What Should You Consider When Writing for a Dental Publication?

Good writing in dentistry involves both a depth of technical knowledge and experience and a command of more "classical" disciplines of knowledge and education, such as language, grammar, rhetoric, and logic. All of these factors influence the psychology and rhetorical interpretive mechanisms by which readers process and derive meaning from written text and are especially relevant to effective technical and medical writing.

Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies.

Implant surfaces are continuously being improved to achieve faster osseointegration and a stronger bone to implant interface. This review will present the various implant surfaces, the parameters for implant surface characterization, and the corresponding in vitro human cell-based studies determining the strength and quality of the bone-implant contact. These in vitro cell-based studies are the basis for animal and clinical studies and are the prelude to further reviews on how these surfaces would perform when subjected to the oral environment and functional loading.

Compressive fatigue limit of four types of dental restorative materials.

The purpose of this study was to evaluate the quasi-static compressive strength and the compressive fatigue limit of four different dental restorative materials, before and after aging in distilled water for 30 days. A conventional glass ionomer cement (Fuji IX GP; IG), a zinc-reinforced glass ionomer cement (Chemfil rock; CF), a light curable resin-reinforced glass ionomer cement (Fuji II LC; LC) and a resin-based composite (Quixfil; QF) were investigated. Cylindrical specimens (4mm in diameter and 6mm in height) were prepared according to the manufacturer׳s instructions. The compressive fatigue limit was obtained using the staircase method. Samples were tested in distilled water at 37°C, at a frequency of 10Hz with 10(5) cycles set as run-out. 17 fatigue samples were tested for each group. Two-way ANOVA and one-way ANOVA followed by Tukey׳s post-hoc test were used to analyze the results. Among the four types of materials, the resin-based composite exhibited the highest compressive strength (244±13.0MPa) and compressive fatigue limit (134±7.8MPa), followed by the light-cured resin reinforced glass ionomer cement (168±8.5MPa and 92±6.6MPa, respectively) after one day of storage in distilled water. After being stored for 30 days, all specimens showed an increase in compressive strength. Aging showed no effect on the compressive fatigue limit of the resin-based composite and the light-cured resin reinforced glass ionomer cement, however, the conventional glass ionomer cements showed a drastic decrease (37% for IG, 31% for CF) in compressive fatigue limit. In conclusion, in the present study, resin modified GIC and resin-based composite were found to have superior mechanical properties to conventional GIC.

Critical Appraisal. Comparative Performance of Mineral Trioxide Aggregate Versus Calcium Hydroxide as a Direct Pulp Capping Agent.

Vital pulp therapy is the general concept involved in the "regenerative" restorative treatment of the reversibly injured dental pulp with the intention of maintaining its vitality in a restored, functioning tooth. While this procedure has been attempted with various materials and techniques over a period of several centuries, the advent of hard-setting calcium hydroxide materials in the late 1950s made the procedure of direct pulp capping a more routine and relatively predictable procedure. More recently, in the mid 1990s, a new type of water-based, "hydraulic-type," calcium silicate-based cement, mineral trioxide aggregate (MTA), was introduced to dentistry as a possible alternative to the established standard of hard-setting calcium hydroxide. Over the last two decades, a slowly growing body of pre-clinical and human clinical studies evaluating and comparing these two materials has developed. Most recently, a number of well-designed, randomized controlled studies and resultant systematic reviews have been completed and published regarding the comparative efficacy of calcium hydroxide versus MTA for direct pulp capping. This Critical Appraisal considers and reviews some of the more recently published reports which provide a more definitive answer to this clinical research question.

Physical effects of non-cavitated explorer probing on enamel smooth-surface carious lesions.

PURPOSE: To assess the physical effects of explorer probing on non-cavitated smooth-surface enamel carious lesions. METHODS: Extracted teeth with white enamel decalcification (ICDAS 2) were used. Indentations were made in decalcified and non-decalcified regions with a #23 explorer using "scratch" or "poke" application and 100g, 300g or 600g force. Specimens were imaged with SEM and polarizing light microscopy. Indentation widths were measured digitally. Two-way ANOVA with pair-wise comparisons was used to assess interactions of force and enamel condition (normal or carious) on indentation groove width. RESULTS: No or minimal effect was seen on normal enamel surface morphology. For the decalcified regions, defects were seen in SEM and polarizing light images. Findings included a smear layer, open clefts, lateral debris and micro-fractures. Two-way ANOVA for effects of force and enamel quality on mean groove width showed statistically significant differences for both variables for all teeth tested.

