The International Journal of Oral & Maxillofacial Implants, 04/2011

Purpose: To describe the use of a computer-aided three-dimensional planning protocol in combination with previously placed reference elements and computer-aided design/computer-assisted manufacture (CAD/CAM) technology to restore the partially edentulous patient. Materials and Methods: Mini-implants and/or reference brackets were inserted or positioned in specified locations in a test cast and in two patients prior to imaging to act as definitive fiducial markers. This served as a fixed base to better define a setup for the fabrication of a surgical template used during computed tomographic imaging. A simulated partially edentulous maxilla was used for the study, and two partially edentulous patients participated. With the CT images, a CAD/CAM superstructure was created prior to surgery and inserted immediately after surgery. Fit of the prosthesis was assessed using three-dimensional tension measurements with strain gauges. Results: Mean misfit for all implants in the x-, y-, and z-axes was 26.6, 24.8, and 10.4 µm, respectively. The total misfit calculated according to the Pythagorean theorem was 42.6 µm. Conclusions: Based upon this pilot study in two patients and an in vitro analysis, it appears that the use of reproducible fiducial markers consisting of mini-implants and reference brackets results in the fabrication of an acceptably accurately fitting definitive prosthesis prior to implant placement. Schlagwörter: dental implants, guided surgery, immediate loading

Purpose: This study was intended to investigate, through resonance frequency analysis (RFA), the stability of implants placed in an early loading protocol via the osteotome sinus floor elevation technique in the posterior maxilla. All implants featured a sandblasted/acid-etched active surface. Materials and Methods: An early loading protocol was considered for patients in whom implants with a sandblasted, large-grit/acid-etched active surface (SLActive) were placed in the posterior maxilla by the osteotome sinus floor elevation technique. Implant stability, which was measured by RFA at surgery and at weekly intervals for the following 6 weeks, was used as the most significant inclusion criterion. At the end of the stability observation period, only implants with a stability quotient of 65 or higher were loaded. Implants were followed for 2 years. Results: Twenty-seven patients received 42 implants, 40 of which were subjected to an early loading protocol 6 weeks after placement. Two years after loading, all 40 implants were surviving, without clinically or radiographically detectible complications. Conclusion: An early loading protocol can be used for SLActive implants placed in the posterior maxilla via the osteotome sinus floor elevation technique if their stability is confirmed by RFA. Schlagwörter: dental implants, early loading, implant stability, resonance frequency analysis, sinus floor elevation, surface properties

Purpose: The achievement of primary stability in porous and soft bone, where implants are more likely to fail, is one of the unresolved challenges of implant dentistry. Therefore, the aim of the study was to validate an osteoporotic animal model for analysis of poor-quality bone. Materials and Methods: Sixteen female New Zealand rabbits, each 6 months old and weighing 4 to 5 kg, were used in this study. The animals were anesthetized, and an in vivo densitometric analysis was performed by dual-energy x-ray absorptiometry (DEXA) to measure bone mineral density (BMD) in the calvaria, cervical spine, and tibia. Ovariectomy was then performed, and animals were fed a low-calcium diet that featured 0.07% calcium, rather than the 0.45% calcium of a standard diet, for 6 weeks. After this period, new densitometric measurements were carried out. Two-way analysis of variance was used for statistical evaluation. A P value of less than .05 was considered to be significant. Results: Together, ovariectomy and a low-calcium diet were able to induce a quick decrease in BMD, as measured at 6 weeks by DEXA. This decrease was statistically significant in the calvaria (P .001) and the cervical spine (P .05) but not in the tibia. Conclusion: Based upon this study, ovariectomy and a low-calcium diet are able to induce experimental osteoporosis in rabbits in a short period of time. Schlagwörter: animal model, bone mineral density, dental implant, dual-energy x-ray absorptiometry, osseointegration, osteoporosis, rabbit

