The International Journal of Oral & Maxillofacial Implants, 02/2010

Purpose: Using the three-dimensional finite element method (FEM), this study compared the biomechanical behavior of the "All-on-Four" system with that of a six-implant-supported maxillary prosthesis with tilted distal implants. The von Mises stresses induced on the implants under different loading simulations were localized and quantified. Materials and Methods: Three-dimensional models representing maxillae restored with an "All-on-Four" and with a six-implant-supported prosthesis were developed in three-dimensional design software and then transferred into FEM software. The models were subjected to four different loading simulations (full mouth biting, canine disclusion, load on a cantilever, load in the absence of a cantilever). The maximum von Mises stresses were localized and quantified for comparison. Results: In both models, in all loading simulations, the peak stress points were always located on the neck of the distal tilted implant. The von Mises stress values were higher in the "All-on- Four" model (7% to 29%, higher, depending on the simulation). In the presence of a cantilever, the maximum von Mises stress values increased by about 100% in both models. Conclusions: The stress locations and distribution patterns were similar in the two models. The addition of implants resulted in a reduction of the maximum von Mises stress values. The cantilever greatly increased the stress. Keywords: atrophic maxilla, biomechanics, finite element analysis, implant-supported prosthesis, tilted implants

Purpose: The objectives of this study are to describe, in vitro, a novel technique to measure the misfit of digitally designed and manufactured implant-supported frameworks according to a new concept based on computer-guided surgery in combination with previously placed mini-implants. Also, the digitally created framework and an impression-based milled structure were compared using strain gauge measurements. Materials and Methods: Acrylic resin and plaster models were prepared to represent the edentulous mandible. After insertion of three mini-implants in the acrylic resin model, a cone-beam computed tomographic scan was performed. The data were imported to planning software, where six implants were virtually inserted. A drill guide and titanium framework were designed and milled using a fully digital computer-aided design/computer-assisted machining protocol. Six implants were inserted using the drill guide attached to the mini-implants. After an impression was made of the acrylic resin model with six implants, the second model (plaster model) was prepared. A second milled titanium structure was fabricated following optical scanning of the acrylic resin model. Strain gauge measurements were done on both structures attached to both models. To validate the results, a high-accuracy industrial optical scanning system was used to capture all connection geometry and the measurements were compared. Results: The accuracy of the digital superstructures was 19, 22, and 10 µm with standard deviations (SD) of 19.2 (17.9), 21.5 (28.3), and 10.3 (10.1) µm for the x-, y-, and z-axes, respectively. For the impression-based superstructure the measured misfit was 11, 20, and 17 µm, with SD 11.8 (10.5), 19.7 (11.7), and 16.7 (8.2) µm for the x-, y-, and z-axes, respectively. Conclusion: The misfit of the digitally designed and produced superstructure on the digitally planned and inserted implants was clinically insignificant. Keywords: dental implants, guided surgery, misfit, superstructure

Purpose: Surgical complications during sinus floor elevation are frequently caused by septa in the maxillary sinus. In this study, the prevalence of septa was retrospectively determined via three-dimensional imaging to assess the necessity for appropriate imaging prior to sinus floor elevation. Materials and Methods: The cone-beam computed tomography scans of 1,029 consecutive patients were evaluated to assess the prevalence of septa, taking into account patient age and sex as well as the number and orientation of septa and their locations. If septa were present, the height was measured and the orientation was determined. Results: Septa were found in 47% of patients and 33.2% of sinuses. There was no statistical difference in prevalence with respect to age, sex, or side. Most patients with septa showed one septum in one sinus (24.6%); 13.7% showed one septum in each sinus. Other combinations (up to three septa per sinus) were found in 8.7% of patients. Septa were most commonly located in the first molar region (256 septa), followed by the second molar region (225 septa), the third molar region (144), second premolar region (136), the first premolar region (44), and the canine region (5). The mean septal height was 11.7 ± 6.08 mm for septa in a sagittal orientation (n = 206, 25.3%; maximum height of 37 mm) and 7.3 ± 5.08 mm for those oriented transversely (n = 608, 74.7%; maximum height of 36 mm). The variance was larger for the sagittal orientation group (37.03 mm) than for transversely oriented septa (25.9 mm). Conclusion: Septa were found in 47% of the patients in this sample. Appropriate imaging prior to performing sinus surgery seems justified, since complications and the success rate of sinus floor elevation are clearly related to the presence of septa. Keywords: antral septa, cone-beam computed tomography, dental implants, dental radiography, sinus floor elevation, sinus membrane