Flexural strength and flexural fatigue properties of resin-modified glass ionomers.

OBJECTIVE: To determine the physical properties of several resin-modified glass ionomers (RMGIs) by means of flexural strength and flexural fatigue testing, and to compare them to conventional glass ionomer cements (GICs) and flowable composite resins. METHODS: RMGI samples were fabricated according to ISO 4049 standard. Rectangular specimens were produced using a polytetrafluoroethylene (PTFE) mold with dimensions of 2 x 2 x 25 mm. Flexural strength and flexural fatigue were measured by means of the 3-point bending tests using an Instron universal testing machine at 0.75 mm/min and 0.03 Hz for 100 cycles, respectively. Flexural stress, load, and displacement were recorded for all tests. Data were statistically compared (ANOVA, SNK, p < 0.05). Statistical data analysis for flexural fatigue was achieved through the least frequent events method (failures versus non-failures). The following RMGIs, flowable composites, and GICs were tested: 1) Activa Bioactive-Restorative; 2) Activa Bioactive-Base/Liner; 3) Tetric EvoFlow; 4) Beautifil Flow Plus; 5) Geristore; 6) Fuji Filling LC; 7) Fuji Lining LC; 8) Ketac Nano; 9) Fuji Triage; 10) Ketac Nano; and 11) Vitrebond Plus. RESULTS: The flexural strength of Activa-enhanced RMGIs was statistically significantly greater than all other RMGIs and GICs (p < 0.001). The flexural fatigue of Activa-enhanced RMGIs and flowable composites was significantly greater than all other materials (p < 0.00 1). The flexural fatigue of the Activa-enhanced RMGIs was comparable to the two flowable composites tested. CONCLUSION: The Activa-enhanced RMGIs demonstrated comparable flexural strength and flexural fatigue to flowable composites. Activa-enhanced RMGIs and flowable composites demonstrated flexural strength and flexural fatigue significantly greater than all other tested materials.

Preliminary Evidence That Bioactive Cements Occlude Artificial Marginal Gaps.

PURPOSE: The objective of this preliminary laboratory study was to explore whether bioactive dental cements have the ability to seal marginal gaps as compared with other classes of dental cements. MATERIALS AND METHODS: Tooth discs (dentin/enamel) were positioned adjacent to a second disc of one of five possible dental cements (two bioactive and three conventional) and separated by a 50-µm Mylar film, creating a controlled gap between the two discs. The edges of the tooth segments were abraded to expose dentin such that the dentin interface was positioned opposite the cement. The artificial gap assembly was stabilized with adhesive and composite resin. Artificial gap assemblies for each cement type were immersed in a phosphate-containing, simulated body fluid (phosphate buffered saline) for up to 8 months. Occlusion of artificial marginal gaps (including deposition of crystal-like, mineralized deposits within the gaps) was observed and scored categorically during the observation period. Deposition of radiodense material within the artificial marginal gap space was confirmed by micro-computerized tomography analysis. RESULTS: There was no evidence of marginal gap occlusion for the three conventional control cements, whereas both bioactive, surface apatite-forming cements demonstrated occlusion of the artificial marginal gaps. CONCLUSIONS: The preliminary findings of this initial study suggest the possible capability of surface apatite-forming, calcium-based, bioactive dental cements to seal or reseal artificial marginal gaps in simulated aqueous physiological conditions. CLINICAL SIGNIFICANCE: The results of this laboratory study, although preliminary in nature, suggest a new functional property for bioactive dental materials, namely the ability to significantly improve marginal stability with tooth/restorative material interface. Such behavior in a restorative material could improve the survival and serviceability of dental restorations.

A meta-analysis on the effect of implant characteristics on the survival of the wide-diameter implant.