Purpose: To evaluate osseointegration of a novel calcium phosphate (CaP)-coated titanium porous oxide implant surface. Materials and Methods: Twenty adult male New Zealand White rabbits were used. Each animal received two titanium porous oxide-surfaced implants (benchmark control: TiUnite, Nobel Biocare) and two novel CaP-coated titanium porous oxide-surfaces implants; they were randomly allocated to contralateral tibia implant sites. The animals were sacrificed after 2 or 4 weeks, and tissues were evaluated histometrically. Results: Healing was generally uneventful. A removal torque analysis showed significantly higher mean (± SE) peak values for the control implants than for the test implants at 2 weeks (31.4 ± 2.5 Ncm versus 20.4 ± 1.8 Ncm) and 4 weeks (48.4 ± 5.5 Ncm versus 30.3 ± 3.9 Ncm). Light microscopy showed no significant differences in local bone density around control and test implants at 2 and 4 weeks (range, 85% to 91% within the thread area and 91% to 95% immediately outside the threads). At 2 weeks, bone-implant contact for control and test implants averaged 81.8% ± 2.8% and 75.7% ± 4.6%, respectively, and at 4 weeks the bone-implant contact values were 79.4% ± 2.8% and 73.5% ± 4.2%, respectively; these differences were not significant. Backscatter scanning electron microscopy also showed no significant differences in local bone density at control and test implants at 2 and 4 weeks (range, 55% to 72% within the thread area and 75% to 81% immediately outside the threads). At 2 weeks, bone-implant contact for control and test implants averaged 66.4% ± 2.9% and 61.5% ± 5.1%, respectively, and at 4 weeks mean values were 60.1% ± 4.2% and 53.3% ± 4.6% (differences not significant). Conclusions: The results suggest that the novel CaP-coated surface effectively supports osseointegration. Schlagwörter: bone-implant contact, calcium phosphate, dental implants, osseointegration, titanium porous oxide

Purpose: To compare the strain development of conventionally cast three-unit fixed dental prostheses (FDPs) and FDPs fabricated through computer-aided design/computer-assisted manufacture (CAD/CAM) using the strain gauge technique. Materials and Methods: A two-implant situation was transferred to an acrylic resin replica, and strain gauges were attached mesially and distally adjacent to the implants. Seven groups (n = 10) of cement-retained FDPs were manufactured from all restorative materials available for the Etkon CAD/CAM system (Straumann CADCAM). Three groups (n = 10) of conventionally cast screw- and cement-retained superstructures served as controls. Strain development during FDP fixation was recorded, and the logarithm of the absolute strain values was used for statistical analysis (multivariate analysis of variance with Pillai's trace; α = .0033). Results: Significantly higher strain values for screw-retained FDPs were found than for all other restorations (P .0000). Conventionally cast cement-retained restorations showed significantly higher strain levels as compared to CAD/CAM restorations fabricated from titanium (P = .0032) and green machined zirconia (P = .0026). Screw-retained superstructures bonded to gold cylinders showed significantly lower strain levels than FDPs made from titanium (P = .0001) and green machined zirconia (P = .0012). No significant differences between the various groups of CAD/CAM restorations could be detected, except that polyamide-resin restorations showed significantly higher strain levels than InCeram Zirconia restorations (P .0000). Conclusions: CAD/CAM-fabricated restorations show fit that is at least as good as that seen for conventionally fabricated superstructures. The choice of restorative material seems to have only a minor effect on the passivity of fit. Schlagwörter: cement retention, computer-aided design, computer-assisted manufacture, passive fit, screw retention, strain development

Purpose: Surface roughness is known to affect the load-bearing strength of implants. However, the underlying mechanisms are not completely understood. This study sought to investigate the potential effects of bone-to-implant contact (BIC) and mechanical interlocking on the stability of titanium implants using a newly established assessment system that combines nondestructive microcomputed tomography (µCT) and the biomechanical push-in test. Materials and Methods: Cylindric implants with a machined or a dual acid-etched (DAE) surface were placed into the distal femurs of Sprague-Dawley rats. At weeks 2 and 4, the femur-implant specimens were harvested and scanned in a desktop µCT device, and the BIC was calculated. The implants were then loaded axially using a universal mechanical testing machine and the breakage force was recorded as a push-in value. Machined and DAE implants were also embedded in histology-quality resin to serve as a nonbiologic reference. Two-way analysis of variance and the Mann-Whitney U test were used for statistical analysis. Results: BIC showed no surface- or time-dependent differences. The mean push-in value of DAE implants was four times greater at week 2 and three times greater at week 4 than that of machined implants. The shear strength at the interface (push-in value/BIC) was greater for DAE surfaces than for machined surfaces in a proportionate manner. When the implants were embedded in the resin with virtually 100% implant-resin contact, DAE implants showed 30% greater push-in values and shear strength than machined implants (P .05). Conclusions: These findings suggest that the percentage of BIC and mechanical interlocking cannot fully explain the surface roughness-related increase in osseointegration, as opposed to the common understanding of osseointegration. Further studies must include more details to discover the precise understanding of the physiology of osseointegration and the potential biologic mechanisms involved. Schlagwörter: dental implants, microcomputed tomography, osseointegration, shear strength

