Marginal Gap,Internal Fit,and Fracture Load of Leucite‐Reinforced Ceramic Inlays Fabricated by CEREC inLab and Hot‐Pressed Techniques

Purpose: This in vitro study was designed to evaluate and compare the marginal gap, internal fit, and fracture load of resin‐bonded, leucite‐reinforced glass ceramic mesio‐occlusal‐distal (MOD) inlays fabricated by computer‐aided design/manufacturing (CAD/CAM) or hot pressing. Materials and Methods: Fifty caries‐free extracted human molars were prepared for standardized MOD inlays. Impressions of each specimen were made and poured using type IV dental stone. Dies were randomly divided into two equal groups. Twenty‐five ceramic inlays were fabricated by the hot‐pressed technique using IPS Empress leucite‐reinforced glass ceramics, and the other 25 ceramic inlays were produced by CAD/CAM technology using ProCAD leucite‐reinforced ceramic blocks and CEREC inLab facilities. Inlays were bonded to the teeth using a dual‐cured resin cement. The specimens were stored in distilled water at 37°C for 24 hours and then thermocycled for 5000 cycles. The marginal gap measurements were taken with a stereomicroscope. Specimens in each group of inlay systems were randomly divided into two subgroups of 10 and 15 specimens each. Ten specimens in each subgroup were sectioned mesiodistally for evaluation of the internal fit. The fracture load of specimens in the second subgroup (n = 15) of the two inlay systems was determined under compressive load in a universal testing machine. Data were analyzed using Student's t‐test at a significance level of p < 0.05. Results: The mean marginal and internal gap size in both IPS Empress and ProCAD inlays were less than 100 μm; however, the marginal gap for the IPS Empress restorations was significantly higher than that of ProCAD restorations (p < 0.05). There was no significant difference in the mean internal fit or the fracture load between the two glass ceramic inlays (p > 0.05). Conclusions: The leucite‐reinforced glass ceramic inlay restorations fabricated by CEREC inLab (CAD/CAM) and the hot‐pressed technique provided clinically acceptable marginal and internal fit with comparable fracture loads after luting.     

Fracture resistance of zirconia‐based all‐ceramic crowns after bur adjustment

Intra‐oral grinding is often required to optimize occlusion of all‐ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty‐eight standardized zirconia copings were produced. The ceramic veneer was designed with a positive ellipsoidal defect on the palatal aspect of the crowns. To simulate adjustment of dental restorations by burs, this palatal defect was removed by use of three different diamond‐coated burs with grit sizes 46, 107, or 151 μm (fine, medium, or coarse, respectively). Each different grit size of bur was used to grind 16 crowns. All crowns were then polished and surface roughness was measured. Half of the specimens underwent thermomechanical aging (10,000 thermocycles between 6.5°C and 60°C) and 1.2 million cycles of chewing simulation (F = 108 N). A linear regression model was computed to test the effect of aging and grinding grit size at a level of significance of α = 0.05. Fracture loads increased with decreasing grit size. Grit size and aging had a significant effect on the fracture resistance of the crowns. Use of fine and coarse burs for intra‐oral adjustments resulted in different fracture resistance of veneered zirconia crowns. Coarse burs should be avoided in the final stage of grinding before polishing.     

Effect of Crystallization Firing on Marginal Gap of CAD/CAM Fabricated Lithium Disilicate Crowns

Purpose

To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite‐reinforced glass‐ceramic (IPS Empress CAD) blocks (LG), and lithium‐disilicate (IPS e.max CAD) blocks before (LD‐B), and after (LD‐A) crystallization firing.

Materials and Methods

A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full‐coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite‐reinforced glass‐ceramic blocks (n = 5) and lithium‐disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (μm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite‐reinforced glass‐ceramic crowns and the lithium‐disilicate crowns before and after crystallization firing. Results were analyzed by two‐way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05).

Results

The overall mean marginal gaps (μm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD‐B = 42.9 ± 12.2, and LD‐A = 57.2 ± 16.0. The marginal gaps for LG and LD‐B were not significantly different, but both were significantly less than for LD‐A.

