The effect of inter-implant distance on retention and resistance to dislodging forces for mandibular implant-tissue-supported overdentures

OBJECTIVES

The effect of inter-implant distance on retention and resistance of implant-tissue-supported overdentures is lacking in the literature. An in vitro study was performed to evaluate this effect for mandibular implant-tissue-supported overdentures retained by two ball attachments.

MATERIALS AND METHODS

An acrylic cast of an edentulous mandible was fabricated. Three pairs of implants were symmetrically placed at both sides of the midline. The inter-implant distance was 10, 25, and 35 millimeters in positions A, B and C, respectively. A framework simulating the overdenture was fabricated on the cast. Six attachment housings were placed within the overdenture. For each sample, two ball abutments were screwed onto the implant pairs and two pink nylon inserts were seated in their respective attachment housings. The samples were tested in three groups of 15 (A, B, and C). The testing machine applied tensile dislodging forces and peak loads were measured in three directions: vertical, oblique, and anterior-posterior. A one-way ANOVA followed by Tukey's HSD was used to determine groups that were significantly different. Tests were carried out at 0.05 level of significance.

RESULTS

Peak loads for the anterior-posteriorly directed dislodging forces were significantly the highest for group C (P<0.05); 21.25 N±3.05 N, while there were no statistically significant differences among groups with vertically and obliquely directed forces (P>0.05).

CONCLUSION

Inter-implant distance did not affect the vertical retention and oblique resistance of mandibular implant-tissue-supported overdentures; however, it affected anterior-posterior resistance.

Dental students' perceptions of dental specialties and factors influencing specialty and career choices

The goals of this study were to 1) evaluate dental students' perceptions of dental specialties, 2) identify factors that play an important role in students' decision to pursue specialty training or career choices, and 3) establish a baseline of students' perceptions of the dental fields with the best future in terms of salary, personal and patient quality of life, and overall impact on the dental profession. Surveys were distributed to 494 students at the University of Pennsylvania School of Dental Medicine. Data were collected from 380 traditional four-year students and thirty advanced standing students. Chi-square tests, multivariate analysis, and logistic regressions were used to determine associations and independent contributions of student demographics to their perceptions of dental specialties and factors influencing specialty training or career choices. Debt was a statistically significant factor (p<0.001) in choosing specialty training or career independent of gender, age, or class year. Enjoyment of providing care in a specialty or field was identified as the single most important factor in choosing a specialty career. Half of the respondents had decided not to specialize. Pursuing postdoctoral general dentistry training and private practice in general dentistry were the most commonly reported plans after completion of dental school. Suggestions are made for ways to inform students about specialty training.

Treatment of a patient with cleidocranial dysplasia using a single-stage implant protocol

This patient report describes the treatment of a 45-year-old Caucasian woman with cleidocranial dysplasia who had significant dental problems that greatly affected her quality of life. The patient had orthodontic treatment in her earlier years along with surgical removal of supernumerary teeth. Using implants, the maxillary and mandibular arches were restored with fixed screw-retained prostheses. Eight implants and six implants were placed in the maxilla and mandible, respectively. Both arches were immediately loaded following the Teeth in a Day™ protocol using an all-acrylic resin provisional prosthesis. Five months later, definitive maxillary and mandibular prostheses were fabricated. The patient has been followed for a period of 5 years, and all postoperative evaluations have been uneventful.

Dentist communication with the dental laboratory for prosthodontic treatment using implants

PURPOSE

A questionnaire was sent to U.S. dental laboratories to evaluate the level of communication between dentists and laboratory technicians and to determine trends in procedures and materials used in fixed and removable implant restorations.

METHODS AND MATERIALS

Dental laboratories were randomly chosen from the National Association of Dental Laboratories for each of the 50 states. The questionnaire was mailed to the laboratory directors for 199 dental laboratories. One hundred fourteen dental laboratories returned the survey, yielding a response rate of 57%. Of those laboratories, 37 indicated that they did not participate in the fabrication of fixed implant restorations, yielding a response rate of 39%. Forty-two dental laboratories indicated that they did not participate in the fabrication of implant-retained overdenture prostheses, yielding a response rate of 36%.

