Comparison of backbone dynamics of the type III antifreeze protein and antifreeze-like domain of human sialic acid synthase.

Antifreeze proteins (AFPs) are found in a variety of cold-adapted (psychrophilic) organisms to promote survival at subzero temperatures by binding to ice crystals and decreasing the freezing temperature of body fluids. The type III AFPs are small globular proteins that consist of one α-helix, three 3(10)-helices, and two ß-strands. Sialic acids play important roles in a variety of biological functions, such as development, recognition, and cell adhesion and are synthesized by conserved enzymatic pathways that include sialic acid synthase (SAS). SAS consists of an N-terminal catalytic domain and a C-terminal antifreeze-like (AFL) domain, which is similar to the type III AFPs. Despite having very similar structures, AFL and the type III AFPs exhibit very different temperature-dependent stability and activity. In this study, we have performed backbone dynamics analyses of a type III AFP (HPLC12 isoform) and the AFL domain of human SAS (hAFL) at various temperatures. We also characterized the structural/dynamic properties of the ice-binding surfaces by analyzing the temperature gradient of the amide proton chemical shift and its correlation with chemical shift deviation from random coil. The dynamic properties of the two proteins were very different from each other. While HPLC12 was mostly rigid with a few residues exhibiting slow motions, hAFL showed fast internal motions at low temperature. Our results provide insight into the molecular basis of thermostability and structural flexibility in homologous psychrophilic HPLC12 and mesophilic hAFL proteins.

NMR study of the Z-DNA binding mode and B-Z transition activity of the Zα domain of human ADAR1 when perturbed by mutation on the α3 helix and ß-hairpin.

The Zα domains of human ADAR1 (ZαADAR1) bind to Z-DNA via interaction mediated by the α3-core and ß-hairpin. Five residues in the α3 helix and four residues in the ß-hairpin play important roles in Zα function, forming direct or water-mediated hydrogen bonds with DNA backbone phosphates or interacting hydrophobically with DNA bases. To understand the roles of these residues during B-Z transition of duplex DNA, we performed NMR experiments on complexes of various ZαADAR1 mutants with a 6-bp DNA duplex at various protein-to-DNA molar ratios. Our study suggests that single mutations at residues K169, N173, or Y177 cause unusual conformational changes in the hydrophobic faces of helices α1, α2, and α3, which dramatically decrease the Z-DNA binding affinity. 1D imino proton spectra and chemical shift perturbation showed that single mutations at residues K170, R174, T191, P192, P193, or W195 slightly affected the Z-DNA binding affinity. A hydrogen exchange study proved that the K170A- and R174A-ZαADAR1 proteins could efficiently change B-DNA to left-handed Z-DNA via an active B-Z transition pathway, whereas the G2·C5 base pair was significantly destabilized compared to wild-type ZαADAR1.

NMR dynamics study of the Z-DNA binding domain of human ADAR1 bound to various DNA duplexes.

The Z-DNA binding domain of human ADAR1 (Zα(ADAR1)) preferentially binds Z-DNA rather than B-DNA with high binding affinity. Here, we have carried out chemical shift perturbation and backbone dynamics studies of Zα(ADAR1) in the free form and in complex with three DNA duplexes, d(CGCGCG)(2), d(CACGTG)(2), and d(CGTACG)(2). This study reveals that Zα(ADAR1) initially binds to d(CGCGCG)(2) through the distinct conformation, especially in the unusually flexible ß1-loop-α2 region, from the d(CGCGCG)(2)-(Zα(ADAR1))(2) complex. This study also suggests that Zα(ADAR1) exhibits a distinct conformational change during the B-Z transition of non-CG-repeat DNA duplexes with low binding affinities compared to the CG-repeat DNA duplex.

Heat transfer to the implant-bone interface during preparation of a zirconia/alumina abutment.

