Bone quality and quantity are important factors with regard to the survival rate of dental implants. The aim of this study was to conduct a systematic review of dental implants inserted in low-density bone and to determine the survival rate of dental implants with surface treatments over time. A systematic review of the literature was undertaken by two independent individuals; the Medline/PubMed database was searched for the period July 1975 to March 2013. Relevant reports on bone quality and osseointegration of dental implants were selected. The search retrieved 1018 references, and after inclusion and exclusion criteria were applied, 19 studies were selected for review. A total of 3937 patients, who had received a total of 12,465 dental implants, were analyzed. The survival rates of dental implants according to the bone density were: type I, 97.6%; type II, 96.2%; type III, 96.5%; and type IV, 88.8%. The survival rate of treated surface implants inserted in low-density bone was higher (97.1%) than that of machined surface implants (91.6%). Surface-treated dental implants inserted in low-density bone have a high survival rate and may be indicated for oral rehabilitation. However, more randomized studies are required to better evaluate this issue.
Currently, the predictability of oral rehabilitations using dental implants is high. Dental implants have been used for overdentures, fixed partial and total dentures, and maxillofacial prostheses, as well as immediate dental loading. However, with regard to the rehabilitation of low density bone, great diversity exists among dental implants from different companies, with different surface treatments and connections.
The dental implant survival rate may be related to the quality and quantity of bone in the dental arch. There are various classifications for the quality and quantity of bone reported in the literature, including the bone type (I–IV) and density (heavy or soft), as well as type V bone. Lekholm and Zarb established a precursor classification for organizing bone tissue into four categories with different degrees of density. This classification allowed the quality of bone tissue to be related to the stability of an implant. Furthermore, it is possible to develop instruments and surgical techniques appropriate for each specific situation. In the previous decade, Bahat proposed a subdivision of the classification of type IV bone, referring to bone type V in situations with a complete absence of cortical tissue (upper and lower). Moreover, there is a classification that considers the bone as dense (high-density), normal (moderate-density), or soft (low-density). One of the main methods used to determine the density of bone tissue is based on the perception of the clinician at the time of preparation of the surgical bed.
There is no agreement among researchers about the predictability of dental implants inserted in low-density bone. Some prospective studies have reported survival rates and bone loss to be similar for implants inserted in poor-quality bone and in good-quality bone. Also, surface treatments can improve the survival rate of dental implants in type IV bone, enhancing osseointegration, and this may be related to bone quality and quantity and associated systemic factors.
Surface-treated dental implants may show a better survival rate in poor-quality bone. However, this improvement has yet to be demonstrated with certainty. Previous studies that have evaluated dental implants with machined surfaces in excellent-quality bone have found a high predictability for rehabilitation. However, when analyzed under conditions of low-density bone, this surface was found to have a higher propensity to fail.
Therefore, a study to assess patients who have received dental implants performed with the PICO design (participants, interventions, comparisons, and outcomes) is warranted, in order to determine the predictability of implants inserted in poor-quality bone and the longevity of rehabilitation with surface-treated implants. Two hypotheses were tested: (1) the survival rate of dental implants inserted in low-density bone is lower than that in better quality bone (types I–III) and (2) the survival rate of treated surface implants in low-density bone is higher compared to machined surface implants.
Materials and methods
The authors selected the articles based on inclusion and exclusion criteria. All disagreements were resolved through discussion, and decisions were made by consensus. This systematic review was performed in accordance with the PRISMA statement, and also followed models proposed in the literature.
A search of the English language literature was conducted by two independent individuals (MCG and JFSJ) using the PubMed/Medline database, covering the period July 1975 to March 2013. The keywords ‘dental implants’ and ‘quality bone’ were used. A broad search strategy was pursued. Studies were selected based on their titles and abstracts according to the exclusion criteria for abstracts and full-text articles. Agreement between the readers was determined statistically, and any conflicts were resolved by discussion or analysis of a third reader (EPP). This procedure was applied at all selection steps. The full-text articles were evaluated by the readers using a pilot test form. The authors of the articles were not contacted.
The studies were selected on the basis of their titles and abstracts; prospective and retrospective studies as well as randomized controlled trials (RCTs) were included. The total sample of selected studies was then evaluated and studies were included or excluded. Participants, interventions, comparisons, and outcomes (PICO), according to the PRISMA statement, were determined to organize a clear clinical question and to focus on suitability for inclusion. ‘Participants’ were patients who had been rehabilitated with dental implants. The ‘intervention’ was dental implants inserted in poor-quality bone (type IV or soft). ‘Comparisons’ were dental implants inserted in normal-density bone and types I–III bone. Finally, ‘outcomes’ evaluated were the survival rate and suitable protocols for implant placement.
