Is cone-beam computed tomography (CBCT) an alternative to plain radiography in assessments of dental disease? A study of method agreement in a medically compromised patient population.

OBJECTIVES: Poor oral health and dental infections can jeopardize medical treatment and be life-threatening. Due to this, patients with head and neck malignancies, generalized tumor spread, organ transplant, or severe infection are referred for a clinical oral and radiographic examination. The aim of this study was to compare the diagnostic agreement of three radiographic modalities: intraoral radiographs (IO), panoramic radiographs (PX), and cone beam computed tomography (CBCT) for diagnosis of dental diseases. MATERIALS AND METHODS: Three hundred patients were examined with IO, PX, and CBCT. Periapical lesions, marginal bone level, and caries lesions were diagnosed separately by four oral radiologists. All observers also assessed six teeth in 30 randomly selected patients at two different occasions. Kappa values and percent agreement were calculated. RESULTS: The highest Kappa value and percent agreement were for diagnosing periapical lesions (0.76, 97.7%), and for the assessment of marginal bone level, it varied between 0.58 and 0.60 (87.8-89.3%). In CBCT, only 44.4% of all teeth were assessable for caries (Kappa 0.68, 93.4%). The intra-observer agreement, for all modalities and diagnoses, showed Kappa values between 0.5 and 0.93 and inter-observer agreement varied from 0.51 to 0.87. CONCLUSIONS: CBCT was an alternative to IO in diagnosing periapical lesions. Both modalities found the same healthy teeth in 93.8%. All modalities were performed equally regarding marginal bone level. In caries diagnosis, artifacts were the major cause of fallout for CBCT. CLINICAL RELEVANCE: Intraoral radiography is the first-hand choice for diagnosing dental disease. For some rare cases where intraoral imaging is not possible, a dedicated panoramic image and/or CBCT examination is an alternative.

Long-term follow-up of osteoradionecrosis of the mandible.

AIM: Investigating the prevalence of mandibular ORN in a single Swedish Oncology Center. METHODS: A total of 450 patients, treated with radiotherapy for squamous cell carcinoma in the oropharynx between 2004 and 2014 were included. Three different techniques of radiotherapy were studied. ORN diagnosis was set when clinical signs according to Marx were observed, or if radiological signs were staged according to Schwartz and Kagan. RESULTS: Using the staging system, 90 patients (20%) were diagnosed with ORN. The mean age of the ORN patients was 56.6 years, the older the patient the lower the risk of developing ORN (p = .01). The risk of developing ORN for patients receiving Intensity Modulated Radiotherapy was lower compared to patients treated with the other techniques in the multivariable analysis. Brachytherapy significantly increases the risk of ORN. The risk of ORN increased by 8% each year after radiation (p = .04). The mean time to the ORN diagnosis was 3.9 years. In the multivariate analysis, the risk of ORN increased by 13% each year after radiation (p = .0013). CONCLUSION: The mean radiation dose was of greater importance for the risk of ORN than the maximum dose. Elderly people with oropharyngeal cancer were less prone to develop ORN.

Choice of radiography in orthodontic treatment on children and adolescents: A questionnaire-based study performed in Sweden.

The aim was to investigate the objective and choice of different radiographic examinations used in orthodontic treatment of children and adolescents, using a web-based questionnaire directed toward specialists in orthodontics. The questionnaire was distributed to 255 orthodontists in Sweden. In total, 142 responses were received, and 11 specialists were interviewed. Questions were related to the use of radiography during different treatment stages; modifications to the treatment regimen owing to radiographic findings; and the use of and/or need for guidelines in radiography. Radiographic examinations were performed in all treatment stages and mainly during treatment planning. Panoramic radiographs were always or often used by the respondents (99%), less frequently used were lateral radiographs (66%) and intra-oral radiographs of the incisor regions (69%). Cone beam computed tomography (CBCT) was sparsely employed. A majority of the respondents considered that radiographic findings often or occasionally affected the treatment. Local- or clinic-specific guidelines were used by 85% of respondents. The need for national guidelines was considered low. The frequent use of panoramic radiography together with application of local guidelines, may indicate that radiographic selection criteria are not individualised. National guidelines might facilitate updates on radiographic techniques, and on radiation doses and risks in young patients.

