Cortical activation resulting from the stimulation of periodontal mechanoreceptors measured by functional magnetic resonance imaging (fMRI).

OBJECTIVE: To describe the normal cortical projections of periodontal mechanoreceptors. MATERIAL AND METHODS: A device using von Frey filaments delivered 1-Hz punctate tactile stimuli to the teeth during fMRI. In a block design paradigm, tooth (T) 11 and T13 were stimulated in ten volunteers and T21 and T23 in ten other subjects. Random-effect group analyses were performed for each tooth, and differences between teeth were examined using ANOVA. RESULTS: The parietal operculum (S2) was activated bilaterally for all teeth; the postcentral gyrus (S1) was activated bilaterally for T21 and T23 and contralaterally for T11 and T13. In the second-level analysis including the four teeth, we found five clusters: bilateral S1 and S2, and left inferior frontal gyrus, with no difference between teeth in somatosensory areas. However, the ANOVA performed on the S1 clusters found separately in each tooth showed that S1 activation was more contralateral for the canines. CONCLUSION: One-hertz mechanical stimulation activates periodontal mechanoreceptors and elicits bilateral cortical activity in S1 and S2, with a double representation in S2, namely in OP1 and OP4. CLINICAL RELEVANCE: The cortical somatotopy of periodontal mechanoreceptors is poorly described. These findings may serve as normal reference to further explore the cortical plasticity induced by periodontal or neurological diseases.

Accuracy assessment of computer-assisted flapless implant placement in partial edentulism.

AIM: To assess the accuracy of implants placed flapless by a stereolithographic template in partially edentulous patients. MATERIAL AND METHODS: Eight patients, requiring two to four implants (maxilla or mandible), were consecutively recruited. Radiographical data were obtained by means of a cone beam or a multi-slice CT scan and imported in a software program. Implants (n=21) were planned in a virtual environment, leading to the manufacture of one stereolithographic template per patient to guide the implant placement in a one-stage flapless procedure. A postoperative cone beam CT was performed to calculate the difference between virtual implant (n=21) positions in the preoperative planning and postoperative situation. RESULTS: A mean angular deviation of 2.7 degrees (range 0.4-8, SD 1.9), with a mean deviation at the apex of 1.0 mm (range 0.2-3.0, SD 0.7), was observed. If one patient, a dropout because of non-conformity with the protocol, was excluded, the angular deviation was reduced to 2.2 degrees (range 0.6-3.9, SD 1.1), and the apical deviation to 0.9 mm (range 0.2-1.8). CONCLUSION: Based on this limited patient population, a flapless implant installation appears to be a useful procedure even when based on accurate and reliable 3D CT-based image data and a dedicated implant planning software.

Assessment of changes in the oral tactile function of the soft tissues by implant placement in the anterior maxilla: a prospective study.

The aim of the present study was to assess the somatosensory function in the peri-implant soft tissues in the anterior jaw bone by means of two psychophysical tests. Light-touch sensation (LTS) and two-point discrimination (2PD) were performed before, and at planned intervals until 18 months after the placement of one or two implants in the anterior maxilla. The same tests were used on the contralateral control sites. The psychophysical threshold was determined by performing the staircase method. The mean values and standard deviation of LTS and 2PD, pooled over the four sessions at each test area, were calculated. Despite a large intersubject variation in both the LTS and 2PD, significantly high intra-individual correlations were found (P < 0.005). For LTS, the thresholds were not significantly affected over time (P > 0.05) on both implant and control sites. The 2PD increased significantly after surgery and maintained the higher discriminatory sense for 1 year (P-value 0.005). The control sites remained stable over time. However, no correlation was revealed between LTS and 2PD perception (Pearson correlation test). In this prospective study, no major differences between the different sites and testing sessions were reported; except for the 2PD thresholds which were lowered after implant surgery. These findings suggest that the regenerated nerves may be responsible for the increased 2PD sensitivity in the peri-implant soft tissue. The unchanged LTS thresholds did not allow confirming this hypothesis.

