Socket Wall Research Articles

Early healing of the alveolar process after tooth extraction: an experimental study in the beagle dog

To describe the early healing events in the alveolar socket during the first 8 weeks of spontaneous healing after tooth extraction. 16 adult beagle dogs were selected and five healing periods were analysed (4 h, 1 week, 2 weeks, 4 weeks, 8 weeks). Mandibular premolars were extracted and each socket corresponding to the mesial root was left to heal undisturbed. In each healing period, three animals were euthanatized, each providing four study sites. Healing was assessed by descriptive histology and by histometric analysis using as landmarks: the vertical distance between buccal and lingual crest (B'L') and the width of buccal and lingual walls at three different levels. Differences between means for each variable for each healing period were compared (ANOVA; p < 0.05). B'L' at baseline was 0.45 (0.18) mm and decreased during the healing period to a final value of 0.18 (0.08) mm. The lingual width (Lw) remains almost unchanged while the buccal width (Bw) at 1 (Bw1) and 2 (Bw2) mm was reduced in about 40% of its initial value. Minor vertical bone reduction in both the buccal and lingual socket walls were observed. A marked horizontal reduction of the buccal bone wall was observed mostly in its coronal aspect.

Classification of Molar Extraction Sites for Immediate Dental Implant Placement: Technical Note

Dental implants may be successfully placed immediately into fresh extraction sockets when primary implant stability can be attained. This article presents a new classification system for molar extraction sites that describes extraction sockets based upon the bone available within the socket for stabilization of an immediately placed implant. Three categories--types A, B, and C--are employed: the type A socket, which allows for the implant to be placed completely within the septal bone, leaving no gaps between the implant and the socket walls; the type B socket, which has enough septal bone to stabilize but not completely surround the implant, leaving gaps between one or more surfaces of the implant and the socket walls; and the type C socket, which has little to no septal bone, thus requiring that the implant engage the periphery of the socket. Treatment protocols and relevant clinical examples are presented based upon the characterization of the socket according to this classification system.

Guided Bone Ridge Augmentation: A Clinicohistologic and Radiographic 2 Years Follow-up

Background: Augmentation of the bone is done to create the sufficient bone volume for ideal implant placement. This case report presents the effective augmentation of the socket using corticocancellous graft and AlloDerm. Methods: Failing 47 was extracted. Socket had a severe buccal dehiscence extending and a thin keratinized mucosa around. After through debridement, socket walls were decorticated and corticocancellous graft and allograft GBR was tacked over the socket. Mucoperiosteal flap was sutured with 5-0 nylon sutures (Ethicon) Bone core biopsy was done for histologic assessment and site was restored with screw-retained implant prosthesis. Results: Histologic assessment revealed ingrowth of new bone around the bone graft. Stable soft and hard tissue results have been seen with 2 years follow-up of the case. Conclusion: Results indicated that ridge preservation using corticocancellous graft and AlloDerm prevented the ridge resorption and helped in enhancement of bone fill and soft tissue volume.

Implants into fresh extraction site: A literature review, case immediate placement report

Immediate implants are positioned in the course of surgical extraction of the tooth to be replaced. The percentage success of such procedures varies among authors from 92.7-98.0%. The main indication of immediate implantation is the replacement of teeth with pathologies not amenable to treatment. Its advantages with respect to delayed implantation include reduced postextraction alveolar bone resorption, a shortening of rehabilitation treatment time, and avoidance of a second surgical intervention. The inconveniences in turn comprise a general requirement for membrane-guided bone regeneration techniques, with the associated risk of exposure and infection, and the need for mucogingival grafts to seal the socket space and/or cover the membranes. The surgical requirements for immediate implantation include extraction with the least trauma possible, preservation of the extraction socket walls and thorough alveolar curettage to eliminate all pathological material. Primary stability is an essential requirement, and is achieved with an implant exceeding the alveolar apex by 3-5 mm, or by placing an implant of greater diameter than the remnant alveolus. Esthetic emergence in the anterior zone is achieved by 1-3 mm subcrest implantation. Regarding guided regeneration of alveolar bone, the literature lacks consensus on the use of membranes and type of filler material required. While primary wound closure is desirable, some authors do not consider it to be of great relevance.

