Within-subject comparisons of implant-supported mandibular prostheses: evaluation of masticatory function.

In the past, fixed prostheses were believed to be more efficient implant-supported devices than removable types for edentulous patients. However, this hypothesis was never properly tested. Therefore, a within-subject crossover clinical trial was designed in which 145 completely edentulous subjects were tested wearing implant-supported mandibular fixed prostheses and long-bar overdentures. Eight subjects received the fixed appliance first and seven the removable type. The patients' perceptions of various characteristics of the implant-supported prostheses were measured after a minimum of two months' adaptation. Mandibular movements and jaw muscle electromyographic activity were recorded while the patients chewed five standard-sized test foods: bread, apple, hard cheese, sausage, and raw carrot. The prostheses were then changed, worn for the same period of adaptation, and the procedures repeated. There were three test sessions per prosthesis, and each included five trials per food. The measurements were repeated three times at one-week intervals. Mastication time was found to be shorter for three foods (bread, cheese, and sausage) when subjects wore the long-bar overdenture. The vertical amplitude of the masticatory strokes was significantly less with the overdenture for all foods except carrot. Cycle duration was significantly longer with the overdenture for sausage and carrot. Contrary to what might be expected, the long-bar overdenture appears to be no less efficient than the fixed prosthesis. Furthermore, these data suggest that patients are capable of adapting their masticatory movements to the characteristics of the two prostheses.

Within-subject comparisons of implant-supported mandibular prostheses: psychometric evaluation.

In a within-subject cross-over clinical trial, psychometric and functional measurements were taken while 15 completely edentulous subjects wore mandibular fixed prostheses and long-bar removable implant-supported prostheses. In this paper, the results of a psychometric assessment are presented. Eight subjects first received the fixed bridge and seven the removable type. After having worn a prosthesis for a minimum of two months, subjects responded to psychometric scales that measured their perceptions of various factors associated with prostheses. They also chewed test foods while masticatory activity was recorded. The prostheses were then changed and the procedures repeated. At the end of the study, patients were asked to choose the prosthesis that they wished to keep. Patients assigned significantly higher scores, on visual analogue scales, to both types of implant-supported prostheses than to their original conventional prostheses for all factors tested, including general satisfaction. However, no statistically significant differences between the two implant-supported prostheses were detected except for the difficulty of chewing carrot, apple, and sausage. For these foods, the fixed prostheses were rated higher. Subjects' responses to category scales were consistent with their responses to the visual analogue scales. These results suggest that, although patients find the fixed bridge to be significantly better for chewing harder foods, there is no difference in their general satisfaction with the two types of prostheses.

A comparison of the effects of two hydroxyapatites and a methacrylate resin on bone formation in the rat ilium.

The bone response to two hydroxyapatite (HA) products (Osteogen and Alveograf) and a porous methacrylate resin material (HTR) in rats was compared. Fifty rats had four holes drilled in each iliac crest. The three alloplasts were placed in separate cavities and the fourth cavity was left empty as an absolute control. The survival times varied. The results were evaluated by subjective and histomorphometric analysis. Data were analyzed with ANOVA. There was a statistical difference in bone apposition between HTR and the HA products. The HTR was less osteoconductive, while HA consistently showed dense bone formation. The HA products are generally associated with greater bone formation, suggesting that HA is a better material for bone replacement than HTR.

Reaction of the dental pulp to hydroxyapatite.

The purpose of this study was to evaluate the action of hydroxyapatite (HA) (Osteogen HA Resorb, GBD Marketing Group Inc., Valley Stream, N.Y.) on the dental pulp of rats. Four upper molar pulps in 45 rats were exposed and capped with synthetic HA (Osteogen) with a stereoscopic microscope. Pulps capped with calcium hydroxide (Dycal, L.D. Caulk Co., Milford, Del.) served as controls. The cavities were filled with amalgam, and the molars on each side of the maxilla were protected by the placement of a pedodontic steel crown. Pulp inflammation and dentin repair were compared by histologic observations and computer image analysis after 7, 14, and 28 days. After 7 days a partial acute pulpitis were observed in specimens treated with Osteogen or Dycal. Reparative dentin formation along the pulp walls was also seen. After 14 days the pulpitis was more extensive in the Osteogen-treated teeth than in the control teeth. Dentin formation as measured by morphometric analysis was more pronounced in Osteogen-treated teeth. Neo-odontoblasts were observed after the use of both materials. After 28 days an acute inflammatory reaction was still evident in the Osteogen-treated group. A complete dentinal bridge was observed more frequently with Dycal than with Osteogen. Despite the putative abilities of HA to be osteoconductive, osteogenic, and dentinogenic, the results of this study indicate that it should not be used as a pulp-capping agent because of its tendency to cause scattered dystrophic calcification in the dental pulp, which could interfere with future endodontic treatment.

Electron microscope characteristics of dentin repair after hydroxylapatite direct pulp capping in rats.

In order to study the osteogenic action of hydroxylapatite (HA) on the dental pulp, a pulp capping experiment was designed using the rat upper molar. Under general anesthesia, molar teeth in 14 male Sprague-Dawley rats were pulp capped with Osteogen (HA) or with Dycal as a control material. After pulp capping, the maxillary molars cavities were restored with amalgam and a pedodontic steel crown was adjusted and sealed over the molar teeth on either side of the maxilla. After 7 days, the areas of necrosis and acute inflammation were more evident in the pulps treated with Dycal than with Osteogen. Hard tissue formation began to appear around dentinal chips in the pulp and extended from the cavity walls into the pulp regardless of the material that was used. Furthermore, this calcified material was scattered throughout the pulp when Osteogen was used, but was not observed in the Dycal treated pulps. The hard tissue formation was thought to be due to the putative fibroblasts and odontoblasts found in the pulp. After 28 days dense dentinal tissue was observed bridging the exposure site when Dycal was used. The dentinal tissues formed with Osteogen was always of a globular type, and showed an irregular distribution. Since Osteogen tends to cause areas of dystrophic calcification in the pulp, its use is not be recommended for pulp capping purposes in humans, because these areas of calcification would make future endodontic treatment difficult.

Effect of hydroxyapatite on bone formation around exposed heads of titanium implants in rabbits.

Dense hydroxyapatite (HA)--collagen was placed around the protruding heads of titanium and titanium alloy implants in the femurs of 38 rabbits. After 6 months, bone apposition was evaluated by gross examination and scanning electron microscopy. Although bone was observed in direct contact with the implant heads, the extremities of the implant heads were surrounded by connective tissue. Compared with the control animals, packing dense HA-collagen around the implant heads did not increase the area of osteogenesis. When the implants penetrated into bone through previously placed HA-collagen blocks, there was a decrease in the amount of bone attached to the body of the implants compared with the controls. The results of this study suggest that the use of dense HA does not increase the amount of bone tissue formed around titanium implants.

Aggressive fibromatosis of the maxilla. Report of a case and review of the literature.

Aggressive fibromatosis is a rare tumor of the jaws. Its occurrence in the maxilla is even more exceptional. The case of a 14-year-old girl with a peripheral fibromatosis of the palatal process of the maxilla is described. The lesion manifested as a painless swelling. On initial excision, a diagnosis of fibroma was made. After recurrence and reevaluation of the microscopic slides, a final diagnosis of aggressive fibromatosis was established. The features of this case and 12 similar lesions of the maxilla previously described in the literature are analyzed and discussed.