Purpose: To evaluate, through a systematic review of the literature, the effects of implant design and attachment type on marginal bone loss in implant-retained/supported overdentures. Materials and Methods: With the combined search terms "implant and overdenture," "implant-supported overdenture," "implant-retained overdenture," and "implant-anchored overdenture," along with specific inclusion and exclusion criteria, eligible articles between 1997 and 2008 (up to April 1) were retrieved from PubMed, EMBASE, OVID, the Cochrane Library databases, and seven journals by hand searching. Marginal bone loss values with regard to time, attachment type, and implant system used were compared by Kruskal- Wallis tests. Means and standard deviations of data were combined using fixed- and random-effect models and evaluated using meta-analysis. Results: Forty-six articles were included in the analyses; data extraction and meta-analysis were able to be conducted on eight studies. Data regarding maxillary overdentures could not be analyzed statistically. Bone loss around mandibular implants did not seem to be influenced by implant system or attachment design (bar, ball, magnet, and other types) in the first year, from 1 to = 5 years, and even after 5 years (P > .05). Meta-analysis could not detect differences in implant systems or attachment types (P > .05). Conclusions: Based upon a systematic review and meta-analysis of the literature that identified a total of 4,200 implants from 13 manufacturers, there was no difference in marginal bone loss around implants retaining/supporting mandibular overdentures relative to implant type or attachment designs. Keywords: attachment, dental implant, marginal bone loss, meta-analysis, overdenture, standard periapical radiograph, systematic review

Purpose: This study evaluated the effects of phosphate coating of acid-etched titanium on the mineral apposition rate (MAR) and new bone-to-implant contact (BIC) in a canine model. Materials and Methods: Titanium implants (2.2 x 4 mm) with acid-etched surfaces that were electrolytically phosphated or not were placed in 48 mandibular sites in six foxhounds. Tetracycline and calcein dyes were administered 1 week after implant placement and 1 week before sacrifice. At 12 weeks after implant placement, the animals were sacrificed. MAR and BIC were evaluated using fluorescence microscopy. Light microscopic and histologic evaluations were performed on undecalcified sections. Results: Microscopic evaluation showed the presence of healthy osteoblasts lining bone surfaces near implants. Similar BIC was observed in phosphated and nonphosphated titanium implant sites. MAR was significantly higher around the nonphosphated titanium implant surfaces than around the phosphated titanium samples. No significant differences were found between dogs or implant sites. Conclusion: Acid-etched implants showed significantly higher MARs compared to acid-etched, phosphate-coated implants. Keywords: acid etching, bone-implant contact, dental implant, mineral apposition rate, phosphate, titanium

Purpose: The objective of this study was to determine whether ultraviolet (UV) light treatment of titanium implants could enhance osseointegration to sufficiently overcome the negative aspects of shorter implants in a rat femur model. Materials and Methods: Acid-etched miniature titanium implants with lengths of 2 mm (longer implants) and 1.2 mm (shorter implants) were prepared. Some of these implants were treated with UV light for 48 hours prior to surgery. The strength of osseointegration generated by these implants was evaluated using a biomechanical implant push-in test in a rat model. Periimplant osteogenesis was examined by scanning electron microscopy for tissue morphology and energy dispersive x-ray spectroscopy for elemental composition. Results: Push-in test values for the longer implants were 80% and 100% greater than those of the shorter implants at weeks 4 and 8 of healing, respectively. UV treatment of the shorter implants significantly increased their push-in value, resulting in a 100% higher value than untreated longer implants at week 2 and a push-in value that was equivalent to that of the untreated longer implants at weeks 4 and 8. Scanning electron micrographs and energy dispersive x-ray spectroscopic examinations after push-in testing revealed that the UV-treated implant surfaces were covered more extensively by bone or tissue remnants containing calcium and phosphorous than the untreated surfaces. The titanium surfaces were converted from hydrophobic to super - hydrophilic status after UV treatment, although the cause-result relationship between the acquired superhydrophilicity and biologic effects remained unclear. Conclusions: Within the limits of this investigation, UV light pretreatment substantially enhanced the osseointegration capacity of acid-etched titanium implants. The deficiencies of osseointegration in implants with a 40% shorter length were overcome by UV treatment in the rat model using miniature implants. These results need to be confirmed in other animal models and implants that more closely resemble human dental implants to determine the true clinical significance. Keywords: arthroplasty, dental implants, orthopedic implants, osseointegration, photocatalysis, titanium dioxide