The inclusion criteria for the studies were the following: English language; more than five patients who received dental implants in poor-quality bone (type IV), according to the Lekholm and Zarb classification, or in soft bone; survival rates of dental implants reported. In addition, these studies had to show comparison parameters (control group) with types I to III bone or normal-density bone. Thus, we included studies that used the classification of Lekholm and Zarb (bone types I–IV), the classification of Bahat, who added bone type V, and the classification by Trisi and Rao, cited by Testori et al., which categorizes the bone type as dense, normal, or soft.
The exclusion criteria were the following: duplicated studies; animal studies; studies of patients during orthodontic treatment; mini-implants; studies related to advanced bone reconstruction surgery; zygomatic implants; studies showing only soft tissue grafting; peri-implantitis; in vitro assays and biomechanical studies; reported cases including patients with osteoporosis, bisphosphonates, radiotherapy, chemotherapy, and cleft palate; studies showing only prosthesis fabrication without analysis of the bone tissue characteristics; studies that analyzed only primary stability; studies evaluating magnetic resonance and computed tomography images without verifying bone quality; and systematic reviews.
Reliability and quality assessment
The assessment of the quality of the methodology was performed in accordance with the PRISMA statement. The studies were ranked in categories as follows: RCTs, prospective studies, and retrospective studies. Independent researchers conducted the development of the systematic review; the different studies were analyzed and discussed, and disagreements were resolved. The assessment of risk quality and bias was performed to eliminate studies that concealed data on bone quality and did not define success criteria for dental implants.
The following data were collected for each article: first author, year, study design, implant surfaces, number of patients, age, where the implants were inserted, implant geometry, implant number, follow-up, type of oral prosthesis, survival rate in different bone types (I–IV) or by bone density (normal and soft), and number of lost implants. Studies reported results for type IV bone compared to other bone types (I–III) for rehabilitation with dental implants. The data collected were related to the survival outcome of each study.
Data were recorded qualitatively to allow comparisons among the selected studies ( N = 19). The total number of implants in low-density bone was calculated, as well as the survival rate in type IV bone compared with the other types (types I–III) or density of bone (normal and soft). Furthermore, the survival rate was calculated for treated surface implants (double etching, micro-texturing) and machined surface implants inserted in poor-quality bone.
The literature search of PubMed/Medline identified 1018 references; after excluding animal studies, 826 studies were selected for the data synthesis. After an analysis of the titles according to the inclusion and exclusion criteria and the elimination of duplicate references, 39 full-text papers were selected for the eligibility assessment. Some of the full-texts were then excluded: studies that showed only partial data (bone quality criteria not well defined), studies with only two categories of bone quality (good or bad, and type IV or other types), studies that evaluated type IV bone without parameters (control), and studies involving bone grafting. Therefore, after the full texts of the articles had been examined, 19 studies were included in the review. The literature research process is shown in Fig. 1 . The 19 studies selected for review were published during the period 1992–2008. The reasons for exclusion of 20 of the articles evaluated are shown in Table 1 .
|There were no reported quality criteria or bone quantity available|
|Bone quality classification into only two bone types|
|Low-density bone analysis without comparisons with the others|
|Failure rate did not include bone type|
|Similar or duplicate data|
Table 2 summarizes the main data collected in this study. Among the 19 studies, 13 were prospective studies, three were retrospective studies, and three were RCTs. The dental implant surface treatments included machined, double-etching, anodic oxidation (TiUnite), sprayed with titanium plasma (SLActive), and titanium dioxide (TiOblast). A total of 3937 patients, with a mean age of 55.2 years, were studied. The anterior regions of the maxilla and mandible were the main areas in which the dental implants were inserted ( Table 2 ).
