Dental implant care and trouble among dependent patients based on the questionnaire survey among Japanese dental practitioners.

BACKGROUND: Self-care and professional care of implants may prove difficult for elderly people who require nursing care. However, the actual state of care and problems remains unknown. In this study, we investigated the actual state of implant problems in elderly people living in their own home or in a nursing home who received visiting dental treatment. METHODS: We mailed questionnaire survey forms to 2339 representatives or specialists who were members of the Japanese Society of Oral Implantology, the Japanese Society of Gerodontology or the Japan Prosthodontic Society. We narrowed down the respondents to those who provided visiting dental treatment, and analyzed the actual state of implants observed during visiting dental treatment (type, care, problems, countermeasures, etc.). RESULTS: Of the 924 dentists who responded to the questionnaire survey, 291 (22%) provided visiting dental treatment. While the majority of implant types encountered in the previous 12 months were root-form implants, there were still a certain number of blade and subperiosteal implants. Daily implant care involved mostly cleaning with a toothbrush + auxiliary tools. The most frequent implant problems encountered in the past were difficulty in cleaning and peri-implantitis. Medication and antiphlogistic treatment were most frequently adopted as countermeasures to implant problems, followed by observation. When we classified the results into those for the dentists who provided implant treatment and those for the dentists who did not, we found that many of the dentists who did not provide implant treatment opted for observation or medication, while those who provided implant treatment also implemented removal of superstructure, retightening of screws, repair and so forth. CONCLUSIONS: We found that many of the implant troubles encountered by dentists who provided visiting dental care were difficulty in cleaning or peri-implantitis, and that the actions taken against these troubles varied depending on the experience of the dentist performing the implant treatment. Our study also revealed that dentists who provide visiting dental care need to acquire knowledge and skills of implant treatment, to have actions prepared in case they encounter such cases, or to closely coordinate with dentists who specialize in implants.

Evaluation of the trueness and tissue surface adaptation of CAD-CAM mandibular denture bases manufactured using digital light processing.

STATEMENT OF PROBLEM: Studies assessing the trueness and tissue surface adaptation of computer-aided design and computer-aided manufacturing (CAD-CAM) mandibular complete denture bases fabricated using digital light processing (DLP) are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the trueness of DLP-generated denture bases and to compare the tissue surface adaptation of DLP with milling and pack and press. MATERIAL AND METHODS: The mandibular denture bases were virtually designed on a reference cast and were fabricated using DLP. Their intaglio surfaces were scanned and superimposed on the reference CAD denture base to evaluate the trueness. The reference cast was duplicated to create 10 identical master casts that were scanned to design 10 virtual denture bases. Twenty denture bases were fabricated with DLP and milling (10 specimens per technique). In addition, 10 denture bases were fabricated with the pack and press technique. The intaglio surfaces of the denture bases were scanned and superimposed on the corresponding master casts to compare tissue surface adaptation among the 3 techniques. The Mann-Whitney test and Kruskal-Wallis analysis of variance (α=.05) were used for statistical analyses. RESULTS: For trueness, the milled denture base was better than the DLP denture base (P<.001). However, no statistically significant difference was detected with respect to tissue surface adaptation of the denture base, regardless of the fabrication technique (P>.05). The DLP denture base showed comparable tissue surface adaptation with the milled base, one with a small interquartile range. CONCLUSIONS: The intaglio surfaces of DLP and milled denture bases corresponded within a 100-µm accuracy compared with the master cast. Although the DLP denture base exhibited tissue compression on the ridge crest, it showed comparable tissue adaptation to the milled denture base.

Complete denture fabrication using piezography and CAD-CAM: A clinical report.

To provide maxillary and mandibular complete dentures for a patient with severe ridge resorption, the denture space was recorded using the piezography technique. After the piezographic space was scanned, a virtual tooth arrangement and festooning were performed within the space using computer-aided design software. The denture bases were milled from a polymethylmethacrylate resin block using computer-aided manufacturing, and commercially available denture teeth were bonded with resin adhesive. Using the piezography technique described, physiologically appropriate complete dentures were fabricated based on the neutral zone concept.