Influence of immediate post-extraction socket irrigation on development of alveolar osteitis after mandibular third molar removal: a prospective split-mouth study, preliminary report

The aim of this prospective comparative split-mouth study was to evaluate the role of socket irrigation with a normal saline solution routinely used at the end of extraction on the development of alveolar osteitis (AO) after removal of impacted mandibular third molars (MTMs). Thirty-five patients who satisfied the inclusion criteria were involved in the study and underwent extraction of four third-molars. To be included in the study, the mandibular third molars had to be impacted (partial or full bone) and require an osteotomy for extraction with use of a motorised drill. All surgeries were done under local anaesthesia or IV sedation. This was a prospective split-mouth study. The patient's left (assistant) side was a control side; it had a standard extraction technique of an impacted mandibular third molar that required a buccal full-thickness flap, buccal trough (osteotomy) and extraction of the tooth (with or without splitting the tooth into segments), followed by a traditional end-of-surgery debridement protocol consisting of a gentle curettage, bone filing of the socket walls, socket irrigation with approximately 5 ml of sterile normal saline solution and socket suctioning. The patient's right (operator) side was an experimental side; it also had a standard extraction technique of an impacted mandibular third molar at the beginning with a flap and osteotomy, but it was followed by a modified end-of-surgery protocol. It consisted of gentle curettage but the socket was not irrigated and not suctioned. It was simply left to bleed. The gauze was placed on top of the socket for haemostasis on both sides and the patient was asked to bite. On both sides, the buccal flap was positioned back without the suture. All patients were seen for a follow-up appointment four to seven days after the surgery to assess healing and check for symptoms and signs of alveolar osteitis, if present, on both irrigated and non-irrigated sides. This study followed the ethical guidelines of human subjects based on the Helsinki Declaration. Thirty-five patients or 70 sockets were evaluated. Eleven out of 35 patients in the study were subjected to a dry socket syndrome (31.4%). The higher number of AO was likely related to specifics of MTM selection in this study - only impacted (partial and full bone) MTMs were chosen. Among eleven patients with AO, two patients had a bilateral condition. By excluding two patients with bilateral dry sockets from the study, there were nine patients (18 extraction sites) with unilateral AO in the study. Seven out of nine patients (14 extraction sites) developed unilateral dry socket on the control (irrigated) side (77.8%) and only two (four extraction sites) on the experimental (non-irrigated) side (22.2%). Therefore, in this study there were 3.5 times more patients (extraction sites) with dry socket syndrome on the irrigated (control) side than patients (extraction sites) in the non-irrigated (experimental) side. A noticeable difference of dry socket syndromes (77.8% on the irrigated versus 22.2% on non-irrigated side) was demonstrated between the traditional extraction protocol versus modified approach without the end-of-surgery irrigation. The study demonstrated that the post-extraction socket bleeding is very important for the proper uncomplicated socket healing. If it's not washed away with irrigation solution at the end of extraction, the normal blood clot has a higher likelihood to form, and therefore, can potentially lead to an uncomplicated socket healing without development of alveolar osteitis. Socket bleeding at the extraction site creates a favourable environment for the formation of a blood clot - a protective dressing - necessary for a favourable osseous healing of the socket.

The Effect of Low-Magnitude, High-Frequency Vibration Stimuli on the Bone Healing of Rat Incisor Extraction Socket

Effects of small vibration stimuli on bone formation have been reported. In the present study, we used morphological and morphometric procedures to elucidate whether low-magnitude, high-frequency (LMHF) vibration stimuli could enhance the bone healing of rat incisor extraction sockets. After extraction of incisors from six-week-old rats, animals were assigned into a control group and two experimental groups to receive 50 Hz stimuli at either 0.05 mm or 0.2 mm peak-to-peak for an hour/day. LMHF vibration stimuli were generated by placing the mandibles of the animals onto a vibration generator. All groups were subdivided into two, according to the study periods (1 and 3 weeks). After the study period, undecalcified ground sections were taken and morphological and morphometric analyses performed. At both 1 and 3 weeks, newly formed bone was observed mainly in the upper wall of the extraction socket in all groups. Morphometric analyses revealed that the trabecular thickness in both experimental groups at 1 week was significantly greater than that in the control. LMHF vibration stimuli had a positive effect on bone at the early stage of bone healing, particularly in trabecular thickness, at the incisor extraction socket.

