Effect of firing and fabrication technique on the marginal fit of heat-pressed lithium disilicate veneers.

STATEMENT OF PROBLEM: Studies on the fit of heat-pressed anterior lithium disilicate veneers are sparse, and whether fit is affected by glaze firing or ceramic addition is unclear. PURPOSE: The purpose of this in vitro study was to evaluate and compare the marginal fit of heat-pressed anterior lithium disilicate veneers (IPS e.max Press) fabricated with the staining or cutback technique by using 3-dimensional analysis. MATERIAL AND METHODS: Two groups of heat-pressed maxillary left central incisor lithium disilicate veneers were fabricated (n=10) differing only in core thickness and the fabrication process. The tooth preparation was standardized at 0.6 mm cervical and middle third and 0.7 mm incisal third, with 1.5 mm of incisal reduction. Group S (staining) was an anatomic contour veneer with 1 glaze firing. Group CB (cutback) had a cutback core of 0.6 mm on the cervical and middle third and 0.5 mm on the incisal areas for ceramic application with 3 firings (wash, incisal, and glaze firing). The amount of ceramic application was standardized, and all veneers had identical final dimensions. Marginal fit was evaluated at 2 stages: after pressing the copings (control) and after glaze firing or ceramic addition using the virtual replica technique and 3-dimensional analysis. The wax copings were invested, eliminated, and pressed with IPS e.max lithium disilicate high translucency ingots, and the overall marginal fit and change in marginal fit after firing were measured in the cervical, mesial, distal, and incisal areas. The Shapiro-Wilk test was used to evaluate normality. Repeated-measures ANOVAs were used to explore differences between the 2 groups (S and CB) as per time (before and after firing) for each location (cervical, mesial, distal, and incisal) (α=.05). RESULTS: A statistically significant change in marginal fit after firing was found for the mesial and distal areas of the CB group (P<.05). In all other areas of measurements, no statistically significant differences were found (P>.05). The mean ±standard deviation marginal fit of group S was 63 ±13 µm and 62 ±9 µm for group CB. CONCLUSIONS: The results suggest that firing affects the marginal fit of heat-pressed anterior lithium disilicate veneers fabricated with the cutback technique but not for the staining technique.

Morphological awareness and reading comprehension: Differential mediation mechanisms in native English speakers, fluent English learners, and limited English learners.

The current study examined how morphological awareness contributes to reading comprehension across three levels of English proficiency designation. Participants were 377 fourth- and fifth-grade students, including 198 native English speakers (NE group) and two groups of English learners: 117 students with fluent English proficiency (FEP) and 62 students with limited English proficiency (LEP). Students were assessed on morphological analysis (the ability to use morphological information to infer word meanings while reading), morphological awareness, word reading fluency, reading vocabulary, and reading comprehension. Results showed that the NE and FEP groups were better able to use morphological analysis to infer new word meanings while reading than the LEP group. Multiple-group path modeling indicated that, for all three groups, the relationship between morphological awareness and reading comprehension was mediated by reading vocabulary and morphological analysis; word reading fluency mediated the relationship only for the LEP group. The results call for attention to the role of English proficiency in how morphological awareness supports reading comprehension.

Flexural strength of denture base acrylic resins processed by conventional and CAD-CAM methods.

STATEMENT OF PROBLEM: High flexural strength is one of the desirable properties for denture base resins, yet only few studies have evaluated the physical properties of newer denture bases such as computer-aided design and computer aided manufacturing (CAD-CAM) milled products. PURPOSE: The purpose of this in vitro study was to compare the flexural strength of 3 different types of denture base resins: compression molded, injection molded, and CAD-CAM milled. MATERIAL AND METHODS: Three groups (n=10) of acrylic denture base resins were tested: injection molded, compression molded, and CAD-CAM milled resin. ISO-compliant, rectangular specimens were fabricated (64×10×3.3 mm) (n=30). Specimens were stored in water for 1 week, and flexural strength was measured by using a 3-point bend test until failure. The Student t test was used to evaluate differences in the flexural strength and modulus of elasticity among specimen groups. The Bonferroni formula was used to set significance at α=.017 to account for multiple comparisons among the 3 groups. RESULTS: The flexural strength of the CAD-CAM milled group was significantly higher than that of the other 2 groups (P<.001), while the strength of the compression molded group was significantly greater than that of the injection molded group (P<.001). The flexural modulus of the CAD-CAM group was significantly higher than that of the other 2 groups (P<.001). CONCLUSIONS: CAD-CAM milled denture bases may be a useful alternative to conventionally processed denture bases in situations where increased resistance to flexural strength is needed.

