Biomedical subjects

T Jemt

Publications and source records attributed to T Jemt.

At least 19 recordsLinked to original sources

PubMed2000

Bone response to implant-supported frameworks with differing degrees of misfit preload: in vivo study in rabbits.

PURPOSE: To study the bone response around implants placed in tibia of rabbits that supported misfitting superstructures secured with different degrees of preload. MATERIALS AND METHODS: Twelve rabbits were provided with two terminal 10-mm and one intermediate 7-mm-long implant in each tibia. After an integration time of about 9 weeks, nine of the animals received one control framework each (n = 9), designed with good fit to all three implants. In the other tibia of these animals, and in both tibias in the remaining three rabbits, test frameworks (n = 15) were connected with a vertical misfit of about 1 mm to the intermediate implant. The intermediate set screws were tightened with a torque ranging from 15 Ncm to 26 Ncm in the different test frameworks. The fascia and skin was then sutured back over the implants. After a loading period of 2 to 3 weeks, the animals were sacrificed, and histomorphometric measurements were made and correlated to the different levels of preload of the central implant. RESULTS: The mean bone-to-metal contact for the three best consecutive threads of the central implant was 40% for both test and control sites (p > .05). Compared to the other regions of the implant thread, less bone-to-metal contact was found at the tip of the test implant threads in the low preload group (p < .05). However, the same relation was not observed in the high preload group. A significant correlation was observed between increasing degree of preload in the central screw joint and increasing bone-to-metal contact, most obviously noticed at the tip of the implant thread (p < .01). CONCLUSIONS: Misfit stress levels of clinical magnitudes do not seem to jeopardize osseointegration per se. On the contrary, clinical levels of preload stress seem to significantly promote bone remodeling at the tip of the implant thread.

Animals↗

PubMed2000

Clinical experiences of CNC-milled titanium frameworks supported by implants in the edentulous jaw: 1-year prospective study.

BACKGROUND: A new type of titanium framework has been introduced, but so far no clinical reports have been made in this treatment modality. PURPOSE: The aim of this study was to report the clinical performance of implant-supported prostheses with computer numeric controlled (CNC)-milled titanium frameworks in the edentulous jaw and to compare the results with prostheses provided with conventional cast frameworks during the first year of function. MATERIAL AND METHODS: A consecutive group of 65 patients with 67 prostheses were provided with CNC-milled titanium frameworks in 23 upper and 44 lower jaws. During the same period, 61 consecutive patients were treated on a routine basis with 31 upper and 31 lower conventional gold alloy casting prostheses. Clinical and radiographic 1-year data were collected for both the test and control groups. RESULTS: A total of 14 of 729 inserted implants were lost during the follow-up period (1.9%). All prostheses were functioning after 1 year except a conventional prosthesis with a cast framework, which was replaced by an implant-supported over-denture due to implant loss. The 1-year cumulative survival rate (CSR) was 100% and 97.8% for CNC prostheses and implants, respectively. The corresponding CSR for the control group was 98.3% and 98.3%, respectively. Few problems were reported in both groups, and the clinical and the radiologic performances were similar for both groups. No mechanical complications except some resin veneer fractures (n = 6) were observed. The mean marginal bone loss for the test group during the first year in function was 0.4 mm (SD = 0.35) and 0.4 mm (SD = 0.33) in the upper and lower jaws, respectively. A similar pattern of bone reaction was also observed in the control group. CONCLUSION: CNC-milled titanium frameworks can be used as an alternative to conventional castings in the edentulous jaw, presenting similar clinical and radiologic performances as conventional cast frameworks during the first year of function.

Adult↗

PubMed1999

Single implants in the upper incisor region and their relationship to the adjacent teeth. An 8-year follow-up study.

