Pre-cementation treatment of glass-ceramics with vacuum impregnated resin coatings

OBJECTIVE

The study aimed to investigate the effectiveness of a vacuum impregnation process to eliminate the porosity at the ceramic-resin interface to optimize the reinforcement of a glass-ceramic by resin cementation.

METHODS

100 leucite glass-ceramic disks (1.0 ± 0.1 mm thickness) were air-abraded, etched with 9.6 % HF acid, and silanated. Specimens were randomly allocated to 5 groups (n = 20). Group A received no further treatment (uncoated control). Groups B and D were resin-coated under atmospheric pressure, whereas groups C and E were resin-coated using vacuum impregnation. The polymerized resin-coating surfaces of specimens in groups B and C were polished to achieve a resin thickness of 100 ± 10 µm, while in groups D and E no resin-coating modification was performed prior to bi-axial flexure strength (BFS) determination. Optical microscopy was undertaken on the fracture fragments to identify the failure mode and origin. Comparisons of BFS group means were made by a one-way analysis of variance (ANOVA) and post-hoc Tukey test at α = 0.05.

RESULTS

All resin-coated sample groups (B-E) showed a statistically significant increase in mean BFS compared with the uncoated control (p < 0.01). There was a significant difference in BFS between the ambient and vacuum impregnated unpolished groups (D and E) (p < 0.01), with the greatest strengthening achieved using a vacuum impregnation technique.

SIGNIFICANCE

Results highlight the opportunity to further develop processes to apply thin conformal resin coatings, applied as a pre-cementation step to strengthen dental glass-ceramics.

Effectiveness and predictability of treatment with clear orthodontic aligners: A scoping review

INTRODUCTION

In an ideal clinical setting, orthodontic therapy with clear aligners (CA) should improve the patients' initial malocclusion and must guarantee equivalence between the results predicted and those obtained clinically to be considered an effective treatment. Therefore, this scoping review aimed to identify the orthodontic literature concerning the effectiveness and predictability of CA treatments.

METHODS

A systematic computerized search was performed in 3 databases: PubMed, Scopus, and Embase. Inclusion criteria selected observational and clinical studies performed in at least 10 adult orthodontic patients, whose results of CA treatment's effectiveness and/or predictability were assessed.

RESULTS

The 3 database computerized searches resulted in 1,553 articles, and 169 full texts were considered potentially relevant. After applying the eligibility criteria, 33 studies were included. Most studies (76%) were designed as cohort studies and have been published in the last 5 years (79%). The majority included only non-extraction treatments (73%), and 79% reported results achieved with the Invisalign® system. The most predictable movement was the buccolingual tipping, while the least predictable movements were rotation, intrusion, and extrusion. Aligner treatment was effective for mild to moderate crowding resolution, and the success of overbite correction still seems to be limited.

CONCLUSIONS

The studies have demonstrated improvement of initial malocclusion through CA treatments. Still, predictability degree is overestimated and does not accurately reflect the occlusion immediately at the end of treatment. In future studies, there should be an effort to broaden the utilization of alternative aligner systems beyond Invisalign® and broadly disseminate their outcomes to strengthen clear aligners evidence base.

Peri-implant bone resorption risk of anterior maxilla narrow single implants: a finite-element analysis

Statement of the problem: Narrow implants have been recommended in high esthetic demand regions to ensure greater buccal bone thickness (BBT) and minimize soft-tissue recession due to insufficient bone support. However, a limited area of bone-implant interface can increase the risk of peri-implant bone resorption due to occlusal forces. Purpose: This article encourages the use of evidence-based finite element analysis to optimize the aesthetic outcomes in maxillary lateral incisor single-supported implant crown by accurate biomechanical planning. This study aimed to analyze the best implant dimensions that would preserve the maximum BBT and avoid peri-implant bone resorption due to occlusal forces. Materials and methods: A maxilla segment was constructed based on anthropological measurements. Four implant diameters (Ø = 3.25; 3.50; 3.75 or 4.00 mm) and two lengths (L = 10 or 13 mm) were simulated. The occlusal force parameters were defined to simulate clinical conditions. The bone resorption risk analysis was based on Frost's mechanostat theory altering the strain output to strain energy density (SED). The peri-implant bone resorption risk indexes (PIBR_ri) were calculated by dividing the average of the top ten SED elements of the cortical and trabecular buccal wall by the pathologic resorption limit for each bone. Results: For trabecular bone, only the model Ø4.00_L13 exhibited a low PIBR_ri. For cortical bone, all models presented a low PIBR_ri, except for models Ø3.25. Conclusion: The selection of a 3.25 mm dental implant to preserve a 2 mm BBT should be avoided since it generates a high peri-implant bone resorption risk induced by occlusal overload.