PURPOSE: Excessive heat at the implant-bone interface may compromise osseointegration. This study examined the heat generated at the implant surface during preparation of a zirconia/alumina abutment in vitro. MATERIALS AND METHODS: Sixty zirconia/alumina abutments were randomized into 12 experimental groups. The abutments were connected to implants and embedded in an acrylic resin block in a 37 degrees C water bath. The abutments were reduced by 1 mm in height over a period of 1 minute with a high-speed handpiece and then polished for 30 seconds with a low-speed handpiece, both with and without an air/water coolant. Temperatures were recorded via thermocouples at the cervical, middle, and apical part of the implant surfaces. The Mann-Whitney rank-sum test was used to assess the statistical significance of the difference in temperature between the abutment/implant complexes altered with and without coolant. RESULTS: The 1-mm reduction with the high-speed handpiece without coolant resulted in a maximum temperature of 41.22 degrees C at the cervical portion of the implant. Three of four temperatures above 40 degrees C were observed at the cervical part of the implant following use of the high-speed handpiece without coolant. The temperature difference between "with coolant" and "without coolant" during both low-speed polishing and high-speed reduction was statistically significant at the cervical portion of the implant (P = .009). In contrast, the temperature difference between "with coolant" and "without coolant" during both low-speed polishing and high-speed reduction was not statistically significant at the middle and apical parts of the implant (P > .05). CONCLUSIONS: Preparation of a zirconia/alumina abutment caused an increase in temperature within the implant, but this temperature increase did not reach the critical levels described in the implant literature.

The effect of several dentin desensitizers on shear bond strength of adhesive resin luting cement using self-etching primer.

OBJECTIVES: Dentin desensitizers can inhibit the bonding between dentin and resin cements. This study examined the effect of the previous application of desensitizers on the shear bond strength of one resin cement using self-etching primer to dentin. MATERIALS AND METHODS: One hundred and twenty-five dentin exposed teeth were randomly assigned to four experimental groups and one control group of 25 teeth each. Four dentin desensitizers were applied to the four experimental groups, respectively. The dentin desensitizers used were SuperSeal (Phoenix Dental, Inc., USA), MS-Coat (Sun Medical Co. Ltd, Japan), Gluma (Heraeus Kulzer, Germany), and Copalite Varnish (Cooley & Cooley Ltd, USA). Panavia F (Kuraray Co. Ltd, Tokyo, Japan) was attached to the top of each experimental and control group teeth using an Ultradent testing jig (Ultradent Product, Inc., Utah, USA), and the shear bond strength was measured using a Universal testing machine (Model 6022, Instron Co., Canton, MA, USA). The tooth surface was examined by scanning electron microscopy (SEM, JSM-T2000, JEOL, Tokyo, Japan). RESULTS: The control group showed the greatest shear bond strength (14.74 MPa) followed by SuperSeal (12.33 MPa), Gluma (5.28 MPa), MS-Coat (4.44 MPa) and Copalite Varnishtrade mark (3.14 MPa). There was no significant difference in shear bond strength between the control group and the experimental group treated with Superseal. The shear bond strength in the other experimental groups treated with Gluma, Varnish, and MS-Coat was similar to each other but significantly lower than control or Superseal. SEM showed revealed resin tags in most of the dentinal tubules in the experimental group treated with the Superseal. CONCLUSION: Among the four dentin desensitizers, Superseal was the only one that did not interfere with the process of resin bonding. The other dentin desensitizers that contained a resin ingredient interfered with resin retention.

Survey of the use of statistical methods in Journal of the Korean Association of Oral and Maxillofacial Surgeons.

