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Biomedical subjects

M S Cune

Publications and source records attributed to M S Cune.

At least 37 records · Page 2Linked to original sources
PubMed2000

Oblique lateral cephalometric radiographs of the mandible in implantology: usefulness and reproducibility of the technique in quantitative densitometric measurements of the mandible in vivo.

In the literature intraoral periapical radiographs are commonly used for densitometric measurements of the mandible with implants. These films give detailed information of the implant and the surrounding bone. However, in extreme mandibular atrophy it can be difficult to obtain intraoral radiographs of adequate diagnostic quality. Extraoral Oblique Lateral Cephalometric Radiographs (OLCRs) can then be the alternative: reproducible images of large parts of the mandible can be obtained. In vitro, the results of densitometry using periapical films and OLCRs were shown to be similar. The present study aims to determine the measurement error of densitometry with OLCRs in vivo. In 16 patients (group I) with atrophic mandible and implants, duplicate OLCRs of one side of the jaw were obtained. The error of measurement for the densitometric measurements of the mandibular bone was 5.5%. The use of a specially developed correction program to compensate for undesired variations in the projection of the soft tissues of the face (tongue, lips, cheek and neck) on the radiographs resulted in a 40% reduction of that measurement error to 3.5%. This remaining error is mainly brought about by an imperfect repositioning of the patient when the duplicate OLCRs are obtained. The error caused by the image acquisition, processing and measurement is less than 1%. Deliberate variation up to 7.5 degrees of the horizontal angle wherein the OLCRs are made, results in a large error of measurement of 13.5% (group II: 17 patients). To reduce this variation the additional soft tissue correction program is unsuitable. It is concluded from this study that the described radiographic and image analysis technique is a promising tool for prospective densitometric studies of the mandible with or without implants. Especially in mandibles with bone grafts and implants, substantial changes in the graft can occur. The described technique may be particularly valuable in analyzing these changes.

Aluminum↗
PubMed2000

Onlay grafts in combination with endosseous implants in severe mandibular atrophy: one year results of a prospective, quantitative radiological study.

In taking an overall view of the radiographs made of patients that underwent simultaneous onlay-grafting and implant placement in the anterior mandible, changes are seen in the grafts. The impression arose that a number of stages could be distinguished in this process of remodelling of the graft. The purpose of the present study was to objectivate the existence of those stages in the first year after bone-grafting by densitometric and height measurements of the onlay grafts using standardized extraoral radiographs (OLCR) and densitometric analysis in a group of 8 patients. OLCRs were taken at regular intervals in the first year after surgery. The measurements were performed in three fixed fields, both ventrally and dorsally of each implant. Generally the densitometric measurement fields were located at the (upper) cortex, the upper spongiosa and the lower spongiosa of the onlay graft. The OLCRs were also used for measurements of the height of the complete graft and of the thickness of the cortex of the graft, using a gauged caliper. The results indicate the following remodelling of the structure of the onlay grafts: 1) decrease in the thickness and the radiographic density of the (upper) cortex of the onlay graft predominantly in the first 6-month period; 2) no significant changes in the radiographic density of the upper spongeous part of the graft; 3) a decrease of approximately 25% in the overall height of the graft, particularly during the first 6-month period; 4) an increase in the radiographic density of the lower part of the spongeous bone in the second 6-month period. It is concluded that the remodelling of the graft has a predictable pattern in time: the first half year being dominated by bone resorption, mainly confined to the cortex of the graft, whereas the second half year is characterized by an increase in bone density in the (remaining) cortex as well as the lower spongeous parts of the graft.

Absorptiometry, Photon↗
PubMed2000

Reliability of some clinical parameters of evaluation in implant dentistry.

Clinical tests that are commonly used to evaluate tissues surrounding natural teeth are also used in implant dentistry. It is unclear if they are equally valid and reflect the condition of the bone surrounding an implant reliably. This study evaluates the use of a plaque index, a gingiva index, the assessment of a probing depth and the Periotest value and relates the findings to the image on a radiograph in 16 patients, involving 32 IMZ implants. All four clinical tests showed poor sensitivity and, in general, only fair specificity when observations from the image on the radiograph were interpreted as the 'golden standard' for the presence or absence of pathology adjacent to the implant. Frequently, based on any clinical parameter, disease was not diagnosed, while the radiograph did show pathological loss of bone at the bone-implant contact area. It is concluded that the aforementioned parameters are unreliable and unfit for clinical evaluation in implant dentistry. Radiographs are needed to evaluate critical marginal bone changes surrounding dental implants.

Adult↗
PubMed1999

[Immediate repair of labial bone defects].

