The International Journal of Oral & Maxillofacial Implants, 05/2016

Purpose: The purpose of this study was to investigate the influence of implant and drill diameters on the stability of implant and bone response. Materials and Methods: An implant (GS II, Osstem Implant) with a 3.5-mm diameter and drills with three different diameters, differentiating the volume of bone compacted by the implant, were used in this study. Measurement of the insertion torque and observation of bone compression patterns were done during implant site preparation in minipigs. Also, analysis of resonance frequency, histomorphology, marginal bone resorption, and new bone formation were performed. Results: Microstrains and microcracks occurred in cortical bone around the thread when a drill with a smaller diameter than that of the thread was used. Higher implant stability was shown and maintained when a small-diameter drill was used. When using a drill with a smaller diameter than the root diameter of the implant thread, the bone-to-implant contact/bone area (BIC/BA) was higher than the wider drill during the whole test period. However, the use of a wide drill was the most rapid in increasing the BIC/BA value by new bone formation. In the cancellous bone, the speed of new bone formation was not different in each test group. However, the formation of new bone was faster when a large-diameter drill was used in the cortical bone. There was no significant difference in marginal bone loss (MBL) according to drill diameters, but the speed of MBL was fast when using a drill that was smaller than the root diameter of the implant thread. Conclusion: Implant stability, BIC, and BA were high when using a final drill that was smaller than the root diameter of the implant thread compared with a wide final drill. However, the speed of new bone formation was relatively slow and the speed of MBL was relatively fast if the final drill was excessively smaller. Schlagwörter: bone response, dental implant, implant stability, osteotomy preparation size

Purpose: Various advanced technologies have been designed to estimate dental implant stability, including insertion torque, implant damping using the Periotest, and resonance frequency analysis expressed in implant stability quotient units. This study aimed to establish the relationship between the estimates for these three techniques. Materials and Methods: Bovine cortical bone blocks were trimmed to square shapes of precisely controlled thickness and density. Thereafter, 4-mm-diameter × 10-mm-long implants were placed in the bone blocks using 30-, 45-, and 60-Ncm insertion torques. Implant damping and resonance frequency analysis were conducted at four angles for each implant. Spearman correlation coefficients were calculated to examine the relationship between insertion torque, resonance frequency analysis, and implant damping measured values. Results: Resonance frequency analysis and implant damping estimates exhibited a strong inverse correlation (r = −0.98, P .001). A linear equation was formulated: Periotest value = 15.54 + (−0.26 × implant stability quotient). Implant damping and resonance frequency estimates revealed a weak correlation with insertion torque (P .05). Conclusion: This study mathematically defined a linear correlation between implant damping and resonance frequency estimates, thereby providing a guide for clinicians when deciding the loading time for dental implants using the implant damping or resonance frequency estimates. Schlagwörter: damping, implant stability, insertion torque, Periotest, resonance frequency analysis

Purpose: Little information is available in the literature regarding the accuracy of marginal fit of abutments made from different materials. The aim of this study was to compare the level of vertical misfit in abutments made from different materials before and after cyclic loading. Materials and Methods: Thirty external hexagon implants, 3.75-mm diameter and 13-mm length, were embedded in epoxy resin and divided into three groups according to abutment type (n = 10): (1) machined titanium (Ti) abutments; (2) premachined gold-alloy (Au) abutments; and (3) machined zirconia (Zr) abutments. The abutments were attached to their respective implants by titanium alloy screws at the manufacturer's recommended torque. A cyclic loading (0.5 × 106 cycles; 15 Hz) between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants. Implant-abutment vertical misfits (μm) were measured at four predetermined points before and after loading with a stereomicroscope at 60× magnification. The group means were compared using a three-way repeated-measure analysis of variance (ANOVA) and Tukey test (α = .05). Results: The results from the ANOVA identified significant effects of the abutment type (P .001). However, there were no significant effects of cyclic loading (P = .978) or measured surfaces (P = .955). When the abutment groups were compared regardless of cyclic loading and measured surfaces, the Au group showed the highest value of vertical misfit (14.93 ± 0.78), followed by the Ti group (8.53 ± 0.44) and the Zr group (5.64 ± 0.73), with statistically significant differences among them (P .05). Conclusion: The abutment groups showed statistically significant differences in vertical misfit. Zr abutments showed the highest accuracy in terms of marginal fit, and Au abutments showed the lowest. Cyclic loading did not significantly change the level of vertical misfit. All experimental groups presented acceptable values of marginal misfit. Schlagwörter: dental abutments, dental implant-abutment interface, dental implants, single-tooth, zirconium

Purpose: Misfit is a risk factor for rehabilitation with implants, and its detection is of fundamental importance to the success of treatment with implants. The use of appropriate radiographic imaging is key for a good prognosis. The aim of this study was to compare the efficacy of film and digital radiographs for the detection of misfit at the implant-abutment interface. Materials and Methods: Digital and conventional (manual and automatic processing) radiography was performed in seven test specimens, each one with a different vertical misfit between the abutment and the platform of the implant. Scanning electron microscopy was used to confirm the misfit and to measure it. Five dental radiologists independently and blindly evaluated the images. Cohen's kappa with linear weighting was calculated to determine interexaminer and intraexaminer concordance. Statistical analyses were performed using the Cochran's Q test and the receiver operating characteristic curve (ROC). Results: Interexaminer analysis showed that the kappa value was equal to 0.74, whereas the average kappa value in the intraexaminer evaluation was 0.90. Digital imaging showed the largest area on the ROC graph, and conventional images with manual processing showed the smallest area. The images obtained through conventional radiography with both manual and automatic processing showed statistically significant differences from the measurement of the gold standard (P .05). Conclusion: Digital imaging can be used to evaluate misfit at the implant-abutment interface. Conventional systems of radiographic imaging do not provide sufficient information to evaluate misfit at the implant-abutment interface. Schlagwörter: dental prosthesis fixed by implants, digital dental radiograph, prosthesis failure