Purpose: The distribution of stresses in bone, implants, and prosthesis were analyzed via three-dimensional finite element modeling in different implant configurations for a fixed implant-supported prosthesis in an edentulous mandible. Materials and Methods: A finite element model was created with data obtained from computed tomographic scans of a human mandible. Anisotropic characteristics for cortical and cancellous bone were incorporated into the model. Six different configurations of intraforaminal implants were tested, with the number of implants varying from three to five and the distal implants inserted either parallel to the other implants or tilted distally by 17 or 34 degrees. A prosthetic structure connecting the implants was designed, with 20-mm posterior cantilevers for the parallel implant configurations, and a load of 200 N was applied to the distal portion of the cantilevers. Stresses were measured at the level of the implant, the prosthetic structure, and the bone. Bone-level stresses were analyzed at the implant-bone interface, at the external cortical bone surface, distal to the terminal implant, and in the cancellous bone along the implant body. Results: A three-parallel-implant configuration resulted in higher stress in the implant and bone than configurations with four or five parallel implants. Configurations with the distal implants tilted resulted in a more favorable stress distribution at all levels. Conclusion: In parallel-implant configurations for fixed implant-supported mandibular prostheses, four and five implants resulted in similar stress distribution in the bone, framework, and implants. A distribution of four implants with the distal implants tilted 34 degrees (ie, the "All-on-Four" configuration) resulted in a favorable reduction of stresses in the bone, framework, and implants. Schlagwörter: anisotropy, edentulous mandible, finite element analysis, implant prosthesis, stress distribution, tilted implants

Purpose: The structure of peri-implant soft tissue that is regenerated after flapless and flap surgery has been shown to differ. However, its underlying mechanisms are relatively unknown. The present study sought to identify differences in the inflammatory cell infiltration and expression of gene transcripts during transmucosal healing between the two approaches with two different implant designs. Materials and Methods: All mandibular premolars were removed from 12 minipigs. One month later, four implants (two NobelReplace Tapered Groovy and two NobelPerfect Groovy, Nobel Biocare) were placed in each quadrant. One quadrant was randomized to flapless insertion, while the other was chosen for flap surgery in each animal. Following 1, 2, 4, and 12 weeks of transmucosal implant healing, biopsy specimens were retrieved from the peri-implant soft tissue according to a standardized procedure to avoid crossover effects. Samples were subjected to a leukocyte count and a gene expression analysis. Results: When the flapless placement technique was used, leukocyte influx in the peri-implant soft tissue was significantly smaller compared to open surgery for both implant designs. Gene expression analysis revealed significant overexpression of molecules associated with detoxification and reepithelialization in the flapless group. In contrast, myofibroblast-associated gene transcripts were significantly enriched in the flap surgery group. Conclusions: The present data indicate perpetuation of inflammatory reactions as well as increased fibrotic scar tissue deposition in the peri-implant area following implant placement by the flap approach. Flapless implant insertion results in less inflammation and early reepithelialization, providing the potential for the formation of a fully functioning as well as esthetically preferable peri-implant soft tissue collar. Schlagwörter: flapless surgery, soft tissue-implant interaction, wound healing

Purpose: This pilot study evaluated the wound healing and tissue response after placement of two different skin substitutes in subgingival mucosal pouches in rabbits. Materials and Methods: Four rabbits were selected to receive a commercially available skin substitute consisting of a collagen matrix with fibroblasts and an epithelial layer (test membrane 1) and a prototype device consisting of a collagen matrix with fibroblasts only (test membrane 2). In each rabbit, two horizontal incisions were made in the buccal alveolar mucosa of the maxilla bilaterally to create submucosal pouches. Three pouches in each animal were filled with either the test 1 or test 2 membranes, and one pouch was left without a membrane (sham-operated control). All rabbits were sacrificed after a healing period of 4 weeks, and histologic samples were prepared and examined. Results: After a healing period of 1 month, both tested membranes were still visible in the sections. Test membrane 1 was still bilayered, contained inflammatory cells in its center, and was encapsulated by a thick fibrous tissue. Numerous ectopic calcifications were evident in the collagenous part of the membrane and in association with some basal epithelial cells. Test membrane 2 was also encapsulated in fibrous tissue, with inflammatory cells present only between the fibrous encapsulation and the remnants of the membrane. For test membrane 2, no calcifications were visible. Conclusions: Test membrane 1 seemed to be more resistant to degradation, but there was also a more pronounced inflammatory reaction in comparison to test membrane 2, especially in the vicinity of the keratinocytes. The significance of the ectopic calcifications, along with that of the resorption or degradation processes of both tested membranes, must be evaluated in future experimental studies, with different time points after implantation examined. Schlagwörter: bioengineered skin substitutes, bioresorbable membranes, keratinocytes, submerged healing, tissue response, wound healing