Facebow Use in Clinical Prosthodontic Practice.

The use of a dental facebow in diagnosis and treatment by the restorative dentist has been controversial in recent years. Digital alternatives have been proposed and hold promise for the future; however, the traditional facebow still has practicality in a modern restorative practice. The purpose of this paper is to review facebow use in clinical prosthodontic practice.

Accuracy of three digital workflows for implant abutment and crown fabrication using a digital measuring technique.

STATEMENT OF PROBLEM: The accuracy of a full digital workflow using an Atlantis abutment and a milled zirconia crown; a full digital workflow with a 3Shape split-file workflow using a zirconia abutment and crown; and an interrupted digital workflow using an Atlantis abutment and a milled zirconia crown is unclear. PURPOSE: The purpose of this in vitro study was to compare 2 full digital workflows relative to an interrupted workflow for restoring an implant with a custom abutment and crown. The secondary purpose of this study was to validate a digital means of measuring internal fit and marginal discrepancy using engineering software programs. MATERIAL AND METHODS: Three workflows were evaluated. The first group, interrupted digital Atlantis (IDA) workflow, included a customized Atlantis abutment that was designed, received, and then rescanned for the definitive crown design. The second group, full digital Atlantis (FDA) workflow, included a customized Atlantis abutment and its corresponding standard tessellation language (STL) file, the Atlantis Core File, which was immediately imported into design software and used for crown design and milling. The third group, full digital split-file (FDSF) workflow, used 3Shape's full digital workflow for abutment and crown design called the split-file workflow, in which the crown and abutment were designed and milled simultaneously. All restorations were evaluated with standardized measurements using a scanning electron microscope (SEM) for 2D measurements, followed by standardized measurements using Geomagic Control, an engineering software program, which facilitated 3D evaluations of the specimens. RESULTS: The 2 Atlantis workflows, IDA and FDA, had statistically smaller marginal openings (P=.002) than the FDSF when measured using 2D SEM. The FDA had a statistically smaller 2D SEM marginal gap than the other 2 groups, IDA (P=.002) and FDSF (P=.002). The FDA had a statistically smaller 3D Geomagic marginal gap than the other 2 groups, IDA (P=.004) and FDSF (P=.006). The FDSF had a statistically smaller 3D Geomagic internal fit than the other 2 groups, FDA and IDA (both P=.006). CONCLUSIONS: All 3 workflows evaluated in this study showed clinically acceptable results in terms of mean marginal gap below 120 µm. The SEM evaluation of mean marginal opening revealed that IDA and FDA mean marginal openings were statistically smaller than the FDSF mean marginal opening. SEM and Geomagic measurements revealed that the FDA mean marginal gap was significantly smaller than IDA and FDSF mean marginal gaps. Geomagic evaluation of mean internal fit revealed that the FDSF was significantly smaller than IDA and FDA. The use of Geomagic to measure and evaluate mean marginal gap and mean internal fit as defined in this study proved to be an acceptable form of measurement with statistical validation.

Fatigue lifetime prediction of a reduced-diameter dental implant system: Numerical and experimental study.

OBJECTIVE: To validate the fatigue lifetime of a reduced-diameter dental implant system predicted by three-dimensional finite element analysis (FEA) by testing physical implant specimens using an accelerated lifetime testing (ALT) strategy with the apparatus specified by ISO 14801. METHODS: A commercially-available reduced-diameter titanium dental implant system (Straumann Standard Plus NN) was digitized using a micro-CT scanner. Axial slices were processed using an interactive medical image processing software (Mimics) to create 3D models. FEA analysis was performed in ABAQUS, and fatigue lifetime was predicted using fe-safe® software. The same implant specimens (n=15) were tested at a frequency of 2Hz on load frames using apparatus specified by ISO 14801 and ALT. Multiple step-stress load profiles with various aggressiveness were used to improve testing efficiency. Fatigue lifetime statistics of physical specimens were estimated in a reliability analysis software (ALTA PRO). Fractured specimens were examined using SEM with fractographic technique to determine the failure mode. RESULTS: FEA predicted lifetime was within the 95% confidence interval of lifetime estimated by experimental results, which suggested that FEA prediction was accurate for this implant system. The highest probability of failure was located at the root of the implant body screw thread adjacent to the simulated bone level, which also agreed with the failure origin in physical specimens. SIGNIFICANCE: Fatigue lifetime predictions based on finite element modeling could yield similar results in lieu of physical testing, allowing the use of virtual testing in the early stages of future research projects on implant fatigue.

