A modified protocol for restorative implant abutment selection by using computer-aided design and computer-aided manufacturing technology.

STATEMENT OF PROBLEM: Implant abutment selection is complex because of the numerous factors involved. Computer-aided design (CAD) technology allows for the virtual selection and placement of abutments after all parameters have been precisely measured. The outcome of this new protocol should be validated. PURPOSE: The purpose of this in vitro study was to validate a new digital protocol in which abutment selection is made through a CAD software program, the abutments are virtually placed, and the restoration is then designed based on the virtual abutments to fit the actual abutments when delivered to the implants intraorally. MATERIAL AND METHODS: A cast with 2 parallel implants was scanned 10 times. Then, 2 abutments were placed and scanned 10 times. Twenty identical superstructures were designed and manufactured to simulate the clinical situation of a 3-unit fixed partial denture, screw-retained to 2 implants. These were divided into 2 groups-A, real abutment and B, virtual abutment-and then compared by means of digital and optical measurements. RESULTS: No significant differences were detected for the measurements between the control and test groups in either the x-axis or y-axis; significant differences were found for the median value of the measurements obtained from both groups regarding the z-axis (P=.046). The mean gap in the virtual abutment group was 50 µm and 35 µm in the real abutment group. CONCLUSIONS: Superstructures produced after the virtual selection and placement of intermediate restorative abutments compared favorably with those produced after the digitalization of actual abutments and placement in the implant model, thus validating the proposed digital protocol for virtual abutment selection and placement.

Influence of a Novel Surface of Bioactive Implants on Osseointegration: A Comparative and Histomorfometric Correlation and Implant Stability Study in Minipigs.

PURPOSE: The objective of this study was to assess the influence of a novel surface of dental implants (ContacTi®) on the osseointegration process in a minipig model. The surface was compared with other existing surfaces on the market (SLA® and SLActive®) by employing bone implant contact analysis (BIC) and implant stability. METHOD: Twelve minipigs were used with prior authorisation from an ethics committee. Three types of surfaces were tested: SLA® (sand-blasted acid-etched titanium), SLActive® (same but hydrophilic, performed under a nitrogen atmosphere), and ContacTi® (alumina particle bombardment of titanium, bioactivated when treated thermochemically) in 4.1 mm × 8 mm implants with internal connection and a polished neck. Twelve implants of each surface type (N = 36) were placed, sacrificing 1/3 of the animals at 2 weeks of placement, 1/3 at 4 weeks and the remaining 1/3 at 8 weeks. Numerical variables were compared with Analysis of Variance, and the correlation between ISQ and BIC was established with the Spearman's rank correlation coefficient. RESULTS: SLActive® and ContacTi® surfaces showed elevated osteoconductivity at 4 weeks, maintaining a similar evolution at 8 weeks (large amount of mature lamellar tissue with high maturity and bone quality). The SLA® surface showed slower maturation. The ISQ values in surgery were elevated (above 65), higher at necropsy and higher at 4 and 8 weeks in the SLA® group than in the other two (SLActive® and ContacTi®). No significant correlation was found between ISQ and BIC for each implant surface and necropsy time. CONCLUSION: The three surfaces analysed showed high RFA and BIC values, which were more favourable for the SLActive® and ContacTi® surfaces. No statistical correlation was found between the RFA and BIC values in any of the three surfaces analysed.

Advances in surfaces and osseointegration in implantology. Biomimetic surfaces.

The present work is a revision of the processes occurring in osseointegration of titanium dental implants according to different types of surfaces -namely, polished surfaces, rough surfaces obtained from subtraction methods, as well as the new hydroxyapatite biomimetic surfaces obtained from thermochemical processes. Hydroxyapatite's high plasma-projection temperatures have proven to prevent the formation of crystalline apatite on the titanium dental implant, but lead to the formation of amorphous calcium phosphate (i.e., with no crystal structure) instead. This layer produce some osseointegration yet the calcium phosphate layer will eventually dissolve and leave a gap between the bone and the dental implant, thus leading to osseointegration failure due to bacterial colonization. A new surface -recently obtained by thermochemical processes- produces, by crystallization, a layer of apatite with the same mineral content as human bone that is chemically bonded to the titanium surface. Osseointegration speed was tested by means of minipigs, showing bone formation after 3 to 4 weeks, with the security that a dental implant can be loaded. This surface can be an excellent candidate for immediate or early loading procedures.