Dentists' awareness and knowledge of evidence- based dentistry principles, methods and practices: a systematic review

Introduction As an attempt to provide supporting evidence for the formulation of future educational strategies on knowledge translation, this systematic review assessed and synthesised the available evidence related to the dentists' awareness, perceived and actual knowledge of evidence-based dentistry (EBD) principles, methods and practices.Methods Primary studies that considered dentists' reports collected from interviews, questionnaires, or conversation sessions were selected. Studies enrolling students, dental hygienists, or other health professionals were not included. Reviews, editorials, letters, study protocols, articles presenting knowledge translation strategies and initiatives, examples of EBD approaches to specific clinical questions, and guidelines focused on EBD implementation were also excluded. Cochrane, Embase, PubMed, Scopus and Web of Science databases were searched. Grey literature was partially covered by the Google Scholar search and the reference lists of the pre-selected studies. The study search was concluded in February 2021. Descriptive data of the selected studies were synthesised, and the risk of bias was assessed according to the National Institutes of Health Quality Assessment Tool for observational cohort and cross-sectional studies.Results Twenty-one articles were included. High percentages of dentists were aware of EBD. Variable proportions of professionals declared to have some understanding of EBD, although few presented actual knowledge of principles, methods and practices.Discussion Methodologically, most studies presented limitations regarding sample representativity, participation rates, detailing of the outcome measures, and validation of the assessment tools. Additionally, extensive overall ranges of responses were often observed across the studies, possibly as a result of heterogeneity across samples and assessment tools. The authors thus suggest developing valid questionnaires including all dimensions (awareness, perceived knowledge and actual knowledge) within an assessment tool. This would contribute to establishing knowledge translation strategies to overcome specific gaps in EBD knowledge.

Intrusion of overerupted periodontally compromised posterior teeth using orthodontic mini‐implants: a mechanobiological finite element study

INTRODUCTION

The intrusion of posterior teeth had been considered challenging up to the development of orthodontic mini implants. In periodontally compromised teeth, the challenge is even greater, because of the root resorption risk due to periodontal ligament over-compression. Still, the precise strategy to determine the force reduction level remains uncertain.

OBJECTIVE

The objective of the study was to determine, by a finite element analysis (FEA), the force reduction needed to avoid root resorption and maintain the efficiency of orthodontic mechanics of periodontally compromised teeth similar to the sound one.

METHODS

An anatomical model was constructed representing a premolar inserted into a maxillary bone. Based on the initial model (R0), three bone height loss conditions were simulated (R2 = 2 mm, R4 = 4 mm, and R6 = 6 mm). Two intrusive movements were simulated: pure intrusion (bilateral mini implant) and uncontrolled-tipping intrusion (buccal mini implant). The hydrostatic stress at the periodontal ligament was used to evaluate the risk of root resorption due to over-compression.

RESULTS

For bilateral mini implant intrusion, the force had to be decreased by 16%, 32% and 48% for R2, R4 and R6, respectively. For buccal mini implant intrusion, the required reductions were higher (20%, 36% and 56%). A linear relationship between the intrusive force reduction and the alveolar bone height loss was observed in both intrusion mechanics.

CONCLUSIONS

According to the FE results, 8% or 9.3% of force reduction for each millimetre of bone height loss is suggested for intrusion with bilateral or buccal mini implant, respectively. The buccal mini implant anchorage must be associated with a supplemental strategy to avoid buccal crown tipping.

