Stabilization of an abutment under a rigidly fixed bridge by holographical-speckle interferometry.

J Zhejiang Univ Sci B. 2007 Jun;8(6):416-21

Authors: Zhang YZ, Zhou YC, Liu L, Lu Y, Hirofumi Y

OBJECTIVE: There are no detailed reports of three-dimensional measurement of abutment teeth in mastication, because it is knotty to observe the rotation in chewing directly, and inexact to estimate indirectly. This work studies the three-dimensional stability of rigidly fixed bridge under the stresses of distributed loads and concentrated loads by optical method that gives the tip angle and rotation angle calculated directly based on measurement data. METHODS: The specimen, taken from a 25-year-old male, was a left mandible without the second premolars and the first molars. As abutments, first premolar and second molar have complete periodontium. The specimen was soaked in formaldehyde solution. The bridge was fixed between two abutment teeth (first premolars and second molars), and the mandible was cemented in a steel box. The load was increased from 0 kg to 23 kg. Laser holographic technique was used to measure the three-dimensional bit shift of the dens, both buccolingual bit shift and mesiodistal bit shift, and determine tip angle and rotation angle. RESULTS: The effects of stress distribution on the rigidly fixed bridge were evaluated, and stabilization of the bridge under the stresses of distributed loads and concentrated loads, respectively, were analyzed. The results showed that the tips of two abutments were very similar, and no distinct difference was observed between the distributed load and the concentrated load. However, the maximum rotation angle for the distributed load was two to four times as large as that for the concentrated load. In the experiment, the tip angle of the abutment teeth was no more than 0.65 degree, and the rotation angle was no more than 0.60 degree. All maximum angles occurred in the second molar. CONCLUSION: The fixed bridge is considered to be safe. In addition, a method for measuring the rotation angle was provided effectively.

PMID: 17565512 [PubMed - indexed for MEDLINE]

Evaluation of the marginal gingival health using laser Doppler flowmetry.

Braz Dent J. 2006;17(3):219-22

Authors: Develioglu H, Kesim B, Tuncel A

The purposes of this study were to compare the gingival blood flow (GBF) in test sites (teeth retaining fixed partial dentures) and control sites (contralateral natural teeth) and investigate whether there is any relationship between clinical indices and GBF values. Twelve healthy subjects (6 females and 6 males) aged 20 to 54 years were enrolled this study. The GBF was measured from the middle point of the marginal gingiva in the test and control sites using laser Doppler flowmetry (LDF). Additionally, plaque index, gingival index and probing depth measurements were recorded. Statistically significant difference (p<0.05) was found between the test and control sites for marginal GBF. In contrast, no significant difference (p>0.05) was found between test and control sites with respect to the clinical indices, except for plaque index. The findings of this study suggest that there is a significant relation between resin-bonded fixed partial dentures with margins located subgingivally and marginal GBF. Clinical indices are helpful to collect information about the clinical health status of gingival tissues, but GBF is a good tool to measure gingival tissue blood flow and assess periodontal health. In conclusion, laser Doppler flowmetry can be used together with clinical indices to evaluate the marginal gingival health.

PMID: 17262128 [PubMed - indexed for MEDLINE]

Evaluation of surface characteristics of Ti-6Al-4V and Tilite alloys used for implant abutments.

Braz Oral Res. 2006 Oct-Dec;20(4):307-11

Authors: Lima EM, Silva WJ, Moura JS, Faot F, Del Bel Cury AA

The aim of this study was to evaluate surface free energy (SFE), surface roughness (SR) and surface hardness (SH) of two commercially available materials for fabricating dental implant abutments. In addition, the specimens were investigated by scanning electron microscopy (SEM) to determine the surface morphology. Twenty five discs (5 x 2 mm) of Ti-6Al-4V and Tilite (Ni-Cr-Ti) alloys were used in this study. Surface free energy was determined by the contact angle formed between a drop of distilled, deionized water and the surface of the specimen of each material. The surface roughness was measured with a mechanical profilometer and the surface hardness was evaluated by means of the Vickers hardness micro indentation test. SFE, SR and SH data were analyzed using one-way ANOVA (p < 0.05). Statistical differences (p < 0.05) were found between Ti-6Al-4V (36.2 erg x cm(-2); 0.2 microm) and Tilite (30.9 erg x cm(-2); 0.16 microm) for SFE and SR. However, the differences between the surface hardness values of Ti-6Al-4V (325.0 kg/mm(2)) and Tilite (324.3 kg/mm(2)) were not statistically significant (p > 0.05). Evaluations by SEM revealed different surface morphology. Within the limits of this study, it can be concluded that the Ti-6Al-4V and Tilite alloys showed differences in surface properties, except for surface hardness, suggesting that both alloys may be considered appropriate for producing abutments. Further studies are, however, necessary to elucidate the biological responses to implant abutments made with these alloys.

PMID: 17242790 [PubMed - indexed for MEDLINE]

Two new clinical/laboratory protocols for CAD/CAM implant restorations.

J Am Dent Assoc. 2006 Jun;137(6):794-800

Authors: Drago CJ

BACKGROUND: Conventional casting technology has some disadvantages for dental laboratory technicians and restorative dentists, including porosity of restorations, miscasting and inaccuracy. It also is labor-intensive. Computer-aided design/computer-aided manufacturing (CAD/CAM) technology was developed in the late 1980s for dentistry, and it significantly reduced and/or eliminated problems associated with dental castings. The purpose of this article is to give readers an overview of the use of CAD/CAM technology for dental implants and illustrate two clinical protocols for that use. CLINICAL IMPLICATIONS: The CAD/CAM technology described in this article can reduce restorative dentists' chairside time associated with implant treatment in both edentulous and partially edentulous patients, can decrease costs without sacrificing accuracy or biocompatibility for both clinicians and dental laboratory technicians, and is available to dental laboratories without the capital expenses associated with purchasing new technology.

PMID: 16803809 [PubMed - indexed for MEDLINE]

A retrospective clinical evaluation of two-unit cantilevered resin-bonded fixed partial dentures.