Detection of odorous compounds in breath.

Previous studies have demonstrated that hydrogen sulfide and methyl mercaptan play a major role in oral malodor. In the present study, we tested the hypothesis that other compounds found in mouth air can also contribute to halitosis. Mouth air of 40 healthy volunteers and 40 persons with halitosis was analyzed and compared by gas chromatography-mass spectrometry, two sulfur monitors, and organoleptically. Nearly 700 different compounds were detected. Hydrogen sulfide, methyl mercaptan, dimethyl sulfide, di- and trisulfide were increased in persons with breath odor. These compounds were all significantly correlated with the organoleptic score. We concluded that hydrogen sulfide, methyl mercaptan and, to a much lesser extent, dimethyl sulfide, di- and trisulfide can contribute to oral malodor. The role of other compounds, such as amines and organic acids, seems insignificant.

Radiographic detection of artificial intra-bony defects in the edentulous area.

BACKGROUND: Since intra-bony pathologies might jeopardize implant outcome, their preoperative detection is crucial. MATERIAL AND METHODS: In sixteen human cadaver bloc sections from upper and lower jaws, artificial defects with progressively increasing size (n=7) have been created. From each respective defect, analogue and digital intra-oral radiographs were taken, the latter processed via a periodontal filter and afterwards presented in black-white as well as in colour, resulting in three sets of 7 images per bloc section. Eight observers were asked to diagnosis an eventual defect on randomly presented radiographs, and at another occasion to rank each set based on the defect size. RESULTS: The clinicians were only able to identify a defect, when the junctional area was involved, except for bony pieces with a very homogeneous structure. CONCLUSION: For longitudinal evaluation of healing bone (e.g. after tooth extraction), colour digital images can be recommended. These observations indicate that intra-oral radiographs are not always reliable for the detection of any intra-bony defect.

Image quality vs radiation dose of four cone beam computed tomography scanners.

OBJECTIVES: To evaluate image quality by examining segmentation accuracy and assess radiation dose for cone beam CT (CBCT) scanners. METHODS: A skull phantom, scanned by a laser scanner, and a contrast phantom were used to evaluate segmentation accuracy. The contrast phantom consisted of a polymethyl methacrylate (PMMA) cylinder with cylindrical inserts of air, bone and PMMA. The phantoms were scanned on the (1) Accuitomo 3D, (2) MercuRay, (3) NewTom 3G, (4) i-CAT and (5) Sensation 16. The structures were segmented with an optimal threshold. Thicknesses of the bone of the mandible and the diameter of the cylinders in the contrast phantom were measured across lines at corresponding places in the CT image vs a ground truth. The accuracy was in the 95th percentile of the difference between corresponding measurements. The correlation between accuracy in skull and contrast phantom was calculated. The radiation dose was assessed by DPI(100,c) (dose profile integral (100,c)) at the central hole of a CT dose index (CTDI) phantom. RESULTS: The results for the DPI(100,c) were 107 mGy mm for (1), 1569 mGy mm for (2), 446 mGy mm for (3), 249 mGy mm for (4) and 1090 mGy mm for (5). The segmentations in the contrast phantom were submillimeter accurate in all scanners. The segmentation accuracy of the mandible was 2.9 mm for (1), 4.2 mm for (2), 3.4 mm for (3), 1.0 mm for (4) and 1.2 mm for (5). The correlation between measurements in the contrast and skull phantom was below 0.37 mm. CONCLUSIONS: The best radiation dose vs image quality was found for the i-CAT.

Comparative study of image quality for MSCT and CBCT scanners for dentomaxillofacial radiology applications.

The image quality of four cone-beam computed tomography (CBCT) scanners dedicated for dentomaxillofacial imaging and one multi-slice computed tomography (MSCT) scanner was compared. For the MSCT scanner, a clinical and a low-dose protocol for oral indications were evaluated. The image quality was assessed by dedicated software that allows an automated analysis of accuracy measurements and evaluation of metal artefacts on two image quality phantoms. Bone was segmented with sub-millimetre accuracyin all scanners.