In this paper some surgical techniques are described to prevent or restore the characteristic and esthetically disturbing resorption defect in the anterior alveolar process as a result of tooth loss. One-stage approaches are described. Submucosal implants are used in combination with conventional fixed prosthodontics. If a single tooth replacement by means of an implant is aimed at, the split-crest technique may be a valuable alternative for an autologous bone graft or guided bone regeneration procedure.

Alveolar Bone Loss↗
PubMed1999

[Considerations of single tooth replacement. The choice between different treatment options].

When a single tooth is lost both functional and aesthetic aspects have to be restored. A fixed prosthodontic restoration such as a conventional bridge, a resin-bonded bridge or a solitary implant is the treatment of choice. The final choice between these three treatment modalities strongly depends upon specific characteristics in the patients' dentition and his preferences. There is a vast amount of clinical experience with the conventional fixed bridge and it is available in every dental office. Without a doubt the resin-bonded bridge is the cheapest option. However, the patient does run the risk of loosening of the bridge, usually at an inconvenient moment. It then has to be recemented or replaced. The solitary implant has several advantages over the fixed and resin-bonded bridge. For optimal results, it does require a physician with a vast experience in the field of oral implantology. For young individuals closure of the diastema by means of orthodontics is also possible. A partial denture is only an option as a temporary provision or when more teeth were lost or are bound to be lost.

Dental Implants, Single-Tooth↗
PubMed1998

Densitometric measurements of the mandible: accuracy and validity of intraoral versus extraoral radiographical techniques in an in vitro study.

In this study a comparison is made between intraoral and extraoral radiographical techniques for quantitative measurements of bone density in the edentulous mandible. A phantom model, composed of a dry mandible surrounded by a soft tissue substitute was used. Radiographs were made of aluminium implants of known volumes. Intra- and extraorally placed reference wedges of aluminium or a combination of aluminium and plexiglas were used for the measurement of the aluminium volume of the above-mentioned implants and compared with the real volume. The IBAS image analysis system was used for image processing and measurements. A systematic deficit in the measured volume of 15 to 29% was found. This error was irrespective of the radiographical technique and indicates a constant underestimation of the aluminium volumes. The differential influence of the secondary radiation on the images of the jaw and the wedge is proposed to be a possible cause of this constant underestimation. The intraoral and extraoral techniques do not display significant statistical differences in the levels of validity or accuracy. Obtaining serial intraoral radiographs of adequate quality in the atrophic edentulous mandible can be problematic. It is concluded from this in vitro study that in these cases Oblique Lateral Cephalometric Radiographs may provide a valuable alternative for quantitative image analysis.

Absorptiometry, Photon↗
PubMed1998

[How do screws work in oral implants (when they are detached)?].

Screw-joint connections are commonly used in oral implantology as a means of connecting various components of an implant system. This article discusses some theoretical and clinical principles with respect to the efficacy of screw joint connections in general and of dental implants in particular.

Biomechanical Phenomena↗
PubMed1998

[Reliability of some clinical parameters in implant dentistry].

OBJECTIVE: This study evaluates if clinical tests that are commonly used to evaluate tissues surrounding natural teeth are equally valid in clinical evaluation of dental implants. DESIGN: A retrospective clinical study. SETTING: Department of Oral and Maxillofacial Surgery, Prosthodontics and Special Dental Care of the University of Utrecht. METHOD: The use of a plaque index, a gingival index, probing depth measurements and the Periotest was evaluated by relating the findings to the image on a radiograph in 16 patients, involving 32 IMZ implants. RESULTS: The four clinical tests show poor sensitivity and in general only fair specificity. CONCLUSION: The parameters are unreliable and unfit for clinical evaluation in implant dentistry during regular recall visits. Radiographs are needed to evaluate the condition of a dental implant and to detect critical marginal bone changes surrounding dental implants at an early stage.

Dental Implants↗
PubMed1997

A nationwide evaluative study on implant-retained overdentures.

OBJECTIVES: In the Netherlands, dental implants have been included in the National Dental Insurance Scheme (NDIS) since 1989. Nowadays, out-of-pocket expenditure is low, making implant treatment financially feasible for a large group of edentulous, potential implant candidates. Treatment can be performed by both oral surgeons and general dentists. Results of implant treatment in the literature are usually obtained in academic and specialized centers. In contrast to this, the present study evaluates the quantitative and qualitative aspects of rehabilitation with oral implants in combination with an overdenture when applied on a nationwide scale. METHODS: For this purpose all patients (n = 5410) treated between January 1989 and July 1992 were extensively documented pre-operatively, implant patients (n = 429) were clinically investigated by two independent observers and the effect of treatment on denture complaints was assessed by means of a questionnaire (n = 460). RESULTS: Only a small proportion of the potential pool of implant candidates is actually being treated, to a constant number of approximately 2000 patients a year. The selected patients have major denture problems and have received relatively high levels of prosthetic care during the last decade. Clinical results are comparable to those reported in the literature, implant survival after 3 years for the lower jaw being 96.3% and for the upper jaw 70.4%. Oral hygiene was frequently considered suboptimal and seen in conjunction with marginal inflammation of the peri-implant mucosa. Subjective results were excellent, patients were quite satisfied with the improvements in the comfort and esthetics of their lower denture. CONCLUSIONS: Implant-overdenture treatment, within the guidelines and regulations set by the Dutch NDIS, is a safe and effective treatment alternative, in particular for the rehabilitation of the lower jaw.

