Assessment of the changes in retention and surface topography of attachments for maxillary 4-implant-retained overdentures.

STATEMENT OF PROBLEM: Restoring the edentulous maxilla with an implant-retained overdenture (IRO) can present a challenge because of increased implant divergence and the added wear of the implant abutments and attachments. However, knowledge pertaining to the degree of implant divergence and its effects on the wear pattern of the implant attachments is lacking. PURPOSE: The purpose of this in vitro study was to investigate the change in the retention and wear characteristics of unsplinted abutments and attachments when used to retain a maxillary 4-implant palateless complete removable overdenture with different implant angulations. MATERIAL AND METHODS: Three groups of specimens of 0-, 15-, and 30-degree implant angulations were evaluated, each with 7 specimens. The retention of specimens was recorded after aging cycles equivalent to 1, 2.5, and 6 years of use. The surface of the attachments was examined with light and scanning electron microscope (SEM). RESULTS: Increasing the interimplant divergence improved the initial retention. After 1 year of use, retention of the 15- and 30-degree groups was significantly higher than that of the 0-degree group (P<.05). No significant difference in retention was found between the 15- and 30-degree groups (P>.05). After 2.5 and 6 years of use, no significant difference in retention was noted between groups (P>.05). Under light and SEM examination, the wear of the abutments and attachments was related to the interimplant divergence. CONCLUSIONS: The initial retention of single attachments increased significantly as the implant divergence increased. The retention of the 15- and 30-degree groups was significantly higher than that of the 0-degree group after 1 year of use. No significant difference in retention was found after 2.5 and 6 years, regardless of implant angulation.

Management of Bleeding After Exodontia, Periodontal, or Implant Surgery.

During and after commonly performed dental surgical procedures, hemorrhaging that is greater than normal can occur in patients who do not have bleeding disorders. This article discusses the management of various potential hemorrhagic scenarios with respect to extractions and periodontal and implant surgeries. Protocols for controlling bleeding are delineated for primary and postoperative hemorrhaging. Background information is provided with respect to blood vessels, hemostatic mechanisms, patient evaluations, and drugs that may need to be suspended prior to dental surgical procedures.

Hierarchy of restorative space required for different types of dental implant prostheses.

BACKGROUND: Management of the full and partially edentulous arch requires an understanding regarding the amount of vertical and horizontal restorative space that is needed for different types of dental implant prostheses. Failure to design a prosthetic construct without considering space issues can result in a rehabilitation with diminished stability, poor esthetics, and inadequate contours. Therefore, available restorative volume must be computed before initiating therapy to ensure proper prosthesis design. TYPES OF STUDIES REVIEWED: The authors searched the dental literature for articles that addressed space requirements for different types of dental implant prostheses and found a few on this subject. RESULTS: The dental literature indicates there is a 3-dimensional hierarchy of restorative space necessary for different types of implant constructs. The minimum amount of vertical space required for implant prostheses is as follows: fixed screw-retained (implant level): 4 through 5 millimeters; fixed screw-retained (abutment level): 7.5 mm; fixed cement-retained: 7 through 8 mm; unsplinted overdenture: 7mm; bar overdenture: 11 mm; and fixed screw-retained hybrid: 15mm. These dimensions represent the minimal amount of vertical rehabilitative space that can accommodate the above implant prostheses. With respect to horizontal space, computations are needed to account for the discrepancy between an implant and tooth position. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Restorative spaces for each type of prostheses are restoration specific and should be considered during treatment planning to facilitate proper case selection and enhance patient satisfaction.

Dental Implantology: Numbers Clinicians Need to Know.

Dental implantology is a discipline that merges knowledge regarding treatment planning, surgical procedures, and prosthetic endeavors. To attain optimal results many numbers pertaining to different facets of therapy are integrated into treating patients. This article outlines a wide range of digits that may assist clinicians in enhancing the performance of implant dentistry. Important integers are presented in three segments related to the sequence of therapy: pre-procedural assessments, surgical therapy, and postsurgical patient management.

Implant Insertion Torque: Its Role in Achieving Primary Stability of Restorable Dental Implants.

A literature review was conducted to determine the role of insertion torque in attaining primary stability of dental implants. The review is comprised of articles that discussed the amount of torque needed to achieve primary implant stability in healed ridges and fresh extraction sockets prior to immediate implant loading. Studies were appraised that addressed the effects of minimum and maximum forces that can be used to successfully place implants. The minimum torque that can be employed to attain primary stability is undefined. Forces ≥30 Ncm are routinely used to place implants into healed ridges and fresh extraction sockets prior to immediate loading of implants. Increased insertion torque (≥50 Ncm) reduces micromotion and does not appear to damage bone. In general, the healing process after implant insertion provides a degree of biologic stability that is similar whether implants are placed with high or low initial insertion torque. Primary stability is desirable when placing implants, but the absence of micromotion is what facilitates predictable implant osseointegration. Increased insertion torque helps achieve primary stability by reducing implant micromotion. Furthermore, tactile information provided by the first surgical twist drill can aid in selecting the initial insertion torque to achieve predictable stability of inserted dental implants.

