The International Journal of Prosthodontics, 04/2004

For most people, the designation Swedish is likely to conjure up immediate word associations. Alfred Nobel's dynamite and his prizes come to mind; or Ikea and Ingmar Bergman movies; and of course Volvos and Saabs in spite of General Motors and Ford involvement. However, if you are a prosthodontist or in another specialty that does preprosthetic surgery, the name which comes to mind is Per-Ingvar Brånemark's. The genesis of osseointegration and its early nurturing are the results of his pioneering research activities, which have dramatically revolutionized the treatment of complete and partial edentulism as well as the management of maxillofacial deficits.

Purpose: This study aimed to compare the prosthetic aspects and patient satisfaction with prosthetic care in two-implant-retained mandibular overdentures, whether implants were splinted with a bar or left with magnets or ball attachments. Materials and Methods: Thirty-six completely edentulous patients had two Brånemark implants placed in the mandibular canine area. A randomized procedure allocated patients into three groups of equal size, each with a different attachment system: bars, magnets, or balls. Prosthesis retention and mechanical as well as soft tissue complications were recorded in addition to patient satisfaction. A linear mixed model was fitted with attachment type and time as classification variables and adjusted by Turkey's multiple range test. Results: Ball-retained overdentures showed at year 10 the greatest vertical retention force (1,327 g), followed by bars (1,067 g) and magnets (219 g). In the ball group, need for tightening of abutment screws was the most common mechanical complication; in the magnet and bar groups, respectively, the most common complications were wear and corrosion, and the need for clip activation. Prosthesis stability and chewing comfort for the overdenture were rated significantly lower for the magnet group compared to the ball and bar groups. Prosthesis stability of the maxillary denture was rated significantly lower in the bar group compared to ball and magnet groups. Conclusion: The ball group scored best in relation to retention of the overdenture, soft tissue complications, and patient satisfaction at year 10. The bar group scored lower for comfort and stability of the maxillary denture. Magnets offered patients the least comfort.

Purpose: This study compared the influence of two luting cements on the clinical performance of single crowns. Materials and Methods: Twenty patients received 39 pairs of metal-ceramic and Procera crowns cemented with zinc phosphate and resinmodified glass-ionomer luting cement (Vitremer) in a split-mouth randomized pattern blinded to the recipient. The crowns were examined immediately after cementation, after 2 weeks, after 6 months, and then yearly. Clinical performance was scored according to CDA criteria, Silness and Löe criteria, patient satisfaction, and operator-appraised general clinical criteria. Three clinicians in private general practice carried out all procedures. Results: During the observation period, which varied between 80 and 104 months, seven clinical events were recorded. Two abutments fractured vertically, two underwent retrograde endodontic surgery, and one developed pulp necrosis. Two crowns were recemented. Estimated survival, defined as no negative events observed, was 89% at 102 months (85% for crowns cemented with zinc phosphate and 93% for crowns cemented with resin-modified glass-ionomer). Estimated survival, defined as no recementation or loss of pulp vitality, was 96% at 102 months (95% with zinc phosphate and 97% with resin-modified glass-ionomer). The differences between cements were not statistically significant. Conclusion: A resin-modified glass-ionomer luting cement was at least as good as zinc phosphate cement to retain single crowns over a 102-month observation period.

Purpose: The aim of this prospective study was to report long-term treatment outcomes (prosthetic and implant related) of edentulous patients treated with implantsupported fixed prostheses who participated in the first clinical implant study in North America. Materials and Methods: Forty-five patients were treated with Brånemark implants supporting a total of 47 fixed prostheses (42 mandibular and 5 maxillary) between 1979 and 1984. All patients were recalled regularly for comprehensive prospective clinical and radiographic assessments. Results: Thirty-one patients (33 prostheses) attended a final recall visit in 2002; 71% of patients had been followed for 20 years (range 18 to 23 years), with overall prosthetic plan and implant outcome success rates of 84% and 87%, respectively. Mean marginal bone loss around the implants after the first year of loading was small (0.05 mm/year), with high individual variations. Poor oral hygiene, smoking history, and implant position appeared to be predictors of marginal bone loss. Prosthetic maintenance was ongoing and included fractured components and replacement of prostheses; the longevity of a fixed prosthesis for this group of patients was 8.39 ± 5.30 years. Conclusion: This study confirmed the overall long-term treatment outcome success of patients treated with fixed prostheses supported by Brånemark implants. Successful osseointegration with small mean bone loss was maintained as study patients aged, although prosthetic maintenance was required. The latter consideration should be discussed with all patients seeking such treatment.

