Biogenic Tooth-Integrated Fixed Functional Space Maintainer for Pediatric Use: A Novel Approach.

Preschoolers frequently experience traumatic dental injuries, particularly during their two to four years of life. The majority of these injuries result in tooth avulsion because of the alveolar bone resiliency around the primary teeth. This study explains an instance of damage sustained during play that resulted in an early knockout of the primary incisor. Hence, a biogenic tooth-integrated space maintainer was created using the natural crown of the traumatized tooth, and the child was asked to come for a regular follow-up. This treatment may be viewed as a great alternative for natural aesthetic rehabilitation as it promotes speech development, improves oral cleanliness, restores aesthetics and masticatory function, and inhibits the development of aberrant tongue habits and malocclusions.

Application of intentional replantation in advanced periodontitis involving teeth preservation.

With the development of periodontal regenerative technology, an increasing number of scholars reported that advanced periodontitis involving teeth can be preserved through intentional replantation. Intentional replantation has become the last possible method to preserve natural teeth for advance periodontitis with signs of tooth extraction. However, the indications of intentional replantation are strict, and the success of the operation is closely related to the condition of cases and the operation skills of doctors. In this article, the operation steps and criteria of intentional replantation were summarized by introducing three success cases of advanced periodontitis involving teeth preserved by intentional replantation. The relevant factors that affect the prognosis of intentional replantation in advanced periodontitis involving teeth preservation were analyzed to help clinicians preserve natural teeth.

Comparative analysis of bonding strength between enamel and overlay of varying thicknesses following an aging test.

Abstract: Background/purpose: Overlay restorations can be used clinically as a treatment option to preserve natural dentine. However, whether the residual enamel thickness and overlay thickness affect the adhesion between the restoration and tooth is still unknown. This study was to investigate effects of the overlay thickness and residual enamel thickness on bonding strength. Materials and methods: Overlays of different thicknesses were prepared with natural teeth which had 2, 4, and 6 mm of occlusal reduction (n = 10). Specimens were subjected to 10,000 cycles in water at 5-55 °C, and finally compressive strength tests were used to evaluate the bonding strength. Results: All groups showed good bond strength (P > 0.05). The overlay restorations of different thicknesses reduced the preparation amount by 30.3%-7.2% and significantly preserved more of the tooth structure (P < 0.005). Compared to the control group, the overlay restoration increased the marginal fitness by about 0.67-0.88 times. The thermal cycling indicated that the decrease in the maximum bearing stress was due to the aging of the ceramic itself. Therefore, the thickness of the overlay had a greater influence on the compressive strength than the bond strength. Conclusion: Based on the above this study recommends an overlay thickness of at least 2 mm in clinical practice. The aging test confirmed that adhesion between the overlay and teeth was quite firm and stable. This shows that a stable adhesive effect of the overlay can be used as a treatment option for preserving a greater amount of a tooth's structure.

Coverage error of three resin composite systems to vital unrestored maxillary anterior teeth.

OBJECTIVE: Define the color of anterior teeth of a selected population and correlate it (by using coverage error [CE] and the frequency of best match) with the final color of all possible enamel-dentine combinations of three different resin composite systems. MATERIALS AND METHODS: Color of 636 vital unrestored anterior teeth (central incisors, lateral incisors and canines; n = 212) and disk specimens (12 mm diameter, varying thickness) corresponding to enamel-dentin combinations of all available enamel (0.5 mm and 1.0 mm thickness) and dentin shades (3.0 mm thickness) of Essentia, Enamel Plus HRi and IPS Empress Direct composite systems was measured using a clinical dental spectrophotometer (Spectroshade Micro). CE and frequency of best match for all composite systems were calculated for the measured in-vivo teeth color space. RESULTS: Natural in-vivo teeth exhibit higher lightness when compared to enamel-dentin composite combinations, independently of the enamel thickness used. The best (lowest) CE was found for IPS Empress, while the highest values were found for Enamel Plus Hri independently of tooth type and enamel thickness (p < 0.001). The use of 0.5 mm instead of 1.0 mm enamel thickness within enamel-dentin composite combinations resulted in a lower CE for in-vivo tooth color (p < 0.001). CONCLUSIONS: The color space defined by all possible enamel-dentin combinations of the studied resin composite systems does not fully match the color range of anterior teeth. All composite systems examined lack combinations with lightness values as high as the population's. IPS Empress Direct composite system represented better the in-vivo teeth color. CLINICAL SIGNIFICANCE: The use of 0.5 mm enamel shade thickness is suggested when building layered restorations, as it provided better color coverage than using 1.0 mm thickness.