A randomized, controlled, clinical study on a new titanium oxide abutment surface for improved healing and soft tissue health.

BACKGROUND: A newly developed, anodized titanium oxide surface containing anatase has been reported to have antimicrobial properties that could reduce bacterial adherence to abutments. PURPOSE: To investigate if abutments with the anodized surface improve healing and soft tissue health in a randomized controlled study. MATERIALS AND METHODS: Test abutments with a nanostructured anodized surface were compared with control machined titanium abutments. In total, 35 subjects each received a pair of test and control abutments. The primary endpoint was reduction of biofilm formation at test abutments at the 6-week follow-up. Secondary endpoints included several soft tissue assessments. qPCR for gene markers was used to indirectly evaluate healing and soft tissue health. RESULTS: No significant differences in biofilm formation were observed between test and control abutments, but soft tissue bleeding upon abutment removal was significantly lower for test abutments compared with control abutments (P = 0.006) at 6 weeks. Keratinized mucosa height was significantly greater at test abutments compared with control abutments at the 6-week, 6-month, and 2-year follow-ups. Significant gene expression differences indicated differences in healing and tissue remodeling. CONCLUSIONS: Abutments with an anodized and nanostructured surface compared with a conventional, machined titanium surface had no significant effect on bacterial colonization and proteolytic activity but were associated with better soft tissue outcomes such as a lower bleeding index at abutment removal and consistently greater height of keratinized mucosa throughout the 2-year follow-up, suggesting improved surface-dependent peri-implant healing and soft tissue health.

Marginal bone loss at implants with different surface characteristics - A 20-year follow-up of a randomized controlled clinical trial.

OBJECTIVE: This report is a 20-year follow-up of a randomized controlled clinical trial evaluating the potential long-term effect of a modified implant surface on the preservation of the peri-implant marginal bone level. MATERIAL & METHODS: In each of 51 patients and for each fixed partial denture (FPD), by randomization at least one implant installed had a non-modified turned surface and one a modified and roughened surface (TiOblast® ). Clinical and radiological examinations were performed at various follow-up intervals. Primary outcome variables were peri-implant marginal bone level change from time of loading and proportion of implants with no bone loss at 20 years. Multilevel analysis followed by nonparametric and Pearson's Chi-Square tests were applied for statistical analysis. RESULTS: At the 20-year follow-up, 25 patients carrying 64 implants were available for evaluation. Turned and TiOblast implants presented with a mean bone level change from the time of FDP delivery amounting to -0.41 mm (95% CI -0.84/0.02) and -0.83 mm (95% CI -1.38/-0.28) respectively (inter-group comparison p > .05). 47% of the Turned and 34% TiOblast implants (p > .05) showed no bone loss. All but one of these implants were free of bacterial plaque and inflammation as well as presented with probing pocket depths ≤5 mm at both the 5- and 20-year follow-up examinations. CONCLUSION: It is suggested that a moderate increase of implant surface roughness has no beneficial effect on long-term preservation of the peri-implant marginal bone level.

Influence of patient position and other inherent factors on image quality in two different cone beam computed tomography (CBCT) devices.

