Immediate and early replacement implants and restorations.

There have been rapid developments in dental implant treatment protocols to reduce the time between implant placement and restoration. Implants may be placed immediately following tooth extraction or following a period of healing to allow resolution of residual infection or sufficient bone and soft tissue healing. Early restoration and loading of implants has to be carefully controlled to avoid increased failure and complications. Advantages and disadvantages of the various techniques are described.

Astra Tech single-tooth implants: an audit of patient satisfaction and soft tissue form.

AIM: To investigate patient centred outcomes, soft tissue morphology, and bone levels. MATERIAL AND METHODS: Sixty-six subjects, who had completed treatment for a single implant restoration at least l year previously. Appearance was recorded photographically and bone levels and interdental contact points measured from intra-oral radiographs using a x 7 scale loupe. Subjects completed a satisfaction questionnaire. RESULTS: Subjects were highly satisfied with all aspects of the restoration including the appearance of the soft tissue (median shape/colour score 6 on scale 1-6). Twenty-eight sites in 20 subjects had no contact point between implant crown and adjacent tooth. A normal height papilla was judged to be present in 19 of these sites. These were excluded from the subsequent analysis. In the remaining 46 subjects with contact points the presence (JEMT score 3) or deficiency (score 1/2) of the papilla was significantly related to the distance to the bone level on the adjacent tooth and implant head. Differences were observed between the mesial and distal aspects of the implant restoration. CONCLUSIONS: Examining clinicians were more critical of the restorations than the patients. The presence of a complete papilla was associated with a slightly greater distance from contact point to bone level than previously reported.

A prospective 3-year study of fixed bridges linking Astra Tech ST implants to natural teeth.

BACKGROUND: Connecting teeth and osseointegrated implants in fixed reconstructions is not generally recommended because of differences in their response to loading. AIM: The aim of the present study was to assess the clinical and radiographic performance of the teeth and implants used to support three unit fixed bridges subjected to normal functional loads. SUBJECTS AND METHODS: Nineteen subjects (10 males, nine females, age range 27-65 years) with an edentulous posterior free end saddle in either maxilla or mandible (Kennedy Class 2), and opposing natural teeth or a tooth-supported fixed bridge were treated and completed the 3-year trial. An Astra Tech ST implant (length: 9 mm (n=2), 11 mm (n=9) or 13 mm (n=8); diameter: 4.5 mm) was placed immediately distal to the last tooth or leaving a single premolar sized space. The distal tooth received a gold coping and the implant was restored with a customised Prepable abutment (Astra Tech Profile BiAbutment: diameter 5.5 or 7 mm). A fixed bridge was placed linking the gold coping and implant abutment either with the pontic as a distal cantilever (n=6, length 7-8 mm) or as a fixed-fixed design (n=13, length 6-12 mm). Standardised radiographs and clinical records were taken at delivery of the prosthesis (baseline BL) and annually. RESULTS: Plaque scores at implant sites increased between BL and subsequent years (P<0.02). Statistically significant increases in probing depth were observed at both abutment teeth and implants between baseline and subsequent years (P<0.001). Marginal bone levels (mm) at the implant and tooth were stable between BL, 1-, 2- and 3-year examinations (implant: BL 0.65+/-0.42, 1 year 0.63+/-0.47, 2 years 0.88+/-0.55, 3 years 0.78+/-0.64; tooth: BL 2.29+/-0.82, 1 year 2.41+/-0.8, 2 years 2.38+/-1.02, 3 years 2.68+/-0.86). No signs of the intrusion of the abutment teeth were detected. One case of abutment screw loosening occurred. Eight bridges required re-cementation with a permanent cement in place of the temporary cement. There were eight subjects presenting with fractures/chips to the composite component of the bridges. CONCLUSION: The 3-year results demonstrate fully functional successful restorations with no evidence of tooth intrusion and with stable bone levels at both teeth and implants.

A 5-year prospective study of Astra single tooth implants.