Burnout, depression and suicidal ideation in dental students.

OBJECTIVES: To investigate the prevalence, gender influence, and relationships between burnout, depression and suicidal ideation within the last year among second, fourth and fifth-year dental students. STUDY DESIGN: A cross-sectional study was carried out in 212 dental students enrolled in the second, fourth and fifth years at the School of Dentistry of Seville using the Maslach Burnout Inventory-Student Survey and the MBI-Human Services Survey, the "Patient Health Questionnaire-2", and the "Questions about Suicidal Ideation and Attempted Suicide". RESULTS: The response rate among dental students was 80%. Burnout prevalence in dental students was higher in second and fourth years than in fifth year (p = 0.059 and p = 0.003, respectively). Depression prevalence in the fourth year approached significance (p = 0.051). Prevalence of suicidal ideation within the past year was higher, yet not reaching significance, in fourth year. No gender-related differences were found. A significant association was observed between burnout and depression, and between depression and suicidal ideation (p < 0.001), but no association was found between burnout and suicidal ideation. CONCLUSIONS: This study has brought our attention to the high prevalence of burnout and depression, and reported for the first time the prevalence of suicidal ideation among dental students in preclinical and clinical years.

SEM Analysis and Micro-CT Evaluation of Four Dental Implants after Three Different Mechanical Requests-In Vitro Study.

STATEMENT OF PROBLEM: Implant-supported rehabilitations are an increasingly frequent practice to replace lost teeth. Before clinical application, all implant components should demonstrate suitable durability in laboratory studies, through fatigue tests. OBJECTIVE: The purpose of this in vitro study was to evaluate the integrity and wear of implant components using SEM, and to assess the axial displacement of the implant-abutment assembly by Micro-CT, in different implant connections, after three distinct mechanical requests. MATERIALS AND METHODS: Four KLOCKNER implants (external connection SK2 and KL; and internal connection VEGA and ESSENTIAL) were submitted to three different mechanical requests: single tightening, multiple tightening, and multiple tightening and cyclic loading (500 N × 100 cycles). A total of 16 samples were evaluated by SEM, by the X-ray Bragg-Brentano method to obtain residual stresses, and scratch tests were realized for each surface and Micro-CT (4 control samples; 4 single tightening; 4 multiple tightening; 4 multiple tightening and cyclic loading). All dental implants were fabricated with commercially pure titanium (grade 3 titanium). Surface topography and axial displacement of abutment into the implant, from each group, were evaluated by SEM and Micro-CT. RESULTS: In the manufacturing state, implants and abutments revealed minor structural changes and minimal damage from the machining process. The application of the tightening torque and loading was decisive in the appearance and increase in contact marks on the faces of the hexagon of the abutment and the implant. Vega has the maximum compressive residual stress and, as a consequence, higher scratch force. The abutment-implant distances in SK2 and KL samples did not show statistically significant differences, for any of the mechanical demands analyzed. In contrast, statistically significant differences were observed in abutment-implant distance in the internal connection implants Vega and Essential. CONCLUSIONS: The application of mechanical compression loads caused deformation and contact marks in all models tested. Only internal connection implants revealed an axial displacement of the abutment into the implant, but at a general level, a clear intrusion of the abutment into the implant could only be confirmed in the Essential model, which obtained its maximal axial displacement with cyclic loading.

Influence of Titanium Surface Residual Stresses on Osteoblastic Response and Bacteria Colonization.