Experimental composite containing silicon dioxide-coated silver nanoparticles for orthodontic bonding: Antimicrobial activity and shear bond strength

Objective:

This study aimed to investigate the antimicrobial activity and shear bond strength (SBS) of orthodontic brackets to bovine enamel using experimental composites with different concentrations of silicon dioxide-coated silver nanoparticles (Ag@SiO₂ NPs).

Methods:

Fifty bovine incisors were divided into five groups according to the composite (n = 10): G1 - Control Group (Transbond XT Resin), G2 - Experimental composite without Ag@SiO₂ NPs; G3 - Experimental composite with 0.5% of Ag@SiO₂ NPs; G4 - Experimental composite with 1% of Ag@SiO₂ NPs; G5 - Experimental composite with 3% of Ag@SiO₂ NPs. The SBS test was performed using a universal mechanical testing machine, and the adhesive remnant index (ARI) was analyzed by optical microscopy. For the antimicrobial activity evaluation, Streptococcus mutans (S. mutans) biofilm was formed for three days in hydroxyapatite discs. Posteriorly, S. mutans colony forming units (CFU) were evaluated. For SBS analysis, Analysis of Variance was used, followed by the Tukey test, at a 5% statistical significance level. The CFU data were analyzed by Kruskal-Wallis, followed by Dunn as a post-hoc test. The ARI results were analyzed descriptively.

Results:

There was no statistically significant difference in SBS values between the experimental and control groups (p>0.05). A 3% incorporation of Ag@SiO₂ NPs statistically reduced the SBS values (p<0.05) compared to the 1% group. The addition of 3% of Ag@SiO₂ NPs to the composites significantly reduced S. mutans biofilm formation, compared to group G2 (p<0.05).

Conclusion:

Composites incorporating 3% of Ag@SiO₂ NPs presented similar SBS values compared to the control group, and showed significant antimicrobial activity.

Streptococcus mutans adherence to conventional and self-ligating brackets: an in vitro study

INTRODUCTION

Although self-ligating brackets presumably provide better hygiene conditions, no consensus has been reached so far.

OBJECTIVE

Therefore, the objective of this study was to evaluate, in an in vitro experimental design, the adherence of Streptococcus mutans (SM) in self-ligating and conventional brackets of different manufacturers and ligature types.

METHODS

Four commercial brands of maxillary premolar metal brackets were tested (Abzil®; Morelli®; 3M Unitek®; and GAC®). Each one was subdivided into three groups, which varied according to the type of ligature and bracket model (metallic, elastic, and self-ligating), totalizing twelve groups, composed of six brackets each. Previously sterilized brackets were initially immersed in saliva for one hour, and subsequently washed and added in a bacterial suspension, maintained in aerobiosis for 72 hours. The adhered bacteria were then separated and quantified by colony forming units (CFU/mL) counting after 48 hours of growth. The groups were compared by Kruskal-Wallis and Dunn post-hoc tests (p< 0.05).

RESULTS

Regardless of the commercial brand, self-ligating brackets had significantly less CFU/mL. However, according to comparisons performed within each commercial brand, only Abzil® self-ligating brackets had significantly lower biofilm adhesion. Among all of the self-ligating models, GAC® brackets presented the highest bacterial adhesion rate.

CONCLUSIONS

Self-ligating brackets are likely to present lower rates of biofilm adhesion. Particularly, Abzil® and GAC® self-ligating brackets are less likely to accumulate biofilm. Although such results are derived from an in vitro study, practitioners might acknowledge findings concerning bacterial adhesion as one of the relevant features to be considered during bracket selection.

Orthodontically induced root resorption: A critical analysis of finite element studies' input and output

INTRODUCTION

Orthodontically induced inflammatory root resorption (OIIRR) constitutes an undesirable risk connected to orthodontic treatment. Finite element analysis (FEA) is a powerful tool to study the risk of OIIRR. However, its efficiency in predicting OIIRR depends on the insertion of the correct inputs and the selection of an output coherent with the clinical failure mechanism.

