Osseointegrated implants for prosthetic rehabilitation of the edentulous patient show high success rates if certain preconditions are fulfilled. Implant stability plays a critical role for a successful critical outcome since short implants and implants placed in soft bone are more prone to failure (13, 49). In the original protocols for implant placement, primary implant stability was ensured by new bone formation and remodelling, termed osseointegration, which was accomplished during an initial healing period in which implants remained nonloaded to secure undisturbed bone formation onto the implant surface. The process of osseointegration increases the stiffness of the bone around the implant, and the bony interlock with the implant surface prevents micro-movement and the formation of fibrous scar tissue at the time of implant loading. However, the development of new implant surfaces and clinical techniques has enabled a marked reduction of the initial healing period, even to the point of an immediate ⁄ early loading of implants that show high primary stability (7, 37). Thus, the success of immediate ⁄ early loading implant techniques is dependent on the ability of the clinician to determine the degree of primary implant stability and changes in stability along with new bone formation and remodelling. The clinical perception of primary implant stability is frequently based on the cutting resistance of the implant during its insertion. The feeling of good stability may be accentuated if there is the sense of an abrupt stop at the seating of the implant. Root forms of tapered implants often have a geometry that will provide a firm stop and perhaps a false perception of high stability. A percussion test has also been used to assess implant stability. The percussion test may involve the tapping of a mirror handle against the implant carrier and is designed to elicit a ringing sound from the implant as an indication of good stability or osseointegration. Percussion tests probably provide more information about the tapping instrument, and will at best only yield poor qualitative information. Insertion torque measurements are sometimes used to determine primary implant stability (6). Application of a reverse or unscrewing torque has also been proposed for the assessment of implant stability at the time of abutment connection (53). Implants that rotate under the applied torque are considered failures and are then removed. However, an implant surface in the process of osseointegrating, albeit slowly, may fracture under the applied torque stress. Moreover, as animal experiments have demonstrated the re-integration of loosened and rotationally mobile implants (26), the reverse torque testing has fallen into disrepute. Other techniques, such as the Periotest and resonance frequency analysis, aim to provide an objective measure of implant stability and osseointegration that is noninvasive and does not damage the implant–tissue interface (6, 28). The resonance frequency analysis technique has been extensively used in experimental and clinical research for the last 10 years. The purpose of this

http://implocerk.com/images/Sennerby%20Perio%202000,%202008.pdf

Implant stability measurements using resonance frequency analysis: biological and biomechanical aspects and clinical implications.

The goal of the current publication is to provide a comprehensive literature review on the topic of dental implant materials. The following paper focuses on conventional titanium implants and more recently introduced and increasingly popular zirconia implants. Major subtopics include the material science and the clinical considerations involving both implant materials and the influence of their physical properties on the treatment outcome. Titanium remains the gold standard for the fabrication of oral implants, even though sensitivity does occur, though its clinical relevance is not yet clear. Zirconia implants may prove to be promising in the future; however, further in vitro and well-designed in vivo clinical studies are needed before such a recommendation can be made. Special considerations and technical experience are needed when dealing with zirconia implants to minimize the incidence of mechanical failure.

https://pure.uva.nl/ws/files/2531883/164424_484372.pdf

A Critical Review of Dental Implant Materials with an Emphasis on Titanium versus Zirconia

Purpose: The aim of this clinical trial was to evaluate the influence of gingival tissue thickness on crestal bone loss around dental implants after a 1-year follow-up. Materials and Methods: Forty-six implants (23 test and 23 control) were placed in 19 patients. The test implants were placed about 2 mm supracrestally, whereas the control implants were positioned at the bone level. Before implant placement, the tissue thickness at implant sites was measured with a periodontal probe. After healing, metal-ceramic cement-retained prostheses were constructed. According to tissue thickness, the test implants were divided into A (thin) and B (thick) groups. Intraoral radiographs were performed and crestal bone changes were measured at implant placement and after 1 year. Results: Mean bone loss around the test implants in group A (thin mucosa) was 1.61 ± 0.24 mm (SE; range, 0.9 to 3.3 mm) on the mesial and 1.28 ± 0.167 mm (range, 0.8 to 2.1 mm) on the distal. Mean bone loss in test group B (thick mucosa) implants was 0.26 ± 0.08 mm (range, 0.2 to 0.9 mm) on the mesial aspect and 0.09 ± 0.05 mm (range, 0.2 to 0.6 mm) on the distal aspect. Mean bone loss around control implants was 1.8 ± 0.164 mm (range, 0.6 to 4.0 mm) and 1.87 ± 0.166 mm (range, 0.0 to 4.1 mm) on the mesial and distal aspects, respectively. Analysis of variance revealed a significant difference in terms of bone loss between test A (thin) and B (thick) groups on both the mesial and the distal. Conclusion: Initial gingival tissue thickness at the crest may be considered as a significant influence on marginal bone stability around implants. If the tissue thickness is 2.0 mm or less, crestal bone loss up to 1.45 mm may occur, despite a supracrestal position of the implant-abutment interface. INT J ORAL MAXILLOFAC IMPLANTS 2009;24:712–719