Purpose: The purpose of this study was to analyze and compare the implant-bone interface stresses in anisotropic three-dimensional finite element models of an osseointegrated implant with platform switching and a conventional matching-diameter implant platform and abutment in the posterior maxilla. Materials and Methods: Three-dimensional finite element models were created of a first molar section of the maxilla and embedded with a single endosseous implant (4.1 x 10 mm). One model simulated a 4.1-mm-diameter abutment connection and the other was a narrower 3.4-mm-diameter abutment connection, ie, simulating a platform-switching configuration. A gold alloy crown with 2-mm occlusal thickness was applied over the titanium abutment. Material properties of compact and cancellous bone were modeled as fully orthotropic and transversely isotropic, respectively. Oblique (200-N vertical and 40-N horizontal) occlusal loads were applied and perfect bonding was assumed at all interfaces. Results: Maximum von Mises, compressive, and tensile stresses in compact bone were lower in the platform- switching model than in the conventional model. However, the maximum von Mises stress in cancellous bone was higher in the platform-switching model than in the conventional model. Conclusion: The platform-switching technique reduced the stress concentration in the area of compact bone and shifted it to the area of cancellous bone during oblique loading. Keywords: finite element analysis, orthotropy, platform switching, stress, transverse isotropy

Purpose: Replacement of missing or lost teeth with dental prostheses supported by oral implants has been accepted and received positive evaluations from patients who have undergone implant treatment. A nationwide survey from a representative sample of the general Indian urban population was made to assess public awareness of oral implant treatment and determine sources of information about implants. Materials and Methods: A survey of 10,000 urban dwellers of India was conducted through a printed questionnaire that was supplied to patients in private clinics and dental hospitals across the country and completed by willing patients. Questionnaires were printed in local languages to enable completion. Results: Of the 10,000 people asked about their awareness of oral implants as a treatment option for rehabilitation of missing teeth, only 2,324 (23.24%) had heard of oral implants as a treatment modality, whereas 7,676 (76.76%) had not. Most of them (9,623, or 96.23%) felt that dental insurance coverage was needed for dental implant treatment and 3.77% thought that insurance was not needed. Conclusion: The survey concluded that only 23.24% of the Indian urban population had heard of dental implants as a treatment option for replacing missing teeth, with dentists being the main source of information. Keywords: dental implant, India, questionnaire, survey, treatment awareness, urban population

Purpose: The purpose of this study was to investigate the early tissue response around three one-piece implant systems with different transmucosal designs. Materials and Methods: Three one-piece dental implant systems with different profiles and surface roughnesses on the transmucosal portion were examined in the current study. The transmucosal portions were flared and machined (FM), concave and machined with microgrooves (CMG), or straight and anodic oxidized (SA). A total of 30 implants (10 of each type) were placed in computer-generated randomized order in the mandibular residual ridges of five beagle dogs. Six months later, all animals were sacrificed and histologic sections were prepared to measure epithelial tissue height, connective tissue contact, and the amount of bone resorption. One-way analysis of variance and the Bonferroni post hoc test were used for statistical evaluation (alpha = 95%). Results: After a 6-month nonfunctional loading period, all 30 implants were clinically immobile. Slight swelling and redness of the peri-implant soft tissue were noticed around most of the implant abutments. Histometric analysis showed that the FM implants had a longer epithelial tissue height than the CMG implants. The CMG implants showed the greatest amount of connective tissue attachment among the three groups and the least amount of marginal bone resorption. The CMG and SA implants showed bone growth above the initial reference point at 10 and 7 measurement sites, respectively, whereas no bone overgrowth was noted around the FM implants. Conclusion: Based on this study conducted in five beagle dogs, a concave transmucosal profile with a microgrooved surface was associated with longer connective tissue attachments and less bone resorption versus implants that were flared with a machined surface or straight with an anodic oxidized surface in the early healing phase. Keywords: connective tissue contact, dental implants, one-piece implant, transmucosal design