Emergence angle: Comprehensive analysis and machine learning prediction for clinical application.

PURPOSE: To analyze and compare the emergence angle (EA) using two measurement methods, conventional and modified (EA-GPT and EA-R), the EAs of all-natural teeth were evaluated and classified to derive a suitable and predictable clinically applicable measurement method. METHODS: Natural human teeth (n=600) were classified, cleaned, and thoroughly inspected. Teeth were scanned using an intraoral scanner. The scanned data were analyzed using three-dimensional analysis software for both methods with several points per surface. A Bland-Altman analysis was used for statistical analysis and a heat map and a nonparametric density plot to assess the repetition and distribution. An XGBoost regression model was used for prediction. RESULTS: The EA-R method showed significantly different values compared to the EA-GPT method, representing an increase of 17.5-20.7% for the proximal surfaces. An insignificant difference between the two methods was observed for other surfaces. Different teeth classes showed variation in the normal range, thereby resulting in a new classification of the EA for all-natural teeth based on the interquartile range. The machine learning gradient boosting model predicted conventional data with an average mean absolute error of 0.9. CONCLUSIONS: Variations in the natural teeth EA and measurement methods, suggest a new classification for EA. The established artificial intelligence method demonstrated robust performance, which could aid in implementing EA measurement in prosthetic designs.

Association of Number of Teeth with ADL/IADL in Korean Middle-Aged and Older Adults: An Analysis of the 7th Korean Longitudinal Study of Aging.

We determined the association between the number of natural and implant teeth with activities of daily living (ADL) and instrumental ADL (IADL) levels in middle-aged and older adults aged ≥ 55 years. We included 6,925 participants, who underwent a computer-assisted personal interview in the 7th Korean Longitudinal Study of Aging. After controlling for general characteristics, the associations between the number of natural and implant teeth with ADL and IADL levels were examined using multiple regression analysis. The participants had 21.2 natural teeth and 1.08 implant teeth on average. The ADL and IADL levels were 0.61 and 1.56, 0.40 and 1.16, and 1.10 and 0.31 in participants with ≤ 9, 10-19, and ≥ 20 teeth, respectively. There was no significant association between ADL and the number of natural and implant teeth (p > 0.05). However, a one-unit increase in IADL score was associated with a reduced number of natural (ß = -0.031, p < 0.001) and implant (ß = -0.194, p = 0.006) teeth. Difficulties regarding IADL were associated with fewer natural and implant teeth, suggesting that maintaining and managing the number of teeth is critical to promoting the health of middle-aged and older adults.

Peri-Implant Marginal Bone Changes around Dental Implants with Platform-Switched and Platform-Matched Abutments: A Retrospective 5-Year Radiographic Evaluation.

Preserving the marginal bone level (MBL) is essential for the long-term success of dental implant therapy, and bone remodeling around dental implants is considered to vary with time. Numerous studies comparing the platform-switching (PS) and platform-matching (PM) dental implants have indicated that PS dental implants showed a lesser reduction for the MBL, and the majority of them had a relatively short period. This study aimed to evaluate vertical and horizontal bone defects by using digital periapical radiographs to examine the changes in MBL around PM and PS dental implants over 5 years after functional loading. The vertical MBL (vMBL) was measured from the implant-abutment junction to the first bone-to-implant contact. The horizontal MBL (hMBL) was measured from the implant-abutment junction to the bone crest. All data were presented as means ± standard errors. Paired and independent t-tests with Welch's correction were used to analyze the data. A total of 61 dental implants in 38 patients after 5 years of functional loading were evaluated. Over time, PS dental implants were more likely to gain bone; by contrast, PM dental implants were more likely to lose bone during the observation time. Changes in vMBL for PS dental implants were significantly less than those for PM dental implants at 1-year (p = 0.045), 3-year (p = 0.021), and 5-year (p = 0.010) loading. Likewise, changes in hMBL for PS dental implants were significantly smaller than in those for PM dental implants at 3-year (p = 0.021) and 5-year (p = 0.006) loading; however, the changes were minimal in both approaches. PS dental implants had a significant increment in the percentage of bone integration, whereas that for PM dental implants dropped over time, with no significance. In PS dental implants that occlude with natural teeth, vertical and horizontal bone gain was observed, and it was significant at 3 years (p = 0.023). A significant horizontal bone gain was observed in the opposing natural teeth at 3-year (p = 0.002) and 5-year loading (p = 0.002). The PS concept appears to preserve more MBL around dental implants by stabilizing the vMBL and hMBL over a 5-year period. A minimal marginal bone change was detected in both concepts. The opposing natural teeth at PS dental implants showed a favorable effect on marginal bone tissues.