RESULTS

Results from this survey show inadequate communication by dentists in completing work authorization forms. Custom trays are used more frequently for implant-retained overdenture impressions and stock trays for impressions of fixed implant prostheses. Poly(vinyl siloxane) is the material most commonly used for both fixed and removable implant-supported prostheses. Two implants with stud attachments are used more widely than those with bar attachments for implant-retained overdentures.

CONCLUSIONS

Most laboratories working on implant prosthodontic cases report inadequate communication between the laboratory and dentists related to materials and techniques used in fabrication of implant restorations.

Communication between the dental laboratory technician and dentist: work authorization for fixed partial dentures

PURPOSE

A questionnaire was sent to laboratory technicians to determine the level of communication between dentists and dental laboratories in specific areas of the work authorization forms for the fabrication of fixed partial dentures.

MATERIALS AND METHODS

A select number of dental laboratories were randomly chosen from the National Association of Dental Laboratories (NADL) for each of the 50 states. The questionnaire was mailed to the laboratory directors for a total of 199 dental laboratories. The survey asked questions pertaining to the following areas of work authorization: legibility and thoroughness of prescriptions, patient information, choice of materials for the prosthesis, design of the prosthesis, and shade description. For each question, the number of responses received was tabulated and converted to a percentage.

RESULTS

Of the 199 laboratories surveyed, 114 (57%) responded to the questionnaire. Results from this survey suggest that there is lack of communication between dentists and dental laboratories through work authorization forms regarding choice of metal alloy, type of porcelain to be used, and choice of margin and pontic design for the prosthesis.

CONCLUSIONS

Information obtained from the responding laboratories included effectiveness of work authorization forms. There were some similar trends indicated by the large percentage of dental laboratories agreeing on lack of communication by the dentists as reflected by the work authorization forms.

Teaching implant dentistry in the predoctoral curriculum: a report from the ADEA Implant Workshop's survey of deans

In 2004, a survey of the deans of U.S. and Canadian dental schools was conducted to determine the implant dentistry curriculum structure and the extent of incorporating implant dentistry clinical treatment into predoctoral programs. The questionnaire was mailed to the deans of the fifty-six dental schools in advance of the ADEA Implant Workshop conference held in Arizona in November 2004. Out of the fifty-six, thirty-nine responded, yielding a response rate of 70 percent. Thirty-eight schools (97 percent) reported that their students received didactic instruction in dental implants, while one school (3 percent) said that its students did not. Thirty schools (86 percent) reported that their students received clinical experience, while five schools (14 percent) reported that theirs did not. Four schools (10 percent) did not respond to this question. Fifty-one percent of the students actually receive the clinical experience in restoring implants, with the range of 5-100 percent. Of those schools that provide clinical experience in restoring implants, four schools (13 percent) reported that it is a requirement for them, while twenty-eight schools (88 percent) reported that it is not a requirement for them. Three schools (9 percent) did not respond. The fee for implants is 45 percent higher than a crown or a denture, with a range of 0-100 percent. Twenty-nine schools (85 percent) indicated that they did receive free components from implant companies, while five schools (15 percent) did not. The conclusions of this report are as follows: 1) most schools have advanced dental education programs; 2) single-tooth implant restorations are performed at the predoctoral level in most schools; 3) implant-retained overdenture prostheses are performed at the predoctoral level in most schools; 4) there is no predoctoral clinical competency requirement for surgical implant placement in all schools that responded to the survey; 5) there is no predoctoral clinical competency requirement for implant prosthodontics in most schools that responded to the survey; 6) prosthodontic specialty faculty are often responsible for teaching implant prosthodontics at the predoctoral level; 7) periodontics and oral and maxillofacial faculty are commonly responsible for teaching implant surgery at the predoctoral level; 8) support from implant companies is common for dental schools, with most providing for implant components at discounted costs; and 9) there is a lack of adequately trained faculty in implant dentistry, which is a significant challenge in providing predoctoral students with clinical experience with dental implants.

Removable Partial Denture Education in U.S. Dental Schools

PURPOSE

A survey of U.S. dental schools was conducted in 2001 to determine the curricular structure, techniques, and materials used in predoctoral clinical removable partial denture (RPD) programs.