Purpose: The purpose of this study was to evaluate the effect of basic fibroblast growth factor (bFGF) in combination with a biodegradable polymer coated onto titanium implants. The implants were inserted in rabbit tibiae, and bone growth was examined by histomorphometric analysis. Materials and Methods: Forty-eight threaded anodized implants were inserted into the tibiae of 12 rabbits. After 12 weeks of healing, an evaluation was made by light microscopy and computerized image analysis. A total of 56 anodized titanium implants were prepared as follows: group 1 was anodized under 300 V; group 2 was anodized then coated with 0.02 mL poly(lactide-co-glycolide) (PLGA) nanoparticles; group 3 was anodized then coated with 0.02 mL PLGA/bFGF nanoparticles (10 ng bFGF); and group 4 was anodized then coated with 0.2 mL PLGA/bFGF nanoparticles (100 ng bFGF). Results: Nanosized particles were observed on the coated implant surfaces. The mean diameter of the nanoparticles was 268.6 ± 93.2 nm. The mean boneto- implant contact (BIC) percentage in group 4 (44.7%) was significantly greater than that seen in groups 1 (31.4%) and 2 (33.6%) (P .05). Conclusions: The results of this preliminary study show that coating a titanium implant with PLGA incorporated with bFGF by electrospray may stimulate bone formation adjacent to the surface of an implant inserted in bone. Keywords: anodized titanium, electrospray, fibroblast growth factor, histomorphometric analysis, poly(lactide-co-glycolide)

Purpose: To investigate the relationship between bone mineral density (BMD) before implant placement, implant stability measures at implant placement, and marginal bone loss of immediately loaded implants after 1 year in situ. Materials and Methods: Consecutively recruited patients received Straumann SLActive implants loaded with fixed provisional prostheses within 24 hours. BMD was measured from computed tomographic images before implant placement. Alveolar bone quality was assessed during surgery. Implant stability-both rotational and as measured with resonance frequency analysis- and marginal bone height were assessed at implant placement and after 1 year. The Pearson correlation coefficient was used to calculate correlations, and significance was considered when P .05. Results: Twenty-one patients received 137 implants (87 in maxillae and 50 in mandibles). BMD was significantly correlated with bone quality classification in both arches (P .001). Mean BMD was also significantly correlated with stability values (P .001). Mean marginal bone loss at implant surfaces differed, but not significantly, at the 1-year follow-up, regardless of BMD values (P = .086) and measured stability (rotational stability P = .34, resonance frequency analysis P = .43) at implant placement. Conclusion: Within the limits of this study, it can be concluded that computed tomographic examination can be used as a preoperative method to assess jawbone density before implant placement, since density values correlate with prevailing methods of measuring implant stability. However, in the short time perspective of 1 year, there were no differences in survival rates or changes in marginal bone level between implants placed in bone tissue of different density. Keywords: bone density, computed tomography, dental implants, immediate loading, implant splinting, radiographic bone density

Purpose: Implants placed in fresh extraction sites and healed sites were restored simultaneously by cross-arch provisional fixed prostheses. Clinical and radiographic parameters were recorded for up to 36 months. Materials and Methods: Treatment with a full-arch implant prosthesis, either screwretained or cemented, was assigned to 54 patients. A total of 676 implants were placed in either immediate extraction sites (n = 367) or in healed alveoli (n = 309), followed by placement of a one-piece provisional prosthesis. The definitive restoration was placed 3 to 6 months after implant placement. Clinical parameters were recorded and digital radiographs obtained at 6, 18, and 36 months. The chi-square test, t test, and analysis of variance with repeated measures were used for statistical analysis of the outcomes. Results: Osseointegration failed in 21 (3.1%) implants; 13 of these (62%) had been placed immediately after extraction. All occurred within 2 months of the surgical healing phase. Short (8-mm) and narrow (3.3-mm) implant configurations were significantly (P .05) associated with failure. At 6, 18, and 36 months, average crestal bone resorption was 0.18 mm, 0.55 mm, and 0.79 mm for implants placed in fresh extraction sites and 0.31 mm, 0.78 mm, and 1.1 mm for implants placed in healed alveoli, respectively. These differences were statistically significant (P .05 between sites at all examined periods). Crestal bone resorption also correlated to sites with simultaneous bone augmentation and implant placement. Conclusions: Implants placed and restored immediately in a cross-arch mode, whether in extraction sites or in healed alveoli, can be clinically successful and maintainable. Keywords: extraction sites, follow-up, fresh sockets, immediate loading, implant prosthesis, implant success rate

