By the basic researches of implant therapy and the accumulated experiences in clinical applications based on those researches, we can achieve the ideal treatment goal with satisfactory aesthetic and function. However, on the other hand, it’s not rare to have postoperative surgical and prosthodontic troubles or complications. The guideline for the peri-implantitis treatment has not yet been clearly defined, which has been apprehensively discussed for more than a decade. Thus, we would like to explain and discuss the transitional history and present status of risk factors and indicators for peri-implantitis and the clinical means to tackle with it.

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To ensure that patients are satisfied with the esthetic outcomes of implant treatment， it is not only essential to restore the crown of the tooth but also to ensure that the peripheral gingiva and interdental papillae are well positioned for long-term stability． To achieve these goals， it is important to secure sufficient bone （hard tissue） and soft tissue at the implant site． Although there are individual differences， it is generally accepted that if the implant and abutment have the same diameter， at least 2 mm of bone must be secured on the buccolingual （labiopalatine） side of the implant， or at least 1.5 mm in the case of platform switching， with at least 1.5 mm between the implant and natural teeth and at least ３ mm between two implants， depending on the design that is used． As it is thought that peri-implant soft tissue must be around ４ mm in height， many authorities suggest that if the implant and abutment have the same diameter the implant insertion depth must be around ３ mm deeper than the peripheral gingiva in the apical direction， and around ４ mm deeper if platform switching is used． The required thickness of buccolingual （labiopalatine） soft tissue is believed to be around 2 mm． The shape of the superstructure is concave below the gingival margin to secure the required thickness of buccolingual （labiopalatine） soft tissue， and the half-pon- tic technique can be used for the abutment shape using the same method as for tooth restoration．

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Hydrofluoric acid etching has been recognized as highly reliable pre-treatment for bonding to silica-based ceramics. However, there are no studies have investigated the effect of elapsed time following hydrofluoric acid etching on bond strength of CAD/CAM feldspathic porcelain block. The aim of this study was to investigate the effect of the timing of hydrofluoric acid etching on shear bond strength (SBS) between enamel to CAD/CAM feldspathic porcelain block. A bovine enamel and CAD / CAM feldspathic porcelain block were used as an adherend. Tested conditions i.e. 1 ) 60 s hydrofluoric acid etching + 5 min ultrasonic cleaning with ethanol (CON), 2 ) saliva contamination + 60 s phosphoric acid etching + rinsed with running water (PA), 3 ) saliva contamination +60 s hydrofluoric acid etching + 5 min ultrasonic cleaning with ethanol (HF), 4 ) 60 s hydrofluoric acid etching ２４ hours before + saliva contamination + 60 s phosphoric acid etching + rinsed with running water (２４HF) , and 5 ) 60 s hydrofluoric acid etching ２４ hours before + saliva contamination + 60 s phosphoric acid etching + rinsed with running water (72HF) were compared. A light-polymerized resin luting cement was used, and bonding procedure was done the manufacturer instruction. From the results, HF (37.1 MPa) and ２４HF (37.4 MPa) showed a significantly higher SBS compared to PA (２２.3 MPa) and 72HF (２３.1 MPa). There were no significantly differences between HF, ２４HF and CON (37.2 MPa), and also between PA and 72HF.

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In recent years, in addition to conventional treatments such as dentures and bridges, treatments using implants have been established as treatment options for defective prostheses. Nowadays, the concept of prosthetic-led implant treatment has permeated and treatments with aesthetics. It is becoming possible to obtain results. However, on the other hand, in the process of folowing the course of implant treatment in the long term, the trouble that we dentists are most troubled with is peri-implan- titis. We evaluated and examined the history of periodontal disease, oral hygiene, maintenance frequency, implant position, cement residue (connection mode of superstructure), and width of keratinized mucosa, which are considered to be the causes. Compared with non-affected patients, patients with peri-implantitis had a higher proportion of patients with a history of peri- odontal disease, poor oral hygiene, and keratinized mucosa width of 2 mm or less, and maintenance frequency was low. On the other hand, there was no difference between the implant position and the connection mode of the superstructure. For this rea- son, for patients with a history of periodontal disease, thorough control of periodontal disease is performed before surgery, and even after the final prosthetic device is instaled, the dentist cooperates with the dental hygienist to perform PMTC at an appro- priate timing. It was suggested that plaque control and preservation and construction of keratinized mucosa of 2 mm or more around the implant are important for the prevention of peri-implantitis.

