The purpose of this review is to search for complications of dental implant superstructures and consider the issues involved. This narrative review was performed by searching through PubMed databases and review articles that were published after 1990. Misfitting of the superstructure can result in loosening of screws, reduced preload, and in some cases, significant stress around the implant. External connection modalities and single implant prostheses have been reported to have more loose or broken abutment screws. In addition, when zirconia abutment was used for platform shifting, the rate of fracture of the abutment was considered to be high. Additionally, it was reported that men were significantly at an increased risk of abutment fracture. As for the retention mechanism of implant overdenture, stud attachment (Locator type) should receive more attention to wear and damage of retention parts than other attachments. The causes of the complications of implant superstructures have not been clarified in some cases, and further verification is required. Verification of complications is considered important to obtain a long-term prognosis for superstructures of implants. It will be necessary to further verify complications of implants in the future.

Purpose: This study evaluated the association of surface degradation and formation of Streptococcus mutans (S. mutans) biofilm in resin-based composites (RBCs) after storage in different acidic liquids.

Methods: To evaluate microhardness and surface micromorphology, hybrid and nanohybrid RBC discs were stored in artificial gastric acid, cola drink, orange juice, artificial saliva, and distilled water for three intervals of 15 min per day for 7, 15, and 30 days. After 30 days of storage, surface roughness was analyzed, and the RBC discs were placed in a biofilm reactor inoculated with S. mutans to evaluate surface biofilm formation.

Results: As compared with nanohybrid RBCs, roughness and surface microhardness values were significantly lower (P < 0.05) for hybrid RBCs stored in artificial gastric acid, followed by specimens stored in cola drink and orange juice. Artificial gastric acid caused greater surface degradation, which increased the biomass of S. mutans on the surface of both RBC types.

Conclusion: Surface degradation of hybrid and nanohybrid RBCs correlated with the pH of the liquid, while S. mutans biofilm formation was associated with increased surface roughness in hybrid RBCs.

Purpose: This study aimed to test the face seal of a surgical mask modified using a custom-made mask fitter or by sealing all borders with micropore tape, in comparison to the N95 mask as a gold standard.

Methods: Fifteen participants were assigned to wear an N95 mask, a surgical mask sealed with a mask fitter, and a surgical mask sealed with micropore tape. A quantitative fit test was performed using a Portacount respirator fit tester in 4 different actions: bending over, talking, moving the head from side to side, and moving the head up and down.

Results: The N95 showed the highest overall fit factor score (134.67 ± 66.62), passing Occupational Safety and Health Administration (OSHA) standards. The surgical mask alone had the lowest overall fit factor score of 4.73 ± 3.30. Modification of the surgical mask using a mask fitter or micropore tape significantly increased the overall fit factor to 35.33 ± 14.58 and 29.33 ± 9.73, respectively. This pattern was similar for all exercises.

Conclusion: The N95 was the only mask type that passed the OSHA standard for protection. Use of a mask fitter or micropore tape significantly increased the face seal of a surgical mask. This could offer useful levels of protection during a non-aerosol dental procedure.

Purpose: This study investigates the attenuation of radiation doses by four materials, heat-polymerized, and self-polymerized polymethyl methacrylate (PMMA), putty-type, and injection-type polyvinyl siloxane (PVS) impression material. This in vitro study should aid in the selection of dental materials for radiotherapy prostheses, thereby minimizing the possibility of radiotherapy side effects.

Methods: Specimens of each type were fabricated as a 5 × 5 cm squares with a thickness of 10 mm. Heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS impression material, and injection-type PVS impression material were selected. A calibration curve was created to determine the association of radiation doses and grayscale value. A linear accelerator was used to irradiate the specimens. The radiation doses above and below the materials were measured using radiochromic film dosimetry. After film irradiation, the pixel scale of color change was used to determine the radiation dose based on the created calibration curve. The results were exported to find average doses to calculate the percentage of the attenuated dose for a comparison of the four materials.

Results: The average attenuated doses of heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS, and injection-type PVS were 10.8%, 6.2%, 17.2%, and 14.2% respectively.