Purpose: The aim of this study was to evaluate the 5-year success rate of zirconia (ZrO2) implants with three different kinds of surfaces. Materials and Methods: One-piece zirconia dental implants (Cera- Root) with three different roughened surfaces were designed and manufactured for this study: coated, uncoated, and acid-etched. Five different implant designs were manufactured. Standard or flapless surgical procedures were used for implant placement. Simultaneous bone augmentation or sinus elevation was performed when bone height or width was insufficient. Definitive all-ceramic restorations were placed 4 months after implant placement (8 months or more for implants when bone augmentation or sinus elevation was performed). The implants were followed up to 5 years (mean, 3.40 ± 0.21). Results: In all, 831 implants were placed in 378 patients with a mean age of 48 years. The overall implant success rate after 5 years of follow-up was 95% (92.77% for uncoated implants, 93.57% for coated implants, and 97.60% for acid-etched implants). The success rate of the acid-etched surface group was significantly better than that of the other two. Conclusion: From this midterm investigation, it can be concluded that zirconia dental implants with roughened surfaces might be a viable alternative for tooth replacement. Further follow-up is needed to evaluate the long-term success rates of the implant surfaces studied. Keywords: acid etching, ceramic, coating, dental implants, surface characteristics, yttria-tetragonal zirconia polycrystal, zirconia, zirconium oxide

Purpose: This clinical study aimed to assess the dimensional stability of peri-implant soft tissues around immediately placed and restored implants in the maxillary esthetic zone. Materials and Methods: Twelve systemically healthy patients presenting with a hopeless maxillary central incisor were selected. Provisional restorations were delivered immediately after tooth extraction and implant placement. Periimplant soft tissue dimensions were measured either by direct clinical examination or evaluation of study casts. Measurements were performed before extraction; immediately after implant and restoration placement; and 6 weeks, 3 months, 6 months, 12 months, and 18 months postoperatively. The distances assessed were: tip of the mesial papilla to the mesioincisal edge of the adjacent central incisor, tip of the distal papilla to the mesioincisal edge of the adjacent lateral incisor, and the length of the clinical crown of the definitive restoration. Results: All patients completed the study, and no implants failed within the 18-month follow-up period (100% survival rate). No statistical differences were observed in the distances between the incisal edge of the adjacent teeth and the mesial and distal papilla tips (P = .303 and .099, respectively) at any follow-up appointment. Likewise, there were no alterations in the definitive clinical crown dimensions during the follow-up period (P = .406). Conclusion: The findings of this 18-month prospective study indicate that, within the selection criteria and technique presented in this study, immediate implants with immediate restorations can be a predictable option for the replacement of teeth in the esthetic zone, providing stability to the peri-implant soft tissue. Keywords: dental implants, immediate implants, immediate loading, soft tissue stability

Purpose: Dental practitioners are instructed to avoid any type of contact with implant surfaces prior to their insertion. However, the probability of contaminating the surface is high, especially when placement of implants necessitates the use of precise surgical guides. The aim of this study was to evaluate the 2-year survival rate of splinted mini-implants that came into contact with stainless steel prior to their insertion. Materials and Methods: During the clinical portion of the study, initiated over a 3-day period, 90 mini-implants were inserted into the anterior mandible of 45 totally edentulous patients; 46 were inserted using a prefabricated stainless steel guide (group 1, bar) and 44 were placed without a guide (group 2, ball). A flapless surgical protocol was used. All implants were immediately loaded with mandibular overdentures, and follow-up was conducted for up to 2 years. The Kaplan-Meier method was used to analyze implant survival in each group, with a confidence level of 95%. In the in vitro phase of the study, five mini-implants were contaminated for 20 seconds with a stainless steel surgical guide. They were then observed using scanning electron microscopy and energy dispersive spectroscopy to identify contaminants and to determine qualitatively the chemical composition of the surface. As a control, five mini-implants recently extracted from their original containers were analyzed. Results: During the 2-year follow-up, one implant failed (97.8% survival rate) in group 1 and four failed in group 2 (90.9% survival rate). The in vitro analysis revealed carbon and oxygen on all implants. On the implants that were in contact with stainless steel, additional elements were identified, including silica, calcium, iron, and chromium. Conclusions: Contact between mini-implants and stainless steel surgical guides does not seem to generate contamination that compromises the survival of splinted mini-implants. Keywords: contamination, edentulous mandible, mini-implants