Digital Relief of the Mental Foramen for a CAD/CAM-Fabricated Mandibular Denture.

Relief of the intaglio surface of a denture base is conventionally performed using thin wax and soft metal foil attached to the master cast. The following report highlights a new relief procedure for the mental foramen using a CT double scan technique on the CAD/CAM dentures fabricated for the patient with paresthesia of the left lower lip and chin during mastication.

Clinical Evaluation of Implant-Supported Removable Partial Dentures With a Stress-Breaking Attachment.

PURPOSE: The stress-breaking ball (SBB) attachment can distribute the occlusal force equally between the alveolar ridge and the implants. The purpose of this study was to evaluate the implant-supported distal extension removable partial dentures (RPDs) with SBB attachment in 10 patients who were partially edentulous. METHODS: This randomized crossover study was designed to compare the function of RPDs with and without healing abutments and SBB attachments to support the posterior aspects of the RPDs. Mandibular jaw movements during mastication and the occlusal force and contact area were measured with a commercially available tracking device and pressure-sensitive sheets. Using a visual analog scale, 4 criteria-chewing, retention, stability, and comfort-were evaluated. All of the data obtained were analyzed using a 1-way analysis of variance (α = 0.05). RESULTS: There were no significant differences in either the mean time or the coefficient of variation among the SBB attachments and healing abutments of implant-supported removable partial dentures (ISRPDs) and conventional removable partial dentures (CRPDs). SBB attachments and healing abutments of ISRPDs had greater forces and contact areas than those of CRPDs with significant differences. For all criteria, patients preferred SBB attachments to healing abutments and CRPDs. CONCLUSIONS: The implant-supported distal extension RPDs with SBB attachment improved denture stability and patients' satisfaction.

Quantitative measurements of the articular areas of mandibular condyles with temporomandibular joint disorders using magnetic resonance imaging.

OBJECTIVE: The authors sought to clarify the variation in the condylar anterior functional surface (AFS) of patients with temporomandibular joint (TMJ) disorders using quantitative measurements by magnetic resonance imaging (MRI). METHODS: MR images of 68 joints (2 males, 32 females) were used. The subjects were classified into three groups: with/without defects of cortical bone groups and a combination group without defects. The AFS was measured as the length between the protrusive point and the apex of the condyle on MRI (4-mm-thick slices), and the quad value of the length was defined as the area on the slice. The summed quad values of all slices were used as the AFS area. Differences in the areas among the three groups were compared by one-way analysis of variance (ANOVA). RESULTS: The non-defect group had significantly larger AFS areas than the defect group. CONCLUSIONS: Quantitative measurement on MR images clarified the changes in the condylar sagittal appearance.

Occlusal contact of fixed implant prostheses using functional bite impression technique.

OBJECTIVE: Functional bite impression (FBI) has been described as a definitive impression made under occlusal force after functional generated path (FGP) recording. This study compared the accuracy of occlusal contact of implant-fixed prostheses using the FBI technique and the conventional impression technique. METHODS: Twelve subjects, each missing a single premolar or molar, were selected for this study. The conditions of the occlusal contacts were identified by the modified transillumination method. The occlusal contact condition was determined by comparing the rate of change in the occlusal contact area of the implant-fixed prostheses and both adjacent teeth before and after occlusal adjustment. RESULTS: The rate of change in the occlusal contact area using the FBI technique was 96%, and the rate using the conventional technique was 54%. The occlusal contact of implant prostheses using the FBI technique revealed better accuracy than that of the conventional technique. CONCLUSIONS: Regarding the FBI technique, a precise and functional prosthesis could be produced by completing the maxillomandibular registration, impression, and FGP at the same time.

Influence of Occlusal Force on Electroencephalograms in Edentulous Patients.