AIM: To evaluate the AstraTech Implant ST (Molndal, Sweden) for single tooth replacement clinically and radiographically after 5 years in function. SUBJECTS AND METHOD: Fifteen patients (age range 16 to 48) with missing maxillary anterior teeth (6 central incisors, 8 laterals, 1 bicuspid) had four 13 mm and eleven 15 mm single tooth implants provided. All patients were seen at 4- to 6-monthly intervals for oral hygiene maintenance. Periapical radiographs using Rinn holders and a long cone technique were taken at the crown insertion and after 1 year, 3 and 5 years. RESULTS: No implant losses were observed in 14 of the 15 patients available for evaluation. No abutment screw loosening or soft tissue problems were observed. At crown insertion the mean bone level was 0.46 +/- 0.55 to 0.48 +/- 0.56 mm apical to the top of the implant neck and there were no statistically significant changes in the radiographic bone level over the 5 years of the study (0.36 +/- 0.37 to 0.43 +/- 0.46 mm at year 5). One crown was recemented after 18 months in function and 1 crown was replaced because of a fracture to the porcelain incisal edge. CONCLUSION: The Astra Tech Implants ST were highly successful in single tooth replacement and bone levels during 5 years of function were stable.

A clinical, radiographic, and microbiologic comparison of Astra Tech and Brånemark single tooth implants.

BACKGROUND: The soft tissues around single tooth implants differ fundamentally from the gingiva around natural teeth. There are very limited data comparing soft tissues around different implant systems. AIM: To assess whether the design characteristics of dental implants, particularly the implant-abutment junction, may affect the dimensions and health of the peri-implant soft tissues and radiographic bone levels. SUBJECTS AND METHOD: Fifteen Astra Tech and 15 Brånemark single tooth implants that had been in function for a minimum of 2 years in 30 partially dentate subjects were examined for plaque accumulation, probing depth, and bleeding on probing and compared to contralateral healthy teeth. Standardized radiographs were taken to measure the most coronal bone to implant contact on the mesial and distal surfaces. In addition, samples of subgingival plaque were taken on paper points and examined by darkfield microscopy. RESULTS: Significantly higher mean probing depths (p < .001) and higher mean percentage of spirochetes (p = .003) were found at implants compared to teeth. In this sample, the Brånemark implants had significantly higher probing depths than the Astra Tech implants (median and interquartile range: Astra Tech 2.7 mm [2-3], Brånemark 3.3 mm [3-3.7] p = .026) and the most coronal bone to implant contact was closer to the implant-abutment junction in the Astra Tech implants (Astra Tech 0.6 mm [0.2-0.9], Brånemark 1.6 mm [1.4-2.0]. p < .001). CONCLUSION: Although there were statistically significant differences between the two implant systems, the clinical differences were small and probably reflect differences in the biologic width in relation to the location and design of the implant-abutment junction.

Effect of loading on bone regenerated at implant dehiscence sites in humans.

Few investigations have studied the long-term fate of bone formed following the technique of guided tissue regeneration. The aim of the present study was to evaluate bone fill around implant fixtures with dehiscence defects and to study its response to loading. Ten patients were treated with overdentures supported by 2 fixtures ad modum Brånemark. A third 7 mm x 3.75 mm diameter fixture was placed for the purposes of the study in the most anterior part of the mandible with a dehiscence defect of 4 to 5 mm on the buccal aspect (and 3 to 4 threads exposed) which was covered with a Gore-Tex membrane and buried beneath the mucosa. Fixtures were exposed after 5 months (stage 2), ball abutments connected and loaded through an overdenture for 1 year. Nine fixtures were functioning well after 1 year of loading, 6 of which were retrieved with a trephine for histological examination and compared with 6 unloaded fixtures retrieved in our previously reported study. The bone area filling the thread profiles (BA%) and the bone to metal contact (BMC%) were measured in the 3 most apical and 3 most coronal thread profiles on the buccal and lingual surfaces. Statistically significant higher BMC% (P < 0.01) were observed in loaded fixtures in the apical regions (buccal: loaded 51%, unloaded 25%; lingual: loaded 49%, unloaded 24%). Differences approached significance for the regeneration site (loaded 22%, unloaded 6%) but were no different for the coronal lingual region (loaded 28%, unloaded 20%). There were no differences for BA%. This study confirms that there is an increase in bone to metal contact with time and following fixture loading and that this may also occur with bone regenerated under Gore-Tex membranes.

A prospective study of Astra single tooth implants.