Purpose: The aim of this retrospective study was to evaluate the long-term survival and success rates of screw-type root-shaped (Camlog) implants of various diameters and their implant-prosthodontic reconstructions for more than 5 years of clinical use. Materials and Methods: A retrospective study of patients receiving root-shaped screw-type dental implants placed between May 2001 and July 2003 was conducted. The cumulative implant survival and success rates and peri-implant conditions (marginal bone loss, pocket depth, Plaque Index, Gingival Index, Bleeding Index) as well as the prosthodontic maintenance requirements were evaluated. Results: In all, 541 implants (3.8 mm: 237 implants; 4.3 mm: 211 implants, 5/6 mm: 93 implants) were placed and restored for implant prosthodontic rehabilitation in 216 patients (134 women, 82 men; mean age 54.3 ± 9.1 years). Of the original 216 patients enrolled, 198 (91.6%; 510/541 implants [94.2%]) were available for a follow-up evaluation after 5 to 7 years (mean follow-up, 68.8 ± 7.4 months). The overall cumulative 5-year survival and success rates were 98.3% and 97.3%, respectively. A failure rate of 3.7% (9/237) was seen for 3.8-mmdiameter implants; the corresponding figures for the 4.3-mm and wide-diameter (5.0/6.0-mm) implants were 1.4% (3/211) and 1.0% (1/93), respectively. For implants classified as successful, the average peri-implant marginal bone resorption value was 1.8 ± 0.4 mm, with no differences among the different implant diameters evaluated. Peri-implant soft tissue conditions such as plaque, bleeding, and pocket depth were also satisfactory. All prostheses were functional throughout the observation period, with no fractures of implants, abutments, or screws. Abutment screw (4.5%) or isolated crown loosening (9.8%) for single-tooth restorations requiring recementation, retightening of screws, and adaptation of removable prostheses were the most frequent prosthodontic maintenance needs. Conclusion: The rootshaped implants and the associated prosthetic constructions used in this study showed excellent survival and success rates. Keywords: dental implants, root-form implants, root-shaped implants, screw-type implants

Purpose: Evaluations of multicenter clinical trials are needed to determine the effectiveness of care in routine implant therapy in clinical practice. Materials and Methods: Ninety-two clinicians in 75 clinics in 13 countries recruited five subjects per clinic who were in need of a minimum of two dental implants to restore a partially edentulous quadrant and were followed for a minimum of 1 year after loading. A centralized Internet-based case report form was developed to coordinate data recording. Data entry was done by each clinic, with follow-up source verification. Results: The study recruited 549 subjects in 101 clinics with 1,893 implants placed. Three hundred forty subjects completed the 1-year recall (gender distribution of 56% female, 44% male; mean age of 57 years with a range of 18 to 84 years). In all, 1,246 dental implants were followed; a majority of subjects had two to four implants. Twenty-eight percent of subjects received osseous grafting prior to or coincident with implant placement. In the maxilla, 779 (63%) implants were placed, 256 in the anterior and 523 in the posterior; in the mandible, 467 implants were placed, 85 in the anterior and 382 in the posterior arch. The median edentulous period prior to implant placement was 24 months (range, 0 to 480 months); 46% of all patients received implants within 12 months of tooth loss. At 1 year after prosthesis insertion, 15 subjects had lost a total of 17 implants, for a cumulative implant survival rate of 98.6%. Chi-square and Fisher exact tests indicated a higher risk of implant loss at sites with advanced resorption and for wider-diameter implants (5-mm tapered body). There was no statistical relationship with implant loss relative to implant length or anatomic location within the oral cavity. Conclusions: The outcomes support the need for ongoing involvement of clinicians in routine practice assessments of patient-based outcomes of implant therapy. Keywords: clinical trial, effectiveness trial, outcomes, risk factors, trial design