OBJECTIVES: The aim of this in vitro study was to evaluate how a deviation from the horizontal plane, affects the image quality in two different CBCT-devices. METHODS: A phantom head SK150 (RANDO, The Phantom Laboratory, Salem, NY, USA) was examined in two CBCT-units: Accuitomo 80 and Veraviewepocs 3D R100 (J. Morita Mfg. Corp. Kyoto, Japan). The phantom head was placed with the hard palate parallel to the horizontal plane and tilted 20 ° backwards. Exposures were performed with different field of views (FOVs), voxel sizes, slice thicknesses and exposure settings. Effective dose was calculated using PCXMC 2.0 (STUK, Helsinki, Finland). Image quality was assessed using contrast-to-noise-ratio (CNR). Region of interest (ROI) was set at three different levels of the mandibular bone and soft tissue, uni- and bilaterally in small and large FOVs, respectively. CNR values were calculated by CT-value and standard deviation for each ROI. Factor analysis was used to analyze the material. RESULTS: Tilting the phantom head backwards rendered significantly higher mean CNR values regardless of FOV. The effective dose was lower in small than in large FOVs and varied to a larger extent between CBCT-devices in large FOVs. CONCLUSIONS: Head position can affect the image quality. Tilting the head backward improved image quality in the mandibular region. However, if influenced by other variables e.g. motion artifacts in a clinical situation, remains to be further investigated. ADVANCES IN KNOWLEDGE: Image quality assessed using CNR values to investigate the influence of different patient positions and FOVs.

Cone-beam computed tomographic evaluation of the long-term effects of orthodontic retainers on marginal bone levels.

INTRODUCTION: Fixed retainers are widely used after orthodontic treatment, sometimes for extended periods, despite insufficient knowledge of their possible long-term adverse effects on the periodontium. The aim of this study was to evaluate whether bonded orthodontic retainers have an adverse long-term effect on the marginal bone levels of the mandibular front teeth. METHODS: The study included 62 consecutive patients in 3 groups: (1) patients who underwent orthodontic treatment and wore a fixed retainer for 10 years, (2) patients who underwent orthodontic treatment but did not have a fixed retainer, and (3) untreated controls. The marginal bone levels were measured by cone-beam computed tomography 10 years after treatment. Additionally, multivariate data analysis was used to analyze possible correlations between the marginal bone levels at 10 years and the variables obtained from the study casts and profile radiographs. RESULTS: The results demonstrated a significantly lower marginal bone level on the buccal side of the mandibular front teeth in the orthodontically treated patients compared with the orthodontically untreated group. There was no difference in the marginal bone levels between the retainer group and the no-retainer group. Multivariate analysis indicated that a low marginal bone level was correlated with a basal open vertical relationship, posterior rotation of the mandible, pretreatment of the incisor protrusion, and extraction therapy. CONCLUSIONS: Within the limits of this research design, the long-term retention phase in general does not seem to cause any adverse effects on the marginal bone levels after 10 years.

Absorbed organ and effective doses from digital intra-oral and panoramic radiography applying the ICRP 103 recommendations for effective dose estimations.

OBJECTIVE: During dental radiography, the salivary and thyroid glands are at radiation risk. In 2007, the International Commission on Radiological Protection (ICRP) updated the methodology for determining the effective dose, and the salivary glands were assigned tissue-specific weighting factors for the first time. The aims of this study were to determine the absorbed dose to the organs and to calculate, applying the ICRP publication 103 tissue-weighting factors, the effective doses delivered during digital intraoral and panoramic radiography. METHODS: Thermoluminescent dosemeter measurements were performed on an anthropomorphic head and neck phantom. The organ-absorbed doses were measured at 30 locations, representing different radiosensitive organs in the head and neck, and the effective dose was calculated according to the ICRP recommendations. RESULTS: The salivary glands and the oral mucosa received the highest absorbed doses from both intraoral and panoramic radiography. The effective dose from a full-mouth intraoral examination was 15 µSv and for panoramic radiography, the effective dose was in the range of 19-75 µSv, depending on the panoramic equipment used. CONCLUSION: The effective dose from a full-mouth intraoral examination is lower and that from panoramic radiography is higher than previously reported. Clinicians should be aware of the higher effective dose delivered during panoramic radiography and the risk-benefit profile of this technique must be assessed for the individual patient. ADVANCES IN KNOWLEDGE: The effective dose of radiation from panoramic radiography is higher than previously reported and there is large variability in the delivered radiation dosage among the different types of equipment used.