The purposes of the study are to study the implant survival of the wide-diameter implant and to analyze if the length, the implant surface, or the placement location has any effect on its survival. Electronic databases were searched from inception to Dec 2014. Studies included in the review had implants placed in areas of adequate bone width and had clear inclusion and exclusion criteria for patient selection. Immediately placed and immediately loaded implants were excluded. A meta-analysis was done using the "random effects" model on the included studies. And, a meta-regression was used to evaluate the effects of location, length, and surface on the implant survival. Of the six studies selected, three evaluated surface-treated implants and three machined implants. The overall pooled survival rate of the wide implant is 96.3 %. The meta-regression showed that when using a wide implant, neither its surface nor its length nor its position in the maxilla or mandible adversely affected its survival (P > 0.05). This meta-analysis concluded that the location, length, and surface of the wide-diameter implant did not affect its survival and therefore suggested that when the conditions of the implant site corresponded to the inclusion criteria of our meta-analysis, choosing a wide-diameter implant in the posterior mandible or maxilla, where implant length may be limited by the nerve or the sinus, the use of a short implant regardless of its surface would not affect its survival.

Advances in remineralization for early carious lesions: a comprehensive review.

A greater understanding of the dental caries process and improved and more diverse methodologies to assess early demineralization and caries has enabled development of a new class of remineralizing therapeutics. Hence, an emerging goal of modern dentistry is to manage non-cavitated carious lesions non-invasively through remineralization in an effort to prevent disease progression and improve strength, esthetics, and function of teeth. A critical element fundamental to this current therapeutic philosophy is the need for new and highly efficacious technologies for enamel remineralization. The aim of this article is to provide an overview of new compositions and to review contemporary nonfluoridated systems in terms of their basic composition, mode of delivery, and currently available evidence.

Bioactive and biomimetic restorative materials: a comprehensive review. Part I.

UNLABELLED: The objective of this two-part review article is to compare and contrast the composition, properties, and performance of the calcium silicate- and calcium aluminate-based, bioactive dental materials, with an emphasis on the restorative applications of this evolving class of materials. Part I examines the development and application of the calcium silicate-based materials ranging from dental materials derived from Portland cement to more recent materials based on further modifications of calcium silicate cement chemistry. Part II will consider the development, composition, properties, and application of the bioactive calcium aluminate-based materials that have recently been developed for several indications in restorative dentistry. CLINICAL SIGNIFICANCE: Bioactive materials have evolved over the past three decades from relatively specialized, highly biocompatible, but low-strength dental materials to now emerge in product compositions for expanded clinical uses in restorative dentistry. Further developments to meet additional restorative clinical needs are anticipated in this newly emerging category of dental materials.

A bioactive dental luting cement--its retentive properties and 3-year clinical findings.

A clinical validation study was conducted to determine the performance of a new bioactive dental cement (Ceramir C&B, Doxa Dental AB) for permanent cementation. The cement is a new formulation class, which is a hybrid material comprised of calcium aluminate and glass-ionomer components. A total of 38 crowns and bridges were cemented in 17 patients; 31 of the abutment teeth were vital and seven were non-vital. Six restorations were bridges with a total of 14 abutment teeth (12 vital/ two non-vital). One fixed splint comprising two abutment teeth was also included. Preparation parameters were recorded, as well as cement characteristics such as working time, setting time, seating characteristics, and ease of cement removal. Baseline data were recorded for the handling of the cement, gingival inflammation, and pre-cementation sensitivity. Post-cementation parameters included post-cementation sensitivity, gingival tissue reaction, marginal integrity, and discoloration. All patients were seen for recall examinations at 30 days and 6 months. Fifteen of 17 subjects and 13 of 17 patients were also available for subsequent comprehensive 1- and 2-year recall examination, and 13 patients were available for a 3-year recall examination. Restorations available for the 3-year recall examination included 14 single-unit full-coverage crown restorations, four three-unit bridges comprising eight abutments, and one two-unit splint. Three-year recall data yielded no loss of retention, no secondary caries, no marginal discolorations, and no subjective sensitivity. All restorations rated excellent for marginal integrity. Average visual analogue scale (VAS) score for tooth sensitivity decreased from 7.63 mm at baseline to 0.44 mm at 6-month recall, 0.20 mm at 1-year recall, and 0.00 mm at 2- and 3-year recall. Average gingival index (GI) score for gingival inflammation decreased from 0.56 at baseline to 0.11 at 6-month recall, 0.16 at 1-year recall, 0.21 at 2-year recall, and 0.07 at 3-year recall. After periodic recalls up to 3 years, Ceramir C&B thus far has performed quite favorably as a luting agent for permanent cementation of permanent restorations. In-vitro crown-coping retention studies were also conducted using this cement and various control cementation materials. Mean laboratory retentive forces measured for Ceramir C&B were comparable to other currently available luting agents for both metal and all-ceramic indirect restorative materials.