The aim of the study was to find out if implant-supported crowns in the upper incisor region run the risk of coming into an infraoccluded position later in life. Ten adolescents with 15 implant-supported crowns were included in the study. The age of the patients at the implant surgery ranged between 14 and 19 years. They were followed up during an 8-year period. No implant loss was observed. A good or acceptable aesthetic appearance at the last observation was found in most subjects. In some of them a change in the vertical position of the implant-supported crown, resulting in infraocclusion, could be registered, especially in subjects with no incisor contact. Throughout the follow-up period, only minor loss of marginal bone support was observed at the implants. At the teeth adjacent to the implant, a reduction of the marginal bone level was observed in some patients. Of importance to consider in single implant therapy is that a fixed chronological age is no guidance for implant placement, due to a slight continuous eruption of the adjacent teeth post adolescence. An orthodontic treatment should be performed not only in order to gain space in the implant area, but also to attain good incisor stability to reduce the risk of infraocclusion of the implant-supported crown. Furthermore, 3 cases will exemplify that infraocclusion also may occur in patients who had received single implants at adult ages.

Adolescent↗

PubMed1999

Complications in partially edentulous implant patients: a 5-year retrospective follow-up study of 133 patients supplied with unilateral maxillary prostheses.

BACKGROUND: Numerous studies have reported successful outcomes for restoration of fully edentulous patients with Brånemark implants. However, some studies indicate more mechanical problems in restored partially edentulous situations. PURPOSE: The objective was to study patients with potential risk for mechanical complications after implant treatment. MATERIALS AND METHODS: Patients were retrospectively evaluated 5 years after implant treatment in upper jaw Appelgate-Kennedy Class II situations. Altogether 422 implants ad modum Brånemark were installed in 137 consecutively treated patients. One hundred thirty-three prostheses were placed and followed-up for 5 years, according to routine clinical protocols. RESULTS: The overall 5-year implant cumulative survival rate (CSR) was 94.0%. The corresponding CSR for loaded implants and prostheses was 97.7% and 98.4%, respectively, and the overall marginal bone loss was 0.8 mm (+/- 0.6 mm) after 5 years. Sixteen abutment screws fractured in seven patients (5%) and 17 prostheses (13%) presented loose abutment or gold screws during the follow-up period. Significantly more problems were reported in association with prostheses that included the canine (p < .05), and significantly more gold screws were working loose when only two implants were supporting the frameworks (p < .01). CONCLUSIONS: Upper jaw implant treatment in unilateral free-end situations seems to involve more mechanical problems than other implant treatment groups when only two implants can be installed and when the canine tooth is missing. However, most of these complications are easily adjusted, and the clinical survival of implants and prostheses is the same for these groups compared to other groups of partially edentulous implant patients.

Adult↗

PubMed1999

Clinical experiences of implant-supported prostheses with laser-welded titanium frameworks in the partially edentulous jaw: a 5-year follow-up study.

BACKGROUND: Titanium frameworks have been used in the endentulous implant patient for the last 10 years. However, knowledge of titanium frameworks for the partially dentate patient is limited. PURPOSE: To report the 5-year clinical performance of implant-supported prostheses with laser-welded titanium frameworks in the partially edentulous jaw. MATERIALS AND METHODS: A consecutive group of 383 partially edentulous patients were, on a routine basis, provided with fixed partial prostheses supported by Brånemark implants in the mandible or maxilla. Besides conventional frameworks in cast gold alloy, 58 patients were provided with titanium frameworks with three different veneering techniques, and clinical and radiographic 5-year data were collected for this group. RESULTS: The overall cumulative survival rate was 95.6% for titanium-framework prostheses and 93.6% for implants. Average bone loss during the follow-up period was 0.4 mm. The most common complications were minor veneering fractures. Loose and fractured implant screw components were fewer than 2%. An observation was that patients on medications for cardiovascular problems may lose more implants than others (p < .05). CONCLUSIONS: The clinical performance of prostheses with implant-supported laser-welded titanium frameworks was similar to that reported for conventional cast frames in partially edentulous jaws. Low-fusing porcelain veneers also showed clinical performance comparable to that reported for conventional porcelain-fused-to-metal techniques.