|Reference||Type of study||Surface||Number of patients||Mean age, years||Sites||Minimum implant size, mm||No. of dental implants||Follow-up, months||Type of prosthesis||Survival rate (%) of dental implants (total) in D1, D2, D3, D4 a||Failures of dental implants||Statistical data|
|Aalam and Nowzari||Prospective||(TiUnite)
|74||52.8||Anterior and premolar||7 c||198||24||Single-unit and fixed prosthesis, overdentures||100%||0||P > 0.05|
|Alsaadi et al.||Retrospective||(TiUnite)
|2004||–||Anterior and posterior||3.3 and <10||6946||252||–||D1: 94.86% (480)
D2: 97.87% (2390)
D3: 96.38% (2074)
D4: 92.67% (632)
|252||D4 > D2
D1 > D2
P < 0.001
|Bahat||Prospective||–||202||18–81||Premolar and molar||3.75 × 7||660||144||–||D2: 89.7% (78)
D3: 94.8% (348)
D4: 96.9% (194)
D5: 67.0% (3)
|Bergkvist et al.||Prospective||Spray plasma titanium||25||64||Anterior and premolar||3.3 × 6||146||60||Fixed dentures||D2: 100% (30)
D3 and D4: 96.6% (116)
|Collaert and De Bruyn||Prospective||TiOblast (titanium dioxide)||25||42–76||Anterior and posterior||3.5 × 8||195||36||Fixed dentures||D1: 100%
|Fischer et al.||Prospective||TiUnite (anodic oxidation)||32||54||Anterior, premolar and molar||4.3 × 10||53||12||Single-unit and fixed prosthesis||D1: 100% (1)
D2: 100% (29)
D3: 100% (20)
D4: 66.6% (3)
|Friberg et al.||Retrospective||Machined||98||62||Anterior, premolar and molar||3.75 × 7||379||32||Fixed dentures||D1: 100% (17)
D2: 86.3% (101)
D3: 99.23% (130)
D4: 97.7% (131)
|Friberg et al.||Prospective||TiUnite||187||53||Anterior, premolar and molar||3.75 × 7||478||12||Single-unit and fixed prosthesis||D1: 100% (12)
D2: 99.36% (158)
D3: 99.56% (230)
D4: 96.15% (78)
|Ganeles et al.,||RCT||SLActive||266||46.3||Premolar and molar||4.1 × 8||383||36||Single-unit and fixed prosthesis||D4: 100% (28)
D1, D2, and D3: 97.0% (355)
|10||P = 0.7519|
|Glauser et al.||Prospective||TiUnite||38||51||Anterior, premolar and molar||–||102||48||Single-unit and fixed prosthesis||D2: 100% (24)
D3: 94.11% (51)
D4: 100% (27)
|Grunder et al.||Prospective||–||143||40–47||Anterior, posterior||3.75 × 7||264||36||Single-unit and fixed prosthesis||D2: 96.51% (86)
D3: 91.51% (165)
D4: 100% (10)
|Hutton et al.||Prospective||–||133||32–76||–||–||510||36||Overdenture||D1: 92.3% (13)
D2: 89.5% (95)
D3: 92.5% (146)
D4: 55.0% (40)
|40||P < 0.05|
|Ivanoff et al.||Retrospective||–||67||59||Anterior, premolar and molar||3.75 × 7||299||60||Single-unit and fixed prosthesis, overdentures||D2: 95.65% (23)
D3: 90.49% (221)
D4: 92.72% (55)
|26||P > 0.05|
|Johns et al.||Prospective||–||133||57||Anterior and posterior||4 × 7||510||60||Overdenture||D1, D2 and D3: 96.46% (453)
D4: 71.92% (57)
|32||P < 0.05|
|Khang et al.||RCT||Double-etching Machined||97||60||Anterior and posterior||3.25 × 7||432||36||Single-unit and fixed prosthesis and overdenture||Good-quality bone d (93.8%) e (87.8%) f
Poor-quality bone d (96.8%) e (84.8%) f
|36||P < 0.05|
|Raghoebar et al.||Prospective||Machined||83||56||Anterior||3.75 × 10||170||36||Fixed dentures and overdentures||D1: 92.3% (13)
D2: 95.69% (93)
D3: 94.73% (57)
D4: 42.85% (7)
|Rocci et al.||RCT||TiUnite
|44||51||Premolar and molar||7 c||66||12||Single-unit and fixed prosthesis||D2: 100% (7) g , 100% (3) h
D3: 95.74% (47) g , 92.68% (41) h
D4: 91.6% (12) g , 54.54% (11) h
|22||P < 0.05|
|Tawil and Younan||Prospective||Machined||111||53.6||Anterior, premolar and molar||3.3 × 6||269||53.7||Single-unit and fixed prosthesis||D1: 100% (3)
D2: 94.93% (79)
D3: 95.0% (160)
D4: 92.59% (27)
|Testori et al.||Prospective||Micro-texturization acid (Osseotite)||175||53.5||Premolar and molar||3.25 × 7||405||36||Single-unit and fixed prosthesis||Dense: 98.48% (66)
Normal: 98.12 (266)
Soft: 95.89% (73)