Microtomographic analysis of healing of femtosecond laser bone calvarial wounds compared to mechanical instruments in mice with and without application of BMP-7.

BACKGROUND AND OBJECTIVE: This study investigated the healing of femtosecond laser created wounds in an animal model. STUDY DESIGN: We have assessed the healing of critical size wounds in mice calvaria using three different wounding techniques: carbide bur, diamond end-cutting bur, and ultrafast femtosecond laser, and in the presence or absence of bone morphogenetic protein-7 (BMP). Wound closure was examined using microcomputerized tomography at 3, 6, 9, and 12 weeks. RESULTS: Results have shown partial closure at up to 12 weeks with all techniques that did not involve the use of BMP, with the least closure noted in the laser groups as suggested by two-dimensional radiographic analysis. Bone volume measurements appeared slightly lower for the laser than for the mechanical groups, however statistically significant differences were seen only at week 6. No significant differences in closure were noted for the different methods in the BMP treated groups. CONCLUSIONS: Femtosecond laser cutting demonstrated an unsurpassed precision when compared to mechanical instruments. The addition of BMP led to very rapid healing with complete closure seen as early as 3 weeks and overcomes any potential healing delays that may arise from laser tissue cutting.

Effects of femtosecond laser irradiation on osseous tissues.

BACKGROUND AND OBJECTIVE: Few studies have investigated femtosecond (fs) lasers for cutting bone tissue. STUDY DESIGN/MATERIALS AND METHODS: A 775 nm, 1 kHz, 200 femtosecond, up to 400 microJ laser system was used to irradiate in vitro calcified cortical bone samples and bone tissue culture samples. RESULTS: The ablation threshold in cortical bone was 0.69+/-0.08 J/cm(2) at 775 nm and 0.19+/-0.05 J/cm(2) at 387 nm. Plasma shielding experiments determined that the ablation plume and the plasma significantly affect material removal at high repetition rates and appear to generate thermal transients in calcified tissue. Confocal analysis revealed intact enzymatic activity on the surface of cells immediately adjacent to cells removed by fs laser irradiation. CONCLUSIONS: These experiments demonstrate that fs lasers used for bone tissue cutting do not appear to generate significant temperature transients to inactivate proteins and that cellular membrane integrity is disrupted for only a few cell layers.

The zygomatic bone as a potential donor site for alveolar reconstruction--a quantitative anatomic cadaver study.

The aim of this cadaver study was to evaluate the possibility of using the zygomatic bone as an intraoral bone harvesting donor site and to determine the safety of this harvesting procedure. In addition, the volume of bone material harvested from the zygomatic bone was measured. Twenty fixed adult cadavers were used to yield a total of 40 zygomatic bone harvest sites, from which bone was collected. The volume of bone obtained from the zygomatic harvests was measured with a water displacement method and by compressing the graft into a syringe. The safety of the technique was evaluated by assessing possible encroachment upon the neighbouring structures. After bone harvesting, the zygomatic sites were exposed and evaluated for visible perforations or fractures. Possible damage to the neighbouring tissues was also examined with computed tomography scans at 18 sites in nine cadavers. The average bone graft volume obtained from the zygomatic bone was measured to be 0.53 ml (SD 0.25) with water displacement and 0.59 ml (SD 0.26) with the syringe. The complications in the zygoma included 15 small perforations into the maxillary sinus and 7 perforations into the infratemporal fossa. CT scans showed that bone could be harvested safely without encroaching upon the orbital floor or the surrounding nerves and vessels in the zygoma. The zygomatic bone is a safe intraoral donor site for the reconstruction of small- to medium-sized alveolar defects.

Impacted third molars and risk of angle fracture.

The purpose of this study was to assess the influence of the presence, position, and severity of impaction of the mandibular third molars, on the incidence of mandibular angle fractures. A retrospective cohort study was designed for patients presenting to the Division of Oral and Maxillofacial Surgery, Toronto General Hospital (Toronto, Canada), for treatment of mandibular fractures from January 1995 to June 2000. The independent variables in this study were the presence, position and severity of impaction of third molars. The outcome variable was the incidence of mandibular angle fractures. Hospital charts and panoramic radiographs were used to determine and classify these variables. The demographic data included age, sex, mechanism of injury and number of mandibular fractures. The study sample comprised 413 mandibular fractures in 214 patients. The incidence of angle fractures was found to be significantly higher in the male population and was most commonly seen in the third decade of life. Assault remained the most significant aetiological factor. Patients with third molars had thrice the increased risk of angle fractures when compared to patients without (P<0.001). Impaction of third molars significantly increased the incidence of angle fractures (P<0.001). The severity and angulation of third molar impactions were not significantly associated with angle fractures. This study provides evidence that patients with retained impacted third molars are significantly more susceptible to angle fracture than those without. The risk for angle fracture, however, does not seem to be influenced by the severity of impaction.

