Effect of Serrating Abutment-Implant Mating Surface on Torque Stability of Implant-Abutment Connection, Before and After Cyclic Loading.

This study evaluated the effect of adding serration to the abutment-implant connection on torque maintenance before and after loading. Two implant systems with the same dimensions and connection design (internal 8° Morse taper octagon) were selected: one with nonserrated abutments (Simple line II) and the other one with serrated abutments (F & B). The removal torque value (RTV) was measured in 2 groups for each system: one group with one-piece abutments and the other group with 2-piece abutments, before and after cyclic loading (n = 10 in each group). The initial RTV of the abutment screw was measured with a digital torque meter. Each abutment received a cement-retained metal crown with 30° occlusal surface. Cyclic axial peak load of 75 ± 5 N was applied to the implants for 500 000 cycles at 1 Hz. The post-load RTV was then measured. Two-way and repeated-measures analysis of variance (ANOVA), and independent t test were applied to assess the effects of cyclic loading, connection design, abutment type, and their interaction on the percentage of torque loss (α = .05). Two-way ANOVA showed that serration of mating surfaces had a significant effect on torque maintenance before (P < .001) and after (P = .004) cyclic loading. Repeated-measures ANOVA also showed that loading had a significant effect on the torque loss percentage (P < .01). Comparison of the groups with t test showed that the torque loss of the serrated groups was lower than that of non- serrated groups. Despite the limitations of this study, the stability of the implant-abutment connection in the serrated design was higher than that of non-serrated group.

Debonding Time and Dental Pulp Temperature With the Er, Cr: YSGG Laser for Debonding Feldespathic and Lithium Disilicate Veneers.

Introduction: The removal of ceramic veneers is a time-consuming procedure in a dental office. Little research has been done in alternative removal techniques for ceramic veneers. The objective of this study was to evaluate the removal of feldspathic and lithium disilicate reinforced glass ceramic veneers by Er, Cr: YSGG and to measure debonding time and pulpal temperature increase during veneer removal. Methods: Fifty-seven bovine incisor teeth were prepared and divided into 3 groups. Ceramic specimens with a thickness of 0.7mm, a width of 4mm and a length of 8 mm were fabricated from feldspathic ceramic, lithium disilicate reinforced glass ceramic HT (high translucency) and lithium disilicate reinforced glass ceramic MO (medium opacity) (19 for each group). Specimens were cemented on the labial surface of incisors using resin cement. The Er, Cr: YSGG laser was applied to each specimen at 2.5 W and 25 Hz. Debonding time was measured for each specimen, and the intrapulpal temperature was detected in 3 specimens for each group. Data were analyzed via one-way analysis of variance (ANOVA) at significance level of 0.05 (α = 0.05). Results: Mean debonding time was 103.68 (26.76), 106.58 (47.22) and 103.84 (32.90) seconds for feldspathic, lithium disilicate MO, and lithium disilicate HT respectively. There was no significant statistical difference among the groups (P value = 0.96). The intrapulpal temperature increase was less than 1°C in all groups. Conclusion: Er, Cr: YSGG can successfully be used to efficiently debond feldspathic and lithium disilicate reinforced glass ceramic veneers. There was no significant difference for debonding time among these ceramic materials. During ceramic laminate veneer removal by laser irradiation, no irritating temperature rise was detected.

Comparing short dental implant and standard dental implant in terms of marginal bone level changes: A systematic review and meta-analysis of randomized controlled trials.

