A comparison of implant-retained mandibular overdentures and conventional dentures on quality of life in edentulous patients: a randomized, prospective, within-subject controlled clinical trial.

OBJECTIVES: To determine any difference in patient response to implant overdentures compared with conventional complete dentures alone. MATERIALS AND METHODS: In a randomized, prospective, controlled study, 122 edentulous patients (Mean age 64; 39 men, 83 women) underwent baseline assessment of denture satisfaction and quality of life using the Oral Health Impact Profile-49 (OHIP-49) and a Denture Satisfaction Questionnaire. All patients were provided with new conventional complete dentures (CCDs) that they wore for 3 months, at which point they were reassessed using the same measures. Patients were randomly assigned either to continue with CCDs (CC group) or to have implant-retained overdentures (IODs) made (CI group). The CC group was assessed after a further 3 months (6 months after receiving CCDs). The CI group was assessed 3 months after receiving IODs. RESULTS: Significant improvements in satisfaction and quality of life were found in the patients 3 months after receiving CCDs (P < 0.05). No further improvements were found in the CC group at 6 months on any of the measures. The CI group showed significant additional improvements at 3 months following IODs on the functional limitation, physical pain, psychological discomfort, physical disability, social disability, psychological disability and handicap scales of the OHIP and on 10 of the 11 scales of the Denture Satisfaction Questionnaire (P < 0.05, ANOVA). CONCLUSIONS: The findings show that, controlling for expectancy bias and variability in baseline levels, IODs significantly increase patient satisfaction, dental function and quality of life over and above those achieved with good quality CCDs.

A radiographic analysis of implant component misfit.

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.

The effect of skeletal pattern on determining articulator settings for prosthodontic rehabilitation: an in vivo study.

PURPOSE: During extensive prosthodontic treatment, the use of an accurately adjusted articulator is recommended to simulate mandibular movements. This clinical study was undertaken to assess any possible effect of the underlying skeletal pattern on programming articulator settings. MATERIALS AND METHODS: Subjects (n = 73, mean age: 22.8 ± 6.8 years) were recruited from a dental school and two regional specialist orthodontic units. Subjects were allocated into groups based on their underlying sagittal (I, II, or III) and vertical (reduced, average, or increased) skeletal patterns by three orthodontists and three prosthodontists who examined their profile photographs. Electronic pantographic recordings were made of each subject using the Cadiax Compact system to record the sagittal condylar inclination (SCI), progressive mandibular lateral translation (PMLT), and immediate mandibular lateral translation (IMLT). RESULTS: Agreement between assessors for sagittal skeletal pattern classification was excellent (97% for total or good agreement); agreement for vertical skeletal pattern was high, but at a lower level than that for sagittal relationships (70% for total or good agreement). SCI settings for sagittal II subjects were significantly higher than those for sagittal I (P < .05) and sagittal III (P < .001) subjects. Differences were statistically significant, with mean SCI differences of 4 and 7 degrees, respectively. No statistical difference could be observed between SCI values in the sagittal I and III groups. Subjects with an average vertical skeletal pattern had SCI values lower than those with a reduced vertical skeletal pattern (P = .058) and an increased vertical skeletal pattern (P < .01, statistically significant). No patterns could be determined for PMLT or IMLT between the study groups. CONCLUSION: During prosthodontic treatment of patients with a noticeable skeletal discrepancy, appropriate consideration should be given to customizing SCI values.

Accuracy of bone mapping and guided flapless implant placement in human cadavers using a model-based planning procedure.

PURPOSE: The objective of this study was to assess the accuracy of the model-based NobelGuide method in transferring preoperative planning and estimation of bone volume to the surgical situation. MATERIALS AND METHODS: Thirteen implant replicas were placed in bounded edentulous spaces in nine human cadavers. Highly restrictive guides were fabricated using preoperative bone mapping data. A stone cast was modified to represent the bone contours at the implant site. Postoperative impressions were taken for comparison with the planning cast that had been used to generate the guides. Mucoperiosteal flaps were raised over each implant site, and the areas were inspected for fenestrations, thread exposures, or dehiscences. A coordinate measuring device was used to obtain positional and angular information from each implant placed in the planned and postsurgical casts. These were compared and analyzed for clinical and statistical significance. RESULTS: The median value for linear accuracy in three dimensions for the model-based NobelGuide was 0.48 mm and the median angular deviation was 2.88 degrees. The greatest measured errors were still within clinically acceptable limits. The bone mapping was of sufficient diagnostic value for implant placement in sites with sufficient bone volume (greater than 5 mm buccolingually). In sites with insufficient bone volume, dehiscences were seen, but the accuracy was independent of bone volume. CONCLUSION: The use of the model-based NobelGuide encourages adherence to the restorative-driven approach. The accuracy of the method is within acceptable limits for guided surgery described in the literature, and the use of the bone mapping is satisfactory in cases with adequate bone volume. The technique can also be used in sites with insufficient bone volume, but a mucoperiosteal flap procedure is recommended. Int J Oral Maxillofac Implants 2010;25:999-1006.