Conclusions

The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium‐disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process. Clinical Relevance: The marginal gap of CAD/CAM‐fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.     

Fracture Loads of All‐Ceramic Crowns under Wet and Dry Fatigue Conditions

Purpose: The aim of this study was to test the hypothesis that fracture loads of fatigued dental ceramic crowns are affected by testing environment and luting cement. Materials and Methods: One hundred and eighty crowns were prepared from bovine teeth using a lathe. Ceramic crowns were prepared from three types of ceramic systems: an alumina‐infiltrated ceramic, a lithia‐disilicate‐based glass ceramic, and a leucite‐reinforced ceramic. For each ceramic system, 30 crowns were cemented with a composite resin cement, and the remaining 30 with a resin‐modified glass ionomer cement. For each ceramic system and cement, ten specimens were loaded to fracture without fatiguing. A second group (n = 10) was subjected to cyclic fatigue and fracture tested in a dry environment, and a third group (n = 10) was fatigued and fractured in distilled water. The results were statistically analyzed using one‐way ANOVA and Tukey HSD test. Results: The fracture loads of ceramic crowns decreased significantly after cyclic fatigue loading (p≤ 0.05); furthermore, fracture loads of crowns fatigued in a wet environment were statistically lower than those in a dry environment (p < 0.05). Crowns luted with a composite resin cement showed statistically greater fracture loads than those luted with a resin‐modified glass ionomer cement (p≤ 0.05). Conclusions: Fracture load of the three ceramic systems was found to be influenced by ceramic composition. Moreover, cement and fatigue condition influenced the fracture loads of the crown specimens evaluated in this study.     

Cutting efficiency of diamond burs operated with electric high‐speed dental handpiece on zirconia

Zirconia‐based dental restorations are becoming used more commonly. However, limited attention has been given to the difficulties experienced, concerning cutting, in removing the restorations when needed. The aim of the present study was to compare the cutting efficiency of diamond burs, operated using an electric high‐speed dental handpiece, on zirconia (Zir) with those on lithium disilicate glass–ceramic (LD) and leucite glass–ceramic (L). In addition, evaluation of the cutting efficiency of diamond burs on Zir of different thicknesses was performed. Specimens of Zir were prepared with thicknesses of 0.5, 1.0, 2.0, and 4.0 mm, and specimens of LD and L were prepared with a thickness of 1.0 mm. Cutting tests were performed using diamond burs with super coarse (SC) and coarse (C) grains. The handpiece was operated at 150,000 rpm with a cutting force of 0.9 N. The results demonstrated that cutting of Zir took about 1.5‐ and 7‐fold longer than cutting of LD and L, respectively. The SC grains showed significantly higher cutting efficiency on Zir than the C grains. However, when the thickness of Zir increased, the cutting depth was significantly decreased. As it is suggested that cutting of zirconia is time consuming, this should be taken into consideration in advance when working with zirconia restorations.     

In Vitro Study of Fracture Load and Fracture Pattern of Ceramic Crowns: A Finite Element and Fractography Analysis