Adult↗

PubMed1999

Restoring the gingival contour by means of provisional resin crowns after single-implant treatment.

A consecutive group of 55 patients was treated with 63 single-implant restorations. The soft tissue was allowed to heal to either provisional resin crowns (n = 25) that were placed at the time of second-stage surgery, or to healing abutments (n = 38) before final crown insertion. An index that assessed the size of the interproximal mucosa adjacent to the single-implant restorations was used to evaluate the volume of the papillae 2 years after crown insertion. The results indicated that the use of provisional crowns may restore soft tissue contour faster than healing abutments alone, but the papillae adjacent to single-implant restorations presented similar volume in both groups after 2 years in function. Furthermore, the mean marginal bone loss at the implants was 0.9 mm after 1 year, and no differences were observed between the 2 groups. The present data focus on the need for more scientific data to evaluate different clinical procedures for optimizing esthetic results in implant dentistry.

Adolescent↗

PubMed1998

Measurements of bone and frame-work deformations induced by misfit of implant superstructures. A pilot study in rabbits.

This in vivo study used a 3-D photogrammetric technique to measure distortion of 3 unit implant frame-works and bone surrounding osseointegrated implants after securing misfitting superstructures to the implants. Four adult loop-eared rabbits were provided with 3 implants each in the proximal part of 1 tibia each. After a healing period of 8 weeks, a titanium frame-work was connected with a misfit to the central implant. Three-dimensional photographs were taken before and after securing the central screw, which induced a calculated mean preload of 246 N. Measurements and comparisons of the topography of the frame-works and surrounding bone before and after tightening the central screw indicated a complex and inconsistent deformation pattern. Generally, it could be observed that the top edge of the central cylinder showed vertical movement towards the bone of about 150 microns, always in combination with a rotation of the entire super-structure. The head of the central implant seemed to show a corresponding displacement towards the frame-work of about 50 to 200 microns. Bone deformation was found to be basically localized between the implants, where compressions of about half a millimetre were observed. This concentration of bone deformation as a result of misfit may be one contributing factor to initial marginal bone loss, occasionally observed after insertion of implant supported prostheses.

Animals↗

PubMed1997

Resonance frequency measurements of implant stability in vivo. A cross-sectional and longitudinal study of resonance frequency measurements on implants in the edentulous and partially dentate maxilla.

The aim of this investigation was to evaluate the use of resonance frequency measurements in the clinical measurement of implant stability. Resonance frequency measurements are undertaken by measuring the response of a small transducer attached to an implant fixture or abutment. Two groups of patients were selected for study. Group A comprised 9 patients who had a total of 56 implants placed. Resonance frequency measurements were made at fixture installation and repeated 8 months later at abutment connection. The resonance frequency of the implant/transducer system increased for 50 out of the 56 implants from a mean value of 7473 Hz +/- 127 Hz (P < 0.05) to a mean of 7915 Hz +/- 112 Hz (P < 0.05). Two implants had failed to integrate and the resonance frequency of these had fallen. Group B comprised 9 patients who had been provided with fixed prostheses and had a total of 52 implants placed. They were examined 5 years after fixture placement and the prostheses removed. All implants were judged clinically to be osseointegrated. The level of the marginal bone around each implant was calculated by measuring the number of exposed threads on intraoral periapical radiographs and added to the length of each abutment to give a value termed the effective implant length (EIL). Measurements indicated a correlation (R = -0.78, P < 0.01) between EIL and resonance frequency. The results support the hypothesis that the resonance frequency of an implant/transducer system is related to the height of the implant not surrounded by bone and the stability of the implant/tissue interface as determined by the absence of clinical mobility.

Aged↗

PubMed1997

Association between marginal bone loss around osseointegrated mandibular implants and smoking habits: a 10-year follow-up study.

