Problems associated with the atrophic mandible

A range of treatment options has been presented regarding the use of dental implants to rehabilitate patients who otherwise have compromised function using conventional tissue-borne prostheses. This patient population offers significant challenges to both the surgeon and the prosthodontist. Generally speaking, IODs retained on two or more endosteal osseointegrated implants; transosteal, subperiosteal, ramus frame implant-supported and implant-retained prostheses, and a totally implant-supported design offer options to treat the severely atrophic mandible. When bone support or volume is so lacking that augmentation procedures are required, bone grafting can be considered as a treatment option. The state-of-the-art of implant treatment for the atrophic mandible offers to the dental professional and patient a variety of options. Thus far, it is too early to make specific recommendations as to which treatment offers the best option for each patient. It is fair to say that the ISP remains the gold standard against which other treatments can be compared.     

Esthetic and prosthetic procedures in single-tooth replacement

Loss of anterior maxillary teeth always results in bone resorption and loss of interdental papillae, and the resorption makes a single tooth replacement by a dental implant very difficult. When infections have been present and the patient's history shows previous surgery at the apex of the root, bone destruction is substantial, which results in an increased resorption defect, thereby further increasing the aesthetic and prosthetic problems. This paper describes the steps necessary for implant surgery and the prosthetics; a brief summary is provided. The quality and quantity of bone, along with the space available between the adjacent teeth, are the basic factors in treatment planning and determine the type of implant to be used. Some resorption and bone defects are usually present after a tooth extraction, and bone regeneration procedures can be performed either before or simultaneously with the implant placement, with numerous flap designs available. Soft tissue augmentation can be achieved by taking a connective tissue graft from the palatal side. Antirotational devices (eg, hex lock abutments) are necessary for all implants in single tooth replacement. Screw-retained abutments can be used in posterior areas and in angled positions in facial areas as well. With proper single tooth implant position, cementation of laboratory fabricated crowns can be considered.     

Blood transfusion practices in Mwanza Region, Tanzania. Bugando Medical Centre

Uncertainty exists about the forces applied by dentists during dental crown cementation. A measuring system was developed based around a commercially available miniature (3.8 mm high and 12.7 mm diameter) load cell. The load cell was mounted in a finger stall and the applied force measured. Experimental results suggest that dentists typically apply a force to metal crowns of about 60 N for a few seconds, followed by the application of a steady force of about 20 to 30 N. Lower forces are applied to porcelain crowns.     

Comparison of position repeatability of a human operator and an industrial manipulating robot

STATEMENT OF PROBLEM: Implant-supported restorations in the partially edentulous jaw have been performed at the Mayo Clinic for more than 10 years. Clinical performance of the implants and the prostheses should be reported to ensure effectiveness of this procedure. PURPOSE: This retrospective study described results for implant survival, implant fracture rate, prosthetic complications, and design changes that may impact these results. MATERIAL AND METHODS: A retrospective chart review was conducted of all registered implant patients in a large multispecialty medical center. Patients with a partially edentulous jaw who had received endosseous implants to support and retain dental prostheses were included in this review. Implant survival and fracture, prosthetic complications, and demographic data were recorded and analyzed through Kaplan-Meier methods. RESULTS: A total of 1170 implants were placed in four anatomic locations: anterior maxilla, posterior maxilla, anterior mandible, or posterior mandible. Location of implants was shown to have no effect on implant survival (p = 0.7398), implant fracture rates (p = 0.2385), screw loosening (p = 0.8253), or screw fracture (p = 0.2737). Development of new restorative components has resulted in significantly better rates of implant survival without fracture (p = 0.0054), screw function without loosening (p < 0.0001) and screw function without fracture (p = 0.0013). Implant survival seems to have been improved with the new components (p = 0.0513). CONCLUSIONS: Implant survival in this study was independent of anatomic location of implants. Virtually all clinical performance factors were improved by design changes in implant restorative components that were brought to market in early 1991.     