The use of CT scan based planning for oral rehabilitation by means of implants and its transfer to the surgical field: a critical review on accuracy.

The purpose of the present paper is to review the literature on the use of CT scan based planning for oral rehabilitation and its transfer to the surgical field by means of a surgical guide. The first part will deal with surgical guides based on tomographies or CT scan data often using dedicated software, but manually fabricated. In the second part, CT-derived drill guides are discussed, which are fabricated by means of CAD/CAM technology or other computer-controlled technology. The deviations between the position of the implants at the planning stage and after the surgery are of utmost importance, especially when flapless procedures are applied. The maximal deviations are often not stated in the literature. This should be taken into account when a system is applied clinically.

Soft tissue augmentation of the cheeks detected on intra- and extraoral radiographs: a case report.

Augmentation material used in plastic surgery such as facelift procedures can be radiopaque and thus become visible on extra- and intraoral radiographs. These objects may obscure anatomical structures and mask critical findings, therefore leading to potential misinterpretation of otherwise successful images. The present report describes a case in which the radiographic intra- and extraoral data are partly masked by a superimposed radiopaque mesh, which was suspected to originate from a facelift procedure. A gold thread lift was confirmed by the plastic surgeon.

Comparative localized linear accuracy of small-field cone-beam CT and multislice CT for alveolar bone measurements.

OBJECTIVES: To compare the accuracy of cone-beam computerized tomography (CBCT) and multislice CT (MSCT) for linear jaw bone measurements. STUDY DESIGN: An ex vivo formalin-fixed human maxilla was imaged with both CBCT (Accuitomo 3D; Morita, Kyoto, Japan) and MSCT (4-slice Somatom VolumeZoom and 16-slice Somatom Sensation 16; Siemens, Erlangen, Germany). The MSCT images were reconstructed using different reconstruction filters to optimize bone visualization (U70u and U90u for VolumeZoom, H30s and H60s for Sensation 16). Before scanning, triplets of small gutta-percha markers were glued onto the soft tissues overlying the maxillary bone on the top and on both sides of the alveolar ridge to define a set of reproducible linear measurements in 11 planes. Image measurements were performed by 2 observers. The gold standard was determined by means of physical measurements with a caliper by 3 observers. RESULTS: The accuracy of the linear measurements was 0.35 +/- 1.31 mm (U70u) and 0.06 +/- 1.23 mm (U90u) for the Somatom VolumeZoom, 0.24 +/- 1.20 mm (H60s) and 0.54 +/- 1.14 mm (H30s) for the Sensation 16, and -0.09 +/- 1.64 mm for the Accuitomo 3D. Statistical analysis with 2-way analysis of variance showed no significant inter- or intraobserver disagreement for the physical or the radiologic measurements. There was also no significant difference for the measurements on the different reconstruction filters. CONCLUSION: Both CBCT and MSCT yield submillimeter accuracy for linear measurements on an ex vivo specimen.

Guiding periodontal pocket recolonization: a proof of concept.

The complexity of the periodontal microbiota resembles that of the gastro-intestinal tract, where infectious diseases are treatable via probiotics. In the oropharyngeal region, probiotic or replacement therapies have shown some benefit in the prevention of dental caries, otitis media, and pharyngitis, but their effectiveness in the treatment of periodontitis is unknown. Therefore, this study addressed the hypothesis that the application of selected beneficial bacteria, as an adjunct to scaling and root planing, would inhibit the periodontopathogen recolonization of periodontal pockets. Analysis of the data showed, in a beagle dog model, that when beneficial bacteria were applied in periodontal pockets adjunctively after root planing, subgingival recolonization of periodontopathogens was delayed and reduced, as was the degree of inflammation, at a clinically significant level. The study confirmed the hypothesis and provides a proof of concept for a guided pocket recolonization (GPR) approach in the treatment of periodontitis.

