BackgroundAlthough the use of removable dentures can improve oral function and esthetics for elderly people, compared to those who do not wear removable dentures, those wearing removable dentures could have worse oral health related-quality of life (OHRQoL). Additional information is required to assess which factors related to denture wearing influence the OHRQoL of elderly individuals. The purpose of this study is to evaluate the association between denture wearing and OHRQoL in a sample of elderly individuals in Taiwan.MethodsThe study population included 277 elderly people wearing removable dentures (mean age = 76.0 years). Using face-to-face interviews, we collected data on the participants’ socio-demographic characteristics, dental care service usage (regular dental checkups, treatment during toothache, dental visits in the last year), and factors related to denture wearing (perceived oral pain, perceived loose denture, perceived oral ulcer, perceived halitosis, perceived dry mouth, and perceived total denture satisfaction scores). OHRQoL was measured using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The location and number of remaining natural teeth and the type of denture were also recorded. Hierarchical multiple regression analysis was performed using GOHAI-T scores as the dependent variable.ResultsAll the predictors together accounted for 50% of the variance in GOHAI-T scores. Further, education level, number of natural teeth, denture status, perceived loose denture, perceived oral ulcer, and perceived total denture satisfaction scores had statistically significant influences on OHRQoL. When compared with other variables, factors related to denture wearing, especially perceived total denture satisfaction scores, had the greatest impact on GOHAI-T scores.ConclusionsOf the factors analyzed in this study, denture satisfaction was the strongest predictor of OHRQoL. This suggests that denture satisfaction is useful for assessing the effect of denture treatment on the OHRQoL of elderly individuals wearing removable dentures.

No abstract

Threaded implants have been shown to play an important role in increasing mechanical osseointegration. The aim of this study was to determine bone stress distribution when using different types of implant thread pitches and designs. Five 3D finite element models were constructed to simulate bone stresses induced in implant bodies with two types of thread form: triangular ("Tri" prefix) and trapezoidal ("Trap" prefix). The former had thread pitches of 0.8, 1.2, and 1.6 mm, while the latter had thread pitches of 1.2 and 1.6 mm. A biting load of 143 N was applied vertically and obliquely to the occlusal central fossa of the crown. The main effects of each level of the three factors investigated (loading type, pitch, and thread form) in terms of the stress value were computed for all models. Results indicated that the loading type was the main factor of influence on the peak compressive stress of the alveolar bone. Optimal thread pitch was 1.2 mm for a triangular-thread implant, and a trapezoidal-threaded implant with thread pitch of 1.6 mm had the lowest stress value among trapezoidal-threaded implants. This study concluded that each thread form has its unique optimal thread pitch with regard to lower concentration of bone stress. Clinically, this study suggests that in biomechanical consideration, thread pitch exceeding 0.8 mm is more appropriate for a screwed implant. For clinical cases that require greater bone-implant interface, trapezoidal-threaded implants with thread pitch of 1.6 mm provide greater primary stability and lower concentration of bone stress under different loading directions.

Evaluation of a self-assessed screening test for masticatory ability of Taiwanese older adultsObjectives: The aim of this study was to evaluate a screening test based on a food intake questionnaire to discriminate the masticatory ability of Taiwanese older adults with 20 and more natural teeth and at least 8 functional tooth units (FTUs) from the masticatory ability of those with fewer than 20 natural teeth and 8 FTUs. Materials and Methods: The subjects were 2244 patients (mean age, 60.4±10.0 years) recruited from 23 counties and cities in Taiwan. Information about their demographic data, dentition, and masticatory ability was collected. Masticatory ability was measured for 23 food groups comprising 35 common Taiwanese foods, and receiver operation characteristic curve analysis was performed. Results:The results showed that the final questionnaire included 14 food groups and a subject choosing 'difficult to eat' responses for 4 and more of these food groups had the same masticatory ability as individuals with fewer than 20 natural teeth and 8 FTUs. Conclusion: In conclusion, foods that are the most difficult to eat are not necessarily good discriminatory indicators. Hence, the 14-food group questionnaire can be considered the best screening test for masticatory ability of Taiwanese older adults in terms of the presence of 20 and more natural teeth and at least 8 FTUs.