A survey of general dentists in Ontario, Part II: Knowledge and use of topical fluoride and dental prophylaxis practices

A mail questionnaire was used to assess variations in the knowledge and practices of Ontario dentists with respect to topical fluoride and prophylaxis procedures. The questionnaire was answered by 1,276 general dentists. A high percentage (72 to 83 per cent) of respondents identified six months as the optimal time interval at which both procedures should be repeated for all patients under 19 years of age. Relatively few dentists (< 10 per cent) indicated that there should be no specific time interval for re-treatment (i.e. that it should be individually selected). The respondents' preventive knowledge was found to be deficient in two areas: few dentists (16 per cent) knew that it is not necessary to provide a prophylaxis prior to topical fluoride application to achieve maximum caries protection; and most dentists overestimated the speed of caries progress from outer enamel to the dentinoenamel junction (DEJ) in both primary (83 per cent) and permanent (82 per cent) approximal tooth surfaces. In bivariate analysis, three variables were found to be consistently and significantly related to optimal time intervals selected for both topical fluoride application and prophylaxis procedures: year of graduation from dental school; level of hygienist employment; and percentage of patients with private insurance. Multivariate analysis also identified three significant variables: year of graduation from dental school; level of dental hygienist employment; and practice business. Continuing education courses are suggested as a means of updating dentists' knowledge regarding preventive services. Studies are needed to determine the extent to which recent recommendations regarding the professional application of topical fluorides have been followed.     

The provision of orthodontic services by general dental practitioners. 1. Methods and descriptive results

Information regarding orthodontic service provision by general dental practitioners in Australia is limited. The aim of this survey was to determine the amount and variety of orthodontic services provided by general dental practitioners in the Melbourne Statistical Division, Victoria, Australia. A random sample of 307 dentists drawn from the Victorian Dentists Register was surveyed by mailed questionnaire: 218 (71%) replied. Data were collected using a fortnight log. During this time 59 per cent of the dentists saw at least one orthodontic patient; one dentist saw 66 orthodontic patients. Removable orthodontic appliances were used by 35 per cent of the dentists and fixed orthodontic appliances by 18 per cent. Twenty-six per cent provided comprehensive orthodontic treatment, 22 per cent aligned incisors, and 21 per cent corrected anterior crossbites. The general dental practitioners surveyed provided a wide range of preventive and interceptive orthodontic services to generally a small percentage of their patients.     

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part I: Methodology and clinical outcomes

STATEMENT OF PROBLEM: Scientific evidence is lacking to support the general application of implant-supported mandibular overdentures. PURPOSE: This randomized clinical trial was undertaken to compare the efficacy of conventional mandibular and implant-supported overdentures in diabetic edentulous patients with clinically acceptable metabolic control. METHOD: A total of 102 diabetic patients, treated with or without insulin, were randomized to receive a new maxillary denture and either a conventional or an implant-supported removable mandibular overdenture. Treatment was completed for 89 patients, 37 with the conventional and 52 with implant-supported dentures. Detailed examinations, tests, and questionnaires were given before and at 6- and 24-months after treatment completion. Comparisons between the two treatment groups were made for treatment failures based on prespecifed criteria and the type and amount of maintenance care provided. RESULTS: The insulin and noninsulin treated groups were collapsed because of the lack of significant differences at entry. The conventional denture and implant-supported overdenture groups were similar in terms of general demographics, medical status, quality of their original dentures and denture support, several functional measures, and patient satisfaction. Treatment was judged to be successful in 56.9% of patients with conventional dentures and 72.1% with overdentures. This difference in success rate was not statistically significant (p > 0.05). Patients with treatment failures in both groups required excessive maintenance care. Those with conventional dentures needed frequent denture base adjustments and relines, whereas those with overdentures required frequent clip replacements and repairs. Although significant improvements were seen with both treatment modalities, a higher percentage of patients with implant-supported overdentures than those with conventional dentures reported improvements in chewing comfort and moderate-to-complete overall satisfaction.     

A new angle on restoring anterior teeth with root-form implants: clinical report

Root-form implants may be indicated for the replacement of missing anterior teeth. Occasionally fixtures are placed in a position inconsistent with proper tooth alignment. The new PreAngled Abutment (Dentsply/Implant Division, Encino, CA) addresses this problem and was used to successfully restore missing tooth numbers 7 and 8 for a patient that had two malpositioned implants.     