Genetic mutations in certain head and neck conditions of interest to the dentist.

This article identifies certain syndromes of the head and neck, which a dentist may see in clinical practice, and relates these syndromes to their sites of mutation on involved genes. This paper is timely with the near completion of the Human Genome Project, the mapping of the entire human genetic material. Knowing the site of the genetic lesion is important in helping clinicians understand the genetic basis for these conditions, and may help in our future understanding of remedies and treatments.

Successful mandibular reconstruction using a BMP bioimplant.

A bone morphogenetic protein bioimplant was used for primary reconstruction of a 6-cm mandibular discontinuity defect, after a segmental resection of an ameloblastoma. Radiographic evidence of new bone induction was seen at 3 and 9 months, postoperatively. A biopsy was taken at 9 months demonstrated viable new bone formation at the bioimplant site. This is the first reported case using a bone morphogenetic protein bioimplant in a human, followed by histological confirmation of new bone.

Autogenous tooth transplantation: an alternative to dental implant placement?

Autogenous tooth transplantation, or autotransplantation, is the surgical movement of a tooth from one location in the mouth to another in the same individual. Once thought to be experimental, autotransplantation has achieved high success rates and is an excellent option for tooth replacement. Although the indications for autotransplantation are narrow, careful patient selection coupled with an appropriate technique can lead to exceptional esthetic and functional results. One advantage of this procedure is that placement of an implant-supported prosthesis or other form of prosthetic tooth replacement is not needed. This article highlights the indications for autogenous tooth transplantation using 3 case reports as examples. A review of the recommended surgical technique as well as success rates are also discussed.

The epidemiology of mandibular fractures treated at the Toronto general hospital: A review of 246 cases.

BACKGROUND: Mandibular fractures constitute a substantial proportion of cases of maxillofacial trauma. This study investigated the incidence, causes and treatment of mandibular fractures at a hospital in Toronto. METHODS: The medical records and radiographs for 246 patients treated for mandibular fracture at the Toronto General Hospital over a 51 2-year period (from 1995 to 2000) were reviewed. Data on the patients age, sex, smoking status, alcohol and drug use, mechanism of injury, treatment modality, and post-operative complications were recorded and assessed. RESULTS: Men 21 to 30 years of age sustained the most mandibular fractures. The ratio of males to females was 5:1. Most fractures were caused by violent assault (53.5%), followed by falls (21.5%) and sports activities (12.2%). Alcohol was a contributing factor at the time of injury in 20.6% of fractures for which this information was available. Nearly half of all cases were treated by open reduction (49.1%). Complications occurred in 5.3% of patients. CONCLUSION: The incidence and causes of mandibular fracture reflect trauma patterns within the community and, as such, can provide a guide to the design of programs geared toward prevention and treatment.

Nodular fasciitis in the oral cavity.

Rapidly growing soft-tissue lesions in the oral and maxillofacial region can represent a variety of diagnoses involving radically different treatment modalities. Accurate diagnosis is important to avoid unnecessary and often mutilating surgery. Nodular fasciitis is a rapidly proliferating fibroblastic lesion that presents as a tumour-like mass. Although up to 20% of cases occur in the head and neck region, lesions of the oral cavity are extremely rare. A case of oral nodular fasciitis is described, and a review of the literature is presented.

Bone morphogenetic protein excipients: comparative observations on poloxamer.