J Am Dent Assoc. 2006 Jun;137(6):783-8

Authors: Botelho MG, Leung KC, Ng H, Chan K

BACKGROUND: The authors conducted a study to examine the clinical performance of two-unit cantilevered resin-bonded fixed partial dentures (RBFPDs) that were inserted at The Prince Philip Dental Hospital, University of Hong Kong. METHODS: The authors recalled patients who had received two-unit cantilevered RBFPDs at least 24 months before the recall examination. The authors recorded the following data: patient's sex and age, operator's experience, prosthesis cementation date, endodontic treatment if performed, bone support, tooth mobility, the presence of shim-stock contacts on the abutment or pontic in intercuspal position, and the presence of aproximal axial contacts adjacent to the prosthesis. They also recorded the date of any debonding with subsequent treatment. They asked the patients qualitative questions about their prostheses. RESULTS: A total of 269 prostheses were placed in 214 patients and had a mean service life of 51.7 months +/- 19.5 months standard deviation, with a range of 13.2 to 141.6 months. Of 14 failed prostheses, 12 debonded, resulting in a success rate of 94.8 percent and clinical retention rate of 95.5 percent. No discernable rotation or drifting of the abutments was apparent in any of the prostheses. Overall patient satisfaction with RBFPDs was good, with an average assessment score of 8.5. CONCLUSIONS: The authors observed a 95.5 percent clinical retention rate of 269 two-unit RBFPDs, with no apparent drifting of the abutments. Longer-term follow-up studies are required. CLINICAL IMPLICATIONS: Two-unit RBFPDs are conservative and clinically retentive prostheses in the short to medium term.

PMID: 16803807 [PubMed - indexed for MEDLINE]

Fixed space maintainers combined with open-face stainless steel crowns.

J Contemp Dent Pract. 2006 May 1;7(2):95-103

Authors: Yilmaz Y, Kocogullari ME, Belduz N

OBJECTIVE: This study investigates the clinical performance of fixed space maintainers placed on seriously damaged abutment teeth. METHODS: Crowns were placed on damaged abutment primary teeth. Fixed space maintainers were prepared by using rectangular wire between the window in the facial surface of the crowns and other abutment teeth and were subsequently bonded with a flowable resin composite. This procedure was introduced clinically, and the cases were observed over a period of twelve months. RESULTS: Twenty-seven fixed space maintainers (25 on lower jaw, two on upper jaw) were included in this study. No clinical failure was recorded in any of the cases in the observation time, and the rate of clinical performance was 100%. CONCLUSION: The study shows the effectiveness of fixed space maintainers combined with stainless steel crowns ("open-face fixed space maintainers") which were placed on primary molar teeth used as abutments in cases with extensive caries and loss of occlusogingival dimension.

PMID: 16685300 [PubMed - indexed for MEDLINE]

Peri-implant inflammation defined by the implant-abutment interface.

J Dent Res. 2006 May;85(5):473-8

Authors: Broggini N, McManus LM, Hermann JS, Medina R, Schenk RK, Buser D, Cochran DL

An implant-abutment interface at the alveolar bone crest is associated with sustained peri-implant inflammation; however, whether magnitude of inflammation is proportionally dependent upon interface position remains unknown. This study compared the distribution and density of inflammatory cells surrounding implants with a supracrestal, crestal, or subcrestal implant-abutment interface. All implants developed a similar pattern of peri-implant inflammation: neutrophilic polymorphonuclear leukocytes (neutrophils) maximally accumulated at or immediately coronal to the interface. However, peri-implant neutrophil accrual increased progressively as the implant-abutment interface depth increased, i.e., subcrestal interfaces promoted a significantly greater maximum density of neutrophils than did supracrestal interfaces (10,512 +/- 691 vs. 2398 +/- 1077 neutrophils/mm(2)). Moreover, inflammatory cell accumulation below the original bone crest was significantly correlated with bone loss. Thus, the implant-abutment interface dictates the intensity and location of peri-implant inflammatory cell accumulation, a potential contributing component in the extent of implant-associated alveolar bone loss.

PMID: 16632764 [PubMed - indexed for MEDLINE]

Quantitative evaluation of axial wall taper in prepared artificial teeth.

J Oral Sci. 2005 Sep;47(3):129-33

Authors: Okuyama Y, Kasahara S, Kimura K

The purpose of this study was to quantitatively evaluate the axial wall taper of prepared artificial teeth using a non-contact three-dimensional shape measuring system. A total of 54 artificial teeth prepared by pre-clinical dental students for complete cast restorations were evaluated. For quantitative analysis, five cross sections were computer-graphically placed perpendicularly to the z-axis. The surface coordinate values (x, y, z) of each cross section were converted into polar coordinate values (r, theta), which were then graphically rendered to a two-dimensional plane. At four points, each 90 degrees from the distal center point of the cross section, the axial wall taper was quantitatively calculated using a formula based on the differences in radius between the highest and lowest positions of the cross sections of the prepared tooth. The average calculated taper was 5.8 degrees in the distal region, 21.7 degrees in the buccal region, 14.9 degrees in the mesial region and 12.5 degrees in the lingual region. These results suggest that the axial wall taper of prepared teeth can be quantitatively evaluated using this measuring system.

PMID: 16313090 [PubMed - indexed for MEDLINE]

Advanced restorative techniques.

Br Dent J. 1999 Dec 11;187(11):593-600

Authors: Howe L, Palmer P, Barrett V

Many alternative techniques are available to ensure the best possible outcome for an implant restoration.

PMID: 16163276 [PubMed - indexed for MEDLINE]

The influence of prosthesis designs and loading conditions on the stress distribution of tooth-implant supported prostheses.

Bull Tokyo Dent Coll. 2004 Nov;45(4):213-21

Authors: Zhiyong L, Arataki T, Shimamura I, Kishi M

The aim of this study was to observe the influence of prosthesis design and loading condition on the stress distributions of tooth-implant supported prostheses. Six 2D finite element models, two reference models, and four experimental models were computed to simulate different prosthesis designs. Six different loading conditions were applied to investigate the stress distributions of tooth and implant, respectively. The stresses of reference models were considered as 100%; the stresses of experimental models at the same locations were compared with those of reference models. The stresses around implants were higher than those around teeth. When vertical loading was applied only on the implant, the stresses to both the implant and teeth were at their lowest. The highest stress to the tooth was in the model TTPF and the lowest in the model TPFF. The highest stress to the implant was in the model TPPF and the lowest in the model TPFF. These data indicated that the loading on the tooth-implant supported prosthesis was mainly supported by the implant. Minimizing the loading on the tooth decreased the stress to both the tooth and the implant. Adding fixtures as abutment was more effective in decreasing the stress than adding tooth as abutment in tooth-implant supported prosthesis.