Three-Dimensional buccal bone anatomy and aesthetic outcome of single dental implants replacing maxillary incisors.

OBJECTIVES: This case series investigated by means of CBCT, buccal bone three-dimensional anatomy at delayed, two-stage implants in the maxillary incisal tooth region. Moreover, the relation between buccal bone anatomy and soft tissue aesthetics was assessed. MATERIAL AND METHODS: Twelve implants were analysed after on average 8.9 years in function. Baseline and re-evaluation photographs were assessed using the pink aesthetic score (PES). Marginal bone changes were measured from intraoral X-rays. The buccal bone volume associated with the implant and the implant surface not covered by visible buccal bone was computed on CBCT data sets. Buccal bone thickness and level were assessed, as well as the thickness of the crest distally and mesially of the implant. Changes in soft tissue forms and correlation between aesthetics and bone anatomy were calculated by nonparametric statistics. RESULTS: Buccal bone level was located 3.8 mm apical of the implant shoulder, and none of the implants had complete bone coverage. Buccal bone volume was 144.3 mm(3) , and 4.29 mm(3) in the more coronal 2 mm portion. PES did not differ at re-evaluation (9.7) and baseline (9.2). PES was directly correlated with crestal thickness mesially and distally of the implant shoulder. No other significant correlations were observed between bone anatomy and PES or buccal peri-implant health. Marginal bone gain over time was associated with greater coronal bone volume buccally and with greater buccal and marginal bone thickness, while loss was related to less or no bone. CONCLUSIONS: Within present limitations, acceptable and stable aesthetics are not jeopardized by a thin or missing buccal bone.

Implant-supported single-tooth restorations. A 12-year prospective study.

OBJECTIVE: The aim of this study was to evaluate prospectively the 12-year outcome of implant-supported single-tooth restorations. MATERIAL AND METHODS: Originally 45 self-tapping Astra Tech TiOblast® ST-implants were installed by a two-stage protocol in 40 subjects requiring single-tooth prosthetic replacement for a missing tooth. Clinical and radiologic examinations were performed at completion of the prosthetic treatment 4-7 months after implant installation surgery and after 5 and 12 years in function. RESULTS: At 12 years 31 patients and 35 implants were available for evaluation. The overall failure rate after 12 years was 10.3% on the subject level and 9.1% on the implant level. The mean bone loss amounted to 0.67 mm (SD 2.20) on a subject level and 0.47 mm (1.72) on an implant level. Three subjects (10%) and three implants (8.6%) were diagnosed with peri-implantitis. Five subjects had experienced technical complications; three incidences of loosening of the abutment retention screw during the first 5 years and two minor porcelain fracture of the crown (two patients) between 5- and 12-years of follow-up. CONCLUSION: The findings reported in this 12-year prospective case series suggest that the use of the Astra Tech dental implants may be a valid treatment alternative for single-tooth replacement prostheses.

A controlled, cross-sectional exploratory study on markers for the plasminogen system and inflammation in crevicular fluid samples from healthy, mucositis and peri-implantitis sites.