Different sympathetic pathways control the metabolism of distinct bone envelopes

Bone remodeling, the mechanism that modulates bone mass adaptation, is controlled by the sympathetic nervous system through the catecholaminergic pathway. However, resorption in the mandible periosteum envelope is associated with cholinergic Vasoactive Intestinal Peptide (VIP)-positive nerve fibers sensitive to sympathetic neurotoxics, suggesting that different sympathetic pathways may control distinct bone envelopes. In this study, we assessed the role of distinct sympathetic pathways on rat femur and mandible envelopes. To this goal, adult male Wistar rats were chemically sympathectomized or treated with agonists/antagonists of the catecholaminergic and cholinergic pathways; femora and mandibles were sampled. Histomorphometric analysis showed that sympathectomy decreased the number of preosteoclasts and RANKL-expressing osteoblasts in mandible periosteum but had no effect on femur trabecular bone. In contrast, pharmacological stimulation or repression of the catecholaminergic cell receptors impacted the femur trabecular bone and mandible endosteal retromolar zone. VIP treatment of sympathectomized rats rescued the disturbances of the mandible periosteum and alveolar wall whereas the cholinergic pathway had no effect on the catecholaminergic-dependent envelopes. We also found that VIP receptor-1 was weakly expressed in periosteal osteoblasts in the mandible and was increased by VIP treatment, whereas osteoblasts of the retromolar envelope that was innervated only by tyrosine hydroxylase-immunoreactive fibers, constitutively expressed beta-2 adrenergic receptors. These data highlight the complexity of the sympathetic control of bone metabolism. Both the embryological origin of the bone (endochondral for the femur, membranous for the mandibular periosteum and the socket wall) and environmental factors specific to the innervated envelope may influence the phenotype of the sympathetic innervation. We suggest that an origin-dependent imprint of bone cells through osteoblast–nerve interactions determines the type of autonomous system innervating a particular bone envelope.

Osteotome-Mediated Sinus Lift without Grafting Material: A Review of Literature and a Technique Proposal.

Implant rehabilitation of the edentulous posterior maxilla may be a challenging procedure in the presence of insufficient bone volume for implant placement. Maxillary sinus augmentation with or without using grafting materials aims to provide adequate bone volume. The aim of the present study was to systematically review the existing literature on transalveolar maxillary sinus augmentation without grafting materials and to propose and describe an osteotome-mediated approach in postextraction sites in combination with platelet derivative. The systematic review showed that high implant survival rate (more than 96% after 5 years) can be achieved even without grafting the site, with a low rate of complications. Available alveolar bone height before surgery was not correlated to survival rate. In the described case report, three implants were placed in posterior maxilla after extraction of two teeth. An osteotome-mediated sinus lifting technique was performed with the use of platelet derivative (PRGF); a synthetic bone substitute was used to fill the gaps between implant and socket walls. No complications occurred, and implants were successfully in site after 1 year from prosthetic loading. The presented technique might represent a viable alternative for the treatment of edentulous posterior maxilla with atrophy of the alveolar bone though it needs to be validated by studies with a large sample size.

Immediate Placement and Provisionalization With Buccal Plate Preservation: A Case Report of a New Technique

Abstract Abstract Post-extraction resorption of the alveolar ridge is known particularly to affect the buccal plate, increasing the risk of facial soft-tissue recession and other adverse clinical effects. The authors have developed a simple technique for buccal plate preservation that involves surgically creating a pouch facial to the buccal plate that is filled with xenograft material. This technique can also be utilized in cases for which immediate implant placement and provisionalization are planned. A case report illustrating this approach is presented.