Purpose: This in vitro study investigated the null hypothesis that metal‐free crowns induce fracture loads and mechanical behavior similar to metal ceramic systems and to study the fracture pattern of ceramic crowns under compressive loads using finite element and fractography analyses. Materials and Methods: Six groups (n = 8) with crowns from different systems were compared: conventional metal ceramic (Noritake) (CMC); modified metal ceramic (Noritake) (MMC); lithium disilicate‐reinforced ceramic (IPS Empress II) (EMP); leucite‐reinforced ceramic (Cergogold) (CERG); leucite fluoride‐apatite reinforced ceramic (IPS d.Sign) (SIGN); and polymer crowns (Targis) (TARG). Standardized crown preparations were performed on bovine roots containing NiCr metal dowels and resin cores. Crowns were fabricated using the ceramics listed, cemented with dual‐cure resin cement, and submitted to compressive loads in a mechanical testing machine at a 0.5‐mm/min crosshead speed. Data were submitted to one‐way ANOVA and Tukey tests, and fractured specimens were visually inspected under a stereomicroscope (20×) to determine the type of fracture. Maximum principal stress (MPS) distributions were calculated using finite element analysis, and fracture origin and the correlation with the fracture type were determined using fractography. Results: Mean values of fracture resistance (N) for all groups were: CMC: 1383 ± 298 (a); MMC: 1691 ± 236 (a); EMP: 657 ± 153 (b); CERG: 546 ± 149 (bc); SIGN: 443 ± 126 (c); TARG: 749 ± 113 (b). Statistical results showed significant differences among groups (p < 0.05) represented by different lowercase letters. Metal ceramic crowns presented fracture loads significantly higher than the others. Ceramic specimens presented high incidence of fractures involving either the core or the tooth, and all fractures of polymer crown specimens involved the tooth in a catastrophic way. Based on stress and fractographic analyses it was determined that fracture occurred from the occlusal to the cervical direction. Conclusions: Within the limitations of this study, the results indicated that the use of ceramic and polymer crowns without a core reinforcement should be carefully evaluated before clinical use due to the high incidence of failure with tooth involvement. This mainly occurred for the polymer crown group, although the fracture load was higher than normal occlusal forces. High tensile stress concentrations were found around and between the occlusal loading points. Fractographic analysis indicated fracture originating from the load point and propagating from the occlusal surface toward the cervical area, which is the opposite direction of that observed in clinical situations.     

Fractographic features of glass‐ceramic and zirconia‐based dental restorations fractured during clinical function

Fractures during clinical function have been reported as the major concern associated with all‐ceramic dental restorations. The aim of this study was to analyze the fracture features of glass‐ceramic and zirconia‐based restorations fractured during clinical use. Twenty‐seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass‐ceramic restorations and 13 zirconia‐based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all‐ceramic single‐tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass‐ceramic, and alumina single‐tooth restorations. Design features seem to be of great importance for fracture initiation.     

Clinical fit of four‐unit zirconia posterior fixed dental prostheses

The objective of this clinical study was to assess the internal and marginal accuracy of computer‐aided design/computer‐aided manufacturing (CAD/CAM)‐generated four‐unit all‐ceramic posterior fixed dental prostheses (FDPs). The data were compared with the results of three‐unit metal‐ceramic and all‐ceramic FDPs that were obtained in a previous study. Twenty‐four patients were provided with all‐ceramic posterior four‐unit FDPs made from semisintered blank zirconia material. Prior to definitive insertion the accuracy was evaluated using a replica technique with a light body silicone that was stabilized with a heavy body material. The replica samples were examined using microscopy. The median marginal gap of the 24 four‐unit FDPs was 77 μm. The median gap widths were 87 μm at the midaxial wall, 167 μm at the axio‐occlusal transition of the abutments, and 170 μm at centro‐occlusal location. Although the marginal accuracy of the four‐unit FDPs differed significantly from that of the three‐unit metal‐ceramic FDPs (median 54 μm), the values obtained were clinically satisfactory and showed that semisintered zirconia blanks could be used for the fabrication of four‐unit FDPs.     

Comparison of peri‐implant clinical and radiographic status around short (6 mm in length) dental implants placed in cigarette‐smokers and never‐smokers: Six‐year follow‐up results

Background

It is hypothesized that peri‐implant clinical and radiographic inflammatory parameters (probing depth [PD], bleeding on probing [BOP] and plaque index [PI]; and radiographic (crestal bone loss [CBL]) are worse among cigarette‐smokers (CS) compared with never‐smokers (NS) with short implants.

Purpose

The present 6‐year follow‐up retrospective study compared the peri‐implant clinical and radiographic parameters in CS and NS with short dental implants (6 mm in length).