Purpose: Few long-term studies on overdentures report both implant and prosthodontic outcomes. The aim of this prospective study was to report long-term prosthodontic- and implant-related treatment outcomes of patients treated with design-specific implantsupported overdentures. Materials and Methods: Between 1982 and 1992, 45 consecutively treated patients received a total of 47 overdentures (42 mandibular and maxillary) supported by Brånemark implants. Prospective clinical and radiographic data were collected over the observation period; this study presents the most recent treatment outcomes. Results: Thirty patients (mean age 70 years) with 32 prostheses attended the final recall visit, with 67% of patients followed for 15.53 years (range 10 to 19 years). Six implants failed, and the prosthetic plan and implant cumulative survival rates were both in excess of 90%. Mean marginal bone loss around implants after the first year of loading was small (0.05 mm/year), although the individual variation was high. Linear regression analysis of bone loss indicated that gender, bicortical stabilization, bone quality, and healing time were predictors of bone loss for the first year of loading but not for the ensuing years. Prosthetic maintenance included fractured components, denture relining, and replacement of prostheses. On average, the longevity of overdenture prostheses was 12 years, and laboratory relining was necessary every 4 years. Conclusion: This study confirmed the long-term outcome success of patients treated with design-specific overdenture prostheses supported by Brånemark implants. However, prosthetic maintenance was required, a fact that should be discussed with patients prior to treatment.

Purpose: The aim of this study was to investigate the impact of both population age changes and falling edentulism rate on the denture market in three European countries. Materials and Methods: Detailed information on the rate of edentulism for only three European countries (Finland, Sweden, and the UK) was available. For the UK and Sweden, published predicted rates of edentulism for the future decades were used, whereas predictions for Finland were computed using published edentulism rates. Edentulousness in one jaw was also predicted and included in the computation. Demographic projections were taken from government agency websites. Results: The denture market will decrease in the three countries. Sweden, where edentulism is already low, will experience the largest percentage decrease (60%) over 20 years, but, in absolute number, the change will be of smaller magnitude than that in the UK and Finland. The range of projections for Finland was large, reflecting the difficulty of predicting trends with incomplete information. Within the limitations of this study's design, the impact of population age changes will not increase the denture market in Europe, even with the most pessimistic projections for edentulism rate. Conclusion: The complete denture market in Europe will fall despite changing age demographics. The falling rates are large enough to markedly affect future patterns of treatment provision and training.

Purpose: This study examined the possible association of three dental factors with total mortality and death from coronary heart disease. Materials and Methods: Samples from two studies were combined, for a total of 2,613 individuals aged 25 to 79 years; a total of 353 deaths occurred, of which 82 were from coronary heart disease. The hazard ratio was calculated for total and coronary heart disease mortality by regression for the dental components; conventional risk factors were controlled for in a stepwise manner. Results: For total and coronary heart disease mortality, associations with both edentulousness and number of years of edentulism were statistically significant until smoking was added into the analysis; then, all significance was lost. When the effect of the oral parameters was studied in relation to total and coronary heart disease mortality, after adjusting for age and gender, there was a significant hazard ratio for total mortality, but only for edentulousness. When examined by stepwise regression of the coronary heart disease risk factors, all significance of risk from the three oral parameters was lost, smoking having the largest effect of all risk factors. Conclusion: Number of remaining teeth, edentulousness, and number of years of edentulism were not independent risk factors for total or coronary heart disease mortality, but they were surrogate markers for the risk from smoking.