Management of the Nasopalatine Canal and Foramen Associated With Dental Implant Therapy.

In some patients, the contents of the nasopalatine canal must be removed to facilitate placement of a dental implant into the canal. Reasons to enucleate the canal in preparation for a bone graft or a dental implant include inadvertent perforation into the canal when creating an osteotomy for an implant, severe atrophy of the maxilla, and a large foramen that precludes placing an implant into the desired location along the bony ridge. The authors searched the dental literature for clinical reports in humans that addressed placement of dental implants into or adjacent to the nasopalatine canal. They found that the nasopalatine canal is usually around 10-mm long and 4-mm wide and slants from the horizontal plane at a 66-degree angle, and there is considerable variation regarding these measurements. Several clinical reports demonstrate that the canal can be enucleated and bone grafted before successful implant placement. It is also possible to place an implant into the canal at the time of surgery and this procedure may or may not be combined with an adjunctive bone graft. Numerous case reports indicate there is usually no permanent loss of sensation of the anterior palate when an implant is placed into the nasopalatine canal. The authors concluded that placing an implant into the nasopalatine canal is a viable procedure as part of a surgical and prosthetic treatment plan when there is a dearth of alternate sites for implant placement. In patients with severe atrophy of the maxilla, combination syndrome, or who have a large or malpositioned nasopalatine canal, the canal can be used as a site to place a dental implant to support a fixed or removable dental prosthesis.

Open contacts adjacent to dental implant restorations: Etiology, incidence, consequences, and correction.

BACKGROUND: The aim of this investigation was to evaluate the potential causes, clinical significance, and treatment of open contacts between dental implant restorations and adjacent natural teeth. TYPES OF STUDIES REVIEWED: The authors searched the dental literature for clinical trials in humans that addressed the incidence of open contacts that develop after implant restorations are placed next to teeth. RESULTS: The authors found 5 studies in which the investigators addressed the incidence of open contacts after implant restorations are inserted next to teeth. Results from these studies indicated that an interproximal gap developed 34% to 66% of the time after an implant restoration was inserted next to a natural tooth. This event occurred as early as 3 months after prosthetic rehabilitation, usually on the mesial aspect of a restoration. CONCLUSIONS: The occurrence of an interproximal separation next to an implant restoration was greater than anticipated. It appears that force vectors cause tooth movement and an implant functions like an ankylosed tooth. PRACTICAL IMPLICATIONS: Clinicians should inform patients of the potential to develop interproximal gaps adjacent to implant restorations, which may require repair or replacement of implant crowns or rehabilitation of adjacent teeth. Furthermore, steps should be taken to check the continuity of the arch periodically. If the clinician detects an open contact, it is prudent to monitor for signs or symptoms of pathosis so that prosthetic repair of the gap can be initiated, if needed. These problems could add to treatment costs and decrease overall patient satisfaction related to implant treatment.

Dental Cone-Beam Scans: Important Anatomic Views for the Contemporary Implant Surgeon.

Intraoral cone-beam computed tomography (CBCT), otherwise known as volume imaging CT scan, provides 3-dimensional images of mandibular and maxillary structures. These images offer highly accurate and valuable diagnostic information to facilitate treatment planning for implant cases. This article serves as a primer on how to read and interpret CBCT cross sectional views. It identifies anatomic structures of interest and discusses their clinical relevance.

Nerve damage related to implant dentistry: incidence, diagnosis, and management.

Proper patient selection and treatment planning with respect to dental implant placement can preclude nerve injuries. Nevertheless, procedures associated with implant insertion can inadvertently result in damage to branches of the trigeminal nerve. Nerve damage may be transient or permanent; this finding will depend on the cause and extent of the injury. Nerve wounding may result in anesthesia, paresthesia, or dysesthesia. The type of therapy to ameliorate the condition will be dictated by clinical and radiographic assessments. Treatment may include monitoring altered sensations to see if they subside, pharmacotherapy, implant removal, reverse-torquing an implant to decompress a nerve, combinations of the previous therapies, and/or referral to a microsurgeon for nerve repair. Patients manifesting altered sensations due to various injuries require different therapies. Transection of a nerve dictates immediate referral to a microsurgeon for evaluation. If a nerve is compressed by an implant or adjacent bone, the implant should be reverse-torqued away from the nerve or removed. When an implant is not close to a nerve, but the patient is symptomatic, the patient can be monitored and treated pharmacologically as long as symptoms improve or the implant can be removed. There are diverse opinions in the literature concerning how long an injured patient should be monitored before being referred to a microsurgeon.