Clinicians await the availability of synthetic bioimplants that will replace the need for autogeneic bone grafts in bone reconstructive surgery. For more than a decade, researchers have evaluated delivery vehicles for the tissue morphogen bone morphogenetic protein. The object of this investigation was to measure induced bone development when bone morphogenetic protein was delivered by human tendon collagen, human demineralized bone matrix, hydroxyapatite, a composite of human tendon collagen and human demineralized bone matrix (tendon collagen + demineralized bone matrix), Poloxamer 407, and a composite of human demineralized bone matrix and Poloxamer 407. Sixty-three adult male Swiss Webster mice (Harlan Sprague-Dawley, Indianapolis, Ind.) received 126 implants. The animals were divided into seven groups of nine animals, depending on carrier (six carriers plus the positive control group) used. Each animal received a bone morphogenetic protein-enhanced carrier in one hindquarter muscle mass, with the contralateral leg being implanted with the carrier alone. Implants were evaluated by quantitative radiomorphometry validated by histologic methods. Radiographically, no significant differences were identified among any of the implants evaluated (p > 0.05). Histomorphometric analysis demonstrated that Poloxamer 407 was significantly (p < 0.05) better at delivering bone morphogenetic protein than the other carriers involved in this investigation. The new bone developed in a tubular or spherical shape. Interaction of endogenous and exogenous delivery systems seems to be essential for optimal transmission of bone morphogenetic protein. The importance of the excipient to deliver bone morphogenetic protein and develop a bone morphogenetic protein concentration gradient has been emphasized by other investigators and confirmed by our research on poloxamer. With further research on the physicochemical mechanisms of localization and transmission of bone morphogenetic protein, it may be possible to avoid hazardous operations with autogeneic bone.

Differences between the sexes in post-surgical pain.

It has been shown that women have a lower pain threshold and lower tolerance to some forms of experimental pain then men. However, the evidence that clinical pain is perceived differently by the two sexes is not yet as strong. The placement of intraoral implants is a highly controlled surgical procedure that we have used to investigate this possibility. Forty-eight edentulous (without teeth) subjects (27 females), aged from 35 to 63 years, received two titanium implants in the anterior mandible under local anesthesia. After the surgery, subjects completed a pain diary three times each day, rating pain intensity and unpleasantness on 100 mm visual analog scales (VAS). Once a day, they chose verbal descriptors from the McGill Pain Questionnaire (MPQ). Age of subjects, duration of surgery, the amount of local anesthetic used and the amount of pain medication taken were not statistically different for the two groups (P>/=0.32). Results showed that the senior surgeon produced significantly less pain than a 4th year resident (P=0.04). Although there were no significant differences between sexes for mean daily ratings of intensity or unpleasantness over time (P>/=0.10), most women experienced the highest intensity of pain during the day, while most men had higher pain in the evening (P=0.025). Also, the relative unpleasantness (unpleasantness/intensity ratio) increased significantly with time for males, but not for females (P=0.016). Males and females did not differ in the total number of words chosen from the MPQ (P=0.61), or in the averaged Pain Rating Index (PRI) (P=0.53). However, women used significantly more evaluative words than men (P=0.04), suggesting that woman found the overall intensity greater. These results indicate that women find post-surgical pain more intense than males, but that men are more disturbed than women by low levels of pain that last several days.

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses: evaluation of masticatory function.

Sixteen edentulous subjects participated in a within-subject crossover clinical trial to test the hypotheses that a long-bar overdenture attached to 4 implants gives greater patient satisfaction and masticatory efficiency than a two-implant hybrid overdenture. All subjects were given a new maxillary conventional denture. Ten received mandibular long-bar overdentures first and six the hybrid overdentures. Two months later, psychometric assessments and functional tests were repeated 3 times at one-week intervals. The mandibular prosthesis was then changed, and recordings were repeated after another 2 months. Mandibular movements and electromyographic activity of jaw muscles were recorded while subjects chewed standard-sized pieces of 5 foods: bread, cheese, apple, sausage, and carrot. Measurements included masticatory time, cleaning time (the time between the end of mastication and the last swallow), and duration and amplitude of masticatory cycles and phases. Multilevel analyses were performed. No significant differences in masticatory time were found between prostheses for any test food. However, cleaning time for carrot [estimated mean of difference (delta) +/- SE: 1.6 sec +/- 0.7] and bread (delta = 1.0 sec +/- 0.4) was slightly but significantly longer for subjects wearing long-bar overdentures. Cycle duration was longer with the long-bar overdenture only for subjects chewing carrot. The opening phase was shorter and the closing phase longer with the long-bar overdenture for almost all test foods. Vertical amplitude was significantly less with the long-bar overdenture for cheese (delta = -2.6 mm +/- 1.1), apple (delta = -2.6 mm +/- 1.0), and sausage (delta = -2.9 mm +/- 1.3). These results suggest that mastication with the 2 prostheses is equally efficient, although clearance of some foods from the mouth is longer with the long-bar overdentures. They also indicate that patients adapt their masticatory movements to the characteristics of different prostheses.