Grit basting is the most common process applied to titanium dental implants to give them a roughness that favors bone colonization. There are numerous studies on the influence of roughness on osseointegration, but the influence of the compressive residual stress associated with this treatment on biological behavior has not been determined. For this purpose, four types of surfaces have been studied using 60 titanium discs: smooth, smooth with residual stress, rough without stress, and rough with residual stress. Roughness was studied by optic interferometry; wettability and surface energy (polar and dispersive components) by contact angle equipment using three solvents; and residual stresses by Bragg-Bentano X-ray diffraction. The adhesion and alkaline phosphatase (ALP) levels on the different surfaces were studied using Saos-2 osteoblastic cultures. The bacterial strains Streptococcus sanguinis and Lactobacillus salivarius were cultured on different surfaces, determining the adhesion. The results showed that residual stresses lead to increased hydrophilicity on the surfaces, as well as an increase in surface energy, especially on the polar component. From the culture results, higher adhesion and higher ALP levels were observed in the discs with residual stresses when compared between smooth and roughened discs. It was also found that roughness was the property that mostly influenced osteoblasts' response. Bacteria colonize rough surfaces better than smooth surfaces, but no changes are observed due to residual surface tension.

Assessment of Osstell ISQ's reliability for implant stability measurement: a cross-sectional clinical study.

UNLABELLED: Resonance frequency analysis (RFA) allows assess implant stability by measuring implant oscillation frequency on the bone. RFA is an objective and non-invasive method for implant stability measurement, although scarce evidence has been provided so far on its reliability. OBJECTIVE: Assess the Osstell ISQ system's reliability (i.e., its measurement reproducibility and repeatability) by means of the intraclass correlation coefficient (ICC) as statistical method. DESIGN OF THE STUDY: Two implant stability registers were completed by means of Osstell ISQ on 85 implants on 23 patients. Six measurements were completed on each implant by means of two different SmartPegs (types I and II); that is, three consecutive measurements with each transducer. RESULTS: Average ISQ was 72.40, 72.22 and 72.79, and 72.06, 72.59 and 72.82 in the first, second, and third measurements with SmartPegs I and II, respectively. Equal values or differences below three ISQ points were observed in 52.9% and 62.4% of the cases with SmartPegs I and II, respectively. The intraclass correlation coefficient was 0.97 for both SmartPegs, and repeatability and reproducibility also reached 0.97 for both SmartPegs. CONCLUSIONS: The RFA system Osstell ISQ presents almost perfect repeatability and reproducibility after intraclass correlation coefficient analysis. Osstell ISQ measurements are highly reliable regarding reproducibility. Therefore, one measurement proves enough.

Job satisfaction and depression in the Spanish Society of Periodontology and Research (SEPA) members, and their relation to the burnout syndrome. Creation of a structural model.

OBJECTIVE: This study is aimed at getting to know the existing relationship between the dimensions of the burnout syndrome and job satisfaction, on one hand, and depressive feelings on the other through the creation of a structural model aimed at relating all these concepts on a sample of Spanish periodontists. STUDY DESIGN: The initial sample comprised 284 individuals, who represented 20% of the members of the Spanish Society of Periodontology and Research (www.SEPA.es). These individuals were chosen randomly by means of stratified sampling with proportional affixation by their autonomous community of residence. All participants were sent by post the MBI, CET and job-satisfaction questionnaires. The software package used for data analysis was LISREL v. 8.7 by checking models of structural equations so as to prove the proposed model's adjustment. RESULTS: The total number of answered questionnaires was 170 (59.85%). A positive relation was observed between emotional tiredness and depersonalization and depression. However, this dimension correlated negatively with job satisfaction and self-realization. CONCLUSIONS: The obtained results show that, in this sample of periodontists, job satisfaction acts as a modulator in the transition from emotional tiredness to depression.

Resonance frequency analysis-reliability in third generation instruments: Osstell mentor®.