MATERIALS AND METHODS

The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 schools returned the completed survey, resulting in a response rate of 82%.

RESULTS

Results from this survey show that a large majority of schools are using similar materials in clinical RPDs; for instance, using modeling compound for border molding final impression trays (61%) and using a semi-adjustable articulator for mounting preliminary casts (90%) and final casts (98%). In addition, a large majority of schools are using similar techniques in clinical RPDs, such as border molding the edentulous areas of the final impression tray (80%) and using the altered cast impression technique (59%). A set post-insertion protocol is present for patients who receive partial dentures in the majority of the schools (93%). Only 25% of schools reported incorporating new educational materials such as the use of Portrait artificial teeth at the predoctoral level. Eighteen percent of schools are allowing students to graduate without a set number of RPD clinical requirements as has been traditionally the case.

CONCLUSIONS

Predoctoral clinical RPD programs vary from school to school, yet a large percentage of schools agree on many topics.

Complete Denture Education in U.S. Dental Schools

PURPOSE

In 2001, a survey of U.S. dental schools was conducted to determine curricular content, teaching philosophies, and techniques used in clinical complete denture programs.

MATERIALS AND METHODS

The questionnaire was mailed to the chairperson of the prosthodontic/restorative department of 54 U.S. dental schools. Of these, 44 schools returned the completed survey, resulting in a response rate of 82%. The mean, median, and range of responses were computed where applicable.

RESULTS

Results from this survey show that a large majority of schools are using similar materials in clinical complete denture treatment: irreversible hydrocolloid for preliminary impression (87%); light-cured composite resin for record base fabrication (70%); a semiadjustable articulator (98%); and semianatomic posterior tooth form used exclusively or in combination with other tooth forms (75%). In addition, a large majority of schools are using similar techniques in clinical complete denture treatment: use of a protrusive record (80%); use of extra-oral measurements, speech, and esthetics for establishing the occlusal vertical dimension (59%); use of the conventional compression molding method for processing complete dentures (82%); occlusal equilibration and face-bow preservation (75%); and the clinical remount procedure (91%). A quality control program is present for cases sent to and returned from the laboratory in 73% and 84% of responding schools, respectively.

CONCLUSIONS

Clinical complete denture predoctoral programs vary from school to school, yet a large percentage of schools agree on many topics. Only 55% of schools reported incorporating new educational materials such as the use of dental implants and treatment of patients with implant-retained overdentures at the predoctoral level. Sixteen percent are allowing students to graduate without a set number of required complete dentures as has traditionally been the case. Sixteen percent are using newer techniques such as injection molding and microwave processing technique in addition to the conventional processing technique.

Predoctoral Implant Education in U.S. Dental Schools

PURPOSE

In 2002, a survey of American dental schools was conducted to determine the curricular structure, teaching philosophies, and materials used in predoctoral implant dentistry courses.

MATERIALS AND METHODS

The questionnaire was mailed to the predoctoral implant dentistry director/chairperson of 54 U.S. dental schools. Of these, 38 schools returned the completed survey resulting in a response rate of 70%.

RESULTS

Eighty-four percent of the respondents indicated that an implant dentistry course is part of their school's requirements. Seventy percent indicated that this course is offered by either the Restorative or Prosthodontics Department in the third year of the predoctoral dental curriculum. For 75% of the schools, the duration of the course ranged from 3 to 6 months (mean of 5.5 months), 57% reported offering between 11 and 20 lecture hours (mean of 20.4 hours), and less than half of the schools (41%) have prosthodontists teaching the predoctoral implant dentistry course. In 78% of the schools, a laboratory course is offered in conjunction with the implant course. The majority of the schools (88%) allow predoctoral students to restore implant cases clinically. Seventy-three percent require some of the implant-related laboratory work to be completed by the students and the single-tooth implant restoration is the most popular type of implant restoration for 78% of the schools.

CONCLUSIONS

Predoctoral implant dentistry educational programs vary from school to school, yet a large percentage of schools agree on certain topics.

Predoctoral implant dentistry curriculum survey: European dental schools

PURPOSE

In 2002 a survey of European dental schools was conducted. The purpose of the survey was to determine the curricular structure, teaching philosophies and materials used in predoctoral implant dentistry courses.

