Impacts of Conservative Endodontic Cavity on Root Canal Instrumentation Efficacy and Resistance to Fracture Assessed in Incisors,Premolars, and Molars

Introduction

Conservative endodontic cavity (CEC) may improve fracture resistance of teeth but compromise the instrumentation of canals. This study assessed the impacts of CEC on both variables in 3 tooth types.

Methods

Extracted human intact maxillary incisors, mandibular premolars, and molars (n = 20/type) were imaged with micro–computed tomographic imaging (20-μm resolution) and assigned to CEC or traditional endodontic cavity (TEC) groups (n = 10/group/type). Minimal CECs were plotted on scanned images. Canals were prepared with WaveOne instruments (Dentsply Maillefer, Ballaigues, Switzerland) using 1.25% sodium hypochlorite and post-treatment micro–computed tomographic images obtained. The proportion of the untouched canal wall (UCW) and the dentin volume removed (DVR) for each tooth type was analyzed with the independent-samples t test. The 60 instrumented and 30 intact teeth (negative control, n = 10/type) were loaded to fracture in the Instron Universal Testing machine (Instron, Canton, MA) (1 mm/min), and the data were analyzed with 1-way analysis of variance and the Tukey test.

Results

The mean proportion of UCW was significantly higher (P < .04) only in the distal canals of molars with CEC (57.2% ± 21.7%) compared with TEC (36.7% ± 17.2%). The mean DVR was significantly smaller (P < .003) for CEC than for TEC in incisors (16.09 ± 4.66 vs 23.24 ± 3.38 mm³), premolars (8.24 ± 1.64 vs 14.59 ± 4.85 mm³), and molars (33.37 ± 67.71 mm³). The mean load at fracture for CEC was significantly higher (P < .05) than for TEC in premolars (586.8 ± 116.9 vs 328.4 ± 56.7 N) and molars (1586.9 ± 196.8 vs 641.7 ± 62.0 N). In both tooth types, CEC did not differ significantly from the negative controls.

Conclusions

Although CEC was associated with the risk of compromised canal instrumentation only in the molar distal canals, it conserved coronal dentin in the 3 tooth types and conveyed a benefit of increased fracture resistance in mandibular molars and premolars.     

Flat-oval root canal preparation with self-adjusting file instrument: a micro-computed tomography study

Introduction

The aim of this study was to evaluate the root canal preparation in flat-oval canals treated with either rotary or self-adjusting file (SAF) by using micro-tomography analysis.

Methods

Forty mandibular incisors were scanned before and after root canal instrumentation with rotary instruments (n = 20) or SAF (n = 20). Changes in canal volume, surface area, and cross-sectional geometry were compared with preoperative values. Data were compared by independent sample t test and χ² test between groups and paired sample t test within the group (α = 0.05).

Results

Overall, area, perimeter, roundness, and major and minor diameters revealed no statistical difference between groups (P > .05). In the coronal third, percentage of prepared root canal walls and mean increases of volume and area were significantly higher with SAF (92.0%, 1.44 ± 0.49 mm³, 0.40 ± 0.14 mm², respectively) than rotary instrumentation (62.0%, 0.81 ± 0.45 mm³, 0.23 ± 0.15 mm², respectively) (P < .05). SAF removed dentin layer from all around the canal, whereas rotary instrumentation showed substantial untouched areas.

Conclusions

In the coronal third, mean increases of area and volume of the canal as well as the percentage of prepared walls were significantly higher with SAF than with rotary instrumentation. By using SAF instruments, flat-oval canals were homogenously and circumferentially prepared. The size of the SAF preparation in the apical third of the canal was equivalent to those prepared with #40 rotary file with a 0.02 taper.     

Sodium hyaluronate accelerates the healing process in tooth sockets of rats

Objective

In this study we evaluated the effects of sodium hyaluronate (HY) in the healing process of tooth sockets of rats.