Frailty and Associated Factors among Chinese Centenarians.

OBJECTIVES: The study aimed to apply the frailty index (FI) to assess frailty status among Chinese centenarians and analyse its associated factors. DESIGN: The study was a cross-sectional study. SETTING AND PARTICIPANTS: The study included 1043 centenarians (742 females and 301 males) aged ≥100 years from the 2018 wave of the China Longitudinal Healthy Longevity Survey. MEASUREMENTS: All participants were assessed for frailty by the FI. Basic characteristics, including age, height, weight, calf circumference, waist circumference, hip circumference, sex, years of education, financial status, exercise, fall status, coresidence, smoking, alcohol consumption, number of natural teeth, denture use, toothache, and tooth brushing, were collected. Multivariate logistic regression was used to analyse the associations between risk factors and frailty. RESULTS: The average age of the participants was 102.06±2.55 years (range: 100-117 years). The FI ranged between 0.00 and 0.63. The mean FI for all participants was 0.27±0.13 (median 0.25; interquartile range 0.20-0.35). Participants were divided into quartiles. The number of natural teeth and denture use, coresidence, sex, exercise, and financial status showed significant associations with frailty classes (all P<0.05). Multivariate logistic regression analysis indicated that having ≤20 natural teeth without dentures (OR, 95% CI= 1.89(0.004-1.246), P<0.05), having ≤20 natural teeth with dentures (OR, 95% CI=2.21(0.158,1.432), P=0.015), living alone or in an institution (OR, 95% CI=1.68(0.182-0.849), P=0.002), lacking exercise (OR, 95% CI=2.54(0.616-1.246), P<0.001), having insufficient financial resources (OR, 95% CI=2.9(0.664-1.468), P<0.001), and being female (OR, 95% CI=1.47(0.137,0.634), P=0.002) were independent risk factors for frailty. CONCLUSION: Chinese centenarian women are frailer than men. Having fewer natural teeth, living alone or in an institution, lacking exercise, and having insufficient financial resources were the factors associated with frailty among Chinese centenarians. Family conditions and healthy lifestyles may be important for frailty status in centenarians.

Comparison of oral hypofunction tests and determination of reference values for a subjective masticatory function test.

BACKGROUND: In Japan, oral hypofunction has been recognized as a disease since 2018. An alternative to occlusal force testing for assessing oral hypofunction is the evaluation of the number of natural teeth. Subjective masticatory function testing, which evaluates the ease or difficulty in chewing foods, is an effective alternative to occlusal force testing. However, no reference values have been established for this test. We determined the reference values of the subjective masticatory function test and evaluated its potential as a substitute for the number of natural teeth for assessing oral hypofunction. METHODS: The sample consisted of 184 older adults who visited the Department of Geriatric Dentistry, Showa University Dental Hospital, from July 2018 to January 2020. The subjective masticatory function test (table for evaluation of chewing function in complete denture wearers [Chewing Score 20]) was performed using 20 foods. The occlusal force test and a receiver operating characteristic curve were used to determine the reference values for Chewing Score 20. The sensitivity, specificity, and positive and negative predictive values were calculated and compared with the occlusal force test and the number of natural teeth. RESULTS: A significant correlation (r) was found between the occlusal force test and the Chewing Score 20 (r = 0.526, p < 0.001). The reference value for Chewing Score 20 was < 85. Although the Chewing Score 20 was less sensitive than the number of natural teeth, it demonstrated a higher specificity and a positive predictive value. CONCLUSION: Herein, a score of < 85 on the subjective masticatory function test was determined to be the optimal quantitative reference. The subjective masticatory function test may be used as an alternative for assessing oral hypofunction.