OBJECTIVES: This study aimed to describe recent patterns in the types of statistical test used in original articles that were published in Journal of the Korean Association of Oral and Maxillofacial Surgeons. MATERIALS AND METHODS: Thirty-six original articles published in the Journal in 2015 and 2016 were ascertained. The type of statistical test was identified by one researcher. Descriptive statistics, such as frequency, rank, and proportion, were calculated. Graphical statistics, such as a histogram, were constructed to reveal the overall utilization pattern of statistical test types. RESULTS: Twenty-two types of statistical test were used. Statistical test type was not reported in four original articles and classified as unclear in 5%. The four most frequently used statistical tests constituted 47% of the total tests and these were the chi-square test, Student's t-test, Fisher's exact test, and Mann-Whitney test in descending order. Regression models, such as the Cox proportional hazard model and multiple logistic regression to adjust for potential confounding variables, were used in only 6% of the studies. Normality tests, including the Kolmogorov-Smirnov test, Levene test, Shapiro-Wilk test, and Scheffé's test, were used diversely but in only 10% of the studies. CONCLUSION: A total of 22 statistical tests were identified, with four tests occupying almost half of the results. Adoption of a nonparametric test is recommended when the status of normality is vague. Adjustment for confounding variables should be pursued using a multiple regression model when the number of potential confounding variables is numerous.

Epidemiology of Implant Mortality Disparity Among Intraoral Positions and Prosthesis Types.

PURPOSE: To examine the disparity of single-crown implant failure with a similar loss of the splinted prosthesis in differing anatomical locations while controlling for other demographic and clinical variables that may confound the relationship between prosthesis types and implant loss. MATERIALS AND METHODS: A multicenter retrospective cohort study was designed to include patients treated with dental implants from 2003 to 2014. The variables included age, sex, systemic disease, bone graft, implant placement date, position of dental implant, length of dental implant, diameter of dental implant, loading time, type of prosthesis, type of opposing occlusion, latest check date, and survival or loss of the dental implant. The demographic and clinical variables' influence on the survival of dental implants was estimated by the Kaplan-Meier method. The position and diameter were adjusted for the accurate estimation of the relationship between the prosthesis type and survival of the dental implant with the Cox proportional hazard method. RESULTS: A total of 1,151 dental implants from 403 patients were ascertained. After adjusting for the confounding effect of position and diameter, single-crown prostheses were 38.1 (95% CI: 15.1-118) times more likely to be lost than the connected-type prostheses. For single-crown implants, the waiting time for osseointegration before loading was the highest for the maxillary molar position and the lowest for the mandibular molar position (P < .0001), while the most frequent implant loss occurred in the maxillary anterior area, and the second frequent area was the maxillary molar position; the lowest occurrence of implant loss was for the mandibular molar position. This disparity was statistically significant (P = .0271). CONCLUSION: Despite the high survival rates of endosseous implants as a whole, since the variation of implant loss was observed among the different anatomical positions for single-crown implants, special attention has to be given to the maxillary anterior and maxillary molar positions. A longer healing time assuming compensation for disadvantageous bone quality was not directly effective in increasing implant longevity in the vulnerable positions.

Retrospective multicenter cohort study of the clinical performance of 2-stage implants in South Korean populations.

PURPOSE: To evaluate long-term follow-up clinical performance of dental implants in use in South Korean populations. MATERIALS AND METHODS: A retrospective multicenter cohort study design was used to collect long-term follow-up clinical data from dental records of 224 patients treated with 767 2-stage endosseous implants at Ajou University Medical Center and Bundang Jesaeng Hospital in South Korea from June 1996 through December 2003. Exposure variables such as gender, systemic disease, location, implant length, implant diameter, prosthesis type, opposing occlusion type, and date of implant placement were collected. Outcome variables such as date of implant failure were measured. RESULTS: Patient ages ranged from 17 to 71.7 years old (mean age, 45.6 years old). Implants were more frequently placed in men than in women (61% versus 39%, or 471 men versus 296 women). Systemic disease was described by 9% of the patients. All implants had hydroxyapatite-blasted surfaces. Most of the implants were 3.75 mm in diameter. Implant lengths 10 mm, 11.5 mm, 13 mm, and 15 mm were used most often. Differences of implant survival among different implant locations were observed. Implants were used to support fixed partial dentures for the majority of the restorations. The opposing dentition was natural teeth for about 50% of the implants. A survival rate of 97.9% (751 of 767) was observed after 4.5 years (mean, 1.95 +/- 1.2 years). CONCLUSION: Clinical performance of 2-stage dental implants demonstrated a high level of predictability. The results achieved with a South Korean population did not differ from results achieved with diverse ethnic groups.