MATERIALS AND METHODS

Fifty-six European dental schools were randomly selected from the Association for Dental Education in Europe representing 33 countries. A questionnaire was mailed to the predoctoral implant dentistry director/chairperson of the selected European dental schools. Of these, 40 schools returned the completed survey, resulting in a response rate of 71%. The mean, median and range of responses were computed where applicable.

RESULTS

The results from this survey show that 80% of the responding schools required a course in implant dentistry. Between 1997 and 1999 over a third of responding schools (36%) incorporated a predoctoral implant dentistry course into their curriculum. Eighty-seven per cent of the schools have some prosthodontists teaching the course. Thirty-seven per cent of schools are offering a laboratory course in conjunction with the implant course. Sixty-three per cent of the schools are not restoring implant cases at the predoctoral level. However, 68% of schools reported students are required to be present during implant surgery. Ten per cent of schools require that the implant-related laboratory work be completed by the students.

CONCLUSIONS

Predoctoral implant dentistry educational programmes vary from school to school. Yet a large percentage of schools agree on certain topics, including the importance of including implant education in predoctoral dental programmes.

Current concepts for determining the postpalatal seal in complete dentures

PURPOSE

In 2001, a survey of U.S. dental schools was conducted to determine the concepts and techniques used for establishing the postpalatal seal (PPS) in a predoctoral dental curriculum.

MATERIALS AND METHODS

The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 returned the completed survey, resulting in a response rate of 82%.

RESULTS

Results from this survey show that 80% of the schools are teaching a combination of phonation with other methods for locating the vibrating line. The 1 vibrating line concept for establishing the PPS is taught by 80% of schools; 77% of these schools locate the posterior termination of the maxillary denture on the vibrating line. Carving the PPS in the maxillary master cast is taught by 95% of the schools. Most of the schools teach the students to carve the PPS to a depth of 1.0-1.5 mm in the maxillary master cast. Compressibility of the palatal tissues is a consideration during PPS carving for 91% of the schools. The butterfly pattern is the most frequently (75%) described pattern for PPS carving.

CONCLUSIONS

There is some variability from school to school on performing the PPS in the maxillary denture, although some trends are evident.

Survey of recently board‐certified prosthodontists on the board‐certification process. Part 2: Preparation and impact

PURPOSE

A 2-part survey of recently board-certified prosthodontists was conducted in 2001. The first part of the survey, published in June 2003, determined the trends that assisted the candidates in attaining diplomate status. The second part of the survey was done to determine the preparation methods and resources used to prepare for the examination, the most difficult part of the examination, the most gratifying aspect of becoming board-certified, their current employment status, and whether board certification had any positive impact on their employment.

MATERIALS AND METHODS

A questionnaire was mailed to 176 diplomates who had become board certified between the years 1993-2001. Of these, 131 board-certified prosthodontists returned the completed survey, resulting in a response rate of 74%.

RESULTS

Results from this survey showed that 91% of the diplomates had taken the American College of Prosthodontists (ACP) Board Preparation course; most of the diplomates (41%) prepared for the boards by reviewing prosthodontic literature, reading textbooks, using the ACP Study Guide, and seeking the help of other board-certified prosthodontists; 89% of the diplomates felt that achieving board certification had a positive influence in their employment; 39% of the diplomates indicated that Part 2 of the examination was the most difficult to prepare for, and 41% indicated that Part 2 was the most difficult section; the majority of diplomates (31%) were employed by the military, and the most gratifying aspect of becoming board-certified was personal accomplishment (83%).

CONCLUSIONS

Trends were observed regarding prosthodontists who succeeded with their efforts to challenge the board examination. The majority of the diplomates were employed by the military. Most of the respondents indicated that they took the ACP Board Preparation course and found it helpful. The largest percentage of respondents reported that Part 2 was both the most difficult part to prepare for, as well as the most difficult to complete. The most gratifying aspect of becoming board-certified was personal accomplishment.

Current concepts and techniques in complete denture final impression procedures

PURPOSE

In 2001, a survey of U.S. dental schools was conducted to determine which concepts, techniques and materials are currently prevalent in the teaching of final impression procedures for complete dentures in the predoctoral clinical curriculum.