Materials and methods

Fifty‐six male individuals were included. These individuals divided into 2 groups as follows: (a) Group‐1: 29 self‐reported systemically healthy CS with 48 short‐implants; and (b) Group‐2: 27 self‐reported systemically healthy NS with 43 short implants. Peri‐implant PD, PI, BOP, and CBL were measured. Group comparisons were done using the Kruskal‐Wallis test and sample size was estimated. Level of significance was set at P values < .05.

Results

In groups 1 and 2, the follow‐up durations were 6.2 ± 0.1 years and 6.1 ± 0.3 years, respectively. A cigarette smoking history of 8.9 ± 3.6 pack years was reported by individuals in Group‐1. At follow‐up, scores of peri‐implant PD, BOP, PI, and mesial and distal CBL were comparable around short implants in both groups.

Conclusion

Under strict oral hygiene maintenance protocols, short dental implants can remain functionally stable in CS in a manner similar to NS.     

Internal fit of three‐unit fixed dental prostheses produced by computer‐aided design/computer‐aided manufacturing and the lost‐wax metal casting technique assessed using the triple‐scan protocol

Suboptimal adaptation of fixed dental prostheses (FDPs) can lead to technical and biological complications. It is unclear if the computer‐aided design/computer‐aided manufacturing (CAD/CAM) technique improves adaptation of FDPs compared with FDPs made using the lost‐wax and metal casting technique. Three‐unit FDPs were manufactured by CAD/CAM based on digital impression of a typodont model. The FDPs were made from one of five materials: pre‐sintered zirconium dioxide; hot isostatic pressed zirconium dioxide; lithium disilicate glass‐ceramic; milled cobalt‐chromium; and laser‐sintered cobalt‐chromium. The FDPs made using the lost‐wax and metal casting technique were used as reference. The fit of the FDPs was analysed using the triple‐scan method. The fit was evaluated for both single abutments and three‐unit FDPs. The average cement space varied between 50 μm and 300 μm. Insignificant differences in internal fit were observed between the CAD/CAM‐manufactured FDPs, and none of the FPDs had cement spaces that were statistically significantly different from those of the reference FDP. For all FDPs, the cement space at a marginal band 0.5–1.0 mm from the preparation margin was less than 100 μm. The milled cobalt‐chromium FDP had the closest fit. The cement space of FDPs produced using the CAD/CAM technique was similar to that of FDPs produced using the conventional lost‐wax and metal casting technique.     

Comparison of Peri‐Implant Soft Tissue Parameters and Crestal Bone Loss Around Immediately Loaded and Delayed Loaded Implants in Smokers and Non‐Smokers: 5‐Year Follow‐Up Results

Background: The aim of this study is to compare peri‐implant soft tissue parameters (plaque index [PI], bleeding on probing [BOP], and probing depth [PD] ≥4 mm) and crestal bone loss (CBL) around immediately loaded (IL) and delayed loaded (DL) implants in smokers and non‐smokers. Methods: Thirty‐one patients with IL implants (16 smokers and 15 non‐smokers) and 30 patients with DL implants (17 smokers and 13 non‐smokers) were included. Personal data regarding age, sex, and duration and daily frequency of smoking were gathered using a questionnaire. Peri‐implant PI, BOP, and PD ≥4 mm were recorded, and mesial and distal CBL was measured on standardized digital radiographs. Multiple group comparisons were performed using the Bonferroni post hoc test (P <0.05). Results: All implants replaced mandibular premolars or molars. Mean scores of PI (P <0.05) and PD ≥4 mm (P <0.05) were statistically significantly higher in smokers compared with non‐smokers in patients with IL and DL dental implants. The mean score of BOP (P <0.05) was statistically significantly higher in non‐smokers compared with smokers in both groups. CBL (P <0.05) was statistically significantly higher in smokers compared with non‐smokers in both groups. There was no statistically significant difference in PI, BOP, PD ≥4 mm, and total CBL among smokers with IL and DL implants. Conclusions: Tobacco smoking enhances peri‐implant soft tissue inflammation and CBL around IL and DL implants. Loading protocol did not show a significant effect on peri‐implant hard and soft tissue status in healthy smokers and non‐smokers.     