Comparison of dental implant systems: quality of clinical evidence and prediction of 5-year survival.

PURPOSE: This literature review was conducted to evaluate the quality of current evidence of clinical performance provided by American Dental Association-certified dental implant manufacturers and manufacturers with strong market penetration in the United States. The study also compared the clinical performance of different dental implant systems. MATERIALS AND METHODS: A letter was sent to 6 implant manufacturers requesting 10 references each that validated the manufacturer's implant system in a variety of clinical applications. References were reviewed and classified relative to strength of evidence. Data extraction was then performed. Comparisons of implant survival data from 5-year studies were made, and data were pooled to establish an overall 5-year survival rate with confidence intervals (CIs). RESULTS: A total of 69 references were provided by the 6 implant manufacturers (Astra Tech, Centerpulse, Dentsply/Friadent, Implant Innovations, Nobel Biocare, and Straumann) but only 59 articles were available for review. Of those references, most were level-4 (case series) or level-5 (expert opinion) articles. Five-year survival data were extracted from 17 articles demonstrating overlap of CIs from the weighted average of the pooled data from each specific manufacturer; substantial equivalence of all implant systems was demonstrated based upon survival alone at 5 years. When all data were pooled, the 5-year survival rate of 96% (CI: 93% to 98%) was observed for a total of 7,398 implants. DISCUSSION: No obvious differences in implant survival were observed when comparing implant systems. CONCLUSIONS: The evidence supporting implant therapy is generally derived from level-4 case series rather than higher-level cohort or controlled clinical trials. Articles that directly compared different implant systems were not found. Five-year implant survival rates easily exceeded the minimums recommended by the American Dental Association certification program. (More than 50 references.)

Methods for comparing the results of different studies.

The reader of oral and maxillofacial implant literature is challenged to be cognizant of the quality of clinical research data. The large variety of possible study designs utilized by clinical researchers requires the reader to have a fundamental awareness of the advantages, disadvantages, and limitations of commonly utilized study designs. This article aims to provide the reader with information to make an informed decision regarding the quality of a clinical research paper, so that he or she can judge whether the information presented in any given manuscript was obtained in a manner that truly minimizes bias, in the form of systematic or random errors, and whether it warrants serious consideration for clinical decision making. Special consideration is given to scientific literature pertaining to the use of oral and maxillofacial implants. In addition, the reader is presented with a method for placing any single manuscript within a "hierarchy of evidence" enabling an "estimate of confidence" in a particular therapy. By utilizing such methods to appraise the quality of research data, clinicians and patients will be better informed when making treatment-planning decisions.

Retrospective cohort study of the clinical performance of 1-stage dental implants.

PURPOSE: To evaluate long-term clinical performance of 1-stage dental implant prostheses at a single clinic, emphasizing clinical and demographic characteristics that affect implant survival. MATERIALS AND METHODS: Dental records of all 308 patients (674 implants) treated with 1-stage implants at Mayo Clinic from October 1993 through May 2000 were reviewed from implant placement to last visit. Exposure and outcome variables affecting performance were collected separately to control bias in the data collection process. Additional confounding factors (age and sex) were adjusted with the stratified Cox proportional hazards model. Implant survival was determined by means of a Kaplan-Meier survival estimate. The log-rank test was used to determine the role of clinical and demographic variables in implant survival. The relative risk associated with the possible effect of clinical and demographic variables on implant survival was estimated with the Cox proportional hazards model. RESULTS: The implant survival rate (n = 654 implants) was 97% (mean +/- SD follow-up, 21.0 +/- 18.8 months; range, 1 to 78 months). Performance bias was limited because nearly all patients were treated by 1 prosthodontist. Two implants failed after loading (6 and 9 months). The incidence of complications was less than 4%. Among the implant failures, use of heterogeneous bone graft was associated with 4.8 times more failures than was use of autogenous bone graft (P = .04). After augmentation, delaying implant placement for 5 to 6 months resulted in 8.6 times more failures than the rate after earlier placement (P < .001). DISCUSSION: Retrospective review of the clinical performance of a 1-stage dental implant system yielded a 97% survival rate, with no failures noted after 13 months. Prosthetic complications were low, especially for fixed implant prostheses. CONCLUSION: Clinical performance of 1-stage dental implant prostheses between 1993 and 2000 demonstrated a high level of predictability.