PMID: 15960158 [PubMed - indexed for MEDLINE]

Effect of direct relining on stresses at the denture base and the metal frame of removable partial dentures.

J Contemp Dent Pract. 2005 Feb 15;6(1):37-47

Authors: Al-Ghannam NA, Fahmi FM

The Kennedy Class I removable partial denture (RPD) can cause stress to supporting hard and soft tissues and may lead to harmful effects. The purpose of this study is to investigate the pattern of these stresses in three different positions before and following a relining procedure. Ten patients, five males and five females, with a lower distal extension RPD and an opposing upper class III type RPD were selected for this study. Strain gauges together with a strain gauge indicator were used to study the pattern of stresses in three selected positions. Some changes were significantly different at the site of the denture base and at the metal frame near the direct retainer. After relining, the stresses were shared partially by the abutments and partially by the tissues. Maximum stresses were reported during swallowing. No significant difference was noticed between males and females.

PMID: 15719075 [PubMed - indexed for MEDLINE]

An eight-year follow-up to a randomized clinical trial of participant satisfaction with three types of mandibular implant-retained overdentures.

J Dent Res. 2004 Aug;83(8):630-3

Authors: Timmerman R, Stoker GT, Wismeijer D, Oosterveld P, Vermeeren JI, van Waas MA

Studies have shown that mandibular implant overdentures significantly increase satisfaction and quality of life of edentulous elders. Improved chewing ability appears to have a positive impact on nutritional state. Therefore, it is important to determine the best design of this prosthesis over the long term. In this randomized controlled trial, three groups of edentulous participants with atrophic mandibles wore 3 types of implant overdentures. During an eight-year follow-up, only seven of the 110 participants had dropped out of this study. Almost all participants were still satisfied with their overdentures. Participant satisfaction concerning retention and stability of the mandibular overdenture had decreased significantly in the two-implant ball attachment group, whereas the opinion of participants in the single- and triple-bar groups was still at the same level. The long-term results suggest that a mandibular overdenture retained by 2 implants with a single bar may be the best treatment strategy for edentulous people with atrophic ridges.

PMID: 15271972 [PubMed - indexed for MEDLINE]

Abutment tooth loss in patients with overdentures.

J Am Dent Assoc. 2004 Jun;135(6):739-46; quiz 795-6

Authors: Ettinger RL, Qian F

BACKGROUND: Since the 1960s, the use of natural teeth as overdenture abutments has become part of accepted clinical practice. Several longitudinal studies have been conducted, but tooth loss has not been reported to be a significant problem. The aim of this study was to identify the incidence and causes of tooth loss in a prospective cohort study of subjects wearing overdentures. METHODS: The study, conducted between 1973 and 1994, evaluated 273 subjects (62.3 percent male) with a mean age of 59.6 years. RESULTS: Of the 273 subjects with 666 abutments, 74 lost 133 abutments. The most common cause of tooth loss was periodontal disease (29.3 percent) followed by periapical lesions (18.8 percent) and caries (16.5 percent). Through logistic regression, the authors found that subjects who lost teeth were more likely to have medical problems that could cause soft-tissue lesions of the oral mucosa, were less likely to use fluoride daily and were less likely to return for yearly recall visits. The authors found 22 vertical fractures in 17 subjects. Chi2 analysis revealed that overdenture teeth in the maxillary arch that were opposed by natural teeth were more likely to experience vertical fractures. CONCLUSIONS: In a study that followed up some patients for as long as 22 years, the rate of tooth loss was 20.0 percent. Many of these failures could have been prevented if patients had practiced better oral hygiene. CLINICAL IMPLICATIONS: The findings suggest that if a dentist recommends overdenture therapy, the patient needs to be examined regularly to reduce the risk of experiencing caries and periodontal disease. Also, if the abutments are in the maxilla and are opposed by natural teeth, the dentist should consider using thimble crowns to reduce the risk of vertical fractures.

PMID: 15270156 [PubMed - indexed for MEDLINE]

Clinical evaluation of osseointegrated implants in Tokyo Dental College Hospital (third report): long-term observation of functioning survival rate of fixtures.

Bull Tokyo Dent Coll. 2003 Aug;44(3):169-75

Authors: Miyashita Y, Arataki T, Nomura T, Suzuki H, Atsuta S, Hotta H, Shimamura I, Adachi Y, Kishi M

The objective of this report was to review 365 cases of Br&#xE5;nemark Implant Bridge including 1,444 fixtures in patients of Tokyo Dental College Chiba Hospital. The term of implantation was divided into several phases; less than 1 year, from 1 year to 3 years, from 3 years to 5 years, from 5 years to 7 years, from 7 years to 10 years, more than 10 years, and the survival rate was calculated for each phase. The removal rate of fixture after connecting the superstructure was 13% in maxillary cases and 2% in mandibular cases. The functioning survival rate in maxillary cases slightly decreased from 91% in less than 1 year to 87% after more than 10 years; however, the functioning survival rate in mandibular cases was about 99% in all periods. The removal rate of fixtures per patient was 23% in maxillary cases and 6% in mandibular ones. The average removal number of fixtures was 1.8 in maxillary cases and 1.2 in mandibular ones. The removal of the fixture occurred most frequently at less than 1 year in maxillary cases, but there was no tendency for a pattern of removal of fixture in mandibular cases.

PMID: 14694832 [PubMed - indexed for MEDLINE]

Caring for the elderly.

J Am Dent Assoc. 2003 Sep;134(9):1164, 1166; author reply 1166

Authors: Vasilakis GJ

PMID: 14528982 [PubMed - indexed for MEDLINE]

Dental tipping and rotation immediately after surgically assisted rapid palatal expansion.