Associations of the number of remaining natural teeth and oral health behaviors with subjective chewing problems based on the Thailand National Oral Health Survey 2017.

PURPOSE: Few studies have examined the association of oral health behaviors with chewing ability.This study aimed to investigate the associations between the number of remaining natural teeth and oral health behaviors with subjective chewing ability among older Thai adults. METHODS: Analysis was carried out using data from the 8th Thailand National Oral Health Survey. Subjective chewing problems were assessed using self-reported questionnaires, and the number of remaining teeth by oral examination. Poisson regression with sampling weights was used to calculate the prevalence ratios (PRs) and 95% confidence intervals (CIs) for having chewing problems. RESULTS: Of the 2,310 participants (mean age, 67.2 ± 4.5 years), 53.3% had chewing problems. After adjusting for all covariates, significantly higher PRs for having chewing problems were observed among the participants without interdental cleaning (PR, 1.32; 95% CI, 1.06-1.65), without night-time brushing (PR, 1.12; 95% CI, 1.01-1.25), who were edentulous (PR, 1.16; 95% CI, 1.02-1.31), had urgent dental treatment within the past 12 months (PR, 1.15; 95% CI, 1.06-1.24), and who brushed for <2 min (PR, 1.10; 95% CI, 1.02-1.20). CONCLUSION: The number of remaining natural teeth and oral health behaviors were significantly associated with subjective chewing problems.

Are there any color match and color correlation between maxillary anterior teeth?

OBJECTIVE: To evaluate the color match and color correlation between maxillary anterior teeth. MATERIALS AND METHODS: CIELab values of 1182 intact maxillary anterior teeth in 197 human specimens were measured through spectrophotometry. ∆E00 color differences between similar regions of the same and different type teeth were calculated and compared with perceptibility and acceptability thresholds using 1-sample t test to evaluate color matches. Regression analyses assessed linear relationships between the color coordinates of similar regions of different type teeth. Percentages of different modes of the color match between the same specimen's teeth (2-tooth/3-tooth color match or color mismatch) were determined. RESULTS: Mean ∆E00 values for the same type teeth were less than 1.8 (p = 1). Mean ∆E00 values for different type teeth were mostly greater than 1.8 (p < 0.001), except for central and lateral teeth in middle (p = 0.29) and incisal (p = 0.75) regions and for lateral and canine teeth in cervical regions (p = 0.33). The 2-tooth color match showed the highest percentage (>50%). CONCLUSIONS: The same type teeth indicated color matches. Central and lateral teeth showed color matches in middle and incisal regions, while lateral and canine teeth disclosed color matches in cervical regions. The corresponding color coordinates of mismatched regions were linearly correlated. CLINICAL SIGNIFICANCE: In order to predict and determine the shade of maxillary anterior teeth and create natural colors for corresponding restorations, some tooth color relationships and equations are presented in this study.

Color changes of maxillary and mandibular incisors following surgical orthodontic treatment : A prospective controlled clinical pilot study.

OBJECTIVE: To assess possible color changes of natural teeth after surgical orthodontic treatment. METHODS: This prospective controlled clinical pilot trial included 6 consecutively treated surgical orthodontic patients with class III malocclusion and neutral vertical relation (ST: surgical treatment), 3 of which received double jaw osteotomies (SGI: surgical subgroup I) and 3 received single mandibular sagittal split ramus osteotomies (SGII: surgical subgroup II). Eleven untreated individuals (UC: untreated control) and 9 individuals who received conventional comprehensive orthodontic treatment only (OC: orthodontic control) served as controls. Tooth color measurements were performed using a reflectance spectrophotometer on the upper and lower incisors before the initiation of the surgical orthodontic treatment (T1) and after its completion (T2). Primary endpoint was ∆E* (T1-T2) of summarized CIE-L*a*b* color differences. The null hypothesis of this study was that there is no statistically significant change in total tooth color difference ∆E* CIE-(L*a*b*) in vivo at baseline and following surgical orthodontic treatment. RESULTS: There was a statistically significant increase in ∆E* (T1-T2) in the ST group compared to the UC and OC groups. Single mandibular surgery had a stronger effect on the lower teeth in comparison to double jaw surgery, while Le Fort I osteotomy, as part SGI, had a stronger effect on the upper teeth. Despite statistical significance, the majority of mean values of these color changes were lower than the threshold value of color alterations considered to be perceivable by the naked eye in a clinical setting (3.7 ∆E units), with the exception of the mandibular incisors in SGII, where this threshold value was slightly exceeded. CONCLUSIONS: Orthognathic surgery showed a measurable effect on tooth color. However, esthetic disturbance or patient discomfort based on these color and lightness alterations are unlikely, due to their small impact and low perceptibility in a clinical setting.