METHODS

By combining a systematic review with a 3-dimensional FEA, this article discusses which are the implications of using certain periodontal ligament (PDL) properties (linear and nonlinear models) and failure criteria. Six orthodontic loading regimes were simulated in a maxillary premolar: pure intrusion, buccal tipping, and their combination applied with either a light (25 cN) or a heavy (225 cN) force. Three stress parameters in the PDL were compared: von Mises stress, minimum principal stress_, and hydrostatic stress (σ_H).

RESULTS

The comparison between linear and nonlinear models showed notable differences in stress distribution patterns and magnitudes. For the nonlinear PDL, none of the light-force models reached the critical compressive hydrostatic stress of 4.7 kPa, whereas all the heavy-force models reached it. In addition, the regions of critical compressive σ_H matched with the regions with resorption craters in clinical studies. In linear models, the σ_H critical value of 4.7 kPa was reached even in the light-force scenario.

CONCLUSIONS

Only compressive hydrostatic stress in PDL satisfied the requirements to be used as an FEA indicator of OIIRR. However, the requirements were satisfied only when a nonlinear PDL model was considered.

Can maxilla and mandible bone quality explain differences in orthodontic mini-implant failures?

Purpose: This study aimed to compare the risk of orthodontic mini-implant (OMI) failure between maxilla and mandible. A critical analysis of finite-element studies was used to explain the contradiction of the greatest clinical success for OMIs placed in the maxilla, despite the higher quality bone of mandible. Materials and Methods: Four tridimensional FE models were built, simulating an OMI inserted in a low-dense maxilla, control maxilla, control mandible, and high-dense mandible. A horizontal force was applied to simulate an anterior retraction of 2 N (clinical scenario) and 10 N (overloading condition). The intra-bone OMI displacement and the major principal bone strains were used to evaluate the risk of failure due to insufficient primary stability or peri-implant bone resorption. Results: The OMI displacement was far below the 50–100 µm threshold, suggesting that the primary stability would be sufficient in all models. However, the maxilla was more prone to lose its stability due to overload conditions, especially in the low-dense condition, in which major principal bone strains surpassed the pathologic bone resorption threshold of 3000 µstrain. Conclusions: The differences in orthodontic mini-implant failures cannot be explained by maxilla and mandible bone quality in finite-element analysis that does not incorporate the residual stress due to OMI insertion.

Comparison of the Condyle Sagittal Position of Class I and Class II Division 2 in Orthodontic Patients

AIM

To compare the condyle sagittal position of class I and class II division 2 in orthodontic patients.

MATERIALS AND METHODS

Fifty orthodontic cases (30 females and 20 males; 12-31 years) from the records of an Orthodontic Graduate Program were collected. Such cases presented cone-beam computed tomography (CBCT) as part of their initial diagnostic examinations. The study sample constituted two groups, i.e. class I and class II division 2 groups. A previously calibrated examiner performed the measurements of the images, representing the distance between the condyle and the articular surface of the glenoid fossa, both anteriorly (anterior disk space-ADS) and posteriorly (posterior disk space-PDS). Descriptive statistics were performed. Data were normally distributed, and parametric tests were used. Paired sample test was used to identify differences between the right and the left joints. Differences between class I and class II/2 groups were tested using independent t test. All statistical tests were interpreted at 5% significance level.

RESULTS

When the study groups were compared in relation to the dimensions observed for the right and the left ADS and PDS, no significant differences were detected. This study also calculated the differences between right and left disk spaces within the groups, and the differences were not significant for both class I and class II/2 groups.

CONCLUSION

The results demonstrated, after the performance of a CBCT comparative analysis, that there is no significant difference between class II/2 and class I orthodontic patients in relation to the condyle sagittal position.

CLINICAL SIGNIFICANCE

The results collected here refute the expectation of spontaneous mandibular anterior repositioning after correcting the overbite in class II/2 patients.