Purpose: The purpose of this study was to evaluate the area and volume of bone available for grafting in a donor retromolar region using computed tomography (CT). Materials and Methods: Ten patients previously scanned by multislice CT were selected for evaluation. Images from partially and completely dentate patients at least 18 years of age were included in the study; those from patients with impacted or erupted third molars or intrabony lesions in the study area were not included. Computer software with appropriate tools was used to handle the images. Two calibrated observers made measurements separately. Safety margins in relation to the lingual cortex, the base of mandible, and the alveolar canal were established in each cross-section of the CTs. Measurements were done by using cross-sectional views, and the results were calculated after three-dimensional reconstruction, providing area and volume data. Results: The mean area of bone available for grafting was 8.12 cm2 (range, 0.00 to 13.60 cm2) and 8.32 cm2 (range, 0.00 to 14.30 cm2) for observers 1 and 2, respectively. Mean available bone volume for grafting was 0.79 cm3 (range, 0.00 to 1.50 cm3) for observer 1 and 0.85 cm3 (range, 0.00 to 1.60 cm3) for observer 2. Interobserver analysis showed substantial agreement. Conclusion: The retromolar region showed a wide variety of anatomic differences among patients. Three-dimensional multislice CT allows reproducible measurements of the area and volume of the retromolar region. Keywords: bone graft, computed tomography, dental implants, retromolar, volume

Purpose: The aim of this study was to investigate the speech ability of patients treated with multiple zygomatic implants. This technique can be used in patients with severe atrophy of the maxilla when there is insufficient residual bone in the anterior region for placement of conventional implants. Materials and Methods: Between 2004 and 2008, audio recordings were performed in patients treated with fixed dental prostheses (FDP) supported by multiple zygomatic implants. Patients with extensive resorption of the basal bone of the maxilla (Cawood and Howell Class VI) were included in the study. No bone grafts were used. Audio recordings were conducted before treatment (pretreatment), within 1 week after the FDP was inserted (1 week posttreatment), and then again after 4 months (4 months posttreatment). Perceptual evaluations of the recordings were performed by a panel of speech and language pathologists (n = 3), and the patients' subjective views of speech quality were investigated on the three different occasions. Results: Seven consecutive patients were treated with a total of 28 zygomatic implants and five conventional implants. All patients received a FDP. According to the evaluations by professionals, five of the seven patients, all of whom wore a removable conventional denture prior to treatment, had normal speech before treatment. One patient could not be evaluated by the professionals because of medical impairment. In five of the six remaining patients, a mild deterioration in articulation was registered at 1 week posttreatment, and these problems remained after 4 months. Patients' subjective views reflected a dramatic improvement in speech at 1 week posttreatment for the two patients presenting with the highest degree of maxillary bone resorption. The three patients who reported completely normal speech before treatment all experienced a drop in their ability at 1 week posttreatment. Four patients displayed a similar pattern after treatment according to the professionals' opinions and the patients' subjective reports. Conclusion: A mild deterioration in speech can be anticipated in patients subjected to treatment with a FDP supported by multiple zygomatic implants. Keywords: dental implants, maxilla, speech, zygoma

Purpose: The aim of this study was to retrospectively determine whether a relationship exists between the length of the distal bar extension and the amount of marginal bone loss around implants supporting cantilevered bar-retained dentures. Materials and Methods: This study was performed using data from patients who had been restored with implant-supported cantilevered bar-retained prostheses. Panoramic radiographs were obtained annually starting at the time of prosthetic loading of the implants; the protocol included a 4-year observation period. Vertical changes in the bone level were measured on the mesial and distal of implant sites with respect to a defined reference point per implant system, and radiographic distortions were compensated. Statistical analysis was performed with the Wilcoxon signed-rank test, the Spearman rank correlation test, and the two-factor nonparametric analysis for repeated measurements. Results: A total of 48 edentulous patients who were consecutively treated with 313 dental implants and rehabilitated with 66 bar-retained prostheses were included in the study. Implants were used to support 30 prostheses in the maxilla (172 implants) and 36 prostheses in the mandible (141 implants). These prostheses were supported by bars with distal cantilevers of up to 12 mm. Patients with bars without cantilevers served as the control group. After 4 years, mean mesial bone loss was 2.20 ± 0.91 mm; for distal implant sites it was 2.31 ± 1.05 mm. The number of implants inserted and implant length did not correlate with bone loss. Jaw (maxilla versus mandible) and implant system exerted a significant influence on the amount of bone lost within the first year. Cantilever length did not influence marginal bone loss. Conclusion: In this clinical study, no influence of the length of cantilever extensions on crestal bone loss was found. Within the limitations of the study, the results indicate that restorations with distal bar extensions up to 12 mm are an adequate treatment option for edentulous patients. Keywords: biologic width, cantilever length, crestal bone loss, dental implants, implant-retained overdenture