Purpose: The aim of this prospective clinical study was to evaluate the survival up to 5 years of Morse cone-connection implants with platform switch considering the influence of biologically relevant, anatomical, and stress-related variables. STROBE guidelines were followed. Materials and Methods: Seven hundred forty-eight implants were inserted in 350 patients. Follow-up visits were scheduled at the time of stagetwo surgery (2 months later) and at 6, 12, 24, 36, and 60 months. All implants were initially loaded with a cemented provisional acrylic restoration. The definitive metal-ceramic restorations were cemented at the 6-month follow-up. Implant cumulative survival rates (CSRs) were calculated using life table actuarial method. Survival data were also analyzed by the log-rank test and Cox regression. The statistical analysis was conducted at the patient level. P ≤ .05 was considered as an indicator of statistical significance. Results: During the follow-up (mean: 40 months; SD: 20.27), 28 patients were considered failed (8%). The CSR and its standard error (SE) was 92% ± 2.17%. Patients with implant-supported single crowns had a CSR of 90%, whereas those with implant-supported fixed dental prostheses had a CSR of 93%. The implant diameter (P = .0399) and implant length (P = .0441) were statistically significant. The probability of failure was almost 75% lower for patients with wide rather than standard implants, 91% lower for patients with long implants, and 69% lower for patients with standard implants compared with short implants. Conclusion: The use of Morse cone-connection implants with platform switch is a safe and reliable treatment method. Stress-related variables influence the risk of failure confirming the importance of biomechanical factors in the longevity of osseointegrated implants; thus, the clinician may obtain better results if attention is paid to these factors. Schlagwörter: cumulative survival rate, dental implant platform switching, dental implants, implant-supported dental prosthesis, Morse-taper dental implant-abutment connection, prospective study

Purpose: The aim of this study was to evaluate and compare the retention and stability of mandibular implant overdentures using different types of resilient attachments. Materials and Methods: Two implant analogs were inserted in the canine areas of an acrylic edentulous mandibular model. A metal-reinforced experimental overdenture was constructed and connected to the implant analogs (on two occasions) using either resilient telescopic or Locator attachments. Locators were divided into three subgroups according to the degree of retention of the male nylon insert: Locator extra-light retention (blue insert), Locator light retention (pink insert), and Locator medium retention (transparent insert). Vertical and oblique (anterior, posterior, and lateral) dislodging forces were measured at the beginning of the study (initial retention) and after 540 cycles of denture insertion and removal (final retention). Results: For all dislodging forces, Locator medium recorded the highest initial and final retention. Telescopic attachments recorded the lowest retention during vertical and anterior dislodging, and Locator extra-light recorded the lowest retention during lateral and posterior dislodging. For all types of Locator attachments, anterior dislodging recorded the highest initial and final retention, and lateral dislodging recorded the lowest retention. For the telescopic attachment, posterior dislodgment recorded the highest initial and final retention, and anterior dislodging recorded the lowest retention. Conclusion: After repeated denture insertions and removals, the highest retention and stability were recorded with Locator medium followed by Locator light. The lowest retention was recorded with resilient telescopic attachment, and the lowest stability was recorded with Locator extra-light. Schlagwörter: attachment, implant overdenture, Locator, retention, telescopic

Purpose: The aims of this study were to develop a device for in vivo measurement of three-dimensional (3D) loads on implants and to investigate the effects of implant configuration on the load distribution under a three-unit fixed partial denture (FPD). Materials and Methods: A 67-year-old female patient with three implants (in the mandibular left second premolar, first molar, and second molar regions) was recruited. Four implant configurations for a three-unit FPD depending on the number and position of the implants were considered in this study. They included a three-implant prosthesis and three types of two-implant prosthesis: a central pontic, posterior cantilever, and anterior cantilever, with the same superstructure (splinted three crowns) for the same occlusal contact. Customized abutments and 3D piezoelectric force transducers were fixed to the implants of the four configurations with the superstructure. The loads on the implants were recorded during maximum voluntary clenching (MVC-test) and when chewing a piece of chewing gum (GUMtest). Results: The occlusal forces on the dental arch during MVC-test with the four implant configurations did not exhibit significant differences. In the three-implant prosthesis, there were no significant differences in the mean maximum resultant load on each implant in both tests. In the central pontic, the load on the second premolar was significantly greater than that on the second molar in the MVC-test but there were no significant differences in the GUM-test. High loads were detected on the first molar in both the posterior cantilever and anterior cantilever. The highest load was detected on the first molar in the posterior cantilever during the GUMtest. Conclusion: The in vivo 3D load-measuring device using the piezoelectric force transducers enabled the measurement of the functional load on implants supporting a FPD. The results suggested, within the limitations of this study, that a three-implant prosthesis and central pontic provide biomechanically beneficial designs compared with the posterior cantilever and anterior cantilever in terms of the equal distribution of loads on supporting implants. Schlagwörter: dental implant, fixed partial denture, occlusal force, transducers