Purpose: According to the so-called All-on-Four protocol, four dental implants are placed in the interforaminal region of the edentulous mandible to support full-arch fixed prostheses. In this design, the posterior implants are tilted distally to a maximum of 45 degrees. The purpose of this finite element study was to evaluate the stress concentration in peri-implant bone during two loading conditions and to compare this design with another design in which the four implants are placed parallel to each other and perpendicular to the occlusal plane. Materials and Methods: Three-dimensional finite element models consisted of mandibular bone, four dental implants inserted in two different configurations-with the distal implants tilted (model A) or four parallel implants (model S)-and hybrid superstructures. Two loading conditions (178 N/central incisors or 300 N/left first molar) were considered, and von Mises stress values were determined. Results: During anterior loading, higher stress concentrations were detected in the peri-implant bone of all four implants in model A. During posterior loading, lower stress concentrations were observed around the anterior implants of model A; however, the tilted posterior implants were subjected to higher stresses in every condition. Conclusions: Application of either of these designs was successful in reducing peri-implant stress in one loading condition. However, neither design demonstrated better performance in both loading conditions; therefore, within the limitations of this study, neither design demonstrated clearly superior performance. Schlagwörter: All-on-Four, edentulous mandible, finite element analysis, tilted implant

The aim of this in vitro study was to evaluate bacterial leakage along the implant-abutment interface under unloaded conditions. Twelve premachined abutments with plastic sleeves and 12 dental implants were used in this study. Prior to tests of bacterial leakage, samples from the inner parts of the implants were collected with sterile microbrushes to serve as negative controls for contamination. After casting, the abutments were tightened to 32 Ncm on the implants. The assemblies were immersed in 2.0 mL of human saliva and incubated for 7 days. After this period, possible contamination of the internal parts of the implants was evaluated using the DNA Checkerboard method. Microorganisms were found in the internal surfaces of all the implants evaluated. Aggregatibacter actinomycetemcomitans and Capnocytophaga gingivalis were the most incident species. No microorganisms were found in the samples recovered from the implants before contamination testing (negative control). Bacterial species from human saliva may penetrate the implant-abutment interface under unloaded conditions. Schlagwörter: bacterial leakage, dental implants, DNA Checkerboard, saliva

Purpose: Three-dimensional finite element analysis was used to evaluate the effect of vertical and angular misfit in three-piece implant-supported screw-retained fixed prostheses on the biomechanical response in the peri-implant bone, implants, and prosthetic components. Materials and Methods: Four three-dimensional models were fabricated to represent a right posterior mandibular section with one implant in the region of the second premolar (2PM) and another in the region of the second molar (2M). The implants were splinted by a three-piece implant-supported metal-ceramic prosthesis and differed according to the type of misfit, as represented by four different models: Control = prosthesis with complete fit to the implants; UAM (unilateral angular misfit) = prosthesis presenting unilateral angular misfit of 100 µm in the mesial region of the 2M; UVM (unilateral vertical misfit) = prosthesis presenting unilateral vertical misfit of 100 µm in the mesial region of the 2M; and TVM (total vertical misfit) = prosthesis presenting total vertical misfit of 100 µm in the platform of the framework in the 2M. A vertical load of 400 N was distributed and applied on 12 centric points by the software Ansys, ie, a vertical load of 150 N was applied to each molar in the prosthesis and a vertical load of 100 N was applied at the 2PM. Results: The stress values and distribution in peri-implant bone tissue were similar for all groups. The models with misfit exhibited different distribution patterns and increased stress magnitude in comparison to the control. The highest stress values in group UAM were observed in the implant body and retention screw. The groups UVM and TVM exhibited high stress values in the platform of the framework and the implant hexagon, respectively. Conclusions: The three types of misfit influenced the magnitude and distribution of stresses. The influence of misfit on peri-implant bone tissue was modest. Each type of misfit increased the stress values in different regions of the system. Schlagwörter: abutment stress, biomechanics, dental implant, dental prosthesis, finite element analysis, implant stress

