Remote implant anchorage for the rehabilitation of maxillary defects.

The rehabilitation of maxillary defects is a significant challenge in terms of creating retention and preserving existing dentition in an environment of expanded functional stress. The advent of osseointegration has enhanced the dental practitioner's capabilities in this regard with a remarkably improved potential for increasing prosthesis stability and preserving tissue. For patients with extensive prosthetic cantilevers, however, the opportunity for implant placement in defect areas is compromised unless remote bone sites are considered. Implants in the defect buttress zone through the maxillary sinus in non-defect sites (zygoma implants) can be valuable in providing a level of functional rehabilitation previously unattainable.

DNA triple-helix formation at pyrimidine-purine inversion sites.

A systematic investigation of a series of triplex forming oligonucleotides (TFOs) containing alpha-, and beta-thymidine, alpha- and beta-N7-hypoxanthine, and alpha- and beta-N7 and N9 aminopurine nucleosides, designed to bind to T-A inversion sites in DNA target sequences was performed. Data obtained from gel mobility assays indicate that T-A recognition in the antiparallel triple-helical binding motif is possible if the nucleoside alpha N9-aminopurine is used opposite to the inversion site in the TFO.

Triple-helix formation in the antiparallel binding motif of oligodeoxynucleotides containing N(9)- and N(7)-2-aminopurine deoxynucleosides.

Triplex-forming oligodeoxynucleotide 15mers, designed to bind in the antiparallel triple-helical binding motif, containing single substitutions (Z) of the four isomeric alphaN(7)-, betaN(7)-, alphaN(9)- and betaN(9)-2-aminopurine (ap)-deoxyribonucleosides were prepared. Their association with double-stranded DNA targets containing all four natural base pairs (X-Y) opposite the aminopurine residues was determined by quantitative DNase I footprint titration in the absence of monovalent metal cations. The corresponding association constants were found to be in a rather narrow range between 1.0 x 10(6) and 1.3 x 10(8) M(-1). The following relative order in Z x X-Y base-triple stabilities was found: Z = alphaN(7)ap: T-A > A-T> C-G approximately G-C; Z = betaN(7)ap: A-T > C-G > G-C > T-A; Z = alphaN(9)ap: A-T = G-C > T-A > C-G; and Z = betaN(9)ap: G-C > A-T > C-G > T-A.

Strong, specific, monodentate G-C base pair recognition by N7-inosine derivatives in the pyrimidine.purine-pyrimidine triple-helical binding motif.

The nucleoside analogs 7-(2'-deoxy-alpha-D-ribofuranosyl)hypoxanthine (alpha7H,1), 7-(2'-deoxy-beta-D-ribofuranosyl)hypoxanthine (beta7H,2) and 7-7-(2'-O-methyl-beta-D- ribofuranosyl)hypoxanthine (beta7HOMe,3) were prepared and incorporated into triplex forming oligodeoxynucleotides, designed to bind to DNA in the parallel (pyrimidine.purine-pyrimidine) motif. By DNase I footprinting techniques and UV-melting curve analysis it was found that, at pH 7. 0, the 15mer oligonucleotides d(TTTTTMeCTXTMeCTMeCTMeCT) (MeC = 5-methyl-deoxycytidine, X =beta7H,beta7HOMe) bind to a DNA target duplex forming a H.G-C base triple with equal to slightly increased (10-fold) stability compared to a control oligodeoxynucleotide in which the hypoxanthine residue is replaced by MeC. Remarkably, triple-helix formation is specific to G-C base pairs and up to 40 microM third strand concentration, no stable triplex exhibiting H.A-T, H.T-A or H.C-G base arrangements could be found (target duplex concentration approximately 0.1 nM). Multiply substituted sequences containing beta7H residues either in an isolated [d(TTTTTbeta7HTbeta7HTbeta7HTbeta7HTbeta7HT)] or in a contiguous [d(TTTbeta7Hbeta7Hbeta7Hbeta7HTTTTbeta7HTTT)] manner still form triplexes with their targets of comparable stability as the control (MeC-containing) sequences at pH 7.0 and high salt or spermine containing buffers. General considerations lead to a structural model in which the recognition of the G-C base pair by hypoxanthine takes place via only one H-bond of the N-H of hypoxanthine to N7 of guanine. This model is supported by a molecular dynamics simulation. A general comparison of the triplex forming properties of oligonucleotides containing beta7H with those containing MeC or N7-2'-deoxyguanosine (N7G) reveals that monodentate recognition in the former case can energetically compete with bidentate recognition in the latter two cases.