A new design of single tooth implant (AstraTech, Molndal Sweden) featuring a microthreaded conical neck and TiO blast surface was evaluated clinically and radiographically after 2 years in function. Fifteen patients (age range 16 to 48) with missing maxillary anterior teeth (6 central incisors, 8 laterals, 1 bicuspid) had 4, 13 mm and 11, 15 mm implants placed under local anaesthesia and left for a period of 6 months before exposure and abutment connection/crown fabrication. All patients were seen at 4 to 6 monthly intervals for hygienist maintenance. Radiographs using Rinn holders and a long cone technique were taken at the crown insertion and after 1 year (14 subjects) and 2 years (12 subjects). All implants were successfully integrated at stage 2, and no implants have been lost. The internal conical seal design of the abutment/implant interface facilitated connection and there were no cases of abutment screw loosening. No soft tissue problems were observed, and the gingival morphology/health was well maintained. One crown was recemented after 18 months in function, and 1 crown was replaced because of a fracture to the porcelain incisal edge. At crown insertion, the mean bone level was 0.46 to 0.48 mm apical to the top of the implant and there were no statistically significant changes in the bone level over the 2 years of the study. In conclusion, the single tooth Astra implants were highly successful and bone changes within the first 2 years of function were comparable with other systems reporting high long-term success rates.

Implant placement: surgical techniques and considerations.

Successful implant surgery largely depends on good planning and meticulous technique. The former requires an appreciation of the restorative requirements and visualization of the desired end result. This may be easier for the clinician who is delivering both aspects of treatment, but in other circumstances requires close collaboration between prosthodontist and surgeon. This paper focuses on the surgical techniques involved in implant surgery, because successful osseointegration is achievable only with careful surgical preparation.

Healing of implant dehiscence defects with and without expanded polytetrafluoroethylene membranes: a controlled clinical and histological study.

Bone augmentation around implant fixtures using the technique of guided tissue regeneration has been described in a number of reports. The aim of this study was to evaluate bone fill around dehiscence defects at matched defects randomly allocated to test (expanded polytetrafluoroethylene; Gore-Tex) or control treatments within the same patient. Six edentulous subjects were treated with overdentures supported by 2 fixtures ad modum Bränemark. In addition, 2 experimental 7-mm fixtures with nearly identical dehiscence defects on the labial aspect were placed in the anterior part of the mandible. Baseline defect heights ranged from 2.5 to 4.0 mm with 2 to 4 threads exposed. The test fixture dehiscence was covered with a Gore-Tex membrane secured with a cover screw. The experimental fixtures were exposed after 5 months at stage 2 surgery and measurements and photographs repeated. The fixtures were then removed with a trephine and processed for histological evaluation. Regeneration of a hard tissue resembling bone was observed in 4 of 6 cases treated with Gore-Tex, amounting to between 95 and 100% elimination of the dehiscence and total coverage of the threads. However, in one of these cases, histological evaluation showed that it was soft tissue and not bone, and in a further case soft tissue regeneration was apparent both clinically and histologically. In another case there was no significant regeneration at either test or control defects. Although there was a trend for the Gore-Tex-treated dehiscences to respond more favourably, the differences in clinical and histological measurements between test and control failed to reach statistical significance.

Successful fertility experiments with cryopreserved spermatozoa of barramundi, Lates calcarifer (Bloch), using dimethylsulfoxide and glycerol as cryoprotectants.

The fertility of cryopreserved Lates calcarifer sperm was studied to increase the availability of semen for routine fertilization of stripped eggs and to provide a tool for selective breeding. Semen diluted (1:4 v/v) and frozen (-196 degrees C) with 5% dimethylsulfoxide (DMSO) or 10% glycerol (final concentration) as cryoprotectants was used to inseminate freshly stripped ova. Frozen-thawed sperm were motile for about 4 min after being mixed with seawater. In the DMSO medium, post-thaw sperm activation was immediate after dilution with seawater, but in the glycerol medium maximum motility intensity was delayed for up to 1 min. When eggs and sperm were mixed before the addition of seawater, semen frozen with DMSO as cryoprotectant gave a mean hatch rate (84.1%) no different (P > 0.05) from that of unfrozen semen diluted with Ringer's solution (80.7%) or with DMSO (83.7%), but higher (P < 0.05) than that of semen frozen with glycerol (60.9%). Adding sperm to seawater 30 s before mixing with eggs did not improve the fertility of sperm cryopreserved with glycerol. Eggs inseminated with glycerol-cryoprotected sperm showed higher mortality during incubation than those inseminated with DMSO-cryoprotected sperm. Sperm held in liquid nitrogen for 90 days with DMSO as cryoprotectant yielded acceptable fertilization and hatching rates with semen-to-ova ratios of up to 1:100 (v/v) , and produced fish with no apparent abnormalities over a 29-day period after hatch. These results show that cryopreservation of L. calcarifer sperm is feasible and well suited to a variety of hatchery purposes.