UNLABELLED: Few studies assess repeatability and reproducibility in registers of resonance frequency analysis (a value of dental implant stability). OBJECTIVE: Few studies assess repeatability and reproducibility in resonance frequency analyses (implant stability evaluation). This study is aimed at assessing reliability (repeatabilty and reproducibility) in the Osstell Mentor® system using the intraclass correlation coefficient (ICC) as the statistical method. STUDY DESIGN: ISQ measurements of RFA were carried out by means of the Osstell Mentor® instrument in 58 implants in 19 patients. Six measurements were performed on each implant by means of two different Smart-Pegs (I and II). Three consecutive measurements were registered with each transducer. RESULTS: Average ISQ varied from 72.43 to 72.60 and 73.26 in the first, second and third measurements, respectively with the SamrtPeg I and from 72.98 to 73.26 and 73.74 in the first, second and third measurements, respectively with the SamrtPeg II . Exactly equal values were observed in 10.43 and 12.1% of the cases with Smart-Pegs I and II, respectively. The intraclass correlation coefficient was 0.96 and 0.96 for Smart Pegs I and II, respectively. Repeatability and reproducibility was 0.97 for both Smart-Pegs I and II. CONCLUSIONS: The RFA system contributed by Osstell Mentor® renders almost perfect reproducibility and repeatability, as proven by statistical analysis carried out by means of ICC with 95% confidence level. This instrument contributes highly reliable RFA measurements in dental implants.

Incidence of Peri-Implantitis and Relationship with Different Conditions: A Retrospective Study.

Articles on the prevalence of peri-implant diseases showed that 90% of peri-implant tissues had some form of inflammatory response and a prevalence of peri-implantitis from 28% to 51% according to various publications. Objective: To provide an overview of how risk factors can be related with peri-implantitis. Methods: A retrospective longitudinal study including 555 implants placed in 132 patients was evaluated based on the presence of peri-implantitis following the criteria of Renvert et al. 2018. Results: In total, 21 patients (15.9%) suffered peri-implantitis (PPG) and 111 patients (84.1%) did not suffer peri-implantitis (NPG). The results reveal that smokers have a high incidence of peri-implantitis (72.7%) compared to non-smokers (27.3%) (p < 0.0005). Another variable with significant results (p < 0.01) was periodontitis: 50% PPG and 23.9% NPG suffered advanced periodontitis. Systemic diseases such as arterial hypertension, diabetes mellitus, osteoporosis, and cardiovascular diseases do not show a statistically significant influence on the incidence of peri-implantitis. Patients who did not attend their maintenance therapy appointment had an incidence of peri-implantitis of 61.4%, compared to 27.3% in those who attend (p < 0.0001). From the results obtained, we can conclude that relevant factors affect peri-implantitis, such as tobacco habits, moderate and severe periodontitis, and attendance in maintenance therapy.

Influence of Bone-Level Dental Implants Placement and of Cortical Thickness on Osseointegration: In Silico and In Vivo Analyses.

The purpose of this research is to study the biomechanical response of dental implants in bone-level type locations, 0.5 mm above and below the bone level. In addition, the influence of the thickness of the cortical bone on osseointegration is determined due to the mechanical loads transfer from the dental implant to the cortical and trabecular bone. The thicknesses studied were 1.5 mm and 2.5 mm. Numerical simulations were performed using a finite element method (FEM)-based model. In order to verify the FEM model, the in silico results were compared with the results obtained from a histological analysis performed in an in vivo study with 30 New Zealand rabbits. FEM was performed using a computerized 3D model of bone-level dental implants inserted in the lower jawbone with an applied axial load of 100 N. The analysis was performed using different distances from the bone level and different thicknesses of cortical bone. The interface area of bone growth was evaluated by analyzing the bone-implant contact (BIC), region of interest (ROI) and total bone area (BAT) parameters obtained through an in vivo histological process and analyzed by scanning electron microscopy (SEM). Bone-level implants were inserted in the rabbit tibiae, with two implants placed per tibia. These parameters were evaluated after three or six weeks of implantation. FEM studies showed that placements 0.5 mm below the bone level presented lower values of stress distribution compared to the other studied placements. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that this position presented the highest BIC value after three or six weeks of implantation. In this placement, vertical bone growth could be observed up the bone level. The smallest thickness of the study showed a better transfer of mechanical loads, which leads to a better osseointegration. In silico and in vivo results both concluded that the implants placed 0.5 mm below the cortical bone and with lower thicknesses presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Corrosion Behavior of Titanium Dental Implants with Implantoplasty.