In vitro evaluation of enamel surface roughness and morphology after orthodontic debonding: Traditional cleanup systems versus polymer bur

INTRODUCTION

The primary aim of this randomized in vitro study was to compare the effectiveness of carbide, fibreglass and polymer burs on resinous remnant removal after bracket debonding, by the evaluation of enamel surface roughness and morphology. The secondary objective was to compare the time dispended on the procedures.

METHODS

The buccal surfaces of 28 bovine incisors were analysed by a profilometer to initial roughness measurement (Ra-T1). Brackets were bonded with a light-cured resin and debonded with a debonding plier. The samples were randomly divided into four groups, according to the bur used (n=7): A-Tungsten carbide; B-Fibreglass; C-Polymer; D-Polymer with 75% ethanol pre-treatment. The second roughness measurements were made after resin removal (Ra-T2). Time for removal procedures was also recorded. The third measurements were made after polishing (Ra-T3). Scanning Electronic Microscopy was performed in two samples of each group: after resin removal and after polishing. Results of roughness and time measurements were statically analysed by analysis of variance with post-hoc Bonferroni.

RESULTS

After polishing, tungsten carbide (P=0.1555) and fibreglass burs provided final surface roughness statistically similar to the baseline condition (P=1.0000). Yet, polymer burs, associated (P<0.0001) or not to alcohol (P<0.0001), provided surface roughness significantly higher when compared to baseline values. Polymer burs were more time-consuming on resinous remnant removal than tungsten carbide and fibreglass burs (P<0.05).

CONCLUSION

Polymer burs were less effective and more time-consuming to remove the remaining resin than tungsten carbide and fibreglass burs. The polishing step created smoother surfaces regardless of the burs used for resin removal.

Barriers involved in the application of evidence-based dentistry principles: A systematic review

BACKGROUND

The authors' objective in this systematic review was to investigate the barriers involved in the application of evidence-based dentistry principles, as reported by dentists. The authors registered the protocol in the PROSPERO database.

TYPES OF STUDIES REVIEWED

Eligible studies included qualitative and quantitative approaches, constituting information about barriers, collected through interviews, questionnaires, or conversation sessions. The authors searched databases and reference lists of preselected studies. After the selection process, the authors evaluated the included studies for potential risk of bias and collected either qualitative or quantitative data.

RESULTS

After the selection process, the authors included 35 studies, of which 16 were reported in this article. The authors synthesized and classified the barriers in 4 categories: self-related, evidence-related, context-related, and patient-related barriers. Shortage of time and financial constraints were the barriers most frequently studied. However, the quantification of these barriers, as well as others, was not possible because of the variability of the results and methodological issues of the included studies.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The authors suggest the development of valid questionnaires and their use in representative samples to quantify the effects of specific barriers. The authors encourage practitioners to participate in educational programs focused on training in evidence-based dentistry abilities, in addition to seeking accessible and synthesized formats of reliable scientific knowledge.

A 12-Year Retrospective Study of Avulsion Cases in a Public Brazilian Dental Trauma Service

Abstract This study assessed the epidemiological characteristics and management of the permanent teeth avulsion cases attended in a Brazilian dental trauma service from December 2005 to August 2016. A retrospective study was conducted of case records of 93 patients involving 139 avulsed teeth. Data included sex, age, trauma etiology, location of the accident, number and position of avulsed teeth, and presence and type of associated traumatic lesions. Management of the avulsed teeth was addressed as: time elapsed until teeth were retrieved from the accident’s location; teeth’s cleaning method and storage media; time elapsed until seeking treatment and replantation. The majority of the patients were children from 6-10 (31.2%) and 11-15 years old (26.9%). Male patients were more affected than female. Bicycle accident was the main etiological factor (31.2%). In 56 (60.2%) cases, traumatic lesions to neighboring teeth were present. In 55 (59.1%) cases, lesions to adjacent soft tissues were reported. In 82 (88.2%) cases, patients requested treatment at the same day of the accident. Sixty-four teeth (46.0%) were immediately retrieved and 28 (20.1%) were not found. Forty-two teeth (30.2%) were kept dry. Only one tooth (0.7%) was immediately replanted at the accident’s site, while 51 teeth (36.7%) were not replanted. Numerous avulsed teeth were inappropriately managed and immediate replantation was not frequent. Public policies must be created to raise awareness towards the particularities of avulsion cases.