MATERIALS AND METHODS

The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 schools returned the completed survey resulting in a response rate of 82%.

RESULTS

Results from this survey show that the majority of schools (71%) teach the selective-pressure technique for final impression making; the majority of the schools (64%) use modeling plastic impression compound for border molding the final impression tray; 39% of the schools do not place vent holes in the final impression tray, 30% of schools place more than one hole and 27% place one hole only; the majority of the schools (98%) are using custom trays for final impressions. Ninety-eight percent of the schools are border molding the custom tray and 70% of schools are using a visible light-cured (VLC) composite resin material to make the trays. Thirty-six percent of the schools are teaching the Boucher impression technique and 34% are teaching the modified Boucher impression technique.

CONCLUSIONS

Predoctoral clinical complete denture educational programs agree on many aspects of final impression making, however, there is variability in their teachings regarding the impression philosophy and the materials used.

Complications of mandibular molar replacement with a single implant: a case report

This case report describes prosthodontic complications resulting from the surgical placement of a single implant and treatment following these complications. Both the surgical and prosthodontic procedures are described for the treatment of a 57-year-old man who had previously received a single implant for the replacement of a missing molar. Using 2 implants, 1 mesial and 1 distal to the previously placed single implant proved reliable. A logical treatment solution is to use 2 implants for the replacement of a single molar to avoid prosthodontic complications.

Treatment of a patient with cleidocranial dysplasia using osseointegrated implants: a patient report

This patient report describes the treatment of a 42-year-old woman with cleidocranial dysplasia. Endosseous implants were used to restore the mandibular and maxillary arches with fixed prostheses. Six implants were placed in the mandible and immediately loaded with an acrylic resin fixed prosthesis. In the maxillary arch, 10 implants were submerged for 4 months prior to functional loading. A transitional denture was relined and placed in the maxilla 10 days after implant placement. Three months later, a definitive mandibular prosthesis was fabricated. The definitive maxillary restoration was delivered 6 months after surgery. The most recent follow-up, 6 months after delivery, confirmed a satisfactory treatment result to date.

Extractions, Implant Placement, and Immediate Loading of Mandibular Implants: A Case Report of a Functional Fixed Prosthesis in 5 Hours

The purpose of this report is to present a reliable surgical and prosthodontic protocol for immediate loading of implants, allowing patients to receive a fixed implant-supported prosthesis in a matter of hours. The surgical, prosthodontic, and laboratory steps for this protocol of immediate functionally loading the implants are described for the treatment of a 51-year-old woman who presented with a hopeless mandibular dentition and an edentulous maxillary arch. It is possible to decrease the treatment time in successfully restoring the patient's oral function by means of immediate functional loading of dental implants and immediately placing a fixed implant-supported prosthesis. Compared with the traditional implant protocols, this protocol of a one-visit approach for patient treatment 1) decreases the number of office visits; 2) decreases the treatment time; 3) reduces the patients' costs; 4) allows the patient to avoid wearing a removable interim prosthesis; and 5) increases the patients' acceptance of treatment while maintaining predictability in treating mandibular edentulism.

Quadruple zygomatic implant support for retreatment of resorbed iliac crest bone graft transplant

PURPOSE

The purpose of this report is to present a reliable surgical and prosthodontic protocol for the treatment of the atrophic maxilla by placing four zygomatic implants.

MATERIALS AND METHODS

The surgical and prosthodontic procedures are described for the retreatment of a 63-year-old woman who had previously undergone an iliac crest bone graft transplant, which had resorbed.

RESULTS

It is possible to place double zygomatic implants bilaterally, in addition to conventional implants in the anterior maxilla. Bone grafting procedures can be avoided, resulting in a fixed implant-supported maxillary prosthesis.

CONCLUSION

A logical treatment solution is four zygomatic implants for the atrophic maxilla, especially because the previous iliac crest bone graft had resorbed.

Survey of recently board-certified prosthodontists on the board certification process. Part 1: Demographics

PURPOSE

A survey of recently board-certified prosthodontists was conducted in 2001. The purpose of this survey was to identify trends that assisted candidates in attaining diplomate status.

