In vitro evaluation of shear bond strength and mode of failure of the interface between an indirect composite bonded to fiber-reinforced composite substructures.

PURPOSE: Failures of fixed partial dentures (FPDs) fabricated with fiber-reinforced composites (FRCs) have been attributed to veneering fractures. The aim of the present study was to investigate the shear bond strength and mode of failure between an indirect composite and FRC substructures. MATERIAL AND METHODS: SR Adoro indirect composite was bonded to the following substructures: (a) flat surface made of unidirectional glass fibers (group A), (b) retentive sticks made of unidirectional glass fibers (group B), (c) flat surface made of fiber net (group C), (d) retentive sticks made of fiber net (group D), (e) nickel-chromium dental alloy (control, group E). For every group, 13 specimens were fabricated. All specimens were hydrothermocycled (5000 cycles, 5°C/30 sec, and 55°C/30 sec). A bond test was performed in a testing machine at a 0.5 mm/min crosshead speed according to ISO 10477. The failure mode was determined by examination of the fractured surfaces under an optical microscope. Selected specimens were examined with scanning electron microscope and with energy dispersive spectroscopy for compositional determination. The morphology (flat-sticks) and the type (unidirectional-net) of fibers on the bond strength were estimated. RESULTS: The mean shear bond strength was significantly different between groups E and A (p= 0.044), and groups A and B (p= 0.010). All FRC specimens showed cohesive failure. Group E showed predominantly adhesive failure. The bond strength was higher when sticks or fiber nets were used. CONCLUSIONS: Fiber nets and retentive sticks increase the shear bond strength between FRCs and indirect composite. CLINICAL IMPLICATIONS: In FPDs, the morphology and type of FRC substructures might influence the shear bond strength between the FRC substructure and the indirect veneering composite. With the proper design of these substructures, the number of veneering fractures may be decreased.

Three-dimensional positional changes of teeth adjacent to posterior edentulous spaces in relation to age at time of tooth loss and elapsed time.

The purpose of this study was to study the stability of teeth adjacent to posterior edentulous spaces and correlate it with patient age and time lapse since tooth loss. Dental casts, panoramic radiographs, and questionnaires of patients treated in a University setting were employed. Teeth adjacent and opposing posterior edentulous spaces were examined for the following parameters: Supraeruption, rotation, space closure, and axial inclination. One hundred twenty three patients with 229 edentulous spaces were analyzed. Statistical analysis showed that the effects of "jaw", "gender", and "age group at the time of tooth loss" were not significant for any of the variables tested. The effect of time lapse since tooth loss was significant regarding the "amount of distal tooth inclination" (P<0.001), the "amount of distal tooth rotation" (P=0.004), and "space closure" (P=0.038). Post-hoc analysis of the "amount of distal tooth inclination" revealed a marked increase in inclination 5 years after tooth loss. Within the limitations of this study, it was concluded that in the group of patients studied, minor positional changes in teeth opposing or adjacent to posterior edentulous spaces had occurred. The greatest changes in position were recorded for mandibular teeth distal to edentulous spaces.

Colour stability of veneering composites after accelerated aging.

OBJECTIVES: To investigate the colour stability of four indirect composite restorative materials after accelerated aging. METHODS: Four indirect composites (Gradia, Signum+, HFO and Adoro) were used. For each material, six specimens were prepared and subjected to accelerated aging (Suntest CPS+, Atlas, Chicago, IL, USA) according to ISO 7491. A Dr. Lange Microcolor Data Station colorimeter (Braive Instruments, Liege, Belgium) was used to measure specimen colour before and after aging. Measurements were performed according to the CIE L*a*b* system, and the mean L*, a* and b* values for each material were calculated. The equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2](1/2) was used to measure the total colour change (DeltaE), where DeltaL*, Deltaa* and Deltab* are the differences in the respective values before and after aging. One-way ANOVA were used to determine statistically significant differences in DeltaL*, Deltaa*, Deltab* and DeltaE. RESULTS: No statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested (PDeltaL*=.063; PDeltaa*=.521; PDeltab*=.984 and PDeltaE=.408). After aging, Gradia specimens showed an increase in lightness (DeltaL*=0.36) and a green-yellow shift (Deltaa*=-1.18, Deltab*=0.6), while Signum+ specimens exhibited an increase in lightness (DeltaL*=0.5) and a green-blue shift (Deltaa*=-0.9, Deltab*=-0.45). HFO specimens exhibited an increase in lightness (DeltaL*=0.75) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.06), and Adoro specimens exhibited an increase in lightness (DeltaL*=2.07) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.68). CONCLUSIONS: Colour changes were found to be within accepted values of perceptibility and clinical acceptance after accelerated aging, and no statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested.

Association between self-reported bruxism activity and occurrence of dental attrition, abfraction, and occlusal pits on natural teeth.

STATEMENT OF PROBLEM: It is unclear whether subjects who report tooth clenching and/or grinding have more noticeable clinical signs of dental attrition, abfractions, and occlusal pits on their natural teeth than subjects who do not report bruxism activity. PURPOSE: The purpose of this study was to determine whether there was an association between self-reported (or not reported) bruxism activity and occurrence of dental attrition (anterior, posterior), abfractions, and occlusal pits on natural teeth. MATERIAL AND METHODS: One hundred and two volunteer adult Greek subjects (mean age 44.6 +/-5.7 years) were classified into 2 groups (50 self-reported bruxers and 52 nonbruxers) according to 2 inquires regarding grinding and/or clenching of their teeth. Dental attrition (anterior, posterior) was assessed by 2 calibrated experienced examiners on diagnostic casts on a tooth-by-tooth basis, using a previously well established ordinal scale. Abfraction lesions (V-shaped, in the cervical region) and occlusal pits were recorded if these clinical signs were found on at least 2 natural teeth. Statistical comparisons between the 2 groups relative to the distribution of the occurrence of the 4 clinical signs were performed by means of the exact version of the chi-square test. The Fisher's exact test was used for the comparison of percentages. The intra- and interexaminer reliability was assessed by means of the Cohen's kappa coefficient (alpha=.05). RESULTS: The results demonstrated that there was a significant association between self-reported bruxism and occurrence of the 4 clinical signs. Although the 2 groups were significantly different according to the distribution of the 4 clinical signs, the greatest differences occurred for the anterior and posterior attrition signs. CONCLUSIONS: In this study, the occurrence of 4 clinical signs (posterior or anterior dental attrition, abfractions, and occlusal pits) was associated with self-reported bruxers. It is suggested that, primarily, signs of dental attrition may differentiate self-reported bruxers from nonbruxer subjects.

