The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns

Load-Bearing Capacity of Zirconia Crowns Screwed to Multi-Unit Abutments with and without a Titanium Base: An In Vitro Pilot Study

The static and dynamic load-bearing capacities and failure modes of zirconia crowns screwed to multi-unit abutments (MUAs) with and without a titanium base (T-base) were determined. Thirty-six monolithic zirconia crowns screwed to straight MUAs torqued to laboratory analogs (30 Ncm) were assigned to two groups (n = 18). In group A, the zirconia crowns were screwed directly to the MUAs; in group B, the zirconia crowns were cemented to the T-base and screwed to the MUAs. All specimens were aged in 100% humidity (37 °C) for one month and subjected to thermocycling (20,000 cycles). Afterwards, the specimens underwent static and dynamic loading tests following ISO 14801. The failure modes were evaluated by stereomicroscopy (20×). There was an unequivocally similar trend in the S-N plots of both specimen groups. The load at which the specimens survived 5,000,000 cycles was 250 N for both groups. Group A failed mainly within the metal, and zirconia failure occurred only at a high loading force. Group B exhibited failure within the metal mostly in conjunction with adhesive failure between the zirconia and T-base. Zirconia restoration screwed directly to an MUA is a viable option, but further studies with larger sample sizes are warranted

Primary Implant Stability Analysis of Different Dental Implant Connections and Designs—An In Vitro Comparative Study

Primary implant stability can be evaluated at the time of placement by measuring the insertion torque (IT). However, another method to monitor implant stability over time is resonance frequency analysis (RFA). Our aim was to examine the effect of bone type, implant design, and implant length on implant primary stability as measured by IT and two RFA devices (Osstell and Penguin) in an in vitro model. Ninety-six implants were inserted by a surgical motor in an artificial bone material, resembling soft and dense bone. Two different implant designs—conical connection (CC) and internal hex (IH), with lengths of 13 and 8 mm, were compared. The results indicate that the primary stability as measured by RFA and IT is significantly increased by the quality of bone (dense bone), and implant length and design, where the influence of dense bone is similar to that of CC design. Both the Osstell and Penguin devices recorded higher primary implant stability for long implants in dense bone, favoring the CC over the IH implant design. The CC implant design may compensate for the low stability expected in soft bone, and dense bone may compensate for short implant length if required by the anatomical bone conditions

Maximal Bite Force Measured via Digital Bite Force Transducer in Subjects with or without Dental Implants—A Pilot Study

The aims of the current study were as following: (1) to evaluate the maximal bite forces in patients with dental implants versus patients without dental implants, as measured by a digital bite force transducer (GM10); (2) to evaluate the influences of sex, age, and sleep/awake bruxism on the maximal bite forces of the two groups. Forty patients recruited to the study were divided into two groups: test group (“implant”) if they had one or more posterior restored implants and control group (“no-implant”) without the presence of posterior dental implants. A digital bite fork (GM10) was used to measure the bite forces from three posterior occluding pairs in all participants. Differences in the mean values between the test and control groups and between different sexes were evaluated using one-way and two-way ANOVA tests. A cross-tabulation analysis was conducted to identify a trend line between the groups. There was no significant difference in the maximal bite force between the test and control groups (p = 0.422), but the cross-tabulation analysis revealed a clear trend of a stronger representation of the “no-implant” group at higher occlusal forces. A significant difference was detected between the maximal biting forces of male and female subjects (p = 0.030 in the implant group, p = 0.010 in the no-implant group), regardless of the experimental group. The presence of bruxism and clenching did not influence the bite force values (p = 0.953), and a significant difference was not found between the age groups (p = 0.393). Within the limitations of this study, it may be assumed that there was no significant difference between the maximal bite forces between patients with and without dental implants but that there was a trend line implicating a stronger representation of the “no-implant” group at higher forces. In addition, the results revealed a significant sex-related difference in the maximal occlusal force. Further studies with larger sample sizes are warranted

The Retentive Strength of Laser-Sintered Cobalt-Chromium-Based Crowns after Pretreatment with a Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