Work‐related traumatic dental injuries: Prevalence,characteristics and risk factors

Background/Aims

The prevalence of work‐related oral trauma is underestimated because minor dental injuries are often not reported in patients with several injuries in different parts of the body. In addition, little data are available regarding their characteristics. The aim of this epidemiological study was to determine the prevalence, types, and characteristics of occupational traumatic dental injuries (TDIs) in a large working community.

Materials and Methods

Work‐related TDIs that occurred during the period between 2011 and 2013 in the District of Genoa (Northwest of Italy, 0.86 million inhabitants) were analyzed. Patients’ data were obtained from the National Institute for Insurance against Accidents at Work database.

Results

During the 2 year period, 112 TDIs (345 traumatized teeth) were recorded. The prevalence was 5.6‰ of the total amount of occupational trauma. The highest prevalence was found in the fourth and fifth decades of life (OR=3.6, P < .001), and males were injured more often than females (70.5% vs 29.5%, OR=2.8, P < .001). Service and office workers represented 52% of the sample, and construction/farm/factory workers and craftsmen were 48%. TDIs involved only teeth and surrounding tissue in 66% of cases, or in combination with another maxillofacial injury in 34%. They were statistically associated with construction/farm/factory workers group (Chi squared P < .01). Crown fracture was recorded in 34.5% of cases, subluxation/luxation in 10.7%, avulsion in 9%, root fracture in 3.8%, and concussion in 3.5%. Thirty‐two subjects (28.6%, 133 teeth, OR=4.3, P < .001) presented at least 1 traumatized tooth with previous dental treatment. Among 212 (61.4%) traumatized teeth, 67.5% were upper incisors, 17.5% were lower incisors, 3.3% were upper canines, 1.9% were lower canines, and 9.9% were bicuspids and molars.

Conclusions

Work‐related TDIs had a low overall prevalence, and fractures were the most frequent dental injury. Age, gender, and preexisting dental treatments represented risk factors for work‐related TDIs.     

Dental status and oral health‐related quality of life. A population‐based study

Oral health‐related quality of life (OHRQoL) is associated with tooth wear and tooth loss. This study investigated the association between OHRQoL and dental status (in terms of natural dentition, partial or complete dentures, or edentulism). Sixteen hundred and twenty‐two persons who participated in a large‐scale Dutch dental survey were interviewed. Dentate persons (n = 1407) were additionally invited for a clinical examination (response rate: 69%). Dental status was based upon the combined data from this clinical examination and the questionnaire (seven dental status groups were defined). OHRQoL was measured by the Dutch translation of the short version of the Oral Health Impact Profile, the OHIP‐NL14. Kruskal–Wallis tests and Mann–Whitney U tests were used to investigate differences in OHRQoL between the dental status groups. For all OHIP‐NL14 scales, differences in OHRQoL were found between the dental status groups (all P‐values <0·001). The Mann–Whitney U tests revealed no differences between persons with a complete natural dentition and persons with a fixed prosthetic replacement. The latter group, however, did show a significantly better OHRQoL as compared to persons with a removable partial denture. Surprisingly, edentulous persons with an overdenture had a more impaired OHRQoL than edentulous persons with non‐supported complete dentures. The results demonstrated that impaired dental status is associated with deteriorations in OHRQoL, especially concerning functional limitations, physical pain and social disability.     