PURPOSE: This study explored the effect of improved occlusal force resulting from complete denture treatment on electroencephalogram (EEG) findings to determine if such an outcome is a factor contributing to activation of synaptic/neuronal dysfunction in the brain. MATERIALS AND METHODS: Twenty-three individuals with complete upper and lower dentures who visited the Department of Removable Prosthodontics at Tsurumi University Dental Hospital were included in this study. The Dental Prescale Occluzer FPD-705 system was used to perform an objective measurement of occlusal force before and after denture treatment. EEGs were recorded for 3 minutes in patients receiving complete dentures before and after denture treatment. Then, Dα values were calculated using a diagnosis method of neuronal dysfunction analysis to evaluate changes in synaptic/neuronal dysfunction of the brain. To investigate whether occlusal force affects Dα, Spearman's rank correlation coefficient (α = 0.05) was used to test the association between occlusal force (N) and Dα based on the rates of change in occlusal force and Dα calculated by dividing the measurement values after denture treatment by the measurement values before denture treatment. RESULTS: Medial occlusal force increased from 184.9 N before treatment to 277.2 N after treatment. A statistically significant increase in occlusal force (p < 0.05) was observed, with a total of 22 participants exhibiting increased occlusal force after denture treatment. The medial Dα value increased from 0.943 before treatment to 0.957 after treatment. A statistically significant increase in Dα (p < 0.05) was observed, and a total of 19 participants exhibited increased Dα values after denture treatment. The regression line was calculated as Y = 14.049X - 12.450. As occlusal force increased, Dα values increased as well. A significant positive correlation was observed between occlusal force and Dα (r = 0.498, p < 0.05). CONCLUSIONS: A positive correlation was observed between improved occlusal force attained via complete denture treatment and the activation of Dα. This finding reveals occlusal force as a denture treatment outcome that contributes to the activation of synaptic/neuronal dysfunction in the brain.

Effects of in vitro cyclic dislodging on retentive force and removal torque of three overdenture attachment systems.

BACKGROUND: Mandibular two-implant-retained overdentures were suggested as first choice of treatment for edentulous mandibles. However, wear of the attachments may reduce their retention and compromise long-term clinical success. AIM: The aim of this in vitro study was to compare the change in the retentive force and removal torque of three attachment systems during simulation of insertion-removal cycles. MATERIALS AND METHODS: Thirty custom-manufactured polyvinyl chloride blocks mimicking an implant-retained overdenture using Locator(®) -, spherical Dalbo(®) -PLUS - and SFI(®) -Bar-attachments on Straumann(®) RN Implants were fabricated. The samples were distributed equally into three groups which were subdivided into two sets of five blocks, one set with implants parallel to one another and the other with angulated implants (12°). All attachments were tightened to 35Ncm, while the fixation screws of the SFI(®) -Bar were tightened to 15Ncm. Testing was carried out with an Instron(®) universal testing machine for a total of 14,600 insertion-removal cycles in 0.9% sodium chloride solution. Retentive forces from cycles 10, 100, 1000, 5000, 10,000 and 14,600 were used for the analysis. The removal torque of the attachments was measured before and at the end of the study. Statistical analysis comprised three-way ANOVA and multiple linear regression models. RESULTS: Initially, all three attachment systems demonstrated increasing retentive forces. From cycle 5000 on, Locator(®) -attachments showed lower mean retentive forces than the Dalbo(®) -PLUS and SFI(®) -Bar-groups. The Dalbo(®) -PLUS and SFI(®) -Bar-attachments showed a steady yet not significant increase during the whole observation period. Implant-angulation had no significant influence on the retention forces. The final mean removal torques were significantly reduced. No complete failure was observed. CONCLUSIONS AND CLINICAL IMPLICATIONS: Within the limits of this in vitro study, it can be concluded that the investigated overdenture attachment systems are sufficiently resistant to wear. However, the Dalbo(®) -Plus- and SFI(®) -Bar- exhibit higher retentive capacities than the Locator(®) -attachment over time. The fixation screw of the SFI(®) -Bar may loosen during long-term use, but these observations might be less important if 1-year recall intervals are respected. An angulation of up to 12° between implants does not seem to have a significant effect on attachment wear.

In vitro assessment of mandibular single/two implant-retained overdentures using stress-breaking attachments.