Cross-sectional study of the factors that influence radiographic magnification of implant diameter and length.

PURPOSE: To study the factors that influence radiographic magnification of implant diameter and length. MATERIALS AND METHODS: The dental records and panoramic radiographs of 80 patients with 210 dental implants treated with implant-supported prostheses at Bundang Jesaeng Hospital in South Korea from January 2000 through February 2003 were reviewed. The panoramic radiographs were developed under standardized conditions. The patient's gender and the anatomic locations of implants were identified from the dental records. To prevent bias, a blinded investigator measured implant diameter and length on a panoramic radiograph. To evaluate intra-examiner variability, the intraclass correlation coefficient (R(I)) was calculated. The Mann-Whitney rank-sum test and the Kruskal-Wallis test were used to determine the statistical significance of the difference between actual length and radiographic length. RESULTS: The intraclass correlation coefficients (R(I)) were 0.83 for diameter and 0.87 for length. There was no statistically significant difference in length in regard to gender (P = .08). Magnification of diameter did differ on the basis of gender (P = .03; 25% magnification in radiographs of women; 20% in men). No difference in diameter was found in regard to anatomic location (P = .51), however, while evidence of difference in length in regard to anatomic location was found (P = .01). DISCUSSION: Radiographic magnification of implant dimensions in diameter and length can have different influencing factors. CONCLUSIONS: This study found that radiographic magnification of implant diameter was influenced by gender, whereas radiographic magnification of implant length was influenced by anatomic location. Each anatomic location had a different amount of radiographic magnification for implant length.

Clinical statistics: five key statistical concepts for clinicians.

Statistics is the science of data. As the foundation of scientific knowledge, data refers to evidentiary facts from the nature of reality by human action, observation, or experiment. Clinicians should be aware of the conditions of good data to support the validity of clinical modalities in reading scientific articles, one of the resources to revise or update their clinical knowledge and skills. The cause-effect link between clinical modality and outcome is ascertained as pattern statistic. The uniformity of nature guarantees the recurrence of data as the basic scientific evidence. Variation statistics are examined for patterns of recurrence. This provides information on the probability of recurrence of the cause-effect phenomenon. Multiple causal factors of natural phenomenon need a counterproof of absence in terms of the control group. A pattern of relation between a causal factor and an effect becomes recognizable, and thus, should be estimated as relation statistic. The type and meaning of each relation statistic should be well-understood. A study regarding a sample from the population of wide variations require clinicians to be aware of error statistics due to random chance. Incomplete human sense, coarse measurement instrument, and preconceived idea as a hypothesis that tends to bias the research, which gives rise to the necessity of keen critical independent mind with regard to the reported data.

Immediate restoration with ti-unite implants: practice-based evidence compared with animal study outcomes.