Knoop Hardness and Effectiveness of Dual‐Cured Luting Systems and Flowable Resin to Bond Leucite‐Reinforced Ceramic to Enamel

Purpose: The aim of this study was to evaluate the Knoop microhardness and microshear bond strength (MSBS) of dual‐cured luting systems and flowable resin bonded to leucite‐reinforced ceramics and enamel. Materials and Methods: Eighty bovine incisors were randomly divided into four groups per test (microhardness and microshear; n = 10) according to the bonding procedure: Excite DSC/Variolink, Clearfil SE Bond/Panavia F, Adper Scotchbond Multi‐Purpose Plus/RelyX ARC, and Adper Single Bond 2/Filtek Z350 Flow. For the KHN measurement, the cement was applied on the enamel surface and light‐cured through a ceramic disk (5 mm diameter × 1.2 mm thick). Five indentations were performed in each specimen and measured at HMV‐2. For the microshear test, two cylinders of a leucite‐reinforced ceramic (1 mm diameter × 2 mm height) were bonded to the enamel substrate in accordance with the bonding procedures previously established. One cylinder was tested 24 hours after cementation, and the other was subjected to thermocycling (2000 cycles) and then submitted to an MSBS test. The data from the hardness and bond strength tests were subjected to one‐ and two‐way repeated‐measures analysis of variance (ANOVA), respectively, and to Tukey's test (α= 0.05). Results: Scotchbond/RelyX ARC presented higher values of bond strength, while Single Bond/Z350 Flow showed lower values. The thermocycling promoted a reduction in the bond strength values for all groups. Panavia F presented higher values of KHN, and the flowable resin presented the lowest. RelyX ARC and Variolink presented intermediate values on hardness evaluation. Conclusions: For ceramic cementation, dual‐cured resin luting systems promoted more reliable bonding and microhardness values than the flowable resin.     

Effect finishing and polishing procedures on the surface roughness of IPS Empress 2 ceramic

Abstract

Objective. To evaluate the surface roughness of IPS Empress 2 ceramic when treated with different finishing/polishing protocols. Materials and methods. Sixteen specimens of IPS Empress 2 ceramic were made from wax patterns obtained using a stainless steel split mold. The specimens were glazed (Stage 0–S0, control) and divided into two groups. The specimens in Group 1 (G1) were finished/polished with a KG Sorensen diamond point (S1), followed by KG Sorensen siliconized points (S2) and final polishing with diamond polish paste (S3). In Group 2 (G2), the specimens were finished/polished using a Shofu diamond point (S1), as well as Shofu siliconized points (S2) and final polishing was performed using Porcelize paste (S3). After glazing (S0) and following each polishing procedure (S1, S2 or S3), the surface roughness was measured using TALYSURF Series 2. The average surface roughness results were analyzed using ANOVA followed by Tukey post-hoc tests (α = 0.01) Results. All of the polishing procedures yielded higher surface roughness values when compared to the control group (S0). S3 yielded lower surface roughness values when compared to S1 and S2. Conclusions. The proposed treatments negatively affected the surface roughness of the glazed IPS Empress 2 ceramic.     

Finite element stress analysis of Ti-6Al-4V and partially stabilized zirconia dental implant during clenching

Abstract

Objective. The purpose of this paper is to compare the differences in stress between Ti-6Al-4V and PS-ZrO₂ dental implant during clenching and whether these changes are clinically significant to limit the use of zirconia in oral implantology. Materials and methods. The model geometry was derived from position measurements taken from 28 diamond blade cut cross-sections of an average size human adult edentulous mandible and generated using a special sequencing method. Data on anatomical, structural, functional aspects and material properties were obtained from measurements and published data. Ti-6Al-4V and PS-ZrO₂ dental implants were modelled as cylindrical structure with a diameter of 3.26 mm and length of 12.00 mm was placed in the first molar region on the right hemimandible. Results. The analysis revealed an increase of 2–3% in the averaged tensile and compressive stress and an increase of 8% in the averaged Von Mises stress were recorded in the bone–implant interface when PS-ZrO₂ dental implant was used instead of Ti-6Al-4V dental implant. The results also revealed only relatively low levels of stresses were transferred from the implant to the surrounding cortical and cancellous bone, with the majority of the stresses transferred to the cortical bone. Conclusion. Even though high magnitudes of tensile, compressive and Von Mises stresses were recorded on the Ti-6Al-4V and PS-ZrO₂ dental implants and in the surrounding osseous structures, the stresses may not be clinically critical since the mechanical properties of the implant material and the cortical and cancellous bone could withstand stress magnitudes far greater than those recorded in this analysis.     