Prosthesis design and treatment planning for the partially edentulous implant patient.

The evolution of prosthesis design principles over the last ten years has contributed to an improved clinical prognosis for the partially edentulous patient. Restorations can now be created with significant cosmetic improvements and less stressful long-term maintenance, due to a better understanding of restorative procedures which include natural tooth connection, biomechanical loading, tooth form modifications, and esthetic componentry. This presentation will review these concepts as the basis for recommending currently acceptable design principles and treatment plans for the fixed reconstruction of the partially edentulous implant patient.

Provisional implant-supported fixed restorations.

Implant-supported provisional restorations serve several valuable functions. In the anterior region, they are beneficial in determining the best restorative design, ultimately allowing for the most appropriate definitive prosthesis. They also provide a template around which soft tissue contours may be evaluated and manipulated. In areas where bone quality is compromised and implant success is suspect, whether it be anteriorly or more likely posteriorly, implant-supported provisional restorations may be used to "test" the osseointegration prior to fabricating and placing the definitive restorations.

A survey of natural tooth abutment intrusion with implant-connected fixed partial dentures.

To elicit information about the phenomenon of intrusion of natural tooth abutments in implant-connected prostheses, a survey was distributed to clinicians with varied experience. Although practitioners with more experience in fabricating implant-supported dentures connected to natural teeth reported fewer instances of intrusion, it cannot be concluded that this observation is significant. The cause of intrusion is probably multifactorial, and respondents suggested several possible causative factors: disuse atrophy, debris impaction, impaired rebound memory, and mechanical binding. Because apical migration of abutment teeth affects occlusion and oral hygiene, the authors make several recommendations for treatment planning for patients who have natural dentition adjacent to proposed implant sites.

Craniofacial osseointegration: the Canadian experience.

A survey was undertaken to determine the number of centers in Canada with an active involvement in extraoral osseointegration. It was found that six centers had placed 222 implants in 91 patients in Canada. The individual implant success rates for the Canadian experience were compared with the published Swedish and United States' experience. The Canadian experience is combined with the Swedish and United States' experience to provide retrospective multinational multicenter data. The data given should be viewed as providing trends only and not as definitive expectations of predictable success rates. The success rates are considered likely to change with time as the number of patients treated increases and the duration of follow-up is extended. The mastoid region in nonradiated patients is considered to provide a high degree of predictable individual implant success. The success rates in radiated patients yield far lower success rates, which vary with anatomic location. The criteria for success in using craniofacial implants need to be defined and should reflect the differences between extraoral and intraoral implants.

Electromyographic activity of the jaw-closing muscles in patients with osseointegrated implant fixed partial dentures.

The control of postural and synergistic jaw reflexes involves interrelated sensory input from receptors in the jaw muscles, temporomandibular joint, periodontal ligament, and mucosa. This investigation was done to determine whether a decrease in intraoral sensory afferent discharge significantly altered the onset of the jaw-unloading reflex. The subject population consisted of three groups with 10 subjects in each group. Group 1 had maxillary and mandibular natural teeth and group 2 consisted of edentulous subjects with complete dentures. Group 3 consisted of edentulous subjects with maxillary complete dentures and mandibular complete implant-supported prostheses. The unloading reflex was initiated with a muscle-unloading device and recorded with a storage oscilloscope. A one-way analysis of variance found no significant differences in the unloading-reflex latency for the masseter or temporal muscles among the three experimental groups (p less than 0.05).

The use and fabrication of a self-retaining surgical guide for controlled implant placement: a technical note.

A technique for using a surgical guide construction with a self-retaining feature, which has proven to be a significant improvement for stage 1 surgical procedures, is described. This design is more convenient to use than previously described occlusal extension splints. It maintains the concepts for ideal fixture placement that have proven so valuable in creating both a functionally and esthetically uncompromised prosthesis supported by implants.

The United States and Swedish experience with osseointegration and facial prostheses.