PURPOSE: To compare short implants (SH; 4-8 mm) to standard implants (ST; longer than 8 mm) in edentulous jaws, evaluating pri-implant marginal bone levels (MBLs) changes, implant failures (IFs), complications, and prosthesis failures (PFs). MATERIALS AND METHODS: Electronic searches were conducted through the PubMed, Web of Science, EMBASE, Scopus, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov to locate all randomized controlled trials (RCTs) comparing SH to ST. Meta-analysis procedures were performed on the weighted mean difference (WMD) and standardized mean difference (SMD) of MBLs using Stata. RESULTS: Twenty-three articles were included in this review. The WMD of MBLs when comparing SH to ST in both jaws up to 1-year follow-up was statistically significant preferring SH (WMD: -0.09 [CI: -0.12, -0.06], I2 : 67.0%). The efficacy of SH vs ST on SMD of MBLs was moderate (SMD: -0.43 [CI: -0.57, -0.28], I2 : 55.7%). There were no significant differences in IF (RR: 0.75 [0.44,1.27]) and PF (RR: 0.58 (0.22,1.581), and significantly higher biological complications (RR: 0.25 [0.15, 0.40]) for SH was observed compared to the ST in both jaws up to 1-year follow-up. CONCLUSIONS: SH and ST implants showed the comparable outcomes except biological complication preferring SH. Future systematic review and meta-analysis with longer and larger RCTs are required to confirm the present outcomes.

Comparing 4-mm dental implants to longer implants placed in augmented bones in the atrophic posterior mandibles: One-year results of a randomized controlled trial.

BACKGROUND: Short implants have been proposed as an alternative for the rehabilitation of atrophic edentulous areas. PURPOSE: To evaluate the efficacy of 4-mm implants vs longer implants in the atrophic posterior mandibles. MATERIALS AND METHODS: Eleven patients with bilateral atrophic mandibles were rehabilitated with two to four 4-mm implants and 10 or 8-mm long implants in augmented bone using Guided Bone Regeneration procedure. One side of the mandibles was randomly allocated to vertical augmentation with mixed autogenous bone and allograft. Implants were placed in both sides of the mandible after 6 months, and loaded after another 2 months. Subsequently, implant and prosthesis failures, marginal bone levels changes, and any complication were evaluated after 1-year follow-up. RESULTS: In this study, one patient dropped out and no failures occurred. However, 4-mm implants loss of 0.30 ± 0.34 mm peri-implant marginal bone and long implants loss of 0.47 ± 0.54 mm marginal bone were observed after 1-year of follow-up. The difference between the two groups was not statistically significant (difference = -0.16 ± 0.68 mm; P = 0.46). Eight complications occurred in five augmented sites of the patients, and no complication was found to occur in the short implants sites. CONCLUSIONS: One-year after loading, 4-mm implants had similar outcomes as long implants in augmented bone. Therefore, short implants might be a feasible treatment in atrophic mandibles.

Inhibitory Effects of Antimicrobial Photodynamic Therapy with Curcumin on Biofilm-Associated Gene Expression Profile of Aggregatibacter actinomycetemcomitans.

OBJECTIVES: Periodontitis is an inflammation of periodontal tissues that is caused by the biofilm of periodontal pathogens. Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is an opportunistic periodontopathogen that can be the cause of periodontal diseases via fimbriae as a virulence factor. In this study, we aimed to determine the expression level of A. actinomycetemcomitans rcpA gene as a virulence factor associated with biofilm formation after antimicrobial photodynamic therapy (aPDT) as a relatively new therapeutic modality. MATERIALS AND METHODS: To determine sub-lethal doses of aPDT against A. actinomycetemcomitans ATCC 33384 strain, we used curcumin (CUR) as a photosensitizer at a final concentration of 40 µmol/ml, which was excited with a light-emitting diode (LED) at the wavelength of 450 nm. Quantitative real-time polymerase chain reaction (qRT-PCR) was then applied to monitor rcpA gene expression in A. actinomycetemcomitans. RESULTS: 10-40 µmol/ml of CUR caused a significant reduction in the growth of A. actinomycetemcomitans compared to control group (P<0.05). Also, the cell viability of A. actinomycetemcomitans was significantly decreased after more than four minutes of LED irradiation. Therefore, the sub-lethal dose of aPDT against A. actinomycetemcomitans was 5 µmol/ml of CUR with three minutes of LED irradiation at a fluency of 180-240 J/cm2, which reduced the expression of the rcpA gene by approximately 8.5-fold. CONCLUSIONS: aPDT with CUR leads to decreased cell survival and virulence of A. actinomycetemcomitans. Thus, CUR-aPDT can be used as an alternative approach for the successful treatment of periodontitis in vivo.