Conclusion: PVS showed higher attenuating radiation exposure compared with PMMA.

Purpose: To evaluate the effect of different surface treatments, ferrule heights, and luting agents on the pull-out bond strength (PBS) of computer-aided design/computer-aided manufacturing (CAD-CAM) monolithic endocrowns.

Methods: After endodontic treatment and preparation for two endocrown designs (ferrule height 0 mm or 2 mm), CAD-CAM monolithic zirconia endocrowns were fabricated for 80 mandibular molars. Each endocrown design group was then divided on the basis of surface treatment into two groups: half were air-abraded and half were air-abraded/laser-irradiated. Then, all treated groups were further divided into two subgroups (n = 10) and cemented to teeth with either a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)–containing resin luting agent (Panavia SA) or a combination of MDP-containing primer and MDP-free resin luting agent (Monobond Plus/Multilink Automix). PBS was measured with a universal test machine after simulated chewing and thermocycling. Three-way ANOVA and the post-hoc Bonferroni test were used for statistical analysis.

Results: PBS was significantly associated with type of surface treatment, type of luting agent, and ferrule height. Air-abraded/laser-irradiated endocrowns with a 2-mm ferrule that were cemented with Monobond Plus/Multilink Automix had the highest PBS (P < 0.05).

Conclusion: Surface treatment with air abrasion/laser irradiation, presence of a ferrule, and priming with an MDP-containing primer increased the PBS of monolithic zirconia endocrowns.

Purpose: A water fluoridation program launched in the United States in 1945 has become a worldwide application for caries prevention. Although such a program is important in Japan, water fluoridation in large communities has not been established. This study aimed to develop safe small-scale water fluoride equipment that can be easily used to carry out water fluoridation programs in areas with children in long-term care facilities, and in developing countries without water supply facilities.

Methods: Batch-type NaF addition adjustment equipment was manufactured as small-scale water fluoride equipment. The fluoride concentration of the adjusted water with this equipment was measured using an ion meter and a fluoride composite electrode. All 51 water quality standards set by the Ministry of Health, Labour, and Welfare of Japan were tested.

Results: The fluoride ion concentration of the adjusted water was 0.7 mg/L and it was constant and stable. The adjusted water conformed to the water quality standard values of the Japanese Water Supply Law.

Conclusion: Water produced with small-scale water fluoridation equipment had a fluoride concentration of 0.7 mg/L, which is the recommended concentration for caries prevention. The fluoride concentration was stable.

Purpose: The purpose of this study was to evaluate the 3-year cumulative survival rates of posterior single monolithic zirconia crowns (MZCs) and their antagonists, and to analyze the influencing factors.

Methods: The clinical outcomes of posterior single MZCs and their abutment teeth with antagonists, and the antagonists between April 2014 and September 2020 were evaluated retrospectively. The 3-year cumulative survival rates were calculated and associations between the survival time and predictor variables (“Jaw”, “Tooth”, and “Pulpal condition”) were also verified using Cox proportional hazards models and hazard ratios (HRs).

Results: The 3-year cumulative survival rate of single MZCs was 89.8% (9 of 177 MZCs, 95% confidence interval (CI): 80.0-95.1%). Cox proportional hazards models showed non-vital teeth were significantly associated with failure (HR: 2.76e + 9, P = 0.012). The 3-year cumulative survival rate of antagonists was 94.8% (7 of 171 antagonists, 95% CI: 89.3-97.6%). Non-vital antagonists were also identified as an independent predictor for failure in Cox proportional hazards models (HR: 7.83, P = 0.03).

Conclusion: Although posterior single MZCs were clinically acceptable, non-vital pulpal condition could be a potential risk factor for failures in the abutment and antagonist teeth of MZCs.

Purpose: This study was designed to compare the levels of Streptococcus mutans (S. mutans) in saliva with those in occlusal plaque on posterior teeth at different stages of dentition, and to explore the correlation with caries experience to determine the most suitable source of S. mutans for research.

