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In clinical practice, the prognosis seems, with some reservations, to be comparable for tooth-implant and implant-implant supported bridges in the middle-long term.This conclusion seems particularly valid for tooth-implant bridges in free-end situations, where a single implant is connected with a tooth. Prerequisites are a healthy tooth abutment, a pontic length not exceeding the width of a bicuspid, a rigid connection between implant and tooth and the use of strong cement.

A 67-year-old woman was referred with a rapidly progressing swelling in the left canine region of the edentulous mandible. Nine months earlier, 2 permucosal implants had been placed in her atrophic anterior mandible. A few weeks after implant placement, an inoperable carcinoma of the lung had been diagnosed. This tumor was treated with a combination of chemotherapy and radiotherapy. After 3 months, the implants were provided with a Dolder bar supporting an overdenture. Subsequently, progressive inflammation developed around the left implant and removal of the implant was necessary. When progressive swelling of the mucosa developed at the previous implant site, the patient was referred to an oral and maxillofacial surgeon. The swelling measured 35 mm in diameter and was biopsied. It was diagnosed as a metastasis of the lung carcinoma to the mandible. The tumor of the jaw was treated with local radiotherapy.

Panoramic radiographs are frequently used for routine follow-up of mandibular implants. The objective of this study was to determine whether measurement on a panoramic radiograph of the vertical dimension of the mandible near by an implant, using the known implant length as a reference, is a reliable method. In 11 patients, 2 permucosal implants were placed in the anterior part of the edentulous mandible. During the first year after implantation, 2 panoramic radiographs and 2 sets of standardized oblique lateral cephalometric radiographs were made. Oblique lateral cephalometric radiographs are the golden standard for measuring the vertical dimension of an edentulous mandible. The length of the implants and the vertical dimension of the mandible dorsally to the implants were measured on all oblique lateral cephalometric radiographs. The measured and known implant length were used to calculate the image enlargement factor. This factor was used to calculate the real vertical dimension of the mandible. The same measurement procedures were performed on the panoramic radiographs. Using a paired t-test, the calculated values of the vertical dimensions of the mandibles found on panoramic radiographs were compared with the calculated values found on oblique lateral cephalometric radiographs. No statistically significant differences were found. It was concluded that under the described circumstances, panoramic radiographs can be used for reliable measurement of the vertical dimension of the mandible near by permucosal implants.

This retrospective study aims to investigate and compare the results obtained with the transmandibular implant (TMI) in two different hospital situations. Group I were patients treated in a teaching hospital since 1984 by a varying group of surgeons and prosthodontists with a varying degree of experience with the TMI. Group II were patients treated in 1993 and 1994 by experienced surgeons and prosthodontists in the hospital where the TMI was originally developed. In group I, a relatively high frequency of reversible (45.4%) and irreversible--i.e. implant loss--(15.2%) complications occurred. In group II, no implants were lost and reversible complications were reported in 10.8% of the patients. In general, the patients of both groups were quite satisfied with the result of the treatment. In both groups, limited bone loss around the implant posts could be observed. An increase in the height of the mandibular bone distal of the lateral posts was frequently observed, especially in group II. It is concluded that both very favourable and less favourable results can be obtained with the TMI. In this study the best results are found in a highly specialized TMI centre, where patients are treated--with only uncompromised implant-posts--by a small group of experienced surgeons and prosthodontics with accurate application of the existing guidelines.

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.

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.

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.

Various radiographic techniques are used for longitudinal studies of changes in the height of the mandible with implants. Advantages and disadvantages of panoramic radiographs, lateral cephalometric radiographs, periapical films and modern CT- and MRI-techniques are briefly discussed. In this study, the usefulness of a conventional radiographic technique for measuring the height of the mandible, i.e. oblique lateral cephalometric radiography (OLCR) is evaluated in vivo. In 16 patients with permucosal implants in the anterior mandible OLCRs were repeated the same day. The mean total error for the radiographic procedure and analysis was 0.38 mm. The intra-observer error for the determination of the mandibular height by means of the image analysis procedure was 0.16 mm (analysis error). In 12 other patients pairs of radiographs of the same area of the mandible were made using both a "standard" horizontal X-ray beam direction and an individually determined "optimal" horizontal X-ray beam direction; the maximum difference between these two angulations was plus or minus 7.5 degrees. The effect of this different angulation on the height measurements is comparable to the above-mentioned total error of the measurement procedure (positioning error). An accurate positioning of the patient seems important for reliable measurements. The described radiographic (OLCR) and analysis (IBAS) technique can be used relatively simply for clinical studies. The described methods appear to be useful for measuring the mandibular height in longitudinal studies in patients with or without implants.

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.