Effective Instruction for Persisting Dyslexia in Upper Grades: Adding Hope Stories and Computer Coding to Explicit Literacy Instruction.

Children in grades 4 to 6 (N=14) who despite early intervention had persisting dyslexia (impaired word reading and spelling) were assessed before and after computerized reading and writing instruction aimed at subword, word, and syntax skills shown in four prior studies to be effective for treating dyslexia. During the 12 two-hour sessions once a week after school they first completed HAWK Letters in Motion© for manuscript and cursive handwriting, HAWK Words in Motion© for phonological, orthographic, and morphological coding for word reading and spelling, and HAWK Minds in Motion© for sentence reading comprehension and written sentence composing. A reading comprehension activity in which sentences were presented one word at a time or one added word at a time was introduced. Next, to instill hope they could overcome their struggles with reading and spelling, they read and discussed stories about struggles of Buckminister Fuller who overcame early disabilities to make important contributions to society. Finally, they engaged in the new Kokopelli's World (KW)©, blocks-based online lessons, to learn computer coding in introductory programming by creating stories in sentence blocks (Tanimoto and Thompson 2016). Participants improved significantly in hallmark word decoding and spelling deficits of dyslexia, three syntax skills (oral construction, listening comprehension, and written composing), reading comprehension (with decoding as covariate), handwriting, orthographic and morphological coding, orthographic loop, and inhibition (focused attention). They answered more reading comprehension questions correctly when they had read sentences presented one word at a time (eliminating both regressions out and regressions in during saccades) than when presented one added word at a time (eliminating only regressions out during saccades). Indicators of improved self-efficacy that they could learn to read and write were observed. Reminders to pay attention and stay on task needed before adding computer coding were not needed after computer coding was added.

An alternative digital workflow for fabricating a mandibular implant-supported complete fixed dental prosthesis with limited restorative space: A clinical report.

This clinical report describes the prosthetic rehabilitation of a patient with a mandibular implant-supported complete fixed dental prosthesis with limited interocclusal restorative space. The problem was manifested by repeated fractures of the acrylic resin teeth and distortion of the supporting framework. The definitive restoration included a custom computer-aided design and computer-aided manufacturing (CAD-CAM) titanium framework with the lingual cusps and most of the occlusal table of the mandibular posterior teeth milled in titanium as part of the framework. An esthetic CAD-CAM milled denture base along with teeth was bonded over this framework.

The Post-endodontic Adhesive Interface: Theoretical Perspectives and Potential Flaws.

INTRODUCTION: The aim of this review was to analyze the potential of successful bonds of endodontic posts to radicular dentin as well as the limitations of the post-endodontic adhesive interface. METHODS: The MEDLINE/PubMed and Web of Science electronic databases were searched. The search was augmented by a manual search of the pertinent bibliographies. RESULTS: The post-endodontic adhesive interface finds application in the endodontic cohesive units. Many techniques and materials exist to improve the bond between endodontic posts and resin-based materials as well as between resin-based materials and radicular dentin. Different techniques used for the adhesion of metallic and fiber-reinforced posts are discussed and critically analyzed. CONCLUSIONS: Although adhesive cementation of endodontic posts is popular, a long-term predictable bond may be compromised because of procedures related to the endodontic treatment and/or the adhesive cementation procedures. Microleakage and degradation phenomena may further jeopardize the post-endodontic adhesive interface.

Relationships between Eye Movements during Sentence Reading Comprehension, Word Spelling and Reading, and DTI and fmri Connectivity In Students with and without Dysgraphia or Dyslexia.