Comparison of Short and Standard Implants in the Posterior Mandible: A 3D Analysis Using Finite Element Method.

OBJECTIVES: This study aimed to analyze functional stresses around short and long implant-supported prostheses with different crown heights. MATERIALS AND METHODS: Four three-dimensional (3D) models were designed with SolidWorks 2015. In models 1 (control) and 2, three dental implants (second premolar 4.1×8 mm, molars: 4.8×8 mm) were placed. In models 3 and 4, three dental implants (second premolar 4.1×4 mm, molars: 4.8×4) were placed. Residual bone height was 10 mm in groups 1 and 2 (grafted bone) models and 6 mm in groups 3 and 4. The crown heights were modeled at 11.5 mm for groups 1 to 3, and 15 mm for group 4. The applied oblique force was 220 N to simulate chewing movements. The maximum von Mises and principal stresses on the implants and the supporting tissues were compared using the 3D finite element method. RESULTS: In all models, the highest stress value was seen within the most coronal part of bone (crestal bone), which was cortical or grafted bone. The highest stress values in the bone supporting the implant neck were seen in the premolar region of each model, especially in model 4 (291.16 MPa). The lowest stress values were demonstrated in the molar region of model 3 (48.066 MPa). The model 2 implants showed the highest von Mises stress concentrated at their neck (424.44 MPa). CONCLUSIONS: In atrophic posterior mandible with increased crown height space, short implants with wider diameter seem to be a more feasible approach compared to grafting methods.

Effect of Various Laser Wavelengths on Temperature Changes During Periimplantitis Treatment: An in vitro Study.

PURPOSE: This study aimed to investigate and compare temperature change during implant decontamination with different laser types (carbon dioxide [Co2]/diode/neodymium-doped yttrium aluminum garnet [Nd:YAG]/erbium-doped yttrium aluminum garnet [Er:YAG]/antimicrobial photodynamic therapy [aPDT]). MATERIAL AND METHODS: Sixty implants were inserted into a bone block cut from a sheep's mandible. A 3 × 8 mm vertical lesion was made at the buccal of each implant. The bone block was placed into a 37°C water bath to simulate the in vivo oral condition. A K-type thermocouple was placed in contact with the implant to register temperature changes at 3 points (apical/middle/coronal). RESULTS: In the entire laser irradiations, the mean of temperature changes remains below 10°C. The apical temperature rise was higher than the coronal and middle regions (P < 0.05), and the apical temperature took longer time to reach the initial temperature (37°C) (P < 0.001). Temperature changes over 10°C occurred at the apical point of the implants with the Co2, Nd:YAG, and diode laser irradiations; however, only the Co2 laser reached the statistical significance in this regard (P < 0.05). CONCLUSION: Our findings indicate the promising results of Er:YAG laser and aPDT in implant decontamination. Precaution should be taken in the application of Nd:YAG, diode, and especially Co2 lasers.

Comparing Short Dental Implants to Standard Dental Implants: Protocol for a Systematic Review.