Purpose: Conical implant-abutment connections for platform switching have been recently introduced in implant systems. This study investigated the load fatigue performance of three conical abutment systems and their corresponding titanium and zirconia abutments. Materials and Methods: Regular-diameter implants of the Ankylos (AK), PrimaConnex (PC), and Straumann (ST) systems were tested with their corresponding titanium (Ti) and zirconia (Zr) abutments tightened to the recommended torque (n = 5 implant-abutment assemblies per group). A rotational load fatigue machine applied a sinusoidally varying tensile-compressive 21 N load to specimens at a 45-degree angle, producing an effective bending moment of 35 Ncm at a frequency of 10 Hz. The number of cycles to failure was recorded, with the upper limit set at 5 million cycles. Results were evaluated through analyses of variance. Results: Except for the ST Zr group, which showed no failures in four samples and one failure just below the screw head, and the AK Ti group, in which one sample was preserved without fracture, all groups experienced failure of at least one of the components, whether the abutment screw only, the abutment, and/or the implant neck. There were significant differences between systems. There was no difference between systems for the Ti abutments, and the ST group was significantly different from the AK and PC groups for the Zr abutments. Conclusions: Ti conical abutments appear to have poorer load fatigue performance compared with earlier studies of external-hexagon connections. The load fatigue performance of Zr conical abutments varied and seemed to be highly system dependent. Many of the fractures in both the Ti and Zr abutment groups occurred within the implant, and retrieval would pose a significant clinical challenge. The clinician should weigh the mechanical, biologic, and esthetic considerations before selection of any implant system, connection type, or abutment material. Schlagwörter: conical implant-abutment connection, implant-abutment interface, load fatigue

Purpose: Radiographs are commonly used to assess the fit of implant components, but there is no clear agreement on the amount of misfit that can be detected by this method. This study investigated the effect of gap size and the relative angle at which a radiograph was taken on the detection of component misfit. Different types of implant connections (internal or external) and radiographic modalities (film or digital) were assessed. Materials and Methods: Twelve internal-connection and 12 external-connection implant analogs with impression copings were assembled, with radiolucent washers interposed, to produce vertical misfits of 0, 12.7, 25, 38, 51, 63, 76, 88, 102, 114, 127, and 190 µm. A custom-made positioning apparatus was used to obtain radiographs of the components at angulations between 0 and 35 degrees. The images were randomized, and three experienced examiners assessed whether a gap was visible at the interface. Their responses were compared to the actual status of the samples, and a probability model was constructed to predict the likelihood of a correct answer at any combination of gap and angle. Results: The relative angulation of the radiograph and the dimension of the gap were the most significant factors affecting an examiner's diagnostic ability. A 0-µm gap viewed at 0 degrees was the combination most accurately diagnosed. Implant component misfits as small as 12.7 µm were reliably detected with radiographs up to 5 degrees from the orthogonal projection; this was similar with configurations of 25 to 38 µm/10 degrees and 51 µm/15 degrees. There was good (inter-)examiner reliability. Neither the type of component used nor the radiographic media used influenced diagnostic ability. Conclusion: The angulation of the x-ray beam relative to implant components needs to be controlled when using radiographs to detect component misfit. Schlagwörter: dental implants, implant abutment, implant failure, implant misfit, radiographs

Purpose: The aim of this study was to evaluate the long-term failure rates of short dental implants (= 10 mm) and to analyze the influence of various factors on implant failure. Materials and Methods: The PubMed and Cochrane Library databases were consulted for follow-up studies published between the years 1980 and 2009. For those studies that met the inclusion and exclusion criteria, data concerning the number of implants (= 10 mm) placed and lost and any related risk factors were gathered in tables and subjected to analysis. Univariate and multivariate analyses were performed. Results: The heterogeneity and low quality of the included studies made meta-analysis impossible. A total of 35 human studies fulfilled the criteria. The studies included 14,722 implants, of which 659 failed. The total failure rate was 4.5%. The failure rates of implants with lengths of 6, 7, 7.5, 8, 8.5, 9, and 10 mm were 4.1%, 5.9%, 0%, 2.5%, 3.2%, 0.6%, and 6.5%, respectively. A majority (57.9%) of failures occurred before prosthesis connection. There was no statistically significant difference between the failure rates of short dental implants and standard implants or between those placed in a single stage and those placed in two stages (multivariate analysis). There was a tendency toward higher failure rates for the maxilla and for dental implants with a machined surface compared with the mandible and dental implants with a rough surface, respectively. Conclusions: Among the risk factors examined, most failures of short implants can be attributed to poor bone quality in the maxilla and a machined surface. Although short implants in atrophied jaws can achieve similar long-term prognoses as standard dental implants with a reasonable prosthetic design according to this review, stronger evidence is essential to confirm this finding. Schlagwörter: bone quality, dental implants, implant length, implant position, implant surface