Purpose: To evaluate the effect of implant coronal wall thickness on load-bearing capacity and screw joint stability. Materials and Methods: Experimental implants were customized after investigation of the thinnest coronal wall thickness of commercially available implant systems with a regular platform diameter. Implants with four coronal wall thicknesses (0.2, 0.3, 0.4, and 0.5 mm) were fabricated. Three sets of tests were performed. The first set was a failure test to evaluate load-bearing capacity and elastic limit. The second and third sets were cyclic and static loading tests. After abutment screw tightening of each implant, vertical cyclic loading of 250 N or static loading from 250 to 800 N was applied. Coronal diameter expansion, axial displacement, and removal torque values of the implants were compared. Repeated measures analysis of variance (ANOVA) was used for statistical analysis (α = .05). Results: Implants with 0.2-mm coronal wall thickness demonstrated significantly low load-bearing capacity and elastic limit (both P .05). These implants also showed significantly large coronal diameter expansion and axial displacement after screw tightening (both P .05). Greater vertical load and thinner coronal wall thickness significantly increased coronal diameter expansion of the implant, axial displacement of the abutment, and removal torque loss of the abutment screw (all P .05). Conclusion: Implant coronal wall thickness of 0.2 mm produces significantly inferior load-bearing capacity and screw joint stability. Schlagwörter: axial displacement, coronal wall thickness, internal conical connection, load-bearing capacity, wedge effect

Purpose: The purpose of this study was to visualize the mode and impact of force transmission in narrowdiameter implants with different implant-abutment designs and material properties and to quantify the displacement of the abutment. Materials and Methods: Narrow-diameter implants from two manufacturers were examined: Astra 3.0-mm-diameter implants (Astra OsseoSpeed TX; n = 2) and Straumann Bone Level implants with a 3.3-mm diameter made of commercially pure titanium (cpTi) Gr. 4 (n = 2) and 3.3-mm TiZr-alloy (n = 2; Bone Level, Straumann) under incremental force application using synchrotron radiography (absorption and inline x-ray phase-contrast) and tomography. Results: During loading (250 N), Astra 3.0 and Bone Level 3.3- mm implants showed a deformation of the outer implant shoulder of 61.75 to 95 μm independent of the implant body material; the inner implant diameter showed a deformation of 71.25 to 109.25 μm. A deformation of the implant shoulder persisted after the removal of the load (range, 42.75 to 104.5 μm). An angulated intrusion of the abutment (maximum, 140 μm) into the implant body during load application was demonstrated; this spatial displacement persisted after removal of the load. Conclusion: This study demonstrated a deformation of the implant shoulder and displacement of the abutment during load application in narrow-diameter implants. Schlagwörter: abutment intrusion, implant diameter, implant shoulder deformation, narrow diameter, overload, synchrotron radiography and tomography

Purpose: To evaluate the maximum strength and the maximum aperture supported by mini-implant screws of three different diameters in an in vitro rapid maxillary expander model. Materials and Methods: Fifteen appliances were mounted in artificial bone polyurethane blocks. In each appliance, a Hyrax expander anchored by four mini-implant screw sets of three different diameters were divided into: group 1 (n = 5), 1.8-mm-diameter screws; group 2 (n = 5), 2.0-mm-diameter screws; and group 3 (n = 5), 2.2-mm-diameter screws. All sets (bone blocks + expander + four mini-implants) were inserted into a customized and standardized device that simulated a mid-palate disjunction. The expanders were activated to mechanically test the insertion of the mini-implant into the devices until breakage or deflection of screws occurred. The number of activations, the maximum supported strength, and the maximum expander aperture values until failure were recorded for each group. Data were subjected to a Student t test at a significance level of 5%. Results: There were no significant differences between the groups regarding the number of activations up to the maximum supported strength. The expander achieved aperture values where differences were slightly significant just between groups 1 and 2 (P = .048). There was a significant difference between groups 1 and 3 regarding the maximum supported load (P = .039). Conclusion: Regardless of the mini-implant screw diameters, the expander device used in this anchorage system model withstood strengths and aperture rates beyond those that may be required during clinical rapid maxillary expansion. Schlagwörter: artificial bone, bone anchorage, mini-implant screws, rapid maxillary expansion

Purpose: The aim of this review was to systematically appraise survival rates of implants placed using the osteotome technique with and without grafting in the published literature. Materials and Methods: An electronic search was conducted to identify prospective and retrospective studies on osteotome sinus floor elevation published between January 1, 2000 and October 30, 2015. Studies were included that (1) involved use of the osteotome technique with or without grafting; (2) provided data regarding the implant survival rates, residual bone height (RBH), and grafting materials; and (3) reported mean follow-up of at least 1 year after functional loading and included a minimum of 10 patients. The mean weighted cumulative implant survival rates were used to compare the two treatment strategies-grafted or nongrafted. The influence of RBH and implant length on weighted cumulative implant survival was also evaluated. Results: After search and evaluation of the literature according to the inclusion criteria, 34 studies involving 1,977 patients and 3,119 implants were included. Eighty-four out of 102 implant failures documented in the studies occurred within 1 year of functional loading. Statistically significant differences in the cumulative survival rates were found in the graft and nongraft groups (95.89% and 97.30%, respectively; P = .05). In the nongraft group, no statistically significant difference in the cumulative survival rate was found when implants were placed at RBH 5 mm or ≥ 5 mm (95.04% and 97.63%, respectively; P = .12). In the graft group, however, a statistically significant difference was found when implants were placed at RBH 5 mm or ≥ 5 mm (92.19% and 97.59%, respectively; P .01). Significantly lower weighted mean cumulative implant survival rates were found in the shorter ( 8 mm) implant group than in the longer (≥ 8 mm) implant group (83.33% and 96.28%, respectively; P .01). Conclusion: The cumulative survival rates were significantly higher in the nongraft group than in the graft group. Early failures ( 1 year functional loading) accounted for the vast majority of the implant failures. The cumulative survival rates in the graft group were significantly lower when the RBH was 5 mm, while the cumulative survival rates in the nongraft group demonstrated no statistically significant difference based on RBH. Shorter ( 8 mm) implants demonstrated significantly lower cumulative survival rates than longer implants. Schlagwörter: dental implants, osteotome technique, survival rates, systematic review