BACKGROUND: Short dental implants have been proposed as a simpler, cheaper, and faster alternative for the rehabilitation of atrophic edentulous areas to avoid the disadvantages of surgical techniques for increasing bone volume. OBJECTIVE: This review will compare short implants (4 to 8 mm) to standard implants (larger than 8 mm) in edentulous jaws, evaluating on the basis of marginal bone loss (MBL), survival rate, complications, and prosthesis failure. METHODS: We will electronically search for randomized controlled trials comparing short dental implants to standard dental implants in the following databases: PubMed, Web of Science, EMBASE, Scopus, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov with English language restrictions. We will manually search the reference lists of relevant reviews and the included articles in this review. The following journals will also be searched: European Journal of Oral Implantology, Clinical Oral Implants Research, and Clinical Implant Dentistry and Related Research. Two reviewers will independently perform the study selection, data extraction and quality assessment (using the Cochrane Collaboration tool) of included studies. All meta-analysis procedures including appropriate effect size combination, sub-group analysis, meta-regression, assessing publication or reporting bias will be performed using Stata (Statacorp, TEXAS) version 12.1. RESULTS: Short implant effectiveness will be assessed using the mean difference of MBL in terms of weighted mean difference (WMD) and standardized mean difference (SMD) using Cohen's method. The combined effect size measures in addition to the related 95% confidence intervals will be estimated by a fixed effect model. The heterogeneity of the related effect size will be assessed using a Q Cochrane test and I2 measure. The MBL will be presented by a standardized mean difference with a 95% confidence interval. The survival rate of implants, prostheses failures, and complications will be reported using a risk ratio at 95% confidence interval (P<.05). CONCLUSIONS: The present protocol illustrates an appropriate method to perform the systematic review and ensures transparency for the completed review. The results will be published in a peer-reviewed journal and social networks. In addition, an ethics approval is not considered necessary. TRIAL REGISTRATION: PROSPERO registration number: CRD42016048363; https://www.crd.york.ac.uk/PROSPERO/ display_record.asp?ID=CRD42016048363 (Archived by WebCite at http://www.webcitation.org/6wZ7Fntry).

Evaluation of the Effect of Different Laser Activated Bleaching Methods on Enamel Susceptibility to Caries; An In Vitro Mode.

Introduction: Today, bleaching is a routine noninvasive alternative for treatment of discolored teeth. The aim of this study was to determine whether conventional or laser activated bleaching predispose teeth to develop caries or not. Methods: Sixty human molars were mounted on acrylic cylinders and their Knoop microhardness (KHN) as well as DIAGNOdent (DD) values were recorded. They were divided into 4 experimental groups; G1) conventional bleaching with 40% hydrogen peroxide gel, G2) Diode laser assisted bleaching with same gel, G3) Nd:YAG laser assisted bleaching with the same gel, G4) control group. After bleaching, all samples were subjected to a three day pH cycling regimen and then, KHN and DD values were measured. Results: All groups had significant reduction in KHN values. It seems that there is no statistically meaningful difference between changes in enamel microhardness of the sample groups and all groups have changed in a similar amount. Reduction of DD scores were significant in Diode laser and conventional groups, however changes in Nd:YAG laser and control groups were not significant. Changes in DD values have followed a similar pattern among groups, except in G1- G4 and G2-G4 couples. Conventional and diode laser groups had a meaningful difference in reduction of DD values in comparison with the control group. Conclusion: It can be concluded that bleaching whether conventional or laser activated, does not make teeth vulnerable to develop carious lesions.

Analysis of gene expression of basic fibroblast growth factor (bFGF) following photodynamic therapy in human gingival fibroblasts.

BACKGROUND: Periodontal diseases are pathological inflammatory conditions of multifactorial etiology that develops in response to periodontopathic bacteria. Recently, photodynamic therapy (PDT) has begun to be incorporated as an adjuvant treatment for periodontal diseases. However, the effect of PDT on tissue regeneration is not yet completely clear. This study aimed to analyze the gene expression of basic fibroblast growth factor (bFGF) following PDT in human gingival fibroblasts (HuGu) cells in vitro. MATERIALS AND METHODS: HuGu cells were treated in different groups: 1) ICG (Indocyanine green) alone, 2) Diode laser irradiation alone, 3) PDT (combined ICG with diode laser) and 4) Control (untreated cells). The expression of bFGF gene was evaluated by real-time quantitative reverse transcription PCR (qRT-PCR) in different groups. RESULTS: ICG-PDT treatment using 1000-2000µg/mL of ICG at fluency of 31.25J/cm2 displayed a significant dose-dependent increase in expression levels of the bFGF (all P<0.05). The expressions of bFGF were upregulated to 4.13-fold following diode laser irradiation alone with a fluency of 31.25J/cm2 (P<0.05) while there was no remarkable difference in expression of bFGF following ICG treatment at concentrations of 500-2000µg/mL (all P>0.05). CONCLUSION: Our results suggest PDT is effective in increasing the expression of bFGF gene, an important factor in periodontal tissue regeneration and could indicate periodontal tissue regeneration.