OBJECTIVE: This study investigated the strain surround implants and the pressure distribution of the alveolar ridge related to implant overdentures with stress-breaking ball (SBB) attachments. METHODS: Simulation models of edentulous mandibles were embedded with 1 and 2 implants to simulate a single implant-retained overdenture (S-IOD) and a two-implant-retained overdenture (T-IOD), respectively. The implants were connected to the denture base with the following conditions: complete separation between the denture base and implant with cover screws as a conventional complete denture (CD), 3 types of settlements with an SBB attachment between them, and a conventional ball attachment (BALL). Strain surround the implant, pressure at 5 different soft tissue areas, and displacement of the denture base were measured with loading up to 50 N. RESULTS: In S-IOD and T-IOD, the strain of each SBB attachment was less than the strain shown by the BALL. The pressure at each region of the SBB attachment was less than the pressure shown with the CD and BALL. CONCLUSIONS: SBB attachments prevented strain surround the implants in loading and provided optimal stress distribution.

In vitro assessment of polishing efficiency for additive-manufactured Co-Cr alloy clasps.

PURPOSE: The processes and methods of treating and polishing additive-manufactured (AMed) cobalt-chromium (Co-Cr) alloy clasps were assessed in vitro to determine their suitability for constant clinical use and the reduction of dental technician work. METHODS: AMed Aker clasps were fabricated by selective laser sintering of approximately 50 µm Co-Cr alloy powders. After the nodules and fins on the inner surface of the AMed clasps were removed and morphological correction was performed, a dental technician manually polished the clasps as a control. Four surface treatments, barrel finishing, shot peening, and wet and dry electropolishing, were performed to obtain smooth surfaces. In addition, hybrid manufacturing, which integrates repeated laser sintering and high-speed milling for one-process molding, was added to this study. After observing the treated surfaces using SEM and Hybrid Laser Microscope (HLM) the surface roughness, fitness accuracy, and retentive forces of the treated AMed clasps were measured, and their polishing efficiencies were compared. RESULTS: Similar to manual polishing, dry electropolishing yielded the smoothest surfaces in all treatments. The fitness accuracy of all clasp regions and treatment methods ranged from 80 to 140 µm, without significant differences among the treatment methods. All treated clasps showed acceptable retentive forces for clinical use, and hybrid manufacturing and wet electropolishing showed significantly higher forces. CONCLUSIONS: AMed Co-Cr clasps with all surface treatments could be clinically used if additional slight manual polishing was performed; however, each processing condition should be carefully selected.

Comparison of joint designs for laser welding of cast metal plates and wrought wires.

The purpose of the present study was to compare joint designs for the laser welding of cast metal plates and wrought wire, and to evaluate the welded area internally using X-ray micro-focus computerized tomography (micro-CT). Cast metal plates (Ti, Co-Cr) and wrought wires (Ti, Co-Cr) were welded using similar metals. The specimens were welded using four joint designs in which the wrought wires and the parent metals were welded directly (two designs) or the wrought wires were welded to the groove of the parent metal from one or both sides (n = 5). The porosity and gap in the welded area were evaluated by micro-CT, and the maximum tensile load of the welded specimens was measured with a universal testing machine. An element analysis was conducted using an electron probe X-ray microanalyzer. The statistical analysis of the results was performed using Bonferroni's multiple comparisons (α = 0.05). The results included that all the specimens fractured at the wrought wire when subjected to tensile testing, although there were specimens that exhibited gaps due to the joint design. The wrought wires were affected by laser irradiation and observed to melt together and onto the filler metal. Both Mo and Sn elements found in the wrought wire were detected in the filler metal of the Ti specimens, and Ni was detected in the filler metal of the Co-Cr specimens. The four joint designs simulating the designs used clinically were confirmed to have adequate joint strength provided by laser welding.

Interdisciplinary treatment of an adult with complete bilateral cleft lip and palate.