Esthetic Evaluation of Single-Tooth Morse Taper Connection Implants Placed in Fresh Extraction Sockets or Healed Sites

The aim of this study was to compare the esthetic outcome of single implants placed in fresh extraction sockets with those placed in fully healed sites of the anterior maxilla. This retrospective study was based on data from patients treated with single-tooth Morse taper connection implants placed in fresh extraction sockets and in fully healed sites of the anterior maxilla. Only single implant treatments were considered with both neighboring teeth present. Additional prerequisites for immediate implant treatment were intact socket walls and a thick gingival biotype. The esthetic outcome was objectively rated using the pink esthetic/white esthetic score (PES/WES). The Mann-Whitney U test was used to compare the PES and the WES between the 2 groups. Twenty-two patients received an immediate implant, and 18 patients had conventional implant surgery. The mean follow-up was 31.09 months (SD 5.57; range 24-46) and 34.44 months (SD 7.10; range 24-48) for immediately and conventionally inserted implants, respectively. No implants were lost. All implants fulfilled the success criteria. The mean PES/WES was 14.50 (SD 2.52; range 9-19) and 15.61 (SD 3.20; range 8-20) for immediately and conventionally placed implants, respectively. Immediate implants had a mean PES of 7.45 (SD 1.62; range 4-10) and a mean WES of 7.04 (SD 1.29; range 5-10). Conventional implants had a mean PES of 7.83 (SD 1.58; range 4-10) and a mean WES of 7.77 (SD 1.66; range 4-10). The difference between the 2 groups was not significant. Immediate and conventional single implant treatment yielded comparable esthetic outcomes.

Bone modelling at fresh extraction sockets: immediate implant placement versus spontaneous healing. An experimental study in the beagle dog

The purpose of this investigation is to describe histologically the undisturbed healing of fresh extraction sockets when compared to immediate implant placement. In eight beagle dogs, after extraction of the 3P3 and 4P4, implants were inserted into the distal sockets of the premolars, while the mesial sockets were left to heal spontaneously. Each animal provided four socket sites (control) and four implant sites (test). After 6weeks, animals were sacrificed and tissue blocks were dissected, prepared for ground sectioning. The relative vertical buccal bone resorption in relation to the lingual bone was similar in both test and control groups. At immediate implant sites, however, the absolute buccal bone loss observed was 2.32 (SD 0.36) mm, what may indicate that while an apical shift of both the buccal and lingual bone crest occurred at the implant sites, this may not happen in naturally healing sockets. The results from this investigation showed that after tooth extraction the buccal socket wall underwent bone resorption at both test and control sites. This resorption appeared to be more pronounced at the implant sites, although the limitations of the histological evaluation method utilized preclude a definite conclusion.

Immediate single-tooth implants in the anterior maxilla: 3-year results of a case series on hard and soft tissue response and aesthetics

The objective of this prospective study was to assess the overall outcome of immediate single implant treatment in the anterior maxilla after a 3-year observation period. Thirty consecutively treated patients with a thick gingival biotype, ideal gingival level/contour and intact socket walls at the time of tooth extraction were treated for single-tooth replacement in the aesthetic zone by two experienced clinicians. Treatment included minimal mucoperiosteal flap elevation, immediate implant placement (NobelReplace TiUnite(®)), insertion of a grafting material between the implant and the socket wall and connection of a screw-retained provisional restoration. The latter was replaced by a cemented crown 6 months thereafter. Patients were clinically and radiographically re-examined after 3 years to assess implant survival, complications and hard and soft tissue conditions. The aesthetic outcome was objectively rated using the Pink Esthetic Score (PES) and White Esthetic Score (WES) by a blinded clinician who had not been involved in the treatment. Twenty-five patients could be re-evaluated after 3 years. One early implant failure had occurred resulting in an implant survival rate of 96%. Radiographic examination yielded on average 1.13 mm mesial, respectively 0.86 mm distal bone loss. The clinical conditions showed fairly low peri-implant plaque (18%) and bleeding (24%) and mean probing depth was 3.17 mm. Mean mesial/distal papilla shrinkage and midfacial soft tissue recession in reference to the pre-operative status accounted for 0.05, 0.08 and 0.34 mm, respectively. Between the 1- and 3-year reassessment mesial papillae showed significant re-growth (0.36 mm; p=0.015). Advanced midfacial recession (>1 mm) was found in 2/25 (8%) cases. Five (21%) cases were aesthetic failures (PES<8 and/or WES<6) and 5/24 (21%) showed an (almost) perfect outcome (PES≥12 and WES≥9). The remainder (14/24 or 58%) demonstrated acceptable aesthetics. The proposed strategy seems a valuable and predictable treatment option for well-selected patients in the mid-long term as shown by almost full papillary re-growth and a low risk for advanced midfacial recession.