Probing and scaling instrumentation on implant abutment surfaces: an in vitro study.

PURPOSE: To investigate surface roughness on the apical collar of implant abutments caused by probing and scaling instruments. MATERIALS AND METHODS: Fourteen transmucosal abutments (BioHorizons, Atlanta, GA) and 4 instruments: UNC-15 metal probe, Periowise plastic probe, McCall SM 17/18 metal scaler, and universal plastic scaler were used to conduct the study. Four abutments were used for nontreated measures, and 10 abutments were treated with the 4 indicated instruments. Surface roughness was assessed with a contact profilometer. RESULTS: Analysis of variance showed significant differences in surface roughness between the treated and untreated surfaces (P < 0.0001). Add hoc analysis using Tukey-Kramer honestly significant difference test showed no statistical differences between untreated measures and metal probe measures. On the other hand, statistical differences were noted between untreated measures with plastic probe measures (P = 0.05), plastic scaler measures (P = 0.05), and metal scaler measures (P = 0.05). The metal scaler measures were higher than plastic probe measures (P = 0.05) and plastic scaler measures (P = 0.05). CONCLUSIONS: Probing around implant abutments with a metal probe seems to have no effect on abutment surfaces. In contrast, instrumentation with scalers (metal and plastic) and plastic probe may cause surface roughness.

Prospective observation of a new bioactive luting cement: 2-year follow-up.

PURPOSE: A pilot study was conducted to determine the 2-year clinical performance of a new bioactive dental cement (Ceramir C&B, formerly XeraCem) for permanent cementation. MATERIALS AND METHODS: The cement used in this study is a new formulation class, a hybrid material comprising calcium aluminate and glass ionomer. Thirty-eight crowns and fixed partial denture (FPD) abutments were cemented in 17 patients. Thirty-one of the abutment teeth were vital, 7 nonvital. Six reconstructions were FPDs comprising 14 abutment teeth (12 vital/2 nonvital). A two-unit fixed splint was also included. Preparation parameters and cement characteristics (dispensing, working time, seating characteristics, ease of cement removal) were recorded. Baseline and postcementation data were recorded for marginal integrity, marginal discoloration, secondary caries, retention, and gingival inflammation. Tooth sensitivity was assessed at pre- and postcementation time points using categorical and visual analogue scale (VAS) assessment measures. RESULTS: Mixing of the cement was reported as "easy." Clinical working time for this cement was deemed acceptable. Assessment of seating characteristics indicated all restorations were seated completely after cementation. Cement removal was determined to be "easy." Fifteen of 17 subjects were available for 1-year recall examination; 13 patients were available for the 2-year recall examination. Restorations at 2-year recall examination included 17 single-unit, full-coverage crown restorations, four 3-unit FPDs comprising 8 abutments, and one 2-unit splint. No retentive failures or sensitivity were recorded at 2-year recall. Marginal integrities of all restorations/abutments at 2 years were rated in the "alpha" category. Average VAS score for tooth sensitivity decreased from 7.63 mm at baseline to 0.44 mm at 6-month recall, 0.20 mm at 1-year recall, and 0.00 mm at 2-year recall. The average gingival index score for gingival inflammation decreased from 0.56 at baseline to 0.11 at 6-month recall, then 0.16 at 1-year recall, and 0.21 at 2-year recall. CONCLUSIONS: Two-year recall data yielded no loss of retention, no secondary caries, no marginal discolorations, and no subjective sensitivity. All restorations rated "alpha" for marginal integrity at the 2-year recall. After periodic recalls up to 2 years, the new bioactive cement tested thus far has performed favorably as a luting agent for permanent cementation.

Conventional polishing techniques versus a nanofilled surface sealer: preliminary findings regarding surface roughness changes and analysis.