Design

Immediately after the extraction of the upper first molars of male Holtzman rats, right sockets were treated with 1% HY gel (∼0.1 ml), while left sockets were used as control (blood clot). The animals were sacrificed at 2, 7, and 21 days after tooth extraction and upper maxillaries processed for histological and morphometric analysis of the apical and medium thirds of the sockets. Carbopol, an inert gel, was used to evaluate the mechanical effect of gel injection into sockets. Expression of bone morphogenetic protein-2 (BMP-2) and osteopontin (OPN) was determined by immunohistochemistry at 1, 2, 3, 4, 5, and 7 days after tooth extraction.

Results

Histological analysis showed that HY treatment induced earlier trabecular bone deposition resulting in a bone matrix more organized at 7 and 21 days after tooth extraction. Also, HY elicited significant increase in the amount of bone trabeculaes at 7 and 21 days after tooth extraction (percentage of trabecular bone area at 7 days: 13.21 ± 4.66% vs. 2.58 ± 1.36% in the apical third of control sockets) and in the vessels counting at 7 days. Conversely, the number of cell nuclei was decreased in HY-treated sockets. Additionally, expression of BMP-2 and OPN was enhanced in HY-treated sockets compared with control sockets.

Conclusions

These findings suggest that HY accelerates the healing process in tooth sockets of rats stimulating the expression of osteogenic proteins.     

Micro-computed tomography evaluation of the preparation of long oval root canals in mandibular molars with the self-adjusting file

Introduction

The aim of this study was to assess the shaping potential of a novel nickel-titanium instrument, the self-adjusting file (SAF), in long oval root canals in distal roots in mandibular molars.

Methods

Twenty mandibular molars with long oval distal root canals were selected and scanned preoperatively and postoperatively by using micro-computed tomography at an original resolution of 20 μm. Canals were shaped with the SAF, three-dimensionally reconstructed, and evaluated for volume, surface area, canal transportation, and prepared surface. Data were statistically contrasted by using paired t tests and regression analysis.

Results

Preoperatively, canal volume was 7.73 ± 2.13 mm³, and canal area was 42.83 ± 8.14 mm². Volumes and surface areas increased significantly (P < .001) by 4.84 ± 1.73 mm³ and 3.34 ± 1.73 mm², respectively, and no gross preparation errors were detected. Unprepared canal surface varied between individual canals, and mean unprepared surface was 23.5% ± 8.9%. Prepared areas were significantly larger compared with rotary canal preparation done in a previous study. Canal transportation scores were higher in the coronal root canal third (106 ± 50 μm) compared with the apical third (81 ± 49 μm).

Conclusions

In vitro, preparation of long oval-shaped root canals in mandibular molars with the SAF was effective and safe. Moreover, shapes generated with the SAF were more complete compared with rotary canal preparation.     

Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns

PURPOSE

This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear.

MATERIALS AND METHODS

There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey''s test (P<.05).

RESULTS

The Leucite group (2.670±1.471 mm³) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm³), Zirconia (1.426±0.477 mm³), and Steel groups (0.397±0.192 mm³). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05).

CONCLUSION

Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia.     

Analisi in vivo del rilascio di bisfenolo A da un sigillante

Objectives

The aim of this work was to measure the amount of bisphenol A (BPA), a substance with low estrogenic activity, present in the saliva before and after (1 min) the application of a commercial dental sealant.

Materials and methods

We recruited 15 healthy subjects (8 men and 7 women, 21-48 years of age). Saliva specimens (4-5 mL) were collected from each immediately before (baseline) and one minute after application and polymerization of the sealant (test). The amount of BPA was measured in all specimens with gas chromatography-mass spectrometry (GC-MS).

Results

BPA was detected in all post-sealant saliva specimens with a mean level of 54.3 ± 74 ng/mL. BPA levels exhibited significant inverse correlation with salivary pH values.

Conclusions

Our results confirm that the sealant releases BPA into the saliva but the concentrations found are lower than those reported to produce estrogen-like biological effects in vivo.     