MATERIALS AND METHODS

A questionnaire was mailed to 176 diplomates who had become board certified between the years 1993 and 2001. Of these, 131 board-certified prosthodontists returned the completed survey, resulting in a response rate of 74%. The mean, median, and range of responses were computed when applicable.

RESULTS

Results from this survey show that the mean number of years from completion of a postdoctoral program to achieving board certification was 6 years, with a median of 4 years and a range of 1 to 23 years. The mean number of years from the time of completion of a postdoctoral program to board eligibility was 2.3 years, with a median of 1 year and a range of 0 to 22 years. The mean number of years from board eligibility to board certification was 3.9 years, with a median of 3 years and a range of 0 to 17 years. The military was the most frequently reported employment status at the time the respondents took Parts 1-4 of the boards. A total of 54% of the diplomates reported that they challenged Part 1 separately, and then challenged Parts 2, 3, and 4 together; 79% of the diplomates were encouraged by their graduate program director/faculty to challenge the board; and 48% of the diplomates reported that their patients received free dental treatment.

CONCLUSIONS

Certain trends were observed regarding diplomates who succeeded in their efforts to challenge the board examination. The largest group who challenged the board certification examinations comprised members of the armed forces. Most prosthodontists challenged Part 1 before challenging the remaining 3 parts. In an effort to encourage more prosthodontists to challenge the board examination, numerous changes were made between 1992 and 1998; however, most of the diplomates did not take advantage of those changes.

Preclinical removable partial dentures curriculum survey

PURPOSE

In 2001, a survey of U.S. dental schools was conducted to determine the curricular structure, teaching philosophies, and techniques used in preclinical removable partial denture (RPD) courses and to also establish what newer educational techniques and materials are currently being used by U.S. dental schools.

MATERIALS AND METHODS

The questionnaire was mailed to the chairpersons of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 43 schools returned the completed survey, resulting in a response rate of 80%. The mean, median, and range of responses were computed where applicable.

RESULTS

Results from this survey show that the mean student-to-faculty ratio in the preclinical RPD course was 12:1, with a median of 10:1 and a range of 6:1 to 27:1. The mean number of laboratory hours was 55, with a median of 50 and a range of 13.5 to 120. The mean number of lecture hours reported was 21, with a median of 20.5 and a range 10 to 60. The mean number of practical examinations was 2, with a median of 3 and a range of 0 to 8. The mean number of written examinations given was 2, with a median of 2 and a range of 1 to 6. Ninety-five percent of the schools have prosthodontists teaching this course. The mean number of months that this course is taught is 4.4 months, with a median of 4 and a range of 1.5 to 10. Fifty-five percent of the schools used the Hanau semiadjustable articulator. One hundred percent of the schools teach students to use a surveyor when designing an RPD, and 84% percent of the schools teach the Krol or the Kratochvil RPI design or a combination of the 2 designs.

CONCLUSIONS

Preclinical RPD educational programs vary from school to school, yet a large percentage of schools agree on certain topics. Only 19% of dental schools are incorporating new technologies, such as the use of the internet, in their preclinical RPD curriculum.

Preclinical complete dentures curriculum survey

PURPOSE

A survey of U.S. dental schools was conducted in 2001 to determine the curricular structure, teaching philosophies, and techniques used in preclinical complete denture courses.

MATERIALS AND METHODS

The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 43 schools returned the completed survey, a response rate of 80%. The mean, median, and range of responses were computed where applicable.

RESULTS

Results from this survey show that the mean student-to-faculty ratio in the preclinical course was 12:1, with a median of 12:1 and a range of 6:1 to 27:1. The mean number of laboratory hours was 74, with a median of 70.5 and a range of 31.5 to 160. The mean number of lecture hours reported was 28, with a median of 25 and a range 12 to 80. The mean number of practical examinations was 3, with a median of 3 and a range of 0 to 11. Eighty-four percent of the schools have prosthodontists teaching the course. The mean number of months that this course is taught is 5 months, with a median of 5 and a range of 2 to 13. Fifty-eight percent of the schools use the Hanau semiadjustable articulator. Sixty-five percent of the schools use protrusive records to set the articulator. The facebow preservation record is used by 84% of the schools.