/pdf/the-influence-of-soft-tissue-thickness-on-crestal-bone-1px60o73y1.pdf

The influence of soft tissue thickness on crestal bone changes around implants: a 1-year prospective controlled clinical trial.

Aim
To provide an overview on the biology and soft tissue wound healing around teeth and dental implants.

Material and Methods
This narrative review focuses on cell biology and histology of soft tissue wounds around natural teeth and dental implants.

Results and conclusions
The available data indicate that:


Oral wounds follow a similar pattern.


The tissue specificities of the gingival, alveolar and palatal mucosa appear to be innately and not necessarily functionally determined.


The granulation tissue originating from the periodontal ligament or from connective tissue originally covered by keratinized epithelium has the potential to induce keratinization. However, it also appears that deep palatal connective tissue may not have the same potential to induce keratinization as the palatal connective tissue originating from an immediately subepithelial area.


Epithelial healing following non-surgical and surgical periodontal therapy appears to be completed after a period of 7–14 days. Structural integrity of a maturing wound between a denuded root surface and a soft tissue flap is achieved at approximately 14-days post-surgery.


The formation of the biological width and maturation of the barrier function around transmucosal implants requires 6–8 weeks of healing.


The established peri-implant soft connective tissue resembles a scar tissue in composition, fibre orientation, and vasculature.


The peri-implant junctional epithelium may reach a greater final length under certain conditions such as implants placed into fresh extraction sockets versus conventional implant procedures in healed sites.

https://www.onlinelibrary.wiley.com/doi/epdf/10.1111/jcpe.12206

Soft tissue wound healing around teeth and dental implants

Objective: The aim of the present study was to analyze the soft tissue barrier formed to implant abutments made of different materials.

Material and methods: Six Labrador dogs, about 1 year old, were used. All mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later four implants (OsseoSpeed™, 4.5 × 9 mm, Astra Tech Dental, Molndal, Sweden) were placed in the edentulous premolar region on one side of the mandible and healing abutments were connected. One month later, the healing abutments were disconnected and four new abutments were placed in a randomized order. Two of the abutments were made of titanium (Ti), while the remaining abutments were made of ZrO2 or AuPt-alloy. A 5-months plaque control program was initiated. Three months after implant surgery, the implant installation procedure and the subsequent abutment shift were repeated in the contra-lateral mandibular region. Two months later, the dogs were euthanized and biopsies containing the implant and the surrounding soft and hard peri-implant tissues were collected and prepared for histological analysis.

Results: It was demonstrated that the soft tissue dimensions at Ti- and ZrO2 abutments remained stable between 2 and 5 months of healing. At Au/Pt-alloy abutment sites, however, an apical shift of the barrier epithelium and the marginal bone occurred between 2 and 5 months of healing. In addition, the 80-μm-wide connective tissue zone lateral to the Au/Pt-alloy abutments contained lower amounts of collagen and fibroblasts and larger fractions of leukocytes than the corresponding connective tissue zone of abutments made of Ti and ZrO2.

Conclusion: It is suggested that the soft tissue healing to abutments made of titanium and ZrO2 is different to that at abutments made of AuPt-alloy.