Use of a Partial Foot Prosthesis With Vacuum-Assisted Suspension: A Case Study

In Brief Vacuum-assisted suspension uses the creation of a negative pressure differential to hold a gel liner securely to the walls of the prosthetic socket to reduce the migration of the residual limb within the prosthesis. The eliminated movement or pistoning of the residual limb within the socket is believed to contribute to increased comfort and function in persons with a transtibial amputation by reducing peak pressures during ambulation. A new socket system was developed with vacuum-assisted suspension for a person with partial foot amputation to take advantage of this better coupling. The purpose of this case study was to evaluate the use of a partial foot prosthesis with vacuum-assisted suspension in a 68-year-old man with a right transfemoral amputation and a left partial foot amputation, both of traumatic origin. A questionnaire was used to compare the subject's satisfaction and function between his previous and new prosthesis. Photographs of the residual limb were taken before initial fitting of the new prosthesis, 10 days after initial fitting, and at 2-month follow-up to document the appearance of the residual limb. The subject rated the prosthesis with vacuum-assisted suspension higher with regards to comfort during standing and walking (i.e., it was more comfortable) and lower for pain while wearing the prosthesis (i.e., it was less painful). Photographs at 2-month follow-up showed that the skin was healthier in overall appearance when compared with initial fitting. This case study suggests that the use of a prosthesis with vacuum-assisted suspension may be a viable design for improving comfort, function, and residual limb health for persons with partial foot amputation. This case study evaluated the use of a partial foot prosthesis with vacuum-assisted suspension in a 68-year-old male with a right transfemoral amputation and a left partial foot amputation. The subject rated the prosthesis with vacuum-assisted suspension higher in comfort and lower in pain than his previous prosthesis. Photographs at two-month follow-up showed that the skin was healthier in overall appearance when compared to initial fitting.

Immediate and conventional single implant treatment in the anterior maxilla: 1-year results of a case series on hard and soft tissue response and aesthetics

The main objective of this clinical study was to document midfacial soft tissue dynamics following single immediate implant treatment (IIT) and conventional implant treatment (CIT) in the anterior maxilla when performed by experienced clinicians in well-selected patients. Appropriate bone volume and ideal soft tissue levels were considered requirements for implant therapy. Additional prerequisites for IIT were intact socket walls and a thick gingival biotype. CIT included standard flap elevation whereas IIT was either performed with a flap or flapless procedure. All implants were provisionally restored using cemented acrylic crowns. Bone levels, papillae and midfacial soft tissue levels were monitored at regular intervals. The aesthetic outcome was assessed after 1 year using the pink aesthetic score (PES) and white aesthetic score (WES). Sixteen patients (10 men, six women; mean age 45) received an immediate implant and 23 patients (12 men, 11 women; mean age 40) had conventional implant surgery. One immediate implant failed in the early healing phase. The mean bone level from the implant-abutment interface was 0.85mm for IIT and 0.65mm for CIT after 1 year (p=0.144). Mesial papillae remained stable over time. Minute loss of distal papillae occurred following IIT (-0.38mm) and a tendency for re-growth was found following CIT (0.60mm). Midfacial soft tissues remained stable over time following IIT with only 7% showing advanced recession (>1mm). Flapless surgery induced less midfacial recession than flap surgery (p=0.023). Significant midfacial recession occurred following CIT (-1mm). Overall, 24% were aesthetic failures (PES<8 and/or WES<6) and 8% showed an (almost) perfect outcome (PES12 and WES9). The remainder (68%) demonstrated acceptable aesthetics. Immediate implants demonstrated fairly stable midfacial soft tissue levels with only a minority of cases showing advanced recession. Irrespective of the timing of implant placement, aesthetic failures seem to be rather common and only a strict minority may show perfection.