Purpose: Dental implant bone cement (DIBC) was developed to rescue unstable implants at the time of placement. The purpose of this study was to compare the mechanical properties of bone-cement-implant interfaces of cemented implants that were unstable initially and bone-implant interfaces of self-threaded implants placed in rabbit femurs after various healing periods. Interfaces and failure modes were also characterized using histology and scanning electron microscopy (SEM). Materials and Methods: Eighty dental implants were placed in 20 rabbits. In each rabbit, two experimental and two control implants were placed in the right or left femur; one was in the distal epiphysis and the other in the cortical shaft. The experimental implants were cemented in loosely prepared bony sockets, while the control implants were self-threaded. The rabbits were sacrificed after varying healing periods. Magnetic pulse stability and push-in yield tests on ex vivo specimens measured secondary implant stability, 0.2% yield load, displacement, interface stiffness, and load at 100 µm. After loading tests, interfaces were evaluated with histology and SEM. Most analyses used mixed linear models. Results: The 0.2% yield load, interface stiffness, load at 100 µm, and secondary stability were significantly higher for bone-cement-implant interfaces than for bone-implant interfaces. Mechanical properties of bone-cement-implant interfaces plateaued at 1 week, with minimal change over the following 12 weeks, whereas bone-implant interfaces improved gradually. SEM and histology showed intimate bone-cement-implant interfaces without soft tissue intervention and mainly cohesive failures within DIBC. Secondary stability was significantly correlated with interface stiffness and load at 100 µm. Conclusion: The results suggest that DIBC can provide early implant stability and mechanical properties superior to those of self-threaded implants while maintaining intimate interfaces without signs of osteonecrosis or soft tissue intervention. Schlagwörter: dental implant bone cement, primary stability, rabbit femur, secondary stability, yield load

Purpose: The purpose of this study was to analyze, in an animal model, the histologic and biomechanical phenomena at the bone-implant interface of implants inserted with high torque (HT) as compared to low torque (LT) during the first 6 weeks of healing. Materials and Methods: Forty tapered-screw-form implants were placed in five hybrid sheep. The implant sites were placed in the mandible, using an extraoral approach; four were placed with HT (test: mean 110 Ncm) on one side and four were placed with LT (control: mean 10 Ncm) on the contralateral side. After 1, 2, 3, 4, and 6 weeks of healing, removal torque testing and resonance frequency analysis were performed and the animals were sacrificed for histologic examination. Results: Implants from the HT group showed significantly higher bone apposition than implants from the LT group at all examined healing times. Similarly, removal torque was consistently higher for the HT as compared to the LT group. A significant loss of primary stability in the HT group was evident 7 days after placement. Implants from the LT group achieved a significant increase in stability after 4 weeks. Resonance frequency analysis was unable to detect these histologic and biomechanical modifications of the bone-implant complex. Conclusions: The results of the study showed that high implant insertion torque in dense cortical bone does not induce bone necrosis or implant failure, but it does increase the primary stability of implants, which is extremely important in immediate loading protocols. Schlagwörter: biomechanics, bone compression, dental implants, histology, insertion torque, primary stability

Purpose: This study was undertaken to assess the predictive usefulness of preoperative bone density, as measured by computed tomography (CT), and the intraoperative implant stability measures of insertion torque (IT), Periotest values (PTV), and resonance frequency analysis (ie, implant stability quotient [ISQ]) toward developing an algorithm for successful immediate loading, one-step exposure, or submergence of dental implants. Materials and Methods: Consecutively presenting patients requesting immediate loading in areas other than the anterior mandible were analyzed retrospectively. The implants were either immediately loaded, left exposed, or submerged on the basis of preoperative CT bone density and intraoperative primary stability measures. All implants surviving the traditional healing period were verified for osseointegration. Results: Eighteen patients were analyzed retrospectively, and they received 58 implants. Seven implants failed, for a survival rate of 88%. Primary stability measurements at insertion were correlated with one another and with preoperative CT bone density. Preoperative mean bone density for surviving implants was greatest for immediately loaded implants (983 ± 83), lower for exposed implants (803 ± 29), and lowest (480 ± 23) for submerged implants. Bone density was significantly different between submerged implants that failed and those that survived. Mean IT for successful implants was higher than for those that failed. Mean PTVs were lower (ie, better) for successful versus failed implants, although this difference was significant only for submerged implants. Conclusions: In this group of patients, objective measures of bone density by CT, IT, PTV, and ISQ correlated with each other and therefore may provide a useful algorithm for making clinical implant loading decisions. Of the technologies applied in this group of patients, PTV was the most reliable predictor at implant placement of failure to osseointegrate. Schlagwörter: algorithm, bone density, immediate loading, partial edentulism, primary stability, retrospective analysis

