RESULTS: The MICs for hexylene glycol were 10%, 30% and 10% for C. albicans, S. aureus and S. mutons respectively. Potassium nitrate and sodium fluoride had no antimicrobial effects. The MIC of Corsodyl was 0.016 mg/ml for all the test organisms. The MIC for Plax varied from 0.0002 mg/ml to 0.001 mg/ml. The kill rates for all mouthrinses were acceptable, with no statistical differences between them. The experimental mouthrinse was not toxic to human oesophageal SCC cells after 1 minute exposure. At the time of the experiment, the costs of a similar quantity of the experimental mouthrinse, Corsodyl and Plax were R5.24, R30.00 and R10.00 respectively. CONCLUSIONS: The experimental mouthrinse was cost-effective and proved to have an antimicrobial effect and could be used safely to alleviate oral infections, desensitize teeth, improve oral hygiene and control dental caries in cancer patients after radiation therapy.

Mechanism of action of a desensitizing fluoride toothpaste delivering calcium and phosphate ingredients in the treatment of dental hypersensitivity. Part III: Prevention of dye penetration through dentin vs a calcium- and phosphate-free control.

It is generally accepted that the pain of dental hypersensitivity resulting from gum recession is from the movement of fluid within the exposed tubules of dentin, causing changes in pressure on the nerve within the pulpal cavity. One method of treating hypersensitivity is to occlude the tubules, preventing fluid movement. This article discusses the use of a dye penetration technique, which establishes this mechanism of action for a desensitizing fluoride toothpaste containing calcium and phosphate. Two groups of intact teeth were perfectly sealed with enamel paint. Windows 100-micro to 200-micro deep were opened on opposite sides of each tooth at the dentin-enamel junction and briefly etched using 20% polyacrylic acid. One batch of teeth was treated eight times for 30 mins each with a 1:3 slurry of the desensitizing toothpaste and another set with a similar slurry prepared from a calcium- and phosphate-free control. A 0.85% aqueous solution of acid red fuchsin dye was applied to each window and allowed to dry. After a brief rinse, the teeth were sectioned across the windows. Almost no dye penetration was seen in teeth treated with the desensitizing toothpaste; however, extensive penetration through the dentin was visible in the control-treated teeth. The differences in dye penetration for the two sets of teeth were significant by both subjective (P < .001) and objective (P < .01) measures. Tubule occlusion because of calcium and phosphate ions from the desensitizing toothpaste accounts for its tooth desensitizing efficacy.

Dentin bonding-variables related to the clinical situation and the substrate treatment.

The wetness of dentin surfaces, the presence of pulpal pressure, and the thickness of dentin are extremely important variables during bonding procedures, especially when testing bond strength of adhesive materials in vitro with the intention of simulating in vivo conditions. The ultimate goal of a bonded restoration is to attain an intimate adaptation of the restorative material with the dental substrate. This task is difficult to achieve as the bonding process is different for enamel and for dentin-dentin is more humid and more organic than enamel. While enamel is predominantly mineral, dentin contains a significant amount of water and organic material, mainly type I collagen. This humid and organic nature of dentin makes this hard tissue very challenging to bond to. Several other substrate-related variables may affect the clinical outcome of bonded restorations. Bonding to caries-affected dentin is hampered by its lower hardness and presence of mineral deposits in the tubules. Non-carious cervical areas contain hypermineralized dentin and denatured collagen, which is not the ideal combination for a bonding substrate. Physiological transparent root dentin forms without trauma or caries lesion as a natural part of aging. Similar to the transparent dentin observed underneath caries lesions, the tubule lumina become filled with mineral from passive chemical precipitation, making resin hybridization difficult. An increase in number of tubules with depth and, consequently, increase in dentin wetness, make bonding to deeper dentin more difficult than to superficial dentin. While the application of acidic agents open the pathway for the diffusion of monomers into the collagen network, it also facilitates the outward seepage of tubular fluid from the pulp to the dentin surface, deteriorating the bonding for some of the current adhesives. Some dentin desensitizers have shown some promise as they can block dentinal tubules to treat and prevent sensitivity and simultaneously blocking the tubular fluid from flowing to the surface. A new approach to stop the degradation of dentin-resin interfaces is the use of MMP inhibitors. Although still in an early phase of in vitro and clinical research, this method is promising.