Purpose: The aim of this study was to determine the prevalence of interproximal open contacts between singleimplant prostheses and adjacent teeth, as well as to provide guidelines to prevent interproximal contact loss (ICL). Materials and Methods: This was a retrospective, cross-sectional study. One hundred twenty-eight patients (174 single-implant restorations) from Columbia University College of Dental Medicine and a private faculty clinic with a single-implant restoration in the posterior or anterior region were selected to participate in this study. Patients between the ages of 19 and 91, both male and female, were included in this pilot study. The period of evaluation after implant restoration insertion was between 3 months and 11 years. Participants were seen at random intervals to identify ICL. Interproximal contacts were evaluated with 0.07-mm-thickness dental floss and visual confirmation. Contact was considered open if floss passed without resistance from adjacent teeth. Results: The results of this study revealed a significant percentage of ICL, 52.8%, between single-implant restorations and adjacent teeth; 78.2% were identified on the mesial surfaces and 21.8% on the distal surfaces. ICL was noted in 57.9% of the maxillary implant restorations and 49% of the mandibular implant restorations. Eight implant restorations in women demonstrated mesial and distal openings. Among the patients with ICL, a significant percentage, 40%, were aware of the presence of ICL and food impaction. Conclusion: In this study, 52.8% of implant restorations demonstrated ICL. This result dictates that ICL should be included as a prosthetic implant complication. The high prevalence of ICL is justification for proper informed consent, and associated clinical problems need to be addressed. Possible causative factors were presented, but further research is necessary to identify the causative factors for ICL. The authors suggest the use of an Essix retainer to prevent ICL between single-implant restorations and adjacent teeth. Evaluation of interproximal contact between implant restorations and the adjacent teeth should be periodically monitored. Schlagwörter: implant complications, implant prosthesis, interproximal open contacts

Purpose: Obesity as a systemic risk factor associated with implant failure or other complications has not been studied. The aim of this study was to compare the frequency of implant failure and complications between obese and nonobese patients. Materials and Methods: Charts from 220 partially edentulous patients with 321 implants were examined for demographic information, medical health history, diabetes, smoking, patient-reported height and weight, periodontal status (no, mild, moderate, or severe periodontitis), tooth number, date of the implant and prosthesis placement, and treatment notes pertinent to the complications or failure. Subjects were classified according to their body mass index (BMI) as normal (18.5 to 24.5 kg/m²), overweight (25 to 29.9 kg/m²), or obese (≥ 30 kg/m²) based on self-reported height and weight. Variables including sex, smoking, diabetes, and periodontal condition were considered as confounders. Data were analyzed to examine differences in frequency of complications and occurrence of failures. Results: Implant failure was low (2.1%) and did not differ by BMI category. Compared with normal BMI patients, obese patients had increased odds of experiencing an implant complication (OR = 4.9, 95% CI [1.4, 17.6]) after adjustment for other variables. Diabetes was not associated with an increased risk of complications; obese patients with diabetes had decreased odds of an implant complication compared with obese patients without diabetes. Conclusion: No association was observed between obesity and implant failures. BMI category was associated with implant complications; obese patients have greater odds of experiencing implant complications postsurgically. Treating obese patients with the existing protocol for diabetic patients (antibiotic regimens, more frequent follow-up, and maintenance appointments) may improve clinical outcomes. Schlagwörter: clinical outcomes, dental implants, obesity, systemic risk factors

Purpose: The aim of this study was to describe the clinical outcome of osteomyelitis of the mandible or maxilla following dental implants. A detailed treatment protocol is also proposed. Materials and Methods: Electronic data of all the patients who were treated between October 2009 and November 2014, in three maxillofacial surgical departments, were reviewed. Computed databases were searched for the diagnosis of osteomyelitis of the mandible or maxillas (ICD9 code 526.2), and medical files were analyzed. Treatment outcome was considered successful if only primary treatment (debridement and antibiotic therapy) was applied. Statistical analysis was performed to compare treatment outcomes in the different etiologic groups. Results: The cohort included 29 men and 25 women, with histologically and clinically proven osteomyelitis. The mean age was 59 years (range, 24 to 70 years). Forty patients had complete remission, as opposed to 14 patients who failed the primary treatment and required a more aggressive surgical intervention (11 had segmental mandibulectomy, 2 patients had marginal mandibulectomy, and 1 patient had maxillectomy). Most failures were in the dental implantation group. A previous dental implant was an independent factor for primary treatment failure and the need for aggressive surgical intervention (P = .0001). Conclusion: The results of this retrospective study suggest that a previous dental implant is an independent predictive factor of failure in primary treatment in osteomyelitis of the mandible or maxilla. Also, dental implant-induced osteomyelitis is a rare pathology, but it presents an aggressive subtype of osteomyelitis, and requires a broader and more comprehensive management. Schlagwörter: dental implant, maxillectomy, osteomyelitis of the jaws, segmental mandibulectomy

