Bo Bergman

Clinical results with titanium crowns fabricated with machine duplication and spark erosion

A new method for fabrication of metal crowns has been developed by one of the authors (M.A.). There are two principles involved: machine duplication of models and electric discharge machining. The metal used is pure unalloyed titanium, which is processed as a coping and later covered by a composite resin. In 1986, 205 separate titanium crowns were made on 149 patients. One year later 192 crowns on 137 patients could be examined. Five crowns had been replaced by new ones owing to fracture of the composite resin. In accordance with the CDA quality evaluation system the following results were obtained for the remaining 187 crowns: margin integrity, 186 excellent or satisfactory (99.5%); anatomic form, 185 excellent or satisfactory (98.9%); and surface and color, 181 excellent or satisfactory results (96.8%). The 1-year results are promising, and further follow-up studies will be made.

Caries, periodontal and prosthetic findings in patients with removable partial dentures: A ten-year longitudinal study

A 10-year longitudinal study was carried out on 27 patients treated with RPDs. Before the prosthetic treatment all patients were given oral hygiene motivation and instruction as well as periodontal therapy where indicated. The aim was a high level of cooperation. The RPDs, most of which were lower bilateral distal-extension dentures, were carefully planned and designed. During the follow-up period the patients were examined at yearly intervals, at which time remotivation and reinstruction regarding oral hygiene was given, and scaling, operative restorations, and prosthetic and other treatment procedures were preformed as required. Patient cooperation was excellent, and no significant deterioration of the periodontal status of the remaining teeth was found. In addition, there was a low increase in the frequency of decayed and filled tooth surfaces during the decade. The dentures showed damage and several changes during the follow-up period, conditions that necessitated various corrective prosthetic procedures.

Mercury, selenium, and glutathione peroxidase before and after amalgam removal in man.

In 10 healthy persons all amalgam fillings were replaced with gold inlays. Blood and urinary levels were measured on 10 occasions during a 4-month period before and a 12-month period after amalgam removal. These variables were also measured three times in 10 healthy controls. A strong statistically significant relation was found between plasma mercury values and both the total number of amalgam surfaces (r = 0.71, p = 0.0006) and the total surface area of the fillings (r = 0.73, p = 0.0004). In the immediate postremoval phase plasma mercury rose three- to four-fold, whereas the urinary and erythrocyte mercury rose about 50%. These peak values declined to the preremoval level at about 1 month. Twelve months after the removal the plasma and urinary mercury levels were significantly reduced to 50% and 25%, respectively, of the initial values for the experimental group. Apart from the significantly lower plasma selenium values 5 and 10 days after removal no significant differences were found with regard to plasma selenium or erythrocyte glutathione peroxidase either within or between the experimental and the control groups. A large number of supplementary biochemical analyses did not show any influence on organ functions or any differences between the groups before or after the amalgam removal. Amalgam fillings considerably contributed to the plasma and urinary mercury levels.

Periodontal and Prosthetic Conditions in Patients Treated with Removable Partial Dentures and Artificial Crowns: A Longitudinal Two-Year Study

In the present longitudinal study the periodontal and prosthetic conditions in 30 patients treated with removable partial dentures and artificial crowns were followed over a period of 2 years. The patients were given individual instructions in oral and denture hygiene and adequate periodontal treatment before the prosthetic therapy was started. The removable partial dentures were carefully planned and designed. The patients were regularly checked, and necessary instructions, scaling and prosthetic corrections were undertaken. The patients cooperated excellently and no significant deterioration was found in the clinical periodontal status of the remaining teeth. Only a few carious lesions were registered. The present study does not support the opinion that a removable partial denture per se will cause periodontal and carious lesions. When teeth with artificial crowns were examined regarding the position of the crown margins it was found that clinically observable gingival inflammations tended to be greates...

A 2-year follow-up study of titanium crowns

In 1986, 149 patients were provided with titanium crowns. The method used for fabrication of the titanium copings involved two principles: machine duplication of models and electric discharge machining. For the veneering of the copings, Isosit was used for the first 90% of the crowns in the series, and the Dentacolor-Silicoater technique for the last 10%. Of 205 individual crowns cemented in 1986, 167 could be examined after 2 years. The crowns were rated by four independent examiners using the CDA quality evaluation system. Bleeding Index and Margin Index were also used. The Margin Integrity score was recorded as satisfactory for all crowns examined over the period studied. A vast majority of the margins were rated as excellent. Isosit (n = 145) disclosed shortcomings including fractures and substantial deteriorations of Surface and Color and of Anatomic Form. With Dentacolor as veneering material (n = 18) the results with the factors Surface and Color and Anatomic Form were still rated satisfactory after 2 years, and no fractures of the veneering material were registered. Bleeding Index and Margin Index showed comparatively small changes after 2 years.

