## 1 Introduction  
The hard tissue examination, including the native bone without decalcification, can be useful for special medical purposes (e.g., stem cell preparation, DNA-sampling, anthropological studies) and the implantology in dentistry. In the case of dental implants which must be tightly integrated into the recipient's hard tissue to provide appropriate supporting/substituting functions, there is a need for rapid osseointegration at the interface to become a steady and stable osteo-metal unification. Therefore, hard tissue studies without decalcification may have great values both in the general medicine (e.g., orthopedic surgery) and in dentistry practice. The use of a specimen exhibiting a dental implant in conjunction with bone border surfaces, without artificial decalcination as an alternative slide preparation technique may have a major role in dental implants' evaluations. With this method, the grade of osseointegration and the extent of newly formed extracellular hard (calcified) tissues in association with implants can be in situ examined. In the case of the traditional histological slide preparation, the paraffin-embedded samples were prepared decalcification prior cut with a traditional microtome for sectioning and staining. However, metal samples cannot be sliced with this traditional microtome. The solution of the processability in metal content cases was first examined by [PERSON] and [PERSON] in 1977 [1], and later the complete technique was established in 1985 by [PERSON] [2] in detail. He was the first who mentioned the hard tissue microtome, which can cut evenly the metal material, including the dental implants. This is the only way to create a correctly evaluable histological slide with metal content substance. Without the decalcification technique, the lime content of the samples is not removed/extracted, so the osseointegration can be examined much better. Accordingly, the embedded samples are cut with hard tissue microtome. These 1 mm thick slices have to be ground until reaching the optimal thickness (less than 10 microns) for a histological slide examination. However, due to mechanical forces, the grinding can remove the sample from the glass, or a part of the sample. Thus, the different adhesive materials have an important role to resist the mechanical forces during the preparation process but without influencing the quality of the specimen for the pathological examination. The dental universal adhesives have been used in clinical practice since 2011. These multicomponent systems contain incorporable monomers to produce chemical and micromechanical bonds to dental substrates. The most often applied incorporable monomers have carboxylate and/or phosphate functional groups that can bind to calcium ions of hydroxylapatite through ionic bonds thus can increase the bonding efficacy [3]. Some universal adhesives may contain silane [4]. Silane and a light-cure adhesive combination were presented in an undecalcified hard tissue histopathology study by [PERSON] et al. [5]. Water cooling is necessary during the grinding process that can bring the main drawback of silane into focus, a tendency to hydrolysis [6], raising the question in the preservation of section. The other molecule that is often used in the universal adhesive is 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP; shortly MDP). This is a non-hydrolysis sensitive, polar functional monomer that is found in new dental adhesives and able to bond to apatite, or dentin, collagen, metals, and zirconia. There is much research that investigates the chemical bond of the 10-MDP molecule to titanium, ceramics, and tooth structure. Researchers described that 10-MDP monomer (10-MDP) formed a strong and stable chemical bond with apatite substrates like human hard tissues (dentin, enamel, and bone) [7; 8]. The 10-MDP is a bifunctional monomer. One side contains hydrophilic phosphate groups until the other side is an unsaturated carbon double bond that connects to a hydrophobic hydrocarbon chain.