Purpose: This pilot study was designed to test the hypothesis that the use of a single oral splint may aggravate respiratory disturbance in sleep apneic patients. Materials and Methods: A group of 10 patients with a history of snoring and a recording night confirming a diagnosis of sleep apnea were included. Patients were then invited to spend 2 nights in the sleep laboratory: night 2 to establish baseline data (baseline night) and night 3, 1 week later, to assess the influence of an occlusal maxillary splint on sleep (splint night). The following variables were analyzed under blind conditions: total sleep time, sleep efficiency and number of awakenings, microarousals, apneahypopnea index per hour of sleep (AHI), respiratory disturbances index per hour of sleep (RDI), and percentage of sleeping time with snoring. Results: No statistically significant difference in AHI was noted between baseline and splint nights. However, four patients experienced an aggravation in apnea diagnosis category on the night they used the splint. The AHI was increased by more than 50% in 5 of the 10 patients. The RDI showed a 30% increase from baseline to splint nights. The percentage of sleeping time with snoring also increased by 40% with the splint. Conclusion: This open study suggested that the use of an occlusal splint is associated with a risk of aggravation of respiratory disturbances. It may therefore be relevant for clinicians to question patients about snoring and sleep apnea when recommending an occlusal splint.

Purpose: The purpose of this study was to compare the accuracy, required time, and potential advantages of rapid prototyping technology with traditional methods in the manufacture of wax patterns for two facial prostheses. Materials and Methods: Two clinical situations were investigated: the production of an auricular prosthesis and the duplication of an existing maxillary prosthesis, using a conventional and a rapid prototyping method for each. Conventional wax patterns were created from impressions taken of a patient's remaining ear and an oral prosthesis. For the rapid prototyping method, a cast of the ear and the original maxillary prosthesis were scanned, and rapid prototyping was used to construct the wax patterns. For the auricular prosthesis, both patterns were refined clinically and then flasked and processed in silicone using routine procedures. Twenty-six independent observers evaluated these patterns by comparing them to the cast of the patient's remaining ear. For the duplication procedure, both wax patterns were scanned and compared to scans of the original prosthesis by generating color error maps to highlight volumetric changes. Results: There was a significant difference in opinions for the two auricular prostheses with regard to shape and esthetic appeal, where the hand-carved prosthesis was found to be of poorer quality. The color error maps showed higher errors with the conventional duplication process compared with the rapid prototyping method. Conclusion: The main advantage of rapid prototyping is the ability to produce physical models using digital methods instead of traditional impression techniques. The disadvantage of equipment costs could be overcome by establishing a centralized service.

Purpose: The purpose of this report is to describe a new technique for fabricating auricular prostheses by a computer-aided design/manufacturing (CAD/CAM) system. Materials and Methods: A spiral CT was performed on a patient who had a right ear defect resulting from an accident. A 3-D image was reconstructed with the CT data. Through image ware, the image of the normal ear was extracted, mirrored, and Boolean operated with the image of the deformed side of the face. It was well modified and smoothed in the FreeForm model system so that it could precisely adapt to the deficient side of the face. A paper model ear was manufactured by rapid prototyping from the digitized data. Finally, silicone was poured into a silicone mold from the paper ear to create a silicone auricular prosthesis. Results: The dimension, shape, and anatomic contour of the auricular prosthesis were quite similar to those of the normal ear and precisely matched the deformed area. Conclusion: The CAD/CAM system for creating auricular prostheses appears to be a practical technique.