Patient satisfaction and oral health-related quality of life outcomes of implant overdentures and fixed complete dentures.

PURPOSE: To assess and compare patient satisfaction and oral health-related quality of life (OHQOL) in patients treated with implant-supported overdentures and complete implant fixed prostheses. MATERIALS AND METHODS: From a database of patients who had undergone implant treatment over a 6-year period, a study population of 62 patients was identified; every patient had at least four implants placed in one edentulous arch and was restored with either an overdenture or a fixed prosthesis. Patients were examined and a self-administered, structured multiple-response questionnaire, including the Oral Health Impact Profile-14 measurement tool and a patient satisfaction survey, was used to evaluate patient-centered treatment outcomes. RESULTS: Generally, patient satisfaction was very high in both the implant overdenture and fixed prosthesis groups, although the subjects in the overdenture group, who had mostly maxillary prostheses, reported significantly lower overall satisfaction and lower satisfaction with chewing capacity and esthetics. In just three categories--cost, satisfaction with treating doctor, and ability to perform oral hygiene measures--the fixed prosthesis group was less satisfied than the removable overdenture group, but the difference was not significant. Similarly, the overall OHQOL was high, although patients receiving a fixed prosthesis demonstrated significantly lower psychologic discomfort and psychological disability compared to the overdenture group. CONCLUSIONS: Among all patients who had similar numbers of implants placed, those who received an implant overdenture were less satisfied and had lower OHQOL than the patients who had a fixed prosthesis. Since patient and dentist preferences influenced the type of prosthesis provided, it is likely that subjective, patient-related factors are major determinants of satisfaction and treatment outcomes.

Demographics of implant placement and complications of a patient subgroup in a dental hospital population.

STATEMENT OF PROBLEM: Little has been reported about the demographics of implant placement in the Irish population and the complications that occur. This is important in terms of service planning and providing patient information. PURPOSE: The purpose of this study was to construct a database of patients who had implants placed in the Dublin Dental School et Hospital from 2000 to 2006. Also, we wanted to compare the complications that occurred in patients who had overdentures to those with a fixed prosthesis. METHODS: Hospital records were searched for all patients who had implants placed over a seven-year period and we recorded demographic information, as well as details of the implant site, implant type and restoration. Patients who had four or more implants placed for an implant-supported overdenture or fixed prosthesis were invited to attend for a clinical examination. RESULTS: A total of 1,111 implants were placed in 452 patients over the study period--half of the implants supported single crowns, while the other half supported mainly overdentures and full arch fixed prostheses, with few fixed partial dentures. The 40- to 60-year-olds had the greatest number of implants placed of any age group and most implants were placed in the anterior region. Patients with implant-supported overdentures recorded more complications (52%) compared to those with fixed prostheses (32%). The most common complications associated with both treatments were gingival inflammation and peri-implant mucositis. Overdentures additionally had a significant number of retentive clip fractures. CONCLUSIONS: Implant-supported overdentures and fixed prostheses were both clinically successful. However, patients and clinicians should be aware that soft tissue and mechanical complications are common.

Altered dendritic integration in hippocampal granule cells of spatial learning-impaired aged rats.