Eur J Orthod. 2003 Aug;25(4):353-8

Authors: Chung CH, Goldman AM

The purpose of this investigation was to evaluate the effects of dental tipping and rotation immediately after surgically assisted rapid palatal expansion (SARPE). Fourteen patients (10 females, four males; mean age 25.6 years) who required a SARPE procedure were available for this study. A palatal expander appliance was cemented on four abutment teeth (first premolars and first molars) of each patient 1 week prior to surgery. Maxillary study models were taken before surgery and 2-3 weeks after full expansion (7 mm). Each model was trimmed to have the base parallel to its occlusal plane. From an occlusal view, measurements were made to determine if the abutment teeth underwent rotation from SARPE. From a postero-anterior view, the abutment teeth were examined for any tipping effect due to SARPE. The results showed that from pre- to post-expansion, the two first premolars displayed 2.32 +/- 8.29 degrees of mesiobuccal rotation (P > 0.05) and the two first molars displayed 3.09 +/- 5.89 degrees of mesiobuccal rotation (P > 0.05). Each first premolar showed 6.48 +/- 2.29 degrees of buccal tipping (P < 0.05) and each first molar 7.04 +/- 4.58 degrees of buccal tipping (P < 0.05). SARPE induced a slight mesiobuccal rotation (P > 0.05) and significant buccal tipping of the first premolars and the first molars (P < 0.05). Some overexpansion is suggested to counteract the relapse effect of buccal tipping of the posterior teeth that takes place during SARPE.

PMID: 12938840 [PubMed - indexed for MEDLINE]

Extraction, immediate-load implants, impressions and final restorations in two patient visits.

J Am Dent Assoc. 2003 Jun;134(6):715-20

Authors: Leary JC, Hirayama M

BACKGROUND: Since the advent of immediately loaded implants, patients have experienced shorter treatment times, reduced amount of surgical therapy, preserved gingival esthetics and the comfort and security of fixed prostheses. Practitioners have experienced less expense in the form of chair time and greater patient satisfaction. CASE DESCRIPTION: The authors present two cases in which, at the first clinical visit, they extracted maxillary incisors, placed hydroxyapatite-coated implants, took impressions for final restorations and stabilized the implants immediately with a fixed interim prosthesis. At the second clinical visit, the authors placed the final restorations. All of the implants were integrated clinically, and gingival esthetics appeared to have benefited from preservation of papillary form, which was made possible with fixed interim anterior restorations. The patients expressed satisfaction with the results particularly because the treatment was accomplished in two clinical visits. CLINICAL IMPLICATIONS: The cases presented demonstrate a technique that may be of value to therapists who place immediate-load implants. The long-term effectiveness of immediate-load implants requires further evidence to ensure their long-term usefulness and safety.

PMID: 12839407 [PubMed - indexed for MEDLINE]

Vertical root fractures: clinical and radiographic diagnosis.

J Am Dent Assoc. 2003 Apr;134(4):434-41

Authors: Cohen S, Blanco L, Berman L

BACKGROUND: Early detection and management of vertical root fractures, or VRFs, remain a vexing issue that has caused needless suffering for patients as well as for dentists. The authors present techniques to aid the dentist in recognizing VRFs. METHODS: During a five-year period, the authors examined 36 patients who had VRFs. Absent control subjects and a larger number of patients, the authors did not design this investigation for statistical analysis. They diagnosed VRFs through dental histories and clinical and radiographic examinations. RESULTS: The study revealed VRFs in 36 teeth, two of which were vital and 34 of which were nonvital (that is, endodontically treated). The 34 VRFs resulted from excessive operative procedures performed in the root canal after endodontic therapy. Thirty-one of these 34 VRFs were caused by poorly designed dowels (too long, too wide or both) or inappropriate selection of the tooth as a bridge abutment; two VRFs were caused by a restoration that exerted lateral pressure on the axial walls of the preparation; and one VRF was caused by overzealous endodontic forces. The VRFs in the two vital teeth were in men who had a history of bruxism or clenching. CONCLUSIONS AND CLINICAL IMPLICATIONS: VRFs can be detected early by listening to the patient's chief complaints, carefully examining periapical and bitewing radiographs and performing a thorough clinical examination.

PMID: 12733776 [PubMed - indexed for MEDLINE]

Works in progress: a comparison of dental school experiences between passing and failing NERB candidates, 2001.

J Dent Educ. 2003 Mar;67(3):311-6

Authors: Ranney RR, Wood M, Gunsolley JC

The purpose of this report is to compare outcomes on the North East Regional Board of Dental Examiners (NERB) clinical examination to selected measures of academic performance in one U.S. dental school. The data came from results of the spring 2001 NERB examination at that school. Five measures of academic performance--number of Class II amalgam restorations completed, number of Class III/IV composite restorations completed, fixed prosthodontic units performed, fourth-year class rank, and GPA-were compared between those who passed and those who failed NERB's restorative exercise (RESTOR) and provisional fixed partial denture exercise (SIM). Analyses could not confirm a positive relationship between the school performance measures and the NERB outcome of passing RESTOR on the first attempt. On the other hand, those who passed SIM on the first attempt had, on the average, performed more amalgams, composites, and fixed prosthodontic units as students than those who failed; they also had, on average, better class rank and higher GPA. Therefore, only performance on SIM related to performance in school. However, both RESTOR and SIM had a similar number of failures from the top as well as the bottom portions of the class. These preliminary data from one dental school class raise questions about the validity of the NERB clinical examination for licensure decisions.

PMID: 12665060 [PubMed - indexed for MEDLINE]

Persistent acute inflammation at the implant-abutment interface.

J Dent Res. 2003 Mar;82(3):232-7

Authors: Broggini N, McManus LM, Hermann JS, Medina RU, Oates TW, Schenk RK, Buser D, Mellonig JT, Cochran DL

The inflammatory response adjacent to implants has not been well-investigated and may influence peri-implant tissue levels. The purpose of this study was to assess, histomorphometrically, (1) the timing of abutment connection and (2) the influence of a microgap. Three implant designs were placed in the mandibles of dogs. Two-piece implants were placed at the alveolar crest and abutments connected either at initial surgery (non-submerged) or three months later (submerged). The third implant was one-piece. Adjacent interstitial tissues were analyzed. Both two-piece implants resulted in a peak of inflammatory cells approximately 0.50 mm coronal to the microgap and consisted primarily of neutrophilic polymorphonuclear leukocytes. For one-piece implants, no such peak was observed. Also, significantly greater bone loss was observed for both two-piece implants compared with one-piece implants. In summary, the absence of an implant-abutment interface (microgap) at the bone crest was associated with reduced peri-implant inflammatory cell accumulation and minimal bone loss.