Purpose: The purpose of this case report is to demonstrate the benefits and applicability of appropriate maxillofacial prosthetic rehabilitation following surgical resection of ameloblastoma of the maxilla in Kenya. Materials and Methods: Five patients presenting with ameloblastoma of the maxilla over 3 years were studied with respect to histologic type, site of tumor, resultant surgical defect, and form of definitive obturator prosthesis. Impressions were taken using irreversible hydrocolloid and poured with dental stone. Immediate surgical obturators were fabricated from casts using clear autopolymerizing acrylic resin. One patient had bilateral partial maxillectomy, whereas the rest had unilateral partial maxillectomy. Immediate surgical obturators were fitted intraoperatively and held in place using Adams clasps on the remaining natural dentition for all patients, except the one who had undergone bilateral partial maxillectomy, whose surgical obturator was held loosely using circumzygomatic wires. After 6 to 8 weeks, surgical obturators and packing were withdrawn, and new impressions were taken to fabricate definitive obturators. Patients were reviewed every 2 weeks for 3 months, then once every 3 months per year for 3 years, and thereafter once per year. Results: The immediate surgical obturators facilitated retention of the surgical packing, promoting healing with minimal postsurgical infection and scar contracture formation. This ensured the restoration of acceptable esthetics and maintenance of oral function at a reasonable level during the initial postoperative period. Definitive obturators restored esthetics, oral function, and ability to handle secretions to a satisfactory level. Conclusion: Satisfactory functional and esthetic results are achievable in patients with extensive acquired maxillary defects by means of obturator prostheses fabricated using readily available materials.

Purpose: The purpose of this research project was to determine the clinical success rate of a lithia disilicate-based core ceramic for use in posterior fixed partial dentures (FPD) as a function of bite force, cement type, connector height, and connector width. Materials and Methods: Thirty ceramic FPD core frameworks were prepared using a heat-pressing technique and a lithia disilicate-based core ceramic. The maximum clenching force was measured for each patient prior to tooth preparation. Connector height and width were measured for each FPD. Patients were recalled yearly after cementation for 2 years and evaluated using 11 clinical criteria. All FPDs were examined by two independent clinicians, and rankings from 1 to 4 were made for each criterion (4 = excellent; 1 = unacceptable). Results: Two of the 30 ceramic FPDs fractured within the 2-year evaluation period, representing a 93% success rate. One fracture was associated with a low occlusal force and short connector height (2.9 mm). The other fracture was associated with the greatest occlusal force (1,031 N) and adequate connector height. All criteria were ranked good to excellent during the 2-year recall for all remaining FPDs. Conclusion: The performance of the experimental core ceramic in posterior FPDs was promising, with only a 7% fracture rate after 2 years. Because of the limited sample size, it is not possible to identify the maximum clenching force that is allowable to prevent fracture caused by interocclusal forces.

Purpose: This study sought to aggregate literature data on in vitro failure loads and failure modes of prefabricated fiber-reinforced composite (FRC) post systems and to compare them to those of prefabricated metal, custom-cast, and ceramic post systems. Materials and Methods: The literature was searched using MEDLINE from 1984 to 2003 for dental articles in English. Keywords used were (post or core or buildup or dowel) and (teeth or tooth). Additional inclusion/exclusion steps were conducted, each step by two independent readers: (1)Abstracts describing postand- core techniques to reconstruct endodontically treated teeth and their mechanical and physical characteristics were included (descriptive studies or reviews were excluded); (2)articles that included FRC post systems were selected; (3)in vitro studies, single-rooted human teeth, prefabricated FRC posts, and composite as the core material were the selection criteria; and (4)failure loads and modes were extracted from the selected papers, and failure modes were dichotomized (distinction was made between "favorable failures," defined as reparable failures, and "unfavorable failures," defined as irreparable [root] fractures). Results: The literature search revealed 1,984 abstracts. Included were 244, 42, and 12 articles in the first, second, and third selection steps, respectively. Custom-cast post systems showed higher failure loads than prefabricated FRC post systems, whereas ceramic showed lower failure loads. Significantly more favorable failures occurred with prefabricated FRC post systems than with prefabricated and custom-cast metal post systems. Conclusion: The variable "post system" had a significant effect on mean failure loads. FRC post systems more frequently showed favorable failure modes than did metal post systems.