While eye movements were recorded and brains scanned, 29 children with and without specific learning disabilities (SLDs) decided if sentences they read (half with only correctly spelled words and half with homonym foils) were meaningful. Significant main effects were found for diagnostic groups (non-SLD control, dysgraphia control, and dyslexia) in total fixation (dwell) time, total number of fixations, and total regressions in during saccades; the dyslexia group had longer and more fixations and made more regressions in during saccades than either control group. The dyslexia group also differed from both control groups in (a) fractional anisotropy in left optic radiation and (b) silent word reading fluency on a task in which surrounding letters can be distracting, consistent with Rayner's selective attention dyslexia model. Different profiles for non-SLD control, dysgraphia, and dyslexia groups were identified in correlations between total fixation time, total number of fixations, regressions in during saccades, magnitude of gray matter connectivity during the fMRI sentence reading comprehension from left occipital temporal cortex seed with right BA44 and from left inferior frontal gyrus with right inferior frontoccipital fasciculus, and normed word-specific spelling and silent word reading fluency measures. The dysgraphia group was more likely than the non-SLD control or dyslexia groups to show negative correlations between eye movement outcomes and sentences containing incorrect homonym foils. Findings are discussed in reference to a systems approach in future sentence reading comprehension research that integrates eye movement, brain, and literacy measures.

Prosthetic rehabilitation following lateral resection of the mandible with a long cantilever implant-supported fixed prosthesis: A 3-year clinical report.

This clinical report describes the prosthetic management of the surgical reconstruction of a patient after mandibular resection. Complete oral rehabilitation was achieved with a maxillary complete denture and a mandibular implant-supported fixed prosthesis with a custom titanium framework and a long unilateral cantilever.

Relationships of Attention and Executive Functions to Oral Language, Reading, and Writing Skills and Systems in Middle Childhood and Early Adolescence.

Relationships between attention/executive functions and language learning were investigated in students in Grades 4 to 9 ( N = 88) with and without specific learning disabilities (SLDs) in multiword syntax in oral and written language (OWL LD), word reading and spelling (dyslexia), and subword letter writing (dysgraphia). Prior attention-deficit/hyperactivity disorder (ADHD) diagnosis was correlated only with impaired handwriting. Parental ratings of inattention, but not hyperactivity, correlated with measures of written language but not oral language. Sustaining switching attention correlated with writing the alphabet from memory in manuscript or by keyboard and fast copying of a sentence with all the letters of the alphabet. Multiple regressions based on a principal component for composites of multiple levels of language (subword, word, and syntax/text) showed that measures of attention and executive function involving language processing rather than ratings of attention and executive function not specifically related to language accounted for more variance and identified more unique predictors in the composite outcomes for oral language, reading, and writing systems. Inhibition related to focused attention uniquely predicted outcomes for the oral language system. Findings are discussed in reference to implications for assessing and teaching students who are still learning to pay attention to heard and written language and self-regulate their language learning during middle childhood and adolescence.

Complete mouth rehabilitation and gastroesophageal reflux disease: Conventional and contemporary treatment approaches.

This report describes the diagnosis and prosthodontic management of 2 patients with a history of chronic gastroesophageal reflux disease and worn dentition. Different treatment approaches were used for oral rehabilitation. Use of conventional and contemporary restorative materials resulted in functional and esthetic prosthodontic rehabilitation with a favorable prognosis.

Relationships between language input and letter output modes in writing notes and summaries for students in grades 4 to 9 with persisting writing disabilities.

This study in programmatic research on technology-supported instruction first identified, through pretesting using evidence-based criteria, students with persisting specific learning disabilities (SLDs) in written language during middle childhood (grades 4-6) and early adolescence (grades 7-9). Participants then completed computerized writing instruction and posttesting. The 12 computer lessons varied output modes (letter production by stylus alternating with hunt and peck keyboarding versus by pencil with grooves alternating with touch typing on keyboard), input (read or heard source material), and task (notes or summaries). Posttesting and coded notes and summaries showed the effectiveness of computerized writing instruction on both writing tasks for multiple modes of language input and letter production output for improving letter production and related writing skills.

Relationships of French and English Morphophonemic Orthographies to Word Reading, Spelling, and Reading Comprehension during Early and Middle Childhood.