While many factors are conceivable, occlusal loading and plaque-induced inflammation are frequently stated as the most important ones negatively affecting the prognosis of oral implants. Currently, little is known about the relative importance of such factors. The aim of this study was to analyze the influence of smoking and other possibly relevant factors on bone loss around mandibular implants. The participants were 45 edentulous patients, 21 smokers and 24 non-smokers, who were followed for 10-year period after treatment with a fixed implant-supported prosthesis in the mandible. The peri-implant bone level was measured on intraoral radiographs, information about smoking habits was based on a careful interview, and oral hygiene was evaluated from clinical registration of plaque accumulation. Besides standard statistical methods, multiple linear regression models were constructed for estimation of the relative influence of some factors on peri-implant bone loss. The long-term results of the implant treatment were good, and only three implants (1%) were lost. The mean marginal bone loss around the mandibular implants was very small, about 1 mm for the entire 10-year period. It was greater in smokers than in non-smokers and correlated to the amount of cigarette consumption. Smokers with poor oral hygiene showed greater marginal bone loss around the mandibular implants than those with good oral hygiene. Oral hygiene did not significantly affect bone loss in non-smokers. Multivariate analyses showed that smoking was the most important factor among those analyzed for association with peri-implant bone loss. The separate models for smokers and non-smokers revealed that oral hygiene had a greater impact on peri-implant bone loss among smokers than among non-smokers. This study showed that smoking was the most important factor affecting the rate of peri-implant bone loss, and that oral hygiene also had an influence, especially in smokers, while other factors, e.g., those associated with occlusal loading, were of minor importance. These results indicate that smoking habits should be included in analyses of implant survival and peri-implant bone loss.

Adult↗

PubMed1997

Regeneration of gingival papillae after single-implant treatment.

An index to assess the size of the interproximal gingival papillae adjacent to single implant restorations was described and preliminary tested in a pilot study of retrospective material comprising 25 crowns in 21 patients. The result indicated a significant spontaneous regeneration of papillae (P < .001) after a mean follow-up period of 1.5 years. Based on these results, the general conclusion was made that the proposed index allows scientific assessment of soft tissue contour adjacent to single-implant restorations. The results also indicated that soft tissue changed in a systematic manner during the time period between insertion of the crowns and follow-up 1 to 3 years later.

Adolescent↗

PubMed1996

Measuring fit at the implant prosthodontic interface.

Four centers in the United States and Sweden have been working for 2 years to develop systems and methods for measuring fit at the prosthodontic interface. Two systems are based on stylus contact techniques, one system uses a laser as its reader source, and one system is photogrammetric. All the systems are capable of providing data as three-dimensional x, y, and z axes coordinate values that can be transformed into linear and angular data that characterize the bearing surfaces of abutments or abutment replicas and their mating components in the prosthesis framework. The centroid, a single point computed from the collected data, was the measurement unit, derived for these bearing surfaces, that was used to compare the systems. All four methods can most likely detect misfits that are relevant in the clinical setting; however, only one system can be used intraorally. When any measurement system is assessed, the data should always be examined for repeatability to establish the reliability of the system. This investigation made comparisons among the measurement methods used at the four centers. It was apparent from this study that comparisons of data from measurement systems should be rounded to the nearest 10 microns. The SDs determined in the comparisons were larger than 5 microns and therefore misfits should be calculated in terms smaller than 10 microns. This final point is important to the clinician who relies on research reports about precision of fit when selecting treatment approaches in caring for the implant prosthodontic needs of their patients.

Calibration↗

PubMed1996

A prospective 15-year follow-up study of mandibular fixed prostheses supported by osseointegrated implants. Clinical results and marginal bone loss.