The procedure generally used to remove bacterial biofilm adhering to the surface of titanium on dental implants is implantoplasty. This treatment is based on the machining of the titanium surface to remove bacterial plaque. In this study, we used 60 grade 4 titanium implants and performed the implantoplasty protocol. Using X-ray diffraction, we determined the stresses accumulated in each of the as-received, machined and debris implants. The resistance to corrosion in open circuit and potentiodynamically in physiological medium has been determined, and the corrosion potentials and intensities have been determined. Tests have been carried out to determine ion release by ICP-MS at different immersion times. The results show that the corrosion resistance and the release of titanium ions into the medium are related to the accumulated energy or the degree of deformation. The titanium debris exhibit compressive residual stresses of -202 MPa, the implant treated with implantoplasty -120 MPa, and as-received -77 MPa, with their corrosion behavior resulting in corrosion rates of 0.501, 0.77, and 0.444 mm/year, respectively. Debris is the material with the worst corrosion resistance and the one that releases the most titanium ions to the physiological medium (15.3 ppb after 21 days vs. 7 ppb for as-received samples). Pitting has been observed on the surface of the debris released into the physiological environment. This behavior should be taken into account by clinicians for the good long-term behavior of implants with implantoplasty.

Digital Impressions in Implant Dentistry: A Literature Review.

INTRODUCTION: Digital impressions in implant dentistry rely on many variables, and their accuracy, particularly in complete edentulous patients, is not well understood. Aim. The purpose of this literature review was to determine which factors may influence the accuracy of digital impressions in implant dentistry. Emphasized attention was given to the design of the intra-oral scan body (ISB) and scanning techniques. MATERIALS AND METHODS: A Medline, PubMed and EBSCO Host databases search, complemented by a hand search, was performed in order to select relevant reports regarding the appliance of digital impressions in implant dentistry. The search subject included but was not limited to accuracy of digital impressions in implant dentistry, digital scanning techniques, the design and material of the ISBs, and the depth and angulation of the implant. The related titles and abstracts were screened, and the remaining articles that fulfilled the inclusion criteria were selected for full-text readings. RESULTS: The literature search conducted for this review initially resulted in 108 articles, among which only 21 articles fulfilled the criteria for inclusion. Studies were evaluated according to five subjects: accuracy of digital impressions in implant dentistry; the design and material of the intra-oral scan bodies; scanning technique; the influence of implants depth/angulations on the digital impression and accuracy of different intra-oral scanner devices. CONCLUSIONS: The accuracy of digital impressions in implant dentistry depends on several aspects. The depth/angulation of the implant, the experience of the operator, the intra-oral scanner used, and environmental conditions may influence the accuracy of digital impressions in implant dentistry. However, it seems that ISBs' design and material, as well as scanning technique, have a major impact on the trueness and precision of digital impressions in implant dentistry. Future research is suggested for the better understanding of this subject, focusing on the optimization of the ISB design and scanning protocols.

A Radiographic and Clinical Comparison of Immediate vs. Early Loading (4 Weeks) of Implants with a New Thermo-Chemically Treated Surface: A Randomized Clinical Trial.

Background: Implant dentistry has evolved over time, resulting in better treatment outcomes for both patients and clinicians. The aim of this trial was to test whether the immediate loading of implants with a platform-switching design influences the marginal bone level, compared to four-week loading, after one year of follow-up. Moreover, a comparison of clinical data regarding implant survival, implant stability, and patient-reported outcome measures (PROMs) was conducted. Methods: Klockner® VEGA® implants with a ContacTi® surface were placed in partially edentulous patients in the posterior areas. Group A received an immediately loaded prosthesis (one week) and Group B received an early-loaded prosthesis (four weeks). All abutments were placed at the time of surgery. Radiographic and clinical data were recorded. Results: Twenty-one patients were treated (35 implants). No implants were lost during the study. The final marginal bone level did not show differences between groups. The bone loss at 12 months at the implant level was 0.00 mm for both groups (median). The final implant quotient stability (ISQ) values did not differ between groups (median 73 and 70.25), nor did the other clinical parameters or PROMs. Conclusions: The results suggest that neither of the loading protocols with the implants used influenced the marginal bone level-not the osseointegration rate, clinical conditions, or PROMs.

Sinus Floor Elevation via an Osteotome Technique without Biomaterials.