OBJECTIVE: To evaluate the effect ofa nanofilled resin surface sealer (Seal&Protect) on the surface roughness of a hybrid composite resin. METHODS: Twelve 15 mm x 2 mm disc composite resin specimens (TPH Spectrum Shade C-2) were fabricated and light-cured under controlled conditions. Specimens were divided into six groups of two discs each. The positive control group was no finishing (Mylar Surface-MS); the remaining five group specimens were all standardized by finishing with an Enhance Finishing Disc prior to a final polishing/surface treatment step or sequence, which included: (1) polishing with a 1 micron aluminum oxide polishing paste; (2) polishing with a sequence of 1 micron and 0.3 micron aluminum oxide polishing pastes; (3) polishing with a one-step diamond polishing cup; (4) application and curing of the nanofiller resin surface sealer; and (5) no further treatment-Enhance finishing disc surface (negative control). Surface roughness (Ra) values (6 Ra values per specimen; 12 Ra values per group) were measured using a Surfcorder SE 1700 profilometer. Data were analyzed by a one-way ANOVA (p < or = 0.05). RESULTS: Polishing or surface treatment techniques significantly affected the surface roughness (Ra) values of the "finished" hybrid composite resin. Enhance Finishing Disc gave the highest Ra values; Mylar Surface gave the lowest. Application of the nanofilled resin surface sealer, after finishing with the elastomeric bonded-abrasive finishing disc, resulted in significantly lower surface roughness (Ra) values (p < 0.001). Other polishing techniques also significantly reduced the surface roughness of the composite resin surface. CONCLUSION: Use of a nanofilled, low-viscosity surface sealer may, after additional laboratory and clinical testing, present an alternative/adjunctive technique in final "polishing"/surface treatment of certain composite resin restoratives.

Effects of a 36% tooth bleaching gel on zinc phosphate cement.

PURPOSE: To assess the effect of a 36% hydrogen peroxide bleaching gel on the roughness, microhardness, indentation modulus, and micromorphology of zinc phosphate cement aged 24 h or 1 week, compared to cement not exposed to bleaching gel. METHODS: Dynamic indentation was performed for microhardness and indentation modulus. Contact profilometry was performed for surface roughness. Scanning electron microscopy assessed micromorphology. Means for microhardness, indentation modulus, and roughness were analyzed for differences among groups (No. 1 = 24 h/control; No. 2 = 24 h/treatment; No. 3 = 1 week/control; No. 4 = 1 week/treatment). RESULTS: Means (SD) for groups 1-4 respectively: Vickers Microhardness (HV): 34.2(8.7)a, 32.8(10.9)a, 24.8(5.0)b, 41.5(7.4)c; Indentation Modulus (EIT, GPa): 14.2(6.9)a,b, 10.6(3.6)a, 11.2(3.8)a, 14.7(2.8)b; and Surface Roughness (Ra, microns): 1.08(0.38)a, 1.21(0.55)a, 1.55(0.21)b, 1.52(0.29)b. Means labeled with the same superscript were not statistically significantly different. Scanning electron microscopy of groups 1 and 2 revealed similar details. Group 3 surfaces had plate-like crystals not present on the group 4 surfaces. CONCLUSIONS: Bleaching gel exposure increased hardness and indentation modulus and caused limited changes in surface morphology, but the cement was not adversely affected by the bleaching protocol.

Comparison of detachment forces of two implant overdenture attachment types: effect of detachment speed.

PURPOSE: To compare detachment (retentive) force for overdenture retainers used with conventional and "mini" implant designs over a range of different detachment (separation) speeds. METHODS: Two dental implant fixtures [Sendax MDI ("mini" dental implant) and Replace Select (conventional dental implant design)] with ball attachments were mounted in brass cylinders. Corresponding attachments were processed into acrylic denture resin blocks and connected to the ball attachments on the implants. The fixture/attachment assemblies were placed in an Instron testing system under ambient room temperature and humidity conditions (approximately 72 degrees F and 35-65% relative humidity). The assemblies were separated under tensile load at 11 speeds from 10-500 mm/minute with 10 replicates at each speed. Maximum detachment (separation) force was recorded. Mean, minimum, maximum, standard deviation and range of maximum detachment (separation) force was calculated. To test the hypothesis "the Sendax MDI and the Replace Select have the same average detachment force, at a given detachment speed", one-way ANOVA was performed. To test the hypothesis that "all detachment speeds have the same average maximum detachment force", one-way ANOVA was performed. To test the hypothesis that "the distribution of maximum detachment forces is the same for all detachment speeds", non-parametric Kruskal-Wallis analysis was performed. RESULTS: For Replace Select, the mean of the maximum force varied from 6.02-3.46 N with a downward trend as detachment speed increased. For Sendax MDI, the mean of the maximum force varied from 3.43-2.86 N. One-way ANOVA and Kruskal-Wallis analyses supported rejection of the hypotheses stated above with more than 99.99% confidence. Within the limitations of this study, the retentive properties of the Sendax MDI and the Replace Select attachment properties were different. Detachment speed had an effect on separation force for the two attachments in this study. Given the range of velocities possible in masticatory function; implant overdenture attachments, optimally, should be evaluated at more than one detachment speed to evaluate clinically-relevant, strain-rate behavior.