In this prospective study 47 edentulous patients were treated with mandibular fixed prostheses supported by osseointegrated Brånemark implants and followed for 12 to 15 years. Three (1%) of the 273 inserted implants were lost, two before and one six years after placement of the fixed prosthesis. The cumulative success rate (CSR) of the implants was 98.9% both after 10 and 15 years. None of the fixed prostheses was lost and at the last follow-up, all patients had stable fixed prostheses in function (CSR 100%). The marginal bone loss around the implants was small, on average 0.5 mm during the first post surgical year and thereafter about 0.05 mm annually. More bone was lost around the anterior implants than around the most posterior ones. Smoking and poor oral hygiene had significant influence on bone loss, while occlusal loading factors such as maximal bite force, tooth clenching and length of cantilevers were of minor importance. It is concluded that the long-term results of the mandibular implant treatment were extremely successful, regarding both the fixed prostheses and implant stability. Bone resorption around the implants, albeit limited, was influenced by several factors, smoking and oral hygiene appeared to be most important.

Adult↗

PubMed1995

Accuracy of implant-supported prostheses in the edentulous jaw: analysis of precision of fit between cast gold-alloy frameworks and master casts by means of a three-dimensional photogrammetric technique.

Distortions of 15 routine implant-supported prostheses were measured in relation to the master casts after completion by means of a 3-dimensional (3-D) photogrammetric technique. All prostheses were designed as one-piece gold-alloy castings with resin teeth. Five of the prostheses were placed in the edentulous maxilla, and the remaining were placed in the lower jaw. Distortion of the cylinders was mostly observed in the horizontal plane (x- and y-axis) while the vertical aspect seemed to be more stable. The mean 3-D center point distortion was 42 (SD 15) and 74 (SD 38) microns for the upper and lower jaws, respectively. The measurements revealed a range of 3-D center point distortion from 16 to 80 and 15 to 165 microns for the different jaws, respectively. The corresponding 3-D mean angular distortion of the cylinders was 51 (SD 35) microns in lower and 70 (SD 75) microns in the upper jaws. A correlation was found between 3-D center point distortion and the width as well as the curvature of the implant arch, indicating more displacement the wider and the more curved the arch was. The 3-D center point distortion was also significantly higher in the upper jaws which could possibly be explained by the curvature of the implant arch and higher numbers of implants in the upper jaws. Further problems with the fit of upper jaw castings could be related to more alloy in the castings and poor alignment of implants.

Dental Prosthesis Design↗

PubMed1995

Three-dimensional distortion of gold alloy castings and welded titanium frameworks. Measurements of the precision of fit between completed implant prostheses and the master casts in routine edentulous situations.

Thirty routine patients, provided with fixed prostheses supported by osseointegrated Brånemark implants in edentulous lower jaws, were arranged into three different groups with regard to design of the metal framework. Ten patients received cast gold alloy frames and the other two groups were provided with two different designs of welded titanium frames. The fit of the completed prostheses was measured in three dimensions (3-D) in relation to the master cast, by means of a photogrammetric technique, prior to insertion. Mean 3-D distortion of the centre point of the gold cylinder was 42 (s.d. 8) microns for the cast framework. The corresponding mean distortion for the two designs of titanium frameworks was 43 (s.d. 16) and 36 (s.d. 10) microns, respectively. Least distortion was observed in vertical direction for all three designs. None of the different designs of metal frames showed a significantly better fit (P > 0.05), but the cast and oldest titanium framework design presented a much wider range of distortion. This indicated a higher risk of sectioning and resoldering during the fabrication of the prostheses as compared to the more consistently fabricated prostheses, with a new titanium framework design.

Dental Casting Technique↗

PubMed1994

Photogrammetric measurements of implant positions. Description of a technique to determine the fit between implants and superstructures.