PMID: 12598555 [PubMed - indexed for MEDLINE]

The role of implants in orthodontics.

J Orthod. 2002 Sep;29(3):239-45

Authors: Ismail SF, Johal AS

PMID: 12218205 [PubMed - indexed for MEDLINE]

Crowns and other extra-coronal restorations: resin-bonded metal restorations.

Br Dent J. 2002 Aug 10;193(3):135-8, 141-2

Authors: Walls AW, Nohl FS, Wassell RW

Resin-bonded metal restorations is the final part of the series. Cast metal restorations which rely on adhesion for attachment to teeth are attractive because of their potential to be much more conservative of tooth structure than conventional crowns which rely on preparation features providing macromechanical resistance and retention.

PMID: 12213007 [PubMed - indexed for MEDLINE]

Influence of connector design on fracture probability of ceramic fixed-partial dentures.

J Dent Res. 2002 Sep;81(9):623-7

Authors: Oh W, G&#xF6;tzen N, Anusavice KJ

Fracture of ceramic fixed-partial dentures (FPDs) tends to occur in the connector area because of stress concentrations. The objective of this study was to test the hypothesis that the radius of curvature at the gingival embrasure of the FPD connector significantly affects the fracture resistance of three-unit FPDs. Two three-dimensional finite element models (FEMs), representing two FPD connector designs, were created in a manner corresponding to that described in a previous experimental study (Oh, 2002). We performed fractographic analysis and FEM analyses based on CARES (NASA) post-processing software to determine the crack initiation site as well as to predict the characteristic strength, the location of peak stress concentrations, and the risk-of-rupture intensities. A good correlation was found between the experimentally measured failure loads and those predicted by FEM simulation analyses. Fractography revealed fracture initiation at the gingival embrasure, which confirms the numerically predicted fracture initiation site. For the designs tested, the radius of curvature at the gingival embrasure strongly affects the fracture resistance of FPDs.

PMID: 12202644 [PubMed - indexed for MEDLINE]

Modified NTP.

J Am Dent Assoc. 2002 Feb;133(2):143; author reply 143-4

Authors: Hammond BD

PMID: 11868828 [PubMed - indexed for MEDLINE]

Good occlusal practice in removable prosthodontics.

Br Dent J. 2001 Nov 10;191(9):491-4, 497-502

Authors: Davies SJ, Gray RM, McCord JF

The loss of teeth may result in patients experiencing problems of a functional, aesthetic and psychological nature. This section addresses the very important subject of occlusal considerations for partial and complete dentures. The occlusion is particularly important given the bearing that occlusal factors have, especially on edentulous patients.

PMID: 11726062 [PubMed - indexed for MEDLINE]

An alternative method for restoring single-tooth implants.

J Am Dent Assoc. 2001 Sep;132(9):1269-73; quiz 1318-9

Authors: McArdle BF, Clarizio LF

BACKGROUND: Having laboratory technicians prepare soft-tissue casts and implant abutments with or without concomitant removable temporary prostheses during the restorative phase of single-tooth replacement is an accepted practice. It can, however, result in functional and esthetic intraoral discrepancies. CASE DESCRIPTION: Single-tooth implants can be restored with crowns (like those for natural teeth) fabricated at a dental laboratory on casts obtained from final impressions of prepared implant abutments. In the case reported, the restorative dentist restored the patient's single-tooth implant after taking a transfer impression. He constructed a cast simulating the peri-implant soft tissue with final impression material and prepared the abutment on this model. His dental assistant then fabricated a fixed provisional restoration on the prepared abutment. At the patient's next visit, the dentist torqued the prepared abutment onto the implant, took a final impression and inserted the provisional restoration. A crown was made conventionally at the dental laboratory and cemented in place at the following visit. CLINICAL IMPLICATIONS: This alternative method for restoring single-tooth implants enhances esthetics by more accurately simulating marginal gingival architecture. It also improves function by preloading the implant through fixed temporization after the dentist, rather than the laboratory technician, prepares the abutment to the dentist's preferred contours.

PMID: 11665352 [PubMed - indexed for MEDLINE]

Changing paradigms in implant dentistry.

Crit Rev Oral Biol Med. 2001;12(3):262-72

Authors: Salvi GE, Lang NP

This review focuses on five paradigms of implant dentistry which have undergone considerable modifications in recent years. An attempt was made to select and include all the relevant citations of the past 10 years. These five paradigms document the debate in the clinical and scientific community and include the aspects of (1) smooth vs. rough implant surfaces, (2) submerged vs. non-submerged implant installation techniques, (3) mixed tooth-implant vs. solely implant-supported reconstructions, (4) morse-taper abutment fixation vs. butt-joint interfaces, and (5) titanium abutments vs. esthetic abutments in clinical situations where esthetics is of primary concern.

PMID: 11497377 [PubMed - indexed for MEDLINE]

Indirect retention.

Br Dent J. 2001 Feb 10;190(3):128-32

Authors: Davenport JC, Basker RM, Heath JR, Ralph JP, Glantz PO, Hammond P

This article explains the mechanism of indirect retention for RPDs and discusses the factors which determine its effectiveness. Examples are given of designs which incorporate indirect retention.

PMID: 11236916 [PubMed - indexed for MEDLINE]

Building up tooth preparations for full crowns--2000.

J Am Dent Assoc. 2000 Apr;131(4):505-6

Authors: Christensen GJ

Many factors influence whether teeth planned for crowns or fixed prosthesis abutments need to be built up. Teeth may now be treated more conservatively with minimal fillers because of the greater strength of current cements, including hybrid ionomers and resins. Teeth planned as fixed prosthesis abutments require more remaining tooth structure and greater buildup strength than those designed for single full crowns. It appears that crown buildup is still necessary, but this procedure is needed less frequently than it was in previous years. Fillers can be used to fill holes left when previous restorations were removed, and are more commonly placed than build-ups.

PMID: 10770014 [PubMed - indexed for MEDLINE]

Initial orthopaedic displacement compared with longitudinal displacement of the maxilla after a forward force application. An experimental study in dogs.

