Providing a monolithic zirconia fixed partial denture with rigid and nonrigid connectors to overcome nonparallel abutment teeth.

This clinical report describes the fabrication of a monolithic zirconia fixed partial denture using rigid and nonrigid connectors to overcome nonparallel abutment teeth. A precise key and keyway in the ceramic material was designed with digital technology, reducing material costs, improving biocompatibility, and using esthetically superior nonmetallic materials.

The efficacy of a novel zinc-containing desensitizer CAREDYNE Shield for cervical dentin hypersensitivity: a pilot randomized controlled trial.

BACKGROUND: Recently, a novel zinc-containing desensitizer, CAREDYNE Shield, was developed. This new type of desensitizer induces chemical occlusion of dentinal tubules for desensitization and releases zinc ion for root caries prevention. Despite these features, its clinical effectiveness in the improvement of cervical dentine hypersensitivity remains to be elucidated. Thus, we aimed to evaluate the effectiveness of CAREDYNE Shield in patients with CDH. METHODS: Forty CDH teeth which matched the eligibility criteria were randomly allocated to two groups in a 1:1 ratio: the CAREDYNE Shield group (intervention group) and the Nanoseal group (control group). The pain intensity in response to air stimuli, gingival condition, and oral hygiene status of CDH teeth were assessed before and at 4 weeks after treatment. The primary outcome was the reduction of pain intensity in response to air stimuli from baseline to 4 weeks after intervention. RESULTS: From November 2019 to April 2021, 24 participants with 40 teeth were enrolled in this study and 33 teeth in 20 participants were assessed at 4 weeks after treatment. A significant reduction of pain in response to air stimuli was observed in both groups; however, no significant difference was observed between the groups. CONCLUSIONS: This study showed that CAREDYNE Shield is effective for CDH and its effectiveness is similar to Nanoseal. TRIAL REGISTRATION: UMIN Clinical Trials Registry (UMIN-CTR), UMIN000038072. Registered on 21st September 2019, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043331.

Characterization of the bone matrix and its contribution to tooth loss in human cadaveric mandibles.

OBJECTIVE: It is uncertain as to what extent the major bone matrix constituents, mineral and collagen, show inter-individual variation and dependence on age and sex in jawbones. The purpose of this study was to clarify this uncertainty using cadaveric mandibles and investigate the association of bone matrix with the number of existing teeth. MATERIALS AND METHODS: Cortical bone samples (1 × 1 cm) collected from the mental of 48 cadaveric mandibles (27 men and 21 women; age range = 56-93 years and 63-103 years, respectively) were used to quantify three bone matrix indices: mineral content, collagen content and extent of lysine hydroxylation of collagen. Associations with age and comparisons by sex were evaluated based on bone matrix indices and the numbers of existing teeth. The numbers of existing teeth were compared between the groups showing low and high bone matrix index values. RESULTS: A great amount of inter-individual variation was seen in all bone matrix indices. No bone matrix indices were associated with age, while the number of existing teeth was negatively associated with age. The bone matrix indices and number of existing teeth did not differ by sex. The number of existing teeth was nearly twice as high in the group showing high collagen content as in the low collagen group; however, an analysis of covariance showed a significant inter-group difference not from bone matrix indices, but rather from age. Interestingly, in comparison to femoral collagen, mandibular collagen showed lower lysine hydroxylation, which can represent an aspect of bone quality. CONCLUSIONS: Mandibular bone matrix shows great inter-individual variation and is independent of age and sex, but did not show as strong a relationship with tooth loss as age. Even so, mandibular collagen may represent a unique characteristic of bone matrix and deserves to be further investigated.

An Evaluation of the Cytocompatibility of Endodontic Bioceramics in Human Periodontal-Ligament-Derived Cells.

The present study evaluated the cytocompatibility of three endodontic bioceramics in human periodontal-ligament-derived cells (hPDLCs): MTA Repair HP (HP), MTA Flow White (F), and Nishika Canal Sealer BG multi (BG). In addition, we also evaluated the effect of the powder-liquid (paste) ratio of F and BG on cytocompatibility. Discs of endodontic bioceramics (diameter = 8 mm, thickness = 1 mm) were prepared with HP, F, and BG. hPDLCs obtained from extracted teeth and cultured for three to five passages were used in the experiment. The prepared discs were placed at the bottom of a 48-well plate, seeded with hPDLCs at 100,000 cells/well, cultured for 7 or 28 days, and subjected to a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay. hPDLCs cultured without any discs were used as a negative control (NC) group. Discs made of F or BG mixed in three different consistencies were also used in this experiment. The absorbance values at days 7 and 28 were high in the order of HP > NC > BG > F. Furthermore, F or BG with higher consistency showed higher absorbance values. MTA Repair HP had the highest cytocompatibility among the three materials. Furthermore, it also showed that higher consistency improved cytocompatibility.