Prosthetic sockets stabilized by alternating areas of tissue compression and release

A prosthetist makes a conventional socket by wrapping plaster bandage around the residual limb and using the resulting shell to create a positive model. After he or she modifies the plaster, it is used to create a laminated socket. Such sockets are almost perfect cylinders that encapsulate the limb. The bone is centered in soft, compressible tissue that must move aside before the bone can push against the socket to transmit force or torque to the prosthesis. In a compression/release stabilized (CRS) socket, three or more longitudinal depressions compress and displace tissue between the socket wall and the bone to reduce lost motion when the bone is moved with respect to the socket. Release areas between depressions are opened to accommodate displaced tissue. Without these openings provided, the CRS socket will not function as intended. Often, the release areas of compression are the struts of a carbon-fiber frame, and the regions between struts are left open. A frame with openings may be modified by the prosthetist adding a thin membrane fully surrounding the limb but allowing the membrane and underlying tissue to enter the release openings. The membrane may contain electrodes, and it may constitute a roll-on liner that helps suspend the prosthesis. We introduce three socket designs: transradial, transfemoral, and transhumeral.

Replacement of Vertically Root-Fractured Endodontically Treated Teeth With Immediate Implants in Conjunction With a Synthetic Bone Cement

The purpose of this prospective study was to evaluate the clinical outcome of implants immediately placed into fresh extraction sockets for the replacement of endodontically treated teeth with signs of vertical root fracture. Sixteen partially edentulous patients, with 1 tooth scheduled for extraction and showing clinical signs and symptoms and/or radiological evidence of vertical root fracture, were included in the study. Sixteen transmucosal implants were installed immediately after extraction and careful debridement. The gap between the implant surface and the socket walls was filled using synthetic bone grafting cement. Prosthetic phase occurred 3 to 4 months after surgery. Implant success and survival and radiographic bone loss were evaluated after 1 year of function. Patient satisfaction for mastication function, phonetics, and aesthetics was also assessed by means of a questionnaire. No implant failure occurred. The overall implant success and survival was 100% at 1 year. The mean follow-up was 13.5 months. All prostheses were successful. Periimplant bone loss after 1 year averaged 0.48 ± 0.20 mm. All patients reported full satisfaction for mastication function, phonetics, and aesthetics. The use of a synthetic bone grafting cement in combination with immediate implant placement procedure can be considered a safe, effective, and predictable treatment option for the rehabilitation of fresh postextraction sockets.

Bio-Oss® Collagen in the buccal gap at immediate implants: a 6-month study in the dog

following tooth extraction and immediate implant installation, the edentulous site of the alveolar process undergoes substantial bone modeling and the ridge dimensions are reduced. objective: the objective of the present experiment was to determine whether the process of bone modeling following tooth extraction and immediate implant placement was influenced by the placement of a xenogenic graft in the void that occurred between the implant and the walls of the fresh extraction socket. five beagle dogs about 1 year old were used. The 4th premolar in both quadrants of the mandible ((4) P(4) ) were selected and used as experimental sites. The premolars were hemi-sected and the distal roots removed and, subsequently, implants were inserted in the distal sockets. In one side of the jaw, the marginal buccal-approximal void that consistently occurred between the implant and the socket walls was grafted with Bio-Oss Collagen while no grafting was performed in the contra-lateral sites. After 6 months of healing, biopsies from each experimental site were obtained and prepared for histological analyses. the outline of the marginal hard tissue of the control sites was markedly different from that of the grafted sites. Thus, while the buccal bone crest in the grafted sites was comparatively thick and located at or close to the SLA border, the corresponding crest at the control sites was thinner and located a varying distance below SLA border. it was demonstrated that the placement of Bio-Oss Collagen in the void between the implant and the buccal-approximal bone walls of fresh extraction sockets modified the process of hard tissue healing, provided additional amounts of hard tissue at the entrance of the previous socket and improved the level of marginal bone-to-implant contact.