Dental Health Surveys↗
PubMed1997

Flexible (Polyactive) versus rigid (hydroxyapatite) dental implants.

In a beagle dog study, the peri-implant bone changes around flexible (Polyactive) and rigid hydroxyapatite (HA) implants were investigated radiographically by quantitative digital subtraction analysis and by assessment of marginal bone height, with the aid of a computerized method. A loss of approximately 1 mm of marginal bone height was observed for both the dense Polyactive and the HA implants, after 6 months of loading. This value appeared to be stable from 12 weeks of loading onward. Along the total length of the implant during the first 6 weeks of loading, both the flexible (dense Polyactive) and the rigid (HA) implants showed a decrease in density. However, after this 6-week period, the bone density around the implants increased, and after 18 weeks the original bone density was reached. The flexible Polyactive implants provoked less decrease in density than the rigid HA implants, although not to a statistically significant level. This finding sustains the hypothesis that flexible implant materials may transfer stresses to the surrounding bone more favorably.

Alveolar Bone Loss↗
PubMed1997

The combined use of endosteal implants and iliac crest onlay grafts in the severely atrophic mandible: a longitudinal study.

Thirteen patients, who received an onlay bone graft augmentation to their severely atrophic mandible in combination with a simultaneous implant insertion, were studied prospectively. A reproducible method that allowed for accurate assessment of graft resorption, consisting of lateral and oblique-lateral cephalometric radiographs in combination with an image analysis system, was used to assess the resorption rate in all patients and between subgroups of patients, according to selected patient and treatment characteristics. Thirty implants were placed, none of which were lost, and all patients expressed satisfaction after a mean observation period of 877 days. A mean resorption rate of 36% of the grafted bone height occurred, mainly during the first year and with some degree of individual variance. After three years the resorption had virtually stopped. No statistically significant differences between any of the subgroups of patients could be distinguished. Peri-implantitis was found around eight implants in seven patients. It is concluded that the described surgical technique should be used only if there are stringent indications.

Aged↗
PubMed1997

A comparative study of flexible (Polyactive) versus rigid (hydroxylapatite) permucosal dental implants. I. Clinical aspects.

Recently, an elastomeric polyethyleneoxide polybutylene-terephthalate (PEO:PBT) copolymer (Polyactive) was introduced, which exhibits bone-bonding characteristics. In contrast to ceramics, bioglass, titanium and other metals, PEO:PBT copolymers are flexible materials that could reduce undesirable peak stresses along the neck of a permucosal implant. The application of three types of Polyactive permucosal dental implants (one dense and two porous types) and one dense hydroxylapatite (HA) implant were clinically tested and compared during 30 weeks of loading in a dog experiment. With respect to the porous Polyactive implants, it was observed that the pore diameter had decreased to such an extent that optimal bone ingrowth was not achieved. Polyactive is known to expand due to water uptake, and, as a consequence, the sizes of the pores of the press-fit inserted implants had decreased to a large extent. This feature explained the high loss of the implants with the porous outer layer (6 out of 22). None of the dense Polyactive implants and only one of the HA implants were lost. Statistical analysis was performed solely on the dense Polyactive and the HA implants. At the lingual sites, plaque scores, gingiva indices, bleeding indices and corresponding pocket depths were statistically significantly lower for both implant types, when compared to the corresponding values at the buccal, mesial and distal sites, irrespective of the observation period. Differences between the dense Polyactive and the HA implants were not observed. A considerable difference in mobility was registered between the Polyactive and the hydroxylapatite implants, as measured by the Periotest. The dense Polyactive implants functioned adequately and had mobility resembling natural teeth. As such, these dense flexible materials showed a favourable clinical function and they seem promising for reducing undesired peak stresses when applied as a dental implant.

Analysis of Variance↗
PubMed1997

[Pre-implantation surgery of the atrophied maxilla. A review of the literature].

The aim of preprosthetic reconstructive surgery of the resorbed maxilla is to create sufficient bone of good quality for implant placement. The classification of the edentulous jaws by Cawood and Howell is mostly used as point of departure in planning preprosthetic reconstructive surgery. In this review article some procedures and results are mentioned as described in recent literature.

Alveolar Bone Loss↗