Monitoring gene expression of rcpA from Aggregatibacter actinomycetemcomitans versus antimicrobial photodynamic therapy by relative quantitative real-time PCR.

BACKGROUND: Aggregatibacter actinomycetemcomitans is an important pathogen that is frequently found in various infections, particularly aggressive periodontitis. In this study, we described the outcome of the expression level of A. actinomycetemcomitans virulence factor following treatment by antimicrobial photodynamic therapy (aPDT) with indocyanine green (ICG) as a photosensitizing agent. MATERIALS AND METHODS: To determine the aPDT effect on the cell-surviving assay and expression ratio of the rcpA gene in A. actinomycetemcomitans by a colony-forming unit and relative quantitative (q) real-time PCR (qRT-PCR) assays, respectively, the proper dosing of sub-lethal aPDT was specified. RESULTS: The results of the current study showed that ICG-mediated aPDT, using 250-1000µg/mL, showed a significant reduction in A. actinomycetemcomitans growth when compared to the control group (P<0.05). Also, a sub-lethal dose of aPDT against A. actinomycetemcomitans was 125µg/mL ICG, with a 30s diode laser irradiation time at fluency of 15.6J/cm2 that could reduce the expression of rcpA gene approximately 6-fold. DISCUSSION: aPDT with ICG could reduce the cell survival and the virulence agent of A. actinomycetemcomitans. Thus, use of the appropriate aPDT dosage can be used for the successful treatment of periodontitis in vivo.

Real-time quantitative reverse transcription-PCR analysis of expression stability of Aggregatibacter actinomycetemcomitans fimbria-associated gene in response to photodynamic therapy.

BACKGROUND: Aggregatibacter actinomycetemcomitans is an etiological agent of both chronic and aggressive periodontitis. Dissemination of A. actinomycetemcomitans from the oral cavity and initiation of systemic infections has led to new approaches for treatment being needed. In this study, a series of experiments presented investigated the effect of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) on cell viability and expression of fimbria-associated gene (rcpA) in A. actinomycetemcomitans. MATERIALS AND METHODS: To determine the dose-depended effects of aPDT, A. actinomycetemcomitans ATCC 33384 strain photosensitized with MB was irradiated with diode laser following bacterial viability measurements. Cell-surviving assay and expression ratio of rcpA were assessed by colony forming unit and real-time quantitative reverse transcription-PCR (qRT-PCR) assays, respectively. RESULTS: In the current study, MB-mediated aPDT using 100µg/mL showed significant reduction in A. actinomycetemcomitans growth when compared to the control (P<0.05). Sub-lethal dose of aPDT against A. actinomycetemcomitans was 25µg/mL MB at fluency of 93.75J/cm2. Sub-lethal dose of aPDT could lead to about four-fold suppression of expression of rcpA. CONCLUSION: High doses of MB-mediated aPDT could potentially exhibit antimicrobial activity, and the expression of rcpA as an important virulence factor of this strain is reduced in cells surviving aPDT with MB. So, aPDT can be a valuable tool for the treatment of A. actinomycetemcomitans infections.

Effect of Splinting on Dimensional Accuracy of Impressions Made of Implants with Different Subgingival Alignments.