The Relative Location of the Dye Staining Endpoint Indicated With Polypropylene Glycol-Based Caries Dye versus Conventional Propylene Glycol-Based Caries Dye.

OBJECTIVES: This study determined the difference in the location of the caries dye staining endpoint of 1% Acid Red dye in propylene glycol versus that of 1% Acid Red dye in polypropylene glycol. METHODS: Freshly extracted permanent molar crowns with primary occlusal carious lesions were chisel-split axially to expose the lesion in cross-section on both halves. One half was stained with propylene glycol-based dye and the other with polypropylene glycol-based dye. For the control group, both halves were stained with propylene glycol-based dye. The dye staining front was marked on digital images of the stained split surfaces, and the images were aligned using reference notches. The distance between the marked staining front lines was measured in five locations, and the measurement protocol was repeated. Weighted averages and a 95% confidence interval for the distance between marked staining front lines were calculated for the control and experimental groups. RESULTS: The weighted average distance for the experimental group (0.298 mm, 95% confidence interval 0.240 mm - 0.357 mm) was about four times that of the control group (0.070 mm, 95% confidence interval 0.051 mm - 0.089 mm). Generally, the marked staining line for the polypropylene glycol-based dye specimens was located shallow (occlusal) to the propylene glycol-based staining line (range -0.12 mm to 0.66 mm). CONCLUSIONS: The staining endpoint of 1% Acid Red dye in polypropylene glycol is shallower than that of 1% Acid Red dye in propylene glycol. The method is useful for comparing staining endpoints of caries dye formulations. (Eur J Dent 2008;2:29-36).

Abrasive finishing and polishing in restorative dentistry: a state-of-the-art review.

Effective finishing and polishing of dental restorations not only result in optimal aesthetics but also provide for acceptable oral health of soft tissues and marginal integrity of the restorative interface. This review of abrasive technology in dentistry provides an overview of basic principles of abrasive science and considers some research concerning clinically relevant questions. The article also discusses some recent innovations in finishing and polishing devices. This review brings forward some newly published, outcome-based information concerning the relevance and importance of an effective knowledge of finishing and polishing techniques and materials. The overall aim is to provide an enhanced awareness and broader knowledge of the principles and tools available to produce optimal surface finishing and integrity in dental restoratives.

An accelerated in vitro model for adhesive testing.

PURPOSE: To develop a pilot in vitro accelerated laboratory testing protocol for assessing marginal sealing capability of dental adhesives. METHODS: Occlusal cavities were prepared in 20 human molar teeth and restored with Spectrum TPH resin composite. Prime & Bond NT and Prompt L-Pop served as the adhesive for eight teeth each. An experimental self-etching adhesive system was used on the remaining four teeth. Each specimen was subjected in sequential fashion to the following challenges: 400,000 wear cycles in a Leinfelder simulator; 5000 thermocycles between water baths maintained at 5 degrees C and 55 degrees C with a dwell time of 40 seconds in each; and a repetition of the 400,000 wear cycles. Polyvinyl siloxane impressions were made at baseline and after each challenge. Microleakage was assessed following silver nitrate staining and marginal degradation was evaluated using light microscopy and the stone casts made from the impressions taken during the project. RESULTS: Microleakage analysis yielded the following median leakage values: Prime & Bond NT - 0; Prompt L-Pop - 1; and experimental self-etching adhesive - 3. The Wilcoxon sign rank test demonstrated significant differences between all three adhesives (P < or = 0.05). Evaluation of the stone casts demonstrated that marginal gaps were more prevalent after the second wear challenge.