Effects of Cachaça, a typical Brazilian alcoholic beverage,on alveolar bone loss and density: A study in peripubertal rats

Objective

The aim of the present study was to assess the impact of chronic consumption of Cachaça on alveolar bone loss (BL) induced by ligature and on alveolar bone density (BD) in peripubertal rats.

Design

Male Wistar rats were assigned into one of the following groups: Control: non-ingestion of Cachaça (n = 15); Cachaça: ingestion of ascending concentrations of Cachaça during 100 days (n = 15). 70th day after the beginning of Cachaça ingestion, one first mandibular molar received a ligature while the contralateral tooth was left unligated. After 30 days, the rats were killed. BL, BD, the positive cells for tartrate-resistant acid phosphatase (TRAP), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) were analyzed in the furcation area of the ligated and unligated mandibular molars.

Results

The Cachaça group presented greater BL (0.75 ± 0.1 mm² for Cachaça and 0.66 ± 0.1 mm² for control group, respectively) and number of RANKL and OPG+ cells and lower BD (60.3 ± 4.2% for Cachaça and 76.8 ± 3.8% for control group, respectively) and number of TRAP+ cells around ligated teeth (p < 0.05), when compared to the control group. The Cachaça group (0.42 ± 0.02 mm²) also presented a higher BL around unligated teeth when compared to control group (0.31 ± 0.05 mm²).

Conclusions

Cachaça consumption per se and in the presence of ligature negatively affects alveolar bone by increasing the alveolar BL and reducing BD.     

Nanomechanical properties of endodontically treated teeth

Introduction

Although it is apparent that teeth become more susceptible to fracture after root canal treatment, the contributing factors for this are not completely established. The purpose of this study was to determine whether there are changes in nanomechanical properties of dentin in root canal–treated teeth compared with non–root canal–treated control teeth.

Methods

Atomic force microscopy–based nanoindentation testing was performed on root canal–treated teeth and age- and type-matched control teeth. Radicular intertubular dentin was indented in 6 locations, and triplicate measurements were averaged. Paired t tests were used to compare root canal–treated teeth with control teeth.

Results

The moduli of elasticity were 17.8 ± 2.9 GPa and 18.9 ± 2.9 GPa for root canal–treated teeth and controls, respectively; the hardness values for the 2 groups were 0.84 ± 0.25 GPa and 0.84 ± 0.18 GPa, respectively. Neither the modulus of elasticity nor the hardness differed between groups (P > .05).

Conclusions

It appears that root canal treatment does not result in nanomechanical changes to radicular intertubular dentin.     

La terapia ortopedico funzionale nella retrusione mandibolare: un approccio teorico-pratico

Objectives

The aim of this study was to evaluate the efficacy of functional orthopedic therapy in growing patients whose facial profiles can be esthetically improved by moving the mandible forward.

Materials and methods

We conducted a controlled longitudinal cohort study of children with receding chins, normodivergent cephalometric profiles, and class II molar relations with an overjet of >5 mm. Ten of the patients (five boys with a mean age of 11.5 years [SD±1.5] and five females with a mean age of 10.5 years [SD±1.5]) were treated with bite jumping and ten served as age- and sex-matched controls. Results were evaluated in terms of esthetic parameters and changes in 11 cephalometric angle measurements. Statistical analysis was based on Student's t test; p values <0.05 were considered significant.

Results and Conclusions

The treated patients present clear esthetic improvement in the facial profile with statistically significant changes in dental, alveolar, and maxillary protrusion, but no significant effects on the mandible.     

Endodontic Working Length Measurement Using Cone-beam Computed Tomographic Images Obtained at Different Voxel Sizes and Field of Views,Periapical Radiography,and Apex Locator: A Comparative Ex Vivo Study

Introduction

The aim of this study was to evaluate the accuracy of working length determination by using an electronic apex locator, periapical radiography, and cone-beam computed tomographic (CBCT) imaging obtained at different voxel sizes and field of views (FOVs) in extracted human teeth.