Failed dental implants: diagnosis, removal and survival of reimplantations.

BACKGROUND: Over time, the percentage of dental implants that fail increases because of biological and technical issues. Inevitably, clinicians will dedicate more time to dealing with ailing and failing dental implants. METHODS: The authors searched the literature for articles that addressed diagnostic manifestations of failed implants and reasons for their demise, as well as survival rates of dental implant reimplantations. RESULTS: The authors found that there is no precise cut point (besides 100 percent) with regard to the amount of bone loss in the absence of mobility that indicates an implant has failed. The decision to treat or explant an ailing implant is a judgment call by the treating clinician. Survival rates found in the literature after first and second reimplantations ranged from 71 percent to 100 percent and 50 percent to 100 percent, respectively. The 100 percent findings were based on small groups of implants, and there were scant data addressing implant survival after second reimplantations. CONCLUSIONS: The decision to remove an implant needs to be based on clinical assessments, radiographic evaluations or both. If the implant is deemed hopeless, there are devices that facilitate their removal. Furthermore, reimplantations can be performed successfully, but their survival rate appears to be lower than that of implants placed at sites from which they were not lost formerly. PRACTICAL IMPLICATIONS: Ailing dental implants should not be condemned prematurely, because patients often respond to treatment of peri-implantitis. Many patients desire reimplantations in sites in which implants have failed. This procedure is valuable, especially if it makes possible the fabrication of an implant-supported fixed or removable prosthesis.

Assessing bone's adaptive capacity around dental implants: a literature review.

BACKGROUND: Increased stress (force) on prostheses induces strain (deformation) in the peri-implant bone. Elevated stress and strain could result in the failure of implants that support prostheses. However, the survival rate of implants supporting prostheses under increased stress is high. Either the bone is stronger than expected or it adapts to increased stress. Concepts regarding bone's adaptive capacity continue to evolve and are the focus of this literature review. TYPES OF STUDIES REVIEWED: The authors searched the literature to find studies that addressed the bone's capacity to adjust to increased stress and strain. They assessed experimental and clinical trials in which investigators monitored healing after placement of dental implants. RESULTS: The data indicate that forces greater than the bone's adaptive ability can induce loss of osseointegration, as well as osseous resorption. In contrast, it is possible that increased stress on prostheses initiates a reparative process, thereby facilitating retention of implants experiencing increased stress. Numerous lines of evidence support the concept that bone can modify itself to withstand increased mechanical forces. PRACTICAL IMPLICATIONS: The authors provide an explanation for the high success rate of prostheses and implants in bone that are exposed to increased stress and strain.

Dental implants typically help retain peri-implant vertical bone height: evidence-based analysis.

The dental literature is assessed regarding the ability of dental implants to maintain vertical bone height after various implant placement scenarios: immediate, delayed, insertion into partially and fully edentate healed ridges, and under overdentures. Studies are also reviewed to determine if bone loss after implant insertion is continuous. Numerous investigations that support the concept that implants preserve bone height are identified. In addition, the data indicate that a minuscule amount of annual bone loss usually persists after implant placement, but it is often clinically imperceptible.

The clinical significance of keratinized gingiva around dental implants.

Whether or not keratinized tissue is needed around dental implants to maintain peri-implant health is a controversial subject. To clarify this issue a search was conducted for clinical trials that appraised the significance ofkeratinized gingiva (KG) around teeth and dental implants. A critical assessment of the data revealed that the literature is replete with studies that contradict one another with respect to the need for KG as it relates to survivability of implants, gingival response to plaque, inflammation, probing depths, recession, and loss of bone. When groups of patients with and without KG were compared with respect to various clinical parameters, a statistically significant better result in the presence of KG could be interpreted to indicate that having KG is advantageous. However, quantitative differences between groups with and without KG were usually very small. Overall, the data was interpreted to indicate that some patients may need augmentation of keratinized tissue to maintain peri-implant health. Ultimately, the decision to augment KG is a judgment call that needs to be made by the treating clinician, because there are not enough data to facilitate development of definitive guidelines relevant to this subject. Apparently, the need for KG is patient specific, and at present there is no method to reliably predict who would benefit from tissue augmentation.