According to classic Hirschfeld studies, the first teeth to be lost are the first and second maxillary molars. After the teeth are extracted and the alveolar process is developed, the maxillary sinus is reabsorbed and pneumatized with a decrease in bone availability in the posterior sector of the maxilla. This process often creates the need to perform regeneration techniques for the placement of implants in this area due to the low availability of bone. The most frequently used and documented technique for the elevation of the sinus maxillary floor is elevation by the side window, as proposed by Tatum. In 1994, Summers proposed a technique that allowed the elevation of the sinus floor from a crestal access using an instrument called an osteotome, as well as the placement of the implant in the same surgical act. The aimed of the study was to evaluate the survival of 32 implants placed in posterior maxilla with bone availability less than 5 mm performing a sinus lift augmentation technique with osteotome without biomaterials. The results of this study show a survival rate of 100% for 32 implants placed in situations with an initial bone availability of 2 to 5 mm without the use of graft material. The infra-drilling technique used offers an increase in the primary stability of implants that allows adequate osteointegration Implants placed were charged at 12 weeks. In all cases, spontaneous bone formation was observed, even in cases where a positive Valsalva maneuver was observed. This proposed technique reduces treatment time and the need for more invasive maxillary sinus augmentation techniques.

Burnout and depression among Spanish periodontology practitioners.

OBJECTIVES: The objective of this study was to determine the prevalence of burnout syndrome and depression symptoms among periodontology practitioners, as well as the relationship with socio-demographic variables and work stress. STUDY DESIGN: A total of 284 subjects, members of the Spanish Society of Periodontology (SEPA), were selected for this study. The Spanish version of the Maslach Burnout Inventory (MBI) and the Tetradimensional Estructural Questionnaire for Depression (TEC-DE) were sent by post to all participants. Descriptive statistics in addition to mean comparison and chi-square test were used for data analysis. RESULTS: A response rate of 59.85% was obtained. From the total sample, 40% shows high levels of emotional exhaustion, 20% increased depersonalization and 11.20% diminished personal accomplishment. The prevalence of any depression symptom was nearly 16%. Moreover, higher prevalence was found among those practitioners not working a continuous shift and not practicing periodontology on an exclusive basis. CONCLUSION: Among Spanish periodontology practitioners, a high prevalence of burnout and depression exists.

Effects of Different Undersizing Site Preparations on Implant Stability.

As immediate loading protocols are becoming more frequent, the primary stability of implants has become an essential criterion for the osseointegration of dental implants. Based on this, the objective of this study was to understand the influence of different undersized surgical preparation sites on the insertion torque (IT) and implant stability quotient (ISQ). Four different site-preparation protocols were performed on fresh humid type III bovine bone: one control, the standard protocol recommended by the manufacturer (P1), and three variations of undersized techniques (P2, P3 and P4). The implant used was VEGA by Klockner Implant System. The sample size was n = 40 for each of the four groups. A torquemeter was used to measure the IT, and the ISQ was measured with a Penguin RFA. Both variables showed a tendency to increase as the preparation technique was reduced, although not all the values were statistically significant (p < 0.05) when comparing with the standard preparation. The preparations without a cortical drill, P2 and P4, showed better results than those with a cortical drill. Given the limitations of this study, it can be concluded that reducing the implant preparation can increase both the IT and ISQ. Removing the cortical drill is an effective method for increasing implant stability, although it should be used carefully.

A Non-Interventional Study Documenting Use and Success of Tissue Level Implants.

Numerous randomised controlled multicentric studies have investigated various responses to different treatment modalities with dental implants. These studies do not always show the results of daily practice as they are performed under controlled and strict clinical conditions. This multicentric, non-interventionist trial aimed to document the behaviour of implants when used in daily dental practice, without inclusion or exclusion criteria. One hundred and ninety-six screw-shaped, tissue-level implants were placed, and each clinician decided which implant, surgical loading and prosthetic protocol to use. At surgery, data related to the implants were recorded. Additionally, the crestal bone level changes were evaluated for up to two years of follow-up. Two implants were lost before they were loaded. The success rate was 98.31%, and the survival rate was 98.79%. The implant stability quotient (ISQ) at surgery was 68.61 ± 10.35 and at 2 years was 74.39 ± 9.64. The crestal-shoulder distances were 1.25 ± 1.09 mm and 1.68 ± 1.07 mm in the mesial and distal aspects on the day of surgery, respectively, and 2.04 ± 0.91 and 2.16 ± 0.99 mm at 2 years, respectively. At 2 years, 69.3% of the patients were highly satisfied. The use of implants under standard conditions seemed to have success rates similar to their placement in controlled studies.