Close linkage of esterase-D to unipolar depression and alcoholism is ruled out in eight pedigrees.

Unipolar depression and alcoholism were tested for genetic linkage to esterase-D at 13q14.1. Tight linkage to esterase-D was ruled out for three phenotypes using three models of penetrance: (1) unipolar depression and alcoholism taken together as affected, (2) unipolar depression alone as affected with alcoholism considered unaffected and (3) alcoholism alone as affected with unipolar depression considered unaffected. This study does not support an earlier finding of possible linkage between the esterase-D locus at 13q14.1 and alcoholism.

Linkage of c-Harvey-ras-1 and INS DNA markers to unipolar depression and alcoholism is ruled out in 18 families.

Eighteen families informative for c-Harvey-ras-1 and INS DNA markers were tested for linkage to unipolar depression and alcoholism. No evidence of linkage was found between these DNA markers and the disorders observed in the families. This study fails to replicate the Old Order Amish Study and suggests that a significant degree of genetic heterogeneity may be present among psychiatric disorders.

Effects of captopril on left ventricular structure and function in SHR with established hypertension.

While antihypertensive therapy is considered to be an important clinical intervention in hypertensive patients, its effects on cardiac structure and function have not been intensely evaluated. In this study we tested the hypotheses that lowering blood pressure (BP) with the angiotensin I-converting enzyme inhibitor captopril, would: 1) normalize left ventricular mass and increase the cardiocyte mitochondria/myofibrils volume (Vmito/Vmyo) ratio; and 2) not compromise peak ventricular performance. We treated 16-week-old SHR and WKY with captopril (40-80 mg/kg) and hydrochlorothiazide (500 mg/l) via their drinking water. After six weeks of treatment peak cardiac performance was measured during rapid volume overload. Tissue samples from the left ventricular wall were analyzed by electron microscopy and stereology. Captopril lowered BP in SHR and WKY but had no affect on the left ventricular/body weight ratio. The only intracellular change in treated SHR was an increase in sarcoplasmic volume density. Treated WKY exhibited decreased midmyocardial mitochondrial volume density. At peak cardiac output, acceleration of flow and cardiac index were not affected by treatment. Stroke work at peak cardiac output was decreased in the treated groups due to a decrease in mean arterial pressure. In addition, captopril treatment resulted in a shift of the cardiac output (CO)-left ventricular end diastolic pressure (LVEDP) curves, such that LVEDP at peak cardiac output was approximately 50% less in the treated groups compared to their respective control groups. Although captopril was efficacious in lowering BP, it is suggested that lowering BP with this agent does not, at least within six weeks, lead to a reversal of hypertrophy or to a significant alteration in the volume densities of myofibrils and mitochondria. However, an important effect of this antihypertensive drug which may be of clinical significance, is that it leads to a leftward shift of the CO-LVEDP curve in both hypertensive and normotensive rats.

Coronary vasodilator reserve, capillarity, and mitochondria in trained hypertensive rats.

To test the hypothesis that exercise training can reverse the decrements in coronary reserve, capillary density, and mitochondrial volume density evident during established hypertension, we trained spontaneously hypertensive (SHR) and normotensive (WKY) rats on a treadmill over a 3-mo period. At 7 mo of age we used microspheres to evaluate myocardial perfusion in conscious rats. Exercise training did not alter hypertension or left ventricular hypertrophy but did increase maximal O2 consumption in both SHR and WKY. A decrement in left and right ventricular coronary reserve in SHR, compared with WKY, was indicated by 1) a smaller increment in myocardial perfusion during maximal vasodilation with dipyridamole and 2) a higher minimal coronary vascular resistance per unit mass. Exercise training had no significant effect on any index of myocardial perfusion in SHR or WKY. A 12% decrement in capillary numerical density in the endomyocardium of SHR was not reversed by exercise training. We estimated the volume densities of mitochondria, myofibrils, and sarcoplasm using electron microscopy and point-counting stereology on perfusion-fixed hearts. None of the parameters in either SHR or WKY was changed by exercise training. It is concluded that exercise training does not reverse the decrements in coronary reserve and capillary numerical density associated with hypertension in adult rats. Moreover the previously observed enhancement of mitochondrial volume density due to exercise in young hypertensive rats was not observed in adult SHR.