Diffusion and concurrent solubility of self-adhering and new resin-matrix composites during water sorption/desorption cycles

Objectives

To investigate the kinetic process of water diffusion and mass change in new resin-matrix composites during water sorption/desorption cycles.

Methods

Five new resin-matrix composites were investigated [Filtek^® Silorane (FS), GC Gradia Direct Anterior (GDA), GC Gradia Direct Posterior (GDP), GC Kalore (GCK), Vertise^® Flow (VF)]. Five disk-shaped specimens, per material (15.0 ± 0.1) mm diameter by (2.0 ± 0.1) mm, were prepared according to ISO 4049. Each disk was immersed separately in de-ionized water for 150 d and then reconditioned for 75 d; all at (37 ± 1) °C. Mass was measured at different time intervals. Perspex disks were used as control. Data analysis was done by repeated measures ANOVA, one-way ANOVA and Tukey's post hoc test (p < 0.05).

Results

The water sorption (μg/mm³) after 150 d immersion ranged from 13.51 μg/mm³ (±0.40) for FS to 71.96 μg/mm³ (±0.90) for VF. The solubility ranged up to 16.95 μg/mm³ (±0.79) for VF. A significant mass reduction occurred in VF after the peak value [73.63 μg/mm³ (±0.31)] of water sorption was reached at 42 d. VF had the highest diffusion-coefficient for sorption: 5.23 × 10⁻⁹ cm²/s (±0.38) and desorption: 11.72 × 10⁻⁹ cm²/s (±0.16). Percentage sorption differences were significant for all materials (p < 0.001), except between GCK and GDP. The early correlation between mass change and square root of time was linear.

Significance

Each resin-matrix composite varied in sorption/desorption cycles which may affect clinical service. A concurrent solubility process occurred during sorption of the self-adhering composite VF. The silorane composite FS exhibited minimal sorption.     

Minivis d’ancrage : étude de l’état de surface sous microscopie optique

Introduction

The aim of this study was to assess the surface changes in orthodontic miniscrew implants retrieved after usage and compare them with brand-new, as-received control miniscrews.

Material and methods

The study sample consisted of 28 miniscrews from the same manufacturer: Dual Top Anchor system^® (Korea) of different diameters and lengths. One brand-new miniscrew served as a control. Surface characterization was carried out using optical microscopy (Leica DM2500 M^®) and image magnification (×5, ×10 and ×20).

Results

Observations under optical microscopy showed signs of pitting and crevice corrosion mainly at manufacturing defects. Retrieved miniscrew implants displayed larger surface cracks from corrosive attacks (pitting and crevice). Qualitative sample analysis suggested a loss of gloss and texture, giving the surface a dull appearance. Localized pitting was the most frequent form of corrosion observed in our sample.

Discussion and conclusion

Despite a smooth appearance to the naked eye, the miniscrews all had crack-like surface manufacturing defects. Examination of the surface of these miniscrews, after usage, evidenced pitting or crevice corrosion principally in the area of enhance corrosion resistance.     

Wear performance of substructure ceramics and veneering porcelains

Aim

The aim of this in vitro study was to compare the two-body wear resistance of substructure zirconia and veneering porcelain versus steatite and human enamel antagonists, respectively.

Materials and methods

Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists (enamel cusps). A pin-on-block design with a vertical load of 50 N for 1.2 × 10⁵ cycles; (f = 1.6 Hz; lateral movement: 1 mm, mouth opening: 2 mm) was used for the wear test. For quantification of the wear resistance, wear tests were performed with standardized steatite spheres. Human enamel was used as a reference. Five zirconia ceramics and four veneering porcelains were investigated. One zirconia ceramic was tested with superficial glaze, which was applied after polishing or sandblasting, respectively. Surface roughness R_a (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D-Profilometer (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures were used for evaluating wear performance of both, ceramics and antagonists.