Purpose: To report the clinical and radiographic outcomes of a 3-year follow-up of immediately and early loaded two-implant-supported mandibular overdentures. Materials and Methods: Forty edentulous patients were randomly subdivided into two groups. In the immediate loading group, two Straumann implants were splinted with a Dolder bar and loaded with a mandibular overdenture within the first 48 hours postoperative. In the early loading group, the two implants were loaded with an overdenture 6 weeks postoperative. Standardized intraoral radiographs using a film holder were obtained at 1 month and 3 years. Two independent observers assessed marginal bone loss twice, independently, and analysis of variance (ANOVA) was used to follow up marginal bone level changes. Results: In total, there were 26 remaining patients available at the 3-year followup (15 immediate and 11 early). One implant was lost in the early loading group, and no implants were lost in the immediate loading group. All superstructures and dentures were adequately functional at the 3-year control. Mean radiographic marginal bone loss between baseline and the 3-year follow-up was 0.35 ± 0.63 mm for immediately loaded implants and 0.31 ± 0.96 mm for early loaded implants. The difference between the two groups was not statistically significant (P = .26). Conclusion: Within the limitations of this trial and the short follow-up period and high dropout rate, the immediate loading protocol was found to be comparable in its clinical and radiographic outcomes to the early loading protocol for the two-implant Dolder bar-supported mandibular overdentures. Schlagwörter: dental implants, early loading, immediate loading, radiographic analysis

Purpose: The purpose of this study was to compare the clinical outcome of and determine the differences in periodonto-pathogenic microbiota around two types of implant collar surfaces: laser-microtextured (test) vs machined (control). Materials and Methods: Seventeen patients (11 periodontally healthy, and 6 periodontally compromised) were selected to receive the two different implants, placed randomly, in two edentulous sites. Six months following the surgical placement of the dental implants, subgingival plaque samples were collected using paper points from the peri-implant sulcus and from the sulcus of an adjacent tooth. The presence of five putative periodontal pathogens, namely, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola, and Tannerella forsythensis, was assessed using real-time polymerized chain reaction (RT-PCR). Peri-implant parameters and intraoral radiographs were recorded up to 1 year after abutment connection. Results: In the main population, and in the periodontally compromised subgroup, the total number of periodontal pathogens around test implant sites was lower than control implant sites and adjacent tooth sites, with a statistically significant difference (P .05). In periodontally healthy patients, the mean probing pocket depth for the test implant was 1.31 ± 0.51 mm, compared with 2.66 ± 0.83 mm for the control implant, while in periodontally compromised patients, it was 1.61 ± 0.58 mm for the test implant, compared with a mean value of 2.84 ± 1.0 mm for the control implant. Conclusion: Implants with a laser-microtextured collar surface are not more vulnerable to pathogenic microflora colonization than implants with a machined collar surface. In both of the subgroups of patients (periodontally healthy and periodontally compromised), implants with a laser-microtextured collar surface have a better clinical outcome at 1 year of loading, compared with implants with a machined collar surface. Schlagwörter: bacteria, implant, microbiology

Purpose: Concerns have been expressed about the possibility of high insertion torque (IT) causing necrosis, impaired osseointegration, and crestal bone loss over time. The present study investigated the relationship between primary stability and implant success, including early and late maintenance of crestal bone levels. Materials and Methods: Implants were placed in patients at three study centers. Every effort was made to achieve the highest possible primary stability, which was measured with IT and implant stability quotient (ISQ). The IT and ISQ at insertion and reopening (3 to 4 months), as well as bone levels at several points in time, were recorded. The correlations between IT, ISQ, and immediate and 3-year crestal bone loss were investigated through linear regression analyses. Results: Average IT was 76.1 ± 20.8 Ncm, while the average ISQ score was 80.4 ± 8.4. The implant success rate at 36 months was 98.6%. The crestal bone loss around most implants (41.0%) ranged from 0.05 to 0.5 mm. None of the osseointegrated implants had crestal bone loss greater than 2.5 mm. The linear regression analysis showed no correlation among early or 3-year crestal bone loss and IT, ISQ at surgery, and ISQ at reopening. Conclusion: The implants studied avoided any negative effects deriving from the high IT values (> 50 Ncm) applied during 3 years of follow-up. Schlagwörter: crestal bone loss, implant stability quotient, implant success, insertion torque, RFA

Purpose: To compare splinted and individual restorations supported by short implants featuring an internal connection utilizing a split-mouth design. Materials and Methods: Splinted and nonsplinted implant crowns were prospectively compared in 18 patients. After verifying the need for at least two consecutive implants bilaterally, computed tomography scans were made, virtual planning was done, and qualifying patients were enrolled. Implants were placed using a two-stage surgical approach. After 3 to 5 months, patients were randomly restored with splinted prostheses on their left or right side. Nonsplinted restorations were made for contralateral sides. Radiographs were taken at prostheses seating and yearly exams. Radiographic bone levels were analyzed and compared (SAS 9.4) to determine differences between splinted and nonsplinted implants. Complications such as screw loosening, screw breakage, or porcelain fracture were assessed at recalls. Results: Eighteen patients (9 men and 9 women) with an age range from 49 to 76 years (mean = 56 years), received ≥ 4 implants in symmetrical posterior locations. Implants (n = 82) ranged in length from 6 to 11 mm with 70 implants ≤ 9 mm and 38 implants = 6 mm. At the time of this report, 3-year examinations and bone level comparisons were completed on 15 patients. One patient was lost to follow-up, one deviated from study protocol by smoking, and one was splinted on both sides due to repeated screw breakage. Screw loosening occurred in five patients on their nonsplinted side. These were 6-mm implants except for one patient. Porcelain chipping occurred for one patient on the splinted side. One 6-mm-length nonsplinted implant was lost after loading; this implant was successfully replaced after grafting. This patient had a total of six implants placed; ongoing bone level measurements included two pairs of implants only. For all implants combined, there was no significant difference (P > .05) at 1, 2, or 3 years for mean bone change around splinted and nonsplinted implants. However, length was identified as a significant factor (P = .0039). Further analysis revealed statistically significant differences between splinted and nonsplinted for 6-mmlength implants at 24 (P = .0061) and 36 (P = .0144) months. A gain in mean bone level of 0.41 and 0.37 mm was observed for nonsplinted implants at 24 and 36 months compared with baseline. Bone levels for the splinted 6-mm implants were not statistically different from baseline measurements (P > .05). Conclusion: Results of this prospective 3-year study of splinted ipsilateral and nonsplinted contralateral implants in 15 patients show: (1) peri-implant bone levels around splinted and nonsplinted implants were not statistically different for implants greater than 6 mm in length; (2) nonsplinted 6-mm implants revealed a gain in bone at 24 and 36 months compared with baseline; (3) all screw loosening only occurred on the nonsplinted side for 5 of 15 patients; and (4) implant loss after loading occurred for one 6-mm nonsplinted implant. Schlagwörter: nonsplinted prostheses, radiographic bone levels, splinted