A survey of experience treating patients with extraoral implants for facial prosthesis retention in 13 United States centers and in Sweden has been completed. Patients who have not received radiation for elimination of malignant disease can be treated with reasonably good expectations for long-term success. Reported success rates indicate that patients who have received radiation should be selected carefully and treated with caution, since overall success rates in this category are disappointingly low.

Mandibular fractures through endosseous cylinder implants: report of cases and review.

These case reports and review focus on three mandibular fractures that occurred through endosseous cylinder implant sites. The first patient, and most likely the second, had osteoporotic changes that affected their already atrophic mandibles. The third patient probably had an area of deficient mineralization or poorly consolidated bone in the region where the fracture developed. These bony conditions increased the potential for fracture. Although the exact mechanism by which such fractures occur is not known, an examination of past research suggests that stress concentration at the mandibular defect prepared for implant placement is a probable explanation. The site of an implant that has not yet osseointegrated acts as a site of tensile stress concentration and ultimately an area of weakness. Consequently, this area of weakness in a mandible with decreased bone density or mineralization is more prone to applied functional forces. Repeated submaximal functional forces in an area of bony weakness, such as an endosseous implant site, may lead to a spontaneous fracture with no associated trauma. With these factors in mind, several extra precautions should be taken when implants are placed in thin or weak mandibles.

Immediate fixture placement: a treatment planning alternative.

The rationale and possible clinical applications of an immediate fixture placement technique are described. Although this concept may be a somewhat radical departure from the conventional mandibular protocol, there are significant potential patient benefits with no apparent change in anticipated fixture survival rates. A similar approach in the maxilla may be less practical with most presenting dentitions, but there is evidence that further research may make immediate fixture placement equally appropriate in this arch.

Microwave techniques for fabrication of provisional facial prostheses.

Timely rehabilitation of facial defects necessitates provisional prostheses during the period following surgery. The possibilities of using microwave radiation in the drying of gypsum casts, the preparation of stone molds, the curing of silicone elastomers, and the extrinsic coloring of silicone prostheses are presented. Microwave radiation has the potential for saving time, energy, and resources during the fabrication of provisional facial prostheses.

Fabrication of facial prostheses by applying the osseointegration concept for retention.

Initial clinical studies applying the osseointegration concept for retention of facial prostheses have been encouraging. The results of these preliminary investigations indicate new treatment possibilities with facial prostheses anchored to the cranial skeleton by osseointegrated implants. Osseointegrated rehabilitation of the maxillofacial prosthetic patient presents the potential for overcoming many of the disadvantages associated with conventional retentive methods. Fabrication and support for facial prostheses by using osseointegrated implants for retention are described.

An intraoral drug delivery system.

Topical drug therapy for ulcerative and vesiculobullous diseases of the oral mucosa has generally proved unsatisfactory because of the turbulent and changing nature of the oral cavity. The construction and use of an intraoral drug delivery system using custom carriers to deliver topical medication is described. The delivery system presented overcomes many of the obstacles associated with topical drug administration for oral lesions and provides a therapeutic alternative to systemic agents.

Modified casting technique for osseointegrated fixed prosthesis fabrication: a preliminary report.

Creating a predictably passive fit of long-span castings supported by osseointegrated implants can be a difficult technical accomplishment. A preliminary report of short-term experience using a modified casting technique that incorporates several new modifications to ensure fit and accuracy is presented. This technique ensures strength in areas where stress concentrations are greatest, while maintaining the philosophy of stress distribution through splinting across the length of the span.

Intranasal prostheses, splints, and stents.

Internal defects of the nose result from congenital abnormalities, trauma, tumor excision, and complications of cosmetic or airway enhancement procedures. Since the nose is a prominent feature of the face, and nasal deformities present complicated reconstructive problems, the rehabilitation of this structure assumes great importance. Surgical and/or prosthetic procedures using intranasal prostheses, splints, or stents have been developed to improve both form and function. Intranasal prostheses, splints, and stents during nasal rehabilitation can (1) establish and maintain airway patency, (2) maintain tissue position, (3) reduce tissue contracture after surgery, or (4) support mobile tissue in the construction and retention of facial prostheses. Although techniques for managing common problems have been presented in this article, unique clinical situations will arise. Much of the execution and ultimate success of nasal prosthetics will depend upon the ingenuity of the dentist performing the service.