PURPOSE: Placement of implants at deeper levels of gingiva is sometimes inevitable because of issues like esthetics or bone availability. The accuracy of impressions may be affected in these situations. The aim of this in vitro study was to evaluate the effects of splinting and length of impression copings on the accuracy of impressions made of deeply placed implants. MATERIALS AND METHODS: A metal model with two parallel implants (Implantium; Dentium) was fabricated. One hundred and twenty impressions were made using the direct impression technique with and without splinting the impression copings (using short and long impression copings). Impressions were made of implants at three subgingival levels (1, 3, and 6 mm) using regular viscosity poly(vinyl siloxane). The impressions were poured with type IV dental stone. Displacements in the x, y, and z axes, as well as rotational discrepancies and interimplant distances were measured with a coordinate measuring machine. Data were analyzed with Kruskal-Wallis, Mann-Whitney, and nonparametric adjusted rank transform tests. RESULTS: There was less rotational displacement using longer impression copings at different subgingival positions of the implants, either with splinted or nonsplinted direct technique (p < 0.05). Also, the nonsplinted technique produced more accurate impressions at different apico-coronal levels of implants than the splinted technique using short impression copings (p < 0.05). CONCLUSIONS: According to the findings of this study, longer impression copings yielded better results than shorter ones in both splinted and nonsplinted techniques. Also, nonsplinted short impression copings produced more accurate impressions than splinted short impression copings.

Surface Treatment by Different Parameters of Erbium:Yttrium-Aluminum-Garnet (Er:YAG) Laser: Scanning Electron Microscope (SEM) Evaluation.

INTRODUCTION: This study aimed to assess the Scanning Electron Microscope (SEM) analysis of tooth surface irradiated by erbium:yttrium-aluminum-garnet (Er:YAG) laser with various parameters. METHODS: Number of 25 extracted human third molars free of caries were used in this study. The teeth were put into 5 groups for laser irradiation as follows: group 1 (power: 0.5 W, Energy: 50 mJ); group 2 (power: 1 W, Energy: 100 mJ); group 3 (power: 1.5 W, Energy: 150 mJ); group 4 (power: 2 W, Energy: 200 mJ); group 5 (power: 2.5 W, Energy: 250 mJ). All samples were prepared by repetition rate of 10 Hz and duration of 230 µs, using a non-contact handpiece at a distance of 4 mm. Then, the samples were prepared for SEM examination. RESULTS: SEM evaluation of every 25 samples, treated by Er:YAG, showed that all groups had exposed dentinal tubules without any melted area or cracks. CONCLUSION: In this study we used SEM to investigate ablated dentine with different parameters of Er:YAG laser energy. Our findings support these conclusions. All powers of laser below 3 W are proper for ablation, and make no cracks.

Antimicrobial photodynamic therapy using diode laser activated indocyanine green as an adjunct in the treatment of chronic periodontitis: A randomized clinical trial.

INTRODUCTION: Clinical studies have shown the usefulness of antimicrobial photodynamic therapy (aPDT) as an adjunctive in periodontal therapy. These studies did not utilize indocyanine green (ICG) as a recently introduced photosensitizer. The aim of this study was to perform a full-mouth double-blind randomized controlled clinical study to test the efficacy of adjunctive aPDT with ICG compared with scaling and root planing (SRP) alone in chronic periodontitis treatment. MATERIALS AND METHODS: Fifty patients were selected for this study. All patients received SRP. Then, each patient was randomly assigned to either the test group (aPDT+SRP) or the control group (SRP). aPDT was performed with a diode laser (wavelength: 810nm, power: 200mW) and ICG as photosensitizer. The adjunctive procedure was repeated after 7, 17 and 27 days. The clinical parameters including bleeding on probing (BOP), clinical attachment loss (CAL), plaque index (PI), probing pocket depth (PPD), full mouth plaque score (FMPS) and full mouth bleeding score (FMBS) were measured at baseline and after 1 and 3 months. RESULTS: There were no significant differences between two groups at baseline. BOP, PPD and FMBS showed significant improvements in the test group (P≤0.001). In terms of PI, FMPS and CAL, no significant differences were observed between both groups (P≥0.05). CONCLUSION: aPDT as an adjunctive approach yielded complete resolution of inflammation and significant reduction in periodontal pocket depth. However, aPDT had no additional advantages in clinical attachment gain and plaque score.