Two longitudinal studies of word reading, spelling, and reading comprehension identified commonalities and differences in morphophonemic orthographies-French (Study 1, n=1313) or English (Study 2, n=114) in early childhood (grade 2) and middle childhood (grade 5). For French and English, statistically significant concurrent relationships among these literacy skills occurred in grades 2 and 5, and longitudinal relationships for each skill with itself from grade 2 to 5; but concurrent relationships were more sizable and longitudinal relationships more variable for English than French especially for word reading to reading comprehension. Results show that, for both morphophonemic orthographies, assessment and instructional practices should be tailored to early or middle childhood, and early childhood reading comprehension may not be related to middle childhood spelling. Also discussed are findings applying only to English, for which word origin is primarily Anglo-Saxon in early childhood, but increasingly French in middle childhood.

The Effect of Artificial Aging on The Bond Strength of Heat-activated Acrylic Resin to Surface-treated Nickel-chromium-beryllium Alloy.

PURPOSE: The debonding load of heat-activated polymethylmethacrylate (PMMA) denture base resin material to a nickel-chromium-beryllium (Ni-Cr-Be) alloy conditioned by three different surface treatments and utilizing two different commercial bonding systems was investigated. MATERIALS AND METHODS: Denture resin (Lucitone-199) was bonded to Ni-Cr-Be alloy specimens treated with Metal Primer II, the Rocatec system with opaquer and the Rocatec system without opaquer. Denture base resin specimens bonded to non-treated sandblasted Ni-Cr-Be alloy were used as controls. Twenty samples for each treatment condition (80 specimens) were tested. The 80 specimens were divided into two categories, thermocycled and non-thermocycled, containing four groups of ten specimens each. The non-thermocycled specimens were tested after 48 hours' storage in room temperature water. The thermocycled specimens were tested after 2,000 cycles in 4°C and 55°C water baths. The debonding load was calculated in Newtons (N), and collected data were subjected by non parametric test Kruskal-Wallis One Way Analysis of Variance on Ranks and Dunn's post hoc test at the α = 0.05. RESULTS: The Metal Primer II and Rocatec system without opaquer groups produced significantly higher bond strengths (119.9 and 67.6 N), respectively, than did the sandblasted and Rocatec system with opaquer groups, where the bond strengths were 2.6 N and 0 N, respectively. The Metal Primer II was significantly different from all other groups (P<0.05). The bond strengths of all groups were significantly decreased (P<0.05) after thermocycling. CONCLUSIONS: Although thermocycling had a detrimental effect on the debonding load of all surface treatments tested, the Metal Primer II system provided higher values among all bonding systems tested, before and after thermocycling.

Brain connectivity associated with cascading levels of language.

Typical oral and written language learners (controls) (5 girls, 4 boys) completed fMRI reading judgment tasks (sub-word grapheme-phoneme, word spelling, sentences with and without spelling foils, affixed words, sentences with and without affix foils, and multi-sentence). Analyses identified connectivity within and across adjacent levels (units) of language in reading: from subword to word to syntax in Set I and from word to syntax to multi-sentence in Set II). Typicals were compared to (a) students with dyslexia (6 girls, 10 boys) on the subword and word tasks in Set I related to levels of language impaired in dyslexia, and (b) students with oral and written language learning disability (OWL LD) (3 girls, 2 boys) on the morphology and syntax tasks in Set II, related to levels of language impaired in OWL LD. Results for typical language learners showed that adjacent levels of language in the reading brain share common and unique connectivity. The dyslexia group showed over-connectivity to a greater degree on the imaging tasks related to their levels of language impairments than the OWL LD group who showed under-connectivity to a greater degree than did the dyslexia group on the imaging tasks related to their levels of language impairment. Results for these students in grades 4 to 9 (ages 9 to 14) are discussed in reference to the contribution of patterns of connectivity across levels of language to understanding the nature of persisting dyslexia and dysgraphia despite early intervention.

Idea units in notes and summaries for read texts by keyboard and pencil in middle childhood students with specific learning disabilities: Cognitive and brain findings.