PURPOSE: To investigate expression of gene markers for the plasminogen system, inflammation, and bone resorption/remodelling in peri-implant crevicular fluid samples from healthy subjects, subjects with mucositis and subjects with peri-implantitis. A possible inhibitory effect of suppuration on the analysis of gene expression in samples from subjects with peri-implantitis was also analysed. MATERIALS AND METHODS: Peri-implant crevicular fluid (PICF) was sampled from 25 healthy subjects (H), 25 subjects with mucositis (M) and 25 subjects with peri-implantitis (P) using paper points and suction tips. The samples were analysed by quantitative polymerase chain reaction (qPCR). The following biomarkers associated with the plasminogen system, inflammation and bone resorption/ remodelling were investigated: interleukin-1 beta (IL-1ß), interleukin 8 (IL-8), tissue plasminogen activator (tPA), plasminogen activator inhibitor 2 (PAI-2), tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CatK). RESULTS: IL-1ß and IL-8 were significantly upregulated in the P group, and tPA and PAI-2 were significantly upregulated in the M group. These four genetic markers were oppositely regulated in samples from the subjects in the mucositis compared with the peri-implantitis group. TRAP and CatK showed no differences between the groups. The presence of suppuration did not have a detectable effect on gene analysis in samples from subjects with peri-implantitis. CONCLUSIONS: Markers for the plasminogen system and inflammation could be used to distinguish between mucositis and peri-implantitis. The results suggested that the plasminogen system was sufficiently upregulated allowing for resolution of inflammation and healing at the inflamed implant site in subjects with mucositis, whereas such upregulation was insufficient resulting in impaired healing and prolonged inflammation in subjects with peri-implantitis. The combination of tissue inflammation and low levels of tPA was a strong predictor of marginal bone loss in this study. It may be an interesting candidate for the unambiguous diagnosis of mucositis and peri-implantitis independent of radiographs and could possibly constitute a powerful future tool for rapid assessment of the periimplant tissue condition and the effect of subject treatment.

Evaluation of cone-beam computed tomography in the diagnosis of vertical root fractures: the influence of imaging modes and root canal materials.

INTRODUCTION: The purpose of this study was to evaluate the influence of cone-beam computed tomography (CBCT) imaging modes in the diagnosis of vertical root fractures with different intracanal materials. METHODS: The sample consisted of 30 single-rooted teeth divided into 3 groups (n = 10), control and complete and incomplete root fracture. In each tooth, different materials were used (gutta-percha, metal post, and fiber post) as well as no filling material. Each tooth/root was scanned in a 3D Accuitomo 170 CBCT device by using 4 different imaging modes (high-resolution, high-fidelity, high-speed, and standard). In addition, the dose-area product was calculated for each CBCT imaging mode. The images were randomly evaluated by 5 dentomaxillofacial radiologists. RESULTS: Complete root fractures were visualized more easily than incomplete fractures. The presence of metal post and gutta-percha negatively influenced the diagnosis of root fracture. Regarding the CBCT imaging modes, there was no influence for complete root fracture diagnosis. In cases of incomplete root fractures, high-fidelity, high-resolution, and standard had a higher diagnostic accuracy, especially in the fiber post and no filling groups. CONCLUSIONS: The CBCT imaging modes had little influence in the diagnosis of complete and incomplete root fractures, whereas the presence of intracanal material had greater impact on the diagnostic ability, demonstrating that CBCT is not beneficial for the diagnosis of root fractures when metal posts are present.

Orthodontic tooth movement into edentulous ridge areas--a case series.

The aim of this case series was to analyse dimensional alterations of the alveolar ridge and tooth-supporting structures, as well as root resorption, following orthodontic tooth movement into edentulous areas with reduced ridge dimensions. The study involved six subjects (30-70 years) with 10 edentulous jaw areas in the premolar regions. Clinical and radiographic examinations and 3D measurements on scanned study casts were performed at baseline, at retention, and after 1 year of (i) the edentulous area into which the tooth was moved and (ii) the established edentulous area from which the tooth was moved. The orthodontic tooth movement into an edentulous area resulted in most individuals in only minor dimensional alterations of the periodontal tissues. With regard to the width of the alveolar process, the results indicated a decreased width in the newly established edentulous area, whereas in the area into which the tooth had been moved, the width increased. In all cases, the moved tooth showed lateral root resorption on its pressure side at the level of the bone crest at time of retention, but signs of repair were noticed at the 1-year follow-up. Within the limitations of the study, it can be concluded that orthodontic tooth movement results in dimensional alterations of the edentulous ridge and that lateral root resorption is an inevitable side-effect.