Results

No wear was found for zirconia substructures. Veneering porcelain provided wear traces between 186.1 ± 33.2 μm and 232.9 ± 66.9 μm (steatite antagonist) and 90.6 ± 3.5 μm and 123.9 ± 50.7 μm (enamel). Wear of the steatite antagonists varied between 0.812 ± 0.256 mm² and 1.360 ± 0.321 mm² for zirconia and 1.708 ± 0.275 mm² and 2.568 ± 0.827 mm² for porcelain. Enamel generally showed wear, cracks or even fractures at the ridge, regardless whether opposed by zirconia or porcelain/glaze. Enamel was polished, when opposed to zirconia, or plowed, provoked and grinded, when opposed to porcelain/glaze.

Conclusion

The results of the wear test with steatite or enamel antagonists indicated no measurable wear on zirconia surfaces. Porcelain showed higher wear than zirconia, but comparable or lower wear than an enamel reference. Antagonistic wear against zirconia was found to be lower than wear against porcelain.     

Is human immunodeficiency virus (HIV) stage an independent risk factor for altering the periodontal status of HIV-positive patients? A South African study

Background

The immunosuppresion in HIV patients makes them highly susceptible to microbial infections. The aim of the study was to establish whether HIV stage (as depicted by CD4+ T lymphocyte counts) could independently be associated with periodontal status (as revealed by the measurement of clinical indices).

Methods

One hundred and twenty HIV-infected patients attending an infectious diseases clinic in the Western Cape, South Africa were included in the study. The periodontal clinical indices such as plaque index, gingival index, pocket probing depth and clinical attachment levels were measured on the mesial aspect of the six Ramfjord teeth. The CD4?+?T cell counts were taken from the patients’ medical records and patients’ HIV stage determined and grouped according to their CD4+ T cell counts into A (<200 cells /mm³), B (200–500 cells /mm³) and C (>500 cells /mm³).

Results

The mean age of 120 HIV-positive patients was 33.25 years and the mean CD4?+?T cell count was 293.43 cells/mm³. The probing depth and clinical attachment loss were found to be significantly associated with the total CD4?+?T cell counts but not with HIV stage. Significant correlations were found between age and all clinical indices except for clinical attachment loss. No correlation was found between age and HIV stage of the patients. The use of antiretroviral therapy was significantly associated with probing depth and clinical attachment loss, but not with plaque nor gingival index. Significant associations were observed between smoking and all of the clinical indices except for the gingival index. A significant association was observed between the use of interdental aids and all the clinical indices except for probing depth, while brushing was significantly associated with plaque index only. CD4?+?T cell counts were significantly associated with brushing frequency (p?=?0.0190) and the use of interdental aids (p?=?0.0170).

Conclusion

The findings of this study conclude that HIV stage, ART and age are not independent risk factors for changes in the periodontal status of HIV-positive subjects but rather that smoking and oral hygiene habits determine their susceptibility to disease.

     

Timing terapeutico e concetto di “urgenza” ortodontica. Linee guida e revisione della letteratura

Objectives

The objective of the study is to define the optimal timing of “urgent” orthodontic treatment of malocclusions.

Materials and methods

We conducted a systematic review of the literature that contained quantitative and qualitative data on the timing of orthodontic treatment of various types of malocclusions. Our analysis centered on articles indexed in the Medline database that had been published from 1970 through November 2010, including review articles, meta-analyses, and randomized and controlled clinical trials (RCT and CCT).

Results and conclusions

Our analysis of the literature indicates that there are “urgent” orthodontic problems that require prompt treatment, even if the permanent teeth have not erupted. These cases include crossbites, skeletal class III malocclusion, certain behavioral anomalies, the presence of obstacles to eruption or supernumerary teeth, and early tooth shedding. In these cases, early treatment often prevents the later development of severe, frequently skeletal malocclusions.     