Altered patterns of DNA methylation on chromosomes from leukemia cell lines: identification of 5-methylcytosines by indirect immunodetection

The feasibility of implant treatment in patients after oral ablative tumor surgery has not yet been investigated with consideration of the requisite high periodontal standards. A report on this topic has to deal not only with implant survival but also with implant health, bone response, soft tissue health, failure pattern, time of failure, and ease of restoration. For the assessment of an implant system, an overview must be accomplished that takes into account the different restorations used and their interaction with the implant system that was used. This study presents the Bone-Lock implant system (Howmedica Leibinger GmbH, Freiburg, Germany) in a retrospective investigation after 5 years of follow-up with special emphasis on the prosthetic restorations used following resection of oral malignancies. From early in 1990 through June 1996, we inserted 210 dental endosteal Bone-Lock implants (58 patients) after oral tumor resectioning. Included in the study were 45 patients with 162 implants and prosthetic restorations that had been loaded for 1 year (dentures retained by telescopic or bar-clip or ball attachments, implant-supported prostheses, tooth-to-implant connected bridges). Regular follow-up consisted of evaluation of the Plaque Index (Silness and L?e) and of the Sulcus Bleeding Index (L?e), measurements of pocket probing depth, implant mobility (by means of the Periotest method), bone resorption (according to X-ray findings), and a questionnaire that registered patient satisfaction. The results were evaluated for each restoration and were compared with baseline standards. The overall 5-year survival rate was 83.2%. For implants that had been in place for over 365 days, the survival rate was 93%. The investigation showed that after resection of oral malignancies, patients could be treated with dental implants and superstructures with long-term efficacy similar to that found in healthy subjects considering internationally accepted standards. Implant treatment in tumor patients appeared to offer the most positive periodontic results when use of bar-clip or telescope-retained overdentures was involved. The patient satisfaction level with the described prosthodontic treatment was satisfactory.     

Radiographic modalities for diagnosis and treatment planning in implant dentistry

Early in the development of implant technology it became apparent that conventional dental imaging techniques were limited for evaluating patients for implant surgery. During the treatment planning phase, the recipient bed is routinely assessed by visual examination and palpation, as well as by periapical and panoramic radiology. These two imaging modalities provide a two-dimensional image of mesial-distal and occlusal-apical dimensions of the edentulous regions where implants might be placed. When adequate occlusal-apical bone height is available for endosteal implants, the buccal-lingual width and angulation of the available bone are the most important criteria for implant selection and success. However, neither buccal-lingual width nor angulation can be visualized on most traditional radiographs. Although clinical examination and traditional radiographs may be adequate for patients with wide residual ridges that exhibit sufficient bone crestal to the mandibular nerve and maxillary sinus, these methods do not allow for precise measurement of the buccolingual dimension of the bone or assessment of the location of unanticipated undercuts. For these concerns, it is necessary to view the recipient site in a plane perpendicular to a curved plane through the arch of the maxilla or mandible in the region of the proposed implants. Implant dentists soon recognized that, for optimum placement of implants, cross-sectional views of the maxilla and mandible were the ideal means of providing necessary pre-operative information. Today, the two most often employed and most applicable radiographic studies for implant treatment planning are the panoramic radiograph and tomography. Although distortion can be a major problem with panoramic radiographs, when performed properly they can provide valuable information, and are both readily accessible and cost efficient. To help localize potential implant sites and assist in obtaining accurate measurements, it is recommended that surgical stents be used with panoramic radiographs. In simple cases, where a limited number of implants are to be placed, panoramic radiography and/or tomography may be used to obtain a view of the arch of the jaw in the area of interest. For complex, cases, where multiple implants are required, the CT scan imaging procedure is recommended. Because of its ability to reconstruct a fully three dimensional model of the maxilla and mandible, CT provides a highly sophisticated format for precisely defining the jaw structure and locating critical anatomic structures. The use of CT scans in conjunction with software that renders immediate "treatment plans" using the most real and accurate information provides the most effective radiographic modality currently available for the evaluation of patients for oral implants. To follow patients after implant surgery, DSR can be helpful by addressing the limitations of other radiographic modalities in detecting postoperative changes. By eliminating unchanged information, DSR allows the clinician's eye to focus on actual changes that have occurred between the recordings of two images.     

Affordable implant prosthetics using a screwless implant system

Many dentists have been reluctant to place dental implants because they have found that most implants are costly and time-consuming to place and have long-term maintenance problems. Most of these problems are caused by using screws to connect the abutment to the implant, the crown to the abutment or both. The use of a screwless implant system and conventional prosthetics, the author contends, can make implant dentistry affordable, versatile and easy to incorporate into all general dental practices.     