Purpose: This prospective clinical study evaluated the incidence of abutment loosening of Morse taper-connection implants used for single-tooth replacement. In addition, the cumulative survival rate and the implant/crown success were evaluated. Materials and Methods: Implants were evaluated 12, 24, 36, and 48 months after insertion. The incidence of abutment loosening, modified Plaque Index, modified Sulcus Bleeding Index, probing depth, distance from the implant-crown margin to the coronal border of the peri-implant mucosa, width of keratinized mucosa, and the distance between implant shoulder and first bone-implant contact (DIB) were assessed. The cumulative survival rates were calculated with Kaplan-Meier estimates. Implant/crown success criteria included absence of abutment loosening, absence of suppuration and mobility, probing depth 5.0 mm, and DIB 1.5 mm after 12 months and not exceeding 0.2 mm for each following year. Results: Over a 4-year period (2003-2007; mean follow-up per implant: 30.79 months), 307 implants (162 maxillary, 145 mandibular) were inserted in 295 patients (125 men and 170 women aged between 24 and 79 years) at six different clinical centers. The sites included anterior (n = 115) and posterior (n = 192) teeth. At the end of the study, a very low percentage of implant-abutment loosening (0.66%) was found, with only two loosened abutments. The cumulative implant survival rate was 98.4%. Mean DIB was 1.14 mm (48 months). Only four surviving implants did not meet the criteria for success, and the implant/crown success rate was 97.07%. Conclusion: Based upon this study of 307 implants observed during a 4-year period, Morse taper-connection implants represent a good solution for single-tooth restorations, with a very low incidence of abutment loosening (0.66%). Keywords: abutment screw loosening, implant-abutment connection, microgap, Morse taper, single-tooth restorations

Purpose: This systematic review and meta-analysis assessed the survival of immediately placed single implants in fresh molar extraction sites and immediately restored/loaded single molar implants in healed molar sites. Materials and Methods: A search of the main electronic databases, including the Cochrane Oral Health Group's Trials Register, was conducted up to November 1, 2008. The meta-analysis was prepared in accordance with the guidelines of the Academy of Osseointegration Workshop on the State of the Science on Implant Dentistry. The data were analyzed with statistical software. Results: For immediately placed molar implants, nine studies describing 1,013 implants were included to support a survival rate of 99.0%. There were no significant differences between immediate and delayed loading/restoration in molar sites (relative risk of 0.30, 95% confidence interval 0.05 to 1.61; P = .16). For immediate restoration/loading of single implants in healed molar sites, seven studies with 188 single implants were identified. In this case, the implant survival rate was 97.9%, with no difference between immediate and delayed loading (relative risk of 3.0, 95% confidence interval: 0.33 to 27.16; P = .33). Favorable marginal bone level changes in the immediate loading group were detected at 12 months (mean difference of -0.31, 95% confidence interval: -0.53 to -0.096; P = .005). Conclusions: The protocols of immediate placement and immediate restoration/loading of single implants in mandibular molar regions showed encouraging results. Keywords: dental implants, immediate loading, immediate placement, immediate restoration, meta-analysis, single implant, systematic review

This case report describes a unique intracerebral penetration of a zygomatic implant inserted in the pterygoid region. A 47-year-old female patient developed severe persistent headaches immediately after two zygomatic and two standard implants were inserted under general anesthesia. However, no additional treatment or radiologic assessment was performed at that time by the treating surgeon. The maxilla was rehabilitated with an implant-supported fixed denture 3 months after the implants were placed. An episode of acute left maxillary sinusitis occurred shortly after insertion of the fixed denture. Treatment with antibiotics was insufficient, and the patient developed chronic left maxillary sinusitis. The patient presented herself to a neurologist with symptoms of chronic fatigue and severe headaches. Cerebral magnetic resonance imaging demonstrated the intracerebral penetration of a foreign body that resembled a dental implant. The authors sought to resolve the intracerebral penetration of the foreign body, along with the persistent maxillary chronic sinusitis with its concomitant risk of ascending cerebral infection. Computer-assisted preoperative planning associated with computer-assisted threedimensional transfer should be used to avoid such a dangerous complication. Postoperative computed tomography assessment should be performed after zygomatic implant surgery. Finally, any neurologic impairment of the patient after pterygoid implantation should also be treated immediately. Keywords: complication, dental implant, headache, neurology, pterygoid, zygoma