Saving a Natural Tooth in the Implant Era: A Case Report on Noninvasive Surgical Root Amputation.

AIM: This report highlights the use of a seldom-used treatment modality to save a diseased multirooted tooth, as an alternative to extraction and implant. BACKGROUND: Root-resection therapy is a simple surgical procedure performed by an endodontist or periodontist to save a multirooted tooth with furcation involvement and/or defective root. CASE DESCRIPTION: A 64-year-old female patient reported a strip perforation in the distobuccal (DB) root of the maxillary left first molar. The tooth had previously undergone endodontic treatment and had a well-fitted crown. After presenting the patient with treatment options and prognosis, a treatment plan of root amputation to save the tooth was formulated. A full mucoperiosteal flap was reflected. The DB root was amputated and GIC was placed to cover the root. Sutures were placed and the patient was given postoperative instructions. A follow-up was carried out with clinical examination, and periapical radiographs were taken at 10 months, 2 years, and 5 years after the procedure. The tooth was intact and functioning; no signs or symptoms were reported. CONCLUSION: Root resection has a deserved place in the modern clinical management of endodontic lesions or injuries. Conventional conservative treatment plans can succeed with proper treatment planning, diagnosis, case selection, maintenance of oral hygiene, and meticulous follow-up. CLINICAL SIGNIFICANCE: This case emphasizes a viable treatment procedure to manage teeth with compromised radicular or restorative presentations. Root resection is a venerable treatment option that is often ignored in the era of implants even though it shows favorable prognosis and success rates.

Gender and age group modified association of dental health indicators with total occlusal force among Korean elders.

BACKGROUND: This study aimed to investigate the distribution of objective total occlusal force (TOF) and its association with dental health indicators: dental status, number of natural teeth (NT), natural and rehabilitated teeth, natural posterior teeth (NT-Post), and natural and rehabilitated posterior teeth among Korean elders after controlling for various confounders encompassing socio-demographic factors, behavioral factors and health/oral health factors. METHODS: This cross-sectional study recruited 551 elders from the Sungbook-Gu health education cohort. TOF was measured using Prescale II as an outcome variable. Dental health indicators assessed by dentists were the main explanatory variables. Analysis of covariance and multivariable linear regression models were applied to evaluate the adjusted association of dental health indicators with TOF. Gender and age group stratified analyses were also applied. RESULT: TOF was higher in dentate elders than denture wearers in males and younger elders. The adjusted mean of TOF and standard error was 464.24 ± 17.15 N for dentate elders, 297.15 ± 28.85 N for partial denture wearers, 280.42 ± 47.71 N for complete denture wearers. Among all dental health indicators, NT-Post showed the highest association with TOF (partial r = 0.330, p < 0.001, R2 = 0.15), followed by NT (partial r = 0.329, p < 0.001, R2 = 0.16). Older elders highlighted the association of NT (partial r = 0.37, p < 0.001, R2 = 0.18). Males decreased the association of NT (partial r = 0.30, p < 0.001, R2 = 0.20) and NT-Post (partial r = 0.29, p < 0.001, R2 = 0.20). CONCLUSION: TOF was significantly associated with dental health indicators, and its association was modified by sex and age group.

Effect of Opposite Tooth Condition on Marginal Bone Loss around Submerged Dental Implants: A Retrospective Study with a 3-Year Follow-Up.