Masticatory efficiency of complete denture patients: A clinical examination of potential changes at the transition from old to new dentures

The masticatory efficiency was studied among 19 complete denture wearers with their old and new dentures. The test chewing material was gelatin hardened by formalin. A standardized preparation of the test chewing material and the sieve-system is described. The patients were tested on seven different occasions from the period with the old dentures until about 1.5 years after the insertion of the new dentures. The test pieces were chewed for ten seconds--a practice test--20 seconds and until ready to be swallowed. The chewed material was strained in a sieve-system and masticatory efficiency indices were calculated. The results revealed no statistical significant differences in masticatory efficiency between any of the seven testing occasions with the method used. Thus no significant difference was noticed when patients changed from old to new dentures or during the first 18 months after insertion of new dentures.

The accuracy of a high-precision digitizer for CAD/CAM of crowns

An alternative method for manufacturing fixed prostheses that uses machine digitalization and a combination of milling and spark erosion has been developed. The digitizer used has a contact probe with a ball-shaped tip. This study evaluated the accuracy of the device and the transfer of data from the individual die to the computer. The dimensions of a square gauge as read by the machine were compared with the known dimensions of the object with a computer, which allowed determination of the accuracy of the digitalization. Procera machining and the implications for reliable prosthodontic treatment are discussed.

Effects of External Radiation Therapy for Cancer of the Prostate on the Serum Concentrations Of Testosterone, Follicle-Stimulating Hormone, Luteinizing Hormone and Prolactin

Testosterone, luteinizing hormone, follicle-stimulating hormone and prolactin were analyzed in serum from 31 patients with carcinoma of the prostate treated primarily with megavoltage radiation therapy. The total tumor dose varied between 58 and 71 gray (mean 63.5 gray). Absorbed doses to the testes were measured at approximately 1 to more than 10 gray. We investigated retrospectively 17 patients 3 to 60 months (mean 20 months) after therapy and found significantly lower serum testosterone concentrations and significantly higher luteinizing and follicle-stimulating hormone concentrations than in age-matched controls. Of the patients 14 were followed before and after radiation treatment. Testosterone concentrations were reduced significantly 1 week as well as 3 months after treatment but pre-treatment values were found on analysis 6 and 12 months after treatment. The values for luteinizing and follicle-stimulating hormones were significantly higher 3, 6 and 12 months after radiation treatment compared to pre-treatment values. The follicle-stimulating hormone value already increased after 1 week. The greatest observed testosterone alteration occurred 1 week after treatment in patients who received more than 10 gray over the gonads. The use of lead shields protecting the testes reduced the dose absorbed to the gonads by approximately 50 per cent.

Accuracy of machine milling and spark erosion with a CAD/CAM system

A method for manufacturing crowns and fixed partial dentures based on CAD/CAM has been developed as an alternative to the lost wax technique and the casting of an alloy. In this process two steps are included: milling and spark erosion. The computer-assisted design (CAD) relies heavily on the accuracy of the milling and spark erosion processes to achieve a clinically acceptable restoration. These two processes must be able to produce the crown data generated in the CAD files. This study evaluated the accuracy of the Procera CAD/CAM system in creating specific geometric bodies that were compared with the known dimensions in the CAD files for these bodies. The manufacturing errors of milling (ellipse +/- 6.5 microm, square +/- 3.4 microm, and cylinder +/- 5.8 microm) and spark erosion (ellipse +/- 8.6 microm and square +/- 10.4 microm) were determined. The accuracy of this manufacturing process demonstrated that this system was capable of producing a crown with a clinically accepted range for marginal opening gap dimension of less than 100 microm.

Mandibular bone resorption in patients treated with tissue-integrated prostheses and in complete-denture wearers

Mandibular bone resorption was studied in patients treated with tissue-integrated prostheses (TIP) and in complete-denture wearers by distance and area measurements on cephalometric radiographs. The area measurements were performed by means of a computer. Two TIP groups with short and long periods (mean = 2.4 and 23.9 years) of edentulousness and wearing complete dentures before fixture installation were followed up over 7-8 years. Mandibular bone resorption was remarkably small behind the distally positioned fixtures in comparison with the corresponding region in complete-denture wearers. Patients with complete dentures showed a continuous resorption of the mandibular alveolar ridge over 21 years, even though there were great individual variations. The bone loss was most pronounced anteriorly and during the first 2 years after extraction of the residual teeth. It is concluded that treatment with tissue-integrated prostheses seems to reduce bone resorption in the mandible, probably owing to favorable load conditions and adequate stimulation of the bone.