Efficiency of polymerization of bulk-fill composite resins: a systematic review

This systematic review assessed the literature to evaluate the efficiency of polymerization of bulk-fill composite resins at 4 mm restoration depth. PubMed, Cochrane, Scopus and Web of Science databases were searched with no restrictions on year, publication status, or article's language. Selection criteria included studies that evaluated bulk-fill composite resin when inserted in a minimum thickness of 4 mm, followed by curing according to the manufacturers' instructions; presented sound statistical data; and comparison with a control group and/or a reference measurement of quality of polymerization. The evidence level was evaluated by qualitative scoring system and classified as high-, moderate- and low- evidence level. A total of 534 articles were retrieved in the initial search. After the review process, only 10 full-text articles met the inclusion criteria. Most articles included (80%) were classified as high evidence level. Among several techniques, microhardness was the most frequently method performed by the studies included in this systematic review. Irrespective to the "in vitro" method performed, bulk fill RBCs were partially likely to fulfill the important requirement regarding properly curing in 4 mm of cavity depth measured by depth of cure and / or degree of conversion. In general, low viscosities BFCs performed better regarding polymerization efficiency compared to the high viscosities BFCs.

Influence of Resin Cements on Color Stability of Different Ceramic Systems

Abstract The purpose of this study was to evaluate color stability of two dental ceramics cemented with two resin cements, assessing the color difference (ΔE00) by the measurement of L*, a*, b*, c* and h* of transmittance. The combination of two ceramic system (feldspathic and lithium disilicate) and two resin cements - color A3 (RelyX ARC and Variolink II) resulted in 4 groups (n=5). Ten disks-shaped specimens were fabricated for each ceramic system (10x1.5 mm), etched with hydrofluoric acid (10%) and silanized prior to cementation. The color analysis was performed 24 h after cementation of the samples and after 6 months of storage in relative humidity by means of spectrophotometry. The ΔE00 values were analyzed statistically by two-way ANOVA followed by the Tukey test (p<0.05). One-way ANOVA were calculated for the means of individual color coordinates (L*, a*, b*, c* and h*). Two-way ANOVA showed that only the ceramic factor was significant (p=0.003), but there was no difference for the cement factor (p=0.275) nor for the ceramic/cement interaction (p=0.161). The feldspathic ceramic showed the highest values of ΔE00. Variations in L*, a*, b*, c* and h* were more significant for feldspathic ceramic. In conclusion, storage alters similarly the optical properties of the resin cements and feldspathic porcelain was more susceptible to cement color change after aging.

Effect of silane type and air-drying temperature on bonding fiber post to composite core and resin cement

This study evaluated the influence of silane type and temperature of silane application on push-out bond strength between fiberglass posts with composite resin core and resin cement. One hundred and sixty fiberglass posts (Exacto, Angelus) had the surface treated with hydrogen peroxide 24%. Posts were divided in 8 groups according to two study factors: air-drying temperature after silane application (room temperature and 60 ºC) and silane type: three pre-hydrolyzed--Silano (Angelus), Prosil (FGM), RelyX Ceramic Primer (3M ESPE) and one two-component silane--Silane Coupling Agent (Dentsply). The posts (n=10) for testing the bond strength between post and composite core were centered on a cylindrical plastic matrix and composite resin (Filtek Z250 XT, 3M ESPE) that was incrementally inserted and photoactivated. Eighty bovine incisor roots (n=10) were prepared for testing the bond strength between post and resin cement (RelyX U100, 3M ESPE) and received the fiberglass posts. Push-out test was used to measure the bond strength. Data were analyzed by two-way ANOVA followed by Tukey's test (α=0.05). ANOVA revealed that temperature and silane had no influence on bond strength between composite core and post. However, for bond strength between post and resin cement, the temperature increase resulted in a better performance for Silane Coupling Agent, Silano and RelyX Ceramic Primer. At room temperature Silane Coupling Agent showed the lowest bond strength. Effect of the warm air-drying is dependent on the silane composition. In conclusion, the use of silane is influenced by wettability of resinous materials and pre-hydrolyzed silanes are more stable compared with the two-bottle silane.