Accuracy of implant placement based on pre-surgical planning of three-dimensional cone-beam images: a pilot study.

AIM: To evaluate the precision of transfer of a computer-based three-dimensional (3D) planning, using re-formatted cone-beam images, for oral implant placement in partially edentulous jaws. MATERIAL AND METHODS: Four formalin-fixed cadaver jaws were imaged in a 3D Accuitomo FPD cone-beam computed tomography (CT). Data were used to produce an accurate implant planning with a transfer to surgery by means of stereolithographic drill guides. Pre-operative cone-beam CT images were subsequently matched with post-operative ones to calculate the deviation between planned and installed implants. RESULTS: Placed implants (length: 10-15 mm) showed an average angular deviation of 2 degrees (SD: 0.8, range: 0.7-4.0 degrees ) as compared with the planning, while the mean linear deviation was 1.1 mm (SD: 0.7 mm, range 0.3-2.3 mm) at the hex and 2.0 mm (SD: 0.7 mm, range 0.7-2.4 mm) at the tip. CONCLUSIONS: Cone-beam images could be used for implant planning, taking into account a maximal 4 degrees angular and 2.4 mm linear deviation at the apical tip.

Neurosensory disturbances after immediate loading of implants in the anterior mandible: an initial questionnaire approach followed by a psychophysical assessment.

The aim of the study was to assess past and present neurosensory disturbances using a questionnaire and a psychophysical approach in patients treated with immediate loaded implants in the edentulous anterior mandible. A group of 65 patients (age range 30-84 years, mean 58 years, 30 women) was enrolled. All were treated by means of three immediately loaded implants (Branemark Novum System). A self-designed questionnaire was used for data collection. The response rate was 89%. Of the 58 responders, 33% (n=19) reported neurosensory disturbances after implant surgery. Nine of these patients (mean age 56 years, seven women) participated in an objective evaluation and were subjected to a psychological and several psychophysical tests. At the moment of the evaluation none of the nine patients still had clinical complaints. Psychological testing revealed no statistical differences between the patients, who had previously experienced subjective complaints, and the control group. Two-point discrimination and thermal sensation tests revealed no sensory lesions. The light touch sensation test at the lower lip indicated a more frequent reduction of tactility for the test group (p

Jaw motor inputs originating from osseointegrated oral implants.

Jaw motor inputs from endosseous oral implants have been investigated to a limited extent. Observations of jaw muscle reflexes in edentulous patients rehabilitated by means of implants do not prove that they originate from the implants unless the stimuli are properly defined. Few studies have isolated inputs, such as electrical of mechanical stimuli, to make sure that they are conveyed through the implants. Even under these conditions one should be aware that such stimuli can trigger distant receptors. The most striking difference is that tapping an upper jaw implant in a fully edentulous patient does not give lead to a silent period in the jaw closing muscles. At the clinical level the changes in neuromuscular reflexes do not lead to significant problems.

From osseoperception to implant-mediated sensory-motor interactions and related clinical implications.

Osseointegration of implants in the jaw bone has been studied thoroughly, dealing with various aspects such as bone apposition, bone quality, microbiology, biomechanics, aesthetics, etc. A key issue that has received much less attention is the physiologic integration of the implant(s) and the associated prosthesis in the body. The latter aspect is however very important to obtain new insights in oral functioning with implant-supported prostheses. Amputated patients rehabilitated with a lower limb prosthesis anchored to the bone by means of an osseointegrated implant, have reported that they could recognize the type of soil they were walking on. Clinical observations on patients with oral implants, have confirmed a special sensory perception skill. The underlying mechanism of this so-called 'osseoperception' phenomenon remains a matter of debate, because extraction of teeth involves elimination of the extremely sensitive periodontal ligaments while functional reinnervation around implants is still uncertain. Histological, neurophysiological and psychophysical evidence of osseoperception have been collected, making the assumption more likely that a proper peripheral feedback pathway can be restored when using osseointegrated implants. This implant-mediated sensory-motor control may have important clinical implications, because a more natural functioning with implant-supported prostheses can be attempted. It may open doors for global integration in the human body.