Advanced dental maturity of Finnish 6‐ to 12‐yr‐old children is associated with high energy intake

We studied the association of dental maturity with body mass index (BMI), energy intake, and macronutrient intake. A randomly selected subset (n = 148) of the Special Turku Coronary Risk Factor Intervention Project (STRIP) was invited to an oral follow‐up study, and the 6‐ and 12‐yr‐examination data (n = 111, 60 boys) were used. Food records for four consecutive days and BMI values were extracted from the databank of the main STRIP project. The developmental stage of seven permanent mandibular teeth was assessed using panoramic radiographs. The resulting maturity scores were converted to dental age estimates. Three dental‐maturity groups (delayed, average, and advanced) and two BMI groups [normal BMI (≤mean+1SD) and high BMI (>mean+1SD)] were formed. The dental age was higher than the chronological age by 0.6–0.8 yr. Maturity scores for girls were statistically significantly higher than for boys. The distribution of girls into dental‐maturity groups at age 12 yr was different from that of the boys and there were more boys than girls among the high‐BMI group. Children of the advanced dental‐maturity group had a statistically significantly higher energy intake than children in the other groups. We conclude that advanced dental maturity is associated with higher energy intake.     

Methods and terminology used in cell‐culture studies of low‐dose effects of matrix constituents of polymer resin‐based dental materials

General comprehension of terms and confounding factors associated with in vitro experiments can maximize the potential of in vitro testing of substances. In this systematic review, we present an overview of the terms and methods used to determine low‐dose effects of matrix constituents in polymer resin‐based dental materials in cell‐culture studies and discuss the findings in light of how they may influence the comprehension and interpretation of results. Articles published between 1996 and 2015 were identified by searches in the Scopus, Web of Science, MEDLINE, PubMed, and Embase databases using keywords associated with low‐dose effects, polymer resin‐based materials, in vitro parameters, and dental materials. Twenty‐nine articles were included. Subtoxic (n = 11), sublethal (n = 10), and nontoxic (n = 6) were the terms most commonly used to describe the low‐dose effects of methacrylates. However, definition of terms varied. Most (82%) studies employed only one method to define the exposure scenario, and no agreement was seen between studies on the use of solvents. Prophylactic use of antibiotics was widespread, and mycoplasma screening was not reported. In conclusion, cell‐culture conditions and tests used to define exposure scenarios have changed little in the last decades, despite development in recommendations. Nomenclature alignment is needed for a better understanding of possible biohazards of methacrylates.     

A 5‐year longitudinal study of association of maximum bite force with development of frailty in community‐dwelling older adults

To determine whether maximum bite force (MBF), an objective measure of oral function, is associated with development of frailty in community‐dwelling older adults. This prospective cohort study included community‐dwelling Japanese adults aged 75 years at baseline (n = 322). Baseline MBF was measured using an electronic recording device (Occlusal Force‐Meter GM10). Follow‐up examinations, including physical fitness and anthropometric evaluation and structured questionnaires, were administered annually over a 5‐year period to determine the incidence of frailty, which was defined by the presence of 3 or more of the following 5 components derived from the Cardiovascular Health Study: low level of mobility, low physical activity level, weakness, shrinking and poor endurance and energy. Adjusted hazard ratios (HRs) of incidence of frailty according to sex‐stratified tertiles of baseline MBF were calculated using Cox proportional hazards regression models. During the follow‐up, 49 participants (15.2%) developed frailty. Participants in the lower tertile of MBF exhibited a significantly greater risk of frailty than those in the upper tertile. After adjustment for sex, depression, diabetes and Eichner index, the adjusted HRs for frailty in the upper through lower tertiles of MBF were 1.00 (reference), 1.27 (95% confidence interval [CI]: 0.50‐3.20) and 2.78 (95% CI: 1.15‐6.72), respectively (P for trend = .01). Poor oral function, as indicated by low MBF, increases the risk of development of frailty among elderly men and women.