Purpose: The aim of this study was to evaluate, in a case control study, the esthetic and functional clinical performance of ceramic inlays used for covering the screw access hole in single monolithic lithium disilicate full-contour crowns bonded on computer-aided design/computer-aided manufacturing (CAD/CAM) prefabricated titanium abutments in order to eliminate the drawbacks of alternative restorative methods. Materials and Methods: Twenty-eight patients with missing teeth in the lateral areas (premolars and molars) received screw-retained implant restorations. In half of the restorations (n = 14), composite fillings were used to seal the access hole (control group), while the other half was sealed with ceramic inlays (test group). To determine the restoration occlusal wear, impressions were obtained after the restorations were finalized, at 1 year, and at 2 years follow-up. The casts were scanned with a 3D Scanner Design System recording the anatomical surfaces of the white model replicates. Wear amounts (μm) were calculated as the maximum loss in height of the occlusal surface. The clinical evaluation was carried out using a kit specifically designed for assessing the FDI criteria. Statistics were performed using analysis of variance (ANOVA). Results: A total of 58 restorations were delivered, and after 2 years of follow-up, the wear values were 228.20 ± 54.68 μm for the control group and 65.20 ± 7.24 μm for the ceramic inlay group. One-way ANOVA showed significant differences among the vertical loss between these two groups (P .001). Clinical outcomes according to the FDI score for assessing dental restorations revealed substantial deterioration within 2 years of follow-up. Conclusion: The use of ceramic inlays appears to be a predictable, esthetic, and successful method of sealing the screw holes of the screw-retained implant restorations. Schlagwörter: composite resins, esthetics, implant-supported dental prostheses, inlays, restoration occlusal wear, screw

Purpose: To compare long-term survival and marginal bone loss of immediate interantral implants in the nonaugmented maxilla subjected to immediate vs delayed loading. Materials and Methods: Graftless maxillary cross-arch rehabilitation was performed in a total of 362 patients in the years 2004 to 2013 (1,797 implants). Of the 240 patients with immediate implants replacing their failing maxillary dentition, 81% were subjected to immediate loading and 19% to delayed loading of their 4 to 6 interantral implants (980 and 235 implants, respectively). Kaplan-Meier survival estimates were computed and marginal bone loss was evaluated in a stratified random sample of 20 patients per group. Results: Thirty-one of 1,215 implants failed within the mean observation period of 3.9 years, and no difference in 8-year survival estimates could be seen between immediate (97.6% [95% CI: 96.7 to 98.6]) and delayed (96.6% [95% CI: 94.3 to 98.9]) loading protocols (P = .359). Mean marginal bone resorption following implant insertion did not differ significantly between the groups (1.5 ± 1.7 mm vs 0.7 ± 1.1 mm, P = .379); however, it was significantly associated with a reduced number of implants (P = .017) and patient history of periodontal disease (P .001). Conclusion: Immediate loading of interantral implants yields satisfactory results in the transition of patients from a failing maxillary dentition to full-arch implant rehabilitation and thus may be favored over delayed loading concepts. Schlagwörter: complete denture, dental implants, edentulous arch, immediate dental implant loading, implantsupported dental prosthesis, maxilla

Purpose: There is a need for more studies evaluating the marginal bone loss (MBL) of rehabilitations in the posterior regions of extremely resorbed maxillae and mandibles supported by short-length dental implants with a high crown/implant ratio (C/I-R). The aim of this study was to evaluate the influence of the C/I-R in implants on MBL considering dental implants with 4 mm of width and 7 mm of length. Materials and Methods: This retrospective cohort study included 59 patients (mean age of 52.8 years) rehabilitated with at least one implant 4 mm in width and 7 mm in length, with an anodically oxidized surface and external connection on the premolar or molar positions, supporting a fixed prosthesis, and in function for a period of 36 months. Periapical radiographs at 36 months were used to calculate the C/I-R and MBL. The Spearman correlation coefficient was used to test the correlation between C/I-R and MBL. The level of significance was set at 5%. Results: One hundred eighteen implants from 59 patients were evaluated. The mean ± SD MBL was 0.67 ± 0.63 mm. The C/I-R mean ± SD was 2.53 ± 0.79 mm. Thirty implants presented a C/I-R ≤ 2, while 88 implants had a C/I-R > 2. A weak nonsignificant inverse correlation (r = -0.081; P = .383, Spearman) was registered between C/I-R and MBL. Conclusion: Within the limitations of this study, it is possible to conclude that implant-supported fixed prostheses with C/I-R > 2 do not correlate positively with MBL. Schlagwörter: crown-to-implant ratio, marginal bone loss, short implant