Fabrication of bioresorbable hydroxyapatite bone grafts through the setting reaction of calcium phosphate cement.

We prepared hydroxyapatite (HAp) bone grafts by the setting reaction of calcium phosphate cement, and investigated the effects of the porosity and crystallinity on the osteoconductivity and bioresorbability. We examined the effect of the water-mixing ratio, pressure, and post-heat treatment temperature during preparation on the crystallite size and porosity of the HAp blocks. The quantity of protein adsorption increased with increasing porosity and specific surface area (SSA) of the HAp blocks, whereas the initial cell attachment was similar despite the different porosities and crystallinities. In in vitro dissolution tests with a pH 5.5 buffer, which mimics an osteoclast-created Howship's lacuna, both the porosity and SSA of the HAp blocks affected the solubility; most likely due to the increased contact area with the buffer. Thus, HAp blocks prepared by the setting reaction of calcium phosphate cement could be applicable for bioresorbable HAp bone grafts because of the high porosity and SSA.

Contact Angle and Cell Adhesion of Micro/Nano-Structured Poly(lactic-co-glycolic acid) Membranes for Dental Regenerative Therapy.

Biodegradable membranes are used in regenerative dentistry for guided tissue regeneration (GTR) and guided bone regeneration (GBR). In this study, patterned poly(lactic-co-glycolic acid) (PLGA) membranes with groove, pillar, and hole structures were successfully fabricated by thermal nanoimprinting. Their surfaces were evaluated for topography by scanning electron microscopy and laser microscopy, for hydrophobicity/hydrophilicity by contact angle analysis, and for MC3T3-E1 cell adhesion. The sizes of the patterns on the surfaces of the membranes were 0.5, 1.0, and 2.0 µm, respectively, with the height/depth being 1.0 µm. The pillared and holed PLGA membranes were significantly more hydrophobic than the non-patterned PLGA membranes (p < 0.05). However, the 0.5 µm- and 1.0 µm-grooved PLGA membranes were significantly more hydrophilic than the non-patterned PLGA membranes (p < 0.05). The 0.5 µm-grooved, pillared, and holed membranes exhibited significantly superior adhesion to the MC3T3-E1 cells than the non-patterned PLGA (p < 0.05). These results suggest that patterned PLGA membranes can be clinically used for GTR and GBR in the dental regeneration field.

Long-term clinical and radiographic evaluation of the effectiveness of direct pulp capping materials: A meta-analysis.

The aim of this review is to evaluate the long-term effectiveness of calcium silicate-based cement (CS) and calcium hydroxide (CH) for direct pulp capping (DPC) to human pulp-exposed permanent teeth. An electronic search and manual search were performed on 21 June 2019. Long-term clinical and radiographic evaluations of the effectiveness of CS and CH for DPC to human pulp-exposed teeth were included, and data extraction, risk-of-bias assessment and meta-analyses were performed. From 645 identified articles, 7 articles met the eligibility criteria. The meta-analyses comparing CS with CH and Biodentine with mineral trioxide aggregates (MTA) on DPC success rate were performed, and significant difference was observed between CS and CH (risk ratio=1.20; p=0.005), whereas no significant difference was observed between Biodentine and MTA. CS seems to be a more effective and predictable DPC material than CH; however, these analyses are based on the studies judged at high risk of bias.

Proliferation of Saos-2 and Ca9-22 cells on grooved and pillared titanium surfaces.

BACKGROUND: Surface nanostructures in titanium (Ti) oral implants are critical for rapid osseointegration. OBJECTIVE: The purpose of this study was to evaluate the growth of osteoblast-like (Saos-2) and epithelial-like (Ca9-22) cells on nanopatterned Ti films. METHODS: Ti films with 500 nm grooves and pillars were fabricated by nanoimprinting, and seeded with Saos-2 and Ca9-22 cells. Cell viability and morphology were assessed by cell proliferation assay and scanning electron microscopy, respectively. RESULTS: As assessed after 1 hour, proliferation of Saos-2 cells was most robust on grooved films than on pillared and smooth films, in this order. These cells approximately doubled on grooved and pillared substrates in 24 hours and after 5 days, but not on smooth surfaces. In contrast, Ca9-22 cells favored smooth surfaces, followed by grooved and pillared films. Indeed, cells sparsely adhered to pillared films over 5 days of incubation (p < 0.05). CONCLUSIONS: The data show that Saos-2 and Ca9-22 cells respond differently to different nanostructures, and highlight the potential use of nanopatterns to promote bone regeneration or to prevent epithelial downgrowth at the implant-bone interface.