Effect of Surface Treatment of Fiberglass Posts on Bond Strength to Root Dentin

This study evaluated the influence of the surface treatments of fiberglass posts on bond strength to root dentin using push-out test. Forty bovine incisor roots were endodontically treated. The surface of the fiberglass posts (Exacto #2, Angelus) were treated using 4 different protocols (n=10): Control - 70% ethanol for 1 min; 37% phosphoric acid for 1 min; 10% hydrofluoric acid for 1 min; and 24% hydrogen peroxide for 1 min. After a silane coupling agent was applied for 1 min and all posts were cemented using self-adhesive resin cement (RelyX Unicem, 3M-ESPE). The roots were sectioned and two 1-mm-thick slices were obtained from each third: cervical, middle and apical. The specimens were subjected to the push-out test with a crosshead speed of 0.5 mm/min. Data were analyzed by repeated measures ANOVA followed by Tukey's HSD tests (=0.05). The surface treatment (p<0.001) and root third region (p=0.007) factors were significant. The retention to root canal was affected by surface treatment type. The post surface treatment with 24% hydrogen peroxide for 1 min yielded significantly higher bond strength when the fiberglass posts were cemented with RelyX Unicem.

Fracture resistance and mode of failure of various types of root filled teeth

AIM

To investigate ex vivo the influence of the post system on fracture resistance and failure mode of root filled incisor, canine, premolar and molar teeth.

METHODOLOGY

Eighty human teeth were divided into eight groups (n = 10) resulting from the interaction between the two study factors: post system (glass fibre post; cast Ni-Cr alloy post and core) and type of tooth (maxillary incisors, maxillary canines, maxillary premolars and mandibular molars). All roots were prepared with a 2-mm ferrule and restored with metal crown. Fracture resistance (N) was assessed in a mechanical testing device, and the data were analysed by two-way anova (4 × 2) followed by Tukey's test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. Failure mode data were analysed by two-factor anova and Student-Newman-Keuls (SNK) tests (α = 0.05). Correlation between fracture resistance and failure mode was analysed by linear regression.

RESULTS

Glass fibre and cast posts and cores had similar fracture resistance, regardless of the type of tooth. Canines and molars had significantly higher fracture resistance (P < 0.001) than premolars. Incisors teeth had significantly lower fracture resistance (P < 0.001) than premolars. The fracture mode for incisors, premolars and molars was more amenable to restoration when the teeth were restored with glass fibre posts. Fracture resistance had no correlation with fracture mode, regardless of the post system and type of tooth analysed.

CONCLUSIONS

Post system had no significant effect on fracture resistance, regardless of the type of tooth. The mode of fracture was more restorable with glass fibre posts.

Impact of rehabilitation with metal-ceramic restorations on oral health-related quality of life

Dental ceramics present excellent ability to reproduce the natural teeth regarding esthetic and biomechanics. Recently, due to the advancement of ceramic technology, metal-free restorations were developed. However, the traditional metal-ceramic restorations still present the requirements of high strength, long survival in the oral environment and favorable aesthetics. In this context, it is essential to know the specificity of each ceramic system available in order to apply it properly to various clinical situations. This report describes an integrated rehabilitation using metal-ceramic restorations of a patient at 50 years of age, who presented edentulous spaces, and previous unsatisfactory composite and amalgam restorations, and indirect metallic restorations, leading to compromised quality of life in both functional and psychosocial aspects. The impact on quality of life was measured using a generic instrument, OHIP-14, validated for the World Health Organization, which covers both the biological and the psychosocial dimensions. This instrument was applied to the patient before and after treatment. The patient had an overall OHIP-14 score of 28 before the treatment and after treatment the score decreased to 0, showing that dental and oral health conditions are factors that do impact on the quality of life. Rehabilitation has provided functional and aesthetic restorations, harmony of the stomatognathic system and improvement of life quality.