A photogrammetric technique was designed to measure the position of dental implants in 3 dimensions to enable assessment of the fit of superstructures placed on the implants. A relatively simple camera set-up was developed and tested. Calibration of the camera was performed in a high-precision analytical plotter and revealed a film measurement accuracy of 0.005 mm. The achieved measuring accuracy for clear and well defined points on clinical components was found to be around 0.02 mm. To find the center points of the implants, points on the circumference were measured. These points are not well defined, which resulted in an estimation of the center point of the implant with a precision of 0.05 mm. Independent measurements of a prosthesis with 5 implants were also within the precision of 0.05 mm. The angular orientation of the top surface of the implant cylinder (abutment, brass replica of gold alloy cylinder of the framework) was measured with a precision of 0.01 radians, which corresponded to an error with a peripheral gap of about 0.03 mm. This value was about 5-10 times lower than the clinical fit between frameworks and abutments, measured in 3 randomly selected clinical cases.

Dental Implants↗

PubMed1994

Fixed implant-supported prostheses in the edentulous maxilla. A five-year follow-up report.

Seventy-six patients were consecutively treated with fixed prostheses supported by osseointegrated implants in the edentulous maxilla and followed up for 5 years. The mean bone quality and resorption indices were 3.1 and 2.7 at the time of implant placement, respectively. Altogether, 449 standard Brånemark implants were placed. Two patients resumed to complete dentures, and the cumulative implant and prosthesis survival rates were 92.1% and 95.9% for 5 years, respectively. The mean marginal bone level was 0.6 mm below the reference point at the time of placement and 1.2 mm below the same point 5 years later. Speech problems was the most frequent complaint during the first year of function, while resin fractures caused most adjustments during the follow-up period. No implant, abutment or gold alloy screws were found to be fractured, and only 4 patients had their prostheses re-tightened due to loose gold alloy screws.

Adult↗

PubMed1994

Mucosal topography around implants in edentulous upper jaws. Photogrammetric three-dimensional measurements of the effect of replacement of a removable prosthesis with a fixed prosthesis.

A photogrammetric technique was tested to measure the topography of the mucosa around implants, placed in edentulous upper jaws. Photographs were taken of casts from 6 patients, who all had used a removable overdenture for one year. Another series of photographs was taken on new casts after the use of a fixed prosthesis for a second year. The 6 pairs of photographs were measured and compared in an analytical stereo plotter for surface contour and implant positions. The results from the measurements indicated a trend of general recession of the mucosa after one year with fixed prosthesis, both on the buccal as well as on the palatal side. The mean volume of recession was 222.4 mm3, corresponding to an average of 0.4 mm3/mm2 of mucosa. More recession was generally observed on the palatal side, but obvious variations between the patients were present. In conclusion, the photogrammetric technique was considered to be well suited for analysing tissue contours in various dental situations.

Aged↗

PubMed1994

Osseointegrated implants as orthodontic anchorage in the treatment of partially edentulous adult patients.

In nine partially edentulous adult patients, mean age 47 years (range 17-64 years) 23 osseointegrated implants were used as orthodontic anchorage to perform the following types of orthodontic tooth movements: tipping, torquing, rotation, intrusion, extrusion, and those associated with bodily movements. The total orthodontic treatment period varied between 4 and 33 months (x = 17 months). Pre-operatively, at the start and end of orthodontic treatment, and at the annual controls, clinical as well as biometric and radiographic (panoramic, lateral cephalograms and periapical radiographs) recordings were performed. The osseointegrated anchorage units were used as reference points for measurements of two- and three-dimensional tooth movements with a co-ordinate machine. The 2-D tooth movements varied between 0.2 and 6.2 mm, whereas movements in the third dimension, extrusion and intrusion, ranged from 0.0 to 13.5 mm. The movement in space for the individual tooth was observed to be, as a mean, 3.9 mm (range 0.6-18.7 mm). However, the osseointegrated titanium implants (fixtures) used as orthodontic anchorage remained in position when orthodontically loaded for the various tooth movements. After completion of the orthodontic treatment the fixtures served as abutments for permanent prosthetic constructions.

Adolescent↗