Occlusal caries detection on 3D models obtained with an intraoral scanner. A validation study.

OBJECTIVES: To evaluate the diagnostic performance of visual caries assessment on 3D dental models obtained using an intraoral scanner and to compare it with the performance of the clinical visual inspection. METHODS: Fifty-three permanent posterior teeth scheduled for extraction were randomly selected and included in this study. One to three independent examination sites on the occlusal surface of each tooth were clinically inspected using International Caries Detection and Assessment System (ICDAS) criteria. Afterwards, the examined teeth were scanned intraorally with a 3D intraoral scanner (TRIOS 4, 3Shape TRIOS A/S, Copenhagen, Denmark) using white and blue-violet light (415 nm wavelength) to capture the colour and fluorescence signal from the tissues. Six months after the clinical examination, the same examiner conducted the on-screen assessment of the obtained 3D digital dental models at the selected examination sites using modified ICDAS criteria. Both tooth colour and fluorescence texture with high resolution were assessed. Lastly, an independent examiner conducted the histological examination of all teeth after extraction. Using histology as the reference test, Sensitivity (SE), Specificity (SP), Accuracy (ACC), area under the Receiver Operating Characteristic (ROC) curve, and Spearman's correlation coefficient were calculated for the clinical and on-screen ICDAS assessments. RESULTS: The ACC values of the evaluated methods varied between 0.59-0.79 for initial caries lesions and 0.77-0.99 for moderate-extensive caries lesions. Apart from SE values corresponding to caries in the inner half of enamel, no significant difference was observed between clinical visual inspection and on-screen assessment. In addition, no difference was found in the assessment of 3D models with tooth colour alone or supplemented with fluorescence for all the evaluated diagnostic measures. CONCLUSIONS: On-screen visual assessment of 3D digital dental models with tooth colour or fluorescence showed a similar diagnostic performance to the clinical visual inspection when detecting and classifying occlusal caries lesions on permanent teeth. CLINICAL SIGNIFICANCE: 3D intraoral scanning can aid the detection and classification of occlusal caries as part of patient screening and can potentially be used in remote caries assessment for clinical and research purposes.

Probing Water Mobility in Human Dentine with Neutron Spectroscopy.

The aim of this study was to investigate hydrogen mobility within innate and demineralized human dentine. Dentine sections from extracted human molars, demineralized or not, were analyzed by combining neutron spectroscopy with thermal analysis. For the thermal analysis of the samples, differential scanning calorimetry and thermal gravimetric analysis, coupled with Fourier transform infrared spectroscopy, were performed. The hydrogen dynamics of water, collagen, and hydroxyl groups present in the samples were investigated via neutron spectroscopy. From the mass loss observed from the thermogravimetric analysis curves up to 600 °C, the same amount of organic content is identified in the samples. From the differential scanning calorimetry curves, a higher change in enthalpy associated with the denaturation of collagen is registered in the demineralized dentine; that is, a structural change occurs in the collagen subsequent to demineralization. Since the intensity measured by neutron spectroscopy is dominated by the signal from hydrogen, in our samples-coming mostly from the bulk-like and loosely bound water as well as from the collagen itself-higher proton mobility within the demineralized dentine was detected when compared with innate dentine. In the demineralized dentine, this proton mobility amounts to 80%, while the remaining hydrogen accounts for a combination of 1) structural hydroxyls, as a result of the incomplete dissolution of the mineral phase by acid etching, and 2) hydrogen tightly bound in the collagen structure. By combining neutron spectroscopy with the calorimetry data, our findings support the idea that hydroxyapatite protects the collagen in innate dentine. Demineralized dentine, however, acts as a sponge where free bulk-like water is trapped.

Oral health-related quality of life and complications after treatment with partial removable dental prosthesis.

The aims of this study were to measure and describe the oral health-related quality of life (OHRQoL) and to identify the complications caused by partial removable dental prosthesis (RDPs) in patients 1-5 years after treatment. Complications were identified in 65 patients who were treated with 83 RDPs (48 upper, 35 lower). OHRQoL was measured using the OHIP-49 before treatment and at the baseline (1-2 months after treatment) and follow-up (1-5 years after treatment) examinations. The types and numbers of oral problems that were experienced were described based on OHIP items with a score of 3 and 4. A significant improvement (P < 0·05) in the total OHIP-49 was registered from pre-treatment (mean 42, SD ± 37) to baseline (mean 29, SD ± 27) and from pre-treatment to 1-5 years after treatment (mean 32, SD ± 30). There was no significant difference between the baseline and 1- to 5-year follow-up examinations. Problems with eating and appearance registered at pre-treatment were improved at baseline and after 1-5 years. Problems with dentures that had been registered pre-treatment were improved at baseline but reoccurred after 1-5 years. The two most frequent complications were ill-fitting RDPs and inflammation of the oral mucosa, followed less frequently by fractures of the clasps. Treatment with RDPs improved OHRQoL, but denture-related problems partly remained, and new problems related to RDPs occurred 1-5 years after treatment. The two most frequent complications were ill-fitting RDPs and inflammation of the oral mucosa.

Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment.

The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc] and a self-etch adhesive resin cement [Panavia F2.0]) were used. After removal of the crowns of 360 extracted premolars, canines, or incisors, the root canals were prepared with a parallel-sided drill system to three different final diameters. Half the posts did not receive any pretreatment. The other half received tribochemical silicate coating according to the manufacturer's instructions. Posts were then luted in the prepared root canals (n=30 per group). Following water storage at 37°C for seven days, retention of the posts was determined by the pull-out method. Irrespective of the luting cement, pretreatment with tribochemical silicate coating significantly increased retention of the posts. Increased cement film thickness resulted in decreased retention of untreated posts and of pretreated posts luted with zinc phosphate cement. Increased cement film thickness had no influence on retention of pretreated posts luted with resin cement. Thus, retention of the posts was influenced by the type of luting cement, by the cement film thickness, and by the post pretreatment.

Bulk-fill resin composites: polymerization contraction, depth of cure, and gap formation.

The bulk-filling of deep, wide dental cavities is faster and easier than traditional incremental restoration. However, the extent of cure at the bottom of the restoration should be carefully examined in combination with the polymerization contraction and gap formation that occur during the restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and three low-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low-viscosity bulk-fill materials produced a significantly larger depth of cure and polymerization contraction. Although most of the bulk-fill materials exhibited a gap formation similar to that of the conventional resin composite, two of the low-viscosity bulk-fill resin composites, x-tra base and Venus Bulk Fill, produced larger gaps.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials.

OBJECTIVES: To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases. METHODS: Twenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n=8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2 mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage. RESULTS: The mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56) µm (Group A) and 4.63 (1.19) µm (Group B) and 4.73 (0.99) µm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P=0.007) and x-tra base (P=0.005) restored teeth was evident. No significant difference in the cervical microleakage scores was recorded between groups AC (P>0.05). CONCLUSIONS: The bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded.

Influence of curing rate of resin composite on the bond strength to dentin.

This study determined whether the strength with which resin composite bonds to dentin is influenced by variations in the curing rate of resin composites. Resin composites were bonded to the dentin of extracted human molars. Adhesive (AdheSE, Ivoclar Vivadent) was applied and cured (10 seconds @ 1000 mW/cm2) for all groups. A split Teflon mold was clamped to the treated dentin surface and filled with resin composite. The rate of cure was varied, using one of four LED-curing units of different power densities. The rate of cure was also varied using the continuous or pulse-delay mode. In continuous curing mode, in order to give an energy density totaling 16 J/cm2, the power densities (1000, 720, 550, 200 mW/cm2) emitted by the various curing units were compensated for by the light curing period (16, 22, 29 or 80 seconds). In the pulse-delay curing mode, two seconds of light curing at one of the four power densities was followed by a one-minute interval, after which light cure was completed (14, 29, 27 or 78 seconds), likewise, giving a total energy density of 16 J/cm2. The specimens produced for each of the eight curing protocols and two resin composites (Tetric EvoCeram, Ivoclar Vivadent; Filtek Supreme XT, 3M ESPE) were stored in water at 37 degrees C for seven days. The specimens were then either immediately subjected to shear bond strength testing or subjected to artificial aging (6,000 cycles between 5 degrees C and 55 degrees C baths) prior to testing. Failure modes were also assessed. The shear bond strengths were submitted to factorial analysis of variance, and the failure modes were submitted to a Chi-square test (alpha = 0.05). All but power density (curing mode, resin composite material and mode of aging) significantly affected shear bond strength. The curing mode and resin composite material also influenced the failure mode. At the selected constant energy density, pulse-delay curing reduced bonding of the resin composite to dentin.

In vitro penetration of bleaching agents into the pulp chamber.

AIM: To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. METHODOLOGY: Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37 degrees C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to anova and Tukey's test (5%). RESULTS: Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 +/- 0.2003 micro g) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 +/- 0.3981 micro g). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. CONCLUSION: Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.