Biomechanical considerations when combining tooth-supported and implant-supported prostheses

The force distribution of multiple tooth-supported and implant-supported prostheses is completely different. A direct correlation exists between the degree of flexion at the site of loading and the amount of force distribution to other members of the prosthesis. Micromovement produced by the periodontal fibers facilitates force distribution to all the root surfaces of the natural tooth abutments. The rigidity of the implant/abutment/prosthesis configuration concentrates the force at the crestal bone at the site of loading with limited distribution to the remaining implants. Differential mobility concentrates the force distribution to the bone support of the most rigid members of splinted natural teeth or to the implants when they are united with natural teeth in a combined prosthesis. Implants always support the natural teeth and never the other way around. Therefore a nonrigid attachment is recommended between a tooth-supported prosthesis and an implant-supported prosthesis when they are combined. However, when implants are interspersed with natural teeth in the same prosthesis, the restoration will be implant borne. This requires special force distribution analysis to prevent implant overload.     

Comprehensive dental treatment of healthy and chronically sick children under intubation general anaesthesia during a 5-year period

OBJECTIVE: To quantify the number of extractions and/or restorations placed in chronically sick children under intubation general anaesthesia and compare these findings with healthy children. SETTING: Two large paediatric dentistry units in Central London: a tertiary referral centre dealing with severe chronic sickness in children and an undergraduate dental school with a large commitment to special needs dentistry in children. DESIGN: Prospective comparison of treatment received for (a) chronically sick children and (b) dentally anxious (otherwise fit) children receiving intubation general anaesthesia during July 1991 to June 1996 inclusive. The statistical tests used were the Shapiro-Wilks test for normality and the Mann Whitney U test for non-parametric comparison of independent groups. MAIN OUTCOME MEASURES: Mean total treatment tally (TTT)--the sum of extractions and restorations for each child presented as summary data. RESULTS: Different patterns of dental care were found between the healthy and chronically sick groups. For similar levels of disease, a significantly greater number of extractions were carried out for chronically sick children (P < 0.0001), and significantly fewer restorations (P < 0.0001). The number of pulpotomies and stainless steel crowns provided to sick children was significantly smaller than to healthy children (P < 0.0001). This paper discusses the influences of chronic ill health on dental treatment provided under general anaesthesia. CONCLUSION: The underlying medical disorder in chronically sick children significantly influences the pattern of treatment when this is provided under general anaesthesia.     

Dentoalveolar morphology: evaluation of natural root form versus cylindrical implant fixtures

The function of implant-supported restorations is now routinely achieved. As a result, the emphasis in restorative implant dentistry has shifted from function to aesthetics and the biocompatibility of the materials utilized. The learning objective of this article is to review the three major components essential to achieving natural aesthetics in implant-supported restorations--hard tissue dynamics, soft tissue dynamics, and dental aesthetics. Particular emphasis is directed to the dentoalveolar anatomy and morphology. Analysis of the tooth root morphology and dimensions has resulted in the design and fabrication of restorative components with dimensions that closely resemble the natural tooth anatomy and aesthetics. A system of transmucosal abutments has been designed, and its utilization is presented in this review.     

Clinical case report: an improved technique for using dental implants as orthodontic anchorage

The use of endosseous implants as intra-oral anchorage to facilitate orthodontic treatment has been reported in the literature for some years, first in rabbits and dogs, and then in adult human patients. The implants were generally used solely for the purpose of anchorage. This paper reports the successful application of orthodontic forces utilizing dental implants to achieve tooth movement. The implants were subsequently used as fixtures in a pre-determined plan to support a fixed prosthesis. A clinical example demonstrates how implants may serve dual roles, for anchorage and then for fixed prosthetic support. The principles involved in using dental implants as part of a multi-disciplinary approach to dental treatment are illustrated.     

Survival of cylindrical implants in composite grafted maxillary sinuses

PURPOSE: This retrospective study investigated the survival of dental implants placed in the maxilla after composite grafting of the sinus and an average of 55 months of loading. PATIENTS AND METHODS: Maxillary sinuses of 88 patients were grafted with autogenous cancellous bone combined with dense hydroxyapatite particles. After an average healing period of 3.4 months, hydroxyapatite-coated titanium endosseous implants were placed. A total of 388 implants were placed in grafted sinus floors, and 82 were placed in onlay grafted nonsinus position in the canine region. The implants were loaded with overdentures and fixed bridges 4 months (mean) after implantation, with a follow-up for a mean of 55 months. RESULTS: The cumulative implant survival was calculated according to the Kaplan-Meier method. Implant survival from the time of loading was 89% in full reconstructed cases and 90% in partially edentulous cases. The overall cumulative implant survival rate, including the loss in the surgical stage, was 82%. CONCLUSION: Implant loss in composite grafted maxillae after 70 months of follow-up was similar to loss in nongrafted maxillae.     