Eur J Orthod. 1999 Dec;21(6):671-8

Authors: de Pauw GA, Dermaut LR, Verbeeck RM

The aim of this study was to compare the initial orthopaedic displacement of the maxilla in vivo and the longitudinal changes after a forward force application. The sample consisted of five 1-year-old dogs. An anterior force of 5 N on the maxilla was applied by a coil spring system pushing between Br&#xE5;nemark implants and a maxillary splint. The initial displacement of the maxilla after force application was measured by means of speckle interferometry. The longitudinal displacement of the maxilla after a force application during 8 weeks was measured by superimposing standardized lateral cephalograms. The initial, as well as the longitudinal, displacement of the maxilla of the dogs was in a forward direction with some counterclockwise rotation. There was no statistical difference between the initial and longitudinal displacement. The biological response after force application during 8 weeks can be predicted by the initial orthopaedic displacement.

PMID: 10665196 [PubMed - indexed for MEDLINE]

A screw lock for single-tooth implant superstructures.

J Am Dent Assoc. 1999 May;130(5):677-82

Authors: Artzi Z, Dreiangel A

BACKGROUND: The most common complication in a single-tooth implant restoration is abutment screw loosening. Instability of the prosthetic superstructure is expressed by difficulty in chewing and functioning, as well as soft-tissue soreness and/or swelling that could lead to screw fracture. Manufacturers of oral implants have attempted to refine the connecting parts of the prosthesis to achieve a more predictable tightening method for the screws. METHODS: To maintain the abutment screw tightly in its correct position, the authors developed a technique in which an elongated hexagonal titanium bar is inserted into the hexed fixed screw head. The screw is locked, and the bar is then fixed with a light-cured composite resin material that serves to seal the retaining screw access hole. The occlusal hexagonal bar thus serves as a secure screw lock that can be easily removed if needed. RESULTS: The authors have used the hexagonal bar for almost three years on 120 single-tooth screw-retained prostheses in 100 patients (65 in the first and second premolar region, 40 in the incisor region and 15 in the posterior molar region). All of these prostheses functioned successfully, including those with wider occlusal planes and increasing occlusal forces. No screw loosening or fractures were noted in any of the fixtures. CLINICAL IMPLICATIONS: This technique secures and stabilizes the single-tooth prosthesis, reduces chair time on follow-up procedures and reduces unnecessary frustration in patients and dental team members.

PMID: 10332132 [PubMed - indexed for MEDLINE]

Affordable implant prosthetics using a screwless implant system.

J Am Dent Assoc. 1998 Dec;129(12):1732-8

Authors: Shepherd NJ

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.

PMID: 9854924 [PubMed - indexed for MEDLINE]

Removing a partially loose fixed prosthesis.

J Am Dent Assoc. 1998 Aug;129(8):1135-7

Authors: Christensen GJ

PMID: 9715015 [PubMed - indexed for MEDLINE]

Replacing posterior teeth with freestanding implants: four-year prosthodontic results of a prospective study.

J Am Dent Assoc. 1998 Aug;129(8):1097-102

Authors: Muftu A, Chapman RJ

This article presents prospective four-year prosthetic results of the placement of 432 posterior freestanding, conventionally cemented prosthetic tooth implants in posterior edentulous spaces using the Bicon Dental Implants system (Bicon Dental Implants). Over four years, 0.74 percent of the abutments loosened, 0.5 percent of the abutments fractured, and 2.47 percent of the crowns experienced porcelain fracture, (all porcelain fractures occurred at time of placement). This low rate of problems appears to make free-standing single-tooth implant restorations a reliable solution to treating posterior edentulism.

PMID: 9715010 [PubMed - indexed for MEDLINE]

A five-year multi-practice clinical study on posterior resin-bonded bridges.

J Dent Res. 1998 Apr;77(4):609-14

Authors: De Kanter RJ, Creugers NH, Verzijden CW, Van't Hof MA

Previous clinical observations have revealed that resin-bonded bridges for posterior tooth replacements are less retentive than anterior resin-bonded bridges. Improved bonding procedures and preparation designs, however, may have a positive effect on the functional durability of these restorations. The present study reports the final analysis of a randomized controlled clinical trial in which different designs of posterior resin-bonded bridges were evaluated for a period of at least 5 years. The operational hypothesis was that the bonding system and the preparation design used in posterior resin-bonded bridges have an influence on the survival and clinical functioning of these restorations. Survival in this study was defined at two levels: (1) 'complete' survival (survival without any debonding), and (2) 'functional' survival (survival including loss of retention on one occasion and successful rebonding of the original RBB without further debonding). With regard to 'complete' survival, no significant differences were found between the bonding systems used for adherence of the restorations to abutment teeth (etching/Clearfil F2, sandblasting/Panavia EX, and silica-coating/Microfill Pontic C). The variable 'preparation form' (conventional preparation form vs. modified preparation form) for complete survival was statistically in favor of the modified preparation form (62% vs. 46%), but did not influence the functional survival. With regard to 'functional' survival, the combination of silica coating and Microfill Pontic C was more retentive than the other bonding systems (90% survival vs. 72% and 75%, p < 0.01). Factor location was found to be highly significant for both survival levels [Cox's PH model, p = 0.0002 (Cox, 1972)]: The five-year 'complete' survival rates were 65% for maxillary restorations and 40% for mandibular restorations, while the five-year 'functional' survival rates were 89% and 68%, respectively. It is concluded that preparation of grooves in abutment teeth for posterior resin-bonded bridges is beneficial to their chance of survival. Resin-bonded bridges placed in the maxilla have a better prognosis than those made in the mandible. The bonding systems used in this study appear to have no influence on the chance of failure. In rebonded posterior resin-bonded bridges, the bonding system silica-coating/Microfill Pontic C was more retentive than the other systems tested.

PMID: 9539464 [PubMed - indexed for MEDLINE]

Isolation with a dual-arch impression tray.

J Am Dent Assoc. 1998 Jan;129(1):103-4

Authors: Kaplowitz GJ

PMID: 9448355 [PubMed - indexed for MEDLINE]

Posts and cores: state of the art.

J Am Dent Assoc. 1998 Jan;129(1):96-7

Authors: Christensen GJ

Post-and-core placement using prefabricated posts and composite resin is an everyday procedure in most general practices. Such posts are easily placed, strong, relatively inexpensive and predictable. The most popular techniques and materials have been described. It is anticipated that post-and-core use will continue to increase because of the current trend to retain natural teeth into the mature years of life.