Interdisciplinary treatment was used for an adult patient born with complete bilateral cleft lip and palate. He had a severe maxillary deficiency with a wide cleft involving the alveolar and maxillary bone and palate. Reconstruction of the arches and occlusion in patients who missed the optimal treatment time is a difficult task for orthodontists. The clinical examination showed severe hypogenesis of the maxillary bone with a total crossbite. The maxillary dental arch was extremely narrow, and the maxillary incisors showed extensive caries caused by improper oral hygiene. Fixed and removable expansion appliances were used to improve the lateral crossbite. Alveolar bone grafting and unilateral LeFort I maxillary osteotomy were performed on the right side for alignment of the maxillary arch. Mandibular setback with bilateral sagittal split ramus osteotomy was also performed to correct the anteroposterior skeletal discrepancy. After postsurgical orthodontic treatment, prosthetic treatment was carried out for final reconstruction of esthetics and orthognathic function. Interdisciplinary treatment was necessary for this patient to achieve a proper occlusion and better esthetics.

Fitness accuracy and retentive forces of milled titanium clasp.

Since cast titanium prostheses have many drawbacks, multi-directionally forged titanium grade 2 (MDF) was developed, and the application of the milling process was proposed for improving the titanium clasp. This in vitro study evaluated milled titanium clasps, including MDF titanium. Milling clasps were manufactured with commercially pure (CP) titanium grade 2 (CP 2), grade 4 (CP 4), Ti-6-Al-4V, and MDF. As a control, a CP 2 cast titanium clasp was fabricated in the conventional manner. No porosities and catastrophic failures were observed in the four milled titanium clasps. Fitness accuracy and retentive forces of milled CP 2 and CP 4 tended to be worse, and the milled MDF showed the higher retentive forces (12.45 N) than did cast and milled CP 2 clasps (9.32 N and 4.42 N). Milled titanium clasps can be recommended for longer-term clinical use as compared to cast clasps.

Application of multi-directionally forged high-strength titanium to dental implants in beagle dogs.

Pure titanium is widely used as a material in dental implants. However, it possesses inferior mechanical strength. This study aimed to elucidate the efficacy of acid treated multi-directionally forged (MDF) pure titanium in vivo. We verified the temporal changes until osseointegration in beagle dogs. Using two types of experimental materials (conventional pure titanium or MDF pure titanium), new bone formation was assessed using morphological examinations, and the bone-to-implant contact (BIC) value was evaluated at each time point (14, 30, and 90 days after the operation). As such, new bone formation was observed around the acid-etched MDF group, in which the BIC value was highest, followed by that in the acid-etched pure titanium group. MDF pure titanium implants showed early promotion of new bone formation compared to conventional titanium implants. The new acid-treated MDF made of pure titanium could be applied to humans in the future to prove its practicality.

Clinical application of an intraoral scanner and CAD/CAM system for a Kennedy class I partially edentulous patient.

Traditionally, removable partial dentures (RPDs) have been made by using an elastic impression material and casting from a framework wax pattern on a refractory cast. In this short communication, the procedures for digitally fabricating removable partial dentures using an intraoral scanner (IOS) and additive manufacturing system (AM) are described. The adaptation accuracy of the RPD using IOS and AM techniques was evaluated subjectively as good or satisfactory.

Characterization of bioactive substances involved in the induction of bone augmentation using demineralized bone sheets.

PURPOSE: To investigate the bone augmentation ability of demineralized bone sheets mixed with allogeneic bone with protein fractions containing bioactive substances and the interaction between coexisting bioactive substances and proteins. METHODS: Four types of demineralized bone sheets mixed with allogeneic bone in the presence or absence of bone proteins were created. Transplantation experiments using each demineralized bone sheet were performed in rats, and their ability to induce bone augmentation was analysed by microcomputed tomography images. Bioactive substances in bone proteins were isolated by heparin affinity chromatography and detected by the measurement of alkaline phosphatase activity in human periodontal ligament cells and dual luciferase assays. Noncollagenous proteins (NCPs) coexisting with the bioactive substances were identified by mass spectrometry, and their interaction with bioactive substances was investigated by in vitro binding experiments. RESULTS: Demineralized bone sheets containing bone proteins possessed the ability to induce bone augmentation. Bone proteins were isolated into five fractions by heparin affinity chromatography, and transforming growth factor-beta (TGF-ß) was detected in the third fraction (Hep-c). Dentin matrix protein 1 (DMP1), matrix extracellular phosphoglycoprotein (MEPE), and biglycan (BGN) also coexisted in Hep-c, and the binding of these proteins to TGF-ß increased TGF-ß activity by approximately 14.7% to 32.7%. CONCLUSIONS: Demineralized bone sheets are capable of inducing bone augmentation, and this ability is mainly due to TGF-ß in the bone protein mixed with the sheets. The activity of TGF-ß is maintained when binding to bone NCPs such as DMP1, MEPE, and BGN in the sheets.