In vitro and ex vivo antimicrobial efficacy of nano-MgO in the elimination of endodontic pathogens.

OBJECTIVES: The use of metal oxide nanoparticles has attracted lots of attention, mostly because of their promising antimicrobial activity along with their biocompatibility with mammalian cells. This study aims to investigate the in vitro and ex vivo antimicrobial efficiency of nano-magnesium oxide (MgO) aqueous solution against endodontic pathogens. MATERIALS AND METHODS: The cytotoxicity of different concentrations of nano-MgO was assessed using lactate dehydrogenase cytotoxicity assay (LDH assay). A comparison of the antimicrobial efficiency of several concentrations of nano-MgO solution, sodium hypochlorite (NaOCl), and chlorhexidine (CHX) gluconate against Staphylococcus aureus, Enterococcus faecalis, and Candida albicans was made using the direct contact method. An ex vivo model of decoronated and experimentally infected human teeth was employed to compare the efficiency of nano-MgO (5 mg/L) solution with NaOCl (5.25 %) in the elimination of E. faecalis. RESULTS: There was no statistically significant difference between nano-MgO solutions (10 and 5 mg/L), 5.25 % NaOCl, and 2 % CHX gluconate in terms of the required time to inhibit the growth of the tested pathogens (p > 0.05). The LDH assay showed no cytotoxicity of different concentrations of nano-MgO used in this study (p < 0.001). In the ex vivo model of infected human teeth, 6 h post-irrigation, there was no statistically significant difference between colony-forming units (CFU) per milliliter of nano-MgO (5 mg/L) and NaOCl (5.25 %)-treated teeth (5-6 log scale reduction). However, the nano-MgO group showed a significant decrease in colony-forming units per milliliter (7 log scale), 24 h post-irrigation (p < 0.05). At other tested time points-24, 48, 72, and 168 h-the levels of CFU per milliliter were significantly less in the nano-MgO group (2-3 log scale difference) compared to the NaOCl group, indicating long-term antibacterial activity of nano-MgO (p < 0.05). At 72 and 168 h post-irrigation, no detectable bacterial growth was observed in the nano-MgO group. The detection limit was 10 CFU/mL. CONCLUSIONS: Nano-MgO aqueous solutions represent promising antimicrobial activities, both in vitro and ex vivo with minimal toxicity. CLINICAL RELEVANCE: Compared to NaOCl (5.25 %), nano-MgO (5 mg/L) exhibits statistically significant long-term efficiency in the elimination of E. faecalis in the root canal system. After further investigations, nano-MgO could be considered as a new root canal irrigant.

An in vivo comparison of two diagnostic methods in secondary caries detection.

OBJECTIVE: The aim of this study was to compare the level of agreement between four operators with different levels of experience for two methods of detecting secondary enamel and dentin carious lesions in composite restored teeth. MATERIALS AND METHODS: Sixty teeth of 40 patients with with secondary carious lesions in the composite resin were selected. The teeth were examined by two methods; visual inspection and a laser fluorescence device (DIAGNO dent pen 2190) by four operators including an undergraduate student, a dentist with 5 years of clinical experience, a general dentist with 12 years of clinical experience and an oral and maxillofacial radiologist. Cohen's kappa statistic was applied in order to assess the agreement between the diagnoses performed by the four operators with each diagnostic method. RESULTS: The diagnosis performed by different operators achieved an excellent agreement with high ICC. CONCLUSION: DIAGNOdent can be a useful device for secondary caries detection in posterior teeth as an adjunct to visual examination.