The neurophysiology of osseointegrated oral implants. A clinically underestimated aspect.

Amputation of a limb or a tooth leads to the loss of a large number of exteroceptors. These play an important role in sensory perception and feedback, which tune the motor control. Even after rehabilitation with a prosthetic device, tactile function remains impaired. This can present a subsequent risk of overloading the prosthesis. The peri-implant interface of oral osseointegrated implants is characterized by the absence of a periodontal ligament, a crucial difference towards the natural dentition, from a biomechanical but also from a neurophysiologic point of view. Patients rehabilitated with osseointegrated implants seem subjectively not much impaired in their masticatory and other oral functions. This observation might be linked to the presence of some peripheral feedback pathway to the sensory cortex. It may be attributed to the activation of receptors in the peri-implant environment (either bone or periosteum). This phenomenon called osseoperception, when it relates to the consciousness of the applied stimuli, has been described for both oral and skeletal implants. In the present review, besides osseoperecption other neurophysiological aspects of oral implants, such their reflex function, will be outlined and their clinical meaning pointed out.

Effect of reducing frequency of augmented feedback on manual dexterity training and its retention.

OBJECTIVE: The study addressed the impact of the frequency of tutorial-enriched augmented visual feedback, provided by a virtual simulation system (DentSim), on the skill acquisition for a cavity preparation task in novice dental students. METHODS: Thirty-six subjects were assigned to two training groups and a control group. The task consisted of a geometrical cross preparation on the lower left first molar. All subjects performed a pre-test to assess their basic skill level. The training groups received simulation feedback, enriched with tutorial information, across acquisition. One group trained under continuous augmented feedback, while a second group trained under an intermittent (66% of the time) feedback. At both 1-day and 4-month interval, subjects performed a retention test to explore learning specific effects. Two transfer tests were added to assess the extrapolation of the learned skills to an adjacent molar. All tests were performed in the absence of feedback. A control group performed all the tests, without preceding training. All preparations were graded by the simulation system. RESULTS: The training groups performed similarly across acquisition and improved with practice (ANOVA, P<0.001). After 1 day and 4 months of no practice, the training groups outperformed the control group on a retention test (ANOVA, P<0.001) and transfer test (ANOVA, P<0.001). CONCLUSIONS: Performance and learning of a cavity preparation task on a simulation unit was independent of the frequency of tutorial-enriched augmented visual feedback within the range tested. Training sessions on a simulation unit could be alternated with training sessions in the traditional phantom head laboratory.

Effect of tutorial input in addition to augmented feedback on manual dexterity training and its retention.

Virtual reality (VR) simulators can be used as tools in manual dexterity training. The visual feedback guides the subject towards proper performance but creates, at the same time, some dependency on this feedback. To overcome this drawback, the effect of adjunct tutorial input on motor learning behaviour was examined. Novice dental students were randomly assigned to one of two training groups or to a non-training control group, given the task of preparing a geometrical class 1 cavity in phantom teeth. The feedback (FB) group trained under augmented visual feedback conditions, provided by the VR system (DentSim). The feedback-plus (FB+) group received, in addition, standardised expert input to enrich the augmented feedback information. The control group, consisting of same year students, did not participate in any training programme. All preparations were evaluated by the VR scoring system. Performance analyses revealed an overall trend towards significant improvement with practice for the training groups. Performance of the FB+ group was most accurate across training. After 1 day and 3 weeks of no practice, both training groups outperformed the control group. After 4 months, however, only the FB+ condition was significantly more accurate than the control group. The same tendency was noted for the transfer tests. Consequently, cavity preparation experience on a VR system under the condition of frequently provided feedback supplemented with expert input was most beneficial to long time learning.