Purpose: Orthodontic miniscrews are commonly used to achieve absolute anchorage during tooth movement. One of the most frequent complications is screw loss as a result of root contact. Increased precision during the process of miniscrew insertion would help prevent screw loss and potential root damage, improving treatment outcomes. Stereolithographic surgical guides have been commonly used for prosthetic implants to increase the precision of insertion. The objective of this paper was to describe the use of a stereolithographic surgical guide suitable for one-component orthodontic miniscrews based on cone beam computed tomography (CBCT) data and to evaluate implant placement accuracy. Materials and Methods: Acrylic splints were adapted to the dental arches of four patients, and six radiopaque reference points were filled with gutta-percha. The patients were submitted to CBCT while they wore the occlusal splint. Another series of images was captured with the splint alone. After superimposition and segmentation, miniscrew insertion was simulated using planning software that allowed the user to check the implant position in all planes and in three dimensions. In a rapid-prototyping machine, a stereolithographic guide was fabricated with metallic sleeves located at the insertion points to allow for three-dimensional control of the pilot bur. The surgical guide was worn during surgery. After implant insertion, each patient was submitted to CBCT a second time to verify the implant position and the accuracy of the placement of the miniscrews. Results: The average differences between the planned and inserted positions for the ten miniscrews were 0.86 mm at the coronal end, 0.71 mm at the center, and 0.87 mm at the apical tip. The average angular discrepancy was 1.76 degrees. Conclusions: The use of stereolithographic surgical guides based on CBCT data allows for accurate orthodontic mini screw insertion without damaging neighboring anatomic structures. Schlagwörter: accuracy, miniscrew, orthodontics, stereolithographic surgical guide

Purpose: Different graft materials have been proposed to minimize the collapse of alveolar bone after tooth extraction. The aim of this study was to examine the use of porcine bone graft in fresh sockets via histomorphometric and in vivo gene expression profiling. Materials and Methods: Thirty fresh extraction sockets with three bone walls in 15 patients were selected. A split-mouth design was employed. On one side of the arch, 15 sockets received corticocancellous porcine bone as a graft, and on the other side, 15 sockets were left unfilled and considered as controls. Four months after surgery, four biopsy specimens were taken from each patient (two from the grafted site and two from the control site). The specimens were analyzed by histomorphometry and ex vivo osteoblast expansion, followed by highly sensitive osteoblast-specific gene expression profiling for Runx2, osteopontin, osteoprotegerin, type I collagen, and alkaline phosphatase by quantitative real-time reverse-transcriptase polymerase chain reaction. Comparisons were made using the Student t test. Results: After healing without complications, the grafted sites showed statistically significantly higher mean vital bone and lower mean connective tissue values than the control sites. Statistically significant higher expression of alkaline phosphatase and the matrix formation markers type I collagen and osteopontin were observed in the grafted group compared to the control group, whereas Runx2 and osteoprotegerin expression was comparable. Conclusions: Within the limits of this study, histologic examination and biomolecular evaluation confirmed good biocompatibility and high osteoconductivity of xenogeneic porcine bone in alveolar bone grafting. Schlagwörter: alveolar ridge preservation, molecular biology, porcine bone, tooth extraction

Purpose: The purpose of this study was to classify the relationship of the sagittal root positions of the maxillary anterior teeth to their respective osseous housings using cone beam computed tomography (CBCT). The frequency of each classification was also reported. Materials and Methods: A retrospective review of CBCT images was conducted on 100 patients (40 men, 60 women; mean age, 53.1 years) who fulfilled the inclusion criteria. The CBCT images were evaluated and the relationship of the sagittal root position of the maxillary anterior teeth to its associated osseous housing was recorded as Class I, II, III, or IV. Results: The frequency distribution of sagittal root position of maxillary anterior teeth indicated that, of the 600 samples, 81.1%, 6.5%, 0.7%, and 11.7% were classified as Class I, II, III, and IV, respectively. Conclusions: An understanding of the clinical relevance of sagittal root position will provide adjunct data for the treatment planning of immediate implant placement and provisionalization in the anterior maxilla. A classification system may lead to improved interdisciplinary communication in treatment planning for implant-based therapy in the anterior maxilla. Schlagwörter: anterior maxilla, cone beam computed tomography, esthetics, immediate implant placement, immediate provisionalization, osseous housing, sagittal root position, single-tooth replacement, treatment planning

