Rate and pattern of interproximal dental attrition

Secondary Dentin Formation Mechanism: The Effect of Attrition

Human dentin consists of a primary layer produced during tooth formation in early childhood and a second layer which first forms upon tooth eruption and continues throughout life, termed secondary dentin (SD). The effect of attrition on SD formation was considered to be confined to the area subjacent to attrition facets. However, due to a lack of three-dimensional methodologies to demonstrate the structure of the SD, this association could not be determined. Therefore, in the current study, we aimed to explore the thickening pattern of the SD in relation to the amount of occlusal and interproximal attrition. A total of 30 premolars (50-60 years of age) with varying attrition rates were evaluated using micro-computerized tomography. The results revealed thickening of the SD below the cementoenamel junction (CEJ), mostly in the mesial and distal aspects of the root (p < 0.05). The pattern of thickening under the tooth cervix, rather than in proximity to attrition facets, was consistent regardless of the attrition level. The amount of SD thickening mildly correlated with occlusal attrition (r = 0.577, p < 0.05) and not with interproximal attrition. The thickening of the SD below the CEJ coincided with previous finite element models, suggesting that this area is mostly subjected to stress due to occlusal loadings. Therefore, we suggest that the SD formation might serve as a compensatory mechanism aimed to strengthen tooth structure against deflection caused by mechanical loading. Our study suggests that occlusal forces may play a significant role in SD formation.

Artificial intelligence-assisted prediction of preeclampsia: Development and external validation of a nationwide health insurance dataset of the BPJS Kesehatan in Indonesia

Background

We developed and validated an artificial intelligence (AI)-assisted prediction of preeclampsia applied to a nationwide health insurance dataset in Indonesia.

Methods

The BPJS Kesehatan dataset have been preprocessed using a nested case-control design into preeclampsia/eclampsia (n = 3318) and normotensive pregnant women (n = 19,883) from all women with one pregnancy. The dataset provided 95 features consisting of demographic variables and medical histories started from 24 months to event and ended by delivery as the event. Six algorithms were compared by area under the receiver operating characteristics curve (AUROC) with a subgroup analysis by time to the event. We compared our model to similar prediction models from systematically reviewed studies. In addition, we conducted a text mining analysis based on natural language processing techniques to interpret our modeling results.

Findings

The best model consisted of 17 predictors extracted by a random forest algorithm. Nine∼12 months to the event was the period that had the best AUROC in external validation by either geographical (0.88, 95% confidence interval (CI) 0.88–0.89) or temporal split (0.86, 95% CI 0.85–0.86). We compared this model to prediction models in seven studies from 869 records in PUBMED, EMBASE, and SCOPUS. This model outperformed the previous models in terms of the precision, sensitivity, and specificity in all validation sets.

Interpretation

Our low-cost model improved preliminary prediction to decide pregnant women that will be predicted by the models with high specificity and advanced predictors.

Funding

This work was supported by grant no. MOST108-2221-E-038-018 from the Ministry of Science and Technology of Taiwan.

The effect of tooth wear, age and sex on facial height assessed by soft tissue analysis

AIM

The aim of the study was to evaluate the effects of tooth wear, age and sex on facial height measurements based on soft tissue analysis.

METHODS

One hundred and twelve subjects (45 males and 67 females), 19-80 years of age (mean 43 ± 0.9 years), which were divided into three age groups, met the inclusion criteria. Tooth wear was assessed using a 5-point ordinal scale (0-4). Based on the tooth wear score, three groups were defined: mild, moderate and severe wear. Facial height was evaluated based on soft tissue measurements using frontal facial photographs. The dimension of the upper facial height (UFH) and lower facial height (LFH) and the ratio between the two (R-U-L) were measured.

RESULTS

Facial height dimensions (UFH, LFH) were significantly different between the three age groups and between the three tooth wear groups. Both the UFH and LFH measurements had a weak positive correlation with age (r = .40; r = .41, respectively) and with tooth wear (r = .40; r = .41, respectively). The R-U-L showed a significant difference (P < .001) between sexes as males showed slightly lower ratio compared with females; however, the R-U-L was not dependent upon age or tooth wear.

CONCLUSIONS

This study demonstrated that although facial height is affected by age and tooth wear, the proportion between the upper to lower facial segments is constant and is not affected by the same parameters. A statistically significant difference in the R-U-L relative to sexes was noted.

Effect of occlusal slope related to uneven attrition on root stress distribution and potential fracture

Background/purpose

Severely uneven occlusal attrition is thought to play an important role in the occurrence of spontaneous vertical root fracture (VRF), a frequent problem among Chinese people. This study evaluated the influence of occlusal slope related to uneven attrition on the root stress condition.

Materials and methods

A finite element model of the mandibular first molar was established. Two different occlusal slope patterns were simulated in 5 models: (A) sound tooth, (B) 0.5–1.5 mm and (C) 2–3 mm attrition increased buccally, and (D) 0.5–1.5 mm and (E) 2–3 mm attrition increased distally. A static load of 200 N was applied vertically or angled at 45° to the longitudinal axis. The von Mises stress was evaluated.

Results

Under vertical loading, more stress was transferred from the cervical to the middle root with attrition, especially the mesial root, while stress declined with attrition under oblique loading. Stress was mainly distributed in the buccal surface and mesial root with vertical loading, or in the lingual surface and distal root with oblique loading. The maximum von Mises with oblique loading was significantly higher than with vertical loading.

Conclusion

Uneven occlusal attrition made the middle of the mesial root bear more stress, increasing fracture risk under vertical load. This finding suggests that timely restoration of the sloped occlusal morphology in teeth with severe attrition should be recommended to prevent VRFs. Lateral loading was not a risk factor of typical vertical root fractures, but the high stress could cause distal root cervical fracture.

Examination of the Interproximal Wear Mechanism: Facet Morphology and Surface Texture Analysis

Dentition is considered a dynamic system with forces that directly affect dental treatment stability and success. Understanding the biomechanical forces that influence tooth alignment is essential for both planning and performing dental treatments, as well as for anthropological and evolutionary studies. While there is currently an abundance of research on the mechanics of dental wear at the occlusal surface, the mechanics of interproximal dental wear is largely unexplored. The fretting mechanism, a wear process resulting from small-amplitude cyclic motion of 2 solid contacting surfaces, was refuted as a possible mechanism for occlusal wear but has never been considered for interproximal wear. Therefore, the aim of the current study was to reveal the biomechanical process of the interproximal wear and to explore whether the fretting mechanism could be associated with this process. Premolar teeth with interproximal wear facets were examined by 3-dimensional surface texture analysis using a high-resolution confocal disc-scanning measuring system. The unique texture topography of 3 areas in the proximal surface of each tooth was analyzed by applying 3D dental surface texture analysis. Each area showed unique texture characteristics, presenting statistically significant differences between the inner area of the facet and its margins or the surface outside the facets borders. Based on these results, we concluded that fretting is a key mechanism involved in interproximal wear.