Shear bond strength of a light-cured veneering composite to fiber-reinforced composite substrates.

PURPOSE: The aim of this study was to compare the shear bond strength of a veneering composite to 2 differently treated fiber-reinforced composite (FRC) substrates and to a base metal alloy. MATERIALS AND METHODS: A veneering composite (SR Adoro) was bonded to the following substrates: (1) a nickel-chromium base metal alloy (control, group A), (2) an FRC substructure (Vectris) with a flat surface (group B), and (3) an FRC substructure (Vectris) with retentive rods 0.5 x 0.5 mm in cross section and 10 mm in length, positioned parallel to each other at a distance of 0.5 mm (group C). Thirty-nine specimens were fabricated and divided into 3 groups of equal size. All specimens were thermocycled for 5,000 cycles at 5 degrees C and 55 degrees C with dwell time of 30 seconds in each bath. Evaluation of shear bond strength was performed at a constant crosshead speed of 0.5 mm/min according to ISO 10477. RESULTS: The mean values for the shear bond strength were 19.29 MPa for the control group (group A), 16.66 MPa for group B, and 16.74 MPa for group C. Despite a tendency to higher bond strength of group A specimens, no statistically significant difference was recorded between the groups (P > .05). CONCLUSIONS: No statistically significant difference was found between the metal and FRC substructures. Retentive rods on the FRO substructure do not seem to increase the bond strength significantly.

Evaluation of the relationship between subjects' perception and professional assessment of esthetic treatment needs.

PURPOSE: The purposes of the present study were to (1) evaluate the esthetic dental treatment need by means of two special questionnaires, (2) determine the reliability and the construct validity of the measurement scales derived from these questionnaires, and (3) investigate the relationship between Greek subjects' perception and a professional examiner's assessment regarding the esthetic treatment need. MATERIALS AND METHODS: Participants in this survey consisted of 132 subjects (48 males with mean age 39.0 +/- 14.5 years old, 84 females with mean age 41.7 +/- 14.5 years old) with natural teeth and fixed restorations. Subjects were asked to complete a special self-evaluation questionnaire consisting of 12 items. During the next stage, all participants were clinically examined by an experienced examiner and the data collected were used to fill out a second special professional assessment questionnaire consisting of 20 items. The forms structure used were in accordance with well-established indices used in orthodontics for assessing esthetic treatment need. RESULTS: The reliability of the multiple correspondence analysis (MCA) analysis-derived scales was very satisfactory (Cronbach's a coefficient: a =0.82) for the total scale of the self-evaluation measurement. For the professional assessment scale, the reliability of the total scale was almost perfect (a=0.92). The MCA revealed one reliable factorial construct for the self-evaluation measurement scale and two reliable constructs for the professional measurement scale. Pearson's correlation coefficient indicated a very low agreement between self-evaluation and professional measurement scales. CONCLUSION: The findings of this survey suggest that there was a relative disagreement between subjects' perception and professional assessment regarding the need for esthetic dental treatment. CLINICAL SIGNIFICANCE In the present survey, the agreement between subjects' perception and clinical assessment of esthetic dental treatment need was found to be very low, which highlighted the discrepancies between patients' and dentists' perceptions of esthetic needs.

Considerations for services from dental technicians in fabrication of fixed prostheses: A survey of commercial dental laboratories in Thessaloniki, Greece.

STATEMENT OF PROBLEM: Effective communication and cooperation between dentists and dental technicians are essential in providing quality services. There has been a lack of information regarding dentist-dental technician communications and current methods and materials used for the fabrication of fixed partial dentures (FPDs). PURPOSE: This cross-sectional study identified the materials and techniques used for fabrication of FPDs, as well as the status of communication between dentists and dental technicians in Thessaloniki, Greece. MATERIAL AND METHODS: A questionnaire was developed with 7 sections pertaining to procedures and materials used for the fabrication of fixed prostheses: general questions, infection control, impressions/interocclusal records, die technique/mounting, information from final casts, prostheses design/materials, and communication/shade selection. The questionnaire was anonymous and distributed by the Association of Dental Technicians of Thessaloniki to all member laboratories (228) in the wider province of Thessaloniki, Greece. Due to the absence of normal distribution of the results, frequencies and medians were reported. RESULTS: Ninety-six of 228 dental laboratories responded (42.1% response rate). Twenty-six percent of dental laboratories did not routinely disinfect incoming items. The dental technicians considered 30% of incoming final impressions and 20% of interocclusal registrations as inadequate. Half of the time (55%) final casts were mounted by technicians on simple hinge articulators. Only 20% of tooth preparations had adequate finish lines. The majority (70%) of fixed restorations were metal-ceramic. Fifty-seven percent of dental technicians considered the delivery time requested by dentists as insufficient. CONCLUSION: The information provided in this study indicates areas of weakness in communication between dentists and dental technicians, along with areas where both parties should use greater care during clinical and laboratory procedures.