Purpose: This study investigated the association between satisfaction with the dentition and dental prostheses and personality profiles among patients who received implant-supported prostheses. Materials and Methods: Patients seeking dental implant therapy were recruited for this study. A Dental Impact on Daily Living questionnaire was used to assess dental satisfaction and the effects of implant-supported prostheses on daily living. The NEO Five Factor Inventory (NEO-FFI) was used to assess participants' personality profiles. Participants completed the questionnaires before implant insertion and 3 months after rehabilitation with implant-supported prostheses. Results: Eighty patients (42 men and 38 women, mean age 40.99 years) participated. Patients were more satisfied with their dentition after implant treatment. Neuroticism and conscientiousness had significant relationships with patient satisfaction and impact on daily living both before and after implant therapy. Openness and agreeableness had significant relationships with patient satisfaction and impact on daily living only after implant treatment. Extraversion had a significant relationship with patient satisfaction and impact on daily living only before treatment. After implant treatment, neuroticism was helpful in predicting total satisfaction, as well as satisfaction with appearance, pain, oral comfort, performance, and eating. Conscientiousness was helpful in predicting satisfaction with appearance, whereas openness was helpful in predicting satisfaction with pain. Before implant treatment, neuroticism was helpful in predicting total satisfaction as well as satisfaction with appearance, oral comfort, and performance. Conclusion: Implant-supported prostheses had positive impacts on participants' daily living and satisfaction with the dentition. Personality traits (such as neuroticism, openness, agreeableness, and consciousness) affect patients' daily living and satisfaction with implant-supported prostheses. Selected personality traits might predict patients' satisfaction with implant-supported prostheses prior to treatment. Schlagwörter: dental impacts on daily living, implant-supported prostheses, NEO Five Factor Inventory, patient satisfaction, personality profiles

Purpose: The aim of this prospective cohort study was to determine the 5-year implant survival and success rates associated with early loading (6 weeks after nonsubmerged placement) of sandblasted and acid-etched (SLA) Straumann implants in the edentulous mandible. A secondary objective was to determine the peri-implant tissue response and measure alterations in peri-implant crestal bone levels. Materials and Methods: SLA implants were placed and primarily loaded 6 weeks later with 35 Ncm during abutment placement. The peri-implant bone and mucosal conditions of the participants were monitored radiographically and clinically over a 5-year period. Results: Fourteen patients received 60 implants. Thirteen patients and 54 implants were examined at the 5-year appointment. Two of 60 implants failed during the healing period, and four implants were lost during follow-up and considered as dropouts. The remaining implants showed favorable clinical and radiographic findings and were considered successfully integrated at the 5-year examination. The mean loss of crestal bone height after 5 years was 0.77 mm (SEM 0.09). This resulted in a 5-year cumulative success rate of 96.7%. Conclusion: In this prospective study, the early loading of Straumann implants with the SLA surface in the edentulous mandible after a healing time of 6 weeks provided successful osseointegration with high predictability. Successful integration was maintained for 5 years. Schlagwörter: dental implant, early loading, edentulous mandible, surface properties

Purpose: The objective of this study was to compare the clinical and histologic peri-implant parameters of a nano-calcium phosphate (CaP)-coated dual acid-etched (DAE) implant (n = 7) to those of an uncoated DAE implant (n = 7). Materials and Methods: The study included seven dogs who received implants bilaterally in edentulous mandibular areas; in the right side, procedures were performed 8 months after procedures in the left mandible. Clinical parameters were measured prior to euthanasia (8 months after the second set of implants was placed), followed by histologic nondecalcified processing for morphometric evaluation. Bone-implant contact (BIC), crestal bone resorption (CBR), intrabony defect (IBD), and bone area fraction (BAF) were measured. Analysis of variance with repeated measures and a two-tailed Pearson correlation test were applied. Results: Probing depth, Bleeding Index, and keratinized mucosal height were stable in both groups; there was a significant improvement in probing depths with time (P = .014). Morphometric measurements showed BIC from 75% to 89% in both groups at 8 and 16 months. The nano-CaP-coated group (n-CaP) showed a significant increase in BIC over time when compared to the DAE group (P = .02). Crestal bone level was maintained in both groups with average resorption of 1.4 to 1.5 mm at the n-CaP implants and 1.1 to 1.2 mm at the DAE implants at 8 and 16 months, respectively. Mean IBD values were 0.88 to 1.18 mm at the n-CaP implants and 0.65 to 0.66 mm at the DAE implants at the respective periods. Conclusions: Within the limitations of this study, both the DAE and the n-CaP-surface implants showed successful osseointegration and functional soft and hard tissue adaptation. Except for the significant increase in BIC around the n-CaP implants over time, both showed similar clinical and histologic findings. Schlagwörter: acid etching, calcium phosphate, dental implant, implant stability, peri-implant healing, surface properties