Influence of the CAD-CAM Systems on the Marginal Accuracy and Mechanical Properties of Dental Restorations.

The aim of this study was to compare the quality of different computer-assisted-design and computer assisted manufacturing systems (CAD-CAM) generated by only one scanner, focusing on vertical fit discrepancies and the mechanical properties. A master model was obtained from a real clinical situation: the replacement of an absent (pontic) tooth, with the construction of a fixed partial denture on natural abutments with three elements. Nine scans were performed by each tested and 36 copies were designed using a dental CAD-CAM software (Exocad). The frameworks were manufactured using three-axis and five-axis, with the same batch of the chrome-cobalt (CrCo) alloy. The frameworks were not cemented. A focus ion beam-high resolution scanning electron microscope (FIB-HRSEM) allowed us to obtain the vertical gap measurements in five points for each specimen. Roughness parameters were measured using white light interferometry (WLI). The samples were mechanically characterized by means of flexural tests. A servo-hydraulic testing machine was used with a cross-head rate of 1 mm/min. One-way ANOVA statistical analysis was performed to determine whether the vertical discrepancies and mechanical properties were significantly different between each group (significance level p < 0.05). The overall mean marginal gap values ranged: from 92.38 ± 19.24 µm to 19.46 ± 10.20 µm, for the samples produced by three-axis and five-axis machines, respectively. Roughness was lower in the five-axis machine than the three-axis one, and as a consequence, the surface quality was better when the five-axis machine was used. These results revealed a statistically significant difference (p < 0.005) in the mean marginal gap between the CAD-CAM systems studied. The flexural strength for these restorations range from 6500 to 7000 N, and does not present any statistical differences' significance between two CAD-CAM systems studied. This contribution suggests that the number of axes improves vertical fit and surface quality due to the lower roughness. These claims show some discrepancies with other studies.

Improvement of Periodontal Parameters with the Sole Use of Free Gingival Grafts in Orthodontic Patients: Correlation with Periodontal Indices. A 15-Month Clinical Study.

The aim of this study was to evaluate the changes in periodontal parameters solely using free gingival grafts during orthodontic treatment without any oral hygiene re-enforcement. METHODS: A total of 19 patients underwent periodontal examination before orthodontic treatment. Patients received oral hygiene instruction and professional hygiene therapy. Where needed; full periodontal treatment was completed. Only periodontally stable patients were included in the study. Periodontal indices and keratinized tissue were recorded at time 0 (T0) (delivery of orthodontic appliances), and at three months (T1) during orthodontic therapy; when surgery was performed. At T1; orthodontically treated sites with minimum keratinized tissue (≤1 mm) received a free gingival graft to enhance the band of keratinized tissue. At three months after surgery (T2), new measurements were recorded. The orthodontics-treated sites after three months (T1) were used as control. The same sites were used as a test three months after mucogingival correction (T2). Between T1 and T2; orthodontics was suspended; no professional oral hygiene was performed; and no additional oral hygiene instructions were given to the patient. No oral hygiene procedures were administered for 15 months (T3), when the final recordings were taken. RESULTS: The results showed that there was a worsening of gingival index (GI) and plaque index (PI) of the treated sites between T0 and T1 during initial orthodontics treatment; whereas there was an improvement of the gingival inflammation at T2 when compared with T1. At T2; there was also a statistically significant improvement in GI and PI compared with T0. A T3 improvement in periodontal parameters was sustained. A non-parametric test (Wilcoxon signed-rank test) was used for statistical analysis. CONCLUSIONS: Augmentation of the width of keratinized gingiva; as the sole treatment; favors the improvement of GI and PI during orthodontic therapy.