Purpose: Successful immediate loading of implants in the edentulous maxilla has been previously reported. The purpose of this 5-year prospective study was to further assess long-term outcomes following immediate loading of implants in the edentulous maxilla with fixed provisional restorations without the use of bone augmentation procedures. Materials and Methods: Subjects with edentulous maxillary arches each received six implants placed in native bone without augmentation. Where insufficient posterior bone volume existed, angled implant placement was employed. Fixed provisional restorations were delivered within 24 hours of implant placement. Implant placement locations, insertion torque values, and implant dimensions were recorded. Definitive fixed prostheses were placed within 24 weeks following implantation. Baseline implant site marginal bone levels were measured using periapical radiographs. Baseline peri-implant plaque and bleeding scores were obtained. Subjects were examined 6 months after implant placement and then annually for 5 years with follow-up periapical radiographs and plaque/bleeding scores obtained. Results: Fifty-one subjects received a total of 306 implants. Forty subjects with 232 implants returned for the final follow-up appointment representing a 5-year implant survival proportion of 93% with a mean marginal bone loss of 0.44 ± 1.25 mm for this group. Thirty-nine of these 40 subjects continued to function with fixed restorations with the remaining subject functioning with a non-implant-retained removable prosthesis. Conclusion: Within the limitations of this study, predictable long-term implant rehabilitation outcomes were demonstrated for the edentulous maxilla using an immediate loading protocol without bone augmentation. Schlagwörter: dental arch, dental implants, immediate dental implant loading, maxilla

Purpose: The aim of this study was to investigate the effect of immediately loaded mini dental implants (MDIs) used to support mandibular overdentures on the peri-implant bone level as well as patients' related levels of satisfaction and quality of life. Materials and Methods: Four MDIs were placed in the interforaminal region of 10 completely edentulous patients, and the implants were loaded immediately (same day) with an overdenture. Radiographic assessment of the bone loss during a period of 18 months was performed by measuring the bone level changes at the mesial and distal aspects of each implant on panoramic radiographs. At the end of this period, patients' satisfaction level on the visual analog scale (VAS) and oral health-related quality of life was assessed by means of questionnaires. Results: A mean bone loss of 1.04 mm on the mesial and distal sides was recorded during the 18-month period after loading of the implants. The score for general satisfaction level was 95.67 ± 5.68. Similarly high VAS scores were given by the patients in all other specific items on patient satisfaction. The total score for the Oral Health Impact Profile-20 (OHIP-20) was 34.07 ± 13.90, which was comparable to that recorded in other studies. Conclusion: The short-term radiographic peri-implant bone level changes of MDIs immediately loaded with overdentures in the edentulous mandible were within the physiologic limits. The patients expressed a high level of satisfaction and oral health-related quality of life with this treatment modality. Schlagwörter: immediate loading, mini dental implants, OHIP-20, radiographic bone loss, VAS

Purpose: To retrospectively compare short implants (6 to 8 mm) (short group) to standard-length implants (≥ 11 mm) inserted in combination with a lateral sinus elevation procedure (sinus group), supporting partial fixed prostheses in the atrophic posterior maxilla. Materials and Methods: Records of 118 patients treated with fluoride-modified implants in the atrophic posterior maxilla between January 2009 and December 2011 were screened in two private practices. Two to four implants were placed in each patient and loaded after 5 to 6 months with partial fixed prostheses. Patients were followed for at least 3 years after implant placement. Patients were contacted and invited for clinical and radiologic follow-up examinations. Outcome measures were implant failures, complications, soft tissue parameters, and marginal bone levels. Fisher exact and unpaired t tests were used to compare proportions and means at the .05 level of significance. Results: A total of 101 patients attended the examination: 53 (112 implants) in the sinus group and 48 (109 implants) in the short group. The mean observation period was 47.03 ± 7.46 months for the sinus group and 44.18 ± 6.42 months for the short group. Ten surgical complications occurred in nine patients of the sinus group versus only one complication in the short group; the difference was statistically significant (P = .01). Six implants failed in five patients of the sinus group versus two implants in two patients of the short group. At follow-up, mean marginal bone loss was 0.64 ± 0.58 mm in the sinus group vs 0.48 ± 0.5 mm in the short group. No significant difference was observed in terms of implant failures, prosthetic complications, soft tissue parameters, or marginal bone loss between the two groups. Conclusion: Within the limitations of this study, both techniques showed similar medium-term outcomes, but short implants provided advantages in terms of a reduced number of surgical complications. Schlagwörter: anorganic bovine bone, complications, marginal bone loss, maxillary sinus augmentation, short dental implants, survival rate