Marginal bone-level alterations at implants installed in block versus particulate onlay bone grafts mixed with platelet-rich plasma in atrophic maxilla. a prospective 5-year follow-up study of 15 patients.

BACKGROUND: Extensive atrophy of the alveolar process may require a bone-grafting procedure prior to implant treatment. Autogenous bone grafts from the iliac crest, used as onlay block and particulate bone, have been used together with sinus-lift procedure in order to rehabilitate patients with extremely resorbed maxillae. However, there are to our knowledge no 5-year follow-up studies evaluating the extent of bone-level change in patients treated with respectively block and particulate autogenous bone grafts. PURPOSE: The purpose of this prospective clinical study was to conduct a 5-year follow-up analysis with focus on bone-level alteration in block versus particulate onlay bone grafts. MATERIAL AND METHODS: Fifteen out of originally 19 patients who were treated with iliac bone grafts and oral implants in the maxilla have been followed through the first 5 postoperative years. In a first study conducted on 19 patients, the role of platelet-rich plasma in conjunction with autogenous bone was evaluated. In this 5-year follow-up study, the marginal bone alterations have been documented at base line, 1 year and 5 years of loading to the nearest 0,1 mm at mesial and distal surfaces of the implants. Two implants were installed on each side of the midline in either block or particulate bone grafts giving test and control sides in each patient. Additionally, two implants on each side were installed in residual bone/grafted sinus floor. RESULT: Marginal bone alteration in the anterior maxilla appeared larger at the side augmented by block bone at baseline, and after 1 and 5 years of loading, but the change was not statistically significant. Moreover, there was a significantly higher degree of marginal alteration during the first year of loading, compared with the examinations after 5 years. CONCLUSION: The present follow-up study showed that there is no significant difference in the extension of resorption between block- and particulate autogenous bone grafts over a 5-year period. Most of the resorption occurred during the first year in function.

Immediate occlusal loading of NanoTite™ tapered implants: a prospective 1-year clinical and radiographic study.

BACKGROUND: During the last decade, high success rates have been reported for implants placed with immediate loading procedures, especially when bone quality and quantity provide good implant stability. In many of these studies, straight-walled implants with moderately rough surfaces were employed. Tapered implants are becoming increasingly more popular due to standardized drilling protocols and reports of high initial primary stability. PURPOSE: The aim of the present prospective, single center clinical study was to evaluate surface topographical analysis and the clinical and radiographic outcomes of the NanoTite™ (BIOMET 3i, Palm Beach Gardens, FL, USA) Tapered Implant when used for immediate loading of fixed prostheses and single-tooth restorations. MATERIALS AND METHODS: Forty-two patients who needed implant treatment and met admission criteria agreed to participate in the study and were consecutively enrolled. Surgical implant placement requirements consisted of a final torque of a least 30 Ncm prior to final seating and an implant stability quotient above 55. A total of 139 NanoTite Tapered implants (112 maxillary and 27 mandibular) were placed by one investigator, and the majority of these implants (n = 77/55%) were placed in posterior regions, and in soft bone (n = 90/65%). A total of 57 prosthetic constructions were evaluated consisting of 20 single-tooth restorations, 30 fixed partial dentures, and 7 complete, fixed maxillary restorations. Radiographs were taken at baseline and at 12 months of follow-up. RESULTS: Of the 139 study implants, one implant failure was declared. The overall cumulative survival rate at 1 year is 99.4%. Mean marginal bone resorption is 1.01 mm (SD 0.85) during the first year of function. CONCLUSION: Although limited to the short follow-up, immediate loading of NanoTite Tapered implants seems to be a viable option in implant rehabilitation, when insertion torque of at least 30 Ncm is achieved. Further studies are needed to authenticate the finding of this study.

Frequency of errors and pathology in panoramic images of young orthodontic patients.