The retention of laser-sintered cobalt-chromium (Co-Cr)-based crowns were examined after dentin pretreatment with desensitizing paste containing 8% arginine and calcium carbonate (DP-ACC). Forty lower first molars were prepared using a standardized protocol. The Co-Cr crowns were produced using selective laser melting. The teeth were either pretreated with the desensitizing paste or not pretreated. After one week, each group was cemented with glass ionomer cement (GIC) or zinc phosphate cement (ZPC). Surface areas of the teeth were measured before cementation. After aging, a universal testing machine was used to test the retentive strength of the cemented crown-tooth assemblies. The debonded surfaces of the teeth and crowns were examined at 2.7× magnification. Pretreating the dentin surfaces with the desensitizing paste before cementation with GIC or ZPC did not affect the retention of the Co-Cr crowns. The retention of the GIC group (6.04 ± 1.10 MPa) was significantly higher than that of the ZPC group (2.75 ± 1.25 MPa). The predominant failure mode for the ZPC and the nontreated GIC group was adhesive cement-dentin failure; for the treated GIC group, it was adhesive cement-crown failure. The desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Co-Cr crowns cemented with GIC or ZPC

An interventional study for improving the manual dexterity of dentistry students.

OBJECTIVES:Traditionally, the acquisition of manual skills in most dental schools worldwide is based on exercises on plastic teeth placed in a "phantom head simulator". No manual trainings are done at home. Studies revealed that preliminary training of one motoric task leads to significant improvement in performance of the required motoric task that has similar components. Performing tasks indirectly via a dental mirror are complicated for the young dental students. We hypothesized that instructed training of basic skills required in dentistry at home on a tool simulating the phantom laboratory will improve the capabilities of the students and will be reflected by their clinical grades. METHODS:We developed a portable tool PhantHome which is composed of jaws, gingival tissue, rubber cover and a compatible stand. Specific teeth produced by a 3D printer with drills in different directions were placed in both jaws. Students were requested to insert pins by using tweezers and dental mirror according to instructions initiating with easy tasks and continue to ones that are more complicated. 106 first clinical year dental students participated in the study; 65 trained only in the traditional phantom lab (control). 41 trained at home by the PhantHome tool two weeks before and 2 months during the initial stage of phantom lab. The students grades routinely provided in the phantom laboratory at different stages were compared. RESULTS:Students who trained with the portable tool performed better than the control group in the first direct and second indirect preparations (p<0.05). These exams were taken when the PhantHome was available to the students. Then, the tool was returned and the phantom course continued regularly. We believe that this is why no differences between the grades of the groups were observed further on. CONCLUSIONS:Training by the PhantHome improves motor skills and consequently the clinical performances

Survival and Success Rates of Monolithic Zirconia Restorations Supported by Teeth and Implants in Bruxer versus Non-Bruxer Patients: A Retrospective Study

The aim of this study was to assess retrospectively the survival and success rates of monolithic zirconia restorations supported by teeth and implants in bruxer versus non-bruxer patients. Methods: A total of 15 bruxer and 25 non-bruxer patients attended the recall appointment. The bruxer group (mean age of 61.2 ± 13.3 years and follow-up of 58.7 ± 16.8 months) were treated with 331 monolithic zirconia restorations, while the non-bruxer group, with a comparable mean age and follow-up time, were treated with 306 monolithic zirconia restorations. Clinical data were retrieved from the patients’ files. At the recall appointment, all supporting teeth and implants were examined for biological and technical complications, and the restorations were evaluated using modified California Dental Association (CDA) criteria. Data were statistically analyzed using survival analysis methods. A significance level of p p = 0.045) was observed in the bruxer group. With regard to biological complications, the only complications that exhibited a borderline, although not significant, difference were three fractured teeth exclusively in the bruxer group (p = 0.051), which were replaced with implant-supported restorations. Within the limitations of this study, we conclude that there were no significant differences in the overall survival and success rates of the monolithic zirconia restorations in bruxer versus non-bruxer patients, although veneered zirconia restorations and single tooth abutments exhibited a higher rate of complications in the bruxer group

Reliability and Correlation of Different Devices for the Evaluation of Primary Implant Stability: An In Vitro Study