Glutamatergic transmission at central synapses undergoes activity-dependent and developmental changes. In the hippocampal dentate gyrus, the non-N-methyl d-aspartate (NMDA) receptor component of field excitatory postsynaptic potentials (fEPSPs) increases with age in Fischer-344 rats. This effect may not depend on the animal's activity or experience but could be part of the developmental process. Age-dependent differences in synaptic transmission at the perforant path-granule cell synapse may be caused by changes in non-NMDA and NMDA receptor-mediated currents. To test this hypothesis, we compared whole cell excitatory postsynaptic currents (EPSCs) in dentate granule cells evoked by perforant path stimulation in young (3-4 mo) and aged (22-27 mo) Fischer-344 rats using a Cs+-based intracellular solution. Aged animals as a group showed spatial learning and memory deficits in the Morris water maze. Using whole cell recordings, slope conductances of both non-NMDA and NMDA EPSCs at holding potentials -10 to +50 mV were significantly reduced in aged animals and the non-NMDA/NMDA ratio in aged animals was found to be significantly smaller than in young animals. In contrast, we detected no differences in basic electrophysiological parameters, or absolute amplitudes of non-NMDA and NMDA EPSCs. Extracellular Cs+ increased the fEPSP in young slices to a greater degree than was found in the aged slices, while it increased population spikes to a greater degree in the aged rats. Our results not only provide evidence for reduced glutamatergic synaptic responses in Fischer-344 rats but also point to differential changes in Cs+-sensitive dendritic conductances, such as Ih or inwardly rectifying potassium currents, during aging.

Preloads generated with repeated tightening in three types of screws used in dental implant assemblies.

PURPOSE: Abutment screw loosening, especially in the case of cemented single tooth restorations, is a cause of implant restoration failure. This study compared three screws (titanium alloy, gold alloy, and gold-coated) with similar geometry by recording the preload induced when torques of 10, 20, and 35 Ncm were used for fixation. MATERIALS AND METHODS: Two abutment types were used-prefabricated preparable abutments and cast-on abutments. A custom-designed rig was used to measure preload in the abutment-screw-implant assembly with a strain gauge. Ten screws of each type were sequentially tightened to 10, 20, and 35 Ncm on ten of the two abutment types. The same screws were then loosened and re-tightened. This procedure was repeated. Thus, each screw was tightened on three occasions to the three insertion torques. A linear regression model was used to analyze the effects on preload values of screw type and abutment type for each of the three insertion torques. RESULTS: The results indicated that the gold-coated screw generated the highest preloads for all insertion torques and for each tightening episode. Further analysis focused on the effects of screw type and abutment type for each episode of tightening and for each fixation torque. The gold-coated screw, fixed to the prefabricated abutment, displayed higher preloads for the first tightening at 10, 20, and 35 Ncm. Conversely, the same screw fixed to the cast-on abutment showed higher values for the second and third tightening for all fixation torques. All screws showed decay in preload with the number of times tightened. Given the higher preloads generated using the gold-coated screw with both abutment types, it is more likely that this type of screw will maintain a secure joint when tightened for the second and third time. CONCLUSION: All screw types displayed some decay in preload with repeated tightening, irrespective of abutment type and insertion torque. The gold-coated screw showed markedly higher preloads for all insertion torques and for all instances of tightening when compared with the uncoated screws.

Recent behavioral history modifies coupling between cell activity and Arc gene transcription in hippocampal CA1 neurons.

The ability of neurons to alter their transcriptional programs in response to synaptic input is of fundamental importance to the neuroplastic mechanisms underlying learning and memory. Because of technical limitations of conventional gene detection methods, the current view of activity-dependent neural transcription derives from experiments in which neurons are assumed quiescent until a signaling stimulus is given. The present study was designed to move beyond this static model by examining how earlier episodes of neural activity influence transcription of the immediate-early gene Arc. Using a sensitive FISH method that detects primary transcript at genomic alleles, the proportion of hippocampal CA1 neurons that activate transcription of Arc RNA was constant at approximately 40% in response to both a single novel exploration session and daily sessions repeated over 9 days. This proportion is similar to the percentage of active neurons defined electrophysiologically. However, this close correspondence was disrupted in rats exposed briefly, but repeatedly, to the same environment within a single day. Arc transcription in CA1 neurons declined dramatically after as few as four 5-min sessions, despite stable electrophysiological activity during all sessions. Additional experiments indicate that the decrement in Arc transcription occurred at the cellular, rather than synaptic level, and was not simply linked to habituation to novelty. Thus, the neural genomic response is governed by recent, but not remote, cell firing history in the behaving animal. This state-dependence of neuronal transcriptional coupling provides a mechanism of metaplasticity and may regulate capacity for synaptic modification in neural networks.