Esthetic alveolar ridge preservation with calcium phosphate and collagen membrane: Preliminary report

The objective of this study was to evaluate clinically, histologically and radiographically a ridge preservation technique used on extraction sockets grafted with biphasic calcium phosphate (BCP) and a resorbable collagen membrane. Patients having a labial socket wall defect more than one-third in mesio-distal socket width after maxillary central incisor tooth extraction were included. The labial defect was sealed with resorbable collagen membrane and the defect filled with BCP. The grafted socket was covered with a resorbable collagen wound dressing material. The treated sockets were evaluated after a 4-month healing period when implants were placed and followed for up to 12 months. There were 8 subjects enrolled in this study. A statistical difference was found only in ridge width reduction at 3 mm below the cement-enamel junction of the adjacent teeth (P < .05) with 1 mm widening at 8 mm. The amount of new bone formation was extensively varied with diminutive graft remnants. Most cells in the connective tissue were osteopontin positive indicating they were osteoblast-like cells. A declination in the radiodensity of the grafted socket was observed during the analyzed period. Ridge preservation with BCP with collagen membrane can be used as an alternative treatment for maintaining ridge dimension before implant placement.

Influence of a microgrooved collar design on soft and hard tissue healing of immediate implantation in fresh extraction sites in dogs

This study compared the alveolar bone reduction after immediate implantation using microgrooved and smooth collar implants in fresh extracted sockets. Four mongrel dogs were used in this study. The full buccal and lingual mucoperiosteal flaps were elevated and the third and fourth premolars of the mandible were removed. The implants were installed in the fresh extracted sockets. The animals were sacrificed after a 3-month healing period. The mandibles were dissected and each implant site was removed and processed for a histological examination. During healing, the marginal gaps in both groups, which were present between the implant and the socket walls at implantation, disappeared as a result of bone filling and resorption of the bone crest. The buccal bone crests were located apical of its lingual counterparts. At the 12-week interval, the mean bone-implant contact in the microgrooved group was significantly higher than that of the turned surface group. From the observations in some of the microgrooved groups, we have found bone attachment to the 12 mum microgrooved surface and collagen fibers perpendicular to the long axis of the implants over the 8 mum microgrooved surface. Within the limitations of this study, microgrooved implants may provide more favorable conditions for the attachment of hard and soft tissues and reduce the level of marginal bone resorption and soft tissue recession.

Transducers for the determination of the pressure and shear stress distribution at the stump—socket interface of trans-tibial amputees

Recent developments in prosthetic socket design have created renewed interest in monitoring the stress distribution at the socket—residual limb interface. Although a few devices for measuring pressure can be found in the literature, none are capable of measuring reliably in areas of high curvature, such as the important area at the patellar tendon bar. Furthermore, few devices can record shear stress, thought to be critical in causing tissue damage. In order to address these issues two new transducers have been designed and evaluated. One design allows the simultaneous recording of the normal and shear stresses at various points of the socket walls, while the other is capable of measuring the three components of the force applied on the patellar tendon. The latter design incorporates a feature that permits displacement of the patellar tendon bar, in order to study the effect of various amounts of indentation of the tendon on the stress distribution around the residual limb. Both transducers were calibrated using dead weights and special jigs to ensure accurate loading conditions. Under laboratory bench conditions the normal—shear force transducer showed: 2.03 per cent full scale output (FSO) hysteresis error for shear stress direction, 1.65 per cent FSO for normal direction; 99.56 per cent FSO overall accuracy for shear direction, and within 99.64 per cent FSO for normal direction; and for the patellar tendon transducer 1.53 per cent FSO hysteresis error for shear direction, 1.85 per cent FSO for shear stress direction; 99.65 per cent FSO overall accuracy for shear direction, and 99.58 per cent FSO for normal direction. During an amputee walking trial the transducers showed 92 per cent to 97 per cent repeatability. The two new transducers were used in conjunction with two other types of transducers, previously designed at the University of Strathclyde, in a series of tests on ten trans-tibial amputees. Sample results for walking activities and a summary of maximum stresses recorded are presented.