CONCLUSIONS

Preclinical complete denture educational programs vary from school to school, yet a large percentage of schools agree on certain topics. Only 28% of dental schools are incorporating new technologies, such as the internet, in their preclinical complete denture curriculum. Nineteen percent of dental schools are using only the Portrait denture teeth, which are newer than the Bioblend and Bioform teeth.

Comparison of load distribution for implant overdenture attachments

PURPOSE

The aim of this study was to compare the force and moment distributions that develop on different implant overdenture attachments when vertical compressive forces are applied to an implant-retained overdenture.

MATERIALS AND METHODS

The following attachments were examined: Nobel Biocare bar and clip (NBC), Nobel Biocare standard ball (NSB), Nobel Biocare 2.25-mm-diameter ball (NB2), Zest Anchor Advanced Generation (ZAAG), Sterngold ERA white (SEW), Sterngold ERA orange (SEO), Compliant Keeper System with titanium shims (CK-Ti), Compliant Keeper System with black nitrile 2SR90 sleeve rings (CK-70), and Compliant Keeper System with clear silicone 2SR90 sleeve rings (CK-90). The attachments were tested using custom strain-gauged abutments and 2 Brånemark System implants placed in a test model. Each attachment type had one part embedded in a denture-like housing and the other part (the abutment) screwed into the implants. Compressive static loads of 100 N were applied (1) bilaterally, over the distal midline (DM); (2) unilaterally, over the right implant (RI); (3) unilaterally, over the left implant (LI); and (4) between implants in the mid-anterior region (MA). Both the force and bending moment on each implant were recorded for each loading location and attachment type. Results were analyzed using 2-way analysis of variance and the Duncan multiple-range test.

RESULTS

Both loading location and attachment type were statistically significant factors (P < .05). In general, the force and moment on an implant were greater when the load was applied directly over the implant or at MA.

DISCUSSION

While not significant at every loading location, the largest implant forces tended to occur with ZAAG attachments; the smallest were found with the SEW, the SEO, the NSB, the CK-70, and the CK-90. Typically, higher moments existed for NBC and ZAAG, while lower moments existed for SEW, SEO, NSB, CK-90, and CK-70.

CONCLUSION

For different loading locations, significant differences were found among the different overdenture attachment systems.

Maximum dislodging forces of implant overdenture stud attachments

PURPOSE

The aim of this study was to compare the retention and stability of the Nobel Biocare standard ball (NBS), Nobel Biocare 2.25-mm-diameter ball (NB2), Zest Anchor (ZA), Zest Anchor Advanced Generation (ZAAG), Sterngold ERA orange (SEO), and Sterngold ERA white (SEW) attachments on an implant-retained overdenture model.

MATERIALS AND METHODS

The attachments were tested using 2 permanently placed Brånemark System implants on a test model that was attached to an Instron machine (crosshead speed 50.8 mm/minute). Each attachment had one part embedded in a denture-like housing and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in 3 directions simulating function: vertical, oblique, and anterior-posterior. Eight tests were done in 3 directions with 6 samples of each attachment. The dislodging forces generated measurements of the peak load (maximum dislodging force). A 1-way analysis of variance followed by the Tukey studentized range test was used to determine groups that were significantly different. All tests for significance were carried out at the .05 level of significance.

RESULTS

Results showed the ZAAG attachment to be the most retentive for the peak load measurement when subjected to vertically directed forces, with mean values and standard deviations of 37.2 +/- 5.5 N. The next most retentive attachment was the NBS, followed by the SEO, NB2, SEW, and ZA. For obliquely directed forces, the ZAAG attachment was the most retentive, with mean values and standard deviations of 27.2 +/- 4.2 N. The next most retentive was the NBS, followed by the NB2, SEO, ZA, and SEW. For anterior-posteriorly directed forces, results showed the NBS had the highest measured retentive force, with mean values and standard deviations of 34.6 +/- 18.8 N, but this was not statistically different from the NB2 and ZAAG; this was followed by the SEO, SEW, and ZA.