Purpose: Compared with the general population, a poorer quality of bone-implant osseointegration occurs and at a higher failure rate in patients with type 2 diabetes mellitus. The aim of this study was to analyze the effects of local injection of nerve growth factor at the bone-implant interface after implantation in type 2 diabetic rats. Materials and Methods: Goto-Kakizaki (GK) rats (n = 30) were used as a model of type 2 diabetes mellitus, and Wistar rats were used as a control (n = 15). GK rats were assigned randomly into two groups (n = 15/group): the diabetes mellitus group (saline only) and the nerve growth factor group (received nerve growth factor treatment). One titanium implant was placed in each rat's left tibia. Immediately postoperatively, nerve growth factor group rats were injected with nerve growth factor (0.4 μg/ day) intramuscularly around the implant, daily for 7 days. Diabetes mellitus and control group rats received normal saline in an identical manner. Rats were sacrificed at 2, 4, and 8 weeks following implant surgery. Results: Traditional light and confocal laser scanning microscopy were used on nondecalcified sections to investigate fluorochrome labeling changes and histologic features of bone adjoining the implants. Bone-toimplant contact and bone volume percentage in the diabetes mellitus group were significantly less than in the control and nerve growth factor groups, with no statistically significant differences between the control and nerve growth factor groups. Confocal laser scanning microscopy showed a significant increase in marked bone around the nerve growth factor group implant at 4 weeks (P .01) and 8 weeks (P .05) compared with the diabetes mellitus group. Conclusion: This study showed that local injection of nerve growth factor could improve implant-bone osseointegration in diabetic rats and may have important clinical implications. Schlagwörter: implants, nerve growth factor, osseointegration, type 2 diabetes mellitus

Purpose: The aim of this study was to investigate the effect of different matrix designs on resilient attachment on an implant-assisted removable partial denture (IARPD) using finite element analysis (FEA). Materials and Methods: A laser scanner was used to extract the geometrical data of a human partially edentulous mandible. A 12-mm-long and 4.8-mm-diameter-wide implant was modeled, and two types of intradental attachment of snap fastener principle (elliptical) and resilient attachment (titanium) matrices were modeled along with tooth roots and periodontal ligaments. The modeling was performed with a combination of reverse engineering and solid modeling. The model incorporated a removable partial denture and was loaded with realistic bilateral forces. The FEA was used to analyze the stress and strain distributions in the IARPD and in the metal framework. Results: Stresses and deformations in the metal framework and resin denture base surfaces were analyzed for the elliptical and titanium matrix designs. The maximum von Mises stresses were 605.85 and 614.96 MPa in the metal framework surface and 10.35 and 10.63 MPa in the resin denture base surface, respectively, for the elliptical and titanium matrix designs. The maximum deformations (displacements) were 418.5 and 428.3 μm in the metal framework surface for the elliptical and titanium matrix designs, respectively. The corresponding values of displacements for the resin denture base surface were 325.52 and 249.22 μm for the elliptical and titanium matrix designs, respectively. The maximum displacements in the matrixes were, however, nearly the same (229.51 and 229.47 μm) for both the elliptical and titanium matrixes. Conclusion: The titanium matrix design was a more favorable design compared with the elliptical design, because it had lower lateral deformation as indicated by the maximum displacement. Schlagwörter: dental implant, elliptical design, implant-assisted, removable partial denture, resilient attachment, titanium matrix

Purpose: Bone density at implant placement sites is one of the key factors affecting implant primary stability, which is a determinant for implant osseointegration and rehabilitation success. Site-specific bone density assessment is, therefore, of paramount importance. Recently, an implant micromotor endowed with an instantaneous torque-measuring system has been introduced. The aim of this study was to assess the reliability of this system. Materials and Methods: Five blocks with different densities (0.16, 0.26, 0.33, 0.49, and 0.65 g/cm3) were used. A single trained operator measured the density of one of them (0.33 g/cm3), by means of five different devices (20 measurements/device). The five resulting datasets were analyzed through the analysis of variance (ANOVA) model to investigate interdevice variability. As differences were not significant (P = .41), the five devices were each assigned to a different operator, who collected 20 density measurements for each block, both under irrigation (I) and without irrigation (NI). Measurements were pooled and averaged for each block, and their correlation with the actual block-density values was investigated using linear regression analysis. The possible effect of irrigation on density measurement was additionally assessed. Results: Different devices provided reproducible, homogenous results. No significant interoperator variability was observed. Within the physiologic range of densities (> 0.30 g/cm3), the linear regression analysis showed a significant linear correlation between the mean torque measurements and the actual bone densities under both drilling conditions (r = 0.990 [I], r = 0.999 [NI]). Calibration lines were drawn under both conditions. Values collected under irrigation were lower than those collected without irrigation at all densities. The NI/I mean torque ratio was shown to decrease linearly with density (r = 0.998). The mean error introduced by the device-operator system was less than 10% in the range of normal jawbone density. Conclusion: Measurements performed with the device were linearly correlated with the blocks' bone densities. The results validate the device as an objective intraoperative tool for bone-density assessment that may contribute to proper jawbone-density evaluation and implant-insertion planning. Schlagwörter: bone density, cone-beam CT, CT scanner, dental implants, osteotomy, x-ray

Purpose: Maxillary implant overdentures are often used in clinical practice. However, there is no agreement or established guidelines regarding prosthetic design or optimal implant placement configuration. The purpose of this study was to examine the influence of palatal coverage and implant number and distribution in relation to impact strain under maxillary implant overdentures. Materials and Methods: A maxillary edentulous model with implants and experimental overdentures with and without palatal coverage was fabricated. Four strain gauges were attached to each implant, and they were positioned in the anterior, premolar, and molar areas. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the implant strains were compared using one-way analysis of variance (P = .05). Results: The palatolabial strain was much higher on anterior implants than on other implants in both denture types. Although there was no significant difference between the strain under dentures with and without palatal coverage, palateless dentures tended to result in higher implant strain than dentures with palatal coverage. Dentures supported by only two implants registered higher strain than those supported by four or six implants. Conclusion: Implants under palateless dentures registered higher strain than those under dentures with palatal coverage. Anterior implants exhibited higher palatolabial strain than other implants regardless of palatal coverage and implant configuration; it is therefore recommended that maxillary implant overdentures should be supported by six implants with support extending to the distal end of the arch. Schlagwörter: implant, load, maxillary implant overdenture, palateless denture, strain