PURPOSE: Clinicians often do not have the benefit of adequate safety or clinical data when evaluating the merit of either newly marketed implant devices or novel clinical procedures. This has been the case for dental implants following the initial documentation of their safety and efficacy and is demonstrated in the evolution of immediate load application. Following demonstration of safety and successful application of an implant in an animal study prior to its market release, this report provides the clinical outcomes for the first 100 Ti-Unite implants provided to 24 patients in a clinical practice over 9 years. MATERIALS AND METHODS: An electronic record/clinical database review of consecutive early loaded implants from a multiple surgeon/single prosthodontist practice was conducted for quality assurance. Data extraction of standard exposure and outcome variables was accomplished by a trained individual not affiliated with the clinical practice. RESULTS: The results revealed one failure before and none following definitive restoration with a variety of prostheses. The mean length of time from immediate to definitive restorations was 5.3 ± 1.1 months for crowns, 3.9 ± 1.3 months for fixed partial dentures, and 7.8 ± 4.1 months for mandibular "hybrid" prostheses. The most common unexpected findings during the initial three postinsertion visits were lost access restoration and cement failure. CONCLUSIONS: Pre-market animal data regarding the safety and success of a new implant used with an early loading protocol was replicated in the clinical results of the first 100 implants used in practice. Additionally, the clinical results are favorable when compared to conventional loading protocols from this same practice and provide helpful comparative metrics (delayed vs immediate loading) to use when discussing implant treatment with patients.

A 5-year retrospective clinical study of the Dentium implants.

PURPOSE: The aim of this retrospective study was to evaluate cumulative survival rate (CSR) of Implantium implants followed for 5 years and association between risk factors and the CSR. MATERIALS AND METHODS: A total of two hundred forty-nine Implantium Implants System (Dentium, Seoul, Korea) placed in ninety-five patients from 2004 to 2009 were investigated with several identified risk factors (sex, systemic disease, smoking, alchohol, reason of tooth loss, length, arch (maxilla or mandible), replace tooth type (incisor, canine, premolar or molar) Kennedy classification, prosthodontic type, prosthodontic design, opposite dentition, abutment type, occlusal material, occlusal unit, splint to tooth, cantilever, other surgery). Clinical examination (mobility, percussion, screw loosening, discomfort, etc.) and radiographic examination data were collected from patient records including all problems during follow-up period according to protocols described earlier. Life table analysis was undertaken to examine the CSR. Cox regression method was conducted to assess the association between potential risk factors and overall CSR. RESULTS: Five of 249 implants were failed. Four of these were lost before loading. The 5-year implant cumulative survival rate was 97.37%. Cox regression analysis demonstrated a significant predictive association between overall CSR and systemic disease, smoking, reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The screw related complication was rare. Two abutment screw fractures were found. Another complications of prosthetic components were porcelain fracture, resin facing fracture and denture fracture (n=19). CONCLUSION: The 5-year CSR of Implantium implants was 97.37%. Implant survival may be dependent upon systemic disease, smoking reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The presence of systemic diseases and combination of other surgical procedures may be associated with increased implant failure.

Evaluation of peri-implant tissue in nonsubmerged dental implants: a multicenter retrospective study.

OBJECTIVES: The objective of this study was to evaluate the peri-implant's hard and soft tissue response associated with the 1-stage, nonsubmerged, endosseous dental implant. STUDY DESIGN: A multicenter retrospective clinical evaluation was performed on 339 nonsubmerged implants placed in 108 patients at 5 clinical centers between January 2003 and December 2007. RESULTS: After a mean follow-up period of 30 months, the mean crestal bone resorption in 339 implants was 0.43 mm. The survival and success rates were observed to be 99.1% and 95.1%, respectively. The mean calculus, inflammatory, and plaque indices were 0.13, 0.37, and 0.73, respectively, and the mean width of buccal keratinized mucosa was observed to be 2.43 mm. CONCLUSION: The short- to intermediate-term evaluation of the 1-stage, nonsubmerged, endosseous implant yields relatively high survival and success rates.

Clinical decision-making practices among a subset of North American prosthodontists.

The aim of this study was to determine the decision-making practices of a subset of North American prosthodontists. A survey was administered to assess practitioner views regarding the relative importance of practitioner, patient, and patient family beliefs and preferences during treatment planning of the edentulous patient. In responses to abstract questions, practitioners appeared to endorse a blending of patient and practitioner beliefs and preferences when treatment planning. However, in response to a question proposing a simulated clinical scenario, practitioners indicated they placed a greater emphasis on their own beliefs when choosing a treatment option.