BACKGROUND: The objective of this study was to evaluate the effects of opposite tooth conditions on change in marginal bone level (MBL) around submerged dental implants. MATERIALS AND METHODS: The study included healthy patients with one or two implants. Structures opposite implants were either natural teeth (NT) or fixed restorations (FRs). MBLs were measured on digital periapical radiographs at the mesial and distal aspects of each implant. RESULTS: Sixty implants were inserted by the 3-year follow-up. Mean MBLs for NT were 0.21 ± 0.33 mm before prosthetic loading and 0.30 ± 0.41 mm 3 years later (p = 0.001). Mean MBLs with FRs were 0.36 ± 0.45 mm before loading and 0.53 ± 0.50 mm 3 years later (p < 0.001). Changes in mean MBL from the 6-month follow-up to the 1- and 3-year follow-ups were statistically significant (p < 0.01) for implants opposite NT. However, changes in mean MBL from the 6-month follow-up to the 1-year (p = 0.161) and 3-year follow-ups (p = 1.000) were not significant for implants opposite FRs. Between baseline and the 3-year follow-up, MBL change was relatively small and did not differ regarding NT and FRs. CONCLUSION: Bone loss was greater if submerged dental implants were opposed by FRs. MBLs around submerged implants continued to change after 3 years if NT opposed implants.

Oral health of the 65+ age group in Israel-2020.

BACKGROUND: In 2019, a reform of dental services for older adults was implemented in Israel to improve access and reduce barriers that stood in their way. The reform stipulated that preventive and restorative dentistry would be included in the basket of services of the National Health Insurance Law. The current study was conducted by the Myers-JDC-Brookdale Institute (MJB) and the Division of Dental Health of Israel's Ministry of Health to examine the dental status and patterns of utilizations of dental services among the 65+ age group. This paper reports on the dental status of the 65+ age group in comparison with the same population two decades earlier. GOALS: To describe the dental status of Israel's 65+ age group, and to identify the population at risk of dental morbidity. METHODOLOGY: Telephone interviews were conducted with a representative sample of 512 older adults aged 65+, from February to April 2020. MAIN FINDINGS: Some two-thirds of the 65+ age group assessed their oral health as good or very good. Twenty-four percent did not have natural teeth, while the rest had 19 teeth on average. Ten percent had not lost any teeth. In the 65-74 age group, 19% had no natural teeth and the rest had 20 teeth on average. In contrast, in the 85+ age group, 38% were edentulous and the rest had 13 teeth on average. Of the older adults who found it difficult to cover their monthly expenses, 39% were edentulous-twice the percentage of those who did manage to cover their monthly expenses (19%). Of the 65+ age group 44% had dentures-37% in the 65-74 age group, and 66% in the 85+ age group. Approximately 40% of the 65+ age group saw a dentist for preventive check-ups. The rest did not, mainly due to lack of awareness of the importance of doing so. CONCLUSIONS AND RECOMMENDATIONS: The perceived status of oral health among the 65+ age group is currently better than it was 22 years ago. However, despite the improvement in oral health and health behavior, there are still barriers to the utilization of dental services. The main barriers are a lack of awareness of the importance of proper health behavior, and the cost of care for people with financial difficulty. This study provides decision-makers with data on the status of oral health, the utilization of dental services and the geographical disparities. The findings will help policy makers evaluate the effectiveness of the reform and fine tuning it in the future. Policies should be instated to increase awareness of constituencies and their access to the services, in addition to the entitlements the reform granted.

Differences in the biomechanical behaviors of natural teeth and dental implants.

OBJECTIVE: The lack of a PDL, which acts as an energy absorber, is a contributor to implants' early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo. METHODS: We designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load-control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants. RESULTS: Biphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load-time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300g in a loading rate 3g/s could dissipate the energy of 7.35±1.18×10-2 mJ, approximately 50 times that of the dental implants (1.47±1.22×10-3) with statistically significant (p<0.05). SIGNIFICANCE: We confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.

A State-of-the-Art Review on the Wear of the Occlusal Surfaces of Natural Teeth and Prosthetic Crowns.