Implant Surface Temperature Changes during Er:YAG Laser Irradiation with Different Cooling Systems.

OBJECTIVE: Peri-implantitis is one of the most common reasons for implant failure. Decontamination of infected implant surfaces can be achieved effectively by laser irradiation; although the associated thermal rise may cause irreversible bone damage and lead to implant loss. Temperature increments of over 10ºC during laser application may suffice for irreversible bone damage. PURPOSE OF STUDY: The purpose of this study was to evaluate the temperature increment of implant surface during Er:YAG laser irradiation with different cooling systems. MATERIALS AND METHODS: Three implants were placed in a resected block of sheep mandible and irradiated with Er:YAG laser with 3 different cooling systems namely water and air spray, air spray alone and no water or air spray. Temperature changes of the implant surface were monitored during laser irradiation with a K-type thermocouple at the apical area of the fixture. RESULTS: In all 3 groups, the maximum temperature rise was lower than 10°C. Temperature changes were significantly different with different cooling systems used (P<0.001). CONCLUSION: Based on the results, no thermal damage was observed during implant surface decontamination by Er:YAG laser with and without refrigeration. Thus, Er:YAG laser irradiation can be a safe method for treatment of periimplantitis.

A comparison of precision of fit, rotational freedom, and torque loss with copy-milled zirconia and prefabricated titanium abutments.

PURPOSE: The present study sought to compare copy-milled zirconia abutments with standard prefabricated titanium abutments in terms of horizontal and vertical misfit, rotational freedom, and torque loss. MATERIALS AND METHODS: Twenty regular-platform implants (Brånemark, Nobel Biocare) with a standard external-hexagon implant-abutment interface were divided into two groups. In one group, prefabricated titanium abutments (Easy Abutment, Nobel Biocare) were used; in the other group, custom-made zirconia abutments were fabricated using the Zirkonzahn milling system. Measurements of geometry, rotational freedom, and marginal discrepancy were performed using a video measuring machine. To measure torque loss, each abutment was torqued to 32 Ncm and then loosened with a digital torque wrench. The torque loss values were reported as a percentage of the applied torque. RESULTS: Rotational freedom and horizontal misfit were significantly higher with the customized abutments. There were no statistically significant differences in vertical misfit or in mean percentage of torque loss between the two groups. CONCLUSIONS: Within the limitations of this study, it could be concluded that copy-milled zirconia abutments do not fit as accurately as prefabricated titanium abutments. However, the less precise fit of customized zirconia abutments does not seem to affect their ability to maintain the applied torque.

Evaluation of the accuracy and related factors of the mechanical torque-limiting device for dental implants.

OBJECTIVE: Accurate delivery of torque to implant screws is critical to generate ideal preload in the screw joint and to offer protection against screw loosening. Mechanical torque-limiting devices (MTLDs) are available for this reason. In this study, the accuracy of one type of friction-style and two types of spring-style MTLDs at baseline, following fatigue conditions and sterilization processes were determined. MATERIALS AND METHODS: Five unused MTLDs were selected from each of Straumann (ITI), Astra TECH and CWM systems. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck was used to hold the driver. Force was applied to the MTLDs until either the friction styles released at a pre-calibrated torque value or the spring styles flexed to a pre-calibrated limit (target torque value). The peak torque value was recorded and the procedure was repeated 5 times for each MTLD. Then MTLDs were subjected to fatigue conditions at 500 and 1000 times and steam sterilization processes at 50 and 100 times and the peak torque value was recorded again at each stage. RESULTS: Adjusted difference between measured torque values and target torque values differed significantly between stages for all 3 systems. Adjusted difference did not differ significantly between systems at all stages, but differed significantly between two different styles at baseline and 500 times fatigue stages. CONCLUSION: Straumann (ITI) devices differed minimally from target torque values at all stages. MTLDs with Spring-style were significantly more accurate than Friction-style device in achieving their target torque values at baseline and 500 times fatigue.