Protective Effects of GIC and S-PRG Filler Restoratives on Demineralization of Bovine Enamel in Lactic Acid Solution.

This study was aimed at investigating the protective effects of glass ionomer cement (GIC) and surface pre-reacted glass ionomer (S-PRG) fillers used as dental restorative materials on demineralization of bovine enamel. GlasIonomer FX ULTRA (FXU), Fuji IX GP Extra (FIXE), CAREDYNE RESTORE (CDR) were used as GICs. PRG Barrier Coat (BC) was used as the S-PRG filler. They were incubated in a lactic acid solution (pH = 4.0) for six days at a temperature of 37 °C. The mineral was etched from the enamel surface, and a large number of Ca and P ions were detected in solution. The Al, F, Na, Sr, and Sr ions were released in GICs and S-RPG fillers. The Zn ion was released only in CDR and the B ion was released only in BC. The presence of apparent enamel prism peripheries was observed after six days of treatment for the group containing only enamel blocks. pH values for the FXU, FIXE, CDR, BC, and enamel block groups after six days were 6.5, 6.6, 6.7, 5.9, and 5.1, respectively. Therefore, the observed pH neutralization effect suppressed progression of caries due to the release of several ions from the restoratives.

The efficacy of the novel zinc-containing desensitizer CAREDYNE Shield on dentin hypersensitivity: a study protocol for a pilot randomized controlled trial.

BACKGROUND: Dentin hypersensitivity (DH) is a condition characterized by short and sharp episodes of pain which will arise in response to tactile, chemical, thermal, evaporative or osmotic stimuli. The painful symptoms cause discomfort in patients and reduce their quality of life. Recently, the novel zinc-containing desensitizer CAREDYNE Shield has been developed as a new type of desensitizer that acts by inducing chemical occlusion of dentinal tubules, and releasing zinc ion for root caries prevention. However, the clinical effectiveness of CAREDYNE Shield on DH remains unclear. Therefore, the aim of this study is to evaluate the effectiveness of CAREDYNE Shield on DH by comparing with that of another desensitizer, Nanoseal, commonly used in Japan. METHODS/DESIGN: This study protocol is a two-arm, parallel, pilot randomized controlled trial. Forty DH patients will be randomly allocated to two groups. Participants in the intervention group will be treated with CAREDYNE Shield, while those in the control group will be treated with Nanoseal. The primary outcome is the reduction of pain intensity in response to air stimuli measured with a 5-point verbal response scale from baseline to 4 weeks after the intervention, and Fisher's exact test will be used for analyses. DISCUSSION: CAREDYNE Shield can be casually applied to subgingival areas and proximal surfaces because it reacts with only tooth substance. Furthermore, zinc has been reported to reduce the demineralization of enamel and dentin and inhibit biofilm formation, plaque growth and dentin-collagen degradation. Therefore, CAREDYNE Shield may be expected to be a useful novel desensitizer that acts not only as a desensitizer but also as a root caries inhibitor. TRIAL REGISTRATION: UMIN Clinical Trials Registry (UMIN-CTR), ID: UMIN000038072. Registered on 21 September 2019. TRIAL STATUS: This study (protocol version number: version 1.4.0; approved on 22 October 2019) is ongoing. The recruitment of participants began in December 2019 and will be continued until November 2020 (Hanke, Am Dent Assoc 27:1379-1393, 1940).

Long-term clinical and radiographic evaluation of the effectiveness of direct pulp-capping materials.

The aim of this review was to assess the effectiveness of different direct pulp-capping (DPC) materials for human pulp-exposed teeth. An electronic search was performed on 20 February 2018. Long-term clinical and radiographic evaluations of the effectiveness of different DPC materials for use on human pulp-exposed teeth were included. Risk-of-bias assessment and data extraction were performed. From the 496 identified articles, 15 met the eligibility criteria. Among the studies included in those articles, a total of 1,322 teeth were treated with 12 types of DPC materials, and 1,136 teeth were evaluated at a final follow-up examination. For mineral trioxide aggregate (MTA) and calcium hydroxide (CH), the number of included studies, the number of treated teeth, and the mean follow-up period of studies were almost equal, and the success rates of MTA was superior to CH. Therefore, MTA is likely to be a more effective and predictable material for DPC compared to CH. However, the results were based on the included studies, which were all judged to have a high risk of bias. Therefore, more long-term clinical and radiographic studies designed with lower risk of bias are needed. Moreover, the other 10 materials were only investigated by a small number of studies; therefore, further studies are required.