Our aim was to analyze the correlation between the IT evaluated by a surgical motor and the primary implant stability (ISQ) measured by two RFA devices, Osstell and Penguin, in an in vitro model. This study examines the effect of bone type (soft or dense), implant length (13 mm or 8 mm), and implant design (CC: conical connection; IH: internal hexagon), on this correlation. Ninety-six implants were inserted using a surgical motor (IT) into two types of synthetic foam blocks. Initial measurements for both the peak IT and ISQ were recorded at the point when implant insertion was stopped by the surgical motor, and the final measurements were recorded when the implant was completely inserted into the synthetic blocks using only the RFA devices. Our null hypothesis was that there is a good correlation between the devices, independent of the implant length, design, or bone type. We found a positive, significant correlation between the IT, and the Osstell and Penguin devices. Implant length and bone type did not affect this correlation. The correlation between the devices in the CC design was maintained; however, in the IH design it was maintained only between the RFA devices. We concluded that there is a high positive correlation between the IT and ISQ from a mechanical perspective, which was not affected by bone type or implant length but was affected by the implant design

Effect of Silica-Modified Aluminum Oxide Abrasion on Adhesion to Dentin, Using Total-Etch and Self-Etch Systems

This study compared the shear bond strength (SBS) and micromorphology of composite resin to human dentin after pre-treatment with silica-modified aluminum oxide air abrasion. Forty-six molar teeth were treated with either Scotchbond Multi-Purpose (SCMP) or Clearfil SE Bond (CLSE) adhesive. Buccal surfaces were pre-treated with the CoJet air abrasion system (SB), and lingual surfaces were controls. The adhesion of light-cured resin composite to the treated dentin surface was evaluated with SBS. After debonding, substrate surfaces were examined with an optical microscope for failure analysis. In addition, 15 molar teeth were sectioned and randomly assigned to one of five groups, according to the dentin surface pre-treatment and adhesive type, and examined with high-vacuum scanning electron microscopy/energy dispersive X-rays (SEM/EDS). The type of adhesive had a significant effect on SBS (p = 0.000); CLSE had the highest values. SB did not affect SBS (p = 0.090). SEM/EDS revealed residual aluminum and/or silicon on all dentin surfaces after SB, except for the control. Treatment with 32% phosphoric acid in the SCMP adhesive decreased the amounts of aluminum and silicon compared to SB dentin only, whereas CLSE resulted in similar quantities of aluminum and silicon as air-abraded dentin. The results of this study indicate that CLSE might have a higher bond strength to dentin than SCMP. Pre-treatment with SB does not appear to affect bonding strength

Retrospective 1- to 8-Year Follow-Up Study of Complete Oral Rehabilitation Using Monolithic Zirconia Restorations with Increased Vertical Dimension of Occlusion in Patients with Bruxism

Aim: The aim of this paper is to perform a retrospective assessment of the clinical performance of the complete oral rehabilitation of patients with bruxism treated with implants and teeth-supported veneered and non-veneered monolithic zirconia restorations with increased occlusal vertical dimension. Methods: In this retrospective follow-up study, 16 bruxer patients, mean age 59.5 &plusmn; 14.9 years, were treated with 152 veneered and 229 non-veneered monolithic zirconia and followed for a mean of 58.8 &plusmn; 18.8 months (range 1&ndash;8 years). The patients were examined clinically and radiographically, annually. Clinical data were extracted from the medical records. In the recall appointments, modified California Dental Association (CDA) criteria were used to evaluate the restorations. Implant and restoration survival and success rates were recorded and analyzed. Results: The cumulative survival rates of implants and restorations were 97.7% and 97.6%, respectively. Nine restorations were replaced: three due to horizontal tooth fractures, two because of implant failure and four had secondary caries. A total of 43 biologic and technical complications were recorded. In the veneered group, the predominant complication was minor veneer chipping (16.4%), which required polishing only (grade 1). In the non-veneered group, the main complication was open proximal contacts between the implant restorations and adjacent teeth (14.5%). Conclusions: The survival rates of restorations and implants in patients with bruxism are excellent, even though veneered zirconia restoration exhibited a high rate of minor veneer chipping, which required polishing only. The biologic complication of fractured single-tooth abutment may occur