PMID: 9448353 [PubMed - indexed for MEDLINE]

An update on fixed prosthodontics.

J Am Dent Assoc. 1997 Apr;128(4):425-36

Authors: Cronin RJ, Cagna DR

The practice of fixed prosthodontics has continually evolved as a result of progress in laboratory and biomaterials science, clinical technologies and adjunctive multidisciplinary treatment advancements. This brief review describes those enhancements and how they affect the state-of-the-art practice of fixed prosthodontics.

PMID: 9103792 [PubMed - indexed for MEDLINE]

A technique for repairing bridge abutments damaged by caries.

J Am Dent Assoc. 1996 Oct;127(10):1531

Authors: Liftig R

PMID: 8908925 [PubMed - indexed for MEDLINE]

Evaluating the longevity of restorative materials that seal the root canals of overdenture abutments.

J Am Dent Assoc. 1995 Oct;126(10):1420-5

Authors: Ettinger RL

Researchers have not established which restorative materials are most appropriate to seal the root canals of overdenture abutments. The author evaluated the longevity of a spherical amalgam, a composite resin and a glass ionomer in 123 patients. Results of this study showed a significant difference between the glass ionomer and the other two materials with regard to the time from placement to replacement of the restorations.

PMID: 7594015 [PubMed - indexed for MEDLINE]

Adjunctive caries control in overdenture abutment teeth: a new modality.

J Am Dent Assoc. 1995 Feb;126(2):213-5

Authors: Kurtz KS

Controlling caries in decoronated abutment teeth is an ongoing concern for the restorative dentist. In the ideal situation, the overdenture abutment is restored with a cast coping, but economic constraints may rule this out in favor of a prefabricated overdenture attachment. This article describes how caries may be controlled in exposed dentin when such a restoration is used.

PMID: 7860890 [PubMed - indexed for MEDLINE]

A multi-practice clinical study on posterior resin-bonded bridges: a 2.5-year interim report.

J Dent Res. 1994 Feb;73(2):529-35

Authors: Verzijden CW, Creugers NH, Mulder J

A clinical trial of 201 posterior resin-bonded bridges (PRBBs) was conducted partially in a University clinic and partially in general dental practices, for study of the influence of some experimental variables on the survival of these restorations. This report contains the results of an interim analysis which was done after 2.5 years' follow-up. No significant differences were found among the bonding systems used to adhere the PRBBs (Clearfil F2/etching, Panavia EX/sandblasting, and Microfill Pontic C/silicate-coating), or among the different preparation forms. PRBBs made in general dental practices were as retentive as those made in the University clinic. The "location" factor was found to be highly significant (p = 0.0001). The survival rates were 81% for maxillary PRBBs and 56% for mandibular PRBBs.

PMID: 8120217 [PubMed - indexed for MEDLINE]

An in vivo study of the influence of the surface roughness of implants on the microbiology of supra- and subgingival plaque.

J Dent Res. 1993 Sep;72(9):1304-9

Authors: Quirynen M, van der Mei HC, Bollen CM, Schotte A, Marechal M, Doornbusch GI, Naert I, Busscher HJ, van Steenberghe D

In nine patients with fixed prostheses supported by endosseous titanium implants, 2 titanium abutments (transmucosal part of the implant) were replaced by either an unused standard abutment or a roughened titanium abutment. After 3 months of habitual oral hygiene, plaque samples were taken for differential phase-contrast microscopy, DNA probe analysis, and culturing. Supragingivally, rough abutments harbored significantly fewer coccoid micro-organisms (64 vs. 81%), which is indicative of a more mature plaque. Subgingivally, the observations depended on the sampling procedure. For plaque collected with paper points, only minor qualitative and quantitative differences between both substrata could be registered. However, when the microbiota adhering to the abutment were considered, rough surfaces harbored 25 times more bacteria, with a slightly lower density of coccoid organisms. The presence and density of periodontal pathogens subgingivally were, however, more related to the patient's dental status than to the surface characteristics of the abutments. These results justify the search for optimal surface smoothness for all intra-oral and intra-sulcular hard surfaces for reduction of bacterial colonization and of periodontal pathogens.

PMID: 8395545 [PubMed - indexed for MEDLINE]

Differences two years after tooth extraction in mandibular bone reduction in patients treated with immediate overdentures or with immediate complete dentures.

J Dent Res. 1993 Jun;72(6):1001-4

Authors: Van Waas MA, Jonkman RE, Kalk W, Van 't Hof MA, Plooij J, Van Os JH

In a randomized controlled clinical trial, 74 patients who required immediate dentures were randomly treated with immediate overdentures on two lower canines or with immediate complete dentures. Mandibular bone reduction was measured by use of oblique lateral cephalometric radiographs made at baseline and the results compared with those of one year and two years after denture treatment. Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.9 mm in the immediate-overdenture group and 1.8 mm in the immediate complete-denture group. In the posterior parts of the mandible, the bone reductions were, respectively, 0.7 mm and 1.9 mm. The differences were statistically significant in all measured regions. During the second year, no significant differences in bone reduction were found. The sums of differences in the first two years were significant in all regions except the molar region, preserving the initial difference. Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all regions of the mandible.

PMID: 8496472 [PubMed - indexed for MEDLINE]

Effects of chlorhexidine-containing gel and varnish on abutment teeth in patients with overdentures.

J Dent Res. 1992 Sep;71(9):1582-6

Authors: Keltjens HM, Creugers TJ, Schaeken MJ, Van der Hoeven JS

Previous experiments have shown that daily use of 1% chlorhexidine gel strongly reduced caries development in the abutment teeth under overdentures. The present experiment was designed to determine whether intermittent application of chlorhexidine, either in a varnish or in a gel, might be used as an alternative preventive method, less demanding for the patient. To this end, 31 patients were distributed among four treatment groups, with the number of mutans streptococci in plaque and saliva used as a balancing criterion. The treatments consisted of a single application of 40% chlorhexidine varnish, daily application of 1% chlorhexidine gel for one week, or the corresponding placebo treatments with varnish or gel without chlorhexidine. Patients were re-called for bacteriological and clinical examination at various intervals during an eight-week period following treatment. Chlorhexidine varnish and chlorhexidine gel applications significantly suppressed mutans streptococci on the abutment teeth for four and eight weeks, respectively. In agreement with earlier findings, the numbers of Actinomyces viscosus/naeslundii in plaque were significantly increased after chlorhexidine varnish treatment. The chlorhexidine gel reduced plaque accumulation and gingival bleeding for one week but had no long-lasting effect. The results seem to justify a long-term clinical test of intermittent chlorhexidine applications as an alternative for daily use in patients with overdentures.