The mucosal barrier at implant abutments of different materials

PURPOSE: The objective of the present experiment was to study the morphogenesis of the mucosal attachment to implants made of c.p. titanium. MATERIAL AND METHODS: All mandibular premolars were extracted in 20 Labrador dogs. After a healing period of 3 months, four implants (ITI Dental Implant System) were placed in the right and left sides of the mandible. A non-submerged implant installation technique was used and the mucosal tissues were secured to the conical marginal portion of the implants with interrupted sutures. The sutures were removed after 2 weeks and a plaque control program including daily cleaning of the remaining teeth and the implants was initiated. The animals were sacrificed and biopsies were obtained at various intervals to provide healing periods extending from Day 0 (2 h) to 12 weeks. The mandibles were removed and placed in the fixative. The implant sites were dissected using a diamond saw and processed for histological analysis. RESULTS: Large numbers of neutrophils infiltrated and degraded the coagulum that occupied the compartment between the mucosa and the implant during the initial phase of healing. At 2 weeks after surgery, fibroblasts were the dominating cell population in the connective tissue interface but at 4 weeks the density of fibroblasts had decreased. Furthermore, the first signs of epithelial proliferation were observed in specimens representing 1-2 weeks of healing and a mature barrier epithelium occurred after 6-8 weeks of healing. The collagen fibers of the mucosa were organized after 4-6 weeks of healing. CONCLUSION: It is suggested that the soft-tissue attachment to implants placed using a non-submerged installation procedure is properly established after several weeks following surgery.

Morphogenesis of the peri‐implant mucosa: an experimental study in dogs

Objective: The aim of the present experiment was to study the healing around two-part implants that were placed in a subcrestal position.

Material and methods: Five mongrel dogs, about 2 years old, were included. The mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later two test and two control implants (OsseoSpeed™, 3.5 mm × 8 mm) were placed in one side of the mandible. The implants were placed in such a way that the implant margin was located 2 mm apical to the bone crest. In the test implants, the surface modification extended to the implant margin and, thus, included the shoulder part of the implant. Regular abutments with a turned surface (Zebra™) were connected to the control implants, while experimental abutments with a modified surface (TiOblast™) were connected to the test implants. A plaque control program that included cleaning of implants and teeth every second day was initiated. Four months later the dogs were euthanized and biopsies were obtained and prepared for histological analysis.

Results: The marginal bone level at the test implants was identified in a more coronal position than that at the control implants. In 40% of the test implants, the bone-to-implant contact extended coronal of the abutment/fixture (A/F) border, i.e. in contact with the abutment part of the implant. The connective tissue portion of the peri-implant mucosa that was facing the test abutments contained a higher density of collagen and a smaller proportion of fibroblasts than that at the control sites.

Conclusion: It is suggested that osseointegration may occur coronal to the A/F interface of two-part implants. Such a result, however, appears to depend on the surface characteristics of the implant components.

Subcrestal placement of two-part implants.

OBJECTIVE: To analyse the soft tissue healing at titanium implants coated with type 1 collagen. MATERIAL AND METHODS: Six dogs were used. The mandibular pre-molars and the three anterior maxillary pre-molars were extracted. Three months later mucoperiosteal flaps were raised and two test and two control implants were installed (3i TG Osseotite 3.75 x 10 and 2.8 mm transmucosal collar). The test implants were coated with a purified porcine type I collagen. Cover screws were placed and flaps were sutured. The sutures were removed 2 weeks later and a plaque-control programme was initiated. Another 2 weeks later, the procedure was repeated in the contra-lateral mandibular region. Four weeks after the second implant surgery, biopsies were obtained and prepared for histological examination. RESULTS/CONCLUSION: The vertical dimensions of the epithelial and connective tissue components as well as the composition of the connective tissue portion facing the implant were similar at collagen-coated and uncoated implants after 4 and 8 weeks of healing. It is suggested that soft tissue healing to implants coated with type I collagen was similar to that at non-coated titanium implants and that no adverse reactions to the collagen-coated implants occurred.

Maria Welander

Papers

The mucosal barrier at implant abutments of different materials

Morphogenesis of the peri‐implant mucosa: an experimental study in dogs

Subcrestal placement of two-part implants.

Soft tissue healing at titanium implants coated with type I collagen. An experimental study in dogs

The mucosal barrier at implant abutments of different materials: The mucosal barrier at implant abutments of different materials