DISCUSSION

There has been a marked resurgence in the treatment of patients with overdentures using implant attachments as retentive devices. The maximum force developed (a measure of retention) as the implant stud attachments were resisting removal from the implant abutments was determined.

CONCLUSIONS

Based on the present study, the clinician may be able to make empirical decisions on attachment selection, depending on the amount of retention desired and the specific clinical situation.

The dental student as a technician: preclinical and clinical laboratory programs in fixed prosthodontics

PURPOSE

A 2-part survey of United States dental schools was conducted. The first part of the survey was published in 1998 and determined the curricular structure, techniques taught, and materials used in predoctoral fixed prosthodontics courses. The purpose of the second part of the survey was to ascertain the delegation of laboratory procedures in preclinical and clinical fixed prosthodontic programs.

MATERIALS AND METHODS

The survey was mailed to the course directors of predoctoral fixed prosthodontic programs at 53 US dental schools. Of these, 42 schools returned the completed survey, resulting in a response rate of 79%.

RESULTS

Results from this survey show that certain laboratory procedures in preclinical and clinical fixed prosthodontics are completed by dental laboratories (either in-house or commercially available laboratories).

CONCLUSIONS

For the preclinical programs of fixed prosthodontics, there is more student involvement in the completion of laboratory procedures in the dental schools surveyed. In clinical fixed prosthodontic programs, there is a high emphasis on patient care and less on laboratory techniques that can be delegated to laboratory technicians.

Predoctoral fixed prosthodontics curriculum survey

PURPOSE

In 1996, a survey of American dental schools was conducted. The purpose of the survey was to determine the curricular structure, techniques taught, and materials used in predoctoral fixed prosthodontics courses.

MATERIALS AND METHODS

The survey was mailed to the course directors of predoctoral fixed prosthodontic programs at 53 American dental schools. Of these, 42 schools returned the completed survey, resulting in a response rate of 79%. The mean, median, and the range of responses were computed where applicable.

RESULTS

The results from this survey show that the mean student-to-faculty ratio in the preclinical course was 11:1, with a median of 10:1 and a range of 5:1 to 25:1. The mean number of laboratory clock hours was 164, with a median of 148 and a range of 81 to 288. The mean number of lecture hours reported was 42, with a median of 35 and a range of 20 to 80. Fifty-five percent of the schools used the Hanau semiadjustable articulator. The most commonly used provisional technique was the thermoplastic custom external surface form (44%). The finish line of choice for the full metal restoration was the chamfer placed circumferentially (74%). The finish line of choice for the porcelain-fused-to-metal restoration was the shoulder placed facially and the chamfer placed lingually (38%).

CONCLUSIONS

Predoctoral fixed prosthodontics education and technical experience varies from school to school, yet a large percentage of schools agree on certain topics.

Comparison of retention and release periods for implant overdenture attachments

The aim of this study was to compare the retention and release periods of the Nobel Biocare bar and clip (NBC), Nobel Biocare ball (NB), Zest anchor (ZA), Zest magnet (ZM), and Sterngold ERA (SE) attachments on an implant-retained overdenture model. The attachments were tested using two permanently placed Brånemark implants on a test model that was attached to an Instron machine (cross-head speed 50.8 mm/minute). Each attachment had one part embedded in a denture-like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with three samples of each attachment. The dislodging forces generated measurements of the peak load, break load, and displacement at peak load and break load. Release periods were calculated using displacements between the peak load and break load and the cross-head speed. Results showed the NBC to be significantly most retentive for the break load when subjected to vertical and oblique forces with mean values and standard deviations of 2104.5 +/- 506.7 g and 1958.1 +/- 165.4 g, respectively. Next most retentive was the SE, followed by the ZA and NB. The ZM was significantly least retentive (127.8 +/- 7.0 g and 143.5 +/- 19.7 g). For the release period, results showed the NBC to have significantly the fastest release period for vertical and oblique forces (1.86 x 10(-3) and 7.35 x 10(-4) minutes). The ZM significantly had the slowest release period for those forces (3.02 x 10(-2) and 2.35 x 10(-2) minutes). The data suggested that the NBC could be selected when a higher degree of retention and fast release period are desired. The next most retentive was the SE; ZM was the least retentive and had the slowest release period.