The effect of CPP-ACP on enamel wear under severe erosive conditions

Objective

In addition to its role as a remineralizing agent in preventing dental caries, recent evidence has shown that casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) can protect teeth against erosion. The aim of this study was to determine whether CPP-ACP could reduce enamel wear rates under severe erosive conditions simulating heavy attrition and gastric regurgitation.

Design

Enamel specimens were subjected to 10,000 wear cycles at a load of 100 N and pH 1.2 in a tooth wear machine. The machine was stopped every 2 min (160 cycles), and CPP-ACP in the form of a paste was applied for 5 min in experimental group 1. A paste with the same formulation but without CPP-ACP was applied in experimental group 2. No paste was applied in the control group.

Results

A linear mixed model analysis indicated that the mean wear rates in experimental group 1 (0.44 ± 0.05 mm³ per 1000 cycles) and in experimental group 2 (0.63 ± 0.06 mm³ per 1000 cycles) were significantly lower than that in the control group (0.92 ± 0.11 mm³ per 1000 cycles) (p < 0.05). The mean wear rate in experimental group 1 was also lower than that in experimental group 2 (p < 0.05). Wear facets in experimental groups 1 and 2 were noted to be smoother and more polished than those in the control group.

Conclusions

Both remineralizing and lubricating properties of the paste containing CPP-ACP appear to contribute to wear reduction in enamel. These findings may lead to new strategies for the clinical management of tooth wear.     

Corone singole su impianti ottenuti per fabbricazione diretta tramite laser. Studio prospettico e multicentrico con follow-up a un anno

Objectives

This prospective study evaluated the survival rate and the implant-crown success of single-tooth titanium dental implants produced with direct laser metal forming (DLMF) after 1-year of functional loading.

Materials and methods

110 maxillary (N = 65) and mandibular (n = 45) implants (TixOs^®, Leader Novaxa, Milan, Italy) were placed in 82 patients (44 males, 38 females; age range 26-67 years) in 7 different clinical centers. The prosthetic restorations included 110 single crowns (SCs) (32 anterior, 78 posterior). The scheduled 1-year follow-up examination focused on several clinical, radiographic, and prosthetic parameters. Implant success was defined as the absence of pain, sensitivity, suppuration, and exudation; absence of clinically detectable implant mobility; absence of peri-implant radiolucency; distance between the implant shoulder and the first visible bone contact (DIB) < 1.5 mm; absence of prosthetic complications at the implant abutment interface.

Results

After 1-year of functional loading, the overall implant survival rate was 99.1% (98.4% maxilla, 100% mandible). The mean DIB was 0.60 mm (± 0.32). All but 3 of the 109 surviving implants fulfilled the implant-crown success criteria (implant-crown success 97.2%).

Conclusions

Titanium dental implants produced with DLMF seem to represent a valid treatment option for single-tooth restorations in the maxilla and in the mandible. Further studies are needed to evaluate the long-term performance of these implants.     

Low concentration alcohol intake may inhibit spontaneous alveolar bone loss in Wistar rats

Objective

The aim of the present study was to evaluate the influence of ethanol in low concentration (5%) in ligature-induced alveolar bone loss in Wistar rats.

Material and Methods

Thirty rats were randomly assigned to test and control groups (n = 15). Test group received a liquid diet containing ethanol 5% (vol./vol.) and standard rat chow. Control group received only tap water as the liquid diet and the same rat chow. In both groups, diet was delivered ad libitum. Alveolar bone loss was induced prior to the beginning of the study by means of ligatures placed around the upper second molars. The contra-lateral tooth remained as intra-group control. At the end of the nine weeks, the animals were killed and morphometric analysis of alveolar bone loss was performed by a blinded and calibrated examiner. Intra-group comparisons were performed by paired sample T-test and inter-group differences were compared by independent sample T-test (α = .05).