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The present research evaluated the possibility to use the membrane that is mainly composed of L-lactide and ε -caprolactone copolymer as the open- barrier membrane. The residual weight ratio of experimental membranes that had been soaked in the simulated body fluid in the centrifuge tubes for １ ,４, and ８ weeks respectively were calculated weight per- cent by comparing with the original weights before soaking as to test the degradation and resorption behavior. As the result, we found the degradation has progressed gradually by hydrolysis, but there was no significant statistical difference between the subjects after ４ weeks and ８ weeks. Tensile strength test was performed to the test materials after the degradation and resorp- tion by the soaking to know the breaking extension or elongation. It revealed the significant decrease in breaking extension from 0 week to ４ weeks and to ８ weeks as the soaking duration increases. However, SEM and Micro CT images had howed that the structure of the membrane was maintained without the structure breaking-down such as making a hole in it. Based on these findings, possibility to apply and use L-lactide and ε -caprolactone copolymer as the open-barrier membrane was suggested even though it is resorbable.

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In recent years, there has been a considerable increase in the number of available digital systems. One of the main rea- sons for this is that Intra-Oral Scanner (IOS) has become increasingly better, smaller, and faster, while the design software has become more and more user-friendly. Therefore, when making a wide range of prostheses with occlusal reconstruction, a digital system is used for the purpose of clarifying diagnostic criteria at the stage of diagnostic examination to make prosthetic treat- ment plans. We decided to apply digital occlusal reconstruction with the aim of obtaining more accurate treatment results by three-dimensionally visualizing diagnostic criteria that were previously invisible and applying them to prosthetic treatment. By integrating Cone Beam CT (CBCT) and IOS data, there are other invisible diagnostic criteria such as the centric relation, which is the reference point for the mandibular position, and the camper’s plane, which is the reference for the maxillary occlusal plane, as criteria for occlusal reconstruction. We report through a clinical case that more accurate treatment results can be derived by visualization.

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Surgery and implant placement of sinus lifts are contraindicated in long-term mucosal thickening due to bacterial infection. Clinically established treatments and procedures require implant placement only after chronic and refractory maxillary sinusitis has been completely cured. The point of diagnosis is the natural ostium of the maxillary sinus, and the presence or absence of the patency of the natural ostium determines the success or failure of the sinus lift. This time, as a case report, I dis- close the limits of removal of infected thickened areas with antibacterial drug administration and a new procedure for sinus lift mucosal thickening resection that does not rely on endoscopic intranasal sinus surgery for implant placement performed by oral surgeons during mucosal thickening in otolaryngology.

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We often experience the resorption of alveolar process after the long-term over load on the alveolar mucosa even after we obtain the recovery of masticatory function ability by the removable denture as the prosthodontic restoration. It is very diffi- cult to deal with the maxillary flabby gum by the extreme resorption of the alveolar ridge and with the mandibular distal exten- sion missing cases. I will report the long -term prognosis of the case with minimal residual teeth that was treated with the over denture for maxilla with the consideration of the preservation of alveolar ridge, and with the Implant restoration for the extremely resorbed mandibular alveolar process after grafting the autogenous iliac bone block.

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Not only endodontic treatment, but also in all dental fields, advances in treatment methods and instruments and equipment continue. The size, shape, and orientation of the open cavity should be determined based on an understanding of the curvature of the root canal to be treated, the degree of stenosis, the amount of opening of the patient, the skill of the opera- tor, and the characteristics of the instruments and equipment used. The NiTi file made of martensite phase is less likely to cause transport and has excellent root canal followability due to its shape memory effect. There is no file system that can be said to use this file system to handle all cases. Continuously collect information on new file systems and understand the characteristics of those file systems. It is important to use the new file system properly.

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