Characterization of mandibular bones in senile osteoporotic mice.

At present, little is known about the age-related changes in jaw bones. The aim of this study was to characterize the mandibles of 6 month-old senile osteoporotic mice, SAMP6, and compare with those of age-matched controls, SAMR1. In comparison to SAMR1, SAMP6 showed thinner cortical bone, lower bone volume, and poorly organized collagen matrix. The collagen fibril diameter in SAMP6 was significantly smaller than that of SAMR1. In SAMP6 both collagen content and cross-links were lower than those of SAMR1, but the ratio of the major mature cross-link (pyridinoline) to its precursor reducible cross-link (dehydrodihydroxylysinonorleucine/its ketoamine) was higher in comparison to SAMR1. In addition, the extent of lysine hydroxylation of collagen was higher in SAMP6 than that of SAMR1. These results indicate that not only the quantity of collagen but also its quality are altered in SAMP6 and may result in the age-associated osteoporotic defects of mandibles.

[A clinical report of application of implant-supported fixed partial denture with a removable gingival veneer to a patient who has severe resorption of maxillary anterior ridge].

PATIENT: A 39-year-old female patient was admitted with mobility of maxillary anterior fixed partial denture. She was diagnosed as severe chronic periodontitis of abutment teeth of the denture, left alveolus cleft, and anterior/posterior crossbites. The crossbites were improved by prosthetic approach using an implant-supported fixed partial denture with a removable gingival veneer at the anterior and crowns at the posterior. The implant-supported fixed partial denture and most teeth have been kept in a stable condition. DISCUSSION: Sufficient lip support and proper phonetic function were recovered by implant-supported fixed partial denture with removable gingival veneer. The long-term stability of implants may be due to easiness of toothbrushing and connection of implants rendered by the fixed prosthesis. CONCLUSION: This case suggests that implant-supported fixed partial denture with removable gingival veneer could be useful for severe ridge resorption.

Cell migration capability of vascular endothelial growth factor into the root apex of a root canal model in vivo.

Once a tooth develops deep caries and the dental pulp tissue is irreversibly infected, the infected dental pulp tissue should be removed, and filling material should be placed in the root canal. Endodontically treated teeth are prone to root fracture or periapical periodontitis; however, dental pulp tissue has the potential to prevent root fracture or periapical periodontitis. Therefore, dental pulp regeneration after pulpectomy may help prolong tooth life. In this study, a new method of dental pulp regeneration was developed. Vascular endothelial growth factor-adsorbed collagen gel was injected into the root canal of a prepared root canal model, placed into the dorsum of a rat, and cultured for 3 weeks. After retrieving the implant, histological analysis was performed. It was found that rat somatic cells were recruited into the root apex of the transplanted root canal model. These findings suggest a new potential technique for engineering dental pulp tissue.

Reliability and validity of the patient disability-oriented diagnostic nomenclature system for prosthetic dentistry.

PURPOSE: The Japan Prosthodontic Society (JPS) has proposed a new diagnostic nomenclature system (DNS), based on pathogenesis and etiology, to facilitate and improve prosthodontic treatment. This system specifies patient disability and the causative factor (i.e. "B (disability) caused by A (causative factor)"). The purpose of this study was to examine the reliability and validity of this DNS. STUDY SELECTION: The JPS Clinical Guideline Committee assessed mock patient charts and formulated disease names using the new DNS. Fifty validators, comprising prosthodontic specialists and dental residents, made diagnoses using the same patient charts. Reliability was evaluated as the consistency of the disease names among the validators, and validity was evaluated using the concordance rate of the disease names with the reference disease names. RESULTS: Krippendorff's α was 0.378 among all validators, 0.370 among prosthodontic specialists, and 0.401 among dental hospital residents. Krippendorff's α for 10 validators (3 specialists and 7 residents) with higher concordance rates was 0.524. Two validators (1 specialist and 1 resident) with the highest concordance rates had a Krippendorff's α of 0.648. Common disease names had higher concordance rates, while uncommon disease names showed lower concordance rates. These rates did not show correlation with clinical experience of the validator or time taken to devise the disease name. CONCLUSIONS: High reliability was not found among all validators; however, validators with higher concordance rates showed better reliability. Furthermore, common disease names had higher concordance rates. These findings indicate that the new DNS for prosthodontic dentistry exhibits clinically acceptable reliability and validity.

A comparative study of computed tomography and magnetic resonance imaging for the detection of mandibular canals and cross-sectional areas in diagnosis prior to dental implant treatment.