Seven children with dyslexia and/or dysgraphia (2 girls, 5 boys, M=11 years) completed fMRI connectivity scans before and after twelve weekly computerized lessons in strategies for reading source material, taking notes, and writing summaries by touch typing or groovy pencils. During brain scanning they completed two reading comprehension tasks-one involving single sentences and one involving multiple sentences. From before to after intervention, fMRI connectivity magnitude changed significantly during sentence level reading comprehension (from right angular gyrus→right Broca's) and during text level reading comprehension (from right angular gyrus→cingulate). Proportions of ideas units in children's writing compared to idea units in source texts did not differ across combinations of reading-writing tasks and modes. Yet, for handwriting/notes, correlations insignificant before the lessons became significant after the strategy instruction between proportion of idea units and brain connectivity at all levels of language in reading comprehension (word-, sentence-, and text) during scanning; but for handwriting/summaries, touch typing/notes, and touch typing/summaries changes in those correlations from insignificant to significant after strategy instruction occurred only at text level reading comprehension during scanning. Thus, handwriting during note-taking may benefit all levels of language during reading comprehension, whereas all other combinations of modes and writing tasks in this exploratory study appear to benefit only the text level of reading comprehension. Neurological and educational significance of the interdisciplinary research findings for integrating reading and writing and future research directions are discussed.

Fracture resistance of lithium disilicate restorations after endodontic access preparation: An in vitro study.

STATEMENT OF PROBLEM: Endodontic access preparation through a lithium disilicate restoration is a frequently encountered clinical situation. The common practice of repairing the accessed crown with composite resin may result in a weakened restoration. PURPOSE: The purpose of this in vitro study was to determine the effect of endodontic access preparation on the fracture resistance and microstructural integrity of monolithic pressed and monolithic milled lithium disilicate complete coverage restorations. MATERIAL AND METHODS: Twenty monolithic pressed (IPS e.max Press) and 20 monolithic milled (IPS e.max CAD) lithium disilicate restorations were fabricated. Ten of the pressed and 10 of the milled crowns were accessed for a simulated endodontic treatment and subsequently repaired by using a porcelain repair system and composite resin. All specimens were submitted to cyclic loading and then loaded to failure. Force data were recorded and analyzed with 2-way ANOVA followed by a post hoc test (Sidak correction) to indicate significant differences among the groups (α=.05). A Weibull analysis was also performed for each group. Eight (4 pressed and 4 milled) additional restorations were fabricated to complete a scanning electron microscope (SEM) analysis and evaluate the surface damage created by the endodontic access preparation. RESULTS: A statistically significant difference (P=.019) was found between the pressed intact and pressed repaired restorations and between the pressed intact and milled repaired restorations (P=.002). Specimens that were examined with an SEM showed edge chipping involving primarily the glaze layer around the access openings. CONCLUSIONS: Endodontic access preparation of lithium disilicate restorations resulted in a significantly reduced load to failure in the pressed specimens, but not in the milled specimens.

Fracture resistance of compromised endodontically treated teeth restored with bonded post and cores: An in vitro study.

STATEMENT OF PROBLEM: It is unclear which post and core system performs best when bonded to severely compromised endodontically treated teeth. PURPOSE: The purpose of this study was to investigate the fracture resistance and mode of failure of severely compromised teeth restored with 3 different adhesively bonded post and core systems. MATERIAL AND METHODS: Thirty extracted endodontically treated maxillary anterior teeth were randomly divided into 3 groups, CPC, gold cast post and core; TPC, titanium prefabricated post/composite resin core; and FPC, quartz fiber reinforced post/composite resin core. All posts were adhesively cemented. All cores resembled a central incisor preparation with no remaining tooth structure above the finish line. Cast gold crowns were fabricated and cemented adhesively. The specimens were aged with thermocycling and cyclic loading. Two specimens per group were randomly selected for micro-computed tomographic imaging before and after aging. Failure was induced with a universal testing machine. The mode of failure was characterized by the interface separation. Data were analyzed with 1-way ANOVA (α=.05) followed by post hoc tests (Bonferroni). RESULTS: A statistically significant difference was found among the 3 groups (P=.002). CPC was significantly different than TPC (P=.008) or FPC (P=.003). The primary mode of failure for CPC and TPC was root fracture, and for FPC post debonding. CONCLUSIONS: Severely compromised endodontically treated teeth restored with bonded gold cast post and cores showed significantly higher fracture resistance.