The purposes of this study were to (1) examine the relationship between the number of various types of healthy remaining natural teeth at different sites and self-rated chewing ability and (2) evaluate the relationship between the number of functional tooth units (FTUs), comprising functional natural teeth (FNT) or fixed prostheses, and self-rated chewing ability. A sample of 296 adults (122 men and 174 women), aged 45 years or older (average age, 56.6±9.7), were recruited from seven dental clinics in Kaohsiung City. Dental information on the number and status of remaining teeth was obtained through examination by trained and calibrated dentists. Self-assessment of chewing ability (masticatory score) was evaluated with a self-administered questionnaire. Results showed that increased age is associated with a greater likelihood of difficulty in chewing. To avoid chewing difficulty, at least 24.7 FNT, 13.3 posterior-FNT, 8.1 units of natural tooth-FTUs, or 9.6 units of fixed tooth-FTUs must remain. Age and the number of healthy remaining teeth, including natural teeth and fixed prostheses, are key factors in chewing ability. Given that aging is unavoidable, the preservation of healthy remaining teeth plays a relatively important role in the maintenance of chewing ability among middle-aged and elderly people.

No study has investigated the effect of learning curves on the accuracy of dental implant navigation systems. This study evaluated the accuracy of the dental implant navigation system and established the learning curve according to operation site and operating time. Each dental model was used for drilling 3 missing tooth positions, and a patient tracking module was created. The same dentist performed the drilling test for 5 sets of dental models. CT back scanning was performed on the dental models. Customized implants based on the drilled holes were inserted. The relative error between the preoperative planning and actual implant was calculated. Using the dental navigation system could help dentists position implants more accurately. Increasing the frequency with which a dentist used the navigation system resulted in shorter operations. Longitudinal and angular deviation were significantly (P < 0.0001 and P = 0.0164). We found that the same level of accuracy could be obtained for the maxilla and mandible implants. The Student's t test demonstrated that the longitudinal error, but not the total or angular error, differed significantly (P = 0.0012). The learning curve for the dental implant navigation system exhibited a learning plateau after 5 tests. The current system exhibited similar accuracy for both maxillary and mandibular dental implants in different dental locations. The one-way ANOVA revealed that the total, longitudinal, and angular errors differed significantly (P < 0.0001, P < 0.0001 and P = 0.0153). In addition, it possesses high potential for future use in dental implant surgery and its learning curve can serve as a reference for dentists.

Since 2008, oral squamous cell carcinoma (OSCC) has climbed to the fourth place in cancer mortality in the male population of Taiwan. Epigenetic regulations including DNA methylation and histone modification control gene expression and play important roles during cancer progression. Since the relationship between histone modification and prognosis of OSCC is inconclusive, we collected 215 formalin-fixed and paraffin-embedded tissues from male patients having OSCC and surveyed them by tissue microarray-based immunohistochemical staining. The association between five histone modification-related genes, clinicopathological parameters, and prognosis of OSCC was examined. From tissue microarray immunohistochemistry staining results, we found that the nuclear staining intensity of ARK2 (Aurora kinase B-a serine/threonine-protein kinase of H3S10) was associated with poor clinical outcomes (≤3-year survival, p = 0.005). The cytosolic staining intensity of the ARK2 protein was associated with tumor stage (p = 0.006) and tumor size (T) of TNM staging system (p = 0.026). Cytoplasmic staining intensity of G9a (H3K9 methyltransferase) was associated with histological grade of differentiation (p = 0.026). EZH2 (H3K27 methyltransferase) and SUV39H1 (H3K9 methyltransferase) overexpressions in nuclei were, respectively, associated with lymph node metastasis (N, p = 0.016) and stage (p = 0.009). Our result suggests that overexpressions of histone modification-related proteins-ARK2, G9a, EZH2, and SUV39H1 but not SUV39H2 are associated with prognosis of OSCC in the male population of Taiwan. These proteins, especially ARK2, may serve as effective prognostic factors and can also be used as biomarkers for predicting various clinical outcomes of OSCCs in the Taiwanese population.

The aim of this study was to compare the accuracy of implant placement by using the conventional freehand method, the surgical guide alone, the dental navigation system alone, and the dental navigation system with a surgical guide. The participants were aged 20 years or older and were requiring dental implant surgery according to an assessment made by a dentist between July 2014 and December 2017. A total of 128 dental implants were inserted, 32 dental implants in each group, and participants with similar or identical age (i.e., 20–50 years or 50 years or above) and missing tooth locations were paired for comparison. Accuracy was measured by overlaying the real position in the postoperative Cone Beam Computerized Tomography (CBCT) on the virtual presurgical placement of the implant in a CBCT image. Using the dental navigation system with a surgical guide could help dentists to position implants more accurately. Total, longitudinal, and angular error deviation were significantly different (p < 0.0001). The same level of accuracy could be obtained for the different jaws and tooth positions. The one-way analysis of variance (ANOVA) showed that the total, longitudinal, and angular errors differed significantly (p < 0.0001). A comparison of the four dental implant surgical methods indicated that the combination of a dental implant navigation system and a surgical guide kit achieved the highest accuracy in terms of the different tooth positions and jaws.