The aims of this study were to evaluate the frequency of errors in panoramic radiographs in young orthodontic patients, to register pathologic and abnormal conditions, and to compare these findings with the patient's record. A total of 1287 panoramic radiographs of children and adolescents (530 boys and 757 girls; mean age 14.2 years) were analyzed. The radiographs were obtained of patients referred for orthodontic treatment during a 1 year period. Four observers evaluated the radiographs for 10 common errors, pathologies, and/or anomalies. Cohen's kappa was used for the calculations of inter- and intraobserver variability. Five of the errors were divided into clinically relevant or not clinically relevant errors, i.e. errors influencing diagnosis. Only those pathological findings with a possible influence on orthodontic treatment were compared with the patient's record. Of the 1287 radiographs, 96 per cent had errors. The number of errors in each image varied between 1 and 5, and in 24 per cent of these images, the errors could be of importance for clinical decision making. The most common error was that the tongue was not in contact with the hard palate. Pathologies or anomalies were found in 558 patients and a total of 1221 findings were recorded. Findings of possible relevance for orthodontic treatment were 63, and 12 of those were registered in the patient records. Pathological findings outside the dental arches were low and could be an argument for minimizing the radiation field.

Particulate vs. block bone grafts: three-dimensional changes in graft volume after reconstruction of the atrophic maxilla, a 2-year radiographic follow-up.

BACKGROUND: Extensive alveolar bone resorption in the maxilla limits the possibility of successful placement and osseointegration of endosseous implants for future prosthetic rehabilitation. Autogenous bone from the iliac crest may be used as lateral onlays in the atrophic maxilla, both as block and particulate bone. To our knowledge, there is no three-dimensional 2-year follow-up study measuring the volumetric reduction of the augmented areas comparing particulate and block bone grafts. PURPOSE: The aim of this study was to conduct a radiographic 2-year follow-up study, using computed tomographic (CT) images in order to evaluate and compare the extent of bone graft resorption in the frontal maxillae augmented by particulate (test) and block bone (control). MATERIAL AND METHODS: Eleven patients treated with iliac bone grafts and oral implants in the maxilla were followed with CT examinations directly post grafting and after 2 years. RESULT: The volumetric changes after 6 months were extensive. Additionally, the changes in particulate bone tended to be larger after 2 years compared to block bone, using this protocol. However, the difference was not statistically significant. CONCLUSION: The present follow-up study showed that there is radiographically complete integration and embedding of implants installed in grafted bone despite extensive initial graft resorption. There was no significant difference in the amount of volumetric reduction between particulate bone and block bone grafts.

Cone-beam CT for preoperative implant planning in the posterior mandible: visibility of anatomic landmarks.

BACKGROUND: The technical development has given a new type of modality, cone-beam computed tomography (CBCT). This technique has a high potential to solve different diagnostic problems among which is preoperative planning for implants in the posterior mandible. PURPOSE: The aim of this retrospective study was to evaluate the visibility of the mandibular canal and the marginal bone crest and the agreement between observers in images from one CBCT technique. MATERIALS AND METHODS: Thirty consecutive patients were examined with 3D Accuitomo (J. Morita Mfg. Corp., Kyoto, Japan) in one side of the mandible, where the second premolar and molars were lost. The examined volume was 30 by 40 mm. Seven observers evaluated the visibility and the location of the mandibular canal and the marginal crest by visually deciding if the structures were clearly visible, probably visible, or invisible in one cross-sectional image, approximately 1 cm posterior to the mental foramen. In a later session, the observers also marked the two anatomic structures. If the decision was not "clearly visible" or if the anatomic structures were difficult to identify, the observers had to use other cross-sectional, axial, and/or sagittal images in the volume. RESULTS: The confidence among the observers evaluating the marginal bone crest was high. Two observers never used any other images, and the rest took help in two to seven cases. When marking the mandibular canal, the observers, in general, used more images. In five cases (17%), all the observers only used the single cross-sectional image. The agreement on the position of the canal was also high. CONCLUSION: With this CBCT modality (3D Accuitomo), the visibility of the mandibular canal and the marginal crest, as well as the observer agreement of the location of these structures, was high. Hence, the 3D Accuitomo can be recommended for implant planning in the posterior mandible.