Maintenance issues of elderly patients requiring nursing care with implant treatments in dental visiting: position paper.

PURPOSE: Japan, with an increasing number of elderly people needing long-term care in a super-aged society, urgent needs to develop the clinical guidelines on implant maintenance for elderly people with declining independence. The purpose is to categorize the troubles encountered in the care of patients with dental implants and to indicate actual practices and points of note. METHODS: From the members of the Japanese Society of Oral Implantology, 12 expert panelists who were experienced with many problems of implant maintenance during dental visits and were familiar with their solutions were selected. Through repeated discussions in the many panel meetings, the problems of implant maintenance during dental visits were distilled. RESULTS: During a dental visit, the oral cavity, general conditions, and background of elderly patients who cannot orally care for themselves must be grasped, and medical staff, care managers, and patients should understand the changes in these factors as time goes by. The solutions and responses that can be made differ greatly depending on the medical care facilities, the environment, differences in the experience of medical staff, and the patient's background. Thus, it is necessary to select safe treatments appropriate to each situation. CONCLUSIONS: This paper features many opinions based on clinical experiences. However, clinical guidelines on implant management during dental visits should be formulated in the future based on the accumulation of evidence through the implementation of clinical research.

Condition of depressive symptoms among Japanese dental students.

The Zung Self-Rating Depression Scale (SDS) is generally used to screen for the presence of depression. The purpose of this study was to investigate scores on the SDS, Japanese version, in undergraduates at Tsurumi University School of Dental Medicine in Yokohama, Japan. A total of 2,197 dental students completed the SDS from 2006 through 2008. The investigation took place each year over a 3-week period from June to July. When investigating, the Institutional Review Board at Tsurumi University approved the study. Students could voluntarily agree or decline to participate in the study, and all responses were provided anonymously. SDS scores by sex, class year, and change over time were analyzed. The mean SDS score ranged from 43.7 ± 8.5 to 44.8 ± 9.0 between 2006 and 2008. Women were significantly more depressed than men in 2007 and 2008. The SDS scores of the same students were high continuously for 2 years. "Diurnal variation," "personal devaluation," and "confusion" had the highest scores of the 20 individual items of the SDS. Of the participating students, 31.4-37.2% were classified as being moderately to severely depressed. Logistic regression analysis was used to compute the odds ratio for SDS scores of ≤47 versus ≥48. The item "suicidal rumination" had the highest chance of being associated with depressive symptoms in all 3 years. Although this research was limited to a single department of dentistry, it appears that dental students experience various levels of depression. Providing mental healthcare options to these students may be helpful.

Laboratory efficiency of additive manufacturing for removable denture frameworks: A literature-based review.

The purpose of this literature review was to verify the laboratory efficiency of additive manufacturing (AM) systems for removable partial denture (RPD) frameworks. All available relevant articles in English published from 1990 to 2020 were found by searching online databases and by hand research. A total of 17 articles dealt with the surface roughness, fitness accuracy, and retentive forces of AM frameworks. The surface roughness of AM was inferior to that of casting and milling. Whether conventional cast or AM RPD frameworks had superior fitness accuracy could not be clarified. As compared with casting and AM, milling enabled the fabrication of RPD clasps with comparable or better fitness accuracy. Over time, AM clasps had retentive force values of superior consistency as compared with those of conventional cast clasps. Clasps fabricated by repeated laser sintering and high-speed milling could obtain smoother surfaces and more suitable retention than those of AM clasps.