BACKGROUND: Computed tomography (CT) is effective in the diagnosis of dental implants. However, it has the disadvantage of exposing patients to high doses of x-rays, and the mandibular canals cannot be detected by CT in some clinical cases. PURPOSE: The purpose of this study was to examine the detectability of the anatomic morphology of the molar region in the lower jaw (where implantation is common) by CT and magnetic resonance imaging (MRI), to compare the data, and to determine the usefulness of MRI in diagnosis prior to dental implant treatments. MATERIALS AND METHODS: Eleven female subjects (average age, 59 years) who had partially edentulous mandibles (total of 19 sites) were included in the study. CT and MRI were performed with the same subjects, and the degrees of identification of the mandibular canal in the first and second molar regions were compared. Dimensional accuracy in the second molar region was also compared. RESULTS: With CT, the canals of the first molar regions were not identified in 11 of 19 sites; however, MRI identified the canals in all 19 sites. Using the kappa index, we found that the inter- and intraobserver identification reliabilities (0.84 and 0.87, respectively) were excellent, especially for MRI. Dimensional positioning of the canal in the second molar region was almost the same with MRI as with CT. CONCLUSIONS: MRI is an alternative method in diagnosis prior to dental implant treatment in the mandibular molar region.

Distinct characteristics of mandibular bone collagen relative to long bone collagen: relevance to clinical dentistry.

Bone undergoes constant remodeling throughout life. The cellular and biochemical mechanisms of bone remodeling vary in a region-specific manner. There are a number of notable differences between the mandible and long bones, including developmental origin, osteogenic potential of mesenchymal stem cells, and the rate of bone turnover. Collagen, the most abundant matrix protein in bone, is responsible for determining the relative strength of particular bones. Posttranslational modifications of collagen, such as intermolecular crosslinking and lysine hydroxylation, are the most essential determinants of bone strength, although the amount of collagen is also important. In comparison to long bones, the mandible has greater collagen content, a lower amount of mature crosslinks, and a lower extent of lysine hydroxylation. The great abundance of immature crosslinks in mandibular collagen suggests that there is a lower rate of cross-link maturation. This means that mandibular collagen is relatively immature and thus more readily undergoes degradation and turnover. The greater rate of remodeling in mandibular collagen likely renders more flexibility to the bone and leaves it more suited to constant exercise. As reviewed here, it is important in clinical dentistry to understand the distinctive features of the bones of the jaw.

Regulation of proliferation and differentiation of mouse tooth germ epithelial cells by distinct isoforms of p51/p63.

OBJECTIVES: p51/p63 gene, one of the p53 families, is specifically expressed in tooth germ epithelial cells and is essential for tooth development. This study aims to elucidate roles of p51/p63 in ameloblastic cell differentiation. MATERIALS AND METHODS: We determined expression pattern of each of p51/p63 isoforms by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting using emtg (epithelium of molar tooth germ)-1, -2, -3, -4, and -5 cell lines established from a mandibular molar tooth germ of p53-deficient mice and SF2 cells which differentiates into ameloblasts upon exposure to NT4. Furthermore, we investigated the function of p51/p63 in these cells by Tet system, which enables inducible expression and knock down of the target genes of interest by exposing cells to doxycycline. RESULTS: The expression of ΔNp51B/ΔNp63α, an isoform without transactivation domain, was detected at high level in immature cells, while the expression of TAp51/TAp63 isoforms, isoforms of with the transactivation domain, was detected at high level in mature cells. Moreover, induction of TAp51A/TAp63γ expression led to down-regulation of ΔNp51B/ΔNp63α expression and cell proliferation. Interestingly, this also led to up-regulation of ameloblastin expression, a differentiation marker of amelogenesis. CONCLUSIONS: The results suggested that p51/p63 might regulate the cell proliferation and differentiation of tooth germ epithelial cells.

Students' opinion of a predoctoral implant training program.

Implant treatment today is highly predictable and provides valid restorative options for the completely or partially edentulous patient. In Japan, many dental care facilities have incorporated implant treatment, and such treatment is no longer rare. For predoctoral students, the educational environment related to implants is not always applicable in present clinical settings. In this article, we describe the implant training program developed at our university for predoctoral education, and we report the changes in student opinions regarding implant treatment by comparing pre- and post-training opinions. The newly developed models for implant training were effective in increasing student understanding that implant treatment is one prosthetic option for restoring missing teeth. In a survey of predoctoral students, responses indicating negative opinions toward implant treatment decreased after training, and responses indicating positive opinions increased. These findings indicated that this training was effective in deepening student understanding of implant treatment.