Results

Animals that drank ethanol in low concentration systematically presented less alveolar bone loss than the control group, regardless of the presence of ligature. Test group showed less alveolar bone loss (p = 0.04) in unligated teeth when compared to control group (0.32 ± 0.07 and 0.37 ± 0.07 mm, respectively). However, no significant difference (p = 0.14) was observed between Test and Control groups (0.78 ± 0.14 and 0.84 ± 0.18 mm, respectively) in ligated teeth.

Conclusion

The results of this study lead to the conclusion that low concentration alcohol intake did not affect the alveolar bone loss in ligature induced periodontal breakdown.     

A study on the in-vitro wear of the natural tooth structure by opposing zirconia or dental porcelain

PURPOSE

This study was conducted to evaluate clinical validity of a zirconia full-coverage crown by comparing zirconia''s wear capacity over antagonistic teeth with that of feldspathic dental porcelain.

MATERIALS AND METHODS

The subject groups were divided into three groups: the polished feldspathic dental porcelain group (Group 1), the polished zirconia group (Group 2), and the polished zirconia with glazing group (Group 3). Twenty specimens were prepared from each group. Each procedure such as plasticity, condensation, and glazing was conducted according to the manufacturer''s manual. A wear test was conducted with 240,000 chewing cycles using a dual-axis chewing simulator. The degree of wear of the antagonistic teeth was calculated by measuring the volume loss using a three-dimensional profiling system and ANSUR 3D software. The statistical significance of the measured degree of wear was tested with a significant level of 5% using one-way ANOVA and the Tukey test.

RESULTS

The degrees of wear of the antagonistic teeth were 0.119 ± 0.059 mm³ in Group 1, 0.078 ± 0.063 mm³ in Group 3, and 0.031 ± 0.033 mm³ in Group 2. Statistical significance was found between Group 1 and Groups 2 and between Group 2 and 3, whereas no statistical significance was found between Group 1 and Group 3.

CONCLUSION

Despite the limitations of this study on the evaluation of antagonistic teeth wear, the degree of antagonistic tooth wear was less in zirconia than feldspathic dental porcelain, representing that the zirconia may be more beneficial in terms of antagonistic tooth wear.     

Effects of surface treatment,hydration and application method on the bond strength of a silorane adhesive and resin system to dentine

Objectives

To evaluate the effects of surface treatment, surface hydration (SH) and application method (AM) on the tensile bond strength of the Silorane Adhesive System (SAS) to dentine.

Methods

Ninety bovine teeth were used. For the control group (n = 10), each dentine surface was treated according to the manufacturer's instructions of the SAS. The remaining teeth were randomly distributed into two groups (n = 40), according to the type of dentine surface treatment (ST)—37% phosphoric acid or Er:YAG Laser prior to the application of the SAS. Each group was further divided into 2 subgroups (n = 20), according to the SH status: dry (D) or wet (W). Each subgroup was further divided into 2 subgroups (n = 10), according to the application method [AM: Active (AC) mode or Passive (PA) mode]. A coat of resin composite (Filtek P90) was applied on the surface. Artificial ageing was performed with a thermo-mechanical cycling machine. The specimens were sectioned into 1 mm × 1 mm × 10 mm sticks and stressed to failure using a universal testing machine. The remaining teeth in each group were used for Scanning Electron Microscopy to examine the fractured area. Data were subjected to a three-way ANOVA, Tukey's test and Dunnet's test (α = 0.05).

Results

The ANOVA showed significant differences for SH and AM, but not for ST. For SH, the results of Tukey's test were (in MPa): D – 14.9(±3.8)^a, W – 17.1(±4.3)^b; and for AM: PA – 14. 9(±4.2)^a, AC – 17.1(±3.9)^b.

Conclusions

Acid etching, when combined with a moist dentine surface and the use of primer agitation, improves the bond strength of the SAS to dentine.

Clinical Significance

According to the results of the present in vitro study, modification of the application protocols for the silorane-based adhesive system may improve its clinical performance.