PMID: 1522289 [PubMed - indexed for MEDLINE]

An analysis of clinical studies on resin-bonded bridges.

J Dent Res. 1991 Feb;70(2):146-9

Authors: Creugers NH, Van 't Hof MA

Many clinical data on resin-bonded bridges (RBBs) have been published in the last ten years. The survival rates vary widely, and the conclusions are sometimes conflicting. A method of combining the results of different studies in order to draw conclusions about the effectiveness of therapeutic concepts is meta-analysis. The aims of the meta-analysis in this study were: (1) to assess an "overall" survival ratio for RBBs and (2) to explore relationships between potential success factors and reported survival times. About 60 publications with clinical data on RBBs were reviewed. Following a number of inclusion criteria (information adequate to calculate or assess survival rates, as well as adequate information about the patients, the designs, and types of RBBs), 16 different samples were used for this meta-analysis. A weighted multiple-regression analysis revealed no significant effects of "type of retention" and "location" on the survival percentages. Kaplan-Meier estimates were used to assess overall survival in a secondary analysis with the data from all 16 samples (n = 1598). The overall survivals were: one year, 89 +/- 1%; two years, 84 +/- 1%; three years, 80 +/- 1%; and four years, 74 +/- 2%.

PMID: 1825091 [PubMed - indexed for MEDLINE]

An in vitro evaluation of the prevention of caries on overdenture abutments.

J Dent Res. 1988 Oct;67(10):1338-41

Authors: Ettinger RL, Manderson D, Wefel JS, Jensen ME

Teeth prepared as overdenture abutments are susceptible to caries, and it has been shown that brushing by itself is not sufficient to prevent this process. This study evaluated the preventive effect of a remineralization gel which has a low fluoride concentration and compared its effects with those of a phosphate fluoride gel (Karigel), which has a much higher concentration of fluoride. Twenty extracted anterior teeth from patients aged 50 to 70 years were prepared as for overdenture abutments. Each tooth was sectioned into three fragments. An acidified gel system was used to produce artificial caries lesions on the occlusal and root surfaces of each fragment. One fragment of each tooth was treated with the remineralizing gel, the second fragment with a high-fluoride gel, and the third fragment served as the control. Ten teeth were removed at two weeks and again at four weeks, and were sectioned and prepared for histological examination. The depth of the lesions was measured from standardized photomicrographs by means of a sonic digitizer. The conclusions were: (1) Lesions on the occlusal tended to be deeper than those on the root surfaces at four weeks but not at two weeks; and (2) the high-fluoride gel was more protective than the low-fluoride remineralizing solution at both time periods on the occlusal but not on the root surface.

PMID: 3049716 [PubMed - indexed for MEDLINE]

An in vitro evaluation of artificial caries-like lesions on restored overdenture abutments.

J Dent Res. 1988 Mar;67(3):582-4

Authors: Kambhu PP, Ettinger RL, Wefel JS

An acidified dialyzed gelatin gel system was used to determine the caries resistance of a variety of restorative materials used to obturate the canal orifice of overdenture abutment teeth. The restorative materials used were Tytin, Tytin + Copalite, P30 + Scotchbond, Fuji Ionomer-Type II, and Miracle Mix. Polarized light microscopy and microradiography were used to examine the caries-like lesions adjacent to the restorations. The lesions formed in the Fuji Ionomer-Type II and Miracle Mix groups appeared arrested at the wall adjacent to the restoration, and did not penetrate apically down the wall as did those associated with the other restorative materials. The mean depths of lesions adjacent to Fuji Ionomer-Type II and Miracle Mix restorations were significantly less than those of Tytin, Tytin + Copalite, or P30 + Scotchbond.

PMID: 3049717 [PubMed - indexed for MEDLINE]

Microbial aspects of preventive regimes in patients with overdentures.

J Dent Res. 1987 Oct;66(10):1579-82

Authors: Keltjens HM, Schaeken MJ, Van der Hoeven JS

The aim of this study was to test effects of preventive regimes using fluoride and chlorhexidine to prevent caries and periodontal diseases in 34 patients with overdentures. The patients, who were treated with immediate overdentures, were distributed at random into three experimental groups. In these groups, different gels--a placebo, a fluoride, and a chlorhexidine-fluoride gel--were tested by daily application. Supragingival plaque samples from selected surfaces of two abutment teeth were taken at one week, and at one, three, and six months after initial insertion of the overdenture. The placebo and fluoride gel influenced neither total CFU nor S. sanguis and A. viscosus/naeslundii counts. In the placebo group, but not in the fluoride group, S. mutans levels increased significantly, indicating the caries risk involved in overdentures. The use of chlorhexidine-fluoride gel resulted in a long-term suppression of total CFU. Further, S. mutans was found to be selectively suppressed to below detection level. A. viscosus/naeslundii was initially strongly suppressed, but after three months a partial return of the population was noticed. S. sanguis was relatively insensitive to the chlorhexidine-fluoride gel. It is concluded that a daily application of a chlorhexidine-fluoride gel is effective against plaque formation and S. mutans on abutment teeth in overdentures.

PMID: 3305620 [PubMed - indexed for MEDLINE]

Compratative distortion in three-unit fixed prostheses joined by laser welding, conventioanl soldering, or casting in one piece.

J Dent Res. 1977 Feb;56(2):128-34

Authors: Huling JS, Clark RE

This study evaluated three different joint-forming procedures: laser welding, soldering, and one-piece casting. Fifteen three-unit bridges were fabricated. The findings showed post-jointing distrotion to be significantly less for laser-welded and one-piece castings than for soldering; and significantly greater reliability (least error variance) in joining with the laser than either one-piece casting or soldering.

PMID: 14178 [PubMed - indexed for MEDLINE]