Methods: Samples of saliva and occlusal plaque were collected from 83 patients (aged 3-17 years) over three months. S. mutans levels were determined by culture-based selective plating, morphological identification, and S.mutans-specific monoclonal antibody labeling.

Results: The mean age of the participants was 8.8 (±3.7) years, and 74.7% of them were Hispanic. Mean caries experience for children with primary, mixed, and permanent dentition was 5.2 (±4.7), 4.0 (±3.3), and 0.8 (±1.3), respectively. Children with primary and mixed dentition had a higher caries experience than children with permanent dentition (P < 0.01), despite having similar S. mutans levels and total bacteria. A positive correlation was observed between S. mutans levels in plaque and those in saliva, but not between S. mutans levels and caries experience. It was noteworthy that plaque samples harbored higher S. mutans levels (>10⁵ CFU/mL) than saliva samples.

Conclusion: Both plaque and saliva samples are useful sources for S. mutans isolation. S. mutans levels from both sources were not significantly correlated with caries experience, but occlusal plaque had greater sensitivity for quantification of high S. mutans levels.

Purpose: This study aimed to investigate the efficacy of piezosurgery (PI) in promoting immediate clotting after flapless extraction in patients undergoing dual antiplatelet therapy (DAPT).

Methods: In this randomized controlled trial, 80 DAPT patients were equally divided into the PI and turbine handpiece (TH) groups. Accordingly, flapless extraction of a single tooth using PI or TH was performed on each patient, and the immediate clotting status was evaluated. The results of the preoperative hematological examinations, surgery-related variables and postoperative complications were recorded for analysis.

Results: Both groups presented with low platelet aggregation and similar coagulation functions. The PI group exhibited a higher proportion of patients with normal intra-alveolar clotting (≤30 min) (70% vs. 40%, P = 0.007) and fewer intraoperative complications (25% vs. 47.5%, P = 0.036) than that in the TH group. Logistic regression analysis indicated that the applied instrument was an independent risk factor for prolonged immediate bleeding (odds ratio = 3.10, 95% confidence interval: 1.20-8.00, P = 0.019). Intergroup differences were insignificant in terms of the other surgery-related variables and postoperative complications, except for the longer surgical duration in the PI group.

Conclusion: The application of PI may contribute to better immediate clotting in DAPT patients after flapless extraction compared with the use of TH.

Purpose: An investigation of the configurations of mandibular premolar roots and canals in a population of Black South Africans.

Methods: Cone-beam computed tomography analysis of 772 mandibular premolars was performed, and the premolars were classified according to the systems proposed by Vertucci and Ahmed et al. Root number, canal morphology, age, and sex were recorded. Fisher’s exact test was used to determine relationships based on age and sex (P < 0.05).

Results: Single roots were seen in the majority of mandibular premolars (97.1%). Single canal configurations (i.e., Vertucci Type 1/Ahmed et al. ¹MP¹) were observed in 48.5% of first and 81.3% of second mandibular premolars. Mandibular first premolars demonstrated multiple canals in more than half of the sample (51.5%), and C-shaped morphology in more than one-tenth (11.1%). A relationship between sex and the presence of radicular grooves was demonstrated (P = 0.049), males being more likely to demonstrate this feature (P = 0.051). Multiple canals in mandibular first premolars also showed a relationship with sex (P = 0.005), a male predilection being evident (P = 0.007). The Ahmed et al. system proved superior to the Vertucci classification for reporting complex configurations and anatomical variations, although a greater number of unique categories were created.

Conclusion: Diverse mandibular premolar root and canal morphology was observed in the studied population. Clinicians must be aware of common morphological features as well as possible anatomical variations in mandibular premolars, as failure to treat complete root canal systems may negatively impact endodontic treatment outcomes.

Clarification of potential factors affecting the occurrence of accidental sharps injuries among students in dental laboratories would likely help to reduce the incidence of such injuries, thus improving dental education, as well as further preventing injury in general healthcare workspaces. In this study, undergraduates at the College of Oral Medicine, Taipei Medical University, were assessed for 10 items: gender, age, course specialty, whether or not framed glasses were worn during operations, speed of assignment completion, dominant hand, self-assessment of performance, whether or not students previewed the classes in advance, sleep duration, and sharps injury experience. The results suggested that course specialty and sleep duration were the major factors associated with the occurrence of sharps injuries among students in the dental laboratory.