This review focuses on the wear mechanisms of natural and restorative dental materials, presenting a comprehensive description and analysis of the works published in the last two decades on the wear at the interface of occlusal surfaces. Different groups of tribological pairs were considered: tooth-tooth, tooth-restorative material (tooth-ceramic, tooth-resin-based-materials, and tooth-metal), and restorative-restorative materials. The lack of standardization of the wear tests impairs the direct comparison of the obtained results. However, it was possible to infer about the main wear mechanisms observed on the different classes of dental materials. Concerning ceramics, their toughness and surface finishing determines the wear of antagonist tooth. Abrasion revealed to be the main wear mechanisms at occlusal interface. In the case of resin-based composites, the cohesion of the organic matrix and the nature, shape, and amount of filler particles greatly influences the dental wear. The protruding and detachment of the filler particles are the main causes of abrasion of antagonist enamel. Metallic materials induce lower wear on antagonist enamel than the other classes of materials, because of their low hardness and high ductility. Most of the studies revealed plastic deformation and adhesive wear as the main wear mechanisms. Overall, more research in this area is needed for a better understanding of the mechanisms involved at the occlusal surfaces wear. This would be essential for the development of more suitable restoration materials.

Effects of Khat on Surface Roughness and Color of Feldspathic and Zirconia Porcelain Materials under Simulated Oral Cavity Conditions.

Background and Objectives: Khat chewing is considered as a daily habit that is practiced by more than five million people globally. The effect of khat chewing on the surface roughness and the color stability of natural teeth and the material used in the fabrication of dental prosthesis remains unknown. This study was conducted to explore and compare the effect of khat homogenate (KH) on the surface roughness (Ra) and the average color changes (ΔE*) amongst natural teeth and selected shades from different porcelain types, namely, feldspathic metal ceramic (MC) VM13, computer-aided design/computer assisted manufacture (CAD/CAM) feldspathic (Vitablocs Mark II), and multilayer zirconia (Ceramill Zolid PS) porcelains. Materials and Methods: Seventy samples were prepared from natural teeth, feldspathic MC, CAD/CAM Vitablocs Mark II, and zirconia porcelain. The Ra values were measured using a profilometer and expressed in micrometers, whereas the ΔE* values were measured using VITA Easyshade® V spectrophotometer for all samples before and after frequent immersion and thermocycling in KH for 30 days. The surface topography was used to assess the materials surfaces (glazed or polished) after KH immersion by using a white light interferometry machine. Results: Results revealed that the Ra and the ΔE* values of the different types of tested porcelain were influenced by KH. The order of surface roughness values was glazed or polished MC > polished Zircon > polished Vitablocs Mark II > natural teeth. The lowest ΔE* values were recorded for glazed Vitablocs Mark II and MC, and the values could be arranged as polished zircon > natural teeth > glazed zircon > polished MC > polished Vitablocs Mark II. P values were significantly varied (< 0.001) among all the tested groups, except the zircon group (>0.05) for both Ra and ΔE*. Conclusion: KH significantly affected both surface parameter and color of glazed or polished porcelain materials and natural teeth.

Estimation of root inclination of anterior teeth from virtual study models: accuracy of a commercial software.

BACKGROUND: The aim of the study was to assess the accuracy of commercially available software in estimating anterior tooth root inclination from digital impressions of the crowns of the teeth. SUBJECTS AND METHODS: Following sample size calculation and application of inclusion and exclusion criteria, 55 anterior natural teeth derived from 14 dry human skulls were selected. Impressions were taken and plaster study models were fabricated. Plaster models were scanned using the high-resolution mode of an Ortho Insight 3D laser scanner. The teeth on the digital scans were segmented and virtual roots were predicted and constructed by the Ortho Insight 3D software. The 55 natural teeth were removed from the dry skulls and scanned using the Identica extraoral white-light scanner in order to calculate their actual root angulation. The teeth were scanned twice, once to acquire the crown and the cervical part of the root, and a second time to acquire the remaining part of the root, including the apex. The two scanned segments were joined in software by superimposing them along their common part. The accuracy of the digital models generated by the Ortho Insight 3D scanner in predicting root angulation was assessed by comparing these results to the corresponding measurements of the 55 natural teeth. The long axes of the tooth models obtained from the software prediction and the scanning of the actual teeth were computed and the discrepancy between them was evaluated. The error of the methods was evaluated by repeating the measurements on 14 teeth and showed an acceptable range. RESULTS: The predicted tooth angulation was found to differ significantly from the actual angulation, both statistically and clinically. The angle between the predicted and actual long axes ranged from 2.0 to 37.6°(average 9.7°; median 7.4°). No statistically significant difference was found between tooth categories. CONCLUSIONS: Further investigations and improvements of the software are needed before it can be considered clinically effective.