Periodontal and dental considerations in clinical crown extension: a rational basis for treatment

When the clinical crowns of teeth are dimensionally inadequate, esthetically and biologically acceptable restoration of these dental units is difficult. Often an acceptable restoration cannot be accomplished without first surgically increasing the length of the existing clinical crowns; therefore, successful management requires an understanding of both the dental and periodontal parameters of treatment. This report provides further insight into this interdependence by examining the effects of tooth form on the periodontal morphology and surgical treatment, while relating them to requirements for esthetically and biologically acceptable full-coverage dental restorations. This report also explains the role that restoration margin location and emergence profile play in the maintenance of periodontal and dental symbiosis. The effects of violation of the supracrestal gingivae by improper full-coverage restorations is also illustrated.     

A longitudinal study of the dental care of adults in the general dental service in Scotland: the first 6 years, 1988-1994

OBJECTIVE: To provide an overview of routine dental care for adults attending the general dental service in Scotland, in a more detailed manner than is currently possible from national data sets. DESIGN AND SETTING: Cohort study in the general dental service. SUBJECTS AND METHODS: The cohort consisted of 992 Scottish dentate adults who participated in the adult dental health survey of 1988, conducted by the Office of Population Censuses and Surveys. Details of subsequent treatment undertaken in the general dental service were provided by Dental Practice Division, Edinburgh. MAIN OUTCOME MEASURES: Production of patient-specific and tooth-specific data on dental attendance and treatment. RESULTS: 71% of the cohort attended at least once in the 6 years. Registration levels, following the introduction of the continuing care contract, reached 42-44%. Observed lapses in registration illustrate the changing membership of the relatively static level of registration year-on-year. Vulnerability to treatment of different tooth sites is illustrated graphically. CONCLUSIONS: Cohort studies provide valuable information on patterns of attendance and treatment needed for planning of dental health services. Growing computer power and increasing demands for management data may mean that future work of this nature can be more appropriately undertaken at the population level.     

Implant-supported overdenture therapy: a retrospective study

All patients (n = 46) treated with implant-supported overdentures at the Department of Prosthetic Dentistry, Dental and Medical Health Centre, Halmstad, Sweden, from 1986 to 1993 were studied. The clinical examination was completed in 1994. The material was divided into two subgroups: Group A had been initially treatment planned for an implant-supported overdenture, and Group B had been planned for fixed prostheses but because of loss of implants before loading, treatment with a fixed prosthesis was not possible. The authors present their experience and patient reactions to overdenture therapy in two defined groups of patients. The implant failure rate before loading for Group A (n = 12) was 15% (six implants out of 39), and the rate before loading for Group B (n = 29) was 43.6% (68 implants out of 156). After prosthodontic treatment in Group A, the implant success rate after loading was 87.9%, and the overdenture stability was 84.6%. In group B, 17 implants placed in the maxillae were lost after overdenture therapy, which resulted in an implant success rate of 79.3%. A total of eight overdentures, all of which had been placed in the maxillae, were lost, resulting in an overdenture stability of 73.3%. In this study "change of retentive clips" was the predominant prosthodontic complication related to the overdentures, especially in Group B. Most of these complications (62%) occurred in patients with clinical signs of bruxism. Patient reactions to treatment with an overdenture were positive regarding esthetics for both groups. More negative views were recorded in Group B than in Group A in response to function and retention of the overdenture.     

The nonsubmerged osseointegrated dental implant

Implant patients are seeking means of restoring their health and appearance with minimal side effects. Dental implant surgery must react to these demands by continuing to develop minimally invasive implant surgery techniques, imaging that customizes surgical procedures, and materials and drugs that reduce surgical costs and complications, shorten recovery, and increase the longevity of components, enabling patients to live active lifestyles. Nonsubmerged osseointegrated implants fit nicely into the future of dental surgery.