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses: psychometric evaluation and patient preference.

Although it has been shown that patients are more satisfied with prostheses supported by implants than with conventional dentures, there have been few direct comparisons of the various designs of implant-supported prostheses. This within-subject crossover clinical trial was designed to compare two forms of removable prostheses which are frequently prescribed for the edentulous mandible: a long-bar overdenture supported by 4 implants and a two-implant hybrid overdenture. Sixteen completely edentulous subjects were given a new maxillary conventional denture: Ten of them received the mandibular long-bar prosthesis first and six the hybrid. After a two-month adaptation period, psychometric measures of various aspects of the prostheses and physiological tests of masticatory efficiency were carried out over three weeks. The mandibular prostheses were then changed and the procedures repeated. At the end of the study, subjects were asked to choose the mandibular prosthesis that they wished to keep, and final psychometric measures were taken. In this paper, the results of the psychometric assessment and patient preference are presented. Subjects assessed factors such as general satisfaction, quality of life, stability, retention, comfort, esthetics, ease of cleaning, speaking, and chewing, and how well-chewed foods were before being swallowed. Most of the factors except ease of cleaning and speaking were rated significantly better with long-bar overdentures than with hybrid ones. These results are consistent with the fact that all subjects chose long-bar overdentures, reporting stability, ease of chewing, and comfort as the most important factors influencing their choice. These results suggest that, although subjects assign high ratings for most factors to hybrid overdentures, they find long-bar overdentures to be significantly more stable, comfortable, and easier for chewing.

Morphologic and radioautographic studies of bone formation in relation to titanium implants using the rat tibia as a model.

A rat tibia model was developed to analyze bone formation leading to osseointegration with threaded titanium implants. Miniaturized titanium implants were placed in the anterior aspect of the upper tibia of rats weighing 350 g. Twenty-four rats were involved; 12 rats were sacrificed at 6 weeks, and another two rats were sacrificed weekly for 6 weeks following implantation. Four days prior to sacrifice, the animals were injected intraperitoneally with 3H-proline (10 microCi/g body weight). The rats were fixed by perfusion with 5% glutaraldehyde, and the tibia were decalcified and embedded in Epon. The implants were removed from the embedded bone by fracturing, and the specimens re-embedded. Sections were prepared for light and electron microscopy and radioautography. Morphologic observations indicated that implant placement resulted in bone necrosis and resorption. This was followed by bone growth from the old bone surfaces filling the threads with vascular channels and new lamellar bone. Osseointegration was complete at 6 weeks in all animals examined. Electron microscopy at various places along the bone-titanium interface showed an amorphous layer, a granular electron-dense layer, or a layer of uncalcified collagen fibrils. At each week after surgery, radioautography showed the position and thickness of new bone labeled with 3H-proline during the last 4 days. Radiolabeled new bone was deposited only on previously existing bone and extended toward the available space. Since there was no apparent relationship between the implant and the new bone, it was suggested that titanium is biocompatible, but not necessarily osteoinductive.

Development of a rat tibia model for morphological studies of the interface between bone and a titanium implant.

Over the last decade, osseointegrated dental implants have become an integral part of the restorative dental armamentarium. Reproducible success rates approaching 100% further emphasize the importance and value of this treatment modality. Still, a significant waiting period is required between implant placement and prosthesis delivery, which necessitates a two-surgery approach for implant protection during healing. This article discusses the development of an animal model that is being used to investigate methods of manipulating the healing process of bone next to dental implants. Osseointegration has been shown to occur at 6 weeks in the rat tibia model, demonstrating many of the same characteristics seen in humans. The successful manipulation of bone next to the implant surface may ultimately lead to a surgical protocol for the placement of dental implants requiring only one surgery, significantly reducing the overall healing time.

Maxillofacial considerations for diagnosis and treatment in Gorlin's syndrome: access osteotomies for cyst removal and orthognathic surgery.

Gorlin's syndrome is a complex hamartomatous/neoplastic syndrome with multisystemic manifestations involving the skin, central nervous system, and bony skeleton. The purpose of this article is to describe how a patient with Gorlin's syndrome was managed with a multipronged approach that included exposure osteotomies for keratocyst removal combined with orthognathic surgery. This case demonstrates the advantages of standard maxillofacial osteotomies to gain access for the removal of odontogenic cysts and benign tumors.