The Japanese Health, Labour, and Welfare Ministry in 2020 identified the following issues for training and recruitment of dental technicians: early involvement of students in dental practice and dental laboratory work, a curriculum in line with the times, and an extension of the years of training. This paper investigates the education and qualifications of dental technicians in other countries to discuss these issues. The survey method was to use the database PubMed to search the literature since 2001 using the keywords “dental technician,” “education,” and license” to collect literature related to the pre-graduate education of dental technicians. Information on educational institutions was also included in the survey. The results showed that the countries that introduced joint education between dental technicians and dentists into their educational programs, and the examinations and years of training required for each certification varied from country to country. The curriculum for dental technicians in Japan changed from a time-based to a credit-based system on April 1, 2018. The credit system is characterized by the possibility of each training institution actively engaging in flexible curriculum organization. Dental technician education programs in other countries can provide a valuable reference for each training institute to demonstrate its uniqueness.

This report discusses a case of a 20 year and 7-month-old female patient with a skeletal maxillary protrusion with gummy smile, crowding, and high angle due to horizontal protrusion of the maxillary anterior teeth. The gummy smile in this case was improved by an upward movement of the occlusal plane associated with maxillary molar intrusion and sufficient lingual movement while performing maxillary anterior teeth intrusion. Following treatment, it was stable even after 8 years of retention. Thus, it is important to ascertain the cause of gummy smile, and establish whether it is due to the vertical maxillary excess in the maxillary anterior teeth, or the horizontal protrusion of the maxillary anterior teeth.

This study investigated olfactory/taste functions in older persons requiring nursing care to clarify whether these functions are associated with appetite or nutritional status. Seventy-two older persons requiring nursing care and 37 unassisted persons were surveyed for olfactory function, taste function, appetite, and nutritional status. Age-adjusted covariance analysis was conducted between the two groups. Both groups showed reduced olfactory and taste functions; these functions were more markedly reduced in participants requiring nursing care compared to those who did not. Both groups had similar appetite and nutritional status findings, suggesting that these factors are not associated with olfactory and taste functions.

The use of a uniform terminology is important to avoid misunderstanding of concepts or procedures in discussion. The usage of English prosthodontic terms in Japan was investigated in the current study. English prosthodontic terms listed in The Glossary of Prosthodontic Terms edited by the Japan Prosthodontic Society (GPTJ-5) were compared to those in The Glossary of Prosthodontic Terms ninth edition (GPT-9). A small number of terms labeled as objectionable in GPT-9 were listed in GPTJ-5. This might indicate that it takes a long time to replace terms that are used widely.

The purpose of the present study was to indicate that patients with anti-centromere antibodies (ACA) also experience ocular/oral dryness like patients with anti-Ro/SSA and/or anti-La/SSB antibodies (anti-SSA/SSB). A total of 80 patients with subjective ocular and/or oral dryness were classified into two groups, namely, anti-SSA/SSB-positive (anti-SSA/SSB [+]) group and ACA-positive (ACA [+]) group. The degree of ocular and oral dryness in ACA (+) patients is similar to that in anti-SSA/SSB (+) patients. On histopathological examination of the labial glands, the area of fibrosis was significantly larger in the ACA (+) group than in the anti-SSA/SSB (+) group. Thus, ACA (+) patients should be examined for Sjögren’s syndrome.

Primordial odontogenic tumor (POT) is a rare mixed odontogenic tumor composed of primitive ectomesenchyme similar to the dental papilla. The outer surface consists of columnar/cuboidal odontogenic epithelium similar to the inner enamel epithelium, and there is no hard tissue formation. Until now, 27 cases have been reported in the English literature. This article describes the clinicopathological characteristics of one case of POT, representing the oldest patient (aged 26 years) reported to date.