Implant-supported single-tooth restorations: a 5-year prospective study.

BACKGROUND: Comparatively few studies are available reporting at least 5 years of follow-up data of implant-supported single-tooth replacements. OBJECTIVE: To evaluate prospectively the 5-year outcome of implant-supported single-tooth prosthetic restorations. MATERIAL AND METHODS: Forty subjects (mean age 41 years), 23 males and 17 females, who required single-tooth prosthetic replacement for a missing tooth were recruited. A total of 45 self-tapping implants (Astra Tech ST-implants)--40 in the maxilla and five in the mandible--were installed in a two-stage procedure. Abutment connection was performed 3-6 months after implant installation. Clinical and radiographic examinations were performed at the completion of the prosthetic treatment and once a year during a 5-year follow-up period. The analysis of peri-implant bone level alteration was performed on subject and implant levels and by the use of analysis of variance and binary logistic regression. RESULTS: Three patients were lost during the 5 years of follow-up. One implant was lost after 2.5 years in function and another four implants could not be accounted for at the 5-year follow-up examination. The overall failure rate at 5 years was 2.6% (subject level) and 2.3% (implant level). The mean loss of marginal bone at the implants during the first year in function was 0.06 mm (SD 0.67) on the subject level and 0.02 mm (0.65) on the implant level. During the subsequent 4 years the annual change in peri-implant bone level amounted to -0.02 mm (0.22) on both subject and implant levels. Thus, the mean total bone level change over the 5-year interval was -0.14 mm (1.04) on subject level and -0.11 mm (1.00) on the implant level of analysis (p>0.05). The frequency of implants with a 5-year bone loss of > or =1 mm was 13%. Approximately 50% of the implants demonstrated no bone loss. CONCLUSION: The present clinical trial on single-tooth replacements with the Astra Tech implant system demonstrated that the bone loss during the first year of function as well as annually thereafter was small.

Bone level change at implant-supported fixed partial dentures with and without cantilever extension after 5 years in function.

OBJECTIVE: The aim of this study was to retrospectively analyze whether the inclusion of cantilever extensions increased the amount of marginal bone loss at free-standing, implant-supported, fixed partial dentures (FPDs) over a 5-year period of functional loading. MATERIAL AND METHODS: The patient material comprised 45 periodontally treated, partially dentate patients with a total of 50 free-standing FPDs supported by implants of the Astra Tech System. Following FPD placement (baseline) the patients were enrolled in an individually designed supportive care program. A set of criteria was collected at baseline to characterize the FPDs. The primary outcome variable was change in peri-implant bone level from the time of FPD placement to the 5-year follow-up examination. The comparison between FPDs with and without cantilevers was performed at three levels: FPD level, implant level, and surface level. Bivariate analysis was performed by the use of the Mann-Whitney U-test and stepwise regression analysis was utilized to evaluate the potential influence of confounding factors on the change in peri-implant bone level. RESULTS: The overall mean marginal bone loss for the implant-supported FPDs after 5 years in function was 0.4 mm (SD, 0.76). The bone level change at FPDs placed in the maxilla was significantly greater than that for FPDs in the mandible (0.6 versus 0.2 mm; p<0.05). No statistically significant differences were found with regard to peri-implant bone level change over the 5 years between FPDs with and without cantilevers at any of the levels of comparisons. The multivariate analysis revealed that the variables jaw of treatment and smoking had a significant influence on peri-implant bone level change on the FPD level, but not on the implant or surface levels. The model explained only 10% of the observed variance in the bone level change. CONCLUSION: The study failed to demonstrate that the presence of cantilever extensions in an FPD had an effect on peri-implant bone loss.