Role of sympathetic nerves during developing cardiac hypertrophy in Grollman hypertensive rats.

Peak left ventricular (LV) function, during rapid volume expansion, and cardiocyte structure were studied in rats with developing cardiac hypertrophy in response to Grollman hypertension (1 kidney, 1 figure 8) after chemical sympathectomy with 6-hydroxydopamine. This form of renovascular hypertension led to the same magnitude of hypertrophy in rats with or without sympathectomy. Indices of peak LV function, measured during acute volume expansion, tended to be normal or slightly higher in hypertensive rats than in controls. Sympathectomy in rats with hypertension significantly improved cardiac and stroke indices while decreasing total peripheral resistance at peak cardiac output. Despite similar magnitudes of LV hypertrophy (LVH) in the two hypertensive groups, cardiocytes in sympathectomized rats had higher mitochondrial volume densities and slightly lower myofibrillar volume densities. After regional sympathectomy of the anterior portion of the LV with phenol, mitochondrial volume density increased by 21% in hypertensive rats with LVH. These data indicate that, during the development of LVH in response to renovascular hypertension, sympathetic nerves do not contribute to the magnitude of LVH but may limit improvement in peak LV performance in response to increased preload. However, sympathetic nerves do play a role in the regulation of mitochondrial and myofibril growth.

Morphometry of canine coronary arteries, arterioles, and capillaries during hypertension and left ventricular hypertrophy.

The mechanisms responsible for the increase in minimal coronary vascular resistance per unit mass of myocardium in animals with chronic hypertension and left ventricular hypertrophy remain unidentified. Because increases in wall thickness of resistance vessels in some vascular beds in response to hypertension may decrease luminal diameter, we hypothesized that similar changes may occur in the coronary vasculature. To test this hypothesis, we performed hemodynamic and morphometric studies on eight dogs with renovascular hypertension (one kidney, one clip) of 6 weeks' duration, and in six normotensive dogs. Hypertension evoked a 27% increase in left ventricular mass and was associated with a 67% increase in left ventricular minimal coronary vascular resistance per 100 g calculated from coronary perfusion measured with microspheres during adenosine infusion. The vasculature was fixed via perfusion of glutaraldehyde and tissue samples from the left ventricle were embedded in Epon. Wall:lumen ratios, determined by light microscopy, of coronary arteries and arterioles were similar in hypertensive and normotensive dogs. Lumen diameters of large epicardial arteries (greater than 640 microns) of hypertensive dogs increased significantly so that wall:lumen ratios were normal despite an increased medial thickness. Ultrastructural analysis, however, showed an enhancement of the relative extracellular compartment of the tunica media of large coronary arteries of hypertensive dogs: 36.4 +/- 3.4% vs. 26.5 +/- 1.6% (mean +/- SEM). Capillary numerical density and surface area (surface area:tissue volume) were significantly lower in the endomyocardium, while capillary volume density (volume:tissue volume) was lower in the midmyocardium and endomyocardium of hypertensive dogs compared to normotensives.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of activated charcoal hemoperfusion in removing lethal doses of barbiturates and salicylate from the blood of rats and dogs.

Rats were injected intraperitoneally with lethal doses of sodium pentobarbital (115 mg/kg) or a lethal mixture of sodium salicylate (500 mg/kg) and sodium acetazolamide (25 mg/kg). Within about 20 min, part of each group was connected to an extracorporeal circuit containing uncoated activated charcoal and part to an empty control circuit. After a 90-min hemoperfusion, the treated groups showed a significantly decreased mortality (58% to 14% for pentobarbital; 100% to 0% for salicylate). Dogs were injected intravenously with lethal doses of sodium phenobarbital (175 mg/kg). One group was treated by hemoperfusion through an empty device in a control extracorporeal circuit, a second group was treated with loose-bed activated charcoal devices, and a third group with fixed-bed activated charcoal devices. For both the fixed and loose-bed devices, a 5-h hemoperfusion markedly decreased mortality (100% to less than or equal to 15%). The lethal combination of salicylate and closed-circuit methoxyflurane anesthesia was also successfully treated in dogs. This study clearly demonstrates the lifesaving potential of uncoated activated charcoal hemoperfusion.